During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure o...During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure of phytoplankton community,resulting in algal blooms and seriously threatening the ecological security of the reservoir.It is of great significance to understand the continuous changes of phytoplankton in the initial impoundment period for the protection of reservoir water quality.Therefore,a two-year in-situ monitoring study was conducted on water quality and phytoplankton in a representative canyonshaped reservoir named Sanhekou and the interannual changes of phytoplankton community and its response to environmental changes during the initial impoundment period were discussed at taxonomic versus functional classification levels.The results showed that the total nitrogen and permanganate index levels were relatively high in the first year due to rapid water storage and heavy rainfall input,and the more stable hydrological conditions in the second year promoted the increase of algae density and the transformation of community,and the proportion of cyanobacteria increased significantly.The succession order of phytoplankton in the first year of the initial impoundment periodwas Chlorophyta-Bacillariophyta-Chlorophyta,or J/F/X1-P/MP/W1-A/X1/MP,respectively.And the succession order in the second year was Cyanobacteria/Chlorophyta-Bacillariophyta-Chlorophyta,or L_(M)/G/P-P/A/X1-X1/J/G.Water temperature,relativewater column stability,mixing depth,and pHwere crucial factors affecting phytoplankton community succession.This study revealed the interannual succession law and driving factors of phytoplankton in the initial impoundment period and provided an important reference for the operation management and ecological protection of canyon-shaped reservoirs.展开更多
Over the last century,the Mediterranean basin has been widely affected by the abandonment of farming activities,leading to a natural succession towards forested ecosystems.This process is resulting in a carbon(C)stock...Over the last century,the Mediterranean basin has been widely affected by the abandonment of farming activities,leading to a natural succession towards forested ecosystems.This process is resulting in a carbon(C)stock increase at an ecosystem level,often assessed through the measurement of aboveground biomass,while the contribution of soil organic carbon(SOC)remains unclear.We investigated C changes caused by secondary succession on previously grazed areas in central Italy,specifically focusing on the SOC pool.The natural succession is described through a chronosequence approach over four successional stages:pastures,shrublands,young and mature forests.Eight replicates per stage were studied,and C stock was estimated in the mineral soil down to a 30-cm depth,and in all other ecosystem C pools:aboveground and belowground biomass,deadwood and litter.In the mature forests,SOC stock was significantly higher(p<0.05)than in pastures by 40±8 Mg ha^(-1),corresponding to 28%of the total ecosystem C stock gain.The same trend was observed for aboveground biomass,the pool that increased the most(62±23 Mg ha^(-1)),with a 43%contribution to total ecosystem gain.Our results point to a substantial contribution of SOC to overall C stock during secondary succession in Mediterranean ecosystems.展开更多
Seasonal variation in phytoplankton composition influences the pathways and efficiency of energy flow,reshaping the structure of the trophic pyramid in the Ross Sea.However,field investigation of grazing processes pre...Seasonal variation in phytoplankton composition influences the pathways and efficiency of energy flow,reshaping the structure of the trophic pyramid in the Ross Sea.However,field investigation of grazing processes presents challenges that hinder our understanding of energy pathways.This study aims to provide insights into energy flow using a three-dimensional ecosystem model applied to the Ross Sea.By analyzing the simulation results,the role of the seasonal phytoplankton succession,specifically the shift from dominance by Phaeocystis antarctica to diatoms,in energy allocation is explored.The short-lived spring bloom of P.antarctica mainly fuels microzooplankton,creating a brief food chain where energy transfers primarily among smaller plankton.In contrast,the subsequent summer bloom of diatoms,which persists longer,provides nearly half of the total phytoplankton energy loss(via ingestion and mortality)to larger mesozooplankton.Our findings indicate that phytoplankton succession in the Ross Sea extends the bloom duration,particularly for diatoms,thereby facilitating energy transfer to higher trophic levels and improving overall energy utilization.This suggests that phytoplankton succession,an ecological strategy adapted to iron-deficient environments in the Ross Sea,explains why the colder region in front of the Ross Ice Shelf is significantly more productive than the northern areas,ultimately favored by top predators.展开更多
The conversion of saline-alkali soils into paddy fields for long-term rice cultivation involves multiple disturbances,and as a result,soil microbial communities are altered to adapt to changing environmental condition...The conversion of saline-alkali soils into paddy fields for long-term rice cultivation involves multiple disturbances,and as a result,soil microbial communities are altered to adapt to changing environmental conditions.However,a comprehensive understanding of the succession of soil bacterial communities that occurs during this process is still lacking.In the present study,we utilized data obtained from paddy fields of different rice cultivation years(0-23 years)to investigate the compositional and functional succession of soil bacterial communities.We focused on core bacterial taxa that were specifically enriched at different successional stages.Generalized joint attribute modeling(GJAM)was used to identify core bacterial taxa.Results indicated that the bare saline-alkali soil(0 year,prior to any rice cultivation)shared few core amplicon sequence variants(ASVs)with paddy fields.In the bare saline-alkali soil,Longimicrobiaceae from the phylum Gemmatimonadetes was dominant,while the dominance was subsequently replaced by Burkholderiaceae and Pedosphaeraceae--phyla affiliated with Proteobacteria and Verrucomicrobia--after 5 and 23 years of rice cultivation,respectively.The relative abundances of nitrogen metabolism functions in the core bacterial communities of the bare saline-alkali soil were higher than those at other successional stages,while sulfur metabolism functions exhibited the opposite trend.These indicated that the role of the core bacterial taxa in mediating nutrient cycling also evolved and adapted to changing soil conditions as rice cultivation was established.Redundancy analysis(RDA)indicated that the composition of the core bacterial community in paddy fields with rice cultivation for 0,2 and 4,6,8,10,and 12,and 20 and 23 years were driven by soil nitrate nitrogen content,pH,available phosphorus content,and the ratio of total carbon to total nitrogen,respectively.In summary,the present study provides insights into the succession of soil bacterial communities and core bacterial taxa that occurs during long-term rice cultivation.展开更多
The occurrence types and controlling factors of organic matter in the sepiolite-containing successions of the first member of Mid-Permian Maokou Formation(Mao-1 Member for short)in the Eastern Sichuan Basin,SW China,h...The occurrence types and controlling factors of organic matter in the sepiolite-containing successions of the first member of Mid-Permian Maokou Formation(Mao-1 Member for short)in the Eastern Sichuan Basin,SW China,have been investigated through outcrop section measurement,core observation,thin section identification,argon ion polishing-field scanning electron microscopy,energy spectrum analysis,X-ray diffraction,total organic carbon content(TOC),major and trace element analysis.Finally,the symbiotic adsorption model of sepiolite for organic matter enrichment has been established.The results show that the sepiolite-containing successions of the Mao-1 Member are composed of the rhythmite of mudstone,argillaceous limestone and limestone,with five depositional intervals vertically and the organic matter mostly developed in the mudstone and argillaceous limestone layers within the lower three intervals.The organic matter occurrence types are mostly layered or nodular in macro to meso-scale,blocky-vein-like under a microscope,but scattered,interstitial or adsorbed at a mesoscopic scale.It underwent transition processes from lower to higher salinity,from oxygen-poor and anoxic reduction to oxygen-poor and localized oxygen enrichment on the palaeo-environment of the Mao-1 Member.The first two intervals of the early depositional phase of Mao-1 Member constitute the cyclothems of mudstone,argillaceous limestone and limestone and quantities of fibrous-feathered sepiolite settle down within the Tongjiang-Changshou sag with continuous patchy organic matter from adsorption of alginate by sepiolite in intercrystalline,bedding surfaces and interlayer pores.The third and fourth intervals in the mid-depositional phase are mostly composed of the mudstone and argillaceous limestone alternations with the continuous patchy or banded organic matter in the surface and inter-crystalline pores of fibrous,feathered and flaky sepiolite.And the fifth interval in the late depositional phase of the Mao-1 Member comprises the cyclothems of extremely thin layered argillaceous limestone and thick-layered limestone with the fibrous sepiolite depositing in the argillaceous limestone and irregular organic matter dispersing around the sepiolite.Therefore,the symbiotic adsorption between organic matter and sepiolite effectively enhances the preservation efficiency of organic matter and improves the source rock quality of the Mao-1 Member,which enhances our understanding on the enrichment model of the depositional organic matter.展开更多
Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession...Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession mechanisms and their association with the N removal performance of bioreactors.The laboratory woodchip bioreactors were continuously operated for 360 days under three influent N level treatments,and the results showed that the average removal rate of TN was 45.80 g N/(m^(3)·day)when the influent N level was 100 mg N/L,which was better than 10 mg N/L and 50 mg N/L.Dynamic succession of bacterial communities in response to influent N levels and DOM characteristics was an important driver of TN removal rates.Medium to high N levels enriched a copiotroph bacterial module(Module 1)detected by network analysis,including Phenylobacterium,Xanthobacteraceae,Burkholderiaceae,Pseudomonas,and Magnetospirillaceae,carrying N-cycle related genes for denitrification and ammonia assimilation by the rapid consumption of DOM.Such a process can increase carbon limitation to stimulate local organic carbon decomposition to enrich oligotrophswith fewer N-cycle potentials(Module 2).Together,this study reveals that the compositional change ofDOMand bacterial community succession are closely related to N removal performance,providing an ecological basis for developing techniques for N-rich effluent treatment.展开更多
Forests undergoing ecological succession following abandonment from agricultural use(i.e.,old fields)are ubiquitous in temperate regions of the U.S.and Europe.Ecological succession in old fields involves changes in ve...Forests undergoing ecological succession following abandonment from agricultural use(i.e.,old fields)are ubiquitous in temperate regions of the U.S.and Europe.Ecological succession in old fields involves changes in vegetation composition influenced by factors such as land-use history,soil conditions,and dispersal limitations.Species’behavioral,morphological,physiological and life-history attributes influence the outcomes of environmental and biotic filters on distribution and abundance.However,many studies have focused on aboveground attributes,while less attention has been placed on belowground species characteristics that influence community assembly and function.In this study,we used a trait-based approach to examine how aboveground plant composition and distribution vary with plant root functional traits(e.g.,mycorrhizal association)that mediate access for nutrients such as nitrogen(N)and phosphorous(P).We inventoried every tree stem(n=11,551)in a 10-ha forested area containing old-field and historical forests and matched every species with root functional traits(n=33)from established databases.We found that land-use history influences community composition and distribution in old-field forests,which also varied with belowground root functional traits.Community composition in old-field forests,which were dominated by Acer saccharum and non-native species,were largely associated with arbuscular mycorrhizae(AM)and higher root nutrient concentrations.On the other hand,community composition in historical forests–largely dominated by Tsuga canadensis–were associated with ectomycorrhiza(EcM)and more variation of root length and depth.These results suggest that changes in aboveground communities have implications for belowground ecosystem services(e.g.,nutrient cycling)which are important to forest ecosystem development.Trait-based approaches can elucidate mechanisms of community assembly,and understanding how traits influence species coexistence and interactions can inform management decisions related to biodiversity conservation and restoration efforts in disturbed or altered forests.展开更多
Soil organic carbon(SOC)affects the function of terrestrial ecosystem and plays a vital role in global carbon cycle.Yet,large uncertainty still existed regarding the changes in SOC stock and quality with forest succes...Soil organic carbon(SOC)affects the function of terrestrial ecosystem and plays a vital role in global carbon cycle.Yet,large uncertainty still existed regarding the changes in SOC stock and quality with forest succession.Here,the stock and quality of SOC at 1-m soil profile were investigated across a subalpine forest series,including shrub,deciduous broad-leaved forest,broadleaf-conifer mixed forest,middle-age coniferous forest and mature coniferous forest,which located at southeast of Tibetan Plateau.The results showed that SOC stock ranged from 9.8 to29.9 kg·m^(-2),and exhibited a hump-shaped response pattern across the forest successional series.The highest and lowest SOC stock was observed in the mixed forest and shrub forest,respectively.The SOC stock had no significant relationships with soil temperature and litter stock,but was positively correlated with wood debris stock.Meanwhile,the average percentages of polysaccharides,lignins,aromatics and aliphatics based on FTIR spectroscopy were 79.89%,0.94%,18.87%and 0.29%,respectively.Furthermore,the percentage of polysaccharides exhibited an increasing pattern across the forest successional series except for the sudden decreasing in the mixed forest,while the proportions of lignins,aromatics and aliphatics exhibited a decreasing pattern across the forest successional series except for the sudden increasing in the mixed forest.Consequently,the humification indices(HIs)were highest in the mixed forest compared to the other four successional stages,which means that the SOC quality in mixed forest was worse than other successional stages.In addition,the SOC stock,recalcitrant fractions and HIs decreased with increasing soil depth,while the polysaccharides exhibited an increasing pattern.These findings demonstrate that the mixed forest had higher SOC stock and worse SOC quality than other successional stages.The high proportion of SOC stock(66%at depth of 20-100 cm)and better SOC quality(lower HIs)indicate that deep soil have tremendous potential to store SOC and needs more attention under global chan ge.展开更多
Given the importance of the intestinal microbiota in life-long health,increasing attention has been paid to ecological mechanisms that govern microbial succession.Both environmental dispersal and host priority effect ...Given the importance of the intestinal microbiota in life-long health,increasing attention has been paid to ecological mechanisms that govern microbial succession.Both environmental dispersal and host priority effect play important roles in intestinal microbiota succession of aquatic animals,but their relative importance is unknown.Here,we explore the intestinal microbiota succession and assembly of Litopenaeus vannamei across larvae,postlarvae,juvenile,and preadult stages.We aimed to clarify the relative contributions between environmental dispersal and host priority effect on intestinal microbiota succession.We found that bothα-andβ-diversity of the intestinal microbiota changed dynamically along with host development.In particular,the intestinal microbiota assemblies were dominated by stochastic processes,except with the larvae stage.The succession of shrimp intestinal microbiota was clearly influenced by internal communities in the intestines of larvae,as well as the external communities in water and sediment.Importantly,the impact of environmental dispersal on the intestinal microbiota succession outweighed the host priority effect during the larvae and postlarvae stages.However,this situation was largely reversed during the juvenile and preadult stages.The possible reason is that,during the larvae and postlarvae stages,shrimp mainly feed on plankton from the environment,and their digestive system remains underdeveloped,the host recruits numerous microbes from the environment and selects specific microbes to aid digestion and nutrient absorption.These findings enhance our understanding of alternate effects of environmental and host factors on the intestinal microbiota succession of aquatic animals and provide a foundation for developing microecological management strategies in shrimp culture.展开更多
Leadership succession in nursing academic programs poses a significant challenge, primarily due to the limited availability of professionals with the competencies required for effective leadership [1]. This study aims...Leadership succession in nursing academic programs poses a significant challenge, primarily due to the limited availability of professionals with the competencies required for effective leadership [1]. This study aims to address this gap by investigating the critical factors in succession planning for nursing program administrators. The research objectives include identifying the competencies necessary for academic administrators, assessing the experience of current administrators, and developing a comprehensive succession plan framework. The research uses qualitative methods, including literature review, interviews with nursing administrators, and analysis of existing succession models. Results highlight the importance of integrating strategic planning into succession processes to ensure smooth transitions and organizational stability. Conclusions suggest that a formalized succession plan, incorporating mentorship and leadership development, can mitigate leadership gaps in nursing academia [2].展开更多
The structure and dynamic succession law of natural secondary forest after severe fire interference in recent 20 years were studied by adopting the method of deducing time series from the spatial sequence of vegetatio...The structure and dynamic succession law of natural secondary forest after severe fire interference in recent 20 years were studied by adopting the method of deducing time series from the spatial sequence of vegetation in Heihe region, Heilongjiang, China. Two typical and widely distributed forest types in the study area, namely forest type A and forest type B, were selected as study subjects. Forest type A is pure broadleaf forest or broadleaf mixed forest mainly composing of superior Betula platyphylla and Populus davidiana in the area with gradient 〈25°, while forest type B is pure forest or mixed forest composing of superior Quercus mongolica and Betula davurica in the area with gradient 〉25°. Species richness, vegetation coverage, important value, and similarity index of commtmity in different layers （Herb, shrub, small tree, and arbor layers） were investigated and analyzed for the two typical forests. The results show that after fire interference, the species richness and coverage in each layer in forest type A were higher than that in forest type B. Both for forest type A and B, with elapse of post-fire years, the species richness and coverage of herbs and shrubs showed a decline tendency, while those of arbor layer present a rising tendency. Through comparison of the important values of species in each layer and analysis of community structure changes, the dynamic process of post-fire vegetation succession for forest type A and B was separately determined. Post-fire 80 years＇ succession tendency of forest type A is B. platyphylla and Larix gmelinii mixed forest. Its shrub layer is mainly composed of Corylus heterophylla and Vaccinium uliginosum, and herb layer is dominated by Carex tristachya, Athyrium multidentatum, and Pyrola incarnate; whereas, the post-fire 80 years＇ succession of forest type B is Q. mongolica and B. davurica mixed forest. Its shrub layer is mainly composed of lespedeza bicolar and corylus heterophylla and herb layer is dominated by Carex tristachya, Asparagus densiflorus, and Hemerocallis minor.展开更多
Background:As a structurally and functionally important component in forest ecosystems,plant debris plays a crucial role in the global carbon cycle.Although it is well known that plant debris stocks vary greatly with ...Background:As a structurally and functionally important component in forest ecosystems,plant debris plays a crucial role in the global carbon cycle.Although it is well known that plant debris stocks vary greatly with tree species composition,forest type,forest origin,and stand age,simultaneous investigation on the changes in woody and non-woody debris biomass and their carbon stock with forest succession has not been reported.Therefore,woody and non-woody debris and carbon stocks were investigated across a subalpine forest successional gradient in Wanglang National Nature Reserve on the eastern Qinghai-Tibet Plateau.Results:Plant debris ranged from 25.19 to 82.89 Mg∙ha−1 and showed a global increasing tendency across the subalpine forest successional series except for decreasing at the S4 successional stage.Accordingly,the ratios of woody to non-woody debris stocks ranged from 26.58 to 208.89,and the highest and lowest ratios of woody to non-woody debris stocks were respectively observed in mid-successional coniferous forest and shrub forest,implying that woody debris dominates the plant debris.In particular,the ratios of coarse to fine woody debris stocks varied greatly with the successional stage,and the highest and lowest ratios were found in later and earlier successional subalpine forests,respectively.Furthermore,the woody debris stock varied greatly with diameter size,and larger diameter woody debris dominated the plant debris.Correspondingly,the carbon stock of plant debris ranged from 10.30 to 38.87 Mg∙ha−1 across the successional series,and the highest and lowest values were observed in the mid-coniferous stage and shrub forest stage,respectively.Most importantly,the carbon stored in coarse woody debris in later successional forests was four times higher than in earlier successional forests.Conclusions:The stock and role of woody debris,particularly coarse woody debris,varied greatly with the forest successional stage and dominated the carbon cycle in the subalpine forest ecosystem.Thus,preserving coarse woody debris is a critical strategy for sustainable forest management.展开更多
Through the field investigation and laboratory analysis,this paper describes the regular pattern of community succession on the deserted land of Shizishan copper tailings in Tongling City.There are 49 species of natur...Through the field investigation and laboratory analysis,this paper describes the regular pattern of community succession on the deserted land of Shizishan copper tailings in Tongling City.There are 49 species of natural colonized plants on the wasteland,which are subordinate to 15 families and 38 genera.The main families are Compositae(12 species),Gramineae(11 species),Leguminosae(8 species)and Hippochaete ramosissimum,which belong to Equisetaceae.The extreme soil infertility and excessively concentration of heavy metals(especially Cu and Cd)are the main limiting factors to plants colonization.The vegetation on the deserted land of copper tailings is distributed in spot piece and scattered mainly with fewer species of plant,with lower species diversity.Annual and biennial herbs and grasses are dominant components.Cynodon dactylon,Imperata cylindrica var.major,Lespedeza chinensis,Erigeron annuus and H.ramosissimum etc.have a higher summed dominance ratio.The natural formation of plant community on the deserted land of copper tailings usually goes through seeds spread,invasion,ecesis,aggregation and species competition.After several years of primary natural restoration,14 communities were formed.According to their community composition and structure level,the 14 communities are divided into three primary succession stages,namely monodominant,subdominant and codominant species communities.With the formation and succession of these communities,species were enriched and diversity increased,the margin of summed dominance ratio of species in each community decreased,and the composition or structure of community became complex.展开更多
The microbiotic crust study is among new focuses in investigating on the desertification control. Based on determination of algal crusts with different successive ages (4-, 8-, 17-, 34-, 42-year-old) and unconsolidate...The microbiotic crust study is among new focuses in investigating on the desertification control. Based on determination of algal crusts with different successive ages (4-, 8-, 17-, 34-, 42-year-old) and unconsolidated sand in the desert area, species composition and clustering analyses were carried out in this study. Results on successional orientation revealed that (1) the abundance of Cyanophyta, specially of Scytonema javanicum gradually decreased; (2) the abundance of Chlorophyta, Bacillariophyta and a species of Cyanophyta, Phormidium tenue increased; (3) the biodiversity increased gradually with the community succession; and (4) biomass of microalgae increased at the early stage, but decreased at the later stage due to the abundance of lichens and mosses. But, the speed of natural succession was so slow that the community-building species was still the first dominant species after 42 years, except that its dominant degree decreased just slightly. However, successive speed and trend were affected by water, vegetation coverage, terrain, time and soil physico-chemical properties as well, especially Mn content in the soil appeared to have a threshold effect.展开更多
Investigations on charcoal in the soil, fire-scarred trees, stand composition, forest structure as well as regeneration status were carried out in the natural broad-leaved/Korean pine (Pinus koraiensis) forest after f...Investigations on charcoal in the soil, fire-scarred trees, stand composition, forest structure as well as regeneration status were carried out in the natural broad-leaved/Korean pine (Pinus koraiensis) forest after fire disturbance at Liangshui Nature Reserve on the mid-north of Xiaoxingan Mountains from 1990 to 1992, and the ecological effects of fire disturbance on the formation and succession of this kind of forest were analyzed according to the survey results. The average depth of charcoal in the soil was related to the timing of the fire. According to the characteristic of fire-scarred trees, the dynamic map of the fire behavior was drawn onto the topographic map. It showed that the dimension and extent of the fire disturbance was closely related with site conditions. Fire disturbance only led to a significant difference in stand composition and diameter class structure for the stands at different locations, rather than completely destroying the forest. After fire disturbance, the horizontal community structure was a mosaic of different patches, which were made up of different deciduous species or different sizes of Korean pines, and the succession trend of each patch was also different. In the sites with the heavy fire disturbance, the intolerant hardwood species were dominant, and there were a large number of regenerative Korean pine saplings under the canopy. In the moderate -disturbed sites, the tolerant hardwood species were dominant, and a small number of large size Korean pines still survived. In the light-disturbed sites, large size Korean pines were dominant.展开更多
Species dynamics in terms of both plant biological traits, ecological strategies and species richness as well as soil chemical variables during a secondary succession in abandoned fields on the Loess Plateau along a t...Species dynamics in terms of both plant biological traits, ecological strategies and species richness as well as soil chemical variables during a secondary succession in abandoned fields on the Loess Plateau along a temporal sere from 3 a to 149 a were studied. The results indicated that (I) Soil total C and N increased while soil pH, total K and Na decreased with years since abandonment. No noticeable trend was found in the case of soil P along the successional sere. On the other hand, total CaO of the surface layer (0 - 10 cm) decreased, but that of the two deeper layer, (20 - 30 cm, 40 - 50 cm) increased with years since abandonment. Soil C, N, K and P decreased, while Na, CaO and soil pH increased with increasing soil depth. (2) Species richness peaked at both mid-stage of the successional sere and the intermediate portion of soil chemical variables gradient. (3) An ideal dominant species in the early successional stage were annuals with stable seed pool, CR-life strategy, S-regeneration strategy, and strong competitive ability on relatively poor soil, while perennials capable of intensive lateral spread and colonal ability, requiring high nutrient supply, and having Clife strategy would be the dominant species in the subsequent stages. Plant traits, such as perennial-life history, C-, CR-, SC-, SR-, S- and R-life strategies, W-, S-, Bs- VBs- and V-regeneration strategies, were over- represented throughout the whole sere among the other species. (4) Some traits, such as C-, SC-life strategies, ability of clonality, perennial-life history, well-developed lateral spread ability, V- and VBs-regeneration strategies, seed animal. dispersal mode, flowering time of autumn, fruit types of legumen and nut, were more or less correlated with increased soil total C, N and K, while S-, SR-, R-, CR-life strategies, annual-, biannual-life history, non-clonal ability, S-regeneration strategy, poor lateral spread ability, and fruit types of utricle, capsule were associated with increased soil total Na, CaO and pH. The results suggested that steppes should be the dominant native vegetation coinciding with the large-scaled eco-climatic conditions on the Loess Plateau.展开更多
Since 1950, 700 plots were established in the alpine and canyon region of western Sichuan. The distribution charac-teristics and the relationships between forest succession and environmental gradients were studied. Th...Since 1950, 700 plots were established in the alpine and canyon region of western Sichuan. The distribution charac-teristics and the relationships between forest succession and environmental gradients were studied. The results showed that the main tree species were Picea and Abies in this region, and there were more than 90 forest types. Abies forests mainly dis-tributed in the middle and upper reaches of rivers and their branches, and Picea forests mainly distributed in wide valleys and on half-shaded and half-sunny slopes. The natural regeneration was poor under primitive spruce and fir forest canopy, but was good in the spruce and fire forest gap. The relationship between forest succession and vertical gradient was closely related to the relationship between forest succession procession and plant synusia under primary forests. Human activities could promote and postpone succession process. The results of expanding regeneration were often influenced by topography, vegetation and wind direction.展开更多
Net N mineralization and nitrification were determined using the closed_top PVC tube in situ incubation method in a subalpine meadow (Saussurea iodostegia Hance + Carex capillaris L.)→shagspine peashrub (Caragana jub...Net N mineralization and nitrification were determined using the closed_top PVC tube in situ incubation method in a subalpine meadow (Saussurea iodostegia Hance + Carex capillaris L.)→shagspine peashrub (Caragana jubata (Pall.) Poir) shrubland→ribbed birch (Betula costata Trautv.) successional sere. The ability of the three communities to supply available N was comparatively studied. The results showed that there were apparent seasonal changes in the inorganic N pools (including NH + 4_N and NO - 3_N) and net N mineralization and nitrification rates in the three sites. There were generally no significant differences in the inorganic N pools among sampling events. But the NH + 4_N concentration in both birch (P<0.01) and meadow (P<0.01) sites was significantly higher than that in peashrub site in June 1996, and the NO - 3_N concentration in peashrub site was significantly higher than that of meadow site (P<0.05) in August 1996. The annual net N mineralization and nitrification rates in peashrub site (16.01 kg·hm -2 ) were higher than in birch (12.05 kg·hm -2 ) and meadow sites (1.64 kg·hm -2 ). The annual net nitrification rate in peashrub site (11.37 kg·hm -2 ) was higher than in meadow site (10.90 kg·hm -2 ) and much lower than in birch site (14.36 kg·hm -2 ). We conclude that the ability of peashrub shrubland soil to supply available N for plant uptake and the ability to prevent available N from denitrification and leaching were higher than that of the other two sites. The leguminous peashrub might play a potential role in supplying more N, which in turn facilitate the invasion of birch saplings during the successional processes.展开更多
Global climate change is having long-term impacts on the geographic distribution of forest species. However, the response of vertical belts of mountain forests to climate change is still little known. The vertical dis...Global climate change is having long-term impacts on the geographic distribution of forest species. However, the response of vertical belts of mountain forests to climate change is still little known. The vertical distribution of forest vegetation(vertical vegetation belt) on Gongga Mountain in Southwest China has been monitored for 30 years. The forest alternation of the vertical vegetation belt under different climate conditions was simulated by using a mathematical model GFSM(the Gongga Forest Succession Model). Three possible Intergovernmental Panel on Climate Change(IPCC) climate scenarios(increase of air temperature and precipitation by 1.8℃/5%, 2.8℃/10% and 3.4℃/15% for B_1, A_1B and A_2 scenarios, respectively) were chosen to reflect lower, medium and higher changes of global climate. The vertical belts of mountainous vegetation will shift upward by approximately 300 m, 500 m and 600 m in the B_1, A_1B and A_2 scenarios, respectively, according to the simulated results. Thus, the alpine tree-line will move to a higher altitude. The simulation also demonstrated that, in a changing climate, the shift in the vegetation community will be a slow and extended process characterized by two main phases. During the initial phase, trees of the forest community degrade or die, owing to an inability to adapt to a warmer climate. This results in modest environment for the introduction of opportunistic species, consequently, the vegetation with new dominant tree species becomes predominant in the space vacated by the dead trees at the expense of previously dominated original trees as the succession succeed and climate change advance. Hence, the global climate change would dramatically change forest communities and tree species in mountainous regions because that the new forest community can grow only through the death of the original tree. Results indicated that climate change will cause the change of distribution and composition of forest communities on Gongga Mountain, and this change may enhance as the intensity of climate change increases. As a result, the alternation of death and rebirth would finally result in intensive landscape changes, and may strongly affect the eco-environment of mountainous regions.展开更多
New terrestrial habitats have emerged and a primary succession has developed in the retreat area （29°34＇N, 102°oo＇E, 2951-2886 m） after the retreat of the Hailuogou glacier. To investigate soil microbial...New terrestrial habitats have emerged and a primary succession has developed in the retreat area （29°34＇N, 102°oo＇E, 2951-2886 m） after the retreat of the Hailuogou glacier. To investigate soil microbial changes along the primary successional chronosequence, mixed soil samples were collected at six sites at different ages （2 young sites, 2 mid-aged sites, and 2 old sites）. The RNA was extracted and amplified. Bacterial 16S rRNA and fungal 18S rRNA were analyzed using high-throughput 454 pyrosequencing analysis. Overall, pyrosequeneing showed that Proteobacteria, Acidobacteria, Baeteroidetes and Actinobacteria were the main bacterial phyla, and the fungal communities were strongly dominated by the phyla Ascomyeota and Basidiomyeota in the retreat area. The Shannon diversity index （Hshannon） of bacteria was 6.5 - 7.9, and that of fungi was 2.2 - 4.1 in these sites. For the bacterial communities, diversity and evenness values were highest on the mid-age sites and were relatively low on the young trend was observed for the and old sites. A similar fungal communities. In contrast, soil properties showed significant linear distributional trends （increase or decrease） with the age of the site. Combining the linear change patterns of soil properties, the highest values of bacterial and fungal evenness and diversity in the mid-aged sites indicated that there was less environmental stress and more niches for microbial communities in the middle successional stage compare with other stages. In addition, our analysis showed that microbial communities were the main drivers that build a soil organic matter pool to expedite pedogenesis for ecosystem succession. This primary succession in the Hailuogou glacier retreat area is developing rapidly compared with that in other glacier retreats.展开更多
基金supported by the National Key R&D Program of China(No.2022YFC3203602)the Natural Science Foundation of China(No.52370018)+1 种基金Shaanxi Provincial Youth Innovation Team Project(No.22JP040)Shaanxi Provincial Key Scientific and Technological Innovation Team(No.2023-CX-TD-32).
文摘During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure of phytoplankton community,resulting in algal blooms and seriously threatening the ecological security of the reservoir.It is of great significance to understand the continuous changes of phytoplankton in the initial impoundment period for the protection of reservoir water quality.Therefore,a two-year in-situ monitoring study was conducted on water quality and phytoplankton in a representative canyonshaped reservoir named Sanhekou and the interannual changes of phytoplankton community and its response to environmental changes during the initial impoundment period were discussed at taxonomic versus functional classification levels.The results showed that the total nitrogen and permanganate index levels were relatively high in the first year due to rapid water storage and heavy rainfall input,and the more stable hydrological conditions in the second year promoted the increase of algae density and the transformation of community,and the proportion of cyanobacteria increased significantly.The succession order of phytoplankton in the first year of the initial impoundment periodwas Chlorophyta-Bacillariophyta-Chlorophyta,or J/F/X1-P/MP/W1-A/X1/MP,respectively.And the succession order in the second year was Cyanobacteria/Chlorophyta-Bacillariophyta-Chlorophyta,or L_(M)/G/P-P/A/X1-X1/J/G.Water temperature,relativewater column stability,mixing depth,and pHwere crucial factors affecting phytoplankton community succession.This study revealed the interannual succession law and driving factors of phytoplankton in the initial impoundment period and provided an important reference for the operation management and ecological protection of canyon-shaped reservoirs.
基金supported by the European Union-Next Generation EU,Mission 4 Component 2 CUP J83 C22000860007.
文摘Over the last century,the Mediterranean basin has been widely affected by the abandonment of farming activities,leading to a natural succession towards forested ecosystems.This process is resulting in a carbon(C)stock increase at an ecosystem level,often assessed through the measurement of aboveground biomass,while the contribution of soil organic carbon(SOC)remains unclear.We investigated C changes caused by secondary succession on previously grazed areas in central Italy,specifically focusing on the SOC pool.The natural succession is described through a chronosequence approach over four successional stages:pastures,shrublands,young and mature forests.Eight replicates per stage were studied,and C stock was estimated in the mineral soil down to a 30-cm depth,and in all other ecosystem C pools:aboveground and belowground biomass,deadwood and litter.In the mature forests,SOC stock was significantly higher(p<0.05)than in pastures by 40±8 Mg ha^(-1),corresponding to 28%of the total ecosystem C stock gain.The same trend was observed for aboveground biomass,the pool that increased the most(62±23 Mg ha^(-1)),with a 43%contribution to total ecosystem gain.Our results point to a substantial contribution of SOC to overall C stock during secondary succession in Mediterranean ecosystems.
基金The National Natural Science Foundation of China under contract No.41941008the National Key Research and Development Program of China under contract No.2023YFC3107702.
文摘Seasonal variation in phytoplankton composition influences the pathways and efficiency of energy flow,reshaping the structure of the trophic pyramid in the Ross Sea.However,field investigation of grazing processes presents challenges that hinder our understanding of energy pathways.This study aims to provide insights into energy flow using a three-dimensional ecosystem model applied to the Ross Sea.By analyzing the simulation results,the role of the seasonal phytoplankton succession,specifically the shift from dominance by Phaeocystis antarctica to diatoms,in energy allocation is explored.The short-lived spring bloom of P.antarctica mainly fuels microzooplankton,creating a brief food chain where energy transfers primarily among smaller plankton.In contrast,the subsequent summer bloom of diatoms,which persists longer,provides nearly half of the total phytoplankton energy loss(via ingestion and mortality)to larger mesozooplankton.Our findings indicate that phytoplankton succession in the Ross Sea extends the bloom duration,particularly for diatoms,thereby facilitating energy transfer to higher trophic levels and improving overall energy utilization.This suggests that phytoplankton succession,an ecological strategy adapted to iron-deficient environments in the Ross Sea,explains why the colder region in front of the Ross Ice Shelf is significantly more productive than the northern areas,ultimately favored by top predators.
基金supported by the National Natural Science Foundation of China(Nos.32371734,42007034,41920104008,and U22A20593)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA28020400)+2 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2023205)the Young Scientist Group Project of Northeast Institute of Geography and Agroecology of China(No.2022QNXZ04)the Science and Technology Development Project of Jilin Province of China(No.YDZJ202101ZYTS006).
文摘The conversion of saline-alkali soils into paddy fields for long-term rice cultivation involves multiple disturbances,and as a result,soil microbial communities are altered to adapt to changing environmental conditions.However,a comprehensive understanding of the succession of soil bacterial communities that occurs during this process is still lacking.In the present study,we utilized data obtained from paddy fields of different rice cultivation years(0-23 years)to investigate the compositional and functional succession of soil bacterial communities.We focused on core bacterial taxa that were specifically enriched at different successional stages.Generalized joint attribute modeling(GJAM)was used to identify core bacterial taxa.Results indicated that the bare saline-alkali soil(0 year,prior to any rice cultivation)shared few core amplicon sequence variants(ASVs)with paddy fields.In the bare saline-alkali soil,Longimicrobiaceae from the phylum Gemmatimonadetes was dominant,while the dominance was subsequently replaced by Burkholderiaceae and Pedosphaeraceae--phyla affiliated with Proteobacteria and Verrucomicrobia--after 5 and 23 years of rice cultivation,respectively.The relative abundances of nitrogen metabolism functions in the core bacterial communities of the bare saline-alkali soil were higher than those at other successional stages,while sulfur metabolism functions exhibited the opposite trend.These indicated that the role of the core bacterial taxa in mediating nutrient cycling also evolved and adapted to changing soil conditions as rice cultivation was established.Redundancy analysis(RDA)indicated that the composition of the core bacterial community in paddy fields with rice cultivation for 0,2 and 4,6,8,10,and 12,and 20 and 23 years were driven by soil nitrate nitrogen content,pH,available phosphorus content,and the ratio of total carbon to total nitrogen,respectively.In summary,the present study provides insights into the succession of soil bacterial communities and core bacterial taxa that occurs during long-term rice cultivation.
基金Supported by National Natural Science Foundation of China(42572132,U24B6001,41872150,42230310,U2344209).
文摘The occurrence types and controlling factors of organic matter in the sepiolite-containing successions of the first member of Mid-Permian Maokou Formation(Mao-1 Member for short)in the Eastern Sichuan Basin,SW China,have been investigated through outcrop section measurement,core observation,thin section identification,argon ion polishing-field scanning electron microscopy,energy spectrum analysis,X-ray diffraction,total organic carbon content(TOC),major and trace element analysis.Finally,the symbiotic adsorption model of sepiolite for organic matter enrichment has been established.The results show that the sepiolite-containing successions of the Mao-1 Member are composed of the rhythmite of mudstone,argillaceous limestone and limestone,with five depositional intervals vertically and the organic matter mostly developed in the mudstone and argillaceous limestone layers within the lower three intervals.The organic matter occurrence types are mostly layered or nodular in macro to meso-scale,blocky-vein-like under a microscope,but scattered,interstitial or adsorbed at a mesoscopic scale.It underwent transition processes from lower to higher salinity,from oxygen-poor and anoxic reduction to oxygen-poor and localized oxygen enrichment on the palaeo-environment of the Mao-1 Member.The first two intervals of the early depositional phase of Mao-1 Member constitute the cyclothems of mudstone,argillaceous limestone and limestone and quantities of fibrous-feathered sepiolite settle down within the Tongjiang-Changshou sag with continuous patchy organic matter from adsorption of alginate by sepiolite in intercrystalline,bedding surfaces and interlayer pores.The third and fourth intervals in the mid-depositional phase are mostly composed of the mudstone and argillaceous limestone alternations with the continuous patchy or banded organic matter in the surface and inter-crystalline pores of fibrous,feathered and flaky sepiolite.And the fifth interval in the late depositional phase of the Mao-1 Member comprises the cyclothems of extremely thin layered argillaceous limestone and thick-layered limestone with the fibrous sepiolite depositing in the argillaceous limestone and irregular organic matter dispersing around the sepiolite.Therefore,the symbiotic adsorption between organic matter and sepiolite effectively enhances the preservation efficiency of organic matter and improves the source rock quality of the Mao-1 Member,which enhances our understanding on the enrichment model of the depositional organic matter.
基金supported by the National Key Research and Development Program of China (Nos.2018YFE0105600 and 2020YFC1806803)the New Zealand MBIE Catalyst Fund (No.92846082).
文摘Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession mechanisms and their association with the N removal performance of bioreactors.The laboratory woodchip bioreactors were continuously operated for 360 days under three influent N level treatments,and the results showed that the average removal rate of TN was 45.80 g N/(m^(3)·day)when the influent N level was 100 mg N/L,which was better than 10 mg N/L and 50 mg N/L.Dynamic succession of bacterial communities in response to influent N levels and DOM characteristics was an important driver of TN removal rates.Medium to high N levels enriched a copiotroph bacterial module(Module 1)detected by network analysis,including Phenylobacterium,Xanthobacteraceae,Burkholderiaceae,Pseudomonas,and Magnetospirillaceae,carrying N-cycle related genes for denitrification and ammonia assimilation by the rapid consumption of DOM.Such a process can increase carbon limitation to stimulate local organic carbon decomposition to enrich oligotrophswith fewer N-cycle potentials(Module 2).Together,this study reveals that the compositional change ofDOMand bacterial community succession are closely related to N removal performance,providing an ecological basis for developing techniques for N-rich effluent treatment.
基金supported financially by the Dartmouth College Guarini Dean's Postdoctoral Fellowship Program
文摘Forests undergoing ecological succession following abandonment from agricultural use(i.e.,old fields)are ubiquitous in temperate regions of the U.S.and Europe.Ecological succession in old fields involves changes in vegetation composition influenced by factors such as land-use history,soil conditions,and dispersal limitations.Species’behavioral,morphological,physiological and life-history attributes influence the outcomes of environmental and biotic filters on distribution and abundance.However,many studies have focused on aboveground attributes,while less attention has been placed on belowground species characteristics that influence community assembly and function.In this study,we used a trait-based approach to examine how aboveground plant composition and distribution vary with plant root functional traits(e.g.,mycorrhizal association)that mediate access for nutrients such as nitrogen(N)and phosphorous(P).We inventoried every tree stem(n=11,551)in a 10-ha forested area containing old-field and historical forests and matched every species with root functional traits(n=33)from established databases.We found that land-use history influences community composition and distribution in old-field forests,which also varied with belowground root functional traits.Community composition in old-field forests,which were dominated by Acer saccharum and non-native species,were largely associated with arbuscular mycorrhizae(AM)and higher root nutrient concentrations.On the other hand,community composition in historical forests–largely dominated by Tsuga canadensis–were associated with ectomycorrhiza(EcM)and more variation of root length and depth.These results suggest that changes in aboveground communities have implications for belowground ecosystem services(e.g.,nutrient cycling)which are important to forest ecosystem development.Trait-based approaches can elucidate mechanisms of community assembly,and understanding how traits influence species coexistence and interactions can inform management decisions related to biodiversity conservation and restoration efforts in disturbed or altered forests.
基金the financial support from the National Natural Science Foundation of China(Nos.32001139,32071554)。
文摘Soil organic carbon(SOC)affects the function of terrestrial ecosystem and plays a vital role in global carbon cycle.Yet,large uncertainty still existed regarding the changes in SOC stock and quality with forest succession.Here,the stock and quality of SOC at 1-m soil profile were investigated across a subalpine forest series,including shrub,deciduous broad-leaved forest,broadleaf-conifer mixed forest,middle-age coniferous forest and mature coniferous forest,which located at southeast of Tibetan Plateau.The results showed that SOC stock ranged from 9.8 to29.9 kg·m^(-2),and exhibited a hump-shaped response pattern across the forest successional series.The highest and lowest SOC stock was observed in the mixed forest and shrub forest,respectively.The SOC stock had no significant relationships with soil temperature and litter stock,but was positively correlated with wood debris stock.Meanwhile,the average percentages of polysaccharides,lignins,aromatics and aliphatics based on FTIR spectroscopy were 79.89%,0.94%,18.87%and 0.29%,respectively.Furthermore,the percentage of polysaccharides exhibited an increasing pattern across the forest successional series except for the sudden decreasing in the mixed forest,while the proportions of lignins,aromatics and aliphatics exhibited a decreasing pattern across the forest successional series except for the sudden increasing in the mixed forest.Consequently,the humification indices(HIs)were highest in the mixed forest compared to the other four successional stages,which means that the SOC quality in mixed forest was worse than other successional stages.In addition,the SOC stock,recalcitrant fractions and HIs decreased with increasing soil depth,while the polysaccharides exhibited an increasing pattern.These findings demonstrate that the mixed forest had higher SOC stock and worse SOC quality than other successional stages.The high proportion of SOC stock(66%at depth of 20-100 cm)and better SOC quality(lower HIs)indicate that deep soil have tremendous potential to store SOC and needs more attention under global chan ge.
基金supported financially by the National Natural Science Foundation of China(31902392)Key-Area Research and Development Program of Guangdong Province(2021B0202040001)+2 种基金Guangxi Science and Technology Major Special Project(AA23062047)Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(SML2021SP203)Earmarked Fund for CARS-48.
文摘Given the importance of the intestinal microbiota in life-long health,increasing attention has been paid to ecological mechanisms that govern microbial succession.Both environmental dispersal and host priority effect play important roles in intestinal microbiota succession of aquatic animals,but their relative importance is unknown.Here,we explore the intestinal microbiota succession and assembly of Litopenaeus vannamei across larvae,postlarvae,juvenile,and preadult stages.We aimed to clarify the relative contributions between environmental dispersal and host priority effect on intestinal microbiota succession.We found that bothα-andβ-diversity of the intestinal microbiota changed dynamically along with host development.In particular,the intestinal microbiota assemblies were dominated by stochastic processes,except with the larvae stage.The succession of shrimp intestinal microbiota was clearly influenced by internal communities in the intestines of larvae,as well as the external communities in water and sediment.Importantly,the impact of environmental dispersal on the intestinal microbiota succession outweighed the host priority effect during the larvae and postlarvae stages.However,this situation was largely reversed during the juvenile and preadult stages.The possible reason is that,during the larvae and postlarvae stages,shrimp mainly feed on plankton from the environment,and their digestive system remains underdeveloped,the host recruits numerous microbes from the environment and selects specific microbes to aid digestion and nutrient absorption.These findings enhance our understanding of alternate effects of environmental and host factors on the intestinal microbiota succession of aquatic animals and provide a foundation for developing microecological management strategies in shrimp culture.
文摘Leadership succession in nursing academic programs poses a significant challenge, primarily due to the limited availability of professionals with the competencies required for effective leadership [1]. This study aims to address this gap by investigating the critical factors in succession planning for nursing program administrators. The research objectives include identifying the competencies necessary for academic administrators, assessing the experience of current administrators, and developing a comprehensive succession plan framework. The research uses qualitative methods, including literature review, interviews with nursing administrators, and analysis of existing succession models. Results highlight the importance of integrating strategic planning into succession processes to ensure smooth transitions and organizational stability. Conclusions suggest that a formalized succession plan, incorporating mentorship and leadership development, can mitigate leadership gaps in nursing academia [2].
文摘The structure and dynamic succession law of natural secondary forest after severe fire interference in recent 20 years were studied by adopting the method of deducing time series from the spatial sequence of vegetation in Heihe region, Heilongjiang, China. Two typical and widely distributed forest types in the study area, namely forest type A and forest type B, were selected as study subjects. Forest type A is pure broadleaf forest or broadleaf mixed forest mainly composing of superior Betula platyphylla and Populus davidiana in the area with gradient 〈25°, while forest type B is pure forest or mixed forest composing of superior Quercus mongolica and Betula davurica in the area with gradient 〉25°. Species richness, vegetation coverage, important value, and similarity index of commtmity in different layers （Herb, shrub, small tree, and arbor layers） were investigated and analyzed for the two typical forests. The results show that after fire interference, the species richness and coverage in each layer in forest type A were higher than that in forest type B. Both for forest type A and B, with elapse of post-fire years, the species richness and coverage of herbs and shrubs showed a decline tendency, while those of arbor layer present a rising tendency. Through comparison of the important values of species in each layer and analysis of community structure changes, the dynamic process of post-fire vegetation succession for forest type A and B was separately determined. Post-fire 80 years＇ succession tendency of forest type A is B. platyphylla and Larix gmelinii mixed forest. Its shrub layer is mainly composed of Corylus heterophylla and Vaccinium uliginosum, and herb layer is dominated by Carex tristachya, Athyrium multidentatum, and Pyrola incarnate; whereas, the post-fire 80 years＇ succession of forest type B is Q. mongolica and B. davurica mixed forest. Its shrub layer is mainly composed of lespedeza bicolar and corylus heterophylla and herb layer is dominated by Carex tristachya, Asparagus densiflorus, and Hemerocallis minor.
基金supported by the National Nature Science Foundation of China(32071554,31570445).
文摘Background:As a structurally and functionally important component in forest ecosystems,plant debris plays a crucial role in the global carbon cycle.Although it is well known that plant debris stocks vary greatly with tree species composition,forest type,forest origin,and stand age,simultaneous investigation on the changes in woody and non-woody debris biomass and their carbon stock with forest succession has not been reported.Therefore,woody and non-woody debris and carbon stocks were investigated across a subalpine forest successional gradient in Wanglang National Nature Reserve on the eastern Qinghai-Tibet Plateau.Results:Plant debris ranged from 25.19 to 82.89 Mg∙ha−1 and showed a global increasing tendency across the subalpine forest successional series except for decreasing at the S4 successional stage.Accordingly,the ratios of woody to non-woody debris stocks ranged from 26.58 to 208.89,and the highest and lowest ratios of woody to non-woody debris stocks were respectively observed in mid-successional coniferous forest and shrub forest,implying that woody debris dominates the plant debris.In particular,the ratios of coarse to fine woody debris stocks varied greatly with the successional stage,and the highest and lowest ratios were found in later and earlier successional subalpine forests,respectively.Furthermore,the woody debris stock varied greatly with diameter size,and larger diameter woody debris dominated the plant debris.Correspondingly,the carbon stock of plant debris ranged from 10.30 to 38.87 Mg∙ha−1 across the successional series,and the highest and lowest values were observed in the mid-coniferous stage and shrub forest stage,respectively.Most importantly,the carbon stored in coarse woody debris in later successional forests was four times higher than in earlier successional forests.Conclusions:The stock and role of woody debris,particularly coarse woody debris,varied greatly with the forest successional stage and dominated the carbon cycle in the subalpine forest ecosystem.Thus,preserving coarse woody debris is a critical strategy for sustainable forest management.
文摘Through the field investigation and laboratory analysis,this paper describes the regular pattern of community succession on the deserted land of Shizishan copper tailings in Tongling City.There are 49 species of natural colonized plants on the wasteland,which are subordinate to 15 families and 38 genera.The main families are Compositae(12 species),Gramineae(11 species),Leguminosae(8 species)and Hippochaete ramosissimum,which belong to Equisetaceae.The extreme soil infertility and excessively concentration of heavy metals(especially Cu and Cd)are the main limiting factors to plants colonization.The vegetation on the deserted land of copper tailings is distributed in spot piece and scattered mainly with fewer species of plant,with lower species diversity.Annual and biennial herbs and grasses are dominant components.Cynodon dactylon,Imperata cylindrica var.major,Lespedeza chinensis,Erigeron annuus and H.ramosissimum etc.have a higher summed dominance ratio.The natural formation of plant community on the deserted land of copper tailings usually goes through seeds spread,invasion,ecesis,aggregation and species competition.After several years of primary natural restoration,14 communities were formed.According to their community composition and structure level,the 14 communities are divided into three primary succession stages,namely monodominant,subdominant and codominant species communities.With the formation and succession of these communities,species were enriched and diversity increased,the margin of summed dominance ratio of species in each community decreased,and the composition or structure of community became complex.
文摘The microbiotic crust study is among new focuses in investigating on the desertification control. Based on determination of algal crusts with different successive ages (4-, 8-, 17-, 34-, 42-year-old) and unconsolidated sand in the desert area, species composition and clustering analyses were carried out in this study. Results on successional orientation revealed that (1) the abundance of Cyanophyta, specially of Scytonema javanicum gradually decreased; (2) the abundance of Chlorophyta, Bacillariophyta and a species of Cyanophyta, Phormidium tenue increased; (3) the biodiversity increased gradually with the community succession; and (4) biomass of microalgae increased at the early stage, but decreased at the later stage due to the abundance of lichens and mosses. But, the speed of natural succession was so slow that the community-building species was still the first dominant species after 42 years, except that its dominant degree decreased just slightly. However, successive speed and trend were affected by water, vegetation coverage, terrain, time and soil physico-chemical properties as well, especially Mn content in the soil appeared to have a threshold effect.
基金Doctor Foundation of Ministry of Education (2000002716)
文摘Investigations on charcoal in the soil, fire-scarred trees, stand composition, forest structure as well as regeneration status were carried out in the natural broad-leaved/Korean pine (Pinus koraiensis) forest after fire disturbance at Liangshui Nature Reserve on the mid-north of Xiaoxingan Mountains from 1990 to 1992, and the ecological effects of fire disturbance on the formation and succession of this kind of forest were analyzed according to the survey results. The average depth of charcoal in the soil was related to the timing of the fire. According to the characteristic of fire-scarred trees, the dynamic map of the fire behavior was drawn onto the topographic map. It showed that the dimension and extent of the fire disturbance was closely related with site conditions. Fire disturbance only led to a significant difference in stand composition and diameter class structure for the stands at different locations, rather than completely destroying the forest. After fire disturbance, the horizontal community structure was a mosaic of different patches, which were made up of different deciduous species or different sizes of Korean pines, and the succession trend of each patch was also different. In the sites with the heavy fire disturbance, the intolerant hardwood species were dominant, and there were a large number of regenerative Korean pine saplings under the canopy. In the moderate -disturbed sites, the tolerant hardwood species were dominant, and a small number of large size Korean pines still survived. In the light-disturbed sites, large size Korean pines were dominant.
文摘Species dynamics in terms of both plant biological traits, ecological strategies and species richness as well as soil chemical variables during a secondary succession in abandoned fields on the Loess Plateau along a temporal sere from 3 a to 149 a were studied. The results indicated that (I) Soil total C and N increased while soil pH, total K and Na decreased with years since abandonment. No noticeable trend was found in the case of soil P along the successional sere. On the other hand, total CaO of the surface layer (0 - 10 cm) decreased, but that of the two deeper layer, (20 - 30 cm, 40 - 50 cm) increased with years since abandonment. Soil C, N, K and P decreased, while Na, CaO and soil pH increased with increasing soil depth. (2) Species richness peaked at both mid-stage of the successional sere and the intermediate portion of soil chemical variables gradient. (3) An ideal dominant species in the early successional stage were annuals with stable seed pool, CR-life strategy, S-regeneration strategy, and strong competitive ability on relatively poor soil, while perennials capable of intensive lateral spread and colonal ability, requiring high nutrient supply, and having Clife strategy would be the dominant species in the subsequent stages. Plant traits, such as perennial-life history, C-, CR-, SC-, SR-, S- and R-life strategies, W-, S-, Bs- VBs- and V-regeneration strategies, were over- represented throughout the whole sere among the other species. (4) Some traits, such as C-, SC-life strategies, ability of clonality, perennial-life history, well-developed lateral spread ability, V- and VBs-regeneration strategies, seed animal. dispersal mode, flowering time of autumn, fruit types of legumen and nut, were more or less correlated with increased soil total C, N and K, while S-, SR-, R-, CR-life strategies, annual-, biannual-life history, non-clonal ability, S-regeneration strategy, poor lateral spread ability, and fruit types of utricle, capsule were associated with increased soil total Na, CaO and pH. The results suggested that steppes should be the dominant native vegetation coinciding with the large-scaled eco-climatic conditions on the Loess Plateau.
基金This article was supported by State Tenth Five-Year Plan Project (2001BA510B0105) and the Project for Pioneering New Knowledge from Chinese Academy of Sciences (KZCX2-SW-319).
文摘Since 1950, 700 plots were established in the alpine and canyon region of western Sichuan. The distribution charac-teristics and the relationships between forest succession and environmental gradients were studied. The results showed that the main tree species were Picea and Abies in this region, and there were more than 90 forest types. Abies forests mainly dis-tributed in the middle and upper reaches of rivers and their branches, and Picea forests mainly distributed in wide valleys and on half-shaded and half-sunny slopes. The natural regeneration was poor under primitive spruce and fir forest canopy, but was good in the spruce and fire forest gap. The relationship between forest succession and vertical gradient was closely related to the relationship between forest succession procession and plant synusia under primary forests. Human activities could promote and postpone succession process. The results of expanding regeneration were often influenced by topography, vegetation and wind direction.
文摘Net N mineralization and nitrification were determined using the closed_top PVC tube in situ incubation method in a subalpine meadow (Saussurea iodostegia Hance + Carex capillaris L.)→shagspine peashrub (Caragana jubata (Pall.) Poir) shrubland→ribbed birch (Betula costata Trautv.) successional sere. The ability of the three communities to supply available N was comparatively studied. The results showed that there were apparent seasonal changes in the inorganic N pools (including NH + 4_N and NO - 3_N) and net N mineralization and nitrification rates in the three sites. There were generally no significant differences in the inorganic N pools among sampling events. But the NH + 4_N concentration in both birch (P<0.01) and meadow (P<0.01) sites was significantly higher than that in peashrub site in June 1996, and the NO - 3_N concentration in peashrub site was significantly higher than that of meadow site (P<0.05) in August 1996. The annual net N mineralization and nitrification rates in peashrub site (16.01 kg·hm -2 ) were higher than in birch (12.05 kg·hm -2 ) and meadow sites (1.64 kg·hm -2 ). The annual net nitrification rate in peashrub site (11.37 kg·hm -2 ) was higher than in meadow site (10.90 kg·hm -2 ) and much lower than in birch site (14.36 kg·hm -2 ). We conclude that the ability of peashrub shrubland soil to supply available N for plant uptake and the ability to prevent available N from denitrification and leaching were higher than that of the other two sites. The leguminous peashrub might play a potential role in supplying more N, which in turn facilitate the invasion of birch saplings during the successional processes.
基金funded by the National Natural Science Foundation of China (Grant Nos. 41671016 and 41671262)
文摘Global climate change is having long-term impacts on the geographic distribution of forest species. However, the response of vertical belts of mountain forests to climate change is still little known. The vertical distribution of forest vegetation(vertical vegetation belt) on Gongga Mountain in Southwest China has been monitored for 30 years. The forest alternation of the vertical vegetation belt under different climate conditions was simulated by using a mathematical model GFSM(the Gongga Forest Succession Model). Three possible Intergovernmental Panel on Climate Change(IPCC) climate scenarios(increase of air temperature and precipitation by 1.8℃/5%, 2.8℃/10% and 3.4℃/15% for B_1, A_1B and A_2 scenarios, respectively) were chosen to reflect lower, medium and higher changes of global climate. The vertical belts of mountainous vegetation will shift upward by approximately 300 m, 500 m and 600 m in the B_1, A_1B and A_2 scenarios, respectively, according to the simulated results. Thus, the alpine tree-line will move to a higher altitude. The simulation also demonstrated that, in a changing climate, the shift in the vegetation community will be a slow and extended process characterized by two main phases. During the initial phase, trees of the forest community degrade or die, owing to an inability to adapt to a warmer climate. This results in modest environment for the introduction of opportunistic species, consequently, the vegetation with new dominant tree species becomes predominant in the space vacated by the dead trees at the expense of previously dominated original trees as the succession succeed and climate change advance. Hence, the global climate change would dramatically change forest communities and tree species in mountainous regions because that the new forest community can grow only through the death of the original tree. Results indicated that climate change will cause the change of distribution and composition of forest communities on Gongga Mountain, and this change may enhance as the intensity of climate change increases. As a result, the alternation of death and rebirth would finally result in intensive landscape changes, and may strongly affect the eco-environment of mountainous regions.
基金funded by the National Natural Science Foundation of China(Grant Nos.41501281 and 41272200)the Chinese Academy of Sciences(CAS "Light of West China" Program)
文摘New terrestrial habitats have emerged and a primary succession has developed in the retreat area （29°34＇N, 102°oo＇E, 2951-2886 m） after the retreat of the Hailuogou glacier. To investigate soil microbial changes along the primary successional chronosequence, mixed soil samples were collected at six sites at different ages （2 young sites, 2 mid-aged sites, and 2 old sites）. The RNA was extracted and amplified. Bacterial 16S rRNA and fungal 18S rRNA were analyzed using high-throughput 454 pyrosequencing analysis. Overall, pyrosequeneing showed that Proteobacteria, Acidobacteria, Baeteroidetes and Actinobacteria were the main bacterial phyla, and the fungal communities were strongly dominated by the phyla Ascomyeota and Basidiomyeota in the retreat area. The Shannon diversity index （Hshannon） of bacteria was 6.5 - 7.9, and that of fungi was 2.2 - 4.1 in these sites. For the bacterial communities, diversity and evenness values were highest on the mid-age sites and were relatively low on the young trend was observed for the and old sites. A similar fungal communities. In contrast, soil properties showed significant linear distributional trends （increase or decrease） with the age of the site. Combining the linear change patterns of soil properties, the highest values of bacterial and fungal evenness and diversity in the mid-aged sites indicated that there was less environmental stress and more niches for microbial communities in the middle successional stage compare with other stages. In addition, our analysis showed that microbial communities were the main drivers that build a soil organic matter pool to expedite pedogenesis for ecosystem succession. This primary succession in the Hailuogou glacier retreat area is developing rapidly compared with that in other glacier retreats.
