To ameliorate soil oxygen deficiencies around subsurface drip irrigation(SDI) drippers, aerated irrigation(AI) was introduced to supply aerated water to the soil through venturi installed in the SDI pipeline. The obje...To ameliorate soil oxygen deficiencies around subsurface drip irrigation(SDI) drippers, aerated irrigation(AI) was introduced to supply aerated water to the soil through venturi installed in the SDI pipeline. The objectives of this study were to assess the effects of AI on soil respiration(SR), air-filled porosity(AFP), soil temperature(ST), and oxygen concentrations(OCC). Total soil respiration(TSR), biological activity temperature index(BAT), and soil oxygen consumption(OCS) based on SR, ST, and OCC, respectively, were subsequently calculated to explore the relationships between TSR, BAT, OCS, OCC, and AFP. Greenhouse-based experiments included two treatments: AI and unaerated SDI(CK), during the tomato growing season in the fall of 2015. The results showed that compared with CK, AI treatment significantly increased OCC and AFP(by 16 and 7.4%, respectively), as well as TSR and OCS(by 24.21 and 22.91%, respectively)(P<0.05). Mean fruit yield with AI treatment was also 23% higher(P<0.05) than that with CK. When BAT was controlled, partial correlations between TSR, OCS, OCC, and AFP were all significant in the AI treatment but not in the CK treatment. TSR was more sensitive to the interaction effects of OCC, OCS, AFP, and BAT under the AI treatment. Thus, the significantly increased TSR with AI appeared to be due to the favorable soil aeration conditi ons(higher OCC and AFP). Furthermore, the improvements in soil aeration conditions and respiration with AI appeared to facilitate the improvement in fruit yields, which also suggests the economic benefits of AI.展开更多
In this study we investigated the rooting ability and the growth performance of juvenile single-node leafy stem cuttings of Litsea monopetala （Roxb） Pers. collected from two mature mother trees preserved in the hill...In this study we investigated the rooting ability and the growth performance of juvenile single-node leafy stem cuttings of Litsea monopetala （Roxb） Pers. collected from two mature mother trees preserved in the hill forest of Chittagong district, Bangladesh. The rooting ability of cuttings was studied under 0%, 0.1%, 0.2% and 0.4% indole-3-butyric acid （IBA） treatments. Significantly better rooting response （p ≤ 0.05） was observed with 0.1% IBA compared to control （0% IBA）. The mean number of roots and the length of the longest root of cuttings in different treatments showed no significant difference （p≤0.05）. After transfer into polythene bags from non-mist propagator, rooted cuttings treated with 0%, 0.1% and 0.2% IBA demonstrated the highest （100 ± 0.00%） survival capacity. The mean number of shoots developed in cuttings in the polythene bags in first three weeks varied significantly （p≤0.05） among the treatments. Effects of three fertilizer treatments, viz. T0 （no fertilizer）, T1 （10g Urea, 20g TSP, 10g MOP dissolved in 1 L water） and T2 （10g Urea, 20g TSP, 10g MOP dissolved in 2 L water） on initial growth ofstecklings were also measured over a 90-days period. The increment of leaf area of stecklings was significantly higher （p≤0.05） under T0 compared with that under T1 and T2 while the increment of stem length, collar diameter and root biomass varied insignificantly among different fertilizer treatments. The results suggest that rooting juvenile single-node leafy stem cuttings could be an effective mean of regenerating L. monopetala. The application of 0.1% IBA concentration is recommended for rooting of juvenile leafy stem cuttings and application of fertilizer appeared unnecessary for the subsequent growth of stecklings in polythene bags.展开更多
Excessive use of nitrogen (N) fertilizers in agricultural systems increases the cost of production and risk of environmental pollution. Therefore, determination of optimum N requirements for plant growth is necessary....Excessive use of nitrogen (N) fertilizers in agricultural systems increases the cost of production and risk of environmental pollution. Therefore, determination of optimum N requirements for plant growth is necessary. Previous studies mostly established critical N dilution curves based on aboveground dry matter (DM) or leaf dry matter (LDM) and stem dry matter (SDM), to diagnose the N nutrition status of the whole plant. As these methods are time consuming, we investigated the more rapidly determined leaf area index (LAI) method to establish the critical nitrogen (Nc) dilution curve, and the curve was used to diagnose plant N status for winter wheat in Guanzhong Plain in Northwest China. Field experiments were conducted using four N fertilization levels (0, 105, 210 and 315 kg ha?1) applied to six wheat cultivars in the 2013–2014 and 2014–2015 growing seasons. LAI, DM, plant N concentration (PNC) and grain yield were determined. Data points from four cultivars were used for establishing the Nc curve and data points from the remaining two cultivars were used for validating the curve. The Nc dilution curve was validated for N-limiting and non-N-limiting growth conditions and there was good agreement between estimated and observed values. The N nutrition index (NNI) ranged from 0.41 to 1.25 and the accumulated plant N deficit (Nand) ranged from 60.38 to –17.92 kg ha?1 during the growing season. The relative grain yield was significantly affected by NNI and was adequately described with a parabolic function. The Nc curve based on LAI can be adopted as an alternative and more rapid approach to diagnose plant N status to support N fertilization decisions during the vegetative growth of winter wheat in Guanzhong Plain in Northwest China.展开更多
Electrical conductivity(EC)of soil-water extracts is commonly used to assess soil salinity.However,its conversion to the EC of saturated soil paste extracts(ECe),the standard measure of soil salinity,is currently requ...Electrical conductivity(EC)of soil-water extracts is commonly used to assess soil salinity.However,its conversion to the EC of saturated soil paste extracts(ECe),the standard measure of soil salinity,is currently required for practical applications.Although many regression models can be used to obtain ECe from the EC of soil-water extracts,the application of a site-specific model to different sites is not straightforward due to confounding soil factors such as soil texture.This study was conducted to develop a universal regression model to estimate a conversion factor(CF)for predicting EC_(e) from EC of soil-water extracts at a 1:5 ratio(EC_(1:5)),by employing a site-specific soil texture(i.e.,sand content).A regression model,CF=8.9105e^(0.0106sand)/1.2984(r^(2)=0.97,P<0.001),was developed based on the results of coastal saline soil surveys(n=173)and laboratory experiments using artificial saline soils with different textures(n=6,sand content=10%-65%)and salinity levels(n=7,salinity=1-24 dS m^(-1)).Model performance was validated using an independent dataset and demonstrated that EC_(e) prediction using the developed model is more suitable for highly saline soils than for low saline soils.The feasibility of the regression model should be tested at other sites.Other soil factors affecting EC conversion factor also need to be explored to revise and improve the model through further studies.展开更多
Forest fire risk estimation constitutes an essential process to prevent high-intensity fires which are associated with severe implications to the natural and cultural environment. The primary aim of this research was ...Forest fire risk estimation constitutes an essential process to prevent high-intensity fires which are associated with severe implications to the natural and cultural environment. The primary aim of this research was to determine fire risk levels based on the local features of an island,namely, the impact of fuel structures, slope, aspects, as well as the impact of the road network and inhabited regions. The contribution of all the involved factors to forest fires ignition and behavior highlight certain regions which are highly vulnerable. In addition, the influence of both natural and anthropogenic factors to forest fire phenomena is explored. In this study, natural factors play a dominant role compared to anthropogenic factors. Hence essential preventative measures must focus on specific areas and established immediately. Indicative measures may include: the optimal allocation of watchtowers as well as the spatial optimization of mobile firefighting vehicles;and, forest fuel treatments in areas characterized by extremely high fire risk. The added value of this fire prediction tool is that it is highly flexible and could be adopted elsewhere with the necessary adjustments to local characteristics.展开更多
Six criteria were used to evaluate 12 metrics for their sensitivity to effluent flowing from the Ferris-Haggarty copper mine into Haggarty Creek and then into Battle Creek West Fork.Through the evaluation process,we f...Six criteria were used to evaluate 12 metrics for their sensitivity to effluent flowing from the Ferris-Haggarty copper mine into Haggarty Creek and then into Battle Creek West Fork.Through the evaluation process,we found that the Shannon-Wiener index,the random runs value,and Ephemeroptera taxa richness appeared to best reflect the impacts that have occurred in both Haggarty Creek and Battle Creek West Fork.In addition,Ephemeroptera/Plecoptera/Trichoptera taxa richness,total taxa richness,and Plecoptera taxa richness,were useful in reflecting those impacts.In contrast,we found that the abundance ratios,the Hilsenhoff Biotic Index,as well as Trichoptera taxa richness,did not reflect the impacts that occurred in Haggarty Creek and Battle Creek West Fork.Finally,this study provided information about the benthic insect communities that are present in the impacted reaches of Haggarty Creek.Such information is needed to assess the potential of those reaches as habitat for the Colorado River cutthroat trout,Oncorhynchus clarki pleuriticus,which is a species of special concern to the Wyoming Department of Game and Fish.展开更多
Nutrient-poor, sandy soils form the prevailing substrate at post-mining sites of the Lusatian region(Brandenburg, Germany) and present a challenge for vegetation development. We studied the organic acid quantity and c...Nutrient-poor, sandy soils form the prevailing substrate at post-mining sites of the Lusatian region(Brandenburg, Germany) and present a challenge for vegetation development. We studied the organic acid quantity and composition of three commonly occurring pioneer plant species, the legumes Lotus corniculatus L. and Trifolium arvense L. and the grass Calamagrostis epigeios(L.) Roth, to determine if plant growth and exudation differed with(non-sterilized soil) and without(sterilized soil) an indigenous soil microbial community. We investigated whether organic acids were found in the rhizosphere and surrounding soil and whether this influenced nutrient mobilization. This study consists of linked field investigations and a greenhouse experiment. Plants were grown in the greenhouse in either sterilized or non-sterilized sandy soil from a reclamation site in the Lusatian mining landscape(Welzow Su¨d, East Germany). After seven months, the plant biomass, root morphology, organic acids, and water-soluble nutrients and root colonization with arbuscular mycorrhizal fungi(AMF) and dark septate endophytes(DSE) were analyzed. Roots of all three plants in the field and greenhouse experiments were highly colonized with AMF. Calamagrostis epigeios and T. arvense had a significantly higher colonization frequency with DSE than L. corniculatus. The quantity and composition of organic acids strongly differed among plant species, with the highest number of organic acids found for L. corniculatus and lowest for C. epigeios. The quantity of organic acids was greatly reduced in all plants under sterilized soil conditions. However, the composition of organic acids and plant growth in sterilized soil were reduced for both legumes, but not for C. epigeios, which had a higher biomass under sterilized conditions. Changes in nutrient concentrations in the field rhizosphere soil relative to those in the control were measurable after seven months. While the spectrum of organic acids and the growth of legumes seemed to be dependent on a highly diverse soil microbial community and a symbiotic partner, the grass C. epigeios appeared capable of mobilizing enough nutrients without an indigenous microbial community, and might be more competitive on sites where soil microbial diversity and activity are low.展开更多
Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal ...Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal diversity gradient.However,few studies have tested which of the two climate variables is the primary determinant.In this study,we assess whether winter coldness or temperature seasonality is more strongly associated with the northern latitudinal limits of tree species and with tree species richness in North America.Tree species were recorded in each of 1198 quadrats of 110 km×110 km in North America.We used correlation and regression analyses to assess the relationship of the latitude of the northern boundary of each species,and of species richness per quadrat,with winter coldness and temperature seasonality.Species richness was analyzed within 38 longitudinal,i.e.,north-south,bands(each being>1100 km long and 110 km wide).The latitudes of the northern range limits of tree species were three times better correlated with minimum temperatures at those latitudes than with temperature seasonality.On average,minimum temperature and temperature seasonality together explained 81.5%of the variation in the northern range limits of the tree species examined,and minimum temperature uniquely explained six-fold(33.7%versus 5.8%)more of this variation than did temperature seasonality.Correlations of tree species richness with minimum temperatures were stronger than correlations with temperature seasonality for most of the longitudinal bands analyzed.Compared to temperature seasonality,winter coldness is more strongly associated with species distributions at high latitudes,and is likely a more important driver of the latitudinal diversity gradient.展开更多
Input of large amounts of N and S compounds into forest ecosystems through atmospheric deposition is a significant risk for soil acidification in the oil sands region of Alberta.We evaluated the sensitivity of forest ...Input of large amounts of N and S compounds into forest ecosystems through atmospheric deposition is a significant risk for soil acidification in the oil sands region of Alberta.We evaluated the sensitivity of forest soils to acidification in two watersheds(Lake 287 and Lake 185)with contrasting hydrological regimes as a part of a larger project assessing the role of N and S cycling in soil acidification in forest ecosystems.Fifty six forest soil samples were collected from the two watersheds by horizon from 10 monitoring plots dominated by either jack pine(Pinus banksiana)or aspen(Populus tremuloides).Soils in the two watersheds were extremely to moderately acidic with pH(CaCl_2)ranging from 2.83 to 4.91.Soil acid-base chemistry variables such as pH,base saturation,Al saturation,and acid-buffering capacity measured using the acetic acid equilibrium procedure indicated that soils in Lake 287 were more acidified than those in Lake 185. Acid-buffering capacity decreased in the order of forest floor>subsurface mineral soil>surface mineral soil.The most dramatic differences in percent Ca and Al saturations between the two watersheds were found in the surface mineral soil horizon.Percent Ca and Al saturation in the surface mineral soil in Lake 287 were 15% and 70%,respectively;the percent Ca saturation value fell within a critical range proposed in the literature that indicates soil acidification.Our results suggest that the soils in the two watersheds have low acid buffering capacity and would be sensitive to increased acidic deposition in the region.展开更多
In an attempt to reconcile wood extraction and forest biodiversity in managed boreal forests,ecosystem-based forest management(EBM)has become the de facto management approach.Retention forestry represents one prominen...In an attempt to reconcile wood extraction and forest biodiversity in managed boreal forests,ecosystem-based forest management(EBM)has become the de facto management approach.Retention forestry represents one prominent way that EBM is implemented in many parts of the world.Retention patches commonly left after harvesting serve as analogues of fire island remnants,which are patches of unburned forests in the burned forest matrix.Although the persistence of retention patches has been questioned,few studies have attempted to quantitatively compare forest attributes in both burned and harvested forests.As part of a larger program examining multiple aspects of ecosystem function in fire and harvest island remnants,we investigated the impact of disturbance type(fire/harvest)and forest edges on C stock in snags and coarse woody debris(CWD)found in island remnants in mixedwood boreal forests of Alberta,Canada.Total C stock(in snags and CWD)was similar between the two disturbance types and edge plots had similar total deadwood C stocks to interiors.The edges of island remnants had about two-fold more snag C stock than their interiors in both disturbance types,but C stock in CWD was unaffected by edge effects and disturbance type.Our results suggest that deadwood C dynamics in island remnants in fire and harvest disturbed boreal forests were similar,thus lending support for the continued implementation of retention forestry in Alberta.展开更多
Deforestation occurs at an alarming rate in upland watersheds of Bangladesh and has many detrimental effects on the environment. This study reports the effects of deforestation on soil biological proper- ties along wi...Deforestation occurs at an alarming rate in upland watersheds of Bangladesh and has many detrimental effects on the environment. This study reports the effects of deforestation on soil biological proper- ties along with some important physicochemical parameters of a southern upland watershed in.Bangladesh. Soils were sampled at 4 paired sites, each pair representing a deforested site and a forested site, and having similar topographical characteristics. Significantly fewer （p〈0.001） fungi and bacteria, and lower microbial respiration, active microbial biomass, metabolic and microbial quotients were found in soils of the deforested sites. Soil physical properties such as moisture content, water holding capacity, and chemical properties such as organic matter, total N, avail- able P and EC were also lower in deforested soils. Bulk density and pH were significantly higher in deforested soils. Available Ca and Mg were inconsistent between the two land uses at all the paired sites. Re- duced abundance and＇biomass of soil mesofauna were recorded in defor- ested soils. However, soil anecic species were more abundant in defor- ested soils than epigeic and endogeic species, which were more abundant in forested soils than on deforested sites.展开更多
A field experiment with 24 treatments consisting of three perennial forage crops [alfalfa (<em>Medicago sativa</em> L. cv. AC Longview), hybrid bromegrass (<em>Bromus riparius</em> Rehm & &...A field experiment with 24 treatments consisting of three perennial forage crops [alfalfa (<em>Medicago sativa</em> L. cv. AC Longview), hybrid bromegrass (<em>Bromus riparius</em> Rehm & <em>Bromus inermis</em> Leyss. cv. AC Success) and their mixture], four Cut 1 dates (approximately June 20, July 10, July 30 or August 20), and two fertilizer levels (unfertilized and fertilized) was established in late May 2014, on a Black Chernozem [Udic Boroll] silty clay soil. Forage dry matter yield [DMY], and concentration (g<span style="white-space:nowrap;">·</span>kg<sup><span style="white-space:nowrap;">−</span>1</sup> DM) of crude protein [CP], total digestible nutrients [TDN] and acid detergent fiber [ADF] data were collected over 3 years from 2015 to 2017. The fertilizer treatments were imposed in 2016 and 2017. Forage crops were initially cut at four Cut 1 dates, and again cut [Cut 2] in autumn (September 2 in 2015, November 7 in 2016 and October 5 in 2017). For all three forage crops, forage DMY usually increased when Cut 1 was delayed. Delaying Cut 1 reduced forage DMY for Cut 2. Total DMY (Cut 1 + Cut 2) for all three forage crops was highest from the combination of July 10 and late Autumn cuts. Alfalfa-bromegrass mixture produced higher DMY than bromegrass or alfalfa alone. Fertilizer application resulted in a significant increase in Cut 1 and total DMY for bromegrass. The CP concentration in Cut 1 forage usually declined as the forage crops matured. The CP concentration was highest for alfalfa, followed by alfalfa-bromegrass mixture, and much lower for bromegrass. There was little or no effect of forage crop maturity on the TDN and ADF concentrations in forage. The TDN concentration was higher and ADF concentration was lower in forage from alfalfa or alfalfa-bromegrass mixture than bromegrass. Fertilizer application significantly increased CP concentration for alfalfa-bromegrass mixture. Delaying harvesting for Cut 1 increased ADF yield and TDN yield until Late July, but CP yield generally decreased with crop maturity. The ADF yield and TDN yield were higher for alfalfa-bromegrass mixture than bromegrass or alfalfa alone, and CP yield was similar for alfalfa and alfalfa-bromegrass mixture but considerably higher than bromegrass. Fertilizer application increased CP yield and ADF yield for bromegrass and alfalfa-bromegrass mixture, and TDN yield only for bromegrass. In conclusion, total DMY (Cut 1 + Cut 2) was highest for a combination of Early July and Autumn cuts. Forage yield was highest for alfalfa-bromegrass mixture, followed by alfalfa and lowest for bromegrass. The CP and TDN concentrations were higher, and ADF concentrations were lower in forage from alfalfa or alfalfa-bromegrass mixture than bromegrass.展开更多
The present study investigated the rooting ability and growth performance of juvenile single-node leafy stem cuttings of Holarrhena pubescens, collected from two mature mother trees preserved in the hill forests of Ch...The present study investigated the rooting ability and growth performance of juvenile single-node leafy stem cuttings of Holarrhena pubescens, collected from two mature mother trees preserved in the hill forests of Chittagong District, Bangladesh. The rooting ability of cuttings was studied with 0, 0.1%, 0.2% and 0.4% indole-3-butyric acid （IBA） treatments. The better rooting response was observed with 0.1% IBA, but was insignificant compared to other treatments. The mean number of roots and length of the longest root of cuttings in different treatments showed no significant difference. After transfer to the polythene bags from a nonmist propagator, rooted cuttings treated with 0.4% IBA demonstrated the highest （50.00± 0.78%） survival capacity. Regarding initial growth of established rooted cuttings （stecklings） over a 90 d period, the increment of stem length of stecklings under T2 （10 g Urea, 20 g TSP, 10 g MOP dissolved in 2 L water） and leaf area expansion of stecklings under T1 （10 g Urea, 20 g TSP, 10 g MOP dissolved in 1 L water） was significantly higher （p 〈 0.05） compared with that under TO （no fertilizer）. The increment of collar diameter and root biomass production varied insignificantly among different fertilizer concentrations, although stecklings under T2 showed the better performance. The results suggest that rooting juvenile single-node leafy stem cuttings can be an effective mean of regenerating H. pubescens. The application of 0.1% IBA or without IBA is recommended for rooting juvenile leafy stem cuttings. Application of fertilizer appears necessary for subsequent growth of stecklings in polythene bags.展开更多
A forest carbon （C） sequestration project was conducted to evaluate the economic incentives that would be required by landowners to engage in C trading under different management regimes. Costs associated with joint...A forest carbon （C） sequestration project was conducted to evaluate the economic incentives that would be required by landowners to engage in C trading under different management regimes. Costs associated with joint management for C sequestration and timber would be valuable for establishing sound forest C trading systems. In this study, we calculated the C yield and amortized value of three Wyoming, ponderosa pine stands. The management practices examined were, unmanaged, even-aged （regeneration after clear-cut） and uneven-aged （selectively harvested）. Costs and revenues associated with three stands were converted into 2006 real dollars using the all commodity producer price index to facilitate a comparison among the net revenues of three stands. Net revenues were annualized using a conservative annual interest rate of 4.5%. Our even-aged stand bad the highest annual average C yield of 2.48 Mg·ha^-1·a^-1, whereas, the uneven-aged stand had the lowest C accumulation （1.98Mg·ha^-1·a^-1）. Alternatively, the even-aged stand had the highest amortized net return of S276·ha^-1·a^-1 and the unmanaged stand had the lowest net return of S64·ha^-1·a^-1. On the plots examined, an annual payment of S22 for each additional Mg of C sequestered would encourage a change from uneven aged management to an unmanaged stand that sequesters additional C, in the absence of transactions costs.展开更多
The increasingly serious problem of acid rain is leading to increased potassium （K） loss from soils, and in our field investigation, we found that even congenerically relative Mosla species show different tolerance ...The increasingly serious problem of acid rain is leading to increased potassium （K） loss from soils, and in our field investigation, we found that even congenerically relative Mosla species show different tolerance to K-deficiency. A hydroponic study was conducted on the growth of two Mosla species and their morphological, physiological and stoichiometric traits in response to limited （0.35 mmol K/L）, normal （3.25 mmol K/L） and excessive （6.50 mmol K/L） K concentrations. Mosla hangchowensis is an endangered plant, whereas Mosla dianthera a widespread weed. In the case of M. hangchowensis, in comparison with normal K concentration, K-limitation induced a significant reduction in net photosynthetic rate （Pn）, soluble protein content, and superoxide dismutase （SOD） actix, ity, but an increase in malondialdehyde （MDA） concentration. However, leaf mass ratio （LMR） and root mass ratio （RMR） were changed little by K-limitation. In contrast, for M. dianthera, K-limitation had little effect on Pn, soluble protein content, SOD activity, and MDA concentration, but increased LMR and RMR. Critical values of N （nitrogen）：K and K：P （phosphorus） ratios in the shoots indicated that limitation in acquiring K occurred under K-limited conditions for M. hangchowensis but not for M. dianthera. We found that low K content in natural habitats was a restrictive factor in the growth and distribution of M.. hangchowensis, and soil K-deficiency caused by acid rain worsened the situation of M. hangchowensis, while M. dianthera could well acclimate to the increasing K-deficiency. We suggest that controlling the acid rain and applying K fertilizers may be an effective way to rescue the endangered M. hangchowensis.展开更多
In this brief report, we analyzed ecological correlates of risk of extinction for mammals endemic to China using phylogenetic eigenvector methods to control for the effect of phylogenetic inertia. Extinction risks wer...In this brief report, we analyzed ecological correlates of risk of extinction for mammals endemic to China using phylogenetic eigenvector methods to control for the effect of phylogenetic inertia. Extinction risks were based on the International Union for Conservation of Nature （IUCN） Red List and ecological explanatory attributes that include range size and climatic variables. When the effect of phylogenetic inertia were controlled, climate became the best predictor for quantifying and evaluating extinction risks of endemic mammals in China, accounting for 13% of the total variation. Range size seems to play a trivial role, explaining -1% of total variation; however, when non-phylogenetic variation partitioning analysis was done, the role of range size then explained 7.4% of total variation. Consequently, phylogenetic inertia plays a substantial role in increasing the explanatory power of range size on the extinction risks of mammals endemic to China. Limitations of the present study are discussed, with a focus on under-represented sampling of endemic mammalian species.展开更多
In the present study, the interplay and higher-order terms of environmental and spatial variables are considered to evaluate the relations of environment and space-species richness rankings at global scale. Three taxo...In the present study, the interplay and higher-order terms of environmental and spatial variables are considered to evaluate the relations of environment and space-species richness rankings at global scale. Three taxonomic groups composed of mammals, birds and amphibians were analyzed for the study. Thek-means clustering method was introduced for richness rankings detection and analysis from published digital maps;and simple regression analysis and AIC criteria were used for identifying mostimportant correlated explanatory variables.When comparing each single variable, I found that latitude was the most important one influencing global vertebrate richness rankings. When onlyconsidering environmental variables, I foundthat precipitation was the only predictor of vertebrate richness rankings. However, when the interaction and high-order terms of different independent variables were considered, it was found that the interaction between latitude and temperature could better explain the global bird richness ranking, while the second-power effectof latitude was the best predictor for amphibianand mammalian richness rankings, as evidenced by the AIC model selection and comparison among the regression models. In conclusion, the inclusion of high-order and interaction terms of environmental and spatial variables could offer more insights into the understanding of global species diversity patterns.展开更多
Background: In this study, the ancestral distributional ranges and the tempo of diversification patterns of global Galliformes were investigated.Methods: Different diversification models characterizing possible tempo ...Background: In this study, the ancestral distributional ranges and the tempo of diversification patterns of global Galliformes were investigated.Methods: Different diversification models characterizing possible tempo patterns were fitted and compared onto the phylogenetic tree for the 197 Galliforme species, consisting of a constant-speciation and constant-extinction model(CONSTANT), a decreasing-speciation and constant-extinction model(SPVAR), a constant-speciation and increasing-extinction model(EXVAR) and a decreasing-speciation and increasing-extinction model(BOTHVAR).Ancestral range reconstruction was conducted using the dispersal-extinction-cladogenesis model.Results: A constant-diversification-rate(CONSTANT) model best quantified the historical speciation patterns of this avian assemblage through model selection. Clade age and species richness are significantly and positively correlated. The most recent common ancestor for Galliformes species was originally found in the disjunctive regions between Southeast Asia and North America. High-frequency dispersal events were identified across the whole evolutionary time.Conclusions: The constant diversification rate for global Galliforme species implied that there were no diversification rate-shifting trends for Galliformes species. The present study may contribute to the understanding of the ecology and diversity patterns of Galliformes from the perspective of historical biogeography, although some limitations existed.展开更多
Cape Dyer (DYE-M), located on the easternmost point of Baffin Island, is a former DEW line radar station built in 1956-57 which was upgraded in 1993 as part of the current North Warning System. Environmental studies i...Cape Dyer (DYE-M), located on the easternmost point of Baffin Island, is a former DEW line radar station built in 1956-57 which was upgraded in 1993 as part of the current North Warning System. Environmental studies in the late 1990s and early 2000s determined that extensive soil contamination existed across the site, and excavation of six landfills and subsequent reshaping of the area in 2008 disturbed approximately 19,700 m2. A four-year pilot project was conducted between 2009 and 2012 to investigate feasibility of, and determine methods to, accelerate revegetation of the disturbed area through assisted seed dispersal of native and non native species and selective transplantation of slow-growing shrub species. Prior to revegetation efforts, plant surveys conducted in July 2009 determined that 15 species were present in the undisturbed areas, of which Salix arctica (~11%), Vaccinium uliginosum L. (~8%), and Empetrum nigrum L. (~5%) were the predominant species. A total of 14 species (three new) were observed growing on the disturbed areas between 2010 and 2012. The majority of Lolium multiflorum (annual ryegrass) seeds planted as a nurse species in 2009 grew in 2010, but most were stunted and only observed in furrows or sheltered areas at a low density. Salix arctica Pall. (willow) cuttings planted in “islands” of 20-30 cuttings in fall 2009 had a three-year survival rate of 82%, while a second set of cuttings planted in fall 2011 had a one-year survival rate of 93%. Visual observations indicate that patches of new vegetation are becoming more predominant on the disturbed area, especially around the willow islands, indicating the importance of microtopography for successful reclamation in arctic environments. Monitoring over ten or more years will be required to determine the long term success of this project.展开更多
基金funded by the National Key Research and Development Program of China (2016YFC0400200 and 2016YFC0400201)the Program of Introducing Talents of Discipline to Universities “111 Project”, China (B12007)
文摘To ameliorate soil oxygen deficiencies around subsurface drip irrigation(SDI) drippers, aerated irrigation(AI) was introduced to supply aerated water to the soil through venturi installed in the SDI pipeline. The objectives of this study were to assess the effects of AI on soil respiration(SR), air-filled porosity(AFP), soil temperature(ST), and oxygen concentrations(OCC). Total soil respiration(TSR), biological activity temperature index(BAT), and soil oxygen consumption(OCS) based on SR, ST, and OCC, respectively, were subsequently calculated to explore the relationships between TSR, BAT, OCS, OCC, and AFP. Greenhouse-based experiments included two treatments: AI and unaerated SDI(CK), during the tomato growing season in the fall of 2015. The results showed that compared with CK, AI treatment significantly increased OCC and AFP(by 16 and 7.4%, respectively), as well as TSR and OCS(by 24.21 and 22.91%, respectively)(P<0.05). Mean fruit yield with AI treatment was also 23% higher(P<0.05) than that with CK. When BAT was controlled, partial correlations between TSR, OCS, OCC, and AFP were all significant in the AI treatment but not in the CK treatment. TSR was more sensitive to the interaction effects of OCC, OCS, AFP, and BAT under the AI treatment. Thus, the significantly increased TSR with AI appeared to be due to the favorable soil aeration conditi ons(higher OCC and AFP). Furthermore, the improvements in soil aeration conditions and respiration with AI appeared to facilitate the improvement in fruit yields, which also suggests the economic benefits of AI.
文摘In this study we investigated the rooting ability and the growth performance of juvenile single-node leafy stem cuttings of Litsea monopetala （Roxb） Pers. collected from two mature mother trees preserved in the hill forest of Chittagong district, Bangladesh. The rooting ability of cuttings was studied under 0%, 0.1%, 0.2% and 0.4% indole-3-butyric acid （IBA） treatments. Significantly better rooting response （p ≤ 0.05） was observed with 0.1% IBA compared to control （0% IBA）. The mean number of roots and the length of the longest root of cuttings in different treatments showed no significant difference （p≤0.05）. After transfer into polythene bags from non-mist propagator, rooted cuttings treated with 0%, 0.1% and 0.2% IBA demonstrated the highest （100 ± 0.00%） survival capacity. The mean number of shoots developed in cuttings in the polythene bags in first three weeks varied significantly （p≤0.05） among the treatments. Effects of three fertilizer treatments, viz. T0 （no fertilizer）, T1 （10g Urea, 20g TSP, 10g MOP dissolved in 1 L water） and T2 （10g Urea, 20g TSP, 10g MOP dissolved in 2 L water） on initial growth ofstecklings were also measured over a 90-days period. The increment of leaf area of stecklings was significantly higher （p≤0.05） under T0 compared with that under T1 and T2 while the increment of stem length, collar diameter and root biomass varied insignificantly among different fertilizer treatments. The results suggest that rooting juvenile single-node leafy stem cuttings could be an effective mean of regenerating L. monopetala. The application of 0.1% IBA concentration is recommended for rooting of juvenile leafy stem cuttings and application of fertilizer appeared unnecessary for the subsequent growth of stecklings in polythene bags.
基金financial support from the National Key Research and Development Program of China (2017YFC0403303)the Shanxi Agricultural University of Science and Technology Innovation Fund, China (2016YJ07 and 2016007)
文摘Excessive use of nitrogen (N) fertilizers in agricultural systems increases the cost of production and risk of environmental pollution. Therefore, determination of optimum N requirements for plant growth is necessary. Previous studies mostly established critical N dilution curves based on aboveground dry matter (DM) or leaf dry matter (LDM) and stem dry matter (SDM), to diagnose the N nutrition status of the whole plant. As these methods are time consuming, we investigated the more rapidly determined leaf area index (LAI) method to establish the critical nitrogen (Nc) dilution curve, and the curve was used to diagnose plant N status for winter wheat in Guanzhong Plain in Northwest China. Field experiments were conducted using four N fertilization levels (0, 105, 210 and 315 kg ha?1) applied to six wheat cultivars in the 2013–2014 and 2014–2015 growing seasons. LAI, DM, plant N concentration (PNC) and grain yield were determined. Data points from four cultivars were used for establishing the Nc curve and data points from the remaining two cultivars were used for validating the curve. The Nc dilution curve was validated for N-limiting and non-N-limiting growth conditions and there was good agreement between estimated and observed values. The N nutrition index (NNI) ranged from 0.41 to 1.25 and the accumulated plant N deficit (Nand) ranged from 60.38 to –17.92 kg ha?1 during the growing season. The relative grain yield was significantly affected by NNI and was adequately described with a parabolic function. The Nc curve based on LAI can be adopted as an alternative and more rapid approach to diagnose plant N status to support N fertilization decisions during the vegetative growth of winter wheat in Guanzhong Plain in Northwest China.
基金support of the Cooperative Research Program of Agriculture Science and Technology Development,Rural Development Administration,Republic of Korea(No.PJ0138732021)。
文摘Electrical conductivity(EC)of soil-water extracts is commonly used to assess soil salinity.However,its conversion to the EC of saturated soil paste extracts(ECe),the standard measure of soil salinity,is currently required for practical applications.Although many regression models can be used to obtain ECe from the EC of soil-water extracts,the application of a site-specific model to different sites is not straightforward due to confounding soil factors such as soil texture.This study was conducted to develop a universal regression model to estimate a conversion factor(CF)for predicting EC_(e) from EC of soil-water extracts at a 1:5 ratio(EC_(1:5)),by employing a site-specific soil texture(i.e.,sand content).A regression model,CF=8.9105e^(0.0106sand)/1.2984(r^(2)=0.97,P<0.001),was developed based on the results of coastal saline soil surveys(n=173)and laboratory experiments using artificial saline soils with different textures(n=6,sand content=10%-65%)and salinity levels(n=7,salinity=1-24 dS m^(-1)).Model performance was validated using an independent dataset and demonstrated that EC_(e) prediction using the developed model is more suitable for highly saline soils than for low saline soils.The feasibility of the regression model should be tested at other sites.Other soil factors affecting EC conversion factor also need to be explored to revise and improve the model through further studies.
基金Significant part of this research was co-financed by the European Union(European Social Fund-ESF)Greek national funds through the Operational Program ‘‘Education and Lifelong Learning’’ of the National Strategic Reference Framework(NSRF)--Research Funding Program:Thales.Investing in knowledge society through the European Social Fund
文摘Forest fire risk estimation constitutes an essential process to prevent high-intensity fires which are associated with severe implications to the natural and cultural environment. The primary aim of this research was to determine fire risk levels based on the local features of an island,namely, the impact of fuel structures, slope, aspects, as well as the impact of the road network and inhabited regions. The contribution of all the involved factors to forest fires ignition and behavior highlight certain regions which are highly vulnerable. In addition, the influence of both natural and anthropogenic factors to forest fire phenomena is explored. In this study, natural factors play a dominant role compared to anthropogenic factors. Hence essential preventative measures must focus on specific areas and established immediately. Indicative measures may include: the optimal allocation of watchtowers as well as the spatial optimization of mobile firefighting vehicles;and, forest fuel treatments in areas characterized by extremely high fire risk. The added value of this fire prediction tool is that it is highly flexible and could be adopted elsewhere with the necessary adjustments to local characteristics.
文摘Six criteria were used to evaluate 12 metrics for their sensitivity to effluent flowing from the Ferris-Haggarty copper mine into Haggarty Creek and then into Battle Creek West Fork.Through the evaluation process,we found that the Shannon-Wiener index,the random runs value,and Ephemeroptera taxa richness appeared to best reflect the impacts that have occurred in both Haggarty Creek and Battle Creek West Fork.In addition,Ephemeroptera/Plecoptera/Trichoptera taxa richness,total taxa richness,and Plecoptera taxa richness,were useful in reflecting those impacts.In contrast,we found that the abundance ratios,the Hilsenhoff Biotic Index,as well as Trichoptera taxa richness,did not reflect the impacts that occurred in Haggarty Creek and Battle Creek West Fork.Finally,this study provided information about the benthic insect communities that are present in the impacted reaches of Haggarty Creek.Such information is needed to assess the potential of those reaches as habitat for the Colorado River cutthroat trout,Oncorhynchus clarki pleuriticus,which is a species of special concern to the Wyoming Department of Game and Fish.
基金funded by the Deutsche Forschungsgemeinschaft (DFG) (No. BO 4201/2-1)
文摘Nutrient-poor, sandy soils form the prevailing substrate at post-mining sites of the Lusatian region(Brandenburg, Germany) and present a challenge for vegetation development. We studied the organic acid quantity and composition of three commonly occurring pioneer plant species, the legumes Lotus corniculatus L. and Trifolium arvense L. and the grass Calamagrostis epigeios(L.) Roth, to determine if plant growth and exudation differed with(non-sterilized soil) and without(sterilized soil) an indigenous soil microbial community. We investigated whether organic acids were found in the rhizosphere and surrounding soil and whether this influenced nutrient mobilization. This study consists of linked field investigations and a greenhouse experiment. Plants were grown in the greenhouse in either sterilized or non-sterilized sandy soil from a reclamation site in the Lusatian mining landscape(Welzow Su¨d, East Germany). After seven months, the plant biomass, root morphology, organic acids, and water-soluble nutrients and root colonization with arbuscular mycorrhizal fungi(AMF) and dark septate endophytes(DSE) were analyzed. Roots of all three plants in the field and greenhouse experiments were highly colonized with AMF. Calamagrostis epigeios and T. arvense had a significantly higher colonization frequency with DSE than L. corniculatus. The quantity and composition of organic acids strongly differed among plant species, with the highest number of organic acids found for L. corniculatus and lowest for C. epigeios. The quantity of organic acids was greatly reduced in all plants under sterilized soil conditions. However, the composition of organic acids and plant growth in sterilized soil were reduced for both legumes, but not for C. epigeios, which had a higher biomass under sterilized conditions. Changes in nutrient concentrations in the field rhizosphere soil relative to those in the control were measurable after seven months. While the spectrum of organic acids and the growth of legumes seemed to be dependent on a highly diverse soil microbial community and a symbiotic partner, the grass C. epigeios appeared capable of mobilizing enough nutrients without an indigenous microbial community, and might be more competitive on sites where soil microbial diversity and activity are low.
基金supported by a grant form the National Key Research and Development Program,No.2019YFA0607302。
文摘Biologists have considered both winter coldness and temperature seasonality as major determinants of the northern limits of plants and animals in the Northern Hemisphere,which in turn drive the well-known latitudinal diversity gradient.However,few studies have tested which of the two climate variables is the primary determinant.In this study,we assess whether winter coldness or temperature seasonality is more strongly associated with the northern latitudinal limits of tree species and with tree species richness in North America.Tree species were recorded in each of 1198 quadrats of 110 km×110 km in North America.We used correlation and regression analyses to assess the relationship of the latitude of the northern boundary of each species,and of species richness per quadrat,with winter coldness and temperature seasonality.Species richness was analyzed within 38 longitudinal,i.e.,north-south,bands(each being>1100 km long and 110 km wide).The latitudes of the northern range limits of tree species were three times better correlated with minimum temperatures at those latitudes than with temperature seasonality.On average,minimum temperature and temperature seasonality together explained 81.5%of the variation in the northern range limits of the tree species examined,and minimum temperature uniquely explained six-fold(33.7%versus 5.8%)more of this variation than did temperature seasonality.Correlations of tree species richness with minimum temperatures were stronger than correlations with temperature seasonality for most of the longitudinal bands analyzed.Compared to temperature seasonality,winter coldness is more strongly associated with species distributions at high latitudes,and is likely a more important driver of the latitudinal diversity gradient.
基金Project supported by the NO_x-SO_2 Management Working Group(NSMWG)under the Cumulative Environmental Management Association(CEMA),Canada(No.2006-0003).
文摘Input of large amounts of N and S compounds into forest ecosystems through atmospheric deposition is a significant risk for soil acidification in the oil sands region of Alberta.We evaluated the sensitivity of forest soils to acidification in two watersheds(Lake 287 and Lake 185)with contrasting hydrological regimes as a part of a larger project assessing the role of N and S cycling in soil acidification in forest ecosystems.Fifty six forest soil samples were collected from the two watersheds by horizon from 10 monitoring plots dominated by either jack pine(Pinus banksiana)or aspen(Populus tremuloides).Soils in the two watersheds were extremely to moderately acidic with pH(CaCl_2)ranging from 2.83 to 4.91.Soil acid-base chemistry variables such as pH,base saturation,Al saturation,and acid-buffering capacity measured using the acetic acid equilibrium procedure indicated that soils in Lake 287 were more acidified than those in Lake 185. Acid-buffering capacity decreased in the order of forest floor>subsurface mineral soil>surface mineral soil.The most dramatic differences in percent Ca and Al saturations between the two watersheds were found in the surface mineral soil horizon.Percent Ca and Al saturation in the surface mineral soil in Lake 287 were 15% and 70%,respectively;the percent Ca saturation value fell within a critical range proposed in the literature that indicates soil acidification.Our results suggest that the soils in the two watersheds have low acid buffering capacity and would be sensitive to increased acidic deposition in the region.
基金provided by NSERC Industrial Research Chair in Ecosystem-based Forest Management(IRCPJ 550067–19,West Fraser Mills Ltd.,Mercer Peace River Pulp Ltd.,Alberta-Pacific Forest Industries,Weyerhaeuser Company Ltd.,Canadian Forest Products Ltd.,Tolko Industries Ltd.,and the Forest Resource Improvement Association of Alberta)provided financial support to R.Odell in the framework of Grants in Biodiversity program.
文摘In an attempt to reconcile wood extraction and forest biodiversity in managed boreal forests,ecosystem-based forest management(EBM)has become the de facto management approach.Retention forestry represents one prominent way that EBM is implemented in many parts of the world.Retention patches commonly left after harvesting serve as analogues of fire island remnants,which are patches of unburned forests in the burned forest matrix.Although the persistence of retention patches has been questioned,few studies have attempted to quantitatively compare forest attributes in both burned and harvested forests.As part of a larger program examining multiple aspects of ecosystem function in fire and harvest island remnants,we investigated the impact of disturbance type(fire/harvest)and forest edges on C stock in snags and coarse woody debris(CWD)found in island remnants in mixedwood boreal forests of Alberta,Canada.Total C stock(in snags and CWD)was similar between the two disturbance types and edge plots had similar total deadwood C stocks to interiors.The edges of island remnants had about two-fold more snag C stock than their interiors in both disturbance types,but C stock in CWD was unaffected by edge effects and disturbance type.Our results suggest that deadwood C dynamics in island remnants in fire and harvest disturbed boreal forests were similar,thus lending support for the continued implementation of retention forestry in Alberta.
文摘Deforestation occurs at an alarming rate in upland watersheds of Bangladesh and has many detrimental effects on the environment. This study reports the effects of deforestation on soil biological proper- ties along with some important physicochemical parameters of a southern upland watershed in.Bangladesh. Soils were sampled at 4 paired sites, each pair representing a deforested site and a forested site, and having similar topographical characteristics. Significantly fewer （p〈0.001） fungi and bacteria, and lower microbial respiration, active microbial biomass, metabolic and microbial quotients were found in soils of the deforested sites. Soil physical properties such as moisture content, water holding capacity, and chemical properties such as organic matter, total N, avail- able P and EC were also lower in deforested soils. Bulk density and pH were significantly higher in deforested soils. Available Ca and Mg were inconsistent between the two land uses at all the paired sites. Re- duced abundance and＇biomass of soil mesofauna were recorded in defor- ested soils. However, soil anecic species were more abundant in defor- ested soils than epigeic and endogeic species, which were more abundant in forested soils than on deforested sites.
文摘A field experiment with 24 treatments consisting of three perennial forage crops [alfalfa (<em>Medicago sativa</em> L. cv. AC Longview), hybrid bromegrass (<em>Bromus riparius</em> Rehm & <em>Bromus inermis</em> Leyss. cv. AC Success) and their mixture], four Cut 1 dates (approximately June 20, July 10, July 30 or August 20), and two fertilizer levels (unfertilized and fertilized) was established in late May 2014, on a Black Chernozem [Udic Boroll] silty clay soil. Forage dry matter yield [DMY], and concentration (g<span style="white-space:nowrap;">·</span>kg<sup><span style="white-space:nowrap;">−</span>1</sup> DM) of crude protein [CP], total digestible nutrients [TDN] and acid detergent fiber [ADF] data were collected over 3 years from 2015 to 2017. The fertilizer treatments were imposed in 2016 and 2017. Forage crops were initially cut at four Cut 1 dates, and again cut [Cut 2] in autumn (September 2 in 2015, November 7 in 2016 and October 5 in 2017). For all three forage crops, forage DMY usually increased when Cut 1 was delayed. Delaying Cut 1 reduced forage DMY for Cut 2. Total DMY (Cut 1 + Cut 2) for all three forage crops was highest from the combination of July 10 and late Autumn cuts. Alfalfa-bromegrass mixture produced higher DMY than bromegrass or alfalfa alone. Fertilizer application resulted in a significant increase in Cut 1 and total DMY for bromegrass. The CP concentration in Cut 1 forage usually declined as the forage crops matured. The CP concentration was highest for alfalfa, followed by alfalfa-bromegrass mixture, and much lower for bromegrass. There was little or no effect of forage crop maturity on the TDN and ADF concentrations in forage. The TDN concentration was higher and ADF concentration was lower in forage from alfalfa or alfalfa-bromegrass mixture than bromegrass. Fertilizer application significantly increased CP concentration for alfalfa-bromegrass mixture. Delaying harvesting for Cut 1 increased ADF yield and TDN yield until Late July, but CP yield generally decreased with crop maturity. The ADF yield and TDN yield were higher for alfalfa-bromegrass mixture than bromegrass or alfalfa alone, and CP yield was similar for alfalfa and alfalfa-bromegrass mixture but considerably higher than bromegrass. Fertilizer application increased CP yield and ADF yield for bromegrass and alfalfa-bromegrass mixture, and TDN yield only for bromegrass. In conclusion, total DMY (Cut 1 + Cut 2) was highest for a combination of Early July and Autumn cuts. Forage yield was highest for alfalfa-bromegrass mixture, followed by alfalfa and lowest for bromegrass. The CP and TDN concentrations were higher, and ADF concentrations were lower in forage from alfalfa or alfalfa-bromegrass mixture than bromegrass.
文摘The present study investigated the rooting ability and growth performance of juvenile single-node leafy stem cuttings of Holarrhena pubescens, collected from two mature mother trees preserved in the hill forests of Chittagong District, Bangladesh. The rooting ability of cuttings was studied with 0, 0.1%, 0.2% and 0.4% indole-3-butyric acid （IBA） treatments. The better rooting response was observed with 0.1% IBA, but was insignificant compared to other treatments. The mean number of roots and length of the longest root of cuttings in different treatments showed no significant difference. After transfer to the polythene bags from a nonmist propagator, rooted cuttings treated with 0.4% IBA demonstrated the highest （50.00± 0.78%） survival capacity. Regarding initial growth of established rooted cuttings （stecklings） over a 90 d period, the increment of stem length of stecklings under T2 （10 g Urea, 20 g TSP, 10 g MOP dissolved in 2 L water） and leaf area expansion of stecklings under T1 （10 g Urea, 20 g TSP, 10 g MOP dissolved in 1 L water） was significantly higher （p 〈 0.05） compared with that under TO （no fertilizer）. The increment of collar diameter and root biomass production varied insignificantly among different fertilizer concentrations, although stecklings under T2 showed the better performance. The results suggest that rooting juvenile single-node leafy stem cuttings can be an effective mean of regenerating H. pubescens. The application of 0.1% IBA or without IBA is recommended for rooting juvenile leafy stem cuttings. Application of fertilizer appears necessary for subsequent growth of stecklings in polythene bags.
文摘A forest carbon （C） sequestration project was conducted to evaluate the economic incentives that would be required by landowners to engage in C trading under different management regimes. Costs associated with joint management for C sequestration and timber would be valuable for establishing sound forest C trading systems. In this study, we calculated the C yield and amortized value of three Wyoming, ponderosa pine stands. The management practices examined were, unmanaged, even-aged （regeneration after clear-cut） and uneven-aged （selectively harvested）. Costs and revenues associated with three stands were converted into 2006 real dollars using the all commodity producer price index to facilitate a comparison among the net revenues of three stands. Net revenues were annualized using a conservative annual interest rate of 4.5%. Our even-aged stand bad the highest annual average C yield of 2.48 Mg·ha^-1·a^-1, whereas, the uneven-aged stand had the lowest C accumulation （1.98Mg·ha^-1·a^-1）. Alternatively, the even-aged stand had the highest amortized net return of S276·ha^-1·a^-1 and the unmanaged stand had the lowest net return of S64·ha^-1·a^-1. On the plots examined, an annual payment of S22 for each additional Mg of C sequestered would encourage a change from uneven aged management to an unmanaged stand that sequesters additional C, in the absence of transactions costs.
基金supported by the National Natural Science Foundation of China (No.30570113)the Research Fund for the Doctoral Program of Higher Education (No.20060335008),China
文摘The increasingly serious problem of acid rain is leading to increased potassium （K） loss from soils, and in our field investigation, we found that even congenerically relative Mosla species show different tolerance to K-deficiency. A hydroponic study was conducted on the growth of two Mosla species and their morphological, physiological and stoichiometric traits in response to limited （0.35 mmol K/L）, normal （3.25 mmol K/L） and excessive （6.50 mmol K/L） K concentrations. Mosla hangchowensis is an endangered plant, whereas Mosla dianthera a widespread weed. In the case of M. hangchowensis, in comparison with normal K concentration, K-limitation induced a significant reduction in net photosynthetic rate （Pn）, soluble protein content, and superoxide dismutase （SOD） actix, ity, but an increase in malondialdehyde （MDA） concentration. However, leaf mass ratio （LMR） and root mass ratio （RMR） were changed little by K-limitation. In contrast, for M. dianthera, K-limitation had little effect on Pn, soluble protein content, SOD activity, and MDA concentration, but increased LMR and RMR. Critical values of N （nitrogen）：K and K：P （phosphorus） ratios in the shoots indicated that limitation in acquiring K occurred under K-limited conditions for M. hangchowensis but not for M. dianthera. We found that low K content in natural habitats was a restrictive factor in the growth and distribution of M.. hangchowensis, and soil K-deficiency caused by acid rain worsened the situation of M. hangchowensis, while M. dianthera could well acclimate to the increasing K-deficiency. We suggest that controlling the acid rain and applying K fertilizers may be an effective way to rescue the endangered M. hangchowensis.
基金This work was supported by the China Scholarship Council （CSC）（201308180004） Acknowledgements： I would like to thank two anonymous reviewers for constructive comments on this manuscript.
文摘In this brief report, we analyzed ecological correlates of risk of extinction for mammals endemic to China using phylogenetic eigenvector methods to control for the effect of phylogenetic inertia. Extinction risks were based on the International Union for Conservation of Nature （IUCN） Red List and ecological explanatory attributes that include range size and climatic variables. When the effect of phylogenetic inertia were controlled, climate became the best predictor for quantifying and evaluating extinction risks of endemic mammals in China, accounting for 13% of the total variation. Range size seems to play a trivial role, explaining -1% of total variation; however, when non-phylogenetic variation partitioning analysis was done, the role of range size then explained 7.4% of total variation. Consequently, phylogenetic inertia plays a substantial role in increasing the explanatory power of range size on the extinction risks of mammals endemic to China. Limitations of the present study are discussed, with a focus on under-represented sampling of endemic mammalian species.
文摘In the present study, the interplay and higher-order terms of environmental and spatial variables are considered to evaluate the relations of environment and space-species richness rankings at global scale. Three taxonomic groups composed of mammals, birds and amphibians were analyzed for the study. Thek-means clustering method was introduced for richness rankings detection and analysis from published digital maps;and simple regression analysis and AIC criteria were used for identifying mostimportant correlated explanatory variables.When comparing each single variable, I found that latitude was the most important one influencing global vertebrate richness rankings. When onlyconsidering environmental variables, I foundthat precipitation was the only predictor of vertebrate richness rankings. However, when the interaction and high-order terms of different independent variables were considered, it was found that the interaction between latitude and temperature could better explain the global bird richness ranking, while the second-power effectof latitude was the best predictor for amphibianand mammalian richness rankings, as evidenced by the AIC model selection and comparison among the regression models. In conclusion, the inclusion of high-order and interaction terms of environmental and spatial variables could offer more insights into the understanding of global species diversity patterns.
基金supported by the China Scholarship Council (CSC)
文摘Background: In this study, the ancestral distributional ranges and the tempo of diversification patterns of global Galliformes were investigated.Methods: Different diversification models characterizing possible tempo patterns were fitted and compared onto the phylogenetic tree for the 197 Galliforme species, consisting of a constant-speciation and constant-extinction model(CONSTANT), a decreasing-speciation and constant-extinction model(SPVAR), a constant-speciation and increasing-extinction model(EXVAR) and a decreasing-speciation and increasing-extinction model(BOTHVAR).Ancestral range reconstruction was conducted using the dispersal-extinction-cladogenesis model.Results: A constant-diversification-rate(CONSTANT) model best quantified the historical speciation patterns of this avian assemblage through model selection. Clade age and species richness are significantly and positively correlated. The most recent common ancestor for Galliformes species was originally found in the disjunctive regions between Southeast Asia and North America. High-frequency dispersal events were identified across the whole evolutionary time.Conclusions: The constant diversification rate for global Galliforme species implied that there were no diversification rate-shifting trends for Galliformes species. The present study may contribute to the understanding of the ecology and diversity patterns of Galliformes from the perspective of historical biogeography, although some limitations existed.
文摘Cape Dyer (DYE-M), located on the easternmost point of Baffin Island, is a former DEW line radar station built in 1956-57 which was upgraded in 1993 as part of the current North Warning System. Environmental studies in the late 1990s and early 2000s determined that extensive soil contamination existed across the site, and excavation of six landfills and subsequent reshaping of the area in 2008 disturbed approximately 19,700 m2. A four-year pilot project was conducted between 2009 and 2012 to investigate feasibility of, and determine methods to, accelerate revegetation of the disturbed area through assisted seed dispersal of native and non native species and selective transplantation of slow-growing shrub species. Prior to revegetation efforts, plant surveys conducted in July 2009 determined that 15 species were present in the undisturbed areas, of which Salix arctica (~11%), Vaccinium uliginosum L. (~8%), and Empetrum nigrum L. (~5%) were the predominant species. A total of 14 species (three new) were observed growing on the disturbed areas between 2010 and 2012. The majority of Lolium multiflorum (annual ryegrass) seeds planted as a nurse species in 2009 grew in 2010, but most were stunted and only observed in furrows or sheltered areas at a low density. Salix arctica Pall. (willow) cuttings planted in “islands” of 20-30 cuttings in fall 2009 had a three-year survival rate of 82%, while a second set of cuttings planted in fall 2011 had a one-year survival rate of 93%. Visual observations indicate that patches of new vegetation are becoming more predominant on the disturbed area, especially around the willow islands, indicating the importance of microtopography for successful reclamation in arctic environments. Monitoring over ten or more years will be required to determine the long term success of this project.
