In this study we assessed the current status of coral reefs along the Saudi Arabian coast of the Red Sea. Among the three growth forms of Acroporid corals, the branching forms were found to dominate in the Farassan Is...In this study we assessed the current status of coral reefs along the Saudi Arabian coast of the Red Sea. Among the three growth forms of Acroporid corals, the branching forms were found to dominate in the Farassan Islands （44.55%±11.10% cover） fol-lowed by tabular forms in the Doga Islands （ranging between 18%±6.47% and 18.30%±9.47% cover）. Digitate forms were rarely found along the coast except at Maqna. Among the five growth forms of non-Acroporid corals, we observed maximum cover of branching forms in the Yanbu offshore area （58.89%±15.11% cover） followed by the Jeddah coast （24.76%±14.04% cover）. The Millepora spp., a non-Scleractinian coral, was abundant at all the near-shore sites, such as Jeddah （10.70%±8.21%） and A1-Wajh （9.81%±6.69%）. The live coral cover （including both Scleractinian and non-Scleractinian corals） of Saudi Red Sea coast was seen to be higher in the north and gradually decrease towards the south. Principal Component analysis showed that the contribution of Acro- porid corals was greater in the southern region than in the northem and middle regions, but vice-versa in the case of non-Acroporid corals. Bray-Curtis cluster analysis categorized all the study sites into two major clusters with 60% similarity. Among them, one cluster-forming sites from Maqna to Masturah （Northem region） and the second one comprised the middle and southem regions （Jeddah to Farassan Islands）, and one outlier Rabigh.展开更多
Cactaceae is an important plant family in the semi-arid ecosystems of the Americas.However,few studies have analyzed their responses after wildfires.In this study,we assessed the survival rate and resprouting capacity...Cactaceae is an important plant family in the semi-arid ecosystems of the Americas.However,few studies have analyzed their responses after wildfires.In this study,we assessed the survival rate and resprouting capacity of cacti from different growth forms one year after a wildfire in the Córdoba Mountains,central Argentina.Eight species are present in the study area,which were classified into four growth forms;then we established 158 plots and recorded the status(dead or alive)of each cactus and size-related variables.We also documented microenvironmental characteristics(percentage cover of grasses,forbs,shrubs,rock and bare ground)and topographic information(slope and slope orientation)for each plot,estimating the resprouting capacity of each growth form.Survival rates and resprouting capacity varied among growth forms.The survival rate for arborescent growth form was 25%,while for globose,opuntioid and short columnar forms were 84%,69%and 55%,respectively.Microenvironmental and topographic factors influenced resprouting capacity,though effects varied among growth forms.Globose growth form showed the highest recovery capacity after the wildfire,contrasting with arborescent growth form,of which only 2%of the individuals resprouted,predominantly on south-and north-facing slopes.In contrast,short columnar and opuntioid growth forms showed no significant relationship between survival or resprouting capacity,and the measured variables.These findings provide key insights into the role of fire in shaping cacti populations and highlight the need to consider species-specific and environmental interactions in conservation and management strategies for the Chaco forest.展开更多
The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empi...The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empirical formulas for the growth of significant wave height and period. The main features of spectrum growth as specified by these parameters agree with those of the JONS-WAP experiments. For given wind speed and fetch, the high frequency parts beyond the peaks of shallow water spectra almost coincide with that of the corresponding deep water spectrum, whereas the low frequency parts differ appreciably. The method developed in this paper predicts smaller significant wave height as well as smaller wave period for shallow water spectra in contrast to the theoretical result of Kitaigorodskii ef al, in which the peak frequency, and consequently the significant wave period, remains basically unchanged for different water depths. Spectra are further reduced to a form in which only significant wave height and period are left as parameters, the peakness factor being replaced by the wave steepness through an empirical relation between them. Spectra in this form have been verified by observations.展开更多
Wind is an environmental stimulus that stresses plants of all growth forms at all life-stages by influencing the development,architecture,and morphology of roots and shoots.However,comparative studies are scarce and n...Wind is an environmental stimulus that stresses plants of all growth forms at all life-stages by influencing the development,architecture,and morphology of roots and shoots.However,comparative studies are scarce and no study directly investigated whether shoot and root morphological traits of trees,grasses and forbs differ in their response to short wind pulses of different wind intensity.In this study,we found that across species,wind stress by short wind pulses of increasing intensity consistently changed root morphology,but did not affect shoot morphological traits,except plant height in four species.Wind effects in roots were generally weak in tree species but consistent across growth forms.Furthermore,plant height of species was correlated with changes in specific root length and average diameter.Our results indicate that short-pulse wind treatments affect root morphology more than shoot morphology across growth forms.They further suggest that wind stress possibly promotes root anchorage in young plants and that these effects might depend on plant height.展开更多
The present study was conducted in the alpine pastures of Tungnath （30° 14＇ N and 79° 13＇ E） to observe life-form and growth-form patterns of alpine plant species under grazed and ungrazed conditions and...The present study was conducted in the alpine pastures of Tungnath （30° 14＇ N and 79° 13＇ E） to observe life-form and growth-form patterns of alpine plant species under grazed and ungrazed conditions and to work out the plant life form spectrum. Species were categorized as plant habit, height and length of growth-cycle and life-form classes according to Raunkiaer＇s system. The results show that in total of 68 species at grazed site, hemicryptophytes （He） accounted for 50.00% species, followed by cryptophytes （26.47%）, chamaephytes （16.18%）, phanemphytes （4.41%） and therophytes （2.94%）. At the ungrazed site in 65 plant species, hemicryptophytes （He） accounted fo＇r 49.23% species, cryptophytes （26.15%）, chamaephytes （15.38%）, phanerophytes （6.15%） and ther6phytes （3.08 % species）. In general, hemicrptophyte are dominant^in both sites i.e. graged and ungrazed. Growth form categories were classified as forbs, shrubs, grasses and sedges＇and undershrubs, according to plant habit and height. On the basis of length of the growth cycle, species were categorized as plant species of short growth cycle, intermediate growth cycle and long growth cycle. The short forbs of plant habit and height, had the highest emergence, and grasses and sedges had the lowest emergence in representative species. Percentage of species with long growth cycle was highest in both sites.展开更多
Invasive species are increasingly spreading,particularly in rangeland ecosystems.It is essential to evaluate the effectiveness of different methods for controlling invasive plants in these ecosystems.This study aimed ...Invasive species are increasingly spreading,particularly in rangeland ecosystems.It is essential to evaluate the effectiveness of different methods for controlling invasive plants in these ecosystems.This study aimed to investigate the effects of three strategies-21-year grazing exclusion(21-YES),mowing-grazing in rotation in alternate years(MGRS),and moderate grazing(MGS)-on the change in cover,density,and biomass of Leucanthemum vulgare Lam.(Ox-eye Daisy=OED)and the plant community.To accomplish this,three sites selected for each treatment.In 2021,270 vegetation plots were sampled using a random systematic method.Subsequently,we recorded the density and canopy cover of all growth forms(forbs,grasses,and ferns),the OED biomass,and the ground cover.The results indicated that MGS reduced OED density,OED canopy,and OED biomass.Furthermore,this strategy demonstrated the highest density and canopy cover of the plant community(including total,forbs,grasses,and ferns).Additionally,the strongest correlation was observed between the total canopy and the OED density(R2=-0.91,-0.95,-0.94 in 21-YES,MGRS,and MGS,respectively),as well as between the total canopy and the OED canopy(R2=-0.51,-0.98,-0.97 in 21-YES,MGRS,and MGS,respectively).The MGS led to an increase in diversity indices.In general,the grazing strategy has proven to be effective in controlling the spread of invasive OED and has also resulted in an increase in canopy cover,density,and diversity indices of the plant community.The study highlights the importance of ongoing management efforts to control invasive species,with moderate grazing potentially serving as a more practical,culturally accepted,and costeffective short-term control strategy for widespread rangeland weed infestations.展开更多
Aerosol particle pollution has become an increasing serious environmental problem,and urban vegetation plays a long-lasting and positive role in mitigating it.This study compared the particle capture abilities of tree...Aerosol particle pollution has become an increasing serious environmental problem,and urban vegetation plays a long-lasting and positive role in mitigating it.This study compared the particle capture abilities of trees,shrubs,and herbs,and examined the compositions and influence of aerosol particles accumulated on leaf functional traits.Retained particles primarily contained Ca^(2+),K^(+),SO_(4)^(2-),NO_(3)^(-)and NH_(4)^(+),indicating their anthropogenic origins.The leathery-leaved tree Osmanthus fragrans and the papery-leaved herb Alternanthera sessilis demonstrated the higher competence in particle accumulation than other plants,and leaf morphologic structures(e.g.,leaf grooves,trichomes,waxy layers,and stomata characteristics)were closely associated with particle capture by plant species.Particle retention negatively impacted stomata,impeding photosynthesis,and reducing transpiration.In response to particle accumulation,plants tended to decrease specific leaf area and adjust stomatal conductance.Both growth form and leaf texture significantly influenced the particle capture abilities of different plant species.The substantial contribution of plants,particularly herbs in the lower vegetation strata,to particle removal should not be overlooked.Vegetation with a tree-shrub-herb configuration excels at particle capture,offering potential advantages in mitigating particle pollution and enhancing ecological benefits.展开更多
Background:Wildfires are one of the major environmental concerns in Mediterranean ecosystems.Thus,many studies have addressed wildfire impacts on soil and vegetation in Mediterranean forests,but the linkages between t...Background:Wildfires are one of the major environmental concerns in Mediterranean ecosystems.Thus,many studies have addressed wildfire impacts on soil and vegetation in Mediterranean forests,but the linkages between these ecosystem compartments after fire are not well understood.The aim of this work is to analyze soil-vegetation relationships in Mediterranean burned forests as well as the consistency of these relationships among forests with different environmental conditions,at different times after fire,and among vegetation with different functional traits.Results:Our results indicate that study site conditions play an important role in mediating soil-vegetation relationships.Likewise,we found that the nature of soil-vegetation relationships may vary over time as fire effects are less dominant in both ecosystem compartments.Despite this,we detected several common soil-vegetation relationships among study sites and times after fire.For instance,our results revealed that available P content and stoichiometry(C:P and N:P)were closely linked to vegetation growth,and particularly to the growth of trees.We found that enzymatic activities and microbial biomass were inversely related to vegetation growth rates,whereas the specific activities of soil enzymes were higher in the areas with more vegetation height and cover.Likewise,our results suggest that resprouters may influence soil properties more than seeders,the growth of seeders being more dependent on soil status.Conclusions:We provide pioneer insights into how vegetation is influenced by soil,and vice-versa,in Mediterranean burned areas.Our results reflect variability in soil-vegetation relationships among study sites and time after fire,but consistent patterns between soil properties and vegetation were also detected.Our research is highly relevant to advance in forest science and could be useful to achieve efficient post-fire management.展开更多
The objectives of this study were to assess distribution patterns of plant species richness,plant diversity and vegetation structure in relation to environmental factors along elevation gradient in Al-Jabal Al-Akhdar,...The objectives of this study were to assess distribution patterns of plant species richness,plant diversity and vegetation structure in relation to environmental factors along elevation gradient in Al-Jabal Al-Akhdar,Libya.For each species,its growth form,chorological affinities,degree of occurrence,endemism status and originality were provided.A total of 534 taxa were generated from 70 families of the flowering plants,and 3 of the non-flowering plants were identified.The native flora of the study area was counted for 80.2%of the total indigenous taxa(465).The hump-shaped pattern of plant species richness was obtained,with the highest species richness at the mid-elevations,and both ends of the gradient have the lowest.The annuals(300 species,56.2%)and non-succulent perennial herbs(165 species,30.9%)were the most dominant growth forms of the total species composition.Along the elevation gradient,Asteraceae,Fabaceae,Poaceae,Lamiaceae and Apiaceae were the dominant families with the highest numbers of species.This investigation recorded 31 endemic taxa,comprising 25 dicots and 6 monocots,primarily of Mediterranean origin,with most belonging to the Asteraceae and Lamiaceae families.Mediterranean chorotype was the dominant,whether pure(mono-),or combined with one(bi-and pluri-regional)or more(pluri-regional).Application of cluster analysis on the vegetation data yielded four cluster groups;each was linked to an elevation level.It emphasized the importance of establishing conservation strategies to minimize human disturbance and safeguard relic habitats of Juniperus phoenicea L.at its southern distribution limits in Africa,underlining the proactive management required for species preservation.The application of Redundancy Analysis revealed that Shannon diversity index(H'),pH and Fe were the determinant soil factor in the mid-elevation levels(L2 and L3)whereas altitude,fine sand,HCO3,OM,and soil contents of Na,SO4 and Cl for the extreme levels(L1 and L4).展开更多
For developing nature-based silvicultural practices in a beech forest to promote, abundance, height, vitality, and preferred growth form, regenerated trees growing in gaps were compared with those under closed canopie...For developing nature-based silvicultural practices in a beech forest to promote, abundance, height, vitality, and preferred growth form, regenerated trees growing in gaps were compared with those under closed canopies. A systematic 50 ×50 m grid was plotted in a beech stand in the Kheyrud Experimental Forest for selecting trees to measure variables in gaps and under closed canopies. Abundance and mean height of regenerated beech trees were significantly higher in closed canopies than in canopy gaps. Beech seedlings with excurrent growth were significantly taller within regeneration patches under closed canopy. Moreover, regenerated trees with high vitality were more abundant in closed canopy areas than in gaps. Thus, beech regeneration should improve under closed canopies; hence, gaps in a near natural forest should be created only after adequate regeneration and appropriate growth under the parent tree in a closed canopy area is ensured. The results of this research have profound implications for the sustainable management of the forest and for ensuring sustainable beech regeneration. The presence of a closed canopy cover likely will reduce potential stresses on oriental beech regeneration.展开更多
Sexual systems play important roles in angiosperm evolution and exhibit substantial variations among different floras. Thus, studying their evolution in a whole flora is crucial for understanding the formation and mai...Sexual systems play important roles in angiosperm evolution and exhibit substantial variations among different floras. Thus, studying their evolution in a whole flora is crucial for understanding the formation and maintenance of plant biodiversity and predicting its responses to environmental change. In this study, we determined the patterns of plant sexual systems and their associations with geographic elements and various life-history traits in dry-hot valley region of southwestern China, an extremely vulnerable ecosystem. Of the 3166 angiosperm species recorded in this area, 74.5% were hermaphroditic,13.5% were monoecious and 12% were dioecious, showing a high incidence of diclinous species. Diclinous species were strongly associated with tropical elements, whereas hermaphroditic species were strongly associated with temperate and cosmopolitan elements. We also found that hermaphroditism was strongly associated with showy floral displays, specialist entomophily, dry fruits and herbaceous plants.Dioecy was strongly associated with inconspicuous, pale-colored flowers, generalist entomophily, fleshy fruits, and woody plants, whereas monoecy was strongly associated with inconspicuous, pale-colored flowers, anemophily, dry fruits, and herbaceous plants. In addition, hermaphroditic species with generalist entomophily tended to flower in the dry season, whereas diclinous species with specialist entomophily tended to flower in the rainy season. However, independent of sexual systems, plants that produce dry fruits tended to flower in the rainy season and set fruits in the dry season, but the opposite pattern was found for fleshy fruit-producing plants. Our results suggest that in the dry-hot valleys, plant sexual systems are associated with geographic elements as well as various life-history traits that are sensitive to environmental change.展开更多
Urban trees are sensitive to extreme weather events under climate change.Freeze-thaw induced hydraulic failure could induce urban tree dieback and nullify the services they provide.Plant height is a simple but signifi...Urban trees are sensitive to extreme weather events under climate change.Freeze-thaw induced hydraulic failure could induce urban tree dieback and nullify the services they provide.Plant height is a simple but significant trait for plant ecological strategies.Understanding how urban trees with different heights adapt to freeze-thaw stress is increasingly important under climate change.We investigated the relationship between tree height and stem hydraulic functional traits of six common urban tree species in North China to explore tree height-related hydraulic strategies to cope with freeze-thaw stress.Results showed that tall trees had wider vessels,higher hydraulic conductivity,more winter embolism,but lower vessel and wood densities.Positive relationships were found between tree height and vessel diameter,hydraulic conductivity,and freeze-thaw induced embolism,and negative relationships were found between tree height and vessel and wood densities,which implied that short trees employ more conservative ecological strategies than tall trees.Tall and short tree species were well separated by multiple stem hydraulic functional traits;this is consistent with the fact that tall and short trees occupy different niches and indicates that different hydraulic strategies for freeze-thaw stress exist between them.Tall trees might face more pressure to survive under extreme cold weather caused by climate change in the future.Therefore,more attention should be paid to tall urban tree management in North China to cope with extreme cold weather.展开更多
This paper presents equations for estimating limiting stand density for Z undulata plantations grown in hot desert areas of Raj asthan State in India. Five different stand level basal area projection models, belonging...This paper presents equations for estimating limiting stand density for Z undulata plantations grown in hot desert areas of Raj asthan State in India. Five different stand level basal area projection models, belonging to the path invariant algebraic difference form of a non-linear growth function, were also tested and compared. These models can be used to predict future basal area as a function of stand variables like dominant height and stem number per hectare and are necessary for reviewing different silvicultural treatment options. Data from 22 sample plots were used for modelling. An all possible growth intervals data structure was used. Both, qualitative and quantitative criteria were used to compare alternative models. The Akaike＇s information criteria differ- ence statistic was used to analyze the predictive ability of the models. Results show that the model proposed by Hui and Gadow performed best and hence this model is recommended for use in predicting basal area development in 12 undulata plantations in the study area. The data used were not from thinned stands, and hence the models may be less accurate when used for predictions when natural mortality is very significant.展开更多
The manglicolous lichens are a specific group of lichens which occur in association with mangrove plants.Mangrove ecosystems have limited accessibility and the lichen study in mangrove forests are less studied and rep...The manglicolous lichens are a specific group of lichens which occur in association with mangrove plants.Mangrove ecosystems have limited accessibility and the lichen study in mangrove forests are less studied and reported.The present study is the first-time report on lichen diversity,their distribution and its associated host mangrove species at eight different sites within the mangrove forests of Bhitarkanika Wildlife Sanctuary and National Park(Odisha),India.The study recorded a total of 49 lichen species which belongs to 26 genera and 14 families.The comparison of growth forms showed presence of 28 species of crustose,18 species of foliose and three species of fruticose type of lichens from the study sites.The analysis of host mangrove species showed Excoecaria agallocha as the most preferable mangrove species as it housed 38 lichen species on its surface(i.e.,45%crustose,47%foliose,and 8%fruticose).The comparison of growth forms of the total recorded lichen species from Bhitarkanika National Park,resulted 57%species crustose,37%foliose and 6%of fruticose type of lichens.The mangrove species,Avicennia officinalis and lichen of the genus Chrysothrix were found as common to all the study sites.The Jaccard similarity index study of lichen species between the study sites showed Kalibhanjadiya Island and Habelikhati as more similar in comparison of lichen species composition(i.e.,0.64).The occurrence of foliose and fruticose type of lichens showed the healthy and undisturbed mangrove forest conditions at many sites within Bhitarkanika National Park.展开更多
Sulfur is an essential functional element in leaves,and it plays important roles in regulating plant growth,development and abiotic stress resistance in natural communities.However,there has been limited information o...Sulfur is an essential functional element in leaves,and it plays important roles in regulating plant growth,development and abiotic stress resistance in natural communities.However,there has been limited information on the spatial variation in leaf sulfur content(LSC)and adaptive characters on a large community scale.Sulfur in leaves of 2207 plant species from 80 widespread ecosystems(31 forests,38 grasslands and 11 deserts)in China was measured.One-way analysis of variance with Duncan’s multiple-range tests were used to evaluate the differences in LSC among different plant growth forms and ecosystems.We fitted the relationships of LSC to spatial and climate factors using regression.Structural equation modeling analysis and phylogenetic analysis helped us further explore the main factors of LSC variation.LSC ranged from 0.15 to 48.64 g·kg^(-1),with an average of 2.13±0.04 g·kg^(-1) at the community scale in China.We observed significant spatial variation in LSC among different ecosystems and taxa.Overall,LSC was higher in arid areas and herbs.Furthermore,higher LSC was observed under environments of drought,low temperatures and intense ultraviolet radiation.Temperature,precipitation,radiation,soil sulfur content and aridity jointly regulated LSC,explaining 79%of the spatial variation.However,LSC was not significantly related to phylogeny.Our results demonstrate that LSC plays an important role in plant adaptations to extreme environments and further extend our understanding of the biological function of sulfur from the organ to the community level.These findings highlight the importance of sulfur metabolism for our understanding of the impact of global climate change on plants.展开更多
Aims Species composition and diversity of the mountainous rangelands are results of interactions between environmental severities,het-erogeneous topography and facilitative effects by nurse plants.This research was ai...Aims Species composition and diversity of the mountainous rangelands are results of interactions between environmental severities,het-erogeneous topography and facilitative effects by nurse plants.This research was aimed to compare relative effects of these three envi-ronmental variables on the natural vegetation of a mountainous rangeland.For a more detailed understanding,effects of four dif-ferent nurse species were separately compared on the various plant growth forms and on two community plant responses(diversity and abundance).Methods A mountainous semiarid rangeland was selected in Baharkish,Quchan,Northeast of Iran.Density and canopy cover of all plant species were recorded under the canopy of four different shrubs and in open areas,in north and south-facing aspects,and in a normal and a drought year.Shannon diversity,total abundance(%cover)and the abundance of different growth forms were used as crite-ria for assessing effects of the environmental variables.Data were arranged in a factorial combination and analyzed by three-way analysis of variance using a GLM analysis.Important Findings(i)Drought,aspect and canopy created niche differentiation:annual forbs and shrubs were more affected by drought,whereas geophytes and grasses were more responsive to slope aspects.Effects of drought and slope aspect were more profound on species diversity,whereas that of canopy facilitation was stronger on plant abundance.(ii)Canopy facili-tation was dependent on severity of the abiotic factors and life history of interacting species.Canopy facilitation allowed for the persistence of only annual forbs,but it was disadvantaged during the drought year.Plant community responses to abiotic factors(slope and drought)were more dependent on the plant growth form,while responses to canopy facilitation were more dependent on the morphology and/or ecology of nurse shrubs.(iii)Effect of shrubs was dependent on their morphology and ecology:shrubs with larger canopy area and nitrogen fixation capa-bility increased,but those with allelopathic effects or a dense canopy structure decreased the diversity of the understory species.展开更多
Aims The importance of quantifying carbon stocks in terrestrial ecosystems is crucial for determining climate change dynamics.However,the present regional assessments of carbon stocks in tropical grasslands are extrap...Aims The importance of quantifying carbon stocks in terrestrial ecosystems is crucial for determining climate change dynamics.However,the present regional assessments of carbon stocks in tropical grasslands are extrapolated to unsampled areas with a high degree of uncertainty and without considering the carbon and nitrogen composition of vegetation and soil along altitudinal ranges.This study aims to assess carbon and nitrogen concentrations in soil and vegetation,aboveground carbon stocks distribution and soil organic carbon stocks along an altitudinal range in the páramo region in the Ecuadorian Andes.Methods The vegetation inventory was conducted using 15×15 m sampling plots distributed in three altitudinal ranges.Based on the patterns exhibited by the dominant vegetation growth forms,biomass and soil were sampled to quantify the corresponding carbon and nitrogen concentrations.Subsequently,the aboveground live biomass along the páramo altitudinal range was estimated using allometric equations.Finally,soil and vegetation carbon stocks were estimated for the entire basin.Important Findings Altitudinal analysis supported a potential distribution of carbon and nitrogen concentrations in soil,litter and live tissues,where higher concentrations were found in the low altitudinal range mainly for tussocks and acaulescent rosettes.Cellulose in litter showed higher concentrations at low altitudinal ranges for acaulescent rosettes and cushions only.For the same growth forms,lignin patterns in litter were higher in high altitudinal ranges.Soil texture provided complementary information:high percentage of silt was highly correlated to high soil nitrogen and carbon concentration.Tussocks were found to be responsive to altitude with their,highest aboveground carbon stocks occurring at the low altitudinal range,but cushions and acaulescent rosettes responded differently.The established relationships among soil,vegetation and altitude shown in this study must be taken into account to estimate both aboveground and soil organic carbon stocks in páramo regions—such estimates will be considerably inaccurate if these relationships are ignored.展开更多
Aims Plants play an important role in ecosystem processes.Functional meaning of trait variation in wide environmental gradients is well known but is scarcely known across narrow gradients.We analyze the variation of m...Aims Plants play an important role in ecosystem processes.Functional meaning of trait variation in wide environmental gradients is well known but is scarcely known across narrow gradients.We analyze the variation of morphological,physical and chemical traits of dom-inant plant species and the potential rates of dry mass loss and N release/immobilization during senesced leaf decomposition of these species across a narrow aridity gradient,and to identify indicative traits useful to set species functional groups sharing decomposition patterns.Methods We analyzed the variation of morphological,physical and chemical traits(specific leaf area,seed mass,N and soluble phenols in green and senesced leaves,plant height)in dominant plant species at 12 sites across an aridity gradient in northern Patagonia,Argentina.We collected senesced leaves of each plant species at each site and used them to estimate the poten-tial rates of dry mass loss and N release/immobilization from decomposing senesced leaves in a microcosm experiment.We analyzed the variation of plant traits and decomposition rates across the aridity gradient.We grouped plants species accord-ing to growth forms(perennial grasses,deciduous shrubs,ever-green shrubs)and different combinations of morpho-physical and chemical traits of green and senesced leaves and compared the potential rates of dry mass loss and N release/immobiliza-tion during leaf decomposition among these groups delimited by each grouping criteria.Important Findings Plant traits did not vary across the aridity gradient.The potential rate of dry mass loss was positively related to aridity,while the potential rate of N release/immobilization did not vary across the gradient.Grouping species by separately morpho-physical and chemical traits resulted in a large overlapping in mean values of decomposition rates among groups.In contrast,plant groupings based on growth forms and those including all morpho-physical and chemical traits of green or senesced leaves yielded groups with differentiated rates of decomposition processes.The two latter groupings clustered spe-cies from more than one growth form indicating some overlapping in the rates of decomposition processes among species of different growth forms.Among traits,N concentration in senesced leaves and plant height explained the highest variation in decomposition rates being positively related to potential rates of dry mass loss and N release/immobilization.We concluded that plant groupings based on morpho-physical and chemical traits of either green or senesced leaves may be more powerful to differentiate functional species groups sharing decomposition patterns than the growth form group-ing.Moreover,plant height and N concentration in senesced leaves may be considered relevant synthetic functional traits in relation to decomposition processes in narrow aridity gradients.展开更多
Aims Several studies have shown that plant height changes along environmen-tal gradients.However,altitudinal patterns of plant height across species are still unclear,especially in regions sensitive to climate change....Aims Several studies have shown that plant height changes along environmen-tal gradients.However,altitudinal patterns of plant height across species are still unclear,especially in regions sensitive to climate change.As canopy height decreases dramatically near the tree line in alpine areas,we hypothesize that plant height across all species also decreases with increasing altitude,and distinct thresholds exist along this gradient.Methods Using a large dataset of maximum plant height and elevation range(400 to 6000 m a.s.l.)of 4295 angiosperms from the regional flora of the Tibetan Plateau,we regressed plant height for every 100 m belt against elevation to explore the relationships.To identify the approximate boundaries where dramatic changes in plant height occurs for herbaceous plants,shrubs,trees,woody plants and all angiosperms,we used piecewise linear regression.Phylogenetically independent contrast was used to test the potential evolutionary influences on altitudinal patterns at the family level.Important Findings Results showed that for herbaceous plants,shrubs,trees,woody plants and all angiosperms,plant height decreases significantly as altitude increases.In addition,we found that altitude,a proxy for many environmental factors,had obvious thresholds(breakpoints)dictating patterns of plant height.The results of phylogenetically independent contrast also emphasized the importance of evolution-ary history in determining the altitudinal patterns of plant height for some growth forms.Our results highlight the relative intense filter-ing effect of environmental factors in shaping patterns of functional traits and how this could vary for different ranges of environmental variables.展开更多
文摘In this study we assessed the current status of coral reefs along the Saudi Arabian coast of the Red Sea. Among the three growth forms of Acroporid corals, the branching forms were found to dominate in the Farassan Islands （44.55%±11.10% cover） fol-lowed by tabular forms in the Doga Islands （ranging between 18%±6.47% and 18.30%±9.47% cover）. Digitate forms were rarely found along the coast except at Maqna. Among the five growth forms of non-Acroporid corals, we observed maximum cover of branching forms in the Yanbu offshore area （58.89%±15.11% cover） followed by the Jeddah coast （24.76%±14.04% cover）. The Millepora spp., a non-Scleractinian coral, was abundant at all the near-shore sites, such as Jeddah （10.70%±8.21%） and A1-Wajh （9.81%±6.69%）. The live coral cover （including both Scleractinian and non-Scleractinian corals） of Saudi Red Sea coast was seen to be higher in the north and gradually decrease towards the south. Principal Component analysis showed that the contribution of Acro- porid corals was greater in the southern region than in the northem and middle regions, but vice-versa in the case of non-Acroporid corals. Bray-Curtis cluster analysis categorized all the study sites into two major clusters with 60% similarity. Among them, one cluster-forming sites from Maqna to Masturah （Northem region） and the second one comprised the middle and southem regions （Jeddah to Farassan Islands）, and one outlier Rabigh.
基金supported by grants from the Research Committee of the Cactus and Succulent Society of America and Secretaría de Ciencia y Tecnología-Universidad Nacional de Córdoba,and a PIP-CONICET grant[11220220100196],Argentina.
文摘Cactaceae is an important plant family in the semi-arid ecosystems of the Americas.However,few studies have analyzed their responses after wildfires.In this study,we assessed the survival rate and resprouting capacity of cacti from different growth forms one year after a wildfire in the Córdoba Mountains,central Argentina.Eight species are present in the study area,which were classified into four growth forms;then we established 158 plots and recorded the status(dead or alive)of each cactus and size-related variables.We also documented microenvironmental characteristics(percentage cover of grasses,forbs,shrubs,rock and bare ground)and topographic information(slope and slope orientation)for each plot,estimating the resprouting capacity of each growth form.Survival rates and resprouting capacity varied among growth forms.The survival rate for arborescent growth form was 25%,while for globose,opuntioid and short columnar forms were 84%,69%and 55%,respectively.Microenvironmental and topographic factors influenced resprouting capacity,though effects varied among growth forms.Globose growth form showed the highest recovery capacity after the wildfire,contrasting with arborescent growth form,of which only 2%of the individuals resprouted,predominantly on south-and north-facing slopes.In contrast,short columnar and opuntioid growth forms showed no significant relationship between survival or resprouting capacity,and the measured variables.These findings provide key insights into the role of fire in shaping cacti populations and highlight the need to consider species-specific and environmental interactions in conservation and management strategies for the Chaco forest.
文摘The spectrum variance m0, peak frequency ω0 and peakness factor p are expressed in terms of nondimensional fetch and duration by making use of relations which are derived through comparing and analyzing existing empirical formulas for the growth of significant wave height and period. The main features of spectrum growth as specified by these parameters agree with those of the JONS-WAP experiments. For given wind speed and fetch, the high frequency parts beyond the peaks of shallow water spectra almost coincide with that of the corresponding deep water spectrum, whereas the low frequency parts differ appreciably. The method developed in this paper predicts smaller significant wave height as well as smaller wave period for shallow water spectra in contrast to the theoretical result of Kitaigorodskii ef al, in which the peak frequency, and consequently the significant wave period, remains basically unchanged for different water depths. Spectra are further reduced to a form in which only significant wave height and period are left as parameters, the peakness factor being replaced by the wave steepness through an empirical relation between them. Spectra in this form have been verified by observations.
文摘Wind is an environmental stimulus that stresses plants of all growth forms at all life-stages by influencing the development,architecture,and morphology of roots and shoots.However,comparative studies are scarce and no study directly investigated whether shoot and root morphological traits of trees,grasses and forbs differ in their response to short wind pulses of different wind intensity.In this study,we found that across species,wind stress by short wind pulses of increasing intensity consistently changed root morphology,but did not affect shoot morphological traits,except plant height in four species.Wind effects in roots were generally weak in tree species but consistent across growth forms.Furthermore,plant height of species was correlated with changes in specific root length and average diameter.Our results indicate that short-pulse wind treatments affect root morphology more than shoot morphology across growth forms.They further suggest that wind stress possibly promotes root anchorage in young plants and that these effects might depend on plant height.
文摘The present study was conducted in the alpine pastures of Tungnath （30° 14＇ N and 79° 13＇ E） to observe life-form and growth-form patterns of alpine plant species under grazed and ungrazed conditions and to work out the plant life form spectrum. Species were categorized as plant habit, height and length of growth-cycle and life-form classes according to Raunkiaer＇s system. The results show that in total of 68 species at grazed site, hemicryptophytes （He） accounted for 50.00% species, followed by cryptophytes （26.47%）, chamaephytes （16.18%）, phanemphytes （4.41%） and therophytes （2.94%）. At the ungrazed site in 65 plant species, hemicryptophytes （He） accounted fo＇r 49.23% species, cryptophytes （26.15%）, chamaephytes （15.38%）, phanerophytes （6.15%） and ther6phytes （3.08 % species）. In general, hemicrptophyte are dominant^in both sites i.e. graged and ungrazed. Growth form categories were classified as forbs, shrubs, grasses and sedges＇and undershrubs, according to plant habit and height. On the basis of length of the growth cycle, species were categorized as plant species of short growth cycle, intermediate growth cycle and long growth cycle. The short forbs of plant habit and height, had the highest emergence, and grasses and sedges had the lowest emergence in representative species. Percentage of species with long growth cycle was highest in both sites.
基金the University of Mohaghegh Ardabili,Department of Natural Resources,Iran for financial support。
文摘Invasive species are increasingly spreading,particularly in rangeland ecosystems.It is essential to evaluate the effectiveness of different methods for controlling invasive plants in these ecosystems.This study aimed to investigate the effects of three strategies-21-year grazing exclusion(21-YES),mowing-grazing in rotation in alternate years(MGRS),and moderate grazing(MGS)-on the change in cover,density,and biomass of Leucanthemum vulgare Lam.(Ox-eye Daisy=OED)and the plant community.To accomplish this,three sites selected for each treatment.In 2021,270 vegetation plots were sampled using a random systematic method.Subsequently,we recorded the density and canopy cover of all growth forms(forbs,grasses,and ferns),the OED biomass,and the ground cover.The results indicated that MGS reduced OED density,OED canopy,and OED biomass.Furthermore,this strategy demonstrated the highest density and canopy cover of the plant community(including total,forbs,grasses,and ferns).Additionally,the strongest correlation was observed between the total canopy and the OED density(R2=-0.91,-0.95,-0.94 in 21-YES,MGRS,and MGS,respectively),as well as between the total canopy and the OED canopy(R2=-0.51,-0.98,-0.97 in 21-YES,MGRS,and MGS,respectively).The MGS led to an increase in diversity indices.In general,the grazing strategy has proven to be effective in controlling the spread of invasive OED and has also resulted in an increase in canopy cover,density,and diversity indices of the plant community.The study highlights the importance of ongoing management efforts to control invasive species,with moderate grazing potentially serving as a more practical,culturally accepted,and costeffective short-term control strategy for widespread rangeland weed infestations.
基金supported by the National Natural Science Foundation of China(No.31700475).
文摘Aerosol particle pollution has become an increasing serious environmental problem,and urban vegetation plays a long-lasting and positive role in mitigating it.This study compared the particle capture abilities of trees,shrubs,and herbs,and examined the compositions and influence of aerosol particles accumulated on leaf functional traits.Retained particles primarily contained Ca^(2+),K^(+),SO_(4)^(2-),NO_(3)^(-)and NH_(4)^(+),indicating their anthropogenic origins.The leathery-leaved tree Osmanthus fragrans and the papery-leaved herb Alternanthera sessilis demonstrated the higher competence in particle accumulation than other plants,and leaf morphologic structures(e.g.,leaf grooves,trichomes,waxy layers,and stomata characteristics)were closely associated with particle capture by plant species.Particle retention negatively impacted stomata,impeding photosynthesis,and reducing transpiration.In response to particle accumulation,plants tended to decrease specific leaf area and adjust stomatal conductance.Both growth form and leaf texture significantly influenced the particle capture abilities of different plant species.The substantial contribution of plants,particularly herbs in the lower vegetation strata,to particle removal should not be overlooked.Vegetation with a tree-shrub-herb configuration excels at particle capture,offering potential advantages in mitigating particle pollution and enhancing ecological benefits.
基金supported by the Spanish Ministry of Economy and Competitivenessthe European Regional Development Fund(ERDF)+4 种基金in the framework of the GESFIRE(AGL2013–48189-C2–1-R)FIRESEVES(AGL2017–86075-C2–1-R)projectsby the Regional Government of Castile and León in the framework of the FIRECYL(LE033U14)SEFIRECYL(LE001P17)projects(funding for data collection and soil analyses)SH was supported by a predoctoral fellowship(EDU/574/2018)from the Regional Government of Castile and León and the European Social Fund。
文摘Background:Wildfires are one of the major environmental concerns in Mediterranean ecosystems.Thus,many studies have addressed wildfire impacts on soil and vegetation in Mediterranean forests,but the linkages between these ecosystem compartments after fire are not well understood.The aim of this work is to analyze soil-vegetation relationships in Mediterranean burned forests as well as the consistency of these relationships among forests with different environmental conditions,at different times after fire,and among vegetation with different functional traits.Results:Our results indicate that study site conditions play an important role in mediating soil-vegetation relationships.Likewise,we found that the nature of soil-vegetation relationships may vary over time as fire effects are less dominant in both ecosystem compartments.Despite this,we detected several common soil-vegetation relationships among study sites and times after fire.For instance,our results revealed that available P content and stoichiometry(C:P and N:P)were closely linked to vegetation growth,and particularly to the growth of trees.We found that enzymatic activities and microbial biomass were inversely related to vegetation growth rates,whereas the specific activities of soil enzymes were higher in the areas with more vegetation height and cover.Likewise,our results suggest that resprouters may influence soil properties more than seeders,the growth of seeders being more dependent on soil status.Conclusions:We provide pioneer insights into how vegetation is influenced by soil,and vice-versa,in Mediterranean burned areas.Our results reflect variability in soil-vegetation relationships among study sites and time after fire,but consistent patterns between soil properties and vegetation were also detected.Our research is highly relevant to advance in forest science and could be useful to achieve efficient post-fire management.
文摘The objectives of this study were to assess distribution patterns of plant species richness,plant diversity and vegetation structure in relation to environmental factors along elevation gradient in Al-Jabal Al-Akhdar,Libya.For each species,its growth form,chorological affinities,degree of occurrence,endemism status and originality were provided.A total of 534 taxa were generated from 70 families of the flowering plants,and 3 of the non-flowering plants were identified.The native flora of the study area was counted for 80.2%of the total indigenous taxa(465).The hump-shaped pattern of plant species richness was obtained,with the highest species richness at the mid-elevations,and both ends of the gradient have the lowest.The annuals(300 species,56.2%)and non-succulent perennial herbs(165 species,30.9%)were the most dominant growth forms of the total species composition.Along the elevation gradient,Asteraceae,Fabaceae,Poaceae,Lamiaceae and Apiaceae were the dominant families with the highest numbers of species.This investigation recorded 31 endemic taxa,comprising 25 dicots and 6 monocots,primarily of Mediterranean origin,with most belonging to the Asteraceae and Lamiaceae families.Mediterranean chorotype was the dominant,whether pure(mono-),or combined with one(bi-and pluri-regional)or more(pluri-regional).Application of cluster analysis on the vegetation data yielded four cluster groups;each was linked to an elevation level.It emphasized the importance of establishing conservation strategies to minimize human disturbance and safeguard relic habitats of Juniperus phoenicea L.at its southern distribution limits in Africa,underlining the proactive management required for species preservation.The application of Redundancy Analysis revealed that Shannon diversity index(H'),pH and Fe were the determinant soil factor in the mid-elevation levels(L2 and L3)whereas altitude,fine sand,HCO3,OM,and soil contents of Na,SO4 and Cl for the extreme levels(L1 and L4).
文摘For developing nature-based silvicultural practices in a beech forest to promote, abundance, height, vitality, and preferred growth form, regenerated trees growing in gaps were compared with those under closed canopies. A systematic 50 ×50 m grid was plotted in a beech stand in the Kheyrud Experimental Forest for selecting trees to measure variables in gaps and under closed canopies. Abundance and mean height of regenerated beech trees were significantly higher in closed canopies than in canopy gaps. Beech seedlings with excurrent growth were significantly taller within regeneration patches under closed canopy. Moreover, regenerated trees with high vitality were more abundant in closed canopy areas than in gaps. Thus, beech regeneration should improve under closed canopies; hence, gaps in a near natural forest should be created only after adequate regeneration and appropriate growth under the parent tree in a closed canopy area is ensured. The results of this research have profound implications for the sustainable management of the forest and for ensuring sustainable beech regeneration. The presence of a closed canopy cover likely will reduce potential stresses on oriental beech regeneration.
基金supported by the Key Projects of the Joint Fund of the National Natural Science Foundation of China (U23A20149)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA20050203)+3 种基金the Second Tibetan Plateau Scientific Expedition and Research program (2019QZKK0502)the National Natural Science Foundation of China (32371702, 32071669 and 31770249)the West Light Foundation of the Chinese Academy of Sciences Interdisciplinary Innovation Team Program (xbzg-zdsys202319)the Ten-thousand Talents Program of Yunnan Province (YNWR-QNBJ-2018-208)。
文摘Sexual systems play important roles in angiosperm evolution and exhibit substantial variations among different floras. Thus, studying their evolution in a whole flora is crucial for understanding the formation and maintenance of plant biodiversity and predicting its responses to environmental change. In this study, we determined the patterns of plant sexual systems and their associations with geographic elements and various life-history traits in dry-hot valley region of southwestern China, an extremely vulnerable ecosystem. Of the 3166 angiosperm species recorded in this area, 74.5% were hermaphroditic,13.5% were monoecious and 12% were dioecious, showing a high incidence of diclinous species. Diclinous species were strongly associated with tropical elements, whereas hermaphroditic species were strongly associated with temperate and cosmopolitan elements. We also found that hermaphroditism was strongly associated with showy floral displays, specialist entomophily, dry fruits and herbaceous plants.Dioecy was strongly associated with inconspicuous, pale-colored flowers, generalist entomophily, fleshy fruits, and woody plants, whereas monoecy was strongly associated with inconspicuous, pale-colored flowers, anemophily, dry fruits, and herbaceous plants. In addition, hermaphroditic species with generalist entomophily tended to flower in the dry season, whereas diclinous species with specialist entomophily tended to flower in the rainy season. However, independent of sexual systems, plants that produce dry fruits tended to flower in the rainy season and set fruits in the dry season, but the opposite pattern was found for fleshy fruit-producing plants. Our results suggest that in the dry-hot valleys, plant sexual systems are associated with geographic elements as well as various life-history traits that are sensitive to environmental change.
基金This work was financially supported by the National Natural Science Foundation of China(30900564,41877542)the Project of Henan Agricultural University Program for Fundamental Research(30900649).
文摘Urban trees are sensitive to extreme weather events under climate change.Freeze-thaw induced hydraulic failure could induce urban tree dieback and nullify the services they provide.Plant height is a simple but significant trait for plant ecological strategies.Understanding how urban trees with different heights adapt to freeze-thaw stress is increasingly important under climate change.We investigated the relationship between tree height and stem hydraulic functional traits of six common urban tree species in North China to explore tree height-related hydraulic strategies to cope with freeze-thaw stress.Results showed that tall trees had wider vessels,higher hydraulic conductivity,more winter embolism,but lower vessel and wood densities.Positive relationships were found between tree height and vessel diameter,hydraulic conductivity,and freeze-thaw induced embolism,and negative relationships were found between tree height and vessel and wood densities,which implied that short trees employ more conservative ecological strategies than tall trees.Tall and short tree species were well separated by multiple stem hydraulic functional traits;this is consistent with the fact that tall and short trees occupy different niches and indicates that different hydraulic strategies for freeze-thaw stress exist between them.Tall trees might face more pressure to survive under extreme cold weather caused by climate change in the future.Therefore,more attention should be paid to tall urban tree management in North China to cope with extreme cold weather.
基金the State Forest Department,Rajasthan for providing financial support for conducting this study and to their officials for rendering necessary assistance during fieldwork
文摘This paper presents equations for estimating limiting stand density for Z undulata plantations grown in hot desert areas of Raj asthan State in India. Five different stand level basal area projection models, belonging to the path invariant algebraic difference form of a non-linear growth function, were also tested and compared. These models can be used to predict future basal area as a function of stand variables like dominant height and stem number per hectare and are necessary for reviewing different silvicultural treatment options. Data from 22 sample plots were used for modelling. An all possible growth intervals data structure was used. Both, qualitative and quantitative criteria were used to compare alternative models. The Akaike＇s information criteria differ- ence statistic was used to analyze the predictive ability of the models. Results show that the model proposed by Hui and Gadow performed best and hence this model is recommended for use in predicting basal area development in 12 undulata plantations in the study area. The data used were not from thinned stands, and hence the models may be less accurate when used for predictions when natural mortality is very significant.
文摘The manglicolous lichens are a specific group of lichens which occur in association with mangrove plants.Mangrove ecosystems have limited accessibility and the lichen study in mangrove forests are less studied and reported.The present study is the first-time report on lichen diversity,their distribution and its associated host mangrove species at eight different sites within the mangrove forests of Bhitarkanika Wildlife Sanctuary and National Park(Odisha),India.The study recorded a total of 49 lichen species which belongs to 26 genera and 14 families.The comparison of growth forms showed presence of 28 species of crustose,18 species of foliose and three species of fruticose type of lichens from the study sites.The analysis of host mangrove species showed Excoecaria agallocha as the most preferable mangrove species as it housed 38 lichen species on its surface(i.e.,45%crustose,47%foliose,and 8%fruticose).The comparison of growth forms of the total recorded lichen species from Bhitarkanika National Park,resulted 57%species crustose,37%foliose and 6%of fruticose type of lichens.The mangrove species,Avicennia officinalis and lichen of the genus Chrysothrix were found as common to all the study sites.The Jaccard similarity index study of lichen species between the study sites showed Kalibhanjadiya Island and Habelikhati as more similar in comparison of lichen species composition(i.e.,0.64).The occurrence of foliose and fruticose type of lichens showed the healthy and undisturbed mangrove forest conditions at many sites within Bhitarkanika National Park.
基金supported by the Natural Science Foundation of China(31988102,31872690)National Key R&D Program of China(2017YFA0604803).
文摘Sulfur is an essential functional element in leaves,and it plays important roles in regulating plant growth,development and abiotic stress resistance in natural communities.However,there has been limited information on the spatial variation in leaf sulfur content(LSC)and adaptive characters on a large community scale.Sulfur in leaves of 2207 plant species from 80 widespread ecosystems(31 forests,38 grasslands and 11 deserts)in China was measured.One-way analysis of variance with Duncan’s multiple-range tests were used to evaluate the differences in LSC among different plant growth forms and ecosystems.We fitted the relationships of LSC to spatial and climate factors using regression.Structural equation modeling analysis and phylogenetic analysis helped us further explore the main factors of LSC variation.LSC ranged from 0.15 to 48.64 g·kg^(-1),with an average of 2.13±0.04 g·kg^(-1) at the community scale in China.We observed significant spatial variation in LSC among different ecosystems and taxa.Overall,LSC was higher in arid areas and herbs.Furthermore,higher LSC was observed under environments of drought,low temperatures and intense ultraviolet radiation.Temperature,precipitation,radiation,soil sulfur content and aridity jointly regulated LSC,explaining 79%of the spatial variation.However,LSC was not significantly related to phylogeny.Our results demonstrate that LSC plays an important role in plant adaptations to extreme environments and further extend our understanding of the biological function of sulfur from the organ to the community level.These findings highlight the importance of sulfur metabolism for our understanding of the impact of global climate change on plants.
文摘Aims Species composition and diversity of the mountainous rangelands are results of interactions between environmental severities,het-erogeneous topography and facilitative effects by nurse plants.This research was aimed to compare relative effects of these three envi-ronmental variables on the natural vegetation of a mountainous rangeland.For a more detailed understanding,effects of four dif-ferent nurse species were separately compared on the various plant growth forms and on two community plant responses(diversity and abundance).Methods A mountainous semiarid rangeland was selected in Baharkish,Quchan,Northeast of Iran.Density and canopy cover of all plant species were recorded under the canopy of four different shrubs and in open areas,in north and south-facing aspects,and in a normal and a drought year.Shannon diversity,total abundance(%cover)and the abundance of different growth forms were used as crite-ria for assessing effects of the environmental variables.Data were arranged in a factorial combination and analyzed by three-way analysis of variance using a GLM analysis.Important Findings(i)Drought,aspect and canopy created niche differentiation:annual forbs and shrubs were more affected by drought,whereas geophytes and grasses were more responsive to slope aspects.Effects of drought and slope aspect were more profound on species diversity,whereas that of canopy facilitation was stronger on plant abundance.(ii)Canopy facili-tation was dependent on severity of the abiotic factors and life history of interacting species.Canopy facilitation allowed for the persistence of only annual forbs,but it was disadvantaged during the drought year.Plant community responses to abiotic factors(slope and drought)were more dependent on the plant growth form,while responses to canopy facilitation were more dependent on the morphology and/or ecology of nurse shrubs.(iii)Effect of shrubs was dependent on their morphology and ecology:shrubs with larger canopy area and nitrogen fixation capa-bility increased,but those with allelopathic effects or a dense canopy structure decreased the diversity of the understory species.
基金Ecuador’s SENESCYT(Secretaría Nacional de Educación Superior,Ciencia,Tecnología e Innovación)Dutch Ministry of Foreign Affairs(DUPC Program at UNESCO-IHE).
文摘Aims The importance of quantifying carbon stocks in terrestrial ecosystems is crucial for determining climate change dynamics.However,the present regional assessments of carbon stocks in tropical grasslands are extrapolated to unsampled areas with a high degree of uncertainty and without considering the carbon and nitrogen composition of vegetation and soil along altitudinal ranges.This study aims to assess carbon and nitrogen concentrations in soil and vegetation,aboveground carbon stocks distribution and soil organic carbon stocks along an altitudinal range in the páramo region in the Ecuadorian Andes.Methods The vegetation inventory was conducted using 15×15 m sampling plots distributed in three altitudinal ranges.Based on the patterns exhibited by the dominant vegetation growth forms,biomass and soil were sampled to quantify the corresponding carbon and nitrogen concentrations.Subsequently,the aboveground live biomass along the páramo altitudinal range was estimated using allometric equations.Finally,soil and vegetation carbon stocks were estimated for the entire basin.Important Findings Altitudinal analysis supported a potential distribution of carbon and nitrogen concentrations in soil,litter and live tissues,where higher concentrations were found in the low altitudinal range mainly for tussocks and acaulescent rosettes.Cellulose in litter showed higher concentrations at low altitudinal ranges for acaulescent rosettes and cushions only.For the same growth forms,lignin patterns in litter were higher in high altitudinal ranges.Soil texture provided complementary information:high percentage of silt was highly correlated to high soil nitrogen and carbon concentration.Tussocks were found to be responsive to altitude with their,highest aboveground carbon stocks occurring at the low altitudinal range,but cushions and acaulescent rosettes responded differently.The established relationships among soil,vegetation and altitude shown in this study must be taken into account to estimate both aboveground and soil organic carbon stocks in páramo regions—such estimates will be considerably inaccurate if these relationships are ignored.
基金This work was supported by the National Agency for Scientific,Technological Promotion(PICTs 1349,1368)the National Research Council of Argentina(PIP-112-200801-01664-CONICET,PIP-112-201301-00449-CONICET)in the framework of the Grant(PUE-IPEEC-CONICET 229201601000044).
文摘Aims Plants play an important role in ecosystem processes.Functional meaning of trait variation in wide environmental gradients is well known but is scarcely known across narrow gradients.We analyze the variation of morphological,physical and chemical traits of dom-inant plant species and the potential rates of dry mass loss and N release/immobilization during senesced leaf decomposition of these species across a narrow aridity gradient,and to identify indicative traits useful to set species functional groups sharing decomposition patterns.Methods We analyzed the variation of morphological,physical and chemical traits(specific leaf area,seed mass,N and soluble phenols in green and senesced leaves,plant height)in dominant plant species at 12 sites across an aridity gradient in northern Patagonia,Argentina.We collected senesced leaves of each plant species at each site and used them to estimate the poten-tial rates of dry mass loss and N release/immobilization from decomposing senesced leaves in a microcosm experiment.We analyzed the variation of plant traits and decomposition rates across the aridity gradient.We grouped plants species accord-ing to growth forms(perennial grasses,deciduous shrubs,ever-green shrubs)and different combinations of morpho-physical and chemical traits of green and senesced leaves and compared the potential rates of dry mass loss and N release/immobiliza-tion during leaf decomposition among these groups delimited by each grouping criteria.Important Findings Plant traits did not vary across the aridity gradient.The potential rate of dry mass loss was positively related to aridity,while the potential rate of N release/immobilization did not vary across the gradient.Grouping species by separately morpho-physical and chemical traits resulted in a large overlapping in mean values of decomposition rates among groups.In contrast,plant groupings based on growth forms and those including all morpho-physical and chemical traits of green or senesced leaves yielded groups with differentiated rates of decomposition processes.The two latter groupings clustered spe-cies from more than one growth form indicating some overlapping in the rates of decomposition processes among species of different growth forms.Among traits,N concentration in senesced leaves and plant height explained the highest variation in decomposition rates being positively related to potential rates of dry mass loss and N release/immobilization.We concluded that plant groupings based on morpho-physical and chemical traits of either green or senesced leaves may be more powerful to differentiate functional species groups sharing decomposition patterns than the growth form group-ing.Moreover,plant height and N concentration in senesced leaves may be considered relevant synthetic functional traits in relation to decomposition processes in narrow aridity gradients.
文摘Aims Several studies have shown that plant height changes along environmen-tal gradients.However,altitudinal patterns of plant height across species are still unclear,especially in regions sensitive to climate change.As canopy height decreases dramatically near the tree line in alpine areas,we hypothesize that plant height across all species also decreases with increasing altitude,and distinct thresholds exist along this gradient.Methods Using a large dataset of maximum plant height and elevation range(400 to 6000 m a.s.l.)of 4295 angiosperms from the regional flora of the Tibetan Plateau,we regressed plant height for every 100 m belt against elevation to explore the relationships.To identify the approximate boundaries where dramatic changes in plant height occurs for herbaceous plants,shrubs,trees,woody plants and all angiosperms,we used piecewise linear regression.Phylogenetically independent contrast was used to test the potential evolutionary influences on altitudinal patterns at the family level.Important Findings Results showed that for herbaceous plants,shrubs,trees,woody plants and all angiosperms,plant height decreases significantly as altitude increases.In addition,we found that altitude,a proxy for many environmental factors,had obvious thresholds(breakpoints)dictating patterns of plant height.The results of phylogenetically independent contrast also emphasized the importance of evolution-ary history in determining the altitudinal patterns of plant height for some growth forms.Our results highlight the relative intense filter-ing effect of environmental factors in shaping patterns of functional traits and how this could vary for different ranges of environmental variables.
