Influence of tree species on soil microbial residue accumulation and distribution among soil aggregates in subtropical plantations of China

Background Microbial residues are significant contributors to stable soil organic carbon(SOC).Soil aggregates effectively protect microbial residues against decomposition;thus,microbial residue accumulation and distribution among soil aggregates determine long-term SOC stability.However,how tree species influence accumulation and distribution of soil microbial residues remains largely unknown,hindering the chances to develop policies for SOC management.Here,we investigated microbial residue accumulation and distribution in soil aggregates under four subtropical tree species(Cunninghamia lanceolata,Pinus massoniana,Michelia macclurei,and Schima superba)after 29 years of afforestation.Results Accumulation of microbial residues in the 0-10 cm soil layer was 13.8-26.7%higher under S.superba than that under the other tree species.A structural equation model revealed that tree species affected the accumulation of microbial residues directly by altering fungal biomass.Additionally,tree species significantly affected microbial residue distribution and contribution to SOC in the top 20 cm soil.In particular,microbial residue distribution was 17.2-33.4%lower in large macro-aggregates(LMA)but 60.1-140.7%higher in micro-aggregates(MA)under S.superba than that under the other species in the 0-10 cm soil layer,and 14.3-19.0%lower in LMA but 43-52.1%higher in MA under S.superba than that under C.lanceolata and M.macclurei in the 10-20 cm soil layer.Moreover,the contribution of microbial residues to SOC was 44.4-47.5%higher under S.superba than under the other tree species.These findings suggest a higher stability of microbial residues under S.superba than that under the other studied tree species.Conclusions Our results demonstrate that tree species influence long-term microbial persistence in forest soils by affecting accumulation and stabilization of microbial residues.

Changes in fish resources 5 years after implementation of the 10-year fishing ban in the Chishui River,the first river with a complete fishing ban in the Yangtze River Basin

Background To rehabilitate the depleted fish resources of the Yangtze River Basin,China,a 10-year fishing ban has been implemented.This national initiative has attracted worldwide attention.The present study aimed to explore the ecological process and recovery effectiveness of this complete fishing ban in the Chishui River,the first river where the fishing ban was enacted in the Yangtze River Basin.Changes in fish resources were analyzed based on investigations conducted 5 years before(2012–2016)and 5 years after(2017–2021)the implementation of the fish-ing ban in four reaches along the longitudinal gradient.Results A total of 140 fish species,including 127 native and 13 exotic species,were collected during the study period.The number of fish species as well as the diversity indices showed no significant temporal changes.However,11 native species that had disappeared for many years appeared again after the fishing ban.The occurrence rates of some key protected species,Procypris rabaudi,Acipenser dabryanus,Euchiloglanis davidi and Myxocyprinus asiaticus,increased after the fishing ban,while Coreius guichenoti,Percocypris pingi,Onychostoma angustistomata and Leptobotia rubrilabris showed no obvious recovery.The fish assemblage structure in nearly all reaches(except the headwater)showed significant temporal changes with an increase in the relative abundance of larger body-sized species.The population structure of most dominant species improved greatly with the mean standard length and the mean body weight as well as the proportion of larger-sized individuals clearly increasing.In addition,the density of fishes changed dramatically with the catch per unit effort(CPUE)increasing by 140–210%for different study reaches.Conclusions The present study confirmed that the complete fishing closure is an effective measure to facilitate fish resources recovery.These results provide valuable references for evaluating the effectiveness of the 10-year fishing ban policy in the entire Yangtze River.

A large carbon sink induced by the implementation of the largest afforestation program on Earth

Background Three-North Afforestation Program(TNAP)in China is the largest ecological restoration project on Earth(ongoing from 1978 to 2050),harboring a huge area of newly planted forests,which provides a wealth of goods and ecosystem services that benefit society at levels ranging from region to East Asia.This project-induced carbon(C)sink has been expected to be large,but its size and location remain uncertain.Results In this study,we investigated the changes in the C stocks of biomass,soil C and the C accumulation ben-efited from the ecological effects in the project areas from 1978 to 2017 within the Three-North regions(4.069×10^(6)km^(2)),and evaluated its project-induced C sequestration.Using a combination of remote sensing images,field obser-vations and national forest inventory data,we estimated a total ecosystem sink of 47.06 Tg C per year(1 Tg=10^(12)g)increased by the TNAP implementation.Importantly,we first found that the C sink via the ecological effects of this project could contribute to a high proportion up to 15.94%,indicating a critical role of ecological effects in shaping the distribution of C stocks in the protective forests.This finding suggests that it is necessary to explicitly consider carbon sequestration benefited from the ecological effects when estimating C sink and parameterizing C models of the restoration projects in China and globally.Conclusions Our results update the estimates of C pools in the world’s largest ecological restoration project area,demonstrating that this project has substantially contributed to mitigating the climate change.

Assessing effectiveness of nature-based solution with big earth data:60 years mangrove plantation program in Bangladesh coast

Background In the climate change context,nature-based solution(NBS)is considered one of the effective tools to increase the resilience of socio-ecological system.The concept coincides with the government’s attempts of afforestation and reforestation programs that have been going on for 60 years in Bangladesh.This study,therefore,envisaged understanding how NBS(mangrove afforestation and reforestation)works to promote climate change resilience through the synthetization of remote sensing-based big earth data,statistical tools,and models.The study took the entire coast of Bangladesh except for Sundarbans Reserve Forest and rolled back to 1962 to work on 60 years’time series data.Declassified CORONA satellite imagery along with Landsat satellite imagery was used,which is the first-ever attempt in the remote sensing-based ecosystem work in Bangladesh.Results The study’s main innovation is to spatially establish the effectiveness of the NBS.The study critically assessed and estimated stable lands and their socio-economic benefits as part of the effectiveness of the NBS.As part of the NBS-derived benefits in the context of climate change,it estimated the sequestrated carbon in mangrove forests.A significant positive relationship was observed between the increase of mangroves and stable lands.Near about 448,011 ha of agricultural land was stabilized due to the NBS intervention whose economic value is 18,837 million USD.In addition,29,755.71 kt of carbon have been sequestrated due to NBS program.Conclusions The concept of NBS is still in the development stage and very little or no work has been done so far in measuring and labeling the effectiveness of the NBS.Therefore,our study can innovatively contribute to the scientific community to show the effectiveness of the NBS in three domains(social,economic and ecological)in the changing climatic scenario.

Application of pressure-state-response approach for developing criteria and indicators of ecological health assessment of wetlands:a multi-temporal study in Ichhamati floodplains,India

Background Tropical floodplain wetlands are among the most disturbed and intensively harvested ecosystems.Their sustainable management is often hindered due to the lack of comprehensive,coherent,and standardized assessment frameworks of wetland ecological health(WEH).In this study,a set of appropriate criteria and indicators(C&I)of WEH assessment was developed and tested on seven wetlands of River Ichhamati,eastern India.Methods Based on the pressure-state-response(PSR)approach,evaluation indicators representing ecological,socio-economic,and institutional sustainability issues of floodplain wetland systems were either selected or formulated through literature survey and stakeholder consensus.Weights of indicators were assigned by the entropy weighting method and then used in the Technique for Order of Preference by Similarity to Ideal Solution model to determine the Euclidean distances of each wetland from the positive ideal solution and negative ideal solution.Subsequently,a comprehensive wetland ecological health index(CWEHI)was constructed from these distances to portray the condition of any PSR system component in a wetland under a fivefold classification scheme,namely‘excellent health’(CWEHI≥0.81),‘good health’(0.61-0.80),‘moderate health’(0.41-0.60),‘weak health’(0.21-0.40),and‘morbid’(≤0.20).Results The developed C&I set contains 8 criteria and 38 indicators under pressure component,7 criteria and 49 indicators under state component,as well as 4 criteria and 18 indicators under response component.When applied in 2016 and 2022,it was found that the Panchita and Aromdanga wetlands were continuously in weak and morbid health status,while the Madhabpur wetland always showed an excellent or good status for all components.Health of other wetlands oscillated between moderate and morbid health across assessment years and system components.Conclusions The developed C&I set was found to be a flexible,holistic,and refined framework that could be applied elsewhere in similar assessments with minor indicator-level adjustments.The present assessment inferred that agriculture-dominated wetlands were more affected by amplified environmental pressure than fishing-dominated wetlands.Absence of persistent water flow from main river channel,wide-spread jute-retting,agriculture-induced eutrophication,proliferation of aquatic weeds were identified as the major causes of rapid ecological deterioration.

Quantifying the impacts of spatiotemporal land use and land cover changes on soil loss across agroecologies and slope categories using GIS and RUSLE model in Zoa watershed,southwest Ethiopia

Background Soil erosion in Ethiopian highlands is highly consistent with land use/land cover(LULC)changes that are associated with deforestation and a decline in biodiversity.However,identifying soil erosion-prone areas and quantifying soil loss in rugged terrains and various agroecologies due to LULC changes have not been dedicated to scientific studies.Therefore,we quantified the impacts of spatiotemporal LULC changes on soil loss across agroecologies and slope categories using GIS and RUSLE model from 1985 to 2021 in Zoa watershed,southwest Ethiopia.Moreover,prioritizing erosion severity risks at sub-watersheds and quantifying temporal sediment yield is essential for better conservation planning.Landsat images,rainfall,Digital Elevation Model,and soil data were obtained from field observations and secondary sources.Results Bareland and farmland have been expanding at the expense of other land use types.The annual soil loss in the watershed ranged from 0 to 113.21 t ha^(-1) year^(-1),0 to 163.16 t ha^(-1) year^(-1),and 0 to 194.58 t ha^(-1) year^(-1)with a mean annual soil loss of 21.07,29.35 and 40.93 t ha^(-1) year^(-1) in 1985,2000,and 2021,respectively.Among LULC classes,the highest soil loss was generated from bareland(31.73 t ha^(-1) year^(-1))and farmland(27.08 t ha^(-1) year^(-1))in 1985 later upsurged to 35.52 t ha^(-1) year^(-1)and 59.91 t ha^(-1) year^(-1) in 2021,respectively,due to the maximum susceptibility of soil erosion risks from unprotected surfaces.The results also revealed that the lowland agroecology generated the highest mean soil loss of 24.05 t ha^(-1) year^(-1)in 1985,39.74 t ha^(-1) year^(-1) in 2000,and increased to 57.55 t ha^(-1) year^(-1)in 2021.Considering the slope categories,the highest and most excruciating soil loss was engendered from steep(35.55–60.78 t ha–1 year–1)and very steep(52.48–72.69 t ha^(-1) year^(-1))slope terrains during 1985–2021.The northwestern part of the watershed is the most erosion-prone area which is now expanding to the central and western parts of the watershed.The sediment yield increased at the fastest rate at the watershed outlet,from 39.3%in 1985 to 94.26%in 2021.Conclusions The results of this study indicated that the conversion of other LULC categories into farmland was the most detrimental to a watershed in terms of soil loss,which necessitates the implementation of appropriate soil and water conservation measures with effective design by considering spatial variability to reduce soil erosion hazards.

The assessment of climatic,environmental,and socioeconomic aspects of the Brazilian Cerrado

Background The Cerrado is the most biodiverse savanna and maintains other biomes.Aware of its significance,this paper evaluated the Brazilian Cerrado’s climatic,environmental,and socioeconomic aspects using remote sensing data and spatial statistics(correlation analysis and principal components analysis—PCA).Following the measures of sample adequacy(MSA)and Kaiser–Meyer–Olkin(KMO)tests,seventeen variables were evaluated.Results The MSA revealed that the dataset had a good quality(0.76),and nine variables were selected:elevation,evapotranspiration,active fires,Human Development Index(HDI),land use and land cover(LULC;shrubland and cropland/rainfed),rainfall(spring and autumn),and livestock.The correlation matrix indicated a positive(negative)association between HDI and autumn rainfall(HDI and active fires)with a value of 0.77(-0.55).The PCA results determined which three principal components(PC)were adequate for extracting spatial patterns,accounting for 68.02%of the total variance with respective values of 38.59%,16.89%,and 12.5%.Due to economic development and agribusiness,Cerrado’s northern(central,western,and southern)areas had negative(positive)score HDI values,as shown in PC1.Climatic(rainfall—spring and fall)and environmental(cropland/rainfed and shrubland)aspects dominated the PC2,with negative scores in northern and western portions due to the transition zone between Amazon and Cerrado biomes caused by rainfall variability.On the other hand,environmental aspects(LULC-shrubland and elevation)influenced the PC3;areas with high altitudes(>500 m)received a higher score.Conclusion Agricultural expansion substantially affected LULC,leading to deforestation-caused suppression of native vegetation.

Symbiotic mycorrhizal types affect patterns of tree aboveground and belowground C allocation in Northeast China

Background Given the ubiquitous nature of mycorrhizal symbioses,different symbiotic fungi have obvious differences in structure and function,which may affect associated tree aboveground and belowground C allocation dynamics.However,the mechanisms underlying tree aboveground and belowground C allocation and its response to symbiotic mycorrhizal types and other factors(e.g.,resource availability)remain poorly understood.Results We used forest inventory data to explore the potential mechanism of tree aboveground and belowground C allocation patterns in Northeast China.Our results showed that tree-fungal symbioses were related to the patterns of tree C allocation.The ratio of aboveground to belowground C pool was significantly higher in ectomycorrhizal(EM)-associated trees than that in arbuscular mycorrhizal(AM)-associated trees.Symbiotic mycorrhizal types were associ-ated with the responses of tree aboveground and belowground C allocation to different factors,such as mean annual precipitation(MAP)and mean annual temperature(MAT).Almost all factors significantly increased aboveground C allocation in AM-associated trees but significantly decreased it in EM-associated trees.Moreover,after controlling the other factors,the effects of climate factors(MAT and MAP)on the C allocation of AM-and EM-associated trees were similar.Increases in MAT and MAP significantly increased belowground and aboveground C allocation,respectively.Conclusions Our results demonstrate symbiotic mycorrhizal types play an important role in controlling tree aboveground and belowground C allocation and dynamics.

Ecological niche modelling of a critically endangered species Commiphora wightii (Arn.) Bhandari using bioclimatic and non-bioclimatic variables

Background The aim of this study is to examine the effects of four different bioclimatic predictors(current,2050,2070,and 2090 under Shared Socioeconomic Pathways SSP2-4.5)and non-bioclimatic variables(soil,habitat heterogeneity index,land use,slope,and aspect)on the habitat suitability and niche dimensions of the critically endangered plant species Commiphora wightii in India.We also evaluate how niche modelling affects its extent of occurrence(EOO)and area of occupancy(AOO).Results The area under the receiver operating curve(AUC)values produced by the maximum entropy(Maxent)under various bioclimatic time frames were more than 0.94,indicating excellent model accuracy.Non-bioclimatic characteristics,with the exception of terrain slope and aspect,decreased the accuracy of our model.Additionally,Maxent accuracy was the lowest across all combinations of bioclimatic and non-bioclimatic variables(AUC=0.75 to 0.78).With current,2050,and 2070 bioclimatic projections,our modelling revealed the significance of water availability parameters(BC-12 to BC-19,i.e.annual and seasonal precipitation as well as precipitation of wettest,driest,and coldest months and quarters)on habitat suitability for this species.However,with 2090 projection,energy variables such as mean temperature of wettest quarter(BC-8)and isothermality(BC-3)were identified as governing factors.Excessive salt,rooting conditions,land use type(grassland),characteristics of the plant community,and slope were also noticed to have an impact on this species.Through distribution modelling of this species in both its native(west-ern India)and exotic(North-east,Central Part of India,as well as northern and eastern Ghat)habitats,we were also able to simulate both its fundamental niche and its realized niche.Our EOO and AOO analysis reflects the possibility of many new areas in India where this species can be planted and grown.Conclusion According to the calculated area under the various suitability classes,we can conclude that C.wight-ii’s potentially suitable bioclimatic distribution under the optimum and moderate classes would increase under all future bioclimatic scenarios(2090>2050≈current),with the exception of 2070,demonstrating that there are more suitable habitats available for C.wightii artificial cultivation and will be available for future bioclimatic projections of 2050 and 2090.Predictive sites indicated that this species also favours various types of landforms outside rocky environments,such as sand dunes,sandy plains,young alluvial plains,saline areas,and so on.Our research also revealed crucial information regarding the community dispersion variable,notably the coefficient of variation that,when bioclimatic non-bioclimatic variables were coupled,disguised the effects of bioclimatic factors across all time frames.

Neocosmopolitan distributions of invertebrate aquatic invasive species due to euryhaline geographic history and human-mediated dispersal:Ponto-Caspian versus other geographic origins

Background:Aquatic invertebrate species that have broad salinity tolerances may be pre-adapted for invasion success and biogeographic distributional range expansions,facilitated by human-mediated dispersal(HMD),leading to a trend to become neocosmopolitan across many regions of the world.This pattern appears to characterize many Ponto-Caspian(P-C)aquatic invertebrates,which have a>100-year history as aquatic invasive species(AIS),spreading throughout much of Eurasia and for some,in North America and beyond.Our study compiles comparative salinity conditions and distributional data for AIS invertebrate species globally versus those originating from the P-C region,to test whether they statistically differ.Results:Our investigation discerns that a total of 1861 invertebrate AIS taxa have been recorded worldwide,with(A)70.5%exclusively living in the saline adaptive zone of brackish(0.5-30 ppt;A1)and/or marine waters(>30 ppt;A2),(B)20%in the freshwater adaptive zone alone(0-0.5 ppt),(C)7.5%being euryhaline(across both A and B),and(D)2%being semi-aquatic in either(D1)freshwater/terrestrial or(D2)saline/terrestrial environments.In contrast,our results indicate the following proportions for AIS invertebrates of P-C origins:(A)27%exclusively inhabit the saline adaptive zone,(B)25%are entirely freshwater,(C)45%are euryhaline,and(D)3%are semi-aquatic,significantly differing from the global pattern.Euryhaline AIS native to the P-C region thus markedly outnumber(45%)those originating from other regions(7.5%),likely pre-adapting them for widespread establishment in harbors,estuaries,and coastal areas.Moreover,most P-C invertebrate AIS(70%)contain freshwater-tolerant populations(B+C),rendering them very successful invaders of inland water bodies.These broad salinity tolerances of P-C AIS underlie their tremendous invasion successes and growing neocosmopolitan distributions with HMD.Conclusions:An evolutionary and recent history of broad salinity tolerances of a large proportion of P-C invertebrates appears to enhance their ability to invade,establish,and spread in new regions,especially harbors,estuaries,and freshwaters,leading to their increasing neocosmopolitan distributions.This trend likely will continue-accelerating with climate change and increased global transportation-meriting worldwide conservation agency focus and cooperation,along with public education programs aimed to rapidly identify and circumvent new introductions and spread.

Non-native plant species richness and influence of greenhouses and human populations in the conterminous United States

Background One issue in invasive plant ecology is identification of the factors related to the invasion process that increase number of non-native species.When invasion by non-native species increases,so does the probability that some non-native species will become harmful,or classified as invasive species,which disrupt natural ecosystems with attendant economic and social costs.I quantified patterns of how non-native species richness varied with vegetation types and human populations.To evaluate the relative importance of different predictor variables for invasion pathways in the conterminous United States,I modeled non-native plant species richness by county compared to current and historical human populations;greenhouses and nurseries;railroads,pipelines,transmission lines,and oil and gas wells;and land covers of impervious surface,development intensity categories,agriculture,and vegetation types.I also modeled these variables within vegetation types,excluding vegetation variables.Results To summarize patterns,non-native plant species richness increased from 72 to 200 with increasing human population density classes.Forests and forest land use mosaics had the greatest mean number of non-native plant species,ranging from 121 to 166,whereas grasslands and grassland mosaics had the least number of non-native plant species,about 70.For modeling variable importance,all combined variables had R^(2)values of 56%(random forests regressor)and 54%(cubist regressor)for predictions of withheld observations of non-native plant species rich-ness,with greenhouse density and percent forestlands as most influential variables.Single variables of greenhouses(R^(2)=29%),historical and current human populations(R^(2)=27%and 23%),impervious surface(25%),and medium intensity development(23%)were most associated with non-native plant species richness.For vegetation types,greenhouse and historical human population densities were influential variables particularly in forestlands,shrublands,and wetlands.Conclusions Based on these models,human population measures and horticultural locations of greenhouses and plant nurseries may have stronger relationships than measures of land use disturbance and transport with non-native plant species richness.

Grazing effects on vegetation dynamics in the savannah ecosystems of the Sahel

Background The savannah ecosystems of Sahel have experienced continuous and heavy grazing of livestock for centuries but still,their vegetation response to grazing pressure remains poorly understood.In this study,we analysed the herbaceous plant dynamics,measured by species diversity,composition,cover,and biomass in response to grazing pressure in the savannah ecosystems of Sahel.In Senegal,we selected four savannah sites represented with high,moderate,light and no grazing intensity levels.Transect survey methods were used for sampling the vegetation data within each of the sites.Species richness and composition were analysed using species accumulation curve and multivariate analyses.Furthermore,we used General Linear Models and a piecewise Structural Equation Model(pSEM)to examine the relationships between grazing intensity,vegetation cover,diversity and biomass.Results The herbaceous species diversity and composition varied significantly among the different grazing intensity levels(p<0.001).The plant species composition shifted from the dominance of grass cover to the dominance of forb cover with increasing grazing pressure.Moreover,the attributes of species diversity,herbaceous biomass,and ground cover were higher on sites with low grazing than sites with high and moderate grazing intensity.Across all sites,species diversity was positively related to total biomass.The pSEM explained 37%of the variance in total biomass and revealed that grazing intensity negatively influenced total biomass both directly and indirectly through its negative influence on species diversity.Conclusions Managing grazing intensity may lead to higher plant production and higher mixed forage establishment in the dryland savannah ecosystems.This information can be used to support land management strategies and promote sustainable grazing practices that balance the needs of livestock with the conservation of ecosystem health and biodiversity.

Relationship between species richness,taxonomic distinctness,functional diversity,and local contribution toβdiversity and effects of habitat disturbance in the riparian spider community of the Ganga River,India

Background In the riverine riparian ecosystem,particularly in India,the knowledge of the effects of habitat disturbance on taxonomic distinctness,functional diversity,and local contribution toβdiversity(LCBD)of spider community is elusive.The present study examined the relationships between the index of taxonomic distinctness(Δ^(+)),index of variation in taxonomic distinctness(λ^(+)),functional evenness(FEve),functional divergence(FDiv),functional dispersion(FDis),and LCBD of spider community of the Ganga River and the effects of habitat disturbance on these indices.A total of 27 sampling sites were selected along the bank of the Ganga River.Based on the rating of the disturbance scores,the sites were classified into lowly,moderately,and highly disturbed sites.To understand the relationships between species richness,Δ^(+),λ^(+),FDis,FDiv,FEve,LCBD,and habitat disturbance score,Pearson’s correlation was calculated,followed by the linear regression model.The one-way multivariate analysis of variance was used to find differences in taxonomic distinctness and functional diversity in the different disturbed sites.Results Significant relationships were found betweenλ^(+)andΔ^(+),FDis andΔ^(+),FDis andλ^(+),FDiv and species richness,FEve and species richness,FEve andλ^(+),FEve and habitat disturbance,LCBD and FEve,and LCBD and habitat disturbance.A significant difference was present in the indices of functional diversity between the lowly,moderately,and highly disturbed sites.Agriculture,garbage dump,human settlement,and created embankment influenced the spider community’sλ^(+),FEve,and LCBD.Conclusion Unrestrained anthropogenic activities exacerbate habitat disturbance by affecting ecological processes.Thus,understanding linkages between ecosystem disturbance,taxonomic,functional,andβdiversity can be fundamental to managing and conserving natural resources.This work highlights the importance of including taxonomic and functional diversity to comprehend the impact of habitat disturbance on riverine riparian spiders beyond just the number of species.An integrated taxonomic and functional diversity approach coupled withβdiversity can be used to support environmental assessment,restoration,and conservation planning of the biological resources of the Ganges River.

Does climate change alter the nutrient trends of Cedrela fissilis Vell.trees in the southern Brazilian Amazon?

Background The increase in the frequency and intensity of droughts is pointed out as one of the main factors altering biogeochemical cycles in the Amazon basin.An eco-nutritional approach using X-ray fluorescence micro-analysis(μXRF)is proposed to verify the long-and short-term effects of droughts on the growth and xylem nutrient concentrations of Cedrela fissilis Vell.Methods Fourteen radii were selected from a tree-ring width chronology and X-rayed by Itrax Multiscanner.Profiles of ring width,wood density,and concentrations of aluminum(Al),phosphorus(P),sulfur(S),calcium(Ca),potassium(K),manganese(Mn),iron(Fe)and strontium(Sr)together with Al/Ca,Ca/Mn,K/Ca,Sr/Ca and Mn/S ratios were constructed and correlated with precipitation,temperature,the difference between precipitation and potential evapotranspiration(P-PET)and standardized precipitation-evapotranspiration index(SPEI).Results During dry years,C.fissilis showed narrower,less dense rings,lower Al,P,S and Ca,and higher K and Fe concentrations(the opposite was found in wet years).Ring width decreased(together with Al,P,S,K,Ca,Mn,Fe,Sr,Al/Ca,K/Ca and Sr/Ca)and wood density increased(together with Ca/Mn and Mn/S),which was associated with an increase in evapotranspiration and temperature over time,mainly since 1990.Cedrela fissilis showed a tendency to increase its capacity for resistance,and a recovery and resilience in growth over time associated with responses in Al,Ca,P and S.However,it showed a risk in the capacity for recovery of the pre-drought density values,associated with unsatisfactory responses in Al,Ca,K,Fe and P.Conclusions This study is the first attempt to analyze tree-ring nutritional evidences of C.fissilis trees to climate sensitivity and resilience to drought,based on long-term data from seasonal moist tropical forests of the Amazon.Our data suggested that C.fissilis is undergoing alterations in the concentration,use and redistribution of nutrients associated with increasing wood density and decreasing growth over time,due to the increase of drought frequency in the southern Amazon.

Functional responses to deforestation in fish communities inhabiting neotropical streams and rivers

Background Deforestation is a widespread disturbance for neotropical freshwater ecosystems.While biodiversity declines have been associated with deforestation,its functional consequences for stream and river fish faunas remain poorly understood.In this study,we explored how deforestation affects the different facets of the functional structure of fish communities inventoried using environmental DNA metabarcoding in 64 river and 35 stream sites of French Guiana.Specifically,we investigated how functional richness,divergence,evenness and identity of fish faunas are affected by deforestation.Results We showed that anthropogenic disturbances in French Guiana are modifying the functional diversity of freshwater fish communities.These disturbances not only affected the amount of functional traits held by the communities but also the identity of the traits and the internal structure of the functional space.Consequently,different facets of the functional diversity supported by fish assemblages were altered.In streams,deforestation did not affect the overall diversity of traits but reduced functional redundancy,underlined by a shift in functional identity towards assemblages dominated by pelagic detritivores.In contrast,river fish faunas experienced a decline in functional richness,paired with shifts in functional identity and a loss of fish species with extreme functions.Conclusions The response to deforestation differed between streams and rivers,but it supports the hypothesis that deforestation is linked to functional changes in fish assemblages.By diminishing the range of the functions in rivers or by jeopardizing the redundancy of functions in streams,deforestation could severely hamper the functioning and stability of neotropical freshwater ecosystems.

Large-diameter trees and deadwood correspond with belowground ectomycorrhizal fungal richness

Background: Large-diameter trees have an outsized influence on aboveground forest dynamics, composition, and structure. Although their influence on aboveground processes is well studied, their role in shaping belowground fungal communities is largely unknown. We sought to test if (i) fungal community spatial structure matched aboveground forest structure;(ii) fungal functional guilds exhibited differential associations to aboveground trees, snags, and deadwood;and (iii) that large-diameter trees and snags have a larger influence on fungal community richness than smaller-diameter trees. We used MiSeq sequencing of fungal communities collected from soils in a spatially intensive survey in a portion of Cedar Breaks National Monument, Utah, USA. We used random forest models to explore the spatial structure of fungal communities as they relate to explicitly mapped trees and deadwood distributed across 1.15 ha of a 15.32-ha mapped subalpine forest. Results: We found 6,177 fungal amplicon sequence variants across 117 sequenced samples. Tree diameter, dead-wood presence, and tree species identity explained more than twice as much variation (38.7% vs. 10.4%) for ectomy-corrhizal composition and diversity than for the total or saprotrophic fungal communities. Species identity and dis-tance to the nearest large-diameter tree (≥ 40.2 cm) were better predictors of fungal richness than were the identity and distance to the nearest tree. Soil nutrients, topography, and tree species differentially influenced the composition and diversity of each fungal guild. Locally rare tree species had an outsized influence on fungal community richness. Conclusions: These results highlight that fungal guilds are differentially associated with the location, size, and species of aboveground trees. Large-diameter trees are implicated as drivers of belowground fungal diversity, particularly for ectomycorrhizal fungi.

Comparing leaf area index estimates in a Mediterranean forest using field measurements, Landsat 8, and Sentinel-2 data

Background Leaf area index(LAI)is a key indicator for the assessment of the canopy’s processes such as net primary production and evapotranspiration.For this reason,the LAI is often used as a key input parameter in ecosystem services’modeling,which is emerging as a critical tool for steering upcoming urban reforestation strategies.However,LAI field measures are extremely time-consuming and require remarkable economic and human resources.In this context,spectral indices computed using high-resolution multispectral satellite imagery like Sentinel-2 and Landsat 8,may represent a feasible and economic solution for estimating the LAI at the city scale.Nonetheless,as far as we know,only a few studies have assessed the potential of Sentinel-2 and Landsat 8 data doing so in Mediterranean forest ecosystems.To fill such a gap,we assessed the performance of 10 spectral indices derived from Sentinel-2 and Landsat 8 data in estimating the LAI,using field measurements collected with the LI-COR LAI 2200c as a reference.We hypothesized that Sentinel-2 data,owing to their finer spatial and spectral resolution,perform better in estimating vegetation’s structural parameters compared to Landsat 8.Results We found that Landsat 8-derived models have,on average,a slightly better performance,with the best model(the one based on NDVI)showing an R^(2) of 0.55 and NRMSE of 14.74%,compared to R^(2) of 0.52 and NRMSE of 15.15%showed by the best Sentinel-2 model,which is based on the NBR.All models were affected by spectrum saturation for high LAI values(e.g.,above 5).Conclusion In Mediterranean ecosystems,Sentinel-2 and Landsat 8 data produce moderately accurate LAI estimates during the peak of the growing season.Therefore,the uncertainty introduced using satellite-derived LAI in ecosystem services’assessments should be systematically accounted for.

Reimagining large river management using the Resist-Accept-Direct(RAD)framework in the Upper Mississippi River

Background Large-river decision-makers are charged with maintaining diverse ecosystem services through unprec-edented social-ecological transformations as climate change and other global stressors intensify.The interconnected,dendritic habitats of rivers,which often demarcate jurisdictional boundaries,generate complex management chal-lenges.Here,we explore how the Resist–Accept–Direct(RAD)framework may enhance large-river management by promoting coordinated and deliberate responses to social-ecological trajectories of change.The RAD frame-work identifies the full decision space of potential management approaches,wherein managers may resist change to maintain historical conditions,accept change toward different conditions,or direct change to a specified future with novel conditions.In the Upper Mississippi River System,managers are facing social-ecological transformations from more frequent and extreme high-water events.We illustrate how RAD-informed basin-,reach-,and site-scale decisions could:(1)provide cross-spatial scale framing;(2)open the entire decision space of potential management approaches;and(3)enhance coordinated inter-jurisdictional management in response to the trajectory of the Upper Mississippi River hydrograph.Results The RAD framework helps identify plausible long-term trajectories in different reaches(or subbasins)of the river and how the associated social-ecological transformations could be managed by altering site-scale conditions.Strategic reach-scale objectives may reprioritize how,where,and when site conditions could be altered to contribute to the basin goal,given the basin’s plausible trajectories of change(e.g.,by coordinating action across sites to alter habitat connectivity,diversity,and redundancy in the river mosaic).Conclusions When faced with long-term systemic transformations(e.g.,>50 years),the RAD framework helps explicitly consider whether or when the basin vision or goals may no longer be achievable,and direct options may open yet unconsidered potential for the basin.Embedding the RAD framework in hierarchical decision-making clarifies that the selection of actions in space and time should be derived from basin-wide goals and reach-scale objectives to ensure that site-scale actions contribute effectively to the larger river habitat mosaic.Embedding the RAD framework in large-river decisions can provide the necessary conduit to link flexibility and innovation at the site scale with stability at larger scales for adaptive governance of changing social-ecological systems.

How can ecosystem engineer plants boost productivity in east Mediterranean drylands

Background Water availability is the key limiting factor for plant productivity in drylands covering ca.40%of Earth’s land surface.For such ecosystems to retain productivity and biodiversity under climatic change,it would be valu-able to identify/promote keystone plant species that(i)have developed strategies to more efficiently utilize moisture resources not easily accessible and(ii)improve moisture conditions for neighboring plants.The very deep-rooted Ziziphus lotus,considered an ecosystem engineer,is one such example.However,it is not known which biotic traits:(a)canopy interception of moisture/rainfall,(b)hydraulic redistribution of deep ground moisture by roots,or non-biotic factors:(c)soil’s volume,and(d)organic matter content,Z.lotus activates/modulates to play such a role.We,thus,selected dryland ecosystems where the plant dominates and measured for potential effects on the less deep-rooted Thymbra capitata.For assessing impacts on ecosystem productivity,we measured the spatial aggregation of ca.3600 T.capitata plants.As a proxy for soil moisture availability and its spatial variability,we conducted a 7-year-long study using thymes’nighttime rehydration.Sampling extended up to 15 m away from Z.lotus.Results The density of T.capitata plants growing up to 5 m around Z.lotus vs.thymes growing 10-15 m away was found significantly increased(2.5-4.5 times),while their stem/leaf moisture was ca.10%higher at predawn compared to nightfall during the dry season.This suggests that ecosystem productivity is driven by a greater soil moisture avail-ability around Z.lotus permitting more thyme daytime transpiration,in contrast to thymes growing further away.The phenomenon appeared only under dry topsoil(during the dry season;becoming stronger during dry years).Morning dew/rainfall interception from the canopy or soil depth/organic matter did not show significant effects,leaving only the hydraulic lift properties of Z.lotus as the most likely driver for soil moisture availability.Conclusions The deep-rooting properties and hydraulic lift potential of Z.lotus may be the key in permitting it to boost ecosystem productivity.Such hydraulic plant traits require more attention as they may prove valuable in com-bating desertification and restoring ecosystems in arid/semiarid regions threatened by climate change.

Modeling effects of abiotic factors on the abundances of eight woody species in the Harana forest using artificial networks,random forest,and generalized linear models

Background Abiotic factors exert different impacts on the abundance of individual tree species in the forest but little has been known about the impact of abiotic factors on the individual plant,particularly,in a tropical forest.This study identified the impact of abiotic factors on the abundances of Podocarpus falcatus,Croton macrostachyus,Celtis africana,Syzygium guineense,Olea capensis,Diospyros abyssinica,Feliucium decipenses,and Coffea arabica.A systematic sample design was used in the Harana forest,where 1122 plots were established to collect the abundance of species.Random forest(RF),artificial neural network(ANN),and generalized linear model(GLM)models were used to examine the impacts of topographic,climatic,and edaphic factors on the log abundances of woody species.The RF model was used to predict the spatial distribution maps of the log abundances of each species.Results The RF model achieved a better prediction accuracy with R^(2)=71%and a mean squared error(MSE)of 0.28 for Feliucium decipenses.The RF model differentiated elevation,temperature,precipitation,clay,and potassium were the top variables that influenced the abundance of species.The ANN model showed that elevation induced a nega-tive impact on the log abundances of all woody species.The GLM model reaffirmed the negative impact of elevation on all woody species except the log abundances of Syzygium guineense and Olea capensis.The ANN model indicated that soil organic matter(SOM)could positively affect the log abundances of all woody species.The GLM showed a similar positive impact of SOM,except for a negative impact on the log abundance of Celtis africana at p<0.05.The spatial distributions of the log abundances of Coffee arabica,Filicium decipenses,and Celtis africana were confined to the eastern parts,while the log abundance of Olea capensis was limited to the western parts.Conclusions The impacts of abiotic factors on the abundance of woody species may vary with species.This ecological understanding could guide the restoration activity of individual species.The prediction maps in this study provide spatially explicit information which can enhance the successful implementation of species conservation.