Indicators Of Ecosystem Function Research Articles

‘rtry’: An R package to support plant trait data preprocessing

AbstractPlant trait data are used to quantify how plants respond to environmental factors and can act as indicators of ecosystem function. Measured trait values are influenced by genetics, trade‐offs, competition, environmental conditions, and phenology. These interacting effects on traits are poorly characterized across taxa, and for many traits, measurement protocols are not standardized. As a result, ancillary information about growth and measurement conditions can be highly variable, requiring a flexible data structure. In 2007, the TRY initiative was founded as an integrated database of plant trait data, including ancillary attributes relevant to understanding and interpreting the trait values. The TRY database now integrates around 700 original and collective datasets and has become a central resource of plant trait data. These data are provided in a generic long‐table format, where a unique identifier links different trait records and ancillary data measured on the same entity. Due to the high number of trait records, plant taxa, and types of traits and ancillary data released from the TRY database, data preprocessing is necessary but not straightforward. Here, we present the ‘rtry’ R package, specifically designed to support plant trait data exploration and filtering. By integrating a subset of existing R functions essential for preprocessing, ‘rtry’ avoids the need for users to navigate the extensive R ecosystem and provides the functions under a consistent syntax. ‘rtry’ is therefore easy to use even for beginners in R. Notably, ‘rtry’ does not support data retrieval or analysis; rather, it focuses on the preprocessing tasks to optimize data quality. While ‘rtry’ primarily targets TRY data, its utility extends to data from other sources, such as the National Ecological Observatory Network (NEON). The ‘rtry’ package is available on the Comprehensive R Archive Network (CRAN; https://cran.r‐project.org/package=rtry) and the GitHub Wiki (https://github.com/MPI‐BGC‐Functional‐Biogeography/rtry/wiki) along with comprehensive documentation and vignettes describing detailed data preprocessing workflows.

Rehabilitation of tropical urban streams improves their structure and functioning

Urban streams are affected by a complex combination of stressors, which modify physical habitat structure, flow regime, water quality, biological community composition, and ecosystem processes and services, thereby altering ecosystem structure and functioning. Rehabilitation projects have been undertaken in several countries to rehabilitate urban streams. However, stream rehabilitation is still rarely reported for neotropical regions. In addition, most studies focus on structural aspects, such as water quality, sediment control, and flood events, without considering ecosystem function indicators. Here, we evaluated the structure and functioning of three 15-y old rehabilitated urban stream sites in comparison with three stream sites in the best available ecological condition (reference), three sites with moderate habitat alteration, and three severely degraded sites. Compared to degraded streams, rehabilitated streams had higher habitat diversity, sensitive macroinvertebrate taxa richness, and biotic index scores, and lower biochemical oxygen demand, primary production, sediment deposition, and siltation. However, rehabilitated streams had higher primary production than moderate and reference streams, and lower canopy cover, habitat diversity, sensitive macroinvertebrate taxa richness, and biotic index scores than reference streams. These results indicate that rehabilitated streams have better structural and functional condition than degraded streams, but do not strongly differ from moderately altered streams, nor have they reached reference stream condition. Nonetheless, we conclude that rehabilitation is effective in removing streams from a degraded state by improving ecosystem structure and functioning. Furthermore, the combined use of functional and structural indicators facilitated an integrative assessment of stream ecological condition and distinguished stream conditions beyond those based on water quality indicators.

The seasonal variability of future evapotranspiration over China during the 21st century

The evapotranspiration (ET) plays a crucial role in shaping regional climate patterns and serves as a vital indicator of ecosystem function. However, there remains a limited understanding of the seasonal variability of future ET over China and its correlation with environmental drivers. This study evaluated the skills of 27 models from the Six Phase of Coupled Model Intercomparison Project in modeling ET and the Bayesian Model Averaging (BMA) method was employed to merge monthly simulated ET based on the top five best-performing models. The seasonal changes in ET under three climate scenarios from 2030 to 2099 were analyzed based on the BMA-merged ET, which was well validated with observed ET collected from fourteen flux sites across China. Significant increasing ET over China are projected under all seasons during 2030–2099, with 0.05–0.13 mm yr−1, 0.11–0.23 mm yr−1, and 0.20–0.41 mm yr−1 under SSP1–2.6, SSP2–4.5 and SSP5–8.5 scenarios, respectively. Relative to the historical period (1980–2014), the relative increase in ET over China is highest in winter and lowest in summer. Seasonal ET increases significantly in all seven climate sub-regions under high forcing scenario. Higher ET increase is generally found in southeastern humid regions, while lowest ET increase occurs in northwest China. At the country level, the primary factor driving ET increase during spring, summer, and autumn seasons is the increasing net radiation and warming. In contrast, ET increase during winter is influenced not only by energy factors but also by vegetation-related factors. Future seasonal ET increase is predominantly driven by increasing energy factors in the southeastern humid region and Tibetan Plateau, while seasonal ET changes in the northwest region prevailingly depend on soil moisture. Results indicate that China will experience a “wet season will get wetter, and dry season will become drier” in the 21st century with high radiation forcing scenario.

Hotter drought and trade‐off between fast and slow growth strategies as major drivers of tree‐ring growth variability of global conifers

Abstract Temporal growth variability is an important indicator of ecosystem function under climate change. However, we still lack a unified understanding of how climate conditions, climate change (trends and variability), nitrogen (N) deposition, functional traits and stand factors together affect radial growth variability. Using global conifer tree‐ring records (123 species from 1780 sites) during 1970–2010 to calculate growth variability, we assessed how abiotic and stand factors affect growth variability directly and indirectly via functional traits with boosted regression tree and structural equation models, and examined the differences among continents (North America, Asia and Europe). We found: (a) growth variability was mainly affected by warm‐induced drought and increased at lower latitudes. Climate warming in winter could decrease growth variability, but this effect is by far not enough to offset the threat of hotter drought; (b) there existed a trade‐off between fast‐ and slow‐growing (drought tolerance) strategies for global conifer species, and abiotic and stand factors affected growth variability via functional traits. Contrary to common conjecture, species with higher drought tolerance revealed higher growth variability due to their occupation of more xeric sites, and may also because higher investment in drought tolerance leads to less investment remaining for growth; (c) older trees revealed higher growth variability due to their more conservative growth strategy, while at large scales, taller trees showed lower growth variability due to occupying more productive sites; and (d) moderate N deposition could reduce growth variability by leading conifers to adopt a more fast‐growing strategy (e.g. in Asia), but long‐term and excessive N deposition led to increased growth variability (e.g. in North America and Europe). Synthesis. Our results suggest that coniferous forests in water‐limited regions should be more vulnerable to hotter drought, and the ‘fast–slow’ growth strategies may be key in regulating the effects of various abiotic and stand factors on ecosystem stability. Moreover, future hotter drought and N deposition will severely threaten conifer growth, especially for old trees and conifers at lower latitudes.

The impact of reclamation and vegetation removal on compositional and functional attributes of soil microbial communities in the Athabasca Oil Sands Region

Large-scale mining for oil extraction in the boreal forests of Northern Alberta has led to a disturbance footprint of ~900 km2 of land; which must be reclaimed to equivalent land capabilities. Microorganisms are sensitive to anthropogenic disturbances and play an essential role in the cycling of soil nutrients and plant growth, making them potential indicators of ecosystem function. Thus, the objective of this work was to determine the impact of land reclamation on the composition and function of soil microbial communities in the Athabasca Oil Sands Region (AOSR). We evaluated bacterial community composition via high throughput sequencing of 16S rRNA genes and soil functional diversity by community-level physiological profiling (CLPP). The ranges of variability for these factors observed in soils reclaimed with either peat-mineral mix (PMM), forest floor-mineral mix (FFM), or FFM diluted with sand (Sand-FFM), were compared to that of undisturbed reference soils (NS) and a vegetation removed soil (VR). Differences between reclamation soils and natural soils were clearly discernible, with reclamation imposing a more drastic disturbance to the boreal forest than that of removal of vegetation alone. VR changed the structure of the soil microbial community and increased the overall diversity, within-community interactions, and heterogeneity; while reclamation shifted the microbial community structure to an even greater extent, placing it outside the range of natural variability. Among reclamation substrates, FFM showed the highest level of similarity to the range of natural variability and PMM showed the least. Altogether, our findings underscore the profound impact of anthropogenic activities associated with large-scale mining on soil biological activity, microbial communities, and edaphic profiles. These alterations are of such magnitude that they render the affected soils significant divergent from the reference undisturbed boreal forest soil.

Growth form, regeneration mode, and vegetation type explain leaf trait variability at the species and community levels in Mediterranean woody vegetation.

Leaf traits are good indicators of ecosystem functioning and plant adaptations to environmental conditions. We examined whether leaf trait variability at species and community levels in Mediterranean woody vegetation is explained by growth form, regeneration mode, and vegetation type. We studied several plant communities across five vegetation types - semi-closed forest, open forest, closed shrubland, open shrubland, and scrubland - in southwestern Anatolia, Türkiye. Using linear mixed models, community-weighted trait means, and principal component analysis, we tested how much variability in three leaf traits (specific leaf area, leaf thickness, and leaf area) is accounted for species, growth form, regeneration mode, and vegetation type. Despite a large amount of leaf trait variability both within- and among-species existed, functional groups still accounted for a significant part of this variability. Resprouters had higher SLA and leaf area and lower leaf thickness than non-resprouters. However, further functional separation in regeneration mode, by considering the propagule-persistence trait and the seed bank locality, explained leaf trait variability better than only resprouting ability. Although no consistent pattern was observed in three leaf traits in the growth form, we found evidence for the difference in SLA and leaf thickness between shrubs and large shrubs, and subshrubs had smaller leaves than other growth forms. Vegetation type also accounted for a substantial amount of leaf trait variability. Specifically, plant communities in closed habitats had larger leaf area than open ones, and those in scrublands had higher SLA, lower leaf thickness, and lower leaf area than other vegetation types. Climate and phylogeny had limited contribution to the results obtained, with the exception of a significant phylogenetic effect in explaining the differences in SLA between resprouters and non-resprouters. Our results suggest that multiple drivers are responsible for shaping plant trait variability in Mediterranean plant communities, including growth form, regeneration mode, and vegetation type.

Satellite-based solar-induced fluorescence tracks seasonal and elevational patterns of photosynthesis in California’s Sierra Nevada mountains

Robust carbon monitoring systems are needed for land managers to assess and mitigate the changing effects of ecosystem stress on western United States forests, where most aboveground carbon is stored in mountainous areas. Atmospheric carbon uptake via gross primary productivity (GPP) is an important indicator of ecosystem function and is particularly relevant to carbon monitoring systems. However, limited ground-based observations in remote areas with complex topography represent a significant challenge for tracking regional-scale GPP. Satellite observations can help bridge these monitoring gaps, but the accuracy of remote sensing methods for inferring GPP is still limited in montane evergreen needleleaf biomes, where (a) photosynthetic activity is largely decoupled from canopy structure and chlorophyll content, and (b) strong heterogeneity in phenology and atmospheric conditions is difficult to resolve in space and time. Using monthly solar-induced chlorophyll fluorescence (SIF) sampled at ∼4 km from the TROPOspheric Monitoring Instrument (TROPOMI), we show that high-resolution satellite-observed SIF followed ecological expectations of seasonal and elevational patterns of GPP across a 3000 m elevation gradient in the Sierra Nevada mountains of California. After accounting for the effects of high reflected radiance in TROPOMI SIF due to snow cover, the seasonal and elevational patterns of SIF were well correlated with GPP estimates from a machine-learning model (FLUXCOM) and a land surface model (CLM5.0-SP), outperforming other spectral vegetation indices. Differences in the seasonality of TROPOMI SIF and GPP estimates were likely attributed to misrepresentation of moisture limitation and winter photosynthetic activity in FLUXCOM and CLM5.0 respectively, as indicated by discrepancies with GPP derived from eddy covariance observations in the southern Sierra Nevada. These results suggest that satellite-observed SIF can serve as a useful diagnostic and constraint to improve upon estimates of GPP toward multiscale carbon monitoring systems in montane, evergreen conifer biomes at regional scales.

Biocrusts Indicators of Livestock Grazing Effects on Soil Stability in Sagebrush Steppe: A Case Study from a Long-Term Experiment in the Northern Great Basin

Biocrusts are sensitive to changes in livestock grazing intensity in arid rangelands and may be useful indicators of ecosystem functions, particularly soil properties like soil stability, which may suggest the potential for soil erosion. We compared biocrust community composition and surface soil stability in a big sagebrush (Artemisia tridentata) steppe rangeland in the northwestern Great Basin in several paired sites, with or without long-term cattle grazing exclusion, and similar soils (mostly sandy loams), climate, and vegetation composition. We found that livestock grazing was associated with both lower surface soil stability and cover of several biocrust morphogroups, especially lichens, compared with sites with long-term livestock exclusion. Surface soil stability did not modify the effects of grazing on most biocrust components via interactive effects. Livestock grazing effects on total biocrust cover were partially mediated by changes in surface soil stability. Though lichens were more sensitive to grazing disturbance, our results suggest that moss (mostly Tortula ruralis in this site) might be a more readily observable indicator of grazing-related soil stability change in this area due to their relatively higher abundance compared with lichens (moss: mean, 8.5% cover, maximum, 96.1%, lichens: mean, 1.0% cover, maximum, 14.1%). These results highlight the potential for biocrust components as sensitive indicators of change in soil-related ecosystem functions in sagebrush steppe rangelands. However, further research is needed to identify relevant indicator groups across the wide range of biocrust community composition associated with site environmental characteristics, variable grazing systems, other rangeland health metrics, and other disturbance types such as wildfire.

Impact of ecological governance policies on county ecosystem change in national key ecological functional zones: A case study of Tianzhu County, Gansu Province

Policy is a key element of ecological governance, however, insufficient attention has been given to how different policies and regulations in a systematic way affect ecosystem processes and functions. This study evaluated the impact of ecological policies in the national key ecological functional areas (NKEFAs) since 1990, taking Tianzhu County as a case study. We first evaluated the change in policy intensity through quantitative analysis of policy texts, then analyzed the change in the ecosystems with carbon storage, habitat quality, ecosystem service and water conservation. Finally, the partial least squares (PLS) was used to quantify the effective path for and effect of policies on the ecosystem through adjustments in agriculture, animal husbandry and population. The results showed that policies have a significant direct impact on the agricultural planting industry, animal husbandry and population size and structure, and have a significant indirect impact on the whole ecosystem. The research demonstrated the usefulness of applying PLS-SEM and ecosystem function indicators to evaluate the impact of ecological governance policies on ecosystems in NKEFAs. The research can provide reference for the ecological policy making of NKEFAs.

Tree islands enhance biodiversity and functioning in oil palm landscapes

In the United Nations Decade on Ecosystem Restoration1, large knowledge gaps persist on how to increase biodiversity and ecosystem functioning in cash crop-dominated tropical landscapes2. Here, we present findings from a large-scale, 5-year ecosystem restoration experiment in an oil palm landscape enriched with 52 tree islands, encompassing assessments of ten indicators of biodiversity and 19 indicators of ecosystem functioning. Overall, indicators of biodiversity and ecosystem functioning, as well as multidiversity and ecosystem multifunctionality, were higher in tree islands compared to conventionally managed oil palm. Larger tree islands led to larger gains in multidiversity through changes in vegetation structure. Furthermore, tree enrichment did not decrease landscape-scale oil palm yield. Our results demonstrate that enriching oil palm-dominated landscapes with tree islands is a promising ecological restoration strategy, yet should not replace the protection of remaining forests.

Spontaneous urban vegetation as an indicator of soil functionality and ecosystem services

AbstractQuestionsOur study focused on spontaneous vegetation in urban greenspaces in a Mediterranean city with the aim of relating plant community properties with ecological services along soil disturbance gradients. We asked which plant communities have the greatest plant biodiversity and soil carbon storage and the best‐performing nutrient cycles and water regulation.LocationMadrid City (Central Spain).MethodsWe studied four types of plant communities following soil disturbance gradients: vegetation on trampled soils, roadside vegetation, annual grasslands and perennial forbs. Regarding vegetation, we studied plant composition and productivity, plant diversity, plant growth forms and functional groups. Regarding soils, we determined soil organic carbon (TOC), available nutrients, the activity of seven enzymes relating to the main macronutrient cycles, and physical properties such as bulk density (BD) and soil water‐holding capacity (WHC). We used one‐way ANOVA to determine the influence of the plant community type on both soil and vegetation variables. Canonical correspondence analysis was performed to interpret the relationships between plant species assemblages with environmental gradients.ResultsPerennial forbs showed greater biomass and developed on soils with the greatest TOC and available phosphorus. Annual grasslands displayed the highest plant diversity. Roadside vegetation developed on soils with higher phenoloxidase activity when compared to vegetation on trampled soils and annual grasslands. Vegetation on trampled soils developed on soils with lower WHC, lower beta‐glucosidase, arylamidase and phosphatase activities and higher BD when compared to perennial forbs. Plant community distribution followed gradients most significantly associated with soil organic matter content, soil compaction and nutrient cycling performance.ConclusionsWe conclude that plant communities are good indicators of ecosystem function and services which are unevenly distributed throughout urban habitats. The management in Mediterranean unmaintained urban greenspaces should be aimed at avoiding soil compaction to promote biodiversity, carbon storage and water regulation.

Rising water-use efficiency in European grasslands is driven by increased primary production

Water-use efficiency is the amount of carbon assimilated per water used by an ecosystem and a key indicator of ecosystem functioning, but its variability in response to climate change and droughts is not thoroughly understood. Here, we investigated trends, drought response and drivers of three water-use efficiency indices from 1995–2018 in Europe with remote sensing data that considered long-term environmental effects. We show that inherent water-use efficiency decreased by −4.2% in Central Europe, exhibiting threatened ecosystem functioning. In European grasslands it increased by +24.2%, by regulated transpiration and increased carbon assimilation. Further, we highlight modulation of water-use efficiency drought response by hydro-climate and the importance of adaptive canopy conductance on ecosystem function. Our results imply that decoupling carbon assimilation from canopy conductance and efficient water management strategies could make the difference between threatened and well-coping ecosystems with ongoing climate change, and provide important insights for land surface model development.

Spaceborne LiDAR for characterizing forest structure across scales in the European Alps

AbstractThe launch of NASA's Global Ecosystem Dynamics Investigation (GEDI) mission in 2018 opens new opportunities to quantitatively describe forest ecosystems across large scales. While GEDI's height‐related metrics have already been extensively evaluated, the utility of GEDI for assessing the full spectrum of structural variability—particularly in topographically complex terrain—remains incompletely understood. Here, we quantified GEDI's potential to estimate forest structure in mountain landscapes at the plot and landscape level, with a focus on variables of high relevance in ecological applications. We compared five GEDI metrics including relative height percentiles, plant area index, cover and understory cover to airborne laser scanning (ALS) data in two contrasting mountain landscapes in the European Alps. At the plot level, we investigated the impact of leaf phenology and topography on GEDI's accuracy. At the landscape‐scale, we evaluated the ability of GEDIs sample‐based approach to characterize complex mountain landscapes by comparing it to wall‐to‐wall ALS estimates and evaluated the capacity of GEDI to quantify important indicators of ecosystem functions and services (i.e., avalanche protection, habitat provision, carbon storage). Our results revealed only weak to moderate agreement between GEDI and ALS at the plot level (R2 from 0.03 to 0.61), with GEDI uncertainties increasing with slope. At the landscape‐level, however, the agreement between GEDI and ALS was generally high, with R2 values ranging between 0.51 and 0.79. Both GEDI and ALS agreed in identifying areas of high avalanche protection, habitat provision, and carbon storage, highlighting the potential of GEDI for landscape‐scale analyses in the context of ecosystem dynamics and management.

Stoichiometric Characteristics of Leaf, Litter and Soil during Vegetation Succession in Maolan National Nature Reserve, Guizhou, China

Carbon (C), nitrogen (N), phosphorus (P) and potassium (K) are the main nutrient elements widely found in soil, litter and leaves, and their stoichiometric ratios are important indicators of ecosystem functions. However, there is little research on the effects that nutrient cycle and vegetation succession have on leaf, litter and soil nutrients and stoichiometric ratios, especially in the fragile karst areas. To reveal the nutrient cycling characteristics and ecosystem stability mechanism during vegetation succession, leaf, litter and soil samples were collected from the herbaceous community (HC), shrub community (SC), secondary forest community (SF) and primary forest community (PF) in a typical karst area at growth and senescence phases. The results showed that the nutrient contents and stoichiometric ratios of leaf, litter and soil in the main layers of each community were significantly different at the growth and senescence phase. The utilization efficiency of N in the leaves of the main layers of each succession community first decreased and then increased at different growth stages, and the utilization efficiency of P increased but the reabsorption rates of N and P showed a continuous decreasing trend. In addition, there was a significant allometric relationship between N and P contents in plant leaves during the growth phase. More importantly, the internal stability of N content in plant leaves was higher than the P content, suggesting that vegetation succession significantly affected leaf, litter and soil nutrient contents and their stoichiometric ratios in our study region. The strength of the relationship between them reflects the inheritance and co–variation of nutrient content to a certain extent, and the differences in the strategies that different species in the community use to adapt to the fragile karst environment. This study concludes that plants in the karst region mainly improve their P utilization efficiency to adapt to low phosphorus stress in soil and ensure the normal physiological and biochemical responses in the process of vegetation succession.

Evaluating Satellite-Observed Ecosystem Function Changes and the Interaction with Drought in Songnen Plain, Northeast China

Drought is considered one of the devastating natural disasters worldwide. In the context of global climate change, the frequency and intensity of drought have increased, thereby affecting terrestrial ecosystems. To date, the interactions between ecosystem change and drought, especially their mutual lag and cumulative effects is unclear. The Songnen Plain in northeastern China is one of the three major black soil areas in the world and is highly sensitive to global change. Herein, to quantify the interaction between drought and ecosystem function changes in the Songnen Plain, integrating with time-series moderate resolution imaging spectroradiometer (MODIS), leaf area Index (LAI), evapotranspiration (ET), and gross primary productivity (GPP) data, we calculated the standardized precipitation and evapotranspiration index (SPEI) based on the meteorological data, diagnosed the causal relationship between SPEI and the ecosystem function indicators i.e., LAI, ET, and GPP, and analyzed the time-lag and cumulative effects between the degree of drought and three ecosystem function indicators using impulse response analysis. The results showed that the trend of SPEI (2000–2020) was positive in the Songnen Plain, indicating that the drought extent had eased towards wetness. LAI showed insignificant changes (taking up 88.34% of the total area), except for the decrease in LAI found in some forestland and grassland, accounting for 9.43%. The pixels showing a positive trend of ET and GPP occupied 24.86% and 54.94%, respectively. The numbers of pixels with Granger causality between LAI and SPEI (32.31%), SPEI and GPP (52.8%) were greater at the significance 0.05 level. Impulse responses between each variable pair were stronger mainly between the 6th and 8th months, but differed significantly between vegetation types. Grassland and cropland were more susceptible to drought than forest. The cumulative impulse response coefficients values indicated that the mutual impacts between all variables were mainly positive. The increased wetness positively contributed to ecosystem function, and in turn enhanced ecosystem function improved regional drought conditions to some extent. However, in the northeastern forest areas, the SPEI showed a significant negative response to increased ET and GPP, suggesting that the improved physiological functions of forest might lead to regional drought. There were regional differences in the interaction between drought conditions and ecosystem function in the Songnen Plain over the past 21 years.

Contributory factors of the secular trends to changes in ecosystem water-use efficiency in China

Ecosystem water-use efficiency (WUE) is an effective indicator of ecosystem functioning, which is widely used to characterize the coupling relationship between terrestrial carbon and the water cycle. Although the linear trends in WUE have been well reported, the nonlinearity of the secular trends in WUE and their relative contribution to the overall changes were still poorly investigated. In this study, we used ensemble empirical mode decomposition (EEMD) to extract the secular trends of the WUE and their relative contribution (RC) to the WUE changes in China, which represents the stability of the ecosystem functioning. We found that although increasing trends dominated the secular trends of the WUE, nearly half of the study areas had experienced trend shifts. Except that deciduous forests and mixed forests were dominated by trend shifts, most of the land cover types were dominated by increasing trends. The RC exhibited a bimodal pattern along the elevation gradient, with peaks at 20 m and 5000 m. Similarly, the RC peaked at the east and south aspects, and was the lowest for the west and north aspects. In comparison, the RC exhibited a U-shaped pattern with the slope, and was the lowest at 80°. For the monotonically increasing trends and decreasing-to-increasing trends, the high RC mainly occurred on the North China Plain and Loess Plateau, indicating ecosystem improvement and strong stability. Meanwhile, it was low in northeastern China and southwestern China, indicating unsustainableecosystem improvement. The RC was always very low for increasing-to-decreasing trends and monotonically decreasing trends, indicating low ecosystem stability with a high possibility for improvement. Temperature and the atmospheric carbon dioxide (CO2) concentration were the two main climatic factors driving the WUE changes. The climatic mean state rather than the climatic variability affected the ecosystem stability. The results of this study highlight the relative contribution of the secular trends to WUE changes and provide a better understanding of the structure and the stability of ecosystem functioning.

Towards a functional assessment of stream integrity: A first large-scale application using leaf litter decomposition

• Litter decomposition exhibits large variability at the regional scale (83 streams). • Litter decomposition does not correlate with the European WFD structural indicators. • Functional and structural indicators are complementary. • A grid is given to translate decomposition rates into functional quality classes. There is increasing recognition that indicators of ecosystem functioning are needed to improve current stream monitoring schemes. However, to date, no attempt has been made to include functional metrics in large-scale routine monitoring programs under the European Water Framework Directive (WFD). One reason is the uncertainty if functional indicators really carry new and independent information about stream status or, to the contrary, remain broadly redundant with existing indicators of biological stream quality (based on stream communities). A second reason is that, despite increasing scientific knowledge on how anthropogenic pressures influence ecosystem process rates, no ‘ready for use’ tool is available to translate them into stream ecosystem status. Litter decomposition probably ranges among the most documented stream ecosystem processes, and its potential for bioindication has been repeatedly demonstrated during the past decade. Here we report an extensive comparison of routine French structural indicators (I 2 M 2 , IBGN, IBD) with alder litter (microbial and total) decomposition rates in 83 streams located in south-western France. Expectedly, microbial decomposition rates were positively correlated with fungal biomass and activity (conidial production rate), while total and invertebrate-driven decomposition rates increased together with detritivore density and diversity in litter bags. By contrast, correlations between litter decomposition rates and routine structural indicators were clearly weak (Spearman’s ρ < 0.20), providing evidence that functional indicators bring new information. We devised a new interpretation grid to translate litter decomposition rates into stream ecological quality in a WFD-compatible design. This system considers the litter decomposition rates measured in both coarse (total decomposition) and fine (microbial decomposition) mesh bags as uncorrelated metrics of ecosystem functioning ( P = 0.898). Streams are considered functionally impaired when total and/or microbial decomposition rates are either higher or lower than in a reference condition. Applying our classification system to the 83 study sites allowed to assign them to 5 functional quality classes: bad (4 streams), poor (26), fair (29), good (21) and high (3). This classification did not match the classes obtained by conventional WFD structural indicators, reflecting that both functional and structural indicators are needed to obtain a comprehensive assessment of stream ecosystem integrity.

Low flows in a regulated river system are associated with reduced breeding bird abundance and diversity in Yosemite National Park, California

AbstractRiver regulation can alter the magnitude, frequency, duration, and timing of flows, which influences the function of downstream ecosystems. Bird communities can be useful indicators of ecosystem function as individual species respond to varied changes in habitat structure and food availability. We examined the relative importance of different aspects of a regulated flow regime (average daily flow, the number of days flows fell below the 25th percentile, the timing and magnitude of maximum flows, and the inter‐annual duration of flows below the historical median) on predicted bird abundance and diversity using 11 years of data collected within a floodplain meadow system located downstream of Hetch Hetchy Reservoir in Yosemite National Park, California. We found that prolonged periods of low flows were negatively associated with the number of breeding birds detected, as well as the species richness of the breeding bird community. Species richness was also negatively correlated with delays in spring runoff delivery. We opportunistically looked at the same hydrologic variables in a parallel unregulated system, the Merced River through Yosemite Valley, and did not find the same strong relationship with bird community data. This suggests that the dam may be exacerbating the effects of drought.

Characteristics of Soil Temperature, Humidity, and Salinity on Bird Island within Qinghai Lake Basin, China

The temperature, moisture, and salt content of soil in alpine regions are sensitive to changes in climatic factors and are important indicators of ecosystem functions. In this study, we collected soil moisture, temperature and electrical conductivity data at different depths at a sampling site on Bird Island in Qinghai Lake during winter using a continuous soil temperature, moisture and salt content monitoring system and analyzed their variations and influential factors. The variation in soil moisture showed an obvious ‘V-shaped’ pattern from 00:00 to 23:00 and an upward trend with soil layer depth. From 00:00 to 23:00, the overall soil temperature data fitted a ‘unimodal’ curve and showed a clear and continuous upward trend with soil layer depth at a rate of 0.684 (p &lt; 0.001). Soil electrical conductivity data also exhibited a distinct ‘V-shaped’ pattern from 00:00 to 23:00 and a continuous increase with increasing soil depth. The correlation between soil temperature, moisture, and conductivity and the spatial distribution of five climate factors indicated that climate factors accounted for 53.6% of the changes in soil temperature, moisture, and salinity. Climate factors showed a significant positive correlation with soil temperature, moisture, and conductivity (p &lt; 0.001), and air temperature was the most important factor influencing soil temperature and soil moisture changes, whereas wind direction was the most important factor influencing soil conductivity. (Wind direction and wind speed affect soil evapotranspiration, and then affect soil moisture and solute transport process). The results of this preliminary study reveal the characteristics associated with soil temperature, moisture, and salinity changes in winter within the wetlands of Bird Island on Qinghai Lake in the context of climate change, and they can be used as valuable reference data in further studies investigating associated changes in ecosystem functions.

Environmental DNA and metagenomics of terrestrial mammals as keystone taxa of recent and past ecosystems

ABSTRACT Terrestrial mammals shape their ecosystems, and mammalian community assemblages can be important indicators of ecosystem functioning and ecosystem changes over time. Numerous taxa of terrestrial mammals are currently threatened by habitat loss and face displacement to new geographical areas or systems to which they are less suited and where they may affect the original communities. Understanding past ecosystem changes is important for predicting future responses of species assemblages to changes in their environments. Thus, ecological and evolutionary history, as well as adaptive capacity, are important predictors of future population viability. Genomic and metagenomic approaches using environmental or ancient DNA offer a wealth of information regarding genome‐wide variation of changing communities or of taxonomic groups over time, which may help explain past changes and predict future responses of communities to changes in their environment; however, to date, such studies are relatively scarce. We review studies on environmental DNA and environmental genomics of terrestrial mammals to assess the potential of such approaches regarding past, contemporary, and future terrestrial ecosystems, identify inherent challenges, and discuss potential applications. We elaborate on lessons to be learned from mammal genomics of past ecosystems and compare metabarcoding with general metagenetic and metagenomic techniques. We provide a comprehensive overview of current applications, challenges, and future potential of environmental DNA with regards to terrestrial mammals. As current major challenges regarding mammalian eDNA we identify its scarcity and patchy distribution, along with the persistent necessity of genomic reference data. While the latter are steadily increasing, the former can only be tackled by explicitly mapping the environment to gain understanding of spatial eDNA distribution. Such understanding may facilitate informed choices of sample sites and substrates and, together with new sequencing techniques, this can allow mammalian eDNA to be maximally exploited as a source of biodiversity data.