Changes In Ecosystem Function Research Articles

Synthesis of interannual variability in spatial demographic processes supports the strong influence of cold-pool extent on eastern Bering Sea walleye pollock (Gadus chalcogrammus)

Attributing variability in fish demographic processes to environmental conditions is helpful when assessing population status and forecasting changes in ecosystem function. Empirical orthogonal function (EOF) analysis has long been used to explore variability in physical processes, but has been only recently employed to study variability in biological processes. EOF analysis estimates dominant modes of variability (indices) and produces maps representing the spatial response for the dependent variable to each of these indices. In the eastern Bering Sea (EBS), research has linked demographic processes to the spatial extent of bottom temperatures less than or equal to 2 °C (the “cold-pool extent” or “CPE”), but has generally not compared effects among different demographic processes. We applied EOF analysis to four types of data measuring the outcome of demographic processes for EBS walleye pollock (Gadus chalcogrammus) over the period 1982–2019: numerical density (outcome of movement), morphometric condition (outcome of bioenergetics), length-at-age (outcome of growth), and prey-biomass-per-predator-mass (a proxy for stomach contents; outcome of consumption). We first designed exploratory factor analysis (EFA) models that did not include a CPE effect. We then applied confirmatory factor analysis (CFA), which differed from EFA by attributing observed patterns to a spatially varying response of demographic processes to CPE. We inferred that CPE was a proxy for demographic variability when there was a strong correlation between (1) the first or second mode of variability in the EFA and CPE or (2) the spatial map associated with the positive phase of the first or second mode of variability from the EFA model and the spatially varying response of CPE from the CFA model. Results showed that prey-biomass-per-predator-mass had the strongest correlation with CPE, numerical density and morphometric condition were also strongly correlated with CPE, and length-at-age was moderately correlated with CPE. The models also identified several anomalous years: 1999 and 2010, which were characterized by a very large CPE and high indices for variables related to demographic processes; and 2016–2019, which were characterized by a small CPE and low indices for variables related to demographic processes. We conclude that demographic processes for EBS walleye pollock show the finger-print of bottom-up environmental variation. Future research can employ CPE projections to forecast spatio-temporal changes in variables related to demographic processes, thereby informing estimates such as weight-at-age that are used in stock assessment models.

Human-driven changes in sediment-water interactions may increase the degradation of ecosystem functioning in the Ganga River

While it is widely accepted that the magnitude of river water quality degradation depends upon the proportion of human interventions, the overall changes are ultimately the consequence of interconnected biogeochemical processes with poorly understood role of ecosystem feedbacks. Here, we conducted in situ and incubation experiments, considering a 620 km Ganga River main stem, two tributaries and two point source downstream locations for trajectory studies to analyze the human-driven changes in ecosystem feedback associated changes in ecosystem functioning of the Ganga River and its tributaries. The main stem coupled trajectory analyses show that benthic hypoxia/anoxia resulting from intensive human releases generates positive feedbacks (sediment-P and –metal release) to exacerbate the degradation of ecosystem functioning in the Ganga River and tributaries. We found 1.9 to 4.6 times higher rates of sediment-P release and about 1.1 to 3.7 times higher rates of sediment-metal releases at sites with DOsw < 2.0 mg/L. Excess release of phosphorus from sediment enhanced the eutrophy whereas sediment-metal release and bioavailability led to a sharp decline in microbial biomass and FDAase activity. The Carlson’s index, ecological response index, Dodds’s trophic state classification, and risk index support these results because the sites with benthic hypoxic/anoxic condition did show trophic state in eutrophic to hypereutrophic range and metal pollution in very high to extremely polluted and high risk category indicating significant effect of these drivers. The study, for the first time, showed that positive feedbacks exacerbate the degradation of ecosystem functioning in human-impacted large rivers. We suggest the need for increased efforts considering the magnitude and connectivity of positive feedbacks and associated repercussions for improving mechanistic understanding of their contributions to overall structural and functional shifts in the large rivers.

Diverging land-use projections cause large variability in their impacts on ecosystems and related indicators for ecosystem services

Abstract. Land-use models and integrated assessment models provide scenarios of land-use and land-cover (LULC) changes following pathways or storylines related to different socioeconomic and environmental developments. The large diversity of available scenario projections leads to a recognizable variability in impacts on land ecosystems and the levels of services provided. We evaluated 16 projections of future LULC until 2040 that reflected different assumptions regarding socioeconomic demands and modeling protocols. By using these LULC projections in a state-of-the-art dynamic global vegetation model, we simulated their effect on selected ecosystem service indicators related to ecosystem productivity and carbon sequestration potential, agricultural production and the water cycle. We found that although a common trend for agricultural expansion exists across the scenarios, where and how particular LULC changes are realized differs widely across models and scenarios. They are linked to model-specific considerations of some demands over others and their respective translation into LULC changes and also reflect the simplified or missing representation of processes related to land dynamics or other influencing factors (e.g., trade, climate change). As a result, some scenarios show questionable and possibly unrealistic features in their LULC allocations, including highly regionalized LULC changes with rates of conversion that are contrary to or exceed rates observed in the past. Across the diverging LULC projections, we identified positive global trends of net primary productivity (+10.2 % ± 1.4 %), vegetation carbon (+9.2 % ± 4.1 %), crop production (+31.2 % ± 12.2 %) and water runoff (+9.3 % ± 1.7 %), and a negative trend of soil and litter carbon stocks (−0.5 % ± 0.4 %). The variability in ecosystem service indicators across scenarios was especially high for vegetation carbon stocks and crop production. Regionally, variability was highest in tropical forest regions, especially at current forest boundaries, because of intense and strongly diverging LULC change projections in combination with high vegetation productivity dampening or amplifying the effects of climatic change. Our results emphasize that information on future changes in ecosystem functioning and the related ecosystem service indicators should be seen in light of the variability originating from diverging projections of LULC. This is necessary to allow for adequate policy support towards sustainable transformations.

Variations of the effects of reduced precipitation and N addition on microbial diversity among different seasons in a temperate forest

Changes in microbial diversity affect biogeochemical cycles and ecosystem functioning. Increasing nitrogen (N) deposition and reducing precipitation significantly affect microbial diversity during the growing season. Furthermore, the variations of the effects of reduced precipitation and N addition on microbial diversity among different periods is still unclear. In order to reveal these effects, an 8-year field experiment was set up in a temperate old growth forest of northeast China, including four treatments: control, reduced precipitation (−30% of through-fall), N addition (50 kg N ha−1 yr−1), and their combined effect (−30% of through-fall and 50 kg N ha−1 yr−1), respectively. To reach a better understanding, microbial diversity among different periods was measured. The results showed that bacterial and fungal diversity significantly decreased in the growing season with N addition but significantly increased in winter. These positive or negative effects of reduced precipitation and N addition on bacterial and fungal diversity were attributed to changes in diversity of the main phyla of bacteria and fungi. Moreover, the positive impact of reduced precipitation on fungal diversity increased with N addition in the winter, while it decreased with N addition in the growing season. Our structural equation modeling showed that the negative impacts of reduced precipitation on soil moisture led to increased bacterial and fungal diversity. Our results illustrate that the direction of effect of reduced precipitation and N addition on microbial diversity may be shifted with seasonal changes and microbial taxonomic level, which provides new insight and framework for understanding and modeling responses of microbial diversity to N deposition and changes in precipitation pattern during different seasons.

Biological traits of seabirds predict extinction risk and vulnerability to anthropogenic threats

ABSTRACTAimSeabirds are heavily threatened by anthropogenic activities, and their conservation status is deteriorating rapidly. Nonetheless, these pressures are unlikely to impact all species uniformly. It remains an open question whether seabirds with similar ecological roles are responding similarly to human pressures. Our aims were as follows: (a) to test whether threatened versus non‐threatened seabirds are separated in trait space; (b) to quantify the similarity of species' roles (redundancy) per IUCN Red List Category; and (c) to identify traits that render species vulnerable to anthropogenic threats.LocationGlobal.Time periodContemporary.Major taxa studiedSeabirds.MethodsWe compile and impute eight traits that relate to species' vulnerabilities and ecosystem functioning across 341 seabird species. Using these traits, we build a mixed‐data principal component analysis of species' trait space. We quantify trait redundancy using the unique trait combinations (UTCs) approach. Finally, we undertake a similarity of percentages analysis to identify which traits explain the greatest difference between threat groups.ResultsWe find that seabirds segregate in trait space based on IUCN threat status, indicating that anthropogenic impacts are selectively removing large, long‐lived, pelagic surface feeders with narrow habitat breadths. We also find that threatened species have higher trait redundancy, whereas non‐threatened species have relatively limited redundancy. Finally, we find that species with narrow habitat breadths, fast reproductive speeds and varied diets are more likely to be threatened by habitat‐modifying processes (e.g., pollution and natural system modifications), whereas pelagic specialists with slow reproductive speeds and varied diets are vulnerable to threats that directly impact survival and fecundity (e.g., invasive species and biological resource use) and climate change. Species with no threats are non‐pelagic specialists with invertebrate diets and fast reproductive speeds.Main conclusionsOur results suggest that both threatened and non‐threatened species contribute unique ecological strategies. Consequently, conserving both threat groups, but importantly with contrasting approaches, might avoid potential changes in ecosystem functioning and stability.

Climate Change Effects in a Mediterranean Forest Following 21 Consecutive Years of Experimental Drought

Research Highlights: A small, long-term decrease in the water availability in a Mediterranean holm oak forest elicited strong effects on tree stem growth, mortality, and species composition, which led to changes in the ecosystem function and service provision. Background and Objectives: Many forest ecosystems are increasingly challenged by stress conditions under climate change. These new environmental constraints may drive changes in species distribution and ecosystem function. Materials and Methods: An evergreen Mediterranean holm oak (Quercus ilex L.) forest was subjected to 21 consecutive years of experimental drought (performing 30% of rainfall exclusion resulted in a 15% decrease in soil moisture). The effects of the annual climatic conditions and the experimental drought on a tree and shrub basal area increment were studied, with a focus on the two most dominant species (Q. ilex and the tall shrub Phillyrea latifolia L.). Results: Stem growth decreased and tree mortality increased under the experimental drought conditions and in hot and dry years. These effects differed between the two dominant species: the basal area of Q. ilex (the current, supradominant species) was dependent on water availability and climatic conditions, whereas P. latifolia was more tolerant to drought and experienced increased growth rates in plots where Q. ilex decay rates were high. Conclusions: Our findings reveal that small changes in water availability drive changes in species growth, composition, and distribution, as demonstrated by the continuous and ongoing replacement of the current supradominant Q. ilex by the subdominant P. latifolia, which is better adapted to tolerate hot and dry environments. The consequences of these ecological transformations for ecosystem function and service provision to human society are discussed.

Lake sedimentary DNA to reveal long-term changes in aquatic biodiversity and ecosystem functioning

The emergence of molecular analyses based on the sequencing of sedimentary DNA has opened up many new areas of inquiry in paleolimnology. DNA preserved in sediments (SedDNA) offers the possibility to consider taxa that were traditionally not accessible because they do not leave distinct morphological fossils. Recent applications that considered a diversity of biological groups (including bacteria, protists, zooplankton, fish) illustrate how efficiently SedDNA-based methods complement both classical paleolimnology proxies and limnological data. The knowledge gained from this approach is very diverse in scope, ranging from quantifying natural variability in population and community dynamics to understanding how these biological variables respond to anthropogenic disturbances and climatic change. The use of lake sedimentary DNA to track long-term changes in aquatic biota is a rapidly advancing field of research. Based on recent applications, this presentation illustrates (i) the potential and challenges associated with the study of SedDNA to address critical research questions in lacustrine ecology (ii) the main methodological precautions to be taken into account for implementing these types of DNA analyses (i.e. best practices) and (iii) the emerging topics that could be addressed using sedimentary DNA, in particular to reconstruct the temporal dynamics of lacustrine biodiversity.

Interaction of climate change, potentially toxic elements (PTEs), and topography on plant diversity and ecosystem functions in a high-altitude mountainous region of the Tibetan Plateau

Potentially toxic elements (PTEs) generated from mining activities have affected ecological diversity and ecosystem functions around the world. Accurately assessing the long-term effects of PTEs is critical to classifying recoverable areas and proposing management strategies. Mining activities that shape geographical patterns of biodiversity in individual regions are increasingly understood, but the complex interactions on broad scales and in changing environments are still unclear. In this study, we developed a series of empirical models that simulate the changes in biodiversity and ecosystem functions in mine-affected regions along elevation gradients (1500–3600 m a.s.l) in the metal-rich Qilian Mountains (∼800 km) on the northeastern Tibetan Plateau (China). Our results confirmed the crucial role of PTEs dispersal, topography, and climatic heterogeneity in the diversification of plant community composition. On average, 54% of the changes in ecosystem functions were explained by the interactions among topography, climate, and PTEs. However, merely 30% of the changes were correlated with a single driver. The changes in species composition (explained variables = 94.8%) in the PTE-polluted habitats located in the warm and humid low-elevation deserts and grasslands were greater than those occurring in the dry alpine deserts and grasslands. The ecosystem functions (soil characteristics, nutrient migration, and plant biomass) experienced greater changes in the humid low-elevation grasslands and alpine deserts. Our results suggest that the processes driven by climate or other factors can result in high-altitude PTE-affected habitat facing greater threats.

Climate and plants regulate the spatial variation in soil multifunctionality across a climatic gradient

A patchy distribution of soil resources is a characteristic of most natural terrestrial biomes, potentially resulting in spatial variation in multiple soil functions (soil multifunctionality). However, less is known about how soil multifunctionality and its spatial variability respond to increasing dryness across extensive climatic gradients, making it difficult to predict changes in ecosystem functions under climate change scenarios. We surveyed 150 sites along a 1500 km climatic gradient in eastern Australia, from humid forests to arid shrublands, to explore the spatial variation in soil multifunctionality with increasing aridity. We assessed four functional groups (carbon stocks, organic matter decomposition, plant structure, soil stability) of multifunctionality and average (net) multifunctionality across four vegetation patch types (tree, shrub, grass and unvegetated open interspaces). We then used average dissimilarity across these four patches as our measure of spatial variability. Our results showed that 1) net soil multifunctionality remained unchanged as aridity increased, because increases in soil stability and plant structure compensated for reductions in carbon stocks and organic matter decomposition; 2) the response of soil multifunctionality to increasing aridity differed among vegetation patch types, with the greatest increases in plant structure and reductions in carbon stocks in the open, but with marginal changes beneath trees; 3) variation in soil multifunctionality increased with increasing aridity and was driven by changes in climate (aridity, rainfall seasonality), soil (pH, sand) and to a lesser extent, variation in plant size, with impacts varying with the target functional group. Our study provides empirical evidence that soils can sustain an average level of multifunctionality across the climatic gradient by regulating the trade-offs between nutrient cycling and soil stability. Furthermore, our results demonstrate that forecasted increases in aridity will increase the spatial variation in soil multifunctionality and enhance the dominance of biocrusts, which would be critical for stabilizing soils under drier global climates.

Housekeeping in the Hydrosphere: Microbial Cooking, Cleaning, and Control under Stress.

Who’s cooking, who’s cleaning, and who’s got the remote control within the waters blanketing Earth? Anatomically tiny, numerically dominant microbes are the crucial “homemakers” of the watery household. Phytoplankton’s culinary abilities enable them to create food by absorbing sunlight to fix carbon and release oxygen, making microbial autotrophs top-chefs in the aquatic kitchen. However, they are not the only bioengineers that balance this complex household. Ubiquitous heterotrophic microbes including prokaryotic bacteria and archaea (both “bacteria” henceforth), eukaryotic protists, and viruses, recycle organic matter and make inorganic nutrients available to primary producers. Grazing protists compete with viruses for bacterial biomass, whereas mixotrophic protists produce new organic matter as well as consume microbial biomass. When viruses press remote-control buttons, by modifying host genomes or lysing them, the outcome can reverberate throughout the microbial community and beyond. Despite recognition of the vital role of microbes in biosphere housekeeping, impacts of anthropogenic stressors and climate change on their biodiversity, evolution, and ecological function remain poorly understood. How trillions of the smallest organisms in Earth’s largest ecosystem respond will be hugely consequential. By making the study of ecology personal, the “housekeeping” perspective can provide better insights into changing ecosystem structure and function at all scales.

Framework to Study the Effects of Climate Change on Vulnerability of Ecosystems and Societies: Case Study of Nitrates in Drinking Water in Southern Finland

Climate change may alter the services ecosystems provide by changing ecosystem functioning. As ecosystems can also resist environmental perturbations, it is crucial to consider the different processes that influence resilience. Our case study considered increased NO3− concentration in drinking water due to the climate change. We analyzed changes in ecosystem services connected to water purification at a catchment scale in southern Finland. We combined climate change scenarios with process-based forest growth (PREBAS) and eco-hydrological (PERSiST and INCA) models. We improved traditional model calibration by timing of forest phenology and snow-covered period from network of cameras and satellite data. We upscaled the combined modelling results with scenarios of population growth to form vulnerability maps. The boreal ecosystems seemed to be strongly buffered against NO3- leaching by increase in evapotranspiration and vegetation NO3- uptake. Societal vulnerability varied greatly between scenarios and municipalities. The most vulnerable were agricultural areas on permeable soil types.

Convergent nitrogen uptake patterns and divergent nitrogen acquisition strategies of coexisting plant species in response to long-term nitrogen enrichment in a temperate grassland

Nitrogen (N) deposition can significantly alter plant diversity and soil N status and cycling. However, there is rare information about the responses of plant N uptake of coexisting species to N deposition, which could facilitate the understanding of these N-induced ecosystem changes, particularly when taking N addition frequency into consideration. We assessed the uptake rates of N of various chemical forms (both inorganic and organic N) among coexisting plant species in response to N enrichment, using in situ stable isotope labeling techniques (15N-labeled ammonium, 15N-labeled nitrate and 13C-15N-labeled glycine), through a long-term N deposition experiment with monthly and biannual N addition frequencies in a temperate grassland. The plants of all three targeted species took up much greater inorganic N than amino acid N (93.4–99.4 % vs. 0.6–6.6 % in relative contributions to the total N uptake). The most abundant soil N form that originally was NH4+, was shifted to be NO3− under low and moderate N additions and back to be NH4+ at high addition level. Plants of not only dominant but also minor species predominantly took up N from the most abundant soil N form along N addition gradient. The dominant species Leymus chinensis, which continued to maintain its dominance under N enrichment, exhibited the ability to capture N of all different forms to tolerate and survive in a wide range of soil N environments. In contrast, another dominant species Stipa grandis, which was losing its dominance with N addition, showed the acquisition capacity of single N form in response to increased N inputs. It should be noted that there were interaction effects of N addition frequency and level on plant N uptake rates. Plant N uptake patterns and acquisition strategies could have important consequences for changes in ecosystem biodiversity and function under current and future N deposition scenarios.

High resilience of the mycorrhizal community to prescribed seasonal burnings in eastern Mediterranean woodlands.

Fire effects on ecosystems range from destruction of aboveground vegetation to direct and indirect effects on belowground microorganisms. Although variation in such effects is expected to be related to fire severity, another potentially important and poorly understood factor is the effect of fire seasonality on soil microorganisms. We carried out a large-scale field experiment examining the effects of spring (early-dry season) versus autumn (late-dry- season) burns on the community composition of soil fungi in a typical Mediterranean woodland. Although the intensity and severity of our prescribed burns were largely consistent between the two burning seasons, we detected differential fire season effects on the composition of the soil fungal community, driven by changes in the saprotrophic fungal guild. The community composition of ectomycorrhizal fungi, assayed both in pine seedling bioassays and from soil sequencing, appeared to be resilient to the variation inflicted by seasonal fires. Since changes in the soil saprotrophic fungal community can directly influence carbon emission and decomposition rates, we suggest that regardless of their intensity and severity, seasonal fires may cause changes in ecosystem functioning.

Living Shoreline Monitoring—How do I evaluate the environmental benefits of my living shoreline?

Living shorelines are structures made of natural materials such as oyster shell, sand, mangroves, salt marsh plants, and other organic materials built to protect properties from erosion. In addition to increasing shoreline stability, living shorelines enhance many valuable ecosystem functions. In this new 11-page publication of the UF/IFAS Department of Soil and Water Sciences, we provide homeowners, land managers, and Extension agents materials lists, protocols, and data sheets for measuring change in ecosystem function. Measuring and interpreting these measurements will help evaluate living shorelines projects as well as provide the foundation for monetarizing the value of these structures. Written by Laura K. Reynolds, Natalie C. Stephens, Savanna C. Barry, and Ashley R. Smyth.https://edis.ifas.ufl.edu/ss694

China’s Key Forestry Ecological Development Programs: Implementation, Environmental Impact and Challenges

Forest ecosystems are in serious trouble globally, largely due to the over-exploitation. To alleviate environmental problems caused by deforestation, China has undertaken a series of key forestry ecological development programs, including the Natural Forest Protection Program (NFPP), the Conversion of Cropland into Forests Program (CCFP), the Desertification Combating Program around Beijing and Tianjing (DCBT), the Key Shelterbelt Development Programs in the Three-North Region and in the Middle and Lower Reaches of the Yangtze River (KSDP) and the Nature Reserve Development Program in Forestry Sector (WCNR). This article aims to make a documentation of the specific contents (duration, major aims, geographic coverage and investment), and environmental impacts of these programs from peer-reviewed literature, official reports and journals. Environmental impact is measured with land area afforested (except the WCNR) and the consequent changes in ecosystem function. Overall, with the huge investment and long-term efforts, these programs have made tremendous progress in increasing vegetative coverage, enhancing carbon sequestration, controlling soil erosion, conservation of biodiversity, etc. For proper implementation and remarkable achievement, a more balanced approach with flexible planning, suitable measures and proper management should be adopted. Meanwhile, the scientific communities need to be more actively involved in execution and assessment of these programs. The environmental impact of the DCBT, the KSDP, and the WCNR deserve more research concern.

Changes in ecosystem functions generated by fish populations after the introduction of a non-native predator (Cichla kelberi) (Perciformes: Cichlidae)

Abstract The introduction of non-native predators is a matter of great concern, but their impacts on ecosystem functions remain poorly understood. We investigated how changes in fish diversity following the invasion of Cichla kelberi affected ecosystem functions generated by fish populations. Fish assemblages were sampled in macrophyte patches in a Neotropical impoundment over a 5-year period, before and after the introduction of the predator. We assigned seven ecosystem functions (26 trait-states) to each fish species, and examined how these functions behaved after the invasion. We collected 577 fish belonging to 25 species. Species richness, fish biomass and main species declined significantly over periods. The biomass of ecosystem functions changed significantly over time, and most trait-states declined. Few trait-states were lost, but all functions had at least one trait-state reduced by more than 85%. A null model analysis showed that changes in functions were not driven by species identities, while species richness correlated positively with total biomass and with most functions, suggesting that the loss of taxa and biomass drove observed changes in ecosystem functions. Our study provided evidence that community disassembly associated with the invasion of C. kelberi translated to the decline of several ecosystem functions, affecting energy mobilization and transference.

Functional redundancy buffers mobile invertebrates against the loss of foundation species on rocky shores

Foundation species are vital to the maintenance of biodiversity and ecosystem functioning in many systems. On rocky shores, rockweeds (large brown algae in the Order Fucales) have the potential to provide habitat and ameliorate stress for mobile invertebrates. To determine the relative role of 2 rockweeds (Silvetia compressaandPelvetiopsisspp.) as foundation species at sites along a latitudinal gradient, we conducted observational surveys and then initiated a 12 mo removal experiment. We found that richness and abundance of mobile invertebrates declined over time when rockweeds were removed, but only at the southernmost site. In contrast, at our other sites, there was no change in the richness and abundance of mobile invertebrates following rockweed removal. At the southern site, rockweeds played an important role in maintaining mobile invertebrate diversity. At our central and northern sites, rockweeds were less important in maintaining the diversity of mobile invertebrates. At these sites, alternative species, including bladed and branching taxa in the generaMastocarpus,Mazzaella,Corallina, andEndocladia, co-occur with rockweeds and can buffer the system against their loss. However, these alternative foundation species are rare to absent at the southern site, potentially due to greater physical stress. The loss of rockweed foundation species, which are declining at our southern site, can have cascading effects by causing local co-extinctions of associated species. This study highlights the importance of foundation species, especially in areas where their functional redundancy is low, and how the loss of foundation species can alter diversity, leading to potential changes in ecosystem functioning.

穿透雨减少和氮添加对毛竹叶片和细根化学计量学的影响

全球气候变化导致的干旱和人类活动引起的大气氮沉降升高，将会直接影响森林生态系统的结构与功能。叶片和细根作为植物最重要的资源获取功能器官，其化学计量学特征可指示其资源利用、生存适应策略。在当前气候变化背景下，了解植物的化学计量特征和适应特征将有助于预测未来森林生态系统功能的变化。通过为期1年的双因素交互实验，探讨了穿透雨减少和氮添加影响下，我国亚热带重要森林类型毛竹林的叶片及细根碳（C）、氮（N）、磷（P）元素化学计量比的响应特征，对于认识毛竹林生态系统对全球变化的适应和养分利用策略具有重要意义。研究表明：（1）穿透雨减少处理显著降低叶片N、P含量，显著增加细根N含量，对叶片C含量和细根C、P含量无显著影响；氮添加处理显著增加土壤N含量和叶片N含量，对叶片C、P含量及细根C、N、P含量无显著影响。（2）穿透雨减少、氮添加处理及两者交互作用对土壤C：N：P均无显著影响。（3）穿透雨减少处理显著增加叶片C：N、C：P和N：P；氮添加处理显著降低叶片C：N，对叶片C：P、N：P无显著影响；穿透雨减少、氮添加交互作用显著降低叶片C：N和C：P，对叶片N：P无显著影响。（4）穿透雨减少处理显著降低细根C：N，对细根C：P及N：P无显著影响；氮添加处理及穿透雨减少、氮添加交互作用对细根C：N：P无影响。综上短期处理的研究结果，穿透雨减少处理产生的水分胁迫对毛竹产生了关键限制作用，毛竹采取了降低叶片N和P含量、增加细根N含量，提高叶片的N和P利用效率、保持细根稳定的P利用效率的策略。氮添加未能缓解穿透雨减少对毛竹产生的干旱胁迫，毛竹通过改变地上部分叶片和地下部分细根之间的N素分配格局和N、P利用效率以应对水分胁迫。氮添加处理下叶片N含量显著增加，C：N显著降低，而细根C、N、P含量及化学计量比没有显著变化。由此可知毛竹地上部分叶片和地下部分细根对穿透雨减少、氮添加及两者交互作用表现出不同的响应策略。本研究可为全球变化背景下毛竹人工林可持续经营提供理论依据。;The drought caused by global climate change and the increased atmospheric nitrogen deposition caused by human activities will directly affect the structure and function of forest ecosystems. Leaves and fine roots are the most important resource-obtaining functional organs of plants, whose stoichiometry characteristics can indicate their resource utilization and survival adaptation strategies. Under the background of climate change, understanding the stoichiometry and adaptive characteristics of plants will be beneficial to predict future changes in the forest's ecosystem functions. Through a two-factor interaction experiment for one year, this study explored the response characteristics of the stoichiometry ratio of carbon (C), nitrogen (N), and phosphorus (P) elements in leaves and fine roots of Moso bamboo (Phyllostachys edulis) forest (an important subtropical forest type in China) under the dual influences of throughfall reduction and nitrogen addition. It is of great significance for understanding the adaptation of Moso bamboo forest ecosystem to global changes and nutrient utilization strategies. The results showed that (1) the throughfall reduction significantly decreased N and P contents in leaves, but significantly increased N content in fine roots, and had no significant effect on C content in leaves as well as C and P contents in fine roots. Nitrogen addition significantly increased N content of soil and N content in leaves, but had no significant effect on C, P contents in leaves and C, N, P contents in fine roots. (2) The throughfall reduction, nitrogen addition and their interaction had no significant effect on the ratio of C:N:P of soil. (3) The throughfall reduction significantly increased the ratios of C:N, C:P, and N:P in leaves. Nitrogen addition significantly decreased the ratio of C:N in leaves, but had no significant effect on the ratios of C:P and N:P in leaves. The interaction of throughfall reduction and nitrogen addition significantly decreased the ratios of C:N and C:P in leaves, but had no significant effect on the ratio of N:P in leaves. (4) The throughfall reduction significantly decreased the ratio of C:N in fine roots, but had no significant effect on the ratios of C:P and N:P in fine roots. Nitrogen addition and the interaction of throughfall reduction and nitrogen addition had no effect on the ratio of C:N:P in fine roots. Our study indicated that Moso bamboo adopted strategies to reduce N and P contents in leaves, increase N content in fine roots, improve N and P utilization efficiency in leaves, and maintain fine roots' stable P utilization efficiency. Nitrogen addition failed to alleviate drought stress caused by the throughfall reduction on Moso bamboo. Moso bamboo coped with drought stress through changed N distribution pattern and N, P utilization efficiency between the aboveground (leaves) and the underground (fine roots). Under the treatment of nitrogen addition, N content in leaves increased significantly, and the ratio of C:N decreased significantly. However, C, N, and P contents in fine roots as well as the stoichiometric ratio did not change significantly. It can be seen that the aboveground (leaves) and the underground (fine roots) of Moso bamboo have different response strategies to the throughfall reduction, nitrogen addition and their interaction. This study can provide theoretical basis for the sustainable management of Moso bamboo plantation under the background of global change.

Impacts of copper contamination on a rocky intertidal predator-prey interaction

Metal contamination can change ecological interactions with potential effects on community dynamics. However, understanding real effects of metals on biota relies on studies undertaken in natural conditions. Through a field experiment, we investigated the effects of copper contamination on the responses of a barnacle prey and its predator, the dogwhelk, and explicitly their interaction. Contamination increased barnacle mortality and reduced predation with no effects on interaction strength. This was because the higher mortality of the prey compensated for the lower consumption of the predator. Despite not affecting the interaction strength, these results suggest a decrease in energy flow in the trophic chain that may lead to important changes in community structure and ecosystem functioning. This study shows the importance of manipulative experiments designed to provide mechanistic insights into ecological interactions to better clarify the effect of stressors on the structure and dynamic of communities.

Post-2020 biodiversity targets need to embrace climate change

Recent assessment reports by the Intergovernmental Panel on Climate Change (IPCC) and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) have highlighted the risks to humanity arising from the unsustainable use of natural resources. Thus far, land, freshwater, and ocean exploitation have been the chief causes of biodiversity loss. Climate change is projected to be a rapidly increasing additional driver for biodiversity loss. Since climate change and biodiversity loss impact human societies everywhere, bold solutions are required that integrate environmental and societal objectives. As yet, most existing international biodiversity targets have overlooked climate change impacts. At the same time, climate change mitigation measures themselves may harm biodiversity directly. The Convention on Biological Diversity’s post-2020 framework offers the important opportunity to address the interactions between climate change and biodiversity and revise biodiversity targets accordingly by better aligning these with the United Nations Framework Convention on Climate Change Paris Agreement and the Sustainable Development Goals. We identify the considerable number of existing and proposed post-2020 biodiversity targets that risk being severely compromised due to climate change, even if other barriers to their achievement were removed. Our analysis suggests that the next set of biodiversity targets explicitly addresses climate change-related risks since many aspirational goals will not be feasible under even lower-end projections of future warming. Adopting more flexible and dynamic approaches to conservation, rather than static goals, would allow us to respond flexibly to changes in habitats, genetic resources, species composition, and ecosystem functioning and leverage biodiversity’s capacity to contribute to climate change mitigation and adaptation.