168 research outputs found

    Data for "Nitrogen enrichment induces more plant species loss under drier conditions"

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    Nitrogen (N) deposition is a major driver of plant species loss worldwide. However, what regulates N-driven species loss remains unclear. Based on a 7-year field experiment on the Qinghai-Tibetan Plateau, we found that the impact of N addition on plant species richness strongly depended on precipitation. During experimental years with lower precipitation, N addition induced more species loss. The main underlying mechanism was that lower precipitation stimulated soil inorganic N accumulation under N addition, resulting in stronger competitive exclusion and ammonium toxicity in plant communities. These site observations were complemented by a global synthesis derived from 45 N addition experiments, showing N-induced more species loss in dry than in wet ecosystems. Given the importance of plant species richness in supporting ecosystem functioning and stability, our findings suggest that ecosystems during drought periods or in arid areas are particularly sensitive to N deposition, having important implications for their management and conservation.</p

    Seed nutrient is more stable than leaf in response to changing multiple resources in an alpine meadow

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    Abstract Background It has been long thought that nitrogen (N), phosphorus (P) concentrations and their ratios (N:P) in metabolically active or functional organs (i.e., leaves) are less responsive to environmental changes. Little attention, however, has been paid to the reproductive organs‚ÄĒseeds, while seeds may maintain their nutrients more stable for the evolutionary fitness of next generation. Methods Here, we conducted a field experiment of N, P addition and drought in an alpine meadow, aiming to compare the difference of leaf and seed nutrients and stoichiometric ratios in response to these resource treatments and their interactions. Four dominant species were selected among grass and forb functional groups, including Elymus nutans, Deschampsia caespitosa, Artemisia roxburghiana and Polygonum viviparum. Results Under natural conditions, leaf N and P concentrations were consistently lower than seed among species. However, leaf nutrients were much more sensitive than seed nutrients to N and P addition. Specifically, N or P addition accordingly increased leaf N or P concentration by 22.20‚Äď44.24% and 85.54‚Äď93.61%, while only enhanced seed N or P concentration by 5.15‚Äď17.20% and 15.17‚Äď32.72%, respectively. Leaf N or P concentration was significantly reduced by P or N addition, but seed nutrients remained unchanged. In contrast, drought did not change both organ nutrients. Similarly, nutrient addition and drought had synergistic interactions on leaf nutrients, but not on seed nutrients. Conclusions This study highlights that seed nutrient concentrations could be more stable than metabolically active leaf organ when facing multidimensional resource changes. This complements the traditional view on the ‚ÄėStable Leaf Nutrient Hypothesis‚Äô with the involvement of reproductive organs. The less responsiveness of seed nutrients suggests the adaptive strategy to ensure the success of next generations and long-term plant demographic stability

    Soil microbial respiration adapts to higher and longer warming experiments at the global scale

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    Warming can affect soil microbial respiration by changing microbial biomass and community composition. The responses of soil microbial respiration to warming under experimental conditions are also related to background conditions and the experimental setup, such as warming magnitude, duration, and methods. However, the global pattern of soil microbial respiration in response to warming and underlying mechanisms remain unclear. Here, we conducted a global meta-analysis of the response of soil microbial respiration to warming by synthesizing data from 187 field experiments. We found that experimental warming significantly increased soil microbial respiration and microbial biomass carbon by 11.8% and 6.4%, respectively. The warming-induced increase in microbial carbon decomposition was positively correlated with increased microbial biomass carbon, but not community composition. Moreover, the positive response of soil microbial respiration marginally increased with warming magnitude, particularly in short-term experiments, but soil microbial respiration adapted to higher warming at longer timescales. Warming method did not significantly affect the response of microbial respiration, except for a significant effect with open top chamber warming. In addition, the impact of warming on soil microbial respiration was more pronounced in wetter sites and in sites with lower soil pH and higher soil organic carbon. Our findings suggest that warming stimulates microbial respiration mainly by increasing microbial biomass carbon. We also highlight the importance of the combination of warming magnitude and duration in regulating soil microbial respiration responses, and the dependence of warming effects upon background precipitation and soil conditions. These findings can advance our understanding of soil carbon losses and carbon-climate feedbacks in a warm world

    Critical role of multidimensional biodiversity in contributing to ecosystem sustainability under global change

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    The 21st century has seen an acceleration of global change, including climate change, elevated carbon dioxide, nitrogen deposition, and land-use intensification, which poses a significant threat to ecosystem functioning. Nevertheless, studies on the relationship between biodiversity and ecosystem functioning (BEF) have consistently demonstrated that biodiversity enhances ecosystem functioning and its stability, even in variable environmental conditions. These findings potentially indicate the critical role of biodiversity in promoting sustainable provisioning of ecosystem functioning under global change. Our paper provides a comprehensive review of current BEF research and the response of BEF to multiple global change factors. We demonstrate that (1) assessing the effects of biodiversity on ecosystem functioning requires consideration of multiple dimensions of diversity, such as diversity across multiple trophic levels (plants, animals, and microbes), multiple facets (taxonomy, functional traits, and phylogeny), and multiple spatial scales (local, regional, and landscape scales). (2) The interaction of multiple global change factors may lead to a greater reduction in biodiversity and ecosystem functioning than a single global change factor. (3) Multidimensional biodiversity regulates the response of ecosystem functioning to global change factors, indicating that high levels of multidimensional biodiversity can mitigate the negative impacts of global change on ecosystem functioning. Overall, we emphasize that recognizing the importance of multidimensional biodiversity is critical for sustaining ecosystem functioning. Therefore, prioritizing conservation efforts to maintain and enhance all dimensions of biodiversity is essential to address the challenges of future global change

    A meta‚Äźanalysis highlights globally widespread potassium limitation in terrestrial ecosystems

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    Summary Potassium (K + ) is the most abundant inorganic cation in plant cells, playing a critical role in various plant functions. However, the impacts of K on natural terrestrial ecosystems have been less studied compared with nitrogen (N) and phosphorus (P). Here, we present a global meta‚Äźanalysis aimed at quantifying the response of aboveground production to K addition. This analysis is based on 144 field K fertilization experiments. We also investigate the influences of climate, soil properties, ecosystem types, and fertilizer regimes on the responses of aboveground production. We find that: K addition significantly increases aboveground production by 12.3% (95% CI: 7.4‚Äď17.5%), suggesting a widespread occurrence of K limitation across terrestrial ecosystems; K limitation is more prominent in regions with humid climates, acidic soils, or weathered soils; the effect size of K addition varies among climate zones/regions, and is influenced by multiple factors; and previous N : K and K : P thresholds utilized to detect K limitation in wetlands cannot be applied to other biomes. Our findings emphasize the role of K in limiting terrestrial productivity, which should be integrated into future terrestrial ecosystems models

    FLUXNET-CH4: a global, multi-ecosystem dataset and analysis of methane seasonality from freshwater wetlands

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    Abstract. Methane (CH4) emissions from natural landscapes constitute roughly half of global CH4 contributions to the atmosphere, yet large uncertainties remain in the absolute magnitude and the seasonality of emission quantities and drivers. Eddy covariance (EC) measurements of CH4 flux are ideal for constraining ecosystem-scale CH4 emissions due to quasi-continuous and high-temporal-resolution CH4 flux measurements, coincident carbon dioxide, water, and energy flux measurements, lack of ecosystem disturbance, and increased availability of datasets over the last decade. Here, we (1) describe the newly published dataset, FLUXNET-CH4 Version 1.0, the first open-source global dataset of CH4 EC measurements (available at https://fluxnet.org/data/fluxnet-ch4-community-product/, last access: 7 April 2021). FLUXNET-CH4 includes half-hourly and daily gap-filled and non-gap-filled aggregated CH4 fluxes and meteorological data from 79 sites globally: 42 freshwater wetlands, 6 brackish and saline wetlands, 7 formerly drained ecosystems, 7 rice paddy sites, 2 lakes, and 15 uplands. Then, we (2) evaluate FLUXNET-CH4 representativeness for freshwater wetland coverage globally because the majority of sites in FLUXNET-CH4 Version 1.0 are freshwater wetlands which are a substantial source of total atmospheric CH4 emissions; and (3) we provide the first global estimates of the seasonal variability and seasonality predictors of freshwater wetland CH4 fluxes. Our representativeness analysis suggests that the freshwater wetland sites in the dataset cover global wetland bioclimatic attributes (encompassing energy, moisture, and vegetation-related parameters) in arctic, boreal, and temperate regions but only sparsely cover humid tropical regions. Seasonality metrics of wetland CH4 emissions vary considerably across latitudinal bands. In freshwater wetlands (except those between 20‚ąė S to 20‚ąė N) the spring onset of elevated CH4 emissions starts 3 d earlier, and the CH4 emission season lasts 4 d longer, for each degree Celsius increase in mean annual air temperature. On average, the spring onset of increasing CH4 emissions lags behind soil warming by 1 month, with very few sites experiencing increased CH4 emissions prior to the onset of soil warming. In contrast, roughly half of these sites experience the spring onset of rising CH4 emissions prior to the spring increase in gross primary productivity (GPP). The timing of peak summer CH4 emissions does not correlate with the timing for either peak summer temperature or peak GPP. Our results provide seasonality parameters for CH4 modeling and highlight seasonality metrics that cannot be predicted by temperature or GPP (i.e., seasonality of CH4 peak). FLUXNET-CH4 is a powerful new resource for diagnosing and understanding the role of terrestrial ecosystems and climate drivers in the global CH4 cycle, and future additions of sites in tropical ecosystems and site years of data collection will provide added value to this database. All seasonality parameters are available at https://doi.org/10.5281/zenodo.4672601 (Delwiche et al., 2021). Additionally, raw FLUXNET-CH4 data used to extract seasonality parameters can be downloaded from https://fluxnet.org/data/fluxnet-ch4-community-product/ (last access: 7 April 2021), and a complete list of the 79 individual site data DOIs is provided in Table 2 of this paper

    A globally robust relationship between water table decline, subsidence rate, and carbon release from peatlands

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    International audienceAbstract Peatland ecosystems are globally important carbon stores. Disturbances, such as drainage and climate drying, act to lower peatland water table depths, consequently enhancing soil carbon release and subsidence rates. Here, we conduct a global meta-analysis to quantify the relationship among water table depth, carbon release and subsidence. We find that the water table decline stimulated heterotrophic, rather than autotrophic, soil respiration, which was associated with an increase in subsidence rate. This relationship held across different climate zones and land uses. We find that 81% of the total annual soil respiration for all drained peatlands was attributable to tropical peatlands drained for agriculture and forestry and temperate peatlands drained for agriculture. Globally, we estimate that, drained peatlands release 645‚ÄČMt‚ÄČC‚ÄČyr ‚Äď1 (401‚Äď1025‚ÄČMt‚ÄČC‚ÄČyr ‚Äď1 ) through soil respiration, equivalent to approximately 5% of global annual anthropogenic carbon emissions. Our findings highlight the importance of conserving pristine peatlands to help mitigate climate change

    Tracking Global Patterns of Drought‚ÄźInduced Productivity Loss Along Severity Gradient

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    International audienceDrought is a major environmental risk for land ecosystems that causes significant mortality and considerable productivity reductions (Allen et al., 2010). In the context of global changes, droughts are increasing rapidly both in frequency and severity (Sheffield & Wood, 2008; Trenberth et al., 2014). Along with this, Earth system model projections show that the frequencies of extreme and severe droughts will vastly expand in the next decades (Dai, 2013; Zhai et al., 2020). For instance, a recent projection by 13 CMIP (coupled model intercomparison project) models showed that the frequencies of extreme droughts were likely to expand to 3.8 times in 2075-2099 relative to 1850-1999 under the high emission scenario RCP (representative concentration pathway) 8.5 (C. Xu, McDowell et al., 2019). The projected increase in drought severities and extreme events are consistent with the observed patterns over the last few decades (Chiang et al., 2021; Vicente-Serrano et al., 2014). For instance, rising temperatures have led to a significant increase in drought severity and the occurrences of extreme droughts in the European region (Grillakis, 2019; Markonis et al., 2021). Drought causes significant reductions in gross primary productivities (GPP)

    State of science in carbon budget assessments for temperate forests and grasslands

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    With the abundance of observations and advancement in modeling, temperate regions allow for a comprehensive comparison of the data-driven and process-based methods of carbon budget estimation. This chapter presents a review of the latest methodologies for carbon budget and component flux estimation, and the key components in the temperate carbon budget, such as forest regrowth, and summarizes uncertainties in the current carbon budget of temperate ecosystems that the research community needs to resolve. Lastly, we describe the key progress made in the carbon budget assessment in past decades, and how it should be further advanced to be useful for policy decision-making
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