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Are there links between responses of soil microbes and ecosystem functioning to elevated CO2, N deposition and warming? A global perspective
Abstract
In recent years there has been an increase in research to understand how global changes’ impacts on soil biota translate into altered ecosystem functioning. However, results vary between global change effects, soil taxa and ecosystem processes studied, and a synthesis of relationships is lacking. Therefore, here we initiate such a synthesis to assess whether the effect size of global change drivers (elevated CO2, N deposition and warming) on soil microbial abundance is related with the effect size of these drivers on ecosystem functioning (plant biomass, soil C cycle and soil N cycle) using meta-analysis and structural equation modeling. For N deposition and warming, the global change effect size on soil microbes was positively associated with the global change effect size on ecosystem functioning, and these relationships were consistent across taxa and ecosystem processes. However, for elevated CO2, such links were more taxon and ecosystem process specific. For example, fungal abundance responses to elevated CO2 were positively correlated with those of plant biomass but negatively with those of the N cycle. Our results go beyond previous assessments of the sensitivity of soil microbes and ecosystem processes to global change, and demonstrate the existence of general links between the responses of soil microbial abundance and ecosystem functioning. Further we identify critical areas for future research, specifically altered precipitation, soil fauna, soil community composition, and litter decomposition, that are need to better quantify the ecosystem consequences of global change impacts on soil biodiversity.This article is protected by copyright. All rights reserved.
... The differential between the climate factors that affect EMF in dry and wet seasons is probably related to water stress. Most soil microorganisms are sensitive to local changes in temperature (Garcıá-Palacios et al., 2015;van der Voort et al., 2016;Karimi et al., 2018). The direct effects of higher temperature and humidity Links between network complexity and multifunctionality in dry and wet season. ...
... can forcefully affect different ecosystem functions related to microbial productivity or metabolism (Yvon-Durocher et al., 2012). Climate change may alter the composition of plant and soil communities and thereby also their interactions (Garcıá-Palacios et al., 2015). Hence the differential relationship arising between network complexity and EMF in dry and wet seasons. ...
Microbial communities, which are affected by soil types and climate factors, contribute to maintain the function of terrestrial ecosystems. Recent studies have shown that interdomain relationships in below–aboveground communities may contribute greatly to ecosystem functioning. However, the responses of interactions among plant, soil fungal, and bacterial communities to the change of woodland use and their effects on ecosystem multifunctionality (EMF) remain poorly understood. In this study, the plant–microbe and fungi–bacteria interdomain ecology network (IDEN) based on SparCC pairwise associations were constructed by simultaneous aboveground plant surveys and belowground microbial analyses among four different woodland use intensities (WUI) along different seasons. The effects of different seasons on these relationships were surveyed to probe into the links to EMF. With the increase of woodland use intensity, the plant–microbe network complexity decreased, while the fungus–bacteria network complexity increased. In both dry and wet seasons, ecosystem multifunctionality decreased with the increase of woodland use intensity. Some tree species are the network hubs and may play a pivotal role in the community structure stability of the forest ecosystem. During the dry season, WUI could indirectly affect EMF through plant–microbial network complexity. During the wet season, WUI had a direct effect on EMF. WUI also indirectly affected EMF through plant–microbial network complexity and fungus–bacterial network complexity. Air temperature is the main climatic factor for EMF in the dry season, while soil moisture content is the climatic factor for EMF in the wet season. Our study revealed the important role of the relationship between plants and their associated soil microbial communities (IDENs) in maintaining ecosystem processes and function. Investigating the recovery dynamics of inter-domain ecological networks after extreme disturbances is important for understanding the overall development of ecosystems.
... Similar to plants, soil microorganisms are sensitive to global changes such as rising atmospheric CO 2 concentrations. As a result, changes in the community structure and diversity of microorganisms can impact ecosystem processes that are influenced by these microorganisms (Garcia-Palacios et al., 2015). The complex, diversified communities that makeup soil biota can alter in abundance, composition, and physiology as a result of climate change (Eisenhauer et al., 2012;Li et al., 2022). ...
... Through our empirical evidence-based metaanalysis, we present a global-scale evaluation of the impact of eCO 2 on plant and soil microbial biomass. Our findings are generally consistent with prior studies that have reported increased biomass production and microbial biomass in response to eCO 2 (De Graaff et al., 2006;Luo et al., 2006;Wang et al., 2012;Garcia-Palacios et al., 2015;Terrer et al., 2021). Our analysis revealed that plant aboveground biomass production is primarily driven by climatic and experimental conditions, whereas belowground /microbial biomass is more influenced by soil properties such as TN/CN, pH, and SOC (Figure 3; Figure 5). ...
Introduction
The stimulation of plant and microbial growth has been widely observed as a result of elevated CO 2 concentrations (eCO 2 ), however, this stimulation could be influenced by various factors and their relative importance remains unclear.
Methods
A global meta-analysis was performed using 884 lines of observations collected from published papers, which analyzed the eCO 2 impact on plant and microbial biomass.
Results
A significant positive impact of eCO 2 was observed on various biomass measures, including aboveground biomass (20.5%), belowground biomass (42.6%), soil microbial biomass (10.4%), fungal biomass (11.0%), and bacterial biomass (9.2%). It was found that eCO 2 levels above 200 ppm had a greater impact on plant biomass compared to concentrations at or below 200 ppm. On the other hand, studies showed that positive effects on microbial biomass were more prominent at lower eCO 2 levels (≤200 ppm) than at higher levels (>200 ppm), which could be explained by soil nitrogen limitations. Importantly, our results indicated that aboveground biomass was controlled more by climatic and experimental conditions, while soil properties strongly impacted the stimulation of belowground and microbial biomass.
Discussion
Our results provided evidence of the eCO 2 fertilization effect across various ecosystem types, experimental methods, and climates, and provided a quantitative estimate of plant and soil microbial biomass sensitivity to eCO 2 . The results obtained in this study suggest that ecosystem models should consider climatic and edaphic factors to more accurately predict the effects of global climate change and their impact on ecosystem functions.
... ability to remain unchanged when subjected to a disturbance) to predicted alterations in temperature and precipitation (Blankinship et al., 2011, 2011de Vries and Griffiths, 2018. Studies on the effects of altered precipitation are particularly scarce since they have traditionally received lower attention than the effects of warming (García-Palacios et al., 2015;Nielsen and Ball, 2015, 2015de Vries and Griffiths, 2018. However, the proliferation in recent years of rainfall exclusion infrastructures in the field has strongly contributed to improve this knowledge, providing empirical support for the large capacity of climate change-related drought to alter the abundance and composition of soil communities, but also evidencing the strong variability of these impacts through spatio-temporal gradients and among taxonomic groups (Blankinship et al., 2011;Ren et al., 2018). ...
... Current knowledge of climate change impacts on soil organisms, and of rainfall reduction effects in particular, is very much based on the study of the two main kingdoms of soil microorganisms (fungi and bacteria), whereas soil animals have been comparatively unexplored (García-Palacios et al., 2015;Ren et al., 2018;Nielsen, 2019). Within soil fauna, nematodes represent the most abundant group (Wilson and Kakouli-Duarte, 2009) and can serve as a unique model taxon for the study of rainfall reduction effects on the soil compartment. ...
... Some studies have demonstrated that after initially being enhanced by warming in the short term, microbial respiration would then be expected to continuously or periodically recover to previous levels-or even decrease-under long-term warming across diverse terrestrial ecosystems due to thermal acclimation driven by changes in the structure and composition of the microbial communities and/or physiological modification (Melillo et al. 2003;Melillo et al. 2017;Bradford et al. 2008;Chen et al. 2020), while others have shown no evidence of any such acclimation (Hartley et al. 2008;Karhu et al. 2014). These contrasting results about microbial thermal response are mostly derived from single warming experiments; however, it is important to recognize that under global change scenarios, the response of microbial respiration to warming is determined by multiple environmental factors simultaneously rather than by the temperature alone (Nie et al. 2013;Garcia-Palacios et al. 2015). Whether other global change factors can mediate the thermal acclimation of microbial respiration is still unknown, limiting our ability to make predictions regarding future soil C-climate feedbacks. ...
... Previous studies have demonstrated that changes in these microbial physiological properties could regulate the thermal acclimation of microbial respiration (Allison et al. 2010;Hall et al. 2010;German et al. 2012;Bradford 2013;Birgander et al. 2018;Donhauser et al. 2020), and thus we propose that the thermal acclimation is likely to be altered by N enrichment. Though previous studies have been focused on the single and/or combined effects of N addition and warming on soil respiration and microbial physiology (Bell et al. 2010;Graham et al. 2014;Garcia-Palacios et al. 2015;Fang et al. 2018), no attempt has been made to examine environmental factors other than temperature that regulate such acclimation or quantify the acclimation strength. Such multifactor experiments are important to improve the predictive ability of coupledclimate models, as single factor experiments may miss the details to predict interactive effects of global change drivers (Norby & Luo 2004;Leuzinger et al. 2011). ...
As the climate warms, the feedback between soil carbon (C) and climate can decrease in magnitude over time due to the thermal acclimation of microbial respiration. However, the strength of microbial thermal acclimation is highly uncertain, partly because the response of microbial respiration is regulated by multiple environmental factors acting simultaneously rather than by temperature alone. Here we use a theoretical representation method to visually quantify the magnitude of thermal acclimation of microbial respiration based on a 9-year two-way factorial experiment involving warming and multilevel nitrogen (N) enrichment treatments in alpine permafrost. The results showed that mass-specific respiration rates were significantly lower in warmed soils when N enrichment was higher. Post-acclimation Q10 was as much as 1.6 times higher for soils sampled from no N enrichment treatment than from the highest N enrichment concentration treatment. These results suggested that respiration rate reductions under warming likely occurred through N-induced changes in the soil and microbial community and that the thermal strength acclimation gradually increases as N enrichment increases. We identified two contrasting pathways by which N enrichment appears to affect the strength of thermal acclimation using the structural equation model—1) via an enhancement of acclimation caused by soil acidification and 2) a weakening of acclimation caused by the inhibition of soil C availability and stimulation of soil C-degrading enzymes. Our findings emphasize the importance of considering multiple environmental change factors in shaping the strength of thermal acclimation when predicting future soil C-climate feedbacks.
... Soil microbial communities have important effects on maintaining multiple ecosystem services and functions simultaneously [70,71]. They are sensitive to environmental changes, and alterations in microbial abundance or diversity can have an impact on ecosystem processes and functions [9,69,70]. ...
... Soil microbial communities have important effects on maintaining multiple ecosystem services and functions simultaneously [70,71]. They are sensitive to environmental changes, and alterations in microbial abundance or diversity can have an impact on ecosystem processes and functions [9,69,70]. In our study, the relative abundance of microbial functional genes involved in N and P cycling was significantly higher at the low-elevation sites (SJY-3490 and SJY-3220) than at the SJY-4790 site, suggesting that soil microbial functions related to N and P cycles might have a faster change than C degradation functions. ...
Soil microbes play important roles in determining plant community composition and terrestrial ecosystem functions, as well as the direction and extent of terrestrial ecosystem feedback to environmental changes. Understanding the distribution patterns of plant and soil microbiota along elevation gradients is necessary to shed light on important ecosystem functions. In this study, soil bacteria along an elevation gradient in an alpine meadow ecosystem of the Qinghai–Tibetan Plateau were investigated using Illumina sequencing and GeoChip technologies. The community structure of the soil bacteria and plants presented a continuous trend along the elevation gradient, and their alpha diversity displayed different distribution patterns; however, there were no linkages between them. Beta diversity of the soil bacteria and plants was significantly influenced by elevational distance changes (p < 0.05). Functional gene categories involved in nitrogen and phosphorus cycling had faster changes than those involved in carbon degradation, and functional genes involved in labile carbon degradation also had faster variations than those involved in recalcitrant carbon degradation with elevational changes. According to Pearson’s correlation, partial Mantel test analysis, and canonical correspondence analysis, soil pH and mean annual precipitation were important environmental variables in influencing soil bacterial diversity. Soil bacterial diversity and plant diversity had different distribution patterns along the elevation gradient.
... As anthropogenic greenhouse gas emissions increased, global warming has become a well-recognized phenomenon of concern among the general public (Yuan & Lu, 2020). Soils are of great importance in delivering ecosystem services, such as long-term carbon storage and mitigation of climate changes (de Vries et al., 2013), which are strongly dependent on soil microbially mediated carbon sequestration and nutrient cycles (Aislabie et al., 2013;de Vries et al., 2013;García-Palacios et al., 2015;J. Li, Nie, et al., 2020). ...
... Global warming is a well-recognized crisis that might alter the services and functions in various ecosystems, especially in coastal nontidal wetlands (Butler et al., 2012;Feher et al., 2017;Zhong et al., 2019), which are related to soil microbial activities (Aislabie et al., 2013;de Vries et al., 2013;García-Palacios et al., 2015;Jansson & Hofmockel, 2020). Studying the resistance of microbial communities to experimental warming helps to predict the stability of ecosystem functions under future warming scenarios (Allison et al., 2010). ...
Global warming may alter microbially mediated ecosystem functions through reshaping of microbial diversity and modified microbial interactions. Here, we examined the effects of 5‐years experimental warming on different microbial hierarchical groups in a coastal non‐tidal soil ecosystem, including prokaryotes (i.e. bacteria and archaea), fungi and Cercozoa which is a widespread phylum of protists. Warming significantly altered the diversity and structure of prokaryotic and fungal communities in soil, and additionally decreased the complexity of the prokaryotic network and fragmented the cercozoan network. By using the Inter‐Domain Ecological Network (IDEN) approach, the cross‐trophic interactions among prokaryotes, fungi, and Cercozoa were further investigated. Under warming, cercozoan‐prokaryotic and fungal‐prokaryotic bipartite networks were simplified, while the cercozoan‐fungal network became slightly more complex. Despite simplification of the fungal‐prokaryotic network, the strengthened synergistic interactions between saprotrophic fungi and certain prokaryotic groups, such as the Bacteroidetes, retained these phyla within the network under warming. Also, the interactions within the fungal community were quite stable under warming conditions, which stabilized the interactions between fungi and prokaryotes or protists. Additionally, we found the microbial hierarchical interactions were affected by environmental stress (i.e., salinity and pH) and soil nutrients. Interestingly, the relevant microbial groups could respond to different soil properties under ambient conditions, while under warming these two groups tended to respond to similar soil properties, suggesting network hub species responded to certain environmental changes related to warming, and then transferred this response to their partners through trophic interactions. Finally, warming strengthened the network modules’ negative association with soil organic matters through some fungal hub species, which might trigger soil carbon loss in this ecosystem. Our study provides new insights into the response and feedback of microbial hierarchical interactions under warming scenario.
... Climate change will continue to have a escalating impact on forests (Newaz et al. 2021;Sperry et al. 2019). Elevated CO 2 and warming are major drivers of global change and may interact with increases in soil nutrient supply associated with increased nitrogen deposition (García P. et al. 2015;M. G. R. et al. 1998;Penuelas et al. 2020). ...
Rising CO2, global warming, and N deposition create challenging environmental conditions to vegetation. Since elevated CO2 and rising temperature are coupled with each other, it is important to understand their combined effects on plants. We investigated the growth and photosynthetic responses of yellow birch to five levels of nitrogen supply under the current (cCT: current CO2 and temperature) and the predicted future CO2 and temperature conditions (fCT: elevated CO2, current + 4℃ temperature). The results show that fCT and high N supply increased seedling growth but fCT reduced photosynthetic capacity (e.g., maximum rate of Rubisco carboxylation-Vcmax, maximum rate of photosynthetic electron transport-Jmax)) and foliar N concentration. However, the magnitude of the fCT effect declined with increases in N supply. Furthermore, the fCT treatment significantly reduced the Jmax/Vcmax ratio, indicating a possible shift of N allocation from Jmax to Vcmax in the photosynthetic machinery. This result suggests that the photosynthesis of yellow birch may be more limited by electron transport under the predicted future climate condition. Both low N supply and fCT significantly increased photosynthetic N use efficiency (PNUE) and there was a negative relationship between PNUE and photosynthetic capacity. In general, yellow birch grew better under fCT than cCT, particularly above-ground growth.
... There are several possible explanations for this change before and after N addition. Firstly, previous studies conducted in semi-arid steppes [14] and on a global scale [39] have documented that decreased pH induced by N fertilization plays a vital role in the soil microbial community [38]. Although our Mantel test and RDA also suggested that pH induced by N addition significantly influenced microbial community composition, pH in our case showed an increasing trend after N additions (Tables 1 and S1; Figures 5 and 6). ...
The effects of increased nitrogen (N) deposition on desert ecosystems have been extensively studied from a plant community perspective. However, the response of soil microbial communities, which play a crucial role in nutrient cycling, to N inputs and plant community types remains poorly understood. In this study, we conducted a two-year N-addition experiment with five gradients (0, 10, 30, 60, and 120 kg N ha −1 year −1) to evaluate the effect of increased N deposition on soil bacterial and fungal communities in three plant community types, namely, Alhagi sparsifolia Shap., Karelinia caspia (Pall.) Less. monocultures and their mixed community in a desert steppe located on the southern edge of the Taklimakan Desert, Northwest China. Our results indicate that N deposition and plant community types exerted an independent and significant influence on the soil microbial community. Bacterial α-diversity and community dissimilarity showed a unimodal pattern with peaks at 30 and 60 kg N ha −1 year −1, respectively. By contrast, fungal α-diversity and community dissimilarity did not vary significantly with increased N inputs. Furthermore, plant community type significantly altered microbial community dissimilarity. The Mantel test and redundancy analysis indicated that soil pH and total and inorganic N (NH 4 + and NO 3 −) levels were the most critical factors regulating soil microbial communities. Similar to the patterns observed in taxonomic composition, fungi exhibit stronger resistance to N addition compared to bacteria in terms of their functionality. Overall, our findings suggest that the response of soil microbial communities to N deposition is domain-specific and independent of desert plant community diversity, and the bacterial community has a critical threshold under N enrichment in arid deserts.
... The criteria of selecting appropriate studies applied were as follows: (1) experimental sites must include both control and N addition treatments; (2) the values and sample sizes for the treatment and control groups were directly reported or could be extracted; (3) in order to compare the soil P fractions of different studies, we only included the uppermost soil layer that is most sensitive to nutrient input (Garcia-Palacios et al. 2015). The methods for soil P fractions in (Hedley et al. 1982;Tiessen and Moir 1993). ...
Purpose
The escalation of nitrogen (N) deposition has resulted in phosphorus (P) limitation in alpine grasslands on the Qinghai–Tibetan Plateau (QTP). However, the impact of N deposition affects soil P transformations in alpine grasslands, and whether there is a universal pattern of N-induced soil P fraction change in terrestrial ecosystems is still not well understood.
Methods
We performed field experiments in two alpine grasslands on the QTP and a meta-analysis including 1033 records worldwide to analyze the responses of soil P fractions to N addition.
Results
We found that N addition significantly altered soil P fractions in alpine meadow, whereas it induced a minor response in alpine steppe. The N addition induced a decrease in soil inorganic phosphorus (Pi) in the alpine meadow, resulting from occluded P (i.e., C.HCl-Pt and residual-Pt). Though N addition did not change total organic P (Po) concentration, there were remarkable changes among soil organic P fractions (C.HCl-Po, NaOH-Po, and NaHCO3-Po) in the alpine meadow, with an increase in NaOH-Po but a decrease in C.HCl-Po. Soil inorganic P in the alpine meadow was associated with Ca²⁺ and soil pH that was also reduced by N addition. By contrast, meta-analysis results showed that N addition significantly increased the lnRR of NaOH-Pi, but decreased lnRR of C.HCl-Pt and marginally reduced lnRR of NaHCO3-Po across all terrestrial ecosystems. Among multiple environmental and experimental variables, soil pH, mean annual temperature (MAT), mean annual precipitation (MAP), N forms, and soil phosphatase activity mainly drove the response of NaHCO3-Po to N addition at the large scale. Structural equation model (SEM) further showed that soil phosphatase activity was the main direct factor controlling NaHCO3-Po response.
Conclusions
Our results suggest that soil P fractions are more sensitive to N addition in alpine meadow than in alpine steppe. The reduction of inorganic P fractions and uneven changes of organic P fractions in alpine meadow suggested that N addition may accelerate inorganic P dissolution but depress organic P mineralization. Environmental factor (e.g., MAP) and experimental variables (N rate) affected soil P fractions in response to N addition mediated by soil pH and enzymatic activities. Collectively, these findings improved our understanding of the consequences of N addition on soil organic and inorganic P transformations and predicted the trajectory of soil phosphorus fraction change under increasing N deposition.
... Sinauer Associates Inc., Sunderland, MA, USA). To mitigate the potential reduction in overall heterogeneity in effect sizes, we included the study ID as a random effect [54]. ...
... Overall when aggregated into a (multi)functionality index and compared across studies, warming tends to have positive effects on EMF (Zhou, Wang, and Luo 2020). This is perhaps due to the larger effect size that warming has on ecosystem functions that are sensitive to kinetic effects (García-Palacios et al. 2015), increased enzyme activity in substrate limited warmed soils , or changes to microbial growth/carbon use efficiency that results in higher respiration relative to biomass accumulation (Li et al. 2019). ...
Across biomes, soil biodiversity promotes ecosystem functions. However, whether this relationship will be maintained under climate change is uncertain. Here, using two long-term warming experiments, we investigated how warming affects the relationship between ecosystem functions and microbial diversity across seasons, soil horizons, and warming duration. The soils in these warming experiments were heated +5 °C above ambient for 13 or 28 years. We measured seven different ecosystem functions representative of soil carbon cycling, soil nitrogen cycling, or nutrient pools. We also surveyed bacterial and fungal community diversity. We found that the relationship between ecosystem function and bacterial diversity and the relationship between ecosystem function and fungal diversity was unaffected by warming or warming duration. Ecosystem function, however, was significantly affected by season, with autumn samples having higher function than summer samples. Our findings further emphasize that season is a consistent driver of ecosystem function and that this is maintained even under simulated climate change.
Importance
Soils perform a variety of ecosystem functions, and soil microbial communities with higher diversity tend to promote the performance of these functions. Yet, biodiversity loss due to climate change threatens this relationship. Long-term global change studies provide the opportunity to examine the trajectory of the effects of climate change. Here, we utilized two long-term warming experiments, where soils have been heated +5 °C above ambient temperature for 13-28 years, to understand how increased temperatures affect the relationship between ecosystem function and soil microbial diversity. We observed that the effects of increased temperature on the relationship between bacterial diversity and ecosystem function were season-specific. This work emphasizes the role that environmental conditions, such as season, have on modulating effects of climate change. Additionally, these findings demonstrate the value of long-term ecological research in furthering our understanding of climate change.
... Further, environmental pollution (such as noise and air pollution) was stated as an impact of urban expansion by 227 (89.4%) respondents, and this viewpoint is supported in literature by Sekovski, (2012); Hammer, 2013;Janhall, 2015;Nieuwenhuijsen, (2016), and diagrammatically epitomized in Figures 6.5 and 6.6 respectively. Further, 138 (54.3%) respondents disclosed that global warming is an aftermath of urban expansion, (which is confirmed in literature by Dossena, 2012;Lu, 2013;García-Palacios, (2015). The impacts of urban expansion in the study area is further explained with a bar chart in Figure 7. ...
The ethical clearance certificate number for this research is KUL011SOLA01. This research elucidates the conceptualization of urbanization, urban sustainability, merits of coastal vegetation, and threats to urban expansion. Furthermore, this paper focuses on the analysis of the questionnaire, of which 300 copies were distributed to different categories of individuals in the study area, out of which a total of 254 copies were returned. The results revealed that 197 (80.7%) respondents confirmed the occurrence of environmental challenges, 33 (13.5%) others stated otherwise, while 14 (5.7%) claimed ignorance. Further, the researcher sought to know the causes of coastal vegetation loss; 190 (74.8%) respondents blamed it on urban expansion, 169 (66.8%) respondents stated it was due to deforestation activities. Other views cited by the respondents in this regard and their corresponding frequencies are as follows: bush fires (132/52.0%) and conversion of ecosystem land uses for crop cultivation (112/44.1%).
... Sinauer Associates Inc., Sunderland, MA, USA). To mitigate this potential reduction in overall heterogeneity in effect sizes, we included the study ID (study site) as a random effect (García-Palacios et al., 2015). Additionally, we performed a sensitivity analysis as suggested to identify studies with exceptionally high or low effects in the Shannon or Chao1 index datasets (Figs. ...
Biochar plays a crucial role in enhancing soil ecological functions and productivity, and mitigating environmental pollution. Despite the available studies conducted through high-throughput sequencing to understand the effects of biochar on soil bacterial diversity and richness, a comprehensive understanding remains elusive. Our global meta-analysis addresses this knowledge gap, incorporating 473 pairs of observations from 84 studies to assess soil bacterial diversity and richness response to biochar addition. We found that biochar application increased bacterial Shannon and Chao1 indices by 0.99 % and 6.45 % respectively. However, these positive effects were context-dependent, especially concerning bacterial diversity. Through aggregated boosted trees analysis, we determined that soil characteristics (including soil organic carbon and nitrogen contents, soil pH, and soil texture) had a more significant influence than biochar properties, experimental conditions, or climatic factors on soil bacterial diversity and richness post biochar addition. In particular, the soil carbon to nitrogen ratio stood out as the leading factor influencing the bacterial Shannon and Chao1 indices following biochar addition. Our findings offer new insights into biochar's influence on soil bacterial activity, taking into account biochar-mediated spatiotemporal variation. This information is pivotal for optimizing biochar characteristics and application to improve soil biological health.
... The stronger impacts of warming on fungi than bacteria have been widely reported [32,33]. One possibility is that most fungi have higher C assimilation efficiency and metabolic ability than bacteria, hence the warming-induced decrease in soil water availability could significantly inhibit the growth and activity of fungi, showing greater suppression on the biomass and diversity of fungi, especially in our experimental grassland which is largely water limited [23]. ...
Simple Summary
Global mean temperature has increased by 1.07 °C since the Industrial Revolution, which arouses people’s widespread concern about climate warming. Nighttime temperatures increase faster and higher than daytime temperatures around the world. Various microbial groups in the soil may respond differently to such asymmetrically diurnal warming and then change ecological functions. In this study, we used a ten-year experiment in a semi-arid grassland to examine the effects of daytime and nighttime warming on soil microbial composition. The results showed that short-term warming did not change soil microbial composition, but long-term daytime warming rather than nighttime warming decreased the fungi-to-bacteria ratio in soils. In addition, soil respiration enhanced with the decreasing fungi-to-bacteria ratio. This work implies the importance of soil microbial composition in regulating grassland C release under long-term warming, which may help us accurately assess the climate-C feedback in terrestrial ecosystems.
Abstract
Climate warming has profoundly influenced community structure and ecosystem functions in the terrestrial biosphere. However, how asymmetric rising temperatures between daytime and nighttime affect soil microbial communities that predominantly regulate soil carbon (C) release remains unclear. As part of a decade-long warming manipulation experiment in a semi-arid grassland, we aimed to examine the effects of short- and long-term asymmetrically diurnal warming on soil microbial composition. Neither daytime nor nighttime warming affected soil microbial composition in the short term, whereas long-term daytime warming instead of nighttime warming decreased fungal abundance by 6.28% (p < 0.05) and the ratio of fungi to bacteria by 6.76% (p < 0.01), which could be caused by the elevated soil temperature, reduced soil moisture, and increased grass cover. In addition, soil respiration enhanced with the decreasing fungi-to-bacteria ratio, but was not correlated with microbial biomass C during the 10 years, indicating that microbial composition may be more important than biomass in modulating soil respiration. These observations highlight the crucial role of soil microbial composition in regulating grassland C release under long-term climate warming, which facilitates an accurate assessment of climate-C feedback in the terrestrial biosphere.
... Global changes have a series of consequences for the stability and resilience of the soil microbiome and its functionality (García-Palacios et al., 2015;Zhou et al., 2020). ...
Microbial necromass is an important source and component of soil organic matter (SOM), especially within the most stable pools. Global change factors such as anthropogenic nitrogen (N), phosphorus (P), and potassium (K) inputs, climate warming, elevated atmospheric carbon dioxide (eCO2 ), and periodic precipitation reduction (drought) strongly affect soil microorganisms and consequently, influence microbial necromass formation. The impacts of these global change factors on microbial necromass are poorly understood despite their critical role in the cycling and sequestration of soil carbon (C) and nutrients. Here, we conducted a meta-analysis to reveal general patterns of the effects of nutrient addition, warming, eCO2 , and drought on amino sugars (biomarkers of microbial necromass) in soils under croplands, forests, and grasslands. Nitrogen addition combined with P and K increased the content of fungal (+21%), bacterial (+22%), and total amino sugars (+9%), consequently leading to increased SOM formation. Nitrogen addition alone increased solely bacterial necromass (+10%) because the decrease of N limitation stimulated bacterial more than fungal growth. Warming increased bacterial necromass, because bacteria have competitive advantages at high temperatures compared to fungi. Other global change factors (P and NP addition, eCO2 , and drought) had minor effects on microbial necromass because of: (i) compensation of the impacts by opposite processes, and (ii) the short duration of experiments compared to the slow microbial necromass turnover. Future studies should focus on: (i) the stronger response of bacterial necromass to N addition and warming compared to that of fungi, and (ii) the increased microbial necromass contribution to SOM accumulation and stability under NPK fertilization, and thereby for negative feedback to climate warming.
... Two primary factors may be responsible for the lack of consensus regarding the influence of N fertilization and warming on nematodes. First, N fertilization and warming have different and partly opposite effects on the basal resources of soil food webs-for example, roots, bacteria and fungi-across ecosystems and climatic conditions, which in turn may influence nematode community structure (García-Palacios et al., 2015;Mueller et al., 2016). Second, the nematode community indices selected to detect environmental effects may not be sufficiently sensitive or focused on the hypotheses (Du Preez et al., 2022). ...
Nitrogen (N) fertilization and warming are two crucial global change factors affecting the soil nematode communities. The effects of N fertilization and warming, however, on nematode communities in soils are inconsistent across ecosystems and maybe be even opposite.
One key reason is that the commonly used taxonomic diversity is less sensitive to environmental changes than the seldom‐used trait‐based indicators. To verify this, we performed an 8‐year field experiment with four N fertilization levels with and without soil warming and collected an extensive dataset consisting of (i) six traits related to the nematode performance, that is, body size, maximum body length, maximum body width, stylet length, oesophagus length and intestinal length; (ii) the taxonomic alpha (richness and abundance) and beta diversity (Bray–Curtis dissimilarities) of the whole nematode community and each nematode functional group, (iii) soil food web resources (the total taxonomic richness and abundance of plant, bacterial and fungal communities) and (iv) soil properties (pH, total, ammonium and nitrate N, microbial N and C, total and available P and soil water content).
We found that N fertilization altered plant diversity and soil nitrate levels, which in turn decreased taxonomic alpha diversity of two nematode functional groups (phytophagous nematodes and predators), but taxonomic diversity for the whole nematode community remained stable. The decreased taxonomic alpha diversity of phytophagous nematodes resulted in increased maximum body width, but decreased stylet length and oesophageal length. Mild warming (~ 0.7°C) had no effects on soil properties and soil food web resources, and the taxonomic diversity or nematode traits remained unchanged.
Our results reveal that nematode functional traits show strong responses to N fertilization as individual nematode groups adapted quickly to changed soil properties and food web resources. Taxonomic diversity indices, however, were more stable under these changes showing that the functional composition of nematode communities may respond in the short term despite little effects on species diversity. Thus, the trait‐based indicators not only reveal how nematodes respond to N fertilization, but also how nematodes mediate the effects of N fertilization on ecosystem functioning (i.e. soil nutrient cycling).
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... For instance, Zhang et al. (2019) showed that warming increased the nitrification process in paddy soils by impacting the abundance of ammonia-oxidizing bacteria and archaea. This effect of GCDs on sBEF via changes in soil biodiversity was also shown in a meta-analysis by García-Palacios et al. (2015), which demonstrated that the effects of warming and N addition on microbial abundances were correlated to changes in ecosystem functions such as plant biomass or C cycling. Still, studies exploring sBEF as affected by GCDs are scarce, partly due to the complexity of interactions as GCDs cooccur in space and time, limiting our understanding of the potential interactive effects of GCDs on sBEF. ...
Biodiversity, both aboveground and belowground, is negatively affected by global changes such as drought or warming. This loss of biodiversity impacts Earth's ecosystems, as there is a positive relationship between biodiversity and ecosystem functioning (BEF). Even though soils host a large fraction of biodiversity that underlies major ecosystem functions, studies exploring the relationship between soil biodiversity and ecosystem functioning (sBEF) as influenced by global change drivers (GCDs) remain scarce. Here we highlight the need to decipher sBEF relationships under the effect of interactive GCDs that are intimately connected in a changing world. We first state that sBEF relationships depend on the type of function (e.g., C cycling or decomposition) and biodiversity facet (e.g., abundance, species richness, or biomass) considered. Then, we shed light on the impact of single and interactive GCDs on soil biodiversity and sBEF and show that results from scarce studies studying interactive effects range from antagonistic to additive to synergistic when two individual GCDs cooccur. This indicates the need for studies quantitatively accounting for the impacts of interactive GCDs on sBEF relationships. Finally, we provide guidelines for optimized methodological and experimental approaches to study sBEF in a changing world that will provide more valuable information on the real impact of (interactive) GCDs on sBEF. Together, we highlight the need to decipher the sBEF relationship in soils to better understand soil functioning under ongoing global changes, as changes in sBEF are of immediate importance for ecosystem functioning.
... The responses of AM fungal communities to N deposition could be driven by abiotic factors such as soil properties, and biotic factors like plant communities. First of all, a primary consequence of N deposition is the increase of soil N pool (Lu et al., 2011), available N (AN) content (García-Palacios et al., 2015) and the changes of soil nutrient stoichiometry (Peñuelas et al., 2013;Yue et al., 2017;Zhao et al., 2020), thus influencing the nutritional status for plant and also the AM fungal community (Johnson et al., 2003;Johnson, 2010;Jiang et al., 2018;Lilleskov et al., 2019). Continuous soil acidification under N deposition in grassland can be another crucial abiotic factor structuring the AM fungal community (Pan et al., 2020), since the ammonium cation (NH þ 4 ) can displace base cations (Na + , K + , Ca 2+ and Mg 2+ ) binding to soil mineral surface, while nitrate (NO À 3 ) can induce the loss of metal cations through leaching, and both of them contribute to the reduction of soil buffering capacity against acidification (Tian & Niu, 2015). ...
Nitrogen (N) enrichment poses threats to biodiversity and ecosystem stability, while arbuscular mycorrhizal (AM) fungi play important roles in ecosystem stability and functioning. However, the ecological impacts, especially thresholds of N enrichment potentially causing AM fungal community shifts have not been adequately characterized.
Based on a long‐term field experiment with nine N addition levels ranging from 0 to 50 g N m ⁻² yr ⁻¹ in a temperate grassland, we characterized the community response patterns of AM fungi to N enrichment.
Arbuscular mycorrhizal fungal biomass continuously decreased with increasing N addition levels. However, AM fungal diversity did not significantly change below 20 g N m ⁻² yr ⁻¹ , but dramatically decreased at higher N levels, which drove the AM fungal community to a potentially unstable state. Structural equation modeling showed that the decline in AM fungal biomass could be well explained by soil acidification, whereas key driving factors for AM fungal diversity shifted from soil nitrogen : phosphorus (N : P) ratio to soil pH with increasing N levels.
Different aspects of AM fungal communities (biomass, diversity and community composition) respond differently to increasing N addition levels. Thresholds for substantial community shifts in response to N enrichment in this grassland ecosystem are identified.
... Soil microorganisms, as an important medium for maintaining ecosystem function [1], directly affect soil carbon (C), the nitrogen (N) cycle and nutrient transformation [2,3]. The structure and functional diversity of soil microbial communities are not only driven by crop diversity, but also disturbed by the soil environment [4]. ...
The soil microbial community is not only driven by plant composition but is also disturbed by the soil environment. Intercropping affects the soil microenvironment through plant interaction, but the understanding of the relationship between soil microbial community and environment in intercropping is still weak. In this study, milk vetch intercropping with rapeseed was used to explore the interaction between soil microorganisms and environment. The results showed that the soil moisture content of intercropping was higher than that of monoculture during the reproductive period of rapeseed growth (flowering and podding stages). The contents of soil total nitrogen and alkali-hydrolyzable nitrogen in intercropping were higher than those in monoculture. The dominant soil microbial communities in intercropping were the same as in monoculture and included Chloroflexi, Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes, Gemmatimonates and Bacteroidetes. However, intercropping increased the Shannon index and decreased the Simpson’s index of the soil microbial community. The changes in the soil microbial community were mainly related to soil temperature, moisture, pH, total nitrogen, alkali-hydrolyzable nitrogen and available potassium. Moreover, there was a negative correlation between soil moisture and microorganisms and a positive correlation between nitrogen and microorganisms. Thus, milk vetch–rapeseed intercropping could not only improve soil nitrogen content, but also change soil microbial community diversity. In dryland red soil, the effect of milk vetch–rapeseed intercropping on soil moisture and nitrogen was the key factor contributing to the changes in the soil microbial community. When planting rapeseed in the future, we could consider the application of intercropping with milk vetch, which can contribute to regulating the soil nitrogen pool and improving microbial diversity.
... The criteria of selecting appropriate studies applied were as follows: (1) only field manipulative experiments in terrestrial ecosystems were included; (2) experimental sites must include both control and P addition treatments, or both N addition and N and P addition; (3) the values and sample sizes for the treatment and control groups were directly reported or could be extracted. (4) if more than one field manipulative experiment was reported in the same article but for various vegetation types, different altitudes, or topography, all the experiments were included and regarded as independent cases; (5) In order to compare the microbial attributes of different studies, we only included the uppermost soil layer that is most sensitive to nutrient input (Garcia-Palacios et al., 2015). ...
Soil microbes play a crucial role in myriad ecological processes in terrestrial ecosystem. With increasing nitrogen (N) loading, phosphorus (P) may become more limiting for soil microbes and these processes. However, it remains unclear to what extent P addition impacts soil microbial communities and respiration at global scale, especially under different N loadings. Therefore, we used a global meta-analysis to examine the effects of phosphorus addition on soil microbes based on 2293 paired observations from 129 studies in the world. Overall, P addition increased significantly total as well as fungal, bacterial, and actinomycete (ACT) phospholipid fatty acids (PLFAs), together with Gram+ bacteria (G+) and Gram- bacteria (G-) abundance regardless of N input or not. The increments were more pronounced under higher P addition rate or places with higher mean annual temperature or mean annual precipitation. Moreover, the fungi: bacteria ratio significantly decreased along elevational gradients. Furthermore, higher P addition frequency tended to have significantly more ACT PLFAs, as well as higher G+:G-, but significantly lower fungi: bacteria ratio (F:B). However, the responses of P addition on bacterial PLFAs and F:B were larger in forest than grassland, and cropland and varied with P fertilizer forms. In addition, the responses of soil organic carbon (SOC) contents was positively correlated with those of microbial biomass carbon (MBC) and bacterial PLFAs, and all these three parameters, in addition to fungal PLFAs, correlated positively with the response of soil respiration (Rs). Our results suggest that phosphorus addition had globally positive effects on soil microbes with different N loadings, and the positive effects of soil microbial abundance tended to promote heterotrophic respiration (Rh) and Rs. These results deepen our understanding of soil microbial community structure and function dynamics under increasing P deposition. They also provide extensive evidences and bases for parameterization of soil carbon cycling models incorporating microbial responses under global climate change.
... and China National Knowledge Infrastructure (http://www.cnki.net/). The following criteria were used to screen collected studies: 1) hay yield or grain yield, and sowing rate of oat were explicitly reported under field experiments (more than three replicates); 2) comparisons between controls (e.g., local recommended sowing rate or the lowest sowing rate) and treatment (i.e., sowing rate) were reported; 3) when the same article reported multiple levels of sowing rate, each of them was considered as an independent study and incorporated in our dataset 22 ; 4) other agronomic practices and factors such as variety, fertilizer management, and irrigation were similar in a given study. Subsequently, measured hay yields or grain yields were extracted from figures using GetData Graph Digitizer (http://getdata-graph-digitizer.com/ version 2.26) as well as from tables, and texts. ...
Background:
Oat (Avena sativa L.) is recognized for its impressive productivity in marginal environments, and the sowing rate is an important crop management practice that potentially enhances oat productivity. Previous studies have reported the effect of sowing rate on oat yield; however, the results from such studies are inconsistent. Thus, based on 43 studies across 8 countries, the current study aimed to assess changes in hay and grain yields in response to sowing rate and, in combination with a boosted regression tree, to evaluate and rank the dominant factors (e.g., climate conditions, soil conditions, and sowing rate) affecting changes in hay and grain yields of oat.
Results:
The results revealed that increasing the sowing rate significantly increased the response ratio of grain yields and hay yields by averages of 7.3% and 7.9%, respectively. However, the response ratios of grain yields and hay yields in response to changes in sowing rate were affected by different factors. Climate condition, and mean annual precipitation primarily affected the response ratios of hay yields; while, the sowing rate dominated changes in the response ratios of grain yields, with the response ratios of grain yields peaking at a sowing rate of 85 kg ha-1 .
Conclusion:
Optimizing the sowing rate with site-specific environmental conditions could be a potential strategy for profitable oat production, given that oat can be produced under marginal environments, e.g., cool-wet climates and soil with low fertility. This article is protected by copyright. All rights reserved.
... We used Web of Science to search for published peer-reviewed articles using the keywords "bacterial wilt of tomato" to investigate the prevalence of binary infection outcomes. Data were extracted according to the following criteria: (i) studies from 2010 to 2020 with tomato as the host plant were selected; (ii) disease incidences of tomato plants grown in water or sterile soil were not included in the dataset; (iii) since we only focused on well-controlled experiments, and complex variable environmental factors exist under field conditions, the disease incidences of tomato grown under field experiments were also excluded from the dataset; (iv) for studies that manipulated multiple factors (e.g., biocontrol agent, specific genes of the pathogen, and management practice), only data from controls and regular fertilization treatments were included; (v) when articles reported multiple independent manipulative experiments (e.g., experiments at separate sites), each experiment was considered as an independent study and included in the dataset [21]; (vi) when articles reported bacterial wilt incidence at different time-points, only the latest time-point was considered; (vii) when data were only reported as figures, the data means were extracted using GetData-Graph Digitizer (www.getdata-graph-digitizer.com). In total, this meta-analysis included 132 observations from 58 articles (External Databases S1). ...
Even in homogeneous conditions, plants facing a soilborne pathogen tend to show a binary outcome with individuals either remaining fully healthy or developing severe to lethal disease symptoms. As the rhizosphere microbiome is a major determinant of plant health, we postulated that such a binary outcome may result from an early divergence in the rhizosphere microbiome assembly that may further cascade into varying disease suppression abilities. We tested this hypothesis by setting up a longitudinal study of tomato plants growing in a natural but homogenized soil infested with the soilborne bacterial pathogen Ralstonia solanacearum. Starting from an originally identical species pool, individual rhizosphere microbiome compositions rapidly diverged into multiple configurations during the plant vegetative growth. This variation in community composition was strongly associated with later disease development during the later fruiting state. Most interestingly, these patterns also significantly predicted disease outcomes 2 weeks before any difference in pathogen density became apparent between the healthy and diseased groups. In this system, a total of 135 bacterial OTUs were associated with persistent healthy plants. Five of these enriched OTUs (Lysinibacillus, Pseudarthrobacter, Bordetella, Bacillus, and Chryseobacterium) were isolated and shown to reduce disease severity by 30.4–100% when co-introduced with the pathogen. Overall, our results demonstrated that an initially homogenized soil can rapidly diverge into rhizosphere microbiomes varying in their ability to promote plant protection. This suggests that early life interventions may have significant effects on later microbiome states, and highlights an exciting opportunity for microbiome diagnostics and plant disease prevention.
... This type of common response is rather unusual owing to the fact that distinct members of the same phylum sometimes respond in different ways to the same changes. Sometimes controversial outcomes are realized for responses to elevated CO 2 in different forest soil atmospheres since the increased population of particular bacterial taxa will actively respond only if their functional traits do not alter in reference to the treatment [140,141]. ...
Forest soils are a pressing subject of worldwide research owing to the several roles of forests such as carbon sinks. Currently, the living soil ecosystem has become dreadful as a consequence of several anthropogenic activities including climate change. Climate change continues to transform the living soil ecosystem as well as the soil microbiome of planet Earth. The majority of studies have aimed to decipher the role of forest soil bacteria and fungi to understand and predict the impact of climate change on soil microbiome community structure and their ecosystem in the environment. In forest soils, microorganisms live in diverse habitats with specific behavior, comprising bulk soil, rhizosphere, litter, and deadwood habitats, where their communities are influenced by biotic interactions and nutrient accessibility. Soil microbiome also drives multiple crucial steps in the nutrient biogeochemical cycles (carbon, nitrogen, phosphorous, and sulfur cycles). Soil microbes help in the nitrogen cycle through nitrogen fixation during the nitrogen cycle and maintain the concentration of nitrogen in the atmosphere. Soil microorganisms in forest soils respond to various effects of climate change, for instance, global warming, elevated level of CO2, drought, anthropogenic nitrogen deposition, increased precipitation, and flood. As the major burning issue of the globe, researchers are facing the major challenges to study soil microbiome. This review sheds light on the current scenario of knowledge about the effect of climate change on living soil ecosystems in various climate-sensitive soil ecosystems and the consequences for vegetation-soil-climate feedbacks.
... The criteria of selecting appropriate studies applied were as follows: (1) only field manipulative experiments in terrestrial ecosystems were included; (2) experimental sites must include both control and P addition treatments, or both N addition and N and P addition; (3) the values and sample sizes for the treatment and control groups were directly reported or could be extracted. (4) if more than one field manipulative experiment was reported in the same article but for various vegetation types, different altitudes, or topography, all the experiments were included and regarded as independent cases; (5) In order to compare the microbial attributes of different studies, we only included the uppermost soil layer that is most sensitive to nutrient input (Garcia-Palacios et al., 2015). ...
Soil microbes play a crucial role in myriad ecological processes in terrestrial ecosystem. With increasing nitrogen
(N) loading, phosphorus (P) may become more limiting for soil microbes and these processes. However, it remains unclear to what extent P addition impacts soil microbial communities and respiration at global scale,
especially under different N loadings. Therefore, we used a global meta-analysis to examine the effects of
phosphorus addition on soil microbes based on 2293 paired observations from 129 studies in the world. Overall,
P addition increased significantly total as well as fungal, bacterial, and actinomycete (ACT) phospholipid fatty
acids (PLFAs), together with Gram+ bacteria (G+) and Gram- bacteria (G-) abundance regardless of N input or
not. The increments were more pronounced under higher P addition rate or places with higher mean annual
temperature or mean annual precipitation. Moreover, the fungi: bacteria ratio significantly decreased along
elevational gradients. Furthermore, higher P addition frequency tended to have significantly more ACT PLFAs, as
well as higher G+:G-, but significantly lower fungi: bacteria ratio (F:B). However, the responses of P addition on
bacterial PLFAs and F:B were larger in forest than grassland, and cropland and varied with P fertilizer forms. In
addition, the responses of soil organic carbon (SOC) contents was positively correlated with those of microbial
biomass carbon (MBC) and bacterial PLFAs, and all these three parameters, in addition to fungal PLFAs,
correlated positively with the response of soil respiration (Rs). Our results suggest that phosphorus addition had
globally positive effects on soil microbes with different N loadings, and the positive effects of soil microbial
abundance tended to promote heterotrophic respiration (Rh) and Rs. These results deepen our understanding of
soil microbial community structure and function dynamics under increasing P deposition. They also provide
extensive evidences and bases for parameterization of soil carbon cycling models incorporating microbial responses under global climate change.
... Supporting data shows a correlation between the concentrations of common rhizospheric gram negative bacteria-derived PLFA (phospholipid fatty acid) with the relative abundance of bacterivores and herbivores (or plant-feeding nematodes) [13,62]. This reflects the outcome on the biological functioning of the soil through bacteria-mediated alterations of the soil food web [63]. The soil food web can be affected by regulating the plant-herbivore interactions through re-allocation of assimilates for the synthesis of secondary metabolites which, in turn, is regulated by the increased C:N ratio in the soil under augmented levels of CO 2 [52,64]. ...
Unsustainable anthropogenic activities over the last few decades have resulted in alterations of the global climate. It can be perceived through changes in the rainfall patterns and rise in mean annual temperatures. Climatic stress factors exert their effects on soil health mainly by modifying the soil microenvironments where the soil fauna reside. Among the members of soil fauna, the soil nematodes have been found to be sensitive to these stress factors primarily because of their low tolerance limits. Additionally, because of their higher and diverse trophic positions in the soil food web they can integrate the effects of many stress factors acting together. This is important because under natural conditions the climatic stress factors do not exert their effect individually. Rather, they interact amongst themselves and other abiotic stress factors in the soil to generate their impacts. Some of these interactions may be synergistic while others may be antagonistic. As such, it becomes very difficult to assess their impacts on soil health by simply analysing the physicochemical properties of soil. This makes soil nematodes outstanding candidates for studying the effects of climatic stress factors on soil biology. The knowledge obtained therefrom can be used to design sustainable agricultural practices because most of the conventional techniques aim at short-term benefits with complete disregard of soil biology. This can partly ensure food security in the coming decades for the expanding population. Moreover, understanding soil biology can help to preserve landscapes that have developed over long periods of climatic stability and belowground soil biota interactions.
... SEM is a popular statistical method for quantifying and determining the causal relationships between dependent and independent variables, and has been applied in many studies of environmental and agricultural fields (Garcia-Palacios et al., 2015;Jin et al., 2020;Zhao et al., 2019). SEMs were established to further explore the relationships between biochar application rate, changes in soil hydrological properties, and changes in crop WUE. ...
The regulation of soil water retention by biochar amendment has been concerned especially in cropland ecosystem. However, the quantification of biochar’s effects on soil hydrological properties and crop water use efficiency (WUE) is still limited, and the factors driving biochar effect need to be investigated. Based on a database with 681 observations, meta‐analysis and structural equation model (SEM) were employed to reveal how biochar amendment affects water supply capacity and WUE. The results showed that biochar application increased available water content (AWC) and WUE by 26.8% and 4.7% on average, respectively. According to the SEM of AWC (R2=0.70~0.96), the increase of soil organic carbon (+36.1%) by biochar application can not only directly improved AWC, but also indirectly improved AWC by affecting permanent wilting point (‐1.0%) and mean weight diameter (+11.1%). The SEM of WUE (R2=0.74) indicated that soil moisture and porosity were increased by 10.8% and 7.0% under biochar amendment, which was the reason why biochar improved WUE. This study emphasized that biochar can improve soil hydrology and crop yield by increasing soil water supply condition. And a rational rate of biochar is the precondition to obtaining the benefits of soil hydrology, otherwise, the excessive use of biochar may lead to the decline of WUE.
... If Q b > of the 95% Chi-squared critical value with k-1 degrees of freedom (k = number of groups) (Alvarez et al., 2017), we calculated lnRR ++ and CIs for each class separately using a random effect model. In some cases, multiple observations shared a common control, such as plantations in one study with multi-levels of plantation ages, mixed proportions, or mixed types, and this violates the assumptions of independence for the meta-analysis; thus, we included the vari-able "study site" as a random factor García-Palacios et al., 2015). Nonetheless, a sensitivity analysis (Lehmann et al., 2014) was performed to identify studies with an exceptionally high or low effect in the SOC stock datasets. ...
Forests play an essential role in mitigating climate change by sequestering carbon dioxide from the atmosphere. The establishment of mixed plantations is a promising way to store carbon (C) in soil compared with monocultures. However, monoculture forests largely dominate the rapid increase in forest areas in China. To optimize afforestation strategies and maximize the subsequent potential of C sequestration, we conducted a meta-analysis with 427 observations across 176 study sites in China. The goal was to quantify changes in the stocks of soil organic carbon (SOC) in mixed plantations compared with monocultures and to identify the predominant drivers for the stocks of SOC, including geological location, climatic factors, land use history, edaphic properties, plantation age, the inclusion of nitrogen-fixing trees, mixing proportion, and mixed plant types. The results showed that mixed plantations significantly increased the SOC stocks by 12% compared with monocultures, and the mixing proportion should not exceed 55% to produce higher SOC stocks in mixed plantations compared with monoculture. Additionally, mixed plantations in barren land are the most likely to increase the SOC stocks with limited water or low temperatures for growth. Additional measures instead of mixed plantations should be explored to increase SOC stocks in north, central, and northwest China. The data from this study demonstrated the spatiotemporal variability on the storage of SOC driven by mixed trees and has valuable implications for the establishment and management of afforestation.
... It has been reported that N deposition has a more significant impact on soil C-cycling functional genes than N-cycling ones. The influence of N addition on C cycling may be due to plant litter quality, the extent of litter decay, litter decomposition rates, and microbial communities (Whittinghill et al., 2012;Garcia-Palacios et al., 2015). However, different types of functional genes associated with N cycling, including denitrification, ammonia oxidation, and N fixation, showed different patterns of responses to N addition, and the insignificant impacts on the overall N-cycling functional genes may be due to the offsets of different functional genes (Fig. 3c). ...
Soil microbial richness, diversity, and functional gene abundance are crucial factors affecting belowground ecosystem functions; however, there is still a lack of systematic understanding of their responses to global change. Here, we conducted a worldwide meta-analysis using 1071 observation data concerning the effects of global change factors (GCFs), including warming (W), increased precipitation (PPT+), decreased precipitation (PPT-), elevated CO2 concentration (eCO2), and nitrogen deposition (N), to evaluate their individual, combined, and interactive effects on soil microbial properties across different groups and ecosystems. Across the dataset, eCO2 increased microbial richness and diversity by 40.5% and 4.6%, respectively; warming and N addition decreased the abundance of denitrification functional genes (nirS, nirK, and nozS); N addition had a greater impact on soil C-cycling functional genes than on N-cycling ones. Long-term precipitation change was conducive to the increase in soil microbial richness, and fungal richness change was more sensitive than bacterial richness, but the sensitivity of bacteria richness to N addition was positively correlated with experimental duration. Soil microbial richness, diversity, and functional gene abundances could be significantly affected by individual or multiple GCF changes, and their interactions are mainly additive. W×eCO2 on microbial diversity, and N×PPT+ and W×N on N-cycling functional gene abundance showed synergistic interactions. Based on the limitations of the collected data and the findings, we suggest designing experiments with multiple GCFs and long experimental durations and incorporating the effects and interactions of multiple drivers into ecosystem models to accurately predict future soil microbial properties and functions under future global changes.
... In parallel, anthropogenic activities have dramatically enhanced soil nutrient availability by global N deposition and excessive fertilization (Galloway et al., 2008). Alterations in these global change factors can strongly affect plant productivity and carbon (C) allocation belowground, modifying the growth and activities of soil microbes (Eisenhauer et al., 2012;García-Palacios et al., 2015;Jansson and Hofmockel, 2020). Changes in microbial biomass could cascade to higher trophic levels, however, direct evidence illustrating the cascading effect from field is scarce. ...
Soil phagotrophic protists are highly abundant and play a vital role in nutrient cycling through feeding on microbes. Global change factors, individually or in combination, often affect soil bacteria and fungi, but whether and how the resulting changes may cascade to affect phagotrophic protists remain largely unknown. Combining direct microscopic counting and high-throughput sequencing of 18s rRNA gene, we examined effects of precipitation changes, warming and nitrogen (N) input on soil phagotrophic protists in a 3-yr manipulation experiment with a Tibetan alpine meadow. Precipitation addition (+30%) enhanced but precipitation reduction (−30%) and warming decreased the alpha diversity of phagotrophic protists, primarily through altering soil moisture. However, N input (12 g N m⁻² y⁻¹) increased protist abundance, and in particular, offset the negative effect of precipitation reduction on the relative abundance of phagotrophic protists through increasing the microbial biomass, implying a bottom-up trophic control. Together, these findings indicate that interactions of multiple global change drivers may affect soil protist communities directly by modifying the soil physiochemical environment and indirectly through trophic cascading, which have implications for the potential changes in their ecosystem functions in alpine meadow under future global change scenarios.
... Global change has led to local environmental shifts that, in turn, trigger detrimental effects on both communities and ecosystem functioning across biomes (e.g. Garcia-Palacios et al. 2015;Till et al. 2019;Pecuchet et al. 2020). In temperate aquatic biomes, global climate change is leading to an increase in water temperature and productivity (Finstad et al. 2016;Hayden et al. 2019;Kritzberg et al. 2020). ...
A mechanistic understanding of how environmental change affects trophic ecology of fish at the individual and population level remains elusive. To address this, we conducted a space-for-time approach incorporating environmental gradients (temperature, precipitation and nutrients), lake morphometry (visibility, depth and area), fish communities (richness, competition and predation), prey availability (richness and density) and feeding (population niche breadth and individual trophic specialisation) for 15 native fish taxa belonging to different thermal guilds from 35 subarctic lakes along a marked climate-productivity gradient corresponding to future climate change predictions. We revealed significant and contrasting responses from two generalist species that are abundant and widely distributed in the region. The cold-water adapted European whitefish (Coregonus lavaretus) reduced individual specialisation in warmer and more productive lakes. Conversely, the cool-water adapted Eurasian perch (Perca fluviatilis) showed increased levels of individual specialism along climate-productivity gradient. Although whitefish and perch differed in the way they consumed prey along the climate-productivity gradient, they both switched from consumption of zooplankton in cooler, less productive lakes, to macrozoobenthos in warmer, more productive lakes. Species with specialist benthic or pelagic feeding did not show significant changes in trophic ecology along the gradient. We conclude that generalist consumers, such as warmer adapted perch, have clear advantages over colder and clear-water specialised species or morphs through their capacity to undergo reciprocal benthic–pelagic switches in feeding associated with environmental change. The capacity to show trophic flexibility in warmer and more productive lakes is likely a key trait for species dominance in future communities of high latitudes under climate change.
... Selected articles met the following criteria: (1) field experiments used paired-site designs, and treatment had occurred for a minimum of one year; (2) treatment sites were free of any other treatment(s); (3) converted lands transitioned from natural forest to a singular type of land-use with either no transition period or a transition period less than or equal to two years; (4) data included means, numbers of replicates, and a mechanism for determining standard deviations (SDs, either reported directly or calculated using reported standard errors); (5) soil characteristics of the uppermost soil layer (<20 cm) were reported (García-Palacios et al., 2015). Using these criteria, 127 independent paired sites from 51 articles were employed for further aggregate analysis. ...
The conversion of natural forest to artificial vegetation may deplete nutrients and thus affect the soil quality. However, little is known about synergetic changes of microbial and physicochemical dynamics in soils after natural forest conversion and their implications. In the current study, we synthesized the responses of soil microbial and physicochemical properties in the uppermost soil layer (<20 cm) following natural forest conversion, as reported in 51 published studies (127 sites). Our results showed that the response ratios of soil moisture, soil microbial carbon and nitrogen, bacteria, fungi, enzymatic activities, soil organic carbon, total carbon, total nitrogen, NO3–, total phosphorus, available phosphorus, cations (K⁺, Mg²⁺ and Ca²⁺), and cation exchange capacity (CEC) overall declined following natural forest replacement. In contrast, natural forest conversion caused significant increases in soil bulk density, soil pH and NH4⁺. Reductions of microbial carbon, organic carbon and total nitrogen in soil were independent of revegetation type, but variations in soil pH, available phosphorus and fungi were correlated to land use. Soil CEC reduction increased soil pH, allowing soils to retain NH4⁺, which promoted fungal growth. Moreover, natural forest replacement led to the loss of soil cations in regions of higher precipitation. Revegetation practices led to greater consumption of soil microbial and chemical nutrients and produced “harder” soils (increased soil compaction and decreased moisture content) in warmer regions. Stand age influenced ratios of soil carbon to nitrogen and ratios of bacteria to fungi following natural forest conversion. Altogether, our study suggests that natural forest conversion results in decreased soil microbial and chemical fertility, and desirable soil properties are more likely to be lost in warmer regions and over time as global climate warming exacerbates, which in turn may potentially damage ecosystem sustainability.
Plant diversity and soil microbial diversity are closely related, and they maintain the health and stability of terrestrial ecosystems. As a hotspot region of global biodiversity research, both air temperature and precipitation of the Qinghai-Xizang Plateau tend to increase in future. Based on an overview of the responses of grassland/alpine ecosystems to seasonal asymmetric warming and increased precipitation worldwide, we elaborated the advancements and uncertainties on the responses of plant diversity and soil microbial diversity to warming and increased precipitation in alpine grasslands on the Qinghai-Xizang Plateau. The future research focus of plant diversity and soil microbial diversity in the alpine grasslands of the Qinghai-Xizang Plateau under climate warming and increased precipitation was proposed. Generally, previous studies found that the responses of plant species diversity and soil microbial species diversity to warming and increased precipitation differed between alpine meadows and alpine steppes, but few studies focused on their responses to warming and increased precipitation in alpine desert steppes. Previous studies mainly focused on species diversity, although phylogenetic and functional diversities are also important aspects of biodiversity. Previous studies mainly explained responses of plant diversity and soil microbial diversity to warming and increased precipitation based on niche theory, although neutral theory is also the other important mechanism in regulating biodiversity. Moreover, previous studies almost ignored the coupling relationship between plant diversity and soil microbial diversity. Therefore, the following four aspects need to be strengthened, including the responses of plant diversity and soil microbial diversity to warming and increased precipitation in alpine desert steppes, the responses of plant and soil microbial phylogenetic diversity and functional diversity to warming and increased precipitation, combining the niche theory and neutral theory to examining the mechanism of biodiversity, and the coupling relationships between plant diversity and soil microbial diversity under warming and increased precipitation.
The CO2 concentration has increased in the atmosphere due to fossil fuel consumption, deforestation, and land-use changes. Brazil represents one of the primary sources of food on the planet and is also the world's largest tropical rainforest, one of the hot spots of biodiversity in the world. In this work, a meta-analysis was conducted to compare several CO2 Brazilian experiments displaying the diversity of plant responses according to life habits, such as trees (79% natives and 21% cultivated) and herbs (33% natives and 67% cultivated). We found that trees and herbs display different responses. The young trees tend to allocate carbon from increased photosynthetic rates and lower respiration in the dark—to organ development, increasing leaves, roots, and stem biomasses. In addition, more starch is accumulated in the young trees, denoting a fine control of carbon metabolism through carbohydrate storage. Herbs increased drastically in water use efficiency, controlled by stomatal conductance, with more soluble sugars, probably with a transient accumulation of carbon primarily stored in seeds as a response to elevated CO2.
Climate change affects soil microbial communities and their genetic exchange, and subsequently modifies the transfer of antibiotic resistance genes (ARGs) among bacteria. However, how elevated CO2 impacts soil antibiotic resistome remains poorly characterized. Here, a free-air CO2 enrichment system was used in the field to investigate the responses of ARGs profiles and bacterial communities to elevated CO2 (+200 ppm) in soils amended with sulfadiazine (SDZ) at 0, 0.5 and 5 mg kg-1. Results showed that SDZ exposure induced the co-occurrence of beta-lactamase and tetracycline resistance genes, and SDZ at 5 mg kg-1 enhanced the abundance of aminoglycoside, sulfonamide and multidrug resistance genes. However, elevated CO2 weakened the effects of SDZ at 0.5 mg kg-1 following an observed reduction in the total abundance of ARGs and mobile genetic elements. Additionally, elevated CO2 significantly decreased the abundance of vancomycin resistance genes and alleviated the stimulation of SDZ on the dissemination of aminoglycoside resistance genes. Correlation analysis and structural equation models revealed that elevated CO2 could directly influence the spread of ARGs or impose indirect effects on ARGs by affecting soil properties and bacterial communities. Overall, our results furthered the knowledge of the dissemination risks of ARGs under future climate scenarios.
As the climate warms, the initial enhancement of soil respiration (Rs) induced by short-term warming has the potential to decrease in magnitude over time due to the apparent thermal acclimation of Rs. However, the existence and magnitude of this kind of thermal acclimation are highly uncertain, partly because the response of Rs to warming is regulated by multiple environmental factors acting simultaneously [e.g., drought, precipitation, nitrogen deposition and elevated atmospheric CO2] rather than by temperature alone. Although extensive manipulative field studies and a few meta-analyses have been conducted to determine the responses of Rs to a single global change factor, the interactive effects of multiple environmental factors on warming remain unknown. In this study, we performed a meta-analysis of 82 multifactor studies to examine the regulatory effect of four main global change factors on the thermal response of Rs to warming. Our results showed that each global change factor exhibited distinct influences on Rs when occurring simultaneously with warming. Elevated CO2 and precipitation largely enhanced the C-climate feedback in the context of warming; however, drought strongly promoted the apparent thermal acclimation of Rs. Nitrogen and warming had an additive effect on Rs. Additionally, the duration of manipulation might be critical in assessing the responses of Rs to global change factors because biotic responses to environmental change may vary over time. Our study demonstrated that after initially being enhanced by warming in the short term, Rs continuously recovered to previous levels—or even decreased—under long-term warming due to apparent thermal acclimation. We therefore suggest that global change experimental studies should focus more on the combined effects of warming with other global change factors. Additionally, long-term studies are needed to fully understand the interactions between warming, Rs, and other ecosystem limitations (e.g., C substrate depletion, C quantity and quality, nutrient availability, and changes in microbial communities and/or physiological modification).
Soil microbes decompose soil organic matter by producing various extracellular enzymes, and also regulate soil carbon (C) and nutrient cycles. However, how shifts in soil microbial community under long-term nitrogen (N) deposition govern soil extracellular enzyme activities (EEAs) is not known. Here, we conducted a decade-long N fertilization experiment consisting of control, low-N (2 g N m⁻² year⁻¹), medium-N (5 g N m⁻² year⁻¹), and high-N (10 g N m⁻² year⁻¹) treatments in a N-limited temperate plantation in northern China. The diversity and community composition of fungi and bacteria were determined with bacterial 16S rRNA genes and fungal internal transcribed spacer genes sequencing. Soil EEAs involved in C, N, and phosphorus (P) cycles were also measured. The results showed that high-N addition increased fungal diversity and altered microbial community composition. In particular, rare fungal diversity and rare bacterial community composition were more sensitive to N addition. N addition improved β-1,4-glucosidase (BG) and acid phosphatase (AP) activities by altering bacterial community composition, and inhibited leucine aminopeptidase (LAP) and polyphenolic oxidase (PPO) activities by affecting fungal functional groups. Specifically, shifts in bacterial community composition caused by N addition were reflected in the significant increase in the dominant class Thermoleophilia, which could be an indicator of secreted hydrolase involved in C and P cycles. Symbiotrophic fungi were more closely associated with LAP for acquiring N and PPO. Our data provide a novel view of the link between major extracellular enzymes and specific microbial taxa under the background of N deposition.
Understanding how ecosystem multifunctionality is maintained in naturally assembled communities is crucial, because human activities benefit from multiple functions and services of various ecosystems. However, the effects of above‐ and below‐ground biodiversity on ecosystem multifunctionality in alpine and boreal moorland ecosystems remain unclear despite their potential as global carbon sinks.
Here we evaluated how ecosystem multifunctionality related to primary production and carbon sequestration, which are crucial for global climate regulation, is maintained in natural systems. We disentangled the relationships between diversity and composition of plants and soil microbes (fungi and bacteria) and ecosystem multifunctionality in subalpine moorlands in northern Japan.
We found that microbial composition primarily regulated carbon sequestration, whereas plant taxonomic and functional composition were related to all functions considered. Plant and microbial α diversity (diversity within local communities) were not generally related to any single function, highlighting the important roles of specific plant and microbial taxa in determining ecosystem functioning. When single functions were aggregated to ecosystem multifunctionality within local communities, plant and microbial community composition rather than diversity regulated ecosystem multifunctionality. We further found that plant and bacterial taxonomic β diversity (taxonomic turnover between local communities) primarily regulated the dissimilarity of ecosystem multifunctionality between local communities.
Synthesis. We provide observational evidence that plant and microbial community composition rather than diversity are essential for sustaining subalpine moorland multifunctionality. Furthermore, plant and bacterial β diversity enhance the dissimilarity of moorland multifunctionality. Our study provides novel insights into biodiversity–ecosystem multifunctionality relationships occurring in nature, and helps to sustain desirable ecosystem functioning to human society.
The development of machine learning and deep learning provided solutions for predicting microbiota response on environmental change based on microbial high-throughput sequencing. However, there were few studies specifically clarifying the performance and practical of two types of binary classification models to find a better algorithm for the microbiota data analysis. Here, for the first time, we evaluated the performance, accuracy and running time of the binary classification models built by three machine learning methods - random forest (RF), support vector machine (SVM), logistic regression (LR), and one deep learning method - back propagation neural network (BPNN). The built models were based on the microbiota datasets that removed low-quality variables and solved the class imbalance problem. Additionally, we optimized the models by tuning. Our study demonstrated that dataset pre-processing was a necessary process for model construction. Among these 4 binary classification models, BPNN and RF were the most suitable methods for constructing microbiota binary classification models. Using these 4 models to predict multiple microbial datasets, BPNN showed the highest accuracy and the most robust performance, while the RF method was ranked second. We also constructed the optimal models by adjusting the epochs of BPNN and the n_estimators of RF for six times. The evaluation related to performances of models provided a road map for the application of artificial intelligence to assess microbial ecology.
The interaction of warming and soil texture on responsiveness of the key soil processes i.e. organic carbon (C) fractions, soil microbes, extracellular enzymes and CO 2 emissions remains largely unknown. Global warming raises the relevant question of how different soil processes will respond in near future, and what will be the likely regulatory role of texture? To bridge this gap, this work applied the laboratory incubation method to investigate the effects of temperature changes (10-50 C) on dynamics of labile, recalcitrant and stable C fractions, soil microbes, microbial biomass, activities of extracellular enzymes and CO 2 emissions in sandy and clayey textured soils. The role of texture (sandy and clayey) in the mitigation of temperature effect was also investigated. The results revealed that the temperature sensitivity of C fractions and extracellular enzymes was in the order recalcitrant C fractions > stable C fractions > labile C fractions and oxidative enzymes > hydrolytic enzymes. While temperature sensitivity of soil microbes and biomass was in the order bacteria > actinomycetes > fungi ≈ microbial biomass C (MBC) > microbial biomass N (MBN) > microbial biomass N (MBP). Conversely, the temperature effect and sensitivity of all key soil processes including CO 2 emissions were significantly (P < 0.05) higher in sandy than clayey textured soil. Results confirmed that under the scenario of global warming and climate change, soils which are sandy in nature are more susceptible to temperature increase and prone to become the CO 2-C sources. It was revealed that clayey texture played an important role in mitigating and easing off the undue temperature influence, hence, the sensitivity of key soil processes.. 2022. Temperature responsiveness of soil carbon fractions, microbes, extracellular enzymes and CO 2 emission: mitigating role of texture.
Land use change (LUC) significantly affects climatic, edaphic conditions and soil microbial attributes in terrestrial ecosystems. However, the overall impacts of LUC type on soil microbial attributes remain limited. Here we synthesized data of soil microbial attributes under different types (i.e. type Ⅰ: conversions from other lands to cropland, with human disturbance land degradation; type Ⅱ: conversions from forestland to grassland, shrubland to grassland, and forestland to shrubland, with natural land degradation) of land use from 90 published studies to quantify the effects of LUC types on soil microbial attributes and their controls. Total phospholipid fatty acids (PLFAs), fungi, bacteria and Actinobacteria (ACT) biomass were largely decreased under the type Ⅰ of LUC, whereas these attributes were generally increased under the type Ⅱ of LUC. The soil organic C (SOC), total N, and C:N ratio were the predominant controllers under the type Ⅰ, and the total N, phosphorus and C:N ratio were the main controllers under the type Ⅱ over soil microbial attributes. Additionally, the basal microbial respiration was decreased under the type Ⅰ due to lower SOC content, but the microbial metabolic quotient was increased under the type Ⅱ due to higher C:N ratio. Overall, our results revealed that the microbial attributes and their controls were highly dependent on the type of LUC, which could provide new insight for land use management under expanded LUC worldwide.
Leaf nitrogen (N) status and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) were used to study environmental factors that control mountain individuals of Picea neoveitchii trees, a coniferous species endemic and endangered in China. From May to September 2016, we carried out observations at four different altitude locations extending southeast of Daba Mountain in western Hubei Province. Needle-shaped leaf δ13C was positively correlated with needle N and C content calculated from the needle area (Narea and Carea content), needle δ15N, needle mass, and leaf mass per area (LMA), respectively. Needle δ15N was also positively correlated with monthly temperature and precipitation for the current month and last month. The seasonal normalised difference vegetation index (NDVI) was highest in June at the lowest altitude and August at the highest altitude. We found that N availability as an important driving factor for tree growth is controlled by surface soil temperature, while in summer, air temperatures above 23 °C exceed the physiological threshold of trees and limit the growth of trees. We concluded that the negative effect of higher temperature on tree growth is greater than the positive effect of higher nitrogen.
Biodiversity, or the diversity of living organisms on Earth, is an important indicator of the planet's health. Climate change mitigation requires preserving biodiversity levels and functional ecosystems; nevertheless, climate change is predicted to create major disturbances to the Earth's natural ecosystems, resulting in loss of biodiversity and a significant decrease in products and services offered to humanity. The present chapter deals with the impact of climate change that is severe to environmental issue that would jeopardize efforts to achieve long-term development and mitigation measures to reduce its impact on biodiversity changes. Furthermore, the impact of local and global species climate change has produced phenological changes in pollinators of flowering plants and insects, resulting in population mismatches, leading to plant and pollinator extinctions, with consequences for the structure of plant-pollinator networks. The loss of biodiversity and rising temperature can have an immediate impact on the water supply, food safety, soil nutrients, and human health. Conservation measure needs to be adopted, the land use pattern can be determined by remote sensing which is particularly valuable for detecting change due to the systematic coverage and lengthy time-series offered by satellite data.
The response of soil microbial communities to a changing climate will impact global biogeochemical cycles, potentially leading to positive and negative feedbacks. However, our understanding of how soil microbial communities respond to climate change and the implications of these changes for future soil function is limited. Here, we assess the response of soil bacterial and fungal communities to long-term experimental climate change in a heathland organo-mineral soil. We analysed microbial communities using Illumina sequencing of the 16S rRNA gene and ITS2 region at two depths, from plots undergoing 4 and 18 years of in situ summer drought or warming. We also assessed the colonisation of Calluna vulgaris roots by ericoid and dark septate endophytic (DSE) fungi using microscopy after 16 years of climate treatment. We found significant changes in both the bacterial and fungal communities in response to drought and warming, likely mediated by changes in soil pH and electrical conductivity. Changes in the microbial communities were more pronounced after a longer period of climate manipulation. Additionally, the subsoil communities of the long-term warmed plots became similar to the topsoil. Ericoid mycorrhizal colonisation decreased with depth while DSEs increased; however, these trends with depth were removed by warming. We largely ascribe the observed changes in microbial communities to shifts in plant cover and subsequent feedback on soil physicochemical properties, especially pH. Our results demonstrate the importance of considering changes in soil microbial responses to climate change across different soil depths and after extended periods of time.
The enzymatic activities and ratios are critical indicators for organic matter decomposition and provide potentially positive feedback to carbon (C) loss under global warming. For agricultural soils under climate change, the effect of long-term warming on the activities of oxidases and hydrolases targeting C, nitrogen (N) and phosphorus (P) and their ratios is unclear, as well as whether and to what extend the response is modulated by long-term fertilization. A 9-year field experiment in the North China Plain, including an untreated control, warming, N fertilization, and combined (WN) treatment plots, compared the factorial effect of warming and fertilization. Long-term warming interacted with fertilization to stimulate the highest activities of C, N, and P hydrolases. Activities of C and P hydrolase increased from 8 to 69% by N fertilization, 9 to 53% by warming, and 28 to 130% by WN treatment compared to control, whereas the activities of oxidase increased from 4 to 16% in the WN soils. Both the warming and the WN treatments significantly increased the enzymatic C:N ratio from 0.06 to 0.16 and the vector length from 0.04 to 0.12 compared to the control soil, indicating higher energy and resource limitation for the soil microorganisms. Compared to WN, the warming induced similar ratio of oxidase to C hydrolase, showing a comparable ability of different microbial communities to utilize lignin substrates. The relationship analyses showed mineralization of organic N to mediate the decomposition of lignin and enzyme ratio in the long-term warming soil, while N and P hydrolases cooperatively benefited to induce more oxidase productions in the soil subject to both warming and N fertilization. We conclude that coupled resource limitations induced microbial acclimation to long-term warming in the agricultural soils experiencing high N fertilizer inputs.
Arbuscular mycorrhizal fungi (AMF), playing critical roles in carbon cycling, are vulnerable to climate change. However, the responses of AM fungal abundance to climate change are unclear. A global-scale meta-analysis was conducted to investigate the response patterns of AM fungal abundance to warming, elevated CO2 concentration (eCO2), and N addition. Both warming and eCO2 significantly stimulated AM fungal abundance by 18.6% (95%CI: 5.9%–32.8%) and 21.4% (15.1%–28.1%) on a global scale, respectively. However, the response ratios (RR) of AM fungal abundance decreased with the degree of warming while increased with the degree of eCO2. Furthermore, in warming experiments, as long as the warming exceeded 4 °C, its effects on AM fungal abundance changed from positive to negative regardless of the experimental durations, methods, periods, and ecosystem types. The effects of N addition on AM fungal abundance are −5.4% (−10.6%–0.2%), and related to the nitrogen fertilizer input rate and ecosystem type. The RR of AM fungal abundance is negative in grasslands and farmlands when the degree of N addition exceeds 33.85 and 67.64 kg N ha⁻¹ yr⁻¹, respectively; however, N addition decreases AM fungal abundance in forests only when the degree of N addition exceeds 871.31 kg N ha⁻¹ yr⁻¹. The above results provide an insight into predicting ecological functions of AM fungal abundance under global changes.
Changes in precipitation regimes have significant effects on soil carbon (C) cycles; however, these effects may vary in arid vs. humid areas. Additionally, the corresponding details of soil C cycles in response to altered precipitation regimes have not been well documented. Here, a meta-analysis was performed using 845 pairwise observations (control vs. increased or decreased precipitation) from 214 published articles to quantify the responses of the input process of exogenous C, the contents of various forms of C in soil and the soil-atmosphere C fluxes relative to increased or decreased precipitation. The results showed that the effects of altered precipitation regimes did not differ between rainfall and snowfall. Increased precipitation significantly enhanced the soil C inputs, pools and outputs by 18.17, 18.50, and 21.04%, respectively, while decreased precipitation led to a significant decline in these soil C parameters by 10.18, 9.96, and 17.98%, respectively. The effects of increased precipitation on soil C cycles were more significant in arid areas (where mean annual precipitation, MAP < 500 mm), but the effects of decreased precipitation were more significant in humid areas (where MAP ≥ 500 mm), indicating that the original MAP partially determined the responses of the soil C cycles to altered precipitation regimes. This study implies that for the same of precipitation variation, soil C cycles respond at different magnitudes: not only should the direction (decrease vs. increase) be counted, but also the region (arid vs. humid) should be considered. These results deepened our understanding on regional differentiation in soil C cycles under climate change scenarios.
Los impulsores de Cambio Global con mayor impacto en los ecosistemas de alta montaña son los cambios climático y de uso del suelo y la deposición de nitrógeno (N). En España, un factor adicional es la deposición de fósforo (P) proveniente del polvo sahariano. La deposición atmosférica de N y P puede tener un gran impacto en el ciclado de nutrientes y en la biota edáfica. Durante tres años hemos simulado deposición atmosférica de N y P en cuatro ecosistemas alpinos de la red de Parques Nacionales siguiendo un gradiente latitudinal de aridez y analizado sus efectos sobre las comunidades de nematodos, hongos y bacterias. La microbiota redujo su presencia con la aridez, pero solo los hongos respondieron a la deposición de N. La abundancia de nematodos también disminuyó con la aridez, y, mientras que la deposición de N aumentó su biomasa debido al incremento de la abundancia de nematodos bacterívoros, el P incrementó la contribución porcentual de bacterívoros y fungívoros simplificando las redes tróficas edáficas. Los nematodos fungívoros fueron más sensibles que los bacterívoros a los desbalances estequiométricos y, en general, las comunidades de sistemas áridos se caracterizaron por una prevalencia del canal bacterívoro de descomposición de la materia orgánica y una menor importancia de la herbivoría subterránea. El incremento de la aridez, la deposición de N atmosférico y potencial aumento de la deposición de P sahariano podrían tener efectos a largo plazo en la composición y funciones ecosistémicas de las redes tróficas edáficas de alta montaña.
Background/Question/Methods Global warming potentially alters terrestrial ecosystem carbon (C) cycle, feeding back to further climate warming. However, how ecosystem C cycle responds and feed backs to warming remain unclear. We here used a meta-analysis to quantify response ratios of 18 variables of ecosystem C cycle to experimental warming.
Results/Conclusions Our results showed that warming stimulated gross ecosystem photosynthesis (GEP) by 15.7%, net primary production (NPP) by 4.4%, and above- and belowground plant C pools by 6.8% and 7.0%, respectively. The experimental warming also accelerated litter mass loss by 6.8%, soil respiration by 9.0%, and dissolved organic C leaching by 12.1%. In addition, the responses of some of those variables to experimental warming differed among the ecosystem types. The warming effects on C influx and efflux are roughly counterbalanced with each other, resulting in insignificant changes in litter and soil C contents, and net ecosystem exchange (NEE). The minor changes in soil C storage and NEE across ecosystems suggest that climate warming might not trigger strong carbon-climate feedback from terrestrial ecosystems. Our results are also potentially useful for parameterizing and benchmarking land surface models in terms of C cycle responses to climate warming.
Significance
Biological diversity is the foundation for the maintenance of ecosystems. Consequently it is thought that anthropogenic activities that reduce the diversity in ecosystems threaten ecosystem performance. A large proportion of the biodiversity within terrestrial ecosystems is hidden below ground in soils, and the impact of altering its diversity and composition on the performance of ecosystems is still poorly understood. Using a novel experimental system to alter levels of soil biodiversity and community composition, we found that reductions in the abundance and presence of soil organisms results in the decline of multiple ecosystem functions, including plant diversity and nutrient cycling and retention. This suggests that below-ground biodiversity is a key resource for maintaining the functioning of ecosystems.
Soil microbial communities are extremely complex, composed of thousands of low-abundance species (<0.1% of total). How such complex communities respond to natural or human-induced fluctuations, including major perturbations such as global climate change, remains poorly understood, severely limiting our predictive ability of soil ecosystem functioning and resilience. In this study, we compared twelve whole-community shotgun metagenomic datasets from a grassland soil in Midwest USA; half representing soil that was undergoing infrared warming by 2°C for 10 years, which simulated the effects of climate change, and the other half representing the adjacent soil that received no warming and thus, served as control. Our analyses revealed that the heated communities showed significant shifts in composition and predicted metabolism, and these shifts were community-wide as opposed to being attributable to a few taxa. Key metabolic pathways related to carbon turnover, e.g., cellulose degradation (∼13%) and CO2 production (∼10%), and nitrogen, e.g., denitrification (∼12%), were enriched under warming, which was consistent with independent physicochemical measurements. These community shifts were interlinked, in part, with higher primary productivity of the aboveground plant communities stimulated by warming, revealing that most of the additional, plant-derived soil carbon was likely respired by microbial activity. Warming also enriched for a higher abundance of sporulation genes and genomes with higher G+C% content. Collectively, our results indicate that the microbial communities of the temperate grassland soils play important roles in mediating the feedback responses to climate change and advance understanding of the molecular mechanisms of community adaptation to environmental perturbations.
Society relies on Earth system models (ESMs) to project future climate and carbon (C) cycle feedbacks. However, the soil C response to climate change is highly uncertain in these models1, 2 and they omit key biogeochemical mechanisms3, 4, 5. Specifically, the traditional approach in ESMs lacks direct microbial control over soil C dynamics6, 7, 8. Thus, we tested a new model that explicitly represents microbial mechanisms of soil C cycling on the global scale. Compared with traditional models, the microbial model simulates soil C pools that more closely match contemporary observations. It also projects a much wider range of soil C responses to climate change over the twenty-first century. Global soils accumulate C if microbial growth efficiency declines with warming in the microbial model. If growth efficiency adapts to warming, the microbial model projects large soil C losses. By comparison, traditional models project modest soil C losses with global warming. Microbes also change the soil response to increased C inputs, as might occur with CO2 or nutrient fertilization. In the microbial model, microbes consume these additional inputs; whereas in traditional models, additional inputs lead to C storage. Our results indicate that ESMs should simulate microbial physiology to more accurately project climate change feedbacks.
Prairie Redux
Tallgrass prairie is extinct across much of its former range in the midwestern United States, but relicts preserved in cemeteries and nature reserves allow functional comparison of former grassland soils with modern agricultural soils. Fierer et al. (p. 621 ; see the Perspective by Scholes and Scholes ) took matched soil samples from sites representing the gamut of climate conditions and modeled the combination of genomic analysis and environmental data to resurrect the historical prairie soil communities, identifying the nutrient-scavenging Verrucomicrobia as keystone bacteria in functioning prairie.
Meta-analysis is a statistical technique that allows one to combine the results from multiple studies to glean inferences on the overall importance of various phenomena. This method can prove to be more informative than common ''vote counting,'' in which the number of significant results is compared to the number with nonsignificant results to determine whether the phenomenon of interest is globally important. While the use of meta- analysis is widespread in medicine and the social sciences, only recently has it been applied to ecological questions. We compared the results of parametric confidence limits and ho- mogeneity statistics commonly obtained through meta-analysis to those obtained from re- sampling methods to ascertain the robustness of standard meta-analytic techniques. We found that confidence limits based on bootstrapping methods were wider than standard confidence limits, implying that resampling estimates are more conservative. In addition, we found that significance tests based on homogeneity statistics differed occasionally from results of randomization tests, implying that inferences based solely on chi-square signif- icance tests may lead to erroneous conclusions. We conclude that resampling methods should be incorporated in meta-analysis studies, to ensure proper evaluation of main effects in ecological studies.
For structural equation models, a huge variety of fit indices has been developed. These indices, however, can point to conflicting conclusions about the extent to which a model actually matches the observed data. The present article provides some guide-lines that should help applied researchers to evaluate the adequacy of a given struc-tural equation model. First, as goodness-of-fit measures depend on the method used for parameter estimation, maximum likelihood (ML) and weighted least squares (WLS) methods are introduced in the context of structural equation modeling. Then, the most common goodness-of-fit indices are discussed and some recommendations for practitioners given. Finally, we generated an artificial data set according to a "true" model and analyzed two misspecified and two correctly specified models as examples of poor model fit, adequate fit, and good fit. In structural equation modeling (SEM), a model is said to fit the observed data to the extent that the model-implied covariance matrix is equivalent to the empirical co-variance matrix. Once a model has been specified and the empirical covariance matrix is given, a method has to be selected for parameter estimation. Different estimation meth-ods have different distributional assumptions and have different discrepancy functions to be minimized. When the estimation procedure has converged to a reasonable
Climate is changing across a range of scales, from local to global, but ecological consequences remain difficult to understand and predict. Such projections are complicated by change in the connectivity of resources, particularly water, nutrients, and propagules, that influences the way ecological responses scale from local. to regional and from regional to continental. This paper describes ecological responses to expected changes in four key meso-scale drivers that influence the ecosystems of the North American continental interior: drought, warming, snowpack disappearance, and altered fire regimes. Changes in these drivers will affect, for example, atmospheric smoke, dust, and reactive nitrogen concentrations; stream discharge; nitrate concentrations; sediment loads; and the vector-borne spread of invasive species and infectious diseases. A continental network of sensors and simulation models is required to detect changes in the transport vectors - atmospheric, hydrologic, and mechanized that connect spatial scales. Knowledge of these downwind, downstream, and down-corridor effects will be critical if we are to understand and forecast responses to climate change at regional to continental scales.
Global warming potentially alters the terrestrial carbon (C) cycle, likely feeding back to further climate warming. However, how the ecosystem C cycle responds and feeds back to warming remains unclear. Here we used a meta-analysis approach to quantify the response ratios of 18 variables of the ecosystem C cycle to experimental warming and evaluated ecosystem C-cycle feedback to climate warming. Our results showed that warming stimulated gross ecosystem photosynthesis (GEP) by 15.7%, net primary production (NPP) by 4.4%, and plant C pools from above- and belowground parts by 6.8% and 7.0%, respectively. Experimental warming accelerated litter mass loss by 6.8%, soil respiration by 9.0%, and dissolved organic C leaching by 12.1%. In addition, the responses of some of those variables to experimental warming differed among the ecosystem types. Our results demonstrated that the stimulation of plant-derived C influx basically offset the increase in warming-induced efflux and resulted in insignificant changes in litter and soil C content, indicating that climate warming may not trigger strong positive C-climate feedback from terrestrial ecosystems. Moreover, the increase in plant C storage together with the slight but not statistically significant decrease of net ecosystem exchange (NEE) across ecosystems suggests that terrestrial ecosystems might be a weak C sink rather than a C source under global climate warming. Our results are also potentially useful for parameterizing and benchmarking land surface models in terms of C cycle responses to climate warming.
Ecologists have long studied the temporal dynamics of plant and animal communities with much less attention paid to the temporal dynamics exhibited by microbial communities. As a result, we do not know if overarching temporal trends exist for microbial communities or if changes in microbial communities are generally predictable with time. Using microbial time series assessed via high-throughput sequencing, we conducted a meta-analysis of temporal dynamics in microbial communities, including 76 sites representing air, aquatic, soil, brewery wastewater treatment, human- and plant-associated microbial biomes. We found that temporal variability in both within- and between-community diversity was consistent among microbial communities from similar environments. Community structure changed systematically with time in less than half of the cases, and the highest rates of change were observed within ranges of 1 day to 1 month for all communities examined. Microbial communities exhibited species-time relationships (STRs), which describe the accumulation of new taxa to a community, similar to those observed previously for plant and animal communities, suggesting that STRs are remarkably consistent across a broad range of taxa. These results highlight that a continued integration of microbial ecology into the broader field of ecology will provide new insight into the temporal patterns of microbial and 'macro'-bial communities alike.The ISME Journal advance online publication, 11 April 2013; doi:10.1038/ismej.2013.54.
Soils are the largest repository of organic carbon (C) in the terrestrial biosphere and represent an important source of carbon dioxide (CO2) to the atmosphere, releasing 60–75 Pg C annually through microbial decomposition of organic materials1,2. A primary control on soil CO2 flux is the efficiency with which the microbial community uses C. Despite its critical importance to soil–atmosphere CO2 exchange, relatively few studies have examined the factors controlling soil microbial efficiency. Here, we measured the temperature response of microbial efficiency in soils amended with substrates varying in lability. We also examined the temperature sensitivity of microbial efficiency in response to chronic soil warming in situ. We find that the efficiency with which soil microorganisms use organic matter is dependent on both temperature and substrate quality, with efficiency declining with increasing temperatures for more recalcitrant substrates. However, the utilization efficiency of a more recalcitrant substrate increased at higher temperatures in soils exposed to almost two decades of warming 5 �C above ambient. Our work suggests that climate warming could alter the decay dynamics of more stable organic matter compounds, thereby having a positive feedback to climate that is attenuated by a shift towards a more efficient microbial community in the longer term.
Litter decomposition recycles nutrients and causes large ?uxes of carbon dioxide into the atmosphere. It is typically assumed that climate, litter quality and decomposer communities determine litter decay rates, yet few comparative studies have examined their relative contributions in tropical forests. 2. We used a short-term litterbag experiment to quantify the effects of litter quality, placement and mesofaunal exclusion on decomposition in 23 tropical forests in 14 countries. Annual precipitation varied among sites (7605797 mm). At each site, two standard substrates (Raphia farinifera and Laurus nobilis) were decomposed in ?ne- and coarse-mesh litterbags both above and below ground for approximately 1 year.
Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 43°S to 68°N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates, but have neutral effects where temperature or moisture constrain biological activity. Our findings highlight that faunal influences on decomposition are dependent on prevailing climatic conditions. We conclude that (1) inclusion of soil animals will improve the predictive capabilities of region- or biome-scale decomposition models, (2) soil animal influences on decomposition are important at the regional scale when attempting to predict global change scenarios, and (3) the statistical relationship between decomposition rates and climate, at the global scale, is robust against changes in soil faunal abundance and diversity.
Decomposition of plant material is a complex process that requiresinteraction among a diversity of microorganisms whose presence and activity issubject to regulation by a wide range of environmental factors. Analysis ofextracellular enzyme activity (EEA) provides a way to relate the functionalorganization of microdecomposer communities to environmental variables. In thisstudy, we examined EEA in relation to litter composition and nitrogendeposition. Mesh bags containing senescent leaves of Quercusborealis (red oak), Acer rubrum (red maple) andCornus florida (flowering dogwood) were placed on forestfloor plots in southeastern New York. One-third of the plots were sprayedmonthly with distilled water. The other plots were sprayed monthly withNH4NO3 solution at dose rates equivalent to 2 or 8 g N m–2 y–1. Mass loss, litter composition, fungal mass, and the activities ofeight enzymes were measured on 13 dates for each litter type. Dogwood wasfollowed for one year, maple for two, oak for three. For each litter type andtreatment, enzymatic turnover activities were calculated from regressions of LN(%mass remaining) vs. cumulative activity. The decomposition of dogwood litterwas more efficient than that of maple and oak. Maple litter had the lowestfungal mass and required the most enzymatic work to decompose, even though itsmass loss rate was twice that of oak. Across litter types, N amendment reducedapparent enzymatic efficiencies and shifted EEA away from N acquisition andtoward P acquisition, and away from polyphenol oxidation and towardpolysaccharide hydrolysis. The effect of these shifts on decomposition ratevaried with litter composition: dogwood was stimulated, oak was inhibited andmaple showed mixed effects. The results show that relatively small shifts intheactivity of one or two critical enzymes can significantly alter decompositionrates.
General concern about climate change has led to growing interest in the responses of terrestrial ecosystems to elevated concentrations
of CO2 in the atmosphere. Experimentation during the last two to three decades using a large variety of approaches has provided
sufficient information to conclude that enrichment of atmospheric CO2 may have severe impact on terrestrial ecosystems. This impact is mainly due to the changes in the organic C dynamics as a
result of the effects of elevated CO2 on the primary source of organic C in soil, i.e., plant photosynthesis. As the majority of life in soil is heterotrophic
and dependent on the input of plant-derived organic C, the activity and functioning of soil organisms will greatly be influenced
by changes in the atmospheric CO2 concentration. In this review, we examine the current state of the art with respect to effects of elevated atmospheric CO2 on soil microbial communities, with a focus on microbial community structure. On the basis of the existing information, we
conclude that the main effects of elevated atmospheric CO2 on soil microbiota occur via plant metabolism and root secretion, especially in C3 plants, thereby directly affecting the
mycorrhizal, bacterial, and fungal communities in the close vicinity of the root. There is little or no direct effect on the
microbial community of the bulk soil. In particular, we have explored the impact of these changes on rhizosphere interactions
and ecosystem processes, including food web interactions.
Background, aim, and scope As the second most important greenhouse gas, methane (CH4) is produced from many sources such as paddy fields. Methane-oxidizing bacteria (methanotrophs) consume CH4 in paddy soil and, therefore, reduce CH4 emission to the atmosphere. In order to estimate the contribution of paddy fields as a source of CH4, it is important to monitor the effects of fertilizer applications on the shifts of soil methanotrophs, which are targets in strategies to combat global climate change. In this study, real-time polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) based on 16S rRNA and pmoA genes, respectively, were used to analyze the soil methanotrophic abundance and community diversity under four fertilization treatments: urea (N), urea and potassium chloride (NK), urea, superphosphate, and potassium chloride (NPK), and urea, superphosphate, potassium chloride, and crop residues (NPK+C), compared to an untreated control (CON). The objective of this study was to examine whether soil methanotrophs responded to the long-term, different fertilizer regimes by using a combination of quantitative and qualitative molecular approaches.
Microbial communities can potentially mediate feedbacks between global change and ecosystem function, owing to their sensitivity
to environmental change and their control over critical biogeochemical processes. Numerous ecosystem models have been developed
to predict global change effects, but most do not consider microbial mechanisms in detail. In this idea paper, we examine
the extent to which incorporation of microbial ecology into ecosystem models improves predictions of carbon (C) dynamics under
warming, changes in precipitation regime, and anthropogenic nitrogen (N) enrichment. We focus on three cases in which this
approach might be especially valuable: temporal dynamics in microbial responses to environmental change, variation in ecological
function within microbial communities, and N effects on microbial activity. Four microbially-based models have addressed these
scenarios. In each case, predictions of the microbial-based models differ—sometimes substantially—from comparable conventional
models. However, validation and parameterization of model performance is challenging. We recommend that the development of
microbial-based models must occur in conjunction with the development of theoretical frameworks that predict the temporal
responses of microbial communities, the phylogenetic distribution of microbial functions, and the response of microbes to
N enrichment.
KeywordsCommunity composition–Functional groups–Global change–Nitrogen–Precipitation–Temporal dynamics–Warming
Evidence is mounting that extinctions are altering key processes important to the productivity and sustainability of Earth's ecosystems. Further species loss will accelerate change in ecosystem processes, but it is unclear how these effects compare to the direct effects of other forms of environmental change that are both driving diversity loss and altering ecosystem function. Here we use a suite of meta-analyses of published data to show that the effects of species loss on productivity and decomposition--two processes important in all ecosystems--are of comparable magnitude to the effects of many other global environmental changes. In experiments, intermediate levels of species loss (21-40%) reduced plant production by 5-10%, comparable to previously documented effects of ultraviolet radiation and climate warming. Higher levels of extinction (41-60%) had effects rivalling those of ozone, acidification, elevated CO(2) and nutrient pollution. At intermediate levels, species loss generally had equal or greater effects on decomposition than did elevated CO(2) and nitrogen addition. The identity of species lost also had a large effect on changes in productivity and decomposition, generating a wide range of plausible outcomes for extinction. Despite the need for more studies on interactive effects of diversity loss and environmental changes, our analyses clearly show that the ecosystem consequences of local species loss are as quantitatively significant as the direct effects of several global change stressors that have mobilized major international concern and remediation efforts.
