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Changes in rainfall patterns are important environmental factors affecting plant growth, especially when larger precipitation events and prolonged drought periods occur in subtropical regions. There are many studies on how drought reduces plant biomass through drought-sensitive functional traits, but how excess water affects plant growth and ecophysiology is still poorly understood. Therefore, a greenhouse experiment was conducted on Schima superba (Theaceae), a dominant tree species in subtropical forests and commonly used in forestry, in a closed chamber under control (25% soil water content (SWC) as in local forests), drought stress (D, 15% SWC) and moisture stress (W, 35% SWC). Plant growth and ecophysiological traits related to morphology, leaf gas exchange, water potential and structural traits were measured. Compared to control, S. suberba under dry conditions significantly decreased its aboveground biomass, photosynthetic rate (A), leaf water potential and nitrogen use efficiency, but increased intrinsic water use efficiency, root to shoot ratio and specific root length. S. superba under wet conditions also significantly decreased its total biomass, aboveground biomass and specific root length, while W had no effect on A and leaf water potential. Our results indicate that S. superba shows a decrease in carbon gain under drought stress, but less response under wet conditions. This emphasizes the need to consider the strength and frequency of rainfall pattern changes in future studies because rainfall may either alleviate or intensify the effects of drought stress depending on the moisture level, thus suitable water conditions is important for better management of this tree species in subtropical China. [ABSTRACT FROM AUTHOR]

Climate change is increasing the variability of precipitation, altering the frequency of soil drying-wetting events and the distribution of seasonal precipitation. These changes in precipitation can alter nitrogen (N) cycling and stimulate nitric oxide (NO) emissions (an air pollutant at high concentrations), which may vary according to legacies of past precipitation and represent a pathway for ecosystem N loss. To identify whether precipitation legacies affect NO emissions, we excluded or added precipitation during the winter growing season in a Pinyon-Juniper dryland and measured in situ NO emissions following experimental wetting. We found that the legacy of both excluding and adding winter precipitation increased NO emissions early in the following summer; cumulative NO emissions from the winter precipitation exclusion plots (2750 ± 972 μg N-NO m-2 ) and winter water addition plots (2449 ± 408 μg N-NO m-2 ) were higher than control plots (1506 ± 397 μg N-NO m-2 ). The increase in NO emissions with previous precipitation exclusion was associated with inorganic N accumulation, while the increase in NO emissions with previous water addition was associated with an upward trend in microbial biomass. Precipitation legacies can accelerate soil NO emissions and may amplify ecosystem N loss in response to more variable precipitation.

Grasslands support a rich diversity that plays a pivotal role in ecological balance, carbon sequestration, and climate regulation. Grassland ecosystems are facing a loss of biodiversity and a decline in soil function due to precipitation variations caused by climate change. However, variations in grassland species diversity are not clearly known, especially under the combined effects of precipitation and grazing. Based on a 5‐year split‐plot experiment with two grazing regimes (i.e., moderate grazing and grazing prohibition) along with three precipitation controls (ambient precipitation and ±50% precipitation) in Inner Mongolian grasslands, we researched the response of precipitation variability and grazing prohibition to vegetation diversity indices and investigated the response of vegetation community composition and biomass to these factors. Five years results showed that increasing precipitation resulted in a significant increase in the coverage of perennial forbs, annual and biennial plants, and Gramineae. Grazing prohibition and increased precipitation significantly increased biomass and species richness compared to all other treatment combinations. Interestingly, grazing exclusion significantly reduced the percentage of Amaryllidaceae, especially in the presence of altered precipitation. The vegetation community composition of a typical grassland was correlated with soil volumetric water content (VWC), bulk density (SBD) and pH, soil organic carbon (SOC), and total nitrogen (TN). VWC, SBD, and TN were found to be the most significant factors affecting vegetation diversity under grazing. Partial canonical ordination revealed that soil moisture, soil bulk density, and SOC had the most significant correlation with vegetation diversity under both grazing prohibition and increased precipitation treatment conditions. These results suggested that alterations in precipitation can change the species composition and ecosystem function of plant communities, leading to a close relationship between species diversity and soil properties. Our results underline the importance of species diversity for soil characteristics and environmental factors in a typical Eurasian steppe ecosystem. [ABSTRACT FROM AUTHOR]

Warming and precipitation anomalies affect terrestrial carbon balance partly through altering microbial eco-physiological processes (e.g., growth and death) in soil. However, little is known about how such processes responds to simultaneous regime shifts in temperature and precipitation. We used the 18O-water quantitative stable isotope probing approach to estimate bacterial growth in alpine meadow soils of the Tibetan Plateau after a decade of warming and altered precipitation manipulation. Our results showed that the growth of major taxa was suppressed by the single and combined effects of temperature and precipitation, eliciting 40–90% of growth reduction of whole community. The antagonistic interactions of warming and altered precipitation on population growth were common (~70% taxa), represented by the weak antagonistic interactions of warming and drought, and the neutralizing effects of warming and wet. The members in Solirubrobacter and Pseudonocardia genera had high growth rates under changed climate regimes. These results are important to understand and predict the soil microbial dynamics in alpine meadow ecosystems suffering from multiple climate change factors.

Abstract Background Changes in soil greenhouse gas (GHG) fluxes caused by nitrogen (N) addition are considered as the key factors contributing to global climate change (global warming and altered precipitation regimes), which in turn alters the feedback between N addition and soil GHG fluxes. However, the effects of N addition on soil GHG emissions under climate change are highly variable and context-dependent, so that further syntheses are required. Here, a meta-analysis of the interactive effects of N addition and climate change (warming and altered precipitation) on the fluxes of three main soil GHGs [carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)] was conducted by synthesizing 2103 observations retrieved from 57 peer-reviewed articles on multiple terrestrial ecosystems globally. Results The interactive effects of N addition and climate change on GHG fluxes were generally additive. The combination of N addition and warming or altered precipitation increased N2O emissions significantly while it had minimal effects on CO2 emissions and CH4 uptake, and the effects on CH4 emissions could not be evaluated. Moreover, the magnitude of the combined effects did not differ significantly from the effects of N addition alone. Apparently, the combined effects on CO2 and CH4 varied among ecosystem types due to differences in soil moisture, which was in contrast to the soil N2O emission responses. The soil GHG flux responses to combined N addition and climate change also varied among different climatic conditions and experimental methods. Conclusion Overall, our findings indicate that the effects of N addition and climate change on soil GHG fluxes were relatively independent, i.e. combined effects of N addition and climate change were equal to or not significantly different from the sum of their respective individual effects. The effects of N addition on soil GHG fluxes influence the feedbacks between climate change and soil GHG fluxes.

While altered precipitation regimes can greatly impact biodiversity and ecosystem functioning, we lack a comprehensive view of how these impacts are mediated by changes to the seasonality of precipitation (i.e., whether it rains more/less in one season relative to another). Over 2 years, we examined how altered seasonal precipitation influenced annual plant biomass and species richness, Simpson’s diversity, and community composition of annual plant communities in a dryland ecosystem that receives both winter and summer rainfall and has distinct annual plant communities in each season. Using a rainfall exclusion, collection, and distribution system, we excluded precipitation and added water during each season individually and compared responses to control plots which received ambient summer and winter precipitation. In control plots, we found five times greater annual plant biomass, twice as many species, and higher diversity in winter relative to summer. Adding water increased annual plant biomass in summer only, did not change richness or diversity in either summer or winter, and modestly shifted community composition. Excluding precipitation in either season reduced annual plant biomass, richness, and Simpson’s diversity. However, in the second winter season, biomass was higher in the plots where precipitation was excluded in the previous summer seasons suggesting that reduced productivity in the summer may facilitate biomass in the winter. Our results suggest that increased precipitation in summer may have stronger short-term impacts on annual plant biodiversity and ecosystem function relative to increased winter precipitation. In contrast, decreasing precipitation may have ubiquitous negative effects on annual plants across both summer and winter but may lead to increased biomass in the following off-seasons. These patterns suggest that annual plant communities exhibit asymmetries in their community and ecosystem responses to altered seasonal precipitation and that considering the seasonality of precipitation is important for predicting the effects of altered precipitation regimes.

Background: Changes in soil greenhouse gas (GHG) fluxes caused by nitrogen (N) addition are considered as the key factors contributing to global climate change (global warming and altered precipitation regimes), which in turn alters the feedback between N addition and soil GHG fluxes. However, the effects of N addition on soil GHG emissions under climate change are highly variable and context-dependent, so that further syntheses are required. Here, a meta-analysis of the interactive effects of N addition and climate change (warming and altered precipitation) on the fluxes of three main soil GHGs [carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)] was conducted by synthesizing 2103 observations retrieved from 57 peer-reviewed articles on multiple terrestrial ecosystems globally. Results: The interactive effects of N addition and climate change on GHG fluxes were generally additive. The combination of N addition and warming or altered precipitation increased N2O emissions significantly while it had minimal effects on CO2 emissions and CH4 uptake, and the effects on CH4 emissions could not be evaluated. Moreover, the magnitude of the combined effects did not differ significantly from the effects of N addition alone. Apparently, the combined effects on CO2 and CH4 varied among ecosystem types due to differences in soil moisture, which was in contrast to the soil N2O emission responses. The soil GHG flux responses to combined N addition and climate change also varied among different climatic conditions and experimental methods. Conclusion: Overall, our findings indicate that the effects of N addition and climate change on soil GHG fluxes were relatively independent, i.e. combined effects of N addition and climate change were equal to or not significantly different from the sum of their respective individual effects. The effects of N addition on soil GHG fluxes influence the feedbacks between climate change and soil GHG fluxes. [ABSTRACT FROM AUTHOR]

Precipitation changes exert a fundamental effect on the nitrogen (N) cycle in water‐limited grasslands. Soil microbes are essential drivers of N cycle, and the rates and their stabilities of interrelated N‐cycling processes are reflected by the abundance and diversity of N‐cycling genes. Yet, little is known about how altered precipitation affects the genes involved in the entire N‐cycling pathways.By combining a 6‐year precipitation manipulation experiment (−30%, ambient, +30%, +50%) with metagenomic sequencing, we investigated the responses of N‐cycling gene abundance and diversity to altered precipitation at two soil depths (0–10 and 30–50 cm).We found that increased precipitation enhanced the abundance of numerous key genes, leading to an acceleration of N turnover, but decreased the diversity of ammonium assimilation genes. Decreased precipitation did not reduce abundance or diversity of N‐cycling genes. Most N‐cycling genes showed generally consistent responses to altered precipitation in the topsoil (0–10 cm) and subsoil (30–50 cm), albeit with clear distinctions in both abundance and diversity by soil depth. These precipitation‐specific responses and depth‐dependent variabilities of functional genes were attributed to the distinct taxonomic composition of each N‐cycling gene. Furthermore, we quantified gross N transformation rates and found that they were well predicted by the abundance of most N‐cycling genes (e.g. genes involved in ammonium assimilation and nitrification).Our study sheds new light on the soil N cycle under precipitation alterations from the perspective of individual gene abundance and diversity and shows that future increases in precipitation could accelerate soil N turnover in arid and semi‐arid lands. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Pest profiles in today’s global food production system are continually affected by climate change and extreme weather. Under varying climatic conditions, plant-parasitic nematodes (PPNs) cause substantial economic damage to a wide variety of agricultural and horticultural commodities. In parallel, their herbivory also accredit to diverse ecosystem services such as nutrient cycling, allocation and turnover of plant biomass, shaping of vegetation community, and alteration of rhizospheric microorganism consortium by modifying the root exudation pattern. Thus PPNs, together with the vast majority of free-living nematodes, act as ecological drivers. Because of direct exposure to the open environment, PPN biology and physiology are largely governed by environmental factors including temperature, precipitation, humidity, atmospheric and soil carbon dioxide level, and weather extremes. The negative effects of climate change such as global warming, elevated CO2, altered precipitation and the weather extremes including heat waves, droughts, floods, wildfires and storms greatly influence the biogeographic range, distribution, abundance, survival, fitness, reproduction, and parasitic potential of the PPNs. Changes in these biological and ecological parameters associated to the PPNs exert huge impact on agriculture. Yet, depending on how adaptable the species are according to their geo-spatial distribution, the consequences of climate change include both positive and negative effects on the PPN communities. While assorting the effects of climate change as a whole, it can be estimated that the changing environmental factors, on one hand, will aggravate the PPN damage by aiding to abundance, distribution, reproduction, generation, plant growth and reduced plant defense, but the phenomena like sex reversal, entering cryptobiosis, and reduced survival should act in counter direction. This seemingly creates a contraposition effect, where assessing any confluent trend is difficult. However, as the climate change effects will differ according to space and time it is apprehensible that the PPNs will react and adapt according to their location and species specificity. Nevertheless, the bio-ecological shifts in the PPNs will necessitate tweaking their management practices from the agri-horticultural perspective. In this regard, we must aim for a ‘climate-smart’ package that will take care of the food production, pest prevention and environment protection. Integrated nematode management involving precise monitoring and modeling-based studies of population dynamics in relation to climatic fluctuations with escalated reliance on biocontrol, host resistance, and other safer approaches like crop rotation, crop scheduling, cover cropping, biofumigation, use of farmyard manure (FYM) would surely prove to be viable options. Although the novel nematicidal molecules are target-specific and relatively less harmful to the environment, their application should not be promoted following the global aim to reduce pesticide usage in future agriculture. Thus, having a reliable risk assessment with scenario planning, the adaptive management strategies must be designed to cope with the impending situation and satisfy the farmers’ need. [ABSTRACT FROM AUTHOR]

Human activities cause a multitude of environmental issues, including increased temperatures and altered precipitation patterns associated with climate change, air pollution, and other impacts of urbanization. One area highly affected by these issues is the Sonoran Desert, specifically the Phoenix metropolitan area where urbanization is among the most rapid in the United States. Most studies investigate these multiple environmental change factors independently or sometimes in pairs, but rarely all together as co-occurring forms of change. We examined how the simultaneous manipulation of increasing temperatures, altered precipitation patterns, nitrogen deposition, and urbanization influenced soil respiration and mineral N pools in the Sonoran Desert. Soil was collected from urban and exurban sites, from both nitrogen-fertilized and control plots. To simulate projected climate change, the soils were incubated in microcosm at the annual average Phoenix temperature as well a 2 ℃ increase under a factorial precipitation treatment of decreased frequency and increased pulse size. Our results show that C and N dynamics were altered by all four forms of environmental change. However, the dominance of significant 3- and 4-way interactions among the four environmental factors for both respiration and mineral N pools demonstrates that the impact of any given form of environmental change will depend on the levels of the other environmental factors. In other words, the cumulative effect of altered precipitation, fertilization, temperature, and urbanization on soil biogeochemical processes is not necessarily predictable from their individual impact. [ABSTRACT FROM AUTHOR]

Pest profiles in today’s global food production system are continually affected by climate change and extreme weather. Under varying climatic conditions, plant-parasitic nematodes (PPNs) cause substantial economic damage to a wide variety of agricultural and horticultural commodities. In parallel, their herbivory also accredit to diverse ecosystem services such as nutrient cycling, allocation and turnover of plant biomass, shaping of vegetation community, and alteration of rhizospheric microorganism consortium by modifying the root exudation pattern. Thus PPNs, together with the vast majority of free-living nematodes, act as ecological drivers. Because of direct exposure to the open environment, PPN biology and physiology are largely governed by environmental factors including temperature, precipitation, humidity, atmospheric and soil carbon dioxide level, and weather extremes. The negative effects of climate change such as global warming, elevated CO2, altered precipitation and the weather extremes including heat waves, droughts, floods, wildfires and storms greatly influence the biogeographic range, distribution, abundance, survival, fitness, reproduction, and parasitic potential of the PPNs. Changes in these biological and ecological parameters associated to the PPNs exert huge impact on agriculture. Yet, depending on how adaptable the species are according to their geo-spatial distribution, the consequences of climate change include both positive and negative effects on the PPN communities. While assorting the effects of climate change as a whole, it can be estimated that the changing environmental factors, on one hand, will aggravate the PPN damage by aiding to abundance, distribution, reproduction, generation, plant growth and reduced plant defense, but the phenomena like sex reversal, entering cryptobiosis, and reduced survival should act in counter direction. This seemingly creates a contraposition effect, where assessing any confluent trend is difficult. However, as the climate change effects will differ according to space and time it is apprehensible that the PPNs will react and adapt according to their location and species specificity. Nevertheless, the bio-ecological shifts in the PPNs will necessitate tweaking their management practices from the agri-horticultural perspective. In this regard, we must aim for a ‘climate-smart’ package that will take care of the food production, pest prevention and environment protection. Integrated nematode management involving precise monitoring and modeling-based studies of population dynamics in relation to climatic fluctuations with escalated reliance on biocontrol, host resistance, and other safer approaches like crop rotation, crop scheduling, cover cropping, biofumigation, use of farmyard manure (FYM) would surely prove to be viable options. Although the novel nematicidal molecules are target-specific and relatively less harmful to the environment, their application should not be promoted following the global aim to reduce pesticide usage in future agriculture. Thus, having a reliable risk assessment with scenario planning, the adaptive management strategies must be designed to cope with the impending situation and satisfy the farmers’ need.

Ecosystems are faced with an onslaught of co-occurring global change drivers. While frequently studied independently, the effects of multiple global change drivers have the potential to be additive, antagonistic, or synergistic. Global warming, for example, may intensify the effects of more variable precipitation regimes with warmer temperatures increasing evapotranspiration and thereby amplifying the effect of already dry soils. Here, we present the long-term effects (11 years) of altered precipitation patterns (increased intra-annual variability in the growing season) and warming (1 °C year-round) on plant community composition and aboveground net primary productivity (ANPP), a key measure of ecosystem functioning in mesic tallgrass prairie. Based on past results, we expected that increased precipitation variability and warming would have additive effects on both community composition and ANPP. Increased precipitation variability altered plant community composition and increased richness, with no effect on ANPP. In contrast, warming decreased ANPP via reduction in grass stems and biomass but had no effect on the plant community. Contrary to expectations, across all measured variables, precipitation and warming treatments had no interactive effects. While treatment interactions did not occur, each treatment did individually impact a different component of the ecosystem (i.e., community vs. function). Thus, different aspects of the ecosystem may be sensitive to different global change drivers in mesic grassland ecosystems. [ABSTRACT FROM AUTHOR]

Changes in precipitation regimes can strongly affect soil nitrogen (N) cycling in terrestrial ecosystems. However, whether altered precipitation regimes may differentially affect soil N cycling between arid and humid biomes at the global scale is unclear. We conducted a meta‐analysis using 1036 pairwise observations collected from 194 publications to assess the effects of increased and decreased precipitation on the input (N return from plants), storage (various forms of N in soil), and output (gaseous N emissions) of soil N in arid versus humid biomes at the global scale. We found that (1) increased precipitation significantly increased N input (+12.1%) and output (+34.9%) but decreased N storage (−13.7%), while decreased precipitation significantly decreased N input (−10.7%) and output (−34.8%) but increased N storage (+11.1%); (2) the sensitivity of soil N cycling to increased precipitation was higher in arid regions than in humid regions, while that to decreased precipitation was lower in arid regions than in humid regions; (3) the effect of altered precipitation regimes on soil N cycling was independent of precipitation type (i.e., rainfall vs. snowfall); and (4) the mean annual precipitation regulated soil N cycling in precipitation alteration experiments at the global scale. Overall, our results clearly show that the response of soil N cycling to increased versus decreased precipitation differs between arid and humid regions, indicating the uneven effect of climate change on soil N cycling between these two contrasting climate regions. This implies that ecosystem models need to consider the differential responses of N cycling to altered precipitation regimes in different climatic conditions under future global change scenarios. [ABSTRACT FROM AUTHOR]

Changes in precipitation regimes have significant effects on soil carbon (C) cycles; however, these effects may vary in arid versus 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. [ABSTRACT FROM AUTHOR]

Exploring the dynamics of soil carbon (C) response to multi-faceted global climate change plays a vital role in facilitating the estimation of carbon-climate feedback. However, the direction and extent of the warming effect on soil carbon pool within different soil fractions considered simultaneously in increased precipitation and decreased precipitation system are not well understood. Here we established a 2-year field manipulation experiment based on open top chamber (OTC) to assess the effects of warming and altering precipitation regimes (40 % reduction, normal, and 40 % increment) on soil physical fractions formation and distribution. Our results showed that in the precipitation increment, warming significantly increased particulate organic carbon (POC) and mineral-associated carbon (MAOC) by an average of 48.10 % and 21.28 % in the 0–5 cm soil layer. And the formation mechanism of POC and MAOC were different. POC was directly affected by the coupling between plant input and C-degradation fungal functional genes adjusted by dissolved organic carbon (DOC) and total nitrogen (TN); and MAOC was affected by increasing labile carbon inputs (such as DOC) of maize residue and belowground biomass. However, precipitation reduction neutralized the beneficial effects of warming, mainly through reducing plant inputs and residue decomposition, thereby suppressing C-degradation fungal functional genes and labile carbon supply. Overall, our results provide new insights into the potential mechanisms through which interaction of warming and altered precipitation controls soil C dynamics. • Plant biomass increased by the interaction of warming and precipitation increment. • Precipitation increment enhanced the effect of warming on POC and MAOC. • POC pool was mainly governed by DOC/SOC and C-degradation fungal genes. • There were significant correlations between DOC/SOC and MAOC pool. [ABSTRACT FROM AUTHOR]

Precipitation and grazing both modify the structure and function of grassland. Although the effects of site-scale precipitation and grazing on vegetation communities have been investigated, the differences between different grassland types at the global scale are still not clear. Therefore, we conducted a global-scale meta-analysis synthesizing 107 field studies with different grassland types (savanna grassland, temperate grassland, cold grassland, and alpine grassland) to quantify the effects of global changes in precipitation and grazing on community structure and function of grassland types. Results showed that regardless of grassland type, increased precipitation increased species richness by 7.8%, decreased belowground biomass (BGB) by 20.0%, and increased aboveground biomass (AGB) by 22.9%, but interestingly, decreased precipitation increased BGB by 17.7%, decreased AGB by 22.8%, and decreased species richness by 13.7%. Species richness of global grassland vegetation was positively correlated with grazing intensity. The total vegetation community biomass (TB) increased by 11.7% under moderate grazing intensity, while the species diversity of global grassland vegetation increased by 10.7% under heavy grazing intensity. Increased precipitation had negatively impacted BGB in temperate grassland, while increased precipitation significantly increased cool grassland BGB. In savanna grasslands, vegetation AGB decreased with increasing precipitation. Our results highlight the impact of altered precipitation on grassland vegetation under different climate types. We suggest that future studies of grassland management should consider incorporating grazing intensity and climate type, which will help to protect grassland vegetation species diversity and predict future carbon dynamics. [Display omitted] • Moderate grazing has a positive impact globally on the composition of vegetation community of different grassland types. • Altered precipitation has a greater impact on vegetation richness with light and moderate grazing. • Increased precipitation reduced global grassland BGB, but decreased precipitation significantly increased the BGB. • The effect size of vegetation in savanna increased with grazing, while alpine grassland saw a decline in RR. [ABSTRACT FROM AUTHOR]

Warming and precipitation anomalies affect terrestrial carbon balance partly through altering microbial eco-physiological processes (e.g., growth and death) in soil. However, little is known about how such processes responds to simultaneous regime shifts in temperature and precipitation. We used the 18 O-water quantitative stable isotope probing approach to estimate bacterial growth in alpine meadow soils of the Tibetan Plateau after a decade of warming and altered precipitation manipulation. Our results showed that the growth of major taxa was suppressed by the single and combined effects of temperature and precipitation, eliciting 40-90% of growth reduction of whole community. The antagonistic interactions of warming and altered precipitation on population growth were common (~70% taxa), represented by the weak antagonistic interactions of warming and drought, and the neutralizing effects of warming and wet. The members in Solirubrobacter and Pseudonocardia genera had high growth rates under changed climate regimes. These results are important to understand and predict the soil microbial dynamics in alpine meadow ecosystems suffering from multiple climate change factors., Competing Interests: YR, NL, SJ, XJ, JH, QS, ZN No competing interests declared, (© 2023, Ruan et al.)

Shrub encroachment has caused a vegetation shift in arid and semiarid grassland ecosystems around the world, leading to marked changes in ecosystem structures and functions. Soil extracellular enzyme activity (EEA) is an informative indicator of microbial decomposition and plays an important role in soil biogeochemical cycles, but it is unclear how shrub encroachment affects soil EEA, especially in the future precipitation pattern under climate change. In this study, we measured soil EEAs in a shrub-encroached grassland in Inner Mongolia, China, after four years of in situ experimental precipitation manipulation. Soil samples were collected from grass patches and shrub patches in four precipitation manipulation treatments (−30%, control, +30%, and +50%). Four soil enzymes involved in carbon cycling (α-glucosidase, AG; β-1,4-glucosidase, BG; β-D-cellobiosidase, CB; and β-xylosidase, XS), two nitrogen-acquiring enzymes (β-1,4-N-acetyl-glucosaminidase, NAG; and leucine amino peptidase, LAP), and one phosphorus-acquiring enzyme (acid phosphatase, AP) were investigated. The results showed that BG, XS, and LAP activities were significantly enhanced in shrub patches than grass patches (p

Estuaries and coastal areas worldwide are rapidly changing, especially those adjacent to urban centers. Physical and ecological stresses are exacerbated by climate change (CC) and sea level rise (SLR). In this research, a salinity transport model for Biscayne Bay is presented. The model is used to estimate salinity under various scenarios of altered precipitation, increased salinity/temperature, and SLR. The simulated scenarios (based on prior studies and existing literature) assumed increases of 1.5 °C in temperature, and 0.6 PSU in ocean salinity. Current precipitation was varied from −10% to +10%. SLR varied from +0.46 m to +2.18 m. The highest increase in bay salinity (worst-case scenario) occurred for 10% decrease in precipitation, and +2.18 m SLR. The lowest increase in salinity (mildest scenario) occurred for 10% increase in precipitation, and +0.46 m SLR. In the mildest scenario, a 50% increase in baseline freshwater inputs is needed to maintain currently observed Bay salinities. For the worst scenario, a 300% freshwater increase would be required. Current Everglades Restoration plans to restore the Bay salinity to "natural" conditions must consider the potential CC-induced effects simulated in this research. Present efforts may not be sufficient to even maintain current salinity conditions in Biscayne Bay. Increasing urban vegetation (urban greening), artificial groundwater recharge with treated wastewater, and decreasing water consumption, are proposed as management measures for reinforcing current and future restoration efforts. • Future simulated scenarios predict that salinity will increase in Biscayne Bay. • For the mildest scenario, 50% freshwater increase would maintain current salinities. • For the worst scenario, 300% freshwater increase would maintain current salinities. • SLR and CC impacts should be considered in coastal waters restoration efforts. [ABSTRACT FROM AUTHOR]

Abstract Global warming and changes in precipitation are altering the phenology of plants that significantly impact the functioning and services of ecosystems. Although a number of studies have addressed responses of plant phenology to warming and altered precipitation individually, their interactions can alter plant phenology differently than either does independently. To explore how the interactions between global change drivers alter alpine ecosystems, we conducted a factorial experiment manipulating warming (ambient and +2°C) and altered precipitation (50% decrease, control, and 50% increase) simultaneously in an alpine meadow on the Tibetan Plateau. Over two years, we monitored plant phenological events, leaf‐out day and first flowering day, for 11 common plant species that account for 74.4% of the total above biomass. Surprisingly, there was no interaction between warming and changes in precipitation on community plant phenology, but warming advanced leaf‐out and first flowering day by 7.10 and 9.79 d, respectively. Unlike the community response, plant functional groups had a variety of direct and interactive responses to the experimental climate drivers. While the phenology of legumes was most influenced by temperature, temperature and precipitation interacted to alter the phenology of grasses and forbs. To explore how plant phenological sensitivity on the Tibetan Plateau is compared with other meadow ecosystems, we combined our dataset with a global plant phenology dataset. Interestingly, the phenological sensitivity of leaf‐out day and first flowering day on the Tibetan Plateau is 7.3 and 37.8 times greater than global phenological sensitivity, respectively. This result highlights that a meta‐analysis of global phenological sensitivity may significantly underestimate change in some regions—even regions as large as the Tibetan Plateau. Together, our results suggest that the Tibetan Plateau may experience rapid change as temperatures warm and that these changes will likely be more rapid than in other regions of the world. Further, our study highlights that if we are to make accurate predictions of how plant phenology may change with warming, we need to understand the specific environmental cues that drive phenological responses across different areas.

Summary: The effects of global change on semi‐natural and agro‐ecosystem functioning have been studied extensively. However, less well understood is how global change will influence fungal diseases, especially in a natural ecosystem.We use data from a 6‐yr factorial experiment with warming (simulated using infrared heaters) and altered precipitation treatments in a natural Tibetan alpine meadow ecosystem, from which we tested global change effects on foliar fungal diseases at the population and community levels, and evaluated the importance of direct effects of the treatments and community‐mediated (indirect) effects (through changes in plant community composition and competence) of global change on community pathogen load.At the population level, we found warming significantly increased fungal diseases for nine plant species. At the community level, we found that warming significantly increased pathogen load of entire host communities, whereas no significant effect of altered precipitation on community pathogen load was detected.We concluded that warming influences fungal disease prevalence more than precipitation does in a Tibetan alpine meadow. Moreover, our study provides new experimental evidence that increases in disease burden on some plant species and for entire host communities is primarily the direct effects of warming, rather than community‐mediated (indirect) effects. [ABSTRACT FROM AUTHOR]

Global warming and changes in precipitation are altering the phenology of plants that signifi- cantly impact the functioning and services of ecosystems. Although a number of studies have addressed responses of plant phenology to warming and altered precipitation individually, their interactions can alter plant phenology differently than either does independently. To explore how the interactions between global change drivers alter alpine ecosystems, we conducted a factorial experiment manipulating warming (ambient and +2°C) and altered precipitation (50% decrease, control, and 50% increase) simultaneously in an alpine meadow on the Tibetan Plateau. Over two years, we monitored plant phenological events, leafout day and first flowering day, for 11 common plant species that account for 74.4% of the total above biomass. Surprisingly, there was no interaction between warming and changes in precipitation on community plant phenology, but warming advanced leaf-out and first flowering day by 7.10 and 9.79 d, respectively. Unlike the community response, plant functional groups had a variety of direct and interactive responses to the experimental climate drivers. While the phenology of legumes was most influenced by temperature, temperature and precipitation interacted to alter the phenology of grasses and forbs. To explore how plant phenological sensitivity on the Tibetan Plateau is compared with other meadow ecosystems, we combined our dataset with a global plant phenology dataset. Interestingly, the phenological sensitivity of leaf-out day and first flowering day on the Tibetan Plateau is 7.3 and 37.8 times greater than global phenological sensitivity, respectively. This result highlights that a meta-analysis of global phenological sensitivity may significantly underestimate change in some regions--even regions as large as the Tibetan Plateau. Together, our results suggest that the Tibetan Plateau may experience rapid change as temperatures warm and that these changes will likely be more rapid than in other regions of the world. Further, our study highlights that if we are to make accurate predictions of how plant phenology may change with warming, we need to understand the specific environmental cues that drive phenological responses across different areas. [ABSTRACT FROM AUTHOR]

Phyllosphere fungi form close ecological ties with their hosts and participate in multiple ecosystem processes. This research investigated simulated climate change effects of warming and precipitation manipulationon the Aster tataricus fungal community in a Qinghai-Tibetan Plateau alpine meadow. Increased precipitation increased the fungal community diversity and richness indices, but warming had the opposite effect. Warming and precipitation adjustment in combination reduced the fungal community diversity. FUNGuild functional analysis of differences in the leaf fungal community in our study, and linked statistical analysis, determined that increasing precipitation significantly reduced relative abundance of pathogenic fungi and incidence of plant diseases, while warming and decreased precipitation did the opposite. Differences in the leaf fungal community in our study under warming and decreased precipitation would be predicted to increase incidence of plant diseases. These climate change simulations improve awareness of future plant disease risks in natural plant communities and provide opportunities to develop responses. [Display omitted] [ABSTRACT FROM AUTHOR]

Background Biocrusts, communities dominated by mosses, lichens, cyanobacteria, and other microorganisms, largely affect the carbon cycle of drylands. As poikilohydric organisms, their activity time is often limited to short hydration events. The photosynthetic and respiratory response of biocrusts to hydration events is not only determined by the overall amount of available water, but also by the frequency and size of individual rainfall pulses. Methods We experimentally assessed the carbon exchange of a biocrust community dominated by the lichen Diploschistes diacapsis in central Spain. We compared the effect of two simulated precipitation patterns providing the same overall amount of water, but with different pulse sizes and frequency (high frequency: five mm/day vs. low frequency: 15 mm/3 days), on net/gross photosynthesis and dark respiration. Results Radiation and soil temperature, together with the watering treatment, affected the rates of net and gross photosynthesis, as well as dark respiration. On average, the low frequency treatment showed a 46% ± 3% (mean ± 1 SE) lower rate of net photosynthesis, a 13% ± 7% lower rate of dark respiration, and a 24% ± 8% lower rate of gross photosynthesis. However, on the days when samples of both treatments were watered, no differences between their carbon fluxes were observed. The carbon flux response of D. diacapsis was modulated by the environmental conditions and was particularly dependent on the antecedent soil moisture. Discussion In line with other studies, we found a synergetic effect of individual pulse size, frequency, environmental conditions, and antecedent moisture on the carbon exchange fluxes of biocrusts. However, most studies on this subject were conducted in summer and they obtained results different from ours, so we conclude that there is a need for long-term experiments of manipulated precipitation impacts on the carbon exchange of biocrusts. This will enable a more complete assessment of the impacts of climate change-induced alterations in precipitation patterns on biocrust communities.

Background: Biocrusts, communities dominated by mosses, lichens, cyanobacteria, and other microorganisms, largely affect the carbon cycle of drylands. As poikilohydric organisms, their activity time is often limited to short hydration events. The photosynthetic and respiratory response of biocrusts to hydration events is not only determined by the overall amount of available water, but also by the frequency and size of individual rainfall pulses. Methods: We experimentally assessed the carbon exchange of a biocrust community dominated by the lichen Diploschistes diacapsis in central Spain. We compared the effect of two simulated precipitation patterns providing the same overall amount of water, but with different pulse sizes and frequency (high frequency: five mm/day vs. low frequency: 15 mm/3 days), on net/gross photosynthesis and dark respiration. Results: Radiation and soil temperature, together with the watering treatment, affected the rates of net and gross photosynthesis, as well as dark respiration. On average, the low frequency treatment showed a 46% ± 3% (mean ± 1 SE) lower rate of net photosynthesis, a 13% ± 7% lower rate of dark respiration, and a 24% ± 8% lower rate of gross photosynthesis. However, on the days when samples of both treatments were watered, no differences between their carbon fluxes were observed. The carbon flux response of D. diacapsis was modulated by the environmental conditions and was particularly dependent on the antecedent soil moisture. Discussion: In line with other studies, we found a synergetic effect of individual pulse size, frequency, environmental conditions, and antecedent moisture on the carbon exchange fluxes of biocrusts. However, most studies on this subject were conducted in summer and they obtained results different from ours, so we conclude that there is a need for long-term experiments of manipulated precipitation impacts on the carbon exchange of biocrusts. This will enable a more complete assessment of the impacts of climate change-induced alterations in precipitation patterns on biocrust communities. [ABSTRACT FROM AUTHOR]

Human activity-induced global change drivers have dramatically changed terrestrial phosphorus (P) dynamics. However, our understanding of the interactive effects of multiple global change drivers on terrestrial P pools remains elusive, limiting their incorporation into ecological and biogeochemical models. We conducted a meta-analysis using 1751 observations extracted from 283 published articles to evaluate the individual, combined, and interactive effects of elevated CO 2 , warming, N addition, P addition, increased rainfall, and drought on P pools of plant (at both single-plant and plant-community levels), soil and microbial biomass. Our results suggested that (1) terrestrial P pools showed the most sensitive responses to the individual effects of warming and P addition; (2) P pools were consistently stimulated by P addition alone or in combination with simultaneous N addition; (3) environmental and experimental setting factors such as ecosystem type, climate, and latitude could significantly influence both the individual and combined effects; and (4) the interactive effects of two-driver pairs across multiple global change drivers are more likely to be additive rather than synergistic or antagonistic. Our findings highlighting the importance of additive interactive effects among multiple global change drivers on terrestrial P pools would be useful for incorporating P as controls on ecological processes such as photosynthesis and plant growth into ecosystem models used to analyze effects of multiple drivers under future global change. [ABSTRACT FROM AUTHOR]

Altered precipitation regimes have a great impact on global climate change, with potentially important effects on below-ground carbon dynamics. Soil microbes and carbon (C)-degrading extracellular enzymes activities (EEAs) are considered as the rate-limiting step in C decomposition. However, the effect of altered precipitation on the microbial biomass, microbial EEAs, and mechanism for soil C dynamics has not been established. In current study, we synthesized the responses of microbial biomass, C-degrading EEAs, soil organic carbon (SOC), dissolved organic carbon (DOC), and soil respiration (SR) to altered precipitation from 70 published studies. The results showed that increased precipitation significantly enhanced soil microbial biomass and oxidative C-degrading EEAs (Ox-EEAs) by 16.18% and 6.58%, respectively, but had no effects on hydrolytic C-degrading EEAs (Hy-EEAs). Decreased precipitation led to a significant decline of soil microbial biomass and Ox-EEAs by 11.61% and 10.99%, respectively; however, Hy-EEAs increased by 25.79%. Furthermore, increased precipitation stimulated soil microbial biomass in shrub and grassland but had no effects in forest, while decreased precipitation repressed soil microbial biomass but increased Hy-EEAs in forest. The response ratios (RRs) of microbial biomass to altered precipitation were negatively correlated with the mean annual precipitation (MAP) and mean annual temperature (MAT); however, the RRs of Hy-EEAs were positively correlated with MAP. Particularly, in low MAP (≤600 mm), increased precipitation significantly increased soil microbial biomass by 21.40% but decreased precipitation did not affect soil microbial biomass; In contrast, in high MAP (>600 mm), decreased precipitation significantly declined soil microbial biomass by 15.37%, and significantly increased Hy-EEAs by 29.31% but increased precipitation did not affect both of them. Moreover, the RRs of microbial biomass and Ox-EEAs were significantly correlated with SOC, DOC, and SR; however, we only observed a negative relationship between RRs of Hy-EEAs and RRs of SOC, suggesting the concurrent responses of microbial biomass and C-degrading EEAs for below-ground C dynamics under simulated precipitation changes, and that a large amount of recalcitrant C in the soils would be highly susceptible to changing precipitation. [ABSTRACT FROM AUTHOR]

Semi-arid ecosystems play an important role in regulating the dynamics of the global terrestrial CO2 sink. These dynamics are mainly driven by increasing inter-annual precipitation variability. However, how ecosystem carbon processes respond to changes in precipitation is not well understood, due to a lack of substantial experimental evidence that combines increased and decreased precipitation treatments., This study, a 3-year field manipulation experiment with five precipitation levels conducted in a semi-arid steppe, examined the impacts of increased and decreased precipitation on ecosystem CO2 ( GEP: gross ecosystem photosynthesis; ER: ecosystem respiration; NEE: net ecosystem CO2 exchange), water exchange ( ET: evapotranspiration), and resource use efficiency ( CUE: carbon use efficiency; WUE: water use efficiency)., We found that decreased precipitation reduced ecosystem CO2, water exchange and resource use efficiency significantly, while increased precipitation did not cause significant influence on them. That is, they responded more sensitively to decreased precipitation. Soil water availability was the most important driver determining changes in GEP, ER and ET. Changes in NEE, CUE and WUE were predominately regulated by soil temperature. Photosynthesis at leaf and ecosystem levels showed significantly greater sensitivity to changed precipitation than respiration and ET, and therefore determined the trends of net carbon uptake and resource use efficiency., This study highlighted an asymmetric response of ecosystem carbon and water processes to altered precipitation. This is potentially important for improving our understanding of how possible future changes in precipitation will affect the carbon cycle. Taking this asymmetric response into consideration will inevitably reduce uncertainties in predicting the dynamics of the global carbon cycle., A is available for this article. [ABSTRACT FROM AUTHOR]

Responses of grassland carbon (C) cycling to climate change and land use remain a major uncertainty in model prediction of future climate. To explore the impacts of global change on ecosystem C fluxes and the consequent changes in C storage, we have conducted a field experiment with warming (+3 °C), altered precipitation (doubled and halved), and annual clipping at the end of growing seasons in a mixed-grass prairie in Oklahoma, USA, from 2009 to 2013. Results showed that although ecosystem respiration ( ER) and gross primary production ( GPP) negatively responded to warming, net ecosystem exchange of CO2 ( NEE) did not significantly change under warming. Doubled precipitation stimulated and halved precipitation suppressed ER and GPP equivalently, with the net outcome being unchanged in NEE. These results indicate that warming and altered precipitation do not necessarily have profound impacts on ecosystem C storage. In addition, we found that clipping enhanced NEE due to a stronger positive response of GPP compared to ER, indicating that clipping could potentially be an effective land practice that could increase C storage. No significant interactions between warming, altered precipitation, and clipping were observed. Meanwhile, we found that belowground net primary production ( BNPP) in general was sensitive to climate change and land use though no significant changes were found in NPP across treatments. Moreover, negative correlations of the ER/ GPP ratio with soil temperature and moisture did not differ across treatments, highlighting the roles of abiotic factors in mediating ecosystem C fluxes in this grassland. Importantly, our results suggest that belowground C cycling (e.g., BNPP) could respond to climate change with no alterations in ecosystem C storage in the same period. [ABSTRACT FROM AUTHOR]

Anthropogenic activities have increased atmospheric N, precipitation, and temperature events in terrestrial ecosystems globally, with N deposition increasing by 3- to 5-fold during the previous century. Despite decades of scientific research, no consensus has been achieved on the impact of climate conditions on soil respiration (Rs). Here, we reconstructed 110 published studies across diverse biomes, magnitudes, and driving variables to evaluate how Rs responds to N addition, altered precipitation (both enhanced and reduced precipitation or precipitation changes), and warming. Our findings show that N addition significantly increased Rs by 44 % in forests and decreased it by 19 % and 26 % in croplands and grasslands, respectively (P < 0.05). In forests and croplands, altered precipitation significantly increased Rs by 51 % and 17 % (all, P < 0.05), respectively, whereas impacts on grassland were insignificant. In comparison, warming stimulated Rs by 62 % in forests but inhibited it by 10 % in croplands (all, P < 0.05), whereas impacts on grassland were again insignificant. In addition, across all biomes, the responses of Rs to altered precipitation and warming followed a Gaussian response, increasing up to a threshold of 1800 mm and 25 °C, respectively, above which respiration rates decreased with further increases in precipitation and temperature. Our work suggests that the dual interaction of warming × altered precipitation promotes belowground CO 2 emission, thus enhancing global warming. In general, the interactive effect of N addition × altered precipitation decreases Rs. Soil moisture was identified as a primary driver of Rs. Given these findings, we recommend future research on warming vs. changed precipitation to better forecast and understand the interaction between Rs and climate change., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Dryland ecosystems represent >40 % of the terrestrial landscape and support over two billion people; consequently, it is vital to understand how drylands will respond to climatic change. However, while arid and semiarid ecosystems commonly experience extremely hot and dry conditions, our understanding of how further temperature increases or altered precipitation will affect dryland plant communities remains poor. To address this question, we assessed plant physiology and growth at a long-term (7-year) climate experiment on the Colorado Plateau, USA, where the community is a mix of shallow-rooted C and C grasses and deep-rooted C shrubs. The experiment maintained elevated-temperature treatments (+2 or +4 °C) in combination with altered summer monsoonal precipitation (+small frequent precipitation events or +large infrequent events). Increased temperature negatively affected photosynthesis and growth of the C and C grasses, but effects varied in their timing: +4 °C treatments negatively affected the C grass early in the growing season of both years, while the negative effects of temperature on the C grass were seen in the +2 and +4 °C treatments, but only during the late growing season of the drier year. Increased summer precipitation did not affect photosynthesis or biomass for any species, either in the year the precipitation was applied or the following year. Although previous research suggests dryland plants, and C grasses in particular, may respond positively to elevated temperature, our findings from a cool desert show marked declines in C and C photosynthesis and growth, with temperature effects dependent on the degree of warming and growing-season precipitation. [ABSTRACT FROM AUTHOR]

Questions: Do increased nitrogen (N) fertilization, altered water supply and increased competition by a nitrophilous plant species alter the establishment of the plant community developed from the soil seed bank present in a semi-arid Mediterranean ecosystem under greenhouse conditions? Does the nitrophilous plant respond in the same way to N addition under field conditions?. Location: The kermes oak/rosemary shrubland in the Nature Reserve El Regajal- Mar de Ontıgola, central Spain. Methods: In September 2008, native soil seed bank was collected in open areas dominated by rosemary shrubs. Seeds of the nitrophilous Diplotaxis siifolia were collected in early summer 2008. Pots with aliquots of soil were distributed among eight treatments, which resulted from combinations of two levels of N fertilization, water supply and density of D. siifolia in the seed bank. The plant community was left to grow for 3 mo, when chlorophyll fluorescence measurements and harvests were made. In summer 2008, the soil seed bank density of 0 and 50 kg N.ha-1.yr-1 plots was also manipulated in the field by broadcasting seeds to a density of 8000 D. siifolia seeds.m-2. Results: Increased N and competition tended to reduce soil water content in 'high water' pots. High water and N fertilization increased total above- and below-ground plant biomass production. Nitrogen fertilization reduced plant root:shoot ratio, had a negative effect on plant richness and, coupled with 'high competition' and 'high water', reduced forb biomass productivity. The competition treatment decreased chlorophyll fluorescence in grasses. Under field conditions, N fertilization increased D. siifolia density and this effect was dependent on soil phosphorus availability. Conclusions: Our results show that nitrophilous plant species such as D. siifolia can be a threat to local plant communities in the context of increased N deposition and altered precipitation events. In particular, local plant communities from semi-arid Mediterranean climates, and especially the forb element, may suffer more from competition in highly polluted and invaded sites during unusually wet years. Finally, we predict a future increase in the relative dominance of these species in semi-aridMediterranean environments where forb species typically adapted to low-nutrient environments will fail to successfully compete with weeds. [ABSTRACT FROM AUTHOR]

Abstract: Climate models for central United States predict increasing temperatures and greater variability in precipitation. Combined, these shifts in environmental conditions impact many ecosystem properties and services. Long-term climate change experiments, such as the Rainfall Manipulation Plots (RaMPs), can be used to address soil community responses to simultaneous manipulation of temperature and temporal variability in precipitation. The RaMPs experiment is located in a native tallgrass prairie at the Konza Prairie Biological Station and has been operational since 1998 providing the potential to address responses to long-term environmental manipulations. To test whether community composition, richness, or diversity respond to environmental change, more than 40 000 fungal amplicons were analyzed from soil samples collected in 2006. The data suggest that soil fungal communities are compositionally resilient to predicted environmental change. This is the case both for the community composition overall as inferred from ordination analyses as well as analyses of variance for each of the most common Operational Taxonomic Units (OTUs). However, while this study suggests compositional resilience, further studies are required to address functional attributes of these communities and their responses to environmental manipulations. [Copyright &y& Elsevier]

Abstract: Greenhouse gas (GHG) emissions play an important role in regulating the Earth surface temperature. GHG emissions from soils are sensitive to climate change and land management practices. According to general circulation model (GCM) predictions, the Earth will experience a combination of increased temperature and altered precipitation regimes which may result in an increase or a decrease of GHG exchange. The effect of climate change on GHG emissions can be examined through both experiments and by applying process-based models, which have become more popular. The performance of those models can be improved significantly by appropriate calibration procedures. The objectives of this study are to: (i) calibrate the DAYCENT model using advance parameter estimation (PEST) software and to (ii) examine simulated GHG dynamics at daily and seasonal time-scales under a climate change scenario of increased temperature (2°C) and a precipitation regime change where 40% of precipitation during the dry season was redistributed to the wet season. The algorithmic calibration improved the model performance by reducing the sum of weighted squared residual differences by up to 223% (decreased from 1635 to 505g N2O-Nha−1 d−1) for N2O and 22% (decreased from 623 to 507% WFPS) for water filled pore space (WFPS) simulation results. In the altered climate scenario, total N2O and CO2 fluxes decreased by 9% (from 2.31 to 2.10kg N2O-Nha−1 yr−1) and 38% (from 1134.08 to 699.56kg CO2 ha−1 yr−1) respectively, whereas CH4 fluxes increased by 10% (from 1.62 to 1.80kg CH4 ha−1 yr−1). Our results show a larger impact of altered climate on CO2 as compared to N2O and CH4 emissions. The main difference in all GHG emissions was observed in summer period due to drought conditions created by reduced precipitation and increased temperatures. However, the GHG dynamics can also be attributed to no-till practices which play an important role in changing the soil moisture conditions for aerobic and anaerobic microsites. These results are based on a process-based model, therefore, we suggest performing experimental studies to examine the GHG emissions under increased temperature and especially under altered precipitation regimes. [Copyright &y& Elsevier]

General circulation models on global climate change predict increase in surface air temperature and changes in precipitation. Increases in air temperature (thus soil temperature) and altered precipitation are known to affect the species composition and function of soil microbial communities. Plant roots interact with diverse soil organisms such as bacteria, protozoa, fungi, nematodes, annelids and insects. Soil organisms show diverse interactions with plants (eg. competition, mutualism and parasitism) that may alter plant metabolism. Besides plant roots, various soil microbes such as bacteria and fungi can produce volatile organic compounds (VOCs), which can serve as infochemicals among soil organisms and plant roots. While the effects of climate change are likely to alter both soil communities and plant metabolism, it is equally probable that these changes will have cascading consequnces for grazers and subsequent food web components aboveground. Advances in plant metabolomics have made it possibile to track changes in plant metabolomes as they respond to biotic and abiotic environmental changes. Recent developments in analytical instrumentation and bioinformatics software have established metabolomics as an important research tool for studying ecological interactions between plants and other organisms. In this review, we will first summarize recent progress in plant metabolomics methodology and subsequently review recent studies of interactions between plants and soil organisms in relation to climate change issues. [ABSTRACT FROM AUTHOR]

Biological soil crusts (biocrusts) are common and ecologically important members of dryland ecosystems worldwide, where they stabilize soil surfaces and contribute newly fixed C and N to soils. To test the impacts of predicted climate change scenarios on biocrusts in a dryland ecosystem, the effects of a 2-3 °C increase in soil temperature and an increased frequency of smaller summer precipitation events were examined in a large, replicated field study conducted in the cold desert of the Colorado Plateau, USA. Surface soil biomass ( DNA concentration), photosynthetically active cyanobacterial biomass (chlorophyll a concentration), cyanobacterial abundance (quantitative PCR assay), and bacterial community composition (16S rRNA gene sequencing) were monitored seasonally over 2 years. Soil microbial biomass and bacterial community composition were highly stratified between the 0-2 cm depth biocrusts and 5-10 cm depth soil beneath the biocrusts. The increase in temperature did not have a detectable effect on any of the measured parameters over 2 years. However, after the second summer of altered summer precipitation pattern, significant declines occurred in the surface soil biomass (avg. DNA concentration declined 38%), photosynthetic cyanobacterial biomass (avg. chlorophyll a concentration declined 78%), cyanobacterial abundance (avg. gene copies g−1 soil declined 95%), and proportion of Cyanobacteria in the biocrust bacterial community (avg. representation in sequence libraries declined 85%). Biocrusts are important contributors to soil stability, soil C and N stores, and plant performance, and the loss or reduction of biocrusts under an altered precipitation pattern associated with climate change could contribute significantly to lower soil fertility and increased erosion and dust production in dryland ecosystems at a regional scale. [ABSTRACT FROM AUTHOR]

Abstract: Many exotic species have been introduced or have escaped into grasslands where they form ‘novel ecosystems’ of species with no evolutionary history of interaction. Novel ecosystems are good model systems for understanding how diversity maintenance mechanisms might differ between species with a history of interaction (natives) and species without a history (exotics) in cases where exotics originated from several continents. We tested for lower species diversity and richness in exotic grasslands and found a negative correlation between species diversity measures and proportion of exotic species across 15 grasslands in an observational study in Texas. We then planted 9-species mixtures of all native or all exotics under ambient or elevated summer precipitation to compare dynamics of diversity and to test if exotic species respond more strongly to altered resource availability. Species diversity was lower in communities of exotic than native species by the second year. Reduced diversity in exotic communities resulted from lower complementarity and higher temporal niche overlap among species and occurred in both ambient and irrigated plots. In general, summer irrigation had additive positive effects and did not interact with native–exotic status. Exotic species and communities had much earlier green-up during spring than natives, and altered inter-correlations among phenology variables. There were no differences in flowering dates. Taken together, our results suggest that rapid and synchronous growth may increase niche overlap among exotic species and reduce local diversity in exotic-dominated grassland communities. Earlier green-up by exotics may complicate attempts to ascertain relationships between phenology and climate. An increase in exotic species may cause earlier green-up regardless of any climate change effects and our results suggest that phenology networks should take a species-based rather than an ecosystem approach to evaluate green-up if the abundance of exotics increases within the time-frame in question. These differences between native and exotic species and communities should be considered in future management and restoration projects. [Copyright &y& Elsevier]

Global environmental changes are expected to impact the abundance of plants and animals aboveground, but comparably little is known about the responses of belowground organisms. Using meta-analysis, we synthesized results from over 75 manipulative experiments in order to test for patterns in the effects of elevated CO, warming, and altered precipitation on the abundance of soil biota related to taxonomy, body size, feeding habits, ecosystem type, local climate, treatment magnitude and duration, and greenhouse CO enrichment. We found that the positive effect size of elevated CO on the abundance of soil biota diminished with time, whereas the negative effect size of warming and positive effect size of precipitation intensified with time. Trophic group, body size, and experimental approaches best explained the responses of soil biota to elevated CO, whereas local climate and ecosystem type best explained responses to warming and altered precipitation. The abundance of microflora and microfauna, and particularly detritivores, increased with elevated CO, indicative of microbial C limitation under ambient CO. However, the effects of CO were smaller in field studies than in greenhouse studies and were not significant for higher trophic levels. Effects of warming did not depend on taxon or body size, but reduced abundances were more likely to occur at the colder and drier sites. Precipitation limited all taxa and trophic groups, particularly in forest ecosystems. Our meta-analysis suggests that the responses of soil biota to global change are predictable and unique for each global change factor. [ABSTRACT FROM AUTHOR]

The article presents a study on the analysis pertaining to the response of salt marshes plant communities to warming and associated response in precipitation in Rowley, Massachusetts. The study intends to supplement previous findings on the impact of climatic changes in salt marshes. It highlights that warming can promote plant growth through an increase on its photosynthetic rates. However, warming has the potential to decrease plant growth because of an increase on soil salinity.

Despite the linkage of arbuscular mycorrhizal (AM) fungi to soil-plant interface, how changes in plant community-level traits and soil properties affect AM fungal communities under global changes remains largely unknown. Here, to investigate whether nitrogen (N) enrichment and altered precipitation can influence AM fungal communities through effects on plant community-level traits and soil properties, a six year-long factorial N and precipitation field experiment (N-addition rate: 10 g m−2 year−1; reduced precipitation by 50% and enhanced precipitation by 50%) was conducted in an alpine steppe of the Tibet Plateau. We observed that reduced precipitation decreased AM fungal diversities, while N enrichment decreased AM fungal biomass. Secondly, N enrichment and reduced precipitation shifted plant community composition from bunchgrass dominance (primarily Stipa purpurea) to rhizomatous grass dominance (primarily Leymus secalinus). N enrichment and reduced precipitation also led to a marked shift in AM fungal community composition. More specifically, reduced precipitation enhanced the relative abundance of the dominant taxa Glomus , while the relative abundance of Scutellospora and Diversispora was decreased. In contrast, N enrichment decreased the relative abundance of Scutellospora and Diversispora , while the relative abundance of Glomus was decreased. Structural equation models (SEMs) demonstrated that precipitation regime affected dominant AM fungal taxa via soil pH, while N enrichment affected dominant AM fungal taxa by changes in plant community-level traits. In addition, N- and precipitation-induced shifts in AM fungal community structure were significantly related to canopy photosynthetic rates and soil pH, indicating that canopy photosynthesis and soil pH may mediate the responses in AM fungal communities to enhanced N deposition and precipitation regime. Therefore, our findings may provide previously unidentified insights into N- and precipitation- evoked differential responses of AM fungal communities by linking plant community-level traits and soil properties. • Reduced precipitation, but not nitrogen (N) enrichment, decreased arbuscular mycorrhizal (AM) fungal diversities such as ENS PIE and community evenness, while N enrichment significantly decreased AM fungal biomass. • N enrichment and reduced precipitation shifted plant community composition from bunchgrass dominance (primarily Stipa purpurea) to rhizomatous grass dominance (primarily Leymus secalinus). • N enrichment and precipitation regimes shifted AM fungal community structure and composition through effects on plant community-level traits and soil properties, especially canopy photosynthetic rates and soil pH. [ABSTRACT FROM AUTHOR]

• Although global change is known to influence plant invasion, little is known about interactions between altered precipitation and invasion. In the North American mixedgrass prairie, invasive species are often abundant in wet and nitrogen (N)-rich areas, suggesting that predicted changes in precipitation and N deposition could exacerbate invasion. • Here, this possibility was tested by seeding six invasive species into experimental plots of mixedgrass prairie treated with a factorial combination of increased snow, summer irrigation, and N addition. • Without added snow, seeded invasive species were rarely observed. Snow addition increased average above-ground biomass of Centaurea diffusa from 0.026 to 66 g m−2, of Gypsophila paniculata from 0.1 to 7.3 g m−2, and of Linaria dalmatica from 5 to 101 g m−2. Given added snow, summer irrigation increased the density of G. paniculata, and N addition increased the density and biomass of L. dalmatica. Plant density responses mirrored those of plant biomass, indicating that increases in biomass resulted, in part, from increases in recruitment. In contrast to seeded invasive species, resident species did not respond to snow addition. • These results suggest that increases in snowfall or variability of snowfall may exacerbate forb invasion in the mixedgrass prairie. [ABSTRACT FROM AUTHOR]