Increasing Mean Annual Precipitation Research Articles

Evaluating the relative influence of climate and human activities on recent vegetation dynamics in West Bengal, India

Assessing the relative importance of climate change and human activities is important in developing sustainable management policies for regional land use. In this study, multiple remote sensing datasets, i.e. CHIRPS (Climate Hazard Group InfraRed Precipitation with Station Data) precipitation, MODIS Land Surface Temperature (LST), Enhanced Vegetation Index (EVI), Potential Evapotranspiration (PET), Soil Moisture (SM), WorldPop, and nighttime light have been analyzed to investigate the effect that climate change (CC) and regional human activities (HA) have on vegetation dynamics in eastern India for the period 2000 to 2022. The relative influence of climate and anthropogenic factors is evaluated on the basis of non-parametric statistics i.e., Mann-Kendall and Sen's slope estimator. Significant spatial and elevation-dependent variations in precipitation and LST are evident. Areas at higher elevations exhibit increased mean annual temperatures (0.22 °C/year, p < 0.05) and reduced winter precipitation over the last two decades, while the northern and southwest parts of West Bengal witnessed increased mean annual precipitation (17.3 mm/year, p < 0.05) and a slight cooling trend. Temperature and precipitation trends are shown to collectively impact EVI distribution. While there is a negative spatial correlation between LST and EVI, the relationship between precipitation and EVI is positive and stronger (R2 = 0.83, p < 0.05). Associated hydroclimatic parameters are potent drivers of EVI, whereby PET in the southwestern regions leads to markedly lower SM. The relative importance of CC and HA on EVI also varies spatially. Near the major conurbation of Kolkata, and confirmed by nighttime light and population density data, changes in vegetation cover are very clearly dominated by HA (87%). In contrast, CC emerges as the dominant driver of EVI (70–85%) in the higher elevation northern regions of the state but also in the southeast. Our findings inform policy regarding the future sustainability of vulnerable socio-hydroclimatic systems across the entire state.

How Accurately Are Climatological Characteristics and Surface Water and Energy Balances Represented for the Colombian Amazon Basin?

Context: The Colombian Amazon basin (CAB) is characterized by having many areas with few or no in situ observations. To help fix this shortcoming, there are different gridded datasets that represent meteorological variable estimates from in situ, satellite-based, merged, and model-based products. However, before using them, it is necessary to evaluate their performance.Methods: We analyzed the capacity of five grid datasets to represent the annual cycle, the annual means, and the interquartile range of temperature and the variables that intervene in the surface water and energy balances of the CAB. The five datasets were a regional climate model (REMO) and four reanalyses (ERA40, ERA-Interim, NCEP/NCAR, and NCEP-v2). For the temperature and precipitation analyses, the Delaware, GPCP, CPC, CMAP, and CMAP-v2 datasets were also taken into account. Results: The average annual temperature cycle in the CAB has an unimodal behavior, with higher values between October and March. Only Delaware and ERA-Interim describe this behavior and exhibit values close to those of the observations. The average annual cycle of precipitation is also unimodal, with higher values between March and July. Delaware, GPCP, CPC, and ERA-Interim describe this behavior, although ERA-Interim overestimates precipitation. Additionally, the four reanalyses, especially ERA-Interim, show an unexpected trend of increase in mean annual precipitation. As for the water balance, the precipitation and runoff maps of ERA-Interim and REMO show higher values in the foothills and east of 73 degrees W, a pattern that shows better agreement with the observations than those of the other datasets. ERA-Interim, REMO, and ERA-40 meet the closure condition of both the long-term water and the energy budgets. However, REMO and ERA-Interim overestimated precipitation, ERA-40 underestimated it, and ERA-Interim overestimated solar radiation. This implies that some of the other variables for the water and energy balances are also poorly estimated. Conclusions: The five gridded datasets that allow studying surface water and energy balances are not adequate, so better models and reanalyses are required.

Nitrogen rather than phosphorous addition alters the asymmetric responses of primary productivity to precipitation variability across a precipitation gradient on the northern Tibetan Plateau

Understanding the response of alpine grassland productivity to precipitation fluctuations is essential for assessing the future changes of ecosystem services. However, the underlying mechanism by which grassland productivity responds to wet and dry years after nitrogen (N) or/and phosphorus (P) nutrient addition remains unclear. In this study, we investigated the dynamics of plant communities based on eight-year N or/and P addition gradient experiments in four grassland types across a precipitation gradient on the north Tibetan Plateau. The asymmetry index (AI) was used to evaluate the responses of aboveground net primary productivity (ANPP) to precipitation fluctuations where AI > 0 indicates a greater increase of ANPP in wet years compared to the decline in dry years, and AI < 0 indicates a greater decline of ANPP in dry years compared to the increase in wet years. Our results showed that the AI values at community level in four natural grasslands were non-significant trend across the precipitation gradient, and showed slightly negative asymmetry, suggesting that the increase of ANPP in wet years was less than the decrease in dry years. N addition resulted in a significant decrease in community-level AI values with increasing mean annual precipitation (MAP), indicating that improved nutrient availability may favor the recovery of productivity in drier grasslands in wet years. At the functional group level, nutrient addition resulted in a significant decrease in the AI values of grasses and legumes and an increase in the AI values of forbs as MAP increased. Furthermore, the coupling of nutrients with precipitation can influence the productivity responses to precipitation changes by affecting soil nutrient availability and species richness. This research provides new insights into better predicting vegetation activity on N deposition rates and precipitation changes exacerbated in the context of climate change.

Climatic factors regulate the assembly processes of abundant and rare microbial communities in desert soil

Abstract Soil microorganisms, which include many rare taxa and a small number of abundant taxa, have different contributions to the ecosystem functions and services. High throughput sequencing technology was used to analyze the species composition of soil samples by DNA sequencing. Soil microorganisms were divided into abundant taxa and rare taxa to reveal their composition. Correlation analysis and random forest method were used to further analyze the influence of environmental factors on the community. Finally, the beta nearest taxon index (βNTI) based on the null model was used to elucidate the mechanisms underlying soil microbial community assembly. We found that, in desert soil, the community assembly of rare bacteria was almost entirely dominated by a homogeneous selection of deterministic processes. For comparison, stochastic processes had more pronounced effects on the abundant bacteria. However, both abundant and rare fungi exhibited similar patterns of community assembly, i.e. deterministic and stochastic processes jointly determined the assembly processes of fungal communities. We also observed that community assembly shifted from stochastic to deterministic processes with increasing mean annual precipitation (MAP) and mean annual temperature (MAT) for abundant bacteria. Conversely, for rare fungi, there was an inclination toward a shift from deterministic to stochastic processes with rising MAT. In conclusion, our findings provide compelling evidence that MAT and MAP regulate the community assembly process of abundant and rare microbial communities in desert soil. These findings establish a theoretical foundation for future investigations into the community structure and ecological functions of soil microorganisms.

Effects of land use and climate on web-building spiders and their prey in dry dipterocarp forests

Dry dipterocarp forest is a key dry forest type across South-East Asia. Despite these dipterocarps being endangered and widely unprotected, the factors that may affect their function at local and landscape scales are unknown. To identify drivers for future conservation programs at both local (habitat structure) and landscape (land use, climate) scales, the prey captured by web-building spiders, which are model predators in dry dipterocarps, were investigated. Overall, 21 dry dipterocarp forest stands representing the gradient of agricultural intensification were selected across North-East Thailand where captured and potential prey of web-building spiders was collected. Within each plot, the percentual coverage of major vegetation types (e.g., trees, shrubs, grass) was quantified. Around each plot, the landscape composition within a 5 km radius was quantified as the proportion of agroecosystems, forests, water bodies, and urban areas. Further, climate data for each plot were extracted from a public database. The prey captured by web-building spiders was most affected by the composition of landscapes; the evenness of captured prey showed a hump-shaped relationship with the proportion of agroecosystems in each landscape. The observed change in captured prey composition between plots was predominantly caused by changes in web type composition between local spider communities. The total number of captured prey decreased with increasing mean annual precipitation which mirrored the decline of total prey availability along this gradient. The results indicate that the predation by web-building spiders in dry dipterocarps is most threatened by changes in rainfall pattern and land-use change, specifically by agricultural intensification at the landscape scale.

Precipitation-based climate change hotspots across India through a Multi-model assessment from CMIP6

This study presents an analysis to identify precipitation-based climate change hotspots and key-vulnerable cities using multi-model, multi-scenario, high-resolution (0.25°×0.25°), bias-corrected precipitation dataset across India from 14 state-of-the-art General Circulation Models (GCMs), participating in Coupled Model Intercomparison Project version 6 (CMIP6). Preliminary analysis indicates an overall wetter future across India with 290 ± 150 mm to 530 ± 260 mm increase in mean annual precipitation towards end of this century under various climate change scenarios. Apart from the mean precipitation, the extremes are also found to be increasing by alarmingly higher rates. However, the spatio-temporal variations of such increments are notably diverse over different seasons in a year and across different Homogeneous Precipitation Zones (HPZs) in the country. Therefore, a new and more inclusive index, named as Precipitation-based Hotspot Index (PHI), is developed to identify the ‘precipitation-based hotspots’, i.e. the places with most pronounced changes in precipitation characteristics. The PHI considers the changes in various aspects of precipitation, such as mean, variability, and characteristics of extremes (magnitude, frequency and intensity). Based on the PHI values in the far-future period (2061–2100) and for the worst climate change scenario, the hotspot regions are identified mostly in the northwest, west-central, west coast, and northeast parts of India. Further, considering two important socio-economic vulnerability factors (population density and human development index) along with PHI, the key-vulnerable tier-I cities are identified across India. The analysis reveals four out of ten tier-I cities will be highly vulnerable towards end of this century. The findings of this analysis (hotspot maps) and the data products (high-resolution, bias-corrected precipitation dataset) are expected to be highly beneficial for impact assessments, hydrologic modelling, and formulating suitable adaptation and mitigation strategies for India over future.

Extracellular enzyme activities response to nitrogen addition in the rhizosphere and bulk soil: A global meta-analysis

Plant roots play a crucial role in acquiring available nutrients and regulating microbial decomposition, leading to faster nutrient cycling in the rhizosphere than in bulk soil. With increasing nitrogen (N) loading, rhizosphere processes may become more crucial than bulk soil processes for accurately predicting nutrient cycling process changes. However, it remains unclear how the rhizosphere and bulk soil extracellular enzyme activities (EEAs) respond to N addition on a global scale. Therefore, we used a global meta-analysis to examine the effects of N addition on EEAs involved in carbon (C), N, and phosphorus (P) acquisition in paired rhizosphere and bulk soils, based on 1992 observations from 40 studies. Overall, N addition significantly increased β-xylosidase (BXYL) activity by 17.0% in bulk soil, together with urease (URE) activity in both the rhizosphere (25.3%) and bulk soil (33.6%). In addition, N addition marginally significantly decreased phenol oxidase (PHEO) activity in the rhizosphere (−18.4%), as well as peroxidase (PERO) activity in both the rhizosphere (−12.6%) and bulk soil (−13.6%). The reductions may be caused by fungi: bacteria ratio and Gram+ bacteria: Gram− bacteria ratio (F: B and G+: G−, respectively) reductions. We also found that EEAs (e.g., acid/alkaline phosphatase (AP) and PHEO) did not always have a simple linear relationship with higher N addition rate and duration. Additionally, the responses of β-1,4-N-acetyl-glucosaminnidase (NAG) and PHEO significantly increased with increase in mean annual temperature (MAT), whereas those of microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) significantly decreased with increase in mean annual precipitation (MAP). Moreover, the responses of PHEO and PERO significantly decreased along altitudinal gradients. Furthermore, we found that the N sensitivity of rhizosphere C-acquisition (BG, PHEO, and PERO) and P-acquisition (AP) enzyme activities was significantly lower than that of bulk soil, but no significant difference was noted in N-acquisition enzyme activities except for the NAG which exhibited marginal significant differences between the rhizosphere and bulk soil. Our results suggest that EEAs in the rhizosphere and bulk soil have different response patterns, and these differences might mainly be caused by soil nutrient availability and microbial attributes. These results deepen our understanding of rhizosphere and bulk soil nutrient cycling processes under increasing N loading. They also provide extensive evidence and a basis for the parameterization of global nutrient cycling models that incorporate rhizosphere responses to climate change.

Climate control on the relationship between erosion rate and fluvial topography

Abstract Conceptual and theoretical models for landscape evolution suggest that fluvial topography is sensitive to climate. However, it remains challenging to demonstrate a compelling link between fluvial topography and climate in natural landscapes. One possible reason is that many studies compare erosion rates to climate data, although theoretical studies show that, at steady state, climate is encoded in the relationship between erosion rate and topography rather than erosion rate alone. We use an existing global compilation of 10Be basin-averaged erosion rates to isolate the climate signal in topography as a function of erosion rate for morphologically steady-state, fluvially dominated basins underlain by crystalline bedrock. Our results show that the relationship between erosion rate (a proxy for rock uplift rate) and the normalized river channel steepness index (a proxy for fluvial relief) becomes increasingly nonlinear with increasing mean annual precipitation and decreasing aridity. This result indicates that erosional efficiency increases in wetter and more humid climates, lowering fluvial relief for a given erosion rate. When interpreted in the context of detachment-limited bedrock incision models that account for incision thresholds and stochastic flood distributions, this systematic pattern can be explained by a decrease in discharge variability in wetter and more humid landscapes, assuming incision thresholds are important on a global scale.

Projection of future extreme meteorological droughts using two large multi-member climate model ensembles

Several studies have looked at the evolution of droughts in a changing climate in various locations and have typically found that droughts are expected to become more severe in the future. However, relatively little work has been done on extreme droughts. This study focuses on the evolution of extreme meteorological droughts over near (2036–2065) and far (2071–2100) future time periods. Monthly precipitation from two large multi-member climate model ensembles: the Canadian Earth System Model (CanESM2) 50-member ensemble and the Community Earth System Model (CESM1) 40-member ensemble, was used to calculate the Standard Precipitation Index (SPI) to quantify and explore the evolution of future meteorological droughts. The use of these large ensembles allows for the calculation of the 20- and 100-year droughts return period and offers a unique perspective into those rare events.Both climate models project increases in extreme meteorological drought frequency over many of the world’s regions. The spatial patterns of regions with worsening droughts generally match those of projected change in mean annual precipitation, although the former is more extensive, indicating that changes in internal variability will increase drought frequency even in some regions projected to see increased mean annual precipitation. The projected increase in meteorological drought frequency is more significant for short-term JJA droughts, and for the larger return periods. Large increases in frequency are observed in many regions, all the way up to 20 times for the historical100-year JJA drought indicating a return period shift from 100 to 5 year.Considering the significant predicted increases in temperature, it follows that future changes for both agricultural (soil water deficit) and hydrological droughts (low stream levels), which result from the interaction between precipitation deficit and temperature (as well as other variables), will be even more severe.

Soil carbon, nitrogen, and phosphorus stoichiometry and its influencing factors in Chinese fir plantations across subtropical China

The crucial roles of soil carbon (C) and nutrients and their stoichiometric characteristics in indicating the soil interior nutrient cycling and plant nutrient supply of forest ecosystems have been widely verified, whereas it has been less explored when considering the influencing factors regionally, especially for the widely cultivated plantation tree species. In the current study, the patterns of soil organic C (SOC), total nitrogen (TN), and total phosphorus (TP) stoichiometry in Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] plantations across subtropical China were analyzed, and their influencing factors were also investigated. The results showed that the range of SOC: TN (C:N), SOC: TP (C:P), and TN: TP (N:P) ratios were 7.32–18.27, 20.15–230.48, and 2.11–15.05 with a mean value of 13.22, 83.50, and 6.05, respectively. Well-constrained correlations were found in SOC and TN, as well as in TN and TP. Soil TN and TP contents increased with increasing altitude, whereas soil C:N, C:P, and N:P ratios decreased. Soil TP content decreased, and the C:P ratio increased with increasing mean annual temperature (MAT) and annual total solar radiation (ATSR). Soil C:N, C:P, and N:P ratios increased with increased mean annual precipitation (MAP) and mean annual evaporation (MAE). Overall, our findings suggested that the soil nutrient supply is relatively adequate in Chinese fir plantations across subtropical China. Meanwhile, soil C, N, and P stoichiometric characteristics were affected by geographical and climatic variables to different degrees.

Ecosystem carbon use efficiency in ecologically vulnerable areas in China: Variation and influencing factors.

Ecologically vulnerable areas (EVAs) are regions with ecosystems that are fragile and vulnerable to degradation under external disturbances, e.g., environmental changes and human activities. A comprehensive understanding of the climate change characteristics of EVAs in China is of great guiding significance for ecological protection and economic development. The ecosystem carbon use efficiency (CUEe) can be defined as the ratio of the net ecosystem productivity (NEP) to gross primary productivity (GPP), one of the most important ecological indicators of ecosystems, representing the capacity for carbon transfer from the atmosphere to a potential ecosystem carbon sink. Understanding the variation in the CUEe and its controlling factors is paramount for regional carbon budget evaluation. Although many CUEe studies have been performed, the spatial variation characteristics and influencing factors of the CUEe are still unclear, especially in EVAs in China. In this study, we synthesized 55 field measurements (3 forestland sites, 37 grassland sites, 6 cropland sites, 9 wetland sites) of the CUEe to examine its variation and influencing factors in EVAs in China. The results showed that the CUEe in EVAs in China ranged from -0.39 to 0.67 with a mean value of 0.20. There were no significant differences in the CUEe among different vegetation types, but there were significant differences in CUEe among the different EVAs (agro-pastoral ecotones < Tibetan Plateau < arid and semiarid areas < Loess Plateau). The CUEe first decreased and then increased with increasing mean annual temperature (MAT), soil pH and soil organic carbon (SOC) and decreased with increasing mean annual precipitation (MAP). The most important factors affecting the CUEe were biotic factors (NEP, GPP, and leaf area index (LAI)). Biotic factors directly affected the CUEe, while climate (MAT and MAP) and soil factors (soil pH and SOC) exerted indirect effects. The results illustrated the comprehensive effect of environmental factors and ecosystem attributes on CUEe variation, which is of great value for the evaluation of regional ecosystem functions.

Global estimates of forest soil methane flux identify a temperate and tropical forest methane sink

Forest ecosystems play an important role in the global CH4 cycle. Understanding and quantifying the contribution and distribution of CH4 sinks and sources in global forest soils is vital for assessing realistic approaches to climate change mitigation. Here, we compiled a dataset of in situ global forest soil CH4 fluxes from published data, incorporating 772 case studies covering boreal (n = 12), temperate (n = 369), subtropical (n = 208), and tropical (n = 183) forests and spanning 1991–2020 as a basis to build the mixed-effect model. Using the screened best model, we identified the main drivers and predicted the global distribution of the forest soil CH4 flux. Our research revealed that global forest soil CH4 uptake decreased significantly with increasing mean annual temperature (MAT), soil bulk density (BD), soil organic carbon (SOC), and soil total nitrogen (TN) but increased significantly with increasing mean annual precipitation (MAP). The global mean CH4 uptake rate in forest soils was 3.95 ± 1.78 kg CH4 ha−1 yr−1, with the total sink of 14.98 ± 6.75 Tg CH4 yr−1. The soil CH4 sinks in temperate and tropical forests contributed 84 % to the total sink of global forests. The CH4 emission rate in global forest soils averaged 1.12 ± 1.11 kg CH4 ha−1 yr−1, with the total source of 0.14 ± 0.14 Tg CH4 yr−1. Nearly 3 % of the total area of global forest soils was a net CH4 source. In summary, we identified the key drivers of forest soil CH4 flux and improved previous estimates of the global CH4 budget in forest soils. These findings can support decision-making related to forest management and greenhouse gas restrictions.

Effects of enhanced-efficiency nitrogen fertilizers on CH4 and CO2 emissions in a global perspective

It is widely recommended that enhanced efficiency nitrogen fertilizers (EENFs; urease inhibitors, nitrification inhibitors, urease and nitrification inhibitors combined, coated controlled-release urea) be applied to croplands to improve N use efficiency and crop yield via regulating N transformations. However, EENFs may inevitably affect soil C dynamics for the coupled relationship between soil carbon (C) and N biogeochemical cycles. Yet, a comprehensive assessment of the effects of EENFs on soil C dynamics is lacking. Here, we conducted a global meta-analysis using 67 publications to assess the overall effects of EENFs on soil CH 4 production, CO 2 emission, organic C (SOC) content, dissolved organic C (DOC) content, microbial biomass C (MBC) content under different environmental and management conditions (climate conditions, soil properties and fertilizer management practices). Our results showed that on average, compared to conventional N fertilizer, EENFs with the same amount of N fertilizer have a non-significant impact on CH 4 emission, which further depended on environmental and management conditions. Best scenarios for CH 4 reduction included: paddy field (25.8%), urease inhibitor (26.9%) and medium N application rate (150–300 kgN ha −1 ; 23.6%), mainly due to the decreased stimulation of NH 4 + on CH 4 production; acid soil (33.7%), which was attributed to the enhanced methanotrophic communities' activities. The positive effect was also amplified by the increased mean annual precipitation and soil clay content that facilitated CH 4 production. Contrarily, EENFs significantly reduced CO 2 emission by 9.3%. The greater reduction was observed for the conditions producing more CO 2 after fertilization, i.e. field experiment, alkaline soils, low soil inorganic N content and high N application rate (≥300 kgN ha −1 ). Nitrification inhibitors and coated N fertilizer were the best available options as they can reduce inorganic C dissolution in calcareous soil and SOC mineralization, respectively. Besides, EENFs application did not significantly alter SOC, DOC and MBC contents. Our findings highlighted the role of EENFs played in decreasing soil C emission in agroecosystems. • Global use of EENFs did not significantly affect SOC, DOC, MBC contents. • EENFs succeed in reducing CO 2 emission (9.3%) rather than CH 4 emission. • EENFs provide a viable solution for decreasing soil C emissions in global agroecosystems.

From permafrost soil to thermokarst lake sediment: A view from C:N:P stoichiometry

Thermokarst lakes are formed as a result of thawing ice-rich permafrost, transforming vast permafrost soil into lake sediment and changing the biogeochemistry of carbon (C), nitrogen (N), and phosphorus (P). Degraded permafrost soil and thermokarst lake sediment are two distinct fates of pristine permafrost in the thermokarst processes. However, we do not clearly understand the differences and relationships between degraded permafrost soil and thermokarst lake sediment from a stoichiometric perspective. In this study, 44 thermokarst lakes across the Qinghai-Tibet Plateau were investigated to collect lake sediment and surrounding degraded permafrost soil. In general, C, N, and P concentrations as well as C:N, C:P, and N:P ratios in soil and sediment decreased with increasing latitude, while increased with increasing mean annual precipitation. The degraded permafrost soil had much higher C, N, and P concentrations and C:N:P stoichiometric ratios than the lake sediment, particularly for C. Moreover, the concentrations of C, N, and P, as well as the ratios of C:P and N:P in sediment showed significant positive relationships with their corresponding components in soil but with different slopes. Standard major axis regression showed allometric scaling relationships between C, N, and P. The C:N:P ratio was 269:18:1 in degraded permafrost soil and 178:15:1 in lake sediment. The results suggest that the process from pristine permafrost to lake sediment releases more C, N, and P than the process from pristine permafrost to degraded permafrost soil, and that C changes more profoundly than N and P. Moreover, thermokarst processes substantially change the elemental balance and decouple the C:N:P relationship between degraded permafrost soil and lake sediment, suggesting that the further transformation from degraded permafrost soil to lake sediment will lose more C, which can be intensified by increasing precipitation. The results enriched our understanding of the variations in C, N, and P biogeochemistry during thermokarst processes.

The influencing factors of leaf functional traits variation of Pinus densiflora Sieb. et Zucc.

Trait-based approaches have emerged as promising strategies for understanding plant adaptation mechanisms to the changing environment. At present, there are a large number of studies on the relationship between plant leaf functional traits and environment, but these studies mostly use the average value of traits instead of species, ignoring the intraspecific changes of traits. Pinus densiflora Sieb. et Zucc. is not only an urban greening tree species, but also an important afforestation tree species, which plays an important role in China's terrestrial ecosystem. In this study, the leaf nitrogen content (LN), the leaf phosphorus content (LP), nitrogen phosphorus ratio (N/P), leaf area (LA) and specific leaf area (SLA) of 16 sites (160 records) distributed in Chinese P. densiflora were measured. (1) The results showed that LN increased with the increase of mean annual precipitation (MAP) and decreased with the increase of soil organic matter (SOM). LP and SLA decreased with the increase of mean annual temperature (MAT) and increased with the increase of AN (soil available phosphorus) and AP (soil available phosphorus). N/P increased with the increase of MAT and MAP, and decreased with the increase of AN and AP. LA increased with the increase of MAT and MAP. (2) Relative importance analysis showed that MAP was the most important driver of LN and LA. The main driving factors of LP is MAT, the main driving factors of N/P is SOM, and the main influencing factors of SLA is AP. Overall, climate was the main driving factor for the variation of leaf functional traits. The variation law of leaf functional traits along environmental gradient strongly supported the temperature-plant physiological hypothesis. It enriches the understanding of leaf functional traits distribution pattern and its driving mechanism under environmental change.

Projection of Streamflow Change Using a Time‐Varying Budyko Framework in the Contiguous United States

AbstractPredicting future streamflow change is essential for water resources management and understanding the impacts of projected climate and land use changes on water availability. The Budyko framework is a useful and computationally efficient tool to model streamflow at larger spatial scales. This study predicts future streamflow changes in 889 watersheds in the contiguous United States based on projected climate and land use changes from 2040 to 2069. The temporal variability of surface water balance controls, represented by the Budyko ω parameter, was modeled using multiple linear regression, random forest (RF), and gradient boosting. Results show that RF is the optimal model and can explain &gt;85% of the variance in most watersheds. Relative cumulative moisture surplus, forest coverage, crop land and urban land are the most important variables of the time‐varying ω in most watersheds. There are statistically significant increases in mean annual precipitation, potential evapotranspiration, and ω in 2040–2069, as compared to 1950–2005. This leads to a statistically significant decrease in the runoff ratio (Q/P). Streamflow is projected to decrease in the central, southwestern, and southeastern United States and increase in the northeast. These projections of water availability which are based on future climate and land use change scenarios can inform water resources management and adaptation strategies.

Archaeal lipids in soils and sediments: Water impact and consequences for microbial carbon sequestration

The mineral protection of microbial necromass is critical for soil carbon stabilization. The water impact on the interactions between minerals and microbial necromass, however, remains unclear due to a lack of proper methods to quantify the mineral-protected microbial necromass. Here, we used offline hydrous pyrolysis to release the archaeal necromass—isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) bound to clay minerals by heating samples at increasing temperatures (150, 200, 250, 300, and 350 °C) under argon atmosphere. The content of extractable isoGDGTs in soils reached the maximum at 200–250 °C, indicating the release of bound isoGDGTs. By investigating the free and bound isoGDGTs along a soil transect with increasing soil water content (SWC), we found that the portion of bound isoGDGTs reached up to 97% of total isoGDGTs in dry soils, and decreased with increased SWC, suggesting that SWC controls isoGDGT stabilization on clay minerals. This relationship was confirmed in the soils from the Northeast China Transect, where the proportion of bound isoGDGTs decreased with increased mean annual precipitation from 160 to 814 mm. Such a connection was further supported by the water-saturated samples of the lake and marine sediments, which have a much lower proportion of bound lipids than the soils. The decrease of bound lipid portion with increasing water content is related to the lower attachment of microbial cells to minerals in wetter soils. Microbial cells are more strongly attached to the mineral phase under drier conditions due to the thin water film on the mineral surfaces. In addition, microorganisms secrete more extracellular polymeric substances under drier conditions, which reinforces the interactions between microbial-derived organic matter and minerals. The increased microbe-mineral interactions under drier conditions offer more stable microbial legacies and stabilize organic matter in the (semi)arid regions.

Temperature effects on root exudation in mature beech (Fagus sylvatica L.) forests along an elevational gradient

AimsRoot exudation may have a large impact on soil biological activity and nutrient cycling. Recent advances in in situ-measurement techniques have enabled deeper insights into the impact of tree root exudation on rhizosphere processes, but the abiotic and biotic controls of exudation rate remain poorly understood. We explored the temperature dependence of root exudation in mature beech (Fagus sylvatica L.) trees.MethodsWe measured fine root exudation in seven beech forests along an elevational gradient (310–800 m a.s.l.) and related carbon (C)-flux rates to mean daily temperature, actual precipitation, mean summer temperature (MST) and precipitation (MAP), soil moisture (SWC), and stand structure.ResultsAverage mass-specific exudation (averaged over all sampling dates) ranged from 12.2 µg C g−1 h−1 to 21.6 µg C g−1 h−1 with lowest rates measured at highest elevations and peak rates at mid-elevation (490 m). Regression analyses showed a highly significant positive effect of site-specific daily air and soil temperature on exudation rates (p < 0.01) with an average increase by 2 µg C g−1 h−1 per 1 °C-temperature increase, while the relation to mean summer or annual temperature and mean temperature of the measuring year was less tight. Exudation decreased with increases in mean annual precipitation and soil moisture, but increased with increasing stem density.ConclusionsThe root exudation rate of beech trees roughly triples between 10 °C and 20 °C mean daily temperature, evidencing a large temperature influence on root-borne C flux to the soil.

Does the recent afforestation program in Ethiopia influenced vegetation cover and hydrology? A case study in the upper awash basin, Ethiopia

The Ethiopian government planned afforestation programs in the past decades whereas more attention was given to tree plantation since the 2010 year. However, the effectiveness of the afforestation programs and its impacts on vegetation cover and hydrology has not been well studied. This study aims to assess the recent campaigned afforestation program and its impact on vegetation cover and hydrology in the upper Awash basin, Ethiopia. Landsat 8 images of 2013–2020 years were used to calculate the NDVI for the upper Awash basin to assess trends in vegetation greenness for the basin. Moreover, observed streamflow and precipitation datasets of the basin were collected and used for assessing the impact of the afforestation on hydrology. The study result showed decreasing NDVI values despite the afforestation programs in the upper Awash basin. This shows either afforestation rate was less than the deforestation rate or the tree plantation campaign was not effective in the basin. In addition, the campaign based tree plantation focused on the number of tree planted not on how many trees are grown. On the other hand, mean annual precipitation and streamflow were generally increased from 2013 to 2020 in the upper Awash basin. Declining NDVI values but increasing mean annual precipitation in the Awash basin indicated that the declining vegetation was attributed to anthropogenic effects. The increasing streamflow during the same time could be due to the increasing mean annual precipitation. Moreover, the decreasing vegetation cover might have contributed for the increasing streamflow through increasing surface runoff and decreasing transpiration. However, further research is required to assess the precise impacts of afforestation on vegetation cover and hydrologic processes. Generally, the study result showed that the focus of afforestation should be on tree growing than on tree plantation alone.

Variation in red fox Vulpes vulpes diet in five continents

Abstract Understanding variation in the diet of widely distributed species can help us to predict how they respond to future environmental and anthropogenic changes. We studied the diet of the red fox Vulpes vulpes, one of the world's most widely distributed carnivores. We compiled dietary data from 217 studies at 276 locations in five continents to assess how fox diet composition varied according to geographic location, climate, anthropogenic impact, and sampling method. The diet of foxes showed substantial variation throughout the species' range, but with a general trend for small mammals and invertebrates to be the most frequently occurring dietary items. The incidence of small and large mammals and birds in fox diets was greater away from the equator. The incidence of invertebrates and fruits increased with mean elevation, while the occurrence of medium‐sized mammals and birds decreased. Fox diet differed according to climatic and anthropogenic variables. Diet richness decreased with increasing temperature and precipitation. The incidence of small and large mammals decreased with increasing temperature. The incidence of birds and invertebrates decreased with increasing mean annual precipitation. Higher Human Footprint Index was associated with a lower incidence of large mammals and a higher incidence of birds and fruit in fox diet. Sampling method influenced fox diet estimation: estimated percentage of small and medium‐sized mammals and fruit was lower in studies based on stomach contents, while large mammals were more likely to be recorded in studies of stomach contents than in studies of scats. Our study confirms the flexible and opportunistic dietary behaviour of foxes at the global scale. This behavioural trait allows them to thrive in a range of climatic conditions, and in areas with different degrees of human‐induced habitat change. This knowledge can help us to place the results of local‐scale fox diet studies into a broader context and to predict how foxes will respond to future environmental changes.