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This study assesses the midsummer precipitation prediction over eastern China by the dynamic downscaling method. Based on the Climate Forecast System version 2 of the National Centers for Environmental Prediction and the Weather Research and Forecasting Model, the prediction performance of global and regional models on the July precipitation over eastern China is further analyzed by hindcast experiments from 1982 to 2010 and prediction experiments from 2011 to 2021. The results suggest that the regional model forced by the global model can noticeably improve the prediction skill for precipitation in eastern China, especially in the region from the South of North China to the Yangtze River Basin, referred as the northern China in this paper. In addition, we perform a diagnostic analysis of the reason for the improvement of the model prediction skill. The results indicate that the high resolution of the regional model and the refinement of physical process parameterizations contribute to improving the simulation ability for the East Asian atmospheric circulation pattern, heat flux, especially for the meridional teleconnection pattern in East Asia and the sensible heat flux in the northern China, thus further improving precipitation prediction. [ABSTRACT FROM AUTHOR]

The 16 years of normalized difference vegetation index (NDVI) and precipitation data are used to analyze the time‐lag effects of the growing‐season NDVI response to precipitation at regional scales. This study focuses on the arid and semi‐arid Hulunbuir grassland dominated by perennials in northeast China. The multi‐month time‐lag effects are examined using simple statistical approaches, which can detect the two distinct time‐lags for four subregions with four major land‐cover types. A "positive" time‐lag effect of the growing‐season NDVI response to precipitation is observed at 1‐month (May in the current year) time‐lag and 13‐month (May in the previous year) time‐lag while a "negative" time‐lag effect is observed at 9‐month (September in the previous year) time‐lag. In addition, the prediction results of NDVI based on precipitation indicate that the NDVI prediction model considered the lagged monthly precipitation has good performance. Therefore, revealing the time‐lag effects is very important for accurately predicting the growing‐season NDVI and evaluating the vegetation dynamics. Recommendations for Resource Managers: The multi‐month time‐lag effects of the growing‐season NDVI to precipitation in arid and semi‐arid grasslands in northeastern China is analyzed in this paper. We can detect the two distinct time‐lags for four subregions with four major land‐cover types. The following implications could be realized based on the observations: The "positive" 1‐month (May in the current year) and 13‐month (May in the previous year) time‐lag memory of the growing‐season NDVI response to precipitation can be found.The "negative" 9‐month time‐lag memory of the growing‐season NDVI response to precipitation associated with September (late growing‐season) meteorological condition can be detected. This "negative" effect does not support the green up of the growing‐season in the next year. [ABSTRACT FROM AUTHOR]

Restoration of natural vegetation in arid and semi‐arid grasslands is facing severe challenges. The vegetation is easy to lose their vitality, resulting in the loss of the cover in natural grasslands under the high grazing pressure. To address this situation, this paper proposes a novel method for accurately predicting the grazing pressure using the nonlinear autoregressive with exogenous input (NARX) network based on the remote sensing data of normalized difference vegetation index (NDVI) and precipitation. The proposed method uses the NARX networks to predict the temporal variations of the NDVI with respect to the precipitation. The grazing pressure can be thus calculated using the predicted values of the NDVI. For practical application, this study investigated an arid and semi‐arid grassland with heavy grazing pressure in Hulunbuir, China. The results demonstrate that the proposed method can provide an accurate prediction of the grazing pressure (mean absolute error 0.103, root‐mean‐square error 0.122, mean absolute percentage error 8.36% and coefficient of determination 0.899 at the confidence interval of 95%). In addition, the predicted values of the grazing pressure in the study area during the years from 2016 to 2020 can be obtained using the proposed method. The proposed method can obtain a good prediction of the grazing pressure, which can be further used as a guidance for the rangeland managers to reduce the occurrence of the overgrazing. [ABSTRACT FROM AUTHOR]

Vegetation restoration in dryland regions may be a powerful way to control desertification and promote local habitat recovery. In these artificial revegetation systems, ecosystem processes and functioning are strongly determined by nitrogen (N) availability, while soil inorganic N (SIN) is the major available N form and is absorbed as a main N source for plants. However, SIN dynamics, their influencing factors, and their relative importance to the ecosystem of these N‐limited systems are not well understood. A field investigation was conducted to examine the monthly variations in SIN and its response to planting age and vegetation type in a typical artificial sand‐fixing system in northwestern China. The SIN content in topsoil (0–20 cm) during the growing season ranged from 7.10 to 95.65 mg kg−1, with a mean value of 27.14 mg kg−1. Soil nitrate N had a dominant role in determining SIN monthly dynamics, which showed a fluctuating trend with two peak values in early July and late August. SIN showed a significant increasing trend with the planting age of sand‐fixing vegetation, and it was highest for Nitraria sphaerocarpa (55.66 ± 5.76 mg kg−1), followed by Haloxylon ammodendron (29.81 ± 3.47 mg kg−1) and interspace (11.39 ± 1.13 mg kg−1). SIN displayed a hump‐shaped relationship with air temperature (R2 = 0.96, p < 0.01) and had a maximum at 19.88°C. The change rate of SIN was positively correlated with accumulated precipitation (R2 = 0.99, p < 0.05). SIN was correlated significantly with soil organic carbon (SOC), total nitrogen (TN), and soil clay content. Our results revealed that climatic (air temperature and precipitation), abiotic (soil texture), plant (planting age and vegetation type), and nutrient‐related (SOC and TN) factors regulate SIN dynamics in artificial sand‐fixing vegetation systems. Climate was the predominant factor affecting soil ammonium N, and soil nutrients (SOC and TN) were the predominant factor affecting soil nitrate N. Therefore, these factors should be integrated into optimizing regional vegetation establishment and improving ecosystem management practices in sand‐fixing lands. [ABSTRACT FROM AUTHOR]

Mesoscale convective systems (MCSs) are important air water sources to the Three‐river‐source (TRS) region known as the "Chinese water tower." Using hourly equivalent blackbody temperature (TBB) data from geostationary satellites of Chinese Fengyun‐2 series during the warm season (May–August) in 2005–2020 and an objective algorithm, MCSs in the TRS are divided into meso‐α (MαCS), meso‐β (MβCS), and meso‐γ (MγCS), and MαCS and MβCS are subdivided into larger meso‐α (LMαCS), smaller meso‐α (SMαCS), larger meso‐β (LMβCS), and smaller meso‐β (SMβCS). Results show that a high‐frequency zone of MCSs in the TRS distributes along the source of the rivers. Most MCSs, except LMαCS, develop and dissipate in situ. The interannual variation in MCS frequency exhibits a decreasing trend, especially after 2013, mainly due to the decrease in MCSs in the source region of the Yellow–Lancang River. The occurrence of MCSs peaks in August, but MCSs are most likely to produce precipitation in July and usually generate between 1600–2200 h LST (UTC + 8). The precipitation caused by MCSs to the total precipitation (precipitation ratio, PR) accounts for about 40%; MCS PR is closely related to, and increases with, the horizontal scale of the MCS, with MαCS PR being the highest, exceeding 67%. The contribution of MCSs to precipitation is mainly reflected in weak precipitation, smaller than 10.0 mm/h. Most of the maximum precipitation of MCSs appears after MCSs reach their prime, with the maximum lag by MαCS up to 2 h. [ABSTRACT FROM AUTHOR]

Projecting precipitation changes is essential for researchers to understand climate change impacts on hydrological cycle. This study projected future precipitation over the Hanjiang River Basin (HRB) based on the multimodel ensemble (ME) of six global climate models from Phase 6 of the Coupled Model Intercomparison Project (CMIP6). An ME method using the fusion of four machine learning (ML) algorithms (random forest [RF], K‐nearest neighbors [KNN], extra tree [ET], and gradient boosting decision tree [GBDT]) was proposed in this study. The future precipitation changes were investigated during 2023–2042 (Near‐term), 2043–2062 (Mid‐term), and 2081–2100 (Long‐term) periods, with reference to the base period 1995–2014, under three integrated scenarios (SSP1‐2.6, SSP2‐4.5, and SSP5‐8.5) of the Shared Socioeconomic Pathways (SSPs) and the representative concentration pathways (RCPs). The results show that: (1) the proposed ME method performs better than the ME mean and individual ML algorithms, with a correlation coefficient value reaching 0.88 and Taylor skill score reaching 0.764. (2) The precipitation under SSP5‐8.5 has the largest upward trend with the annual precipitation variation range of −9.27% to 112.84% from 2023 to 2100, followed by SSP2‐4.5 with −30.48% to 44.67%, and the smallest under SSP1‐2.6 with −37.19% to 37.78%, which show a significant trend of humidification over the HRB in the future. (3) The precipitation changes over the HRB are projected to increase over time, with the largest in the Long‐term, followed by Mid‐term, and the smallest in the Near‐term. (4) The northeastern parts of the HRB are projected to experience a large precipitation in the future, and the southeastern parts are smaller. (5) Uncertainties in the projected precipitation over the HRB still exist, which can be reduced by ME. The findings obtained in this study have important implications for hydrological policymakers to make adaptive strategies to reduce the risks of climate change. [ABSTRACT FROM AUTHOR]

Aim: Significant changes in species elevational ranges in mountains have been repeatedly documented, yet the direction, magnitude and drivers of these shifts remain controversial. Presently, there is still lacking evidence about the general nature of species elevational range shifts in eastern Eurasia in response to anthropogenic climate change. By using historical specimen records and recent field observations for 735 seed plant species across 29 China's mountains, we assessed changes in species' elevational centroids and their drivers. Location: China. Time Period: 1950–2018. Major Taxa Studied: Seed plant species. Methods: The elevation records of all sampled occurrences in each mountain during the two time periods were estimated, and the null models were developed to test the sampling bias. Ecological niche models (ENMs) were used to evaluate the relative importance of climate factors in constraining each species distribution. Generalized linear models (GLMs) to test the relationships between the centroid elevational range shifts of species and different divers. Results: We found that 54% of the species shifting upward and 46% downhill. However, species' elevational shifts significantly differed among species and mountains. Herbaceous and lowland species moved upward faster than woody and high‐elevation species. Species in temperate mountains and in mountains with taller elevational gradients moved upward, while species in subtropical mountains and in mountains with shorter elevational gradients moved downward. Precipitation changes experienced by species, species' climatic adaptations, several species' functional traits and mountain size all contributed to explain the magnitude of species' centroid elevational range shifts. Main Conclusions: Our results highlight complex biodiversity redistribution of seed plants across Chinese mountains, not necessarily conforming to the trend of species upward shifts in elevation. Changes in precipitation regimes may blur the simplistic assumption of isotherm tracking. This study fills an important geographic shortfall for our understanding of biodiversity redistribution under anthropogenic climate change. [ABSTRACT FROM AUTHOR]

Aim: Amphibians require both terrestrial and aquatic environments to complete their life cycles. Thus, they are subject to complex selection pressures stemming from different environments, and these selection pressures are likely to vary geographically with variation in temperature and precipitation. Studies of genetic differentiation along geographical clines allow identification of footprints of these selection pressures. Location: China. Methods: To identify possible signatures of local adaptation to particular environmental conditions, we conducted a genome‐scan with 20,572 single‐nucleotide polymorphisms (SNPs) obtained with restriction site‐associated DNA sequencing of pooled samples from 10 Microhyla fissipes populations spanning a 1,398 km long latitudinal gradient in China. Results: The results revealed significant genetic differentiation among populations (FST =0.090). Numerous outlier SNPs associated with variation in both annual average temperature (n = 69) and precipitation (n = 248) were detected. Main conclusions: The degree and pattern of population differentiation in the SNPs supported the hypothesis that these SNPs have been subject to directional natural selection associated with temperature and precipitation and, hence, are reflective of geographically varying local adaptation. Hence, conservation and management plans for Microhyla fissipes should take into account this heterogeneity in genetic constitution in its populations. [ABSTRACT FROM AUTHOR]

1. It is increasingly being recognized that tree species diversity has positive effects on forest ecosystem carbon (C) stock. However, at broad spatial scales, this relationship may depend on climate conditions and species mycorrhizal associations. 2. Here, observations from 667 forest plots in subtropical China were used to investigate the effects of species diversity, mean annual precipitation (MAP), mean annual temperature (MAT) and mycorrhizal type (arbuscular or ectomycorrhizal) on the forest C stock and its components (tree C stock, shrub layer C stock, herb layer C stock, litter layer C stock, root C stock and soil C stock). 3. We found positive effect of tree species diversity on total forest C stock. MAP had positive effects on total forest C stock and its components, while MAT had consistently negative effects on total forest C stock and most of its components. Different levels of MAP and MAT did modulate the strength of effect of species diversity on forest C stock and its components. In addition, species diversity, MAT and MAP showed a significant positive relationship with arbuscular mycorrhiza-associated tree C stock but had no or negative relationship with ectomycorrhiza-associated tree C stock. 4. Synthesis. Our results indicate that maintaining high level of species diversity may support the buffering of negative effects resulting from climate warming. Furthermore, under climate warming the specific C stock of AM trees can increase, which can potentially promote forest C stock. Taken together, our study suggests that afforestation policies should consider not only tree species diversity to increase forest C stock but also the effects of different tree mycorrhizal types. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore the response of the stoichiometric and photosynthetic characteristics of a dominant plant species in a typical grassland to changes in precipitation. Rain shelter technology was used to simulate 50%, 100%, and 150% of natural rainfall. The photosynthetic rate (Pn), intercellular CO2 concentration (Ci), transpiration rate (Tr), stomatal conductance (Gs), and ecological stoichiometry of the rhizosphere soil and Stipa bungeana at different growth stages were measured in May, July), and September, 2019 after 2 years of rainfall control. The results showed that the aboveground carbon (C) content of plants grown under 150% precipitation was significantly higher than that of plants grown under 100% precipitation in September. The aboveground nitrogen (N) content of plants under 50% precipitation was significantly higher than the plants grown under 100% precipitation. Under all different precipitation treatments, the aboveground C:N ratio was the lowest (16.4–19.6) in May. The range of average aboveground C: phosphorous (P) ratio was 373.7–617.8, and the N:P ratio in the descending order was July > May > September. The 50% precipitation treatment promoted the highest accumulation of underground C at all the growth stages. The productivity of the grassland under the 100% and 150% precipitation treatments was limited by the rhizosphere soil N and P. The underground C, P, C:P, and aboveground C:N ratios were sensitive indicators. Aboveground and underground N:P ratio showed the strongest significant correlation (P < 0.001), and the correlation between underground stoichiometry and rhizosphere soil P (P < 0.001) was stronger than that with rhizosphere soil N (P < 0.05). The correlation between Ci and stoichiometry was opposite in direction to the correlation between Pn, Tr, Gs, and stoichiometry. The research results will provide a scientific reference for understanding of the material cycle and judgment of vegetation nutrient limitations in the Loess Plateau. [ABSTRACT FROM AUTHOR]

The data of lightning flash count, rainfall, radar reflectivity, vertical wind shear (WS), surface dew point temperature (DP) and particulate matter up to 10 μm in size (PM10) over Guilin, China from July 2010 to December 2019 were studied to check whether aerosol invigoration effect (AIV) exists in the study area. It was found that convective rainfall fluctuates less when compared with lightning in convective system. A hypothesis was put forward that the difference in fluctuations between convective rainfall and lightning is attributed to AIV. To test this hypothesis, lightning yield, which is defined as the ratio between lightning and rainfall, was analyzed. It was found that lightning yield has a positive correlation with PM10 when WS is low and DP is high for convective precipitation. It was also found that for the weak WS cases, when aerosol conditions are shifted from super pristine to the optimal concentration (Nop), lightning yield increases with increasing PM10; whereas for concentrations greater than Nop, lightning yield decreases with increasing PM10. Nop would be larger for higher DP. The results are in line with the previous studies showing that AIV depends strongly on weak wind shear and/or warm cloud base. This suggests that AIV exists in the study area, and suggests that the hypothesis is reasonable, and lightning yield can be used as a surrogate to study AIV. [ABSTRACT FROM AUTHOR]

Long‐term, accurate soil moisture (SM) estimates are crucial for climate, hydrology, and agriculture. Multisource SM products are available at high spatiotemporal coverage, but their uncertainties have yet to be fully evaluated in China. Ten SM products (i.e., reanalysis, assimilation, and satellite) were intercompared and evaluated over 18 hydroclimatic regions of China during 2000–2018 at different scales. The results show that all SM products share similar spatial patterns but exhibit significant differences in regions and products. The interannual fluctuations and differences between these products are relatively small, except for the anomalies of ESA CCI ACTIVE and PASSIVE in southern China. At a seasonal scale, the estimates of NCEP R2, ACTIVE, and PASSIVE for specific regions are significantly different from other products. Moreover, all SM products correlate well with precipitation in summer and have their own dominant areas. Among them, ERA5 shows a comprehensive potential for application in China. The temporal correlation coefficient (R), root mean square difference (RMSD), and standard deviation (σ) demonstrate that ERA5 performs better in southern China, while CLSM performs better in the northeast and throughout China, with R exceeding 0.7 for both products. For the Equitable Threat Score (ETS), ERA5 has a better overall performance with scores greater than 0.03 distributed in more regions of China, followed by ACTIVE and CFSR/CFSV2. This study not only provides a reasonable reference for the targeted selection of SM products in different hydroclimatic regions of China but also establishes a preliminary data basis for the integration of multiple products. Key Points: Ten soil moisture products from multiple sources were intercompared and evaluated in 18 hydroclimatic regions of China during 2000–2018All products share similar spatial patterns to precipitation in China, but with subtle interannual and seasonal variationThe optimal SM products are found in different regions of China, among which ERA5 shows the superior overall performance(R>0.7&ETS¯>0.03) [ABSTRACT FROM AUTHOR]

Aim: A predictive understanding of the mechanisms underlying microbial biogeographical patterns is of great interest, particularly with respect to phylogenetic distributions of their ecological adaptations. Here, we test whether phylogenetic information can predict the biogeographical distributions, community assembly and species co‐occurrence of soil archaea. Location: Northern China. Time period: July and August 2017. Major taxa studied: Archaeal communities. Methods: By conducting a large‐scale (transect intervals of 1,257.6 km) study across agricultural field, forest, wetland, grassland and desert biomes, we applied the phylogenetic framework of niche conservatism to investigate archaeal biogeography, community assembly and network topology. We examined the phylogenetic signal based on Blomberg's K to test whether the environmental preference of a given archaeal taxon was related to the phylogeny, corresponding to the degree of phylogenetic conservatism for environmental niches across complex environmental gradients. We evaluated the assembly processes of archaeal communities based on null model and Sloan neutral model analyses. We then explored the major factors that influenced the species coexistence and assembly processes of soil archaeal communities. Results: Soil archaeal taxa exhibited strong climate‐related niche conservatism of ecological preferences. Mean annual precipitation (MAP) had the strongest phylogenetic signal, and this mediated both community assembly processes and species coexistence, with stronger deterministic assembly and less species coexistence in environments with lower precipitation. Phylogenetic diversity was closely linked to the balance of community assembly processes; that is, stochastic assembly processes were dominant in low‐diversity communities, whereas variable selection of deterministic processes promoted high phylogenetic diversity. Main conclusions: We conclude that strong phylogenetic niche conservatism of soil archaea drives their biogeographical distributions. Our findings represent a considerable advance in linking phylogenetic niche conservatism to soil archaeal biogeography, community assembly and species coexistence, and therefore forecasting soil archaeal evolutionary adaptations in response to ongoing environmental changes. [ABSTRACT FROM AUTHOR]

Future climate may profoundly impact the functioning of terrestrial ecosystems. However, we do not know well how the functioning of different types of grassland ecosystems is associated with variation in temperature and precipitation. Here, we used long‐term field measurements to examine how climatic changes between the 1980s and the 2010s (i.e., growing season temperature, precipitation, habitat moisture index, solar radiation, and sunshine duration) have affected aboveground net primary productivity (ANPP) for all major grassland types in northern China. We found that ANPP consistently declined over the 30‐year period across all types of grassland, on average by about 6.1%. Warming, associated with increased solar radiation and, hence, soil temperature, was the primary factor driving the decrease of ANPP. We further show that ANPP was more sensitive to climate change in alpine and lowland grasslands than in temperate grasslands. Together, our findings indicate that climate warming consistently reduces plant productivity of different types of grassland ecosystems, and emphasize the importance of soil temperature in driving the decline in grassland productivity under climate change. Plain Language Summary: Future climate may profoundly impact the functioning of terrestrial ecosystems. However, we do not know well how the functioning of different types of grassland ecosystems is associated with variation in temperature and precipitation. Here, we used long‐term field measurements to examine how climatic changes between the 1980s and the 2010s (i.e., growing season temperature, precipitation, habitat moisture index, solar radiation, and sunshine duration) have affected aboveground net primary productivity (ANPP) for all major grassland types in northern China. We found that ANPP consistently declined over the 30‐year period across all types of grassland, on average by about 6.1%. Warming, associated with increased solar radiation and, hence, soil temperature, was the primary factor driving the decrease of ANPP. We further show that ANPP was more sensitive to climate change in alpine and lowland grasslands than in temperate grasslands. Together, our findings indicate that climate warming consistently reduces plant productivity of different types of grassland ecosystems, and emphasize the importance of soil temperature in driving the decline in grassland productivity under climate change. Key Points: There is a universal decrease in aboveground net primary productivity (ANPP) over 30 years across different grassland types, and the magnitude of ANPP decline differed between typesThe air temperature and soil temperature rather than precipitation were the primary drivers of ANPP decline to climate changeThe increased air temperature and soil temperature from increased total solar radiation were the main drivers for ANPP decline [ABSTRACT FROM AUTHOR]

Using the NCEP/NCAR reanalysis and station observations in China during 1979–2018, features of propagation of baroclinic wave packets in the upper troposphere and their relationships with precipitation over the middle and lower reaches of the Yangtze River (MLRYR) in daily climatology are investigated after having components with periods longer than 9 days filtered out. It is demonstrated that in the filtered daily climatology, the baroclinic wave packets still exist. The wave packet migrates eastward on the northern sides of the westerly jet stream axis whereas it does not move explicitly in the southern side of the axis in the upper troposphere. The filtered daily precipitation over MLRYR is mainly affected by the wave packets in the region south of the westerly jet axis. These results are very meaningful for better understanding behaviors of Rossby waves in daily climatology and the causes of daily precipitation variations in MLRYR. [ABSTRACT FROM AUTHOR]

Summary: Heavy rainfall events are expected to increase in frequency and severity in the future. However, their effects on natural ecosystems are largely unknown, in particular with different seasonal timing of the events and recurrence over multiple years.We conducted a 4 yr manipulative experiment to explore grassland response to heavy rainfall imposed in either the middle of, or late in, the growing season in Inner Mongolia, China. We measured hierarchical responses at individual, community and ecosystem levels.Surprisingly, above‐ground biomass remained stable in the face of heavy rainfall, regardless of seasonal timing, whereas heavy rainfall late in the growing season had consistent negative impacts on below‐ground and total biomass. However, such negative biomass effects were not significant for heavy rainfall in the middle of the growing season. By contrast, heavy rainfall in the middle of the growing season had greater positive effects on ecosystem CO2 exchanges, mainly reflected in the latter 2 yr of the 4 yr experiment. This two‐stage response of CO2 fluxes was regulated by increased community‐level leaf area and leaf‐level photosynthesis and interannual variability of natural precipitation.Overall, our study demonstrates that ecosystem impacts of heavy rainfall events crucially depend on the seasonal timing and multiannual recurrence. Plant physiological and morphological adjustment appeared to improve the capacity of the ecosystem to respond positively to heavy rainfall. [ABSTRACT FROM AUTHOR]

The impact of urbanization for a summertime rainstorm process in the Yangtze River Delta was investigated based on two 96 member ensembles using the Weather Research and Forecasting (WRF) model. Results show that the increase of precipitation mainly occurs downwind of the city belt in this region. The increase and decrease of precipitation forms two zigzag belts in the precipitation area. The t-test illustrates that the discrepancies of near-surface environment around the city belt, the precipitation downwind of the city belt as well as the atmospheric variables in the lower troposphere over the rain belt, caused by urbanization, is significant in such a short-term rainstorm process. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Aim The long-term cyclical patterns of China's geopolitical shifts are of great interest to scholars and the public, but to date there has been no satisfactory explanation for the alternating occupancy patterns of the country's pastoral and agrarian polities. We fill this gap by differentiating the agroecological settings of these polities over time and quantitatively analysing the relationships between climate change and historical geopolitical variations. Location China. Methods Our dataset comprised 38 palaeohydroclimate reconstructions, the historical boundaries of China's empire and the changes in its size, and 1028 wars and 2737 battle locations over the past 2300 years. China-wide precipitation during the period was reconstructed using the 'weighted composite plus scale' method. Time-series analyses were performed to identify the strength of the associations between climate change and the geopolitical variables. Granger causality analysis and wavelet analysis were performed to verify the hypothesized causal links. Wavelet analysis was also used to identify the possible interactions (i.e. frequencies, significance, consistency and synchrony) between the signal components of the climatic and geopolitical variables at different temporal scales. Results China's mean precipitation fell into three multicentennial cycles. The geopolitical variables corresponded to those cycles in the imperial era. The spatial-temporal frequencies of the boundaries and size of the agriculturalist empires and its frontiers with pastoralist empires were regulated by the long-term (low-frequency) precipitation fluctuations at the multicentennial scale. Wars of aggression were an important explanatory factor driving the land-occupancy patterns of the two ecoempires under climate change, and caused most of the territorial shifts. Short-term (high-frequency) geopolitical changes were not associated with climate change. Main conclusions Precipitation-induced ecological change was an important factor governing the macrogeopolitical cycles in imperial China. Long-term territorial expansion favoured the polity (agriculturalist or pastoralist) that was better adapted to the changing ecological conditions in the country's heartland. [ABSTRACT FROM AUTHOR]

The current study investigates the variability of vertical structure of precipitation in the Huaihe River Basin (HRB) of China. The precipitation characteristics have been revealed by the long-term observations of vertical profile of reflectivity (VPR) from the first spaceborne precipitation radar (PR) onboard the National Aeronautics and Space Administration (NASA)'s Tropical Rainfall Measuring Mission (TRMM) satellite. This study has statistically analyzed the latest TRMM 2A-23 and 2A-25 products (version 7, released in 2012) with ∼15 years time span (from 11 December 1997 to 19 August 2012). First, the spatial and seasonal variations of storm height and freezing level have been investigated. The results show a climatological relation connecting the storm height with the rainfall rate in HRB. Second, mean VPRs have been studied for the stratiform and convective precipitation. The VPR variability has been analyzed for different seasons and rain intensities. Third, the characteristics of rain intensification and weakening in the vertical direction have been examined by the statistical analysis of VPR slope below the melting layer. The results show that the rainfall tends to be reduced (or intensified) with the height changing downward in the light (or moderate and heavy) precipitating clouds, no matter stratiform or convection. Finally, the S-band climatological VPRs have been characterized by converting the VPR from Ku-band to S-band. Considering the wide application of national radar network for weather surveillance in China, the developed S-band climatological VPRs can be potentially applied in a VPR correction scheme to improve the ground radar-based quantitative precipitation estimation (QPE) in this river basin. [ABSTRACT FROM AUTHOR]

• Global climate change is generally expected to increase net primary production, resulting in increased soil carbon (C) inputs. To gain an understanding of how such increased soil C inputs would affect C cycling in the vast grasslands of northern China, we conducted a field experiment in which the responses of plant and microbial biomass and respiration were studied. • Our experiment included the below-ground addition of particulate organic matter (POM) at rates equivalent to 0, 60, 120 and 240 g C m−2, under either natural precipitation or under enhanced precipitation during the summer period (as predicted for that region in recent simulations using general circulation models). • We observed that addition of POM had a large effect on soil microbial biomass and activity and that a major part of the added C was rapidly lost from the system. This suggests that microbial activity in the vast temperate grassland ecosystems of northern China is energy-limited. Moreover, POM addition (and the associated nutrient release) affected plant growth much more than the additional water input. • Although we performed no direct fertilization experiments, the response of plant productivity to POM addition (and associated release of nutrients) leads us to believe that plant productivity in the semiarid grassland ecosystems of northern China is primarily limited by nutrients and not by water. [ABSTRACT FROM AUTHOR]