Search

Aiming to reveal the humification process of organic waste and its contribution to the heavy metal behaviour affected by earthworm activity, it was studied about the variation of humic acid (HA) and heavy metal behaviour during vermicomposting of the mixed pig manure and 13C-labelled rice straw. The results showed that earthworms could well adapt to the culturing environment and feed organic matter for its growth and reproduction, the vermicomposting process increased the content of humic substances (HS), HA, and fulvic acid (FA) in substrate residues, but led to less transformation of HA into FA. The elemental, ultraviolet absorption spectroscopy, Fourier transform infrared (FTIR) and fluorescence excitation–emission matrix (EEM) analysis indicated that vermicomposting led to more aromatic structures and much higher humification degree in HA, whereas less protein, FA-like substances and plastein in HA. Vermicomposting could enhance the total Cu content and decrease Cu/Zn bioavailability in the substrate residues, and vermicomposting especially can help stabilize Cu in the substrate residues by forming more complexed HA–Cu.

Northwest China is one of the most arid regions in the world and has experienced intriguing climate warming and humidification. Nonetheless, future climate conditions in Northwest China still remain uncertain. In this study, we applied an ensemble of the 12 latest model simulations of the Coupled Model Intercomparison Project Phase 6 (CMIP6) to assess future drought conditions until 2099 in Northwest China, as inferred from the Palmer Drought Severity Index (PDSI). Future drought conditions were projected under three climate change scenarios through the combination of shared socioeconomic pathways (SSPs) and representative concentration pathways (RCPs), namely, SSP126 (SSP1 + RCP2.6, a green development pathway), SSP245 (SSP2 + RCP4.5, an intermediate development pathway), and SSP585 (SSP5 + RCP8.5, a high development pathway). For 2015–2099, drought severity showed no trend under SSP126, in contrast, for the SSP245 and SSP585 scenarios, a rapid increase during 2015–2099 was observed, especially under SSP585. We also found that the drought frequency in Northwest China under SSP585 was generally lower than that under SSP126 and SSP245, although the drought duration under SSP585 tended to be longer. These findings suggest the green development pathway in drought mitigation and adaptation strategies in Northwest China, an arid and agricultural region along the Silk Road.

The rate of warming of the Arctic surface temperature has exceeded that of the global surface temperature in recent decades. However, the underlying process and causes of the long-term warming remain uncertain. In this paper, we explored the factors underlying variation in Arctic mean surface temperature anomalies (AMTA) using a piecewise linear model for 1920–2018. This analysis indicated that the change in AMTA during the study period could be divided into three segments, with AMTA increasing from 1920 to 1938, declining from 1939 to 1976, and finally increasing rapidly after 1977. By a newly developed rigorous formalism of information flow, we found a one-way causality from the driving forces to AMTA. Moreover, the AMTA evolution could mainly be attributed to a combined effect of anthropogenic and natural factors (e.g., CO2, aerosol, and PDO). During the first warming stage (1920–1938), the PDO and aerosols are the main factors determining the change in AMTA. During the second warming stage (1977–2018), greenhouse gases, dominated by CO2, are the major factors accounting for the Arctic warming. In 1939–1976, the observed cooling may be associated with aerosols, clouds, and land use. A better understanding of the driving mechanism underlying AMTA evolution provides insight into the historical Arctic climate change, and can improve the prediction of future changes in AMTA.

Ice clouds are mostly composed of different ice crystal habits. It is of great importance to classify ice crystal habits seeing as they could greatly impact single‐scattering properties of ice crystal particles. The single‐scattering properties play an important role in the study of cloud remote sensing and the Earth's atmospheric radiation budget. However, there are countless ice crystals with different shapes in ice clouds, and the task of empirical classification based on naked‐eye observations is unreliable, time consuming and subjective, which leads to classification results having obvious uncertainties and biases. In this paper, the images of ice crystals observed from airborne Cloud Particle Imager in China are used to establish an ice crystal data set called Ice Crystals Database in China, which consists of 10 habit categories containing over 7,000 images. We propose an automatic classification model of ice crystal habits, called TL‐ResNet152, which is a deep convolutional neural network based on the newly developed method of transfer learning. The results show that the TL‐ResNet152 model could achieve reliable performance in ice crystal habits classification with the accuracy of 96%, which is far more accurate than traditional classification methods. Achieving high‐precision automatic classification of ice crystal habits will help us better understand the radiation characteristics of ice clouds.

The 2015 Gorkha earthquake (Mw = 7.8) caused significant earthquake triggered landslides (ETL) in a landscape that is heavily intervened by rainfall triggered landslides (RTL). China’s Belt and Road Initiative plan to boost South-Asian regional trade and mobility through two key highway corridors, i.e. 1) Longmu–Rasuwa–Kathmandu (LRK) and 2) Nyalam–Tatopani–Kathmandu (NTK) route, that dissect the Himalayas through this geologically unstable region. To understand the spatial characteristics and susceptibility of these ETL and RTL, we delineate the landslides by means of time variant satellite imageries, assess their spatial distribution and model their susceptibilities along the highway slopes. We use a coupled frequency ratio (FR) – analytical hierarchy process (AHP) model by considering nine landslide determinants, e.g. geomorphic type (slope, aspect, curvature, elevation), hydrologic type (erosive potential of gullies, i.e. stream power index and distance to streams), normalized difference vegetation index, lithology and civil structure type (i.e. distance to roads). The results demonstrate that elevation and slope predominantly control both these landslide occurrences. The model predicts locations of ETL with higher accuracy than RTL. On comparison, NTK was safer with 133.5 km2 of high RTL or ETL (or both) landslide susceptible areas, whereas LRK has 216.04 km2. For mapping the extent of these landslides, we constricted it to the slope units of highways to reduce the computational effort, but this technique successfully achieved an acceptable threefold average model prediction rate of 82.75% in ETL and 77.9% in RTL. These landslide susceptibility maps and route comparisons would provide guidance towards further planning, monitoring, and implementing landslide risk mitigation measures for the governments.

A spatially-explicit cropland distribution time-series dataset is the basis for the accurate assessment of biogeochemical processes in terrestrial ecosystems and their feedback to the climate system; however, this type of dataset is lacking in China. Existing cropland maps have a coarse resolution, are intermittently covered, or the data are inconsistent. We reconstructed a continuously covered cropland distribution dataset in China spanning from 1900 to 2016 by assimilating multiple data sources. In total, national cropland acreage expanded from 77.72 Mha in 1900 to the peak of 151.00 Mha in 1979, but it consistently decreased thereafter to 134.92 Mha in 2016. The cropland was primarily distributed in three historically cultivated plains in China: the Sichuan Plain, the Northern China Plain, and the Northeast China Plain. Cropland abandonment was approximately 29.90 Mha; it was mainly concentrated in the Northern China Plain and the Sichuan Plain and occurred during the 1990–2010 period. Cropland expansion was over 74.30 Mha; it was primarily found in the southeast, northern central, and northeast regions of China and occurred before 1950. In comparison, the national total and spatial-distribution of cropland in the Food and Agriculture Organization (FAO) of the United Nations and the History Database of the Global Environment (HYDE) were distorted during the period of 1960–1980 due to the biased signal from the Chinese Agricultural Yearbook. We advocate that newly reconstructed cropland data, in which the bias has been corrected, should be used as the updated data for regional and global assessments, such as greenhouse gas emission accountings and food production simulations. The cropland dataset is available via an open-data repository (https://doi.org/10.6084/m9.figshare.13356680) (Yu et al., 2020).

Changes in land management and climate alter vegetation dynamics, but the determinants of vegetation changes often remain elusive, especially in global drylands. Here we assess the determinants of grassland greenness on the Mongolian Plateau, one of the world's largest grassland biomes, which covers Mongolia and the province of Inner Mongolia in China. We use spatial panel regressions to quantify the impact of precipitation, temperature, radiation, and the intensity of livestock grazing on the normalized difference vegetation indices (NDVI) during the growing seasons from 1982 to 2015 at the county level. The results suggest that the Mongolian Plateau experienced vegetation greening from 1982 to 2015. Precipitation and animal density were the most influential factors contributing to higher NDVI on the grasslands of Inner Mongolia and Mongolia. Our results highlight the dominant effect of climate variability, and especially of the precipitation variability, on the grassland greenness in Mongolian drylands. The findings challenge the common belief that higher grazing pressure is the key driver for land degradation. The analysis exemplifies how representative wall‐to‐wall results for large areas can be attained from exploring space–time data and adds empirical insights to the puzzling relationship between grazing intensity and vegetation growth in dryland areas., European Union's Framework Programme for Research and Innovation ‐ Horizon 2020 (2014‐2020), Alexander von Humboldt Foundation of Germany

Drought has become a major threat to local sustainable development in dryland Asia, one of the largest grassland ecosystems in the world. However, empirical‐ and science‐based evidence regarding the extent of drought changes and the future trends of these changes in dryland Asia is variable and incomplete. Here, we first investigate the historical variations in drought conditions in dryland Asia, as measured by the drought intensity and arid area, using three widely used drought indices (the Palmer Drought Severity Index, the Standardized Precipitation Index, and the Standardized Precipitation Evapotranspiration Index). Then, we use Bayesian model averaging to reproduce the future drought conditions under two representative concentration pathways (RCP2.6 and RCP4.5) from the Coupled Model Intercomparison Project Phase 5 Earth system models. The Palmer Drought Severity Index, Standardized Precipitation Index, and Standardized Precipitation Evapotranspiration Index illustrate that dryland Asia has experienced an overall drying trend and an expansion of arid areas over the past 100 years (1901–2016). Both temperature and precipitation are projected to increase under both the 1.5 and 2.0 °C warming scenarios compared with the values from the reference period (1986–2005). The projected drought conditions in the 1.5 and 2.0 °C warming scenarios will worsen, especially across Kazakhstan and Northwest China. We found that the drought conditions under the 2.0 °C warming conditions will not be as severe as those under the 1.5 °C warming conditions due to the mitigating effect of the projected precipitation increase under RCP4.5. These results call for short‐term and long‐term mitigation and adaptation measurements for drought events in dryland Asia.

In recent years, flash floods and urban waterlogging have become a widespread phenomenon in Fuzhou, which pose a serious threat to people’s lives and property. The primary disaster-causing factors include the intensity and duration of rainfall. Therefore, this article analyzes the characteristics, causes of rainfall, and the existing problems of the two disasters in Fuzhou. The main conclusions are as follows: (1) The rainfall in Fuzhou is concentrated in March to September, with high rainfall intensity and rainfall amounts, and frequent extreme rainfall events combined with high rainfall intensity in flash flood-prone areas are higher than that in the plains area. (2) Precipitation, geographical conditions, and urban construction mainly caused the two major disasters and are weak in technology and management. Therefore, it is necessary to adhere to both the structural measures and non-structural measures to coordinate the relationship between people and floods, to strengthen the research on the mechanisms of precipitation, and to forecast and provide early warning of flash floods and urban waterlogging, all of which can provide reference for the defensive disasters in mountainous coastal cities.

The warming climate has rapidly altered vegetation growth in drylands, and consequently, has put great pressure on sustainable livelihoods. Various datasets have been applied from local to global scale to study vegetation dynamics and there is a lack of solid comparison among multiple datasets. Note that vegetation growth might shift over time and the greening and browning components over a long-time span might be masked by a linear trend. Here, we aim to monitor the long-term and nonlinear dynamics in vegetation greenness for Inner Mongolia (an important part of dryland Asia). As a useful tool that indicates vegetation greenness, NDVI (Normalized Difference Vegetation Index) and LAI (Leaf Area Index) integrals derived from the GIMMS (Global Inventory Modelling and Mapping Studies) NDVI3g and the GIMMS LAI3g products are applied. During the period of 1982-2016, NDVI/LAI integrals have an overall acceptable consistency in characterizing the trends of vegetation greenness, with NDVI large/small integrals and LAI large/small integrals increase at a rate of 0.96, 1.72, 2.23, and 3.13 per decade, respectively. Inner Mongolia experienced a noticeable greening process (71% and 82% greening area in NDVI large/small integrals, 67% and 73% greening area in LAI large/small integrals), despite the fragmentally distributed browning trends in eastern and partial northern Inner Mongolia. As inferred from nonlinear trend analysis, we found the greening process is still prevalent. The browning of eastern Inner Mongolia under the linear analysis was actually transferring from browning to greening, while the greening trend in northern Inner Mongolia was changing to browning. Increased occurrences in the frequency of breakpoints after 1999 suggest that previously stable vegetation ecology is more sensitive to external disturbances such as altered climatic impact and anthropogenic intervention.

Cadmium (Cd) contamination has become serious in soil and in situ stabilization technology has been widely used for heavy metal remediation. A field study was conducted to determine the effect of amendments with the doses of 3 kg/m2, including single vermicompost (A1), a 95% vermicompost mixed with 5% shell powder composite (A2) and a 95% vermicompost mixed with 5% modified shell powder composite (A3), on the Cd bioavailability, enzyme activity and bacterial community in soil, and the experiment was conducted with lettuce (Lactuca sativa L.) grown in a Cd-contaminated farmland soil. The results showed that the application of amendments increased the pH, cation exchange capacity (CEC), organic matter (OM), available nutrients, catalase (S-CAT), invertase (S-SC) and urease (S-UE) activities in soil, while significantly reduced the Cd bioavailability with the lowest Cd bioavailability being observed in the soil with A3 application. The soil bacterial richness and diversity increased after amendments application, and the bacterial community was characterized by an increase in metal-tolerant bacteria but a decrease in Proteobacteria, Acidobacteria and Gemmatimonadetes. In addition, the application of amendments significantly improved the growth of lettuce (Lactuca sativa L.) and inhibited Cd accumulation in its edible parts, especially, the Cd content in lettuce (Lactuca sativa L.) grown in soil with A3 application was below the limit of the National Food Safety Standard of China (maximum level ≤ 0.2 mg/kg). Thus, composite amendment obtained from vermicompost mixed with modified shell powder can be used as potential remediation material in Cd-contaminated soil. Capsule Composite amendment obtained from vermicompost and modified shell powder had good effects on remediation of Cd-contaminated soil.

The development of animal husbandry in China is facing enormous pressure from increasing demand of meat consumption, climate change, degrading grassland, and changing national policies. This paper presents the latest findings from an anthropological field investigation interviewing local herders, traders, and local officials from farming–pastoral ecotone in Inner Mongolia and shed lights on how locals have adapted their lives to climate change and the new national husbandry policies of the twenty-first century. Based on the anthropological interviews, we discussed the future opportunities and challenges of animal husbandry development in farming–pastoral ecotone. Results suggested that national ecological conservation policies and meat price have much larger impacts on animal husbandry than climate change, as perceived by locals. Family Fencing Policy, a relatively new policy aiming to avoid overgrazing and restore vegetation, was neither well accepted nor well implemented by the local herders. This is partially explained by the poor fencing technology, insufficient support facilities, as well as the high costs and low-profit margins in the animal husbandry. We conclude by suggesting that pastoralism in Northern China may greatly benefit from the development of rural cooperatives and active participation of locals in policy designing and implementation.

International research has focused more attention on arid and semiarid regions in recent years, as climate change has already had adverse impacts on grasslands and local households in the Mongolian plateau. Based on meteorological data, GIMMS AVHRR NDVI3g data, and livestock records, through statistical analysis, a significantly strong warming trend and a slightly decreasing trend in precipitation were ascertained in this region. Precipitation patterns are shifting, and intensifying, extreme events, such as droughts and dzud (extremely harsh winters characterized by heavy snow and low temperature), are a major threat to vegetation growth and animal husbandry development. Following a comparative analysis approach, we explored how the vegetation and animal husbandry response to climate change and extreme weather differ between Inner Mongolia and Mongolia. We found that vegetation growth generally decreased after the mid-1990s, but began to recover from 2001 over the entire region. The agricultural intensification level is higher in Inner Mongolia than in Mongolia, and residents in Inner Mongolia have a greater awareness of unexpected disasters than those in Mongolia. To deal with these challenges, this region warrants further study on how climate extremes will impact on regional animal husbandry and local social economics on the arid and semiarid regions. This could have implications for the international community, local government, local residents, and future scientific activities in this space.

Consumption of fossil fuel resources leads to global warming and climate change. Apart from the negative impact of greenhouse gases on the climate, the increasing emission of anthropogenic heat from energy consumption also brings significant impacts on urban ecosystems and the surface energy balance. The objective of this work is to develop a new method of estimating the global anthropogenic heat budget and validate it on the global scale with a high precision and resolution dataset. A statistical algorithm was applied to estimate the annual mean anthropogenic heat (AH-DMSP) from 1992 to 2010 at 1×1 km2 spatial resolution for the entire planet. AH-DMSP was validated for both provincial and city scales, and results indicate that our dataset performs well at both scales. Compared with other global anthropogenic heat datasets, the AH-DMSP has a higher precision and finer spatial distribution. Although there are some limitations, the AH-DMSP could provide reliable, multi-scale anthropogenic heat information, which could be used for further research on regional or global climate change and urban ecosystems.

Understanding the processes of historical land-use change is crucial to the research of global environmental sustainability. Here we examine and attempt to disentangle the evolutionary interactions between land-use change and its underlying causes through a historical lens. We compiled and synthesized historical land-use change and various biophysical, political, socioeconomic, and technical datasets, from the Qing dynasty to modern China. The analysis reveals a clear transition period between the 1950s and the 1980s. Before the 1950s, cropland expanded while forested land diminished, which was also accompanied by increasing population; after the 1980s land-use change exhibited new characteristics: changes in cropland, and decoupling of forest from population as a result of agricultural intensification and globalization. Chinese political policies also played an important and complex role, especially during the 1950s–1980s transition periods. Overall, climate change plays an indirect but fundamental role in the dynamics of land use via a series of various cascading effects such as shrinking agricultural production proceeding to population collapse and outbreaks of war. The expected continuation of agricultural intensification this century should be able to support increasing domestic demand for richer diets, but may not be compatible with long-term environmental sustainability.