ABSTRACT
Soil moisture (SM) directly controls the land surface energy partition which plays an important role in the formation of extreme weather events. However, its dependence on specific climatic conditions is not thoroughly understood due to the complexity of soil moisture effects. Here, we examine the relationship between SM and surface energy partitioning under different climate conditions, and identify the influence paradigms of soil moisture on surface energy partition. We find that temperature changes can explicitly determine the impact paradigm of different physical processes, i.e. evapotranspiration, soil freezing and thawing, and such influence paradigms are also affected by atmospheric aridity (VPD). Globally, there are five paradigms that effects on surface energy partitioning, including the warm-wet paradigm (WW), transitional paradigm (TP), warm-dry paradigm (WD), cool-wet paradigm (CW) and cold paradigm (CP). Since 1981, the global area proportion for TP is observed to increase pronouncedly. We also find that the critical SM threshold exhibits regional variations and the global average is 0.45 m3/m3. The identified paradigms and their long-term change trends provide new insights into the global intensification of land-atmosphere interaction, which has important implications for global warming and the formation of heatwaves.
ABSTRACT
Soil moisture (SM) and atmospheric humidity (AH) are crucial climatic variables that significantly affect the climate system. However, the combined influencing mechanisms of SM and AH on the land surface temperature (LST) under global warming are still unclear. Here, we systematically analyzed the interrelationships among annual mean values of SM, AH, and LST using ERA5-Land reanalysis data and revealed the role of SM and AH on the spatiotemporal variations of LST through mechanism analysis and regression methods. The results showed that net radiation, SM, and AH could well model the long-term variability of LST well and explain 92% of the variability. Moreover, SM played an essential and different role under the different LST backgrounds. The AH always displayed a greenhouse effect on the LST. This study provides essential insights into the global climate change mechanism from the surface hydrothermal processes perspective.
ABSTRACT
To explore the effects of different long-term fertilization treatments on soil microbial diversity and community structure in the drylands of an agro-pastoral ecotone, a long-term fertilization experiment at the Inner Mongolia cultivated land conservation science observation and experiment station, Ministry of Agriculture, and rural areas was taken as the research object. Four treatments, including no fertilizer (CK), single nitrogen fertilizer (NF), single chemical fertilizer (CF), and the combined application of organic manure and chemical fertilizer (CFM), were selected for the collection of 0-10 cm and 10-20 cm soil at potato maturity 16 years after the experiment (2019). High-throughput sequencing technology was used to assess the soil bacterial and fungal communities to explore the effects of different fertilization measures on soil quality from the perspective of microorganisms, and the partial least squares path model (PLS-PM) was used to reveal the key environmental driving factors of soil microbial community alternation and crop yield improvement in dryland during fertilization mode transformation. The results showed that:â the CF and CFM treatments significantly improved soil fertility, but the effect of the latter was significantly better than that of the former. Soil available nitrogen, available phosphorus, and available potassium in the CFM treatment increased by 131.9%-174.7%, 216.9%-283.3%, and 103.3%-109.3%, respectively, and organic matter and total nitrogen content also increased significantly. The CF treatment still maintained a high soil pH, whereas the NF treatment significantly decreased soil pH and had little effect in improving soil fertility. â¡ Compared with that under CK, the NF treatment significantly reduced the soil bacterial Chao1 and Shannon index, and the CFM treatment significantly increased the soil bacterial species richness, Chao1 index, and soil fungal Shannon index, whereas soil bacterial and fungal diversity in the CF treatment did not reach a significant difference level with CK. ⢠The soil microbial community composition at 0-10 cm and 10-20 cm was similar. The CFM treatment increased the relative abundance of soil beneficial bacteria and decreased the relative abundance of pathogenic bacteria. The relative abundance of dominant bacteria such as Proteobacteria, Bacteroidetes, and Gemmatimonadetes increased. The relative abundances of Actinobacteria, Ascomycota, and Basidiomycota were decreased, whereas the NF and CF treatments showed the opposite trend. ⣠PLS-PM analysis showed that with the gradual change in fertilization mode from CKâNFâCFâCFM, the driving factors affecting microbial community succession and yield increase were also changed from soil pHâsoil NPK contentâsoil pH, SOM, and NPK content. In general, long-term fertilization had significant effects on soil chemical properties and microbial communities in drylands in the agro-pastoral ecotone. As the optimal fertilization choice, CFM was significantly better than NF and CF in improving soil fertility and inhibiting the growth of pathogenic microorganisms. The number of pathogens in long-term non-fertilization and unbalanced fertilization soil was significantly increased, and the risk of crop infection to indigenous diseases was increased. The research results can provide scientific reference for farmland nutrient balance management and soil microenvironment improvement of the agricultural ecosystem in the agro-pastoral ecotone in North China.
