Search

Compound droughts and heatwaves (CDHWs) are likely to cause more severe natural disasters than a single extreme event, and they have been exacerbated by rapid global warming. Based on high-resolution grid data, this study combines the daily-scale ERA5-Land dataset and the monthly-scale SPEI dataset with multiple indicators to analyze CDHWs. We calculated and analyzed the temporal and spatial modal distribution of CDHWs in Central Asia from 1981 to 2018, and in this paper, we discuss the sequence relationship between drought events, heatwave events, and CDHWs. The results show that the number of CDHWs in the study region have increased over time and expanded in terms of area, especially in eastern and southwestern Central Asia. The tsum (total frequency of CDHWs) was 0.5 times higher than the total heatwave frequency and it increased at a rate of 0.17/yr. The maximum duration of tmax (maximum duration of CDHWs in days) was 17 days. Furthermore, the occurrence rate of tmax was 96.67%, and the AH (CDHWs' accumulated heat) had a rate of 97.78%, which, upon examination of the spatial trend pattern, accounted for the largest increase in terms of area. We also found that the TAH (CDHWs' average temperature anomalies, SPEI < −0.5) shows obvious seasonality, with the increases in winter and spring being significantly greater than the increases in summer and autumn. The intensity of the CDHWs was stronger than that of a single extreme event, the temperature anomaly was higher than the average of 0.4–0.8 °C, and there was a north–south spatial pattern across the study region. In eastern and northwestern Central Asia, the AH and heatwaves (SPEI < −0.5) increased by 15–30 times per year on average. During the transition from the base period to the reference period, CDHWs increased by 25%, and the number of dry days prior to the CDHWs decreased by 7.35 days. The conclusion of our study can provide a theoretical basis for coping with climate change in arid zones. [ABSTRACT FROM AUTHOR]

• Heatwaves in CA are becoming earlier, more frequent, more intense, more persistent. • Heatwaves are more frequently observed in the west but less in the central CA. • Soil moisture depletion is the main factor in formulating heatwaves in CA. Heatwaves pose increasing threats on water resources for ecosystems and human consumption especially in arid region, such as Central Asia (CA). As the hinterland of Eurasia, water scarcity and land degradation in CA have increased its vulnerability to heatwaves. While the frequency of heatwaves has been examined, more heatwave metrics such as timing are less known, possible influences of soil moisture on heatwave changes in this region are not fully understood. Using reanalysis and observational datasets, here we examine the spatial–temporal changes of heatwaves in CA during 1981–2020 and the role of various associated factors including soil moisture. The results show that the extreme heatwaves occurred more frequently in northwestern Kazakhstan. Temporally, heatwaves have been intensifying with significant increases in frequency (0.10 events/year), intensity (0.81 °C/year), and duration (0.08 days/year) since the 1980 s, and these trends have accelerated since 1997. The first yearly heatwave event tended to occur earlier in more recent decades, indicating an advanced heatwave season. We also found that the heatwave occurrences were significantly correlated with hydro-meteorological factors. In northwestern of CA, extreme heatwaves are exacerbated by a rapid decrease in soil moisture resulting from reduced precipitation and increased solar net radiation in this area. Our findings provide a scientific basis for understanding the mechanisms and predictions of heatwave in arid regions from the climate change perspective. [ABSTRACT FROM AUTHOR]

[Display omitted] • Long-term land use change from paddy land (PL) to dry land influenced soil microbiota and physicochemical properties. • Conversion to dry lands decreased bacterial diversity and evenness in 3 years, while it significantly increased in 5–10 years. • Conversion to dry lands increased fungal diversity and evenness in 3, 5, and 10 years. • Conversion to dry lands increased relative abundance of Nitrospirae , Chloroflexi , Proteobacteria , and Basidiomycota. Agricultural land use changes are essential in addressing global urbanization demands. The improper management of agricultural land may lead to the alteration of the microbial ecosystem, which ultimately affects soil quality. Here, we assessed how soil microbial diversity, communities, and physicochemical properties in three layers of soil; upper (0–15 cm), middle (15–30 cm), and lower (30–45 cm), responded to a long-term land use change from paddy land (PL) to dry land of different chronosequences; PD3 (3 years), PD5 (5 years), and PD10 (10 years). We found PL conversion into dry lands increased soil pH, soil 3 phase R-value, bulk density (BD), organic matter (OM), total phosphorus (TP), total nitrogen (TN), and decreased electrical conductivity (EC), water holding capacity (WHC), and moisture content (MC) in all three layers. The land use change from PL to dry lands initially (PD3) decreased (11–25 %) bacterial diversity, while it significantly increased in PD5 (0.1–16 %), and PD10 (1–14 %) in all three layers. Unlike bacterial diversity, fungal diversity was high in PD5 in the upper layer, while the middle and lower layer was the least affected. We also found the conversion of PL to dry land altered relative abundance (RA) of bacteria on the upper layer, while RA of fungi was reshaped in all three layers. The Pearson's correlation coefficient showed that MC, OM, pH, R-value, TN, TP, and WHC were important physicochemical factors, which significantly (P < 0.05) influenced Nitrospirae , Chloroflexi , Proteobacteria , and Basidiomycota composition. Briefly, our study show that land use change initially (3 years) caused huge changes in the microbiome, which improved somehow in further years (5 and 10 years), and we conclude that land use changes impact positively on functional biodiversity and biological quality of the soil. [ABSTRACT FROM AUTHOR]