[Theoretical basis of ecology for the influence of global change on resources, environment, and ecosystems.] / å ¨çƒå˜åŒ–å¯¹èµ„æºçŽ¯å¢ƒåŠç”Ÿæ€ç³»ç»Ÿå½±å“çš„ç”Ÿæ€å­¦ç†è®ºåŸºç¡€.

With the deepening of global change research, the applied problems such as global change risk and response for social sustainable development, temporal and spatial allocation of resources and environmental elements and impact assessment of ecosystem are becoming a new trend in the research field of global change. Based on the ecological framework, we focused on clarifying the connotations of resources and the environment and their components. Resources refer to all substances consumed by organisms in the process of producing organic matter from inorganic matter and transferring energy and matter among organisms. These include inorganic resources (e.g., solar radiation, CO2, O2, water, and mineral elements) and organic resources (as a source of food for other organisms). In contrast, the environment can not be consumed or depleted by organisms. In addition, we described the components of global change and the associated variations of resources and environmental factors, as well as current research progress on the responses of ecosystem to global change. We scientifically described the processes and mechanisms of global change in terms of their influence on resources, the environment, and ecosystems within a theoretical framework based on ecological principles. Our goal was to provide a strong theoretical foundation for future research on coping with the risks of global change.

Variations in seasonal and inter-annual carbon fluxes in a semi-arid sandy maize cropland ecosystem in China's Horqin Sandy Land.

Sandy cropland ecosystems are major terrestrial ecosystems in semi-arid regions of northern China's Horqin Sandy Land, where they play an important role in the regional carbon balance. Continuous observation of the CO2 flux was conducted from 2014 to 2018 using the eddy covariance technique in a sandy maize cropland ecosystem in the Horqin Sandy Land. We analyzed carbon fluxes (the net ecosystem exchange (NEE) of CO2, ecosystem respiration (Reco), and the gross primary productivity (GPP) and their responses to environmental factors at different temporal scales using Random Forest models and correlation analysis. We found that the sandy cropland was a carbon sink, with an annual mean NEE of -124.4 g C m-2 yr-1. However, after accounting for carbon exports and imports, the cropland became a net carbon source, with net biome production ranging from -501.1 to -266.7 g C m-2 yr-1. At a daily scale, the Random Forest algorithm revealed that photosynthetic photon flux density, soil temperature, and soil moisture were the main drivers for variation of GPP, Reco, and NEE at different integration periods. At a monthly scale, GPP and Reco increased with increasing leaf area index (LAI), so the maize ecosystem's carbon sequestration capacity increased with increasing LAI. At an annual scale, water availability (precipitation and irrigation) played a dominant role in explaining inter-annual variability of GPP and Reco. Affected by climate (e.g., precipitation) and field management (e.g., cultivation, irrigation), carbon fluxes differed greatly between years in the maize system.

Temporal and spatial variation of extreme temperatures in an agro-pastoral ecotone of northern China from 1960 to 2016.

The agro-pastoral ecotone of northern China is one of the areas most sensitive to global temperature change. To analyze the temporal and spatial trends of extreme temperature events in this area, we calculated the values of 16 extreme-temperature indices from 1960 to 2016 based on data from 45 national meteorological stations. We found that the coldest-temperature indices decreased significantly and the warmest-temperature indices increased significantly. The warming of night temperatures contributed more than warming of day temperatures to the overall warming trend. In addition, the warm-temperature indices appeared to be increasing since the late 1980s and early 1990s. Overall, though the four extremal indices showed an increasing trend, the rate of change in the minimum temperature was greater than that of the maximum temperature; thus, the minimum temperature contributed most strongly to the overall temperature increases. The growing season is being prolonged in higher-elevation areas, but vegetation maturation in lower-elevation areas has been accelerated by the high temperatures, potentially leading to a shorter growing season at low altitudes. However, the impacts of land-use changes caused by human activities on the temperature increases will require additional study.

Spatial pattern of soil organic carbon and total nitrogen, and analysis of related factors in an agro-pastoral zone in Northern China.

The spatial pattern of soil organic carbon (SOC) and total nitrogen (TN) densities plays a profound important role in estimating carbon and nitrogen budgets. Naiman Banner located in northern China was chosen as research site, a total of 332 soil samples were taken in a depth of 100 cm from the low hilly land in the southern part, sandy land in the middle part and an alluvial plain in the northern part of the county. The results showed that SOC and TN density initially decreased and then increased from the north to the south, The highest densities, were generally in the south, with the lowest generally in the middle part. The SOC and TN densities in cropland were significantly greater than those in woodland and grassland in the alluvial plains and for Naiman as a whole. The woodland SOC and TN density were higher than those of grassland in the low hilly land, and higher densities of SOC and TN in grassland than woodland in the sandy land and low hilly land. There were significant differences in SOC and TN densities among the five soil types of Cambisols, Arenosols, Gleysols, Argosols, and Kastanozems. In addition, SOC and TN contents generally decreased with increasing soil depth, but increased below a depth of 40 cm in the Cambisols and became roughly constant at this depth in the Kastanozems. There is considerable potential to sequester carbon and nitrogen in the soil via the conversion of degraded sandy land into woodland and grassland in alluvial plain, and more grassland should be established in sandy land and low hilly land.