Understanding the feedback and reactions of soil moisture to meteorological factors in meteorological-hydrological processes is essential due to the growing importance of soil moisture in energy and water cycles in critical zones. Using soil moisture and meteorological data from 1984 to 2018, based on Mann-Kendall and Sen slope trend, two possible patterns of land–atmosphere interaction were discovered in the Yangtze River Basin (YRB), low soil moisture model with less precipitation and higher evapotranspiration, and high-temperature mode with less soil moisture and less evapotranspiration. To measure the hysteresis between soil moisture and precipitation, temperature, and evapotranspiration, a novel method named Three-Step Method was put out. The lag times were measured at ground stations spread across various climatic zones and timescales. The findings demonstrated that the lag times are generally controlled by the regional climate, with shorter lag times in drier regions. Both long-term and short-term responses were seen in soil moisture to meteorological variables. On a monthly scale, soil moisture correlated positively with precipitation but negatively with temperature and evapotranspiration. On an annual scale, precipitation (temperature, evapotranspiration) lagged by roughly 0 to 2 months in the upper and middle regions and by -2 to -6 months in the lower region of the YRB. The contribution rates of meteorological elements on soil moisture were enhanced by taking lag time into account. This study provides a unique perspective for better understanding climate process forecasts and related drought management by considering the hysteresis of soil moisture on the feedback and responses of climate variables.
Subsequent findings reveal the combination characteristics and spatial patterns of plant functional traits, and their response and adaptation to environmental changes in the Qinghai-Tibet Plateau. We analyzed the variation in characteristics and the influence of environmental factors on leaf functional traits from 78 quadrats in July 2021, using: one-way ANOVA, Tukey's Honest Significant Difference (HSD) post hoc test, Pearson correlation coefficient (r) analysis, and redundancy analysis (RDA) in the Qilian Mountains. Only the leaf carbon content (LCC) of arbors was a weak variation indicator in leaf function traits of different plant types, whereas other leaf function traits including: the LCC of herbaceous plants (herbs) and shrub plants (shrubs), and the leaf nitrogen content (LNC) and carbon to nitrogen (C/N) ratio of arbors were medium variation indicators. The LNC, leaf phosphorus content (LPC), C/N ratio(C/N), C/P ratio(C/P), and N/P ratio (N/P)of herbs and shrubs, and the LPC, C/P, and N/P of arboreal plants (arbors) were strong variation indicators. Altitude was also one of the main factors affecting functional traits of plants in cold regions. Electrical conductivity (EC) and soil phosphorus content (SPC) were the main factors affecting changes in the leaf functional traits of herbs. Soil bulk density (SBD) and Soil salinity (SAL) were the main factors affecting changes in the leaf functional traits of shrubs. Soil nitrogen content (SNC) and soil temperature (ST) were the main factors affecting changes in the leaf functional traits of arbors.
In this paper, the rainfall features in southwestern China are studied using daily rainfall station data. The rainfall features are distinct along the eastern and western edges of the Hengduan Mountains and over the mountains, especially in terms of rainfall frequency. The rainfall amounts and frequencies are much higher along the eastern and western edges than over the mountains, particularly during spring, which is partly contributed by the number and duration of rainfall events. The differences are more obvious in the nocturnal rainfall than in the daytime rainfall. The rainfall differences over the three regions could be affected by the large-scale environment. By analyzing reanalysis data, the large-scale circulations linked to the different rainfall features over southwestern China, and the interactions of these circulations with the topography are also discussed.
Plant functional traits are adaptive traits formed by interactions between plants and the environment. Considering the Three-River Headwaters Region as a case study, this study systematically analyzed the relationship between plant functional traits and environmental factors in cold regions. The results show that there were significant differences in plant functional traits among the different vegetation types (herbs, shrubs, and arbor plants). Leaf traits such as leaf area (LA), leaf length (LL), leaf width (LW), leaf circumference (LC), and shape coefficient (SC) showed the same trends among herbs, shrubs, and arbor plants. The correlation between leaf functional traits of plants in alpine regions shows that the unique growth mode of different plants and their degree of adaptation to alpine environments ultimately determine the leaf functional trait variations. Moreover, there was a negative correlation between soil temperature and the nitrogen balance index (NBI), chlorophyll content (Chl), flavonoid content (Flv), and SC, whereas there was a trend of first increasing and then decreasing relationship between soil temperature, LL (P < 0.05), and LC (P < 0.05). Similar to herb and shrub plants, arbor plants also showed significant differences in altitude in cold regions. There were significant negative correlations between altitude and NBI (P < 0.05), Chl (P < 0.05), Flv (P < 0.05), and anthocyanin content (P < 0.05), whereas LA (P < 0.05), LL (P < 0.05), and LC (P > 0.05) were significantly positively correlated with altitude. Conversely, there was no significant negative correlation between LW and altitude (P > 0.05). We conclude that climate factors play a decisive role in the distribution of plant functional traits at a global scale, whereas land use and disturbances play a major role at a regional scale, and topographic and soil factors determine the distribution of local characteristics.
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