Mesoscale spatial variability of soil‐water content in an alpine meadow on the northern Tibetan Plateau

Abstract

Soil water is an important limiting factor for restoring alpine meadows on the northern Tibetan Plateau. Field studies of soil‐water content (SWC), however, are rare due to the harsh environment, especially in a mesoscale alpine‐meadow ecosystem. The objective of this study was to assess the spatial variability of SWC and the temporal variation of the spatial variability in a typical alpine meadow using a geostatistical approach. SWC was measured using a neutron probe to a depth of 50 cm at 113 locations on 22 sampling occasions in a 33.5‐hm2 alpine meadow during the 2015 and 2016 growing seasons. Mean SWC in the study plot for the two growing seasons was 18.7, 14.0, 13.9, 14.3, and 14.8% for depths of 10, 20, 30, 40, and 50 cm, respectively, and SWC was significantly larger at 10 cm than at other depths. SWC was negatively correlated with its spatial variability, and the spatial variability was higher when SWC was lower. Thirty‐three sampling locations in this study plot met the requirement of accuracy of the central limit theorem. A Gaussian model was the best fit for SWC semivariance at depths of 10, 20, and 30 cm, and the spatial structural ratio was between 0.997 and 1, indicating a strong spatial dependence of SWC. The sill and range fluctuated temporally, and the nugget and spatial structural ratio did not generally vary with time. The sill was significantly positively correlated with SWC and was initially stable and then tend to increase with SWC. The nugget, range, and spatial structure ratio, however, were not correlated with SWC. These results contribute to our understanding of SWC spatial distribution and variation in alpine meadows and provide basic empirical SWC data for mesoscale model simulations, optimizing sampling strategies and managing meadows on the Tibetan Plateau.

Spatial Heterogeneity and Driving Factors of Soil Moisture in Alpine Desert Using the Geographical Detector Method

“…Compared with the previous studies, such as those of [35] and [44], the spatial heterogeneity of soil gravimetric water content in an alpine desert is higher than that in alpine meadows and shrubs. This condition depends mainly on the capability of soil water conservation and the sensitivity of vegetation cover to precipitation and perched aquifer.…”

“…The influencing factors of soil gravimetric water content are mainly natural and human factors, but most of the Qinghai-Tibet Plateau is dominated by natural factors [38]. Among the natural factors, the primary driver of the vegetation coverage factor is soil gravimetric water content [35]. In a previous study on soil gravimetric water content, the influence of climate factors on soil moisture is mainly reflected in the difference between water infiltration and evapotranspiration caused by rainfall and solar radiation [39].…”

“…On a small scale, soil types, topographic factors, and vegetation factors are the main factors affecting the soil water pattern; on a large scale, climatic factors, such as rainfall and evapotranspiration, are the main factors controlling the soil water pattern [24]. The impacts of soil types, vegetation factors, and topographic factors on soil water are generally consistent with depth, such that the variation in deep soil water mainly depends on soil types, vegetation, and topographic factors [2,35,[41][42][43]. Therefore, the factors adopted in this study are mainly different dune locations, vegetation, elevation, aspect, and slope.…”

“…The geographical detector method is used to explore the potential impact factors versus the spatial distribution of soil moisture and to identify each explanatory variable's relative importance [32]. In this study, the elevation, slope, location, vegetation, and aspect were selected as explanatory variables for considering being the main driving factors [2,[33][34][35].…”

Impacts of alpine meadow degradation on the soil moisture and hydrological processes in the three river source region on the Qinghai Tibetan plateau

“…It is a widespread land cover type comprising the representative vegetation of the plateau (Cao et al, 2004), which plays a very important ecological role in protecting water source conservation, preserving biodiversity, and maintaining soil carbon and nitrogen sequestration in the Three River Source Region (Wang et al, 2012; Yang et al, 2016). However, the alpine meadow is fragile and susceptible to climate change and human activities (Zhu et al, 2019). Due to the combined effects of global climate change, overgrazing, human activities and rodents, the alpine meadow in the Three River Source Region has experienced serious degradation during the past 40 years (Xue et al, 2009), and approximately 30% of the alpine meadow was degraded to “Black soil land”, which was also known as black soil‐type degraded grassland (Shang et al, 2008).…”