Abstract
Soil moisture is a reliable water resource for plant growth in arid and semi-arid regions. Characterizing the interaction between soil moisture and vegetation is important for assessing the sustainability of terrestrial ecosystems. This study explores the spatiotemporal characteristics of four soil moisture layers (layer 1: 0–7 cm, layer 2: 7–28 cm, layer 3: 28–100 cm, and layer 4: 100–289 cm) and the time-lagged correlation with the normalized difference vegetation index (NDVI) for different vegetation types on an intra-annual scale on the Mongolian Plateau (MP). The most significant results indicated that: (1) the four layers of soil moisture can be roughly divided into rapid change (layers 1 and 2), active (layer 3), and stable (layer 4) layers. The soil moisture content in the different vegetation regions was forest > grassland > desert vegetation. (2) The soil moisture in layer 1 showed the strongest positive correlation with NDVI in the whole area; meanwhile, the soil moisture of layers 2 and 3 showed the strongest negative correlation with the NDVI mainly in grassland and desert, and layer 4 showed the strongest negative correlation with the NDVI in the forest. (3) Mutual responses of NDVI and deep layer soil moisture required a longer time compared with the shallow layer. In the annual time scale, the NDVI was affected by the change in soil moisture in most of the study area, except for coniferous forest and desert vegetation regions. (4) Under the different stages of vegetation change, the soil moisture changes advance than NDVI about 3 months during the greening stage, while the NDVI changes advance than soil moisture by 0.5 months during the browning stage. Regardless of the stage, changes in soil moisture are initiated from the shallow layer and advance to the deep layer. The results of this study provide deep insight into the relationship between soil moisture and vegetation in arid and semi-arid regions.
Highlights
Soil moisture is an important driver of the productivity and sustainability of terrestrial ecosystems [1,2], and a limiting factor for plant transpiration and photosynthesis, which determines the vegetation type and structure during ecological construction, in arid and semiarid regions [3]
We found that the changes in soil moisture at each level during the browning stage were less dynamic and decreased at a constant rate in that in the top 1 m layer being 2.5 months in northern China [66], so the deeper layer’s soil comparison with that during the greening stage
We investigated spatiotemporal soil moisture at consumption intensity during the different stages of vegetation changes
Summary
Soil moisture is an important driver of the productivity and sustainability of terrestrial ecosystems [1,2], and a limiting factor for plant transpiration and photosynthesis, which determines the vegetation type and structure during ecological construction, in arid and semiarid regions [3]. Vegetation in an ecosystem controls the soil moisture distribution pattern [4], and affects soil moisture to varying degrees in two opposing aspects through the ecological functions of water storage and conservation, and the absorption and consumption of soil moisture [5,6]. Different plant species cause different rainfall-runoff and evaporation, thereby inducing spatial distribution of soil moisture at various depths and different hydraulic properties [9,10]. We hope to discover the time-lagged correlation between soil moisture and vegetation, e.g. the correlation at the various soil depths, under the different vegetation types, and in different growth stages of vegetation, 4.0/).
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