Stochastic modelling of soil water dynamics and sustainability for three vegetation types on the Chinese Loess Plateau

Abstract

Soil water dynamics play an active role in ecological and hydrologic processes. Soil water exhibits a stochastic nature because of the large temporal variations in precipitation and evapotranspiration. Objectives of this study were to analyse the probabilistic nature of soil water under three vegetation types, to simulate their probability density functions (PDFs) using a stochastic model, and to determine the most sustainable vegetation types. Soil water data were collected over a 3-year period with a bi-weekly frequency at plots in the Loess Plateau, China, under grass (Bothriochloa ischaemum L., BOI), shrub, sea-buckthorn (Hippophae rhamnoides L., SEB) and tree, Chinese pine (Pinus tabulaeformis Carr, CHP). The data were compared with values simulated using the Laio stochastic model. The results showed that the mean relative soil water contents differed in the order: BOI > CHP > SEB. Soil water was related to the daily rainfall and evapotranspiration. Under the same climate, topography and soil conditions, the soil water PDF was sensitive to a critical water content at which plants begin closing stomata and the mean maximum daily evapotranspiration rate. Based on the shape of the PDFs and their statistical moments, the Laio stochastic model accurately simulated the soil water PDFs under all three vegetation types in the semi-humid area of the Loess Plateau. The soil water PDFs for three vegetation types were simulated with four leaf area index scenarios; BOI and CHP were the most sustainable vegetation types compared with SEB in terms of maintaining soil water availability and soil erosion control.

Tradeoffs between soil conservation and soil‐water retention: The role of vegetation pattern and density

“…Overall, vegetation both promoted the recharging of soil water during the rainfall episodes and increased soil water consumption. These two processes highlighted the dual roles of vegetation density on soil water, which accords with earlier studies (Huang et al, 2014;Suo and Huang, 2019).…”

“…The reason for FULL having the largest EEW was that the plot had a dense enough vegetation cover for some to be redundant while it still consumed water (Ludwig et al, 1999;Suo & Huang, 2019). A threshold of vegetation coverage may exist above which SC gradually increases (Shachak et al, 1998;Yao et al, 2018).…”

Forecasts of Opportunity for Northern California Soil Moisture

“…As a result, many have approached the problem of predicting soil moisture with the notion that one must have considerable information about each of these factors. A number of studies have thus employed the soil water balance equation to explore the potential predictability of soil moisture based on stochastic rainfall inputs drawn from pre-determined distributions [1][2][3][4][5][6][7]. However, this approach must necessarily rely on a number of assumptions to represent the many controlling factors that act on soil moisture.…”

“…To their credit, these highly detailed models are firmly rooted in physical theory and perform reasonably well when their parameters are carefully tuned for specific sites [1][2][3][4][5][6][7]. However, as with any model, there are unavoidable downsides to this approach.…”