Effect of Grass Components on the Temporal Response of Surface Soil Water to Precipitation and Air Temperature in the Loess Plateau

Abstract

The Loess Plateau of China is facing increasingly serious challenges related to water shortage issues despite the successful vegetation restoration. Surface soil water (0–40 cm) is crucial to water transfer and discharge in the soil-plant-atmosphere continuum, which is controlled by precipitation (P), air temperature (Ta), and plant components. This study selected one typical grass species and set different treatments of natural condition (NC), removing litter (CR), and only roots (OR), to analyze the responses of soil water storage (W) and its change (∆W) to P and Ta at different time scales (including daily, weekly and monthly scales). The results showed that P had significantly positive effects on W and ∆W, while Ta negatively influenced W and ∆W. Meanwhile, Ta also controlled the significance of P affecting W. P contributed more (53–63%) to ∆W variation at the daily scale, but Ta showed more effect (73–80%) at the weekly scale, and both of them contributed more than 77% at the monthly scale. P and Ta existed a threshold phenomenon for increasing soil water, where P thresholds were higher than 0.93, 4.98, and 28.17 mm and Ta threshold were lower than 28.69, 28.89, and 29.96°C at the daily, weekly and monthly scales, respectively. Moreover, grass components also affected the responses of ∆W to P and Ta, and the OR treatment displayed the lowest sensitivity and had the lowest loss rate of soil water. The total infiltration, total loss amount, and rainwater retention rate exhibited: NC > CR > OR. Overall, grass canopy and litter improved soil water condition, and the roots most strongly protected soil water after infiltration. This study can provide a better understanding of surface soil water responding to climate change under drought stress with water shortage implications, and may strength the management of grassland in semi-arid region.

Sub-Shrub Components Change the Soil Water Storage Response to Daily Precipitation and Air Temperature in the Loess Plateau

“…Through an analysis of the processes (infiltration, loss and retention) of soil water storage, we found that the final order of the rainwater retention rate was NC (26.43%) > OR (13.71%) > CR (4.58%) in sub-shrub land, which differs from that in grassland [38]. The roots were useful for soil water conservation during the whole growing season, the canopy showed a negative effect on conserving soil water since it depleted the increased amount of infiltration derived from the roots, and the litter generally improved soil water by offsetting the water depletion of the canopy.…”

“…The litter is beneficial as it shelters the soil to reduce soil evaporation and reduces soil water loss from solar radiation; meanwhile, it also improves soil properties to increase infiltration and reduce runoff. The roots provide channels for water infiltration [38,39]. Consequently, different components have different functions in soil water infiltration or loss.…”