The Spatial Distribution and Temporal Stability of Soil Water Content During Monsoon Season in Forested Slopes on the Loess Plateau, China

黃土高原林地坡面雨季期土壤水分空間分佈及時間穩性

王添(TIAN WANG) ； 徐國策(GUOCE XU) ； 李鵬(PENG LI) ； 李占斌(ZHANBIN LI) ； 任宗萍(ZONGPING REN) ； 魯克新(KEXIN LU) ； 蘇遠逸(YUANYI SU) ； 王飛超(FEICHAO WANG)

《台灣水利》 68卷2期 (2020/06) Pp. 88-102

https://doi.org/10.6937/TWC.202006/PP_68(2).0008

摘要

Altitudinal patterns in soil water content (SWC) have an important role in ecological and hydrological processes. SWC is the primary restrictive factor affects the vegetation restoration on the Loess Plateau, China. It is necessary to fully clarify the changes in temporal and spatial stability of SWC within the whole slope which facilitate the understandings of SWC dynamics that affect the vegetation restoration. The current research investigated the spatial distribution of SWC, its temporal stability, and to evaluate the factors that affect SWC temporal stability on a forested slope of the Loess Plateau during the monsoon season. The SWC at interval of 0.2 m within a 0-1.6 m soil vertical profile was measured at 21 positions on the hillslope with the growth Chinese pine (Pinus tabulaeformis Carr). The result showed that average SWCs at all soil depths were low and demonstrated moderate spatial variability. SWC in three soil depths were observed: SWC increases when the depth was 0 to 0.6 m; decreases in 0.6 to 1.0 m layer; and slowly increases in 1.0 to 1.6 m layer. The average soil water content reached the lowest at the mid-slope point. The SWC in every soil layer showed strong temporal stability. With the increase of soil layer, the degree of temporal stability became stronger. The representative position of SWC varies with increasing depth. There was no significant difference root mean square error (RMSE) and mean absolute error (MAE) values of the eight layers for both the period of entire year and monsoonal (p ＞ 0.05), which suggested that seasonal variation had no significant effect on the SWC of different locations. The best representative location could accurately assess the average SWC. The mean relative difference (MRD) was significantly positively correlated with the content of clay and silt and significantly negatively correlated with the content of sand. The clay content, silt content, elevation, soil organic and root density significantly positively affected the standard deviation of the relative differences (SDRD). In conclusion, SWC exhibited strong spatial and temporal patterns at different soil depths and hillslope locations after rainfall.

關鍵字

Soil water content ； Forestland ； Temporal stability ； Spatial distribution ； Hillslope

並列摘要

土壤含水量在生態水文過程中起著重要作用，是黃土高原植被重建的首要限制性因素。因此，掌握坡面土壤含水量的時空動態變化是十分必要的。本文調查研究了雨季時期黃土高原坡面林木的土壤水分的空間分佈和時間穩定性，進一步分析了影響其時空穩定性的因素。在生長著中國油松的坡面上選取了21個監測點，沿0-1.6 m的土壤剖面來測量8個土層的含水量。結果表明：所有土層的土壤含水量較低，且呈現中等變異。土壤含水量在0-1.6 m的土壤深度呈現3種變化趨勢：0-0.6 m土層呈現增長趨勢，0.6-1.0 m土層呈現下降趨勢，1.0-1.6 m土層呈現緩慢增長趨勢。坡面中間位置監測點的平均土壤含水量最低。土壤含水量在空間上呈現出強烈的時間穩定性，且隨著土壤深度的增加土壤含水量的時間穩定性增強。土壤含水量的代表性位置點隨著土壤深度的增加而變化。全年和雨季期在8個土層的土壤含水量沒有顯著性差異。最佳代表性位置點能夠準確地評價區域平均土壤含水量。平均相對差分與土壤黏粒和砂粒含量分別呈現顯著的正和負的相關性。土壤粉粒，黏粒，高程，土壤有機碳和根系密度顯著影響相對差分的標準差。總之，雨後土壤含水量在不同土壤深度和坡面位置上呈現出強烈的時空穩定性。

並列關鍵字

土壤含水量 ； 林地 ； 時間穩定性 ； 空間分佈 ； 山坡

參考文獻

Biswas, A.,Si, B.C.(2011).Scale and locations of time stability of soil water storage in a hummocky landscape.Journal of Hydrology.408,100-112.

Brocca, L.,Melone, F.,Moramarco, T.,Morbidelli, R.(2010).Spatial-temporal variability of soil moisture and its estimation across scales.Water Resources Research.46(2)

Cao, C.,Jiang, S.,Ying, Z.,Zhang, F.,Han, X.(2011).Spatial variability of soil nutrients and microbiological properties after the establishment of leguminous shrub Caragana microphylla Lam. plantation on sand dune in the Horqin Sandy Land of Northeast China.Ecological Engineering.37(10),1467-1475.

Chaney, N.W.,Roundy, J.K.,Herrera-Estrada, J.E.,Wood, E.F.(2015).High-resolution modeling of the spatial heterogeneity of soil water: applications in network design.Water Resources Research.51,619-638.

Chen, H.,Shao, M.,Li, Y.(2008).Soil desiccation in the Loess Plateau of China.Geoderma.143(1-2),91-100.