Study Of Mechanism Of Soil Water Change During Natural Vegetation Restoration In Ziwuling Forest Area On The Loess Plateau

The water resources in the Loess Plateau are relatively insufficient,and the soil water is seriously deficient.Coupled with human disturbance,the ecosystem is seriously damaged.How to use the limited soil water reasonably and effectively has become the focus of researchers.By combining field sampling and indoor analysis,we carried out a study on soil moisture and temperature changes that have a significant impact on natural vegetation restoration in Ziwuling forest area of the Loess Plateau,and analyzed the temporal and spatial changes of soil properties,including soil bulk density,particle composition,porosity,soil temperature,soil carbon,nitrogen and phosphorus.The interaction among soil moisture,temperature and soil characteristics in the process of natural vegetation restoration was determined,the coupling mechanism of soil moisture and soil temperature was clarified,and the variation mechanism of soil moisture and temperature under different natural succession vegetation was finally revealed.The results are helpful to provide theoretical basis for vegetation restoration and sustainable development on the Loess Plateau.The main conclusions are as follows:(1)There are significant differences in soil moisture and soil chemical properties of different vegetation types during natural vegetation restoration.With the restoration of natural vegetation,soil organic carbon in 0-200 cm soil layer decreased with the increase of soil depth.In 0-20 cm soil layer,total phosphorus and soil water content of Quercusliaotungensis community were the highest,soil organic carbon content of Hippophaerhamnoides community was the lowest,soil total nitrogen content of Populus davidiana and Quercusliaotungensis mixed forest community was the lowest,and soil water content of grassland community was the lowest.With the increase of soil depth,soil total nitrogen,carbon phosphorus ratio,nitrogen phosphorus ratio,total phosphorus gradually decreased,and tended to remain unchanged below 60 cm soil layer.With the restoration of natural vegetation,the soil moisture content in 0-200 cm soil layer increased with the increase of soil depth.Soil total nitrogen,soil total phosphorus,soil organic carbon,soil C/N ratio,N/P ratio and soil water content were significantly negatively correlated.(2)In the process of natural vegetation restoration,there are significant differences in soil physical properties of different vegetation types.From grassland to forestland,long-term natural vegetation restoration had significantly improved soil physical properties.In terms of soil particle composition,sand had the highest content compared with clay and silt.The clay and silt contents of Bothriochloa ischemum community in 0-10 cm and 10-20 cm soil layers were the highest.With the deepening of soil layer,the total soil porosity increased significantly.In 0-10 cm soil layer,the highest value was found in Populus davidiana and Quercusliaotungensis mixed forest community and Hippophaerhamnoides forest community,and the lowest value was found in Populus davidiana forest community.In 20-30 cm soil layer,the highest value was found in Quercusliaotungensis community.In the 0-10 cm soil layer,soil bulk density from Bothriochloa ischemum community to Quercusliaotungensis community decreased significantly with vegetation restoration.In the 10-20 cm soil layer,the Bothriochloa ischemum community was the highest and significantly higher than other communities.There was a significant negative correlation between soil water content and soil bulk density,clay content and silt content,and a significant positive correlation between soil water content and sand content.(3)There were significant differences in soil moisture and soil temperature among different vegetation types during natural vegetation restoration.It was found that soil moisture decreased gradually with vegetation recovery in rainy August and less rainy November.On the contrary,with the restoration of natural vegetation in rainy September and less rainy October,there was no significant difference in soil moisture,and the change trend was the same.The soil water content of Bothriochloa ischemum community was significantly higher than other communities during the whole study period(August to November).The results showed that soil moisture would decrease with vegetation restoration to a certain extent,but its general trend over time was not affected,with a certain time stability.The soil temperature of Bothriochloa ischemum community was the highest in August to October,which was higher than that of other communities,and Quercusliaotungensis community was the highest in November.In general,soil temperature changes gradually weakened with vegetation recovery.In addition,in this study,the correlation between soil temperature and water in the top community was more significant,and the correlation between soil temperature and water in the three soil layers of 0-10 cm,10-20 cm and 20-30 cm tended to be similar.