黄土丘陵区主要树种土壤水分动态变化特征及影响因子

为揭示黄土丘陵区土壤贮水状况与植被生长的关系,得到该区最优适生树种,以4类树种作为研究对象,基于ECH₂O-5TM监测系统和U30-NRC气象站2019—2020年每30 min数据,采用Excel和SPSS对土壤体积含水量、降雨、空气温度、空气相对湿度进行月、季节尺度处理,运用多重差异性比较和曲线估算阐释了该区土壤水分时间变化特征及其与影响因子的关系。结果表明:(1)刺槐(Robinia pseudoacacia)、辽东栎(Quercus wutaishanica)、侧柏(Platycladus orientalis)土壤水分分为耗损期(5—10月)、衰退期(10月—次年1月)、提升期(2—4月)及低位期(3—5月),油松(Pinus tabuliformis)和撂荒地对照(CK)在1—5月则表现为稳升期,各树种土壤水分和降雨存在约30 d的滞后时差。(2)50—80 cm土壤剖层处于水分高峰,随着深度的增加,不同树种土壤水分存在正负变化趋势; 油松土壤水分在表层(20 cm)变异程度最弱。(3)全年与非生长季时期辽东栎土壤水分状况最佳,生长季时期辽东栎、撂荒地对照和油松土壤水分显著大于其余树种,同树种不同时期土壤水分未表现出显著差异。(4)不同树种土壤水分与温度呈负相关性,与降雨和湿度表现为正相关关系,土壤水分与降雨量之间存在阈值(约70 mm)。综上,黄土丘陵区主要树种土壤水分在生长季时期变化最为显著,辽东栎和油松土壤水分在不同时间阶段均较为充沛,可作为当地贮水保水树种选择。

Dynamic Changes and Influencing Factors of Soil Moisture of Main Tree Species in Loess Hilly Region

In order to reveal the relationship between the soil-water storage status and vegetation growth in the Loess Hilly Area, and obtain optimal suitable tree species in the area, four types of tree species were taken as research objects. Based on the ECH₂O-5TM monitoring system and the U30-NRC weather station's data every 30 min from 2019 to 2020, the temporal variation characteristics of soil-water in this area and its relationship with the influencing factors were explained by using Excel and SPSS in order to process the soil volume water content, rainfall, air temperature, air relative humidity on monthly and seasonal scales, and multiple difference comparisons and curve estimation. The results showed that:(1)Soil moisture of Robinia pseudoacacia, Quercus wutaishanica and Platycladus orientalis was divided into a loss period(May—October), a recession period(October—January of the following year), an ascending period(February—April)and low-level period(March—May), Pinus tabuliformis and abandoned land control(CK)showed a steady ascending period from January to May, and there was a 30-day lag time difference between soil moisture and rainfall for each tree species.(2)The 50—80 cm soil section was at the peak of water content. With the increase of depth, the soil water content of different tree species had a positive and negative trend. The soil water content of Pinus tabuliformis had the weakest variation in the surface layer(20 cm).(3)The soil moisture status of Quercus wutaishanica was the best in whole year and non-growing season. During the growing season, the soil moisture of Quercus wutaishanica, CK and Pinus tabuliformis was significantly higher than that of other tree species. There was no significant difference in soil moisture of the same tree species in different periods.(4)The soil moisture of different tree species was negatively correlated with temperature, and positively correlated with rainfall and humidity. There was a threshold(about 70 mm)between soil moisture and rainfall. In conclusion, the soil moisture of the main tree species in the Loess Hilly Area changed most significantly during the growing season, and the soil moisture of Quercus wutaishanic and Pinus tabuliformis were abundant in different time periods, which can be selected as local water-storage and water-retention tree species.