毛乌素沙地杨柴和黑沙蒿灌丛土壤水分状况及水量监测

【目的】研究毛乌素沙地杨柴和黑沙蒿灌丛的土壤剖面水分状况和土壤水分消耗与平衡方式。【方法】以该区的杨柴灌丛、黑沙蒿灌丛、杨柴-黑沙蒿混生灌丛为研究对象,采用TDR法对土壤剖面监测水分,灌丛水量平衡方程计算土壤水分收支比。【结果】(1)0~300 cm土壤剖面水分含量随着土壤深度的增加先降低后升高,根据土壤剖面水分时空变化将土层大致分为速变层(0~40 cm)、活跃层(40~100 cm)、次活跃层(100~200 cm)和稳定层(200~300 cm)。速变层受降雨影响较大,在强降雨后,速变层不同样地土壤剖面出现多个“高水分中心”,稳定层土壤水分受植被生长影响较大,杨柴灌丛与混生灌丛土壤剖面出现多个“低水分中心”。(2)不同灌丛化样地对降雨的响应方式不同,裸地与杨柴灌丛对降雨的响应方式为脉冲式响应,混生灌丛与黑沙蒿灌丛对降雨的响应方式为延迟聚积式响应。(3)土壤活跃层(40~100 cm)土壤水分含量在趋势为黑沙蒿灌丛>杨柴-黑沙蒿混生灌丛>裸地>杨柴灌丛,在次活跃层(100~200 cm)土壤水分含量趋势为黑沙蒿灌丛>杨柴-黑沙蒿混生灌丛>杨柴灌丛>裸地,在稳定层(200~300 cm)水分土壤水分含量趋势为裸地>黑沙蒿灌丛>杨柴灌丛>杨柴-黑沙蒿混生灌丛。(4)2019年样地贮水变化量由大到小为黑沙蒿灌丛>杨柴-黑沙蒿混生灌丛>裸地>杨柴灌丛,黑沙蒿灌丛为积累水分型的灌丛,2019年共累积124 mm的降雨;混生灌丛为平衡水分收支型的灌丛,一部分水分进行贮藏另一部分进行蒸散;裸地与杨柴样地都为消耗水分型,蒸散量与全年降雨量大致相等。【结论】杨柴灌丛水分出现负平衡,大气-植被-土壤间的水分不能闭合循环,随着时间尺度增长,土壤水分的植被承载力达到极限,黑沙蒿群落合理的水分平衡策略驱动了杨柴群落向黑沙蒿群落的演替。

Soil Moisture Dynamics and Water Balance of Hedysarum mongolicum Turez and Artemisia ordosica Shrubs in Mu Us Sandy Land

【Objective】 To reveal the soil profile water status and soil water consumption and balance pattern of Hedysarum mongolicum Turez and Artemisia ordosica shrubs in Mu Us Sandy land. 【Methods】 His study took the Hedysarum mongolicum Turez shrubs, Artemisia ordosica shrubs and mixed shrubs as the research objects and TDR method was employed to monitor soil profile and the ratio of soil water storage revenue. Soil moisture ratio was calculated by water balance equation of shrubbery. 【Results】 (1)The soil moisture content of 0-300 cm soil profile first decreased and then increased with the increase of soil depth. According to the spatial and temporal changes of soil moisture, the soil layer could be roughly divided into: rapidly active layer (0-100 cm), secondary active layer (100-200 cm) and stable layer (200-300 cm). The fast-changing active layer was greatly affected by rainfall. After a heavy rainfall event, multiple "high-moisture centers" appeared in the soil profile of the fast-changing active layer. The soil moisture of the sub-active layer and the stable layer was greatly affected by vegetation growth. The soil profiles of Hedysarum mongolicum Turez shrubs and mixed shrubs showed multiple "low-moisture centers". (2)The response mode of bare land and Hedysarum mongolicum Turez shrubs were impulse response, while that of Artemisia ordosica and mixed shrubs was delayed accumulation response. (3) The soil moisture content of the fast-changing active layer (0-100 cm) tended to be: Artemisia ordosica shrubs > mixed shrub> bare land> Hedysarum mongolicum Turez shrubs; The soil moisture content of sub-active layer (100-200 cm) tended to be: Artemisia ordosica shrubs > mixed shrub> Hedysarum mongolicum Turez shrubs > bare land, and the soil moisture content of the stable layer (200-300 cm) tended to be: bare land > Artemisia ordosica shrubs > Hedysarum mongolicum Turez shrubs > mixed shrub. (4) In 2019, the change of water storage in the sample plots was from large to small: Artemisia ordosica shrubs > Hedysarum mongolicum Turez and Artemisia ordosica mixed shrubs > bare land > Hedysarum mongolicum Turez shrubs. Artemisia ordosica shrubs was the shrubs of water accumulation type, with a total rainfall of 124 mm in 2019; the mixed shrubs was a shrubs of water balance type, the part of water was stored and the other part was evapotranspiration; The bare land and Hedysarum mongolicum Turez shrubs sample plots were water consuming type, almost the same amount of moisture as rainfall used for evapotranspiration. 【Conclusion】 In this study area, there is a negative water balance ofHedysarum mongolicum Turez shrub, and the water between atmosphere, vegetation and soil can not recycle closely. With the increase of time scale, the vegetation carrying capacity of soil water in the study area reaches the limit. The reasonable water balance strategy of the Artemisia ordosica drives the succession of the Hedysarum mongolicum Turez shrubs to the Artemisia ordosica shrubs.