ISWC OpenIR  > 水保所2018--届毕业生论文
自然降雨条件下黄土丘陵深层干化土壤水分运移试验研究
fu guo peng
Subtype硕士
2019-05-29
Degree Grantor中国科学院大学
Place of Conferral中国科学院教育部水土保持与生态环境研究中心
Degree Name农学硕士
Keyword黄土丘陵区 降雨 入渗 运移 土壤水分
Abstract

黄土高原丘陵区人工林地普遍存在土壤干化现象,并且随着时间的推移,干化现象有逐年加重的趋势,甚至出现永久性土壤干层。土壤干化问题的防治与恢复也成为生态学科与水土保持学科关心的热点问题。该地区地下水埋藏较深,且不具备灌溉条件,降雨是干化土壤水分的唯一补给来源。为了探索自然降雨条件下干化土壤水分的运移规律本文利用野外10m大型土柱模拟枣林地干化土壤,通过对土壤水分和气象要素的长期定位监测,探讨不同时间尺度下土壤水分的动态变化特征、单次降雨和累积降雨入渗深度及干化土壤水分恢复深度和程度,对当地干化土壤后期的恢复具有重要的理论和实践意义。试验主要得出以下结论:

10~1000cm土层周年土壤水分呈现明显的周期变化,4-11月,土壤水分持续上升;12-次年3月,土壤水分变幅较小。从整体看,土壤储水量呈现增长态势。休眠期平均蒸发量84.1mm,为同期降雨量的2.25倍,该时期是土壤水分损失期,且损失的部分主要来自0-300cm土层;生育期平均蒸发量288.1mm,为同期降雨量的0.56倍,生育期降雨贮存效率与同期降雨量呈正相关关系。

22015-2018年蒸发损失量分别为360.2384.2353.2367.7mm,年际差异不明显,与当年降雨量关系不明显;土壤水分四年补给量分别为74.6206.6266.4168.1mm,与当年降雨量成正比。降雨贮存效率及土壤水分恢复度均与降雨量成正比。

32015201620172018年年内单次降雨土壤水分最大入渗深度分别为4080120120cm。试验期间,无效入渗降雨次数为321次,有效入渗降雨次数为106次,降雨次数有效率为24.8%,降雨量有效率为62.7%。入渗深度在10~3030~6060~100120cm的降雨次数分别为613744次。单次降雨情况下,降雨量是影响单次降雨入渗深度最主要的因素,两者呈显著的正相关关系;前期土壤含水量是影响入渗深度的次要因子。单次有效入渗降雨的雨量(Pmm)与补给量(Wmm)呈明显的正相关关系,两者之间的关系为W=0.504P-2.774(R2=0.901,P<0.01)

42015-2018年土壤水分累积入渗深度分别为300400700900cm。深层土壤水分的入渗是多年累积降雨共同作用的结果。试验期间依据蒸发影响程度的大小可将土壤剖面分为:0~60cm为蒸发层,60~160cm为蒸发入渗混合层,160cm以下为入渗层。入渗深度(Z, m)与累积降雨量(x, mm)呈指数正相关关系:Z=1.2983e0.0009x(R2=0.9529)

5)试验初期,土壤干层分布在140~900cm土层,干层厚度为760cm;经过四年的降雨入渗补给,至2018年末,140~550cm土层土壤水分完全恢复,550~900cm土层土壤水分轻度亏缺。试验期间,土壤水分累积恢复度为87.07%0~1000cm土壤水分完全恢复还需要1年时间。

 

关键词:黄土丘陵区,降雨,入渗,运移,土壤水分

Other Abstract

Soil desiccation is a common phenomenon in the artificial forest in the hilly area of the Loess Plateau, and as time goes, the drying phenomenon tends to increase year by year, and even permanent soil drying layer appears. The prevention and restoration of soil drying has become a hot issue in the field of ecology and soil and water conservation. The groundwater in this area is deeply buried and does not have irrigation conditions. Rainfall is the only source of water supply for day soil. In order to explore the regularity of soil moisture movement under natural rainfall, the filed 10m soil column was used to simulate the drying soil of jujube forest land. Through long-term positioning monitoring of soil moisture and meteorological factors, the dynamic change characteristics of soil moisture at different time scales, the infiltration depth of single rainfall and cumulative rainfall, and the depth and degree of soil moisture recovery from drying were discussed. The study has important theoretical and practical significance for the late recovery of local dried soil. The main conclusions are as follows:

(1) The annual soil moisture of 0~1000cm showed obvious periodic change. From April to November, soil moisture continued to rise. From December to March, the variation of soil moisture is small. Overall, soil water storage showed an increasing trend. The average evaporation during dormancy period is 84.1 mm, which is 2.25 times of rainfall in the same period. Soil moisture loss is serious during dormancy period, and the loss mainly comes from 0~3 m soil layer. The average evaporation during growth period is 288.1 mm, which is 0.56 times of rainfall in the same period. Rainfall storage efficiency during growth period is positively correlated with rainfall in the same period.

(2) From 2015 to 2018, the evaporation water consumption was 360.2, 384.2, 353.2 and 367.7 mm, respectively, with no significant inter-annual difference and no obvious relationship with the current rainfall; the corresponding four-year recharge was 74.6, 206.6, 266.4 and 168.1 mm, which was in direct proportion to the current rainfall. Rainfall storage efficiency and soil moisture recovery are directly proportional to rainfall.

(3) The maximum soil water infiltration depth of single rainfall in 2015, 2016, 2017 and 2018 were 40, 80, 120 and 120 cm, respectively. During the experiment, 321 times of invalid infiltration rainfall, 106 times of effective infiltration rainfall, 24.8% of effective rainfall and 62.7% of effective rainfall were observed. Rainfall times with infiltration depth of 10~30, 30~60, 60~100 and 120 cm were 61, 37, 4 and 4, respectively. In the case of single rainfall, rainfall is the most important factor affecting the infiltration depth of a single rainfall, and there is a significant positive correlation between them; the soil moisture content in the early stage is the secondary factor affecting the infiltration depth. The rainfall (P, mm) of single effective infiltration rainfall is positively correlated with the recharge (W recharge, mm), and the relationship between them can be expressed by W recharge= 0.504P-2.774 (R = 0.901, P < 0.01).

(4) From 2015 to 2018, the accumulative infiltration depth of soil moisture was 300 cm, 400 cm, 700 cm and 900 cm, respectively. The infiltration of deep soil moisture is the result of years of cumulative rainfall. According to the degree of evaporation influence, the soil profile can be divided into 0~60 cm evaporation layer, 60~160 cm evaporation infiltration mixed layer and below 160 cm infiltration layer. Infiltration depth (Z, m) is positively correlated with cumulative rainfall (x, mm) exponentially:Z=1.2983e0.0009x(R2=0.9529)

(5) At the beginning of the experiment, the dry layer was distributed in 140~900 cm soil layer, with a thickness of 760 cm. After four years of rainfall infiltration recharge, by the end of 2018, the soil moisture of 140~550 cm layer was completely restored, and the soil moisture of 550~900 cm layer was slightly deficient. During the experiment, the cumulative recovery degree of soil moisture was 87.07%. It would take another year for 0~1000cm soil moisture to recover completely.

 

Key Words: Loess Hilly Region, Rainfall, Infiltration, Migration, Soil Moisture

MOST Discipline Catalogue农学::林学
Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8789
Collection水保所2018--届毕业生论文
Recommended Citation
GB/T 7714
fu guo peng. 自然降雨条件下黄土丘陵深层干化土壤水分运移试验研究[D]. 中国科学院教育部水土保持与生态环境研究中心. 中国科学院大学,2019.
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