Dynamics Of Soil Moisture And Response To Rainfall Of Secondary Forests In The Southern Part Of Daxing' Anling Mountains

In order to explore the soil moisture and response to rainfall of broad-leaved secondary forests in the southern Daxing'anling.The statistical characteristics of rainfall,soil moisture and soil moisture response to rainfall in this deciduous broad-leaved secondary forest were studied by statistical methods,and the influence law of soil water change characteristics was revealed.The results showed that:1.Characteristics of rainfall:The average rainfall in the study area from 2016 to 2017 was 355 mm,of which the rain frequency of light rain during the two years was 87.94%,and the contribution rate was 41.85%.The light rain mainly occurred in August and September,the rainfall frequency was 22.58%and 30.65%respectively,and the contribution rates were 30.46%and 28.81%respectively;the rain frequency of moderate rain was 10.64%,the contribution rate was 38.09%,and the moderate rain mainly occurred in July and August,the rainfall frequency was 33.33%and 26.67%respectively,and the contribution rates were 33.91%and 30.99%respectively;the rain frequency of heavy rain was 0%,the rainstorm frequency was less than 3%,and the rainstorm contribution rate was 20.06%.2.Dynamic characteristics of soil moisture:(1)Seasonal variation characteristics:The annual variation of soil water content ranges from 9.05%to 28.23%,and the soil moisture has obvious seasonal variation characteristics.The soil water content in September(21.42%),July(19.03%),June(16.71%),and August(16.52%)in descending order.(2)Vertical variation characteristics:The soil water content increases with the depth of the soil layer,according to the coefficient of soil water content variation,it is divided into:rapid change layer(0?10 cm),coefficient of variation is 26.67%;active layer(10-20 cm),coefficient of variation is 20.57%;the secondary active layer(20-40 cm),and coefficient of variation is 14.47%-17.48%.(3)Characteristics of slope change:There is no significant difference in the soil water content of each slope at each level(ca=0.05),and the slope position has little effect on soil water content.3.Response relationship between soil moisture and rainfall:Under light rain,moderate rain and rainstorm three kinds of conditions,different soil moisture level of the response to rainfall woodland canopy of order was small crown>medium crown>large crown,and the larger the crown canopy interception more significant role,the more obvious hysteresis;For the same level of canopy forest land,the response degree of soil water content to different grades of rainfall increases with the increase of rainfall,and the response of soil water content to single field rainfall decreases with the depth of soil layer,and The soil moisture within 0-20 cm soil layer of small crown forest land responded to a single rainfall of 3.5 mm,while the soil moisture in the medium crown forest land only 0-10 cm soil layer responded.The effective infiltration depth of rainfall in this area is mainly 0-20 cm soil layer.In summary,rainfall and canopy interception have a greater impact on the soil water content of the secondary forest,and the shallow distribution of the secondary forest roots has a greater correlation with rainfall and soil moisture in the area.