水保所知识产出(1956---)知识库

对黄土塬区不同土地利用方式下 2012 年 3—10 月 7 龄果园(挂果初期)、17 龄果园(盛果期)、小麦地、玉米地土壤水文状
况进行分析，结果显示，0—600 cm 试验土层 7 龄果园土壤贮水量最高，其次为玉米地、小麦地，17 龄果园最低，且不同土地利用
方式下贮水量随着降水量的变化而上下波动，但其变化滞后于降水。不同土地利用方式均表现为随土壤深度增加土壤含水量
变异程度减弱的特征，且其土壤剖面的水分含量变化存在季节变异。农田和 7 龄果园中不存在土壤干燥化现象，而 17 龄果园
土壤剖面存在较厚的干燥化土层，其分布深度为 320—600 cm。不同的土地利用方式的土壤水分的消耗和补充深度有较大差
异，17 龄果园消耗深度为 500 cm，补充深度为 200 cm;7 龄果园、玉米地和小麦地消耗深度分别为 200、300 cm 和 300 cm，且补充
深度均超过了测定的土壤深度，大于 600 cm。

 Soil moisture has large impacts on agricultural production and regional ecosystems． The Loess Tableland was
selected as the study area，and the characteristics of soil moisture in different land use types were measured and analyzed
from March to October 2012． The objectives of this study were to characterize the dynamic changes in soil water，determine
the soil moisture depletion and replenishment depths，and compare the differences in water consumption under the different
land uses． The results showed that: (1) Soil moisture content recorded in the 0—600 cm layer in a 7-year-old apple
orchard was the highest，followed by that in a corn field，wheat field，and a 17-year-old apple orchard． Soil moisture
contents in different land use types had the same variation trends as precipitation during the observation period，but their
responses lagged changes in precipitation． (2) Soil moisture variation declined with increasing soil depth in different land
use types． The variation in surface soil water content was greater than that of deep soil water content because the surface
layer (0—100 cm) was influenced by multiple processes，including rainfall infiltration，soil evaporation，and plant root
water uptake． Soil moisture was less affected by outside conditions as soil depth increased; therefore，soil moisture tended to
be relatively stable． In addition，because of complicated functions of plant growth regulation and local phenological   characteristics，seasonal variation was also observed in the soil water profile in each land use type． The shape of the average
soil moisture profile for the 7-year-old apple orchard was an S-type curve，while the soil moisture profile for the 17-year-old
apple orchard showed an initial decrease，followed by an increase and a final decrease． The deep soil moisture stabilized
around 13．5%． The shapes of the soil moisture profile in wheat and corn fields were similar; they both increased at first and
then decreased． (3) No soil desiccation occurred in farmland or in the 7-year-old apple orchard，while relatively deep
desiccated soil layers existed in the 17-year-old apple orchard at depths of 320—600 cm． This was because the water
consumption in the 17-year-old apple orchard was greater than water replenishment． In lower rainfall years，the precipitation
was not enough to meet the demand from tree growth，so water stored in deep soil was used． Due to the limitation of rainfall
infiltration depth，it was hard for water to be replenished once it was depleted． Thus，desiccated soil layers formed under
continuous dry years． (4) There were some differences between the soil moisture depletion and replenishment in different
land use types． The depths of soil water depletion in the 7-year-old apple orchard，corn field，and wheat field were 200 cm，
300 cm，and 300 cm，respectively，and their replenishment depths were beyond the measured depth of 600 cm． Their deep
soil moisture conditions got compensation and improvement after the seasonal precipitation． The depth of soil water depletion
in the 17-year-old apple orchard was 500 cm，while the replenishment depth was about 200 cm． As the replenishment depth
was less than the consumption depth，the desiccated soil layers already present in the 17-year-old apple orchard will
continue to exist for some time if there is no human intervention．