东北黑土漫岗区春耕期土壤水分空间变异及地形影响

Spatial Variability and Its Controlling Topographic Factors of Soil Moisture During Spring Plowing Season in Black Soil Hilly Region of Northeast China

土壤水分存在强空间变异特征,在多重尺度上受地形、土壤、土地利用、植被等因素综合影响,是农业生产和耕作的关键要素。为了揭示东北黑土漫岗区春耕期农田土壤水分空间变异特征及分析地形因子对其影响,以赵光农场为研究对象,利用Sentinel-1数据反演的土壤水分和DEM数据,采用半方差函数、集成推进树算法(ABT)等方法分析了春耕期土壤水分的空间变异及地形因子(坡度、坡向、坡位、高程、地形湿度指数)对土壤水分空间异质性的相对影响,并系统分析了土壤水分在不同坡位、坡度和坡向的变化特征。结果表明:研究区2018年4月24日处于春耕时期黑土漫岗区的土壤质量含水量分布在25%~37%;地块内部变异系数为5.81%,相邻地块间变异系数为4.16%;针对整个农场尺度土壤水分空间变异的有效变程为3000 m,地块尺度上有效变程为300 m。土壤水分分布与地形湿度指数呈显著正相关,与坡度、坡向、高程、坡位呈显著负相关;坡位、坡度、坡向是影响土壤水分空间变异的主控因子,其累计相对解释率超过了70%,其中坡位占36.28%。研究结果有助于了解东北黑土漫岗区春耕期农田土壤水分空间分异规律及影响机制,对黑土漫岗区土壤水分管理、春耕春播期农机科学调度、保障粮食安全具有重要意义。

Black soil region of northeast China is an important national commodity grain base.Most of cultivated lands distribute in seasonally frozen hilly regions.The spring hydrothermal condition is the main limiting factor for agricultural production in this region.The spring low-temperature and wet waterlogging are prominent,especially with the thawing of frozen soil and rainy and snowy weather,causing a significant delay in spring plowing and sowing for the agricultural tractor cannot work on the waterlogged field.Soil moisture is affected by topography and geomorphology,soil texture,land use type,vegetation,and other factors on multiple scales,as a central factor of agricultural production and ploughing.To reveal the spatial variability of soil moisture on different scales during spring plowing season in black soil hilly region of northeast China,and the impact of topographic factors,Zhaoguang Farm in Heilongjiang Province was selected as the study area.Soil moisture was retrieved using Sentinel-1 SAR data.The spatial variability of soil moisture on farm scale and field scale,the variation of soil moisture at different slope positions and aspects,and the controlling topographic factors were analyzed by semi-variogram and aggregated boosted trees(ABT)methods.The results showed that:on April 24,2018,the retrieved soil moisture content varied from 25%to 38%;the coefficient of variation(CV)at field scale(5.81%)was higher than at farm scale(4.16%);the ranges of semi-variograms at farm scale and field scale were 3000 m and 300 m;the soil moisture was positively and significantly correlated with Topographic Wetness Index(TWI),and negatively and significantly correlated with slope,aspect,elevation and slope position.ABT analysis indicated the combined-scale slope position,slope,and aspect were the main controlling factors affecting the spatial variability of soil moisture.The cumulative relative interpretation rate of these three factors exceeded 70%,of which the combined-scale slope position accounted for 36.28%;the soil moisture content declined with the increasing of the slope position at farm scale and field scale,except the fields on the upland;on each type of aspect,the soil moisture content followed the order:semi-sunny slope>flat>shady slope>semi-shady slope>sunny slope,under the impact of the wind direction.These results can benefit the understanding of soil water distribution regime and the influence mechanism during spring plowing season in black soil hilly region of northeast China,and are valuable for cultivated land water management and agricultural machinery scheduling during spring plowing and sowing season.