古尔班通古特沙漠春季土壤含水量空间格局

Spatial pattern of soil water content in spring of the Gurbantunggut Desert

春季积雪融水是古尔班通古特沙漠土壤水分的重要补给源之一,为早春植物的萌发和生长创造了有利的条件。为掌握该地区春季沙丘的土壤水分分布状况,采用探地雷达测量技术,于2010年4月进行了多次野外测量,并通过对地面直达波信号的提取和分析,初步获得了一致的测量结果。结果表明:(1)探地雷达地面直达波测量的土壤平均含水量与20 cm深同步TDR的测量结果非常接近,两者总体相差在0.02 cm3/cm3以内,充分反映了GPR地面直达波测量结果的有效性和精确性;(2)春季积雪完全融化后,沙丘/沙垄顶部土壤水分明显低于垄间低地,这与前人的研究一致,反映了积雪和冻土层在消融过程中,沙丘表面融水在坡面重力作用下,沿难以透水的冻土层上界自坡上向坡下迁移,形成了垄间最高、坡部次之和垄顶最少的分布格局;(3)垄间低地的土壤水分明显受到低矮灌草丛的影响进行再分布,这是由于积雪最初沿植丛基部开始消融,并以植丛为中心形成漏斗状融洞,从而形成以植丛为中心汇集较多融雪水的格局,而垄间低地中较为高大的梭梭乔木对融雪水的再分布影响明显不如低矮的灌草丛,这与其地表茎基过少有关。此外,探地雷达测量实验提供了详实可靠的表层土壤含水量分布信息,可为荒漠生态系统的空间尺度研究提供真实可靠的数据基础。

Rapid acquirement of soil moisture changes of the desert in early spring is of great significance to moni tor the germination and growth condition of plants. To measure the soil water distribution of sand dunes, ground-pen etrating radar （GPR） was used to carry out a number of field measurements in at south edge of the Gurbantunggut Desert, Xinjiang, China April 2010, obtaining initially consistent results through extracting and analyzing the direct ground wave signals. Time-domain reflectometry （TDR） measurements were also aggregated to support GPR re sults. It is showed that the soil water content derived from GPR direct ground wave was very close to the TDR results at a 20 cm depth, with the overall difference approximate to 0.02 cm^3/cm^3 or less, fully reflecting the effectiveness and accuracy of the GPR ground direct wave measurements. Additionally, The GPR derived surface soil water con tent indicated redistribution rules of snowmeh water in early spring. In larger scale snowmeh water immigrated from dune tops to interdune lowlands along the impermeable interface of the upper boundary of frozen soil, forming a dis tribution pattern of soil water content as lowest in dune tops, highest in interdune bottoms and intermediate on slopes; while in interdune lowlands at a small scale, the surface soil water content had been redistributed under the influence of low shrubs and grasses, as the snow and frozen soil around plant stems first melt, which formed such stem-centered funnel holes and collected more melt water, and the taller Haloxylon trees with relevantly fewer stems contributed less to the redistribution of surface moisture. In conclusion, the GPR methods can rapidly obtain an accurate, continuous, detailed information about soil water distribution and provide an important data base to re- search soil hydrological processes and the influencing factors in intermediate scales.