哈尼梯田景观水源区土壤水分时空变异性

Spatial and temporal variability of soil moisture in water source region of Hani terrace landscape

哈尼梯田景观的稳定维持依赖于上游水源区对水资源的涵养,土壤水分的时空变异性是揭示水源区土壤水源涵养格局的重要指标。通过网格法采集水源区表层（0～20cm）土样162个（旱季81个,雨季81个）,应用经典统计学和地统计学方法分析水源区旱、雨季土壤水分空间变异特征。结果表明：（1）以200 m的间距采样,旱季土壤水分变异系数（Cv）为18.50%,半变异函数结构比值为99.9%,变程为383 m;雨季土壤水分Cv为18.19%,半变异函数结构比值为99.9%,变程475 m。土壤水分均呈中度变异,表现出高度的空间自相关性。从旱季到雨季,土壤水分的空间结构参数存在差异,变程变化最明显;各向异性存在一致性但各向异性比值差异明显。（2）Kriging插值图表明,旱季土壤水分空间格局明显呈斑块分布,斑块破碎度较大,空间连续性较差。雨季呈阶梯状分布,空间连续性强,土壤水分变异的复杂程度变小。旱、雨季土壤水分格局总体变化趋势较一致,但旱季的格局更显著,基本与土地利用格局分布相一致。（3）旱、雨季土壤含水量及其变异受降雨量影响而存在相一致的变化趋势,但旱季土壤水分对降雨量的反应较敏感。（4）土地利用是导致土壤水分空间变异的主要因素,降雨会加强或减弱这种差异的趋势;土壤水分含量受海拔的影响大,受坡度的影响小。（5）土壤水分时空变异能够反映水源涵养格局,对识别水源涵养关键区,保护水源区生态安全格局,维持整个流域水源供给平衡,维持梯田景观的稳定性意义重大。

The water conservation of the water source region in the upper reaches is the key to the sustainability of the landscape of Hani Terraces. The heterogeneity of soil moisture is an important indicator to reveal the pattern of water conservation. Using the grid sampling method,we collected 162 samples（ 81 in the dry season,81 in the rainy season） from surface soil（ 0-20 cm） of the water source region,and analyzed the spatial variability of soil moisture on Hani Terraces based on classical statistics and geostatistics method. The results indicated that：（ 1） Soil moisture in the dry season is of moderate variation（ Cv is 18. 19%）,the ratio of semivariogram＇s structure is 99.9%,and the range is 383 m. Soil moisture in the rainy season is also of moderate variation（ Cv is 18.50%）,the ratio of semivariogram＇s structure is 99.9%,and the range is 475 m,indicating a high spatial autocorrelation of soil moisture. From the dry season to the rainy season,the spatial structure parameters of soil moisture are different,and the most obvious one is the range. There is a consistency of the anisotropy,but the ratio is different.（ 2） Kriging interpolation figure indicates that soil moisture＇s spatial pattern in the dry season shows obvious patches with high fragmentation and poor continuity of space. Soil moisture＇s spatial pattern in the rainy season shows stripes with good continuity of space. The overall trends of the soil moisture pattern are consistent in the two seasons,but the spatial pattern of the dry season is more significant and is almost same as the land use pattern.（ 3） Soil moisture and its variation are consistent regarding their spatial tendencies in the dry and rainy seasons because they are both affected by rainfall,but the response of soil moisture in the dry season is more sensitive to rainfall.（ 4） Land use types are the key factors affecting the heterogeneity of soil moisture,but meteorological factors（ such as rainfall） can reinforce or weaken that trend. Soil moisture is significantly correlated with the elevation,but less affected by the slope gradient.（ 5） Spatial and temporal variability of soil moisture can reflect the differences of water conservation pattern,being of great significance in identifying the key water conservation region,protecting the ecological security pattern,and maintaining the balance of water supply and the stability of the terrace landscape.