雨季红壤坡地油茶林土壤水势变化特征及耗水规律

Soil Water Potential Dynamics and Water Consumption of Oil-Tea Camellia Woods on Slope Land of Red Soil During Rainy Season

利用野外定位观测数据,研究了雨季红壤坡地油茶林土壤水势变化特征及耗水规律。结果表明,土壤水势及其变异系数均为坡上大于坡下,坡上深度50cm、坡下深度40cm以上土层显著受到土壤蒸发和植物蒸腾的双重影响,坡上、坡下深度90cm附近土壤水势变化大于相邻层次。土壤物理性质、根系分布对土壤水势影响显著,深度40、90cm分别为黏土层向砾石层、砾石层向网纹层的转变,水分容易积聚,根系易于向此靠近;吸水根(根直径<1mm)根干重与土层深度呈显著指数型相关,且在深度90cm处所占比例最大,达46.95%;吸水根干重所占比例与深层(70—110cm)土壤水势变化量呈明显正相关。通过零通量面分析,雨季持续干旱时段深层水分整体向上蒸发,但深度90cm处水势变化最大,证实土层深度90cm附近为雨季油茶林主要耗水区域。

Based on fixed field monitoring data, soil water potential dynamics and water consumption in the oil-tea camellia woods on slope land of red soil were studied. Results show that during the rainy season in 2007 soil water potential and its variation coefficient at the upper slope was greater than at the lower slope. Soils, 0 - 50 cm in depth in the upper slope and 0 - 40 cm in the down slope were obviously exposed to dual impacts of evaporation and transpiration, and the soil water potential at 90 cm in depth varied more sharply than in other soil horizons nearby. Soil physical properties and root distribution affected significantly water potential and water consumption. At 40 and 90 cm in depth, where the soil was turning from clay horizon into gravel horizon, and from gravel horizon to mottling horizon, respectively, water tended to accumulate and roots were apt to extend towards there. A significant exponential-correlation between dry weight of fine roots （dr 〈 1 mm） and depth of soil layer was observed and about 46.95% of the fine roots were distributed in the 90 cm soil layer. The proportion of fine roots was significantly and positively related to soil water potential（70 -110 cm）. Zero flux plane analysis revealed that： during the continuous dry period in the rainy season, water moved upwards from the deep layers, with water potential varying the most sharply at 90 cm in depth. It was also confirmed that the soil layer around 90 cm is the leading zone of water consumption in the oil-tea camellia woods during the rainy season.