湘北红壤坡地土壤水分特征及其水分运移

Character and Movement of Soil Moisture in Red Loam Sloping Field in North of Hunan Province

湘北红壤坡地土壤持水力强,有效水含量低(10％左右),含水量呈季节性变化(年变化可分为饱和、亏缺和补充3个时期);土壤结构性差,养分贫乏,原始生产力低,易产生降雨土壤侵蚀。湘北红壤坡地雨水自然资源化程度为降雨量的(46±2)％,农业利用中必须强化雨水资源化过程。坡地典型农业利用系统(旱季)地表/大气界面的水分传输表现为:植被构成是影响传输通量的第一要素;气温和界面水势是影响土/气界面水分传输的主导环境气象因子;辐射和空气饱和水气压差是影响叶/气界面水分传输的主导环境气象因子;在一定的土壤含水量范围内,土/气界面水分传输通量受表层土壤含水量控制。土壤水分变化影响能量平衡,土壤蒸发量与土壤表层水分含量之间有线性正相关;土壤水分除通过影响能量分配来影响植物蒸腾外,土壤水分还能通过影响叶片气孔导度来影响植物蒸腾速率。

Red loam sloping field in the north of Hunan province is characterized as strong water-holding capacity, low available moisture (10% or so), seasonal fluctuation of moisture content(saturation, deficient and supplement are the three stages of the moisture content yearly change); With poor soil texture, poor nutrient, lower initial productivity, soil erosion by rainfall frequently outlier. In the research region, only about is 46±2 percent of rain- fall can be used as natural water resource. It is therefore, necessary to strengthen the process of putting rain water into natural water resource for agricultural utilization. Water movement of under laying surface (interface between ground surface and atmosphere) in a typical agriculture system of sloping loam shows as follow: The vegetation composition is the first essential factor to influence transmitting flux. Temperature and water potential are the dominant environmental meteorological factors to influence moisture movement of under laying surface. Radiation and draught head of air saturation water are the leading environmental meteorological factors to influence the mois- ture movement of interface between foliage and atmosphere. ln a certain range of soil moisture content , the mois- ture transmitting flux is controlled by the topsoil moisture content of under laying surface. The soil moisture change influences its energy balance, alters distribution of radioactive energy. When soil moisture is(0～20 cm) between available moisture content and field capacity, it has a linear positive correlation between evaporation ca- pacity and moisture content of surface soil, besides influencing the plant's transpiration through influencing the distribution of energy, soil moisture also influences plant's transpiration through influencing the porosity resis- tance.