林(竹)草不同植被恢复模式下的土壤物理特性

利用建立生态定位观测场，对华西雨屏区洪雅县低山区退耕还林中的桦木+扁穗牛鞭草、苦竹+扁穗牛鞭草、纯扁穗牛鞭草和撑绿杂交竹＋扁穗牛鞭草4种林（竹）草植被类型进行定位观测，研究不同植被恢复类型对土壤物理特性的改良。试验结果表明：林（竹）草不同植被类型植被恢复5年后，土壤0～40 cm土层的砂粒和粗粉粒百分含量均有一定的下降，在一定程度上逆转了原坡耕地土壤继续“粗化”的趋势；4种植被恢复类型土壤0～40 cm土层的物理性粘粒含量与农耕地相比均有一定提高，在一定程度上增强了固持土壤养分的能力，以苦竹＋扁穗牛鞭草改良效果最好；与农耕地相比，4种植被恢复类型土壤0～40 cm土层土壤容重有增有减，以苦竹＋扁穗牛鞭草和撑绿杂交竹＋扁穗牛鞭草植被恢复类型改良效果相对较优；虽然除纯牛鞭草地外其它3种植被恢复类型土壤0～40 cm的总孔隙度与农耕地相比都有一定程度的增加，但土壤总孔隙度都偏小，非毛管孔隙/毛管孔隙值也不合理。可见土壤结构的改良并非退耕后植被恢复短期内就能实现的，还需长时间的植被保护、合理的经营。〖

SOIL PHYSICAL PROPERTIES UNDER DIFFERENT TREE OR BAMBOO PLUS GRASS VEGETATION RESTORATION PATTERNS

Fixed ecological observation plots were established to study the effects of four vegetation patterns—〖WTBX〗Betula luminifera+H. compressa〖WTBZ〗(L.f), 〖WTBX〗Pleioblastus+H.compressa〖WTBZ〗(L.f), pure 〖WTBX〗H.compressa〖WTBZ〗(L.f) and 〖WTBX〗Bambusa pervariabilis×Dendrocala mopsis+H. compressa〖WTBZ〗(L.f)—on soil physical properties. The results showed that the percentage of soil sand and coarse silt of four vegetation restoration patterns declined at the layer 0~40 cm, reversed the trend of soil coarseness of the slope farmland to some degree; the soil physical clay granule content of the four vegetation restoration patterns at the layer 0~40 cm was higher than that of slope farmland, the ability of soil nutrient holding was strengthened to some degree, and 〖WTBX〗Pleioblastus+H. compressa〖WTBZ〗(L.f) exhibited the best effect at this aspect. Compared with the farmland, the soil bulk density of four vegetation restoration patterns was higher or lower at the layer 0~40 cm, and 〖WTBX〗Pleioblastus+H. compressa〖WTBZ〗(L.f) and 〖WTBX〗Bambusa pervariabilis×Dendrocala mopsis〖WTBZ〗 showed relatively better effect. Despite of 〖WTBX〗H. compressa〖WTBZ〗(L.f), the other three vegetation patterns showed better effects on soil porosity than farmland at the layer 0~40 cm, but in general the soil porosity was still low, especially the ratio between non capillary porosity and capillary porosity, indicating that soil improvement was unable to be achieved in short time after cease farming and vegetation recovery. Vegetation restoration was just the first step. Only with long period of vegetation root system accumulation in the soil, underground creature amount increased and microorganism built up, can soil have a better structure in full range. Reasonable management and utilization of the vegetation is also important.〖