山坡退化林地林木生长对微地形人工干预的响应

为探究水土保持微地形人工干预措施(等高反坡阶)对坡面退化林地林木生长的影响,在昆明市松华坝水源区内选取典型山坡退化林地,通过动态观测和对比分析不同样地林木胸径、树高、新枝生长量及样地叶面积指数(LAI)的变化差异,再结合土壤水分有效性分析以探讨差异原因.结果表明:等高反坡阶样地云南松胸径和树高的最大值和均值均大于对照样地(CK),退化林群落中小径阶和低矮的植株占更大比例,表明等高反坡阶样地中优势木新生植株和退化严重植株的生长潜力得到激发,不同样地云南松植株新枝平均枝长和枝径的年变化差异率达到了72.4%和39.1%.等高反坡阶样地云南松植株新枝生长量和样地LAI的变化及新枝生长的速度大于CK.土壤含水率和新枝生长量与LAI均呈显著相关,对水分有效性分析后得到等高反坡阶样地易效水比例(64.2%)整体高于CK(54.7%),5月至9月雨季中,等高反坡阶样地易效水存在时间更长,这有利于林木的生长,进而改变退化林地植物群落结构.

Responses of tree growth to artificial intervention on micro-topography in degraded woodland on hillslope

We explored the effects of microtopography changes from artificial intervention of soil and water conservation (contour reverse-slope terrace, CRT) on tree growth in a degraded woodland on hillslope in water resource area of Songhua dam in Kunming City. The differences of the diameter at breast height (DBH), tree height, new branch increment, and leaf area index (LAI) of dominant tree species in different plots were compared through dynamic monitoring. Then, the causes of differences were analyzed by combining the soil water availability. The results showed that the maximum and mean values of DBH and height of Pinus yunnanensis (dominant species) in contour reverse-slope terrace plot were larger than those in control plot (CK), and the proportion of small-sized and low-dwarf trees in degraded forest community was higher, which indicated that the growth potential of new and seriously degraded forest was stimulated. The annual variation rate of the ave-rage new branch length and diameter of P. yunnanensis in different plots reached 72.4% and 39.1%, respectively. The changes of new branch growth of P. yunnanensis, LAI of plots, and the new branch growth rate were greater in CRT than those in CK. Soil water content was significantly correlated with both the new branch growth and LAI. The ratio of available water in plot (64.2%) was higher than that in CK (54.7%). During the rainy season (from May to September), the available water in CRT existed longer, which was conducive to tree growth and the improvement of plant community structure in degraded woodland.