关于人工林的地力下降问题

栽培生长迅速和对土壤肥力要求高的树种, 有导致地力下降的趋势。早期欧洲, 近期新西兰、澳大利亚以及我国南方杉木林区, 都有人工林地力下降的报道。从林业技术措施来说。促进人工林地力下降的主要因素有轮伐期短、全树采伐利用、火烧清理采伐剩余物和强度整地等。栽培固氮植物和肥土植物, 可显著改善土壤肥力。在造林中遵循适地适树的原则, 避免同一树种的大面积集中连片, 也有助于地力的维持。

On the Decrease of Soil Fertility in Plantations

Cultivation of fast growing tree species which has a high demand for nutrients in soil tends to lead to the decrease of soil fertility. Early in the initial period of 19th century, attention had been paid to the soil fertility in plantations. In early period in Europe, and in recent years in New Zealand, Australia and areas of Chinese fir Forests in South China, decrease of soil fertility in monocultured plantations were and arc repeatedly reported. The causes arc consumption of soil fertility by trees, the inadaptability of cdaphic conditions and the improper forest management measures. In this paper an analysis is emphatically made of the effccts on soil fertility of cycle of rotation, form of utilization of the felled trees, way in cleaning the slashes and ground vegetation, management measures such as farming practice site preparation, nitrogen fixing plants and plants adding fertility to soils. In order to stabilize the level of soil fertility, in addition lo observing the rule of suitable tree species for suitable sites, and avoiding concentrated planting of the same tree species in large areas, care should be taken in handling the following problems:(1) relative prolongation of the cycle of rotation, which is better to be longer than the quantitative maturity.(2) In felling, only the trunk is used, and utilization of the whole tree is harmful.(3) Burning of slashes and ground vegetation often leads to great loss pf nutrients to soil.(4) High intensity of site preparation and tilling is unfavorable to the preservation of organic matter and nitrogen, though it may be conductive to the growth of young stands for the time being.(5) Attention should be paid to cultivating nitrogen-fixing plants and plants adding fertility to soils, which can contribute greatly to the increase of soil fertility.