关于人工林的地力下降问题

On the Decrease of Soil Fertility in Plantations

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.

Cultivation of fast growing tree species which has a high demand for nutrientsin soil tends to lead to the decrease of soil fertility. Early in the initial period of 19th centu-ry, attention had been paid to the soil fertility in plantations. In early period inEurope, and in recent years in New Zealand, Australia and areas of Chinese fir For-ests in South China, decrease of soil fertility in monocultured plantations were and arerepeatedly reported. The causes are consumption of soil fertility by trees, theinadaptability of edaphic conditions and the improper forest management measures. Inthis paper an analysis is emphatically made of the effects on soil fertility of cycle of rota-tion, form of utilization of the felled trees, way in cleaning the slashes and ground veg-etation, management measures such as farming practice site preparation, nitrogen fix-ing plants and plants adding fertility to soils. In order to stabilize the level of soilfertility, in addition to observing the rule of suitable tree species for suitable sites, andavoiding concentrated planting of the same tree species in large areas, care should betaken in handling the following problems: (1) relative prolongation of the cycle of rota-tion, which is better to be longer than the quantitative maturity. (2) In felling, onlythe trunk is used, and utilization of the whole tree is harmful. (3) Burning of slashesand ground vegetation often leads to great loss of nutrients to soil. (4) High intensity ofsite preparation and tilling is unfavorable to the preservation of organic matter and nitro-gen, 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 addingfertility to soils, which can contribute greatly to the increase of soil fertility.