桉树人工林可持续的土壤经营——以广西东门林场为例

桉树人工林在全世界的发展迅速,没有比在中国南部地区更需要一种新的木材和木纤维产品的需求。在桉树迅猛的扩张过程中,人工林可持续的生产力和合理的生态系统管理将扮演至关重要的角色。以往非可持续的农业经营导致了东门林场的土地严重退化,东门项目期间,在这些立地上重新造林证明了土壤营养的缺乏严重影响了退化立地的潜在生产力。1988年在东门进行了一个巨桉(E.grandis)早期施肥试验林植株地上部分不同器官的生物量和养分库的研究,以便更好地了解一些经营管理措施的养分结论。另一方面,林木采伐过程中养分的丧失,枯枝落叶的收集和燃烧使得土壤表面裸露,并加剧了土壤侵蚀。目前,在东门第3代、第4代集约经营的人工林的高生产力证明是高标准的经营管理的结果,林地上枯枝落叶和采伐剩余物的保留,细致的整地,土壤侵蚀的控制以及科学的施肥是关键因素;另外加上改良的遗传材料增强了生产力和收益,也增强了东门桉树人工林土壤可持续经营。一个国际林业研究中心网络得以建立,为了调查研究在同一立地上是否有可能进行连续的种植速生丰产林而对立地土壤和水资源没有损害,研究提供了大量的热带人工林有关立地管理的信息。为了优化集约经营人工林的生产力、收益率及可持续性,在华南地区有必要继续进行土壤和养分研究。

Sustainable Soil Management of Eucalypt Plantations: with Reference of the Dongmen Situation

There is rapid expansion of eucalypt plantations throughout the world and none more so than in southern China where there is an burgeoning demand for wood and wood fiber products. Sustainable productivity of plantations and wise management of ecosystems will play a critical role in this expansion. In the past unsustainable agricultural practices which resulted in severely degraded landscapes were carried out in the area which became the Dongmen Forest Farm. Reforestation of these sites was subject of the Dongmen project which inter alia demonstrated that soil nutrient deficiencies impact on the potential productivity of the degraded sites. A study undertaken at Dongmen in 1988 in young fertilized stands of Egrandis estimated biomass production and nutrient pools in various fractions of the above ground biomass in order to better understand the nutrient consequences of some management options. In addition to removal of nutrients in harvestion, losses resulting from removal of litter and burnt soil production resulted in significant nutrient losses and exposed the soil surface to accelerated soil erosion.The high productivity currently being achieved in the third and fourth rotation intensively managed plantations at Dongmen attests to the high standards of management being implemented. Maintenance of litter and logging residues on site, careful and sensitive site preparation and control of soil erosion coupled with the judicious use of fertilizer are key initiatives, together with use of improved genetic materials, which have contributed to enhanced productivity and profitability and sustainable soil management of eucalypt plantations at Dongmen. A Centre for International Forestry Research (CIFOR) network set up to investigate whether it is possible to produce successive harvests of fast-growing plantations on the same land without damaging soil and water resources has provided a large amount of information relevant to site management in tropical forest plantations.There is an ongoing need to continue soils and nutrition studies in eucalypt plantations in southern China in order to optimise productivity, profitability and sustainability of intensively managed plantatations.