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澳洲东部维多利亚山脚的按树林,作为木材的持续生产基地起码有80年的历史了。本文测定了桉树林生态系统中的N,S,P,K,Ca,Mg,Zn,Cu和B的分配状况及其在集约采伐中的迁移状况,如收获锯材及纸浆材所引起的养分迁移。根据出版资料估算了焚烧迹地所引起的大气流失量,还测定了母岩的土壤养分总含量,并且在土壤测试的基础上,估算了土壤有效养分保留量。然后查明集约采伐对土壤养分保留量的可能影响。木材(锯材和纸浆材)的养分迁移量仅占土壤有效养分保留量的少数。与树干相比,树皮的养分含量高,由于在伐木地点剥下树皮,使养分的输出(尤其是Ca和Mn)显著减少。由于焚烧迹地引起的养分挥发和木灰的飘逸,估计养分的大气损失比原木迁移的要大的多。排除采用焚烧迹地的方法重新造林,可以使林地保存一定数量的有机物和养分。与土壤贮存量比较,从收获和燃烧中迁移的S,P,K,Mg,Zn和Cu为数比较少,且在80年的多次轮伐中不致于引起这些养分有效性的明显下降。假如森林中的豆科植物有足够的更新能力,在每个轮伐期计划的焚烧后,由于生物固氮和降雨的补充,N的迁移有可能获得平衡。然而,由于采伐和焚烧,Ca和B的迁移却占土壤中可交换Ca和抽提B的绝大部分。并且还由于这些养分的严重耗损,可能会限制这些森林生态系统未来的持续生产力。所以应尽量避免在桉树林中强度焚烧迹地。
At the base of the foot of Victoria in the east of Australia, there is at least 80 years of history as a sustainable timber production base. In this paper, the distribution of N, S, P, K, Ca, Mg, Zn, Cu and B in eucalyptus forest ecosystem and their migration in intensive harvesting were measured, such as the nutrient content of harvested sawn timber and pulp material migrate. Based on the published data, the amount of atmospheric loss caused by the incineration site was estimated, and the total content of soil nutrients in the parent rock was also determined. Based on the soil tests, the effective soil nutrient reserves were estimated. The potential impact of intensive harvesting on soil nutrient retention was then identified. Nutrients of timber (sawn timber and pulpwood) only account for a small proportion of the effective soil nutrient reserves. The bark has a high nutrient content compared to the trunk, and the output of nutrients (especially Ca and Mn) is significantly reduced by stripping the bark at the logging site. Owing to the volatilization of nutrients and the sootiness caused by incineration, it is estimated that the loss of nutrients to the atmosphere is much greater than the migration of logs. Reforestation, which excludes sites of incineration, allows the preservation of a certain amount of organic matter and nutrients in the woodlands. S, P, K, Mg, Zn and Cu migrated from harvesting and combustion in relatively small quantities compared with soil storage, and did not cause significant reductions in the availability of these nutrients during many rounds of 80 years. If the leguminous plants in the forest have adequate renewal capacity, the migration of N may be balanced due to biological nitrogen fixation and rainfall after the incineration of each rotation plan. However, due to logging and incineration, the migration of Ca and B accounts for the vast majority of exchangeable Ca and B in the soil. And because of the heavy depletion of these nutrients, the future productivity of these forest ecosystems may be limited. Therefore, we should try our best to avoid the intensity burning in the eucalyptus forest.