从适地适树到适钙适树的理论与例证

适地适树是造林学理论与实践的基本原则。实现树种和立地“配对”即适地适树的传统方法是:首先对有林地目标造林树种的生长指标(通常是树高)和根据经验所选定的立地指标(通常包括气候、地形地貌、土壤、植被等)进行相关分析; 然后根据相关结果选定主要立地指标,并依据这些指标对有林和无林地的立地质量进行分类; 最后划分该树种的最适宜、较适宜、一般适宜和不适宜生长的立地类型,以用于指导造林生产活动。但基于经验和相关分析对立地质量进行评价的方法中存在其立地指标因人、因地和因树的改变而无法重复的缺陷。为此,提出以土壤钙的供应潜力作为立地质量的统一指标,以树种最大生长对钙的需求作为树种的生物学特性指标,当树种最大生长的钙需求与立地钙供应潜力相吻合时,树种与立地则满足适地适树原则。依此原理,以辽东栎(Quercus liaotungensis Koidz)为例,建立了基于钙供给与需求平衡的理论数学模型。运用该模型计算造林树种的理论生长指数,通过理论生长指数与最大实际生长量的比值得到适钙适树指数。通过对适钙适树指数与实际生长量进行相关分析验证了适钙适树理论模型的可预测性和真实性。结果表明,用土壤钙供应潜力作为立地质量评价指标可以很好地在造林生产活动中贯彻适地适树原则。适地适树的本质即为适钙适树。

From matching site with trees towards matching calcium with trees

“Matching site with trees” is a fundamental principle in silviculture. It refers to finding the right tree species for a given site, or finding the right site for a given tree species for a maximum tree growth. This matching of tree species with site was conventionally achieved through correlation analyses between tree growth(typically tree height)and empirically chosen site physicochemical variables(including topographical, soil and climatic parameters)with subsequent site quality classification for high, medium, fare and poor tree-growth sites. Noticeably, physicochemical variables used for evaluating site quality vary with evaluators, locations and tree species, thus the approach for site quality evaluation is unreplicatable and unscientific. Here we propose using site calcium supply potentials as an unified site quality index. A site is suited for a tree species, or a tree species grows well in a site, when a tree’s calcium demand for a maximum growth coincides with the site calcium supply potential. Based on this principle, we calculated the calcium supply potentials for Liaoning Province of China. Using leaf tissue calcium concentration we estimated the growth index of cross section area at DBH for Liaodong oak(Quercus liaotungensis Koidz). This index correlated notably well with the forestry inventory data in permanent plots spaced at 4 km×8 km across Liaoning Province. Our analyses demonstrated that calcium supply potential can reflect site quality for silvicultural practices, and the principal foci for “matching site with trees” is “matching calcium with trees”.