Quantifying differences between ecosystems with particular reference to selection forests in Durango/Mexico

Abstract

Continuous cover forestry (CCF), which is characterized by selective tree removals in uneven-aged forests, is often believed to be superior to single-species planted forests in addressing a wide range of requirements. Sustainability, which is an important component of CCF, implies limiting the harvested timber volume and often also the structural disturbance by harvest events. Structure is central to CCF silviculture because it determines the current output of products and services as well as the resilience and future dynamics of the managed ecosystem. Therefore, measuring deviations from a desired target structure is a fundamental requirement of CCF. Quantitative description of the differences between ecosystems is necessary for classification of forest types and silvicultural targets, as well as for harvest event analysis and nature conservation. The objective of this study is to present such an approach in the context of exploring new methods of measuring structural differences between forest communities. We investigate the dependence of such differences on the scale of resolution. The general approach is based on measuring discrepancies between relative frequencies involving tree species, tree sizes and spatial patterns. Data from selectively managed mixed and uneven-aged pine-oak forests in Mexico provide the empirical basis for the study. The approaches presented in this study can be used to quantify structural differences between forests and between a given structure and some theoretical target structure. A quantitative measure of the difference between two ecosystems can provide foresters with information about the consequences of particular silvicultural activities. The approach presented in this study therefore offers great potential for analysing the impact of human disturbance on forest ecosystems.