Towards The Challenge of Biodiversity in Forests and Forestry

The UNCED Convention on Biodiversity commits governments to report regularly on the state of forest biodiversity. This includes the development of a system of indicators. For indicators to be useful they should constitute a feedback mechanism in the decision-making process. They should form a comprehensive and integrated system. Much of the discussions on possible forestry indicators revolve around the identification of speciesbased and system-based indicators. The former category includes the use of endangered or flagship species as well as indicators of intraspecific variation. The latter category is intended to cover measures of forest structure and composition, the use of vegetation associations and ecological regionalizations, and measures of soil erosion or nutrient loss. From those two long lists of biodiversity indicators, a short list can be distilled, referring to the two major elements of the model framework, viz. Drivers of Change and Attributes Inventoried and Monitored. Despite the general objective of forest biodiversity conservation, it is important to look closely at some of the current challenges that exists for the future in forest management. In summary, changes in forestry practices are heavily influenced by economic realities, particularly the supply/demands variables. The shortage of information and knowledge implies that it will take time and effort and many iterative revisions to improve and refine the array of indicators that are required

Predicting the spatial distribution of leaf litterfall in a mixed deciduous forest

An accurate prediction of the spatial distribution of litterfall can improve insight in the interaction between the canopy layer and forest floor characteristics, which is a key feature in forest nutrient cycling. Attempts to model the spatial variability of litterfall have been made across forest types, but the reported models have not yet been compared. We predicted the spatial distribution of leaf litterfall for the same mixed hardwood stand using inverse distance interpolation, ordinary kriging, single and multiple regressions based on plot basal area, and three individual-tree models. Models were calibrated using litterfall data (n = 67) of white birch (Betula pendula Roth), pedunculate oak (Quercus robur L.), and northern red oak (Quercus rubra L.). Model performance was compared using an independent validation data set (n = 37). Interpolation techniques did not reliably estimate spatial patterns of leaf litterfall (r < 0.60, n = 37). However, models incorporating tree data, such as linear regressions and individual-tree models, successfully reproduced the observed spatial litterfall heterogeneity of each species (r > 0.80). No model was able to predict the variability of the total leaf litterfall of the three species. We conclude that, for an intimately mixed forest stand, a model that simulates leaf dispersal of individual trees is likely to be the best choice for predicting the spatial distribution of leaf litterfall

A model of wind-influenced leaf litterfall in a mixed hardwood forest

Litterfall is an important ecological process in forest ecosystem functioning. Some attempts have been made to develop spatially explicit models of litterfall, but wind influence has never been included. Therefore, we studied the effect of wind on litterfall in an intimately mixed birch-oak forest using tree diameter and position as input data. After testing a litterfall model that assumed isotropic leaf dispersal, an anisotropic dispersal module was developed to account for wind influence. Using leaf fall data of 104 litter traps, isotropic and anisotropic models were optimized for silver birch (Betula pendula Roth), pedunculate oak (Quercus robur L.), and red oak (Quercus rubra L.) and model quality was compared. The anisotropic leaf litterfall model proved to be relevant because (i) the estimated litterfall directions corresponded very well to prevailing wind directions during leaf fall and (ii) including directionality significantly increased the goodness of fit of the models for both oak species but not for birch. Consequently, prevailing wind directions during leaf fall affected leaf dispersal in a broad-leaved deciduous forest. Insight into the spatial variability of the litter layer in forest ecosystems can benefit from the improved understanding of small-scale litterfall processes

Response of oriental beech (Fagus orientalis Lipsky) seedlings to canopy gap size

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