Stabilizing forest productivity and resilience at multiple scales

The objective of this study is to introduce a coherent theoretical perspective for sustaining forested landscapes at different scales:meta(forest region),gamma(forest property)and alpha(forest stand),with some details on practical implementation.The main part introduces an integrated set of approaches under three headings:a)gamma design,b)alpha jardinage,and c)continuous observation.The study is based on evidence gathered in the broadleaf and conifer mixed forests of north-eastern China,in European temperate forests,in various forest regions in India,in the afro-montane forests of Southern Africa,and in the pine-oak forests of the Mexican Sierra Madre Occidental.

The national forest inventory in China:history-results-international context

Background： National forest resource assessments Inventories （NFI＇s）, constitute an important nationa and monitoring, commonly known as National Forest information infrastructure in many countries. Methods： This study presents details about developments of the NFI in China, including sampling and plot design and the uses of alternative data sources, and specifically · reviews the evolution of the national forest inventory in China through the 20th and 21st centuries, with some reference to Europe and the US; · highlights the emergence of some common international themes： consistency of measurement; sampling designs; implementation of improved technology; expansion of the variables monitored more efficient scientific transparency;· presents an example of how China＇s expanding NFI exemplifies these global trends. Results： Main results and important changes in China＇s NFI are documented, both to support continued trend analysis and to provide data users with historical perspective. Conclusions： New technologies and data needs ensure that the Chinese NFI, like the national inventories in other countries, will continue to evolve. Within the context of historical change and current conditions, likely directions for this evolution are suggested.

Diversity and production in an Afromontane Forest

Background：This contribution evaluates the effect of forest structure and tree species diversity on plot productivity and individual tree growth in the unique Knysna forests in Southern Africa using mapped tree data from an observational study that has been re-measured over a period of 40 years.Methods：The effects of tree species diversity and forest structure on tree growth and forest production are evaluated on three levels of resolution：a） the forest community（canopy,sub-canopy species）,b） the subplots（number of trees per ha,skewness of the diameter distribution,diameter coefficient of variation） and c） the immediate neighborhood of selected reference trees（＂Mingling＂,＂Dominance＂,Aggregation＂ and ＂Size Variation＂）.Results：An analysis of the community level identified two distinct clusters,one including dominant/canopy species with the highest growth rates and a greater variation of growth,and another cluster which includes the remaining subcanopy species which have a smaller maximum size and lower rates of growth.The area-based structure variables on plot level have a highly significant effect on total basal area growth.However,the effects of forest density and species richness on productivity were not straight forward.Maximum basal area production of about 0.75 m^2/ha/year is achieved at medium levels of richness（around 20 species per ha） and medium levels of density（around 30 m^2/ha basal area） using percentile regression estimates.The relative ＂Dominance＂ of a selected reference tree had a highly significant effect on individual tree growth on all investigated species.Other neighbourhood structure variables were only occasionally significant or not significant at all.Conclusion：This contribution presents a new theoretical framework for analysing natural forests that includes community,plot and neighborhood variables of forest structure and diversity,and a first specific analysis of the structure and dynamics of the Knysna Afromontane Forest,based on a unique set of longterm observations.The species-area（SAR） model developed in this study,represents a new general approach that can be used to derive a common standard of tree species diversity for different plot sizes,the species richness per hectare.

Tree survival and maximum density of planted forests–Observations from South African spacing studies

Background：Among the most important aspects of risk and hazard studies relating to forest ecosystems are maximum forest density and density-dependent tree survival.Methods：Long-term observations about the maximum density of unthinned Pinus patula and P.elliottii field plots based on the Correlated Curve Trend（CCT）spacing studies which were established almost 8 decades ago by O’Connor（Forest Research with Special Reference to Planting Distances and Thinning,1935）in South Africa.Three specific approaches were introduced for analysing maximum density and tree survival,namely the‘limiting line’,Nilson’s sparsity and tree survival with the Weibull function.Results：The main results are：a）Maximum densities differ greatly among the two species grown on the same site and within the same species grown on different sites;it is possible to relate these differences to site index in both species.b）The relationship between the quadratic mean diameter and the minimum average spacing of surviving trees（known as Nilson’s Sparsity）appears to be surprisingly similar in both species.c）An analysis of tree survival in response to different initial planting espacements shows that the Weibull survival function parameters can be estimated if the initial planting density is known.This result is presented for each of the eight large experiments used in this study.Conclusions：This study contributes to a better understanding of tree survival and maximum density which are the key factors required for estimating risk and uncertainty.The risk of tree mortality is not constant,but varies with tree species,planting density,tree age and growing site.For estimating that risk,therefore,continuous long-term observation on different sites and with varying planting densities,as provided by the unthinned CCT series,are essential.