Spatial Heterogeneity And Pattern And Process Of Manchurian Ash(Fraxinus Mandshurica Rupr.)Regeneration

Pattern and Process have historically been among the central themes of ecology. Spatial pattern,which has important effects on future ecological process,mainly generated by spatial heterogeneity,all pervasive in natural environment,at a variety of spatial scales. Therefore,the clear and objective description of characteristics of stand environment heterogeneity is a first step to search for relationships between the process that occurs in forest regeneration dynamics and the spatial pattern that is observed in the dynamics at stand level. And thus,the quantification of stand environment heterogeneity,including intensity,scale and spatial structure,is imperative for us to accurately describe and in order to better understand its effects on pattern performances of forest regeneration. In addition,detailed examination and analysis of regeneration patterns are also important for us to relate these observed pattern characteristics to underlying processes,to understand how tree respond to the stand environment heterogeneity in regeneration,and to evaluate what extent can regeneration dynamics be inferred from pattern. With this ecological paradigm,the relationships between stand environment spatial heterogeneity and Manchurian ash (Fraxinus mandshuricd) regeneration pattern were examined in the present study. Research was mainly conducted in secondary hardwood forests in the northeast of China during 1999 and 2001. Spatial sampling methods were based on geostatistical theory and methodology,which can provide much information about spatial sampling area. Spatial data analysis,including spatial heterogeneity intensity,autocorrelated scale and spatial structural variance,was performed by using semivriogram analysis,fractal dimension analysis,Kriging map and Moran's I.To characterize the intensity,autocorrelated scale and structure of spatial heterogeneity of stand environment factors,and relationship of these variables to regeneration patterns,two permanent plots and 22 temporary plots and 17 transects were established. The spatial distribution of understory light availability was examined by measuring leaf area index at two seasons. The spatial variation and dynamics of other stand environment factors,such as soil surface temperature,soil pH,soil bulk density and soil water content,soil root biomass and soil earthworm number,litter and forest floor vegetation biomass were examined at different time within a growing season. The potential ecological consequences,specifically on regeneration,of stand environment spatial heterogeneity were discussed based on the results of spatial heterogeneity quantification.The level-stand spatial patterns of several distinct regeneration phases,involved seed dispersal,seed bank,germination,seedling growing and survival of Manchurian ash,were examined in research area. The spatial variation of seed dispersal,mainly seed rain,was estimated by collected spatial data at 12 line transects radiating from the sample trees. Variation of seed rain at different directions and at different distance from adult female trees was also examined. Meanwhile,seed predation was assessed for seeds placed at plots todetermine the influence of seed predators on seed dispersal pattern. To examine soil seed bank spatial patterns and its dynamics among seasons,soil seed bank samples were collected at permanent plots in different seasons. And annual loss rate of seed bank was also studied. A combination of observational and experimental data was collected to assess the spatial patterns of germination,growing,and survival,by surveying natural seedling establishment,sowing Manchurian ash seed and planting seedlings in secondary forests. In particular,the focus of this study was to probe relationships between the regeneration spatial pattern and environment spatial heterogeneity.The results demonstrated that there was significant spatial patterning for the stand environment factor. (1) Understory light was markedly spatial heterogeneous,representing as a heterogeneous mosaic pattern of both low-ligh...