This investigation provides a realistic assessment of the biological diversity of regenerating eastern deciduous forests by describing the rate and trajectory by which forest communities re-assemble. These results also elucidate the process by which various forms of heterogeneity re-emerge in regenerating forests, including microsite differentiation and the development of spatial pattern in forest herb populations. To chronicle the re-assembly of forest herb communities, and to provide a more comprehensive picture of how sources of pattern interact to structure herb populations, a fine-scale survey was designed as follows: 1) a 50-meter transect, composed of 100 1m x .5m quadrats, was established in 37 stands of successional forest, ranging in age from 0 to 160 years. 2) In each quadrat, the number of stems of each species was recorded, along with values for 12 environmental variables. 3) Each species' spatial distribution was characterized using spatial autocorrelation and regressed on each environmental variable.
Results/Conclusions
Interior forest species arrive late on successional sites, delaying full assembly of forest communities for at least a century. Co-ordinate with the rise of interior forest species is the decline of non-native and early-successional species. Eventually, forest herb populations in this study exhibit fine-scale spatial patterns that reflect two dominant influences: environmental variables and life-history traits. The interaction of these two primary sources of pattern most likely creates a continuum-type phenomenon, in which the relative influence of each depends on the strength of expression of the other. Easily detectable patterns in herb populations are likely expressions of one dominant source of heterogeneity. Yet, interacting sources of heterogeneity can multiply the complexity of patterns that arise from them, making herb spatial patterns difficult to detect and interpret. Understanding herb distributions across scales and landscapes requires understanding the dynamics of heterogeneity.
