|Johnson, Daniel -|
|Clay, Keith -|
Submitted to: Forest Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 27, 2011
Publication Date: January 1, 2012
Citation: Reinhart, K.O., Johnson, D., Clay, K. 2012. Effects of trees on their recruits in the southern Appalachians, USA. Forest Ecology and Management. 263:268-274. Interpretive Summary: By querying a national database, we were able to describe recruitment patterns of tree species for an entire region. This information was then used to develop and test hypotheses regarding the processes structuring these forests. An experiment was performed to identify whether plant-soil biotic interactions explained the observed recruitment patterns. Contrary to predictions, belowground biological interactions (e.g. plant-pathogen) do not appear to be structuring these regional forests. Furthermore, above-ground interactions also do not appear to be shaping these forests as predicted. This suggests that although biotic interactions may be locally important that they may not be regionally. Other factors in this region are driving recruitment patterns and maintaining forest diversity such as abiotic heterogeneity.
Technical Abstract: Questions Can tree species be grouped into recruitment classes and be used to make generalizations about forest structure? Then will soil inocula origin (conspecific vs. heterospecific) affect plant performance and plant mutualists, and will responses vary by recruitment classes (inhibitors vs. facilitators)? Will species vary in their susceptibility to pathogens, and will species grouped as inhibitors be more negatively affected by soil inocula from facilitators than other inhibitor species? Location Recruitment patterns and soil inocula from the southern Appalachian Mountains region of USA Methods Database query revealed a continuum of recruitment patterns among regional species. Hypotheses were tested with three common tree species from each end of the continuum (inhibitors vs. facilitators). Soil inoculum was collected from around trees at 14 sites. An experiment tested the effect of soil source on seedling performance and compared responses of two recruitment classes. Results Species varied in their susceptibility to soil pathogens, but trends across all species revealed that inhibitors were not more negatively affected by conspecific than heterospecific soil inocula or more susceptible to pathogenic effects than facilitators. Inocula from facilitators did not affect growth performance relative to growth in soil from inhibitors. Root nodulation of a legume was greater in soil from heterospecific nonlegumes than from the legume. Discussion Although plant-soil biota interactions may be important for individual species and sites, it may be difficult to scale these interactions over space or levels of ecological organization. Production of generalizations for a region may be especially problematic for hyperdiverse forests where interactions appear idiosyncratic.