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Abstract:We used classification and regression tree analysis to determine the primary variables associated with the occurrence of cavity trees and the hierarchical structure among those variables. We applied that information to develop logistic models predicting cavity tree probability as a function of diameter, species group, and decay class. Inventories of cavity abundance in old-growth hardwood forests in Missouri, Illinois, and Indiana found that 8-11% of snags had at least one visible cavity (as visually detected from the ground; smallest opening ≥2 cm diameter), about twice the percentage for live trees. Five percent of live trees and snags had cavities on mature (≥110 years) second-growth plots on timberland in Missouri. Because snags accounted for typically no more than 10% of standing trees on any of these sites, 80-85% of cavity trees are living trees. Within the subset of mature and old-growth forests, the presence of cavities was strongly related to tree diameter. Classification and regression tree models indicated that 30 cm diameter at breast height (DBH) was a threshold size useful in distinguishing cavity trees from noncavity trees in the old-growth sample. There were two diameter thresholds in the mature second-growth sample: 18 and 44 cm DBH. Cavity tree probability differed by species group and increased with increasing decay class.Résumé : Nous avons utilisé la classification et l'analyse d'arbres de régression pour identifier les principales variables associées à l'occurrence d'arbres à cavité et la structure hiérarchique entre ces variables. Nous avons utilisé cette information pour développer des modèles de régression logistique visant à prédire la présence de cavités en fonction du diamètre, du groupe d'essences et de la classe de carie de l'arbre. Des inventaires d'abondance de cavités dans des forêts anciennes de feuillus au Missouri, en Illinois et en Indiana ont montré que 8-11 % des chicots ont au moins une cavité visible (détectée par examen visuel à partir du sol; diamètre de la plus petite ouverture ≥2 cm), soit le double du pourcentage correspondant pour les arbres vivants. Cinq pourcent des arbres vivants et des chicots avaient des cavités dans des placettes en forêt de seconde venue mature (≥110 ans) dans les régions boisées au Missouri. Étant donné que les chicots ne comptent typiquement pas pour plus de 10 % des arbres sur pied à chacun de ces sites, 80-85 % des arbres à cavités sont donc des arbres vivants. Si on prend en compte seulement les forêts matures et les forêts anciennes, la présence de cavités est fortement reliée au diamètre de l'arbre. Les modèles de classification et d'arbres de régression indiquent qu'un diamètre à hauteur de poitrine (DHP) de 30 cm constitue une taille seuil pour distinguer les arbres avec cavités de ceux sans cavités dans les forêts anciennes. Dans les forêts de seconde venue, il y a deux seuils : 18 et 44 cm DHP. La probabilité qu'un arbre ait une cavité varie selon les groupes d'essences et augmente avec la classe de carie.[Traduit par la ...

There is little information on the effects of tree harvest on salamander populations in the midwestern United States. We present data on plethodontid salamander densities in replicated stands of three forest age classes in the southeastern Ozarks of Missouri. Forest age classes consisted of regeneration‐cut sites <5 years old, second‐growth sites 70–80 years old, and old‐growth sites> 120 years old. Salamander abundance on 21, 144‐m2 plots was determined by area‐ and time‐constrained searches. We also compared age‐class habitat characteristics, including downed woody debris, canopy cover, ground area cover, herbaceous vegetation, and woody vegetation. Salamander density was lowest in newly regenerated forests and highest in forests> 120 years old. Comparisons of recently regenerated forests with mature forests> 70 years old indicated that terrestrial salamanders were reduced to very low numbers when mature forests had been intensively harvested. This reduction may result from a decrease in microhabitat availability. Forest age‐class comparisons further indicated that salamander abundance slowly increased over time after forests had regenerated. Management decisions that take into account plethodontid salamander abundance and their response to forest structural diversity are important components in sustaining ecosystem integrity while maximizing economic yield.

Abstract. Two challenges confronting forest landscape models (FLMs) are how to simulate fine, standscale processes while making large-scale (i.e., .10 7 ha) simulation possible, and how to take advantage of extensive forest inventory data such as U.S. Forest Inventory and Analysis (FIA) data to initialize and constrain model parameters. We present the LANDIS PRO model that addresses these needs. LANDIS PRO adds density and size mechanisms of resource competition. This is achieved through incorporating number of trees and DBH by species age cohort within each raster cell. Forest change is determined by the interactions of species-, stand-, and landscape-scale processes. Species-scale processes include tree growth, establishment, and mortality. Stand-scale processes include density and size-related resource competition that regulates self-thinning and seedling establishment. Landscape-scale processes include seed dispersal, as well as natural and anthropogenic disturbances. LANDIS PRO is designed to be straightforwardly comparable with forest inventory data, and thus the extensive FIA data can be directly utilized to initialize and constrain model parameters before predicting future forest change. We initialized a large landscape (;10 7 ha) from historical FIA data (1978) and the predicted forest structure and composition following 30 years of simulation were statistically calibrated against a prior time-series of sequential FIA data (1978 to 2008). The results showed that the initialized conditions realistically represented the historical forest composition and structure at 1978, and the constrained model parameters predicted reasonable outcomes at both landscape and land type scales. The subsequent evaluation of model predictions showed that the predicted forest composition and structure were comparable with old-growth oak forests; predicted forest successional trajectories were consistent with the expected successional patterns in oak-dominated forests in the study region; and the predicted stand development patterns were in agreement with the established theories of forest stand development. This study demonstrated a framework for forest landscape modeling including model initialization, calibration, and evaluation of predictions.

Multivariate regression tree methodology is developed and illustrated in a study predicting the abundance of several cooccurring plant species in Missouri Ozark forests. The technique is a variation of the approach of Segal (1992) for longitudinal data. It has the potential to be applied to many different types of problems in which analysts want to predict the simultaneous cooccurrence of several dependent variables. Multivariate regression trees can also be used as an alternative to cluster analysis in situations where clusters are defined by a set of independent variables and the researcher wants clusters as homogeneous as possible with respect to a group of dependent variables.

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