tailieunhanh - Báo cáo lâm nghiệp: "Oak decline risk rating for the southeastern United States"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế, đề tài: "Oak decline risk rating for the southeastern United States. | Ann Sci For 1996 53 721-730 Elsevier INRA 721 Original article Oak decline risk rating for the southeastern United States s Oak 1 F Tainter2 J Williams 2 D Starkey 1 1 USDA Forest Service Southern Region Forest Health 1720 Peachtree Road NW Atlanta GA 30367 2 Department of Forestry Clemson University Clemson sc 29634-1103 USA Received 1 November 1994 accepted 22 June 1995 Summary Oak decline risk rating models were developed for upland hardwood forests in the southeastern United States using data gathered during regional oak decline surveys. Stepwise discriminant analyses were used to relate 12 stand and site variables with major oak decline incidence for each of three subregions plus one incorporating all subregions. The best model for the northern Appalachian subregion included soil depth class oak basal area site index and stand age R2 . In the southern Appalachian subregion significant variables included slope gradient soil depth class oak basal area and clay content R2 . The Ozark model included clay content slope gradient and oak basal area R2 . The composite model included site index age clay content slope gradient soil depth class and oak basal area R2 . The relatively low R2 values and variation in the relationships for some attributes suggest that major oak decline events may be influenced by additional factors. oak decline risk rating predictive model Resume Evaluation du risque de dépérissement des chênes pour le sud-est des États-Unis. Des modèles d evaluation du risque de dépérissement de chênes ont été établis pour des forets feuillues d altltude du sud-est des États-Unis en utilisant des données recuelllies au cours des enquêtes régionales sur le dépéríssement des chênes. Au total 15 variables relatives au site et aux placettes ont été corrélées à 1 intensité du dépérissement en utilisant des analyses discriminantes par étapes. Des modèles prédictits ont été développés pour chacune des trois sous-régions ainsi que pour une zone .