Đang chuẩn bị liên kết để tải về tài liệu:
Báo cáo lâm nghiệp: "Multiaged silviculture in North America"

Tuyển tập những bài báo cáo nghiên cứu khoa học hay nhất được đăng trên tạp chí JOURNAL OF FOREST SCIENCE đề tài: Multiaged silviculture in North America. | JOURNAL OF FOREST SCIENCE 55 2009 9 432-436 SHORT COMMUNICATION Multiaged silviculture in North America K. L. O Hara University of California Berkeley USA ABSTRACT Multiaged silviculture is highly variable across North America but a commonality is the ties to the negative exponential diameter distribution to guide stocking control. These methods have evolved in several regions to include alternative stand structures and new stocking control tools are being developed. A trend in these new developments is integrating disturbance regimes and their effects on stand structure. The result in some cases is a movement towards longer cutting cycles and more flexible guidelines for stand structure. Keywords multiaged silviculture North America diameter distribution stocking control Multiaged silviculture in North America is as varied as the forest types where this form of silviculture is practiced. In eastern North America these forest types include the northern hardwood forests with many shade tolerant broadleaved species and where wind is the dominant disturbance regime. In the southeast mixtures or pure stands of southern pines Pinus taeda P echinata P palustris can be managed in multiaged stands as can the upland hardwood forests that are found throughout eastern North America. Both of these forest types were influenced by a pre-European settlement disturbance regime of fire that varied in intensity and effects. There are also highly productive bottomland sites where multiaged stands can be promoted to grow high quality stems of various broadleaf species. In western North America fire is the dominant disturbance regime in most forest types. These include very frequent fire regimes in ponderosa pine Pinus ponderosa forests or mixed western larch Larix occidentalism forests that may include fires that occur on less than five-year intervals and kill very few trees. Other forest types experience fires on less frequent intervals and these fires often have severe to .