Đang chuẩn bị liên kết để tải về tài liệu:
Báo cáo lâm nghiệp: "Response of Douglas-fir leaf area index and litterfall dynamics to Swiss needle cast in north coastal Oregon, USA"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Response of Douglas-fir leaf area index and litterfall dynamics to Swiss needle cast in north coastal Oregon, USA. | Ann. For. Sci. 64 2007 121-132 121 INRA EDP Sciences 2007 DOI 10.1051 forest 2006096 Original article Response of Douglas-fir leaf area index and litterfall dynamics to Swiss needle cast in north coastal Oregon USA Aaron R. WEISKITTEL Douglas A. Maguire Department of Forest Science Oregon State University Corvallis OR 97331 USA Received 22 May 2006 accepted 6 September 2006 Abstract - Sources of variation in leaf area index LAI m2 of projected leaf area per m2 of ground area and its seasonal dynamics are not well known in managed Douglas-fir stands despite the importance of leaf area in forecasting forest growth particularly in stands impacted by insects or disease. The influence of Swiss needle cast SNC on coastal Douglas-fir Pseudotsuga menziesii var. menziesii Mirb Franco LAI and litterfall dynamics was quantified by destructively sampling 122 stems from 36 different permanent plots throughout north coastal Oregon USA and by monitoring litterfall for 3 years in 15 of these plots. LAI total annual litterfall and the seasonal distribution of foliage and fine woody litterfall were all influenced by stand structural attributes physiographic features and SNC severity. Mean LAI in this study was 5.44 2.16. The relatively low LAIs were attributed primarily to the effects of SNC on foliage retention and secondarily to its direct measurement by hierarchical foliage sampling in contrast to indirect measurement by light interception or tree allometry. For a given stand structure and SNC severity LAI was 36 greater in the fall after current year foliage was fully developed and older aged classes had not yet senesced. Annual litterfall expressed as a proportion of LAI at the start of the growing season varied from 0.13 to 0.53 and declined with increasing initial LAI. SNC also shifted more of the annual foliage litterfall to earlier in the spring. Fine woody litterfall experienced a different seasonal shift as the peak occurred later in the year on sites with high SNC but .