tailieunhanh - Báo cáo khoa học: "Structure and yield of all-sized and even-sized conifer-dominated stands on fertile sites"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: Structure and yield of all-sized and even-sized conifer-dominated stands on fertile sites. | Ann Sci For 1994 51 97-109 97 Elsevier INRA Original article Structure and yield of all-sized and even-sized conifer-dominated stands on fertile sites E Lâhde o Laiho Y Norokorpi T Saksa The Finnish Forest Research Institute Box 18 FIN-01301 Vantaa Finland Received 4 June 1993 accepted 22 September 1993 Summary The material studied consisted of 807 sample plots located in sw Finland. The data were inventoried in 1951-1953 using a systematic temporary circular plot line survey. Each plot represented a particular stand. An all-sized stand structure ie a stem distribution resembling an inverted letter J amounted to 62 of sample plots whereas 25 were even-sized resembling a normal distribution and 13 were irregularly uneven-sized. The number of stems per ha in allsized stands was nearly twice that of even-sized stands. The mean annual increment increased linearly with an increase in volume. Consequently there was no difference in increment between all-sized and even-sized stands because the volume of the growing stock in the latter group was greater than in the former. The mean annual increment in stands with equal average volumes was however greater in all-sized mixed stands than in even-sized conifer stands. The relative growth in all-sized mixed stands was approximately 25 higher than in corresponding even-sized stands. stem distribution stand structure yield all-sized stand even-sized stand fertile site Résumé structure et rendement de peuplements irréguliers et réguliers à majorite de coniferes sur terrains fertiles. Le materiel d etude est constitué de 807 placettes d echantillonnage réparties dans le sud-ouest de la Finlande fig 1 . Les données étaient inventoriées 1951-1953 au moyen de placettes circulaires temporaires systématiques alignées. Chaque placette représentait un peuplement particulier. Des placettes d echantillonnage 62 avaient une structure de peuplement irrégulière c est-à-dire avec une distribution des diamètres des tiges ressemblant à la lettre