Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí lâm nghiệp đề tài:"Decline in relative growth rate of 3 juvenile radiata pine clones subjected to varying competition levels in Canterbury, New Zealand" | Ann. For. Sci. 60 2003 585-591 INRA EDP Sciences 2004 DOI forest 2003050 585 Original article Decline in relative growth rate of 3 juvenile radiata pine clones subjected to varying competition levels in Canterbury New Zealand Balozi B. KIRONGOa Euan G. MASONb a Research Scientist at the Kenya Forestry Research Institute KEFRI Gede Regional Research Centre PO Box 201 Malindi Kenya b Associate Professor School of Forestry University of Canterbury Private Bag 4800 Christchurch New Zealand Received 24 June 2002 accepted 7 August 2003 Abstract - Relative growth rate RGR is the ratio of growth to size at the beginning of the growth period. The assumption that RGR is constant has been the subject of debate for a long time. In this study the changes in mean RGR RGR of 3 clones of Pinus radiata D. Don grown under varying weed competition levels complete weeding weeding of 2 m diameter circles weeding of 1 m diameter circles and no weeding were quantified for 3 consecutive years. RGR change which quantified as follows was calculated each winter using the morphological and physiological characteristics of RGR dW 1 LA Lw RGR ------ X -T- X -A X -AA dT X LA Lw W ULR SLA LWR where LA leaf area Lw leaf weight W dry weight of the plant SLA specific leaf area . the ratio of area and leaf weight LWR leaf weight ratio . the ratio of total leaf weight of the plant and the total dry weight of the plant T time age ULR unit leaf rate. The results showed that the unweeded control treatment had the lowest absolute RGR. RGR declined with time and tree size in all the weeded treatments but increased in the control. The theory that RGR is constant RGR k model is shown to be false as it varies with both time and tree size. Changes in RGR during the period studied were best described by an exponential decay function RGR a b X exp -cW . Clonal differences were also demonstrated clone 3 showed a lower RGR than the other two clones. This was due to the increased LWR and LAR leaf area
