tailieunhanh - Báo cáo lâm nghiệp: "Forest and shrubland canopy carbon uptake in relation to foliage nitrogen concentration and leaf area index: a modelling analysis"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài:"Forest and shrubland canopy carbon uptake in relation to foliage nitrogen concentration and leaf area index: a modelling analysis" | Ann. For. Sci. 62 2005 525-535 INRA EDP Sciences 2005 DOI forest 2005045 525 Original article Forest and shrubland canopy carbon uptake in relation to foliage nitrogen concentration and leaf area index a modelling analysis David WHITEHEADa Adrian S. WALCROFTb a Landcare Research PO Box 69 Lincoln 8152 New Zealand b Landcare Research Private Bag 11052 Palmerston North New Zealand Received 2 August 2004 accepted 8 March 2005 Abstract - A multi-layer canopy model was used to simulate the effects of changing foliage nitrogen concentration and leaf area index on annual net carbon uptake in two contrasting indigenous forest ecosystems in New Zealand to reveal the mechanisms regulating differences in light use efficiency. In the mature conifer-broadleaved forest dominated by Dacrydium cupressinum canopy photosynthesis is limited principally by the rate of carboxylation associated with low nutrient availability. Photosynthesis in the secondary successional Leptospermum scoparium Kunzea ericoides shrubland is limited by electron transport. Maximum carbon uptake occurred in spring at both sites. Annual increases in canopy photosynthesis with simulated increases up to 50 in leaf area index L or foliage nitrogen concentration per unit foliage area Na were largely offset by increases in night-time respiration. A realistic simulation where L was increased by 50 and Na by 20 together equivalent to an increase in total canopy nitrogen of 80 led to decreases in net annual carbon uptake because the increase in photosynthesis was offset by the increase in respiration. Given the environmental constraints both canopies in their natural states appear to be operating at the optimum conditions of leaf area index and nitrogen concentration for maximum net carbon uptake. photosynthesis respiration leaf area index nitrogen light use efficiency Résumé - Assimilation de carbone par une canopée forestiere et une vegetation buissonnante en relation avec l indice foliaire et les teneurs .