Báo cáo lâm nghiệp: Carbon and nitrogen allocation in trees

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Báo cáo lâm nghiệp: "Carbon and nitrogen allocation in trees" allocation in treesCarbon and nitrogenR.E. DicksonUSDA-Forest Service, NCFES, Rhinelander, WI, U.S.A. compared to agronomic crops, we haveIntroduction only limited knowledge of carbon and interactions and for any growth nitrogen species in natural ecosystems. AlthoughGrowth of trees and all plants depends up- there have been many studies on compo- positive carbon balance maintainingon a nent biomass, nutrient content, and netdespite continually changing environmen- primary production, the results are difficulttal stresses. Under natural conditions, to interpret and generally do not providegrowth is commonly limited by several information on changes over time inenvironmental stresses operating at the varying environments. The primary reasonsame time. Thus, growth is the summation for interpretation problems is the lack ofof a plant’s response to multiple environ- ’standard’ carbon allocation data setsmental stresses (Chapin et aL, 1987; developed for trees grown under ’opti-Osmond et al., 1987). Light, carbon, water mum’ conditions to compare with carbonand nitrogen are fundamental factors most allocation patterns found in stress situa- to limit growth. On a world-widelikely tions. A major objective of tree researchbasis, water availability is probably the should be to develop such ’standard’ datamajor factor limiting plant growth (Schulze sets on a few key or indicator species.et al., 1987). However, in many temperate Then carbon and nitrogen allocation pat-and tropical forests, nitrogen availability is terns found in trees under stress can bethe most critical limiting factor (Agren, interpreted, and changes in allocation can1985a). Thus, information provided by stu- be predicted for other species and otherdies of carbon and nitrogen metabolism stress situations.and their interactions is necessary tounderstand plant growth. In this paper,I plan to review the current There has been an enormous amount of literature on carbon and nitrogen alloca-research on carbon and nitrogen interac- tion (the movement of carbon within thetions and plant growth, primarily with agri- plant) in trees. Because of space limita-cultural plants and primarily directed tions and other recent reviews on thetowards harvestable plant parts. However, regulation of carbon partitioning (carbonflow among different chemical fractions Smith and P;aul, 1988). Additional com-over time) at the cellular level (Champigny, plexities and differences arise between1985; Huber, 1986; Geiger, 1987), parti- deciduous and evergreen trees. Deci- will not be addressed. Even aftertioning duous and evergreen trees use differentmany years of research, we still know little strategies to maximize carbon gain andabout the processes involved and the fac- utilization of both internal and externaltors that regulate carbon and nitrogen allo- 1982). Deciduous resources (Schulze,cation in trees. Quantitative information on trees rapidly renew all of their leaves inbasic allocation patterns and how these the spring at a relatively low carbon costpatterns change during the season is per unit leaf area but at a high cost ofavailable for only a few annual plants of stored carbohydrate. Deciduous leaves ...