Establishment, Resource Acquisition, and Early Productivity as Determined by Biomass Allocation Patterns of Three Tropical Tree Species
Speed of stand establishment and rate of stem biomass production after canopy closure are two important criteria in the selection of species in the expanding field of tropical reforestation. How biomass allocation patterns determine establishment and stem production was studied in 0 to 2-yr-old plantations of Cedrela odorata, Cordia alliodora, and Hyeronima alchorneoides on fertile soil in the humid Atlantic lowlands of Costa Rica. The species were evaluated by: (1) their allocation of biomass to leaves and fine roots; (2) the resource-capturing capacity of the stands as expressed in leaf area, cover, fine-root length, and root distribution; and (3) biomass accrual and aboveground productivity. All species grew very fast: average stand heights at 2 yr ranged from 4 to 6 m, and some individuals were >12 m tall. Canopy closure and root-system overlap were fastest in Cordia, occurring within a year after planting. Cordia's rapid stand closure was achieved by its higher specific leaf area and specific root length, plus an architecture that distributed leaves and fine roots more widely. Maximum aboveground net primary productivities after canopy closure were 7.3, 4.9, and 3.3 g m-2d-1 for Hyeronima, Cordia, and Cedrela stands, respectively. High productivity of Hyeronima correlated with development of a high LAI coupled with a low leaf turnover rate. Cordia and Cedrela, on the other hand, had higher rates of leaf turnover, so a higher rate of leaf production was required to maintain a given leaf area; this, in turn, limited biomass allocation to production of stem biomass. Cedrela productivity was severely reduced by attacks of the stem-borer Hypsipyla grandella. Biomass allocation patterns that promoted rapid establishment of a tree stand, such as broad crowns, high specific leaf area, and high specific root length, did not lead to the highest levels of stem biomass production after canopy closure. Once stand closure is achieved, species having low rates of leaf turnover, high leaf area indices, and high density of fine roots are likely to be most productive. Fast-growing tropical tree species should be evaluated not just on initial growth but also on the stem production attained after stand closure. For. Sci. 41(4):689-708.
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