Raaimakers Dorinne, Lambers Hans
Department of Plant Ecology and Evolutionary Biology, Utrecht University, PO Box 800,84, 3505 TB Utrecht, The Netherlands.
Tropenbos Office, Lot 12E Garnett Street, Campbellville, Georgetown, Guyana.
New Phytol. 1996 Jan;132(1):97-102. doi: 10.1111/j.1469-8137.1996.tb04513.x.
The highly-weathered acid sandy soils in Guyana, South America, art very low in nutrients, especially in phosphorus (P) Earlier experiments demonstrated that P was growth-limiting for some tree seedlings on these soils, but other species failed to increase their growth in response to greater P-availability. To investigate this, we measured growth and distribution (if biomass and P of tree seedlings, of a pioneer tree species, Tapirira obtusa (Benth.) Mitchell, and of a climax tree species, Lecythis corrugata Poit., at 10 levels of P-supply under controlled conditions in a glasshouse. At intervals of 3 wk. dry weights of plant parts and their phosphorus concentrations were measured. The pioneer and the climax species took up similar amounts of P when grown at high P-supply. The pioneer tree T. obtusa maintained a low P concentration (0.25 mg g ) independent of P-supply, and used the P taken up Hi increase growth., At high P-supply it invested little biomass in roots, and reached a relative growth rate (RGR) of 40 mg g d . The climax, tree species, L, corrugate, maintained a low RGR of 10 mg g d and a constant distribution of biomass at all P-supply rates. It stored the extra P in a structure between the stem and root derived from the former hypocotyl, which persisted for over 6 months after germination. The differences m growth and distribution of biomass and P in response to P-supply of the two species are likely to contribute to the establishment of their seedlings in the field. If L. corrugata is capable of re-translocating P from the hypocotyl, this storage of P has ecological advantages for long-term survival, which might be important under low light conditions. Together with a low RGR, it enables a seedling to maintain P-reserves until a gap occurs. In a newly created gap, P-availability per seedling increases, and pioneers, with their higher P uptake and growth potential, can benefit from these relatively higher levels of P-availability. This is an important advantage in high-light gap environments where the tallest tree seedling is generally the most competitive one.
