What determines biomass in indigenous forests? An analysis of the Knysna Forest, South Africa
J. J. Midgley A C and A. Seydack BA Botany Department, University of Cape Town, P Bag Rondebosch 7701, South Africa.
B South African National Parks, PO Box 3542, Knysna, South Africa.
C Corresponding author. Email: midgleyj@botzoo.uct.ac.za
Australian Journal of Botany 54(8) 701-705 https://doi.org/10.1071/BT05139
Submitted: 8 February 2005 Accepted: 13 June 2006 Published: 29 November 2006
Abstract
We tested the widely held assumption that indigenous forests contain maximum biomass and growth rates for local resource supply. We analysed 10 years of diameter growth of trees >10 cm in diameter from 108 plots, each 0.04 ha, in the Knysna Forest, South Africa. No correlation was found between radiation index and standing mass or growth, suggesting low environmental constraints on variation in growth rates and biomass accumulation. Gross growth and mortality rates per plot were unrelated, whereas growth rates and stocking rate per plot were positively correlated. Net growth per plot was not correlated with standing stock. Mortality rates of stems are low and, therefore, residence times are long (105 years). Despite long residence times this forest is not at aboveground biomass carrying capacity, as is indicated by weak density-dependent limits to growth.
Acknowledgments
We thank W. Bond for comments and his radiation index program, and the referees for useful comments.
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