The limited importance of size-asymmetric light competition and growth of pioneer species in early secondary forest succession in Vietnam.
It is generally believed that asymmetric competition for light plays a predominant role in determining the course of succession by increasing size inequalities between plants. Size-related growth is the product of size-related light capture and light-use efficiency (LUE). We have used a canopy model to calculate light capture and photosynthetic rates of pioneer species in sequential vegetation stages of a young secondary forest stand. Growth of the same saplings was followed in time as succession proceeded. Photosynthetic rate per unit plant mass (P(mass): mol C g(-1) day(-1)), a proxy for plant growth, was calculated as the product of light capture efficiency [Phi(mass): mol photosynthetic photon flux density (PPFD) g(-1) day(-1)] and LUE (mol C mol PPFD(-1)). Species showed different morphologies and photosynthetic characteristics, but their light-capturing and light-use efficiencies, and thus P (mass), did not differ much. This was also observed in the field: plant growth was not size-asymmetric. The size hierarchy that was present from the very early beginning of succession remained for at least the first 5 years. We conclude, therefore, that in slow-growing regenerating vegetation stands, the importance of asymmetric competition for light and growth can be much less than is often assumed.
van Kuijk
Marijke
M
Department of Plant Ecology and Biodiversity, Institute of Environmental Biology, Utrecht University, P.O. Box 80084, 3508 TB Utrecht, The Netherlands. marijkevankuijk@hotmail.com
Anten
N P R
NP
Oomen
R J
RJ
van Bentum
D W
DW
Werger
M J A
MJ
D018533:Biomass; D019665:Euphorbiaceae / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D029624:Ferns / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D008027:Light; D036461:Mallotus Plant / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D035322:Melastomataceae / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D010788:Photosynthesis; D006109:Poaceae / Q000033:anatomy & histology / Q000254:growth & development / Q000378:metabolism; D013045:Species Specificity; D014197:Trees / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism; D014744:Vietnam