The effects of gap size and age on the understorey herb community of a tropical Mexican rain forest

R. Dirzo, Carol C Horvitz, H. Quevedo, M. A. Lopez

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Abstract

At Los Tuxtlas, Veracruz, 13 gaps, ranging in size from 70-700m2 and ranging in age from young (1-2 yr old) to old (>>5 yr old), were studied. Mean amounts of relative indirect skylight and relative direct sunlight were 0.083 and 0.116, respectively. Both kinds of light increased significantly with gap size and decreased significantly with gap age, but a significant interaction indicated that size was more important in new gaps than in intermediate-aged gaps. Herbaceous communities were very diverse: 52 species were found in total. Most species occurred at low frequencies in most sites. Number of species per gap (mean 15.2) was not affected significantly by gap age or size, although the Shannon-Weaver diversity index H' (mean 2.1) was significantly highest in young gaps (mean 2.4) followed by intermediate-aged gaps (mean 2.1). Total standing leaf area produced by herbs (mean 0.795 m2m-2) was significantly affected by both gap size and age; it was highest in intermediate-aged, medium-sized gaps (1.935 m2m-2). Hemiepiphytic aroids were numerically important a most sites. Terrestrial aroids and large monocots were also important groups at many sites by their relative contributions to total standing leaf area. Species assemblages differed considerably between sites. Intermediate-aged gaps were more similar to each other than young gaps were to each other. Mature forest sites were the least similar to all the other sites. There were reproductives at all sites: the highest relative number was in the intermediate-aged sites, not the bright sites, new gaps or young gaps. -from Authors

Original languageEnglish
Pages (from-to)809-822
Number of pages14
JournalJournal of Ecology
Volume80
Issue number4
StatePublished - Dec 1 1992
Externally publishedYes

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ASJC Scopus subject areas

  • Ecology

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