Seedling regeneration, environment and management in a semi-deciduous African tropical rain forest
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Date
2009
Authors
Mwavu, Edward N.
Witkowski, Edward T.F.
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Vegetation science
Abstract
How is seedling regeneration of woody species
of semi-deciduous rain forests affected by (a) historical
management for combinations of logging, arboricide
treatment or no treatment, (b) forest community type and
(c) environmental gradients of topography, light and soil
nutrients?
Location: Budongo Forest Reserve, Uganda.
Methods: Seedling regeneration patterns of trees and
shrubs in relation to environmental factors and historical
management types were studied using 32 0.5-ha plots laid
out in transects along a topographic gradient. We
compared seedling species diversity, composition and
distribution patterns along topographic gradients
and within types of historical management regimes
and forest communities to test whether environmental
factors contributed to differences in species composition
of seedlings.
Results: A total of 85 624 woody seedlings representing
237 species and 46 families were recorded in this rain
forest. Cynometra alexandri C.H. Wright and Lasiodiscus
mildbraedii Engl. had high seedling densities and were
widely distributed throughout the plots. The most speciesrich
families were Euphorbiaceae, Fabaceae, Rubiaceae,
Meliaceae, Moraceae and Rutaceae. Only total seedling
density was significantly different between sites with
different historical management, with densities highest in
logged, intermediate in logged/arboricided and lowest in
the nature reserve. Forest communities differed significantly
in terms of seedling diversity and density. Seedling
composition differed significantly between transects and
forest communities, but not between topographic positions
or historical management types. Both Chao-Jaccard
and Chao-S rensen abundance-based similarity estimators
were relatively high in the plot, forest community and
in terms of historical management levels, corroborating
the lack of significant differences in species richness within
these groups. The measured environmental variables
explained 59.4% of variance in seedling species distributions,
with the three most important being soil organic
matter, total soil titanium and leaf area index (LAI). Total
seedling density was positively correlated with LAI.
Differences in diversity of 42.0 cm dbh plants (juveniles
and adults) also explained variations in seedling species
diversity.
Conclusions: The seedling bank is the major route for
regeneration in this semi-deciduous tropical rain forest,
with the wide distribution of many species suggesting that
these species regenerate continuously. Seedling diversity,
density and distribution are largely a function of adult
diversity, historical management type and environmental
gradients in factors such as soil nutrient content and
LAI. The species richness of seedlings was higher in soils
both rich in titanium and with low exchangeable cations,
as well as in logged areas that were more open and had a
low LAI.
Description
Keywords
Albertine rift ecoregion, Analysis of similarity, Chao’s Similarity estimators, Continuous regeneration, Ecological resilience, Leaf area index
Citation
Mwavu, E. N., & Witkowski, E. T. (2009). Seedling regeneration, environment and management in a semi‐deciduous African tropical rain forest. Journal of Vegetation science, 20(5), 791-804.