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The Effects of Removing Dominant Species on an Early Successional Herbaceous Community in Xishuangbanna, SW China

Author: ShenWei
Tutor: CaoMin
School: Xishuangbanna Tropical Botanical Garden
Course: Ecology
Keywords: early successional community species-removal experiment soil seed bank seedlings of woody plants invasive species native specie
CLC: S451
Type: Master's thesis
Year: 2009
Downloads: 15
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Abstract


To examine the effects of dominant herbaceous species in early successional community and to identify these effects between invasive species and native species, we conducted a species-removal experiment in an early successional community dominated by an exotic species (Chromolaena odorata) and a native species (Digitaria ciliaris) in Xishuangbanna, southwest China. After the removal treatment, we investigated the recruitment, growth and mortality for the seedlings of woody species in above ground vegetation and the changes in its soil seed bank. We also measured microenvironmental factors and aboveground biomass of the community. The results show that:1. In the study period, removing Chromolaena odorata and Digitaria ciliaris from the community increased the diffuse non-interceptance value (DIFN) significantly, but it showed little effects on soil moisture or soil nutrients, although the aboveground biomass was reduced significantly. As substitutes, Pleioblastus amarus and Thysanolaena maxima dominated aboveground biomass.2. The density of seedlings of woody plants in above ground vegetation was less than 1 individual/m", even though some seedlings of pioneer tree species were also found in our study plot. The seedling height increment in the removal treatments was substantially greater than that in control plots, the mortality of seedlings of woody plants decreased, and the number of new seedlings increased after removal treatments. The effect of removing dominant species on height increment and seedling mortality was larger on 0-50 cm seedlings than on seedlings taller than 50 cm.3. Both Chromolaena odorata and Digitaria ciliaris could form dense canopies that inhibited the growth of seedlings of woody plants by competing for light. No significant difference between these two species was detected.4. The proportion of seeds of herbaceous plants in the soil seed bank of this community was much bigger than that of local secondary forests. The dominant species in soil seed bank greatly differed from those of aboveground vegetation. Woody species were rare in the soil seed bank of this community. The numbers of species and seeds in the soil were increased after removing the two species in the aboveground vegetation. However, the increase in the number of seeds was more drastical than that of woody plant species.5. The study results suggested that the lack of seeds and seedlings of woody plants and the predominance of the two species in the canopy restrain the succession of the community. Therefore, recruiting the seed resource of woody plant species and controlling the dense closure of the two herbaceous species in the canopy are key measures in promoting the vegetation restoration in this area. And more attention should be paid to the dynamics of both invasive paint species and native weeds in early successional plant communities.

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CLC: > Agricultural Sciences > Plant Protection > Harmful plants and their removal > Weeds
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