Do Forest Gaps Influence the Population Structure and Species Composition of Mangrove Stands in Northern Australia?1

Clarke, Peter J.; Kerrigan, Raelee

doi:10.1646/0006-3606(2000)032[0642:dfgitp]2.0.co;2

Cited by 45 publications

(32 citation statements)

References 23 publications

(7 reference statements)

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“…light requirement) of canopy dominants may contribute to the maintenance of the present species composition in each vegetation zone. Clarke and Kerrigan (2000) proposed that gapphase regeneration of mangroves appears to follow a simple 'direct replacement' model in which a species population is replaced by members of the same species in forest gaps. This contrasts with tropical rain forests in which micro-succession, i.e.…”

Section: Discussionmentioning

confidence: 99%

Gap formation and regeneration of tropical mangrove forests in Ranong, Thailand

et al. 2006

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Tropical mangrove forests are characterized by clear zonation along a tidal gradient, and it has been supposed that the zonation is primarily controlled by soil factors. However, effects of disturbance on mangrove forests are still not well understood and may play an important role on the vegetation patterns and forest dynamics in some forest formations. In this study, the pattern of disturbance regime and its effects on regeneration of tropical mangrove forests along a tidal gradient were investigated in Ranong, Thailand. We established one or two 0.5 ha plots in four vegetation zones, i.e. Sonneratia alba -Avicennia alba zone, Rhizophora apiculata zone, Ra -Bruguiera gymnorrhiza zone, Ceriops tagal -Xylocarpus spp. zone. Gap size (percentage gap area to total study area and individual gap size) was the largest in Sa -Aa zone which is located on the most seaward fringe, and it declined from seaward to inland. Canopy trees of S. alba and A. alba had stunted trunks and showed low tree density. On the contrary, canopy dominants in the other three inland zones, e.g. R. apiculata, B. gymnorrhiza, and Xylocarpus spp., had slender trunks and showed high tree density. Accordingly, differences in disturbance regime among the four zones were resulted from the forest structural features of each zone. Disturbance regime matched with regeneration strategies of canopy dominants. Seedlings and saplings of S. alba and A. alba, which need sunny condition for their growth, were abundant in gaps than in understorey. By contrast, R. apiculata, B. gymnorrhiza, and Xylocarpus spp., which can tolerate less light than S. alba and A. alba, had greater seedling and sapling density under closed canopy than gaps. Many large gaps may enhance the abundance of S. alba and A. alba in Sa -Aa zone, and a few small gaps may prevent the light demanding species to establish and grow in the other inland zones. Correspondence of disturbance regime and regeneration strategies (e.g. light requirement) of canopy dominants may contribute to the maintenance of the present species composition in each of the vegetation zones.

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Section: Discussionmentioning

confidence: 99%

Gap formation and regeneration of tropical mangrove forests in Ranong, Thailand

et al. 2006

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“…Furthermore, at both low and high salinity, seedling survivorship increased with light availability. A number of studies have found that in general there is higher mangrove seedling survivorship in gaps than non-gaps (Ball 2002;Clarke and Kerrigan 2000). Ball (2002) proposes two explanations: that there is more herbivory under closed canopies (e.g., Osborne and Smith 1990;Sousa et al 2003b;Lindquist and Carroll 2004); and that mortality in the shade could be due to below ground competition with surrounding adults (Passioura et al 1992).…”

Section: Whole-plant Responses To Light and Salinitymentioning

confidence: 99%

Salinity and light interactively affect neotropical mangrove seedlings at the leaf and whole plant levels

et al. 2006

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We have studied the interactive effects of salinity and light on Avicennia germinans mangrove seedlings in greenhouse and field experiments. We hypothesized that net photosynthesis, growth, and survivorship rates should increase more with an increase in light availability for plants growing at low salinity than for those growing at high salinity. This hypothesis was supported by our results for net photosynthesis and growth. Net daily photosynthesis did increase more with increasing light for low-salinity plants than for high-salinity plants. Stomatal conductance, leaf-level transpiration, and internal CO 2 concentrations were lower at high than at low salinity. At high light, the ratio of leaf respiration to assimilation was 2.5 times greater at high than at low salinity. Stomatal limitations and increased respiratory costs may explain why, at high salinity, seedlings did not respond to increased light availability with increased net photosynthesis. Seedling mass and growth rates increased more with increasing light availability at low than at high salinity. Ratios of root mass to leaf mass were higher at high salinity, suggesting that either water or nutrient limitations may have limited seedling growth at high salinity in response to increasing light. The interactive effects of salinity and light on seedling size and growth rates observed in the greenhouse were robust in the field, despite the presence of other factors in the field-such as inundation, nutrient gradients, and herbivory. In the field, seedling survivorship was higher at low than at high salinity and increased with light availability. Interestingly, the positive effect of light on seedling survivorship was stronger at high salinity, indicating that growth and survivorship rates are decoupled. In general, this study demonstrates that environmental effects at the leaf-level also influence whole plant growth in mangroves.

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“…Firstly, some demographic studies have shown that densities of naturally occurring seedlings are greater beneath porous canopies than dense canopies (Ball 1980), and are greater in gaps than in closed forests (Sukardjo 1987). Other studies, however, found no differences in seedling densities between gaps and the surrounding forest, but reported more recruitment to the sapling stage in gaps (Jimenez 1988;Clarke and Allaway 1993;Clarke and Kerrigan 2000;Sherman et al 2000). Secondly, experimental studies have found that growth and survival of seedlings of several species are lower in the dense shade of closed canopies than in gaps (Smith 1987a, b;Clarke and Allaway 1993;Sherman et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Interactive effects of salinity and irradiance on growth: implications for mangrove forest structure along salinity gradients

Ball

2002

Trees

168

114

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Early growth of Ceriops australis and C. decandra was studied in response to salinity and irradiance under laboratory conditions. These results provided a basis for interpretation of growth patterns during seedling establishment by seven species of Rhizophoraceae with variation in irradiance under natural low and high salinity regimes in a tropical mangrove forest. Survival declined with decrease in irradiance, except where very low salinities apparently induced sensitivity to high irradiance in vulnerable species. Survival in understorey shade was lower in the high than low salinity environment. However, these apparent effects of salinity were eliminated by reducing below-ground interactions with adult trees. Interspecific differences in initial propagule mass had no effect on survival, but were correlated with differences in average shoot mass after 1 year, emphasising the importance of juvenile reserves to early growth. There were interspecific differences in the salinity regime in which seedlings grew best, but shoot growth declined with decreasing irradiance. In most species, shoot mass of plants grown under natural canopy shade was less than initial propagule mass and was little affected by salinity. Salinity had greater effects on shoot growth under high irradiance than under natural canopy shade, implying effects of salinity on the capacity to use resources in growth. Each species exhibited a different pattern of shoot growth relative to initial propagule mass in response to salinity and irradiance. These patterns were consistent with, but do not fully explain, the distribution of the Rhizophoraceae along a natural salinity gradient in the Adelaide River system.

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Do Forest Gaps Influence the Population Structure and Species Composition of Mangrove Stands in Northern Australia?1

Cited by 45 publications

References 23 publications

Gap formation and regeneration of tropical mangrove forests in Ranong, Thailand

Gap formation and regeneration of tropical mangrove forests in Ranong, Thailand

Salinity and light interactively affect neotropical mangrove seedlings at the leaf and whole plant levels

Interactive effects of salinity and irradiance on growth: implications for mangrove forest structure along salinity gradients

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