GROWING NIPA PALM FOR RESTORATION OF ABANDONED SHRIMP PONDS

Rapid increase in the production of marine shrimps in the coastal zone has resulted in large-scale con-version of mangrove forests to shrimp ponds.Productions of the shrimps in some regions have been unstable.Conse-quently,a number of ponds are left idle.Restoring environmental conditions within the pond site by planting a suitablemangrove species considered an option.The experiment herein was carried out to explore the effect of planting methodson growth of Nipa palm in abandoned shrimp ponds in the Southern Thailand.Economically,coastal villagers in this areaearn their income from the palm in several ways,the most importantly in Nipa sugar production.Most seedlings wereplanted on top of furrows were constructed in the pond to avoid flooding,except for some seedlings which were planted inthe pond base where additional pond sludge were slightly filled up to compare their growth rates.The results showed thatplanting seedlings with attached rhizomes had the best growth rate and without seedling death at 14 months after plant-ing.At this stage,however,the height of seedlings grown from the fallen fruits was similar to those growth from barerooted seedlings(70 cm tall).Also,seedling mortality was not observed when growth from fallen fruits whereas about6% mortality was experienced by the bare rooted ones.Among the bare rooted seedling treatments,however no signifi-cant differences in growth rates were found when applying the soil with chemical fertilizers or farm manure or liming withCaCO3.In addition,it was found that seedling growth measured at 40 months after planting for those growths in pondbase was almost100% greater than those grown on the furrows.Therefore,this finding may be applied for the restorationof abandoned shrimp ponds by growing Nipa palm.

Ecological influence of exotic plants of Sonneratia apetala on understory macrofauna

The study aims to compare the differences of macrofauna communities of wetlands at 3-year-forest- age, 5-year-forest-age Sonneratia apetala artificial mangroves, 5-year-forest-age Kandelia candel ar- tificial mangroves with the same restoration background, and the naked tidal flat in the Qi’ao Island Mangrove Nature Reserve of Zhuhai, Guangdong Province. The results show that there were signif- icant structural differences in macrofauna communities among four kinds of habitats. The increase of biomass and species diversity of macrofauna at 3-year-forest-age S. apetala artificial mangroves was obviously faster than that at 5-year-forest-age K. candel artificial mangroves whose average tree height was close to that of 3-year-forest-age S. apetala artificial mangroves. The BIOENV analysis shows that it was related to the rapid growth of S. apetala, which rapidly changed the light level and shading conditions in the forests. The 5-year-forest-age S. apetala artificial mangroves had lower macrofauna species diversity but higher density and biomass than K. candel artificial mangroves with the same forest age. This was due to the rapid changes of physical and chemical properties of habitat soil by the ecological restoration of S. apetala artificial mangroves as well as the changed food sources possibly caused by the leaf-litter of such non-indigenous mangrove species S. apetala. However, further survey should be conducted on whether there are any negative ecological impacts of large-scale cultivation of S. apetala on macrofauna communities, so as to evaluate correctly S. apetala’s role in the restoration of coastal mangrove ecosystems.

Invaders’ control on post-disturbance succession in coastal mangroves

Aims In recent years,coastal mangroves have been frequently affected by large disturbances(cyclones,hurricanes,flooding and tsunamis)and post-disturbance vegetation is often dominated by small stature mangrove,mangrove-associate and non-mangrove species potentially affecting ecosystem functioning.Knowledge on the processes of mangrove vegetation development and recovery(succession)following normal and large disturbances will benefit practitioners in designing robust ecosystem management/restoration plans.Here we propose a conceptual model of disturbance-mediated succession in mangroves.Methods Based on field observations and species’life history traits,we develop conceptual models of mangrove succession under normal disturbance regime and recently experienced increased frequency of large disturbances.We evaluate our conceptual models by conducting a scenario testing experiment.Important Findings We suggest two predominant processes affecting mangrove succession after disturbance:propagule limitation due to damage of seed producing mature trees and dispersal barrier resulting from biological invasion associated with large disturbance.We argue that large disturbances affect mature trees more than the small-stature non-tree(shrubs,herbs and climbers)species creating a larger propagule shortage for mangrove tree species than non-tree species.Secondly,large disturbances facilitate invasion of free-floating aquatics,which may interfere with the flow-facilitated propagule dispersal and seedling establishment of mangrove species.In a scenario testing experiment,we have shown that similar levels of disturbance impact vegetation development and recovery differently depending on the presence or absence of invasive species.We conclude that since biological invasion is one of the major drivers of post-disturbance mangrove succession,the dimension of biological invasion should be included in prediction,management and restoration of mangrove forests.