Rapid ecological assessment surveysat coastal areas of Ban Don Bay (Final Report)

Contents Page

1. Geographical and Environmental Status 1

2. Mangroves of Bandon Bay 5

3. Rapid Assessment of Mangrove Communities at some specific sites along the bay

9

4. Work Plan for Mangrove Restoration at the Selected Sites 11

5. Mangrove Restoration at Selected Specific Sites and Recommended Action

12

Foreword In support of the project: Reversing Environmental Damage through Community Focused Sustainable Livelihoods in Ban Don Bay, Surat Thani Province, Southern Thailand” Wetlands International Thailand Office has been fielding a multidisciplinary team of project partners for assessment of ecological, socio-economic and institutional status, threats and needs. As part of this output, the project needs to produce a detailed ecological status report of Ban Don Bay, Surat Thani Province, which include amongst others baseline ecological and socio-economic information. The ecological assessment has been conducted would provide information and support to the identification of appropriate interventions in rehabilitation and management of natural resources that take into account both the ecological and socio-economic benefits. The information collected through this process will also serve as baseline data to measure the success of the proposed interventions. Specifically, Wetlands International-Thailand Office has been contracted to conduct an ecological survey in Ban Don Bay within specific area of Bandon Bay Surat Thani Province include providing mangrove restoration techniques and process for relevant stakeholders as identified by the project.

1 Wetlands International-Thailand Office

Rapid ecological assessment surveys at coastal areas of Ban Don Bay,

Surat Thani Province

1. Geographical and Environmental Status

The proposed area is Bandon Bay (latitude 9°10′–9°40′N, longitude 99°20′–99°60′E) on the east coast of Suratthani Province, southern Thailand . It has an area of approximately 1070 km2 (from Chaiya District on the west side to Don Sak District on the east side), and a population of approximately 861,200 in 1997. The bay is exposed to monsoon climate with north-east winds from October to April and south-west winds from May to November. Therefore two pronounced seasons prevail in the area; the dry season, from January to May with scarce rainfall and high evaporation rate, and the wet season from June to December with higher rainfall and lower evaporation rate.

The inner bay, from Chaiya District to Kanchanadit District, covers an area of 480 km2 with 80 km of coastline. The area of the mangrove swamps fringing the bay is about 20 km2. The coastal area has a gradual slope and the water is shallow. A band of mudflats extends along the coast to about 2 km from the shore, resulting from high sedimentation in the bay area. Water depths vary from less than 1 to 5 m near the mouth of the bay, with a mean depth of 2.9 m with respect to mean sea level. The system is a mixed tidal type with principally semidiurnal tide. Tidal amplitudes range from about 0.70 m at neap tides to about 1.90 m at spring tides. The average tidal range is 1.0 m. The volume of the inner bay is estimated to be 1392×106 m3.


The bay receives most of the surface freshwater runoff from Tapi–Phumduang River watershed (latitude 7°58.2′– 9°31.0′N, longitude 97°28.4′–99°46.0′E), which is situated between the Nakorn Si Thammarat mountain range and the Phuket mountain range in southern Thailand. The watershed consists of two catchment areas with an approximate area of 11,585 km2. It has two major river basins, namely Tapi River Basin and Phumduang River Basin, with an area of 5460 and 6125 km2, respectively. Tapi River, which is approximately 230 km long, originates in the Nakorn Si Thammarat Range, while the Phumduang River (120 km long) originates in the Phuket Range. The two rivers join to become one at Phunphin District (30 km west of Suratthani), and flow through Muang District and Municipality then empties into Bandon Bay which is connected to the Gulf of Thailand. Tapi River has natural flow while the Phumduang River has a large reservoir (Rajjaprapa Dam) located on the upper reach; hence the flow in the Phumduang is highly regulated. The high flows normally occur during August–December. The Phumduang River has an average annual stream flow of 265×106 m3, while Tapi River has an average annual flow of 300×106 m3. The estuarine section of Tapi–Phumduang river occupies an area of 12×106 m2, while the volume of the estuary is estimated to be 84×106 m3.


Bandon bay has tropical monsoonal climate with an average annual rainfall of 1,755.3 mm, the heaviest rain usually falling in November (346.2 mm). February is the driest months, receiving an average of 13.2 mm. Most rain falls during the southwest monsoon (May to October), but the season is extended into December by the onset of the northeast monsoon. The prevailing winds are northeast from November to April and southwest from May to October. The mean annual temperature is 26.3°C (range 22.2-32.1°C). The relative humidity varies from 76% in March to 88% in November. Along the coast are mudflats due to the high rate of sedimentation, which were naturally overgrown with mangroves (Sonneratia spp., Rhizophora spp.), but now mostly replaced by shrimp farms.

Bandon Bay is the largest estuarine and mangrove inlet on the east coast of the Malay Peninsula. A huge area of intertidal mudflats, extending 1-2 km offshore, encompasses the delta of the Tapi River and at least nine other smaller rivers. The area is backed up inland to a distance of two km by shrimp ponds and degraded mangrove, including large areas of dead and dying trees. Most of the mangrove has been cleared leaving a narrow fringe of tallish trees (10-15m high) along the seaward edge. The bay is very shallow with extensive areas less than one metre deep at mean low water. In areas of shrimp ponds, the salinity ranges from 15 p.p.t. in the rainy season to 33 p.p.t. in the dry season. The mean tidal range is l.10m; the amplitude at spring tides is l.90m (occasionally as much as 2.2m), and that at neap tides, 0.7m. Tidal influences are modified by freshwater run-off from the Tapi River catchment.

In Bandon Bay area, two main soil types can be distinguished : the muddy soil developed in lower part of the tidal range and the acid sulfate soil in the upper part. The less developed muddy soils are mostly found in the submerged condition and are alkaline in reaction. They have dark gray color, clayey texture and many decayed roots in the profile The surface layer is about 20-30 cm thick.

Meteorological data for 1997–1998 from the Bandon Bay (Fig. 2) are based on observations made at Suratthani weather stations. The wet season started in May and lasted until December with monthly rainfall ranging from 77 to 412 mm. The highest amount of rainfall was in August. The dry condition, from January to April, had an average rainfall of 4.5 mm d−1 and an average evaporation of 4.5 mm d−1. Relative humidity was 81% (range 61–95%). Annual rainfall for 1997–1998 was 1525 mm, which is less than the mean annual rainfall for 1951–1996 (1690 mm). The rainfall patterns for 1997–1998 also deviate somewhat from the mean pattern of rainfall for 1951–1996.

Fig. 2. Monthly rainfall for Suratthani in 1997–1998 as compared to the mean annual rainfall for 1951–1996. (Source: Royal Irrigation Department).


Fig. 3. Monthly discharge of Tapi and Phumduang rivers into Bandon Bay in 1997–1998

(Source: Royal Irrigation Department).

Figure 4 presents the salinity structures in Bandon Bay during the October and April 1997 surveys. Average salinity in the bay ranged from 17 psu in the wet season to 20 psu in the dry season. In the sea, salinity ranged from 29 psu in the wet season to 32 psu in the dry season. Seasonal variations in river flow cause marked changes in salinity intrusion and resulting in stratification. Salinity in the estuary ranged from 0 to 23 psu in the dry season, but slightly lower in the wet season (0–14 psu). A longitudinal transect in Tapi Estuary revealed that the estuary was vertically well mixed at the head of the estuary but slightly stratified towards the mouth . In the wet season, the entire estuary showed near freshwater conditions at the surface.

Fig. 4. Salinity (in psu) distribution in Bandon Bay in 1997.


Fig. 5. Longitudinal distribution of salinity (in psu) in Tapi Estuary in the dry season.

(Gullaya Wattayakorn, Panyanee Prapong and Damrongsak Noichareon ,2001 , Journal of sea research(Den Burg) 46:22, 133-142, Elsevier, Department of Marine Science, Chulalongkorn University, Bangkok 10330, Thailand)

2. Mangroves of Bandon Bay

As has been mentioned earlier, Bandon Bay is one of the most productive coastal areas in southern Thailand. The Tapi River and 18 channels are the main sources of freshwater, nutrients, organic matter and sediment to the bay and the loading of freshwater and nutrients provide essential support for the production of phytoplankton in the estuarine ecosystem. Along the coast are mudflats due to the high rate of sedimentation, which were naturally overgrown with mangroves (Sonneratia spp., Rhizophora spp.), but now mostly replaced by shrimp farms.

Gullaya Wattayakorn (2001) reported that water, salt, dissolved nitrogen, and dissolved phosphorus budgets have been constructed for Bandon Bay for the wet and dry periods of 1997 and 1998. The two-box model shows that while most of the dissolved N and P loading is taken up in the estuarine section of Tapi River and Bandon Bay, a significant portion is exported to the Gulf of Thailand. In general, the export fluxes are higher during the wet season than in the dry season. The export flux of DIN is normally dominated by NH4, and generally greater than the export flux of DON, while DIP is exported at about the same rate as that of DOP. Bandon Bay appears to be in balance metabolically (p - r = 0), suggesting a very high efficiency within the Bay for recycling organic material. The system consumes about 3% more organic matter than it produces in the dry season and produces about 4% more organic matter than it consumes in the wet season. Tapi Estuary is a net denitrifying system while Bandon Bay is slightly net nitrogen fixing. The presence of benthic algae on the mud flats and the mangrove fringe around the bay could account for nitrogen fixation in the bay. Seasonal variations in biogeochemical rates were attributable to differences in magnitude of freshwater inputs. Under conditions of high river flow, overall rates of net production were enhanced by increased nutrient delivery.


Bandon Bay is the largest estuarine and mangrove inlet on the east coast of the Malay Peninsula. A huge area of intertidal mudflats, extending 1-2 km offshore, encompasses the delta of the Tapi River and at least nine other smaller rivers. The area is backed up inland to a distance of two km by shrimp ponds and degraded mangrove, including large areas of dead and dying trees. Most of the mangrove has been cleared leaving a narrow fringe of tallish trees (10-15m high) along the seaward edge. The bay is very shallow with extensive areas less than one meter deep at mean low water. In areas of shrimp ponds, the salinity ranges from 15 ppt. in the rainy season to 33 ppt. in the dry season. The mean tidal range is l.10m; the amplitude at spring tides is l.90m (occasionally as much as 2.2m), and that at neap tides, 0.7m. Tidal influences are modified by freshwater run-off from the Tapi River catchment.

Sonneratia is dominant in the mangrove on the seaward edge, and is fringed behind with Rhizophora. In only a few areas is the belt of mangroves more than l00m wide, and along much of the coastline it is much less. There are extensive areas of dead mangrove among the shrimp ponds.

Ban Don is a large estuarine mangrove system as the rain flow have resulted in considerable deposition of sediment, clay, silt and organic matter. The forest is dominated by Sonneratia caseolaris, followed by sparse populations of Avicennia alba, Kandelia candel, Rhizophora mucronata and Rhizophora apiculata. Rapid sedimentation at mangrove ground developed the new mudflat which had not been occupied by any plant species yet. The new mudflat was affected by freshwater from the rivers and canal and was flooded whole day only in the heavy rainy season (October-January). Back mangroves have been converted for shrimp farming since 1982.

Distribution of Mangrove and other land use types in Bandon Bay, 1987

(Source: The integrated Management Plan for Bandon Bay and Phangnga Bay, Thailand, Office of the National Environment Board, Ministry of science ,Technology and Environment, 1992)


In the case of Ban Don Bay, the damage schedule indicates that according to the public's judgment, clear-cutting of mangrove forests and shrimp farming activities that involve clear-cutting of mangrove forest are of high importance.

Strong wave energy inhibits the formation of extensive mangrove forests at Bandon Bay. Muddy sediments have been deposited along the river mouths and mangroves are well established there. Coverage , however, is along a narrow strip as tidal range is not great. It has a very gentle sloping or flat land form.

According to Aksornkoae (1987), mangrove in Bandon Bay covered 4160 ha. The figures for various districts are present in Table 5.

District ( Amphur) Hectares

Chaiya 1,784

Tha Chang 404

Phunpin 411

Muang 508

Kanchanadit 836

Don Sak 217

Table 5 Area of mangrove in Bandon Bay in 1987

Increasing areas are being given over to human habitation, and there is further clearance of mangroves for aquaculture. There is also the likelihood of further industrialization of the areas immediately adjacent to the town of Surat Thani. Increased destruction of the forests of the uplands in the water catchment area may lead to increased amounts of silt entering the estuarine ecosystem.

Continued clearance of mangroves for aquaculture may eventually threaten the site with irreparable damage due to erosion of the seaward bunds. Most clearance has taken place in the past five years as a result in part to an influx of settlers from elsewhere. The fishery is of immense importance and the remaining mangroves are probably essential in maintaining its productivity. Different species tend to dominate certain bands or zones which are clearly differentiated. Still, some overlapping occur. The zonation patterns may result from differences in species adaptation to adverse site conditions.

In Bandon Bay , Rhizophora spp. Generally occupy an area along the margin estuaries, rivers and canals where the soil are muddy. The Avicennia community is mainly found on new mudflat developments especially at Donsak and Kanchanadit while Sonneratia community found at Moung districts where the salinity is much lower. These communities, however, are also found at forest margins along the coastline. The Sonneratia spp. also occur on the area along the bank of the estuary but they mainly dominates soils of the sandy loam type. The Xylocarpus community is usually formed behind the Rhizophora zone and Bruguiera and Ceriops communities are foond only associated with Xylocarpus community. The Excoecaria ap. can be found through the mangrove area at Bandon Bay. However, during last decades, large area of mangrove was replaced by shrimp ponds and agricultural land. In some cases , replacement vegetation may take over.



Studies were conducted during June 2009 to August 2009. Mangrove community and at different sites where the project would be carried out , are shown below.

3.1 Chaiya ( Pumriang Site)

Mostly, land are sandy loam with mangroves along the coast and the river bank. Large area of mangrove was replaced by shrimp ponds which influenced by tidal water. Dominant species were Rhiziphora mucronata, Avicennia spp, Sonneratia sp and Nypa fruticans. Some associated species were also found such as Bruguiera cylindrica, Lumnizera racemosa, Ceriops tagal and Hibiscus tiliaceus. Potential area to be restored with mangrove is approx. 500 rai ( 1 ha = 6.25 rai).

3.2 Thachang ( Kao Tan Site)

The area was muddy clay with several creeks pass through the forest. Some natural regenerations of mangrove were also observed in abandoned shrimp ponds. The forest was occasionally flooded by sea water. Some dominant species were Excoecaria ap, Sonneratia ovata, Sonneratia caseolaris, Nypa fruticans and Avicennia spp. Natural establishment of some mangrove in abandoned shrimp ponds were Sonneratia caseolaris and Avicennia sp. Potential area to be restored is approx. 150 rai.

3. Rapid Assessment of Mangrove Communities at some specific sites along the bay.


3.2 Moung ( klong Chanak Site)

Mangrove were formed on mudflat caused by sedimentation from two canals . In the rainy season the area is mostly influenced by fresh water where about 1000 rai of Sonneratia caseolaris establishs well. However, at the landward zone where the deposition is high some species such as Sonneratia caseolaris Avicennia sp, Rhiziphora mucronata , Rhiziphora apiculata, Xylocarpus granatum, Bruguiera cylindrical and Nypa fruticans were found. At the upper part of the canals , Nypa fruticans occupies the bank. The area to be restored needs to be confirmed.

3.3 Kanchanadit ( Takianthong and Tatong Site)

Most area on these sites were converted to abandoned shrimp ponds where the soil were muddy clay. For mangrove seedlings establishment, the water levels in the ponds can be controlled by sluice gates. Also, for both sites, both planted and natural mangroves were observed. Natural mangroves dominated the area were Rhizophora spp, Sonneratia spp, Bruguiera spp,Avicennia spp, Lumnizera racemosa, Hibiscus tiliaceus, Xylocarpus granatum and Nypa fruticans . Potential area to be restored which has been confirmed is approx. 700 rai.

3.4 Punpin (Liled Site)

Similar to 3.2, muddy sediments deposited along the river mouths causes a formation of large mudflat area resulting in the pioneer species of Sonneratia caseolaris is well established there. At the upper zones, however, mixed species of mangrove are formed. More than 800 rai of Sonneratia caseolaris has been naturally regenerated there. The potential area to be restored as a mixed mangrove forest in Sonneratia zone is approx. 750 rai.

Sonneratia caseolaris as a pioneer species on new mudflat at Punpin (Liled Site)


3.5 Donsak site

Donsak district was located in southernmost part of Surat thani province . Donsak was formerly extensively covered with mamgroves of larger than 2,000 ha ( 12,500 rai ). Dominant species were similar to those of Kanchanadit such as Rhizophora spp, Sonneratia spp, Bruguiera spp,Avicennia spp, Lumnizera racemosa, Hibiscus tiliaceus, Xylocarpus granatum and Nypa fruticans. In the 80’s ,a majority of these areas was cleared for commercial shrimp farms, which were mostly owned by business people or outside investors . Since 1993, the villagers have been protesting seriously to the government against the forest encroachment by shrimp farmers, especially as local communities have faced several problems of resources and environment degradation, such as a drastic decline in offshore fishery yields and water pollution from the ponds. There were also events in which some villagers had to move temporarily from their houses during storms because the mangroves no longer protect them from strong gales. Meanwhile, a majority of shrimp farms in Donsak were abandoned due to drastic yield decline induced by viral shrimp disease. The local villagers were therefore keen to protect the remaining mangrove forests and to rehabilitate abandoned forests. As a result, a large scale of mangrove experimental plantation by Rhizophora apiculata, with an area of about 25 ha was conducted in August 2001 which they are growing relatively well.

4. Work Plan for Mangrove Restoration at the Selected Sites

As has been previously mentioned in the proposal that Liled site ( 3.4) is a target site for mangrove restoration, but after field surveys as well as several meetings and discussions with stakeholders and authorities in the bay, some conclusions must be considered.

At this stage, Liled village, as for natural regeneration process, will be the site to restore 80 hectares by replanting suitable mangrove species for biodiversity and ecology of the area. From observation, it appears that the density of Sonneratia as the pioneer species becoming less as approaching landward zone ( probably from the competition effect ) leaving little empty areas for the light to pass through which can be filled up with other species such as Nypa fruticans, Rhizophora spp, Bruguiera spp, Avicennia spp and Lumnizera racemosa. Thus the main task for this village is to plant the mentioned species in patchy patterns for mangrove diversity and ecology.

As for Kanchanadit ( 3.3) most of the area are being dominated by abandoned shrimp ponds , thus manual planting for 40 hectares will be carried out. The area to be planted, however, has already been offered and confirmed by the head of villagers. However, due to requests proposed by other villages around the bay , small scale planting will also consider.


5. Mangrove Restoration at Selected Specific Sites

Some more detailed studies and Recommended Action at each selected site are shown below . 1. Tha Chana Site Geography of the Restoration Area The site is located near the shore line of Tha Chana district. Some abandoned shrimp ponds surround the site, some of which have a regenerated species by natural regeneration. The site itself is also an abandoned pond, within the tidal zone, abandoned 17 years ago. Soil condition is silty mud, with a layer of organic material underneath. Currently, the condition of the mangroves in this pond is poor due to cutting for wood and charcoal. Also many trees are standing dead (snags). Local Plant Community Components The site and in particular the surrounding site is diverse. Dominant species are Rhizophora apiculata, Bruguiera sp, Excoecaria agallocha, Ceriops sp, Avicennia alba and Sonneratia sp. Back mangrove includes Hibiscus tiliaceus, Pluchea indica, Clerodendrum inerme, Acanthus sp, Acrostichum sp and Nypa fruticans Size of Sites 1st. 8ha 2nd. 2haRecommended Action 1. Stopping the cutting by patrolling and talking with local people 2. Education programme with local people run by WI-TO staff 3. Channel cleaning and removal of previous cutting debris, and general hydrological improvement. This work must be sufficient to allow the water to drain from the site at low tide. Cleaning and hydrological work must happen BEFORE any planting happens. 4. In-fill planting in the two areas. Consider Nypa palm or other species desired by the local people, if appropriate to local conditions.


2. Pum Riang Site of Amphur Chai Ya Geography of the Restoration Area This area is more exposed to wind and waves, being on the north east corner of Bandon bay . There is a valuable narrow belt of mangrove, perhaps 10m deep, between the mudflat and the raised ground and road behind the site. Near and within the mangrove area the soil is muddy. The soil outside the mangrove is sandier, with some broken shell fragments, with thin mud layers underneath. This area is influenced by the outflow from a local canal, further south, and by natural movement of sandy sediment around the bay, due to tides and weather. This area is exposed to the full influence of the tide. It is also open to the public, who come to collect clams. Local Plant Community Components Reasonably diverse, with pioneer species of Sonneratia sp and Avicennia sp at the sea front, with Rhizophora sp behind mixed with Excoecaria sp, Bruguiera sp and Xylocarpus sp . Higher up the beach is Hibiscus sp. Site size 30ha belt Recommended Action 1. Here the Department of Marine and Coastal Resource (DMCR) wants to test planting young saplings of between 1-2 meters tall, in front of the current belt of mangrove. The species will be a mix of Avicennia and Rhizophora saplings and Sonneratia wildlings facing the sea. Inside the belt, filling gaps Rhizophora will be used. Only 20% of the budget will be used for this work, as planting in front of mangrove is more risky. 2. Remove large debris within the belt, up onto higher ground. 3. Keep looking for another site


3.) Tha Chang Site Geography of Restoration Area The area is characterised by abandoned extensive shrimp ponds just inside the coastal mangrove belt. Around the edges of these ponds and between them run a series of small canals providing good flushing and drainage. The soil is silty clay. Local Plant Community Components In pockets and canal edges around these ponds is well developed and biodiverse mangrove. A few ponds have been able to regenerate on their own. Dominant species are Sonneratia sp, Avicennia sp and Nypa while Rhizophora is rare. Further there are many back mangrove and associated species present. Site 1. On the slightly higher areas within the extensive pond grass grows. The occasional mangroves, is scattered around within the grasses. The community desires a mix of mangrove species: Avicennia as Sersamid crabs like their leaves, Nypa for livelihood activities and Rhizophora for building wood and charcoal. Site Size Pond is 24ha. Site 2. Similar to Pond 1: abandoned extensive ponds. Grasses and Pluchea indica present on the higher ground within the pond. Local village desire Rhizophora wood products. This pond is likely to enjoy natural regeneration as well as being planted. Site Size Pond is 32ha. Recommended Action 1. WI-TO ( Wetland Internationals , Thailand Office) staff to conduct an education day to explain the benefits of biodiversity 2. Zone these ponds and surrounding area for activities, control cutting and to help planning activity 3. Before any planting is carried out the debris must be removed from the channels, and hydrology checked.


4.) Klong Chanak and nearby Liled site Geography of the Restoration Area Klong Chanak is in the middle of the south side of Ban Don Bay. Two rivers drain into this area, Klong Ril and Klong Chana, bringing a lot of fresh water and sediment. As a result , new mud flats are being generated. The soil is clay with broken shell fragments. Local Plant Community Components There are two mangrove zones in this area. First, new mudflats which tend to be colonised by mono-specific Sonneratia stands, normally in front of existing mangrove. The second zone is behind the first, towards the land. This second zone is also slowly rising due to sedimentation, and thus becoming suitable for other mangrove species and more biodiverse. Site Size 160ha, including the new mud flats. The local villagers want to demark new mud flats and patrol this area to keep out push nets. Protecting this area will encourage new mudflats to be naturally colonised by mangrove as they appear. Between the new zone one and older forest in zone two, more species can be added to speed up the transition from mono-specific stands to biodiverse mangrove. Here, 14ha will be planted with a mix, included Rhizophora apiculata and Nypa fruticans. Recommended Action WI-TO to facilitate Liled to help Klong Chanak demark their mudflat areas with Dept of Fisheries and DMCR. The area demarked will be controlled by budget levels as this is an expensive operation (inserting concrete poles into the mud).


5. Tha Khian Thong Site (of Amphur Kanchanadit ) Geography of Restoration Area Site is series of abandoned intensive shrimp ponds. Two have been naturally restored, one five years ago, the other three years ago. Being close to the bay, the hydrology is good. The soil is clay. The size of each pond is approximately 0.5-0.8ha. Local Plant Community Components The surrounding area is very biodiverse, including Rhizophora apiculata and R. mucronata, Avicennia sp, Bruguiera sp, Lumnitzera sp, Nypa, Xylocarpus sp and so on. Site Size: 8ha. The local villagers want to plant in the ponds. Desired species are Rhizophora mucronata and R. apiculata, Bruguiera sp, and Nypa. Xylocarpus and Hibiscus will be planted on the bunds. Hibiscus wood is used for bird cages. Recommended Action 1. WI-TO need to see ponds allocated for restoration before action starts to collect baseline data. 2. Transects to be performed of mangrove outside the ponds. 3. Studies to be done of the ponds that have been naturally regenerated 5 an 3 years ago. 6.) Tha Thong Site ( of Amphur Kanchanadit ) Geography of Restoration Area For most of the year this area is dry clay soil with minor amount of broken shell fragments. The tides rarely get to this area; very much back mangrove. Only in peak tides is the area inundated, or from rain run off. Local Plant Community Components As a result the surrounding trees are back mangrove and associate species , dominated by Excoecaria sp. Previous efforts to plant Rhizophora mucronata have produce poor results. Recommended Action

1. The village should consider planting ‘back mangrove’ species that are more tolerant of drier soils, like Thespesia, Hibiscus, Heritiera. 2. Find an alternative site


6) Donsak Site Geography of Restoration Area Site is series of abandoned intensive shrimp ponds. Some areas have been restored. Due to the pond construction and / or the change of sedimentation dynamics after the abandonment of the pond, former ground condition was drastically changed . Organic carbon of the soils was reported to be lower than mangrove soil (Matsui and Yamatani 2000, Phuket marine biological center special publication 22,15-25 ). Carbon in may have lost during abandonment of shrimp ponds or at the time of mangrove exploitation. Also, soil properties were reported to be predominantly related to relative ground level. Namely, relatively elevated areas were drier and more oxidized with less salt and organic matter than lower areas (Matsui 2007, Final meeting of the joint project on Development of Reforestation Techniques for Rehabilitating Mangrove Ecosystem, Kansai Electric Power Co.,Inc. Osaka, Japan. March,2007 ) Local Plant Community Components As has been mentioned, dominant species were similar to those of Kanchanadit such as Rhizophora spp, Sonneratia spp, Bruguiera spp,Avicennia spp, Lumnizera racemosa, Hibiscus tiliaceus, Xylocarpus granatum and Nypa fruticans. Site Size: 8ha. Recommended Action 1. Control of water status of the planting areas 2. Organic matter application in abandoned shrimp ponds 3 . Select natural and fast growing species

Documents

Rapid ecological assessment surveysat coastal areas of Ban Don Bay (Final Report)