Growth and regeneration characteristics of sonneratia caseolaris (l) engl in thuy truong commune, thai thuy district, thai binh province

ACKNOWLEDGEMENT Firstly, I would like to express my sincere gratitude to my advisor Dr Pham Minh Toai for the continuous support of my thesis and related research, for his patience, motivation, and immense knowledge His guidance helped me in all the time of research and writing of this thesis I could not have imagined having a better advisor and mentor for my thesis Besides my advisor, I would like to say thank to Asso.Prof.Dr Bui TheDoi, Asso.Prof.Dr Nguyen PhanThiet and Dr Bui Xuan Dung who always gave me kindly helps whenever I need in the time I studied at VFU My sincere thanks also go to Prof Lee MacDonald, Prof Steve Leisz who always supported me, read all my email and tried to help as much as possible with all of their enthusiasm I also dedicate my grateful for all the Doctors, Masters and Lecturers in VFU, who gave me a lot of knowledge, favors as well as memories Another thank is for all the people in Thuy Truong commune who helped me in my researching process I thank my fellow classmates for the stimulating discussions, for the sleepless nights we were working together before deadlines, and for all the fun we have had in the last four years Last but not the least, I would like to thank my family: my parents and to my brothers and sister for supporting me spiritually throughout writing this thesis and my life in general ABSTRACT Mangrove forest is one of the important ecosystems on earth that plays a role in preventing natural disasters Thuy Truong is a coastal commune that has a large area of mangrove, with the availability of Sonneratia caseolaris as a big part of that important ecosystem The purpose of this thesis is to gain an in-depth understanding of how natural factors can affect the growth and regeneration characteristics of Sonneratia caseolarisin mangrove forest Furthermore, based on data measured and topography make recommendations for the authority or government to put efforts on mangrove forest sustainable development, especially Sonneratia caseolarisspecies To gain the knowledge required for the thesis, a method of measure regeneration in gap and under canopy was conducted Results from investigation process indicate that growth and regeneration of Sonneratia caseolaris in gap are more developed than one beneath canopy due to the competition for spaces, light and nutrients Keyword: Sonneratia caseolaris, gap, regeneration, growth, measurement TABLE OF CONTENT I INTRODUCTION II GOALS AND OBJECTIVES III STUDY SITE AND METHODS 3.1 Study site characteristic 3.2 Study methods 3.2.1 Secondary data collection 3.2.2 Field investigation IV RESULTS AND DISCUSSIONS 14 4.1 Seedling density of Sonneratia caseolaris in study area 14 4.2 Tree height (Hvn) of Sonneratia caseolarisseedingsin the studied area 16 4.3 Tree Root collar diameter (Doo) of Sonneratia caseolaris seedlings in the studied area 17 4.4 Impacts of natural factors to the growth and regeneration of Sonneratia caseolaris seedlings 18 4.4.1 Impacts of LAI to seedlings abundances beneath surrounding canopy 18 4.4.2 Impacts of gap size to seedlings abundance of studied species 19 4.4.3 Impacts of coastal zone to the proportion of studied species 22 4.4.4 Impacts of coastal zone to seedling density 23 4.4.5 Impact of coastal zone to seedling quality 24 V CONLUSIONS AND DICUSSION 26 5.1 Conclusions 26 5.2 Suggestions 27 LIST OF TABLES Table 3.1 Regeneration in gaps investigation Table 3.2.Regeneration in surrounding canopy investigation 11 Table 4.1 Seedling density of Sonneratia caseolaris beneath surrounding canopy and in forest gap 14 Table 4.2 Tree height of seedlings regenerate under canopy and in forest gap 16 Table 4.3 Tree Root collar diameter of seedlings regenerate under canopy and in canopy gap 17 Table 4.4 LAI and seedlings abundance under canopy correlation 19 Table 4.5 Gap size and species abundances correlation 20 Table 4.6.Coastal zone characteristics of studied area 23 Table 4.7 Seedling density in types of coastal zone 23 Table 4.8.Seedling quality in types of coastal zone 24 LIST OF FIGURES Figure 3.1 Thai Binh Administrative Map Figure 3.2 Gap selection method Figure 3.3 Regeneration in gap survey design Figure 3.4 Regeneration in gap and surrounding canopy survey design 10 Figure 4.1 Coastal zone of mangrove 22 LIST OF GRAPHS Graph 4.1.Seedling density of Sonneratia caseolaris beneath surrounding canopy and in forest gap 15 Graph 4.2 Tree height of seedlings regenerate under canopy and in gap 17 Graph 4.3.Tree Root collar diameter of seedlings regenerate under canopy and in gap 18 Graph 4.4.LAI and seedlings abundance under canopy correlation 19 Graph 4.5.Gap size and species abundances correlation in the near shore region 21 Graph 4.6.Gap size and species abundances correlation in the middle region 21 Graph 4.7.Gap size and species abundances correlation in the waterside region 22 Graph 4.8.Seedling quality in types of coastal zone 25 LIST OF ACRONYMS Acronyms Explanation Doo Root colar diameter Hvn Tree height D1.3 Diamter at breast height Dt Canopy diameter 1st transect Near shore region 2nd transect Middle region 3rd transect Waterside region LAI Leaf Area Index I INTRODUCTION The appearance of mangrove has a huge role in environment and socio-economic aspects Mangrove forest is an important ecosystem which has high productivity in the tropical estuary and coastal region, is sensitive with artificial and natural impacts This forest type provides not only valuable products such as timber, wood, tannin, food but also the shelter for several animals, aqua birds, migratory birds and some animals which have high economic value such as Monkey, Crocodile, Iguana, and Snake, etc This type of forest ecosystem has a huge value to environment and disaster prevention such as reduce erosion, increase accretion in coastal land, protect dyke, production field and human habitat from storm and flood In the past few years abnormal climate has happened more unpredictably such as El Nino and La Nina with flood and whirlwind It has caused huge damage for coastal regions Therefore, to develop and protect mangrove forest is definitely urgent There have been many studies of mangrove forest in the world Especially, researches about regeneration of mangrove forest have attracted attention of so many experts Most of the study about mangrove’s regeneration applies the method of measuring tree’s parts and monitor the growing speed of tree under the impacts of environmental factors such as: soil structure, tidal wave, temperature and salinity, etc In 1959, Steru and Voight carried out a study about the impact of sea water salinity to Rhizophoea mangle’s growth and claimed that this species grew best in the condition which had equivalent sea water salinity In the periods of 1962-1966, Scholander published some studies about the growth of Rhizophoea mangle in different salinity condition According to that, this species can best adjust salt concentration in the salinity condition equal ½ of sea water salinity Inaddiltion, Snedaker(1979) believed that “fresh water is physiological condition and salt water is requirment for mangrove.” In general, when studying about the growth and regeneration of mangrove forest, scientists in the world mainly focus on the impacts of sea water salinity to the growth rate of mangrove ecosystem There were also some studies about the impacts of soil nutrients, tidal amplitude to the growing process as well as diameter and height of mangrove forest, however, there were still limitation in methods, orientation, content and quantity In Vietnam, growth and regeneration characteristics of mangrove forest have interested scientists since 1975 There were some typical researches that could be noteworthy such as Phan Nguyen Hong (1991) used methods of Logo and Sedake (1975) to monitor the growth of buds and obtained results on the general size and commented that “The ability to grow in tree diameter and height depends on factors such as site conditions, soil conditions, tidal regime and tree density" In the year of 1994, when studied about the growth and biomass of mangrove species in Thach Ha - Ha Tinh, Nguyen Duc Tuan reported that “At the same age, the growth of height, diameter and quantity of branch of a Bruguieragymnorrhiza tree is lowest” For Sonneratia caseolaris,according to some studies, this species often widely distributes in the estuary regions in many countries In some region far from the equator, there is no Sonneratia caseolaris while there is still mangrove available Regarding ecological characteristic of Sonneratia caseolaris, somescienties such as Toble, F et al (1923), Grant, D.K.S (1938), Walsh (1967), Tomlison (1999) found out that this species has a big trunk, tree height can reach 15m with a lot of braches and large canopy In addition, Takechisa Nakamura (2000) described types of breathing roots of Sonneratia caseolaris He also published some interesting information about the relation between environmental impacts as well as age of the species and types of breathing roots His study has opened a new direction to analyze the adaptation of Sonneratia caseolaris with the environment based on root morphology In the early of 70s, Phan Nguyen Hong (1970), Nguyen Khoa Lan (1980), Phan Nguyen Hong and Hoang Thi San (1984), Ngo Dinh Loc and Phan Nguyen Hong (1984) reported that Sonneratia caseolaris is popular in most of the tidal and alluvial salt regions in Vietnam However, those authors have not been showed the impact of tidal wave to the growth of this species In 2003, Dao Van Tan studied about the impact of low temperature to Sonneratia caseolaris He concluded that, the ability to put up with low temperature depends on age of tree When average air temperature decreases from 27 oC to 16oC, growth of this species also decreases If average air temperature is lower than 10oC, the species will stop growing In general, researches about biological characteristic of Sonneratia caseolaris in term of distribution, morphology, physiology and surgery have been attracting a lot of concern However, to deeply study about the impacts of soil, temperature, salinity and planting techniques to the growing process of Sonneratia caseolaris has not been mentioned in any study in Vietnam Thuy Truong is a coastal commune located in the Red river delta with a large area of mangrove forest Especially, this commune has 100years-oldSonneratia caseolaris forest with typical characteristic of tropical mangrove forest There have been a lot of studies about mangrove forest conducted here However, there have not been so many researches about regeneration characteristic of this mangrove species beneath forest canopy and in forest gap Therefore, effects of forest structure and environment factors to regeneration of this species is still lacking With those reasons above, I conduct the study on “Growth and Regeneration Characteristics of Sonneratia caseolaris(L.) Engl in Thuy Truong commune, Thai Thuy district, Thai Binh province” 4.2 Tree height (Hvn) of Sonneratia caseolarisseedingsin the studied area Table 4.2 Tree height of seedlings regenerate under canopy and in forest gap Beneath surrounding Transect In gap canopy Hvn (cm) S S% Hvn (cm) Comparison S S% 1.27 0.46 24.16 1.28 0.31 36.08 U = -0.2 1.15 0.52 28.2 1.27 0.36 45.18 U= -2.37 1.02 0.37 37.66 1.23 0.36 36.68 U = -4.16 Comparison Average = 1.15 m Average = 1.26 m From the result table, we can see that growth of Hvn of seedlings regenerate under canopy and in gap is quite different With the 2nd and 3rd transects, │U│> 1.96 refers that growth of Hvn of seedlings is not homogenous While in the 1st transect, │U│ 1.96 which means growth of tree stem is not homogenous in conditions for regeneration Average Doo measured of seedlings under canopy is 1.125cm, while Doo measured of seedlings in gap is 1.34cm 17 Variation coefficient of seedlings in status of regeneration is also different With seedlings in gap, S% is 16.62%, 31.62% and 32.95% larger than S% of seedlings under canopy, 15.87%, 23.24% and 23.82% respectively We can conclude that, Doo growth of Sonneratia caseolaris seedlings in gap happens stronger than one happens under canopy and Doo growth of seedlings regenerate in near shore and middle region is better than one in waterside region It can be seen in the graph below 1.6 1.4 1.2 Beneath canopy gap 0.8 In gap 0.6 0.4 0.2 Graph 4.3.Tree Root collar diameter of seedlings regenerate under canopy and in gap 4.4 Impacts of natural factors to the growth and regeneration of Sonneratia caseolaris seedlings 4.4.1 Impacts of LAI to seedlings abundances beneath surrounding canopy Mangrove forest has a huge advantage of regeneration Seedlings in mangrove forest are originally regenerated by the fallen seeds or by spread seeds transported by tidal way from other places Like the natural regeneration of terrestrial forests, regeneration process of mangrove forest is influenced by many factors such as mother tree density, canopy cover and site condition… In which, canopy cover and soil structure are two of the 18 most important factors that affect growth and regeneration of vegetation beneath canopy, especially density, quality and seedlings distribution beneath canopy Canopy cover of a stand can be demonstrated by LAI indicator, which refers to the area of leaves Correlation of LAI and studied species are described in the table below Table 4.4 LAI and seedlings abundance under canopy correlation Seedling abundance LAI m2/m2 (seedlings/m2) Average 1.69 7.93 Variance 0.33 5.88 Pearson -0.78 Table 4.4.showed that the correlation of LAI and seedlings abundance is not significant Seedling abundances of Sonneratia caseolaris considerably decreased with increasing LAI of the surrounding trees In other words, seedling abundances of studied species increase when canopy cover decreases Sonneratia Caseolaris Seedlings 16 14 y = 0.1607x2 - 3.9037x + 14.03 R² = 0.638 12 10 Sonneratia Caseolaris Poly (Sonneratia Caseolaris) m2/m2 Graph 4.4.LAI and seedlings abundance under canopy correlation 4.4.2 Impacts of gap size to seedlings abundance of studied species Results of the linear regression analysis indicated a positive relationship between the canopy-gap size and the sapling abundance 19 Table 4.5 Gap size and species abundances correlation Transects Near shore Gap size N Features (m2) (Seedlings) Total 1209.5 135 Average 60.475 6.75 S 196.43 3.88 R Middle region 0.9 Total 1682 186 Average 84.1 9.3 S 400.12 6.22 R Waterside 0.94 Total 1595 156 Average 79.75 7.8 S 423.0395 4.694737 R 0.84 They showed a strong and positive correlation with the abundances of seedling tree species for pooled data of three studied sites This means that saplings of regenerated tree species tended to abundance in the larger size of canopy gaps while this size factor appeared to have not so much influence on the abundance of seedlings As seen in the result table, the lowest values of species richness were found in the smallest canopy gap size (< 50 m2) While the largest values of species abundance felt into the gap size of > 50m2 Gap size average in the middle region is largest Smallest average value of gap size is in near shore region The reason for that is because in the waterside region, there are larger gaps than near shore region due to storm and huge tidal wave that can kill or wash tree away and create gap In the near shore region, Sonneratia caseolaris grows with high density in the bracket water condition, which keeps them more stable 20 Seedlings Seedlings/gap 12 y = 0.135x - 1.4145 R² = 0.9224 10 Seedlings Linear (Seedlings) M2 0 20 40 60 80 100 Graph 4.5.Gap size and species abundances correlation in the near shore region Seedlings Seedlings/gap 16 14 y = 0.1183x - 0.6496 R² = 0.9002 12 10 Seedlings Linear (Seedlings) M2 0 20 40 60 80 100 120 Graph 4.6.Gap size and species abundances correlation in the middle region 21 Seedlings Seedlings/gap 14 12 y = 0.0888x + 0.7207 R² = 0.71 10 Seedlings Linear (Seedlings) M2 0 20 40 60 80 100 120 Graph 4.7.Gap size and species abundances correlation in the waterside region 4.4.3 Impacts of coastal zone to the proportion of studied species To study impacts of soil structure to regeneration of Sonneratia caseolaris, data was investigated along transects that were described in figure below: 0m 330m 770m Figure 4.1 Coastal zone of mangrove Coastal zone characteristics are summarized in the table below: 22 1140m Table 4.6.Coastal zone characteristics of studied area Coastal zone Characteristic Distance to the bank (m) Elevation above sea level (m) Depth in flood tide (m) Depth in low tide (m) Tidal regime Canopy species composition Other characteristic I II III - 330 330 - 770 770 - 1140 1.7 -2.2 1.2 -1.5 0.8-1.0 0.5-1.5 0.8-1.7 1.5-2.3 Not submerged 0.2-0.5 Diurnal tide Diurnal tide Diurnal tide 36.2% Sonneratia sp + 47.3% Sonneratia 17.8%Kandelia sp.+ sp + 52.7% 46% Aegiceras sp Aegiceras sp Fallen leaves layer Sedge abundance Not submerged 100% Sonneratia sp Few sedge According to the table above, we can see that at the 1stcoastal zone, Sonneratia is abundant, Kandelia is the 2nd abundant species and the least is Aegiceras Tree density at the 1stcoastal zone is quite high At the 2ndcoastal zone, there is only Sonneratia and Aegiceras dominates The 3rdcoastal zone has only Sonneratia 4.4.4 Impacts of coastal zone to seedling density Investigated results for seedling density are summarized in the table below: Table 4.7 Seedling density in types of coastal zone Coastal Trees /100m2 tree/ha I 800 II 32 3,200 III 14 1,400 zone Table 4.7.shows the differences among seedling density in the 2ndcoastal zone with the others Seedling density in coastal zone II is really high, 3200 tree/ha The reason for that is because of that sedge With high density, sedge can prevent seeds from being carried by tide Sometime, seeds from other places often get stuck in sedge when traveling 23 In the 1stcoastal zone, seedling density is quite low It is explained that canopy cover has influences High tree canopy is an important factor on supplying seeds for regeneration process However, in mangrove, most of the species is light demanded, high canopy cover has its bad impacts in the growth of seedlings On other hand, this coastal zone is in higher elevation than the 2nd and the 3rd one with thin mud layer, dense structure, thick fallen leaves layer, which can prevent seeds from reaching the soil to sprout In the 3rdcoastal zone, there is low canopy cover and low high tree density The source of regeneration comes almost from other places This position is suitable for Sonneratia to regenerate, however, thin mud layer in here makes it difficult to steadily stand 4.4.5 Impact of coastal zone to seedling quality Results investigated are recorded in the table below Table 4.8.Seedling quality in types of coastal zone Seedling quality Coastal zone Good Medium Bad Amount % Amount % Amount % I 12.5 62.5 25 II 12.5 21 65.63 21.8 III 11.3 35.71 14 53 In types of coastal zone, the proportion of good quality seedlings is smaller than the others, 12.5%, 12.5% and 11.3% In coastal zone I and II, percentage of medium tree is 62.5% and 65.63% In coastal zone III, percentage of bad quality seedlings reaches 53% The reasons are in the 3rdcoastal zone, salinity is quite high, which is unsuitable for regeneration Due to high salinity, shipworms develop stronger than the other coastal zone They stick to the tree stem, root and branch They reduce the contact of stem, branch and leaves with light leads to reduce the photosynthesis ability of Sonneratia caseolaris 24 70 60 50 40 30 I 20 II III 10 % % Good % Medium Bad Seedlings quality Graph 4.8.Seedling quality in types of coastal zone It can be concluded that in coastal zone II with fixed mud layer and sedge abundant is the most ideal condition of all coastal zones in the study area to help growth and regeneration of Sonneratia caseolaris happen strongly 25 V CONLUSIONS AND DICUSSION 5.1 Conclusions a) Sonneratia caseolaris’s natural regeneration in studied area In the 2nd coastal zone with stable mud layer and thick sedge density is the best suitable condition for Sonneratia caseolaris to better grow Sapling density is 3,200 trees/ Percentage of good quality trees is 12.5%, medium quality tree is 65.63% There is only 21.88% of bad quality tree The 1st coastal zone is less affected by shipworm There is also no competition of sedge for space However, mud layer here is quite thin And it is light limited by canopy, which has bad effects on density and regeneration of studied species Sapling density in this coastal zone is only 800 trees/ Percentage of good quality trees is 12.5%, medium quality tree is 62.5%, and 25% of bad quality tree In the 3rdcoastal zone, saplings which are fixed here appear due to dispersal There are a lot of shipworms stick to the tree stem prevents the growth and regeneration A number of trees are topless Mud covers tree leaves and prevents respiration and photosynthesis Sapling density in this coastal zone is 1,400 trees/ Percentage of good quality trees is 12.9%, medium quality tree is 35.7%, and 53% of bad quality tree b) Growth of Sonneratia caseolaris in gap in studied transects Growth of seedlings of Sonneratia caseolaris in gap is better than ones regenerates beneath gap canopy in both quality and quantity In term of species richness, average seedling density beneath canopy gap is 1,120 tree/ha while there is 1,265 tree/ha in gap Growth of seedlings of Sonneratia caseolaris in gap is better than ones regenerates beneath gap canopy in both quality and quantity Mean seedling density beneath canopy gap is 1,120 tree/ha while there is 1,265 tree/ha in gap Root collar diameter measured in seedlings beneath canopy gap and in gap is also differentiated between regenerated conditions Mean Doo of seedlings beneath 26 canopy gap is 1.125 smaller than ones in gap, 1.34cm Hvn of seedlings in gap is 1.26 cm in average, while it is 1.15cm for the Hvn of seedlings in gap Due to getting more light as well as spaces and nutrients, seedlings in gap have higher growing characteristic than seedlings beneath canopy gap c) Impacts of natural factors to seedling abundances LAI is an important factor which can affect the growth and regeneration of seedlings beneath Data analysis showed that there is unclear correlation between LAI and seedlings abundance Consider the correlation of gap size and seedling abundance, when the bigger the gap size is, the larger seedlings abundance is Sonneratia caseolaris is species that regenerates by fruit They need spaces and light to regenerate Gap in the forest is one of the most ideal conditions for them to rebirth d) Shortcoming In study process, I realize that the Study still has some shortcomings, which are listed below:Due to limited time and research scope, I could only found 12 gaps and set up transects to study Therefore, the accuracy of the study is not so high The Study only focused on growth and regeneration of Sonneratia caseolaris in the studied area without analyzing the impacts of natural and ecological factors to the growth and regeneration of studied species 5.2 Suggestions Mangrove forest is a special ecosystem which has an important role in many aspects of nature and human life Study about mangrove ecosystem in general and mangrove forests in particular are essential Below are some suggestions that can be used to improve the quality of mangrove forests as well as sustainable exploit benefits from them i) Set up navigation plots to monitor mangrove in different site condition to long – term collect data and study mangrove 27 ii) Plant Sonneratia caseolaris near the shore Choose the species which have ability to adapt with high salinity to plant in the waterside region to improve forest quality iii) Should have more researches about the growth and regeneration of mangrove species to develop techniques in planting and monitoring mangrove iv) Should have planning in aquaculture to not only utilize benefit for human, but also minimize the bad impacts on the sustainable development of mangrove forest v) Strengthening the management mechanisms of the Government and the Authorities Promote the inspection and monitor to detect, prevent and process illegal activities related to mangrove forest management Propagandize people about the role of mangrove forest in order to raise the awareness 28 REFERENCES Tran Van Ba (1984), “Kết bước đầu nghiên cứu giải phẫu hình thái rễ số loài thực vật rừng ngập mặn”, Proceedings of Conferences of Mangrove Ecosystem in Vietnam, first time, Hanoi Nguyen Thị Ngọc Cham (1999) “Ảnh hưởng bồi tụ số đặc điểm sinh học rừng Trang (Kandelia candel Druce), huyện Thái Thụy, tỉnh Thái Bình”, Biology Master Thesis, Hanoi Educational University Phan Nguyên Hong (1970), “Đặc điểm sinh thái, phân bố thực vật thảm thực vật ven biển 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