Kandelia candel (L.) Druce in the Philippines

Hikobia 15: xx–xx. 2008

Does mangrove Kandelia candel (L.) Druce follows a mangrove zona-tion, soil salinity and substrate for survival?

EUTIQUIO L. ROTAQUIO, JR., NOBUKAZU NAKAGOSHI AND RONALDO L. ROTAQUIO

ROTAQUIO, JR., E. L., NAKAGOSHI, N. & ROTAQUIO, R. L. 2008. Does mangrove Kan-delia candel (L.) Druce follows a mangrove zonation, soil salinity and substrate for survival? Hikobia 15: xx–xxx.

The question why mangrove plants are forming mangrove zonation or distinct divi-sion or separation among each species in the ntertidal flat has been the subject of arguments among mangrove scientists and researchers. How zonation affects the survival of a certain mangrove is still unclear. It is in this light that this study was conducted to verify the significance of mangrove zonation to the species of Kandelia candel (L.) Druce. The findings showed that this species has a higher chance of sur-vival if planted in its preferred zone with due consideration to its required soil salin-ity and soil substrate type. This study also revealed that mangrove zonation is a natu-ral pattern to follow or as a basis of what type of species should be planted in order to attain a higher planting survival in the mangrove reforestation activity. Eutiquio L. Rotaquio, JR., Graduate School for International Development and Coop-eration, Hiroshima University, Kagamiyama, Higashi-Hiroshima, 739–8529, Japan; Aurora State College of Technology Baler 3200 Aurora Province, Philippines. E-mail Address: [email protected] Nakagoshi, Graduate School for International Development and Coopera-tion, Hiroshima University, Kagamiyama, Higashi-Hiroshima, 739–8529, Japan. E-mail Address: [email protected] L. Rotaquio, Provincial Environment and Natural Resources Office, Depart-ment of Environment and Natural Resources, Baler 3200, Philippines. E-mail Address: [email protected]

1. Introduction

　One of the distinguishing characteristics of major mangrove plants is the formation of zona-tion, of which each species from seaward zone going to the landward most part has its own distinct division of species association vary-ing in different length and width parallel to the shoreline or river edge. The extent in terms of wideness and length depend on the availability of the mudflat and the topography of the area. It can also be described as the distinctive formation of pure community of each species with visible boundary and growing parallel to the coastal wa-terline from lowest tide line to the maximum tide line. It is the distinct separation of each major mangrove species in the inter-tidal flat from sea-

ward to landward. 　There are several definitions of mangrove zo-nations given by mangrove scientists and ecolo-gists. Primavera (2000) defined it as the presence of stands of one or two species depending on in-ter-tidal position and location within an estuary. According to Tomlinson (1986) the existence of zone is often mono-specific and an impression that it is a series of vegetational bands parallel to the coastline. Zonation could be defined as the structural feature of mangrove forest in some parts of the world (Woodroffe 1992). The simple explanation for mangrove zonation according to Hogarth (1999) is that, it represents a steady state response to a gradient in some critical physical variable, and in the case of upshore/downshore gradients that this gradient is maintained by the

Hikobia Vol. 15, No. 2, 20082

tidal inundation regime. Zonation is modified by local topography, which determines tidal and fresh-water runoff, and by sediment composition and stability (Semeniuk 1980).　The formation of mangrove species zonation has been the subject of several studies and argu-ments among ecologists arguing that the tropical mangrove forest is characterized by clear zona-tion along tidal gradient, and it has been sup-posed that the zonation is primarily controlled by soil factors. Hogarth (1999) stated that there are four main approaches to the causes of spe-cies zonation which have emerged based on the concepts of population dynamics, ecophysiology, and geomorphology. The first one is that, zona-tion results from the physical sorting of floating propagules by water movement, the position of an adult tree within a forest being determined by the point at which a propagule was stranded. Sec-ond, selection might take place after settlement, (e.g. different species thriving at different posi-tions along some physical gradient). Third, zona-tion might be a consequence of gradients created by major geomorphological changes and finally, zonation might be the product of ecological in-teractions between species in the community, the sequence of species along a transect in space corresponding to a natural succession of species with time. Rabinowitz (1978) in her observation in Panama that the shore level at which a species occurred correlated with propagule size, that the species thriving in the landward most part of the mangrove were those with smaller propagules. Larger propagules were more likely settled and established at the seaward, which is regularly flooded. Kathiresan and Bingham (2001) stated that one potential cause of mangrove zonation is the differential ability of propagules to establish at different tidal heights. According to them it is directly related to propagule size. It has been sug-gested that small propagules drift further inland and establish better in shallow water than large propagules however, this case is not true in the case of Avicennia marina, of which the seed is generally small but most likely appeared in sea-ward mangrove where strong water current and tide is relatively strong and high as in the case of mangrove in Aurora Province, Philippines where this study was conducted.　Woodroffe (1992) pointed out that the contrib-

uting factors in the formation of zonation may include plant succession, geomorphology, physi-ological adaptation, propagule size, seed preda-tion, and interspecific interactions. However, these factors depend also on the individual habi-tat type or requirements of each species. On the other hand, Robertson and Alongi (1991) argued that plant succession plays a minor role in man-grove zonation and that simple erosion and sedi-mentation control the distribution of mangroves along the seaward edge of the mangal. 　Tidal regime or current also affects the forma-tion of some mangrove zonations such as in In-dian Sunderbans, the mangal areas that regularly inundates by tide diurnally is dominated by Avi-cennia marina and Avicennia alba while Excoe-caria agallocha, Ceriops decandra and Acanthus ilicifolius dominate sites that are not completely indundated (Saha & Choudhury 1995).　Tomlinson (1986) stated that there are actually 35 interconnecting environmental variables in determining vegetation zonation. However, these variables might be contrasted on the basis of whether the influence is abiotic or biotic. Major abiotic include geomorphology, tidal inundation classes and physiological responses to gradients such as salinity. Biotic factors influencing zona-tion include propagule sorting and competition. Semeniuk’s (1980) interpretation of physiography and hydrology provides evidence that ground-water salinities are an important inf luence on mangrove distribution, that if there is great ground-water seepage, there was a formation of landward fringe and the lack of ground-water seepage, almost no formation of landward fringe of mangroves. 　Based on the foregoing premises, it is impor-tant to point out about what is the limiting fac-tor in the formation of mangrove zonation? The above-mentioned arguments are too general with a wide range of scope and therefore requires ex-perimental works to answer. This study aimed to answer some of the foregoing questions deal-ing and limited only to the two most important ecological factors affecting the formation of mangrove zonation- the soil salinity and type of soil substrate. This particular study was also intentionally conducted to answer why most of the local and national mangrove reforestations in the Philippines were always failure. In the lo-

R, JR., N. NAKAGOSHI AND R, L. ROTAQUIO 3

cal place of Aurora, Philippines alone, five major reforestation projects have been implemented, however, the average percentage survival was 45% and below (AIADP II 1988) far behind to the national standard of 80% reforestation sur-vival rate to be considered as successful one. Possible common mistake based on the actual observation of the authors were the mismatched of the kind of planted propagules in different zonations since most of the propagule used was only one species, Rhizophora stylosa, for all the zonations in the mangrove areas because of abundant and available propagules. Aside from this, common people who were involved in the reforestation strongly believed that any kind of species of mangrove can survive everywhere in mangrove forest because it is considered as halo-phyte plants, which means according to them, it has the ability to cope up or has the tolerance with saline environment. However, in the opinion of the author, this idea is too general and may provide half-baked information for mangrove researchers. To test this notion and to provide evidence, we conducted an experimental test for the survival and adaptability of Kandelia can-del (L.) Druce in different mangrove zonations. This species is the latest major mangrove species added to the list of existing mangrove species in the Philippines and discovered existing naturally only in the mangroves of Aurora throughout the entire Philippine archipelago. So far, no other records of its natural population in other suit-able mangrove areas in the Philippines have been reported. Our hypothesis is that each species of mangrove follows a zonation appropriate for them to survived, disregarding their required zonation, the type of substrate and its level of soil salinity requirements in planting, efforts in reforestation activities might possibly fail. This study aimed to test the survival and adaptability of Kandelia candel in the different mangrove zonations with due respect to the soil salinity and type of soil substrate.

2. Materials and methods

2.1 Plant materials and experimental site　A total of 330 fallen and mature propagules of Kandelia candel was collected around the vigorous mother trees in the mangroves of Baler

(15°44′936″ N; 121°34′633″ E), Aurora, Philip-pines. Thirty propagules were planted in Oc-tober, 2005 in an open space in each zone in the same mangrove forest, with spacing of 0.5 m × 0.5 m. No other silvicultural treatment and management have been applied in the planted propagules and assumed that the growth and survival were just affected by natural factors ex-isting in the mangroves. The planted propagules were monitored and checked its survival month-ly, including the in situ soil salinity in each zona-tions. The monitoring period lasted for one year.

2.2 Methods of Monitoring the Survival of Kan-delia candel

　Initially, prior to planting, each propagules were checked. Damaged and deformed propagules were eliminated. Only sound and vigorous propagules with closed terminal shoot and/or leaf bud was chosen for the experiment. The basis for survival was the continuous presence of terminal bud and production of leaves until the end or ter-mination of observation period.

2.3 Determination of soil salinity　In measuring soil salinity, the Twin Cond Horiba Conductivity Meter B–173, which was calibrated with 1.41 standard solution into the sensor cell following the 1:1 soil to water method (Whitney 1998). Three replicates of 20 g of soil samples were taken randomly from each zonation at 20 cm soil depth, and then, 20 mL of distilled water was added and mixed to the samples and allowed it to settle for 15 minutes. The conduc-tivity meter was then dripped into the suspension to get the conductivity readings. The conductiv-ity readings were then converted into salinity in parts per thousand (ppt) unit of measurement. The monthly in situ soil salinity readings in dif-ferent zones where Kandelia candel has been planted is presented in Table 1.

2.4 Determination of mangrove zonation and identification of mangroves

　To measure the extent of mangrove zonation, three transect lines in the whole mangrove for-est were laid out perpendicular to the shoreline or river edge ranging from 1–782 m using a steel transect tape from the lowest tide level line up to the maximum tide level line. The two transect


Tabl

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with 4–55 m, Sonneratia alba zone with 5–25 m, Rhizophora apiculata with 0–20 m, Bruguiera (mixed varieties) having a zone width of 0–200 m, Kandelia candel zone on the other hand can be found along the river bank of Zabali and sparsely distributed up to the small creek closed to the Aurora State College of Technology (AS-COT) Marine Laboratory. The zonation width is relatively small ranging from 0–5 m and/or an average of 1.6 m and growing mostly as frontal pioneer species in muddy river edge. Huge trees of old growth Lumnitzera littorea having a zone width of 0–250 m can be found on the inner side of mangrove forest. This was followed by Heri-tiera littorea zone, with an average zone width of 5 m, Acanthus ebracteatus zone with 4–10 m and Acrostichum aureum zone with small zone width of 0–2 m located in the landward most and well disturbed areas. Extent of each zonation from seaward to landward in the mangroves of Baler, Aurora Province, Phillippines is presented in Table 2.

3.2 Survival and adaptability of Kandelia candel in different mangrove zonations　There were 11 distinct zonations identified in Baler mangroves from seaward to landward most part. These include Rhizophora stylosa zone,

lines were set at the two end parts of the man-grove forest and the other one was set on the middle of the forest all starting from seaward going to the landward. It was followed by mea-suring the extent width of each zonation across the transect lines and then the mean average was computed for each zone.　Species were identified using the dichotomous key in mangrove identification (Tomlinson 1986), using portable monographs and other mangrove reference books. One dendrologist and one for-ester joined in the fieldwork to make sure with the identification and field data gathering. Sample specimen for unidentified and species with doubt identifications were sent to the University of the Philippines experts for further verification and proper identification of the species.

3. Results

3.1 Baler mangroves and its zonation　The mangal areas of Baler has a total area of 19.7 ha (AIADP II 1988). The mangrove zona-tions are represented by Rhizophora stylosa (arti-ficially planted) occupying the most seaward part with sandy to coralline soil substrate on the east-ern side of Baler port. Zone width ranges from 0–250 m, followed by Avicennia marina zone

Fig. 1. Vertical profile of mangrove zonations at Baler, Aurora Province, Philippines.


test, there was no survival in two seaward most zones (Rhizophora stylosa & Avicennia marina zones). In Rhizophora stylosa zone, all seedlings planted were already died after 7th months of planting, worst case in Avicennia marina zone wherein no more surviving propagules just only after four months of planting. On the other hand, four zonations were noted having highest per-centage survival. These are the Bruguiera gymn-orrhiza zone with 57%, Nypa fruticans zone with 63%, Rhizophora apiculata zone with 67% and the highest was recorded from its original zone (Kandelia candel zone) with 70%. The adapt-ability percentage survival of planted Kandelia candel in each zone for one year monitoring is

Avicennia marina zone, Sonneratia alba zone, Rhizophora apiculata zone, Bruguiera zone , Kandelia candel zone, Lumnitzera littorea zone, Heritiera littoralis zone, Acanthus ebracteatus zone, Nypa fruticans zone and Acrostichum au-reum zone. Although the Heritiera littoralis, Acanthus ebracteatus and Acrostichum aureum are not considered as major mangrove based on the criteria set by Tomlinson (1986), they formed a distinctive zonation in Baler mangrove and therefore we tried to include these zones in do-ing the experiment. The vertical profile of Baler mangrove zonations from seaward going to the landward is presented in Fig. 1.　Based on the data gathered at the end of the

Table 3. Adaptability survival of planted Kandelia candel in different mangrove zonations.

Fig. 2. Percentage survival of Kandelia candel planted in different mangrove zonations at Baler, Aurora, Philippines.


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both riverine mangrove with muddy substrate and coastal type of mangrove with coralline and rocky substrate directly facing the Pacific Ocean and usually exposed to strong tidal current and waves especially during bad weather conditions. Although disturbed by such conditions, the spe-cies of Rhizphora stylosa is still surviving and had formed a distinct zonation. The stilt or aerial roots of this species lying in between the holes of dead corals and rocks which make the stem more stable to withstand against strong tidal current. Following this zonation is the Avicennia marina zone, then, Sonneratia alba zone, which some-times overlapped and mixed together with almost the same substrate types combination of coral-line, rocky and sandy. The three foregoing zona-tions can be generally categorized as seaward part of the mangroves. It was important to note that very few seedlings have been observed in these zonations maybe due to usual disturbance by waves and water current. The propagules used in the experiment were planted in the open space or gap in between the mature trees. The result showed that all the propagules planted in Rhizophora stylosa zone and Avicennia marina zone yielded zero survival at the end of the ex-perimental period, which lasted for one year. In the Sonneratia alba zone, 23% or 7 propagules remain alive out of the 30 propagules planted. With respect to the in situ soil salinity, in Rhizo-phora stylosa zone, the salinity ranges from 8.7–19.7 parts per thousand (ppt) with annual mean soil salinity of 15 ppt, while in Sonneratia alba zone, the soil salinity ranges from 9–19.6 ppt, with similar annual mean salinity of that Rhizophora stylosa zone. Sonneratia alba zone on the other hand, had a lower salinity ranging from 8.3–17.4 ppt with annual mean of 14 ppt.　The next zones following the first three most seaward vegetations are Rhizophora apiculata, Bruguiera gymnorrhiza and Kandelia candel zones which based on the actual observation can be generally categorized as middle part of the mangrove forest because they are located in between seaward and landward most parts of the mangrove where shallow out f low of fresh water from Baler river and an inflow of saline water from the Pacific Ocean meets during high tide. The type of soil or substrate in these zones is almost the same and can be categorized as

numerically presented in Table 3 and graphically presented in Fig. 2.

3.3 Soil substrate 　The type of soil for each zonation was gener-ally categorized into rocky or coralline, sandy, muddy and muck based on the description given by Melana et al. (2000). Rocky or coralline substrate is characterized as hard shelves where small or thin pockets of softer sediment and dead coral reefs are found. Sandy substrate comprises of tiny grains of sediments e.g. coral usually less than 2 mm in diameter. There is no organic mat-ter to speak of, although it may overlay mud or muck. Like mud, sand may be as shallow as 2–3 cm or up to several meters. The species recom-mended in rocky or coralline substrate can also grow well in sandy substrate. Muck substrate has similarity with mud except that it contains a large amount of plant debris, this means that the organic matter is higher than mud. It also tends to be deeper starting at more than 10 centimeters thick up to a few meters. It has similar smell with mud just like foul and/or rotten egg. 　In the most seaward part of the mangroves the substrate is coralline and rocky with some patches of sandy areas, which favor the growth of Rhizophora stylosa, Avicennia marina and Son-neratia alba. In the middle mangrove, wherein the substrate is generally muddy, the zonations of Rhizophora apiculata, Bruguiera gymnor-rhiza and Kandelia candel are naturally grow-ing. Extending to the landward most part are the zonations of Lumnitzera littorea, Heritiera litto-ralis, Acanthus ebracteatus, Nypa fruticans and Acrosticum aureum. The preferred soil type and habitat location in the mangroves of each species is presented in Table 4.

3.4 Identified mangroves　There were about 12 major species, 5 minor species, 12 mangrove associates and 3 special-ized groups identified. The category and identifi-cation were based on the criteria used by Tomlin-son (1986). The complete list is also presented in Table 4.

4. Discussion

　The zonation in Baler is a representative of


pear that Kandelia candel can withstand well in association with Nypa fruticans zonation based on the number of survived propagules (63%). Lumnitzera littorea on the other side formed the tallest canopy in the whole forest having bigger trunk diameter with muck type of soil substrate, meaning that there are more plant debris than mud, has small percentage survival of 13%. The dominant canopy of this species covered almost all the under suppressed saplings and seedlings from the direct exposure to sunlight. This might also one of the possibilities that contribute to the lower survival of the planted Kandelia can-del propagules. The soil salinity ranges from 4–12 ppt, with annual mean salinity of 7.8 ppt. The Heritiera littoralis zone usually formed vegetation in an elevated muddy and sandy soil substrates or mounds believed to be created by mud crabs and other soil animals and organisms in mangroves that the area is usually inundated by saline water only during high tide. Higher mortality of the seedlings planted in this zone was recorded leaving only 1 or 3% survival. Acanthus ebracteatus zone yielded 7% survival rate, with soil salinity readings ranging from 0.9– 6ppt, and with an annual mean of 3.2 ppt, which strategically located just closer to Nypa fruticans zone. The substrate is a combination of muddy to sandy. On the other hand, Acrostichum aureum is

muddy. In terms of soil salinity, Rhizohora api-culata zone recorded an annual salinity range of 4–16.7 ppt with mean of 8.1 ptt, while Bruguiera gymnorrhiza zone has a salinity range of 3.9–11 ppt and Kandelia candel zone ranges from 4–11.5 ppt. Comparatively, the last two zones have similar annual mean salinity of 7 ppt dur-ing the entire duration of the observation period. With regards to percentage survival of planted propagules, it was interesting to note that these three zones yielded lower mortality and almost more than half of the planted propagules sur-vived with 67% for Rhizophora apiculata zone, 57% for Bruguiera gymnorrhiza zone and the highest was recorded in its original zone (Kande-lia candel zone) with 70% survival rate.　In the landward most part of the mangal area which comprises of Lumnitzera littorea zone, Heritiera littoralis, Acanthus ebractetus, Nypa fruticans and Acrostichum aureum zones showed a higher mortality except for Nypa fruticans which yielded 63% survival rate with soil salin-ity ranging from 0.7–4 ppt, having annual mean of 2.1 ppt. The presence of small creek flowing in the middle of this zone might be one of the reasons of lower salinity readings. Although, it is hard to find open space in Nypa fruticans zone because of its natural behaviour of forming a dense clumps or vegetation, it seemed to ap-

Fig. 3. Percentage survival of Kandelia candel in different mangrove zonations with varying levels of soil salinity.


stylosa and Avicennia marina wherein the soil salinity readings were generally higher among all other zonations. Although, this species is con-sidered halophyte or plant that can tolerate saline environment, certainly, it has minimum and maxi-mum tolerance limitations. Several studies which supported the above-mentioned fact include: Kameya et al. (1996), stated that the growth inhi-bition for both Kandelia candel and Rhizophora stylosa is 1.8%, which is almost equivalent to 18 ppt. Hwang (1983) stated that this species grows in the intertidal zone along estuarian river banks of which the tidal salinity ranges from 10–36 ppt. Hwang and Chen (1995) stated that Kandelia candel seedlings grows well at salinity level up to 260 mM (15 ppt) with 85 mM (5 ppt) as the optimum level and with 340 mM (20 ppt) salin-ity, the growth will be impaired and/or inhibited. Wakushima et al. (1994) revealed that the stem elongation was observed in Kandelia candel seed-lings were inhibited with soil salinity of 100 mM (6ppt) and a salinity concentration of 600 mM (35 ppt) was fatal or detrimental for it. The study of Hwang and Chen (2001) revealed that salinity was the primary factor affecting the growth of Kandelia candel. Their findings stated that the uptake water salinity of Kandelia candel growing in situ was 6–14 ppt based on the Na content on its tissue. Although, their findings vary from each other because of the effects of external factors such as precipitation, topography, underground

the farthest of all zonations but also thriving near small tributaries of the creek with muddy type of substrate. This is known as the mangrove fern in the Philippines because it resembles leaves simi-lar to tropical ferns. The record shows that 27% or 8 seedlings survived in this zone after the end of experiment. The percentage survival rate of Kandelia candel in different mangrove zonations with varying levels of soil salinity is presented in Fig. 3.

5. Conclusion

　Based on the results of this study particularly on the number of survived propagules planted in different mangroves zones, it is concluded that the mangroves Kandelia candel follows its origi-nal zonation for greater survival with soil prefer-ences to muddy soil subtrate in the middle portion of mangroves which is not expose to strong tidal current and with an appropriate level of in situ salinity ranging from 4–11.5 ppt or annual mean salinity of 7 ppt. The relationship of soil salinity and percentage survival of this species in its orig-inal zone is presented in Fig. 4, indicating that if salinity is low, the percentage survival is higher and vice versa. The same interpretation can also be made in Figure 3, that the survival of Kandelia candel in zonations with high salinity readings, a lower trend of survival was noted. Zero survival on the most seaward zonations of Rhizophora

Fig. 4. Survival of planted Kandelia candel in its original zone with monthly in situ soil salinity level.


36: 25–31.Hwang, Y. H. & Chen, S. C. 2001. Effects of am-

monium, phosphate, and salinity on growth, gas exchange characteristics, and ionic contents of seedlings of mangrove Kandelia candel (L.) Druce. Bot. Bull. Acad. Sinica 45: 131–139.

Kathiresan, K. & Bingham, B. L. 2001. Biology of mangroves and mangrove ecosystems. Adv. Mar. Biol. 40: 1–251.

Kameya, H., Nehira, K. & Nakagoshi, N. 1996. Growth of cultivated seedlings of Kandelia candel and Rhizophora stylosa. TROPICS 6 (1/2): 51–64.

Melana, D. M., Atchue, J., Yao, C. E., Edwards, R., Malana, E. E. & Gonzales, H. I. 2000. Mangrove Management Handbook. 96 pp. Dept. Env. Nat. Res., Manila Philippines through the Coastal Resource Management Project, Cebu City, Philip-pines.

Primavera, J. H. 2000. Philippine Mangroves: Status, Threats and Sustainable Development. A paper presented during the International Workshop Asia–Pacific Cooperation–Research for Conservation of Mangroves. Okinawa, Japan.

Rabinowitz, D. 1978. Early growth of mangrove seed-lings in Panama, and a hypothesis concerning the relationship of dispersal and zonation. J. Biogeogr. 5: 113–33.

Robertson, A. I. & Alongi D. M. 1991. Tropical Man-grove Ecosystems. 329 pp. American Geophysical Union Press, Washington.

Saha, S. & Choudhury, A. 1995. Vegetation analysis of restored and natural mangrove forest in Sagar Island, Sunderbans, East Coast of India. Indian J. Mar. Sci. 24: 133–136.

Semeniuk, V. 1980. Mangrove zonation along an eroding coastline in King Sound, North Western Australia. J. Ecol. 68: 789–812.

Tomlinson, P. B. 1986. The Botany of Mangroves. 441 pp., Press Syndicate of the Cambridge Univ., New York.

Wakushima, S., Kuraishi, S. & Sakurai, N. 1994. Soil salinity and pH in Japanese mangrove forest and growth of cultivated mangrove plants in different soil conditions. J. Plant Res. 107: 39–46.

Whitney, D. A. 1998. Soil salinity, In: Recommended Chemical Soil Test Procedures for the North Cen-tral Region, pp. 59–60. NCR Publication No. 221. 72 pp. Missouri Agricultural Experiment Station, Sait Louis.

water and inflow of fresh water from springs, creeks and rivers. The findings in this study were gathered in the actual field and may therefore vary on the level of soil salinity that could be ob-tained in an experiment conducted in a controlled or laboratory areas such as green houses or other artificial settings. Other possible major factors that contributed to the zero survival rate at the two seaward most zones were the disturbance caused by strong current and wave actions, which sometimes brought debris that washed or injured the planted propagules.　Other zonation which yielded more than 50% survival were Rhizophora apiculata zone, Nypa fruticans and Bruguiera gymnorrhiza zones. Therefore, it can also be recommended that Kan-delia candel could also be planted in these zones, but careful consideration with soil preferences and salinity should not be neglected. Other ef-fects of biotic and abiotic factors such as fresh water inflow, tidal inundation, water pH, dispersal ability of the propagules, physical and chemi-cal elements present in the soil, geomorphology, competition, pests and all others factors which may possibly play important roles in the oc-currence of zonation are stongly recommended for specific study. It is therefore worthwhile to conclude that mangrove zonation is a natural pattern or guide to follow in planting or doing reforestation efforts to attain higher percentage survival with due consideration to the type of soil substrate and soil salinity requirements of each species.

Literature cited

Aurora Integrated Area Development Project II (AIADP–II). 1988. A Management and Protection Strategy for Aurora Province. 98 pp. AIADP II Project Management Office, Baler, Aurora Philip-pines.

Hogart, P.T. 1999. The Biology of Mangroves. 228 pp. Oxford Univ. Press. New York.

Hwang, Y. H. 1983. Dynamics of Nutrient Flow in the Chuwei Mangrove Ecosystem. MS Thesis. Depart-ment of Botany, National Taiwan University, Tai-pei.

Hwang, Y. H. & Chen, S. C. 1995. Salt tolerance in seedlings of the mangrove Kandelia candel (L.) Druce, Rhizophoraceae. Bot. Bull. Acad. Sinica


Woodroffe, C. D. 1992. Mangrove sediments and geomorphology. In Robertson, A. I. & Alongi, D. M. (eds.), Tropical Mangrove Ecosystem, pp. 7–14. American Geophysical Union Press, Washington.

Accepted 5. IX. 2008

Documents

Kandelia candel (L.) Druce in the Philippines