Assessment of litterfall production is essential to ascertain the status of nutrient cycling and forest health. Sarawak, Malaysia, is endowed with numerous pristine and estuarine mangroves; however, research on primary productivity of these forests is scanty. Therefore, litterfall production in a pristine Sibuti mangrove of Sarawak was estimated using litter traps for one year (January-December 2013), and forest structure was studied through tree census. The forest was dominated by Rhizophora apiculata (relative density [RD] was 77.11%), followed by Xylocarpus granatum (RD was 16.92%) and other species (RD was only 5.97%). The annual dry weight of litterfalls was estimated to be 1640.82 g m −2 , of which R. apiculata contributed 92.94%, followed by X. granatum (4.01%) and other species (3.05%). Leaves were the most abundant (57.21%) contributory component of litters, followed by propagules (11.89%), flowers (10.85%), twigs (8.56%), and stipules (8.45%). No significant correlations were found for total litterfall and its major components with climatic variables and forest structure. Total litterfall of R. apiculata and X. granatum did not show any seasonal variations. However, leaf litter of R. apiculata showed a significant seasonal variation between intermediate (January-April) and wet (September-December) seasons. The litterfall production of Sibuti mangrove forest is higher in comparison to other tropical mangroves of the world. The higher productivity of the forest could be due to nutrient availability, pristine nature, and stand maturity of the forest rather than climatic influences. The findings of the study suggest that litterfall production of the pristine Sibuti mangrove is not influenced by the variability of climatic factors.Maisto medžiagų apykaitos miške ir jo būklės įvertinimui labai svarbūs nuokritų susidarymo tyrimai. Daug žmogaus veiklos nepaliestų ir nepakankamai ištirtų estuarinių mangrovių yra Malaizijoje, Saravako valstijoje. Saravake esančioje Sibuti mangrovėje nuo 2013 m. sausio iki gruodžio miško nuokritų susidarymas buvo tiriamas nuokritų gaudyklėmis. Įvertinta medžių rūšinė sudėtis: dominavo Rhizophora apiculata -77,11% ir Xylocarpus granatum -16,92%, kitų rūšių medžiai sudarė 5,97%. Sausas nuokritų svoris per metus buvo 1640,82 g/m 2 , iš jų R. apiculata -92,94%; X. granatum -4,01%, kitų rūšių -3,05%. 57,21% nuokritų sudarė lapai, 11,89% -vegetatyvinio dauginimosi dalys, 10,85% -žiedai, 8,56% -šakelės, 8,45% -prielapiai. Nuokritų ir jų dalių kiekis nebuvo patikimai susijęs su klimato sąlygų kaita ar miško struktūra. Nustatyta, kad bendras R. apiculata ir X. granatum nuokritų gausumas nepriklauso nuo sezono, tačiau R. apiculata lapų nuokritų gausumas ženkliai skyrėsi pereinamojo (sausio-balandžio) ir drėgnojo (rugsėjo-gruodžio) sezonų metu. Sibuti mangrovėje nuokritų susidarymo produktyvumas yra didesnis nei kitose pasaulio tropinėse mangrovėse. Didesnis šio miško produktyvumas daugiau priklauso nuo maisto medžiagų kiekio, gamtos natūralumo ir miško brandos negu nuo klimatinių sąlygų. T...

Sarawak is endowed with numerous pristine and estuarine mangroves. However, information pertaining to the species composition and diversity of pristine mangroves of Sarawak is scanty. Hence, this study was carried out to assess the plant composition and diversity of Sibuti mangrove forest, Miri, Sarawak to investigate the current status and diversity of vegetation. Nine mangrove plant species were recorded employing the line transect (100À240 m) survey method. Major mangrove species were Rhizophora apiculata, Xylocarpus granatum, and Nypa fruticans. The stand density was recorded as 1938.46 § 482.24 trees ha ¡1 , 1722.22 § 254.58 saplings ha ¡1 , and 6222.22 § 384.90 seedlings ha ¡1 . The mean diameter, height, and basal area for the whole forest stand were 20.83 § 13.79 cm, 13.53 § 5.55 m, and 201.83 § 12.68 m 2 ha ¡1 , respectively. The mean diameter of the dominant species R. apiculata was 24.10 § 13.90 cm, height 15.18 § 5.09 m, and basal area 176.13 § 12.73 m 2 ha ¡1 . The importance value index (IVI) of R. apiculata was 202.24 followed by 63.85 for X. granatum. Shannon diversity indices (H 0 ), Margalef richness (D), and Peilou evenness (J 0 ) of the forest stand were 1.18, 1.41, and 0.54, respectively. Similarity of species composition showed two major clusters for the whole forest stand. The findings of this study suggest that Sibuti mangrove forest stand is undisturbed and healthy. This forest could be managed and conserved for multi-sectoral uses such as ecotourism, biodiversity, research, and education rather than solely as a wildlife sanctuary.

This study was carried out to assess the fishery resources of the Sibuti River estuary, Sarawak, Malaysia. Data were collected from the study area for a period of one year in different seasons. The estuary is relatively species-rich and a total of 4675 individuals of 32 families from 60 species of fish (55), crab (four) and shrimp (one) were collected. Coilia dussumieri was the dominant species (22.63%) followed by Nemapteryx caelata (11.85%), Otolithes ruber (7.85%) and Ilisha elongata (5.80%). Marked seasonal variations were found among most of the hydrobiological factors; however, seasonal variations were not significant for the diversity indices such as Shannon-Wiener, Margalef and Evenness. The number of fish taxa caught in different mesh size gill nets was 1 inch (42 species) > 2 inch (36 species) > 4 inch (25 species), suggesting that smaller mesh nets are more suitable for assessing the diversity of fishery resources. SIMPER analysis showed that Coilia dussumieri was the most abundant species in the dry (10.3%) and intermediate (8.1%) seasons, whereas N. caelata was most abundant in the wet season (7.1%). Significant differences (ANOSIM and nMDS) were observed in the species community structure between dry-intermediate and dry-wet seasons; however, species compositions were not significantly different between intermediate and wet seasons. Canonical correspondence analysis (CCA) showed that most of the species assemblages were positively correlated with turbidity and chlorophyll a, followed by phosphate, nitrate and zooplankton density. The findings suggest that the Sibuti mangrove estuary is productive in terms of diversified fishery resources, which are influenced by the hydrobiological factors.

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This baseline study was carried out to investigate the physicochemical factors such as pH, salinity, temperature, turbidity, total dissolved solids (TDS), total suspended solids and dissolved oxygen (DO), as well as nutrient (nitrate, phosphate, ammonium) concentrations and the level of heavy metals (Fe, Zn, Cu, Mn) in the surface water of the Miri estuary at four sampling times based on the four seasons of Malaysia. Results indicated marked temporal differences in each of the water characteristics measured (except ammonium), where DO level (mean: 3.6 mg/L) was found in a concern level. The principle component analysis (PCA) was applied to the hydrological and hydrochemical data set of the Miri estuary; results indicated that principle component 1 and principle component 2 explained 61.78 and 18.69%, respectively, of the total variance in the data set. Besides, results of PCA also indicated that the factors for water characteristics variations were mainly related to TDS, salinity, and Fe. The data presented here will serve as benchmark information, especially to the agencies related to the formulation of suitable policy on water quality in such areas.

Mangroves have substantial roles to induce sedimentation in the vulnerable coastal regions, which subsequently helps to combat climate change induced impacts like sea level rise. Although Sarawak has numerous pristine estuarine mangroves, studies on the roles of these mangroves in regards to sediment deposition are scanty. Therefore, this study was carried out to determine the sediment accretion and accumulation pattern of pristine Sibuti mangrove using tiles and sediment traps from January to December 2013. Monthly average accretion and accumulation rate of sediments of this mangrove were 0.55 mm and 0.08 g cm -2 , respectively. A total of 6.56 mm and 0.93 g cm -2 sediments were accreted and accumulated annually. Significantly positive correlation (r=0.794) was found for the monthly accretion of sediments with accumulation. Accretion and accumulation of sediments were also positively correlated with rainfall. Comparatively higher rate of accretion and accumulation of sediments were estimated in the months of wet season when the rainfall and tidal inundation duration were high. Erosion was found higher in the months of dry season when the rainfall was low. Seasonal variations were not found for sediment accretion as well as accumulation in the study area. The findings of the study suggest that the roles of this forest in regards to sediment accretion through retention is compatible with the predicted annual rate of sea level rise of 1.8 to 5.9 mm within 21 st century by IPCC.

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