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Mangrove forests play crucial roles in the coastal ecosystems of the tropics. Few studies have addressed long-term changes in the net primary productivity (NPP) of mangroves in relation to the tropical monsoon climate. We conducted a tree census from 2008 to 2018 in a permanent plot at a secondary mangrove forest under the tropical monsoon climate of Eastern Thailand. During this period, the mortality of fast-growing species and the increasing number of newly recruited trees revealed a temporal change in the plant composition and distribution. Total tree biomass linearly increased from 283.64 to 381.72 t&middot, ha&minus, 1 during the study period. The NPP was calculated by using the summation method, which included fine root production. The NPP ranged from 21.19 to 29.04 t&middot, 1&middot, yr&minus, 1. The fluctuation in NPP and its components were analyzed in relation to climatic factors by the linear regression model. The NPP did not relate with the annual climatic factors, such as the mean temperature and annual rainfall. However, both increments in the basal area and living tree biomass, which is a major component of NPP, were negatively related with the maximum and mean monthly temperatures in the dry season. The annual mortality rate related positively with annual rainfall and the maximum monthly temperature in the dry season. Linear regression analyses showed that some major components of NPP were chiefly affected by the temperature environment in the dry season. These results indicated that the weather in the dry season was largely restricting the mangrove NPP due to effects on the saline water dynamics of the soils under the tropical monsoon climate, which were revealed by our recent study. It implies that the hot-dry season may lead to high mortality, long-term reduction in the increment of living-trees biomass, and thus lowered the ability to maintain high NPP of mangrove forests over the long-term.

Because endophytic fungi are widely known for producing secondary metabolites and bioactive compounds, they are of interest to pharmaceutical and biotechnology industries. Many species are found in mangrove forests that are habitats for marine animals, especially in their early life stages. In this research, we screened 42 endophytic fungi originating from Thai mangrove forests for inhibitors of biofilm and planktonic cell growth of 7 Vibrio isolates. Some of these isolates were collected from shrimp ponds exhibiting early mortality syndrome (EMS) and diagnosed as outbreaks of acute hepatopancreatic necrosis disease (AHPND) that is caused by specific isolates of Vibrio parahaemolyticus (VPAHPND). Cell-free supernatants (CFS) of two fungal isolates (MCR433 and MCR 440) that inhibited biofilm growth for at least 5 out of the 7 Vibrio isolates were chosen for further study in shrimp feeding trials. One (MCR433) had strong biofilm inhibition and the other (MCR 440) weak biofilm inhibition for VPAHPND. Feed supplementation with CFS of MCR 433 protected shrimp against AHPND (72% mean survival) when compared to control shrimp given un-supplemented feed (20% mean survival) or given feed supplemented with CFS of MCR 440 (0% survival). Histological analysis of the hepatopancreas confirmed that shrimp given feed supplemented with MCR 433 showed little or no signs of AHPND pathology while shrimp in the other two groups showed histopathology typical AHPND. Using a multigene molecular typing approach, both MCR 433 and MCR 440 were identified as distinct members of the order Muyocopronales, class Dothideomycetes and phylum Ascomycota with differing biological activities. Further research is needed on the lead compounds generated by these strains. Those from MCR 433 have potential for use as feed additives against VPAHPND as an alternative to antibiotics.

A new species of Helicascus, H. mangrovei, on dead intertidal mangrove wood was collected. Morphology of this fungus was studied and DNA sequence analyses of the internal transcribed spacers (ITS), small subunit (SSU) and large subunit (LSU) ribosomal (r) DNA, the translation elongation factor 1-alpha gene (TEF-1α) and the RNA polymerase II gene (RPB2) were used to determine the phylogeny of this fungus. Helicascus mangrovei possesses semi-immersed lenticular ascomata and stroma-like structures covered with a carbonaceous, dark brown to black pseudoclypeus. Its ascomata do not have a separate locule. The bitunicate asci have an ocular chamber and a long stipe. Ascospores are obovoid, 1-septate, uniseriate, unequally two-celled, slightly constricted at the septum, thick-walled, with larger brownish apical cells and smaller basal cells, one apiculate end, hyaline when young, becoming dark brown when mature. Helicascus mangrovei forms a well-supported clade within Helicascus species and is closely related to marine species within the Morosphaeriaceae, Pleosporales. Based on the morphological features and molecular data, a new marine species of Helicascus is proposed.

Coarse woody debris (CWD) plays an important role in long-term carbon storage in forest ecosystems. However, few studies have examined CWD in mangrove forests. A secondary mangrove forest on an estuary of the Trat River showed different structures along vegetation zones ranging from the river’s edge to inland parts of the forest (the Sonneratia–Avicennia, Avicennia, Rhizophora, and Xylocarpus zones, respectively). The mass distribution of CWD stock in downed wood and standing dead trees along these vegetation zones was evaluated. Most of the CWD stock in the Sonneratia–Avicennia and Avicennia zones was found in downed wood, while it mainly accumulated in standing dead trees in the Rhizophora and Xylocarpus zones. The total mass of CWD stock that accumulated in each zone ranged from 1.56–8.39 t ha−1, depending on the forest structure and inundation regimes. The annual woody debris flux in each zone was calculated by summing the necromass (excluding foliage) of dead trees and coarse litter from 2010 to 2013. The average woody debris flux was 5.4 t ha−1 year−1, and its zonal variation principally depended on the necromass production that resulted from forest succession, high tree-density, and lightning. Over all the zones, the above- and below-ground net primary production (ANPP and BNPP, respectively) was estimated at 18.0 and 3.6 t ha−1 year−1, respectively. The magnitude of BNPP and its contribution to the NPP was markedly increased when fine root production was taken into consideration. The contribution of the woody debris flux without root necromass to the ANPP ranged from 12 to 28%.

Songklanakarin Journal of Science and Technology, 40, 6, 1315-1323

High root productions, especially in the fine roots, estimated by ingrowth cores were confirmed in mangrove forests. The zonal variation in root production was caused by inundation regime and soil temperature. Mangrove forests have high net primary productivity (NPP), and it is well known that these trees allocate high amounts of biomass to their root systems. In particular, fine root production (FRP) comprises a large component of the NPP. However, information on root production remains scarce. We studied FRP in three zones (Avicennia, Rhizophora, and Xylocarpus) of a mangrove forest in eastern Thailand using ingrowth cores (0–30 cm of soil depth). The root biomass and necromass were periodically harvested from the cores and weighed during the one-year study. The FRP was determined by summation of the fine root biomass (FRB) and root necromass. The results showed that the FRB clearly increased in the wet and cool dry seasons. Magnitude of FRB in the Rhizophora and Xylocarpus zones was 1171.07 and 764.23 g/m2/30 cm, respectively. The lowest FRB (292.74 g/m2/30 cm) was recorded in the Avicennia zone locating on the river edge where there is a greater frequency of inundation than the other zones. Root necromass was high in the Rhizophora and Xylocarpus zones, and accumulated noticeably when soil temperatures rapidly declined during the middle of the wet season to cool dry season. However, root necromass in the Avicennia zone varied within a small range. We attributed the small accumulation of root necromass in the Avicennia zone to the relative high soil temperature that likely caused a high root decomposition rate. The average FRP (3.403–4.079 ton/ha/year) accounted for 74.4, 81.5, and 92.4 % of the total root production in the Avicennia, Rhizophora, and Xylocarpus zone, respectively. The root production and causative factors (i.e., soil temperature and inundation regime) are discussed in relation to the carbon cycle of a mangrove forest.

The species diversity of marine fungi was investigated in eastern and southern Thailand. Senescent and decaying woody substrata were collected from intertidal mangrove forests located in Trat, Prachuap Khiri Khan and Phetchaburi Provinces. A total of 99 fungal species was recorded. These included 84 Ascomycota (85%), two Basidiomycota (2%) and 13 asexual fungi (13%). The average percentage occurrence of the fungi recorded from each site ranged from 0.1% to 13.7%. Based on the percentage of samples in which a particular taxon was found, the most frequent fungi were

Carbon dioxide emission through soil respiration is an important component of the carbon balance in forest ecosystems. However, little information is available on the rates of soil respiration in mangrove forests. We studied the rate of soil respiration in a secondary mangrove forest in eastern Thailand on an estuary of the Trat River during both the wet and dry seasons. A study site of 40 × 110 m was established and a series of vegetation zones identified: Sonneratia, Avicennia, Rhizophora and Xylocarpus, in order of increasing elevation inland. Soil respiration was measured during low tide, using an infrared gas analyser connected to a respiratory chamber, by excluding the respiration of above-ground roots from the chamber. At least 19 measurements were performed in each zone for each season. The rate of soil respiration significantly increased with increasing soil temperature. The soil temperature which was usually lower than that of sea water showed a trend that decreased with distance from the river in both wet and dry seasons. The relative land elevation causes different periods of inundation among the vegetation zones. The period was longest in the Sonneratia zone located on the river fringe, and became shorter moving inland. Thus, the elevation and relevant period of inundation are considered to be causal factors warming the soil. Consequently, the difference in soil temperature caused significantly different rates of soil respiration among the vegetation zones in the mangrove forest. Overall, the average rate of soil respiration ranged from 0.456 to 0.876 μmol CO2 m−2 s−1, supporting the view that mangrove forests have lower rates of soil respiration than do upland forests.

The allometric relationship for stem weight Ws is usually expressed as a function of stem diameter and height, similar to the variable d.b.h. 2 H, which equals the squared diameter at breast height multiplied by tree height. However, this relationship often differs between tree species, and this segregation of the relationship by species forces the researcher to do a tremendous amount of field work to determine a series of allometric equations for all tree species in the forest. In this study, we examined the segregation in the d.b.h. 2 H–Ws allometric relationship for five mangrove species. We examined the overall stem shape and the specific gravity of stem relating to the allometric relationships. The difference in the specific gravity was found to be the main cause of the segregation in the d.b.h. 2 H–Ws relationship. By taking into consideration the specific gravity of stem, we established a common equation for the five mangrove species.

Eight species of ectomycorrhizal (ECM) fungi in the genera Amanita. Gymnoboletus, Lactarius, and Russula were isolated from subtropical plant communities in eastem Australia. Two species were isolated from each of rainforest, Nothofagus forest, Eucalyptus forest, and Eucalyptus dominated wallum (heath) forest. These communities differ strongly in their soluble soil nitrogen (N) composition. The ability of the fungi to use inorganic (nitrate, ammonium) and organic (amide, peptide, protein) nitrogen sources was determined. As the fungi did not grow in liquid culture, a 'floating culture' technique was devised that allows hyphal growth on a screen floating on liquid medium. With some exceptions, fungal biomass production in floating culture closely reflected fungal growth on solid media assessed by total colony glucosamine content. Most isolates grown in floating culture had similar glucosamine concentrations on all N sources, with isolate specific concentrations ranging from 6 to 12 mug glucosamine g(-1) DW. However, Russula spp. had up to 1.7-fold higher glucosamine concentrations when growing with glutamine or ammonium compared to nitrate, glutathione or protein. Floating cultures supplied with 0.5, 1.5. 4.5, or 10 mm N mostly produced greatest biomass with 4.5 mM N. In vitro nitrate reductase activity (NRA) ranged from very low (0.03 mumol NO2- g(-1) fw h(-1)) in Russula sp. (wallum) to high (2.16 mumol NO2- g(-1) fw h(-1)) in Gymnoboletus sp. (rainforest) and mirrored the fungi's ability to use nitrate as a N source. All Russula spp. (wallum, Nothofagus and Eucalyptus forests), Lactarills sp, (rainforest) and.4manita sp. (wallum) utilized ammonium and glutamine but had little ability to use other N sources. In contrast,Amanita species (Nothofagus and Eucalyptus forests) grew on all N sources but produced most biomass with ammonium and glutamine. Only Gymnoboletus sp. (rainforest) showed similar growth with nitrate and ammonium as N sources. Fungal N source use was not associated with taxonomic groups, but is discussed in the context of soil N sources in the different habitats.

A quantitative analysis was done for the root system of Xylocarpus granatum with reference to the Pipe model theory of tree form proposed by Shinozaki et al. (1964a, b). For this objective, six root systems of X. granatum were excavated using a water-pump, and the roots were weighed for respective diameter categories. A significant allometric relationship between the squared stem-base diameter and the individual root weight was seen. The coefficient of this relationship was statistically regarded to be 1.0, meaning that the individual root weight is proportional to the squared value of stem-base diameter. We also analyzed the relationship between diameter and number of roots for the six sample trees. The number of roots with a given diameter and length was calculated from the weight and the specific gravity of roots. Significant linear relationships were recognized in this relationship for the six sample trees. For all sample trees, the coefficients of relationships were statistically regarded to be - 2.0. From these analyses based on population and individual level, we conclude that the root system of X. granatum obeys the pipe model. Application of this model is helpful in the estimation of root biomass, since individual root weight can be estimated from a proportional constant and the stem-base diameter of a mangrove tree.

We assembled a dataset tabulating the weights of Thai and Indonesian mangrove trees that we measured between 1982 and 2001. We selected four Thai study sites in Phang Nga, Ranong, Satun, and Trat Provinces and one site in eastern Indonesia on Halmahera Island in Maluku Province. The stands in Ranong Province and on Halmahera Island were in primary forests with data collected in the 1980s and the remaining stands were in secondary forests with data collected later. We collected 124 tree samples from ten species (Avicennia alba, Bruguiera cylindrica, B. gymnorrhiza, Ceriops tagal, Rhizophora apiculata, R. mucronata, Sonneratia alba, S. caseolaris, Xylocarpus granatum, and X. moluccensis) and measured the root weights of 32 individuals of nine species (A. alba, B. cylindrica, B. gymnorrhiza, C. tagal, R. apiculata, R. mucronata, S. alba, S. caseolaris, and X. granatum). All sampled trees were subjected to a standardized protocol to obtain aboveground weights. The trunks were divided into horizontal segments from which the leaves and branches were collected separately. Roots were collected by winching them out of the ground, by trench digging, or by complete excavation. Thus, we were able to compile the weights of the trunk, branches, leaves, and roots of each tree sampled. Aerial roots were included in root weight measurements, although they were collected above ground. We compiled separate lists of trunk diameters, trunk heights, heights of the lowest living branches, and the heights of aerial roots on the trunks of trees in different size categories. Our dataset includes a wide range of tree sizes (maximum trunk diameter 48.9 cm), geographical locations (1°10′N–12°24′N, 98°32′E–123°49′E) and organ weights (trunks, branches, leaves, and roots), and therefore should prove useful in future biomass studies of mangrove forests.

Ectomycorrhizal (EM) associations facilitate plant nitrogen (N) acquisition, but the contribution of EM associations to tree N nutrition is difficult to ascertain in ecosystems. We studied the abilities of subtropical EM fungi and nutritionally contrasting Eucalyptus species, Eucalyptus grandis W.Hill ex Maiden and Eucalyptus racemosa Cav, to use N sources in axenic and soil cultures, and determined the effect of EM fungi on plant N use and plant

Ectomycorrhizal (EM) associations facilitate plant nitrogen (N) acquisition, but the contribution of EM associations to tree N nutrition is difficult to ascertain in ecosystems. We studied the abilities of subtropical EM fungi and nutritionally contrasting Eucalyptus species, Eucalyptus grandis W.Hill ex Maiden and Eucalyptus racemosa Cav, to use N sources in axenic and soil cultures, and determined the effect of EM fungi on plant N use and plant 15N natural abundance (δ15N). As measured by seedling growth, both species showed little dependence on EM when growing in the N-rich minerotrophic soil from E. grandis rainforest habitat or in axenic culture with inorganic N sources. Both species were heavily dependent on EM associations when growing in the N-poor, organotrophic soil from the E. racemosa wallum habitat or in axenic culture with organic N sources. In axenic culture, EM associations enabled both species to use organic N when supplied with amide-, peptide- or protein-N. Grown axenically with glutamine- or protein-N, δ15N of almost all seedlings was lower than source N. The δ15N of all studied organisms was higher than the N source when grown on glutathione. This unexpected 15N enrichment was perhaps due to preferential uptake of an N moiety more 15N-enriched than the bulk molecular average. Grown with ammonium-N, the δ15N of non-EM seedlings was mostly higher than that of source N. In contrast, the δ15N of EM seedlings was mostly lower than that of source N, except at the lowest ammonium concentration. Discrimination against 15N was strongest when external ammonium concentration was high. We suggest that ammonium assimilation via EM fungi may be the cause of the often observed distinct foliar δ15N of EM and non-EM species, rather than use of different N sources by species with different root specialisations. In support of this notion, δ15N of soil and leaves in the rainforest were similar for E. grandis and co-occurring non-mycorrhizal Proteaceae. In contrast, in wallum forest, E. racemosa leaves and roots were strongly 15N-depleted relative to wallum soil and Proteaceae leaves. We conclude that foliar δ15N may be used in conjunction with other ecosystem information as a rapid indicator of plant dependency on EM associations for N acquisition.