Tropical Montane Rain Forest Research Articles

Two new species of Acromastigum (Lepidoziaceae: Jungermanniopsida) from Queensland, Australia

As a result of fieldwork on Cape York Peninsula, and ongoing revision of type specimens in lieu of the recent revision of Australian Acromastigum, two new species are described. Acromastigum carcinum represents a newly discovered species, currently known only from one location within the Jardine River National Park. The lowland and tropical monsoonal habitat of this species is highly unusual within the genus, and hints at the existence of a distinct, if species poor, bryofloristic element within tropical monsoon lowland habitats. Acromastigum implexum has been long recognised in Australia under the name A. echinatiforme, however comparison with the original material of that species confirms Australian plants represent a distinct species. Acromastigum implexum inhabits tropical montane rainforest habitats. Both species are currently known only from Australia, but both, particularly A. carcinum, may occur in similar habitats overseas.

A new genus and new species of a semi-terrestrial freshwater crab from montane tropical rainforests in Java, Indonesia (Decapoda: Brachyura: Gecarcinucidae)

A new genus and new species of a semi-terrestrial freshwater crab from montane tropical rainforests in Java, Indonesia (Decapoda: Brachyura: Gecarcinucidae)

Fagaceae tree species allocate higher fraction of nitrogen to photosynthetic apparatus than Leguminosae in Jianfengling tropical montane rain forest, China.

Variation in photosynthetic-nitrogen use efficiency (PNUE) is generally affected by several factors such as leaf nitrogen allocation and leaf diffusional conductances to CO2, although it is still unclear which factors significantly affect PNUE in tropical montane rain forest trees. In this study, comparison of PNUE, photosynthetic capacity, leaf nitrogen allocation, and diffusional conductances to CO2 between five Fagaceae tree species and five Leguminosae tree species were analyzed in Jianfengling tropical montane rain forest, Hainan Island, China. The result showed that PNUE of Fagaceae was significantly higher than that of Leguminosae (+35.5%), attributed to lower leaf nitrogen content per area (Narea, –29.4%). The difference in nitrogen allocation was the main biochemical factor that influenced interspecific variation in PNUE of these tree species. Fagaceae species allocated a higher fraction of leaf nitrogen to the photosynthetic apparatus (PP, +43.8%), especially to Rubisco (PR, +50.0%) and bioenergetics (PB +33.3%) in comparison with Leguminosae species. Leaf mass per area (LMA) of Leguminosae species was lower than that of Fagaceae species (-15.4%). While there was no significant difference shown for mesophyll conductance (gm), Fagaceae tree species may have greater chloroplast to total leaf surface area ratios and that offset the action of thicker cell walls on gm. Furthermore, weak negative relationship between nitrogen allocation in cell walls and in Rubisco was found for Castanopsis hystrix, Cyclobalanopsis phanera and Cy. patelliformis, which might imply that nitrogen in the leaves was insufficient for both Rubisco and cell walls. In summary, our study concluded that higher PNUE might contribute to the dominance of most Fagaceae tree species in Jianfengling tropical montane rain forest.

Diurnal variations and gap effects of soil CO2, N2O and CH4 fluxes in a typical tropical montane rainforest in Hainan Island, China

AbstractAccurate estimations of soil greenhouse gas (GHG) fluxes in tropical montane rainforests are critical for assessing the role of tropical forests in influencing global climate change. This research aimed to determine the diurnal variation in soil GHG fluxes and understand the effects of forest canopy gaps on GHG fluxes, and their major controlling factors. The diurnal fluxes of soil carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) inside and outside three forest canopy gaps in a tropical montane rainforest were measured with a closed static chamber system in June 2015. The main results are as follows. (1) There was an obvious single‐peak daily variation of soil GHG fluxes. (2) The averaged soil CO2, N2O and CH4 fluxes of the whole day were closest to the daily average emission fluxes at 9:00 and 12:00 for CO2, 6:00 and 9:00 for N2O, and 9:00 and 12:00 for CH4, respectively. (3) Soil CO2 and N2O emissions (positive values) and CH4 uptake (negative values) were higher inside gaps than outside. (4) There were stronger exponential relationships between soil CO2 and N2O emissions and temperature inside gaps than outside, and there was a stronger quadratic relationship between CH4 uptake and temperature outside gaps than inside. However, significant relationships between soil CO2 (or CH4) and soil moisture only occurred inside gaps (P < 0.01). There were clear diurnal variations and significant effects of gaps on soil CO2, N2O and CH4 fluxes. Our study indicated that understanding the different diurnal variations of soil CO2, N2O and CH4 fluxes inside and outside canopy gaps could improve the accurate evaluation of soil GHG fluxes in tropical montane rainforests under a changing climate.

New Species of Miconia (Melastomataceae; Miconieae) from Brazilian Atlantic Forest

Abstract Miconia bradeana is described from the state of Rio de Janeiro, in southeastern Brazil. It is endemic to the municipality of Santa Maria Madalena and to the Brazilian Atlantic Forest, occurring in dense montane tropical rainforest. The main diagnostic characteristics of this new species are the rigid-membranaceous to chartaceous and narrowly elliptic to lanceolate leaves, 5(-6)-merous flowers, well-defined, deltoid calyx lobes, apiculate petals, stamens 14–16, connectives with dorsal-basal, usually glandulose appendages, and glandulose ovary apex. Miconia bradeana is an endangered (EN) species.

Generalism in the interaction of Tulasnellaceae mycobionts with orchids characterizes a biodiversity hotspot in the tropical Andes of Southern Ecuador

Biotic interactions play an important role in the assembly and stability of communities. All orchids depend on mycobionts for early establishment, but whether individual orchid species depend on a specific or broad spectrum of mycobionts is still a matter of debate. Tulasnellaceae (Basidiomycota) is the richest and most widespread mycobiont worldwide. We assessed Tulasnellaceae richness in epiphytic and terrestrial orchids in different habitats, and evaluated the degree of generalism in orchid-Tulasnellaceae interactions and the robustness of this mutualistic system to the extinction of mycobiont partners. We sampled 114 orchid individuals including all common and rare species in 56 plots of 1 m2 in 3 habitats: pristine forest, regenerating forest and a landslide site in a tropical montane rainforest in Southern Ecuador. We found 52 orchid and 29 Tulasnellaceae species. The composition of Tulasnellaceae OTUs was moderately to highly similar across habitats and between orchid growth forms. A significantly nested network architecture indicated the existence of a core of generalist Tulasnellaceae OTUs interacting with both rare and common orchids. Terrestrial and epiphytic orchids showed significant differences in robustness to the extinction of their Tulasnellaceae mycobionts. Thus, generalist mycobionts may be relevant for the preservation of hyperdiverse orchid communities in the tropics.

The response of tree growth to nitrogen and phosphorus additions in a tropical montane rainforest

Rapid increase of global nitrogen (N) deposition has greatly altered carbon cycles and functioning of forest ecosystems. Previous studies have focused on changes in carbon dynamics of temperate and subtropical forests through N enrichment experiments; however, the effects of N deposition on tree growth remain inconsistent, especially in tropical forests. Here, we conducted a five-year N addition experiment (0 and 50kgNha−1yr−1) in a tropical montane rain forest in Hainan Island, China, to explore the effects of enhanced N deposition on growth of trees. We also set phosphorus (P) treatment (50kgPha−1yr−1) and N+P treatment (50kgNha−1yr−1+50kgPha−1yr−1) to examine potential P limitation driven by N deposition. Our results showed that N addition has not significantly influenced tree growth, while P addition significantly increased the relative growth rate of small (diameter at breast height, DBH≤10cm) and medium (10<DBH≤20cm) trees. The combined N and P addition accelerated the growth of small trees, but did not affect the growth of medium and large (20cm<DBH) trees. These contrasting effects of N and P addition on tree growth indicate that the tropical montane forest is mainly limited by P, which suggests the importance of P in regulating growth of trees in tropical forests.

Endemic trees in a tropical biodiversity hotspot imperilled by an invasive tree

Non-native plants invade some tropical forests but there are few long-term studies of these invasions, and the consequences for plant richness and diversity are unclear. Repeated measurements of permanent plots in tropical montane rain forests in the Blue and John Crow Mountains National Park in Jamaica over 24 to 40years coincided with invasion by a non-native tree, Pittosporum undulatum. By 2014, P. undulatum comprised, on average, 11.9% of stems≥3cm diameter and 10.4% of the basal area across 16 widespread plots within c. 250ha of the forests. Across these plots, the more P. undulatum increased in basal area over 24years, the greater the decline in local, plot-scale tree species richness, and the greater the reduction in the percentage of stems of endemic tree species. Plot-scale tree diversity (Shannon and Fisher's alpha) also declined the more P. undulatum basal area increased, but beta diversity across the plots was not reduced. Declines in local-scale tree species diversity and richness as the invasion progresses is especially concerning because Jamaica is a global biodiversity hotspot. Native birds disperse P. undulatum seeds widely, and future hurricanes will probably further increase its invasion by reducing canopy cover and therefore promoting growth rates of its established shade-tolerant seedlings. Remedial action is needed now to identify forest communities with greatest endemism, and to protect them through a continuing programme of control and removal of P. undulatum.

Nutrient addition affects net and gross mineralization of phosphorus in the organic layer of a tropical montane forest

In tropical ecosystems with highly weathered soils, transformation of organic phosphorus (P) to bioavailable inorganic P plays a crucial role for the nutrition of organisms. In these ecosystems, P is suspected to be growth-limiting and might therefore be affected by atmospheric nutrient deposition occurring even in remote areas such as montane rainforests. We assessed effects of P and nitrogen (N) addition on net and gross P mineralization rates, and microbial P immobilization in the organic layer along an altitudinal gradient of a tropical montane rainforest in Ecuador. Net P mineralization rates amounted to 1.8 ± 0.9 (at 1000 m a.s.l.), 3.7 ± 0.6 (at 2000 m) and 2.0 ± 0.4 (at 3000 m) mg P kg−1 day−1. Altitudinal differences led to an increased microbial P immobilization at 1000 m compensating for a higher gross P mineralization. P addition increased net P mineralization rates at 2000 and 3000 m, suggesting a higher P demand at 1000 m. At higher altitudes, P likely was released as a by-product during organic matter decomposition. Gross P mineralization, determined by means of the isotopic dilution approach, could not be calculated for control and N treatments due to rapid microbial P immobilization. For P (+N) treatments, gross P mineralization rates were lowest at the 1000 m site towards the end of the long-term incubation period. Atmospheric P deposition in the tropics might lead to P fertilization effects through direct input as well as through acceleration of P release from organic matter, thereby increasing P availability for organisms.

Leaf and root litter decomposition is discontinued at high altitude tropical montane rainforests contributing to carbon sequestration.

We investigated how altitude affects the decomposition of leaf and root litter in the Andean tropical montane rainforest of southern Ecuador, that is, through changes in the litter quality between altitudes or other site‐specific differences in microenvironmental conditions. Leaf litter from three abundant tree species and roots of different diameter from sites at 1,000, 2,000, and 3,000 m were placed in litterbags and incubated for 6, 12, 24, 36, and 48 months. Environmental conditions at the three altitudes and the sampling time were the main factors driving litter decomposition, while origin, and therefore quality of the litter, was of minor importance. At 2,000 and 3,000 m decomposition of litter declined for 12 months reaching a limit value of ~50% of initial and not decomposing further for about 24 months. After 36 months, decomposition commenced at low rates resulting in an average of 37.9% and 44.4% of initial remaining after 48 months. In contrast, at 1,000 m decomposition continued for 48 months until only 10.9% of the initial litter mass remained. Changes in decomposition rates were paralleled by changes in microorganisms with microbial biomass decreasing after 24 months at 2,000 and 3,000 m, while varying little at 1,000 m. The results show that, irrespective of litter origin (1,000, 2,000, 3,000 m) and type (leaves, roots), unfavorable microenvironmental conditions at high altitudes inhibit decomposition processes resulting in the sequestration of carbon in thick organic layers.

The assembly and interactions of tree species in tropical forests based on spatial analysis

AbstractTree species were assembled into forest communities by various processes, and it was found that trees are spatially arranged in a community by the abiotic and biotic conditions within that community. Here, we explore the abiotic processes and biotic interactions in the spatial patterning of tree species across six old‐growth forest types in a tropical nature reserve. Four spatial point process models (the homogeneous Poisson process, inhomogeneous Poisson process, homogeneous Thomas process, and inhomogeneous Thomas process) were used to evaluate the potential contribution of the random processes, habitat heterogeneity, dispersal limitation, and the joint effects of dispersal and habitat heterogeneity to the formation of the spatial patterns of tree species. A combination of the null model and size–distance regression analysis was applied to assess the effect of competition and facilitation on the tree species assembly. We found that the homogeneous and inhomogeneous Thomas processes were the best models for describing the spatial patterns of more than 85% tree species across the six tropical forests. The combination of the null model and size–distance regression analysis showed that 37–44% of tree species were affected by competition and 9–24% of tree species were affected by facilitation across the six tropical forest types. Competition was the dominant form of species interactions in forests with mild abiotic conditions such as the tropical montane rain forest and tropical lowland rain forest. Meanwhile, facilitation was the most important biotic interaction in the abiotically harsh tropical montane dwarf forest on mountaintops. Our study suggests that dispersal limitation and the joint effects of dispersal and habitat heterogeneity were the dominant abiotic processes in controlling the spatial patterning of trees in tropical forests. Moreover, the relative importance of competition and facilitation in the assembly of the tree species varied among the forest types with different abiotic conditions.

Four new species of terrestrial-breeding frogs of the genus Phrynopus(Anura: Terrarana: Craugastoridae) from Río Abiseo National Park, Peru.

We describe four new species of terrestrial-breeding frogs belonging to the genus Phrynopus from specimens collected on the eastern slopes of the Cordillera Oriental (2800-3850 m) near and within Río Abiseo National Park, Provincia Mariscal Cáceres, Departments of San Martín and La Libertad, northeastern Peru. All four species lack a visible tympanum and inhabit the upper ridges and slopes within or adjacent to the Park. Phrynopus anancites sp. nov. and P. capitalis sp. nov. inhabit the wet montane grasslands on the upper ridges and valleys from 3600 to 3850 m. Phrynopus anancites (SVL = 25.3 mm) has coarsely aerolated skin and olive green coloration and has small vomerine teeth, while P. capitalis (female SVL = 35.6 mm) is characterized by a large head, short limbs, and distinctive dorsal pattern. Phrynopus dumicola sp. nov. (female SVL = 25.3 mm) has a short head and dark colored body with granular skin on the flanks, and is known only from forest patches along the treeline from 3225 to 3550 m, whereas P. personatus sp. nov. (female SVL = 28.2 mm) has a dark facemask and bright yellow groin spots (possibly aposematic), and inhabits a narrow band of continuous tropical montane rain forest from 2890 to 3110 m. We report infection with Batrachochytrium dendrobatidis from one specimen of P. dumicola collected in July of 1988. With the addition of these four new species, Phrynopus now includes 32 nominal species.

炭素とミネラルのバランスから見た熱帯山地林生態系の長期動態 : 物質循環における種交代の重要性( 森林生態系における物質循環研究の新しい展開)

炭素とミネラルのバランスから見た熱帯山地林生態系の長期動態 : 物質循環における種交代の重要性( 森林生態系における物質循環研究の新しい展開)

Effects of canopy gaps on N2O fluxes in a tropical montane rainforest in Hainan of China

Background and aimsTropical montane rainforests play an important role in increasing atmospheric N2O concentration. Although accurate estimations of N2O fluxes in tropical montane rainforests are critical for predicting global climate change, there are still considerable uncertainties about the spatial and temporal variability of the emissions. This study aims to investigate the effects of canopy gap caused by typhoons on N2O emissions, a key factor for understanding the spatial heterogeneity and supporting environmental regulations. MethodsN2O fluxes were measured monthly using static chambers both inside and outside two large canopy gaps in the tropical montane rainforest of the Jianfengling National Natural Reserve on Hainan Island, south of China, from August 2012 to July 2013. ResultsMean annual N2O emissions were 2.19±0.43kgN2O-Nha−1yr−1 inside canopy gaps, and 1.19±0.29kgN2O-Nha−1yr−1 outside canopy gaps, revealing substantial differences in N2O emissions resulting from forest structure. Moreover, N2O emission rates within canopy gaps during the wet season (2.89kgN2O-Nha−1yr−1) were significantly higher than those during the dry season (1.34kgN2O-Nha−1yr−1), suggesting strong regulation of soil moisture and precipitation in controlling soil N dynamics. However, there were significant nonlinear relationships between N2O fluxes and water filled pore space, and soil temperature within canopy gaps, but no significant relationships were found under the closed canopy. ConclusionsContribution of canopy gaps should be considered to avoid underestimation of N2O emission rates from disturbed forests. Interestingly, emissions from gaps are more strongly coupled with climate drivers (moisture and temperature), with important implications for climate change projections. Therefore, the further research is needed to study the biogeochemical processes and mechanisms behind such phenomenon.

Characteristics of typhoon disturbed gaps in an old-growth tropical montane rainforest in Hainan Island, China

Disturbances that create gaps can shape the structure and function of forests. However, such disturbance regimes in Asian tropical montane rainforests remain largely unquantified. Least studied are typhoon disturbances that are attributable to climate change. We investigated gap characteristics in terms of size, age, and gap-maker to quantify the gap disturbance regimes in an intact old-growth tropical montane rainforest on Hainan Island, China. The intensity of typhoons has increased since 1949, and typhoon winds blow mostly (45.5%) from the northeast corner of Hainan Island, resulting in a higher frequency of gaps in the northeast. A total of 221 gap-makers (trees that fell to create canopy gaps) and 53 gaps were observed in a 3.16 ha old-growth rainforest. Most canopy gaps (85%) were <200 m2. The average size of canopy gaps was smaller in the rainforest than in other tropical forests, while the average size of expanded gaps was similar to those in other tropical forests. The maximum age of gaps was 23.5 years indicating that gaps had more rapid turnover than other parts of tropical forests. The frequency distribution of gap-makers followed a lognormal distribution with a distinctive peak at three gap-makers, which was different from the inverse J-shaped curve typical of other tropical forests. Gaps were recorded mainly on slopes between 20° and 35° and wood density of gap-makers was between 0.6 and 0.7 g cm−3. Our results suggest that small-scale disturbance was the dominant agent of gap formation in this old-growth rainforest that is subject to increasing typhoon disturbances.

Diversity and distribution of soil micro-invertebrates across an altitudinal gradient in a tropical montane rainforest of Ecuador, with focus on free-living nematodes

Here we describe the community structure of soil micro-invertebrates at three altitudes (1000, 2000, and 3000m) and two soil layers (upper L/F layer and deeper H/Ah layer) of a tropical montane rainforest situated on the eastern slope of the Andes (southern Ecuador) with special focus on nematodes. Nematodes dominated the micro-invertebrate assemblage (average density 1.82×105ind.m−2), accompanied by populations of typical aquatic invertebrates, such as harpacticoid copepods and rotifers, which increased with increasing altitude. Among 1217 nematode individuals inspected, 143 morphospecies were identified. The equitability index was remarkably high. Sample rarefaction curves suggested that up to 244 nematode species dwell in soils of the studied area. Nematode diversity was affected neither by altitude nor by layer; however, the community structure changed with altitude. Bacterial-feeding nematodes dominated throughout the altitudinal gradient whereas at higher altitude populations of plant-feeding nematodes were replaced by hyphal-feeding nematodes, presumably because of changes in habitat and resource availability. Canonical correspondence analysis identified litter C/N ratio and fungal biomass as major drivers of the changes in nematode community composition with altitude. Abundant and diverse assemblages of large predacious and omnivorous nematode species were found at each of the study sites, suggesting that omnivory and animal predation compensate for the lower abundance/quality of basal resources.

Leaf Litter Chemistry Drives the Structure and Composition of Soil Testate Amoeba Communities in a Tropical Montane Rainforest of the Ecuadorian Andes.

We investigated the role of leaf litter chemistry and richness in affecting testate amoeba communities of tropical rainforest in the Ecuadorian Andes. Litterbags containing leaf litter from four dominating tree species (Clusia sp., Myrcia pubescens, Graffenrieda emarginata, and Cecropia andina) with richness 1, 2, and 4 species were established and exposed in the field for 12months at 2000m a.s.l. Chemical elements and compounds of leaf litter were analyzed before exposure. At the end of exposure, microbial biomass and litter mass loss were measured, and living testate amoeba species number, density, biomass, and community composition were determined. In total, 125 testate amoeba species colonized the litter in litterbags. The results suggest that high litter nitrogen and low lignin concentrations are indicators of high litter quality for testate amoebae density and species richness. Their species number and density significantly declined in the order 1>4>2 leaf litter species and varied with leaf litter chemistry being at a maximum in high-quality single leaf litter species and low in low-quality leaf litter. Further, the addition of litter of high-quality to low-quality litter increased testate amoebae biomass and density; however, the values did not exceed the ones in single high-quality litter treatments. Moreover, the structure of testate amoeba communities varied with litter chemistry, with Fe, Na, lignin, and litter C-to-N ratio being of major importance, and indicating that litter chemistry reflects habitat quality for testate amoebae. Overall, the data show that leaf litter chemistry overrides leaf litter richness in structuring testate amoeba communities.

The ecology of the tropical salamander, Bolitoglossa subpalmata, in Costa Rica.

The ecology of the tropical salamander, Bolitoglossa subpalmata, in Costa Rica.

Hydrological functions of the litters and soil of tropical montane rain forest in Xishuangbanna, Yunnan, China

A study of the hydrological functions of litters and soil of the tropical montane rain forest in Xishuangbanna was carried out. The results showed that the soil bulk density decreased with the increase of altitude, while the soil total porosity, the noncapillary porosity, the capillary porosity, the maximum soil moisture rate, the maximum water holding capacity, the effective water holding capacity, the soil moisture increased with the increase of altitude with local fluctuation. In addition, the soil moisture in early stage of rainy season, the saturated water content and the effective reservoir space increased with the increasing altitude, and the saturated water content and the effective reservoir space had a significant difference at different altitudes (P<0.05). The soil permeability had a significantly positive correlation to the soil total porosity and non-capillary porosity (P<0.01), moreover, the soil non-capillary porosity had a more significant effect on the soil permeability. The thickness of under-composed layer at different altitudes was half more than that of the total litter thickness, which showed that the under-composed layer > semi-decomposed layer. The total volume of litters and the ratio of the volume of semi-decomposed layer to the total volume of litters increased with the increasing altitude, which indicated that the decomposition speed of litters was slower at a low altitude and faster at a high altitude. The maximum capacity of soil moisture, the maximum rate of soil moisture, the natural moisture rate, the effective rate of interception and the effective capacity of interception increased with the increasing altitude in under-composed layer and semi-decomposed layer, and their values in under-composed layer were higher than those in semi-decomposed layer. However, the depth of effective capacity of interception decreased with the increasing altitude with local fluctuation. Comprehensive analysis demonstrated that the water conservation ability was stronger at a high altitude and weaker at a low altitude. The water holding capacity of litters at different altitudes increased and the water absorption rate of litter decreased with the soaking time, while after 12 hours, the water absorption rate of litters gradually became saturated. Moreover, the water holding capacity of litters at different altitudes and soaking time had a logarithmic relationship, and the relationship between the water absorption rate of litters and soaking time was described by power function. In short, there was a stronger water conservation function at high altitude compared with low altitude of the tropical montane rain forest in Xishuangbanna.

尖峰岭热带山地雨林林冠层乔木某些功能性状的系统发育信号、关联性及其演化模式

尖峰岭热带山地雨林林冠层乔木某些功能性状的系统发育信号、关联性及其演化模式