Epiphytic Communities of Bryophytes and Macrolichens in a Costa Rican Montane Oak Forest

Aspects dealt with in this study are the diversity and biogeography of bryophytes, the distribution patterns of life forms and species in microhabitats and along ecological gradients, the host preference and community composition of epiphytic bryophytes and macrolichens, the secondary succession of epiphytic vegetation and the selection of indicator species. For the first time recovery of epiphytic cryptogam communities in secondary tropical montane forests receives full attention. The study took place in the upper Río Savegre watershed area on the Pacific-facing slope of the western Talamanca Mountain Range, Costa Rica.In Chapter 1 a general introduction to tropical montane rain forests and to bryophytes and macrolichens as an important component of these ecosystems is presented. The reader is introduced to the study area, its climate, geology and vegetation. In Chapter 2 the phytogeographical patterns of bryophytes of Costa Rica's Talamancan montane oak forests are analysed and discussed.Chapter 3 deals with bryophyte diversity, microhabitat differentiation and distribution of live forms in an Costa Rican upper montane Quercus forest. It gives a comprehensive overview on the bryophyte flora of all microhabitats, including forest floor and the understorey of the forest.Chapter 4 and 5 contain the description of epiphytic cryptogam communities (bryophytes and macrolichens) in primary and secondary forests. Trees were climbed using a mountaineering-derived single rope technique and were sampled from the base up to the twigs of the outer canopy. The relevés taken in each height zone represented the complete variation of the epiphytic vegetation. Percentage cover of corticolous bryophyte and macrolichen species was estimated and later compared using Detrended Correspondence Analysis (DCA) and non-metric Multi-response Permutation Procedure (MRPP). Bark samples from the investigated trees were extracted with deionized H2O and analysed for pH.Chapter 4 pays attention to the epiphytic cryptogam communities on the two dominant host tree species (Quercus copeyensis and Q. costaricensis) of upper montane oak forests in Costa Rica. For the first time, a detailed description of epiphytic cryptogam communities of whole standing canopy trees in an upper montane oak forest is given.Chapter 5 compares species richness, community composition and ecology of cryptogamic epiphytes in primary and recovering upper montane Quercus forests of Costa Rica. Canopy trees of Quercus copeyensis were sampled with the aim of getting insights into recovery potential, underlying patterns and processes of epiphyte succession following anthropogenic disturbance.

The impacts of selective logging and clear-cutting on woody plant diversity after 40years of natural recovery in a tropical montane rain forest, south China.

Tree 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.

Reprint of “Biodegradation of low molecular weight organic acids in rhizosphere soils from a tropical montane rain forest”

Biodegradation of low molecular weight organic acids in rhizosphere soils from a tropical montane rain forest

Biomass carbon sequestration and sink capacities of tropical rainforests are vital for addressing climate change. However, canopy height must be accurately estimated to determine carbon sink potential and implement effective forest management. Four advanced machine-learning algorithms—random forest (RF), gradient boosting decision tree, convolutional neural network, and backpropagation neural network—were compared in terms of forest canopy height in the Hainan Tropical Rainforest National Park. A total of 140 field survey plots and 315 unmanned aerial vehicle photogrammetry plots, along with multi-modal remote sensing datasets (including GEDI and ICESat-2 satellite-carried LiDAR data, Landsat images, and environmental information) were used to validate forest canopy height from 2003 to 2023. The results showed that RH80 was the optimal choice for the prediction model regarding percentile selection, and the RF algorithm exhibited the optimal performance in terms of accuracy and stability, with R2 values of 0.71 and 0.60 for the training and testing sets, respectively, and a relative root mean square error of 21.36%. The RH80 percentile model using the RF algorithm was employed to estimate the forest canopy height distribution in the Hainan Tropical Rainforest National Park from 2003 to 2023, and the canopy heights of five forest types (tropical lowland rainforests, tropical montane cloud forests, tropical seasonal rainforests, tropical montane rainforests, and tropical coniferous forests) were calculated. The study found that from 2003 to 2023, the canopy height in the Hainan Tropical Rainforest National Park showed an overall increasing trend, ranging from 2.95 to 22.02 m. The tropical montane cloud forest had the highest average canopy height, while the tropical seasonal forest exhibited the fastest growth. The findings provide valuable insights for a deeper understanding of the growth dynamics of tropical rainforests.

Aggregating diverse plant species into a few functional groups based on functional traits provides new insights for promoting landscape planning and conserving biodiversity in species-diverse regions. Ecophysiological traits are the basis of the functioning of an ecosystem. However, studies related to the identification of functional groups based on plant ecophysiological traits in tropical forests are still scarce because of the inherent difficulties in measuring them. In this study, we measured five ecophysiological traits: net photosynthetic capacity (Amax), maximum stomatal conductance (gmax), water use efficiency (WUE), transpiration rate (Trmmol), and specific leaf areas (SLA) for 87 plant species dominant in a chronosequence of secondary succession, using four time periods (5 year-primary, 15 year-early, and 40 year-middle successional stages after clear cutting and old growth) in the tropical montane rainforest on Hainan Island, China. These species were grouped using hierarchical cluster analysis and non-metric multidimensional scaling. Finally, the changes in the composition of functional groups and species richness along the chronosequence were analyzed. Results showed that the plant species in the tropical montane rainforest could be classified into eight distinct functional groups. The richness of functional groups was low during the initial early stage and increased as the early and middle stages progressed, and then declined in the late successional stage. The dominant functional groups in the primary stages had the highest Amax, gmax, Trmmol, and SLA, as well as the lowest WUE, while those in the early and middle successional stages had functional traits at a moderate level, and at the late stage they had the lowest Amax, gmax, Trmmol, and SLA, and highest WUE. Our study showed that the diverse plant species in the tropical montane rainforest could be grouped into a few functional groups according to major ecophysiological traits, and the composition and relative abundance of different groups changed with the successional dynamics of the forest ecosystem.

Two new species of of Bunomys are described, B. karokophilus and B. torajae, both from the west-central mountain region of central Sulawesi. The descriptions are presented within the context of a systematic review of Bunomys in which are provided characteristics of the genus and species (external form, secondary sexual traits, spermatozoa, stomach morphology, skull, dentition, chromosomes); diagnoses, geographic and elevational distributions; sympatric, syntopic, and parapatric distributional relationships; morphological, distributional, and in some cases ecological comparisons among the species; natural histories for certain species derived from field observations; parasites; allocation of generic and specific synonyms; and documentation of subfossils for two of the species.Eight species are recognized; all are nocturnal, terrestrial, and endemic to the island of Sulawesi. Bunomys chrysocomus has been collected from most regions of the island and inhabits both lowland tropical evergreen and montane rain forests (elevational range = 250–2200 m). Bunomys coelestis is endemic to montane forests on Gunung Lompobatang, the high volcano at the southern end of the southwestern peninsula (1829–2500 m). Bunomys prolatus has been reported only from mountain forest on Gunung Tambusisi at the western end of the eastern peninsula (1829 m). Bunomys torajae, n. sp., is described from a small sample collected in montane forest on Gunung Gandangdewata at the southern end of the west-central mountain block (2500–2600 m). Bunomys fratrorum is currently documented only from the northeastern area of the northern peninsula where it occupies habitats in lowland tropical evergreen and montane rain forests (coastal plain to 1982 m). Bunomys andrewsi has been collected primarily in lowland tropical evergreen rain forests in the core of Sulawesi and on the eastern, southeastern, and southwestern peninsula (coastal plain to 1600 m). Bunomys penitus is strictly montane and recorded only from the west-central mountain block and Pegunungan Mekongga on the southeastern peninsula (1285–2287 m). Bunomys karokophilus, n. sp., is currently known only from lowland tropical evergreen rain forest in the northern portion of the west-central mountain block (823–1150 m).Analyses of morphometric traits (cranial and dental measurements) results in a phenetic relationship among the species in which B. chrysocomus, B. coelestis, B. prolatus, and B. torajae, n. sp., form one group characterized by small physical size and small molars, and B. fratrorum, B. andrewsi, B. penitus, and B. karokophilus another group in which larger physical size and heavier molars are the phenetic definers. Whether or not the integrity of this phenetic pattern will withstand testing by analyses of DNA sequences, it remains a convenient arrangement in which to present and define the eight species.The morphological, elevational, and ecological relationships among the four species of Bunomys (B. chrysocomus, B. andrewsi, B. penitus, and B. karokophilus, n. sp.) collected along my transect area in the northern portion of the west-central mountain block (presently known as Lore Lindu National Park) and comparison between them and the elevational distributions of the other murids encountered along the transect are described.Finally, a brief introduction to the species of murid rodents that have been recorded from mainland Sulawesi and nearby islands is provided, which defines the murine faunal context for the species of Bunomys.The treatment of Bunomys offered here focuses on definitions of the species as outlined by phenetic traits, elevational and geographic distributions, and the natural history characteristics that are available for some of the species, and does not cover an analysis of the phylogenetic relationships between Bunomys and other Indoaustralian murines.

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

The study determined the carbon stocks and litter nutrient concentration in tropical forests along the ecological gradient in Kenya. This could help understand the potential of mitigating climate change using tropical forest ecosystems in different ecological zones, which are being affected by climate change to a level that they are becoming carbon sources instead of sinks. Stratified sampling technique was used to categorize tropical forests into rain, moist deciduous and dry zone forests depending on the average annual rainfall received. Simple random sampling technique was used to select three tropical forests in each category. Modified consistent sampling technique was used to develop 10 main 20 m × 100 m plots in each forest, with 20 2 m × 50 m sub-plots in each plot. Systematic random sampling technique was used in selecting 10 sub-plots from each main plot for inventory study. Non-destructive approach based on allometric equations using trees’ diameter at breast height (DBH), total height and species’ wood specific gravity were used in estimating tree carbon stock in each forest. Soil organic carbon (SOC) and litter nutrient concentration (total phosphorus and nitrogen) were determined in each forest based on standard laboratory procedures. The results indicated that, whilst trees in rain forests recorded a significantly higher (p < 0.001) DBH (20.36 cm) and total tree height (12.1 m), trees in dry zone forests recorded a significantly higher (p < 0.001) specific gravity (0.67 kg m−3). Dry zone tropical forests stored a significantly lower amount of total tree carbon of 73 Mg ha−1, compared to tropical rain forests (439.5 Mg ha−1) and moist deciduous tropical forests (449 Mg ha−1). The SOC content was significantly higher in tropical rainforests (3.9%), compared to soils from moist deciduous (2.9%) and dry zone forests (1.8%). While litter from tropical rain forests recorded a significantly higher amount of total nitrogen (3.4%), litter from dry zone forests recorded a significantly higher concentration of total phosphorus (0.27%). In conclusion, ecological gradient that is dictated by the prevailing temperatures and precipitation affects the tropical forests carbon stock potential and litter nutrient concentration. This implies that, the changing climate is having a serious implication on the ecosystem services such as carbon stock and nutrients cycling in tropical forests.

We investigated the role of carbon, nitrogen and phosphorus as limiting factors of microorganisms and microbial grazers (testate amoebae) in a montane tropical rain forest in southern Ecuador. Carbon (as glucose), nitrogen (as NH 4 NO 3 ) and phosphorus (as NaH 2 PO 4 ) were added separately and in combination bimonthly to experimental plots for 20 months. By adding glucose and nutrients we expected to increase the growth of microorganisms as the major food resource of testate amoebae. Th e response of microorganisms to experimental treatments was determined by analysing microbial biomass (SIR), fungal biomass and microbial community composition as measured by phospholipid fatty acids (PLFAs). We hypothesized that the response of testate amoebae is closely linked to that of microorganisms. Carbon addition strongly increased ergosterol concentration and, less pronounced, the amount of linoleic acid as fungal biomarker, suggesting that saprotrophic fungi are limited by carbon. Microbial biomass and ergosterol concentrations reached a maximum in the combined treatment with C, N and P indicating that both N and P also were in short supply. In contrast to saprotrophic fungi and microorganisms in total, testate amoebae suff ered from the addition of C and reached maximum density by the addition of N. Th e results indicate that saprotrophic fungi in tropical montane rain forests are mainly limited by carbon whereas gram positive and negative bacteria benefi t from increased availability of P. Testate amoebae suff ered from increased dominance of saprotrophic fungi in glucose treatments but benefi ted from increased supply of N. Th e results show that testate amoebae of tropical montane rain forests are controlled by bottom–up forces relying on specifi c food resources rather than the amount of bacterial biomass with saprotrophic fungi functioning as major antagonists. Compared to temperate systems microbial food webs in tropical forests therefore may be much more complex than previously assumed with trophic links being rather specifi c and antagonistic interactions overriding trophic interactions.

Tropical rain forests as carbon sinks

The availability of phosphorus (P) can limit net primary production (NPP) in tropical rainforests growing on highly weathered soils. Although it is well known that plant roots release organic acids to acquire P from P-deficient soils, the importance of organic acid exudation in P-limited tropical rainforests has rarely been verified. Study sites were located in two tropical montane rainforests (a P-deficient older soil and a P-rich younger soil) and a tropical lowland rainforest on Mt. Kinabalu, Borneo to analyze environmental control of organic acid exudation with respect to soil P availability, tree genus, and NPP. We quantified root exudation of oxalic, citric, and malic acids using in situ methods in which live fine roots were placed in syringes containing nutrient solution. Exudation rates of organic acids were greatest in the P-deficient soil in the tropical montane rainforest. The carbon (C) fluxes of organic acid exudation in the P-deficient soil (0.7 mol C m−2 month−1) represented 16.6% of the aboveground NPP, which was greater than those in the P-rich soil (3.1%) and in the lowland rainforest (4.7%), which exhibited higher NPP. The exudation rates of organic acids increased with increasing root surface area and tip number. A shift in vegetation composition toward dominance by tree species exhibiting a larger root surface area might contribute to the higher organic acid exudation observed in P-deficient soil. Our results quantitatively showed that tree roots can release greater quantities of organic acids in response to P deficiency in tropical rainforests.

This article reviews literature and summarizes experiments to investigate the extent to which productivity of tropical montane rain forests is constrained by low nutrient supply. On any one mountain, with increase in altitude foliar N decreases, and P and K usually decrease, but Ca and Mg show no consistent trend. However for a wide range of sites N, P, K, Mg, and Ca show no trends. Litterfall contents of N and P and often K, Ca, and Mg are lower in montane forests than in lowland forests, mainly because of reduced litterfall mass, but N and P concentrations are also lower in forests above 1500 m. Tropical montane soils usually have more soil organic matter per unit ground area; N mineralization levels are lower at higher altitudes in Costa Rica, and extractable and total soil P are lower in sites with lower litterfall P concentrations. We speculate that many lowland forests are limited by P and many montane forests by N. Fertilization studies on ash-derived montane soils in Hawai‘i showed a trend for a switch from N limitation on young soils to P, or N and P, limitation on soils over older substrates. Jamaican montane trees were limited by N and by P separately. Venezuelan montane trees were limited by N. The sites in Jamaica and Venezuela have soils of indeterminate age. Taken together these results show that nutrient limitation is widespread in montane soils (all sites have responded to at least one nutrient) and that the particular nutrient(s) that limit(s) production may differ for explicable reasons. First results from lowland forests on sandy soils in Kalimantan show N or simultaneous N and P limitation. Many more experiments, especially in lowland forests, are needed to test our speculation that P usually limits productivity in tropical lowland rain forests and that N limits productivity in tropical montane rain forests.

This article reviews literature and summarizes experiments to investigate the extent to which productivity of tropical montane rain forests is constrained by low nutrient supply. On any one mountain, with increase in altitude foliar N decreases, and P and K usually decrease, but Ca and Mg show no consistent trend. However for a wide range of sites N, P, K, Mg, and Ca show no trends. Litterfall contents of N and P and often K, Ca, and Mg are lower in montane forests than in lowland forests, mainly because of reduced litterfall mass, but N and P concentrations are also lower in forests above 1500 m. Tropical montane soils usually have more soil organic matter per unit ground area; N mineralization levels are lower at higher altitudes in Costa Rica, and extractable and total soil P are lower in sites with lower litterfall P concentrations. We speculate that many lowland forests are limited by P and many montane forests by N. Fertilization studies on ash-derived montane soils in Hawai‘i showed a trend for a switch from N limitation on young soils to P, or N and P, limitation on soils over older substrates. Jamaican montane trees were limited by N and by P separately. Venezuelan montane trees were limited by N. The sites in Jamaica and Venezuela have soils of indeterminate age. Taken together these results show that nutrient limitation is widespread in montane soils (all sites have responded to at least one nutrient) and that the particular nutrient(s) that limit(s) production may differ for explicable reasons. First results from lowland forests on sandy soils in Kalimantan show N or simultaneous N and P limitation. Many more experiments, especially in lowland forests, are needed to test our speculation that P usually limits productivity in tropical lowland rain forests and that N limits productivity in tropical montane rain forests.