Trees as net sinks for methane (CH4 ) and nitrous oxide (N2 O) in the lowland tropical rain forest on volcanic Réunion Island.

Trees are known to emit methane (CH4 ) and nitrous oxide (N2 O), with tropical wetland trees being considerable CH4 sources. Little is known about CH4 and especially N2 O exchange of trees growing in tropical rain forests under nonflooded conditions. We determined CH4 and N2 O exchange of stems of six dominant tree species, cryptogamic stem covers, soils and volcanic surfaces at the start of the rainy season in a 400-yr-old tropical lowland rain forest situated on a basaltic lava flow (Réunion Island). We aimed to understand the unknown role in greenhouse gas fluxes of these atypical tropical rain forests on basaltic lava flows. The stems studied were net sinks for atmospheric CH4 and N2 O, as were cryptogams, which seemed to be co-responsible for the stem uptake. In contrast with more commonly studied rain forests, the soil and previously unexplored volcanic surfaces consumed CH4 . Their N2 O fluxes were negligible. Greenhouse gas uptake potential by trees and cryptogams constitutes a novel and unique finding, thus showing that plants can serve not only as emitters, but also as consumers of CH4 and N2 O. The volcanic tropical lowland rain forest appears to be an important CH4 sink, as well as a possible N2 O sink.

31P-NMR Metabolomics Revealed Species-Specific Use of Phosphorous in Trees of a French Guiana Rainforest.

Productivity of tropical lowland moist forests is often limited by availability and functional allocation of phosphorus (P) that drives competition among tree species and becomes a key factor in determining forestall community diversity. We used non-target 31P-NMR metabolic profiling to study the foliar P-metabolism of trees of a French Guiana rainforest. The objective was to test the hypotheses that P-use is species-specific, and that species diversity relates to species P-use and concentrations of P-containing compounds, including inorganic phosphates, orthophosphate monoesters and diesters, phosphonates and organic polyphosphates. We found that tree species explained the 59% of variance in 31P-NMR metabolite profiling of leaves. A principal component analysis showed that tree species were separated along PC 1 and PC 2 of detected P-containing compounds, which represented a continuum going from high concentrations of metabolites related to non-active P and P-storage, low total P concentrations and high N:P ratios, to high concentrations of P-containing metabolites related to energy and anabolic metabolism, high total P concentrations and low N:P ratios. These results highlight the species-specific use of P and the existence of species-specific P-use niches that are driven by the distinct species-specific position in a continuum in the P-allocation from P-storage compounds to P-containing molecules related to energy and anabolic metabolism.

Climate Warming and Soil Carbon in Tropical Forests: Insights from an Elevation Gradient in the Peruvian Andes.

The temperature sensitivity of soil organic matter (SOM) decomposition in tropical forests will influence future climate. Studies of a 3.5-kilometer elevation gradient in the Peruvian Andes, including short-term translocation experiments and the examination of the long-term adaptation of biota to local thermal and edaphic conditions, have revealed several factors that may regulate this sensitivity. Collectively this work suggests that, in the absence of a moisture constraint, the temperature sensitivity of decomposition is regulated by the chemical composition of plant debris (litter) and both the physical and chemical composition of preexisting SOM: higher temperature sensitivities are found in litter or SOM that is more chemically complex and in SOM that is less occluded within aggregates. In addition, the temperature sensitivity of SOM in tropical montane forests may be larger than previously recognized because of the presence of "cold-adapted" and nitrogen-limited microbial decomposers and the possible future alterations in plant and microbial communities associated with warming. Studies along elevation transects, such as those reviewed here, can reveal factors that will regulate the temperature sensitivity of SOM. They can also complement and guide in situ soil-warming experiments, which will be needed to understand how this vulnerability to temperature may be mediated by altered plant productivity under future climatic change.

Negative density-dependent mortality varies over time in a wet tropical forest, advantaging rare species, common species, or no species.

Although one of the most widely studied hypotheses for high tree diversity in the tropics, the Janzen-Connell hypothesis (JC), and the community compensatory trend upon which it is based, have conflicting support from prior studies. Some of this variation could arise from temporal variation in seedling survival of common and rare species. Using 10 years of data from La Selva Biological Station in Costa Rica, we analyzed annual seedling survival and found that negative density-dependence (negative DD) was significantly stronger for rare species than for common species in 2 years and was significantly stronger for common species than for rare species in 4 years. This temporal variation in survival was correlated with climatic variables: in warmer and wetter years, common species had higher negative DD than rare species. The relationship between climate and variation in JC effects on seedling survival of common and rare species could have important consequences for the maintenance of tree species diversity in Central America, which is predicted to experience warmer and wetter years as global change proceeds.

Combining spaceborne lidar from the Global Ecosystem Dynamics Investigation with local knowledge for monitoring fragmented tropical landscapes: A case study in the forest-agriculture interface of Ucayali, Peru.

Improving our ability to monitor fragmented tropical ecosystems is a critical step in supporting the stewardship of these complex landscapes. We investigated the structural characteristics of vegetation classes in Ucayali, Peru, employing a co-production approach. The vegetation classes included three agricultural classes (mature oil palm, monocrop cacao, and agroforestry cacao plantations) and three forest regeneration classes (mature lowland forest, secondary lowland forest, and young lowland vegetation regrowth). We combined local knowledge with spaceborne lidar from NASA's Global Ecosystem Dynamics Investigation mission to classify vegetation and characterize the horizontal and vertical structure of each vegetation class. Mature lowland forest had consistently higher mean canopy height and lower canopy height variance than secondary lowland forest (µ = 29.40 m, sd = 6.89 m vs. µ = 20.82 m, sd = 9.15 m, respectively). The lower variance of mature forest could be attributed to the range of forest development ages in the secondary forest patches. However, secondary forests exhibited a similar vertical profile to mature forests, with each cumulative energy percentile increasing at similar rates. We also observed similar mean and standard deviations in relative height ratios (RH50/RH95) for mature forest, secondary forest, and oil palm even when removing the negative values from the relative height ratios and interpolating from above-ground returns only (mean RH50/RH95 of 0.58, 0.54, and 0.53 for mature forest, secondary forest, and oil palm, respectively) (p < .0001). This pattern differed from our original expectations based on local knowledge and existing tropical forest succession studies, pointing to opportunities for future work. Our findings suggest that lidar-based relative height metrics can complement local information and other remote sensing approaches that rely on optical imagery, which are limited by extensive cloud cover in the tropics. We show that characterizing ecosystem structure with a co-production approach can support addressing both the technical and social challenges of monitoring and managing fragmented tropical landscapes.

Secondary Succession Altered the Diversity and Co-Occurrence Networks of the Soil Bacterial Communities in Tropical Lowland Rainforests.

The characteristics of plant and soil bacterial communities in forest ecosystems have been reported, but our understanding of the relationship between plant communities and soil bacteria in different stages of secondary tropical rainforest succession is still poor. In June 2018, three different natural successional stages of tropical lowland rainforests, early (33 years), early-mid (60 years), and mid successional stage (73 years), in Hainan Island, China, were selected for this study. By conducting field investigation and 16S rRNA gene high-throughput sequencing, the composition and diversity of tree communities, the niche overlap of tree species with legumes among tree species, and the diversity and composition of soil bacterial communities and co-occurrence networks within communities across the successional stages were investigated. The results showed that plant richness and species diversity increased significantly during the secondary succession of tropical lowland rainforests. The order of positive correlations between nitrogen-fixing legumes and other species in plant communities was early-mid > mid > early successional stage. Soil nutrient content and soil bacterial richness were highest in the early-mid stages of succession, followed by mid and early stages of succession. Organic matter (OM), total nitrogen (TN), alkali nitrogen (AN), and available phosphorus (AP) had a stronger positive impact on soil bacterial communities. Co-occurrence network analysis showed that with the advancement of rainforests succession, the negative correlation between soil bacterial species decreased, and the community stability increased. Overall, as a result of tropical lowland rainforest secondary natural succession, the richness and diversity of plant communities increased, which altered the living conditions of nitrogen-fixing legumes and the soil properties, and the network complexity of soil bacterial communities increased with the rising of rainforest soil nutrient content.

Review of the mite genus Krantzolaspina Datta & Bhattacharjee (Mesostigmata, Parholaspididae) with re-description of K. angustatus comb. nov. (Ishikawa) from Indonesia.

Herein, we update the diagnosis and description of the genus Krantzolaspina Datta & Bhattacharjee and provide a list of the three valid species including new combinations and synonyms, as follows: 1) Krantzolaspina angustatus (Ishikawa, 1987) comb. nov. (= Indutolaelaps jiroftensisHajizadeh et al., 2017syn. nov.), 2) K. rebatii Datta & Bhattacharjee, 1989 and 3) K. solimani (Metwali, 1983) comb. nov. Finally, we re-describe K. angustatus (Ishikawa, 1987) comb. nov. based on the holotype from Japan, voucher specimens from Iran and additional females that we found in soil samples from oil palm plantations in Sumatra, Indonesia.

Shrews (Soricidae) of the lowland forests around Kisangani (DR Congo).

BACKGROUND: The Congo Basin rainforest is the second largest rainforest in the world and one of the most biodiverse regions on Earth. Nevertheless, the Congo Basin biodiversity remains to be fully mapped, with many species awaiting discovery or official description. In recent years, much effort has been put into research on shrews (Soricidae), particularly in the region around Kisangani (D.R. Congo). Shrews are opportunistic feeders that are able to forage on a large diversity of invertebrate prey and therefore play an important role in the forest ecosystem. Furthermore, as they largely depend on forest habitats and have limited dispersal capacities, shrews form an interesting model group to study biogeographic patterns in the Congo Basin. NEW INFORMATION: This paper collates the efforts on shrew research from the wider region around Kisangani, in the centre of the Congo Basin. Apart from sampling information, the dataset includes morphological measures, DNA sequences and photographs. This dataset is therefore critical in the study of the taxonomy and ecology of Soricidae in the Congo Basin lowland rainforests.

Do ant mosaics exist in pristine lowland rain forests?

Ant mosaics have been described as characteristic elements of arboreal ant communities from tropical plantations, and it is often assumed that they also exist in undisturbed lowland rain forests. Until now, however, there have been no studies from pristine rain forests to show this. Our investigations on the mechanisms structuring arboreal arthropod communities in a southeast-Asian lowland rain forest allowed us to compare our results with the predictions of the ant mosaic theory. According to this theory aggressive dominant ant species should maintain mutually exclusive territories. Furthermore, communities of associated nesting species dominated by the same dominant species should be more similar to each other than communities governed by other dominants. The ant communities of 19 individuals of three understorey tree species were collected with an improved method of canopy fogging that guaranteed selective tree sampling in a multilayered rain forest. Ten trees were re-fogged after 6 months and seven again after 3 years to investigate whether the reorganization of the ant communities occurred in a similar way. To test whether the pattern of an ant mosaic emerged when not only single trees but also somewhat larger areas containing several adjacent trees were sampled, we collected the nesting ant species from a group of Aporusa lagenocarpa with tuna baits. All ant communities were highly heterogeneous in their species composition and neither negative nor positive species associations were found. The lack of an ant mosaic in mature forests is also suggested by a Monte Carlo computer simulation, according to which ant community composition differed only slightly from random. The re-fogged communities showed the same structural heterogeneity as was found in the first fogged communities, without any observable convergence to the original species composition. No pioneer or climax species could be identified. All results combined indicate that the ant mosaic theory does not apply to the mature lowland rain forest investigated, where community organization seems to be the product of very complex dynamic processes.

A trait-based trade-off between growth and mortality: evidence from 15 tropical tree species using size-specific relative growth rates.

A life-history trade-off between low mortality in the dark and rapid growth in the light is one of the most widely accepted mechanisms underlying plant ecological strategies in tropical forests. Differences in plant functional traits are thought to underlie these distinct ecological strategies; however, very few studies have shown relationships between functional traits and demographic rates within a functional group. We present 8 years of growth and mortality data from saplings of 15 species of Dipterocarpaceae planted into logged-over forest in Malaysian Borneo, and the relationships between these demographic rates and four key functional traits: wood density, specific leaf area (SLA), seed mass, and leaf C:N ratio. Species-specific differences in growth rates were separated from seedling size effects by fitting nonlinear mixed-effects models, to repeated measurements taken on individuals at multiple time points. Mortality data were analyzed using binary logistic regressions in a mixed-effects models framework. Growth increased and mortality decreased with increasing light availability. Species differed in both their growth and mortality rates, yet there was little evidence for a statistical interaction between species and light for either response. There was a positive relationship between growth rate and the predicted probability of mortality regardless of light environment, suggesting that this relationship may be driven by a general trade-off between traits that maximize growth and traits that minimize mortality, rather than through differential species responses to light. Our results indicate that wood density is an important trait that indicates both the ability of species to grow and resistance to mortality, but no other trait was correlated with either growth or mortality. Therefore, the growth mortality trade-off among species of dipterocarp appears to be general in being independent of species crossovers in performance in different light environments.