Undisturbed Rainforest Research Articles

Assessing the invasion potential of five common exotic vine species in temperate Australian rainforests

To compare the capacity of native and exotic vine species established under a rainforest canopy, a comparison of growth rates and resource allocation was made amongst five exotic vine species that are serious and common invaders and two common native vine species under two light conditions reflective of edge and interior canopy conditions. All species experienced heavy reductions in growth parameters in the low-light treatment, but three exotic species showed stronger growth under the low light. All exotic species had higher plasticity in leaf morphology showing a significant increase in SLA under low light. Native vines may have a lower capacity to change leaf morphology in shade, as a result of local adaptation to edge habitats. Higher SLA under both low and high light conditions suggests that exotic vines species are able to exploit a range of forest conditions better than the native species. Three species, Anredera cordifolia, Araujia sericifera and Cardiospermum grandiflorum, appear particularly capable of invading rainforest interiors. Individuals produced few leaves, focusing resources on roots and stems suggesting a response to reach the canopy quickly. With their long-distance seed dispersal, plasticity in leaf SLA and high RGR, these species appear most likely to invade undisturbed rainforest.

New data on and the easternmost record of the Javan endemic Pearly Tree Frog, Nyctixalus margaritifer Boulenger, 1882 (Anura, Rhacophoridae)

New locality records and a range extension of the Javan endemic Pearly Tree Frog, Nyctixalus margaritifer Boulenger, 1882 are reported from Central Java and East Java. Our new data include the easternmost record in Java, a record from the eastern edge of Bromo Tengger Semeru National Park, which is approximately 142 km west of the species’ type locality in Gunung Willis in East Java. This tree-frog species inhabits undisturbed rainforest with a dense canopy and vegetation at elevations up to 1,200 m a.s.l. Based on a morphometric analysis of newly collected specimens, we found observable differences in several morphological characters. However, more specimens are needed to confirm the taxonomic status of the rare, endemic, and poorly known N. margaritifer.

Amazonian mixed‐species flocks demonstrate flexible preferences for vertical forest structure

AbstractHow species interact with human‐disturbed environments is a central focus of conservation biology. Within disturbed landscapes, regenerating forests have potential to provide habitat for forest species, especially as increasing amounts of primary forest are lost. As secondary forest regenerates beside primary forest, it increases habitat heterogeneity. However, relatively little is known about the influence of habitat heterogeneity on space use. In this study, we analyzed the topography and vertical vegetation structure of regenerating forest, small forest fragments, and undisturbed rainforest in the central Amazon to determine (1) how these structural characteristics influence understory mixed‐species flock space use and (2) how the vegetative preferences of flocks varied across a disturbance gradient. We first used behavioral observations to quantify the vertical foraging niche of flocks and then associated variation in horizontal space use with the three‐dimensional features of forest structure. Surprisingly, we found that flock space use was not consistently associated with any variable, even though available habitat differed both within and across forest types. Overall, the best predictors were elevation and leaf area density within the subcanopy (16–25 m), yet most flock foraging occurred in the midstory (6–15 m). Together, these results indicate that while flocks may have certain habitat preferences, these preferences are flexible or idiosyncratic and do not correspond to a specific vertical profile. For example, flocks spent a disproportionate amount of time in low elevations when available, but not all flocks had access to low‐lying areas within their home ranges. Although other studies show flock size and diversity can be highly sensitive to habitat disturbance, mixed‐species flocks demonstrate remarkable plasticity as a unit, virtually saturating undisturbed and disturbed forest at our site, as long as regeneration has passed a certain threshold.

Living in human-modified landscapes narrows the dietary niche of a specialised mammalian scavenger

Anthropogenic impacts on carnivores can be complex, posing numerous threats to many species, yet also benefits to those able to exploit certain resources. This balancing act is particularly precarious for those adapters that exploit dietary resources provided by humans, but still require other resources only available in native habitat. Here we measure the dietary niche of one such species, the Tasmanian devil (Sarcophilus harrisii), a specialised mammalian scavenger, across an anthropogenic habitat gradient stretching from cleared pasture to undisturbed rainforest. Populations inhabiting areas of greater disturbance showed restricted dietary niches, suggesting that all individuals fed on similar food items, even within regenerated native forest. Populations in undisturbed rainforest habitats had comparatively broad diets and showed evidence of niche partitioning by body size, which may reduce intraspecific competition. Despite the potential benefits of reliable access to high-quality food items in anthropogenically-modified habitats, the constrained niches we observed may be harmful, indicating altered behaviours and potentially increasing the rate of fights between individuals over food. This is of particular concern for a species at risk of extinction due to a deadly cancer primarily transmitted through aggressive interactions. The lack of diversity in devil diets within regenerated native forest compared to those in old-growth rainforest also indicates the conservation value of the latter for both the devil and the species which they consume.

Soil potassium isotope composition during four million years of ecosystem development in Hawai‘i

We combine spectroscopic and geochemical approaches to interpret the fate of potassium (K) during forest soil development along a 4-million-year chronosequence sampled from relatively undisturbed rainforests in Hawai‘i. Potassium derived from weathering of lava is dominant in the youngest site (0.3 ky), but its contribution to the soil K budget declines as weathering progresses. Sites older than 0.3 ky are characterized by substantial K depletion (τK,Nb ∼−1), with soil isotopic composition (41K/39K, δ41K) varying from −1.91 ± 0.08‰ to −0.09 ± 0.08‰, relative to the homogeneous basaltic substrate (−0.48‰). Exchangeable and interlayered K show δ41K values ranging from −1.32 ± 0.06‰ to 0.06 ± 0.08‰, higher than their corresponding bulk δ41K values. The δ41K patterns of soils and exchangeable components are vertically similar, implying similar environmental controls. The variability in K phase and isotope composition reflects the accumulative effect of different processes. Chemical weathering and plant cycling retain isotopically light K in soils, in particular for 20–150 ky sites. In contrast, atmospheric inputs of marine aerosols (0.14‰) and mineral aerosols (−0.44‰) add heavier K (than native basalts) and crust-like K (similar to basaltic δ41K) in soils, respectively. In sites older than 150 ky, nearly complete depletion of basaltic K and reduced plant K imprints result in the dominance of atmospheric inputs in soils. In sum, this study emphasizes the sensitivity of δ41K to terrestrial biotic and abiotic K cycles.

Climate trends and behavior of a model Amazonian terrestrial insectivore, black‐faced antthrush, indicate adjustment to hot and dry conditions

Rainforest loss threatens terrestrial insectivorous birds throughout the world's tropics. Recent evidence suggests these birds are declining in undisturbed Amazonian rainforest, possibly due to climate change. Here, we first asked whether Amazonian terrestrial insectivorous birds were exposed to increasingly extreme ambient conditions using 38 years of climate data. We found long‐term trends in temperature and precipitation at our study site, especially in the dry season, which was ~1.3°C hotter and 21% drier in 2019 than in 1981. Second, to test whether birds actively avoided hot and dry conditions, we used field sensors to identify periodic intervals of ambient extremes and prospective microclimate refugia within undisturbed rainforest from 2017 to 2019. Simultaneously, we examined how tagged black‐faced antthrushes Formicarius analis used this space. We collected > 1.3 million field measurements quantifying ambient conditions in the forest understory, including along elevation gradients. For 11 birds, we obtained GPS data to test whether birds adjusted their cover usage using variation in GPS fix success (n = 2724) as a proxy and elevation using successful locations (n = 640) across seasonal and daily cycles. For four additional birds, we collected > 180 000 light and temperature readings to assess exposure. Field measurements in the modern landscape revealed that temperature was higher in the dry season and highest on plateaus. Thus, low‐lying areas were relatively buffered, providing microclimate refugia during hot afternoons in the dry season. At those times, birds apparently entered cover and shifted downslope. Because climate change intensifies the hot, dry conditions that antthrushes seemingly avoid, our results are consistent with the hypothesis that climate change decreases habitat quality for this species. If other terrestrial insectivores are similarly sensitive, climate‐induced changes to otherwise intact rainforest may be related to their recent declines.

Abundance and nesting sites characteristics of red-headed picathartes Picathartes oreas in Cross River State, Nigeria

This study assessed the abundance and nesting sites characteristics of red-headed picathartes (Picathartes oreas) in protected and unprotected forest in Cross River State, from August 2016 to January 2017. Data were collected through oral interviews, and field observations, using area search and quadrant methods. Data on bird and nest were tested using one-way ANOVA and t-test while tree species diversity indices were calculated using Paleontological Statistics Software Package, version 16. Results revealed that a mean of 38±52 individual bird from six colonies were sighted during the survey. Higher number of 20 (52.63%) individuals from two colonies was recorded in the undisturbed montane rain forest of the Okwangwo Division of the Cross River National Park than the disturbed montane rain forest with 18 (47.37%) individuals from four colonies. A total of 40 (50%; n = 20 each) nests of red-headed picathartes were sighted during the survey around the undisturbed and disturbed montane rain forest respectively. All (100%; n = 40) the nests observed were attached to the south-eastern side of the rocks and all the nests were constructed with mud mixed with grass. Colony Six was on the highest altitude with an elevation of 529 m, followed by colony two with an elevation of 342 m while the lowest elevation was 195 m recorded in colony three. Tree diversity index was higher in the protected forest (3.352; 3.227) than in the unprotected forest (1.846). Characteristic features of Picathartes oreas habitat were rock, hill, valleys and rivers and streams. It was evidenced by the study that Picathartes oreas still nests both in the disturbed and undisturbed forest but the level of disturbance and type of crops grown may have impact on the nesting behaviour. Therefore, anthropogenic activities should be regulated in the area, to ensure the conservation of Picathartes oreas.
 Keywords: Picathartes oreas; abundance; nesting sites characteristics; unprotected and protected forest.

Fig development in two Neotropical Ficus species, Ficus (subg. Pharmacosycea) yoponensis and Ficus (subg. Spherosuke) colubrinae: comparing rainforest and pasture trees

In the fragmented landscape of Los Tuxtlas, adult fig trees are found in both rainforest remnants and in pastures. Syconium (fig) development is known to vary between and within Ficus species, but it is not known whether it differs between rainforest and pasture trees. Here, we describe syconium development for two Ficus species with different life forms (free-standing and hemi-epiphytic) in two contrasting, adjacent habitats: an undisturbed rainforest and active pastures. Over three months, we monitored 15 reproductive events in Ficus (subg. Pharmacosycea) yoponensis Desv. and Ficus (subg. Spherosuke) colubrinae Standl., collecting and dissecting syconia every 3–4 days (1291 and 815 syconia per species, respectively). External and internal structural changes in the syconia are described, including foundress occurrence and the maximum duration of the receptive phase while waiting for pollinators. The duration of both the reproductive events (<8 weeks) and the developmental phases in the two species did not differ between rainforest and pasture trees and are within the lower range of time reported for other Ficus species. After pollinator exclusion, the receptive phase lasted up to four times its normal duration. Syconia were slightly larger in rainforest trees than in pasture trees, and the infestation of F. yoponensis syconia by non-pollinating insects was higher in rainforest trees.

In remembrance of: Scott A. Mori (1941–2020), Tropical Botanist Extraordinaire

In remembrance of: Scott A. Mori (1941–2020), Tropical Botanist Extraordinaire

Impacts of sediment derived from erosion of partially-constructed road on aquatic organisms in a tropical river: The Río San Juan, Nicaragua and Costa Rica.

Throughout the humid tropics, increased land disturbance and concomitant road construction increases erosion and sediment delivery to rivers. Building road networks in developing countries is commonly a priority for international development funding based on anticipated socio-economic benefits. Yet the resulting erosion from roads, which recent studies have shown result in at least ten-fold increases in erosion rates, is not fully accounted for. While effects of road-derived sediment on aquatic ecosystems have been documented in temperate climates, little has been published on the effects of road-induced sediment on aquatic ecosystems in developing countries of the tropics. We studied periphyton biomass and macroinvertebrate communities on the deltas of Río San Juan tributaries, comparing north-bank tributaries draining undisturbed rain forest with south-bank tributaries receiving runoff from a partially-built road experiencing rapid erosion. Periphyton biomass, richness and abundance of macroinvertebrates overall, and richness and abundance of Ephemeroptera, Plecoptera and Trichoptera were higher on the north-bank tributary deltas than the south-bank tributary deltas. These findings were consistent with prior studies in temperate climates showing detrimental effects of road-derived fine sediment on aquatic organisms. A Non-Metric Multidimensional Scaling (NMDS) analysis showed the impacted community on the south-bank deltas was influenced by poorly-sorted substrate with greater proportions of fine sediment and higher water temperatures.

The Progressive Spread of the Vascular Wilt Like Pathogen of Calophyllum Detected in Ranomafana National Park, Madagascar.

Pathogens are threatening crops worldwide, but little attention has been given to the threat to tree species in undisturbed rainforest. This communication reports the first case of a tree die off caused by a “wilt” in Madagascar. In 2016 while monitoring monthly tree phenology of Ranomafana National Park (RNP), the Centre ValBio research station observed that many Calophyllum adult trees had brown wilted leaves. There are three species of Calophyllum in this rainforest, C. paniculatum, C. drouhardii, and C. milvum, and all three have contracted this pathogen. Our goal was to document the spead of this suspected wilt in Calophyllum trees and determine if site, elevation and DBH had an influence on tree mortality. In 2019 we conducted an inventory of all Calophyllum trees in RNP and 42% of the observed trees were dead. The species with the highest mortality was C. paniculatum, with 53% of trees dead, followed by C. milvum with 18%, and C. drouhardii with only 2% of surveyed trees dead. Bark beetle traces were observed in all dead Calophyllum trees. Tree death caused by this suspected fungal pathogen has spread across a major river in the area and has been found at mid and high elevations. Our results show that C. paniculatum trees with a larger DBH have a higher mortality risk. Our report highlights the importance of fighting invasive pathogens that threaten protected ecosystems.

Land use affects temperature sensitivity of soil organic carbon decomposition in macroaggregates but not in bulk soils in subtropical Oxisols of Queensland, Australia

The turnover of soil organic carbon (SOC) under different land uses plays an important role in terrestrial carbon (C) cycling. However, the effects of warming on C decomposition dynamics have not been resolved due to seemingly inconsistent results among different experiments. Hence, the objective of this work was to assess soil aggregate-associated C and temperature sensitivity of SOC decomposition within bulk soils and aggregates under two contrasting land management systems in subtropical southern Queensland.We examined the temperature sensitivity of SOC decomposition (Q10) and activation energy required for soil C mineralization (Ea) from bulk soils (<8 mm), large macroaggregates (2−8 mm) and small macroaggregates (0.25−2 mm), as well as key C and N cycling enzyme activities in the surface (0−10 cm) soils of an Oxisol. The two land uses studied were: undisturbed rainforest and 115-year-old kikuyu grass (Pennisetum clandestinum) pasture. Bulk soils as well as their large and small macroaggregates were separately incubated at two temperatures (17 °C and 27 °C) for 124 d. We observed that the pasture soils had more small macroaggregates but less microaggregates than the forest soils. However, all fractions in the forest contained significantly higher SOC than those in the pasture. Potential soil enzyme activities per unit SOC within bulk soils and macroaggregates for N-acetyl β-glucosaminidase, α-glucosidase, and phenol oxidase were higher in the pasture than in the forest. The cumulative C mineralization values of bulk soils under the forest vegetation were 16 % higher than for pasture at 17 °C and 97 % higher than pasture at 27 °C. Cumulative C mineralization from large macroaggregates of both land uses were more than that from small macroaggregates. However, the Ea and Q10 values of bulk soils were similar for both the forest and pasture soils. For the large macroaggregates, the Ea value was ∼78 % higher for the pasture soil than for the forest soil, with the Q10 value also being 73 % higher in the pasture soil. However, the opposite was observed for the small macroaggregates, with Ea and Q10 values being higher in the forest soil. The contrasting nature of Q10 from large and small macroaggregates in Oxisols suggests that the feedback from SOC decomposition in response to changing temperature, that is, global warming is closely associated with soil aggregation.

Cacao agroforestry in Belize: Effects on soil nematode community structure

Cacao (Theobroma cacao L.) is a shade tolerant crop that can be grown beneath the rainforest canopy rather than in a conventional monoculture. Cacao agroforestry has been proposed as a more sustainable method of farming to mitigate climate change and protect above-ground biodiversity, yet impacts on soil biodiversity and function have rarely been investigated. Our goal was to study how the diversity and community structure of soil nematodes are impacted by planting the rainforest understory with cacao. At field sites in southern Belize and during two growing seasons, nematodes were extracted from soil from cacao agroforestry plots, undisturbed rainforests, and a banana plantation. Nematodes were enumerated and visually identified, and communities were analyzed using several community and diversity indices. In both the dry and wet seasons, soils from cacao plots contained similar nematode communities to the rainforest with respect to all measured variables, including the abundance of nematodes from each trophic group, the Bongers Maturity and Plant-Parasite indices, and the Shannon and Simpson’s diversity indices. In contrast, the banana plantation soils were dominated by plant-parasitic nematodes with lower Shannon and Simpson’s diversity indices. Overall, it appears that cacao agroforestry plots maintain nematode community structure relative to the undisturbed rainforest they were created from, suggesting that soil health is not compromised by this land-use strategy.

Habitat use and seed removal by invasive rats (Rattus rattus) in disturbed and undisturbed rain forest, Puerto Rico

AbstractDespite frequent occurrences of invasive rats (Rattus spp.) on islands, their known effects on forests are limited. Where invasive rats have been studied, they generally have significant negative impacts on native plants, birds, and other animals. This study aimed to determine invasive rat distribution and effects on native plant populations via short‐term seed removal trials in tropical rain forest habitats in the Luquillo Experimental Forest, Puerto Rico. To address the first objective, we used tracking tunnels (inked and baited cards inside tunnels enabling animal visitors’ footprints to be identified) placed on the ground and in the lower canopy within disturbed (treefall gaps, hurricane plots, stream edges) and undisturbed (continuous forest) habitats. We found that rats are present in all habitats tested. Secondly, we compared seed removal of four native tree species (Guarea guidonia, Buchenavia capitata, Tetragastris balsamifera, and Prestoea acuminata) between vertebrate‐excluded and free‐access treatments in the same disturbed and undisturbed habitats. Trail cameras were used to identify animals responsible for seed contact and removal. Black rats (Rattus rattus) were responsible for 65.1% of the interactions with seeds, of which 28.6% were confirmed seed removals. Two plant species had significantly more seeds removed in disturbed (gaps) than undisturbed forest. Prestoea acuminata had the lowest seed removal (9% in 10 days), whereas all other species had &gt;30% removal. Black rats are likely influencing fates of seeds on the forest floor, and possibly forest community composition, through dispersal or predation. Further understanding of rat–plant interactions may be useful for formulating conservation strategies.

Herpetological surveys in two proposed protected areas in Liberia, West Africa

In March and April 2018 we surveyed amphibians and reptiles in two Proposed Protected Areas (PPAs) in Liberia. In the Krahn-Bassa Proposed Protected Area (KBPPA) in eastern Liberia 36 species of amphibians and 13 species of reptiles were recorded. In the Foya Proposed Protected Area (FPPA) in western Liberia 39 species of amphibians and 10 species of reptiles were recorded. The encountered herpetological communities in both sites were typical for West African rainforests. However, some species indicated disturbances, in particular at the edges of the study areas, the surrounding villages and plantations, and old artisanal gold mining sites within forests. Of particular conservation interest was the discovery of a high percentage of typical rainforest specialists with ranges restricted to the western part of the Upper Guinea rainforest biodiversity hotspot. Outstanding discoveries in KBPPA were two new species of puddle frogs, and the first country record for the arboreal, parachuting lizardHolaspisguentheri. Remarkable records in FPPA comprise a new species of stiletto snake, a new puddle frog and records of various frog species typically breeding in undisturbed rainforest streams, such asOdontobatrachusnatatorandConrauaalleni. Both study areas comprise an important proportion of the remaining rainforests in the Upper Guinea forest zone. The new discoveries indicate that within this biogeographic area, southeastern and western Liberian rainforest may still hold various undiscovered species and species of conservation concern. Further surveys in KBPPA and FPPA and nearby forests should clarify the distribution and conservation status of the new taxa.This study also emphasizes that the western part of the Liberian forests comprise at least partly a herpetofauna which differs from that of the East of the country. The recorded threatened amphibian species are all specialized on relatively undisturbed rainforests and they all have only small geographic ranges. The remaining parts of undisturbed or little disturbed forests thus have high importance for the long-term survival of these species. In conclusion the study areas have a high conservation potential and should be urgently protected from any further forest loss degradation and uncontrolled hunting.

Vegetation Change in Southwestern Amazonia (Brazil) and Relationship to the Late Pleistocene and Holocene Climate

AbstractThe Late Quaternary climate in Amazonia is an issue still open to debate, with hypotheses varying from alternate dry and wet episodes to stable climate with undisturbed rainforest. We approach this question using δ13C, C/N, and, to a lesser extent, δ15N from deposits derived from four cores, with the results combined with published pollen data from two of these cores. These data were analyzed within the context of radiocarbon dating, which revealed ages ranging from 42.8–41.8 to 2.3–2.2 cal ka BP. Fluvial channel and floodplain deposits with freshwater phytoplankton recorded a trend of wet climate with dry episodes before ~40 cal ka BP, followed by humid and cold climate until the Last Glacial Maximum, with intensified aridity towards the end of the Late Pleistocene. Peaks of increased contributions in C4land plants in the mid- to late Holocene were not synchronous and have no correspondence with Amazonian Holocene dry episodes, being due to sedimentary processes related to fluvial dynamics during the establishment of herbaceous fields on abandoned depositional sites. Thus, the climate remained wet in the Holocene, which would have favored the expansion of the Amazonian rainforest as we see today.

Effects on soil chemistry of tropical deforestation for agriculture and subsequent reforestation with special reference to changes in carbon and nitrogen

While soils can act either as a source or as a sink for atmospheric carbon dioxide and nitrogen, depending on land cover change and management, there is a great need to improve our understanding of the dynamics of soil structure and chemistry following land conversion in tropical regions. In this study, we investigated various soil structural and chemical variables (bulk density, pH, cation exchange capacity, phosphorus, magnesium, potassium), soil carbon (C), soil nitrogen (N), δ13C, and δ15N in relation to conversion of rain forest to tea cultivation and subsequent changes due to agricultural abandonment and reforestation with Caribbean pine. Although Caribbean pine has shown potential for reforestation throughout Asia and Latin America, effects on soil properties in comparison with other land uses have not been quantified. Our study compared: (1) the original mixed-dipterocarp rain forest, (2) tea plantations, (3) Kekilla fernlands and (4) Caribbean pine plantations. Tea plantations show higher bulk density (BD) as an evidence of compaction. Although soil C concentration in tea plantations were lower than other land uses at 0–10cm, when bulk density was used with C as a composite measure, tea plantation showed the highest value for both soil C and N stocks. Disregarding tea plantations, Caribbean pine plantations had the highest C but showed the lowest N stocks at both soil depths. Soil δ13C and δ15N values of all land uses increase with increasing soil depth; but Caribbean pine plantations showed the greatest increase in δ13C at both soil depths (e.g. −27.82±0.38‰ at 0–10cm to −26.50±0.37‰ at 10–20cm). For both Kekilla fernlands and Caribbean pine plantations the relationship between δ13C and δ15N was strongly linear. By comparing the physical and chemical soil properties of these land uses with undisturbed rain forest, we established baseline data to determine influence of land conversion on soil properties. Based on soil pH, CEC and other major nutrients (P, K, Mg), there are strong legacy effects of land use potentially from both fertilization and fire. Our results also showed strong evidence that δ13C and δ15N was both increased with depth under pine reforestation and fernlands, suggesting soils can recuperate with a consistent input of litter and slower decomposition processes. There is some evidence that recruitment of natural regeneration beneath pine can help facilitate faster litter decomposition that can revert soil structure and fertility to a status similar to that of the original forest.

Low Herbivory among Targeted Reforestation Sites in the Andean Highlands of Southern Ecuador.

Insect herbivory constitutes an important constraint in the viability and management of targeted reforestation sites. Focusing on young experimental stands at about 2000 m elevation in southern Ecuador, we examined foliar damage over one season as a function of tree species and habitat. Native tree species (Successional hardwood: Cedrela montana and Tabebuia chrysantha; fast-growing pioneer: Heliocarpus americanus) have been planted among prevailing local landcover types (abandoned pasture, secondary shrub vegetation, and a Pinus patula plantation) in 2003/4. Plantation trees were compared to conspecifics in the spontaneous undergrowth of adjacent undisturbed rainforest matched for height and foliar volume. Specifically, we tested the hypotheses that H. americanus as a pioneer species suffers more herbivory compared to the two successional tree species, and that damage is inversely related to habitat complexity. Overall leaf damage caused by folivorous insects (excluding leafcutter ants) was low. Average leaf loss was highest among T. chrysantha (7.50% ± 0.19 SE of leaf area), followed by H. americanus (4.67% ± 0.18 SE) and C. montana (3.18% ± 0.15 SE). Contrary to expectations, leaf area loss was highest among trees in closed-canopy natural rainforest, followed by pine plantation, pasture, and secondary shrub sites. Harvesting activity of leafcutter ants (Acromyrmex sp.) was strongly biased towards T. chrysantha growing in open habitat (mean pasture: 2.5%; shrub: 10.5%) where it could result in considerable damage (> 90.0%). Insect folivory is unlikely to pose a barrier for reforestation in the tropical Andean mountain forest zone at present, but leafcutter ants may become problematic if local temperatures increase in the wake of global warming.

Spatial Structure of Above-Ground Biomass Limits Accuracy of Carbon Mapping in Rainforest but Large Scale Forest Inventories Can Help to Overcome.

Precise mapping of above-ground biomass (AGB) is a major challenge for the success of REDD+ processes in tropical rainforest. The usual mapping methods are based on two hypotheses: a large and long-ranged spatial autocorrelation and a strong environment influence at the regional scale. However, there are no studies of the spatial structure of AGB at the landscapes scale to support these assumptions. We studied spatial variation in AGB at various scales using two large forest inventories conducted in French Guiana. The dataset comprised 2507 plots (0.4 to 0.5 ha) of undisturbed rainforest distributed over the whole region. After checking the uncertainties of estimates obtained from these data, we used half of the dataset to develop explicit predictive models including spatial and environmental effects and tested the accuracy of the resulting maps according to their resolution using the rest of the data. Forest inventories provided accurate AGB estimates at the plot scale, for a mean of 325 Mg.ha-1. They revealed high local variability combined with a weak autocorrelation up to distances of no more than10 km. Environmental variables accounted for a minor part of spatial variation. Accuracy of the best model including spatial effects was 90 Mg.ha-1 at plot scale but coarse graining up to 2-km resolution allowed mapping AGB with accuracy lower than 50 Mg.ha-1. Whatever the resolution, no agreement was found with available pan-tropical reference maps at all resolutions. We concluded that the combined weak autocorrelation and weak environmental effect limit AGB maps accuracy in rainforest, and that a trade-off has to be found between spatial resolution and effective accuracy until adequate “wall-to-wall” remote sensing signals provide reliable AGB predictions. Waiting for this, using large forest inventories with low sampling rate (<0.5%) may be an efficient way to increase the global coverage of AGB maps with acceptable accuracy at kilometric resolution.

Corynespora aquatica . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Corynespora aquatica . This fungus has been observed on decaying leaves submerged in a freshwater stream, in undisturbed rain forest. It is presumably a saprobe for at least part of its life cycle, but nothing else is known about its relation with associated plants. Some information on its dispersal and transmission and conservation status is given, along with details of its geographical distribution (North America (Mexico)).