Land-use change occurs nowhere more rapidly than in the tropics, where the imbalance between deforestation and forest regrowth has large consequences for the global carbon cycle. However, ...considerable uncertainty remains about the rate of biomass recovery in secondary forests, and how these rates are influenced by climate, landscape, and prior land use. Here we analyse aboveground biomass recovery during secondary succession in 45 forest sites and about 1,500 forest plots covering the major environmental gradients in the Neotropics. The studied secondary forests are highly productive and resilient. Aboveground biomass recovery after 20 years was on average 122 megagrams per hectare (Mg ha(-1)), corresponding to a net carbon uptake of 3.05 Mg C ha(-1) yr(-1), 11 times the uptake rate of old-growth forests. Aboveground biomass stocks took a median time of 66 years to recover to 90% of old-growth values. Aboveground biomass recovery after 20 years varied 11.3-fold (from 20 to 225 Mg ha(-1)) across sites, and this recovery increased with water availability (higher local rainfall and lower climatic water deficit). We present a biomass recovery map of Latin America, which illustrates geographical and climatic variation in carbon sequestration potential during forest regrowth. The map will support policies to minimize forest loss in areas where biomass resilience is naturally low (such as seasonally dry forest regions) and promote forest regeneration and restoration in humid tropical lowland areas with high biomass resilience.
Habitat spatial distribution, seasonal variation, and activity patterns influence changes in vertebrate assemblages over time. Terrestrial birds play major roles in the dynamics of tropical forests, ...but there are few effective methods to study these species due to their cryptic coloration and elusive behavior. We used camera-trap data collected during 16 mo (February 2017-June 2018) to describe the terrestrial avifauna in southeastern Peru, assess to what extent the composition of terrestrial avifauna changes among seasons and across two major habitats (terra firme and floodplain forests), and determine daily activity patterns of terrestrial birds. We used overlap analyses to examine temporal co-occurrence between ecologically similar and sympatric species. Camera traps recorded 16 species, including eight species in the family Tinamidae. Capture rates were highest for Pale-winged Trumpeters (Psophia leucoptera; Psophiidae) and Gray-fronted Doves (Leptolila rufaxilla; Columbidae). Species composition did not differ between habitats or seasons, and capture rates between habitats only differed for White-throated Tinamous (Tinamus guttatus). Overlaps of activity patterns were high between ecologically similar species and species found in terra firme habitats (White-throated Tinamous and Cinereous Tinamous, Crypturellus cinereus) and in both habitat types (Palewinged Trumpeters and Gray-fronted Doves). Low numbers of captures of possibly locally rare or less abundant species hindered a complete analysis of spatial and seasonal patterns of terrestrial bird assemblages. We suggest a greater sampling effort and greater spatial replication to better understand the spatial and seasonal dynamics of the terrestrial avifauna. Further studies that assess the mechanisms that allow the coexistence of sympatric tinamous would be valuable, both in our study area and elsewhere. The use of camera traps in long-term monitoring projects proved to be an effective tool for monitoring terrestrial birds, identifying cryptic and often rare animals to species level, and providing valuable ecological information at species and community levels. La distributión espacial en el hábitat, variatión estacional y patrones de actividad influencian cambios en los ensambles de vertebrados a lo largo del tiempo. Las aves terrestres juegan papeles de gran importancia en la dinámica de los bosques tropicales, aunque hay pocos métodos efectivos para estudiar estas especies dada su coloratión críptica y comportamiento esquivo. Usamos datos de cámaras-trampa colectados durante 16 meses (febrero 2017 - junio 2018) para describir la avifauna terrestre en el sureste del Perú, determinar la magnitud del cambio de la avifauna terrestre entre estaciones y en dos hábitats mayores (terra firme y bosques inundables), así como determinar los patrones diarios de actividad de estas aves. Usamos análisis de trasfape para examinar la presencia simultánea entre especies ecológicamente similares y simpátricas. Las cámarastrampa registraron 16 especies, incluidas ocho de la familia Tinamidae. Las tasas de captura más altas fueron para los trompeteros Psophia leucoptera (Psophiidae) y palomas Leptotila rufaxilla (Columbidae). La compositión de especies no difiere entre hábitats temporadas, y las tasas de captura entre hábitats solo difieren para los tinamúes Tinamus guttatus. El traslape de patrones de actividad fue alto entre especies ecológicamente similares y para especies que se encuentran en hábitats de terra firme (T. guttatus y Crypturellus cinereus) y en ambos tipos de hábitat (P. leucoptera y L. rufaxilla). La baja cantidad de capturas para especies posiblemente raras localmente y menos abundantes limitó un análisis completo de patrones espaciales y estacionales de los ensambles de aves terrestres. Sugerimos un mayor esfuerzo de muestreo y una réplica espacial mayor para entender mejor la dinámica espacial y estacional de la avifauna terrestre. También serán valiosos más estudios para determinar los mecanismos que permiten la coexistencia de tinamúes simpátricos, tanto en nuestra área de estudio como en otros sitios. El uso de cámaras-trampa en proyectos de monitoreo a largo plazo ha demostrado ser una herramienta efectiva para monitorear especies terrestres, identificar animales crípticos y raros a nivel de especie, y para proveer información ecológica valiosa a niveles de especie y comunidad.
Airborne laser scanning has proven useful for rapid and extensive documentation of historic cultural landscapes after years of applications mapping natural landscapes and the built environment. The ...recent integration of unoccupied aerial vehicles (UAVs) with LiDAR systems is potentially transformative and offers complementary data for mapping targeted areas with high precision and systematic study of coupled natural and human systems. We report the results of data capture, analysis, and processing of UAV LiDAR data collected in the Maya Lowlands of Chiapas, Mexico in 2019 for a comparative landscape study. Six areas of archaeological settlement and long-term land-use reflecting a diversity of environments, land cover, and archaeological features were studied. These missions were characterized by areas that were variably forested, rugged, or flat, and included pre-Hispanic settlements and agrarian landscapes. Our study confirms that UAV LiDAR systems have great potential for broader application in high-precision archaeological mapping applications. We also conclude that these studies offer an important opportunity for multi-disciplinary collaboration. UAV LiDAR offers high-precision information that is not only useful for mapping archaeological features, but also provides critical information about long-term land use and landscape change in the context of archaeological resources.
Development in biodiversity rich areas is of global concern. While development may lead to socioeconomic benefits, this often comes concomitant with biodiversity loss and deforestation. Biodiversity ...rich areas present the opportunity for both improvements in socioeconomic conditions and conservation; however numerous challenges exist. Costa Rica’s Manuel Antonio National Park presents an ideal case study to investigate the balance between alternative forms of development which have contrasting environmental impacts. The Manuel Antonio region is a highly dynamic landscape experiencing deforestation, from agriculture, cattle ranching and oil palm plantations; and also reforestation from abandonment of land holdings and nature oriented tourism. Landscape dynamics are closely intertwined with the livelihoods and perspectives on biodiversity conservation of local communities, determining ecological sustainability. We use an analysis combining multi-temporal remote sensing of land cover dynamics from 1985 to 2008 with questionnaire data from local families on their socioeconomic status, perspectives on conservation, and perceived changes in local wildlife populations. Our results show that, while regeneration occurred and forest fragmentation in the area decreased from 1985 to 2008, Manuel Antonio National Park is rapidly becoming isolated. Decreasing ecological connectivity is related to the rapid expansion of oil palm plantations adjacent to the park and throughout the lowland areas. Perceived decreases in wildlife abundance and compositional change are evident throughout the area, with local communities attributing this primarily to illegal hunting activities. Nature based tourism in the area presents an effective strategy for conservation, including reductions in hunting, through increased valuation of biodiversity and protected areas, and socioeconomic advantages. However, without urgent efforts to limit deforestation and preserve the remaining forested corridor connecting the park to core primary forest, the ability to maintain biodiversity in the park will be reduced.
Constructed landscapes are composed of diverse communities, representing different social strata and perspectives of a place. In turn, the risks associated with inhabiting unpredictable environments ...are disproportionately felt across urban and rural landscapes. The mitigation and management of risks often fall on farming and smallholder communities, influencing decentralized strategies. These themes are explored in an archaeological context surrounding the confluence of the Upper Usumacinta and Lacantún Rivers in the neotropical Maya lowlands of Chiapas, Mexico. LiDAR data collected recently with the GatorEye unoccupied aerial vehicle (UAV) and NASA's GLiHT system have aided in the mapping of the archaeological urban centre of Benemérito de las Américas, Primera Sección and the surrounding landscape. These data have revealed coupled settlement with land management, in the form of wetland fields, reservoirs, and riverways, emphasizing the interconnectivity of household practice and land use in the region.
Secondary forests cover large areas of the tropics and play an important role in the global carbon cycle. During secondary forest succession, simultaneous changes occur among stand structural ...attributes, soil properties, and species composition. Most studies classify tree species into categories based on their regeneration requirements. We use a high-resolution secondary forest chronosequence to assign trees to a continuous gradient in species successional status assigned according to their distribution across the chronosequence. Species successional status, not stand age or differences in stand structure or soil properties, was found to be the best predictor of leaf trait variation. Foliar δ(13)C had a significant positive relationship with species successional status, indicating changes in foliar physiology related to growth and competitive strategy, but was not correlated with stand age, whereas soil δ(13)C dynamics were largely constrained by plant species composition. Foliar δ(15)N had a significant negative correlation with both stand age and species successional status, - most likely resulting from a large initial biomass-burning enrichment in soil (15)N and (13)C and not closure of the nitrogen cycle. Foliar %C was neither correlated with stand age nor species successional status but was found to display significant phylogenetic signal. Results from this study are relevant to understanding the dynamics of tree species growth and competition during forest succession and highlight possibilities of, and potentially confounding signals affecting, the utility of leaf traits to understand community and species dynamics during secondary forest succession.
Recently, remotely sensed measurements of the
near-infrared reflectance (NIRv) of vegetation, the fluorescence correction
vegetation index (FCVI), and radiance (NIRvrad) of vegetation have emerged
as ...indicators of vegetation structure and function with potential to enhance
or improve upon commonly used indicators, such as the normalized difference
vegetation index (NDVI) and the enhanced vegetation index (EVI). The
applicability of these remotely sensed indices to tropical forests, key
ecosystems for global carbon cycling and biodiversity, has been limited. In
particular, fine-scale spatial and temporal heterogeneity of structure and
physiology may contribute to variation in these indices and the properties
that are presumed to be tracked by them, such as gross primary productivity
(GPP) and absorbed photosynthetically active radiation (APAR). In this
study, fine-scale (approx. 15 cm) tropical forest heterogeneity represented by
NIRv, FCVI, and NIRvrad and by lidar-derived height is investigated and
compared to NIRv and EVI using unoccupied aerial system (UAS)-based
hyperspectral and lidar sensors. By exploiting near-infrared signals, NIRv,
FCVI, and NIRvrad captured the greatest spatiotemporal variability, followed
by the enhanced vegetation index (EVI) and then the normalized difference
vegetation index (NDVI). Wavelet analyses showed the dominant spatial scale
of variability of all indicators was driven by tree clusters and
larger-than-tree-crown size gaps rather than individual tree crowns. NIRv,
FCVI, NIRvrad, and EVI captured variability at smaller spatial scales
(∼ 50 m) than NDVI (∼ 90 m) and the lidar-based
surface model (∼ 70 m). We show that spatial and temporal
patterns of NIRv and FCVI were virtually identical for a dense green canopy,
confirming predictions in earlier studies. Furthermore, we show that
NIRvrad, which does not require separate irradiance measurements, correlated
more strongly with GPP and PAR than did other indicators. NIRv, FCVI, and
NIRvrad, which are related to canopy structure and the radiation regime of
vegetation canopies, are promising tools to improve understanding of
tropical forest canopy structure and function.
Over 140 Mha of restoration commitments have been pledged across the global tropics, yet guidance is needed to identify those landscapes where implementation is likely to provide the greatest ...potential benefits and cost-effective outcomes. By overlaying seven recent, peer-reviewed spatial datasets as proxies for socioenvironmental benefits and feasibility of restoration, we identified restoration opportunities (areas with higher potential return of benefits and feasibility) in lowland tropical rainforest landscapes. We found restoration opportunities throughout the tropics. Areas scoring in the top 10% (i.e., restoration hotspots) are located largely within conservation hotspots (88%) and in countries committed to the Bonn Challenge (73%), a global effort to restore 350 Mha by 2030. However, restoration hotspots represented only a small portion (19.1%) of the Key Biodiversity Area network. Concentrating restoration investments in landscapes with high benefits and feasibility would maximize the potential to mitigate anthropogenic impacts and improve human well-being.
Lianas are a key growth form in tropical forests. Their lack of self-supporting tissues and their vertical position on top of the canopy make them strong competitors of resources. A few pioneer ...studies have shown that liana optical traits differ on average from those of colocated trees. Those trait discrepancies were hypothesized to be responsible for the competitive advantage of lianas over trees. Yet, in the absence of reliable modelling tools, it is impossible to unravel their impact on the forest energy balance, light competition, and on the liana success in Neotropical forests. To bridge this gap, we performed a meta-analysis of the literature to gather all published liana leaf optical spectra, as well as all canopy spectra measured over different levels of liana infestation. We then used a Bayesian data assimilation framework applied to two radiative transfer models (RTMs) covering the leaf and canopy scales to derive tropical tree and liana trait distributions, which finally informed a full dynamic vegetation model. According to the RTMs inversion, lianas grew thinner, more horizontal leaves with lower pigment concentrations. Those traits made the lianas very efficient at light interception and significantly modified the forest energy balance and its carbon cycle. While forest albedo increased by 14% in the shortwave, light availability was reduced in the understorey (−30% of the PAR radiation) and soil temperature decreased by 0.5°C. Those liana-specific traits were also responsible for a significant reduction of tree (−19%) and ecosystem (−7%) gross primary productivity (GPP) while lianas benefited from them (their GPP increased by +27%). This study provides a novel mechanistic explanation to the increase in liana abundance, new evidence of the impact of lianas on forest functioning, and paves the way for the evaluation of the large-scale impacts of lianas on forest biogeochemical cycles.
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