90 research outputs found
Long-term carbon sink in Borneo's forests halted by drought and vulnerable to edge effects
Less than half of anthropogenic carbon dioxide emissions remain in the atmosphere. While carbon balance models imply large carbon uptake in tropical forests, direct on-the-ground observations are still lacking in Southeast Asia. Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43 Mg C ha−1 per year (95% CI 0.14–0.72, mean period 1988–2010) in above-ground live biomass carbon. These results closely match those from African and Amazonian plot networks, suggesting that the world's remaining intact tropical forests are now en masse out-of-equilibrium. Although both pan-tropical and long-term, the sink in remaining intact forests appears vulnerable to climate and land use changes. Across Borneo the 1997–1998 El Niño drought temporarily halted the carbon sink by increasing tree mortality, while fragmentation persistently offset the sink and turned many edge-affected forests into a carbon source to the atmosphere
THE CARBON SINK IN INTACT AMAZONIAN FORESTS IS AN OPPORTUNITY TO ACHIEVE SUSTAINABLE CONSERVATION
Los bosques primarios intactos de la Amazonía peruana se comportan como sumideros de carbono: un servicio ecosistémico clave a nivel mundial. Este sumidero fue cuantificado en 0.54 Mg C ha-1 año-1 (1990-2017) para los bosques amazónicos intactos de las Áreas Naturales Protegidas (ANPs) de Perú y las zonas de amortiguamiento. En otras palabras, la conservación de bosques intactos en ANPs ayudó a remover 9.6 millones de toneladas de carbono de la atmósfera por año, lo cual equivale aproximadamente al 85% de las emisiones de la quema de combustibles fósiles del país durante el 2012. Este servicio de remoción de CO2 atmosférico es necesario incluir en el inventario nacional de gases de efecto invernadero, y en los compromisos nacionales de reducción de emisiones, por dos razones. Primero, debido a ser un flujo importante, nos ayudaría a tener una aproximación más real del balance de carbono en Perú. Segundo, fortalecería la necesidad de mantener la integridad de estos bosques tanto por el servicio de almacenamiento de carbono (evitar emisiones) como el servicio de sumidero (remoción de emisiones) y la diversidad biológica que albergan. La provisión del servicio de sumidero solo se asegurará con una gestión efectiva y adaptativa de las ANPs. El reporte de este servicio ambiental a nivel nacional debe ser implementado a través del monitoreo a largo plazo de la dinámica del carbono y el impacto del cambio climático a través de la red de parcelas forestales permanentes de RAINFOR (Red Amazónica de Inventarios Forestales) y el proyecto MonANPeru. El establecimiento de este sistema de monitoreo permitirá el desarrollo de los mecanismos financieros para cerrar la brecha y lograr la sostenibilidad de la conservación de los bosques en las ANPs de Perú.The primary intact forests of the Peruvian Amazon act as a carbon sink: a key ecosystem service of international importance. This sink has been quantified as 0.54 Mg C ha-1 year-1 (1990-2017) for the intact Amazonian forest in the protected areas and associated buffer zones of Peru. In other words, the conservation of intact forests in protected areas has helped to remove 9.6 million tonnes of carbon from the atmosphere per year, which is equivalent to approximately 85% of the emissions from fossil fuel combustion in Peru during 2012. It is necessary to include this carbon sink in the national inventory of greenhouse gas emissions for two reasons. Firstly, because it is a an important flux, it would help for estimating the carbon balance of Peru more accurately. Secondly, it would strengthen the need to maintain the integrity of these forests, for their role both as a stock and sink of carbon and for their biological diversity. The provision of this service as a sink can only be assured with effective and adaptive management of the protected areas of Peru. Reporting of this environmental service at a national level should be implemented through long-term monitoring of the carbon dynamics and impact of climate change on these forests via the RAINFOR (Amazon Forest Network) network of permanent forest plots and the MonANPeru project. The establishment of this monitoring system would allow the development of the finanancial mechanisms to close the funding gap and achieve sustainable conservation of the forests of the protected area network of Peru
La impresionante diversidad y estructura del bosque tropical a través de una gradiente altitudinal en la selva central del Perú
Los bosques pre-montanos y montanos son poco estudiados y su composición florística es muy poco conocida, aunque últimamente aquí se han descubierto nuevas especies de árboles. Describimos la diversidad, composición florística y estructura del bosque en 13 parcelas permanentes de 1 ha, evaluadas en el 2018 en el Transecto Yanachaga en el Perú (400 a 3170msnm). Registramos un total de 6998 árboles, 617 especies, 249 géneros y 82 familias. Existe unas altas correlaciones entre la altitud, la riqueza y diversidad de especies. La mayor riquezaocurre en la parcela PNY-05 a 470 msnm con 202 especies y la menor con 43 especies en la parcela PNY-01 a 3170 mnsm. La altura promedio del dosel es mayor entre los 400 y 800 msnm, y disminuye progresivamente a medida que se va subiendo, presentando alturas mínimas entre 2800 y 3170 msnm. Este mismo comportamiento ocurre con respecto al área basal y volumen de madera. Los individuos muestreados están representados por especies de árboles (88%), palmeras (4%), helechos arborescentes (6.5%), lianas (1.5%) y hemiepífitos leñosos (0. 03%). Las f ormas de vi da varí an notablemente en el transecto altitudinal, los árboles y palmeras son más abundantes y diversos en la parte baja, mientras los helechos arborescentes son abundantes por encima de los 1800 m. Existen diferencias en la diversidad, composición y estructura de árboles entre parcelas y también si se compara al llano amazónico. Los bosques del Transecto Yanachaga juegan un papel importante, puesto que conservan una alta diversidad de especies y hábitats
Above-ground biomass and structure of 260 African tropical forests.
We report above-ground biomass (AGB), basal area, stem density and wood mass density estimates from 260 sample plots (mean size: 1.2 ha) in intact closed-canopy tropical forests across 12 African countries. Mean AGB is 395.7 Mg dry mass ha⁻¹ (95% CI: 14.3), substantially higher than Amazonian values, with the Congo Basin and contiguous forest region attaining AGB values (429 Mg ha⁻¹) similar to those of Bornean forests, and significantly greater than East or West African forests. AGB therefore appears generally higher in palaeo- compared with neotropical forests. However, mean stem density is low (426 ± 11 stems ha⁻¹ greater than or equal to 100 mm diameter) compared with both Amazonian and Bornean forests (cf. approx. 600) and is the signature structural feature of African tropical forests. While spatial autocorrelation complicates analyses, AGB shows a positive relationship with rainfall in the driest nine months of the year, and an opposite association with the wettest three months of the year; a negative relationship with temperature; positive relationship with clay-rich soils; and negative relationships with C : N ratio (suggesting a positive soil phosphorus-AGB relationship), and soil fertility computed as the sum of base cations. The results indicate that AGB is mediated by both climate and soils, and suggest that the AGB of African closed-canopy tropical forests may be particularly sensitive to future precipitation and temperature changes
Hyperdominance in Amazonian Forest Carbon Cycling
While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant’ species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region
Tree mode of death and mortality risk factors across Amazon forests
The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth–survival trade-off in driving tropical tree mortality
The global abundance of tree palms
Aim Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location Tropical and subtropical moist forests. Time period Current. Major taxa studied Palms (Arecaceae). Methods We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests
Mapping density, diversity and species-richness of the Amazon tree flora
Using 2.046 botanically-inventoried tree plots across the largest tropical forest on Earth, we mapped tree species-diversity and tree species-richness at 0.1-degree resolution, and investigated drivers for diversity and richness. Using only location, stratified by forest type, as predictor, our spatial model, to the best of our knowledge, provides the most accurate map of tree diversity in Amazonia to date, explaining approximately 70% of the tree diversity and species-richness. Large soil-forest combinations determine a significant percentage of the variation in tree species-richness and tree alpha-diversity in Amazonian forest-plots. We suggest that the size and fragmentation of these systems drive their large-scale diversity patterns and hence local diversity. A model not using location but cumulative water deficit, tree density, and temperature seasonality explains 47% of the tree species-richness in the terra-firme forest in Amazonia. Over large areas across Amazonia, residuals of this relationship are small and poorly spatially structured, suggesting that much of the residual variation may be local. The Guyana Shield area has consistently negative residuals, showing that this area has lower tree species-richness than expected by our models. We provide extensive plot meta-data, including tree density, tree alpha-diversity and tree species-richness results and gridded maps at 0.1-degree resolution
Consistent patterns of common species across tropical tree communities
Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe
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