Despite their fundamental importance the links between forest productivity, diversity and climate remain contentious. We consider whether variation in productivity across climates reflects adjustment among tree species and individuals, or changes in tree community structure. We analysed data from 60 plots of humid old-growth forests spanning mean annual temperatures (MAT) from 2.0 to 26.6 °C. Comparing forests at equivalent aboveground biomass (160 Mg C ha–1), tropical forests ≥24 °C MAT averaged more than double the aboveground woody productivity of forests <12 °C (3.7 ± 0.3 versus 1.6 ± 0.1 Mg C ha–1 yr–1). Nonetheless, species with similar standing biomass and maximum stature had similar productivity across plots regardless of temperature. We find that differences in the relative contribution of smaller- and larger-biomass species explained 86% of the observed productivity differences. Species-rich tropical forests are more productive than other forests due to the high relative productivity of many short-stature, small-biomass species.
Tag: Aboveground biomass
Carbon stocks and fluxes in Asia-Pacific mangroves: current knowledge and gaps
Mangrove forest plays a key role in regulating climate change, earth carbon cycling and other biogeochemical processes within blue carbon ecosystems. Therefore, mangrove forests should be incorporated into Earth system climate models with the aim of understanding future climate change. Despite multiple carbon stock and flux assessments taking place over the past couple of decades, concrete knowledge of carbon source/sink patterns is largely lacking, particularly in the biodiversity-rich Asia-Pacific (AP) region with its 68 493 km2 of mangrove area. Thus, to understand the gaps in mangrove blue carbon research in the AP region, we summarize a recent decade-long inventory of carbon stock pools (aboveground, belowground and soil) and biogeochemical flux components (burial, export/import, soil-air and water-air CO2 flux) across 25 AP countries to understand the current knowledge and gaps. While carbon stock assessments of individual components are available for all 25 countries, whole ecosystem carbon stocks—including live and standing dead aboveground and belowground, downed woody debris and soil carbon stocks—are often lacking, even in highly researched countries like Indonesia. There is restricted knowledge around biogeochemical carbon fluxes in 55% of the countries, suggesting poor carbon flux research across the region. Focusing on flux components, reports on sediment-to-sea carbon exports are extremely limited (coming from just nine countries in the AP region). There is notable scarcity of data on carbon export fluxes in Indonesian mangroves. Given the key role AP mangroves play in climate change mitigation worldwide, more detailed and methodologically comparable investigation of biogeochemical source/sink processes is required to better understand the role of this large carbon source in global carbon stocks and fluxes, and hence, global climate.
Forest disturbance and recovery in Peruvian Amazonia
Amazonian forests function as biomass and biodiversity reservoirs, contributing to climate change mitigation. While they continuously experience disturbance, the effect that disturbances have on biomass and biodiversity over time has not yet been assessed at a large scale. Here, we evaluate the degree of recent forest disturbance in Peruvian Amazonia and the effects that disturbance, environmental conditions and human use have on biomass and biodiversity in disturbed forests. We integrate tree-level data on aboveground biomass (AGB) and species richness from 1840 forest plots from Peru’s National Forest Inventory with remotely sensed monitoring of forest change dynamics, based on disturbances detected from Landsat-derived Normalized Difference Moisture Index time series. Our results show a clear negative effect of disturbance intensity tree species richness. This effect was also observed on AGB and species richness recovery values towards undisturbed levels, as well as on the recovery of species composition towards undisturbed levels. Time since disturbance had a larger effect on AGB than on species richness. While time since disturbance has a positive effect on AGB, unexpectedly we found a small negative effect of time since disturbance on species richness. We estimate that roughly 15% of Peruvian Amazonian forests have experienced disturbance at least once since 1984, and that, following disturbance, have been increasing in AGB at a rate of 4.7 Mg ha−1 year−1 during the first 20 years. Furthermore, the positive effect of surrounding forest cover was evident for both AGB and its recovery towards undisturbed levels, as well as for species richness. There was a negative effect of forest accessibility on the recovery of species composition towards undisturbed levels. Moving forward, we recommend that forest-based climate change mitigation endeavours consider forest disturbance through the integration of forest inventory data with remote sensing methods.
Growth and biomass production of five exotic bamboo species in North-western Ethiopia
Forests provide goods and services and the demand for these has increased over the years. To meet this demand, reforestation using fast-growing species is crucial. Bamboo is amongst the fastest-growing plant species. Consequently, the Ministry of Agriculture/East Africa Bamboo Project and the European Union Energy Project/INBAR introduced twenty-three bamboo species to Ethiopia. This study assessed the growth and biomass production potential of five of these exotic bamboo species (Dendrocalamus membranaceus, Dendrocalamus asper, Dendrocalamus hamiltonii, Bambusa vulgaris and Guadua amplexifolia). A randomized complete block design (RCBD) with three replications was used. Nine seedlings of each species were planted per plot using two meters spacing between and within rows. Sprouted culms per clump, culm length, culm diameter at breast height (DBH), average number of nodes and internode length per culm were measured. At age of 3½ years after planting, one clump of each species per plot in each block was uprooted and sorted into different components (rhizome, culm, branch and leaves). The fresh weight of each component was measured and sub-samples were taken to dry to constant weight. One-way ANOVA and then Tukey’s test were used to find significantly different group means. The growth performance, in terms of culm production, culm height, internode length and biomass production, of the species was significantly different. D. asper and D. hamiltonii had superior growth and biomass production. We therefore recommend planting these two species in Guangua district and other similar areas where they can enhance the livelihoods of the communities.
Assessing Sumatran Peat Vulnerability to Fire under Various Condition of ENSO Phases Using Machine Learning Approaches
In recent decades, catastrophic wildfire episodes within the Sumatran peatland have contributed to a large amount of greenhouse gas emissions. The El-Nino Southern Oscillation (ENSO) modulates the occurrence of fires in Indonesia through prolonged hydrological drought. Thus, assessing peatland vulnerability to fires and understanding the underlying drivers are essential to developing adaptation and mitigation strategies for peatland. Here, we quantify the vulnerability of Sumatran peat to fires under various ENSO conditions (i.e., El-Nino, La-Nina, and Normal phases) using correlative modelling approaches. This study used climatic (i.e., annual precipitation, SPI, and KBDI), biophysical (i.e., below-ground biomass, elevation, slope, and NBR), and proxies to anthropogenic disturbance variables (i.e., access to road, access to forests, access to cities, human modification, and human population) to assess fire vulnerability within Sumatran peatlands. We created an ensemble model based on various machine learning approaches (i.e., random forest, support vector machine, maximum entropy, and boosted regression tree). We found that the ensemble model performed better compared to a single algorithm for depicting fire vulnerability within Sumatran peatlands. The NBR highly contributed to the vulnerability of peatland to fire in Sumatra in all ENSO phases, followed by the anthropogenic variables. We found that the high to very-high peat vulnerability to fire increases during El-Nino conditions with variations in its spatial patterns occurring under different ENSO phases. This study provides spatially explicit information to support the management of peat fires, which will be particularly useful for identifying peatland restoration priorities based on peatland vulnerability to fire maps. Our findings highlight Riau’s peatland as being the area most prone to fires area on Sumatra Island. Therefore, the groundwater level within this area should be intensively monitored to prevent peatland fires. In addition, conserving intact forests within peatland through the moratorium strategy and restoring the degraded peatland ecosystem through canal blocking is also crucial to coping with global climate change.
Growth and aboveground carbon of trees estimated using the FORCASTREE (SExI-FS) model: possible inputs for land restoration and carbon project in the Philippines
In this report, we present the results of a projection of potential aboveground carbon storage of four tree-based practices using FORCASTREE (a model FOR simulating growth and CArbon of foreST and agroforest tREEs): a tree-tree growth and interaction model, formerly known as SExI-FS (Spatially Explicit Individual-based Forest Simulator), developed by the World Agroforestry (ICRAF). The four tree-based practices combine fast- and slow-growing and native and exotic tree species: (1) a mixture of different Dipterocarp species, (2) native and exotic non-Dipterocarp species, (3) Dipterocarp, fruit trees, and cacao, and (4) Dipterocarp species, native non-Dipterocarp species, fruit trees, and cacao. Scenarios of tree mortality (with or without mortality) and tree density (400 or 1100 trees per hectare) were considered for each practice.
Risks to carbon storage from land-use change revealed by peat thickness maps of Peru
Tropical peatlands are among the most carbon-dense ecosystems but land-use change has led to the loss of large peatland areas, associated with substantial greenhouse gas emissions. To design effective conservation and restoration policies, maps of the location and carbon storage of tropical peatlands are vital. This is especially so in countries such as Peru where the distribution of its large, hydrologically intact peatlands is poorly known. Here field and remote sensing data support the model development of peatland extent and thickness for lowland Peruvian Amazonia. We estimate a peatland area of 62,714 km2 (5th and 95th confidence interval percentiles of 58,325 and 67,102 km2, respectively) and carbon stock of 5.4 (2.6–10.6) PgC, a value approaching the entire above-ground carbon stock of Peru but contained within just 5% of its land area. Combining the map of peatland extent with national land-cover data we reveal small but growing areas of deforestation and associated CO2 emissions from peat decomposition due to conversion to mining, urban areas and agriculture. The emissions from peatland areas classified as forest in 2000 represent 1–4% of Peruvian CO2 forest emissions between 2000 and 2016. We suggest that bespoke monitoring, protection and sustainable management of tropical peatlands are required to avoid further degradation and CO2 emissions.
Aboveground forest biomass varies across continents, ecological zones and successional stages: refined IPCC default values for tropical and subtropical forests
For monitoring and reporting forest carbon stocks and fluxes, many countries in the tropics and subtropics rely on default values of forest aboveground biomass (AGB) from the Intergovernmental Panel on Climate Change (IPCC) guidelines for National Greenhouse Gas (GHG) Inventories. Default IPCC forest AGB values originated from 2006, and are relatively crude estimates of average values per continent and ecological zone. The 2006 default values were based on limited plot data available at the time, methods for their derivation were not fully clear, and no distinction between successional stages was made. As part of the 2019 Refinement to the 2006 IPCC Guidelines for GHG Inventories, we updated the default AGB values for tropical and subtropical forests based on AGB data from >25 000 plots in natural forests and a global AGB map where no plot data were available. We calculated refined AGB default values per continent, ecological zone, and successional stage, and provided a measure of uncertainty. AGB in tropical and subtropical forests varies by an order of magnitude across continents, ecological zones, and successional stage. Our refined default values generally reflect the climatic gradients in the tropics, with more AGB in wetter areas. AGB is generally higher in old-growth than in secondary forests, and higher in older secondary (regrowth >20 years old and degraded/logged forests) than in young secondary forests (⩽20 years old). While refined default values for tropical old-growth forest are largely similar to the previous 2006 default values, the new default values are 4.0–7.7-fold lower for young secondary forests. Thus, the refined values will strongly alter estimated carbon stocks and fluxes, and emphasize the critical importance of old-growth forest conservation. We provide a reproducible approach to facilitate future refinements and encourage targeted efforts to establish permanent plots in areas with data gaps.
Asset-Based Adaptation Project Promotes Tree and Shrub Diversity and Above-Ground Carbon Stocks in Smallholder Agroforestry Systems in Western Kenya
Agroforestry has potential to address the adverse effects of climate change through carbon sequestration, increasing biodiversity and improving adaptive capacity and resilience among smallholder farmers. However, this potential is context specific and insufficiently quantified in smallholder faming systems, partly because of inherent variability of smallholder farms. Our study aimed to determine the tree/shrub diversity and carbon stocks in different agroforestry systems within smallholder farms in two 100 km2 sites, the so-called lower and middle Nyando sites, in western Kenya. In both, context-specific agroforestry adoption had been promoted among households of four community associations through an asset-based community development (ABCD) approach. Their farms were assessed and compared with those of relevant comparison samples. Trees and shrubs were inventoried on a total of 106 farms, and their formations classified in five major agroforestry practices: hedgerows, multipurpose trees on farm (MPT), riparian buffers, woodlots, and boundary planting. To assess above-ground biomass (AGB) of individual trees/shrubs, diameter at breast height measurements were taken. Strong regional differences were considered in data analysis and presentation. Altogether, 3,353 and 6,346 trees/shrubs were inventoried in the lower and middle Nyando sites, respectively. AGB was significantly higher in middle than in lower Nyando. Woodlots had the highest amount of AGB carbon stock, while MPT had the highest diversity of tree/shrub species in all the groups. Conversely, boundary planting had the highest number of trees/shrubs inventoried and hence was the most common agroforestry practice across all the samples in both regions. Dominant AGB contributor species were Grevillea robusta (37.8%) in middle, and Eurphobia tirucalli (16.5%) in lower Nyando. This study provides empirical evidence that asset-based and community-driven selection and implementation of both tree/shrub species and agroforestry practices can contribute positively to species and practice diversity, which are associated with AGB carbon stock levels and wider agro-ecosystem diversity. This study hence provides benchmark information that is relevant for SDG goal 15 on “life on land,” and various specific targets, and can inform sustainable establishment of carbon sink facilities by supporting smallholders to uptake contextually suitable and economically sensible agroforestry practices in an overall effort to foster and support sustainable development.
Indigenous Sacred Forests as a Tool for Climate Change Mitigation: Lessons from Gedeo Community, Southern Ethiopia
Sacred forests are patches of remnant natural forests, protected through social laws by the local communities near their villages and are always dedicated to cultural purposes. They are playing a significant role in combating climate change and informal enhancing biodiversity conservation. The aim of this study was to estimate carbon stocks of sacred forests by quantifying the aboveground biomass (AGB), and belowground (BGB) carbon of trees. The estimation of carbon stocks was conducted across the three sacred forests of Bolocho sacred forest (BSF), Ejjerissa sacred forest (ESF), and Amba sacred forest (ASF). A total of 30 plots: 10 BSF, 10 ESF, and 10 ASF were sampled and trees with DBH ≥5 cm and a height of ≥3 m was considered for biomass-carbon determination. We compared tree biomass, carbon stocks, stem densities, basal area, and importance value index of trees. Nondestructive methods of woody species biomass measurement was used by using allometric equations developed for application in tropical forests and/ or agroforestry system. A total of 4216 individuals representing 87 different species and 44 families were recorded. Statistical the highest stem density was recorded. Total biomass considered as AGB+BGB, which is highest for ASF followed by ESF and BSF (one way ANOVA, F = 98.66, df, 2, p < .001). The estimated amount of AGB across the three sacred forests were (505 Mg ha−1), (267 Mg ha−1) and (202 Mg ha−1) in ASF, ESF, and BSF, respectively. Total biomass stored, both aboveground and belowground (AGB+BGB) significantly higher for ASF (637 Mg ha−1) followed by ESF (338 Mg ha−1) and BSF (255 Mg ha−1). Total biomass carbon (C) was 318.5 Mg C ha−1 for ASF, 169 Mg C ha−1 for ESF, and 127.5 Mg C ha−1 for BSF. From the present study, it can be concluded that, sacred forests and indigenous way of forest protection has playing an enormous roles in carbon sequestration. Perhaps it could be accepted as best practices in climate change (CC) mitigation and reducing deforestation. Hence, it needs urge calls for an immediate attention for conservation, protections and documentation of indigenous knowledge.