Ecosystem services of Amazonian forests are disproportionally produced by a limited set of hyperdominant tree species. Yet the spatial variation in the delivery of ecosystem services by individual hyperdominant species across their distribution ranges and corresponding environmental gradients is poorly understood. Here, we use the concept of habitat quality to unravel the effect of environmental gradients on seed production and aboveground biomass (AGB) of the Brazil nut, one of Amazonia’s largest and most long-lived hyperdominants. We find that a range of climate and soil gradients create trade-offs between density and fitness of Brazil nut trees. Density responses to environmental gradients were in line with predictions under the Janzen–Connell and Herms–Mattson hypotheses, whereas tree fitness responses were in line with resource requirements of trees over their life cycle. These trade-offs resulted in divergent responses in area-based seed production and AGB. While seed production and AGB of individual trees (i.e., fitness) responded similarly to most environmental gradients, they showed opposite tendencies to tree density for almost half of the gradients. However, for gradients creating opposite fitness-density responses, area-based seed production was invariable, while trends in area-based AGB tended to mirror the response of tree density. We conclude that while the relation between environmental gradients and tree density is generally indicative of the response of AGB accumulation in a given area of forest, this is not necessarily the case for fruit production.
Tag: Carbon sequestration
Ten golden rules for reforestation to optimize carbon sequestration, biodiversity recovery and livelihood benefits
Urgent solutions to global climate change are needed. Ambitious tree-planting initiatives, many already underway, aim to sequester enormous quantities of carbon to partly compensate for anthropogenic CO2 emissions, which are a major cause of rising global temperatures. However, tree planting that is poorly planned and executed could actually increase CO2 emissions and have long-term, deleterious impacts on biodiversity, landscapes and livelihoods. Here, we highlight the main environmental risks of large-scale tree planting and propose 10 golden rules, based on some of the most recent ecological research, to implement forest ecosystem restoration that maximizes rates of both carbon sequestration and biodiversity recovery while improving livelihoods. These are as follows: (1) Protect existing forest first; (2) Work together (involving all stakeholders); (3) Aim to maximize biodiversity recovery to meet multiple goals; (4) Select appropriate areas for restoration; (5) Use natural regeneration wherever possible; (6) Select species to maximize biodiversity; (7) Use resilient plant material (with appropriate genetic variability and provenance); (8) Plan ahead for infrastructure, capacity and seed supply; (9) Learn by doing (using an adaptive management approach); and (10) Make it pay (ensuring the economic sustainability of the project). We focus on the design of long-term strategies to tackle the climate and biodiversity crises and support livelihood needs. We emphasize the role of local communities as sources of indigenous knowledge, and the benefits they could derive from successful reforestation that restores ecosystem functioning and delivers a diverse range of forest products and services. While there is no simple and universal recipe for forest restoration, it is crucial to build upon the currently growing public and private interest in this topic, to ensure interventions provide effective, long-term carbon sinks and maximize benefits for biodiversity and people.
Grazing exclosures increase soil organic carbon stock at a rate greater than “4 per 1000” per year across agricultural landscapes in Northern Ethiopia
The establishment of grazing exclosures is widely practiced to restore degraded agricultural lands and forests. Here, we evaluated the potential of grazing exclosures to contribute to the”4 per 1000” initiative by analyzing the changes in soil organic carbon (SOC) stocks and sequestration (SCS) rates after their establishment on degraded communal grazing lands in Tigray region of Ethiopia. We selected grazing areas that were excluded from grazing for 5 to 24 years across the three agroecological zones of the region and used adjacent open grazing lands (OGLs) as control. Soil samples were collected from two depths (0-15 cm and 15-30 cm) and SOC and aboveground C stocks were quantified in both exclosures and OGLs. The mean SOC stock and SCS rate in exclosures (0-30 cm) were 31 Mg C ha-1 and 3 Mg C ha-1 year-1, which were respectively 166% and 12% higher than that in the OGLs, indicating a positive restoration effect of exclosures on SOC storage. With increasing exclosure age, SOC stock and SCS rate increased in the exclosures but decreased in the OGLs. Higher SOC stock and SCS rate were recorded in 0-15 cm than in 15-30 cm. The relative (i.e., to the SOC stock in OGLs) rates of increase in SOC stocks (70-189‰ year-1) were higher than the 4‰ year-1 and were initially high due to low initial SOC stock but declined over time after a maximum value of SOC stock is reached. Factors such as aboveground biomass, altitude, clay content and precipitation promoted SOC storage in exclosures. Our study highlights the high potential of exclosure for restoring SOC in the 0-30 cm soil depth at a rate greater than the 4‰ value. We argue that practices such as grazing exclosure can be promoted to achieve the climate change mitigation target of the “4‰” initiative.
Future carbon emissions from global mangrove forest loss
Mangroves have among the highest carbon densities of any tropical forest. These ‘blue carbon’ ecosystems can store large amounts of carbon for long periods, and their protection reduces greenhouse gas emissions and supports climate change mitigation. Incorporating mangroves into Nationally Determined Contributions to the Paris Agreement and their valuation on carbon markets requires predicting how the management of different land‐uses can prevent future greenhouse gas emissions and increase CO2 sequestration. We integrated comprehensive global datasets for carbon stocks, mangrove distribution, deforestation rates, and land‐use change drivers into a predictive model of mangrove carbon emissions. We project emissions and foregone soil carbon sequestration potential under ‘business as usual’ rates of mangrove loss. Emissions from mangrove loss could reach 2391 Tg CO2 eq by the end of the century, or 3392 Tg CO2 eq when considering foregone soil carbon sequestration. The highest emissions were predicted in southeast and south Asia (West Coral Triangle, Sunda Shelf, and the Bay of Bengal) due to conversion to aquaculture or agriculture, followed by the Caribbean (Tropical Northwest Atlantic) due to clearing and erosion, and the Andaman coast (West Myanmar) and north Brazil due to erosion. Together, these six regions accounted for 90% of the total potential CO2 eq future emissions. Mangrove loss has been slowing, and global emissions could be more than halved if reduced loss rates remain in the future. Notably, the location of global emission hotspots was consistent with every dataset used to calculate deforestation rates or with alternative assumptions about carbon storage and emissions. Our results indicate the regions in need of policy actions to address emissions arising from mangrove loss and the drivers that could be managed to prevent them.
Strong priming of soil organic matter induced by frequent input of labile carbon
Labile carbon (C) inputs to soil (e.g., litter and root exudation) can prime soil organic matter (SOM) decomposition, and strongly influence SOM dynamics. The direction and intensity of priming, as well as the net C balance in soil, depend on the amount and frequency of labile C inputs. Most recent priming studies are based on single C additions, which are not truly representative of common litter inputs or root exudation in terrestrial ecosystems. Here, we evaluated the effects of 14C-labeled glucose addition to soil in the same final amounts (360 μg C g−1) split into two temporal patterns: seldom (20% of microbial biomass every two months) and frequent addition (4% of microbial biomass every 10 days) on the dynamics of CO2 production and SOM priming over a 200-day incubation. For the first time, we combined enzyme kinetics with substrate-induced growth respiration and fungal diversity to monitor microbially mediated SOM mineralization in response to the labile C input frequency. Frequent glucose addition decreased 14C incorporation into microbial biomass and almost doubled cumulative priming compared to seldom addition, resulting in a net loss of SOM for seldom and frequent C additions of −94 and −367 μg C g−1 respectively. Larger priming loss of SOM with frequent C inputs was accompanied by increased activities of β-glucosidase, chitinase, and acid phosphatase, and by a shift in fungal community towards increased abundance of K-strategist fungal species (mainly Mortierellales sp. and Trichoderma sp.) capable of SOM mineralization. In conclusion, frequent labile C inputs (e.g., rhizodeposits in rhizosphere or litterfall in disturephere) to soil will stimulate a shift in fungal community structure and functions, resulting in intensive priming of SOM decomposition and CO2 losses. © 2020 Elsevier Ltd
Effects of agroforestry and other sustainable practices in the Kenya Agricultural Carbon Project (KACP)
With growing global demand for food, unsustainable farming practices and large greenhouse gas emissions, farming systems need to sequester more carbon than they emit, while also increasing productivity and food production. The Kenya Agricultural Carbon Project (KACP) recruited farmer groups committed to more Sustainable Agricultural Land Management (SALM) practices and provided these groups with initial advisory services on SALM, farm enterprise development and village savings and loan associations. Recommended SALM practices included agroforestry, cover crops, mulching, composting manure, terracing, reduced tillage and water harvesting. The effects of the KACP on the uptake of SALM practices, maize yield, perceived food self-sufficiency and savings during the initial four years were assessed comparing control and project farmers using interviews, field visits and measurements. Farmers participating in the KACP seemed to have increased uptake of most SALM practices and decreased the use of practices to be avoided under the KACP recommendations. Agroforestry and terraces showed positive effects on maize yield. During all four years, the KACP farms had higher maize yield than control farms, but yield differences were similar in 2009 and 2012 and there was no overall significant effect of the KACP. In 2012, the KACP farms had higher food self-sufficiency and tended to have higher monetary savings than control farms. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Spatial analysis of area and carbon stocks under Populus deltoides based agroforestry systems in Punjab and Haryana states of Indo-Gangetic Plains
Towards improving the assessment of rainforest carbon: Complementary evidence from repeated diameter measurements and dated wood
We explore whether a growth-ring analysis can produce additional information about carbon budgets in tropical forests. Such forests are characterized by a high number of species and by trees that rarely have anatomically distinct annual growth rings, which hampers the application of dendrochronological tools in carbon balance assessments in the tropics. We use forest inventory data and archived annual diameter measurements from the Luki Biosphere Reserve in the southwestern margin of the Congo Basin forest massif. In addition, dated wood data are available from the same location thanks to tag nail traces that allow for the measurement of growth increments over a period of 66 years.
We find that precise increment measurements based on dated wood are advisable for small subsets of many less abundant species and for functional species groups characterized by slow growth. The dated wood approach shows that many understory trees with non-periodical rings remain in a steady state for long periods of time. These results suggest a dated wood approach is advisable for studies of growth trajectories of individual trees that might be of importance for carbon assessments in degraded forests.
Soil carbon stocks in Indonesian (agro) forest transitions: Compaction conceals lower carbon concentrations in standard accounting
Soil changes matter for the global carbon (C) balance although belowground response to land use change is slower and less obvious than that aboveground. Impacts of changes from natural forest to a range of intermediate tree-based land uses (‘agroforestry’) and non-tree agriculture remain contested. Standard C-stock accounting for a fixed sampling depth depends on changes in both Corg concentrations and bulk density, often with opposite effects. Confounding factors that, beyond current vegetation, influence Corg (soil texture, minerology, drainage, elevation and soil pH) may also influence bulk density. Because land use may not be random with respect to inherent soil properties, differences in soil C-stock between land uses can have multiple causes. We compiled and analysed data from six landscapes in Indonesia (volcanic and other mineral soils; Sumatra, Kalimantan; Java, Sulawesi) where chronosequences of forest, various agroforestry systems and open-field agriculture had been sampled. Our data analysis (617 samples within 0−30 cm depth; 8 land use types) showed that a pedotransfer function for effects on Corg of texture, elevation and soil pH reduced the relative standard error of means per land use type, reduced the range (Max–Min)/Avg and led to a more consistent pattern in apparent land use effects. Relative to natural forest reductions in Corg concentration in the 0−30 cm layer (corrected for confounding factors) averaged 8–20 % in degraded forest, complex agroforest, oil palm plantations and older forest plantation plots, and 25–30 % in simple agroforestry, monoculture tree crops and woodlots, or over 40 % in non-tree (mostly cropped) plots. However, calculated C-stock change was small due to an observed increase (up to 30 %) of bulk density relative to that of natural forest. This implies that up to 23 % additional Corg became included in the soil sampling, resulting in a non-negligible bias (underestimate) in estimated soil carbon loss based on internationally agreed C-stock accounting.
Agroforestry for Carbon Sequestration in Tropical India
Our atmosphere naturally contains CO2, CH4, N2O, water vapor, and other gases creating a natural greenhouse effect. But increased concentrations of these gases in the atmosphere have created an imbalance and have enhanced the greenhouse effect causing warming of the globe. Global warming will adversely affect hundreds of millions of people and will pose serious threats to the global food system and to rural livelihoods. Global warming is mainly the result of rising CO2 levels in the Earth’s atmosphere. CO2 concentration in the atmosphere is increasing at greater pace from decade to decade. To assure food security, adaptation, and mitigation to climate change is unavoidable. Many organizations worldwide are working for lowering CO2 concentration through various strategies like reduction in energy use, developing low- or no-carbon fuel, and CO2 sequestration by forestry/agroforestry and engineering techniques. Agroforestry has been recognized as a means to reduce CO2 emissions and enhance carbon sinks. Agroforestry systems (AFS) offer important opportunities of creating synergies between both adaptation and mitigation actions. Recent studies under various AFS in diverse ecological conditions showed that these systems increase and conserve aboveground and soil carbon stocks and also have an important role in increasing livelihood security and reducing vulnerability to climate change. The potential of agroforestry systems to accumulate C is estimated to 0.29–15.21 Mg ha−1 year−1. The carbon sequestration potential of AFS can be enhanced by stabilizing soil organic carbon through possible mechanisms including biochemical recalcitrance and physical protection and also reducing C losses. Furthermore, effectiveness of AFS to carbon sequestration depends on structure and functions of different component, environmental, and socio-economic factors. Carbon sequestration can be quantified by destructive or nondestructive methods. Implementing agroforestry on farmers’ fields for carbon sequestration will have major challenges which deserve to be addressed in an effective manner.