Ongoing conversion of forests in Sumatra to agricultural lands might affect the biodiversity of soil fauna, such as termites, and emissions of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2). To assess the impact of such forest conversions, this study was conducted in Jambi, Sumatra in an undisturbed forest (FR), a disturbed forest (DF), a one year old rubber plantation (RB1), a twenty year old rubber plantation (RB20) and an oil palm plantation (OP). The plantations belonged to smallholders and were not usually fertilized. The effect of fertilizer was assessed by applying N fertilizer and taking a series of intensive measurements. The N2O, CH4 and CO2 fluxes were measured using static chamber methods and termite species richness was assessed using a standard semi quantitative transect method. Forest conversion to smallholder plantations did not significantly affect the N2O, CH4 and CO2 fluxes, but the diversity and relative abundance of termites was decreased. this implies that the ecosystem services regulated by termites might decline. The application of N fertilizer at the conventional rate (141 kg N ha-1 y-1), with an emission factor of 3.1 % in the oil palm plantation, increased N2O emissions to twice as high as that in the undisturbed forest. The annual N2O and CH4 fluxes from termites amounted to 0.14, 0.21, 0.88, 2.47 and – 0.56 kg ha-1 y-1 N2O-N and 0.85, 1.65, 3.80, 0.97 and 2.30 kg ha-1 y-1 CH4-C in the FR, DF, RB1, RB20 and OP, respectively. Further research is needed to understand the interannual variability of the N2O, CH4 and CO2 fluxes from soils and termites. Understanding the key drivers and underlying processes which regulate them would help to control the biodiversity loss and the change of N2O, CH4 and CO2 fluxes from soils and termites.
Tag: carbon dioxide
Vietnam blue carbon opportunity assessment
Marine and coastal ecosystems, including mangroves and seagrass meadows, are global hotspots for “blue carbon” storage in vegetation and soils, but face mounting pressure from human activities and climate change. Mechanisms that mobilize foreign direct investment to reduce anthropogenic greenhouse gas emissions and enhance sustainable development, such as voluntary carbon projects, offer financing that can complement government efforts. We assessed blue carbon opportunities in Vietnam focusing on mangroves and seagrass in the Mekong Delta coastal provinces (Kien Giang, Ca Mau, Bac Lieu, Soc Trang, Tra Vinh, Ben Tre and Tien Giang). Object-based image analysis was used to quantify changes in the extent of mangroves from 2016 – 2024. To assess fluctuations in seagrass meadow areas we projected historical changes in seagrass coverage reported in the literature. Emissions of CO2 resulting from changes in mangrove forest and seagrass meadow coverages were estimated using literature-based emission factors. Overall, mangrove coverage in the Mekong Delta coastal provinces declined between 2016 and 2024, despite areas of mangrove expansion. CO2 removals from mangrove area increase did not offset CO2 emissions from mangrove loss during 2016–2024. Our analysis revealed substantial losses in some areas, highlighting the complex dynamics of mangrove conservation. The total net impact of mangrove loss and reforestation in the seven provinces during this period was 14.5 million Mg CO2, with Ca Mau province contributing 77% of emissions. The magnitude of potential CO2 emissions from seagrass loss was smaller, at 31.4 thousand Mg CO2, concentrated in the area of Phu Quoc Island in Kien Giang province. Our results emphasize the need to avoid continued conversion of mangroves, despite gains in mangrove forest areas.
Making trees count: Measurement and reporting of agroforestry in UNFCCC national communications of non-Annex I countries
Subsidence and carbon dioxide emissions in a smallholder peatland mosaic in Sumatra, Indonesia
Most attention in quantifying carbon dioxide (CO 2 ) emissions from tropical peatlands has been on large-scale plantations (industrial timber, oil palm (Elaeis guinensis)), differing in drainage and land-use practices from those of smallholder farms. We measured subsidence and changes in bulk density and carbon organic content to calculate CO 2 emissions over 2.5 years in a remnant logged-over forest and four dominant smallholder land-use types in Tanjung Jabung Barat District, Jambi Province, Sumatra, Indonesia: (1) simple rubber (Hevea brasiliensis) agroforest (> 30 years), (2) mixed coconut (Cocos nucifera) and coffee gardens (Coffea liberica) (> 40 years), (3) mixed betel nut (Areca catechu) and coffee gardens (> 20 years), and (4) oil palm plantation (1 year). We quantified changes in microtopography for each site for greater accuracy of subsidence estimates and tested the effects of nitrogen and phosphorus application. All sites had a fibric type of peat with depths of 50 to > 100 cm. A recently established oil palm had the highest rate of peat subsidence and emission (4.7 cm year −1 or 121 Mg CO 2 ha −1 year −1 ) while the remnant forest had the lowest (1.8 cm year −1 or 40 Mg CO 2 ha −1 year −1 ). Other land-use types subsided by 2–3 cm year −1 , emitting 70–85 Mg CO 2 ha −1 year −1 . Fertilizer application did not have a consistent effect on inferred emissions. Additional emissions in the first years after drainage, despite groundwater tables of 40 cm, were of the order of belowground biomass of peat forest. Despite maintaining higher water tables, smallholder landscapes have CO 2 emissions close to, but above, current IPCC defaults. © 2018, The Author(s).
Field-Level Evidences of Climate Change and Coping Strategies of Smallholder Farmers in Molawin-Dampalit Sub-Watershed, Makiling Forest Reserve, Philippines
This article confirms that climate change is indeed a real phenomenon as observed and experienced by smallholder farmers in the Molawin-Dampalit Sub-Watershed. Using semi-structured interviews and focus group discussions, the smallholder farmers articulated their own indications of climate change. These include increasing temperature, stronger and more frequent typhoons, excessive rainfall, drought, early rainy season, and delayed dry season. Among the effects of climate change on their agricultural production include stunted growth of crops, aborted fruiting of trees, incidence of pests and diseases, and growth of unknown weeds. These have led to increase in the use and dosage of farm inputs, particularly pesticides and fertilizers; decline in crop yield; and ultimately, decline in farm income. To cope with these impacts, the farmers employed strategies such as replanting, use of chemical pesticides and fertilizers to control pests and improve crop growth, pruning, watering and diversion of water source, changing crops, and harvesting their crops earlier to minimize crop loss. Considering the vulnerability of smallholder farmers, the results suggest the need to enhance their adaptive capacities for climate change impacts using a holistic approach via human capital development, improvement of physical capital, and building their social capital.
Sensitivity of Grapevine Phenology to Water Availability, Temperature and CO2 Concentration
In recent decades, mean global temperatures have increased in parallel with a sharp rise in atmospheric carbon dioxide (CO2) levels, with apparent implications for precipitation patterns. The aim of the present work is to assess the sensitivity of different phenological stages of grapevine to temperature and to study the influence of other factors related to climate change (water availability and CO2 concentration) on this relationship. Grapevine phenological records from 9 plantings between 42.75°N and 46.03°N consisting of dates for budburst, flowering and fruit maturity were used. In addition, we used phenological data collected from 2 years of experiments with grapevine fruit-bearing cuttings with two grapevine varieties under two levels of water availability, two temperature regimes and two levels of CO2. Dormancy breaking and flowering were strongly dependent on spring temperature, while neither variation in temperature during the chilling period nor precipitation significantly affected budburst date. The time needed to reach fruit maturity diminished with increasing temperature and decreasing precipitation. Experiments under semi-controlled conditions revealed great sensitivity of berry development to both temperature and CO2. Water availability had significant interactions with both temperature and CO2; however, in general, water deficit delayed maturity when combined with other factors. Sensitivities to temperature and CO2 varied widely, but higher sensitivities appeared in the coolest year, particularly for the late ripening variety, ‘White Tempranillo’. The knowledge gained in whole plant physiology and multi stress approaches is crucial to predict the effects of climate change and to design mitigation and adaptation strategies allowing viticulture to cope with climate change.
Greenhouse gas fluxes from agricultural soils of Kenya and Tanzania
Knowledge of greenhouse gas (GHG) fluxes in soils is a prerequisite to constrain national, continental, and global GHG budgets. However, data characterizing fluxes from agricultural soils of Africa are markedly limited. We measured carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) fluxes at 10 farmer-managed sites of six crop types for 1 year in Kenya and Tanzania using static chambers and gas chromatography. Cumulative emissions ranged between 3.5–15.9 Mg CO2-C ha−1 yr−1, 0.4–3.9 kg N2O-N ha−1 yr−1, and −1.2–10.1 kg CH4-C ha−1 yr−1, depending on crop type, environmental conditions, and management. Manure inputs increased CO2 (p = 0.03), but not N2O or CH4, emissions. Soil cultivation had no discernable effect on emissions of any of the three gases. Fluxes of CO2 and N2O were 54–208% greater (p < 0.05) during the wet versus the dry seasons for some, but not all, crop types. The heterogeneity and seasonality of fluxes suggest that the available data describing soil fluxes in Africa, based on measurements of limited duration of only a few crop types and agroecological zones, are inadequate to use as a basis for estimating the impact of agricultural soils on GHG budgets. A targeted effort to understand the magnitude and mechanisms underlying African agricultural soil fluxes is necessary to accurately estimate the influence of this source on the global climate system and for determining mitigation strategies.
Unexpected results of a pilot throughfall exclusion experiment on soil emissions of CO2, CH4, N2O, and NO in eastern Amazonia
The eastern Amazon Basin may become drier as a result of less regional recirculation of water in a largely deforested landscape and because of increased frequency and intensity of El Niño events induced by global warming. Drier conditions may affect several plant and soil microbial processes, including soil emissions of CO2, CH4, NO, and N2O. We report here unanticipated results of a pilot study that was initiated to test the feasibility of a larger-scale throughfall exclusion experiment. In particular, soil drying caused a switch from net consumption of atmospheric CH4 by soils in the control plot to net CH4 emission from soils in the experimentally dried plot. This result is surprising because production of CH4 requires anaerobic microsites, which are uncommon in dry soil. A plausible explanation for increased CH4 emissions in the dried plot is that dry soil conditions favor termite activity and increased coarse root mortality provides them with a substrate. Another surprise was that both NO and N2O fluxes were elevated several years after initiation of the drying experiment. Apparently, a pulse of N availability caused by experimental drying persisted for at least 3 years. As expected, CO2 emissions were lower in the dried plots, which is consistent with lower rates of root growth observed in root in-growth cores placed in the dried plots. More work is needed to test these explanations and to confirm these phenomena, but these results demonstrate that changes in climate could have unanticipated effects on biogeochemical processes in soils that we do not adequately understand.
Spatiotemporal variability in carbon exchange fluxes across the Sahel
Semi-arid regions play an increasingly important role as a sink within the global carbon (C) cycle and is the main biome driving inter-annual variability in carbon dioxide (CO2) uptake by terrestrial ecosystems. This indicates the need for detailed studies of spatiotemporal variability in C cycling for semi-arid ecosystems. We have synthesized data on the land-atmosphere exchange of CO2 measured with the eddy covariance technique from the six existing sites across the Sahel, one of the largest semi-arid regions in the world. The overall aim of the study is to analyse and quantify the spatiotemporal variability in these fluxes and to analyse to which degree spatiotemporal variation can be explained by hydrological, climatic, edaphic and vegetation variables. All ecosystems were C sinks (average ± total error -162 ± 48 g C m-2 y-1), but were smaller when strongly impacted by anthropogenic influences. Spatial and inter-annual variability in the C flux processes indicated a strong resilience to dry conditions, and were correlated with phenological metrics. Gross primary productivity (GPP) was the most important flux process affecting the sink strength, and diurnal variability in GPP was regulated by incoming radiation, whereas seasonal dynamics was closely coupled with phenology, and soil water content. Diurnal variability in ecosystem respiration was regulated by GPP, whereas seasonal variability was strongly coupled to phenology and GPP. A budget for the entire Sahel indicated a strong C sink mitigating the global anthropogenic C emissions. Global circulation models project an increase in temperature, whereas rainfall is projected to decrease for western Sahel and increase for the eastern part, indicating that the C sink will possibly decrease and increase for the western and eastern Sahel, respectively. © 2016 Elsevier B.V.
Ecology and management of tropical secondary forest: science, people and policy: proceedings of a conference held at CATIE, Costa Rica, November 10-12, 1997
The disturbance and destruction of the old-growth forests of the tropics continue to monopolize attention in international fora and the popular media, but a steadily growing land area is covered by secondary forest developing on sites which have been deforested and then abandoned by their owners. The natural process of secondary forest succession offers hope that the unique combination of goods and services provided by the original old-growth forests may be at least partially recovered. An enormous number of questions concerning secondary tropical forests and their potential role in sustainable land management and biodiversity conservation remain to be answered, however. Many of these questions are biological and ecological: What are the factors that bring about successional change in vegetation? How does biodiversity change during succession, does its similarity to the biodiversity of old-growth forests increase over time and why, or why not? How might secondary forests be manipulated to optimize their value for a given set of management objectives? Many more questions nevertheless concern people and their actions: what factors bring about land abandonment? How are secondary forests perceived and utilized by rural people? What market or policy changes may contribute to a more profitable and sustainable use of secondary forests? This volume contains 16 papers presented at a conference which brought together researchers concerned with biological, ecological, social/organizational, financial/economic and political aspects of secondary forests and their management with a strictly neo tropical focus. Although the biophysical side of secondary forest research dominated this conference, it is becoming clear that sound management of this resource will depend on interdisciplinary approaches.