Linking tree biodiversity to belowground process in a young tropical plantation: Impacts on soil CO2 flux

This study examined the effect of tree species identity and diversity on soil respiration in a 3-year-old tropical tree biodiversity plantation in Central Panamá. We hypothesized that tree pairs in mixed-species plots would have higher soil respiration rates than those in monoculture plots as a result of increased primary productivity and complementarity leading to greater root and microbial biomass and soil respiration. In addition to soil respiration, we measured potential controls including root, tree, and microbial biomass, soil moisture, surface temperature, bulk density. Over the course of the wet season, soil respiration decreased from the June highs (7.2 ± 3.5 μmol CO₂/(m² s⁻¹) to a low of 2.3 ± 1.9 μmol CO₂/(m² s⁻¹) in the last 2 weeks of October. The lowest rates of soil respiration were at the peak of the dry season (1.0 ± 0.7 μmol CO₂/(m² s⁻¹)). Contrary to our hypothesis, soil respiration was 19–31% higher in monoculture than in pairs and plots with higher diversity in the dry and rainy seasons. Although tree biomass was significantly higher in pairs and plots with higher diversity, there were no significant differences in either root or microbial biomass between monoculture and two-species pairs. Path analyses allow the comparison of different pathways relating soil respiration to either biotic or abiotic controls factors. The path linking crown volume to soil temperature then respiration has the highest correlation, with a value of 0.560, suggesting that canopy controls on soil climate may drive soil respiration.     

Carbon pools in tree biomass and the soil in improved fallows in eastern Zambia

This study quantified tree and soil C stocks and their response to different tree species and clay contents in improved fallows in eastern Zambia. From 2002 to 2003, soil, and destructively harvested two-year old tree, samples were analysed for C. There were significant differences (P < 0.05) in aboveground tree C stocks, and in net organic C (NOC) intake rates across coppicing tree species at Msekera and Kalunga. Aboveground C stocks ranged from 2.9 to 9.8 t ha^-1, equivalent to NOC intakes of 0.8–4.9 t ha^-1 year^-1. SOC stocks in non-coppiced fallows at Kalichero and Msekera significantly differed (P < 0.05) across treatments. SOC stocks to 200 cm depth ranged from 64.7 t C ha^-1 under non-coppicing fallows at Kalunga to 184.0 t ha^-1 in 10-year-old coppicing fallows at Msekera. Therefore, tree and soil C stocks in improved fallows can be increased by planting selected tree species on soils with high clay content.     

Carbon storage of a subtropical forest ecosystem: a case study of the Jinggang Mountain National Nature Reserve in south-eastern China

The carbon cycle of forest ecosystems plays a key role in regulating CO2 concentrations in the atmosphere. Research on carbon storage estimation of forest ecosystems has become a major research topic. However, carbon budgets of subtropical forest ecosystems have received little attention. Reports of soil carbon storage and topographic heterogeneity of carbon storage are limited. This study focused on the Jinggang Mountain National Nature Reserve as an example of a mid-subtropical forest and evaluated soil and vegetation carbon storage by field sampling combined with GIS, RS and GPS technology. We classified the forest into nine forest types using ALOS high-resolution remote sensing images. The evergreen broad-leaved forest has the largest area, occupying 26.5% of the total area, followed by coniferous and broad-leaved mixed forests and warm temperate coniferous forest, occupying 24.2 and 22.9%, respectively. The vegetation and soil carbon storage of the whole forest ecosystem were 1,692,344 and 5,514,707 t, with a carbon density of 7.4 and 24.2 kg/m^2, respectively, which suggests that the ecosystem has great carbon storage capacity. The topographic heterogeneity of the carbon storage was also analysed. The largest vegetation storage and soil storage is at 700–800 and 1000–1100 m, respectively. The vegetation carbon storage is highest in the southeast, south and southwest.     

Ecosystem carbon storage and partitioning in a tropical seasonal forest in Southwestern China

Tropical forests play an important role in the global carbon cycle. Despite an increasing number of studies have addressed carbon storage in tropical forests, the regional variation in such storage remains poorly understood. Uncertainty about how much carbon is stored in tropical forests is an important limitation for regional-scale estimates of carbon fluxes and improving these estimates requires extensive field studies of both above- and belowground stocks. In order to assess the carbon pools of a tropical seasonal forest in Asia, total ecosystem carbon storage was investigated in Xishuangbanna, SW China. Averaged across three 1 ha plots, the total carbon stock of the forest ecosystem was 303 t C ha⁻¹. Living tree carbon stocks (both above- and belowground) ranged from 163 to 258 t C ha⁻¹. The aboveground biomass C pool is comparable to the Dipterocarp forests in Sumatra but lower than those in Malaysia. The variation of C storage in the tree layer among different plots was mainly due to different densities of large trees (DBH > 70 cm). The contributions of the shrub layer, herb layer, woody lianas, and fine litter each accounted for 1–2 t C ha⁻¹ to the total carbon stock. The mineral soil C pools (top 100 cm) ranged from 84 to 102 t C ha⁻¹ and the C in woody debris from 5.6 to 12.5 t C ha⁻¹, representing the second and third largest C component in this ecosystem. Our results reveal that a high percentage (70%) of C is stored in biomass and less in soil in this tropical seasonal forest. This study provides an accurate estimate of the carbon pool and the partitioning of C among major components in tropical seasonal rain forest of northern tropical Asia. Results from this study will enhance our ability to evaluate the role of these forests in regional C cycles and have great implications for conservation planning.     

Carbon fluxes and their response to environmental variables in a Dahurian larch forest ecosystem in northeast China

The Dahurian larch forest in northeast China is important due to its vastness and location within a transitional zone from boreal to temperate and at the southern distribution edge of the vast Siberian larch forest. The continuous carbon fluxes were measured from May 2004 to April 2005 in the Dahurian larch forest in Northeast China using an eddy covariance method. The results showed that the ecosystem released carbon in the dormant season from mid-October 2004 to April 2005, while it assimilated CO2 from the atmosphere in the growing season from May to September 2004. The net carbon sequestration reached its peak of 112 g.m^-2.month ^-1 in June 2004 （simplified expression of g （carbon）.m^-2.month^-1） and then gradually decreased. Annually, the larch forest was a carbon sink that sequestered carbon of 146 g-m^-2.a^-1 （simplified expression of g （carbon）.m^-2.a^-1） during the measurements. The photosynthetic process of the larch forest ecosystem was largely affected by the vapor pressure deficit （VPD） and temperature. Under humid conditions （VPD 〈 1.0 kPa）, the gross ecosystem production （GEP） increased with increasing temperature. But the net ecosystem production （NEP） showed almost no change with increasing temperature because the increment of GEP was counterbalanced by that of the ecosystem respiration. Under a dry environment （VPD 〉 1.0 kPa）, the GEP decreased with the increasing VPD at a rate of 3.0 μmol.m^-2.s^-1kPa -1 and the ecosystem respiration was also enhanced simultaneously due to the increase of air temperature, which was linearly correlated with the VPD. As a result, the net ecosystem carbon sequestration rapidly decreased with the increasing VPD at a rate of 5.2 μmol.m^-2.s-1.kPa^-1. Under humid conditions （VPD 〈 1.0 kPa）, both the GEP and NEP were obviously restricted by the low air temperature but were insensitive to the high temperature because the observed high temperature value comes within the category of the optimum range.     

Carbon emissions due to land-use change and logging in Cambodia: a modeling approach

Land-use change and forestry in the tropics have caused huge carbon emissions to the atmosphere. The magnitude of these emissions, however, remains debatable. Therefore, there is a need to further develop appropriate methods that would reduce the estimation uncertainties. From a modeling perspective, this report is aimed at estimating carbon emissions from deforestation and logging activities in Cambodia just after it opened its door to the world. Recently available land-use and forest inventory data were used to develop simple models capable of estimating the change of carbon stocks in, and carbon emissions from, dryland and edaphic forests. This study estimated the annual deforestation rate to be 0.1 million ha between 1973 and 2003, or about 0.7%. Between 1993 and 2003, annual carbon emissions amounted to about 13.7 TgC, owing to deforestation and logging. The emissions calculated here are higher than those reported by the Cambodian government, which claimed that Cambodia was once a net sink of carbon. The models developed in this study will be a useful tool for further study of carbon emissions in tropical countries where selective logging is practiced. Part of this article was presented at the International Symposium on the Role of Forests for Coming Generations: Philosophy and Technology for Forest Resource Management, October 2004, Utsunomiya, Japan     

An approach to achieve sustainable development goals through participatory land and forest conservation: a case study in South Kalimantan Province,Indonesia

The delivery of sustainable development goals (SDGs) through a participatory land and forest conservation initiative was evaluated in South Kalimantan Province, Indonesia. The initiative focused on the rehabilitation of a 410 ha forest that was managed by local villagers. A forest rehabilitation and management initiative was developed through participatory action, establishing a well-managed rubber plantation that provided new livelihood opportunities. Poverty reduction was promoted, evidenced by a reduction in inequality amongst the local community. Between 2010 and 2018 the Gini coefficient of inequality declined from 34.6% to 31.3%, demonstrating a contribution to SDGs 1 (No Poverty) and 10 (Reduced Inequalities). In addition, forest rehabilitation resulted in improved carbon stock and biodiversity management contributing to SDG15 (Life on Land). This was attributed to successful forest rehabilitation and the reduced incidence of forest fires. Cooperation amongst local villagers categorized as living in poor households was improved, facilitated by capacity building. This focused on rubber plantation management, cooperative action, and firefighting activities. This capacity building contributed to the delivery of SDG 17 (Partnerships for the Goals). Results from a socio-economic survey demonstrated that group activities and cooperation amongst stakeholders were essential to improve both livelihoods and forest management practices.