Carbon Storage In Forest Soils Research Articles

Microbial community shifts correspond with suppression of decomposition 25 years after liming of acidic forest soils

Microbial community structure and function regularly covary with soil pH, yet effects of these interactions on soil carbon are rarely tested experimentally within natural ecosystems. We investigated the enduring (25 year) impacts of liming on microbial community structure and decomposition at an acidic northern hardwood forest, where experimental liming increased pH one unit and surprisingly doubled the organic carbon stocks of the forest floor. We show that this increase in carbon storage corresponded with restructuring of the bacterial and fungal communities that drive decomposition. In the Oe horizon, liming reduced the activities of five extracellular enzymes that mediate decomposition, while the Oa horizon showed an especially large (64%) reduction in the activity of a sixth, peroxidase, which is an oxidative enzyme central to lignocellulose degradation. Decreased enzyme activities corresponded with loss of microbial taxa important for lignocellulose decay, including large reductions in the dominant ectomycorrhizal genera Russula and Cenococcum, saprotrophic and wood decaying fungi, and Actinobacteria (Thermomonosporaceae). These results demonstrate the importance of pH as a dominant regulator of microbial community structure and illustrate how changes to this structure can produce large, otherwise unexpected increases in carbon storage in forest soils.

Moth Outbreaks Reduce Decomposition in Subarctic Forest Soils

Tree mortality from insect infestations can significantly reduce carbon storage in forest soils. In subarctic birch forests (Betula pubescens), ecosystem C cycling is largely affected by recurrent outbreaks of defoliating geometrid moths (Epirrita autumnata, Operophtera brumata). Here, we show that soil C stocks in birch forests across Fennoscandia did not change up to 8 years after moth outbreaks. We found that a decrease in woody fine roots was accompanied by a lower soil CO2 efflux rate and a higher soil N availability following moth outbreaks. We suggest that a high N availability and less ectomycorrhiza likely contributed to lowered heterotrophic respiration and soil enzymatic activity. Based on proxies for decomposition (heterotrophic respiration, phenol oxidase potential activity), we conclude that a decrease in decomposition is a prime cause why soil C stocks of mountain birch forest ecosystems have not changed after moth outbreaks. Compared to disturbed temperate and boreal forests, a CO2-related positive feedback of forest disturbance on climate change might therefore be smaller in subarctic regions.

Soil Carbon Storage Potential of the Home Gardens Adjoining Selected Natural Forests of the Southern Sri Lanka

Conversion of forests to other land uses is inevitable despite the environmental issues associated with forest clearing. Tropical home gardens have long been identified as a land-use system analogous to forests from various perspectives. Carbon storage in the tropical forest soils is estimated to be nearly 32% of the global soil carbon. Although few in number, research conducted in Sri Lanka has shown that the home garden soils could store relatively a large amount of carbon. Present study was conducted in the low country wet zone of Sri Lanka (WL2) using the topsoil (0-15 cm) and subsoil (15-30 cm) samples taken from two sets of home gardens (HG) adjoining two natural forests (Mulatiyana and Wilpita) where latter was used as benchmark sites. Twelve samples each was collected from the topsoil and the subsoil under each system reaching a total of 96 samples for the four systems. The objective was to assess the potential of the home garden soils to sequester carbon as an alternative to the dwindling carbon storage in forest soils. Analysis of bulk density data of 12 samples each from the HGs and forests showed no significant difference (T-test, α=0.05) between the forests and the HGs for the selected soil depths. Therefore, the assessment of the systems was done in terms of the percentages of soil organic matter (SOM). All the comparisons were done using T test with α=0.05. For the topsoil, Mulatiyana HGs and the forest had mean SOM contents of 4.14%±0.98SD and 5.50%±0.71SD, respectively and, it was significantly different (p=0.001). On the contrary, Wilpita HGs and the forest had values 3.71%±1.6SD and 3.17%±0.059SD, respectively and, they were not significantly different (p=0.296). When the two forests and the home gardens were compared separately, Mulatiyana forest had significantly higher SOM content (p=0.000) over Wilpita forest while the home gardens had no significant difference (p=0.437). When the subsoil was compared neither Mulatiyana forest and the HGs (3.62%±0.64SD, 3.18%±0.70SD; p=0.072) nor Wilpita forest and the HGs (2.60%±1.01SD, 3.10%±1.14SD; p=0.268) had significant differences in the SOM contents. When the two forests and home gardens were compared separately, Mulatiyana forest had significantly higher SOM compared to Wilpita forest (p=0.008) while HGs had no significant difference (p=0.985). These results indicate that the soils of the home gardens adjoining the forests are capable of storing carbon almost up to the natural storage limit for a given locality. Hence, it can be envisioned that the carefully structured home gardens in view of capturing and storage of carbon could be a good alternative for the dwindling forests in the humid tropical environments. Keywords: Soil carbon, Home gardens, Low country, Wet zone

Charcoal and carbon storage in forest soils of the Rocky Mountain West

Charcoal represents a super-passive form of carbon (C) that is generated during fire events and is one of the few legacies of fire recorded in the soil profile; however, the importance of this material as a form of C storage has received only limited scientific attention. Here, we review the formation of charcoal in temperate and boreal forest ecosystems, discuss some of its desirable properties, and estimate the potential contribution charcoal to long-term C sequestration in forest ecosystems. Charcoal deposition over the course of several mil lennia probably accounts for a substantial proportion of the total soil C pool in fire-maintained forest ecosystems. Forest management processes that interfere with natural fire processes eliminate the formation of this passive form of C. We recommend that charcoal be considered in C storage budgets and modeling of forest ecosystems, especially in light of climate change and increasing occurrence of wildfire.

Effects of Different Management Regimes for Cutover Areas on Soil Carbon Storage in Chinese Fir Plantations

Based on data collected (through local observations) for several consecutive years, comparative analyses of Chinese fir plantations in Huitong, Hunan, were made. Results show that, before harvesting, carbon storage in forest soils in these 22-year-old plantations (0–60 cm) amounted to 160.38 t/hm2; 1 year after a 100% clear-cutting, loss of carbon storage in the soil (0–60 cm) of cutover areas was 35.00%; 2 years later, the rate was 44.65%; and, after 3 years, the rate was 43.93% compared with a control area of a standing forest. Three years after 50% thinning and 100% clear-cutting, the loss of carbon storage in the soil (0–60 cm) of cutover areas was 16.14 and 45.15%, respectively. There existed an evident difference in carbon storage in the soil (0–60 cm) of cutover areas in four kinds of management regimes, which followed the order: closed Chinese fir forests (108.20 t/hm2) > fallow lands after farming (92.68 t/hm2) > commercial forests (85.80 t/hm2) > naturally regenerated forestlands after harvesting. Carbon storage in unburnt soil (0–45 cm) reached 73.36 t/hm2, which was 15.20 t/hm2 higher than that in the soil of burnt areas. A total of 20.7% of carbon storage in the soil (0–45 cm) of burnt areas was lost 40 days after burning. Carbon storage in surface soil (0–15 cm) was higher than in the lower soil layer, which amounted to 30.04% (0–60 cm) and 53.52% (0–30 cm) of total carbon storage in the soil.

Long-Term Fire Regime Estimated from Soil Charcoal in Coastal Temperate Rainforests

Coastal temperate rainforests from southeast Alaska through to southern Oregon are ecologically distinct from forests of neighboring regions, which have a drier, or more continental, climate and disturbance regimes dominated by fires. The long-term role of fire remains one of the key outstanding sources of uncertainty in the historical dynamics of the wetter and less seasonal forests that dominate the northerly two thirds of the rainforest region in British Columbia and Alaska. Here, we describe the long-term fire regime in two forests on the south coast of British Columbia by means of 244 AMS radiocarbon dates of charcoal buried in forest soils. In both forests, some sites have experienced no fire over the last 6000 years and many other sites have experienced only one or two fires during that time. Intervals between fires vary from a few centuries to several thousand years. In contrast to other conifer forests, this supports a model of forest dynamics where fires are of minor ecological importance. Instead, forest history is dominated by fine-scale processes of disturbance and recovery that maintain an ubiquitous late-successional character over the forest landscape. This has significant implications for ecosystem-based forest management and our understanding of carbon storage in forest soils.

More Rain, Less Decay

ECOLOGY The amount of carbon stored in soils is an important component of the global carbon cycle and therefore is relevant to calculations of the effects of climate change on the biosphere. There is a correlation between increased rainfall and increased carbon storage in forest soils, but the

Carbon Cycling and Soil Carbon Storage in Mesic to Wet Hawaiian Montane Forests

Global surveys have shown that increased precipitation in mesic to wet ecosystems increases soil carbon storage, but it is not clear how changes in water availability act to affect soil carbon since water is generally in excess of plant demand within these humid ecosystems. Differences in precipitation can affect soil carbon storage either by altering the biotic processes involved in carbon cycling or by altering abiotic processes such as carbon adsorption on soil minerals. We compared the relative effect of water on net primary productivity and decomposition, and on soil weathering and mineralogy in controlling soil carbon storage in forests. Patterns of ecosystem carbon cycling and soil carbon storage were measured in Hawaiian montane forest sites similar in temperature regime, parent material, ecosystem age, vegetation, and topographical relief, while mean annual precipitation alone varied from 2200 to >5000 mm/yr. Soil carbon storage ranged from 30.9 to 62.5 kg/m2 and increased by a factor of 1.7 with increased precipitation across the gradient. Neither changes in total secondary minerals nor noncrystalline mineral content could explain increased soil carbon as both decreased with increasing precipitation. Aboveground net primary productivity, soil carbon dioxide flux, and plant litter decomposition rates also decreased with increased precipitation. These data suggest that increased soil carbon storage was not stimulated by an increase in net primary productivity, but instead by a decrease in decomposition rates. Decreased decomposition rates corresponded with low soil reduction–oxidation potentials, suggesting that soil oxygen availability was limiting to microbes. While soil oxygen did not appear to affect plant growth directly, the decline in net primary productivity corresponded with decreased nitrogen availability, a consequence of slower decomposition and nutrient release. Thus, in humid environments the most important effect of variation in water on carbon cycling appears to be its control on the diffusion of oxygen into the soil.

CARBON CYCLING AND SOIL CARBON STORAGE IN MESIC TO WET HAWAIIAN MONTANE FORESTS

Global surveys have shown that increased precipitation in mesic to wet ecosystems increases soil carbon storage, but it is not clear how changes in water availability act to affect soil carbon since water is generally in excess of plant demand within these humid ecosystems. Differences in precipitation can affect soil carbon storage either by altering the biotic processes involved in carbon cycling or by altering abiotic processes such as carbon adsorption on soil minerals. We compared the relative effect of water on net primary productivity and decomposition, and on soil weathering and mineralogy in controlling soil carbon storage in forests. Patterns of ecosystem carbon cycling and soil carbon storage were measured in Hawaiian montane forest sites similar in temperature regime, parent material, ecosystem age, vegetation, and topographical relief, while mean annual precipitation alone varied from 2200 to >5000 mm/yr. Soil carbon storage ranged from 30.9 to 62.5 kg/m2 and increased by a factor of 1.7 with increased precipitation across the gradient. Neither changes in total secondary minerals nor noncrystalline mineral content could explain increased soil carbon as both decreased with increasing precipitation. Aboveground net primary productivity, soil carbon dioxide flux, and plant litter decomposition rates also decreased with increased precipitation. These data suggest that increased soil carbon storage was not stimulated by an increase in net primary productivity, but instead by a decrease in decomposition rates. Decreased decomposition rates corresponded with low soil reduction–oxidation potentials, suggesting that soil oxygen availability was limiting to microbes. While soil oxygen did not appear to affect plant growth directly, the decline in net primary productivity corresponded with decreased nitrogen availability, a consequence of slower decomposition and nutrient release. Thus, in humid environments the most important effect of variation in water on carbon cycling appears to be its control on the diffusion of oxygen into the soil.

Carbon storage in forest soils

Carbon storage in forest soils