Indonesia’s blue carbon: a globally significant and vulnerable sink for seagrass and mangrove carbon

The global significance of carbon storage in Indonesia’s coastal wetlands was assessed based on published and unpublished measurements of the organic carbon content of living seagrass and mangrove biomass and soil pools. For seagrasses, median above- and below-ground biomass was 0.29 and 1.13 Mg C ha^?1 respectively; the median soil pool was 118.1 Mg C ha^?1. Combining plant biomass and soil, median carbon storage in an Indonesian seagrass meadow is 119.5 Mg C ha^?1. Extrapolated to the estimated total seagrass area of 30,000 km², the national storage value is 368.5 Tg C. For mangroves, median above- and below-ground biomass was 159.1 and 16.7 Mg C ha^?1, respectively; the median soil pool was 774.7 Mg C ha^?1. The median carbon storage in an Indonesian mangrove forest is 950.5 Mg C ha^?1. Extrapolated to the total estimated mangrove area of 31,894 km², the national storage value is 3.0 Pg C, a likely underestimate if these habitats sequester carbon at soil depths >1 m and/or sequester inorganic carbon. Together, Indonesia’s seagrasses and mangroves conservatively account for 3.4 Pg C, roughly 17 % of the world’s blue carbon reservoir. Continued degradation and destruction of these wetlands has important consequences for CO₂ emissions and dissolved carbon exchange with adjacent coastal waters. We estimate that roughly 29,040 Gg CO₂ (eq.) is returned annually to the atmosphere–ocean pool. This amount is equivalent to about 3.2 % of Indonesia’s annual emissions associated with forest and peat land conversion. These results highlight the urgent need for blue carbon and REDD+ projects as a means to stem the decline in wetland area and to mitigate the release of a significant fraction of the world’s coastal carbon stores.     

Carbon sequestration in wetland soils of the northern Gulf of Mexico coastal region

Coastal wetlands play an important but complex role in the global carbon cycle, contributing to the ecosystem service of greenhouse gas regulation through carbon sequestration. Although coastal wetlands occupy a small percent of the total US land area, their potential for carbon storage, especially in soils, often exceeds that of other terrestrial ecosystems. More than half of the coastal wetlands in the US are located in the northern Gulf of Mexico, yet these wetlands continue to be degraded at an alarming rate, resulting in a significant loss of stored carbon and reduction in capacity for carbon sequestration. We provide estimates of surface soil carbon densities for wetlands in the northern Gulf of Mexico coastal region, calculated from field measurements of bulk density and soil carbon content in the upper 10–15 cm of soil. We combined these estimates with soil accretion rates derived from the literature and wetland area estimates to calculate surface soil carbon pools and accumulation rates. Wetlands in the northern Gulf of Mexico coastal region potentially store 34–47 Mg C ha^?1 and could potentially accumulate 11,517 Gg C year^?1. These estimates provide important information that can be used to incorporate the value of wetlands in the northern Gulf of Mexico coastal region in future wetland management decisions related to global climate change. Estimates of carbon sequestration potential should be considered along with estimates of other ecosystem services provided by wetlands in the northern Gulf of Mexico coastal region to strengthen and enhance the conservation, sustainable management, and restoration of these important natural resources.     

Predicted risks of groundwater decline in seasonal wetland plant communities depend on basin morphology

In regions of the world where the climate is expected to become drier, meeting environmental water needs for wetlands and other dependent ecosystems will become increasingly challenging. Ecological models can play an important role, by quantifying system responses to reduced water availability and predicting likely ecological impacts. Anticipating these changes can inform both conservation and monitoring effort. We used water-plant functional group models to predict the effects of a declining water table for two wetland types reliant on the surface expression of groundwater but of contrasting basin morphology. Our interest was in quantifying the relative sensitivity of these wetland types to different amounts of groundwater decline. For the shallower, grass-sedge wetland, terrestrial plant probabilities increased markedly for declines between 0.25 and 0.5 m, but amphibious and submerged functional groups changed predictably, or not at all. However, mean inundated area reduced by over 70% for a 0.5 m groundwater decline, suggesting loss of area posed the greatest risk in this wetland type. In the deeper, steep-sided interdunal wetland, inundated area changed little, but models suggest clear transitions in plant functional group composition. Sedge-group probabilities increased sharply for declines between 0.25 and 0.5 m, while declines between 0.5 and 1.0 m predicted the loss of submerged species. As might be anticipated, the risks associated with groundwater level decline depend on basin morphology. However, by quantifying probable ways in which this will manifest in different wetland types, model predictions improve our ability to recognise and manage change.     

Significance of Over-Mature and Decaying Trees for Carbon Stocks in a Central European Natural Spruce Forest

Old-growth forests are important stores for carbon as they may accumulate C for centuries. The alteration of biomass and soil carbon pools across the development stages of a forest dynamics cycle has rarely been quantified. We studied the above- and belowground C stocks in the five forest development stages (regeneration to decay stage) of a montane spruce (Picea abies) forest of the northern German Harz Mountains, one of Central Europe’s few forests where the natural forest dynamics have not been disturbed by man for several centuries. The over-mature and decay stages had the largest total (up to 480 Mg C ha^?1) and aboveground biomass carbon pools (200 Mg C ha^?1) with biomass C stored in dead wood in the decay stage. The soil C pool (220–275 Mg C ha^?1, 0–60 cm) was two to three times larger than in temperate lowland spruce forests and remained invariant across the forest dynamics cycle. On the landscape level, taking into account the frequency of the five forest development stages, the total carbon pool was approximately 420 Mg C ha^?1. The results evidence the high significance of over-mature and decaying stages of temperate mountain forests not only for conserving specialized forest organisms but also for their large carbon storage potential.     

The impact of land degradation on the C pools in alpine grasslands of the Qinghai-Tibet Plateau

Aims

To determine the effect of grassland degradation on the soil carbon pool in alpine grassland.

Methods

In this study, we calculated the carbon pool in the above-and below-ground biomass, the soil microbial biomass carbon pool, the total organic carbon pool and the soil total carbon.

Results

Grassland degradation has resulted in decreases in biomass and carbon content and has changed the ratio of roots to shoots. However, there was less influence of degradation on dead root biomass. There was most likely a lag effect of changes in dead root biomass following grassland degradation. In the alpine grassland ecosystem, the carbon pool in soil accounts for more than 92 % of the total carbon both in vegetation and soil. The carbon in alpine grassland is stored primarily in the form of total organic carbon below-ground. As organic carbon decreases, the ratio of the microbial biomass carbon pool to the total organic carbon pool increases and then declines with increasing degradation level. Along the grassland degradation gradient, the total vegetation biomass (above-and below-ground) and the soil carbon pool (microbial biomass C, total organic C and total C) all decreased.     

Effects of Water Table Drawdown on Root Production and Aboveground Biomass in a Boreal Bog

We studied the effect of long-term water table drawdown on the vascular plant community in an ombrotrophic bog in central Finland by measuring aboveground biomass and belowground production (by in-growth cores) across plant functional groups including herbs, shrubs, and trees. We compared drained and undrained portions 45 years after the installation of a drainage ditch network, which has lowered water levels of 15–20 cm on average in the drained part of the site. Although shrub fine root production did not differ significantly between sites, water table drawdown increased belowground tree fine root production by 740% (3.8 ± 5.4 SD and 28.1 ± 24.1 g m^?2 y^?1 in undrained and drained sites, respectively) at the expense of herb root production, which declined 38% (27.62 ± 16.40 and 10.58 ± 15.7 g m^?2 y^?1 in undrained and drained sites, respectively) yielding no significant overall change in total fine root production. Drainage effects on aboveground biomass showed a similar pattern among plant types, as aboveground tree biomass increased dramatically with drainage (79 ± 135 and 2546 ± 1551 g m^?2 in drained and undrained sites, respectively). Although total shrub biomass was not significantly different between sites, shrubs allocated more biomass to stems than leaves in the drained site. Drainage also caused a significant shift in shrub species composition. Although trees dominated the aboveground biomass following water table drawdown, understorey vegetation, mainly shrubs, continued to dominate belowground fine root production, comprising 64% of total root production at the drained site. Aboveground biomass proved to be a good predictor of belowground production, suggesting that allometric relationships can be developed to estimate belowground production in these systems. Increase in tree root production can counteract decrease in herb fine root production following water table drawdown, emphasizing the importance of plant functional type responses to water table drawdown. Whether these changes will offset ecosystem C loss via increased plant C storage or stimulate soil organic matter decomposition via increased above- and belowground litter inputs requires further study.     

The ecological adaptability of <Emphasis Type="Italic">Phragmites australis</Emphasis> to interactive effects of water level and salt stress in the Yellow River Delta

Soil salinity and waterlogging are two major environmental problems in estuarine wetlands. To prevent the typical wetland plants from degradation by soil salinization and salt waterlogging and more effectively use the plants to provide wetland ecosystem services, we examined the ecological adaptability of Phragmites australis, a characteristic plant species in the Yellow River Delta, to the interactive effects of water level and salt stress. The results showed that P. australis adapts to salt and water table stressed environments through slowing down the growth rate, maintaining the tiller number, and adjusting the biomass allocation of different organs. The highest plant height and the largest leaf area were at 0 cm water table treatment; the 0.5 % NaCl treatment increased the aboveground biomass; higher water table increased the fibrous root biomass allocation, but largely decreased the leaf biomass. The exclusion of toxic inorganic ions such as Na⁺ and Cl^? and the accumulation of organic solutes are also important mechanisms to aid survival in saline wetlands. On average 35.1 % of Cl^? and 53.9 % of Na⁺ accumulated in belowground organs. The study could provide fundamental guidance for wetland restoration projects and wetland sustainable use in coastal zones such as the Yellow River Delta.     

Detecting soil and plant community changes in restored wetlands using a chronosequence approach

Wetland restoration aims to recreate or enhance valuable ecosystem services lost during wetland destruction. Regaining wetland ecosystem services depends on restarting basic wetland functions, like carbon (C) storage, which are unmeasured in many Wetlands Reserve Program (WRP) restoration sites. We collected soil and plant data from 17 WRP sites in western New York that were used for tillage or non-tillage agriculture and then actively restored as isolated depressional wetlands by excavating basins and disabling drainage systems. Sites had been restored for 0–15 years when sampled in August-October 2010. We analyzed data as chronosequences and tested whether soil and vegetation parameters in restored wetlands, over time, (1) departed from pre-restoration baselines, estimated using active agricultural fields paired to each WRP site, and (2) converged towards “natural” benchmarks, estimated from four naturally-occurring wetlands. Restored WRP soils remained similar to agricultural soils in organic matter, density, moisture, and belowground plant biomass across chronosequences, indicating negligible C storage and belowground development for 15 years following restoration. Soil changes were limited in sites restored after both tillage and non-tillage agriculture and throughout the upland meadow, emergent shoreline, and open-water habitat zones that characterize these sites. Many plant metrics like aboveground biomass matched natural wetlands within 15 years, but recovered inconsistently among tilled and untilled sites and across all habitat zones, suggesting land-use history impacts and/or zonation effects. Disparities in recovery times exists between vegetation, which can respond quickly to wetland restoration, and underlying soils, which show limited signs of recovery 15 years after being restored.     

Soil volume and carbon storage shifts in drained and afforested wetlands of the Paraná River Delta

Wetland ecosystems have a high carbon storage potential as a result of high primary productivity and low decomposition rates dictated by water saturation. In the herbaceous wetlands of the Paraná River Delta, drainage and afforestation with poplars represents one of the dominant land uses. We explored the effects of these interventions on the volume and carbon storage of the young sedimentary soils of the region. At three sites we identified paired stands occupying similar landscape positions and soil types but subject to natural flooding and covered by natural herbaceous communities or drainage and flood control by dikes and covered by poplar plantations established 12, 17 and 19 years ago. Soil sampling at these sites revealed a reduction of the litter compartment (?86 %) and decreasing volume and porosity of its underlying mineral layer (0–10 cm in the wetland reduced to 0–4 cm in the plantation). Our comparisons of carbon storage accounted for these volumetric shifts by using accumulated mineral mass rather than depth as a reference, showing that tree plantations gained in the mineral soil (22 Mg C ha^?1) almost as much as what they lost in the litter. These gains were particularly large at intermediate depths (4–43 cm in the plantations) were soil porosity remained unaffected and C was raised by 64 % explained by (1) the pulse of inputs from overlaying litter and organic layers subject to rapid decomposition and mobilization after drainage and (2) root colonization, since tree plantations had 75 % of their fine root biomass at these intermediate soil depths, whereas roots in the wetlands did not explore the mineral soil profile and were completely confined to the organic layer. A neutral C balance following wetland drainage and afforestation resulted from the opposing effects of aeration, favoring decomposition in the organic layer, root colonization and organic matter stabilization, favoring its accumulation in the mineral soil.     

Soil microbial biomass and the fate of phosphorus during long-term ecosystem development

Background

Soil phosphorus availability declines during long-term ecosystem development on stable land surfaces due to a gradual loss of phosphorus in runoff and transformation of primary mineral phosphate into secondary minerals and organic compounds. These changes have been linked to a reduction in plant biomass as ecosystems age, but the implications for belowground organisms remain unknown.

Methods

We constructed a phosphorus budget for the well-studied 120,000 year temperate rainforest chronosequence at Franz Josef, New Zealand. The budget included the amounts of phosphorus in plant biomass, soil microbial biomass, and other soil pools.

Results

Soil microbes contained 68–78 % of the total biomass phosphorus (i.e. plant plus microbial) for the majority of the 120,000 year chronosequence. In contrast, plant phosphorus was a relatively small pool that occurred predominantly in wood. This points to the central role of the microbial biomass in determining phosphorus availability as ecosystems mature, yet also indicates the likelihood of strong competition between plants and saprotrophic microbes for soil phosphorus.

Conclusions

This novel perspective on terrestrial biogeochemistry challenges our understanding of phosphorus cycling by identifying soil microbes as the major biological phosphorus pool during long-term ecosystem development.     

Responses of soil respiration to reduced water table and nitrogen addition in an alpine wetland on the Qinghai-Xizang Plateau

近20年来, 青藏高原高寒湿地经历了明显的气候变化, 从而导致多数湿地水位下降和氮沉降的增加。对于湿地生态系统来说, 水位下降意味着土壤通气性能的改善, 可能会导致土壤呼吸的增加; 而氮沉降的增加可能会降低土壤微生物生物量和pH值, 从而可能抑制土壤呼吸。为此, 在青海海北高寒草地生态系统国家野外科学观测研究站利用中宇宙(Mesocosm)实验方法, 探讨了青藏高原高寒泥炭型湿地土壤呼吸对水位降低和氮添加的响应。结果表明: (1)水位降低显著增强了土壤呼吸, 而氮添加对土壤呼吸的影响依赖于水位的变化: 对照水位下, 氮添加显著抑制土壤呼吸; 而水位降低时, 氮添加对土壤呼吸速率无显著影响。(2)土壤呼吸速率与地上生物量、枯落物累积量之间呈显著正相关关系, 而与根系生物量无显著相关关系。(3)水位降低显著提高了土壤呼吸的温度敏感性, 而氮添加对其无显著的影响。因此预测: 随着氮沉降的升高, 高寒泥炭湿地土壤CO₂的排放量将会减少; 然而随着暖干化背景下水位的降低, 青藏高原高寒湿地会排放更多的CO₂。     

青藏高原海北高寒湿地土壤呼吸对水位降低和氮添加的响应

近20年来, 青藏高原高寒湿地经历了明显的气候变化, 从而导致多数湿地水位下降和氮沉降的增加。对于湿地生态系统来说, 水位下降意味着土壤通气性能的改善, 可能会导致土壤呼吸的增加; 而氮沉降的增加可能会降低土壤微生物生物量和pH值, 从而可能抑制土壤呼吸。为此, 在青海海北高寒草地生态系统国家野外科学观测研究站利用中宇宙(Mesocosm)实验方法, 探讨了青藏高原高寒泥炭型湿地土壤呼吸对水位降低和氮添加的响应。结果表明: (1)水位降低显著增强了土壤呼吸, 而氮添加对土壤呼吸的影响依赖于水位的变化: 对照水位下, 氮添加显著抑制土壤呼吸; 而水位降低时, 氮添加对土壤呼吸速率无显著影响。(2)土壤呼吸速率与地上生物量、枯落物累积量之间呈显著正相关关系, 而与根系生物量无显著相关关系。(3)水位降低显著提高了土壤呼吸的温度敏感性, 而氮添加对其无显著的影响。因此预测: 随着氮沉降的升高, 高寒泥炭湿地土壤CO₂的排放量将会减少; 然而随着暖干化背景下水位的降低, 青藏高原高寒湿地会排放更多的CO₂。     

模拟氮沉降对湿地植物生物量与土壤活性碳库的影响

在两种水分条件下(W₁:非淹水,W₂:淹水)分4个氮处理(分别相当于氮沉降率0、1、3、5 g N·m^-2·a^-1)模拟了三江平原典型湿地植物湿草甸小叶章(Deyeuxia angustifolia)植株及土壤活性碳库对氮沉降的响应.结果表明：模拟氮沉降下小叶章的生物量(总生物量、地上生物量、根生物量)均高于对照,其中根生物量的增长程度最大;根中碳含量及分配比例均显著提高,而地上部位的碳含量则显著降低(P<0.05).氮沉降对土壤活性碳库具有显著影响,各活性碳库含量均以5 g N·m^-2·a^-1处理最高,氮沉降对各活性碳库的影响程度依次为CHC(碳水化合物碳)＞LBC(易氧化有机碳)＞DOC(水溶性有机碳)＞MBC(微生物量碳),氮沉降与淹水条件的耦合作用有利于活性碳的释放;回归分析表明,土壤活性碳库与小叶章相关参数间存在显著相关性.氮沉降显著提高了小叶章植株生物量及土壤的活性碳含量.     

Carbon stocks,sequestration, and emissions of wetlands in south eastern Australia

Nontidal wetlands are estimated to contribute significantly to the soil carbon pool across the globe. However, our understanding of the occurrence and variability of carbon storage between wetland types and across regions represents a major impediment to the ability of nations to include wetlands in greenhouse gas inventories and carbon offset initiatives. We performed a large‐scale survey of nontidal wetland soil carbon stocks and accretion rates from the state of Victoria in south‐eastern Australia—a region spanning 237,000 km² and containing >35,000 temperate, alpine, and semi‐arid wetlands. From an analysis of >1,600 samples across 103 wetlands, we found that alpine wetlands had the highest carbon stocks (290 ± 180 Mg C_org ha^?1), while permanent open freshwater wetlands and saline wetlands had the lowest carbon stocks (110 ± 120 and 60 ± 50 Mg C_org ha^?1, respectively). Permanent open freshwater sites sequestered on average three times more carbon per year over the last century than shallow freshwater marshes (2.50 ± 0.44 and 0.79 ± 0.45 Mg C_org ha^?1 year^?1, respectively). Using this data, we estimate that wetlands in Victoria have a soil carbon stock in the upper 1 m of 68 million tons of C_org, with an annual soil carbon sequestration rate of 3 million tons of CO₂ eq. year^?1—equivalent to the annual emissions of about 3% of the state's population. Since European settlement (~1834), drainage and loss of 260,530 ha of wetlands may have released between 20 and 75 million tons CO₂ equivalents (based on 27%–90% of soil carbon converted to CO₂). Overall, we show that despite substantial spatial variability within wetland types, some wetland types differ in their carbon stocks and sequestration rates. The duration of water inundation, plant community composition, and allochthonous carbon inputs likely play an important role in influencing variation in carbon storage.     

Carbon sequestration in freshwater wetlands in Costa Rica and Botswana

Tropical wetlands are typically productive ecosystems that can introduce large amounts of carbon into the soil. However, high temperatures and seasonal water availability can hinder the ability of wetland soils to sequester carbon efficiently. We determined the carbon sequestration rate of 12 wetland communities in four different tropical wetlands—an isolated depressional wetland in a rainforest, and a slow flowing rainforest swamp, a riverine flow-through wetland with a marked wet and dry season, a seasonal floodplain of an inland delta—with the intention of finding conditions that favor soil carbon accumulation in tropical wetlands. Triplicate soil cores were extracted in these communities and analyzed for total carbon content to determine the wetland soil carbon pool. We found that the humid tropic wetlands had greater carbon content (P ≤ 0.05) than the tropical dry ones (96.5 and 34.8 g C kg^?1, respectively). While the dry tropic wetlands had similar sequestration rates (63 ± 10 g Cm^?2 y^?1 on average), the humid tropic ones differed significantly (P < 0.001), with high rates in a slow-flowing slough (306 ± 77 g Cm^?2 y^?1) and low rates in a tropical rain forest depressional wetland (84 ± 23 g Cm^?2 y^?1). The carbon accumulating in all of these wetlands was mostly organic (92–100%). These results suggest the importance of differentiating between types of wetland communities and their hydrology when estimating overall rates at which tropical wetlands sequester carbon, and the need to include tropical wetland carbon sequestration in global carbon budgets.     

Consequences of Lemur Loss for Above-Ground Carbon Stocks in a Malagasy Rainforest

Anthropogenic disturbances have resulted in declines of seed-dispersing primate frugivores in tropical forests. Previous work has suggested that loss of seed dispersal by large frugivores may have a negative impact on ecosystem carbon storage by reducing tree biomass. However, we know little about the potential impacts of losing frugivores in Madagascar’s diverse rainforest ecosystem. Understanding the effects of frugivore extinction on carbon loss is relevant in Madagascar, where threatened lemur taxa are the only dispersers of many large-seeded plant species. Using a dataset of tree species composition and traits from the southeastern rainforests of Ranomafana National Park, we examined whether seed size and lemur-dependent dispersal are positively associated with above-ground tree biomass. We then simulated different scenarios of population declines of large-seeded trees (>10 mm seed length) dependent on lemur-mediated seed dispersal, to examine potential directional changes in carbon storage capacity of Malagasy forests under lemur loss. Lemur-dispersed tree species, which have large seeds, had higher above-ground biomass than other species. Our simulations showed that the loss of large frugivorous primates in Madagascar may decrease the forest’s potential to store carbon. These results demonstrate the importance of primate conservation for maintaining functioning ecosystems and forest carbon stocks in one of the world’s hottest hotspots of biodiversity.     

Linkage of MIKE SHE to Wetland-DNDC for carbon budgeting and anaerobic biogeochemistry simulation

This study reports the linkage between MIKE SHE and Wetland-DNDC for carbon dynamics and greenhouse gases (GHGs) emissions simulation in forested wetland.Wetland-DNDC was modified by parameterizing management measures, refining anaerobic biogeochemical processes, and was linked to the hydrological model – MIKE SHE. As a preliminary application, we simulated the effect of water table position and forest management practices on GHGs emissions and carbon dynamics to test the capabilities of the models for simulating seasonal and long-term carbon budget. Simulation results show that water table changes had a remarkable effect on GHGs fluxes. Anaerobic conditions in forested wetland soils reduce organic matter decomposition and stimulate CH₄ production. Decrease in the water table from the wetland surface decreases methane flux, while CO₂ emission was lower with a rise in the water table. When there is a drop in water availability, wetlands can become a net source of atmospheric CO₂ as photosynthesis is decreased and respiration loss enhanced. Forest management activities i.e. harvest, fertilization and reforestation practices were parameterized in the model. We predicted carbon fluxes and stores on a pine forest under different forest management scenarios during 160 years. Results show that average long-term carbon storage in ecosystem pools increased with increasing rotation length; Soil carbon showed only minor, long-term responses to harvesting events. In contrast, carbon sequestered in tree biomass and litter fluctuated widely, in concert with the harvest cycle. Application of nitrogen fertilizer increased average carbon storage in all ecosystem pools and wood products. We presented the linkage of MIKE SHE and Wetland-DNDC as a way to use of simulation modeling tools for assessing GHGs mitigation strategies, carbon budgeting and forest management.     

Trade‐offs between savanna woody plant diversity and carbon storage in the Brazilian Cerrado

Incentivizing carbon storage can be a win‐win pathway to conserving biodiversity and mitigating climate change. In savannas, however, the situation is more complex. Promoting carbon storage through woody encroachment may reduce plant diversity of savanna endemics, even as the diversity of encroaching forest species increases. This trade‐off has important implications for the management of biodiversity and carbon in savanna habitats, but has rarely been evaluated empirically. We quantified the nature of carbon‐diversity relationships in the Brazilian Cerrado by analyzing how woody plant species richness changed with carbon storage in 206 sites across the 2.2 million km² region at two spatial scales. We show that total woody plant species diversity increases with carbon storage, as expected, but that the richness of endemic savanna woody plant species declines with carbon storage both at the local scale, as woody biomass accumulates within plots, and at the landscape scale, as forest replaces savanna. The sharpest trade‐offs between carbon storage and savanna diversity occurred at the early stages of carbon accumulation at the local scale but the final stages of forest encroachment at the landscape scale. Furthermore, the loss of savanna species quickens in the final stages of forest encroachment, and beyond a point, savanna species losses outpace forest species gains with increasing carbon accumulation. Our results suggest that although woody encroachment in savanna ecosystems may provide substantial carbon benefits, it comes at the rapidly accruing cost of woody plant species adapted to the open savanna environment. Moreover, the dependence of carbon‐diversity trade‐offs on the amount of savanna area remaining requires land managers to carefully consider local conditions. Widespread woody encroachment in both Australian and African savannas and grasslands may present similar threats to biodiversity.     

Carbon storage dynamics of temperate freshwater wetlands in Pennsylvania

Healthy wetlands play a significant role in climate change mitigation by storing carbon that would otherwise contribute to global warming, leading to the reduction of water and food resources as well as more extreme weather phenomena. Investigating the magnitude of carbon storage potential of different freshwater wetland systems using multiple ecological indicators at varying spatial scales provides insight and justification for selective wetland restoration and conservation initiatives. We provide a holistic accounting of total carbon values for 193 wetland sites, integrating existing carbon algorithms to rapidly assess each of the following carbon pools: above-ground, below-ground, soil, woody debris, shrub cover, and herbaceous cover. Aspects of soil, vegetation, and ecosystem characteristics and stressors were measured to obtain an overall understanding of the ecosystems ability to store carbon (long-term) along a gradient of human disturbance. Based on a review of the literature, methods were prioritized based on the initial data available from field measurements as well as their practicality and ease in replicating the process in the future. Lacustrine human impounded (88.7?±?18.0 tC/ha), riverine beaver impounded (116.2?±?29.4 tC/ha), riverine upper perennial (163.3?±?11.8 tC/ha), riverine lower perennial (199.2?±?24.7 tC/ha), riverine headwater complex (159.5?±?22.2 tC/ha), perennial/seasonal depression (269.6?±?42.4 tC/ha), and slope (162.2?±?14.6 tC/ha) wetland types were compared. Overall results showed moderate variability (9.33–835.95 tC/ha) for total carbon storage values across the wetland types, with an average total carbon storage of 174.6?±?8.8 tC/ha for all wetlands. Results show that carbon storage was significantly higher (p?=?0.002) in least disturbed wetland sites. Apart from perennial/seasonal depression wetlands, all reference standard wetlands had greater carbon storage, less disturbance impact, and a greater extent of forest cover than non-reference wetlands. Carbon storage values calculated were comparable to published literature.     

Temperature and Microtopography Interact to Control Carbon Cycling in a High Arctic Fen

High arctic wetlands hold large stores of soil carbon (C). The fate of these C stores in a changing climate is uncertain, as rising air temperatures may differentially affect photosynthesis and ecosystem respiration (ER). In this study, open-top warming chambers were used to increase air and soil temperatures in contrasting microtopographic positions of a high arctic fen in NW Greenland. CO₂ exchange between the ecosystem and the atmosphere was measured on 28 dates over a 3-year period. Measurements of the normalized difference vegetation index, leaf and stem growth, leaf-level gas exchange, leaf nitrogen, leaf δ¹³C, and fine root production were made to investigate the mechanisms and consequences of observed changes in CO₂ exchange. Gross ecosystem photosynthesis (GEP) increased with chamber warming in hollows, which are characterized by standing water, and in hummocks, which extend above the water table. ER, however, increased only in hummocks, such that net ecosystem exchange (NEE) increased in hollows, but did not change in hummocks with chamber warming. Complementary measurements of plant growth revealed that increases in GEP corresponded with increases in C allocation to aboveground biomass in hummocks and belowground biomass in hollows. Our results and those of several recent studies clearly demonstrate that effects of climate change on the C balance of northern wetlands will depend upon microtopography which, in turn, may be sensitive to climate change.