The potential response of global terrestrial carbon storage to a climate change

An analysis is undertaken to examine the potential impacts of a global climate change on patterns of potential terrestrial C storage and resulting fluxes between terrestrial and atmospheric pools. A bioclimatic model relating the current distribution of vegetation to global climate patterns is used to examine the potential impacts of a global climate change on the global distribution of vegetation. Climate change scenarios are based on the predictions of two general circulation model equilibrium simulations for a 2XCO₂ atmosphere. Current estimates of C reserves in the vegetation types and associated soils are then used to calculate changes in potential terrestrial C storage under the two climate change scenarios. Results suggest a potential negative feedback to increasing atmospheric concentrations of CO₂, with the potential for terrestrial C storage increasing under both scenarios. These results represent an equilibrium analysis, assuming the vegetation and soils have tracked the spatial changes in climate patterns. An approach for providing an estimate of the transient response between the two equilibria (i.e., current and 2XCO₂ climates) is presented. The spatial transitions in vegetation predicted by the equilibrium analyses are classified as to the processes controlling the transition (eg., succession, dieback, species immigration). Estimates of the transfer rates related to these processes are then used to estimate the temporal dynamics of the vegetation/soils change and the associated C pools. Results suggest that although the equilibrium analyses show an increased potential for C storage under the climate change, in the transient case the terrestrial surface acts as a source of CO₂ over the first 50 to 100 yrs following climate change.     

Vegetation redistribution: A possible biosphere source of CO2 during climatic change

A new biogeographic model, MAPSS, predicts changes in vegetation leaf area index (LAI), site water balance and run off, as well as changes in Biome boundaries. Potential scenarios of equilibrium vegetation redistribution under 2 × CO₂ climate from five different General Circulation Models (GCMs) are presented. In general, large spatial shifts in temperate and boreal vegetation are predicted under the different scenarios; while, tropical vegetation boundaries are predicted (with one exception) to experience minor distribution contractions. Maps of predicted changes in forest LAI imply drought-induced losses of biomass over most forested regions, even in the tropics. Regional patterns of forest decline and dieback are surprisingly consistent among the five GCM scenarios, given the general lack of consistency in predicted changes in regional precipitation patterns. Two factors contribute to the consistency among the GCMs of the regional ecological impacts of climatic change: 1) regional, temperature-induced increases in potential evapotranspiration (PET) tend to more than offset regional increases in precipitation; and, 2) the unchanging background interplay between the general circulation and the continental margins and mountain ranges produces a fairly stable pattern of regionally specific sensitivity to climatic change. Two areas exhibiting among the greatest sensitivity to drought-induced forest decline are eastern North America and eastern Europe to western Russia. Drought-induced vegetation decline (losses of LAI), predicted under all GCM scenarios, will release CO₂ to the atmosphere; while, expansion of forests at high latitudes will sequester CO₂. The imbalance in these two rate processes could produce a large, transient pulse of CO₂ to the atmosphere.     

Future productivity of fallow systems in Sub-Saharan Africa: Is the effect of demographic pressure and fallow reduction more significant than climate change?

In this century climate change is assumed to be the major driver for changes in agricultural systems and crop productivity at the global scale. However, due to spatial differences in cropping systems and in the magnitude of climatic change regional variations of climate change impact are expected. Furthermore, the recent climate projections are highly uncertain for large parts of West Africa. In particular with respect to annual precipitation and variability the projections vary between trends with decreasing precipitation and trends with slightly increasing precipitation within the next decades. On the other hand, the extensive fallow systems in this region suffer from increasing population pressure, which compromises soil fertility restoration. In the Republic of Benin, the demographic projections for the first half of this century indicate a continuous growth of the population with a narrow interval of confidence. Thus, in the absence of an adequate soil fertility management with judicious use of mineral fertilizers, the soil degradation process with decreasing crop yields is expected to continue. The objective of this paper was, therefore, to quantify the regional effect of future population growth on crop yields in West Africa and to compare it with the potential effects of climate change scenarios. Three land use scenarios (L1, L2 and L3) for the Upper Ouémé catchment where derived from different demographic projections combined with assumptions regarding future road networks and legal frameworks for forest protection using the CLUE-S modeling approach. The fallow-cropland ratio decreased in the three scenarios from 0.87 in the year 2000 to 0.66, 0.48 and 0.68 for L1, L2 and L3, respectively in 2050. Based on the projected ratio of fallow and cropland, trends of maize yield for the three land use scenarios were calculated using the EPIC (Environmental Policy Integrated Climate) model coupled with a spatial database. Maize yields followed the decreasing trend of the fallow-cropland ratio and estimated yield reductions amounted to up to 24% in the period 2021-2050. This trend was compared with the impact of the SRES climate scenarios A1B and B1 based on the output of the GCM ECHAM5 downscaled with the REMO model and the A1B scenario output of the GCM HADC3Q0 downscaled with the RCMs SMHIRCA and HADRM3P. The yield reductions due to the projected climate change in the three models accounted for a yield decrease of up to 18% (REMO A1B scenario) in the same period. Taking into account the smaller uncertainties in the scenario assumptions and in the model output of the land use scenarios, it is concluded that, in low input fallow systems in West Africa, land use effects will be at least as important as climate effects within the next decades.     

Modeling the effects of climatic and co2 changes on grassland storage of soil C

We present results from analyses of the sensitivity of global grassland ecosystems to modified climate and atmospheric CO₂ levels. We assess 31 grassland sites from around the world under two different General Circulation Models (GCM) double CO₂ climates. These grasslands are representative of mostly naturally occurring ecosystems, however, in many regions of the world, grasslands have been greatly modified by recent land use changes. In this paper we focus on the ecosystem dynamics of natural grasslands. The climate change results indicate that simulated soil C losses occur in all but one grassland ecoregion, ranging from 0 to 14% of current soil C levels for the surface 20 cm. The Eurasian grasslands lost the greatest amount of soil C (～1200 g C m^?2) and the other temperate grasslands losses ranged from 0 to 1000 g C m^?2, averaging approximately 350 g C m^?2. The tropical grasslands and savannas lost the least amount of soil C per unit area ranging from no change to 300 g C m^?2 losses, averaging approximately 70 g C m^?2. Plant production varies according to modifications in rainfall under the altered climate and to altered nitrogen mineralization rates. The two GCM's differed in predictions of rainfall with a doubling of CO₂, and these differences are reflected in plant production. Soil decomposition rates responded most predictably to changes in temperature. Direct CO₂ enhancement effects on decomposition and plant production tended to reduce the net impact of climate alterations alone.     

农田土壤有机碳固存的主要影响因子及其稳定机制

农田生态系统作为陆地生态系统的重要组成部分,在陆地生态系统碳循环过程中发挥重要作用。明确影响农田土壤有机截获的主要因素及土壤固碳的稳定机制,有助于控制和加强农田土壤碳库的固碳潜力,以及正确评价农业生产对全球气候变化的影响。因此,本文综合论述了影响农田土壤碳含量的自然和人为因素,详细阐述了土壤碳固定的物理、化学和生物稳定机制。并总结了已有研究的不足,对今后土壤固碳研究中的热点问题进行了展望。认为从土壤微生物学角度出发,深入研究微生物在土壤有机碳循环中的作用机制,并将地上部和地下部生态系统联系起来探讨土壤碳素稳定性机制更具有重要的意义。     

Aspects of the interaction between vegetation and soil under global change

Responses of terrestrial ecosystems to a world undergoing a change in atmospheric CO₂ concentration presents a formidable challenge to terrestrial ecosystem scientists. Strong relationships among climate, atmosphere, soils and biota at many different temporal and spatial scales make the understanding and prediction of changes in net ecosystem production (NEP) at a global scale difficult. Global C cycle models have implicitly attempted to account for some of this complexity by adapting lower pool sizes and smaller flux rates representing large regions and long temporal averages than values appropriate for a small area. However, it is becoming increasingly evident that terrestrial ecosystems may be experiencing a strong transient forcing as a result of increasing levels of atmospheric CO₂ that will require a finer temporal and spatial representation of terrestrial systems than the parameters for current global C cycle models allow. To adequately represent terrestrial systems in the global C cycle it is necessary to explicitly model the response of terrestrial systems to primary environmental factors. While considerable progress has been made experimentally and conceptually in aspects of photosynthetic responses, and gross and net primary production, the application of this understanding to NEP at individual sites is not well developed. This is an essential step in determining effects of plant physiological responses on the global C cycle. We use a forest stand succession model to explore the effects of several possible plant responses to elevated atmospheric CO₂ concentration. These simulations show that ecosystem C storage can be increased by increases in individual tree growth rate, reduced transpiration, or increases in fine root production commensurate with experimental observations.     

An integrated analysis of sulfur emissions,acid deposition and climate change

This paper presents one of the first integrated analyses of acidification and climate change on a geographically-detailed basis, and the first linkage of integrated models for acid deposition (RAINS) and for climate change (IMAGE 2). Emphasis in this paper is on Europe. Trends in driving forces of emissions are used to compute anthropogenic SO₂ emissions in 13 world regions. These emissions are translated into regional patterns of sulfur deposition in Europe and global patterns of sulfate aerosols using source-receptor matrices. Changes in climate are then computed based on changes in sulfate and greenhouse gases. Finally, we compute ecosystem areas affected by acid deposition and climate change based on exceedances of critical loads and changes in potential vegetation. Using this framework, information from global and regional integrated models can be used to link sulfur emissions with both their global and regional consequences. Preliminary calculations indicate that the size of European area affected by climate change in 2100 (58%) will be about the same as that affected by acid deposition in 1990. By the mid 21st century, about 14% of Europe's area may be affected by both acid deposition and climate change. Also, reducing sulfur emissions in Europe will have both the desirable impact of reducing the area affected by acid deposition, and the undesirable impact of enhancing climate warming in Europe and thus increasing the area affected by climate change. However, for the scenarios in this paper, the desirable impact of reducing sulfur emissions greatly outweighs its undesirable impact.     

基于CLIGEN和GCM模型预测未来40年黄土丘陵沟壑区的气候变化——以安塞为例

为预测3种温室气体排放情景（A2、B2和GGa1）下未来40年黄土丘陵沟壑区的气候变化,利用安塞试验站1986—2003年的气候观测资料以及1986—2049年GCM（HadCM3）栅格数据,通过空间转换和时间转换,利用CLIGEN和GCM模型,预测未来40年以安塞为代表的黄土高原丘陵沟壑区的气候变化。结果表明：与当前条件相比,到2049年,A2、B2和GGa1 3种情景下预测的降雨量分别增加37%、22%和12%;3种情景下预测的最大月均降雨量出现在夏季;到2049年,A2、B2和GGa1 3种情景下预测的月均最低气温和月均最高气温皆增加,但差异不明显,年均最低气温和年均最高气温分别增加1.41-1.56℃和0.92-1.57℃。     

Modeling potential changes of forest area in Thailand under climate change

The forest cover of Thailand has been characterized according to the Holdridge Life Zone Classification, a model that correlates climatic features with vegetation distribution. Six Holdridge life zone types of forest cover are found in Thailand: subtropical dry forest, subtropical moist forest, subtropical wet forest, tropical dry forest, tropical moist forest, and tropical wet forest. Climate change scenarios were simulated by three general circulation models: two United Kingdom Meteorological Office models (the low and high resolution versions) and the Goddard Institute for Space Studies model. These scenarios were used to simulate the effects of future climate change on Thai forests. The ratios of precipitation and the absolute values of temperature changes were incorporated into a baseline climate scenario from the International Institute of Applied Systems Analysis. Under the climate change scenarios simulated by the three general circulation models, the subtropical dry forest could potentially disappear, and areas of tropical very dry forest would appear. In general, the area of subtropical life zone would decline from about 50% to 20%–12% of total cover, whereas the tropical life zone would expand its cover from 45% to 80%. All three general circulation model scenarios suggest that the tropical dry forest has the greatest potential to extend into the subtropical moist forest. This analysis suggests that global climate change would have a profound effect on the future distribution and health of Thai forests.     

Landscape‐scale modelling of erosion processes and soil carbon dynamics under land‐use and climate change in agroecosystems

Soil organic carbon (SOC) sequestration and soil redistribution are linked to soil properties, land use, farming system and climate. In a global‐change context, landscape and climate changes are expected and will most probably have impacts on changes in the soil. Soil change was simulated from 2010 to 2100 in an 86‐ha hedgerow landscape under different scenarios of landscape and climate changes. These scenarios combined contrasting land uses, hedgerow networks and climates. Two models were combined to evaluate the impact of these scenarios on soils: LandSoil, a soil redistribution model, and a SOC model based on RothC‐26.3. A soil thickness of 105 cm was considered. The results indicate that the main factor influencing soil degradation was land‐use change: when compared with the baseline business‐as‐usual landscape, the landscape with the most intensive agricultural systems had the greatest soil erosion (+0.26 t ha^?1 year^?1) and reduced mean SOC stocks (?17 t ha^?1 after 90 years). The second significant factor was climate change, followed by hedgerow network density. Sensitivity to climate change differed between landscapes, and the most sensitive were those with continuous winter wheat. The results indicate that a hedgerow landscape is well adapted to protect soil (regarding carbon storage and soil erosion) in a context of climate change. However, this type of landscape is highly sensitive to cropping intensification and should be protected.     

Integrated model systems for national assessments of the effects of climate change: Applications in New Zealand and Bangladesh

To examine the sensitivity of environmental systems to climatic variability and change, integrated model systems for climate impact assessment are being developed for New Zealand (CLIMPACTS) and Bangladesh (BDCLIM). Features common to both model systems include a global climate model, regional modules for generating climate scenarios, and models for biophysical impact analyses. For CLIMPACTS, modified ecosystem models for horticultural crops, arable crops, and pasture production are being incorporated. For BDCLIM, the emphasis is on analysis ofpossible changes in agroclimatic zones and hydrology, including the risks of floods and droughts. The initial emphasis of both systems is on nationwide spatial analyses, using simplified models as much as possible. The development of integrated model systems supports the needs of the respective countries in assessing scientific uncertainties, evaluating vulnerabilities, and identifying adaptation options as a basis for international reporting requirements under the U.N. Framework Convention on Climate Change and for policy and planning at national and regional levels. The major advantage of such integrated model systems is that they can readily be updated as the science of climate change advances, thus providing an evolving tool for future reassessments of climate impacts.     

Vulnerability assessment of Angat water reservoir to climate change

Global warming due to an anticipated doubling of carbon dioxide concentration in the atmosphere is expected to alter the earth's climate system within the next century. The potential changes in the climate system could affect hydrological cycles and processes. Possible impacts of climate change on water resources should be assessed to evaluate probable adaptation measures. In the Philippines, a preliminary assessment of the vulnerability of water resources to climate change and variability was undertaken. For this particular study, the Angat Reservoir was chosen as the study area. Because of its socioeconomic importance, it is useful to assess its vulnerability to climate change. A rainfall-runoff simulation model, WATBAL, was used to determine the effect of temperature and rainfall changes, based on CO₂ doubling, on inflow to the reservoir. Climate change scenarios developed from results from three general circulation models and incremental changes were used. The results showed that changes in temperature and rainfall could affect runoff either positively or negatively. Using the temperature and rainfall changes from the Geophysical Fluid Dynamics Laboratory model there was a 32% increase in runoff, and with the Canadian Climate Centre Model, there was a 15% decrease in runoff. Under a climate scenario generated by the United Kingdom Meteorological Office model, runoff is estimated to increase by 5%. The use of incremental scenarios revealed the strong sensitivity of runoff to changes in rainfall as compared with changes in temperature.     

VEGETATION RESPONSE TO GLOBAL WARMING: THE ROLE OF HYSTERESIS EFFECT

A new approach is proposed for the evaluation of vegetation equilibrium response to global warming. The approach considers the dependence of the position of biome boundaries as significantly multi-valued function of climatic conditions; the reason for the multiplicity may be partly due to capacity of vegetation to change its environment. This result in hysteresis manifestations (threshold and irreversibility effects) in response to climate change. Matthews' global vegetation data set and IIASA climatic data base were used to reconstruct the domains of different biomes in a space of climatic factors (biotemperature and average precipitation). Based on the overlap of these domains, the maps of biomes' potential extent are calculated for present climate and for two scenarios of global warming (GISS and GFDL). These results imply a significant role for hysteresis phenomena in the global vegetation pattern. Maps of vegetation changes under two climate scenarios calculated with the help of a new algorithm to account for hysteresis indicate much less change than equivalent maps obtained by other equilibrium approaches under the two climate change scenarios. Changes are predicted for 20% of terrestrial area. A relatively small increase of forest and decrease of nonforest vegetation area predicted by both scenarios.     

Contrasting Effects of Aridity and Grazing Intensity on Multiple Ecosystem Functions and Services in Australian Woodlands

Global change is expected to reduce the provision of multiple ecosystem services in drylands, the largest biome on Earth. Understanding the relative importance of climate change and overgrazing on ecosystems services is critical for predicting the effects of global change on ecosystem well‐being. We generated a system‐level understanding of the effects of climate (aridity intensity) and land use intensification (herbivore grazing intensity) on four regulating ecosystem services (C‐storage, N‐availability and P‐availability, and organic matter decomposition) and one provisioning service (plant production) in wooded drylands from eastern Australia. Climate change and grazing intensity had different effects on multiple ecosystem services. Increasing aridity from 0·19 (dry subhumid) to 0·63 (arid) had consistent suppressive effects on C‐storage, N‐availability, decomposition and plant biomass services, but not on P‐availability. The magnitude of these suppressive effects was greater than any effects due to grazing. All sites showed evidence of kangaroo grazing, but the heaviest grazing was due to cattle (dung: range 0–4545 kg ha⁻¹; mean 142 kg ha⁻¹). Any effects of grazing on ecosystem services were herbivore specific and ranged from positive to neutral or negative. Sheep, and to a lesser extent cattle, were associated with greater N‐availability. Rabbits, however, had a greater effect on P‐availability than aridity. Our study suggests that increases in livestock grazing may fail to sustain ecosystem services because of the generally stronger negative effect of increasing aridity on most ecosystem services in our model dryland. These services are likely therefore to decline with global increases in aridity. Copyright © 2017 John Wiley & Sons, Ltd.     

Effects of grazing on CO2 balance in a semiarid steppe: field observations and modeling

Purpose

Carbon (C) dynamics in grassland ecosystem contributes to regional and global fluxes in carbon dioxide (CO₂) concentrations. Grazing is one of the main structuring factors in grassland, but the impact of grazing on the C budget is still under debate. In this study, in situ net ecosystem CO₂ exchange (NEE) observations by the eddy covariance technique were integrated with a modified process-oriented biogeochemistry model (denitrification–decomposition) to investigate the impacts of grazing on the long-term C budget of semiarid grasslands.

Materials and methods

NEE measurements were conducted in two adjacent grassland sites, non-grazing (NG) and moderate grazing (MG), during 2006–2007. We then used daily weather data for 1978–2007 in conjunction with soil properties and grazing scenarios as model inputs to simulate grassland productivity and C dynamics. The observed and simulated CO₂ fluxes under moderate grazing intensity were compared with those without grazing.

Results and discussion

NEE data from 2-year observations showed that moderate grazing significantly decreased grassland ecosystem CO₂ release and shifted the ecosystem from a negative CO₂ balance (releasing 34.00 g C?m^?2) at the NG site to a positive CO₂ balance (absorbing ?43.02 g C?m^?2) at the MG site. Supporting our experimental findings, the 30-year simulation also showed that moderate grazing significantly enhances the CO₂ uptake potential of the targeted grassland, shifting the ecosystem from a negative CO₂ balance (57.08?±?16.45 g C?m^?2?year^?1) without grazing to a positive CO₂ balance (?28.58?±?14.60 g C?m^?2?year^?1) under moderate grazing. The positive effects of grazing on CO₂ balance could primarily be attributed to an increase in productivity combined with a significant decrease of soil heterotrophic respiration and total ecosystem respiration.

Conclusions

We conclude that moderate grazing prevails over no-management practices in maintaining CO₂ balance in semiarid grasslands, moderating and mitigating the negative effects of global climate change on the CO₂ balance in grassland ecosystems.     

Global forest systems: An uncertain response to atmospheric pollutants and global climate change?

Forest systems cover more than 4.1×10⁹ ha of the Earth's land area. The future response and feedbacks of forest systems to atmospheric pollutants and projected climate change may be significant. Boreal, temperate and tropical forest systems play a prominent role in carbon (C), nitrogen (N) and sulfur (S) biogeochemical cycles at regional and global scales. The timing and magnitude of future changes in forest systems will depend on environmental factors such as a changing global climate, an accumulation of CO₂ in the atmosphere, and increase global mineralization of nutrients such as N and S. The interactive effects of all these factors on the world's forest regions are complex and not intuitively obvious and are likely to differ among geographic regions. Although the potential effects of some atmospheric pollutants on forest systems have been observed or simulated, large uncertainty exists in our ability to project future forest distribution, composition and productivity under transient or nontransient global climate change scenarios. The potential to manage and adapt forests to future global environmental conditions varies widely among nations. Mitigation practices, such as liming or fertilization to ameliorate excess NO_x or SO_x or forest management to sequester CO₂ are now being applied in selected nations worldwide.The U.S. Government's right to a non-exclusive, royalty free licence in and to any copyright is acknowledged.     

Effects of simulated nitrogen deposition on soil respiration components and their temperature sensitivities in a semiarid grassland

Nitrogen (N) deposition to semiarid ecosystems is increasing globally, yet few studies have investigated the ecological consequences of N enrichment in these ecosystems. Furthermore, soil CO₂ flux – including plant root and microbial respiration – is a key feedback to ecosystem carbon (C) cycling that links ecosystem processes to climate, yet few studies have investigated the effects of N enrichment on belowground processes in water-limited ecosystems. In this study, we conducted two-level N addition experiments to investigate the effects of N enrichment on microbial and root respiration in a grassland ecosystem on the Loess Plateau in northwestern China. Two years of high N additions (9.2 g N m⁻² y⁻¹) significantly increased soil CO₂ flux, including both microbial and root respiration, particularly during the warm growing season. Low N additions (2.3 g N m⁻² y⁻¹) increased microbial respiration during the growing season only, but had no significant effects on root respiration. The annual temperature coefficients (Q₁₀) of soil respiration and microbial respiration ranged from 1.86 to 3.00 and 1.86 to 2.72 respectively, and there was a significant decrease in Q₁₀ between the control and the N treatments during the non-growing season but no difference was found during the growing season. Following nitrogen additions, elevated rates of root respiration were significantly and positively related to root N concentrations and biomass, while elevated rates of microbial respiration were related to soil microbial biomass C (SMBC). The microbial respiration tended to respond more sensitively to N addition, while the root respiration did not have similar response. The different mechanisms of N addition impacts on soil respiration and its components and their sensitivity to temperature identified in this study may facilitate the simulation and prediction of C cycling and storage in semiarid grasslands under future scenarios of global change.     

Impacts of climate change on irrigated potato production in a humid climate

The impacts of climate change on the irrigation water requirements and yield of potatoes (Solanum tuberosum L.) grown in England have been assessed, by combining the downscaled outputs from an ensemble of general circulation models (GCM) with a potato crop growth model. The SUBSTOR-Potato model (embedded within the DSSAT program) was used to simulate the baseline and future irrigation needs (mm) and yield (t ha⁻¹) for selected emissions scenario (SRES A1FI and B1) for the 2050s, including CO₂ fertilisation effects. The simulated baseline yields were validated against independent experimental and field data using four reference sites. Probabilistic distribution functions and histograms were derived to assess GCM modelling uncertainty on future irrigation needs. Assuming crop husbandry factors are unchanged, farm yields would show only marginal increases (3-6%) due to climate change owing to limitations in nitrogen availability. In contrast, future potential yields, without restrictions in water or fertiliser, are expected to increase by 13-16%. Future average irrigation needs, assuming unconstrained water availability, are predicted to increase by 14-30%, depending on emissions scenario. The present ‘design’ capacity for irrigation infrastructure would fail to meet future peak irrigation needs in nearly 50% of years. Adaptation options for growers to cope with these impacts are discussed.     

Modeling Regional Carbon Dynamics and Soil Erosion in Disturbed and Rehabilitated Ecosystems as Affected by Land Use and Climate

The quantification of carbon (C) and nitrogen (N) cycling inecosystems is important for (a) understanding changes inecosystem structure and function with changes in land use, (b)determining the sustainability of ecosystems, and (c) balancingthe global C budget as it relates to global climate change.A meso-scale study was conducted to determine regional effectsof climate change on C and N cycling within disturbedecosystems. Objectives of the research were to quantify (a)sediment yield, (b) current C storage in vegetation and soils,and (c) soil C efflux from both abandoned and rehabilitatedcoal surface-mined lands in Ohio. A dynamic model was developedto simulate sediment yield, grassland production, and C and Ncycling on surface-mined lands. Evaluation of plant productionand soil erosion submodels with data sets from surface-minedlands in the mid-western U.S. resulted in r² values of 0.99 and0.97, respectively. Depending on the initial values of soil organic carbon (SOC),model simulations estimated that unvegetated surface-mined landsin Ohio yield approximately 441,325 Mg yr^-1 of sediment andemit between 2,000–20,000 Mg yr^-1 of C to the atmosphere fromdecomposition of SOC. While rehabilitated lands had a higher Cefflux rate than barren lands, a positive C sequestration rateof 18.4 Mg km^-2 yr ^-1 was estimated as a result oforganic matter additions. This sequestion rate increasedconsiderably under projected climate change scenarios, while itdecreased when simulated rehabilitated grasslands were harvestedfor hay. Changes in land use and cover can cause surface-minedlands to be either a net sink or source for C. Successful rehabilitation of mined lands can decrease erosion and promotesoil C sequestration, while at the same time providingadditional lands for the management of natural resources.     

Can barley (Hordeum vulgare L. s.l.) adapt to fast climate changes? A controlled selection experiment

The projected future climate will affect the global agricultural production negatively, however, to keep abreast of the expected increase in global population, the agricultural production must increase. Therefore, to safeguard the future crop yield and quality, the adaptive potential of crops to environmental change needs to be explored in order to select the most productive genotypes. Presently, it is unknown whether cereal crops like spring barley can adapt to climate stressors over relatively few generations. To evaluate if strong selection pressures could change the performance of barley to environmental stress, we conducted a selection experiment over five plant generations (G0–G4) in three scenarios, where atmospheric [CO₂] and temperature were increased as single factors and in combination. The treatments represented the expected environmental characteristics in Northern Europe around year 2075 [700 ppm CO₂, 22/17 °C (day/night)] as well as a control mimicking present day conditions (390 ppm CO₂, 19/12 °C). Two different barley accessions, a modern cultivar and an old landrace, were evaluated in terms of yield and biomass production. In all treatments representing future environmental scenarios, the G4-generation of selected plants did not improve its reproductive output compared to the G0-generation, as G4 produced less seeds and had a lower yield than unselected plants. These results indicate that barley might not respond positively to rapid and strong selection by elevated [CO₂] and temperature, contrary to previous results from oilseed rape. The two barley accessions analyzed presented almost the same response pattern in a given treatment, though the modern cultivar had the highest yield in the climate scenarios, while the landrace was superior in yield under present day climate conditions.