Carbon Sequestration In Grasslands Research Articles

Estimation, Spatiotemporal Dynamics, and Driving Factors of Grassland Biomass Carbon Storage Based on Machine Learning Methods: A Case Study of the Hulunbuir Grassland

Precisely estimating the grassland biomass carbon storage is vital for evaluating grassland carbon sequestration potential and the monitoring and management of grassland resources. With the increasing intensity of climate change (CC) and human activities (HA), it is necessary to explore spatiotemporal variations in biomass carbon storage and its response to CC and HA. In this study, we focused on the Hulunbuir Grassland, utilizing sample plots data, MODIS data, environmental factors (terrain, soil, and climate), location factor, and texture characteristics to assess the performance of four machine learning algorithms: random forest, support vector machine, gradient boosting decision tree, and extreme gradient boosting in estimating grassland aboveground biomass (AGB). Based on the optimal model combined with root-shoot ratio data, grassland distribution data, and carbon content coefficients, the spatiotemporal characteristics and driving factors of biomass carbon storage from 2001–2022 were analyzed. The results showed that (1) the random forest achieved the highest prediction accuracy for grassland AGB, making it appropriate for AGB estimation in the Hulunbuir Grassland. (2) The spectral indices were the key variables of the grassland AGB, especially the enhanced vegetation index and difference vegetation index. (3) The 22-year average total biomass (TB) of the study area was 1037.10 gC/m2, of which the 22-year average AGB was 48.73 gC/m2 and 22-year average belowground biomass was 988.37 gC/m2, showing a spatial distribution feature of gradual increase from west to east. (4) From 2001–2022, TB carbon storage showed an insignificant growth trend (p > 0.05). The 22-year average carbon storage of TB was 72.34 ± 18.07 gC. (5) Climate factors were the main driving factors for the spatial pattern of grassland TB carbon density, while the combined effects of CC and HA were the main contributors to the interannual increase in grassland TB carbon density.

Forecasting Carbon Sequestration Potential in China’s Grasslands by a Grey Model with Fractional-Order Accumulation

This study aims to predict the carbon sequestration capacity of Chinese grasslands to address climate change and achieve carbon neutrality goals. Grassland carbon sequestration is a crucial part of the global carbon cycle. However, its capacity is significantly impacted by climate change and human activities, making its dynamic changes complex and challenging to predict. This study adopts a fractional-order accumulation grey model, using 11 provinces in China as samples, to analyze and forecast grassland carbon sequestration. The study finds significant differences in grassland carbon sequestration trends across the sample regions. The carbon sequestration capacity of the grasslands in Xizang (Tibet) and Heilongjiang province is increasing, while it is decreasing in other provinces. The varying prediction results are influenced not only by regional climatic and natural conditions, but also by human interventions such as overgrazing, irrational reclamation, excessive mineral resource exploitation, and increased tourism development. Therefore, more region-specific grassland management and protection strategies should be formulated to enhance the carbon sequestration capacity of grasslands and promote the sustainable development of ecosystems. The significance of this study lies not only in providing scientific guidance for the protection and sustainable management of Chinese grasslands, but also in contributing theoretical and practical insights into global carbon sequestration strategies.

Natural grassland restoration exhibits enhanced carbon sequestration and soil improvement potential in northern sandy grasslands of China: An empirical study

Vegetation restoration is an effective measure for restoring degraded ecosystems. Soil carbon mineralization, a crucial indicator for evaluating the effectiveness of vegetation restoration, is essential in soil carbon cycling. However, the response of soil carbon mineralization to different vegetation restoration types remains unclear. In this study, grassland (Leymus chinensis and Stipa bungeana), shrubland (Corethrodendron fruticosum), and forestland (Ulmus pumila) with 20 years of consistent restoration in the Xilingol sandy grassland were selected to determine the effects of vegetation restoration types on soil carbon mineralization. The results showed that the soil cumulative carbon dioxide emissions (CCE) and microbial respiration rate (SMR) in grassland and forestland were significantly higher than those in shrubland, while soil carbon mineralization efficiency (CME) and microbial metabolic quotient (MQ) were significantly lower than those in shrubland. Furthermore, soil organic carbon (SOC) and its fractions were influenced considerably by vegetation restoration types, with grassland exhibiting the highest SOC content. The ratios of soil total effective nutrients (C/N, N/P, and C/P) and the content of active organic carbon (DOC, MBC, EOC, and POC) can effectively reflect the changes in soil carbon mineralization and the stability of SOC pools. The variations in CCE were influenced by litter biomass, macroaggregates organic carbon, mineral-associated organic carbon (MAOC), and dissolved organic carbon (DOC), while the changes in SMR were affected by aboveground biomass (AGB), soil total nitrogen and phosphorus ratios (N/P), and microaggregate organic carbon and microbial biomass carbon. The changes in CME were affected by AGB, N/P, pH, MAOC, and DOC, while the changes in MQ were influenced by AGB, N/P, DOC, MAOC, and easily oxidizable organic carbon. Given the higher carbon sequestration benefits and soil quality improvement capability of naturally restored grassland, this study suggests that grassland could be considered the primary vegetation restoration type in the Xilingol sandy grassland.

Drought and warming interaction cause substantial economic losses in the carbon market potential of China's northern grasslands

Grasslands are being threatened by global drought and warming. Economic assessments of changing grassland carbon sequestration, a prerequisite for nature-based climate-change mitigation policies, are limited when researchers inadequate consider interactions between drought and warming. Here, we quantified the responses of 35 grass biomasses to combined drought and warming, based on manipulation experiments from 34 peer-reviewed papers; subsequently, we matched them with grasslands in northern China—the eastern range of the larger Eurasian Steppe—and further projected the economic implications for carbon market trading and carbon-sequestration costs. The results show that carbon sequestration in all grassland types, except for forbrich steppe, was significantly reduced by the synergistic interactions of drought and warming. Approximately 10 % of the grasslands in central Xinjiang, identified as forbrich steppe, showed resilience to these stressors. In contrast, the rest of northern China's grasslands suffered increased carbon losses due to drought and warming. The combined effects of drought and warming have caused a loss of 1.6 × 104 million Chinese yuan (CNY) in revenue and excess carbon-sequestration costs exceeding 1.1 × 105 million CNY. Overall, our study results indicate that the synergistic effects of drought and warming significantly undermine the economic viability of carbon sequestration in most of northern China's grasslands. As climate change intensifies, understanding and incorporating the complex interactions of drought and warming can aid in the sustainable management of grassland ecosystems and the development of effective climate-change mitigation policies in arenas, including carbon markets.

Bacteria-Like Gaiella Accelerate Soil Carbon Loss by Decomposing Organic Matter of Grazing Soils in Alpine Meadows on the Qinghai–Tibet Plateau

The alpine meadows of the Qinghai–Tibet Plateau have significant potential for storing soil carbon, which is important to global carbon sequestration. Grazing is a major threat to its potential for carbon sequestration. However, grazing poses a major threat to this potential by speeding up the breakdown of organic matter in the soil and releasing carbon, which may further lead to positive carbon-climate change feedback and threaten ecological security. Therefore, in order to accurately explore the driving mechanism and regulatory factors of soil organic matter decomposition in grazing alpine meadows on the Qinghai–Tibet Plateau, we took the grazing sample plots of typical alpine meadows as the research object and set up grazing intensities of different life cycles, aiming to explore the relationship and main regulatory factors of grazing on soil organic matter decomposition and soil microorganisms. The results show the following: (1) soil microorganisms, especially Acidobacteria and Acidobacteria, drove the decomposition of organic matter in the soil, thereby accelerating the release of soil carbon, which was not conducive to soil carbon sequestration in grassland; (2) the grazing triggering effect formed a positive feedback with soil microbial carbon release, accelerating the decomposition of organic matter and soil carbon loss; and (3) the grazing ban and light grazing were more conducive to slowing down soil organic matter decomposition and increasing soil carbon sequestration.

Screening of environmental stimuli for the positive regulation of stomatal aperture in centipedegrass

Grasslands, the largest carbon pool in China, possess enormous potential for carbon sequestration. Increasing the stomatal aperture to increase the CO2 absorption capacity is a potential method to improve plant photosynthetic efficiency and ultimately enhance the carbon sequestration capacity of grass plants. Research on stomatal aperture regulation has focused mostly on Arabidopsis or crops, while research on grass plants in these areas is scarce, which seriously restricts the implementation of this grassland carbon sequestration strategy. Here, a widely used ecological grass, centipedegrass, was used as the experimental material. First, a convenient method for observing the stomatal aperture was developed. The leaves were floated in a potassium ion-containing open solution (67 mM KCl, pH 6.0) with the adaxial surface rather than the abaxial surface in contact with the solution and were cultivated under light for 1.5 h. Then, nail polish was applied on the adaxial surface, and a large number of open stomata were imprinted. Second, with the help of this improved method, the concentration‒response characteristics of the stomatal aperture to eleven environmental stimuli were tested. The stomatal aperture is dependent on these environmental stimuli in a concentration-dependent manner. The addition of 100 μM brassinolide led to the maximal stomatal aperture. This study provided a technical basis for manipulating stomatal opening to increase the carbon sequestration capacity of centipedegrass.

Optimizing grazing exclusion duration for carbon sequestration in grasslands: Incorporating temporal heterogeneity of aboveground biomass and soil organic carbon

Grasslands account for approximately one-third of the global terrestrial carbon stocks. However, a limited understanding of the impact of grazing exclusion on carbon storage in grassland ecosystems hinders progress towards restoring overgrazed grasslands and promoting carbon sequestration. In this study, we conducted a comprehensive meta-analysis to investigate the effects of grazing exclusion on aboveground biomass (AGB) and soil organic carbon (SOC) in four grasslands: alpine grasslands (AP), tropical savannas (TS), temperate subhumid grasslands (TG), and a semi-desert steppe (SD). Our meta-analysis indicated that grazing exclusion significantly enhanced carbon sequestration in grassland ecosystems, and the benefits of carbon sequestration were most pronounced in the AP, followed by the TG, SD, and TS. Grazing exclusion duration (DUR) was a significant factor associated with the response of aboveground biomass (AGB) and soil organic carbon (SOC) to grazing exclusion. Moreover, the relationships between AGB and DUR were nonlinear, with existence thresholds of 18, 21, 12, 19, and 23 years in global grasslands (ALL), AP, TS, TG, and SD, respectively. However, the relationship between SOC and DUR was linear, with SOC continuing to increase as DUR increased (up to 40 years). The multi-objective optimization indicated that the optimal duration of grazing exclusion for grassland carbon sequestration was 18–20, 21–23, 12–14, 19–21, and 23–25 years for ALL, AP, TS, TG, and SD, respectively. Our study contributes to the enhancement of grazing management and offers better options for increasing carbon sequestration in grasslands.

Inundation impacts on diversified pasture biomass allocation and soil particulate organic matter stocks

AbstractNatural soil inundation caused by frequent and intense precipitation affects carbon allocation in grassland biomass, ultimately leading to changes in soil carbon storage. Increasing forage diversity could provide resiliency to inundation of grassland. The objective was to evaluate forage and root biomass and C and N stocks in the soil particulate organic matter (POM) from pastures under recurring short‐term inundation. Three forage species combinations were evaluated in an inundated (typically lasting for a few days after heavy rain events) and a non‐inundated pasture: (1) predominantly tall‐fescue (Festuca arundinacea Schreb.); (2) mixture of cool‐season perennials composed of tall‐fescue, orchardgrass (Dactylis glomerata L.), bluegrass (Poa pratensis L.) and white (Trifolium repens L.) and red clover (Trifolium pratense L.); (3) and cool‐season mixture of perennials overseeded with oats (Avena strigosa Schreb.) and rye (Secale cereale L.). Roots and forage biomass were sampled during the growing seasons of 2021 and 2022. Soil POM was evaluated 2.5 years after establishment. Inundation reduced forage and root biomass mainly during periods of higher inundation frequency, leading to lower C‐POM stocks (p < .05). Inundation caused a shift in the forage botanical composition, that is, higher occurrence of weeds and less productive grass species with shallow roots. The perennial cool‐season mixture did not increase forage yield compared with tall fescue only but did increase root mass. This occurred mainly at deeper layers and, consequently, increased C‐POM stocks (p < .05). Overseeding of winter annuals reduced overall forage production, despite increasing spring biomass when inundated in the first year, but reduced C and N‐POM stocks (p < .05). Perennial cool‐season forage mixtures can increase the resilience of pastures to inundation events and contribute to increased carbon sequestration in grasslands where inundation is prevalent.

Risk to rely on soil carbon sequestration to offset global ruminant emissions

Carbon sequestration in grasslands has been proposed as an important means to offset greenhouse gas emissions from ruminant systems. To understand the potential and limitations of this strategy, we need to acknowledge that soil carbon sequestration is a time-limited benefit, and there are intrinsic differences between short- and long-lived greenhouse gases. Here, our analysis shows that one tonne of carbon sequestrated can offset radiative forcing of a continuous emission of 0.99 kg methane or 0.1 kg nitrous oxide per year over 100 years. About 135 gigatonnes of carbon is required to offset the continuous methane and nitrous oxide emissions from ruminant sector worldwide, nearly twice the current global carbon stock in managed grasslands. For various regions, grassland carbon stocks would need to increase by approximately 25% − 2,000%, indicating that solely relying on carbon sequestration in grasslands to offset warming effect of emissions from current ruminant systems is not feasible.

Simulation-based assessment of the soil organic carbon sequestration in grasslands in relation to management and climate change scenarios

Soil organic carbon (SOC) is crucial for the quality and productivity of terrestrial ecosystems and its sequestration plays an important role in mitigating climate change. Understanding the effects of agricultural management under future climate on the SOC balance helps decision making in environmental policies. Thereby, grasslands will play a key role, since future climate change may prolong the vegetation period.We used 24 representative grassland sites in Germany to assess the SOC balance obtained from the CANDY model in relation to ten management regimes, 18 future climate change scenarios and different soil types. Simulations were conducted over a period of 110 years.For most of the selected grassland sites an increase in both air temperature and precipitation was observed in the future climate. The effect of management on the SOC balance largely exceeded the effect of soil type and climate. An increasing management intensity (i.e. three to five cuts) generally increased the SOC balance, while extensive management (i.e. two or fewer cuts) lead to SOC losses. The seasonal variation of precipitation was the most important climate metric, with increased SOC sequestration rates being observed with increasing growing season precipitation. Clay soils had the potential for both highest gains and highest losses depending on management and precipitation. Given an overall lower SOC storage potential in sands and loams, the SOC balance in those soil types varied the least in response to climate change.We conclude that fostering SOC sequestration is possible in grassland soils by increasing management intensity, which involves increased fertilizer input and field traffic. This however may stand in conflict with other policy aims, such as preserving biodiversity. Multicriterial assessments are required to estimate the nett greenhouse gas balance and other aspects associated with these management practices at a farm scale.

Composition and contribution of Stipa bungeana root exudates to soil organic carbon fractions in the Loess Plateau

Root exudates play an important role in carbon sequestration in grassland, but the contribution of root exudates to soil organic carbon (SOC) fractions remains unclear. In this study, Stipa bungeana was analyzed, determined the composition and content of root exudates by GC–MS in a soil culture experiment and labeled with 13CO2 in a rhizibox experiment. Esters accounted for 65.38 % of root exudates, among which 1-propen-1, 2, 3-tricarboxylic acid-tributyl ester, and acetyl-tributyl citrate were the main components. During a 65-day chase period, the contents of SOC and its fractions in the rhizosphere were higher than those in bulk soil. After first day of labeling, the SOC concentration decreased by 16.95 % in the rhizosphere and reached the minimum level. Except for 13C-HC in bulk soil, which was detected three days after labeling, the rest were detected 2 h after labeling. In the rhizosphere soil, the amount of 13C in MBC and HC peaked after one day of labeling. At 65 days after labeling, the 13C-DOC, 13C-HC, and 13C-MBC in the rhizosphere significantly decreased by 59.79 %, 75.99 %, and 55.56 %, respectively. Root exudates had a rapid effect on active organic carbon fractions (MBC and DOC), and also affect the humus carbon (HC) in the short term. This study reveals the mechanism of root exudates on SOC pool during plant growth.

Differential effects of grazing intensity on carbon sequestration in arid versus humid grasslands across China

Livestock grazing, as a primary utilization practice for grasslands, plays a crucial role in carbon cycling process and its budget. Whether the impacts of different grazing intensities on carbon sequestration vary with precipitation over a broad geographic scales across China's grasslands remains unclear. In the context of striving for carbon neutrality, we carried out a meta-analysis based on 156 peer-reviewed journal articles to synthesize the general impacts of different grazing intensities on carbon sequestration with different precipitations. Our results showed that light, moderate, and heavy grazing dramatically reduced the soil organic carbon stocks by 3.43 %, 13.68 %, and 16.77 % in arid grasslands, respectively (P < 0.05), while light and moderate grazing did not alter soil organic carbon stocks in humid grasslands (P > 0.05). Moreover, the change rates of soil organic carbon stocks were all tightly positively associated with those of soil water content under different grazing intensities (P < 0.05). Further analysis revealed strong positive relationships between mean annual precipitation with the change rates of above- and belowground biomasses, soil microbial biomass carbon, and soil organic carbon stocks under moderate grazing intensity (P < 0.05). These findings imply that carbon sequestration is relatively less tolerant to grazing disturbance in arid grasslands than humid grasslands, which may be primary due to the grazing-intensified water limitation for plant growth and soil microbial activities under low precipitation. Our study is of implication to predict carbon budget of China's grasslands and help adopt sustainable management to strive for carbon neutrality.

Litter accumulation retards the positive effects of nitrogen inputs on plant carbon sequestration in grassland

Litter accumulation retards the positive effects of nitrogen inputs on plant carbon sequestration in grassland

Effects of the Main Ecological Restoration Projects on Grassland Carbon Sequestration in Ningxia on the Loess Plateau

The temperate steppe experienced degradation and desertification as a result of long-term heavy grazing and excessive reclamation. Some major ecological projects, such as the Grain for Green Program (GGP) and Grazing Exclosure (GE), have been implemented to promote ecological restoration in grassland ecosystems. With the goal of carbon neutrality, the effects of the GGP and GE on grassland carbon sequestration need to be further explored. Based on soil data from the second soil survey in the 1980s, a field survey in 2021, and the land-use/land-cover datasets of 2000–2018, we characterized the changes in soil C stock following grazing exclosure, analyzed the effect of GGP on land-use changes and soil C accumulation, and then estimated the overall grassland carbon sequestration in Ningxia on the Loess Plateau of China. From 2000 to 2018, GE increased the grassland SOCD from 49.60 Mg ha−1 to 90.71 Mg ha−1, and the C stock increased by 65.55 T g. Under the influence of the GGP, 347.62 km2 of cultivated land was converted into grasslands, increasing the grassland soil carbon sequestration by 1.31 T g. Subsequently, the grassland organic carbon storage increased by 66.86 T g, which accounted for approximately 4.26% of the grassland organic carbon storage in the Loess Plateau of China. In the southern Loess hilly area, which experienced high precipitation and low temperatures, grasslands increased by 95.55 km2; the average organic carbon density increased 46.95 Mg ha−1 due to a rate of increase of 2.61 Mg ha−1 yr−1; and the corresponding values for those in the middle arid zone were 36.25 Mg ha−1 and 2.01 Mg ha−1 yr−1, with grasslands decreasing by 147.41 km2. The follow-up policies of the GGP and GE should be implemented and improved according to local conditions to improve the carbon sink and ecological services in grassland ecosystems.

Life cycle assessment of pasture-based dairy production systems: Current and future performance

To overcome the environmental challenges faced by the global agricultural sector while also ensuring economic viability, dairy farmers must improve the efficiency of their systems. To improve system efficiency, the performance of an average production system must be determined, as it establishes a benchmark from which the efficacy of proposed management practices and mitigation strategies can be assessed. Identified management practices and mitigation strategies can then be compiled to create ambitious but realistic targets for the sector to strive toward. Therefore the objective of this study was to calculate the environmental performance of an average spring-calving pasture-based dairy system and an ambitious target dairy system. Life cycle assessment (LCA) of 2 pasture-based dairy systems were conducted: (1) current average spring-calving pasture-based dairy system (current), and (2) a spring-calving pasture-based dairy system that has achieved key performance targets set by the most efficient dairy systems (target). An existing dairy LCA model was updated with country-specific emission factors, life cycle inventory data, and recommended methodologies. The environmental impact categories assessed were global warming potential, nonrenewable energy depletion, acidification potential, and eutrophication potential (marine and freshwater). Two functional units were used: per kilogram of fat- and protein-corrected milk (FPCM), and per hectare. To assess the effects of the model updates, the current dairy system was simulated twice, once with the previous version of the dairy LCA model, and second with the updated LCA model. The addition of country-specific emission factors, updated inventory data, and implementation of recommended methods has resulted in global warming potential and nonrenewable energy depletion being reduced by 10.4% and 10.9%, respectively. The updates had negligible effects on acidification and eutrophication potential. The inclusion of assumptions around carbon sequestration in grassland further reduced global warming potential by 16.4%. Moving from the current dairy system to the target dairy system was reported to reduce the environmental impact per kilogram of FPCM across all impact categories investigated. When expressed per hectare, transitioning toward the target dairy system reduced acidification, freshwater eutrophication, and nonrenewable energy depletion by 2.0%, 8.8%, and 13.8%, respectively. In contrast, transitioning toward the target dairy system increased global warming per hectare and, to a lesser degree, marine eutrophication potential per hectare. The increase in global warming and marine eutrophication potential per hectare was attributed to the increase in stocking rate and subsequently milk production per hectare (9,950 vs. 14,100 kg of FPCM/ha). This study demonstrates that the adoption of management practices that improve system efficiency will reduce the environmental impact per kilogram of FPCM and can contribute to the future sustainability of pasture-based dairy systems. However, improved system efficiency can be offset by the associated increase in productivity, highlighting the importance of reporting multiple environmental impact categories and functional units to prevent pollution swapping. New research and mitigation strategies will be required to improve the environmental sustainability of dairy systems beyond the target system in the future.

Microbial necromass carbon and nitrogen persistence are decoupled in agricultural grassland soils

Microbial necromass is an important component of soil organic matter, however its persistence and contribution to soil carbon sequestration are poorly quantified. Here, we investigate the interaction of necromass with soil minerals and compare its persistence to that of plant litter in grassland soils under low- and high-management intensity in northwest England. During a 1-year laboratory-based incubation, we find carbon mineralization rates are higher for plant leaf litter than root litter and necromass, but find no significant difference in carbon persistence after 1 year. During a field experiment, approximately two thirds of isotopically-labelled necromass carbon became mineral-associated within 3 days. Mineral-associated carbon declined more rapidly than nitrogen over 8 months, with the persistence of both enhanced under increased management intensity. We suggest that carbon mineralisation rates are decoupled from carbon persistence and that necromass carbon is less persistent than necromass nitrogen, with agricultural management intensity impacting carbon sequestration in grasslands.

Effects of grazing on soil organic carbon stocks in the revegetated grasslands on the Loess Plateau, China

Grazing is an important driving factor for soil carbon sequestration in grasslands. The objective of this study was to clarify the effects of grazing and its intensity on soil organic carbon stocks (SOCS) in the revegetated grasslands in the Loess Plateau region. With the grasslands excluded from grazing ＞20 years as the control, we investigated the SOCS in the 0-20 cm soil layer in three grazing intensities in the west, middle, and east of wind-water erosion crisscross region and the water erosion region. The intensity of grazing in the study was represented by the number of goat dung in the sampling sites, which included 0-10, 10-20, and more than 20 goat dung·m-2, respectively. Results showed that grazing significantly affected SOCS in the 0-20 cm soil layer in the west of crisscross region, 0-10 cm soil layer in the east of crisscross region, and 0-5 cm soil layer in the water erosion region. There was no significant effect in each soil layer in the middle of crisscross region. Only in the west of crisscross region, the SOCS in the grazing intensity of 0-10 and ＞20 goat dung·m-2 significantly decreased by 34.8%-50.9%, whereas the SOCS in each grazing intensity was not different from that in the enclosure in the other three regions. The SOCS was mainly affected by grazing intensity in the east of crisscross region and by soil physical and chemical properties and (or) litter biomass in the other three regions. In conclusion, grazing intensity of 10-20 goat dung·m-2 did not affect SOCS in the 0-20 cm soil layer in the revegetated grassland on the Loess Plateau, China.

147 Use of Productivity Enhancing Technologies in Beef Steers Reduces Greenhouse Gas Emission Intensity

Abstract In the last decade, the cattle industry has witnessed increased demand from domestic and international markets for hormone and antibiotic free beef. However, the environmental consequences of switching from conventional production to “natural” beef have not been extensively examined. This study explored greenhouse gas (GHG) emissions estimated using a whole-farm model, Holos (www.agr.gc.ca/holos-ghg) with model inputs from a 2-year replicated study in which calves were managed from weaning to finishing with 6 treatments based on body weight and feeding strategy. Treatments included Heavy (H), which were directly finished, Medium (M), which were backgrounded prior to finishing, and Light (L), which were backgrounded and then grazed during the summer before being placed on a finishing diet. Each treatment was subdivided into two management practices: Conventional (CON) in which productivity enhancing technologies (PETs) were used (ionophores, steroid implants and beta-adrenergic agonists) and Natural (NAT) in which PETs were removed. Emission intensity (kg CO2e kg-1 boneless beef) of HNAT was 17.3 to 20.1% higher than HCON, MNAT was 20.3 to 20.5% higher than MCON and LNAT were 11.5–12.6% higher than LCON treatment. Conventional treatments, using PET’s, reduced GHG emissions, however grazing should be considered for its potential to store and promote carbon sequestration in perennial grasslands.

Soil properties as key predictors of global grassland production: Have we overlooked micronutrients?

Fertilisation experiments have demonstrated that nutrient availability is a key determinant of biomass production and carbon sequestration in grasslands. However, the influence of nutrients in explaining spatial variation in grassland biomass production has rarely been assessed. Using a global dataset comprising 72sites on six continents, we investigated which of 16soil factors that shape nutrient availability associate most strongly with variation in grassland aboveground biomass. Climate and N deposition were also considered. Based on theory-driven structural equation modelling, we found that soil micronutrients (particularly Zn and Fe) were important predictors of biomass and, together with soil physicochemical properties and C:N, they explained more unique variation (32%) than climate and N deposition (24%). However, the association between micronutrients and biomass was absent in grasslands limited by NP. These results highlight soil properties as key predictors of global grassland biomass production and point to serial co-limitation by NP and micronutrients.

Modeling long-term attainable soil organic carbon sequestration across the highlands of Ethiopia

The objectives of this study across the highlands of Ethiopia were: (i) to characterize the association between soil organic carbon (SOC) stocks and biophysical variables and (ii) to model and map attainable SOC sequestration associated with five improved land management practices. The spatial distribution of the SOC stock was studied using a multiple linear regression model driven by eight biophysical predictors. A widely used SOC model (RothC) was then used to model changes in SOC over the next 20–50 years of improved land management. Simulations were driven by the derived SOC stocks, pH and clay contents that are available in the ISRIC soils database at 250 m resolution and climate data from the “Enhancing National Climate Services Initiative” database. Organic carbon inputs to the model were estimated from the “Improved Crop Varieties Yield Register” of the Ministry of Agriculture and Livestock Resource and the Central Statistics Authority. After 50 years of conservation tillage with 80% of available manure applied to cultivated land, the total SOC stock increased by 169,182,174 t, which is 2.8 times higher than the stock increase with only 50% of available manure applied. Introduction of improved pasture species and measures to control soil erosion was an important source of net carbon sequestration in grasslands. Afforestation and reforestation of degraded landscapes and protection of natural ecosystems further increased soil carbon. This highlights the importance of improved land management practices to SOC sequestration, which in turn could enhance agricultural productivity, food security and sustainable development.