Sensitivity of soil organic carbon to grazing management in the semi-arid rangelands of south-eastern Australia

This study compared the effects of grazing management on soil organic carbon (OC) stocks in the semi-arid rangelands of New South Wales, Australia. A field survey was conducted at three locations (Brewarrina, Cobar–North and Cobar–South), with paired sites of long-term (>8 years) rotational grazing management and continuously grazed pastures (either set stocked or no stocking). At each location, soil OC, carbon (C) fractions, soil nitrogen (N) and microsite and site factors (including ground cover and woody vegetation) were measured. The control of total grazing pressure (TGP) through rotational grazing and exclusion fencing did not increase soil C stocks compared with continuous grazing for the majority of comparisons. However, in some parts of the landscape, higher soil C stock was found with TGP control, for example on the ridges (21.6 vs 13.3 t C ha–1 to 0.3 m). C stocks increased with litter and perennial ground cover and with close proximity to trees. At Brewarrina, C stocks were positively affected by perennial plant cover (P < 0.001) and litter (P < 0.05), whereas at Cobar–North and Cobar–South C stocks were positively affected by the presence of trees (P < 0.001), with higher C stocks in close proximity to trees, and with increasing litter cover (P < 0.01). The present study demonstrates that natural resource benefits, such as increased perennial cover, can be achieved through controlling TGP in the rangelands but increases in soil C may be limited in certain parts of the landscape. These findings also highlight that interactions between managed and unmanaged TGP and microsite factors, such as ground cover and proximity to woody vegetation, need to be considered when evaluating the role of changed grazing management on soil C.

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Effect of Grazing Management and Land Cover Types on Mineral-Associated Organic Carbon and Particulate Organic Carbon in a Semi-arid Rangelands in Kenya

10.21203/rs.3.rs-768864/v1 ◽

2021 ◽

Author(s):

Angela Nduta Gitau ◽

R.N. Onwonga ◽

J. S. Mbau ◽

J. Chepkemoi ◽

S. M. Mureithi

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Land Cover ◽

Particulate Organic Carbon ◽

Grazing Management ◽

Bare Ground ◽

Land Cover Types ◽

Continuous Grazing ◽

Arid Rangelands ◽

Semi Arid

Abstract BackgroundEnhancing soil organic carbon storage in areas under extensive livestock grazing has become a challenge in most arid and semi-arid rangelands in Sub-Saharan Africa. In Kenya for instance, continuous unplanned grazing in community lands has led to overgrazing and degradation of the rangelands. For decades, livestock production has shaped the landscape through various management practices. Grazing can be used to increase soil organic carbon (SOC) content but intensive use of land can lead to its depletion. This study was set out to elucidate the effect of two types of grazing management under varying land cover types on mineral-associated organic carbon (MAOC) and particulate organic carbon (POC) in the soil. The study was carried out in two ranches, Mpala Research Centre (controlled grazing) and Ilmotiok Community Group Ranch (continuous grazing). The experimental design was a completely randomized block design in split-plot arrangement with three replicates. The main plots were the grazing practices; (controlled grazing and continuous grazing); and sub-plots were the land cover types: (bare ground, patches of grasses, and mosaics of trees). These treatments were randomly selected and replicated three times. Three topographical positions (mid-slope, foot slope and bottom land) were used as a blocking factor.ResultsThe interaction had no significant effect on MAOC fraction in any soil depth interval. Controlled grazed zones significantly recorded higher organic carbon content (POC= 0.887% CC SD=0.49) compared to zones under continuous grazing (POC = 0.718% CC SD=0.3). Mosaic of trees (POC =1.15% CC, SD = 0.22) recorded the highest concentration of carbon followed by patches of grass (POC = 0.87% CC, SD= 0.37) and bare ground (POC = 0.38% CC SD = 0.12) had the least.ConclusionThis study shows that grazing practices as well as land cover types have a significant effect on POC but not on MAOC. Mosaic of trees under controlled grazing has higher POC whereas bareground under continuous grazing had the least POC. Destocking should be done under continuous grazed zones to reduce further loss of POC and MAOC and allow vegetation recovery.

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Simulating Grazing Effects on Soil Organic Carbon Dynamics in Semi-arid Rangelands (Southern Iran)

10.21203/rs.3.rs-519337/v1 ◽

2021 ◽

Author(s):

sayed fakhreddin afzali ◽

Bijan AZAD ◽

Rosa FRANCAVIGLIA

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Grazing Intensity ◽

Grazing Management ◽

Southern Iran ◽

Rangeland Degradation ◽

Grazing Intensities ◽

Arid Rangelands ◽

Few Data ◽

Semi Arid

Abstract Grazing is one of the main causes of rangeland degradation worldwide, due to the effects of overgrazing on vegetation cover and biodiversity. But few data are available on the effect of grazing intensity on the dynamics of soil organic carbon (SOC) and soil labile organic carbon (SLOC). So far, very few studies have addressed the modeling of SOC dynamics under different grazing intensities, and SLOC dynamics has not been modeled yet. In this study, we used the CENTURY model to select the most effective grazing management in terms of carbon sequestration (SOC and SLOC stocks) in semi-arid rangelands of Southern Iran. The effect of four different scenarios of grazing intensity was simulated: no grazing, light grazing (LG), moderate grazing (MG), and heavy grazing (HG). The results of long-term model simulations (2015–2100), indicated that SOC stocks will change by 2.7, 1.7, -23.4, and − 24.6% in the scenarios of exclusion, LG, MG, and HG respectively compared to 2014. With increasing grazing intensities, SLOC stocks in LG, MG, and HG scenarios significantly decreased compared to the no grazing scenario by 26.1, 59.6, and 70%, respectively. Thus, this study suggests recommending light grazing management for semi-arid rangelands of Iran and also SLOC as a suitable index for studying the effect of grazing on soil carbon.

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The influence of grazing exclosure on soil C stocks and dynamics, and ecological indicators in upland arid and semi-arid rangelands

Ecological Indicators ◽

10.1016/j.ecolind.2014.01.040 ◽

2014 ◽

Vol 41 ◽

pp. 145-154 ◽

Cited By ~ 41

Author(s):

Fayez Raiesi ◽

Maryam Riahi

Keyword(s):

Ecological Indicators ◽

Soil C ◽

C Stocks ◽

Arid Rangelands ◽

Semi Arid

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Effects of species-dominated patches on soil organic carbon and total nitrogen storage in a degraded grassland in China

PeerJ ◽

10.7717/peerj.6897 ◽

2019 ◽

Vol 7 ◽

pp. e6897 ◽

Cited By ~ 1

Author(s):

Yujuan Zhang ◽

Shiming Tang ◽

Shu Xie ◽

Kesi Liu ◽

Jinsheng Li ◽

...

Keyword(s):

Microbial Biomass ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Total Nitrogen ◽

Microbial Biomass Nitrogen ◽

Soil C ◽

Artemisia Frigida ◽

C Stocks ◽

Soil C And N ◽

C And N

Background Patchy vegetation is a very common phenomenon due to long-term overgrazing in degraded steppe grasslands, which results in substantial uncertainty associated with soil carbon (C) and nitrogen (N) dynamics because of changes in the amount of litter accumulation and nutrition input into soil. Methods We investigated soil C and N stocks beneath three types of monodominant species patches according to community dominance. Stipa krylovii patches, Artemisia frigida patches, and Potentilla acaulis patches represent better to worse vegetation conditions in a grassland in northern China. Results The results revealed that the soil C stock (0–40 cm) changed significantly, from 84.7 to 95.7 Mg ha−1, and that the soil organic carbon content (0–10 cm) and microbial biomass carbon (0–10 and 10–20 cm) varied remarkably among the different monodominant species communities (P < 0.05). However, soil total nitrogen and microbial biomass nitrogen showed no significant differences among different plant patches in the top 0–20 cm of topsoil. The soil C stocks under the P. acaulis and S. krylovii patches were greater than that under the A. frigida patch. Our study implies that accurate estimates of soil C and N storage in degenerated grassland require integrated analyses of the concurrent effects of differences in plant community composition.

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Comparing microbial and chemical approaches for modelling soil organic carbon decomposition using the DecoChem v1.0 and DecoBio v1.0 models

Geoscientific Model Development Discussions ◽

10.5194/gmdd-7-33-2014 ◽

2014 ◽

Vol 7 (1) ◽

pp. 33-72 ◽

Cited By ~ 3

Author(s):

G. Xenakis ◽

M. Williams

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Microbial Activity ◽

Biological Model ◽

Chemical Model ◽

Soil C ◽

Model Soil ◽

Carbon Decomposition ◽

C Stocks ◽

Soil Organic Carbon Decomposition

Abstract. Soil organic matter is a vast store of carbon, with a critical role in the global carbon cycle. Despite its importance the dynamics of soil organic carbon decomposition, under the impact of climate change or changing litter inputs, are poorly understood. Current biogeochemical models usually lack microbial processes and thus miss an important feedback when considering the fate of carbon. Here we use a series of modelling experiments to evaluate two different model structures, one with a standard first order kinetic representation of soil decomposition (DecoChem v1.0, hearafter chemical model) and one with control of soil decomposition through microbial activity (DecoBio v1.0, hereafter biological model). We tested two hypotheses. First, that increased litter inputs and glucose addition prime microbial activity and reduce soil carbon stocks in the biological model, but increase C stocks in the chemical model. Experiments provided some support for this hypothesis, with soil C stocks increasing in the chemical model in response to litter increases. In the biological model, responses to changed litter quantity were more rapid, but with the residence time of soil C altering such that soil C stocks were buffered. However, in the biological model there was a strong response to increased glucose additions (i.e., changes in litter quality), with significant losses to soil C stocks over time, driven by priming. Secondly, we hypothesised that warming will stimulate decomposition in the chemical model, and loss of C, but in the biological model soil C will be less sensitive to warming, due to complex microbial feedbacks. The experiments supported this hypothesis, with the chemical model soil C residence times and steady state C stocks adjusting strongly with temperature changes, extending over decades. On the other hand, the biological model showed a rapid response to temperature that subsided after a few years, with total soil C stocks largely unchanged. The microbial model shows qualitative agreement with experimental warming studies, that found transient increases in soil respiration that decline within a few years. In conclusion, the biological model is largely buffered against bulk changes in litter inputs and climate, unlike the chemical model, while the biological model displays a strong priming response to additions of labile litter. Our result have therefore highlighted significantly different sensitivities between chemical and biological modelling approaches for soil decomposition.

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Estimating soil organic carbon stocks using machine learning methods in the semi-arid rangelands of New South Wales

Syme, G., Hatton MacDonald, D., Fulton, B. and Piantadosi, J. (eds) MODSIM2017, 22nd International Congress on Modelling and Simulation. ◽

10.36334/modsim.2017.g1.wang ◽

2017 ◽

Keyword(s):

Machine Learning ◽

Organic Carbon ◽

Soil Organic Carbon ◽

New South ◽

Carbon Stocks ◽

Machine Learning Methods ◽

South Wales ◽

Soil Organic Carbon Stocks ◽

Arid Rangelands ◽

Semi Arid

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Estimating soil organic carbon stocks using different modelling techniques in the semi-arid rangelands of eastern Australia

Ecological Indicators ◽

10.1016/j.ecolind.2018.01.049 ◽

2018 ◽

Vol 88 ◽

pp. 425-438 ◽

Cited By ~ 44

Author(s):

Bin Wang ◽

Cathy Waters ◽

Susan Orgill ◽

Annette Cowie ◽

Anthony Clark ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Carbon Stocks ◽

Soil Organic Carbon Stocks ◽

Eastern Australia ◽

Modelling Techniques ◽

Arid Rangelands ◽

Semi Arid

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Stable isotopic constraints on global soil organic carbon turnover

Biogeosciences ◽

10.5194/bg-15-987-2018 ◽

2018 ◽

Vol 15 (4) ◽

pp. 987-995 ◽

Cited By ~ 17

Author(s):

Chao Wang ◽

Benjamin Z. Houlton ◽

Dongwei Liu ◽

Jianfeng Hou ◽

Weixin Cheng ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Linear Relationship ◽

Root Decomposition ◽

Mean Annual Precipitation ◽

Mean Annual Temperature ◽

Turnover Rates ◽

Decomposition Rates ◽

Soil C ◽

C Stocks

Abstract. Carbon dioxide release during soil organic carbon (SOC) turnover is a pivotal component of atmospheric CO2 concentrations and global climate change. However, reliably measuring SOC turnover rates on large spatial and temporal scales remains challenging. Here we use a natural carbon isotope approach, defined as beta (β), which was quantified from the δ13C of vegetation and soil reported in the literature (176 separate soil profiles), to examine large-scale controls of climate, soil physical properties and nutrients over patterns of SOC turnover across terrestrial biomes worldwide. We report a significant relationship between β and calculated soil C turnover rates (k), which were estimated by dividing soil heterotrophic respiration rates by SOC pools. ln( − β) exhibits a significant linear relationship with mean annual temperature, but a more complex polynomial relationship with mean annual precipitation, implying strong-feedbacks of SOC turnover to climate changes. Soil nitrogen (N) and clay content correlate strongly and positively with ln( − β), revealing the additional influence of nutrients and physical soil properties on SOC decomposition rates. Furthermore, a strong (R2 = 0.76; p < 0.001) linear relationship between ln( − β) and estimates of litter and root decomposition rates suggests similar controls over rates of organic matter decay among the generalized soil C stocks. Overall, these findings demonstrate the utility of soil δ13C for independently benchmarking global models of soil C turnover and thereby improving predictions of multiple global change influences over terrestrial C-climate feedback.

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Fractionation of soil organic carbon under different land management in dry tropics, south India

10.5194/egusphere-egu2020-21025 ◽

2020 ◽

Author(s):

Eito Nonomura ◽

Soh Sugihara ◽

Mayuko Seki ◽

Hidetoshi Miyazaki ◽

Muniandi Jegadeesan ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Land Management ◽

Soil Ph ◽

Southern India ◽

Alkaline Soil ◽

Alkaline Soils ◽

Soil C ◽

C Stocks

An understanding of the mechanisms of soil organic carbon (SOC) stabilization is essential to develop the appropriate management for C sequestration and soil health. In southern India, where neutral-alkaline soils are mainly distributed, soil C stocks are inherently low in cropland, despite relatively high clay contents (Clay>ca. 30%, OC<ca. 5 g C kg-1 soil). To consider this reason of low SOC in this area, we evaluated the fractionated C contents and its controlling factors, by measuring the particulate organic matter (POM). The objective of this study was to evaluate the effect of land management on the amount and composition of each fraction of soil in southern India. We collected the surface soils (0-10 cm) from two representative sites of southern India; Vertisols with alkaline soil pH (8.4-8.8) and Alfisols with neutral soil pH (6.0-7.0). At each site, two different land management were selected; forest and cropland of Vertisols, and cropland with no organic matter application (no-OM) and with manure application (with-OM) of Alfisols. Soils were separated into the four fractions; (1) Light Fraction; LF (<1.7 g cm-3) , (2) Coarse POM; cPOM (>1.7 g cm-3, 250-2000 &#181;m), (3) Fine POM; fPOM(>1.7 g cm-3, 53-250 &#181;m), and (4) Silt+Clay; S+C (>1.7 g cm-3, <53 &#181;m). Each fraction was analyzed by elemental analysis (C, N) and CPMAS 13C NMR spectroscopy. In Vertisols, C contents of cPOM, fPOM, S+C were significantly higher in forest (0.65, 0.91, 4.8 g kg-1 soil, respectively) than those of cropland (0.17, 0.22, 4.1 g kg-1 soil, respectively), causing the higher total SOC in forest (7.8 g kg-1 soil) than in cropland (4.5 g kg-1 soil). C concentration of cPOM, fPOM, and S+C fractions were also significantly higher in forest (3.7, 7.6, 6.7 g kg-1 fraction, respectively) than those of cropland (1.0, 2.7, 5.4 g kg-1 fraction, respectively). In particular, increasing rates in cPOM and fPOM (180-280 %) were greater than S+C (24 %), possibly suggesting that forest management should increase the relatively active and intermediate SOC pools through the C accumulation in cPOM and fPOM fractions of Vertisols. In Alfisols, C contents in LF and S+C were significantly higher in with-OM (1.1 and 5.2 g kg-1 soil, respectively) than in no-OM (0.76 and 4.7 g kg-1 soil, respectively). C concentration of S+C fraction was significantly higher in with-OM (14 g kg-1 fraction) than in no-OM (11 g kg-1 fraction), but not of cPOM and fPOM fractions. It suggests that the OM application to cropland should increase the slow SOC pool through the C accumulation in S+C fractions of Alfisols. These results indicate that different fraction may contribute to SOC stabilization between Vertisols and Alfisols in southern India.

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