Land use intensification effects on soil C dynamics in subtropical grazing land ecosystems

Abstract. Montane tropical soils are a large carbon (C) reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM) following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands; an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A combination of density and particle-size fractionation was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free LF, especially at the lower depths (10–20 and 20–30 cm). The free LF in the control soils made 20 % of the bulk soil mass and 30 % of the soil C content compared to the burnt-grazed soils, which had the smallest recovery of free LF (10 %) and significantly lower C content (14 %). The burnt soils had a much higher proportion of C in the occluded LF (12 %) compared to the non-burnt soils (7 %) and there was no significant difference among the treatments in the heavy F (~ 70 %). The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2 fluxes were increased and the dominant temperature driver was obscured by some other process, such as changes in plant C and N allocation promoting autotrophic respiration. In addition, the free LF was negatively affected when these two anthropogenic activities took place on the same site. Most likely a result of reduced detritus being incorporated into the soil. A positive finding from this study is that the total soil C stocks were not significantly affected and the long term C storage in the occluded LF and heavy F were not negatively impacted. Possibly this is because of low intensity fire, fire-resilient grasses and the grazing pressure is below the threshold to cause severe degradation.

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Free and protected soil organic carbon dynamics respond differently to abandonment of mountain grassland

Biogeosciences ◽

10.5194/bg-9-853-2012 ◽

2012 ◽

Vol 9 (2) ◽

pp. 853-865 ◽

Cited By ~ 31

Author(s):

S. Meyer ◽

J. Leifeld ◽

M. Bahn ◽

J. Fuhrer

Keyword(s):

Land Use ◽

Organic Matter ◽

Driving Forces ◽

Carbon Accumulation ◽

European Alps ◽

Dominant Form ◽

Soil C ◽

Mountain Grassland ◽

C Dynamics ◽

C Input

Abstract. Land-use change (LUC) and management are among the major driving forces of soil carbon (C) storage. Abandonment of mountain grassland promotes accumulation of aboveground biomass and litter, but related responses of soil organic matter (SOM) dynamics are uncertain. To determine SOM-C turnover we sampled 0–10 cm of soils in the European Alps along two land-use gradients (hay meadows, grazed pastures and abandoned grasslands) of different management intensity. A first land-use gradient was located at Stubai Valley (MAT: 3 °C, MAP: 1097 mm) in Austria and a second at Matsch Valley (MAT: 6.6 °C, MAP: 527 mm) in Italy. We estimated C input and decomposition rates of water-floatable and free particulate organic matter (wPOM, fPOM <1.6 g cm−3) and aggregate-occluded particulate and mineral-associated organic matter (oPOM <1.6 g cm−3, mOM >1.6 g cm−3) using bomb radiocarbon. In mountain grasslands average C turnover increased from roots (3 yr) < wPOM (5 yr) < fPOM (80 yr) < oPOM (108 yr) < mOM (192 yr). Among SOM fractions the turnover of fPOM-C varied most in relation to management. Along both land-use gradients C input pathways shifted from root-derived towards litter-derived C. The C input rates of both wPOM-C and fPOM-C were affected by land management at both sites. In contrast, oPOM-C and mOM-C dynamics remained relatively stable in response to grassland abandonment. Carbon accumulation rates of free POM decreased strongly with time since LUC (10, 25 and 36 yr). For wPOM-C, for example, it decreased from 7.4 > 2.2> 0.8 g C m−2 yr−1. At both sites, most C was sequestered in the first years after LUC and free POM reached new steady state within 20–40 yr. We conclude that w-and fPOM-C vs. oPOM-C dynamics respond differently to grassland management change and thus POM does not represent a homogeneous SOM fraction. Sequestered C is stored in the labile POM and not stabilized in the long-term. Thus, it is unlikely that abandonment, the dominant form of LUC in the European Alps, provides a substantial net soil C sink.

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Soil greenhouse gas emissions under different land-use types in savanna ecosystems of Kenya

Biogeosciences ◽

10.5194/bg-17-2149-2020 ◽

2020 ◽

Vol 17 (8) ◽

pp. 2149-2167 ◽

Cited By ~ 3

Author(s):

Sheila Wachiye ◽

Lutz Merbold ◽

Timo Vesala ◽

Janne Rinne ◽

Matti Räsänen ◽

...

Keyword(s):

Land Use ◽

Soil Moisture ◽

Co2 Emissions ◽

Vegetation Cover ◽

Ghg Emissions ◽

N2o Emissions ◽

Grazing Land ◽

Soil C ◽

Land Use Types ◽

Soil Co2 Emissions

Abstract. Field measurement data on greenhouse gas (GHG) emissions are still scarce for many land-use types in Africa, causing a high level of uncertainty in GHG budgets. To address this gap, we present in situ measurements of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions from the lowlands of southern Kenya. We conducted eight chamber measurement campaigns on gas exchange from four dominant land-use types (LUTs) comprising (1) cropland, (2) bushland, (3) grazing land, and (4) conservation land between 29 November 2017 and 3 November 2018, accounting for regional seasonality (wet and dry seasons and transitions periods). Mean CO2 emissions for the whole observation period were the highest by a significant margin (p value < 0.05) in the conservation land (75±6 mg CO2-C m−2 h−1) compared to the three other sites, which ranged from 45±4 mg CO2-C m−2 h−1 (bushland) to 50±5 mg CO2-C m−2 h−1 (grazing land). Furthermore, CO2 emissions varied between seasons, with significantly higher emissions in the wet season than the dry season. Mean N2O emissions were highest in cropland (2.7±0.6 µg N2O-N m−2 h−1) and lowest in bushland (1.2±0.4 µg N2O-N m−2 h−1) but did not vary with season. In fact, N2O emissions were very low both in the wet and dry seasons, with slightly elevated values during the early days of the wet seasons in all LUTs. On the other hand, CH4 emissions did not show any significant differences across LUTs and seasons. Most CH4 fluxes were below the limit of detection (LOD, ±0.03 mg CH4-C m−2 h−1). We attributed the difference in soil CO2 emissions between the four sites to soil C content, which differed between the sites and was highest in the conservation land. In addition, CO2 and N2O emissions positively correlated with soil moisture, thus an increase in soil moisture led to an increase in emissions. Furthermore, vegetation cover explained the seasonal variation in soil CO2 emissions as depicted by a strong positive correlation between the normalized difference vegetation index (NDVI) and CO2 emissions, most likely because, with more green (active) vegetation cover, higher CO2 emissions occur due to enhanced root respiration compared to drier periods. Soil temperature did not show a clear correlation with either CO2 or N2O emissions, which is likely due to the low variability in soil temperature between seasons and sites. Based on our results, soil C, active vegetation cover, and soil moisture are key drivers of soil GHG emissions in all the tested LUTs in southern Kenya. Our results are within the range of previous GHG flux measurements from soils from various LUTs in other parts of Kenya and contribute to more accurate baseline GHG emission estimates from Africa, which are key to reducing uncertainties in global GHG budgets as well as for informing policymakers when discussing low-emission development strategies.

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The effects of burning and grazing on soil carbon dynamics in managed Peruvian tropical montane grasslands

Biogeosciences ◽

10.5194/bg-14-5633-2017 ◽

2017 ◽

Vol 14 (24) ◽

pp. 5633-5646 ◽

Cited By ~ 3

Author(s):

Viktoria Oliver ◽

Imma Oliveras ◽

Jose Kala ◽

Rebecca Lever ◽

Yit Arn Teh

Keyword(s):

Land Use ◽

Organic Matter ◽

Co2 Fluxes ◽

Soil Co2 ◽

Soil C ◽

C Dynamics ◽

Total Soil ◽

C Stocks ◽

Montane Grasslands

Abstract. Montane tropical soils are a large carbon (C) reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM) following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long-term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands, an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A density fractionation method was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free light fraction (LF), especially at the lower depths (10–20 and 20–30 cm). In the control soils, 20 % of the material recovered was in the free LF, which contained 30 % of the soil C content. In comparison, the burnt–grazed soil had the smallest recovery of the free LF (10 %) and a significantly lower C content (14 %). The burnt soils had a much higher proportion of C in the occluded LF (12 %) compared to the not-burnt soils (7 %) and there was no significant difference among the treatments in the heavy fraction (F) ( ∼  70 %). The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2 fluxes were increased and the dominant temperature driver was obscured by some other process, such as changes in plant C and N allocation. In addition, the free LF was reduced when these two anthropogenic activities took place on the same site – most likely a result of reduced detritus being incorporated into the soil. A positive finding from this study is that the total soil C stocks were not significantly affected and the long-term (+10 years) C storage in the occluded LF and heavy F were not negatively impacted. Possibly this is because of low-intensity fire, fire-resilient grasses and because the grazing pressure is below the threshold necessary to cause severe degradation.

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Land use intensification in tropical uplands: Effects on vegetation, soil fertility and erosion

Forest Ecology and Management ◽

10.1016/0378-1127(87)90071-5 ◽

1987 ◽

Vol 21 (1-2) ◽

pp. 37-56 ◽

Cited By ~ 17

Author(s):

Stephen F. Siebert

Keyword(s):

Land Use ◽

Soil Fertility ◽

Land Use Intensification

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Spatial Differentiation of Cultivated Land Use Intensification in Village Settings: A Survey of Typical Chinese Villages

Land ◽

10.3390/land10030249 ◽

2021 ◽

Vol 10 (3) ◽

pp. 249

Author(s):

Quanfeng Li ◽

Zhe Dong ◽

Guoming Du ◽

Aizheng Yang

Keyword(s):

Land Use ◽

Food Security ◽

Socioeconomic Development ◽

Agricultural Land ◽

Spatial Differentiation ◽

Cultivated Land ◽

Output State ◽

Land Use Intensification ◽

Development Levels ◽

Business Entities

The intensified use of cultivated land is essential for optimizing crop planting practices and protecting food security. This study employed a telecoupling framework to evaluate the cultivated land use intensification rates in typical Chinese villages (village cultivated land use intensifications—VCLUIs). The pressure–state–response (PSR) model organizes the VCLUI indexes including the intensity press, output state, and structural response of cultivated land use. Empirical analysis conducted in Baiquan County, China, indicating that the cultivated land use intensification levels of the whole county were low. However, the intensifications of villages influenced by physical and geographic locations and socioeconomic development levels varied significantly. This paper also found that variations in the VCLUIs were mainly dependent on new labor-driven social subsystem differences. Thus, the expanding per capita farmland scales and increasing numbers of new agricultural business entities were critical in improving the VCLUI. Overall, the theoretical framework proposed in this study was demonstrated to be effective in analyzing interactions among the natural, social, and economic subsystems of the VCLUI. The findings obtained in this study potentially have important implications for future regional food security, natural stability, and agricultural land use sustainability.

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