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

2011 ◽  
Vol 8 (5) ◽  
pp. 9943-9976 ◽  
Author(s):  
S. Meyer ◽  
J. Leifeld ◽  
M. Bahn ◽  
J. Fuhrer

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 along land-use gradients (hay meadows, grazed pastures and abandoned grasslands) in the European Alps varying in management intensity at Stubai Valley (MAT: 3 °C, P: 1097 mm) in Austria and Matsch Valley (MAT: 6.6 °C, P: 527 mm) in Italy. We determined C input and decomposition rates of labile water-floatable and free particulate organic matter (wPOM, fPOM <1.6 g cm−3) and stable aggregate-occluded particulate and mineral-associated organic matter (oPOM <1.6 g cm−3, mOM >1.6 g cm−3) using bomb radiocarbon. At both sites C turnover decreased from w- and fPOM (4–8 yr) to oPOM (76–142 yr) to mOM (142–250 yr). Following abandonment C input pathways shifted from root-derived towards litter-derived C. The decomposition rates of labile wPOM-C declined with a decrease in litter quality, while both C input and C decomposition rates of labile fPOM increased with an increase in litter quantity. In contrast, protected stable SOM-C (oPOM-C, mOM-C) dynamics remained relatively unaffected by grassland abandonment. Carbon accumulation rates of labile POM fractions decreased strongly with time since LUC (10, 25 and 36 yr). For wPOM-C, for example, it decreased from 7.45 &amp;pm; 0.99 to 2.18 &amp;pm; 1.06 to 0.82 &amp;pm; 0.21 g C m−2 yr−1. At both sites, most C was sequestered in the first years after LUC and labile SOM fractions reached new steady state within 20–40 yr. We concluded 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 readily decomposable POM fractions 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.

2012 ◽  
Vol 9 (2) ◽  
pp. 853-865 ◽  
Author(s):  
S. Meyer ◽  
J. Leifeld ◽  
M. Bahn ◽  
J. Fuhrer

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.


2017 ◽  
Author(s):  
Viktoria Oliver ◽  
Imma Oliveras ◽  
Jose Kala ◽  
Rebecca Lever ◽  
Yit Arn Teh

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.


2017 ◽  
Vol 14 (24) ◽  
pp. 5633-5646 ◽  
Author(s):  
Viktoria Oliver ◽  
Imma Oliveras ◽  
Jose Kala ◽  
Rebecca Lever ◽  
Yit Arn Teh

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.


Ecography ◽  
2006 ◽  
Vol 29 (4) ◽  
pp. 541-548 ◽  
Author(s):  
Thomas Spiegelberger ◽  
Diethart Matthies ◽  
Heinz Müller-Schärer ◽  
Urs Schaffner

One Ecosystem ◽  
2021 ◽  
Vol 6 ◽  
Author(s):  
Tatiana Trifonova ◽  
Natalia Mishchenko ◽  
Pavel Shutov

Environmental research addresses ecosystems of various hierarchical levels. One of the ecosystem types is the river basin. The basin approach has been applied in the research. We consider the river basin as a single ecosystem of complex landscape structure. The research objective was to assess the biological processes in various landscapes within a holistic natural geosystem – a catchment area. The Klyazma River Basin (a part of the Volga River of 40 thousand km2 area) was the research object. It is a complex combination of different landscapes, each marked by a diverse composition of geomorphological and soil-vegetation structures. According to the geomorphological structure and soil and vegetation cover, four landscape provinces and eight key sites have been identified in the studied catchment area where the ecosystem parameter have been measured. The study is based on remote sensing data and the Trends. Earth Land Degradation Monitoring. The calculation of productivity indicators (GPP, NPP) in carbon units and the land use structure analysis are based on Modis data. The soil organic carbon pool was determined by the UN FAO’s data, based on Trends. Earth and QGIS 2.18. The two-factor variance analysis ANOVA has been used for the data statistic processing. The cartographic analysis of the land use structure dynamics of the entire Klyazma Basin resulted in revealing the areas where various land transitions from one category to another have been identified. They are basically associated with the agricultural land overgrowth. The forest area increased by 9% during the period from 2001 to 2017. Considerable increase in the waterlogged, wetlands areas was observed in the eastern part of the Basin, in the Volga-Klyazma Province. The landscapes react differently to changes in climatic parameters and land use. Thus, the active revegetation of farmland by forests gives the increased rate of carbon accumulation in the soil. Landscapes covered with grasses and shrubs are more productive those covered with forest. On the other hand, woody biotopes are more stable in their development over time. Statistical analysis using the two-factor variation analysis ANOVA method resulted in demonstrating that phytoproductivity dynamics of the key sites does not depend on their productivity parameters nor on the site landscape structure, but is mainly determined by a time factor. In different landscapes the biological processes, characterising the organic matter dynamics in the form of plant production, organic matter accumulation and others are shown to differ both in rate and intensity and ambiguously respond to changes in climate parameters and land use. The river basin, as a single ecosystem, showed sufficient stability of the dynamic processes. This suggests that holistic natural ecosystems, such as catchment areas, have internal compensatory mechanisms that maintain the development stability for a long time, while unplanned land use remains the main damaging factor.


2012 ◽  
Vol 19 (5) ◽  
pp. 1182-1189 ◽  
Author(s):  
Qiao-Li HU ◽  
Yong-Qing QI ◽  
Yin-Cui HU ◽  
Yu-Cui ZHANG ◽  
Cheng-Ben WU ◽  
...  

2021 ◽  
Vol 10 (5) ◽  
pp. 348
Author(s):  
Zhenbo Du ◽  
Bingbo Gao ◽  
Cong Ou ◽  
Zhenrong Du ◽  
Jianyu Yang ◽  
...  

Black soil is fertile, abundant with organic matter (OM) and is exceptional for farming. The black soil zone in northeast China is the third-largest black soil zone globally and produces a quarter of China’s commodity grain. However, the soil organic matter (SOM) in this zone is declining, and the quality of cultivated land is falling off rapidly due to overexploitation and unsustainable management practices. To help develop an integrated protection strategy for black soil, this study aimed to identify the primary factors contributing to SOM degradation. The geographic detector, which can detect both linear and nonlinear relationships and the interactions based on spatial heterogeneous patterns, was used to quantitatively analyze the natural and anthropogenic factors affecting SOM concentration in northeast China. In descending order, the nine factors affecting SOM are temperature, gross domestic product (GDP), elevation, population, soil type, precipitation, soil erosion, land use, and geomorphology. The influence of all factors is significant, and the interaction of any two factors enhances their impact. The SOM concentration decreases with increased temperature, population, soil erosion, elevation and terrain undulation. SOM rises with increased precipitation, initially decreases with increasing GDP but then increases, and varies by soil type and land use. Conclusions about detailed impacts are presented in this paper. For example, wind erosion has a more significant effect than water erosion, and irrigated land has a lower SOM content than dry land. Based on the study results, protection measures, including conservation tillage, farmland shelterbelts, cross-slope ridges, terraces, and rainfed farming are recommended. The conversion of high-quality farmland to non-farm uses should be prohibited.


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