Items
Subject is exactly
Drylands
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Effects of land clearing for agriculture on soil organic carbon stocks in drylands: a meta-analysis
Agricultural activities have been expanding globally with the pressure to provide food security to the earth’s growing population. These agricultural activities have profoundly impacted soil organic carbon (SOC) stocks in global drylands. However, the effects of clearing natural ecosystems for cropland (CNEC) on SOC are uncertain. To improve our understanding of carbon emissions and sequestration under different land uses, it is necessary to characterize the response patterns of SOC stocks to different types of CNEC. We conducted a meta-analysis with mixed-effect model based on 873 paired observations of SOC in croplands and adjacent natural ecosystems from 159 individual studies in global drylands. Our results indicate that CNEC significantly (P < 0.05) affects SOC stocks, resulting from a combination of natural land clearing, cropland management practices (fertilizer application, crop species, cultivation duration) and the significant negative effects of initial SOC stocks. Increases in SOC stocks (in 1m depth) were found in croplands which previously natural land (deserts and shrublands) had low SOC stocks, and the increases were 278.86% (95% confidence interval, 196.43–361.29%) and 45.38% (26.53–62.23%), respectively. In contrast, SOC stocks (in 1m depth) decreased by 24.11% (18.38–29.85%) and 10.70% (1.80–19.59%) in clearing forests and grasslands for cropland, respectively. We also established the general response curves of SOC stocks change to increasing cultivation duration, which is crucial for accurately estimating regional carbon dynamics following CNEC. SOC stocks increased significantly (P < 0.05) with high long-term fertilizer consumption in cleared grasslands with low initial SOC stocks (about 27.2 M g/ha). The results derived from our meta-analysis could be used for refining the estimation of dryland carbon dynamics and developing SOC sequestration strategies to achieve the removal of CO2 from the atmosphere. -
Effects of land clearing for agriculture on soil organic carbon stocks in drylands: a meta-analysis
Agricultural activities have been expanding globally with the pressure to provide food security to the earth’s growing population. These agricultural activities have profoundly impacted soil organic carbon (SOC) stocks in global drylands. However, the effects of clearing natural ecosystems for cropland (CNEC) on SOC are uncertain. To improve our understanding of carbon emissions and sequestration under different land uses, it is necessary to characterize the response patterns of SOC stocks to different types of CNEC. We conducted a meta-analysis with mixed-effect model based on 873 paired observations of SOC in croplands and adjacent natural ecosystems from 159 individual studies in global drylands. Our results indicate that CNEC significantly (P < 0.05) affects SOC stocks, resulting from a combination of natural land clearing, cropland management practices (fertilizer application, crop species, cultivation duration) and the significant negative effects of initial SOC stocks. Increases in SOC stocks (in 1m depth) were found in croplands which previously natural land (deserts and shrublands) had low SOC stocks, and the increases were 278.86% (95% confidence interval, 196.43–361.29%) and 45.38% (26.53–62.23%), respectively. In contrast, SOC stocks (in 1m depth) decreased by 24.11% (18.38–29.85%) and 10.70% (1.80–19.59%) in clearing forests and grasslands for cropland, respectively. We also established the general response curves of SOC stocks change to increasing cultivation duration, which is crucial for accurately estimating regional carbon dynamics following CNEC. SOC stocks increased significantly (P < 0.05) with high long-term fertilizer consumption in cleared grasslands with low initial SOC stocks (about 27.2 M g/ha). The results derived from our meta-analysis could be used for refining the estimation of dryland carbon dynamics and developing SOC sequestration strategies to achieve the removal of CO2 from the atmosphere. -
The efficiency of organic C sequestration in deep soils is enhanced by drier climates
Accurate assessment of organic C sequestration in deep soils is crucial to C management and understand the role of deep-rooted vegetation in the C cycle. Trees in drylands usually develop roots to access deep water resources. Deep soils typically contain large stores of sequestrated C because the microbial activities that decompose C are limited and C turnover time is long. However, we know little about whether root water uptake can benefit organic C sequestration in deep soils and the effect of precipitation on organic C sequestration. To address this, we selected five sites along a precipitation gradient from 422 mm to 606 mm on China’s Loess Plateau, and collected soil samples down to 1000 cm to measure soil organic C (SOC) content and soil water content (SWC) in both apple orchards and arable lands. We found that SOC storage (SOCS) and soil water storage (SWS) of two vegetation types in 0–800 cm soil layers increased significantly with increasing mean annual precipitation (MAP). Apple orchards showed greater SOC sequestration, particularly in deep soils (200–1000 cm), across each precipitation gradient relative to the corresponding arable lands. The ΔSOCS (difference in SOCS between apple orchards and the corresponding arable lands) in deep soils gradually decreased as MAP increased, and ΔSOCS for MAP = 422 mm was almost twice as great as that for MAP = 606 mm. Moreover, the ratio of ΔSOCS/ΔSWS in deep soils significantly increased as MAP decreased in the interval 400–610 mm. This indicates that the efficiency of SOC sequestration in deep soils is enhanced in a drier climate. The findings here indicate that deep soils may contribute greatly to organic C sequestration, and may provide insights into the water-C relationships in deep soils.