Tag: soil


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  • Spatial Gradients of Ecosystem Health Indicators across a Human-Impacted Semiarid Savanna

Spatial Gradients of Ecosystem Health Indicators across a Human-Impacted Semiarid Savanna

09 July, 2018

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Drivers of soil organic carbon (SOC) dynamics involve a combination of edaphic, human, and climatic factors that influence and determine SOC distribution across the landscape. High-resolution maps of key indicators of ecosystem health can enable assessments of these drivers and aid in critical management decisions. This study used a systematic field-based approach coupled with statistical modeling and remote sensing to develop accurate, high-resolution maps of key indicators of ecosystem health across savanna ecosystems in South Africa. Two 100-km2 landscapes in Bushbuckridge Local Municipality were surveyed, and 320 composite topsoil samples were collected. Mid-infrared spectroscopy was used to predict soil properties, with good performance for all models and root mean squared error of prediction (RMSEP) values of 1.3, 0.2, 5, and 3.6 for SOC, pH, sand, and clay, respectively. Validation results for the mapping of soil erosion prevalence and herbaceous cover using RapidEye imagery at 5-m spatial resolution showed good model performance with area under the curve values of 0.80 and 0.86, respectively. The overall (out-of-bag) random forest model performance for mapping of soil properties, reported using R2, was 0.8, 0.77, and 0.82 for SOC, pH, and sand, respectively. Calibration model performance was good, with RMSEP values of 2.6 g kg?1 for SOC, 0.2 for pH, and 6% for sand content. Strong gradients of increasing SOC and pH corresponded with decreasing sand content between the study sites. Although both sites had low SOC overall, important driving factors of SOC dynamics included soil texture, soil erosion prevalence, and climate. These data will inform strategic land management decisions focused particularly on improving ecosystem conditions.

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  • Spatial and seasonal variation in soil respiration along a slope in a rubber plantation and a natural forest in Xishuangbanna, Southwest China

Spatial and seasonal variation in soil respiration along a slope in a rubber plantation and a natural forest in Xishuangbanna, Southwest China

06 July, 2018

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Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest (SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements. Research was conducted over one year in Xishuangbanna during May, June, July and October 2015 (wet season) and January and March 2016 (dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha-1 yr-1 in natural forest and 11.7 and 5.7 Mg C ha-1 yr-1 in rubber plantation. Using a linear mixed effects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.

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  • On the critical role of soil organic carbon in landscapes

On the critical role of soil organic carbon in landscapes

30 June, 2017

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Presentation by World Agroforestry Centre (ICRAF) scientist Tor-Gunnar Vågen, who is also part of the CGIAR Research Program on Forests, Trees and Agroforestry (FTA).

On June 19, 30 CGIAR scientists, representing seven CGIAR Centers and six CGIAR Research Programs, exchanged recent research findings and identified priorities for a future research agenda on soil carbon and climate change. The meeting was hosted by the CGIAR Research Programs on Climate Change, Agriculture and Food Security (CCAFS), Water, Land and Ecosystems (WLE) and Forests, Trees and Agroforestry (FTA).

 

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  • A Three-Dimensional View on Soil Biogeochemistry: A Dataset for a Forested Headwater Catchment

A Three-Dimensional View on Soil Biogeochemistry: A Dataset for a Forested Headwater Catchment

31 January, 2017

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Authors: Gottselig, N.; Wiekenkamp, I.; Weihermüller, L.; Brüggemann, N.; Berns, A.E.; Bogena, H.R.; Borchard, N.; Klumpp, E.; Lücke, A.; Missong, A.; Pütz, T.; Vereecken, H.; Huisman, J.A.; Bol, R.

Current understanding of the variability in soil properties and their relationship to processes and spatial patterns in forested landscapes is limited due to the scarcity of datasets providing such information. Here we present a spatially highly resolved dataset that provides detailed information on the three-dimensional variability of biogeochemical properties in the Wüstebach catchment (western Germany), a long-term environmental observation site of the TERENO (Terrestrial Environmental Observatories) project. High-resolution soil sampling was conducted, and physical and biogeochemical soil parameters were recorded per horizon. The dataset is helpful in the analysis of the spatial heterogeneity in biogeochemical properties within soil horizons and with depth through the soil profile. In addition, it shows links between hydrological and biogeochemical properties and processes within the system. Overall, the dataset provides a high-resolution view into (re)cycling, leaching, and storage of nutrients on the catchment scale in a forested headwater catchment.

Publication Year: 2017

ISSN: 1537-2537

Source: Journal of Environmental Quality 46(1): 210-218

DOI: 10.2134/jeq2016.07.0276

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