Biogeochemical indicators of peatland degradation – a case study of a temperate bog in northern Germany

Peatland degradation indicated by stable isotope depth profiles and soil carbon loss

Conversion Conversion and drainage of peat land stimulate soil organic matter (SOM) mineralization, which substantially increase carbon loss from soils. Carbon losses from peat lands are probably a major component in global greenhouse gas emissions. The objectives of this study are to evaluate carbon loss from several land use of peat drained, and to evaluate factors affected carbon loss from several land use on peat drained. The study was conducted in Nanggroe Aceh Darussalam Province from May 2008 until October 2009. Carbon losses were calculated by interpretation data of bulk density (BD), ash content and carbon content from 0-50 cm top soil of peat lands. Peat lands characteristics i.e. physical, chemical and biological properties were investigated by field observation and analysis of peat soil samples on the laboratorium. The results showed that: 1) ash content and bulk density of the peat are related, indicating the partial lost of soil C during decomposition and compaction, 2) an “internal tracer” estimate of peat C loss yields estimates of CO2 flux up to 56 t CO2-eq ha-1 year-1 for young oil palm, highly correlated with the measured rates of subsidence of the surface, 3) landscape level variation in maximum water table, salinity and Fe of peat are correlated with measured peat carbon loss.

Improved sampling methods document decline in soil organic carbon stocks and concentrations of permanganate oxidizable carbon after transition from swidden to oil palm cultivation

The influence of land use on desertification processes

The influence of land use on desertification processes

Analysing the effects of soil properties changes associated with land use changes on the simulated water balance: A comparison of three hydrological catchment models for scenario analysis

Soil carbon is a large component of the global carbon cycle and its management can significantly affect the atmospheric CO2 concentration. An important management issue is the extent of soil carbon (C) release when forest is converted to agricultural land. We reviewed the literature to assess changes in soil C upon conversion of forests to agricultural land. Analyses are confounded by changes in soil bulk density upon land‐use change, with agricultural soils on average having 13% higher bulk density. Consistent with earlier reviews, we found that conversion of forest to cultivated land led to an average loss of approximately 30% of soil C. When we restricted our analysis to studies that had used appropriate corrections for changes in bulk density, soil C loss was 22%. When, from all the studies compiled, we considered only studies reporting both soil C and nitrogen (N), average losses of C and N were 24% and 15%, respectively, hence showing a decrease in the average C : N ratio. The magnitude of these changes in the C : N ratio did not correlate with either C or N changes. When considering the transition from forest to pasture, there was no significant change in either soil C or N, even though reported changes in soil C ranged from −50% to +160%. Among studies that reported changes in soil N as well as soil C, C : N ratios both increased and decreased, with trends depending on changes in system N. Systems with increasing soil N generally had decreased C : N ratios, whereas systems with decreasing soil N had increased C : N ratios. Our survey confirmed earlier findings that conversion of forest to cropland generally leads to a loss of soil carbon, although the magnitude of change might have been inflated in many studies by the confounding influence of bulk‐density changes. In contrast, conversion of forest to uncultivated grazing land did not, on average, lead to loss of soil carbon, although individual sites may lose or gain soil C, depending on specific circumstances, such as application of fertiliser or retention or removal of plant residues.

Soil erosion is a severe problem in the karst watershed, and analysis of soil erosion at the watershed scale is urgently needed. This study tried to estimate the soil erodibility factor (K-factor) using the Erosion Productivity Impact Calculator (EPIC) nomograph and evaluate the spatial distribution of the predicted K-factor in a karst watershed. Soil properties and K-factors of five land use types (NF: natural mixed forest, CF: cypress forest, EF: economic forest, ST: stone dike terrace, VF: vegetable land) in the Xialaoxi small watershed were compared and key factors affecting erodibility were analyzed. Results showed that (1) The erodibility K-factor was unevenly distributed within different site types and strongly influenced by anthropogenic activities. The soil K-factors of sample sites subjected to frequent human disturbance (ST, VF) were high, ranging from 0.0480-0.0520 thm2h/(MJmmhm2), while the soil K-factors of natural site types (NF, CF, and EF) were low, ranging from 0.0436-0.0448 thm2h/(MJmmhm2). (2) The soil texture in the Xialaoxi watershed was mostly loamy, and that of the agricultural areas frequently disturbed by agricultural practices (ST, VF) was silty loam. (3) Soil carbon fractions were affected by land use types. Soil organic carbon storage of NF and CF had strong spatial heterogeneity. The soil organic carbon (SOC) and labile organic carbon (LOC) of the two were significantly higher than those of the disturbed EF and cultivated land soil. (4) There was a synergistic effect between the soil properties and the K-factor. K was significantly negatively related to sand fractions (2-0.05 mm) and non-capillary porosity, while positively related to silt content (0.05-0.002 mm). Overall, changes in bulk density (BD), total porosity (TP), non-capillary porosity (NCP), texture, and organic matter content caused by natural restoration or anthropogenic disturbance were the main reasons for soil erodibility. Natural care (sealing) and construction of stone dike planting practices were effective ways to reduce soil erosion in small karst watershed areas of western Hubei.

Towards sound comparisons of soil carbon stocks: A proposal based on the cumulative coordinates approach

Evaluation of the use of pre- and post-harvest bulk density measurements in wet Eucalyptus obliqua forest in Southern Tasmania

The effect of drying 10 organic and mineral soils originating from the Florida Everglades Agricultural Area upon extractable levels of phosphorus and potassium was studied. When measurements of phosphorus and potassium were expressed volumetrically (w/v), variability in soil test levels of phosphorus and potassium were largely a result of changes in water content and dry bulk density. This variability was reduced when the results were expressed gravimetrically (w/w) or when the drying procedures were standardized. The variability of soil test levels of phosphorus and potassium expressed volumetrically was present in mineral and organic soils but was more pronounced on organic soils which were susceptible to large changes in dry bulk density upon extensive drying.

Functional morphology and productivity of a tussock grassland in the Bolivian Altiplano

Impact of Rain Forest Transformation on Roots and Functional Diversity of Root-Associated Fungal Communities

BackgroundAs interest in the voluntary soil carbon market surges, carbon registries have been developing new soil carbon measurement, reporting, and verification (MRV) protocols. These protocols are inconsistent in their approaches to measuring soil organic carbon (SOC). Two areas of concern include the type of SOC stock accounting method (fixed-depth (FD) vs. equivalent soil mass (ESM)) and sampling depth requirement. Despite evidence that fixed-depth measurements can result in error because of changes in soil bulk density and that sampling to 30 cm neglects a significant portion of the soil profile’s SOC stock, most MRV protocols do not specify which sampling method to use and only require sampling to 30 cm. Using data from UC Davis’s Century Experiment (“Century”) and UW Madison’s Wisconsin Integrated Cropping Systems Trial (WICST), we quantify differences in SOC stock changes estimated by FD and ESM over 20 years, investigate how sampling at-depth (> 30 cm) affects SOC stock change estimates, and estimate how crediting outcomes taking an empirical sampling-only crediting approach differ when stocks are calculated using ESM or FD at different depths.ResultsWe find that FD and ESM estimates of stock change can differ by over 100 percent and that, as expected, much of this difference is associated with changes in bulk density in surface soils (e.g., r = 0.90 for Century maize treatments). This led to substantial differences in crediting outcomes between ESM and FD-based stocks, although many treatments did not receive credits due to declines in SOC stocks over time. While increased variability of soils at depth makes it challenging to accurately quantify stocks across the profile, sampling to 60 cm can capture changes in bulk density, potential SOC redistribution, and a larger proportion of the overall SOC stock.ConclusionsESM accounting and sampling to 60 cm (using multiple depth increments) should be considered best practice when quantifying change in SOC stocks in annual, row crop agroecosystems. For carbon markets, the cost of achieving an accurate estimate of SOC stocks that reflect management impacts on soils at-depth should be reflected in the price of carbon credits.

Soil compaction negatively affects soil productivity, fertilizer use efficiency and water infiltration. The extent of compaction is dependant on soil strength, which is influenced by the soil moisture content. The purpose of this study was to determine the extent of soil compaction (measured by changes in soil bulk density and shear strength) and soil deformation incurred due to a single pass of a tractor and a fully loaded slurry tanker over grassland soils at a range of soil moisture deficits (SMD). The study should identify threshold values of SMD at which adverse soil compaction becomes significant for the soil-crop system. These values may be incorporated into the forecasting and decision making process for slurry spreading. SMD was used as a proxy for volumetric water content. Treatments of a single pass by a Landini Vision 105 tractor and a loaded 7.2 m³ single axle slurry tanker (total weight of c. 18 tonnes) were conducted on well, moderate and poorly drained grassland soils at forecasted SMD of 0, 5, 10 and 20 mm. The moderately drained soil was classified as a loam, while the well and poorly drained sites were classified as sandy loams. Changes in soil bulk density and torsional shear strength were used as indicators of compaction, with rut profile measurements taken to measure the extent of surface deformation, which is often the most visible indicator of compaction on the soil surface. Grass yields were measured at 30 and 60 days subsequent to trafficking. Results showed that SMD at the time of traffic had an effect on the changes in bulk density, shear strength and the extent of soil rutting following wheel traffic. Preliminary results indicate that higher SMD at the time of trafficking resulted in smaller changes to soil characteristics and more rapid recovery from surface deformation than when trafficking occurred at lower SMD. Trafficking at an SMD of 20 mm led to mean increases in soil bulk density of 8% and formation of ruts with cross sectional areas in the range of 29.4 cm² to 98.3 cm². Trafficking at 0 SMD (field capacity) led to mean increases in bulk density of 15% and the formation of rut profiles in the range of 91.6 cm² to 197.9 cm². These preliminary results indicate that forecasted SMD provides a valuable tool to determine the suitability of the soil for supporting farm vehicle operations such as slurry spreading. This study is still ongoing, with more detailed results and analysis to be forthcoming.