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Fayez Raiesi - One of the best experts on this subject based on the ideXlab platform.

  • a minimum data set and soil quality index to quantify the effect of land use conversion on soil quality and degradation in native Rangelands of upland arid and semiarid regions
    Ecological Indicators, 2017
    Co-Authors: Fayez Raiesi
    Abstract:

    Abstract Conversion of native Rangelands to croplands potentially influences soil functions and quality. The aim of the current study was to assess soil quality (SQ) after Rangeland conversion and degradation for more than 40 years using an indexing framework and integrated approach. Fifteen soil attributes were measured at two sampling depths (0–20 and 20–40 cm) of paired native undisturbed and adjacent cultivated Rangelands at three Rangeland sites. The soil organic carbon (OC), electrical conductivity (EC) and arylsulphatase (ARY) activity were found to be the key indicators of the minimum data set and these indicators greatly affected the computed soil quality index (SQI), particularly in the soil surface. The contribution of OC, EC and ARY to the overall SQI was 77, 13 and 10%, respectively. Although Rangeland conversion reduced other soil attributes (including aggregate stability, available water capacity, cation exchange capacity, microbial biomass, microbial activity and the activities of urease and invertase enzymes), in particular at the 0–20 cm depth, these variables did not contribute to the estimated SQI values because of their high correlation with OC contents (i.e., strong interdependency). Cultivated Rangelands were characterized by a low soil OC content, EC and ARY activity, and consequently a low SQI. A significant decline in SQI value (29–47%) was observed as a result of Rangeland conversion to croplands, depending on soil depth considered and scoring function used to compute the SQI. Overall, converting native Rangelands to croplands decreased SQ to 52–64% of their potential capacity using a non-linear scoring method. In summary, soil OC, EC and ARY are the most important indicators, which can be used to monitor and asses the degradation of Rangeland SQ after conversion to croplands in these arid and semiarid upland environments. This finding is of especial importance because the assessment of SQ allows the successful and straightforward discrimination between Rangeland and cropland ecosystems or to quantify land use conversion effects on SQ. It is concluded that the rate of soil changes can be assessed and compared more accurately in the studies of land use conversions in native Rangeland ecosystems using the current indexing framework due to its simplicity and quantitative flexibility.

  • Bulk soil and particle size-associated C and N under grazed and ungrazed regimes in Mountainous arid and semi-arid Rangelands
    Nutrient Cycling in Agroecosystems, 2012
    Co-Authors: Najmeh Ghorbani, Fayez Raiesi, Shoja Ghorbani
    Abstract:

    Sheep grazing is known to influence soil organic carbon (SOC) storage and dynamics in Rangelands. However, very little is known of grazing impacts on measurable SOC pools associated with primary particles, particulate organic matter (POM) and carbohydrates in the heavily grazed Rangelands of Zagros Mountains, Iran. Bulk SOC, total nitrogen (N), POM and hot-water extractable carbohydrates (HWC) as well as different SOC and N fractions in particle-size separates were studied in natural mountainous Rangelands of arid (Boroujen with 255 mm annual rainfall) and semi-arid (Sabzkouh with 860 mm annual rainfall) sites, Central Zagros. Two sheep grazing regimes including grazed and ungrazed (for 20–25 years) Rangelands with four replicates were identified as the grazing treatments at each site. Soil samples (0–15 cm) were taken and analyzed for bulk SOC, total N, POM, HWC, and SOC and N associated with physical fractions. Bulk SOC contents were similar for both ungrazed and grazed regimes, while total N contents significantly decreased under grazed conditions. Bulk soil POM and HWC contents decreased considerably and clearly by sheep grazing, indicating that these fractions of total soil organic matter (SOM) pool may be suitable indicators for detecting the grazing effects on bulk SOC changes and storage in these arid and semi-arid ecosystems. Semi-arid Rangeland sites contained more bulk SOC, total N and POM contents than arid Rangeland sites. These differences were primarily due to the large differences in vegetation composition, annual rainfall and soil conditions between the two Rangelands. After 20–25 years of grazing over 10–33 % of SOC and total N losses occurred in the sand- and clay-size fractions with 10 % increases in the silt fraction. This means sheep grazing increases the contribution of the silt fraction to bulk soil N. We found evidence that sheep grazing decreases soil POM and HWC pools, and the sand fraction C, suggesting a lower recent annual input of decomposable organic C in heavily grazed Rangelands. Sheep grazing had no influence on the potential C mineralization of the bulk soil at the semi-arid site (Sabzkouh), but reduced C mineralization at the arid-site (Boroujen), indicating that sheep grazing may affect SOC dynamics by changes in substrate quality at the former, but by substrate quantity at the later. In brief, long-term sheep grazing can potentially lead to losses of both labile and no-labile SOM in these arid and semi-arid Rangelands.

Shoja Ghorbani - One of the best experts on this subject based on the ideXlab platform.

  • Bulk soil and particle size-associated C and N under grazed and ungrazed regimes in Mountainous arid and semi-arid Rangelands
    Nutrient Cycling in Agroecosystems, 2012
    Co-Authors: Najmeh Ghorbani, Fayez Raiesi, Shoja Ghorbani
    Abstract:

    Sheep grazing is known to influence soil organic carbon (SOC) storage and dynamics in Rangelands. However, very little is known of grazing impacts on measurable SOC pools associated with primary particles, particulate organic matter (POM) and carbohydrates in the heavily grazed Rangelands of Zagros Mountains, Iran. Bulk SOC, total nitrogen (N), POM and hot-water extractable carbohydrates (HWC) as well as different SOC and N fractions in particle-size separates were studied in natural mountainous Rangelands of arid (Boroujen with 255 mm annual rainfall) and semi-arid (Sabzkouh with 860 mm annual rainfall) sites, Central Zagros. Two sheep grazing regimes including grazed and ungrazed (for 20–25 years) Rangelands with four replicates were identified as the grazing treatments at each site. Soil samples (0–15 cm) were taken and analyzed for bulk SOC, total N, POM, HWC, and SOC and N associated with physical fractions. Bulk SOC contents were similar for both ungrazed and grazed regimes, while total N contents significantly decreased under grazed conditions. Bulk soil POM and HWC contents decreased considerably and clearly by sheep grazing, indicating that these fractions of total soil organic matter (SOM) pool may be suitable indicators for detecting the grazing effects on bulk SOC changes and storage in these arid and semi-arid ecosystems. Semi-arid Rangeland sites contained more bulk SOC, total N and POM contents than arid Rangeland sites. These differences were primarily due to the large differences in vegetation composition, annual rainfall and soil conditions between the two Rangelands. After 20–25 years of grazing over 10–33 % of SOC and total N losses occurred in the sand- and clay-size fractions with 10 % increases in the silt fraction. This means sheep grazing increases the contribution of the silt fraction to bulk soil N. We found evidence that sheep grazing decreases soil POM and HWC pools, and the sand fraction C, suggesting a lower recent annual input of decomposable organic C in heavily grazed Rangelands. Sheep grazing had no influence on the potential C mineralization of the bulk soil at the semi-arid site (Sabzkouh), but reduced C mineralization at the arid-site (Boroujen), indicating that sheep grazing may affect SOC dynamics by changes in substrate quality at the former, but by substrate quantity at the later. In brief, long-term sheep grazing can potentially lead to losses of both labile and no-labile SOM in these arid and semi-arid Rangelands.

Najmeh Ghorbani - One of the best experts on this subject based on the ideXlab platform.

  • Bulk soil and particle size-associated C and N under grazed and ungrazed regimes in Mountainous arid and semi-arid Rangelands
    Nutrient Cycling in Agroecosystems, 2012
    Co-Authors: Najmeh Ghorbani, Fayez Raiesi, Shoja Ghorbani
    Abstract:

    Sheep grazing is known to influence soil organic carbon (SOC) storage and dynamics in Rangelands. However, very little is known of grazing impacts on measurable SOC pools associated with primary particles, particulate organic matter (POM) and carbohydrates in the heavily grazed Rangelands of Zagros Mountains, Iran. Bulk SOC, total nitrogen (N), POM and hot-water extractable carbohydrates (HWC) as well as different SOC and N fractions in particle-size separates were studied in natural mountainous Rangelands of arid (Boroujen with 255 mm annual rainfall) and semi-arid (Sabzkouh with 860 mm annual rainfall) sites, Central Zagros. Two sheep grazing regimes including grazed and ungrazed (for 20–25 years) Rangelands with four replicates were identified as the grazing treatments at each site. Soil samples (0–15 cm) were taken and analyzed for bulk SOC, total N, POM, HWC, and SOC and N associated with physical fractions. Bulk SOC contents were similar for both ungrazed and grazed regimes, while total N contents significantly decreased under grazed conditions. Bulk soil POM and HWC contents decreased considerably and clearly by sheep grazing, indicating that these fractions of total soil organic matter (SOM) pool may be suitable indicators for detecting the grazing effects on bulk SOC changes and storage in these arid and semi-arid ecosystems. Semi-arid Rangeland sites contained more bulk SOC, total N and POM contents than arid Rangeland sites. These differences were primarily due to the large differences in vegetation composition, annual rainfall and soil conditions between the two Rangelands. After 20–25 years of grazing over 10–33 % of SOC and total N losses occurred in the sand- and clay-size fractions with 10 % increases in the silt fraction. This means sheep grazing increases the contribution of the silt fraction to bulk soil N. We found evidence that sheep grazing decreases soil POM and HWC pools, and the sand fraction C, suggesting a lower recent annual input of decomposable organic C in heavily grazed Rangelands. Sheep grazing had no influence on the potential C mineralization of the bulk soil at the semi-arid site (Sabzkouh), but reduced C mineralization at the arid-site (Boroujen), indicating that sheep grazing may affect SOC dynamics by changes in substrate quality at the former, but by substrate quantity at the later. In brief, long-term sheep grazing can potentially lead to losses of both labile and no-labile SOM in these arid and semi-arid Rangelands.

César Mario Rostagno - One of the best experts on this subject based on the ideXlab platform.

  • Soil erodibility and quality of volcanic soils as affected by pine plantations in degraded Rangelands of NW Patagonia
    European Journal of Forest Research, 2016
    Co-Authors: Ludmila La Manna, Carlos Guillermo Buduba, César Mario Rostagno
    Abstract:

    NW Patagonia in Argentina has high potential for planting fast-growing exotic conifers, supported by its volcanic soils. Nonetheless, many aspects related to the effects of pine plantations on soil are still unknown. We aimed to evaluate the quality and erodibility of volcanic soils under the hypothesis that Pinus ponderosa plantations increase the quality and decrease the erosion rate of soils compared to degraded Rangelands. Rainfall simulation experiments were performed in degraded Rangeland soils and in pine plantations with none, partial and complete removal of fresh litter and duff layers. Results showed that Rangeland soils were highly susceptible to water erosion. Sediment production in the Rangeland varied between 144 and 750 g m^−2. Loamy sand soils, poor in organic matter (OM) and without non-crystalline aluminosilicates, were the most erodible soils. The plantations improved soil quality, with positive changes in OM content and total and effective porosity, mainly in soils without non-crystalline materials. Soil erosion in pine plantations was negligible when fresh litter was either conserved or removed, with erosion rates as low as 6.2 ± 1.5 and 23.7 ± 7.9 g m^−2, respectively. Even when fresh litter and duff layers were totally removed, soil erosion rates in the pine plantations (129.1 ± 23.2 g m^−2) were lower than in the Rangeland sites; however, this reduction was significant only for the most erodible soils. The high erodibility of volcanic soils and the low soil cover in overgrazed Rangelands revealed the fragility of the soils in the study area. We show that pine plantations, an alternative land use of Rangelands, improve some aspects of soil quality, provide a mulching effect through the litter layer and became a mean for controlling soil erosion.

D Stafford M Smith - One of the best experts on this subject based on the ideXlab platform.

  • a synthesis of recent global change research on pasture and Rangeland production reduced uncertainties and their management implications
    Agriculture Ecosystems & Environment, 2000
    Co-Authors: B D Campbell, D Stafford M Smith
    Abstract:

    There is significant uncertainty about the effects of global change on the vegetation and animal productivity of pasture and Rangeland ecosystems. This paper presents a synthesis of progress made between 1994 and 1999 in the Global Change and Terrestrial Ecosystems (GCTE) Pastures and Rangelands Core Research Project 1 (CRP1) network, a world-wide network of 83 full-time equivalent researchers established in different pasture and Rangelands systems to reduce these uncertainties. The network focuses on key processes controlling forage and animal production at a paddock/landscape scale, in order to improve the ability to model animal production. To date, the network has resulted in a considerable reduction in the uncertainties about the effects of elevated CO2 on growth, and to a lesser extent composition and forage quality, of intensive pastures in cool, wet climatic zones. However, knowledge of other grazed ecosystems and processes is more limited. The greatest confidence is in predicting implications for vegetation production, with lesser confidence in implications for vegetation composition, animal production and adaptation options. Overall, the stimulatory effect of double ambient CO2 on grassland production averages about C17% in ecosystem-based experiments. This is less than previous estimates. Individual system responses to elevated CO2 can vary widely and are predicted to be higher in moisture-limited and warm-season grassland systems. Species composition change is likely to be an important mechanism altering grassland production and its value for grazing livestock, especially in drier Rangelands with woody shrub invasion. On average, the legume content of productive grass‐legume swards is increased by C10% due to CO2 enrichment. Leaf nitrogen reductions due to elevated CO2 are often observed but are generally modest compared with effects of other management factors. New data collection efforts should be focused in areas of the world which are most sensitive to food security issues and most subject to global change, in particular humid semi-arid margins and subtropical grasslands. There remains no good basis for extrapolating findings between different pasture and Rangeland systems. This synthesis indicates that greater focus is required on the linkages between the biophysical, social and economic factors that will influence future changes in pasture and Rangeland ecosystems and their implications for food security. © 2000 Elsevier Science B.V. All rights reserved.