• Authors:
    • Herel, C. H.
    • Pieper, R. D.
    • Holechek, J. L.
  • Year: 2004
  • Summary: Offering complete, up-to-date coverage of the primary subject areas in range management, this book brings the concepts of rangeland management into clear focus establishing important fundamentals and perspectives of key subjects in the field, and helping rangeland managers and laymen broaden their overall education in natural resource use and management using the most recent scientific reports.<p>Provides current information and approaches on dealing with modern range management problems in the U.S. as well as developing countries. It also includes management strategies for various range types, and detailed discussions on multiple use of rangeland. Looks at the latest data on practical range management problems, offering useful approaches for setting stocking rates, and analyzes rangeland economics and ranch management using the most up-to-date research.
  • Authors:
    • Lindwall, W.
    • Kulshreshtha, S.
    • Desjardins, R.
    • Junkins, B.
    • Boehm, M.
  • Source: Climatic Change
  • Volume: 65
  • Issue: 3
  • Year: 2004
  • Summary: Net greenhouse gas (GHG) emissions from Canadian crop and livestock production were estimated for 1990, 1996 and 2001 and projected to 2008. Net emissions were also estimated for three scenarios (low (L), medium (M) and high (H)) of adoption of sink enhancing practices above the projected 2008 level. Carbon sequestration estimates were based on four sink-enhancing activities: conversion from conventional to zero tillage (ZT), reduced frequency of summerfallow (SF), the conversion of cropland to permanent cover crops (PC), and improved grazing land management (GM). GHG emissions were estimated with the Canadian Economic and Emissions Model for Agriculture (CEEMA). CEEMA estimates levels of production activities within the Canadian agriculture sector and calculates the emissions and removals associated with those levels of activities. The estimates indicate a decline in net emissions from 54 Tg CO2-Eq yr-1 in1990 to 52 Tg CO2-Eq yr-1 in 2008. Adoption of thesink-enhancing practices above the level projected for 2008 resulted in further declines in emissions to 48 Tg CO2-Eq yr-1 (L), 42 TgCO2-Eq yr-1 (M) or 36 Tg CO2-Eq yr-1 (H). Among the sink-enhancing practices, the conversion from conventional tillage to ZT provided the largest C sequestration potential and net reduction in GHG emissions among the scenarios. Although rates of C sequestration were generally higher for conversion of cropland to PC and adoption of improved GM, those scenarios involved smaller areas of land and therefore less C sequestration. Also, increased areas of PC were associated with an increase in livestock numbers and CH4 and N2O emissions from enteric fermentation andmanure, which partially offset the carbon sink. The CEEMA estimates indicate that soil C sinks are a viable option for achieving the UNFCCC objective of protecting and enhancing GHG sinks and reservoirs as a means of reducing GHG emissions (UNFCCC, 1992).
  • Authors:
    • Singh, J.
    • Bhandral, R.
    • Luo, J. F.
    • Saggar, S.
    • Bolan, N. S.
  • Source: Advances in Agronomy
  • Volume: 84
  • Year: 2004
  • Summary: Grazing-managed pasture is a major system of livestock production in many countries. Grazed pastures receive large inputs of nitrogen (N), derived from biological fixation of atmospheric N, through the addition of manures and fertilizers, and the deposition of animal excreta. However, only a small proportion of the N ( < 15%) consumed by grazing animals is converted to milk or live weight gain, the reminder is excreted. Loss of N occurs mainly through ammonia (NH3) volatilization, release of gaseous N such as nitric oxide (NO) and nitrous oxide (N2O) through biological denitrification, and nitrate (NOD leaching, which has both economical and environmental implications. Nitrogen is an important plant nutrient and its loss affects both the quality and quantity of feed, thereby leading to poor animal production. Recently there have been increasing concerns about the environmental impacts of N loss through leaching (i.e., methaemoglobinaemia) and gaseous emission (i.e., greenhouse gas). In this chapter, the various sources of N input to grazed pasture are discussed in relation to the dynamics of N, the measurement and modelling gaseous emissions of N, and the implications of gaseous emission in relation to economic loss and environmental degradation. The dynamics of N transformations in soil-plant system with particular emphasis on the biochemistry of gaseous emission, and the measurement techniques and the use of process-based models to predict gaseous emissions are discussed. The practical implications of gaseous emission are discussed in relation to acid rain and climate change (i.e., the Kyoto Protocol). Grazing and farm management practices to mitigate gaseous emissions are highlighted. (C) 2004 by Elsevier Inc.
  • Authors:
    • Chapman, D. F.
    • White, R. E.
    • Chen, D.
    • Eckard, R. J.
  • Source: Australian Journal of Agricultural Research
  • Volume: 54
  • Year: 2003
  • Authors:
    • Intergovernmental Panel on Climate Change
  • Year: 2003
  • Summary: This report on Good Practice Guidance for Land Use, Land-Use Change and Forestry (GPG-LULUCF) is the response to the invitation by the United Nations Framework Convention on Climate Change (UNFCCC)1 to the Intergovernmental Panel on Climate Change (IPCC)2 to develop good practice guidance for land use, land-use change and forestry (LULUCF). GPG-LULUCF provides supplementary methods and good practice guidance for estimating, measuring, monitoring and reporting on carbon stock changes and greenhouse gas emissions from LULUCF activities under Article 3, paragraphs 3 and 4, and Articles 6 and 12 of the Kyoto Protocol.
  • Authors:
    • Paustian, K.
    • Six, J.
    • Conant, R. T.
  • Source: Biology and Fertility of Soils
  • Volume: 38
  • Issue: 6
  • Year: 2003
  • Summary: Changes in grassland management intended to increase productivity can lead to sequestration of substantial amounts of atmospheric C in soils. Management-intensive grazing (MiG) can increase forage production in mesic pastures, but potential impacts on soil C have not been evaluated. We sampled four pastures (to 50 cm depth) in Virginia, USA, under MiG and neighboring pastures that were extensively grazed or hayed to evaluate impacts of grazing management on total soil organic C and N pools, and soil C fractions. Total organic soil C averaged 8.4 Mg C ha -1 (22%) greater under MiG; differences were significant at three of the four sites examined while total soil N was greater for two sites. Surface (0-10 cm) particulate organic matter (POM) C increased at two sites; POM C for the entire depth increment (0-50 cm) did not differ significantly between grazing treatments at any of the sites. Mineral-associated C was related to silt plus clay content and tended to be greater under MiG. Neither soil C:N ratios, POM C, or POM C:total C ratios were accurate indicators of differences in total soil C between grazing treatments, though differences in total soil C between treatments attributable to changes in POM C (43%) were larger than expected based on POM C as a percentage of total C (24.5%). Soil C sequestration rates, estimated by calculating total organic soil C differences between treatments (assuming they arose from changing grazing management and can be achieved elsewhere) and dividing by duration of treatment, averaged 0.41 Mg C ha -1 year -1 across the four sites.
  • Authors:
    • Thornton, P. K.
    • Jones, P. G.
  • Source: Conservation Ecology
  • Volume: 5
  • Issue: 2
  • Year: 2003
  • Summary: Making decisions in natural resource management involves an understanding of the risk and uncertainty of the outcomes, such as crop failure or cattle starvation, and of the normal spread of the expected production. Hedging against poor outcomes often means lack of investment and slow adoption of new methods. At the household level, production instability can have serious effects on income and food security. At the national level, it can have social and economic impacts that may affect all sectors of society. Crop models such as CERES-Maize are excellent tools for assessing weather-related production variability. WATBAL is a water balance model that can provide robust estimates of the potential growing days for a pasture. These models require large quantities of daily weather data that are rarely available. MarkSim is an application for generating synthetic daily weather files by estimating the third-order Markov model parameters from interpolated climate surfaces. The models can then be run for each distinct point on the map. This paper examines the growth of maize and pasture in dryland agriculture in southern Africa (includes the southern part of Tanzania, Malawi, much of Mozambique, and all of Zimbabwe, and extends west from the Indian Ocean to include Zambia, the southeastern part of the Democratic Republic of Congo and small portions of Angola). Weather simulators produce independent estimates for each point on the map; however, we know that a spatial coherence of weather exists. We investigated a method of incorporating spatial coherence into MarkSim and show that it increases the variance of production. This means that all of the farmers in a coherent area share poor yields, with important consequences for food security, markets, transport, and shared grazing lands. The long-term aspects of risk are associated with global climate change. We used the results of a global circulation model to extrapolate to the year 2055. We found that low maize yields would become more likely in the marginal areas, whereas they may actually increase in some areas. The same trend was found with pasture growth. We outline areas where further work is required before these tools and methods can address natural resource management problems in a comprehensive manner at local community and policy levels.
  • Authors:
    • Schuman, G. E.
    • Reeder, J. D.
  • Source: Environmental Pollution
  • Volume: 116
  • Issue: 3
  • Year: 2002
  • Summary: We evaluated the effects of livestock grazing on C content of the plant-soil system (to 60 cm) of two semi-arid grasslands: a mixed-grass prairie (grazed 12 years), and a short-grass steppe (grazed 56 years). Grazing treatments included season-long grazing at heavy and light stocking rates, and non-grazed exclosures. Significantly higher soil C (0-30cm) was measured in grazed pastures compared to non-grazed exclosures, although for the short-grass steppe higher soil C was observed with the heavy grazing treatment only. Excluding grazing caused an immobilization of C in excessive aboveground plant litter, and an increase in annual forbs and grasses which lack dense fibrous rooting systems conducive to soil organic matter formation and accumulation. Our data indicate that higher soil C with grazing was in part the result of more rapid annual shoot turnover, and redistribution of C within the plant-soil system as a result of changes in plant species composition.
  • Authors:
    • Albrecht, A.
    • Sa, J. C. D.
    • Ogle, S. M.
    • Denef, K.
    • Feller, C.
    • Six, J.
  • Source: Agronomie
  • Volume: 22
  • Issue: 7
  • Year: 2002
  • Summary: The long-term stabilization of soil organic matter (SOM) in tropical and temperate regions is mediated by soil biota (e. g. fungi, bacteria, roots and earthworms), soil structure (e. g. aggregation) and their interactions. On average, soil C turnover was twice as fast in tropical compared with temperate regions, but no major differences were observed in SOM quality between the two regions. Probably due to the soil mineralogy dominated by 1:1 clay minerals and oxides in tropical regions, we found a higher aggregate stability, but a lower correlation between C contents and aggregate stability in tropical soils. In addition, a smaller amount of C associated with clay and silt particles was observed in tropical versus temperate soils. In both tropical and temperate soils, a general increase in C levels (approximate to 325 +/- 113 kg C.ha(-1).yr(-1)) was observed under no-tillage compared with conventional tillage. On average, in temperate soils under no-tillage, compared with conventional tillage, CH4 uptake (approximate to0.42 +/- 0.10 kg C-CH4.ha(-1) yr(-1)) increased and N2O emissions increased (approximate to 1.95 +/- 0.45 kg N-N2O.ha(-1).yr(-1)). These increased N2O emissions lead to a negative global warming potential when expressed on a CO2 equivalent basis.
  • Authors:
    • Cross, A. F.
    • Engle, D. M.
    • Tunnell, T. R.
    • Zhang, H.
    • Fuhlendorf, S. D.
  • Source: Restoration Ecology
  • Volume: 10
  • Issue: 2
  • Year: 2002
  • Summary: A comparative analysis of soils and vegetation from cultivated areas reseeded to native grasses and native prairies that have not been cultivated was conducted to evaluate restoration of southern mixed prairie of the Great Plains over the past 30 to 50 years. Restored sites were within large tracts of native prairie and part of long-term grazing intensity treatments (heavy, moderate, and ungrazed), allowing evaluation of the effects of grazing intensity on prairie restoration. Our objective was to evaluate restored and native sites subjected to heavy and moderate grazing regimes to determine if soil nutrients from reseeded cultivated land recovered after 30 years of management similar to the surrounding prairie and to identify the interactive influence of different levels of grazing and history of cultivation on plant functional group composition and soils in mixed prairies. For this mixed prairie, soil nitrogen and soil carbon on previously cultivated sites was 30 to 40% lower than in uncultivated native prairies, indicating that soils from restored sites have not recovered over the past 30 to 50 years. In addition, it appears that grazing alters the extent of recovery of these grassland soils as indicated by the significant interaction between grazing intensity and cultivation history for soil nitrogen and soil carbon. Management of livestock grazing is likely a critical factor in determining the potential restoration of mixed prairies. Heavy grazing on restored prairies reduces the rate of soil nutrient and organic matter accumulation. These effects are largely due to changes in composition (reduced tallgrasses), reduced litter accumulation, and high cover of bare ground in heavily grazed restored prairies. However, it is evident from this study that regardless of grazing intensity, restoration of native prairie soils requires many decades and possibly external inputs to adequately restore organic matter, soil carbon, and soil nitrogen.