Land Management

is seen as a basic premise of soil quality (Larson and Pierce, 1991, 1994). If a soil is not suitable for a specific Soil quality concepts are commonly used to evaluate sustainable use, then it is not appropriate to attempt to assign or land management in agroecosystems. The objectives of this review were to trace the importance of soil organic matter (SOM) in Canadian describe quality for that specific use or function. In many sustainable land management studies and illustrate the role of SOM cases, however, it is not possible to make a perfect match and aggregation in sustaining soil functions. Canadian studies on soil between the soil and its intended use. Under these cirquality were initiated in the early 1980s and showed that loss of SOM cumstances, quality must be built into the system using and soil aggregate stability were standard features of nonsustainable best management scenarios. land use. Subsequent studies have evaluated SOM quality using the Ecosystem concepts such as function, processes, attrifollowing logical sequence: soil purpose and function, processes, prop- butes, and indicators, have proved to be a useful frameerties and indicators, and methodology. Limiting steps in this soil work to describe soil quality (Larson and Pierce, 1991, quality framework are the questions of critical limits and standardiza1994; Doran and Parkin, 1994; Doran et al., 1996; Carter tion for soil properties. At present, critical limits for SOM are selected et al., 1997; Karlen et al., 1997). However, a precise using a commonly accepted reference value or based on empirically derived relations between SOM and a specific soil process or function definition of soil quality proves to be elusive. This is (e.g., soil fertility, productivity, or erodibility). Organic matter frac- probably related to the innate difficulty in defining soil tions (e.g., macro-organic matter, light fraction, microbial biomass, itself and to the multifaceted nature (i.e., scientific, perand mineralizable C) describe the quality of SOM. These fractions sonal, and social) of environmental concerns. Carter and have biological significance for several soil functions and processes MacEwan (1996) suggested that although soil quality and are sensitive indicators of changes in total SOM. Total SOM describes an objective state or condition of the soil, it influences soil compactibility, friability, and soil water-holding capac- also is subjective, i.e., evaluated partly on the basis of ity while aggregated SOM has major implications for the functioning personal and social determinations. The above frameof soil in regulating air and water infiltration, conserving nutrients, work of soil quality has utility when it is directed or and influencing soil permeability and erodibility. Overall, organic focused towards the manipulation, engineering, and/or matter inputs, the dynamics of the sand-sized macro-organic matter, and the soil aggregation process are important factors in maintaining management of the soil resource. Thus, soil quality is a and regulating organic matter functioning in soil. technology, an applied science, directed towards better soil management. The objective of this paper is to review the context

The sight of land managers poring over ant checklists is a regular occurrence in Australia, where ant monitoring has been successfully applied to a wide range of land-use situations. The robustness of ants as ecological indicators has been consistently demonstrated, and is supported by an extensive understanding of their community dynamics in relation to disturbance. Despite the widespread recognition of the value of terrestrial invertebrates as bioindicators, the use of ants represents one of the few examples where invertebrates are widely adopted in land management as indicator organisms, as opposed to being consigned to the “too hard” basket. The use of invertebrates as bioindicators in land management will always require specialist expertise and a substantial investment in resources. However, research in Australia shows that invertebrate monitoring does not require comprehensive surveys, and that it is possible to simplify sampling and processing without compromising indicator performance. This should...

The spread of farming from western Asia to Europe had profound long-term social and ecological impacts, but identification of the specific nature of Neolithic land management practices and the dietary contribution of early crops has been problematic. Here, we present previously undescribed stable isotope determinations of charred cereals and pulses from 13 Neolithic sites across Europe (dating ca. 5900–2400 cal B.C.), which show that early farmers used livestock manure and water management to enhance crop yields. Intensive manuring inextricably linked plant cultivation and animal herding and contributed to the remarkable resilience of these combined practices across diverse climatic zones. Critically, our findings suggest that commonly applied paleodietary interpretations of human and herbivore δ15N values have systematically underestimated the contribution of crop-derived protein to early farmer diets.

Summary 1. The indicator qualities of terrestrial invertebrates are widely recognized in the context of detecting ecological change associated with human land-use. However, the use of terrestrial invertebrates as bioindicators remains more a topic of scientific discourse than a part of land-management practice, largely because their inordinate numbers, taxonomic challenges and general unfamiliarity make invertebrates too intimidating for most land-management agencies. Terrestrial invertebrates will not be widely adopted as bioindicators in land management until simple and efficient protocols have been developed that meet the needs of land managers. 2. In Australia, ants are one group of terrestrial insects that has been commonly adopted as bioindicators in land management, and this study examined the reliability of a simplified ant assessment protocol designed to be within the capacity of a wide range of land managers. 3. Ants had previously been surveyed intensively as part of a comprehensive assessment of biodiversity responses to SO 2 emissions from a large copper and lead smelter at Mt Isa in the Australian semi-arid tropics. This intensive ant survey yielded 174 species from 24 genera, and revealed seven key patterns of ant community structure and composition in relation to habitat and SO 2 levels. 4. We tested the extent to which a greatly simplified ant assessment was able to reproduce these results. Our simplified assessment was based on ant ‘bycatch’ from bucket-sized (20-litre) pitfall traps used to sample vertebrates as part of the broader biodiversity survey. We also greatly simplified the sorting of ant morphospecies by considering only large (using a threshold of 4 mm) species, and we reduced sorting time by considering only the presence or absence of species at each site. In this manner, the inclusion of ants in the assessment process required less than 10% of the effort demanded by the intensive ant survey. 5. Our simplified protocol reproduced virtually all the key findings of the intensive survey. This puts effective ant monitoring within the capacity of a wide range of land managers.

ABSTRACT: Management of rangelands can aid in the mitigation of rising atmospheric carbon dioxide concentrations via carbon storage in biomass and soil organic matter, a process termed carbon sequestration. Here we provide a review of current knowledge on the effects of land management practices (grazing, nitrogen inputs, and restoration) and precipitation on carbon sequestration in rangelands. Although there was no statistical relationship between change in soil carbon with longevity of the grazing management practice in native rangelands of the North American Great Plains, the general trend seems to suggest a decrease in carbon sequestration with longevity of the grazing management practice across stocking rates. The relationship of carbon sequestration to mean annual precipitation is negative for both the 0 to 10 cm (0 to 3.9 in) and 0 to 30 cm (0 to 11.8 in) soil depths across stocking rates. The threshold from positive to negative carbon change occurs at approximately 440 mm (17.3 in) of precipitation for the 0 to 10 cm soil depth and at 600 mm (23.6 in) for the 0 to 30 cm soil depth. We acknowledge that largely unexplored is the arena of management-environment interactions needed to increase our understanding of climate-plant-soil-microbial interactions as factors affecting nutrient cycling. Continued refinement of estimates of terrestrial carbon storage in rangelands will assist in the development of greenhouse gas emissions and carbon credit marketing policies, as well as potentially modifying government natural resource conservation programs to emphasize land management practices that increase carbon sequestration.

Abstract Much concern has been raised about population increase in the highlands of Ethiopia and its potential to decrease runoff from the upper Nile Basin to the lowland countries of Sudan and Egypt. The present article examines long-term data on population, land use, land management, rainfall, and surface runoff rates from small test plots (30 m2) and micro-catchments (73–673 ha) in the highlands of Ethiopia and Eritrea. Although the data were generated only on small areas, the results of the analyses can nevertheless be used to draw some conclusions relevant to the highland–lowland water controversies that have persisted in this particular region for many decades. The data indicate that there have been no significant trends over the long term in total annual rainfall in the highlands over the past 30–50 years. Nevertheless, test plot surface runoff rates are clearly influenced by land use and soil degradation, and hence by population density and duration of agriculture. In effect there is 5–30 times more surface runoff from cultivated or degraded test plots than from forested test plots. Analysis and interpretation of data support the hypothesis that surface runoff and sediment yield from the Ethiopian and Eritrean highlands into the upper Nile Basin have most probably increased in the long term due to intensified land use and land degradation induced by population increase, when seen in a historical perspective. Rates of base flow, in turn, must have decreased during the same period, but to a much lesser extent, although conclusive empirical evidence cannot be gained from this experimental setting. One can assume that soil and water conservation measures aiming to ensure long-term livelihoods in the humid to sub-humid highlands will, on the one hand, barely affect overall catchment runoff to the downstream areas, though they will considerably reduce surface runoff and soil loss on slopes as well as river sedimentation rates. On the other hand, in a semiarid catchment where intensive soil and water conservation was carried out, reduction in runoff rates was more pronounced. It can be concluded that population increase in the Ethiopian highlands increased overall runoff rates to lowland areas in earlier times, while recent efforts to conserve watersheds might affect total runoff rates in catchments only in semiarid parts, and much less in humid parts of the Ethiopian highlands.

This paper investigates the land management practices used in the highlands of Tigray, northern Ethiopia, the factors influencing them and their implications for crop production and income. Several factors commonly hypothesised to have a major impact on land management and agricultural production--including population pressure, small landholdings, access to roads and irrigation and extension and credit programmes--are found to have limited direct impact on crop production and income, though most affect the intensity of production. The increase in farming intensity due to these factors has limited impact on value of crop production and income due to low marginal product of labour in crop production, limited productivity impact of inputs such as fertiliser in the moisture-stressed environment of Tigray and limited adoption of such inputs. We find that profitable opportunities exist to increase agricultural production and achieve more sustainable land management in the highlands of Tigray. These opportunities include improvement of crop production using low-external input investments and practices such as stone terraces, reduced tillage and reduced burning. The comparative advantage of people in the Tigray highlands is apparently not in input-intensive cereal crop production but more in such low-input approaches and in alternative livelihood activities such as improved livestock management and non-farm activities. As a result, greater emphasis on developing these alternatives in agricultural extension--as the government of Tigray has been pursuing more recently with its extension programme--and other development programmes is needed. Food crop production should not be ignored in the development strategy, but more prudent use of external inputs such as fertiliser and improved seeds, and greater emphasis on low external input sustainable land management practices, would be helpful. Copyright 2008 The author 2007. Published by Oxford University Press on behalf of the Centre for the Study of African Economies. All rights reserved. For permissions, please email: j[email protected], Oxford University Press.

Abstract. Land use change and land management practices affect the net emissions of the trace gases methane (CH4) and nitrous oxide (N2O), as well as carbon sources and sinks. Changes in CH4 and N2O emissions can substantially alter the overall greenhouse gas balance of a system. Drainage of peatlands for agriculture or forestry generally increases N2O emission as well as that of CO2, but also decreases CH4 emission. Intermittent drainage or late flooding of rice paddies can greatly diminish the seasonal emission of CH4 compared with continuous flooding. Changes in N2O emissions following land use change from forest or grassland to agriculture vary between climatic zones, and the net impact varies with time. In many soils, the increase in carbon sequestration by adopting no‐till systems may be largely negated by associated increases in N2O emission. The promotion of carbon credits for the no‐till system before we have better quantification of its net greenhouse gas balance is naïve. Applying nitrogen fertilizers to forests could increase the forest carbon sink, but may be accompanied by a net increase in N2O; conversely, adding lime to acid forest soils can decrease the N2O emission.

"The government of Uganda, with help from its development partners, is designing and implementing policies and strategies to address poverty, land degradation, and declining agricultural productivity. Land degradation, especially soil erosion and depletion of soil nutrients, is widespread in Uganda and contributes to declining productivity, which in turn increases poverty. The report has four major objectives: (1) to examine the causes of land degradation in Uganda; (2) to identify the determinants of income strategies and land management decisions and their impacts on agricultural productivity, soil erosion, and household income; (3) to assess the trade-offs and complementarities among these different objectives; and (4) to analyze the soil nutrient depletion in eastern Uganda to determine the factors that influence it." from Text

ABSTRACT Knowing spatial patterns of functional microbial guilds can increase our understanding of the relationships between microbial community ecology and ecosystem functions. Using geostatistical modeling to map spatial patterns, we explored the distribution of the community structure, size, and activity of one functional group in N cycling, the denitrifiers, in relation to 23 soil parameters over a 44-ha farm divided into one organic and one integrated crop production system. The denitrifiers were targeted by the nirS and nirK genes that encode the two mutually exclusive types of nitrite reductases, the cd1 heme-type and copper reductases, respectively. The spatial pattern of the denitrification activity genes was reflected by the maps of the abundances of nir genes. For the community structure, only the maps of the nirS community were related to the activity. The activity was correlated with nitrate and dissolved organic nitrogen and carbon, whereas the gene pools for denitrification, in terms of size and composition, were influenced by the soil structure. For the nirS community, pH and soil nutrients were also important in shaping the community. The only unique parameter related to the nirK community was the soil Cu content. However, the spatial pattern of the nirK denitrifiers corresponded to the division of the farm into the two cropping systems. The different community patterns, together with the spatial distribution of the nirS/nirK abundance ratio, suggest habitat selection on the nirS- and nirK-type denitrifiers. Our findings constitute a first step in identifying niches for denitrifiers at scales relevant to land management.