Seasonal migration and land‐use change in Ghana

When farmers migrate yearly to a village to carry out intense farming during the rainy season, and thereafter return to a more permanent place of abode this is referred to as seasonal migration. The impact of such migration on land‐use/land‐cover change in an area within the Volta Basin of Ghana was examined using satellite image analysis and socioeconomic surveys. The most drastic land‐cover change involved the conversion of woodland to agricultural land, while there was also a general transition to less vegetation cover. Socioeconomic surveys revealed that most of the migration occurred during the post‐structural adjustment period in Ghana with declining soil fertility accounting for the highest per cent of causes of migration. Multiple regression results highlighted the role of population size and distribution, marketing of agricultural produce and technological evolution of the household in determining agricultural land‐use change. Policy initiatives that could lead to environment conservation are suggested. Copyright © 2004 John Wiley & Sons, Ltd.     

Impact of land‐use changes on soil hydraulic properties of Calcaric Regosols on the Loess Plateau,NW China

Vegetation restoration efforts (planting trees and grass) have been effective in controlling soil erosion on the Loess Plateau (NW China). Shifts in land cover result in modifications of soil properties. Yet, whether the hydraulic properties have also been improved by vegetation restoration is still not clear. The objective of this paper was to understand how vegetation restoration alters soil structure and related soil hydraulic properties such as permeability and soil water storage capacity. Three adjacent sites with similar soil texture, soil type, and topography, but different land cover (black locust forest, grassland, and cropland) were selected in a typical small catchment in the middle reaches of the Yellow River (Loess Plateau). Seasonal variation of soil hydraulic properties in topsoil and subsoil were examined. Our study revealed that land‐use type had a significant impact on field‐saturated, near‐saturated hydraulic conductivity, and soil water characteristics. Specifically, conversion from cropland to grass or forests promotes infiltration capacity as a result of increased saturated hydraulic conductivity, air capacity, and macroporosity. Moreover, conversion from cropland to forest tends to promote the creation of mesopores, which increase soil water‐storage capacity. Tillage of cropland created temporarily well‐structured topsoil but compacted subsoil as indicated by low subsoil saturated hydraulic conductivity, air capacity, and plant‐available water capacity. No impact of land cover conversion on unsaturated hydraulic conductivities at suction > 300 cm was found indicating that changes in land cover do not affect functional meso‐ and microporosity. Our work demonstrates that changes in soil hydraulic properties resulting from soil conservation efforts need to be considered when soil conservation measures shall be implemented in water‐limited regions. For ensuring the sustainability of such measures, the impact of soil conversion on water resources and hydrological processes needs to be further investigated.     

Multi‐factorial causes of land‐use change: land‐use dynamics in the agropastoral village of Im Mial,northwestern Syria

Land‐use dynamics in drylands are complex processes. In the context of a typical agropastoral village in northwestern Syria Im Mial, the effects of demographic and social changes, reduced soil productivity, changes in agricultural technologies and historical events on land use and land productivity are examined. Decreasing yields, mainly the result of reduced fallow periods and low investments in the land, and the deterioration of the grazing resources are the two main signs of the loss of land productivity in the area. The growing population forces the villagers to practise continuous rainfed barley cultivation with no or only occasional fallow, and without any application of plant nutrients. Also, technological changes, from the use of donkey ploughs and hand harvesting to less labour‐intensive and time‐consuming cultivation practices with tractors and combine harvesters, and the increased importance of stubble in the livestock diet have contributed to the reduction of the fallow periods. The villagers attribute the yield decreases mainly to the low rainfall in the area. The high rainfall variability discourages the fallowing of fields because continuous cultivation maximizes the chances for good harvests in years with high rainfall. There is also an expansion of cultivation into the less fertile and sloping traditional grazing areas. Population growth, increased numbers of livestock and the expansion of cultivated land into grazing areas has also put pressure on the grazing resources of the village. The possession of livestock is seen as a sign of wealth and the villagers aim to have large flocks of animals. For them, livestock is also an important means for investment of cash earned from off‐farm work, which is the main source of income for most of the households in the village. There is a recent trend of increasing levels of crop‐livestock integration with less free grazing that produces higher return to the land users. This may also have a positive effect on the restoration and conservation of the degraded natural traditional grazing grounds. The stabilization and productive use of the land resources in this dry environment requires the combined and interdisciplinary effort from both the land‐users and the policy‐makers. Copyright © 2001 John Wiley & Sons, Ltd.     

Soil carbon and related soil properties along a soil type and land‐use intensity gradient,New South Wales,Australia

The aim of this study was to systematically quantify differences in soil carbon and key related soil properties along a replicated land‐use intensity gradient on three soil landscapes in northwest New South Wales, Australia. Our results demonstrate consistent land‐use effects across all soil types where C, N and C:N ratio were in the order woodland > unimproved pasture = improved pasture > cultivation while bulk density broadly showed the reverse pattern. These land‐use effects were largely restricted to the near surface soil layers. Improved pasture was associated with a significant soil acidification, indicating that strategies to increase soil carbon through pasture improvement in these environments might also have associated soil degradation issues. Total soil carbon stocks were significantly larger in woodland soils, across all soil types, compared with the other land‐uses studied. Non‐wooded systems, however, had statistically similar carbon stocks and this pattern persisted whether or not carbon quantity was corrected for equivalent mass. Our results suggest that conversion from cultivation to pasture in this environment would yield between 0.06 and 0.15 t C/ha/yr which is at the lower end of predicted ranges in Australia and well below values measured in other cooler, wetter environments. We estimate that a 10% conversion rate (cultivation to pasture) across NSW would yield around 0.36 Mt CO₂‐e/yr which would contribute little to emission reductions in NSW. We conclude that carbon accumulation in agricultural soils in this environment might be more modest than current predictions suggest and that systematically collected, regionally specific data are required for the vegetation communities and full range of land‐uses before accurate and reliable predictions of soil carbon change can be made across these extensive landscapes.     

论耕地利用可持续集约化与农户生计转型

借鉴国际可持续集约化思想理念,从思想缘起、概念内涵、目标设定和理论推演等4个方面厘清耕地利用可持续集约化的科学问题;基于农户微观视角,从生计环境、生计资本、生计策略和结果演替等4个方面解构生计转型的客观规律;进而探究耕地利用可持续集约化与农户生计转型之间的互馈关系。研究发现：1）耕地利用可持续集约化具有经营集约化、产出高效化、资源节约化、生态环境不退化和社会可持续五方面内涵,彼此之间存在制衡与协同;通过追求生态、经济和社会效益之间的最优解,使耕地利用的复合效益达到最佳状态。2）农户生计转型是生计环境、生计资本和生计策略共同作用,渐次演变的结果,生计环境影响早期生计资本的积累,生计资本影响生计策略的选择,生计策略决定生计转型的方向。3）耕地利用可持续集约化与农户生计转型在耕地依存关系和土地意识、耕地利用水平和行为响应等方面存在互馈关系。     

Global coffee market influence on land‐use and land‐cover change in the Western Ghats Of India

In this study, we used image‐processing techniques to examine the spatial pattern of land‐use and land‐cover (LULC) change that occurred in the coffee growing area in the Western Ghats of India during the international coffee crisis in the 1990s. The study also ascertains the driving forces of these changes using qualitative research methods that include archival studies and interviews of knowledgeable individuals. We analyzed Landsat Thematic Mapper (TM) for 1991 and Landsat ETM+ for 2002 to quantify LULC. Historical land‐use changes in different land ownership regimes were also analyzed. Global coffee market fluctuations were found to be the major cause of landscape change in the study region. When the global coffee prices increased, more forested areas were cleared for coffee cultivation. Failure of global coffee market forced farmers to convert land from subsistence farming (rice) to short‐period commercial crops like ginger. This also resulted in land degradation in rice paddies. For the farmers in the Western Ghats, LULC decisions are one of the methods used to cope with the vulnerability created due to the international coffee crisis. Copyright © 2009 John Wiley & Sons, Ltd.     

Enhancement of area‐specific land‐use objectives for land development

Maps of land‐use classes and soil series were analysed to identify areas having specific priorities with respect to agricultural land‐use analysis. Remote sensing data supported by field investigations was used to generate land‐use and soil maps. Present relationships between soils and associated land cover/use are analysed and patterns in these relationships are identified using GIS techniques. Relationships observed on the basis of a priori knowledge of the area and the available statistics are compared and these relationships in the field and through interviews with farmers are correlated. This allows three land‐use analysis objectives to be formulated: crop management improvement; crop selection; and conservation. The results can be used to focus the efforts of planning and extension services in the area. The method was tested using a participatory rural appraisal in eighteen villages in which the areas for the three land‐use analysis objectives were identified. The findings are that the areas identified for crop management improvement require knowledge about management practices for a specific crop to optimize yield and water use. Most areas identified for crop selection are occupied by smallholder subsistence farmers with insufficient water for irrigation, and a lack of contact with the extension service. In these areas, identifying suitable crops to minimize risk and allow subsistence for the resource‐poor farmers may be the priority. In areas identified for conservation the question to be addressed is whether to grow a crop at all, or to encourage alternative activities. Copyright © 2004 John Wiley & Sons, Ltd.     

Integrating socio‐economic and biophysical models: revision of a land‐use allocation model

Integration of large‐area, economically driven macro‐models and small‐area, biophysically based models in the Canadian agricultural sector was described recently in the development of a land‐use allocation model (LUAM). We have since developed and integrated an improved methodology for allocating crop area changes generated for large areas by the Canadian Regional Agricultural Model (CRAM) to much smaller Soil Landscapes of Canada (SLC) polygons. Validation of outputs showed considerable improvement. The new coefficients of determination (R²) between simulated and actual data, with previous values in brackets, were 0.69 for fodder corn (0.54), 0.88 for wheat (0.62), 0.77 for hay (0.26), 0.54 for alfalfa (not previously reported), 0.88 for soya bean (0.26) and 0.86 for grain corn (0.22). The best result was obtained for soya bean, with a normalized root mean square error (NRMSE) of 0.31%, and the poorest for alfalfa, with NRMSE = 17.34%.     

The impact of land‐cover change on soil properties in northern Ghana

Effects of changes in land‐cover on soil quality parameters in an area in northern Ghana were studied. Land‐cover changes were derived from maps of the study area for 1984, 1992 and 1999. There were no significant differences between properties of soils under natural vegetation and soils put under cultivation from 1992, but permanently cultivated soils (1984–1999) showed significantly lower physical and chemical soil properties. Soils recently opened up since 1992 for cultivation in the last seven years (i.e. 1992–1999) were found to manifest significantly higher contents of organic C, N, Ca, Mg and ECEC than those under permanent cultivation, suggesting that continuous cropping is responsible for deterioration in soil quality. Minimum organic C contents necessary to meet critical levels of selected soil quality parameters were estimated. The organic C content of recently cultivated soils would need to be increased by about 7 t ha⁻ to replenish soil nutrient capital. This calls for a strategy to synchronize organic matter management with inorganic fertilizer application. Further research is also needed to develop farming systems that conserve organic matter and also improve the quality of organic matter in the study area. Copyright © 2004 John Wiley & Sons, Ltd.     

Consequences of feasible future agricultural land‐use change on soil organic carbon stocks and greenhouse gas emissions in Great Britain

The aim of this study was to assess the consequences of feasible land‐use change in Great Britain on GHG emissions mainly through the gain or loss of soil organic carbon. We use estimates of per‐area changes in soil organic carbon (SOC) stocks and in greenhouse gas (GHG) emissions, coupled with Great Britain (GB) county‐level scenarios of land‐use change based on historical land‐use patterns or feasible futures to estimate the impact of potential land‐use change between agricultural land‐uses. We consider transitions between cropland, temporary grassland (<5 yr under grass), permanent grass (>5 yr under grass) and forest. We show that reversion to historical land‐use patterns as present in 1930 could result in GHG emission reductions of up to ca. 11 Mt CO₂‐eq./yr (relative to a 2004 baseline), because of an increased permanent grassland area. By contrast, cultivation of 20% of the current (2004) permanent grassland area for crop production could result in GHG emission increases of up to ca. 14 Mt CO₂‐eq./yr. We conclude that whilst change between agricultural land‐uses (transitions between permanent and temporary grassland and cropland) in GB is likely to be a limited option for GHG mitigation, external factors such as agricultural product commodity markets could influence future land‐use. Such agricultural land‐use change in GB could have significant impacts on Land‐use, Land‐Use Change and Forestry (LULUCF) emissions, with relatively small changes in land‐use (e.g. 5% plough out of grassland to cropland, or reversion of cropland to the grassland cover in Nitrate Vulnerable Zones of 1998) having an impact on GHG emissions of a similar order of magnitude as the current United Kingdom LULUCF sink. In terms of total UK GHG emissions, however, even the most extreme feasible land‐use change scenarios account for ca. 2% of current national GHG emissions.     

Carbon stock assessment and soil carbon management in agricultural land‐uses in Thailand

The organic carbon pool in agricultural land‐uses is capable of enhancing agricultural sustainability and serving as a potential sink of atmospheric carbon dioxide. A study was carried out to estimate and map carbon stock of different agricultural land‐uses in a sub‐watershed of Thailand and to assess the land‐use sustainability with respect to carbon management. A quadrat sampling methodology was adopted to estimate the biomass and its carbon content of 11 different land‐uses in the study area. Existing soil data were used to calculate the soil carbon. GIS was used for integrating biomass carbon, soil carbon and carbon stock mapping. Roth carbon model was used to project the soil carbon of present land‐uses in the coming 10 years and based on which the sustainability of land‐uses was predicted. The total carbon stock of agricultural land‐uses was estimated to be 20·5 Tg, of which 41·49 per cent was biomass carbon and 58·51 per cent was soil carbon. Among the land‐uses, para rubber had the highest average biomass C (136·34 Mg C ha⁻¹) while paddy had the lowest (7·08 Mg C ha⁻¹). About four‐fifths of agricultural land‐uses in the watershed are sustainable in maintaining the desired level of soil carbon in coming 10 years while one‐fifths are unstable. Such information on carbon stock could be valuable to develop viable land‐use options for agricultural sustainability and carbon sequestration. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of land‐use on soil nutrients and microbial biomass of an alpine region on the northeastern Tibetan plateau,China

Land‐use patterns affect the quantity and quality of soil nutrients as well as microbial biomass and respiration in soil. However, few studies have been done to assess the influence of land‐use on soil and microbial characteristics of the alpine region on the northeastern Tibetan plateau. In order to understand the effect of land‐use management, we examined the chemical properties and microbial biomass of soils under three land‐use types including natural grassland, crop‐field (50 + y of biennial cropping and fallow) and abandoned old‐field (10 y) in the area. The results showed that the losses of soil organic carbon (SOC) and total nitrogen (TN) were about 45 and 43 per cent, respectively, due to cultivation for more than 50 y comparing with natural grassland. Because of the abandonment of cultivation for about a decade, SOC and TN were increased by 27 and 23 per cent, respectively, in comparison with the crop field. Microbial carbon (ranging from 357·5 to 761·6 mg kg⁻¹ soil) in the old‐field was intermediate between the crop field and grassland. Microbial nitrogen (ranging from 29·9 to 106·7 mg kg⁻¹ soil) and respiration (ranging from 60·4 to 96·4 mg CO₂‐C g⁻¹ C_mic d⁻¹) were not significantly lower in the old‐field than those in the grassland. Thus it could be concluded that cultivation decreased the organic matter and microbial biomass in soils, while the adoption of abandonment has achieved some targets of grassland restoration in the alpine region of Gansu Province on the northeastern Tibetan plateau. Copyright © 2010 John Wiley & Sons, Ltd.     

Soil structure of arable and non‐arable land in the Western Siberian Grain Belt in Russia—Application of the soil fingerprint code for topsoil characterization

Soil structure is a key indicator for soil quality. Often, a degradation of the soil structure is the result of inappropriate land management. This investigation was carried out in the Western Siberian forest steppe, because soil degradation is an important issue in this part of the Siberian Grain Belt. Therefore, soil structure and further soil properties were examined in the vicinity of the city of Tyumen, Russia. Arable and non‐arable sites were compared by means of the soil fingerprint code (SFC). With SFC the soil surface conditions, chemical and physical parameters of the topsoil were recorded and evaluated in two depths: 0–5 cm and 5–30 cm. The suitability of the SFC to quantify changes of the soil structure of the topsoil was tested. The SFCs of arable and non‐arable sites show that soil structure deteriorates due to arable use. The percentage of granular aggregates decreases and the percentage of subangular blocky and angular blocky aggregates increases. Furthermore, ploughing leads to strong clod formation. Differences in soil structure between 0–5 cm and 5–30 cm soil depth were smaller at arable sites in comparison to non‐arable sites. It was ascertained the SFC is suitable to quantify changes of the soil structure.     

Land Use and Cover Dynamics Since 1964 in the Afro‐Alpine Vegetation Belt: Lib Amba Mountain in North Ethiopia

Human‐induced land use and land cover (LUC) changes threaten the ecosystem services of the vulnerable tropical afro‐alpine vegetation. Several LUC change studies are available for the Ethiopian highlands, but relatively little is known about LUC change in the afro‐alpine zones. In this study, LUC changes between 1964 and 2012 were mapped for the afro‐alpine zone of Lib Amba Mountain, part of the Abune Yosef Mountains in North Ethiopia. Historical LUC was derived from georeferenced aerial photographs of 1964 and 1982, and the present LUC (2012) from Bing Map satellite imagery. Based on these successive LUC maps a time‐depth map, LUC proportions, LUC transition matrices and LUC change trajectories were calculated. Two main phases of LUC change could be distinguished linked to the neo‐Boserupian perspective. (i) Between 1964 and 1982, there were large‐scale deforestation and general degradation of the vegetation above 3500 m, in a period of low population pressure; (ii) Between 1982 and 2012, an intensification of land use prevailed accompanied with a slight regeneration of the vegetation and the Erica arborea L. forest, under increased population pressure. Depth interviews indicated that local and governmental land management measures are very important for the protection against vegetation depletion and soil degradation. Quick recovery of the forest on Lib Amba provides confidence that degraded afro‐alpine areas would benefit in a short time from complete protection, given the vicinity of remaining patches of afro‐alpine vegetation. Management interventions are thus vital to restore the important ecosystem services of the afro‐alpine vegetation belt. Copyright © 2015 John Wiley & Sons, Ltd.     

Transition from Forest‐based to Cereal‐based Agricultural Systems: A Review of the Drivers of Land use Change and Degradation in Southwest Ethiopia

The southwestern Ethiopian montane forests are one of the most species‐rich ecosystems and are recognised globally as a priority area for the conservation of biodiversity. Particularly, in contrast to the drier central and northern Ethiopian highlands, they have received little attention by researchers. Here, we review changes to agricultural systems in and around these forests that are known as the genetic home of coffee (Coffea arabica L.) and that are important to the livelihoods of many rural people who have developed traditional management practices based on agro‐ecological knowledge, religious taboos and customary tenure rights. We explored the impacts of conversions to agroforestry and cereal‐based cropping systems on biodiversity, soil fertility, soil loss and the socio‐economic conditions and culture. The increasing trend of cereal cropping, resettlement and commercial agriculture causes the deterioration of natural forest cover in the region and threatens biodiversity, land quality, sustainable, traditional farming practices and the livelihood of the local community. Large‐scale plantations of tea, coffee, soapberry locally known as endod (Phytolacca dodecandra L'Hér.) and cereals have resulted in biodiversity loss. Following the conversion of forests, cultivated fields exhibit a significant decline in soil fertility and an increase in soil loss as compared with the traditional agroforestry system. The establishment of a sustainable agricultural system will require a change in paradigm, whereby the intrinsic values of the traditional forest‐based agricultural system are recognised, rather than the ongoing mimicking of agricultural policies that were developed for the open fields of central Ethiopia. Copyright © 2016 John Wiley & Sons, Ltd.     

Land‐use evolution and degradation in Lesvos (Greece): a historical approach

An analysis has been undertaken of the land‐use evolution in the island of Lesvos for the last 5000 years, based on historical and archaeological documents and recent soil and vegetation survey data. A series of maps were compiled using historical documents for the period from 3300 bc to 1886 bc and vegetation field survey data for the period from 1886–1996. A soil survey (scale 1:50 000) was conducted in 1996 in order to relate the land‐use changes to the present physical environment. Cultivation of the land started around 3300 bc and intensified during the 18th century bc . During the Roman period forests were already significantly reduced to satisfy the increasing demands for agricultural products, timber and heating. In the Byzantine period (4th–15th century), vineyards and pastures expanded, mainly by clearing the forests. Olive plantations increased during the 13th century, motivated by the allocation of subsidies. During the first centuries of the Ottoman period, there was a further expansion of olive groves and pastures by reducing forests, while vineyards declined. Great changes occurred in the last century in the geographical distribution and the total area occupied by the various types of land use. Olive groves significantly expanded and were redistributed covering more fertile and productive land on hilly areas by clearing mainly pine forests. Oak forests increased on previous pasture areas. Today, pasture is the main type of land use in hilly areas. These previously forested areas have been cleared without any accompanying measures against soil erosion. This highly degraded land with shallow and severely eroded soils is not able to sustain any profitable agricultural use or natural forest. However, areas cultivated with olives remained sustainable for more than seven centuries without being significantly degraded. Copyright © 2000 John Wiley & Sons, Ltd.     

利用方式和土壤肥力对土壤团聚体和养分的影响

The size distribution of water-stable aggregates and the variability of organic C, N and P contents over aggregate size fractions were studied for orchard, upland, paddy, and grassland soils with high, medium, and low fertility levels. The results showed that > 5 mm aggregates in the cultivated upland and paddy soils were 44.0% and 32.0%, respectively, less than those in the un-tilled orchard soil. Organic C and soil N in different size aggregate fractions in orchard soil with high fertility were significantly higher than those of other land uses. However, the contents of soil P in different size aggregates were significantly greater in the paddy soil as compared to the other land uses. Soil organic C, N and P contents were higher in larger aggregates than those in smaller ones. The amount of water-stable aggregates was positively correlated to their contribution to soil organic C, N and P. For orchard and grassland soils, the > 5 mm aggregates made the greatest contribution to soil nutrients, while for upland soil, the 0.25-0.053 mm aggregates contributed the most to soil nutrients. Therefore, the land use with minimum disturbance was beneficial for the formation of a better soil structure. The dominant soil aggregates in different land use types determined the distribution of soil nutrients. Utilization efficiency of soil P could be improved by converting other land uses to the paddy soil.     

Effects of short‐rotation Eucalyptus plantations on soil quality attributes in highly acidic soils of the central highlands of Ethiopia

In recent decades, conversion of agricultural land to short‐rotation (5–10 years) Eucalyptus plantations has become a common practice in the highlands of Ethiopia. Yet, we have a poor understanding of the effect of these land conversions on soil quality attributes under acidic soil conditions. Previous studies along the same line but based merely on physico‐chemical properties of soils were inconsistent and contradictory. We compared soil physical, chemical and biological properties under 5‐ and 10‐year‐old Eucalyptus plantations with adjacent grassland soils. Results revealed that soil bulk density of adjacent grassland was significantly smaller than in the two Eucalyptus plantations. Although land‐use change from grassland to short‐rotation Eucalyptus did not affect soil texture significantly, values of soil pH, organic carbon, total nitrogen, calcium and cation exchange capacity (CEC) values in adjacent grassland were greater at both 0–10 cm and 10–20 cm depths compared with 5‐ and 10‐year‐old Eucalyptus plantations. Available phosphorus, exchangeable potassium and magnesium were not significantly affected under the three land‐use systems. Generally, no differences were observed in available phosphorus, potassium, calcium and magnesium concentrations or in CEC between the two sampling depths (0–10 cm and 10–20 cm). The microbial biomass carbon and microbial biomass nitrogen recorded in 5‐ and 10‐year‐old Eucalyptus plantations were comparable but significantly smaller than in adjacent grasslands. Kinetics parameters calculated using a first‐order equation (C_t = C_o (1?e^?kt)) showed potentially mineralizable carbon (C_o) was significantly larger (P < 0.001) under grassland compared with 5‐ and 10‐year‐old Eucalyptus plantations. Conversion of grassland to 5‐year‐old and 10‐year‐old Eucalyptus reduced the values of C_o by 21 and 43%, respectively. However, soil physical and chemical properties were not adversely affected by age of Eucalyptus over a 5‐year period. It is concluded that Eucalyptus plantations degrade soil ecosystem functioning and environmental sustainability compared with grassland.