Land Degradation and Development

Published by Wiley
Online ISSN: 1099-145X
Print ISSN: 1085-3278
A long-term experiment comparing no-till with conventional tillage systems across five rotations was evaluated 11 years after initiation. The objectives of the present paper are (1) to report differences in soil chemical properties (namely soil organic matter, total nitrogen, phosphorus, potassium and pH) that have resulted by converting from conventional to no-till under contrasting cropping systems and (2) to draw tentative conclusions and recommendations on fertility status and fertilizer use and management. Soil in the no-till system had increased surface soil organic C levels relative to conventional tillage regardless of rotation. In addition, depending on the rotation, the N and P content of the soil improved with no-till compared with conventional tillage. In other words, no-till has helped to retain soil organic matter (SOM), conserved more N, and resulted in increased extractable P and exchangeable K concentrations in the upper root-zone. Hence, wheat produced in a no-till system may receive more nutrients from decomposition of SOM and acidification of the seed zone. It is possible that lesser amounts of fertilizer nutrients will be needed because of the greater efficiency of nutrient cycling in no-till systems relative to conventional systems. Copyright © 2001 John Wiley & Sons, Ltd.
The principal objective of this investigation was to quantify erosion rates for five agricultural fields in three separate study areas in Saskatchewan. The radionuclide tracer caesium-137 (137Cs) was used to quantify net erosion and net deposition within the landscape over a 3-yr period. Uneroded (native) sites were used to establish the mean background level of 137Cs in each of the study areas. The results indicate significant degradation of the non-renewable soil resource has occurred over the past 30 years and is still presently active. Land degradation by accelerated erosion would result in reductions in effective rooting depth, soil moisture holding capacity, essential nutrient stores, and would adversely effect the physical structure of the topsoil. The major reason for accelerated erosion on arable land in Saskatchewan is the practice of summer fallowing, where the field is left in a "bare' state and repeatedly tilled every second or third year. -from Author
Increasing concern for problems of soil degradation and the off-site impacts of accelerated erosion has generated a need for improved methods of estimating rates and patterns of soil erosion by water. The use of environmental radionuclides, particularly 137Cs, to estimate erosion rates has attracted increased attention and the approach has been shown to possess several important advantages. However, the use of 137Cs measurements to estimate erosion rates introduces one important uncertainty, namely, the need to employ a conversion model or relationship to convert the measured reduction in the 137Cs inventory to an estimate of the erosion rate. There have been few attempts to validate these theoretical conversion models and the resulting erosion rate estimates. However, there is an important need for such validation, if the 137Cs approach is to be more widely applied and reliance is to be placed on the results obtained. This paper reports the results of a study aimed at validating the use of two theoretical conversion models, namely the exponential depth distribution model and the diffusion and migration model, that have been used in several recent studies to convert measurements of 137Cs inventories on uncultivated soils to estimates of soil erosion rates. The study is based on data assembled for two small catchments (1.38 and 1.65 ha) in Calabria, southern Italy, for which measurements of sediment output are available for the catchment outlet. The two catchments differ in terms of the steepness of their terrain, and this difference is reflected by their sediment yields. Because there is no evidence of significant deposition within the two catchments, sediment delivery ratios close to 1.0 can be assumed. It is therefore possible to make a direct comparison between the estimates of the mean annual erosion rates within the two catchments derived from 137Cs measurements and the measured sediment outputs. The results of the comparison show that the erosion rate estimates provided by both models are reasonably consistent with the measured sediment yields at the catchment outlets. However, more detailed assessment of the results shows that the validity of the erosion rate estimates is influenced by the magnitude of the erosion rates within the catchment. The exponential depth distribution model appears to perform better for the catchment with higher erosion rates and to overestimate erosion rates in the other catchment. Similarly, the basic migration and diffusion model performs better for the catchment with lower erosion rates and overestimates erosion rates in the other catchment. However, the improved migration and diffusion model appears to perform satisfactorily for both catchments. There is a need for further studies to extend such independent validation of the 137Cs technique to other environments, including cultivated soils, and to other conversion models and procedures. Copyright © 2003 John Wiley & Sons, Ltd.
This paper reports the results of an investigation of the erosional response of the 3·86 km2 Zhaojia Gully catchment in the rolling loess plateau region of Zichan County, Shaanxi Province, China. In the absence of direct measurements, information derived from reservoir deposits and from caesium-137 measurements on both the catchment soils and reservoir deposits was used to obtain a retrospective assessment of the longer-term (ca. 30 year) erosional response of the catchment and of the relative contributions of the rolling plateau surface and the gully areas to the sediment output from the basin. Net erosion rates on cultivated land occupying the gentle crest slopes and steeper lower slopes of the rolling plateau and the steep gully slopes were estimated to be 4500 t km−2 year−1, 8584 t km−2 year−1 and 15851 t km−2 year−1, respectively. Estimates of annual sediment yield from the study catchment based on analysis of sediment deposits in the two sediment-trap reservoirs ranged between 4627 and 32472 t km−2 year−1. Almost all the sediment transported from the catchment was contributed by 2–4 large floods each year. Measurements of the caesium-137 content of recent sediment deposits in a sediment-trap reservoir allowed the relative contributions of the total sediment yield derived from the rolling plateau and gully areas of the catchment to be estimated at 23 and 77 per cent, respectively. Analysis of the sediment deposits dating from 1973–1977 in another sediment trap reservoir allowed individual flood event couplets to be identified and indicated that the sediment associated with the first one or two floods in a season, when the soils of the plateau area were relatively dry, was derived primarily from the gully areas. The cultivated soils of the rolling plateau contributed an increased proportion of the total sediment yield during the latter stages of the flood season when the soils were wetter, and surface runoff and erosion were more widespread. Based on analysis of the caesium-137 content of the sediment deposited in this sediment-trap reservoir, the relative contributions of sediment from the rolling plateau and gully areas over the period 1973–1977 were estimated to be 21 and 79 per cent, respectively. The results obtained demonstrate the potential for using caesium-137 measurements and analysis of reservoir deposits to document the erosional response of a drainage basin. © 1997 John Wiley & Sons, Ltd.
This study analysed medium-term degradation in Pinus sylvestris L. woodland affected by wildfire. To investigate recovery, a range of pedological (including thickness of the organic horizon, soil structure and texture, organic matter content, pH and the percentage of carbonates), geomorphological and vegetation parameters were assessed in comparable burnt and control plots. Main findings suggest that fire in the medium-term leads to severe degradation of P. sylvestris L. woodland ecosystems. The main consequences of the passage of fire are: (1) transformation of P. sylvestris L. woodlands into shrublands dominated by Genista scorpius (L.) DC, Buxus sempervirens L. and herbaceous species; (2) decrease in the thickness of the O horizon and its degradation and (3) increase in soil erosion features, due to the detachment of soil particles by rain-splash or overland flow and their transport downslope. These results could help to provide guidelines for the restoration of burnt areas to minimise the effects of wildfires. Copyright © 2009 John Wiley & Sons, Ltd.
Many of the soils in Santa Cruz Department, Bolivia, are degraded by serious weed infestation, subsoil compaction, and low organic matter and nitrogen contents. Fallow periods with cover crops are frequently used to recuperate the fertility of degraded soils, but little information exists on the desired characteristics of cover crops for this purpose. The aim of this study was to describe those characteristics, believed to be most relevant to the rehabilitation of degraded soils in Santa Cruz, of 14 cover crops, which included three grasses, nine legumes, and two winter cover crops sown after summer soybean (Glycine max). The cover crop characteristics, evaluated over two years, were ease of establishment, competitiveness against weeds, tolerance to drought, dry matter production and nutrient contents of the above-and below-ground residues, nodulation, rooting density and root diameters. The three grasses Tobiata (Panicum maximum var. Tobiatd), Centenario (Panicum maximum var. Centenario) and Brizantha (Brachiaria brizantha) appeared to be the most promising for increasing soil organic matter contents, and the three grasses and groundnuts (Arachis hypogaea)/pigeon pea (Cajanus cajan) for the recuperation of subsoil structure. Mucuna deeringiana and Lablab (Dolichos lablab) were the most promising for increasing soil N status. All of these cover crops competed successfully with weeds.
Soil quality evaluation is the process of predicting the capacity of a soil to function. Due to the many possible soil functions, simple measuring of an individual soil parameter is not sufficient. These soil-quality parameters or indicators are grouped in physical, chemical and biological components. Land evaluation, which tries to predict land behaviour for each particular use, is not the same as soil-quality assessment, basically because the biological parameters of the soil are not considered by land evaluation. However, the process of evaluating soil is not new, and agro-ecological land evaluation has much to offer in this sense. A state-of-the-art review of soil quality evaluation and monitoring is presented in this paper, focusing on the possibilities of applying the accumulated knowledge from past studies of land evaluation. An agro-ecological approach is suggested to facilitate the monumental task of relating the nearly infinite list of soil quality indicators to the numerous soil functions, such as an application of MicroLEIS DSS to soil quality. Copyright © 2005 John Wiley & Sons, Ltd.
The severity of the landslide hazard in Hong Kong has resulted in the establishment of a comprehensive landslide database, the Natural Terrain Landslide Inventory (NTLI). It is derived mainly from the interpretation of medium to large-scale aerial photographs, and describes the location of all landslides. In view of the labour-intensive nature of air photo interpretation, as well as the lack of regular air photo cover in many countries, satellite images were examined for their ability to monitor landslides at a similarly detailed level, using the NTLI database as a reference. Using automated change detection with SPOT XS® images it was possible to identify 70% of landslides, the main omissions being due to those less than 10 m in width, and many of those identified were of sub-pixel width. The study also examined different techniques of image fusion for the enhancement of IKONOS images, and demonstrated that landslides on fused images are of similar detail to those on air photos. A methodology for regional scale monitoring is proposed which combines the efficiency of automated techniques for large area monitoring using SPOT® with the qualitative detail obtained from Pan-sharpened IKONOS images. Copyright © 2005 John Wiley & Sons, Ltd.
Australia's environments have been dramatically transformed by immigrant communities who were impelled by a simple utilitarian dream and obliged by geographical and historical circumstance to contend with accumulating uncertainties, including those connected with the operation of Nature's own independent dynamic. With the exception of a few critical junctures and significant but highly localized settings which are reasonably well supplied with primary material, the historical records are scarcely satisfactory for fine-textured reconstructions of changing physical landscapes. There is certainly some potential for very broad ‘indicative’ stocktaking, but unavoidable imprecisions and the irritating problem of discontinuities rule out the most ambitious of International Geosphere-Biosphere Programme (IGBP) style studies. Therefore a major premise of this discussion is the acceptance that we are obviously better placed to offer a range of underpinning social, political and economic analyses than to launch into the production of confident, large-scale reconstructions of the past ‘faces’ of Australia. The bulk of this paper explores that proposition and is confined to such analyses. On the other hand, it also suggests that the time is ripe for tailoring novel co-operative research into landscape change in the ‘European’ era, especially by combining physical and documentary evidence in the investigation of carefully selected sites and situations.
Alluvial forests are under high pressure from human activities because of their value as agricultural, wildlife, timber and recreational land. Despite this, spatial patterns of alluvial forest deforestation are not well known. We studied forest alterations in a 2800 ha alluvial ecosystem using aerial photographs. During the study period (1939–1997), forests with canopy heights greater than 15 m (high canopy mature forest; HCM forest) decreased by 70·4 per cent while forests with canopy heights less than 15 m (low canopy mature forest; LCM forest) forests decreased by 51 per cent, producing a highly fragmented landscape. Factors responsible for forest change included human activities and river dynamics. Although most of the deforestation was related to human disturbance, almost 27 per cent of forest losses were due to channel migration of the Meta River. HCM forests were the most affected land cover since they are easily accessed, viable for logging and occurred on fertile soils, which are valuable for agriculture. LCM forests were less affected since their soil fertilities and inundation regimes were unfavourable to human uses, and thus, less prone to anthropogenic disturbances. Copyright © 2006 John Wiley & Sons, Ltd.
Western Hainan Island is the only tropic region in China that is experiencing desertification. In this paper, we hope to reconstruct the evolution of desertification from 1959 to 2003 and identify the driving force during this process. Using remote sensing, mapping, GIS analysis and statistical analysis with climatic factors and human factors, we found five phases of desertification in the western part of Hainan Island between the late-1950s and the early-2000s. Desertification first developed rapidly, then reversed, and is now fluctuating, due to natural and human driving forces. Human activities interact with climatic factors. Copyright © 2007 John Wiley & Sons, Ltd.
Spatiotemporal analysis of landscape dynamics is crucial in formulating an appropriate set of actions in landscape management. This paper presents a large scale analysis of the spatiotemporal structure of Istanbul, a highly urbanized city in Turkey, from 1971 to 2002 using forest cover type maps analysed with geographical information systems (GIS) and a spatial statistics programme. The quantitative evidence indicated that increasing population and expanding urbanization caused drastic changes to the temporal and spatial dynamics of land use/land cover pattern in Istanbul. There was a net increase of 5387·3 ha in total forested areas (1·0 per cent) due to mainly reforestation activities even though the population increased three times over a 31-year period. Increase in number of patches and decrease in mean patch size together demonstrated that the landscape developed into a more fragmented structure that would negatively affect biodiversity and the resilience of the ecosystems. In conclusion, plain increase in forest areas may not always be a favourable situation. The quality, composition and the configuration of forest landscape should also be analysed to present the dynamics of ecosystem in terms of ecological and economical sustainability over a longer time and larger area. Copyright © 2008 John Wiley & Sons, Ltd.
Changes in land use/land cover have important consequences on the management of natural resources including soil and water quality, global climatic systems and biodiversity. This study analysed the spatial and temporal pattern of land use/land cover change in the Camili forest planning unit that includes the Camili Biosphere Reserve Area within the Caucasian hotspot, in the northeast corner of Turkey. To assess the patterns during a 33-year period, the necessary data were obtained from forest stand maps and evaluated with Geographic Information Systems and FRAGSTATS. Results showed that the total forested areas increased from 19 946·5 ha (78·6% of the study area) in 1972 to 20 797·3 ha (81·9 per cent) in 2005 with a slight net increase of 851 ha. Softwood cover types (411·8 ha) completely transitioned to other cover types over 33-year period. In terms of spatial configuration, the total number of forest fragments increased from 172 to 608, and mean size of forest patch (MPS) decreased from 147·7 ha to 41·8 ha during the period. Nearly 84 per cent of the patches in 1972 and 93 per cent of them in 2005 generally seem to concentrate into 0–100 ha patch size class, indicating more fragmented landscape over time that might create a risk for the maintenance of biodiversity of the area. There were apparent trends in the temporal structure of forest landscape, some of which may issue from mismanagement of the area, social conflict, and illegal utilization of forest resources due to ineffective forest protection measurements. The study revealed that it is important to understand both spatial and temporal changes of land use/land cover and their effects on landscape pattern to disclose the implications for land use planning and management. Copyright © 2007 John Wiley & Sons, Ltd.
Study area. (A) Location of the volcano Mount Usu in Hokkaido Island, Japan. Sapporo is the capital city of Hokkaido. (B) the crater basin surveyed. CB: crater basin; CR: inner-wall of caldera rim. 4th C: 4th crater of which eruption was the most catastrophic during the years of 1977 and 1978. On the crater basin, two major gullies were developed. A closed circle indicates the location of study plot.  
Microtopography of volcanic deposits on the ground surface and distribution of soil particles. In the top figure, relief is indicated with the heights from the bottom in the first time, that is early-May in 1988. Shadowed areas indicate the inside of rills. Distribution of texture: (*) ¼ pumice (empty cell) ¼ ash.  
Seed germination percentage (column) with standard error (bars) of Pe. japonicus var. giganteus and Po. sachalinense along the experimental gradient of soil particle sizes. Gravel: >2.00 mm in diameter. Sand: from 0.50 to 2.00 mm. Silt <0.50 mm. p < 0.01; germination percentages are significantly different (ANOVA). NS: not significant.  
The effects of microtopographical characteristics of the thick accumulation of ash and pumice, which were produced from 1977–78 eruptions, on seedling emergence and survival were monitored on the volcano Usu, northern Japan, 10 years after the eruptions. The characteristics included microtopography, texture of volcanic deposits on ground surface, volcanic-deposit movements, water content on ground surface and chemical nature of volcanic deposits (ignition loss, P, K and pH). Polygonum sachalinense showed a higher seed germination percentage on finer-particle ground surface under lab conditions, and Petasites japonicus var. giganteus germinated well on the ground surface with any particle sizes. However, in the field, the seedling densities of those two species and Anaphalis margaritacea var. angustior (three dominant species in this region) were higher on the sites with coarse particles and/or the rill inside the crater basin. The seedling germination timing and space overlapped among these species in the field. Those facts suggested that the seedling colonisation pattern was influenced more by the topographical characteristics of ground surface rather than the germination abilities. The amount of organic matter in the volcanic deposits was very low, even 11 years after the eruptions, and was not related to microtopography, suggesting that the effects of organic matter on seedling emergence did not differ along microtopographical characteristics. Inside of rills, higher water content seemed to be more advantageous for seed germination of those species. Volcanic deposits were physically stable in summer, but were heavily eroded after winter due to snowmelt. Most seedlings did not overwinter in the inside of rills with pumice where the volcanic deposits eroded intensively, indicating that the patterns of land degradation by melting snow should be mentioned carefully even with narrow scale. Copyright © 2007 John Wiley & Sons, Ltd.
From the 1980s onward studies on interrill soil erosion were intensified in SE Spain. The main achievements of the research carried out in the field areas of Alicante and Murcia concern: first, (1) the estimation of erosion rates directly in the field under a wide range of methodologies, different scales and different environmental conditions; (2) estimations based on existing models, such as the USLE, carried out for different subcatchments of the Segura and Júcar catchments; and (3) other parametric and physical event-based models have also been calibrated and validated.Second, the progress of the knowledge in understanding erosion mechanisms. New and reviewed concepts regarding mainly hydrological behaviour and sediment movement and transport at patch, slope and catchment scale have improved our understanding of soil-erosion processes in Mediterranean-type ecosystems. These concepts focus on: (1) the definition of runoff generation models more appropriate to Mediterranean conditions; (2) the definition of thresholds for runoff generation; (3) the definition of models of soil water redistribution within soils and at landscape level; (4) the establishment of conditions and controls for sediment detachment and movement; and (5) the characterization of the change in the controlling factors of soil erosion and degradation under different environmental characteristics (climatic or human-induced). The insights into soil-erosion processes obtained and the renewed hydrological and geomorphological concepts achieved can be very valuable for the design of new strategies of erosion management and ecosystems restoration. Copyright © 2005 John Wiley & Sons, Ltd.
Concern for the better management of environmental resources grew during the 1980s. While this concern encompassed the misuse of the Third World's resources, those nations' governments and their peoples showed less awareness of the environmental damage being done in their quest for development. Environmental degradation has reached serious proportions in Algeria where oil wealth has masked failings of agricultural production and, together with industrialization, has provided a ‘veneer’ of economic development. The vulnerability of Algeria's natural environment and the fragility of its ecosystems have been stressed by Cǒte (1983). Once cleared, Algeria's woodlands and forests are slow to re-establish and surface deposits are easily erodable. Soils were largely formed under past climatic conditions, and so cannot be restored naturally by present pedogenetic processes. Such an environment is difficult and delicate to exploit to any high degree of agricultural intensification and is under increasing demographic pressure. Culturally and organizationally the agricultural system is far from ideal if agriculture is to be sustained. Often in Algeria the highest rainfall falls on the steeper slopes while the gentler slopes receive insufficient for agriculture. Only 500 000 hectares out of Northern Algeria's 38–40 million hectares receive more than 600 mm of rainfall and have slopes of less than three per cent (Cǒte, 1983). As much as 20 million hectares of Northern Algeria were identified by Dregne (1983) as … ‘vulnerable to desertification’ with large areas falling into his ‘severe’ risk category. This study seeks to demonstrate the dimensions of environmental degradation through observations and the monitoring (during the 1980s) of Algeria's media: largely newspaper and television reports. Particular emphasis is placed on the growing environmental ‘crisis’ since 1988. It should be stressed that the Algerian Government uses a controlled media to disseminate official information. Misuse and overuse of environmental resources have combined with inadequate government economic policies and a neglect of ecological issues to cause the ‘crisis’.
Vegetation significantly influences human health in the Yellow River basin and the plant cover is vulnerable to people. Typical types of erosion in the Yellow River basin include that caused by water, wind and freeze–thaw. In this paper, vegetation cover change from 1982 to 2006 was studied for a number of different erosion regions. The Global Inventory Monitoring and Modeling Studies Normalized Difference Vegetation Index (GIMMS NDVI) data were employed, while climatic data were also used for analysis of other influencing factors. It was shown that: (1) generally the vegetation cover in different erosion regions displayed similar increasing trends; (2) spatially the vegetation cover was highest in the water erosion region, the second highest was in the freeze–thaw region and the lowest in the wind erosion region; and (3) vegetation cover in the Yellow River basin is influenced by climate factors, especially by temperature. In water erosion regions, the temporal change of vegetation cover seemed complicated by comprehensive climatic and human influences. In wind erosion regions, the vegetation cover had close relations to precipitation. In freeze–thaw erosion regions, the vegetation cover was primarily altered by temperature. In all the three erosion regions, significant change of the vegetation cover occurred from 2000 just after the ‘Grain for Green’ (GFG) programme was implemented throughout China. Copyright © 2010 John Wiley & Sons, Ltd.
Land-use and cover changes around Budongo Forest Reserve (BFR) were analysed from multi-temporal LandSat images (1988 and 2002) and associated field-based studies in 2003–2004. Three major land-use and cover classes: forest/woodland, sugarcane plantations and grassland/shifting-cultivation/settlements were clearly discriminated. The area under sugarcane cultivation increased over 17-fold, from 690 ha in 1988 to 12729 ha in 2002, with a concomitant loss of about 4680 ha (8·2 per cent) of forest/woodland, mainly on the southern boundary of BFR. Land-use and cover changes were a result of (a) agricultural expansion, (b) increasing human population, exacerbated by large influxes of refugees, (c) conflicts of interest and political interference in the management of BFR and (d) unclear land tenure. Agriculture is the main land-use practice and source of income to local people, with commercial sugarcane and tobacco as the primary cash crops. Individual smallholder sugarcane plantations covered distances ranging from 30 to 1440 m along the BFR edge, with no buffer zone, resulting in direct conflicts between farmers and forest wild animals. There is an ever-increasing need for more land for agricultural expansion, resulting in continued loss of forest/woodland on private/communal lands and encroachment into BFR. This unsustainable agricultural expansion and the local people's perception of BFR as an obstacle to agriculture, threatens the conservation of its threatened wild plants (e.g. Raphia farinifera) and the endangered chimpanzees. Therefore, their sustainable management for both development and conservation will require strong and incorruptible institutions that will seek a balance between resource exploitation and conservation. Copyright © 2008 John Wiley & Sons, Ltd.
Vegetative growth in planting treatments meas- ured as ground cover at five months after planting 
This paper examines soil amelioration by planting 15 leguminous and graminaceous plant species, including herbaceous annuals, perennials and biennials, and woody perennials and biennials. Disturbed and undisturbed natural regrowth were planted with leguminous species, in some cases with fertilizer applied at planting (400 kg ha−1 of 15:15:15 NPK). The studies were made on two highly degraded sites in southwestern Nigeria which had been subjected to intensive mechanized cropping for a period of 10 years. Changes in soil physical and chemical properties were monitored from 1989 to 1991. Acacia difficilis, Brachiaria lata and Mucuna utilis had the lowest survival rates by the following growing season. Soil fertility and compaction levels differed between sites. Planting had no effect on the latter. The decreases in compaction (i.e. macroporosity) between 0.00 and 0.10 m depth at both sites one month before and five and 17 months after planting were 43, 59 and 61 per cent, respectively were attributed to exclusion of heavy machinery from the sites. Large decreases in fertility occurred at both sites and were attributed to a combination of nutrient extraction and to leaching. Between fallow species, exchangeable Ca, pH and the cation-exchange capacity (CEC) were greater and total acids lower for herbaceous cover compared with woody perennials, and was attributed to a higher Ca demand by the latter. Highest and lowest values of Ca, CEC and pH occurred in plots where plant material was returned to the soil (i.e. by cutting or die-back) and in cropped plots, respectively. Natural regrowth was as effective or better than planted species in improving soil physical and chemical properties. Therefore the use of exotic plant species for ameliorating highly degraded alfisols is unnecessary. Amelioration of highly degraded alfisols may be best effected by allowing natural regrowth to occur while excluding all mechanized traffic from the site.
In this study, we investigated the extent of peatland degradation and development in Peninsular Malaysia and in the islands of Sumatra and Borneo, in the western part of insular Southeast Asia, since 1990. Furthermore, carbon emissions caused by these land cover changes were estimated in order to evaluate their contribution to global climate change. High resolution Landsat (30 m spatial resolution) and Satellite Pour l'Observation de la Terre (SPOT; 10–20 m) satellite images were used to derive information on land cover in 1990 and 2008. Analysis of land cover changes since 1990 revealed remarkable reduction and degradation of peatswamp forest ecosystems. In less than 20 years, 5·1 Mha of the total 15·5 Mha of peatland had been deforested (11·6 Mha → 6·5 Mha; 75 per cent → 42 per cent) and the great majority of the remaining forests had been selectively logged. Simultaneously, area covered by unmanaged secondary growth ecosystems had doubled to nearly a quarter of all peatlands and industrial plantations had expanded dramatically (0·3 Mha → 2·3 Mha; 2 per cent → 15 per cent). It was conservatively estimated that these changes have caused minimum of 1·5 Gt carbon emissions into the atmosphere since 1990. Currently, peatlands of the study area emit at least 81 Mt of carbon (equivalent to 300 Mt of carbon dioxide) on annual basis due to mere peat decomposition. Thereby, it was concluded that peatland degradation and development in insular Southeast Asia during the past two decades have not only put the existence of Southeast Asian peatswamp forest ecosystems in danger but it has also caused globally significant carbon emissions and created a constant source of carbon dioxide. Copyright © 2010 John Wiley & Sons, Ltd.
China has long been experiencing intense land use/cover changes (LUCC). Undesirable land use/cover changes have resulted in widespread land degradation. This study examines the temporal and spatial dynamics of land use change and land degradation as evident from land use survey datasets (1991–2001). Six prominent land degradation processes were identified, namely: desertification, secondary salinisation, loss of agricultural use, deforestation, grassland degradation and loss of wetland. Rates of conversion were calculated and distribution patterns were mapped with the aid of GIS. The results showed that these land use changes have affected the wider environment and accelerated land degradation. It provided a more complete and up-to-date picture of China's land degradation which helps to develop improved conservation policies that combat land degradation and promote sustainable land management. Copyright © 2006 John Wiley & Sons, Ltd.
During July, August and September 1998, Bangladesh was subjected to the most extensive flood in living memory. At peak flood, approximately two-thirds of the country was under water. The media showed submerged houses, drowned livestock, and women and children wading neck deep in water carrying water jars or food on their heads. Such images reinforce many people's perceptions of Bangladesh as a country incessantly subjected to devastating floods that destroy crops and cause untold misery to the nation's people. Yet, beyond this media-generated view, there is a country where agricultural production is still the mainstay of the rural population's livelihood system. The nation's water resources, both above and below ground, provide a multitude of services to the population: water to drink and in which to bathe, fish to eat and water to irrigate crops. This paper outlines the local-level research indicating that most rural Bangladeshis living on the central Bangladesh floodplain, view the annual monsoon flood season not as an inconvenience but as a necessity. It suggests that many people in the research areas recognize the benefits associated with extreme flood events. The 1998 flood provided plentiful amounts of fish, a staple diet and labouring work in the form of building up flood defences. It also flushed out stagnant water in ponds and pagars (open system ponds), and in time, led to a bumper harvest of rice. The research highlights the lives of those whose livelihoods are devastated by such events, describes the nature of the monsoon of 1998, analyses the effects on the community's livelihood systems and describes the nature of their coping strategies. It also suggests ways in which the government and aid agencies could better assist those whose livelihoods are most vulnerable. Copyright © 2001 John Wiley & Sons, Ltd.
Palaeoecological analysis of a 3 m sediment core from a coastal site in the western Algarve, near Lagos, Portugal, reveals the changing ecological characteristics of the wetland environment during the late Holocene. The dinoflagellate record and sedimentary characteristics show that approximately 2000 years ago the modern Boca do Rio wetlands were an estuary. By about 1200 14C years BP, transition to a lower energy environment was taking place. The pollen record at this time indicates the existence of typical salt marsh vegetation. There is a likely hiatus in the sedimentary record caused by the tsunami associated with the Lisbon earthquake of ad 1755. A barrier lake, impounded by tsunami deposits, existed for approximately 60 years before being breached, followed by a reoccurrence of saline conditions. A comparison of the mineral magnetic signature of the sediments with that of soil samples from the catchment suggests a relatively local provenance for some of the sediments, rather than the highly erodible Carboniferous rocks of the Algarve's Serra uplands. However, it is also suggested that there is a biogenic component to the magnetic mineralogy. Coastal wetlands are among the most vulnerable Mediterranean environments. The history and future of the Boca do Rio wetlands is examined in the context of alluviation history, rising sea levels, both past and future, and catchment land use. Changing patterns of cultivation, irrigation and land abandonment during the last 50 years are likely to have increased water demands within the catchment and therefore decreased river discharge to the wetlands. Consequently, the continued existence of the wetlands in their present form is in doubt, despite being part of a protected natural park. Copyright © 2003 John Wiley & Sons, Ltd.
The soils of the South Downs in East Sussex, England (UK), are dominated by loessic silt (>70 per cent) and are prone to crusting. Continuing erosion of these soils means that they are thin, typically less than 25 cm thick and are becoming stonier, more droughty and less easier to work. Rates of erosion are relatively low but during extreme events, soils are vulnerable and on- and off-site erosion is a current and long-term risk. Property damage due to muddy flooding is of particular concern. Due to a long history of research interest, a rich database exists on the erosional history of an area of approximately 75 km2 of these thin, calcareous South Downs soils. In particular, during the winter of 2000–2001, Hortonian overland flow was common on certain crop types. Consequent sheet, rill and gully erosion was intense.The gullies and rills formed by runoff during these winter events were mapped in detail. In this paper, a method to estimate soil vulnerability to erosion is described and illustrated. Then, to validate the predictive efficacy of the algorithm used, the actual mapped distribution of rills and gullies following the winter events of 2001 on a particularly badly-affected site are compared with predictions from our soil erosion vulnerability model. Methods for adjusting the land-cover weightings to optimise the map fit are outlined.In a further survey of the utility of the map, it was discovered that farmers' recollections of events provided additional verification. Thus, one implication of our research is that erosion models can be validated by inviting farmers to comment on their efficacy to predict known histories. Copyright © 2010 John Wiley & Sons, Ltd.
Gully erosion plays an important role in degradation processes of Mediterranean environments. In this paper aerial orthophotographs were used for (i) analysing the evolution of a valley bottom gully and its relation with land use and vegetation cover, (ii) exploring the role of land use and vegetation cover on the coefficients of the equation S = aA−b (where S is slope at the headcut and A is drainage area), which is based on the topographical threshold concept and is commonly used to predict gully initiation. The study was carried out in a small catchment (99·5 ha) located in the southwest of the Iberian Peninsula. Gullies and headcuts were mapped together with land use and vegetation cover using aerial photographs for the years 1945, 1956, 1989, 1998, 2002 and 2006, which had to be digitized and orthorectified in advance. The results showed an increase of the area affected by gullying from 695 m2 in 1945–1009 m2 in 2006, reaching a maximum of 1560 m2 in 1956. Gullying was closely related with land use, especially with the amount of cultivated areas within the catchment and also with grazing intensity. No clear relationship was found between the evolution of the gullied area and rainfall amounts. Finally, the values of the exponent b obtained for different headcuts and different dates (close to 0·4) were similar to those proposed by other authors for gully erosion caused by Hortonian overland flow in semiarid environments. Copyright © 2009 John Wiley & Sons, Ltd.
Location of study area. 
The structure of the RBFN layers.
Maps of standard value of the affecting factors of wind erosion hazard in Inner Mongolia. (a) percentage of vegetation; (b) the contents of fine sand; (c) percentage of sandy land; (d) average relief degree of land surface; (e) the degree of soil dryness; (f) the intensity of wind energy. 
Map of different levels of wind erosion hazard. 
Soil wind erosion is the primary process and the main driving force for land desertification and sand-dust storms in arid and semi-arid areas of Northern China. While many researchers have studied this issue, this study quantified the various indicators of soil wind erosion, using the GIS technology to extract the spatial data and to construct a RBFN (Radial Basis Function Network) model for Inner Mongolia. By calibrating sample data of the different levels of wind erosion hazard, the model parameters were established, and then the assessment of wind erosion hazard. Results show that in the southern parts of Inner Mongolia wind erosion hazards are very severe, counties in the middle regions of Inner Mongolia vary from moderate to severe, and in eastern are slight. Comparison of the results with other research shows conformity with actual conditions, proving the reasonability and applicability of the RBFN model. Copyright © 2007 John Wiley & Sons, Ltd.
Wetlands inventory is one of the goals of conservation plans on a national scale and a global scale. Inventories are needed for long-term monitoring or for identifying lost wetlands and those where restoration is feasible. In this article, we present an updated inventory of the saline wetlands of Southern Monegros, Spain. We depicted the evolution of these saline wetlands, locally named saladas with a unique long-term retrospective study based on aerial photographs from 1927. Their inventory has been accomplished through a map analysis based on a geographical information system using aerial photographs and orthophotographs, topographic maps, unpublished local studies and field surveys. Remaining vegetation, changes in soil moisture and colour, and geomorphology have been the key features in identifying the saladas. Their changes in number, size and shape have been driven by human pressure, the main modifier of landscape in the last 80 years. The information gathered will contribute to the awareness of stakeholders and decision makers for their conservation as natural resources. Moreover, our large retrospective approach is a consistent base from which to propose the inclusion of the saladas of Monegros in the Ramsar list of Wetlands of International Importance. Copyright © 2011 John Wiley & Sons, Ltd.
We studied total Cu content and its distribution in 33 surface soil samples cultivated with vines for variable lengths of time in the Monterrei designation of origin (DO), located in Galicia (NW Spain). The study was focused on the influence of land use changes on soil degradation by effect of Cu accumulation and availability. Total copper concentration in soils ranged from 25 to 272 mg kg−1. The time during which each soil was cultivated with vines was found to affect both the total concentration of copper and its distribution. The average concentration of copper in young vineyards was 64 mg kg−1, whereas those in old and abandoned vineyards were 100 and 132 mg kg−1, respectively. Copper bound to organic matter and to amorphous inorganic colloids were greater in old and abandoned vineyards, where they accounted for 51 and 52 per cent, respectively, of total copper, than in young vineyards (39 per cent). Copper bound to crystalline Al and Fe colloids accounted for 21, 22 and 12 per cent of total Cu in old, abandoned and young vineyards respectively.The prevalence of Cu bound to the organic fraction reduces the adverse environmental effects of this metal on soil organisms and plants. However, some management practices such as organic matter addition or liming should be implemented in order to delay or avoid soil degradation in young vineyards. For abandoned vineyards, the influence of new land uses on potential Cu mobilisation necessitates careful examination. Copyright © 2007 John Wiley & Sons, Ltd.
It is suggested that stopping liming on agricultural land could lead to a potential chemical time bomb (CTB). the sequence of interrelated events leading to the CTB include the end of liming, perhaps caused by a change in land use, a progressive decrease in soil pH and increased solubility of potentially toxic contaminants that accumulate in soils as a result of agricultural practices. Data are presented on rates of long-term soil acidification and modelled changes in the solubility of some trace metals in soil as a result of acidification. Soil acidification rates depend primarily on acid input rates and the soil's acid neutralizing capacity, possibly limited by neutralization kinetics. Experimental data illustrating this point show that the pH decreased rapidly in a field soil receiving ammonium rather than nitrate fertilizer treatment. on a limed agricultural field that was later abandoned and converted to deciduous woodland, The pH of the 0-23 cm soil layers decreased over 100 years from pH 7 to 4.2. Deeper layers acidified at a slower rate. Thermodynamic model calculations simulating the solubilities of metals in a sandy topsoil showed zinc, cadmium and aluminium solubilities increasing exponentially with decreasing pH, resulting in several-fold solubility increases between pH 5 and 4. These results suggest how metal solubility increases after liming stops. the model pH-solubility relationships depended on the type of metal, The solid phase controlling the solubility, and the amount of metal in the soil if adsorption controlled the solubility. Decreasing pH and the resultant increase in metal solubility expected on abandoned farmland might be managed through techniques such as liming or planting forests of selected tree species.
Four hundred soil samples were obtained from a 4 km2 area close to the abandoned Kgwakgwe Mn oxide ore mine in order to investigate the environmental association of Mn minerals and concentrations in the soils. Manganese minerals and Mn concentrations in samples were identified by X-ray diffractometry and atomic absorption spectrometry, respectively, and results statistically analysed. Bixbyte, Mn2O3; braunite, Mn+2MnSiO12; ramsdellite, MnO2; pyrolusite, β-MnO2 and cryptomelane, K2 − xMn8O16 were identified in soil samples at the study site but none of these minerals found in soil samples from the control site. Manganese concentrations in samples from the study area were significantly higher than those from the control site. Statistical data yielded seven clusters with distribution of the Mn minerals and concentrations as follows: cluster 1 dominated by Mn concentrations in soil, cluster 2 by none of the seven Mn minerals, cluster 3 by pyrolusite, cluster 4 by braunite, cluster 5 by cryptomelane, cluster 6 by bixbyite and cluster 7 by ramsdellite. Very weak associations of these minerals were depicted from their correlations. The clusters had a bearing on the spatial distribution of the different minerals. Comparing results obtained from the control site, and geological materials, to the soils from the study area, it is certain that Mn minerals and high Mn concentrations in soils originated from the surrounding geological materials. The mining activities most possibly have affected Mn concentrations' and minerals' occurrences in the soils at the study area. Copyright © 2009 John Wiley & Sons, Ltd.
Location of the study site. 
Plot layout.
The lag time for natural recruitment of tropical rainforest species in abandoned pastureland is very long, therefore artificial restoration techniques have been employed to accelerate natural seedling recruitment. The objectives of this study were to investigate: (1) the success/failure of establishment 502 seedlings belonging to 15 species from 11 families planted approximately ten years ago; and (2) the influence of different restoration techniques on enhancing natural recruitment during this period. The study was conducted in the wet tropical rainforest region of northeast Queensland, Australia as a completely randomized block design involving five treatments with two replicates. In each plot, 63 tropical rainforest seedlings from one or a combination of species were planted randomly. Two control plots were laid out where no seedlings were planted. Survival, height and diameter data were taken on the seedlings ten years after planting. Each 11×17 m2 plot was further divided into 187, 1×1 m2 subplots. Within each subplot all seedlings recruited were located and identified. Canopy cover was estimated using belt transects 1 m apart that ran in an east–west direction across the plots. Within each plot the percentage of grass, and the crown cover were estimated using the Braun-Blanquet cover abundance scale. Survival rate of planted seedlings varied across the treatment plots. The survival rate ranged from 65 to 75 per cent for primary-promoter species, 85 to 100 per cent in middle-phase species and 42 to 57 per cent for mature-phase species. No Pilidiostigma tropicum seedlings survived in any treatment. Fourteen species recruited naturally across the treatment plots. A total of 410 seedlings were naturally recruited from 11 different families in the ten-year-old reforested site. The highest natural recruitment (236 seedlings) occurred in Treatment 3, where Omalanthus novo-guineensis seedlings were planted with eight primary-promoter species, followed by 99 in Treatment 5 where a group of primary-promoters, middle phase species and mature-phase species were planted together, 36 in Treatment 4 (Alphitonia petriei planted with eight primary-promoter species), 10 in Treatment 2 where only Omalanthus novo-guineensis seedlings were planted, and 13 in control plots. Grass cover declined with increasing species diversity and increased canopy cover. The results indicate that the diversity of species used in restoration had a major influence on natural recruitment. Copyright © 2004 John Wiley & Sons, Ltd.
The Pyrenean and Pre-Pyrenean mountain areas have been intensively used at least since roman times, but nowadays depopulation has lead to widespread land abandonment without a steering land-management. Vegetation recovery is weak in most abandoned fields. Soil formation and characteristics are conditioned by this fact, and for this, soils show past degradation processes and are mostly predominant factors for continuing land degradation or restoration. Three study areas were set up along a climatic gradient with increasing summer water deficit in the sub-humid zone between the Central Pyrenees and Pre-Pyrenees. Soil survey combined with experiments for the determination of infiltration, runoff and erosion were applied for understanding the degradation history and the future development of the soils. All areas are dominated by Entisols, but also Inceptisols and Alfisols are found, and even soils with hydromorphic features. The soils show signs of heavy erosion. The parental material determines the nutrient supply and the general chemical properties. All sites show a weak water storing capacity, as a result of the removal of fine material by erosion and due to the depletion of soil organic matter. In addition, infiltration capacity and runoff generation are high within the studied areas, averaging between 27 and 37 per cent. The driest area studied shows an ongoing trend to degradation, with high erosion rates combined with a high degradations status of the soil. The other areas are characterised by a patchy pattern of soil degradation and regradation processes. Copyright © 2008 John Wiley & Sons, Ltd.
The state of soil degradation/regeneration in abandoned agricultural terraced fields over pumiceous tuffs has been assessed in this paper. In an initial stage, the relationships between soil types, surface microfeatures as indicators of soil degradation, physicochemical properties, plant colonization and vegetation structure were studied by means of multivariate statistical analyses (PCA, DCA, CCA and TWINSPAN®). Aerial photographs interpretation, DEMs and field surveys allowed us to identify 47 different environments for abandoned fields along 7 altitudinal transects (33 abandoned field terraces). In each study site, an inventory of the existing plant species and of morphological surface microfeatures were also made, by the line-intercept method.Plant colonization in the field plots studied relates to the variation of soils properties according to a climatic altitudinal gradient. The soil properties most closely related to the abandonment age (decrease of soil salinity and clay content, and increase of soil alkalinity and total organic C and N), have contributed to the growth of plant communities with a high degree of climacity.The protection degree offered to the soils by the different vegetation types as a function of their structure and life-forms strongly determines the occurrence of the different soil surface microfeatures as indicators of soil degradation or recovery.The acceleration of the early stages of succession by active planting of seeds from shrub species in the lower and upper areas, followed by reforestation in the latter ones, may be the best improvement practices to achieve an effective ecological recovery of the fields and simultaneously to attenuate soil degradation. The reassuming of agriculture may be desirable in those fields placed in middle heights, provided they show the best soil and climate conditions. Copyright © 2006 John Wiley & Sons, Ltd.
Rangeland management can affect plant diversity and plant functional groups of native grassland communities. To improve pasture for livestock grazing from the existing poisonous and ruderal vegetation in the ‘black soil land’ grassland in the headwaters of the Yangtze and the Yellow Rivers (HAYYR) of the Qinghai-Tibetan Plateau, three treatments (fencing-FT, artificial seeding with local grasses-ST and abandonment-AT) were applied during a 5-year period (2000–2005). Plant diversity and groups (sedges, grasses and dwarf shrubs) in the treated plots were compared with non-treated control plots. Results showed that (1) FT promoted an increase in forbs species, but there was no change in the other plant functional groups; (2) with ST, species richness of forbs decreased but grass species increased indicating that sowing local grasses could change plant composition of black soil land in the short-term, and increase the proportion of grasses and, thus, forage for grazing and (3) AT, after plowing, was similar to CK plots, with forbs being the dominant plant functional group for the 5 years. In conclusion, the goal to alter black soil land cover from poisonous and ruderal plants to more useful plants for livestock grazing by either fencing, artificial seeding or abandonment was not successful in the long term. Copyright © 2008 John Wiley & Sons, Ltd.
This paper analyses the effects of land abandonment on runoff and sediment yield in a central inland area of Portugal. Rainfall simulation experiments were performed in areas of traditional land use (land cultivated with cereals) with various types of soil plant cover associated with the period of abandonment (4–5 years, 15–20 years and 30–40 years) in two different seasons, namely under very dry conditions and after a long wet period.Statistical analysis showed a notable difference between the cultivated soils and those abandoned for a long period of time, which included appreciable vegetation recovery, higher organic matter content and negligible overland flow and soil loss. Cereal cultivation, in particular ploughing, is a very negative land management practice, due to the high runoff and soil loss. Within 4–5 years a crust develops over abandoned soils with sparse herbaceous plant cover, particularly after a dry season, which enhances runoff and sediment yield. In scrubland and oak plots, although marked water repellency was registered at the end of a dry, warm season, its influence seems to be irrelevant in terms of overland flow and erosion yield. The major factor in controlling overland flow and reducing soil erosion rates appears to be the role played by vegetation in protecting the soil surface and supplying organic carbon to the top layer. Copyright © 2010 John Wiley & Sons, Ltd.
Total area of the two main crops in the Gadarif region for the period 1954-2003. Source: MFC (2007).
Location map of the study area. The background is Landsat ETM image (March 2003). This figure is available in colour online at
In the Gadarif Region of Sudan, destruction of the natural vegetation for agricultural expansion is one of the major causes of the degradation of renewable resources and the environment. This study identifies and analyses the farmers' attitudes and perceptions towards agricultural land degradation and abandonment. The cross-sectional data collected from ten key informants and 41 large-scale farmers focussed on the degradation and abandonment of mechanized agricultural land. The results of the study show that the respondents are well aware that soil degradation is in various forms are taking place on their cultivated agricultural land. This is based on their perception and interpretation of indicators such as weed infestation, poor soil fertility and soil compaction. Continuous cropping, mono-cropping, rainfall shortage and the use of inferior seeds are the main reasons of land degradation as indicated by farmers. The main measures acknowledged to maintain and improve land productivity are repeated soil ploughing, abandonment/fallow periods and crop rotation. The study adduces evidence of widespread land degradation. The mitigation measures followed by the farmers may though not be sufficient to restore the soil fertility. The application of appropriate chemical fertilizers, sound crop rotation and long fallow periods can be recommended. Any management and research intervention regarding the problem of land degradation should; however, be concerted with the farmers' knowledge. Copyright
The environmental impact of recent changes in land use is assessed in a part of Andalucia, southern Spain, where the deintensification and abandonment of low productivity upland areas is taking place. In the uplands of the Alpujarra, the traditional landscape most at risk is that of the irrigated cultivation terraces. These have often been established centuries ago and rely on water abstracted from streams draining the southern slopes of the Sierra Nevada. The causes of this deintensification include labour shortages, with many Alpujarra municipios reporting population decreases of up to 50 per cent since 1950. Landsat Thematic Mapper digital data from May and August 1992 have been used to identify the various land cover components of the Alpujarra. Ground verification undertaken in September 1992 and April 1993 has confirmed that deintensification of terraced areas around the villages of Trevélez (at 1500m, the highest village in Spain) and Pórtugos (1300 m) can be identified as either grassland or matorral. It is recognized that many classes of land cover are mosaics with several elements at a subpixel scale (e.g. terrace risers with fruit trees). However, the output from image processing has allowed areal estimates of the main land covers representing deintensification within the terraced zone. The pattern of deintensification of terraced land is fairly complex. It can be assumed that all terraces were irrigated and cropped at some stage. Land which is no longer cropped is usually grazed and the invasion of matorral species is common, particularly when irrigation ceases. Unirrigated tree crops and vines are sometimes planted on terraces no longer used for cropping. A model of deintensification of farming on terraced land in the Alpujarra is presented.
This study aimed to determine microbial biomass carbon and microbial abundance immediately after, and two years after, forest soil erosion, so as to estimate the degree of damage, including the rate of recovery of microorganisms, in each area. It also aimed to determine the community diversity, and to establish relationships between microbial biomass, microbial abundance and the physico-chemical properties of the soil. Three different study areas in Hiroshima Prefecture, Japan, were used. One undisturbed area and two eroded areas (one immediately after and one two years after erosion). The analysis of variance showed a highly significant difference in microbial biomass carbon and abundance between the study areas. The undisturbed area showed the highest value, followed by the area eroded two years ago, then lastly the area studied immediately after the erosion. The biomass carbon was highly correlated with gram positive bacteria with r2 = 0·983, p < 0·01. The biomass carbon and microbial population were shown to be significantly correlated to the soil's physico-chemical properties, such as pH, moisture content, water-holding capacity and CN ratio. However, CN ratio proved to be closely correlated to biomass carbon with r2 = −0·978, p < 0·01, to Gram-positive bacteria with r2 = −0·977, p < 0·01, to Gram-negative bacteria with r2 = −0·989, p < 0·01 and to fungi with r2 = −0·977, p < 0·01. The undisturbed area showed a highly diverse community in both of the restriction enzymes used, followed by the area affected by erosion two years ago, then the area immediately after erosion. Copyright
Map showing location of the study area. This figure is available in colour online at Copyright # 2010 John Wiley & Sons, Ltd. LAND DEGRADATION & DEVELOPMENT, 22: 425-431 (2011)
Mean monthly total rainfall distributions between 1981 and 2006.
Relationship between SOC (per cent) and total N (per cent). This figure is available in colour online at
Relationship between SOC (per cent) and total N (per cent). This figure is available in colour online at ldr
Continued conversion of woodlands into grazing and farmland is seriously undermining the natural ecosystem of the dry and fragile Rift Valley areas of Ethiopia. This study investigated the effects of land-use change on soil organic carbon (SOC), total nitrogen (N), pH, exchangeable bases, cation exchange capacity (CEC) and base saturation (per cent) in three adjacent land-use types: controlled grazing, open-grazing and farmland. A total of 81 soil samples were collected and analysed. Contents of SOC and total N decreased drastically in open-grazing and farmland (p < 0·001), and were significantly higher in the top 0·2 m than in the subsurface soil layer. Compared with the controlled grazing, reductions in the contents of SOC and total N in the top 1 m soil layer were 22–30 and 19 per cent, respectively, due possibly to the decrease in plant biomass input into the soil and the fast decomposition of organic materials. Long-term cultivation had significantly increased the concentration of exchangeable K. Exchangeable Na was high in the lower layers, while Mg was higher in the top surface soil. CEC also varied with soil depth (p = 0·016); it was higher in the topsoil than in the subsurface soil, which may be, among others, due to the differences in soil organic matter distribution with depth. Although these semi-arid soils are known to have low organic carbon and CEC levels, the values from the current study area are critically low, and may indicate the further impoverishment of the soils under high agricultural and grazing pressures. Copyright © 2010 John Wiley & Sons, Ltd.
Throughout Rwanda, terracing was reintroduced in 1973 as the major conservation practice to minimize soil loss on its steep agricultural lands.1 Terracing has been partially successful in reducing soil losses resulting from nonchannelized runoff, the goal of this practice. However, because of the widespread fragile environmental conditions in the highlands, soil fertility has decreased and soil acidity increased in numerous fields as a direct result of the terracing. To maintain sufficient agricultural yields, within the constraints of a low resource agricultural system, farmers have responded to the acidity and soil fertility problems by systematically removing a portion of the terrace berm during field preparation. This practice, in response to the changing environmental situation due to terracing, results in significant amounts of soil displaced downslope year after year. This human-induced soil erosion process seriously counters many of the intended benefits of terrace construction and is contributing to the land degradation problem. The results of this study emphasize the need for both conservation strategies and the measurement of soil loss to be sensitive to human-induced as well as natural erosional processes. By not considering the human response to terrace construction, the benefits of this conservation practice have been seriously offset.
The need of Fulanis for secured access to land is a long time policy challenge in Nigeria but progress in achieving this is far from being made. Meanwhile, access to land, of Fulanis that are settled among the Yorubas in southwest Nigeria, is dependent on land rights regimes operating in Yoruba communities. The study examines the nature of land rights in southwest Nigeria and how these provide access to Fulanis for their livelihoods activities. The study hypothesised that land access and land rights relate significantly to livelihood security of the Fulanis. The study was conducted in three States, namely, Ogun, Oyo and Ekiti States. Two major settlements of the Fulanis were selected from each of the States and 20 Fulani households were sampled purposively from each settlement. Forty-two Yoruba farmers were also interviewed to understand the land rights regimes operating in their communities. Non-parametric Chi-square analysis was conducted to test the hypotheses. The study revealed that communal land right regime operates in most communities in the region and designates use rights to Fulanis. Fulanis in Oyo State had management rights which gave them secured access to land in their host communities than their counterparts in other States. The hypotheses tested show significant relationship between land rights and livelihood security of the Fulanis (α < 0·05). The rehabilitation of existing grazing reserves in the region is therefore recommended to grant the Fulanis ownership rights and secured access to land for the security of their livelihoods. Copyright © 2007 John Wiley & Sons, Ltd.
The relationships between pastoralists, livestock, and the environment in dryland Africa are complex. Over the last half-century dominant narratives have portrayed pastoralists and their livestock as being responsible for ‘over grazing’ and ‘degradation’ without attention to how resource availability and cattle mobility are spatially distributed and temporally variable. The objective of this study is to test hypotheses on the nature, magnitude, and extent of the spatially and temporally explicit interactions between the density and distribution of pastoral cattle and resource availability. The study relies on coupling remotely sensed vegetation indices with cattle Global Positioning Systems (GPS) collar data for a pastoral community in southern Kenya. Data are temporally stratified in order to account for seasonal effects. Across seasons, there is a positive relationship between cattle mobility and resource availability with the trend more pronounced during drier periods, reflecting a strategy of increased resource access. The relationship between cattle density and vegetation reveals a strategy of increased resource utilization during wetter periods. The spatiality of high-density areas differs by season, revealing that cattle intensively utilize different parts of the landscape at different times. Areas closest to the household are consistently impacted by cattle across all seasons. These findings have implications on how the savanna vegetation may be impacted as trends towards sedentarization and reduced pastoral mobility continue. Copyright © 2010 John Wiley & Sons, Ltd.
We compared the effects of young high-density plantations of three native trees (legumes: Albizia lebbeck, A. procera and a non-legume: Tectona grandis) and one fast growing woody grass species (Dendrocalamus strictus) on carbon and nutrients stock and their accretion rates in a redeveloping soil. This soil was the early phase of mine spoil restoration in a dry tropical environment. The soil bulk density and accumulation rates of C, N and P at 0–10 and 10–20 cm soil depth were determined in 4- to 5-year-old plantations. The total nutrient stock of soil C, N, P significantly varied in redeveloping soil according to plantation type, plantation age and soil depth. A. lebbeck greatly improved C and N content followed by D. strictus, A. procera and T. grandis plantations. However, accretion rates of C and N were substantially high in the D. strictus plantation. Therefore, D. strictus, contributed significantly to the redevelopment of mine spoil soils. In the case of total P nutrient, A. procera showed the greatest amount among the plantations but the accretion rate was also high for T. grandis followed by A. procera, A. lebbeck and D. strictus. This study indicates that all N-fixing species may not be equally efficient in improving soil qualities especially N in the soil. Copyright © 2006 John Wiley & Sons, Ltd.
Reclaimed coal mine lands have the potential to sequester atmospheric carbon (C); however, limited information exists for the western USA coalfields. This study was carried out on two chronosequences (BA-C3 grasses and DJ-shrubs) of reclaimed sites at two surface coal mines to determine the effects of vegetation, soil texture, and lignin content on soil total organic carbon (TOC) accumulations. In the BA chronosequence, TOC increased over 26 years at an average rate of 0·52 Mg C ha−1 yr−1 in the 0–30 cm depth and was significantly correlated with clay content. Comparison between < 1 and 16-year-old stockpile soils indicated TOC content did not differ significantly. In the DJ chronosequence, TOC content in the 0–30 cm depth declined from 31·3 Mg ha−1 in 5-year-old soils to 23·4 Mg ha−1 in 16-year-old soils. The C:N ratios suggested that some (up to 2·0 per cent) of the TOC was potentially derived from coal particles in these reclaimed soils. Soil total N (TN) contents followed a similar trend as TOC with TOC and TN concentrations strongly correlated. Lignin contents in TOC of all reclaimed soils and topsoil stockpiles (TSs) were higher than that of nearby undisturbed soils, indicating the recalcitrant nature of TOC in reclaimed soils and/or possibly the slow recovery of lignin degrading organism. Results indicated that TOC accumulations in DJ were largely controlled by its composition, particular lignin content. In BA sites TOC accumulation was strongly influenced by both clay and lignin contents. Copyright © 2008 John Wiley & Sons, Ltd.
Particulate organic matter (POM) plays important role in soil organic carbon (SOC) retention and soil aggregation. This paper assesses how quality (chemical composition) of four different-quality organic residues applied annually to a tropical sandy loam soil for 10 years has affected POM pools and the development of soil aggregates. Water-stable aggregate size distribution (>2, 0·25–2, 0·106–0·25 mm) was determined through wet sieving. Density fractionation was employed to determine POM (light—LF, and heavy—HF fractions, 0·05–1 mm). Tamarind leaf litter showed the highest SOC (<1 mm) accumulation, while rice straw showed the lowest. LF-C contents had positive correlations with high contents of C and recalcitrant constituents, (i.e. lignin and polyphenols) of the residues. Dipterocarp, a resistant residue, showed the highest LF-C, followed by the intermediate residues, tamarind, and groundnut, whereas HF was higher in groundnut and tamarind than dipterocarp residues. Rice straw had the lowest LF- and HF-C contents. Tamarind had the highest quantity (51 per cent) of small macroaggregates (0·25–2 mm), while dipterocarp had the most (2·1 per cent) large macroaggregates (>2 mm). Rice straw had the lowest quantities of both macroaggregates. Similar to small-sized HF (0·05–0·25 mm), small macroaggregates had positive correlation with N and negative correlation with C/N ratios, while large macroaggregates had positive correlations with C and recalcitrant constituents of the residues. Tamarind, with intermediate contents of N and recalcitrant compounds, appears to best promote small macroaggregate formation. Carbon stabilized in small macroaggregates accounted for the tamarind treatment showing the largest SOC accumulation. Copyright © 2010 John Wiley & Sons, Ltd.
A field trial investigated the early performance of six tree species planted into an acidic minespoil ameliorated by ploughing or incorporation of 10 per cent by weight of pulverized fuel ash (PFA). Common alder, Italian alder and silver birch produced the greatest total shoot extensions for PFA-ameliorated minespoil. Rowan, sycamore and aspen were unsatisfactory for both ameliorative treatments. PFA increased the pH of the minespoil for a period of time potentially beneficial for the establishment of the tree species. For the rate of PFA application studied, general salinity effects and cold-water-soluble boron both presented problems for successful tree growth.
Salinity, sodicity and acidity are three major soil constraints that limit crop and pasture yields in Australia. In this paper estimates are made of the potential benefits arising from their treatment by measuring and mapping their impact on agricultural profit. This is achieved by estimating the increase in profit for Australia's main commodities that would occur if the three soil constraints were costlessly ameliorated. These estimates reveal the upper achievable limit on investment returns. They are also indicative of each soil constraint's economic significance to Australian agriculture. It was found that costless removal of salinity would increase annual profits by A$187 million, sodicity by A$1034·6 million and acidity by A$1584·5 million. This equates to 2·9 per cent, 15·8 per cent and 24·2 per cent of total net economic return. It was also found that worsening salinity extent and severity over 2000–2020 has a present value of A$496–A$712 million. Although soil salinity is currently the focus of much public attention, this analysis suggests that from a production viewpoint the correction of sodic and acidic soils may create greater private economic benefit. Opportunities vary considerably among industries. In particular, there is considerable opportunity for the horticultural and viticultural sector to address acidity issues. Whether gross benefits translate into net benefits is a complex question requiring access to context and location-specific information. Copyright © 2005 John Wiley & Sons, Ltd.
Soils located at the Mexican Trans-Volcanic Belt (MTB) have a worrying degree of degradation due to inappropriate management practices. Early indicators of soil changes are very useful to alert about negative impacts of wrong managements on these volcanic soils. The aim of this work was to evaluate the short-term effects (4 years) of different agricultural practices on soil organic matter (SOM) quality and to validate the potential of the selected biochemical properties as optimal early indicators of soil quality in Mexican cultivated Acrisols. During 2002–2005 four agronomic management systems: conventional (Tc); improved conventional (Ti); organic (To) and fallow (Tf) were assayed in plots located at the MTB. An uncultivated soil under grass cover (Sg) was used as reference. Soil samples were collected at 0–10 cm depth and were analysed chemically (soil organic C, total N, water-soluble C and humic C), and biochemically (total and extra-cellular enzyme activity). After 4 years, soil organic C, total N, water-soluble C, and dehydrogenase activity had higher values in To, followed by Ti treatment. A similar response pattern was observed in the extra-cellular enzyme activity. The highest total enzyme activity was found in Sg, followed by Ti and To treatments, and the lowest values appeared in Tc and Tf. To and Ti increased SOM contents of the degraded Acrisols studied, while Tc and Tf managements decreased the quality of these soils. The results showed that the assayed soil enzymes can be used as indicators of quality changes of these Mexican volcanic soils. Copyright © 2010 John Wiley & Sons, Ltd.
This work analyses the contribution of the largest events to suspended sediment transport on the continental scale. The analysis is based on the United States Geological Survey (USGS) Suspended Sediment and Ancillary database. Data were obtained from 1314 catchments, comprising more than 2 500 000 daily events. The total number of days in the dataset amounts to 10 000 years. Catchments are of different sizes and belong to distinct climatic environments; they are distributed for the analysis according to USA hydrological divisions (HDs). The main objective of the research is to examine the effect of the n-largest event on the total suspended sediment load over recorded periods, and to discuss different behaviour between HDs. To accomplish this, the daily events at each catchment are ranked by magnitude, and then the percentage represented by the n-largest event (e.g. 3-largest, 5-largest, 10-largest, 15-largest, 20-largest, 25-largest) is calculated from the total accumulated load. Results indicate that suspended sediment transported by the 25-largest events represents on average more than 50 per cent of the total load. The California HD, mostly under Mediterranean climatic conditions, accounts for the highest percentage of sediment transport across conterminous USA, whatever n-largest daily events are selected. There, the 3-largest events contribute, on average, 38 per cent of the total sediment load, the 10-largest events represent 61 per cent and the 25-largest events produce more than 76 per cent of the total sediment transport. Overall, the contribution of largest daily events seems not to depend on the climatic conditions in small catchments (<100 km2) and, in addition, the percentage of suspended sediment increases over all HDs, while, at the same time, the catchment size decreases. Finally, we discuss differences between catchments across the USA, according to climatic and historical (i.e. land use) factors. Copyright © 2009 John Wiley & Sons, Ltd.
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