Home About us Contact
|
Home About us Contact | ||
|
|
||
Land Abandonment (land + abandonment)
Selected AbstractsScale dependence of spatial patterns and cartography on the detection of landscape change: relationships with species' perceptionECOGRAPHY, Issue 4 2002Susana Suárez-Seoane This paper analyses how landscape pattern detection changes when different spatial and temporal scales and several levels of detail of the cartography are used to describe a landscape affected by land abandonment in northern Spain. In order to integrate landscape composition and structure at different temporal and spatial scales in the same framework, a multiple correspondence factorial analysis was ran for each typology of landscape units. Annual rates of change and scale dependencies were calculated for each typology from the Euclidean distances in the factorial space. Finally, the potential assessment of habitat utilisation by species with different landscape perception and movement capacity was modelled for the range of typologies. The amount of variance explained by the factorial analysis decreased with the complexity of the typology. Annual rates of change appeared different according to the time span and the detail of the landscape unit typology used. For all typologies, changes were faster during 1983,95, a period characterised by massive land abandonment. However, when the whole period (1956,95) was considered, annual changes were much lower, showing differences between typologies. As a general trend, the variance of the mean annual change decreased with the size of the analysis units. In response to land abandonment, different scale dependencies were found for different levels of detail of the cartography. Coarser typologies are suitable when analysing highly mobile species. However, species with small movement capacity or with a preference for homogeneous habitats perceive more detail in landscape. In this case, a detailed typology is more appropriate. [source] A 3.5 ka record of paleoenvironments and human occupation at Angkor Borei, Mekong Delta, southern CambodiaGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2003Paul Bishop Microfossil and sedimentological data from a 3.1 m core extracted from a reservoir (baray) at the ancient Cambodian settlement of Angkor Borei in the Mekong Delta have provided a continuous record of sedimentation and paleoenvironments dating from about 2000 cal yr B.C. Palynological data indicate that for much of the cal. 1st and 2nd millennia B.C. mangroves dominated the regional vegetation, while extensively and regularly burnt grasslands dominated the local vegetation. Turbid, nutrient-rich standing water characterized the core locality, perhaps suggesting a connection with rivers in the area. An abrupt change during the cal. 5th to 6th centuries A.D. involved a dramatic reduction in grasslands and the expansion of secondary forest or re-growth taxa. These changes are synchronous with an abrupt decline in the concentration of microscopic charcoal particles in the sediments, and the colonization of the core locality by swamp forest plants. These changes are taken to indicate a shift in land-use strategies or, possibly, a period of land abandonment. The age for the construction of the baray is interpreted to be in the 17th,19th centuries, but this dating remains speculative. Construction of the Angkor Borei baray exploited a preexisting body of standing water, so its construction was fundamentally different from the methods used at the Angkorian capital in northern Cambodia. © 2003 Wiley Periodicals, Inc. [source] Climate change and grasslands through the ages: an overviewGRASS & FORAGE SCIENCE, Issue 2 2007L. 't Mannetje Summary Change from cool to warm temperatures and vice versa have occurred throughout geological time. During the Jurassic and Cretaceous periods (206,65 million years ago, Ma) the climate was more uniformly warm and moist than at present and tropical rainforests were widespread. Grasses evolved during the Jurassic period and they expanded greatly as the climate differentiated with reduced rainfall and temperatures. C4 -grasses probably arose during the Oligocene period (24,35 Ma). During the Miocene period (23·8,5·3 Ma) grasslands expanded into huge areas (e.g. prairies in the USA, steppe in Eurasia, and pampas and llanos in South America). During the Quaternary period (1·8 Ma till now) some twenty-two different ice ages with periodicities of about 100 000 years occurred. Eighteen-thousand years ago, north-western Europe had a polar climate with tundra vegetation and the Mediterranean region was covered by steppe. During that time Amazonia was so dry that it was covered in extensive areas of savanna and the Sahara expanded rapidly. Only in the last 10 000 years has a closed rainforest covered the Amazonian region again. However, 9000 years ago a brief period of global warming caused excessive rains, which caused the sea and river levels to rise in north-western Europe with tremendous loss of life. The present period of extreme dryness in the Sahara only started some 5000 years ago and then the desert expanded rapidly into the Sahel. Before that the Sahara was covered by steppe. Global warming took place between about ad 900 and about ad 1200 or 1300 just before the Little Ice Age (1550,1700 ad). The article concludes with a description of temperature and vegetation changes that are occurring in Europe at present. It is predicted that C4 -grasses, which are already present in southern Europe, will further expand but that, in the short term, land abandonment will have much more deleterious effects than temperature change due to increased wild fires, loss of biodiversity and desertification. [source] Economic determinants of biodiversity change over a 400-year period in the Scottish uplandsJOURNAL OF APPLIED ECOLOGY, Issue 6 2008Nick Hanley Summary 1Economic forces are recognized as an important driving factor behind current biodiversity losses. This study investigates whether such factors have been important in determining one measure of biodiversity change over the ,long run', in our case, 400 years , for upland sites in Scotland. 2A combination of palaeoecological, historical and economic methods is used to construct and then analyse a database of factors contributing to changes in plant diversity over time for 11 upland sites. 3Using an instrumental variables panel model, we find livestock prices, our proxy for grazing pressure, to be a statistically significant determinant of diversity change, with higher grazing pressures resulting in lower diversity values on average, although site abandonment is also found to result in a fall in plant diversity. Technological change, such as the introduction of new animal breeds, was not found to be a statistically significant determinant. 4Using later period data (post 1860) on livestock numbers at the parish (local) level, we were able to confirm the main result noted above (3) in terms of the effects of higher grazing pressures on plant diversity. 5Synthesis and applications. This study shows how data from very different disciplines can be combined to address questions relevant to contemporary conservation and understanding. This novel, interdisciplinary approach provides new insights into the role of economic factors as a driver of biodiversity loss in the uplands. Biodiversity levels have varied considerably over 400 years, partly as a function of land management, suggesting that establishing baselines or ,natural' target levels for biodiversity is likely to be problematic. Changes in livestock grazing pressures brought about by changes in prices had statistically significant effects on estimated plant diversity, as did land abandonment. This suggests that long-term management of upland areas for the conservation of diversity should focus on grazing pressures as a key policy attribute. Another policy implication is that drastic cuts in grazing pressures , such as might occur under current reforms of the Common Agricultural Policy , can have adverse biodiversity consequences. [source] Anthropogenic disturbance and the formation of oak savanna in central Kentucky, USAJOURNAL OF BIOGEOGRAPHY, Issue 5 2008Ryan W. McEwan Abstract Aim, To deepen understanding of the factors that influenced the formation of oak savanna in central Kentucky, USA. Particular attention was focused on the link between historical disturbance and the formation of savanna ecosystem structure. Location, Central Kentucky, USA. Methods, We used dendrochronological analysis of tree-ring samples to understand the historical growth environment of remnant savanna stems. We used release detection and branch-establishment dates to evaluate changes in tree growth and the establishment of savanna physiognomy. We contrasted our growth chronology with reference chronologies for regional tree growth, climate and human population dynamics. Results, Trees growing in Kentucky Inner Bluegrass Region (IBR) savanna remnants exhibited a period of suppression, extending from the establishment date of the tree to release events that occurred c. 1800. This release resulted in a tripling of the annual radial growth rate from levels typical of oaks suppressed under a forest canopy (< 1 mm year,1) to levels typical of open-grown stems (3 mm year,1). The growth releases in savanna trees coincided with low branch establishment. Over the release period, climatic conditions remained relatively constant and growth in regional forest trees was even; however, the growth increase in savanna stems was strongly correlated with a marked increase in Euro-American population density in the region. Main conclusions, Our data suggest that trees growing in savanna remnants originated in the understorey of a closed canopy forest. We hypothesize that Euro-American land clearing to create pasturelands released these trees from light competition and resulted in the savanna physiognomy that is apparent in remnant stands in the IBR. Although our data suggest that savanna trees originated in a forest understorey, this system structure itself may have been a result of an unprecedented lack of Native American activity in the region due to population loss associated with pandemics brought to North America by Euro-Americans. We present a hypothetical model that links human population dynamics, land-use activities and ecosystem structure. Our model focuses on the following three land-use eras: Native American habitation/utilization; land abandonment; and Euro-American land clearance. Ecological understanding of historical dynamics in other ecosystems of eastern North America may be enhanced through recognition of these eras. [source] Enrichment planting does not improve tree restoration when compared with natural regeneration in a former pine plantation in Kibale National Park, UgandaAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Patrick A. Omeja Abstract Given the high rates of deforestation and subsequent land abandonment, there are increasing calls to reforest degraded lands; however, many areas are in a state of arrested succession. Plantations can break arrested succession and the sale of timber can pay for restoration efforts. However, if the harvest damages native regeneration, it may be necessary to intervene with enrichment planting. Unfortunately, it is not clear when intervention is necessary. Here, we document the rate of biomass accumulation of planted seedlings relative to natural regeneration in a harvested plantation in Kibale National Park, Uganda. We established two 2-ha plots and in one, we planted 100 seedlings of each of four native species, and we monitored all tree regeneration in this area and the control plot. After 4 years, naturally regenerating trees were much taller, larger and more common than the planted seedlings. Species richness and two nonparametric estimators of richness were comparable between the plots. The cumulative biomass of planted seedlings accounted for 0.04% of the total above-ground tree biomass. The use of plantations facilitated the growth of indigenous trees, and enrichment planting subsequent to harvesting was not necessary to obtain a rich tree community with a large number of new recruits. Résumé Étant donné le rythme élevé de déforestation et, par la suite, d'abandon de terres, il y a des demandes croissantes pour repeupler les terrains dégradés; cependant, de nombreuses surfaces se trouvent dans un état de succession interrompu. Des plantations peuvent mettre fin à cette succession stoppée, et la vente de grumes peut financer les efforts de reforestation. Pourtant, si les prélèvements d'arbres endommagent la régénération naturelle, il peut être nécessaire d'intervenir avec des plantations d'appoint. Malheureusement, il n'est pas toujours facile de savoir quand une intervention est nécessaire. Nous documentons ici le taux d'accumulation de biomasse dans des jeunes arbres replantés par rapport à la régénération naturelle dans une plantation exploitée, à l'intérieur du Parc National de Kibale, en Ouganda. Nous avons établi deux parcelles de deux hectares et, dans une, nous avons repiqué 100 plants de chacune des quatre espèces natives. Nous avons ensuite suivi la régénération de tous les arbres dans cette parcelle et dans la parcelle témoin. Après quatre ans, les arbres provenant de la régénération naturelle étaient beaucoup plus grands, plus gros et plus abondants que les arbres replantés. La richesse en espèces et deux estimateurs nonparamétriques de la richesse étaient comparables dans les deux parcelles. La biomasse cumulée des jeunes arbres plantés comptait pour 0,04% de la biomasse aérienne totale des arbres. Le recours à des plantations a facilité la croissance d'arbres indigènes et la plantation d'appoint faisant suite à l'exploitation ne fut pas nécessaire pour obtenir une communauté d'arbres riche, avec un grand nombre de nouvelles recrues. [source] Spatial pattern of Quercus ilex and Quercus pubescens recruitment in Pinus halepensis dominated woodlandsJOURNAL OF VEGETATION SCIENCE, Issue 4 2000T.R. Lookingbill Abstract. European Mediterranean landscapes have undergone changes in structure in recent years as a result of widespread agricultural land abandonment and cessation of silvicultural regimes. Studies concerning the regeneration dynamics of dominant forest species have become critical to the prediction of future landscape trends in these changing forest stands. Quercus ilex (holm oak) and Q. pubescens (downy oak) are considered to be the terminal point of secondary succession in extensive areas of the Mediterranean region. Recent studies, however, have suggested the existence of recruitment bottlenecks in oak genet populations as a result of current management regimes. In this study, we present evidence of the successful establishment of Q. ilex and Q. pubescens in Pinus halepensis (Aleppo pine) woodlands. We investigate the distribution patterns and spatial relationships among oak recruits and resident pines. Established P. halepensis is randomly distributed throughout the study area. Oak seedlings are positively associated with pine trees, suggesting that P. halepensis individuals provide safe sites for oak genet recruitment. We show that spatial patterns of recruitment are in agreement with the general model of spatial segregation described for other Mediterranean plant communities, with seeder species colonizing large openings after disturbance, followed by a more aggregated recruitment of resprouter species. [source] Soil degradation and soil surface process intensities on abandoned fields in Mediterranean mountain environmentsLAND DEGRADATION AND DEVELOPMENT, Issue 5 2008M. Seeger Abstract 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. [source] Effect of agro-forestry and landscape changes on common buzzards (Buteo buteo) in the Alps: implications for conservationANIMAL CONSERVATION, Issue 1 2005Fabrizio Sergio In Italy, pre-Alpine forests, once managed through coppice silviculture, are being converted to mature woodland, while land abandonment is causing woodland expansion and erosion of open habitats. Based on habitat-selection analyses, we predicted the impact of such changes on common buzzards (Buteo buteo), which depend on forested and open areas for nesting and foraging. Compared to availability, at a micro-scale buzzards selected nests higher above ground and on trees frequently covered by ivy. At the landscape-scale, buzzards avoided roads and conspecifics, while selecting rugged areas with high habitat heterogeneity, probably related to a varied food supply. Productivity was related to the availability of arid habitats, probably because of their richness in main prey species. Finally, population density was negatively related to the abundance of eagle owls (Bubo bubo), a potential predator of adults and nestlings, and positively related to the availability of woodland, a low predation-risk habitat rich in food and nest-sites. Therefore, buzzard settlement, density and productivity depended on the complex interplay of food availability, human persecution and predation risk. Thus, the current landscape changes would benefit buzzards by providing more nest-sites, but would be detrimental because of the lower productivity associated with the disappearance of dry open areas. Proposed conservation guidelines focus on conversion of coppice woodland to mature forests and active management of dry heath, a conservation sensitive habitat, through controlled burning. [source] | |||||||||||||