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1.
This paper focuses on understanding human impact on landscape. Both ecological and human practices are analysed as interacting
processes. An agent-based model integrating biological and historical knowledge is used to analyse the pattern of Scots Pine
encroachment in a French Mediterranean upland. In the STIPA model, pine trees are autonomous agents and a cellular automaton
simulates land-use. We test the effects of shifting cultivation on tree establishment at the landscape scale. This allows
us to understand how agropastoral practices patterned this area from the 17th to 19th century: simulations show the importance
of shifting cultivation in limiting woodland progression. Fallow duration linked to environmental heterogeneity is a significant
factor for explaining pine dynamics and landscape patterning at the scale of the study region. We put this result in perspective
with current rangeland management policies that often consider grazing as the most relevant tool for open landscape maintenance.
Our results also show the importance of taking into account time-scale effects when linking landscape patterns to agricultural
systems. 相似文献
2.
S. Fujisaka 《Agroforestry Systems》1991,13(2):95-109
About 25% of Laos' four million people practise shifting cultivation (mainly of rice) on a third of the country's cropped area. Official policy is to eliminate shifting cultivation by the year 2000. Diagnostic surveys of shifting cultivation were conducted in Luang Prabang and Oudomsay Provinces in northern Laos to understand the practice from a farmer's perspective, to observe fields, and to identify and give priority to problems and research to address problems. Weeds, low and possibly declining soil fertility, intensification of the cropping cycle, rats (plus birds, wild pigs), and insects lowered rice yields or reduced system sustainability. The forest ecosystem has been degraded by logging, burning, and rice monocropping; and potentials for environmental rehabilitation through natural succession are minimal. Farmers cannot adopt high labor and cash cost innovations; and improved fallow is needed as an intermediate step prior to crop diversification, adoption of agroforestry technologies, and sedentary agriculture. 相似文献
3.
Nutrient stocks of short-term fallows on a high base status soil in the humid tropics of Papua New Guinea 总被引:1,自引:0,他引:1
Alfred E. Hartemink 《Agroforestry Systems》2004,63(1):33-43
In order to understand nutrient dynamics in tropical farming systems with fallows, it is necessary to assess changes in nutrient
stocks in plants, litter and soils. Nutrient stocks (soil, above ground biomass, litter) were assessed of one-year old fallows
with Piper aduncum, Gliricidia sepium and Imperata cylindrica in the humid lowlands of Papua New Guinea. The experiment was conducted on a high base status soil (Typic Eutropepts), and
in Papua New Guinea such soils are intensively used for agriculture. Soil samples were taken prior to fallow establisment
and after one year when the fallows were slashed and above ground biomass and nutrients measured. The above ground and litter
biomass of piper was 13.7 Mg dry matter ha-1, compared to 23.3 Mg ha-1 of gliricidia and 14.9 Mg ha-1 of imperata. Gliricidia produced almost 7 Mg ha-1 wood. Total above ground biomass returned to the soil when the fallows were slashed was the same for piper and gliricidia
(8 Mg ha-1). Gliricidia accumulated the largest amounts of all major nutrients except for K, which was highest in the above ground piper
biomass. Imperata biomass contained the lowest amount of nutrients. The largest stocks of C, N, Ca and Mg were found in the
soil, whereas the majority of P was found in the above ground biomass and litter. Almost half of the total K stock of piper
and gliricidia was in the biomass. During the fallow period, soil organic C significantly increased under gliricidia fallow
whereas no net changes occurred in piper and imperata fallows. The study has shown large differences in biomass and nutrient
stocks between the two woody fallows (piper, gliricidia) and between the woody fallows and the non-woody fallow (imperata).
Short-term woody fallows are to be preferred above grass (imperata) fallows in the humid lowlands of Papua New Guinea because
of higher nutrient stocks. 相似文献
4.
Amazonian deforestation and global warming: carbon stocks in vegetation replacing Brazil''s Amazon forest 总被引:8,自引:0,他引:8
Philip M. Fearnside 《Forest Ecology and Management》1996,80(1-3):21-34
Carbon stocks in vegetation replacing forest in Brazilian Amazonia affect net emissions of greenhouse gases from land-use change. A Markov matrix of annual transition probabilities was constructed to estimate landscape composition in 1990 and to project future changes, assuming behavior of farmers and ranchers remains unchanged. The estimated 1990 landscape was 5.4% farmland, 44.8% productive pasture, 2.2% degraded pasture, 2.1% ‘young’ (1970 or later) secondary forest derived from agriculture, 28.1% ‘young’ secondary forest derived from pasture, and 17.4% ‘old’ (pre-1970) secondary forest. The landscape would eventually approach an equilibrium of 4.0% farmland, 43.8% productive pasture, 5.2% degraded pasture, 2.0% secondary forest derived from agriculture, and 44.9% secondary forest derived from pasture. An insignificant amount is regenerated ‘forest’ (defined as secondary forest over 100 years old). Average total biomass (dry matter, including below-ground and dead components) was 43.5 t ha−1 in 1990 in the 410 × 103 km2 deforested by that year for uses other than hydroelectric dams. At equilibrium, average biomass would be 28.5 t ha−1 over all deforested areas (excluding dams). These biomass values are more than double those forming the basis of deforestation emission estimates currently used by the Intergovernmental Panel on Climate Change (IPCC). Although higher replacement landscape biomass decreases net emissions from deforestation, these estimates still imply large net releases. 相似文献
5.
Shiang‐Lin Huang Haiping Wu Xianyan Wang Chongwei Peng Chun‐Chieh Wang 《水产资源保护:海洋与淡水生态系统》2020,30(9):1775-1782
- Protecting critical habitats of the Indo‐Pacific humpback dolphin, Sousa chinensis, is a hot topic of discussion for marine biodiversity conservation in China and many Southeast Asian countries. In practice, sound habitat protection action (HPA) planning often suffers from information gaps in macroscopic habitat configurations and changes in the habitat conditions of humpback dolphins.
- Recent publications in the journal Aquatic Conservation: Marine and Freshwater Ecosystems (AQC) have served to advance humpback dolphin conservation in Chinese waters by resolving such habitat configurations and indicating significant changes in distribution patterns and habitat characteristics under intense coastal anthropogenic activity.
- We highlight an integrative research framework to investigate habitat configuration and long‐term habitat changes when planning a holistic HPA programme for humpback dolphins. When constructing habitat configuration baselines, field surveys should be designed and conducted in a systematic manner to ensure survey efforts cover diverse environments equally, in either a spatially stratified or gridded pattern, to minimize potential spatial sampling biases. Long‐term habitat changes can be revealed by comparing satellite images from different decades. Changes in habitat preferences and habitat characteristics can be explored through questionnaire surveys on local ecological knowledge, associating historical occurrences with coastline features and projecting historical habitat configuration by species distribution modelling exercises.
- A lack of good communication and sharing of information between research and management sectors can still be an obstacle to the implementation of sound conservation practices, however, even though there is robust scientific evidence to fill knowledge gaps in distribution and habitat baselines. We have addressed the need to establish a mechanism to improve and streamline information sharing between research teams, management sectors, and stakeholder groups.
6.
Hiromitsu Samejima Marfaizal Marzuki Teruyoshi Nagamitsu Tohru Nakasizuka 《Biological conservation》2004,120(4):577-587
Human disturbance of tropical rainforests may change pollinator communities indirectly as a result of changes in resource availability. We studied the mechanisms by which human disturbance affects a community of major pollinators, stingless bees, in Sarawak, Malaysia. We surveyed forest structure and flowering activity, and conducted a nest census and a bait-trap survey of stingless bees, both in primary forests and in forests disturbed by logging and shifting cultivation. The densities of late successional trees and large trees (diameter at breast height >50 cm) were higher in the primary forests than in the disturbed forests. The density of flowering trees was lower one year after logging, but recovered in old disturbed forests because of the active flowering of pioneer trees that became established after the disturbance. Stingless bees nest only in large trees, and nest density was positively correlated with the density of large trees. However, we found no relationship between the numbers of foragers and floristic parameters. Some species preferred nesting in dipterocarps, while others preferred dead trees. The results of the bait-trap survey also indicated that some species were abundant in the primary forests, whereas other species were abundant in the disturbed forests. These results suggest that human disturbance alters the species composition of the stingless bee community. Such changes in the bee community may affect the reproductive success of plants, and ultimately forest composition. 相似文献
7.
David Parsons Charles F. NicholsonRobert W. Blake Quirine M. KetteringsLuis Ramírez-Aviles Jerome H. CherneyDanny G. Fox 《Agricultural Systems》2011,104(1):13-19
Simulation models are effective tools to examine interactions between livestock, cropping systems, households, and natural resources. Our study objective was to use an integrated livestock and crop model to assess the outcomes from selected suites of management decisions observed in smallholder sheep-cropping systems of Yucatán, Mexico. The scenarios contrasted specialized systems versus mixed farming, and evaluated the outcomes of increased crop-livestock integration. Mixed enterprise scenarios involving sheep provided more income than specialized enterprises, and capitalized on a lower price of on-farm maize grain, efficient utilization of surplus labor, and availability of common land. Labor and management income was greatest for the unintegrated and partially integrated crop and livestock scenarios. It was more profitable for producers to sell excess grain and maize stover, and use common land to feed the livestock, suggesting that increased integration does not always result in improved outcomes. The results are consistent with a system not yet pushed to the point where integration is inevitable. For all sets of scenarios, the model structure was able to accommodate subtle management differences to produce appropriate biophysical, labor, and economic outcomes. We conclude there is potential to use similar model development methods to describe other crop-livestock systems, thus providing tools for learning, scenario analysis, and impact assessment. 相似文献
8.
We report the effects of shifting cultivation on water quality in 16 creeks investigated once in 2007 and twice in 2008 in 16 apparently similar small neighboring watersheds,each of 3 to 5 ha,at four locations around Barkal sub-district under Rangamati District of Chittagong Hill Tracts in Bangladesh.Concentrations of SO 4 2and K +,and pH in creek water were lower,and NO 3-N and Na + concentrations were higher in shifting-cultivation land compared to land with either plantation or natural forest or a combination of these cover types.Shifting cultivation effects on some water quality parameters were not significant due to change in land cover of the watershed between two sampling periods either through introduction of planted tree species or naturally regenerated vegetation.Conductivity and concentrations of HCO 3,PO 4 3,Ca 2+ and Mg 2+ in creek water showed no definite trend between shifting cultivation and the other land cover types.At one area near the Forest Range Office of Barkal,creek water pH was 5.8 under land cover with a combination of shifting cultivation and plantation.At this area Na + concentration in shifting-cultivation land ranged from 32.33 to 33.00 mg L-1 and in vegetated area from 25.00 to 30.50 mg L-1 in 2007.At another area,Chaliatali Chara,SO 4 2concentration in a shifting-cultivation watershed ranged from 4.46 to 10.51 mg L-1,lower than in a vegetated watershed that ranged from 11.69 to 19.98 mg L-1 in 2007.SO 4 2concentration in this shifting-cultivation area ranged from 1.28 to 1.37 mg L-1 and in the vegetated area from 1.37 to 3.50 mg L-1 in 2008. 相似文献
9.
10.