共查询到20条相似文献，搜索用时 489 毫秒
1.
The climatic controls on decomposition rates have gained considerable interest in recent years because of a perceived risk that elevated global temperatures could lead to positive green house gas feedbacks from soil ecosystems. Previous relationships between decomposition rates and abiotic variables like temperature and moisture have been proved confounding, particularly for dryland ecosystems. Decomposition rates of two grass species, Pseudoroegneria spicata (Pursh) Á. Löve and Calamagrostis rubescens Buckley, which represent dominant understory cover at either end of a semi-arid grassland to forest ecocline near Kamloops, British Columbia, Canada, were measured. Despite differences in %N and C:N, decomposition rates between the two species were similar. Elevation was strongly correlated with rate of decomposition for both species. We provide evidence of a positive correlation of water availability and a negative correlation of temperature on decomposition rates along the elevational ecocline. Decomposition rates were higher during the wetter spring period than during summer, at higher elevations and in more mesic ecosystems. We found no ‘home-field’ advantage for P. spicata and C. rubescens on decomposition rates. Our results provide evidence that available moisture is an important control on decomposition rates in dryland ecosystems. 相似文献
2.
While studies on deforestation of protected areas (PAs) have been conducted in many parts of the world, no comparative study has been done over an entire country in the tropics. Thus, we conducted a country-wide assessment of forest cover loss in all terrestrial protected areas of the Philippines, covering 198 PAs with a total area of 4.68 million ha. This study utilised Hansen's Landsat-derived global maps of forest cover change from 2000 to 2012, with tree canopy cover data for 2000 as the base year. Correlation and logistic regression analyses were employed to determine the significance and magnitude of the relationships between forest cover and 11 predictor variables. The assessment of forest loss reveals that the terrestrial protected areas are generally effective in reducing forest loss. Over the 12-year period, the average rate (2.59%) of forest clearing in protected areas is marginally lower by 0.1% than the entire country (2.69%). Within the same duration, the average forest loss rate within the 2-km buffer zones of selected protected areas is 1.4 times of those inside PAs. However, there was a significant number of PAs with phenomenal forest cover loss in terms of extent (48,583 ha over 12 years) and rate (up to 21%). We found that spatial predictor variables included in this study have weak or no relationships with forest cover, and hence they are not reliable inputs for predictive modelling. Comprehensive assessments of deforestation are needed at the micro-scale (e.g. single PA level) level and relatively shorter historical timeframe (e.g. less than a decade), to generate useful information for policy formulation, planning, and management. 相似文献
3.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(4):233-245
Analysing forest history is crucial to understanding how shifting harvesting methods have different effects on forest landscape structure. Two main harvesting regimes in a Norwegian boreal forest landscape over a period of 150 years were detected by the study. A homogeneous impact regime resulting from selective logging changed the forest structure by logging the oldest and largest trees evenly throughout the forest, resulting in a homogeneous landscape structure. However, population growth in the 19th century led to a substantial increase in traditional subsistence forestry to obtain building materials, firewood, etc. The most intensive stage of this regime started in c.1860 when farmers began selling logging contracts to companies and timber traders. Despite this being termed a homogeneous landscape impact, the actual exploitation of the forest was strongly influenced by local factors such as the location of farms, summer farms, lakes, and rivers. Clear-cutting from the 1950s has resulted in a new heterogeneous impact regime, giving a landscape structure dominated by patches of even-aged stands. This regime still predominates. The analysis is based on a study of Nordli and the Sand?la drainage basin in Nord-Tr?ndelag. Such studies should give a better understanding of the interaction between natural ecological conditions in and human impact on boreal forest landscapes. 相似文献
4.
We developed an approach using remote sensing and modeling, applicable to Algerian forest inventory, for estimating the volume of timber in Aleppo pine stands. We used ordinary linear regression (OLR) and reduced major axis (RMA) regression to assess an operational model to map stand volume from satellite images. Our analysis was supported by measurements from 151 sample plots and spectral values from remote sensing imagery. Fifteen candidate models were tested through the Akaike Information Criterion to assess their predictive power. For the 2009 Landsat TM image, we found that the best models for both regression methods used the NDVI as the independent variable. The RMSEs were 20.3% (16.10 m3 ha−1) and 22.5% (17.83 m3 ha−1), respectively, for OLR and RMA. We chose the RMA regression models because they had realistic standard deviation values for the estimated volumes, and they gave lower RMSEs in volume classes over 40 m3 ha−1. Our method gave similar results for two other images, which demonstrated that our approach was robust when applied to data from a different year (2006 Landsat TM), but from the same sensor, and also to data from a different sensor (2005 Alsat-1). 相似文献
5.
The planned construction of hundreds of hydroelectric dams in the Amazon basin has the potential to provide invaluable ‘clean’ energy resources for aiding in securing future regional energy needs and continued economic growth. These mega-structures, however, directly and indirectly interfere with natural ecosystem dynamics, and can cause noticeable tree loss. To improve our understanding of how hydroelectric dams affect the surrounding spatiotemporal patterns of forest disturbances, this case study integrated remote sensing spectral mixture analysis, GIS proximity analysis and statistical hypothesis testing to extract and evaluate spatially-explicit patterns of deforestation (clearing of entire forest patch) and forest degradation (reduced tree density) in the 80,000 km2 neighborhoods of the Brazil's Tucuruí Dam, the first large-scale hydroelectric project in the Amazon region, over a period of 25 years from 1988 to 2013. Results show that the average rates of deforestation were consistent during the first three time periods 1988–1995 (620 km2 per year), 1995–2001 (591 km2 per year), and 2001–2008 (660 km2 per year). However, such rate dramatically fell to half of historical levels after 2008, possibly reflecting the 2008 global economic crisis and enforcement of the Brazilian Law of Environmental Crimes. The rate of forest degradation was relatively stable from 1988 to 2013 and, on average, was 17.8% of the rate of deforestation. Deforestation and forest degradation were found to follow similar spatial patterns across the dam neighborhoods, upstream reaches or downstream reaches at the distances of 5 km–80 km, suggesting that small and large-scale forest disturbances may have been influencing each other in the vicinity of the dam. We further found that the neighborhoods of the Tucuruí Dam and the upstream region experienced similar degrees of canopy loss. Such loss was mainly attributed to the fast expansion of the Tucuruí town, and the intensive logging activities alongside major roads in the upstream reservoir region. In contrast, a significantly lower level of forest disturbance was discovered in the downstream region. 相似文献
6.
As land use change continues to increase throughout the Amazon basin, there is a pressing need to accurately map, quantify and assess the effects of different factors on forest cover change (FCC). Land tenure may sometimes have important effects on forest cover, yet such effects remain poorly understood in Amazonia, particularly outside Brazil. In this paper we assess whether significant differences in trends of FCC can be partially explained by different land tenure arrangements, using a case study in southwestern Beni (Bolivian Amazon). We examine spatio-temporal dynamics of FCC across four land tenure systems (indigenous titled territory, protected area, logging concession, and private land) by classifying forests using a time-series of Landsat satellite imagery consisting of four dates (1986, 1996, 2001, 2009). Specifically, we unravel (1) trends in early growth and old-growth forest extent, including changes in total cover area, annual change rates, and spatial change dynamics, and (2) trends in old-growth forest fragmentation. To better understand the association between land tenure and FCC, we qualitatively assess the potential role that other underlying and proximate drivers may have had in FCC over the study period. We found that private lands underwent, by far, the largest FCC, that indigenous territories and the protected area had little FCC, and that logging concessions were responsible for the lowest FCC. Our findings suggest that land tenure played a key role in FCC except in private areas, where many other drivers had operated. Our study sheds light into the potential role of land tenure in FCC and has important implications for public policies aimed at socioeconomic development and environmental conservation in the Amazon. We give some policy recommendations drawn from a biocultural conservation perspective that could contribute to implement more inclusive conservation policies in the region. 相似文献
7.
Phenology is an important indicator of climate change. Studying spatiotemporal variations in remote sensing phenology of vegetation can provide a basis for further analysis of global climate change. Based on time series data of MODIS-NDVI from 2000 to 2017, we extracted and analyzed four remote sensing phenological parameters of vegetation, including the Start of Season(SOS), the End of Season(EOS), the Middle of Season(MOS) and the Length of Season(LOS), in tundra-taiga transitional zone in the... 相似文献
8.
Maya Pasgaard Tania Fredborg Nielsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2016,116(2):134-146
Explicit notions of “communities”, as key actors in conservation and development projects across the Global South, are common. Narratives about “indigenous people” or “forest-dependent communities” in forest conservation programmes prevail, portraying a picture of “communities” as homogeneous and harmonious entities. In this study, we unfold “communities” as a construct with an empirical example of a community-based forest protection project, Northern Cambodia. Based on qualitative interviews, field observations and document analysis, we examine the “community” construct in terms of establishment of boundaries, geographical composition and social coherence. We not only find that the establishment of forest “community” boundaries are dominated by powerful external actors rather than the “community members” themselves, but that the spatial composition of “communities” is complex, and affects the ability of local people to benefit from the project. We also find that the studied “communities” show low levels of social coherence and mainly consist of migrant farmers, as opposed to common policy narratives. Taking these inconsistencies into account, we discuss implications of constructing “communities” for the success of forest conservation projects, and argue in favour of more discursive and political analyses to better understand, acknowledge and adapt to existing and changing conditions in present and prospective project locations. 相似文献
9.
D. T. Robinson D. G. Brown 《International journal of geographical information science》2013,27(9):1211-1232
We use a GIS‐based agent‐based model (ABM), named dynamic ecological exurban development (DEED), with spatial data in hypothetical scenarios to evaluate the individual and interacting effects of lot‐size zoning and municipal land‐acquisition strategies on possible forest‐cover outcomes in Scio Township, a municipality in Southeastern Michigan. Agent types, characteristics, behavioural methods, and landscape perceptions (i.e. landscape aesthetics) are empirically informed using survey data, spatial analyses, and a USDA methodology for mapping landscape aesthetic quality. Results from our scenario experiments computationally verified literature that show large lot‐size zoning policies lead to greater sprawl, and large lot‐size zoning policies can lead to increased forest cover, although we found this effect to be small relative to municipal land acquisition. The return on land acquisition for forest conservation was strongly affected by the location strategy used to select parcels for conservation. Furthermore, the location strategy for forest conservation land acquisition was more effective at increasing aggregate forest levels than the independent zoning policies, the quantity of area acquired for forest conservation, and any combination of the two. The results using an integrated GIS and ABM framework for evaluating land‐use development policies on forest cover provide additional insight into how these types of policies may act out over time and what aspects of the policies were more influential towards the goal of maximising forest cover. 相似文献
10.
This study answers the following research questions: 1) What are the change trajectories of woody vegetation elements at the landscape level? 2) What are the differences in change trajectories amongst the various categories of forest, non-forest and reclamation woody vegetation? 3) How do the change trajectories differ in mining and non-mining landscapes? The study area, measuring 209.6 km2, is located in the north-western part of the Czech Republic and may be broken down into 76.8 km2 of mining landscape and 132.8 km2 of non-mining landscape. Brown coal mining began in this region during the second half of the 18th century and led to the radical transformation of the landscape, including woodlands, during the second half of the 20th century. The source data for this study was obtained from the original stable cadastre maps (1842) and the landscape field mapping performed in 2010. The various woody vegetation elements (forest, non-forest, and reclamation woody plants) and land use/cover (LULC) categories were identified. The GIS symmetrical difference tool was subsequently used to perform an overlay analysis for the individual woody vegetation elements in order to study the change trajectories and to obtain information about the woodlands that have remained unchanged (continuous), the ones that have disappeared (extinct), and the ones that have newly appeared in the landscape (recent). In the case of the non-mining landscape, the total proportion of woodlands has increased (from 17 to 32%), but there has been a decline in the overall volume of forest woody plants found in these areas (from 93 to 74%). As far as the mining landscape is concerned, there has also been an increase in the area covered by woodlands (from 10 to 20%), however, the proportion of forest woody plants has decreased to a much greater extent (from 90 to 31%). From the perspective of extinct woody vegetation, 23.3% of all types of woodlands in the mining landscape may be classified as such, as compared to 10.8% in the non-mining landscape. The primary causes of this decline are mining activities and newly built-up areas. More continuous woody vegetation may be found in the non-mining landscape (42.1%) as compared to the mining landscape (15.4%). Recent woody vegetation, which has primarily replaced grasslands and partially arable land, prevails in both the mining (61.3%) as well as the non-mining (47.1%) landscapes. Different categories of woodlands (forest, non-forest, and reclamation woody vegetation elements) exhibit various change dynamics due to their different structure and the functions they serve. At the most basic level, there has been an overall increase in the occurrence of woodlands in the studied areas. However, once GIS spatial analysis is applied it is possible to see more complex processes in the development of woodland areas as characterised by gains and losses, and it is possible to identify mining and agricultural extensification as the two most significant factors behind the historical changes. Mining leads to a direct decrease in the area of woodlands; conversely, the spontaneous succession of vegetation resulting from agricultural extensification and forest reclamation facilitates woodland recovery. Forest reclamation and reforestation are essential on order to ensure the time continuity of woodlands in both types of landscape, i.e. mining and non-mining. The study presented in this paper proves that it is relevant to analyse the changes occurring in different woodland categories separately. The same methodology may be applied when studying the change dynamics of other important landscape elements, such as wood pastures and wetlands. 相似文献
11.
Human-driven topographic effects on the distribution of forest in a flat,lowland agricul-tural region简 总被引：1，自引：0，他引：1
Mette V. ODGAARD Peder K. B CHER Tommy DALGAARD Jesper E. MOESLUND Jens-Christian SVENNING 《地理学报(英文版)》2014,24(1):76-92
Complex topography buffers forests against deforestation in mountainous regions. However, it is unknown if terrain also shapes forest distribution in lowlands where human impacts are likely to be less constrained by terrain. In such regions, if important at all, to- pographic effects will depend on cultural-historical factors and thus be human-driven （an- thropogenic） rather than natural, except in regions where the general climate or extreme soils limit the occurrence of forests. We used spatial regression modeling to assess the extent to which topographic factors explain forest distribution （presence-absence at a 48x48 m resolu- tion） in a lowland agricultural region （Denmark, 43,075 km2） at regional and landscape scales （whole study area and 10x10 km grid cells, respectively）, how landscape-scale for- est-topography relationships vary geographically, and which potential drivers （topographic heterogeneity, forest cover, clay content, coastal/inland location） determine this geographic heterogeneity. Given a moist temperate climate and non-extreme soils all landscapes in Denmark would naturally be largely forest covered, and any topographic relationships will be totally or primarily human-driven. At regional scale, topographic predictors explained only 5% of the distribution of forest. In contrast, the explanatory power of topography varied from 0%-61% at landscape scale, with clear geographic patterning. Explanatory power of topog- raphy at landscape scale was moderately dependent on the potential drivers, with topog- raphic control being strongest in areas with high topographic heterogeneity and little forest cover. However, these conditioning effects were themselves geographically variable. Our findings show that topography by shaping human land-use can affect forest distribution even in flat, lowland regions, but especially via localized, geographically variable effects. 相似文献
12.
《地理学报(英文版)》2021,(10)
Urban forests play an important role in the thermal comfort and overall life of local populations in large-and medium-sized cities. This study analyzes urban forest loss and maps land use and land cover(LULC) changes between 1991 and 2018 by evaluating the use of urban planning instruments for the mitigation of urban forest loss in Jo?o Pessoa, Brazil. For this purpose, satellite-derived LULC images from 1991, 2006, 2010 and 2018 and data on urban forest loss areas obtained using the Google Earth Engine were used. In addition, this paper also discusses the instruments used for integrated urban planning, which are(a) the legal sector, responsibility and nature;(b) the urban expansion process; and(c) the elements of urban infrastructure. The results show a clear shift in land use in the study area. The major changes in LULC classes occurred in urban areas and herbaceous vegetation, while the greatest loss was in arboreal/shrub vegetation. Thus, an increase in the pressure to occupy zones intended for environmental preservation could be estimated. Our results showed similar accuracies with other studies and more spatial details. The characteristics of the patterns, traces, and hotspots of urban expansion and forest cover loss were explored. We highlighted the potential use of this proposed framework to be applied and validated in other parts of the world to help better understand and quantify various aspects of urban-related problems such as urban forest loss mapping using instruments for integrated urban planning and low-cost approaches. 相似文献
13.
《Polar Science》2014,8(2):183-195
Tree-ring chronologies of ring width and stable carbon isotope ratios (δ13C) over the past 160 years were developed using living larch trees at two forest sites, each with different annual precipitation, in eastern Siberia: Spasskaya Pad (SP) (62°14′N, 129°37′E); and Elgeeii (EG) (60°0′N, 133°49′E). Intrinsic water-use efficiency (iWUE) was derived from tree-ring δ13C. The physiological responses of the larch trees to climate varied between these sites and over time. Ring widths correlated negatively with summer temperatures at SP, where summer precipitation is lower than at EG, probably due to temperature-induced water stress. Since the 1990s, however, the negative effect of warming has been more severe at EG, where the productivity of larch trees is higher than at SP. A greater reduction of larch tree growth and higher increase rate of iWUE at EG reflects greater temperature-induced water stress, which is incident to the larger forest biomass. Our results suggest that effect of increase in atmospheric CO2 on larch tree growth is not sufficient to compensate for temperature-induced water stress on larch growth in eastern Siberia and differences in precipitation and forest productivity largely affect the larch tree response to changing climate in eastern Siberia. 相似文献
14.
Combining LPJ-GUESS and HASM to simulate the spatial distribution of forest vegetation carbon stock in China简 总被引：5，自引：2，他引：3
It is very important in accurately estimating the forests＇ carbon stock and spatial distribution in the regional scale because they possess a great rate in the carbon stock of the terrestrial ecosystem. Yet the current estimation of forest carbon stock in the regional scale mainly depends on the forest inventory data, and the whole process consumes too much labor, money and time. And meanwhile it has many negative influences on the forest carbon storage updating. In order to figure out these problems, this paper, based on High Accuracy Surface Modeling （HASM）, proposes a forest vegetation carbon storage simulation method. This new method employs the output of LPJ-GUESS model as initial values of HASM and uses the inventory data as sample points of HASM to simulate the distribution of forest carbon storage in China. This study also adopts the seventh forest resources statistics of China as the data source to generate sample points, and it also works as the simulation accuracy test. The HASM simulation shows that the total forest carbon storage of China is 9.2405 Pg, while the calculated value based on forest resources statistics are 7.8115 Pg. The forest resources statistics is taken based on a forest canopy closure, and the result of HASM is much more suitable to the real forest carbon storage. The simulation result also indicates that the southwestern mountain region and the northeastern forests are the important forest carbon reservoirs in China, and they account for 39.82% and 20.46% of the country＇s total forest vegetation carbon stock respectively. Compared with the former value （1975-1995）, it mani- fests that the carbon storage of the two regions do increase clearly. The results of this re- search show that the large-scale reforestation in the last decades in China attains a signifi- cant carbon sink. 相似文献
15.
E. I. Ducheyne R. R. De Wulf B. De Baets 《International journal of geographical information science》2013,27(8):917-928
Forest‐management decision‐support systems are largely monolithic structures. Spatial details are left out during the optimization process and are elaborated during the operational planning. This might produce misleading results and plans that are impossible to implement. In this paper, a forest‐management spatial decision‐support systems is presented, in which spatial formulation needed for wildlife models is included during the optimization process. To this end, a multiple‐objective genetic algorithm is combined with a geographical information system. An online spatial evaluation of the objective functions is made possible. This is illustrated by a pilot study in Kirkhill forest, Aberdeen. 相似文献
16.
Decentralization in access to and control of Bolivia's forest resources, coupled with a rising global demand for tropical hardwoods, raises important questions about whether increased trade and community forest management (CFM) initiatives can enable forms of market integration that have more favourable outcomes for rural communities. This paper assesses the prospects for such a transition through an examination of the relationships linking wood product market intermediaries (brokers and buyers) to rural suppliers and forest communities in Bolivia. The analysis centres on whether trust – conceptualized as a power‐laden sociospatial process driven by multiscalar factors – can evolve between buyers and suppliers such that more progressive (sustainable and mutually beneficial) partnerships devolop. Focusing on three types of buyer–supplier relationships in Bolivia – direct ties between wood brokers/buyers and suppliers, nongovernmental organization (NGO) mediated exchange relationships and Forest Stewardship Council (FSC) certification of suppliers – our findings show how trust building initiatives that focus on one scale may fail if factors at other scales create obstacles to collaboration, Given these relational constraints, CFM strategies in Bolivia currently face limitation on their viability as economic development strategies. 相似文献
17.
James B. Elsner 《The Professional geographer》2013,65(4):559-560
Books reviewed: Bassin, Mark, Imperial Visions: Nationalist Imagination and Geographical Expansion in the Russian Far East, 1840 – 1865 Shortridge, James R., Our Town on the Plains: J. J. Pennell's Photographs of Junction City, Kansas, 1893 – 1922 Jakle, John A. and Sculle, Keith A., Fast Food: Roadside Restaurants in the Automobile Age Boeschenstein, Walter, Historic American Towns along the Atlantic Coast McKee, Jesse O., Ethnicity in Contemporary America: A Geographical Appraisal Luciuk, Lubomyr Y., Searching for Place: Ukrainian Displaced Persons, Ottawa, and the Migration of Memory Hausladen, Gary, Places for Dead Bodies Phillips, Richard, Watt, Diane and Shuttleton, David, De-Centering Sexualities: Politics and Representations beyond the Metropolis Goldin, Liliana R., Identities on the Move, Transnational Processes in North America and the Caribbean Basin McDonald, David A., On Borders: Perspectives on International Migration in Southern Africa Fox, Roddy and Rowntree, Kate, The Geography of South Africa in a Changing World Takeuchi, Keiichi, Modern Japanese Geography: An Intellectual History Amery, Hussein A., and Wolf, Aaron T., Water in the Middle East: A Geography of Peace Karl, Thomas R., Nicholls, Neville and Ghazi, Anver, Weather and Climate Extremes: Changes, Variations, and a Perspective from the Insurance Industry Pittman, Blair, Texas Caves 相似文献
18.
19.
20.