共查询到20条相似文献,搜索用时 31 毫秒
1.
Joon Kim Dongho Lee Jinkyu Hong Sinkyu Kang Su-Jin Kim Sang-Ki Moon Jong-Hwan Lim Yowhan Son Jaeseok Lee Sanghyun Kim Namchil Woo Kyongha Kim Buyong Lee Byong-Lyol Lee Sung Kim 《Ecological Research》2006,21(6):881-889
The KoFlux program is dedicated to understanding the fluxes of energy and matter, water resource management, and net ecosystem
production in key ecosystems of Monsoon Asia. Under the framework of AsiaFlux, it is a joint effort with determined, comprehensive
international strategies to bring Asia’s key ecosystems under observation. Built upon the augmented KoFlux infrastructure
(i.e., Gwangneung supersite), the ‘HydroKorea’ and ‘CarboKorea’ projects pursue new methodologies to assess water and carbon
cycles at various temporal, spatial, and process scales. Particularly, the multiscaling approaches are used to link process-level
studies, flux footprint, ecohydrological and biogeochemical schemes, and high-resolution satellite images. We hope that the
work presented here encourages more ground-breaking studies aimed at bridging the gaps in the cross-scale studies of ecohydrological
and biogeochemical cycles in heterogeneous and complex landscapes. 相似文献
2.
Defining historic grazing pressures and rangeland management is vital if early landscape threshold crossing and long–term
trajectories of landscape change are to be properly understood. In this paper we use a new environmental simulation model,
Búmodel, to assess two contrasting historical grazing landscapes in Myvatnssveit Iceland for two key periods—the colonization
period (ca. Landnám, a.d. 872–1000) and the early eighteenth century a.d. Results suggest that there were spatial and temporal variations in productivity and grazing pressure within and between historic
grazing areas and indicate that land degradation was not an inevitable consequence of the livestock grazing introduced with
settlement. The results also demonstrate the significance of grazing and livestock management strategies in preventing overgrazing,
particularly under cooler climatic conditions. The model enables detailed consideration of historic grazing management scenarios
and their associated landscape pressures. 相似文献
3.
《Ecological Complexity》2007,4(3):113-127
Landscape ecology and complex adaptive systems (CAS) research provide numerous examples of systems with complex non-linear feedbacks, but our understanding of these systems is severely limited by a lack of conceptual frameworks built on these foundations. Here, we develop a conceptual framework by combining CAS organisation with landscape structure, functioning and change. The resulting framework, ‘complex adaptive landscapes’ (CAL), explicitly captures the reciprocal feedbacks and non-linear nature of interactions between components within and between system levels, and the consequent possibility of multiple functional states (alternate systems functioning). The CAL framework highlights six core tenets that describe landscape complexity and dynamics. CAL provides examples of how the complex ecohydrological interactions at finer-scale hillslope levels manifest changes to broader landscape levels, as well as multi-temporal feedbacks and change (days to decades). Understanding the specific feedback and non-linear responses of different components of the landscape, such as plant functional types, are of paramount importance for adequately designing monitoring and analytical frameworks for adaptive natural resource management. The CAL framework allows us to better understand the scale of ecohydrological functions within the landscape, and how substituted component types and their spatial and temporal configuration may cause dysfunctional states to arise as a result of human land use. 相似文献
4.
Contributions of Ignitions,Fuels, and Weather to the Spatial Patterns of Burn Probability of a Boreal Landscape 总被引:2,自引:0,他引:2
Marc-André Parisien Sean A. Parks Carol Miller Meg A. Krawchuk Mark Heathcott Max A. Moritz 《Ecosystems》2011,14(7):1141-1155
The spatial pattern of fire observed across boreal landscapes is the outcome of complex interactions among components of the
fire environment. We investigated how the naturally occurring patterns of ignitions, fuels, and weather generate spatial pattern
of burn probability (BP) in a large and highly fire-prone boreal landscape of western Canada, Wood Buffalo National Park.
This was achieved by producing a high-resolution map of BP using a fire simulation model that models the ignition and spread
of individual fires for the current state of the study landscape (that is, the ‘control’). Then, to extract the effect of
the variability in ignitions, fuels, and weather on spatial BP patterns, we subtracted the control BP map to those produced
by “homogenizing” a single environmental factor of interest (that is, the ‘experimental treatments’). This yielded maps of
spatial residuals that represent the spatial BP patterns for which the heterogeneity of each factor of interest is responsible.
Residuals were analyzed within a structural equation modeling framework. The results showed unequal contributions of fuels
(67.4%), weather (29.2%), and ignitions (3.4%) to spatial BP patterning. The large contribution of fuels reflects how substantial
heterogeneity of land cover on this landscape strongly affects BP. Although weather has a chiefly temporal control on fire
regimes, the variability in fire-conducive weather conditions exerted a surprisingly large influence on spatial BP patterns.
The almost negligible effect of spatial ignition patterns was surprising but explainable in the context of this area’s fire
regime. Similar contributions of fuels, weather, and ignitions could be expected in other parts of the boreal forest that
lack a strong anthropogenic imprint, but are likely to be altered in human-dominated fire regimes. 相似文献
5.
Sylvi Haldorsen Hasan Akan Bahattin ?elik Manfred Heun 《Vegetation History and Archaeobotany》2011,20(4):305-318
The domestication of the Neolithic founder crops of the Near East has recently been a topic of debate particularly with respect
to how rapidly the domestication of these crops occurred. One school of thought maintains that these processes lasted several
thousand years (‘protracted model’ with ‘gathering’, ‘cultivation’ and ‘domestication’ as three stages of a continuum, each
taking up to several thousand years), while another favors the view that domestication occurred much more quickly, over several
hundred years at most (‘rapid transition’). Our study focuses on one of these crops, 1-grained domesticated Einkorn wheat,
incorporating data from geology, vegetation history, and climate. In the Karacadağ region of southeastern Turkey, where 1-grained
Einkorn wheat was domesticated, the climate was severe (i.e. cold and dry) during the Younger Dryas. The climate of the Younger
Dryas acted as boundary during which a) conditions were not suitable for ‘cultivation’, and b) Einkorn would have retreated
to refugia exhibiting more suitable moisture-bearing soils that would have made ‘gathering’ difficult. Around 11600 cal. b.p., the Younger Dryas ended and a very rapid climatic amelioration commenced at the beginning of the Early Holocene, enabling
grasses to spread throughout the region. A ritual PPNA/PPNB site (G?bekli Tepe) and associated PPNB settlements such as Nevali
?ori and ?ay?nü were established at this time. In the settlements of Nevali ?ori and Cafer H?yük, the oldest domesticated
Einkorn was found in the earliest archaeological layers. This confirms that the inhabitants made use of domesticated 1-grained
Einkorn from the very beginning of settlement activity, although they continued to practice a mixed lifestyle as hunter-gatherers
and farmers. For ?ay?nü the issue is more complex, but here domesticated Einkorn also appears around the same time. In summary,
by 10400 cal. b.p. domesticated 1-grained Einkorn was present in large quantities at a variety of sites. This would give a maximum window of
time lasting approximately 1,200 years and is therefore not in agreement with the ‘protracted’ model but would be consistent
with a ‘rapid transition’. It is improbable that the ‘cultivation’ of wild Einkorn was practiced in the Karacadağ region,
since wild Einkorn was plentiful during the favorable growing conditions following the Younger Dryas, making it more likely
that ‘gathering’ would have been practiced. Because Einkorn has not been found in early settlements in the southern Levant,
this crop cannot have been ‘gathered’ and ‘cultivated’ there but instead was ‘domesticated’ independently and solely in southeastern
Turkey. Therefore, the YD acts as a boundary, providing a maximum time frame for 1-grained Einkorn domestication. 相似文献
6.
Götz Schroth Deborah Faria Marcelo Araujo Lucio Bede Sunshine A. Van Bael Camila R. Cassano Leonardo C. Oliveira Jacques H. C. Delabie 《Biodiversity and Conservation》2011,20(8):1635-1654
A recent debate has contrasted two conservation strategies in agricultural landscapes; either “land sparing” farm development
combining intensive production practices with forest set-asides, or “wildlife-friendly” farming with greater on-farm habitat
value but lower yields. We argue that in established mosaic landscapes including old cacao production regions where natural
forest has already been reduced to relatively small fragments, a combination of both strategies is needed to conserve biodiversity.
After reviewing the evidence for the insufficiency of either strategy alone if applied to such landscapes, the paper focuses
on the cacao production landscape of southern Bahia, Brazil, once the world’s second largest cacao producer. Here, small remaining
areas of Atlantic Forest are embedded in a matrix dominated by traditional cacao agroforests, resulting in a landscape mosaic
that has proven favorable to the conservation of the region’s high biodiversity. We show that current land use dynamics and
public policies pose threats but also offer opportunities to conservation and describe a three-pronged landscape conservation
strategy, consisting of (i) expansion of the protected areas system, (ii) promotion of productive yet biodiversity-friendly
cacao farming practices, and (iii) assistance to land users to implement legally mandated on-farm reserves and voluntary private
reserves. We discuss recent experiences concerning the implementation of this strategy, discuss likely future scenarios, and
reflect on the applicability of the Bahian experience to biodiversity rich cacao production regions elsewhere in the tropics. 相似文献
7.
Walter W. Ferguson 《Primates; journal of primatology》1989,30(4):561-569
Leonard andHegmon (1987) compare a series of dental metrics of ‘Australopithecus afarensis
Johanson, White, andCoppens, 1978’ with criteria for modern apes, to test the hypothesis that ‘A. afarensis’ represents a single species. They also compare the morphology of the lower third premolar. The dental breadth of ‘A. afarensis’ shows a wide range of variation, particularly in the lower third premolar morphology which displays greater variation than
in modern apes—yet the study concludes that the single species hypothesis cannot be rejected.
The study is flawed by applying criteria for pongids inappropriate for a hominid. When ‘A. afarensis’ is compared with criteria for hominids, the range of variation in dental size, breadth, and third premolar morphology is
greater than that in any hominid species. The single species hypothesis is, therefore, once again rejected. Moreover, the
name ‘A. afarensis’ is preoccupied byPraeanthropus africanus (Weinert) and must be dropped. 相似文献
8.
Interactions Across Spatial Scales among Forest Dieback,Fire, and Erosion in Northern New Mexico Landscapes 总被引:2,自引:0,他引:2
Craig D. Allen 《Ecosystems》2007,10(5):797-808
Abstract
Ecosystem patterns and disturbance processes at one spatial scale often interact with processes at another scale, and the
result of such cross-scale interactions can be nonlinear dynamics with thresholds. Examples of cross-scale pattern-process
relationships and interactions among forest dieback, fire, and erosion are illustrated from northern New Mexico (USA) landscapes,
where long-term studies have recently documented all of these disturbance processes. For example, environmental stress, operating
on individual trees, can cause tree death that is amplified by insect mortality agents to propagate to patch and then landscape
or even regional-scale forest dieback. Severe drought and unusual warmth in the southwestern USA since the late 1990s apparently
exceeded species-specific physiological thresholds for multiple tree species, resulting in substantial vegetation mortality
across millions of hectares of woodlands and forests in recent years. Predictions of forest dieback across spatial scales
are constrained by uncertainties associated with: limited knowledge of species-specific physiological thresholds; individual
and site-specific variation in these mortality thresholds; and positive feedback loops between rapidly-responding insect herbivore
populations and their stressed plant hosts, sometimes resulting in nonlinear “pest” outbreak dynamics. Fire behavior also
exhibits nonlinearities across spatial scales, illustrated by changes in historic fire regimes where patch-scale grazing disturbance
led to regional-scale collapse of surface fire activity and subsequent recent increases in the scale of extreme fire events
in New Mexico. Vegetation dieback interacts with fire activity by modifying fuel amounts and configurations at multiple spatial
scales. Runoff and erosion processes are also subject to scale-dependent threshold behaviors, exemplified by ecohydrological
work in semiarid New Mexico watersheds showing how declines in ground surface cover lead to non-linear increases in bare patch
connectivity and thereby accelerated runoff and erosion at hillslope and watershed scales. Vegetation dieback, grazing, and
fire can change land surface properties and cross-scale hydrologic connectivities, directly altering ecohydrological patterns
of runoff and erosion. The interactions among disturbance processes across spatial scales can be key drivers in ecosystem
dynamics, as illustrated by these studies of recent landscape changes in northern New Mexico. To better anticipate and mitigate
accelerating human impacts to the planetary ecosystem at all spatial scales, improvements are needed in our conceptual and
quantitative understanding of cross-scale interactions among disturbance processes. 相似文献
9.
Regression Techniques for Examining Land Use/Cover Change: A Case Study of a Mediterranean Landscape 总被引:4,自引:0,他引:4
In many areas of the northern Mediterranean Basin the abundance of forest and scrubland vegetation is increasing, commensurate
with decreases in agricultural land use(s). Much of the land use/cover change (LUCC) in this region is associated with the
marginalization of traditional agricultural practices due to ongoing socioeconomic shifts and subsequent ecological change.
Regression-based models of LUCC have two purposes: (i) to aid explanation of the processes driving change and/or (ii) spatial
projection of the changes themselves. The independent variables contained in the single ‘best’ regression model (that is,
that which minimizes variation in the dependent variable) cannot be inferred as providing the strongest causal relationship with the dependent variable. Here, we examine the utility of hierarchical partitioning and multinomial regression
models for, respectively, explanation and prediction of LUCC in EU Special Protection Area 56, ‘Encinares del río Alberche
y Cofio’ (SPA 56) near Madrid, Spain. Hierarchical partitioning estimates the contribution of regression model variables,
both independently and in conjunction with other variables in a model, to the total variance explained by that model and is
a tool to isolate important causal variables. By using hierarchical partitioning we find that the combined effects of factors
driving land cover transitions varies with land cover classification, with a coarser classification reducing explained variance
in LUCC. We use multinomial logistic regression models solely for projecting change, finding that accuracies of maps produced
vary by land cover classification and are influenced by differing spatial resolutions of socioeconomic and biophysical data.
When examining LUCC in human-dominated landscapes such as those of the Mediterranean Basin, the availability and analysis
of spatial data at scales that match causal processes is vital to the performance of the statistical modelling techniques
used here. 相似文献
10.
Plant diversity is threatened in many agricultural landscapes. Our understanding of patterns of plant diversity in these landscapes is mainly based on small‐scale (<1000 m2) observations of species richness. However, such observations are insufficient for detecting the spatial heterogeneity of vegetation composition. In a case‐study farm on the North‐West Slopes of New South Wales, Australia, we observed species richness at four scales (quadrat, patch, land use and landscape) across five land uses (grazed and ungrazed woodlands, native pastures, roadsides and crops). We applied two landscape ecological models to assess the contribution of these land uses to landscape species richness: (i) additive partitioning of diversity at multiple spatial scales, and (ii) a measure of habitat specificity – the effective number of species that a patch contributes to landscape species richness. Native pastures had less variation between patches than grazed and ungrazed woodlands, and hence were less species‐rich at the landscape scale, despite having similar richness to woodlands at the quadrat and patch scale. Habitat specificity was significantly higher for ungrazed woodland patches than all other land uses. Our results showed that in this landscape, ungrazed woodland patches had a higher contribution than the grazed land uses to landscape species richness. These results have implications for the conservation management of this landscape, and highlighted the need for greater consensus on the influence of different land uses on landscape patterns of plant diversity. 相似文献
11.
12.
Theophilus M. Mutui Vallantino E. Emongor Margaret J. Hutchinson 《Plant Growth Regulation》2006,48(3):207-214
Leaf yellowing is a major problem in Alstroemeria and absence of leaf senescence symptoms is an important quality attribute. Two Alstroemeria cultivars ‘Yellow King’ and ‘Marina’ were sourced from a commercial farm and harvested when sepals began to reflex. Stems
were re-cut under water and kept in vase solutions of gibberellin A4+7 (0, 2.5, 5.0, 7.5, 10.0, 12.5 or 15.0 mg l−1 [Provider]). Treatments and cultivars were combined in a factorial fashion and arranged in a completely randomised design. Application
of GA4+7 in the holding solution at 2.5–10.0 mg l−1 significantly delayed the onset of leaf senescence by around 7 days and significantly increased days to 50% petal fall by
ca. 2 days. Additionally, these GA4+7 concentrations resulted in higher retention of leaf nitrogen, leaf chlorophyll and also increased leaf water content, while
reducing leaf dry weight, all relative to untreated controls. Cultivar ‘Yellow King’ had significantly longer vase life and
a better retention of leaf quality than ‘Marina’. Our results suggest that a concentration of 10 mg l−1 GA4+7 can be used to prolong vase life, delay leaf senescence and enhance post-harvest quality of Alstroemeria cut flowers during their transport to market. 相似文献
13.
Laura I. Kooistra 《Vegetation History and Archaeobotany》2008,17(1):113-125
Botanical investigation of archaeological sites situated in the northwest of the region bounded by the rivers Maas, Scheldt
and Demer (‘MSD region’), west of the city of Breda, has provided a great deal of evidence about the landscape and its use
in the period between 2000 b.c. and a.d. 1500. From pollen analysis, it appears that this cover-sand area gradually lost its woodlands through human activity after
the beginning of the Bronze Age (ca. 2000 b.c.). Patches of woodland did survive there, however, until the early Middle Ages. In contrast to the cover-sand area in the
vicinity of ’s-Hertogenbosch and Oss-Ussen in the northeast of the MSD region, the first large heathlands in the Breda area
did not evolve until the early Middle Ages. In late prehistory, land use in this area was not much different from that in
the micro-region of ’s-Hertogenbosch and Oss-Ussen. In the Bronze Age, Hordeum vulgare ssp. vulgare (hulled six-row barley) and Triticum dicoccon (emmer wheat) were grown. During the Iron Age, Panicum miliaceum (common millet) and T. spelta (spelt wheat) were introduced, but these crops disappeared during the Roman period. The Roman period is remarkable because
of the lack of any Mediterranean culinary herbs or exotic fruits. Only pollen of Juglans regia (walnut), found around the transition from the Roman period to the early Middle Ages, indicates the introduction of an exotic
tree into the region. From the early Middle Ages onwards, Secale cereale (rye) was the most important cereal, which was grown as a winter crop. In the course of the Middle Ages, arable weeds of
the Sclerantho annui-Arnoseridetum plant community appeared, which is associated with the continuous growing of rye. 相似文献
14.
Patrick D. Nunn Rosalind Hunter-Anderson Mike T. Carson Frank Thomas Sean Ulm Michael J. Rowland 《Human ecology: an interdisciplinary journal》2007,35(4):385-401
During the last millennium in the Pacific Basin (islands and continental rim) there was a marked contrast between ‘times of
plenty’ and ‘times of less’ for its human societies. This contrast is attributable to climate and sea-level variations, notably
the Medieval Warm Period (a.d. 700–1250) and the Little Ice Age (a.d. 1350–1800) separated by a time of rapid cooling and sea-level fall called the ‘a.d. 1300 Event.’ Outlines of the times of plenty during the Medieval Warm Period and the times of less during the Little Ice
Age are given, supported by a number of examples. These confirm a general picture of societal collapse as a result of the
a.d. 1300 Event. Well-dated human responses to the a.d. 1300 Event (establishment of fortified settlements, end of ocean voyaging) allow links to potential nonhuman causes to be
strengthened. Although more data referring to both (natural) changes and their human effects are needed, a conclusion involving
environmental determinism is inescapable. 相似文献
15.
Walter W. Ferguson 《Primates; journal of primatology》1989,30(3):383-387
A partial mandible with two molars intact was recovered between 1981 and 1984 from deposits of the Middle Pliocene at Tabarin,
in Kenya. It has been described and assigned toAustralopithecus cf.afarensis
Johanson, White, andCoppens, 1978, with the condition that if ‘A. afarensis’ is revised, then the attribution may change. The taxon ‘A. afarensis’ was found to be invalid and was revised. The smaller specimens of ‘A. afarensis,’ to which the Tabarin mandible was said to be similar, were redescribed asHomo antiquus
Ferguson, 1984. Since the Tabarin mandible andH. antiquus are successive transients of the same gens and are allopatric, the Tabarin hominid population is described as an earlier
chronosubspecies,Homo antiquus praegens ssp. n. 相似文献
16.
The impact category ‘land use’ describes in the Life Cycle Assessment (LCA) methodology the environmental impacts of occupying,
reshaping and managing land for human purposes. Land use can either be the long-term use of land (e.g. for arable farming)
or changing the type of land use (e.g. from natural to urban area). The impact category ‘land use’ comprises those environmental
consequences, which impact the environment due to the land use itself, for instance through the reduction of landscape elements,
the planting of monocultures or artificial vegetation, or the sealing of surfaces. Important environmental consequences of
land use are the decreasing availability of habitats and the decreasing diversity of wildlife species. The assessment of the
environmental impacts of land use within LCA studies is the objective of this paper. Land use leads to a degradation of the
naturalness of the area utilised. In this respect the naturalness of any area can be defined as the sum of land actually not
influenced by humans and the remaining naturalness of land under use. To determine the remaining naturalness of land under
use, this study suggests applying the Hemeroby concept. “Hemeroby is a measure for the human influence on ecosystems” (Kowarik
1999). The Hemeroby level of an area describes the intensity of land use and can therefore be used to characterise different
types of land use. Characterization factors are proposed, which allow calculating the degradation of the naturalness of an
area due to a specific type of land use. Since the resource ‘nature/naturalness’ is on a larger geographical scale by far
not homogeneous, the assessment of land use needs to be regionalised. Therefore, the impact category ‘land use’ has been subdivided
into the impact sub-categories ‘land use in European biogeographic regions’. Following the general LCA framework, normalization
values for the impact sub-categories are calculated in order to facilitate the evaluation of the characterization results
with regard to their share in a reference value. Weighting factors, which enable an aggregation of the results of the different
land use sub-categories and make them comparable to other impact categories (e.g. climate change or acidification) are suggested
based on the assumption that the current land use pattern in the European biogeographic regions is acceptable. 相似文献
17.
Thomas Haack Ma. José González Yolanda Sánchez Ernest Giralt 《International journal of peptide research and therapeutics》1997,4(4-6):377-386
Summary With a few exceptions, proteins in our biosphere are based exclusively onl-amino acids. The inversion of configuration of all the stereogenic centers in a protein leads to anall-d compound with ‘mirror image’ properties and ‘mirror image’ structure. We propose to use the termprotein-enantiomerism to describe the relationship between two proteins that have the same sequence but whose amino acids have opposite configuration.
We will use the termprotein-diastereomerism to define the relationship between two proteins that have the same sequence in which some amino acids have opposite configurations.
A classification of type I, II, III, and IV protein-diastereomerism is proposed. By extension, a diastereoprotein is a protein
where some amino acids have the same configuration (l ord) while others have the opposite one (d orl). A particular case of diastereoproteins aremesoproteins, also analyzed in this article. In addition to the goal of making proteins resistant to protease degradation, the use ofd-amino acids in protein de novo design may give rise to proteins with structures, and perhaps properties, very different to
those of nativeall-l-proteins. 相似文献
18.
Coutu C Brandle J Brown D Brown K Miki B Simmonds J Hegedus DD 《Transgenic research》2007,16(6):771-781
We present a series of 14 binary vectors suitable for Agrobacterium-mediated transformation of dicotyledonous plants and adaptable for biolistic transformation of monocotyledonous plants. The
vector size has been minimized by eliminating all non-essential elements from the vector backbone and T-DNA regions while
maintaining the ability to replicate independently. The smallest of the vector series is 6.3 kb and possesses an extensive
multiple cloning site with 21 unique restriction endonuclease sites that are compatible with common cloning, protein expression,
yeast two-hybrid and other binary vectors. The T-DNA region was engineered using a synthetic designer oligonucleotide resulting
in an entirely modular system whereby any vector element can be independently exchanged. The high copy number ColE1 origin
of replication has been included to enhance plasmid yield in Escherichia coli. FRT recombination sites flank the selectable marker cassette regions and allow for in planta excision by FLP recombinase. The pORE series consists of three basic types; an ‘open’ set for general plant transformation, a ‘reporter’ set for promoter analysis and an ‘expression’ set for constitutive expression of transgenes. The sets comprise various combinations of promoters (P
HPL, P
ENTCUP2 and P
TAPADH), selectable markers (nptII and pat) and reporter genes (gusA and smgfp). 相似文献
19.
This paper explores the spatial and temporal land-cover variability within the main cultural landscape units in Denmark during
the last 3,000 years. Quantitative estimates of the cover of trees, grasses, Cerealia and Calluna around nine Danish lakes were obtained using the recently developed Landscape Reconstruction Algorithm (LRA) (Sugita 2007a, b). The performance of the approach was evaluated by comparing reconstructed vegetation based on a.d. 1800 pollen spectra to land cover from historical maps of the same period. Although the model tended to overestimate grassland
cover by 10–20%, the reconstructed vegetation was much more similar to the observed than the uncorrected pollen proportions.
The LRA was then applied to 3,000 year long pollen records to reconstruct the vegetation development around each of the nine
sites. The results support earlier conclusions regarding the relative stability of woodland, agrarian and heathland dominated
landscapes in Denmark (Odgaard and Rasmussen 2000), with the distribution of the main landscape types determined by topography and soil characteristics. The present study
indicates that the transition zones between agricultural and forest dominated landscapes were the most dynamic, acting as
buffer zones where most of the expansions and contractions of agricultural activities took place. The quantitative vegetation
reconstructions underline the importance of farming and especially pastoral activities in shaping the Danish landscapes throughout
the study period. 相似文献
20.
ABSTRACT
Well-founded methods to assess habitat connectivity are essential to inform land management decisions that include conservation
and restoration goals. Indeed, to be able to develop a conservation plan that maintains animal movement through a fragmented
landscape, spatial locations of habitat and paths among them need to be represented. Graph-based approaches have been proposed
to determine paths among habitats at various scales and dispersal movement distances, and balance data requirements with information
content. Conventional graphs, however, do not explicitly maintain geographic reference, reducing communication capacity and
utility of other geo-spatial information. We present spatial graphs as a unifying theory for applying graph-based methods in a geographic context. Spatial graphs integrate a geometric reference
system that ties patches and paths to specific spatial locations and spatial dimensions. Arguably, the complete graph, with
paths between every pair of patches, may be one of the most relevant graphs from an ecosystem perspective, but it poses challenges
to compute, process and visualize. We developed Minimum Planar Graphs as a spatial generalization of Delaunay triangulations
to provide a reasonable approximation of complete graphs that facilitates visualization and comprehension of the network of
connections across landscapes. If, as some authors have suggested, the minimum spanning tree identifies the connectivity “backbone”
of a landscape, then the Minimum Planar Graph identifies the connectivity “network”. We applied spatial graphs, and in particular
the Minimum Planar Graph, to analyze woodland caribou habitat in Manitoba, Canada to support the establishment of a national
park. 相似文献