Spatial Heterogeneity Of Landscape Research Articles

Searching for optimal solutions in a landscape fragmentation assessment: A case study from Poland – Identification of spatial data and methods

There is no single correct or optimal scale for describing spatial landscape heterogeneity. However, since landscape patterns are scale-dependent, using different scales in the analysis may result in different outcomes, which can affect landscape management options. The main goal of our research was to identify the most adequate GIS solution for converting vector data to raster data while keeping the spatial continuity of most linear features and input land cover data as detailed as possible. In addition, to compare our database with the CORINE Land Cover data approach, we used 3 different rasterization methods and raster data with 100- and 50-m pixel sizes, first, to match the geometric accuracy of the CORINE Land Cover data and second, to compare the calculation results acquired with the higher-resolution rasterized BDOT10k data. We found that it was possible to compare these methods and assess how much data resolution and selection of rasterization methods affected the calculations of the landscape metrics. The calculation results of specific fragmentation metrics differed tremendously when higher data resolutions and rasterization methods were used, especially when using the custom priority rasterization method.

Anthropogenic and landscape features are associated with ink disease impact in Central Italy

AbstractInk disease of sweet chestnut (Castanea sativa) caused by the oomycetes Phytophthora cinnamomi and P. x cambivora is the limiting factor for chestnut cultivation in several European regions. The objective of this study was to explore how the spatial landscape heterogeneity affects the distribution pattern of ink disease over a large chestnut area in Central Italy using an approach that combined remote sensing, ground truthing activities and GIS. A multivariate model was developed that explained a large proportion of the variance of the impact of the disease using the density of roads and drainage networks as predictor variables. The association of these landscape elements, specifically with ink disease foci, also provides practical tool to improve the accuracy of monitoring of this disease and the preparation of risk maps.

Spatial heterogeneity facilitates carnivore coexistence.

Competitively dominant carnivore species can limit the population sizes and alter the behavior of inferior competitors. Established mechanisms that enable carnivore coexistence include spatial and temporal avoidance of dominant predator species by subordinates, and dietary niche separation. However, spatial heterogeneity across landscapes could provide inferior competitors with refuges in the form of areas with lower competitor density and/or locations that provide concealment from competitors. Here, we combine temporally overlapping telemetry data from dominant lions (Panthera leo) and subordinate African wild dogs (Lycaon pictus) with high-resolution remote sensing in an integrated step selection analysis to investigate how fine-scaled landscape heterogeneity might facilitate carnivore coexistence in South Africa's Hluhluwe-iMfolozi Park, where both predators occur at exceptionally high densities. We ask whether the primary lion-avoidance strategy of wild dogs is spatial avoidance of lions or areas frequented by lions, or if wild dogs selectively use landscape features to avoid detection by lions. Within this framework, we also test whether wild dogs rely on proactive or reactive responses to lion risk. In contrast to previous studies finding strong spatial avoidance of lions by wild dogs, we found that the primary wild dog lion-avoidance strategy was to select landscape features that aid in avoidance of lion detection. This habitat selection was routinely used by wild dogs, and especially when in areas and during times of high lion-encounter risk, suggesting a proactive response to lion risk. Our findings suggest that spatial landscape heterogeneity could represent an alternative mechanism for carnivore coexistence, especially as ever-shrinking carnivore ranges force inferior competitors into increased contact with dominant species.

Does spatial heterogeneity of landscape explain the process of plant invasion? A case study of Hyptis suaveolens from Indian Western Himalaya.

Biological invasion is probably one of the most serious threats to biodiversity after climate change. Landscape distinguished by the heterogeneity of structure, forms, human interferences, and environmental settings plays an important role in the establishment and spread of invasive species. We investigated the effect of the spatial heterogeneity for a selected landscape upon the invasion process through a case study of Hyptis (Hyptis suaveolens) in the Indian Western Himalayan region. The selected study site constitutes a heterogeneous landscape of 32,300 ha in the state of Uttarakhand, placed at the lower elevation of the Indian Himalaya. The landscape has varying levels and patterns of Hyptis invasion. We quantified the spatial heterogeneity in terms of elevation; distance from the canal, river, road, and settlement; and 18 landscape metrics (at the patch and land use class level) to investigate their influence on the invasion; for this purpose, a logistic regression model was developed. The invasion of Hyptis was found to be governed by spatial heterogeneity. The highest probability of invasion was found in the areas adjacent to rivers and roads. The analysis at patch level revealed that the invasion is largely governed by the perimeter-area ratio of patches and is positively correlated. This suggests for greater invasion chances in smaller patches as compared with larger ones. The analysis for the land use class metrics indicated a higher influence of edge density expressed as total edge length of patches per unit area, followed by patch density expresses as a total number of patches per unit area. Hence, the landscapes with larger edges and more number of patches are supposed to be more prone to invasion risks. The results of the study can be used by forest managers in designing a landscape-level system to control invasion.

Effect of the landscape matrix on gene flow in a coastal amphibian metapopulation

Functional connectivity is crucial for the persistence of a metapopulation, because migration among subpopulations enables recolonization and counteracts genetic drift, which is especially important in small subpopulations. We studied the degree and drivers of connectivity among occupied patches of a coastal dune metapopulation of the Natterjack Toad (Epidalea calamita Laurenti), on the basis of microsatellite variation. As spatial landscape heterogeneity is expected to influence dispersal and genetic structure, we analyzed which landscape features affect functional connectivity and to what extent. Sixty different landscape resistance scenarios as well as the isolation-by-distance model were compared using two landscape genetics approaches. We identified three subpopulations with unidirectional levels of gene flow among the two most geographically separated subpopulations, while inferred gene flow into the geographically intermediate subpopulation was limited. Urbanization and vegetation height negatively affected connectivity. Low estimates of genetic diversity and effective population size indicate that conservation measures in the smallest and most isolated subpopulation are required.

Scenario simulation and landscape pattern dynamic changes of land use in the Poverty Belt around Beijing and Tianjin: A case study of Zhangjiakou city, Hebei Province

Land use/cover change has been recognized as a key component in global change and has attracted increasing attention in recent decades. Scenario simulation of land use change is an important issue in the study of land use/cover change, and plays a key role in land use prediction and policy decision. Based on the remote sensing data of Landsat TM images in 1989, 2000 and 2010, scenario simulation and landscape pattern analysis of land use change driven by socio-economic development and ecological protection policies were reported in Zhangjiakou city, a representative area of the Poverty Belt around Beijing and Tianjin. Using a CLUE-S model, along with socio-economic and geographic data, the land use simulation of four scenarios–namely, land use planning scenario, natural development scenario, ecological-oriented scenario and farmland protection scenario–were explored according to the actual conditions of Zhangjiakou city, and the landscape pattern characteristics under different land use scenarios were analyzed. The results revealed the following: (1) Farmland, grassland, water body and unused land decreased significantly during 1989–2010, with a decrease of 11.09%, 2.82%, 18.20% and 31.27%, respectively, while garden land, forestland and construction land increased over the same period, with an increase of 5.71%, 20.91% and 38.54%, respectively. The change rate and intensity of land use improved in general from 1989 to 2010. The integrated dynamic degree of land use increased from 2.21% during 1989–2000 to 3.96% during 2000–2010. (2) Land use changed significantly throughout 1989–2010. The total area that underwent land use change was 4759.14 km2, accounting for 12.53% of the study area. Land use transformation was characterized by grassland to forestland, and by farmland to forestland and grassland. (3) Under the land use planning scenario, farmland, grassland, water body and unused land shrank significantly, while garden land, forestland and construction land increased. Under the natural development scenario, construction land and forestland increased in 2020 compared with 2010, while farmland and unused land decreased. Under the ecological-oriented scenario, forestland increased dramatically, which mainly derived from farmland, grassland and unused land. Under the farmland protection scenario, farmland was well protected and stable, while construction land expansion was restricted. (4) The landscape patterns of the four scenarios in 2020, compared with those in 2010, were more reasonable. Under the land use planning scenario, the landscape pattern tended to be more optimized. The landscape became less fragmented and heterogeneous with the natural development scenarios. However, under the ecological- oriented scenario and farmland protection scenario, landscape was characterized by fragmentation, and spatial heterogeneity of landscape was significant. Spatial differences in landscape patterns in Zhangjiakou city also existed. (5) The spatial distribution of land use could be explained, to a large extent, by the driving factors, and the simulation results tallied with the local situations, which provided useful information for decision-makers and planners to take appropriate land management measures in the area. The application of the combined Markov model, CLUE-S model and landscape metrics in Zhangjiakou city suggests that this methodology has the capacity to reflect the complex changes in land use at a scale of 300 m×300 m and can serve as a useful tool for analyzing complex land use driving factors.

The role of individual variation in marine larval dispersal

The exchange of individuals among patchy habitats plays a central role in spatial ecology and metapopulation dynamics. Dispersal (e.g. short vs. long) is frequently observed to vary non-randomly within populations, indicating that variability among individuals may shape heterogeneity in patterns of connectivity. The concept of context- and condition-dependent dispersal describes the balance between the costs and benefits of dispersal that arises from the interaction of temporal and spatial landscape heterogeneity (the context) with phenotypic variability among individuals (the condition). While this hypothesis is widely accepted terrestrial theory, it remains questionable to what extent the concept of adaptive dispersal strategies may apply to marine larval dispersal, a process that is largely determined by stochastic forces. Yet, larvae of many taxa exhibit strong navigational capabilities and there is mounting evidence of widespread intra-specific variability in biological traits that are potentially correlated with dispersal potential. While so far there are few known examples of real larval dispersal polymorphisms, intra-specifically variable dispersal strategies may be common in marine systems. Whether adaptive or not, it is becoming apparent that inter-individual heterogeneity in morphology, behaviour, condition, and life history traits may have critical effects on population-level heterogeneity in dispersal. Here, we explore the eco-evolutionary causes and consequences of intrinsic and extrinsic variability on larval dispersal by synthesizing the existing literature and drawing conceptual parallels from terrestrial theory. We emphasize the potential importance of larval dispersal polymorphisms in marine population dynamics.

Is genetic structure of the southern pygmy mouse Baiomys musculus (Cricetidae) related to human-induced spatial landscape heterogeneity in a tropical dry forest?

Tropical dry forests are biologically important biomes sustaining a high rate of endemic species. However, these forests are highly threatened by human activities that negatively impact them on distinct levels, including the genetic diversity. Within the framework of landscape genetics (that seeks to evaluate the relation of characteristics of the environmental matrix with population genetics), we used ISSR markers to evaluate the relationship between the alteration of tropical dry forest by human-induced activities (conserved vs. disturbed) with the genetic structure of four breeding sites of the southern pygmy mouse Baiomys musculus. Averaging among the 105 loci used, the unbiased heterozygosis per population (0.247-0.305) was statistically similar among the four sites, as well as between conserved and disturbed conditions (2-way ANOVA F ((3,16)) = 1.47, P = 0.1984). The genetic differentiation among the four breeding sites was high (F (ST) = 0.1122; 95 % CI 0.082-0.146) considering the geographical scale evaluated (ca. 4 km). Both, a factorial correspondence analysis and a model-based clustering analysis showed the existence of four genetic groups (one per breeding site). However, no association of genetic structure with disturbance conditions was revealed by these analyses. The absence of differences in mean genetic diversity and the lack of association of genetic structure with habitat transformation suggest that B. musculus has enough behavioral plasticity and enough genetic diversity to respond to environmental heterogeneity caused by human activities. We discussed conditions in which habitat transformation could indeed favor B. musculus.

Spatial variation in land use and landscape pattern—A case study of Ji County of Tianjin City

景观格局变化反映了区域生态功能与过程的变化, 而景观格局变化的空间分异显示了景观过程及其驱动力的空间差异, 有利于从空间上把握该区景观格局动态变化过程与特征。本文以天津市蓟县地区为例, 在遥感和GIS技术支持下结合多年统计资料, 分析研究区土地利用景观的时空动态变化过程与景观格局变化的空间分异特征。结果表明: 景观格局变化主要表现为景观呈破碎化趋势, 形状更加复杂, 多样性指数呈增加趋势, 生态系统正朝着多样性、均匀化的方向发展; 发生变化的土地利用类型以耕地转为林草地和建设用地为主。将研究区划分成3 km网格, 计算各网格内景观格局指数变化。景观格局动态变化的区域差异分析结果显示, 中南部平原区破碎化程度加剧, 而北部山区和自然保护区内人类活动干扰强度减弱。研究表明, 地形、交通和人口空间分布是景观格局变化的主要原因, 人口增加与经济发展是该区土地利用及景观变化的主要驱动力。

Quantifying historic landscape heterogeneity from aerial photographs using object-based analysis

Spatial landscape heterogeneity is routinely used to characterize ecological processes, particularly over time. Critical to the use of landscape heterogeneity as an ecological indicator, is a consistent and quantitative definition, especially in terms of a baseline description. As the oldest and most frequently used form of remotely sensed data, aerial photographs are a unique source of detailed, historic landscape information with the potential to provide this baseline data. Using aerial photographs, texture information, and terrain data of an unharvested watershed in 1937/1938, we quantify baseline heterogeneity. To do this, we explore the use of a relatively new spatial method which utilizes an object-based approach to quantify landscape pattern over multiple spatial scales. Based on quantitative metrics derived from our object-based analysis, the primary dimensions of landscape heterogeneity were first identified using factor analysis, and subsequently summarized with cluster analysis. Sixteen distinct elements of heterogeneity were identified which explained over 76% of the overall variance within the original factors. Several elements of heterogeneity extracted using this approach are common in landscape ecology, including patch compaction, shape, size, texture, and neighboring characteristics (context). However, new elements of spatial heterogeneity were also identified, representing tonal, textural, topographic, and positional variability over multiple spatial scales. We also explored differences in heterogeneity between landscape types of contrasting structure and ecology (riparian versus upland). Few quantitative differences were identified between landscapes, despite obvious ecological and biophysical differences. The results of this analysis provide an alternative description of baseline landscape heterogeneity, which recognizes elements not previously identified.