ABSTRACT
Landscape structure and spatial pattern are the core issues in landscape ecology. The application of graph theory provides a research framework for landscape pattern analysis. Landscape graph based on graph theory is gradually applied to the connectivity modeling of biodiversity conservation and decision support of landscape planning. The representation, analysis and application of landscape graph have become a hot topic in conservation biology and landscape ecology. In this review, we first introduced the graph theory basis of landscape map. Based on the Scopus database, 257 published journal papers with the words "landscape graph", "connectivity" and "network" in titles, abstracts, and keywords from 1993 to 2019 were retrieved. We analyzed the research progress and development trend of this field from the aspects of annual published papers, journal sources, research areas, research institutions and landscape types involved. The results showed that before 2017, the number of journal papers published showed an overall increasing trend, and after 2017, the annual number of published papers decreased year by year. The main research forces were concentrated in United States, France, Canada, and China, contributing to 86.8% of the total published papers. Most of the research results were published in "Landscape Ecology", "Landscape and Urban Planning", and "Biological Conservation". In the research content, the representation of landscape graph mainly included the definition of nodes, the measurement of edges and the simulation of landscape. The analysis of landscape graph involved analysis index and landscape graph partitioning. This study mainly focused on the application of landscape graph in science and practice, including biodiversity conservation, landscape (ecological network) planning and management, the assessment of landscape impacts. Landscape graph based on graph theory influences conservation science and planning practitioners by helping understand landscape connectivity changes, animal behavior and habitat conservation. The impact of graph theory on conservation science and planning comes from the rich theoretical basis and mature research methods. Landscape graph based on graph theory provides a springboard for ecological understanding of landscape structure and pattern, and is an important tool for global researchers and practitioners.
Subject(s)
Conservation of Natural Resources , Ecosystem , Animals , Biodiversity , Canada , China , EcologyABSTRACT
In order to study the pollution status of heavy metals in sediments of Suya Lake, the concentrations of heavy metals Cu, Cd, Cr, Zn, Pb and Ni in sediments were measured at three locations in the center, middle and periphery of Suya Lake, the content characteristics and the pollution status of heavy metals in the study area were analyzed by the method of geoaccumulation index and potential ecological risk index, and the distribution and interrelation of heavy metals were evaluated by Kriging method and correlation analysis. The results showed that, on average, Zn was the highest, 112.87 mg·kg-1, followed by Cr, the smallest average of Cd was only 0.41 mg·kg-1. In addition to Cd and Cr, the coefficients of variation of Cu, Zn, Pb and Ni were relatively small, ranging from 24% to 31%, with moderate degree of variation. The coefficients of variation of Cd and Cr were 50.41% and 41.92%, respectively, and the spatial variation was obvious, which indicated that the variation of Cd and Cr was more significant than the others; 2The heavy metals Cu, Cd, Cr, Zn, Pb and Ni had a strong linear relationship, and there was a significant positive correlation, and six kinds of heavy metals had some homologous characteristics, with a common external input; 3The main pollution elements in the study area were Cd, Cr and Zn, the pollution degree was relatively serious, and the scope was extensive. Among them, the pollution degree of Cd was the most serious, the overall pollution level was moderate, and the pollution degree in some sample areas reached up to severe pollution, the pollution status of Cr, Zn and Pb was relatively mild, the pollution status of Cu, Pb and Ni was better, and there was no ecological risk; 4On the whole, the pollution level of the northeastern part of Suya Lake was relatively light, the degree of pollution in the southwest was relatively serious, showing a significant spatial distribution characteristics of decreasing from southwest to northeast, the contents of heavy metals in the samples were higher than those in the southwest of the reservoir, while the northeastern part of the periphery was the area with accumulation of low concentrations of heavy metals., and there was no pollution from Cu, Cr, Zn and Ni.
ABSTRACT
Landscape connectivity is considered as an extraordinarily important factor affecting various ecological processes. The least cost path (LCP) on the basis of minimum cumulative resis-tance model (MCRM) may provide a more efficient approach to identify functional connectivity in heterogeneous landscapes, and is already adopted by the research of landscape functional connecti-vity assessment and ecological corridor simulation. Connectivity model on circuit theory (CMCT) replaced the edges in the graph theory with resistors, cost distance with resistance distance to measure the functional connectivity in heterogeneous landscapes. By means of Linkage Mapper tool and Circuitscape software, the simulated landscape generated from SIMMAP 2.0 software was viewed as the study object in this article, aimed at exploring how to integrate MCRM with CMCT to identify ecological corridors and relative importance of landscape factors. The results showed that two models had their individual advantages and mutual complement. MCRM could effectively identify least cost corridors among habitats. CMCT could effectively identify important landscape factor and pinch point, which had important influence on landscape connectivity. We also found that the position of pinch point was not affected by corridor width, which had obvious advantage in the research of identifying the importance of corridors. The integrated method could provide certain scientific basis for regional ecological protection planning and ecological corridor design.
Subject(s)
Conservation of Natural Resources , Ecosystem , Models, Biological , Ecology , SoftwareABSTRACT
The distributions, soil environment status and potential ecological risk of heavy metals were studied in beach soil of returning the cropland into Yellow River beach region in Kaifeng by the Nemerows and Håkansons methods. The results showed that (1) as Among the average contents of the five heavy metals Pb, Cr, Hg, As and Cd, the highest was the average content of Cr, and the lowest was the average content of Pb and Hg. In addition to Hg, the coefficients of variation of other heavy metals were relatively small, indicating that the content of heavy metals was quite different at different sites, and to some extent, relecting that Hg, As and Pb were the major elements polluting the soil, among which, Pb pollution was the pollution with universality. There was little difference in the contents of Cr and Cd from village to village the coefficient of variation was small, and the contents were below the national standard level. (2) There was significant difference in the spatial distribution of soil heavy metal elements in the upper, the middle and lower sections of the study area. The upper section was clean, the middle section was slightly polluted, and the lower section was enriched with pollutants. (3) The distribution of heavy metals in the beach region inside and outside the levees of Yellow River was closely related to the distribution of the residential regions. In the upper section of the beach region (southwest), the population was large and the contents of heavy metals were high. The contents of heavy metals were lower in the near river zone than outside the levees of Yellow River. And the heavy metal contents in the middle and lower section were higher than those outside the levees of Yellow River, while the lower section (northwest) showed a tendency of pollution enrichment. (4) In the view of the average individual potential ecological risk index of heavy metals (E(r)i), the potential ecological risk of Hg reached intense levels, and the potential ecological risk of Pb's contribution to the integrated risk was 50.5%, which was the heavy metal with highest ecological risks. Cd and Pb had a moderate ecological risk, while As and Cr had minor ecological risk. Ecological hazards of heavy metals ranked in the ascending order of Hg > Pb > As > Cd > Cr. (5) The ecological hazard of the heavy metals was ranked in the order Hg > Cd > As > Pb > Cr. Based on the potential ecological risk level corresponding to the RI values, it was shown that there was moderate potential ecological risks of heavy metals in the Yellow River beach region in Kaifeng.
