Study On Comparison Of Effect Of Grain Size About Different Patch Types

Patches are the basic elements of landscape, and they are carriers with the process of relevant information. Pattern consists of patches with different size and shape which are arranged in space. Patches reflect the structure and function of the corresponding pattern in a certain extent. Taking patches as objects helps to grasp the changes of landscape pattern and landscape function, the logistics and energy flow of landscape, and the relationship between scale. In research of large scale problems, scaling is essential, which must aggregate data information of small scales and transfer information between different scales, so the research on effect of grain size is of important significance. The research on effect of grain size of patches can reveals the information transitive rules about the landscape pattern composition, configuration feature and ecological process between scales, then we can get relatively stable region or critical point, namely the scale domain or the critical grain size. It can provide reference for scaling or appropriate scale, because the pattern and process in the same scale domain are similarity, and it is easier to scaling, and the appropriate scale can improve the analysis and research accuracy of results.At present, in the research on effect of grain size, the patch type which scholars select focused on land use patches, thermal degree patches or soil erosion degree patches, and the research about the ecological patches were limited, also, in the research on ecological patches, influence from surrounding environment and land use situation was less consideration. In addition, scholars selected landscape metrics generally which was highly concentrated on the landscape pattern information, but cannot reveal the process of ecology research object. Landscape connectivity indicators which can reflect the contact of landscape elements in function and ecological process, are important indicators to measure the landscape ecological process, and they play a very good complement in analysis on effect of grain size, which can explain the landscape ecological processes effectively. So this paper tried to analysis effect of grain size from the perspective of patch types through landscape metrics, landscape connectivity indicators and area changing indicators, and investigate the information transitive situation about the characteristics of landscape pattern and ecological process between scales, and identify the scale domain which counter the characteristics of the research area. On this basis, under the same situation of research area, indicators and grain sizes, this paper this paper tried to comparative analysis of spatial distribution characteristics and effect of grain size of different patch types of through landscape metrics and spatial autocorrelation index, and to compare rules and the similarities and differences of mosaic feature information which transfer between scales with different patch types.This paper chooses Wuxi city as an example, which is the typical case of the Yangtze River Delta area with the rapid economic development and intensive human disturbance. It’s land use structure and spatial pattern change significantly, and is a typical ecological fragile zone. This paper choosed ecological degree patches, the thermal degree patch and land use patches as the research objects, drww the following conclusion:(1) The effect of grain size of landscape metrics was obvious in view of ecological patches, and according to the trend of curves in response to changing grain size at the class level and landscape level of landscape metrics, they can be divided into two categories:the first category was the metrics which falling gently, the second category was the metrics of irregular oscillatory fluctuation, and they all had scale domain significantly, the scale domain of landscape metrics at the class level was not the same as the landscape level, and they were (2,30) and (2,10) respectively.(2) Landscape connectivity were used to detect the scale effects of spatial grain sizes of ecological pattern. The effect of grain size of landscape connectivity indicators was also obvious in view of ecological patches. The overall trend from curves in response to changing grain size of number of links (NL) and number of components (NC) was manifested by decrease gradually. The trend from curves in response to changing grain size of integral index of connectivity (EC) and probability of connectivity (PC) was manifested by three sections:increase in the grain size of 1 to 2, slack in the grain size of 2 to 7, and obvious oscillation in the grain size of 7 to 100, also the trend was same at the three distance threshold. From importance value of PC (dPC) in response to changing grain size, we can drew in the grain size of 2 to 7, as the spatial grain size increased, the number and area of every important level of patch did not change significantly, and it indicated that the feature of pattern, structure, configuration and implied ecological process did not change significantly, the scale domain of landscape connectivity indicators was (2,7). The scale domain of landscape metrics was more precise than the scale domain of landscape connectivity indicators, therefore the scale domain which pointed at the research area is (2, 7) ultimately, and the actual scale is (60m,210m).(3) The overall trend of curves in response to changing grain size at landscape level of landscape metrics of the different patch types was consistent, except little differences of small fraction of metrics, there was no opposite change trend. According to the comparison of three patch types, the landscape metrics can be divided into two categories:the first category was a significant difference of the trend between the three patch types, and the second category was a similarity of the trend between the three patch types. This paper drew that the grain size of 40 was the same critical grain size of the three patch types. The overall trend of different patch types of spatial autocorrelation Moran ’s I index were very similar, which showed the little change firstly and decreased finally, and the size of 40m to 150m were the same scale domain of the three patch types.Through the above analysis, according to the indicators, the difference of the effect of grain size about the different patch types was not obvious, and the characteristics in response to changing grain size about the different patch types was certain similar, and that mean in the same area the different patch types was associated in a certain extent. Scale must be considered in study on the corresponding patch patterns, and different patch types had the same critical grain size and scale domain, thus the scaling model in the corresponding scale domain also can referenc each other.