The Effect of Change in Land Use on the indicators of Ecosystem Function and Soil Erosion via Landscape Function Analysis Method (LFA)

1- INTRODUCTION Over the past few decades, the objective of the evaluation and monitoring of the optimal utilization of sustainable natural resource services and ecosystem performance has been the successor to the ecosystem structure. Tongway and Hindley introduced a Landscape Function Analysis (LFA) method in 2004 to evaluate the ecosystem Function. In the new method, soil is considered as the most important element in rangeland ecosystems in order to determine the spectacle function, because the ecosystem status can be determined by examining the changes in the soil surface indexes, and this was possible for the expert to judge the changes brought about by the management and ecological practices of the rangeland.This research was carried out with the aim of evaluating the effect of change of rangeland conversion to farmland and its land use change effect on ecosystem function in rangelands of Navar area in the suburbs of Sanandaj. 2- THEORETICAL FRAMEWORK The importance of soil surface indexes has been expressed by various researchers such as the high correlation between basal cover and disruption of water flow, the importance of canopy size as an indicator of the distribution of soil resources, the effect of plant composition on organic carbon changes, soil permeability, the effect of bare soil on the potential of erosion and the importance of cryptogam cover in soil stabilization. Landscape Performance Analysis (LFA) is a method of monitoring with quantitative indicators. In this method, 11 indicators of soil surface area have been used to evaluate three functional properties including stability, permeability and elemental cycle. 3- METHODOLOGY The study area was divided into two landscapes. Based on the LFA method, three 50-meter transects were deployed in a 10-meter intervals along the slopes. During each transect, the length and width of patches included shrub, grass, forb and combination (combination of all patches and space between pieces (bare soil) were recorded. For each patch and inter-patch, five replicates were determined and for each replication the 11 soil surface parameters were evaluated. The soil surface parameters were evaluated for each ecological patch and inter-patch according to the LFA method. To evaluate three functional properties including stability, permeability and elemental cycle, and calculating 11 soil surface indexes, the LFA guidelines and the LFA software designed in the Excel environment were used. 4- RESULTS The results showed that the total stability index in the rangeland (47.2%) was higher than that of the dryland (24.4%) and their difference was significant (p <0.05). Due to the variety of ecological patches and their number, as well as the irregular and discontinuous pattern of water flow in the rangeland, the stability index in the rangeland was more than the drayland. The results showed that in the rangeland the ecological shrub patche had the highest stability, and in the dryland the combined patch had the highest stability. With regard to stability index, there was a significant difference between the combination of patches with other ecological components and inter patches (bare soil) in dryland, and in the case of rangeland, the shrub patch also yielded a similar result (p <0.05). Regarding permeability index in rangeland and dryland, grass and combined patch had the highest amount, respectively. With regard to nutrient cycle index in the rangeland, grass patch had the highest amount. The combined patch in the dryland had the highest amount of nutritional cycle index. 5- CONCLUSIONS AND SUGGESTIONS In general, the two landscapes have different functions depending on environmental factors and vegetative forms. The presence of independent grass patches in the rangeland (ecological indicator of rangeland) and the presence of a small number of combined patches (3 pieces) and shrub patches in the abandoned dryland (the ecologically indicator of this landscape) are due to the difference in the function of these landscapes. The rangeland has the highest function and the abandoned dryland has the lowest function. It can also be argued that LFA is a simple and fast method for assessing the function of rangeland ecosystems. In fact, saving time and cost of decision-making on management projects will reduce the risk of any operation at natural ecosystems. According to the results, it can be stated that the change in the utilization of the rangeland to dryland has reduced the ecosystem stability index and thus provided the soil surface with more soil erosion. Therefore, we must strictly prevent rangeland conversion to dryland.