Effect of visitors' pressure on soil and vegetation in several different micro-environments in urban parks in Tel Aviv

The effect of the pressure imposed by visitors on urban soil and herbaceous vegetation was investigated in seven micro-environments in parks in Tel Aviv. Soil properties (organic matter content, soil moisture, soil surface compaction/penetration depth), litter biomass, and herbaceous vegetation characteristics (vegetation cover, number of species, height) were determined in seven micro-environments: oak and pine trees, each under high and under low visitors' pressure; a herbaceous area without visitors' pressure; paths; and a resting area. Soil samples were collected from the upper 0-5 cm soil depth. In addition, in the tree micro-environments soil samples were taken at 0.5, 1, 2, and 3 m from the tree trunk. Averages and variances of soil properties and the vegetation characteristics varied among the various micro-environments and according to visitors' pressure. Soil organic matter and soil moisture contents were significantly higher under oak trees with low visitors' pressure than in other micro-environments. Litter biomass and penetration depth significantly decreased with increasing visitors' pressure under pine and, especially, oak. The vegetation cover, number of species, and height of herbaceous vegetation were greatest in the herbaceous area, lower under with the trees where there was high visitors' pressure and lowest in paths and resting areas. Thus, the soil properties in the oak micro-environment and the vegetation characteristics in the herbaceous area were the most sensitive to visitors' pressure. For each tree and open area, increasing visitors' pressure was accompanied by increasing spatial homogeneity of soil and vegetation. A radial spatial pattern of soil properties developed under oak with low visitors' pressure.