Effects of clearing and herbicide treatments on coniferous seedling establishment and growth in newly planted Mediterranean forests

The clearing of the natural vegetation and herbicide applications are commo nly used to facilitate the establishment and growth of coniferous seedlings in newly planted forests in the Mediterranean region. Casual observations in Israel indicated that these operations drastically reduce biomass and sp ecies diversity of the herbaceous vegetation in the first years. The subjec tive impressions created by the effect of the herbicides have caused severa l public confrontations between foresters and conservationists in Israel. L ess vegetation control may reduce tensions. However, no quantitative data w as available on tree seedling performance under lower amounts of herbicide applications than those typically used for the region. The aim of the prese nt study was to evaluate coniferous seedling establishment and growth under different intensities and frequencies of simazine applications in newly af forested areas in the Judean Mountains, Israel. Two experimental sites diff ering in soil types, temperature and rainfall were selected. In each site o f 0.7 ha, 6-months-old seedlings of Pinus brutia, Pinus pinea and Cupressus sempervirens were planted at standard densities. The results for both expe rimental sites showed that seedling mortality significantly increased with decreasing intensities and frequencies of simazine applications. However. h eight and crown diameter of the surviving seedlings were not always signifi cantly correlated to the amounts of herbicide sprayed in the adjacent areas . Standard current management practices showed highest seedling establishme nt success. The present study provides for the first time in Israel meaning ful insights into the early stages of coniferous seedling establishment in newly planted Mediterranean forests after disturbance by clearing and simaz ine applications. (C) 2001 Elsevier Science B.V. All rights reserved.