EFFECTS OF SOIL EXTRACTS FROM REPEATED PLANTATION WOODLAND OF CHINESE-FIR ON MICROBIAL ACTIVITIES AND SOIL-NITROGEN MINERALIZATION DYNAMICS

Effects of soil extracts from repeated plantation woodlands of Chinese -fir on soil fungi growth, the activities of microbial communities, an d rates of net soil nitrogen mineralization were investigated. Soil ex tracts from replanted woodlands significantly inhibited soil non-patho genic fungi growth, reduced soil respiration activities, and net soil nitrogen mineralization rates. However, soil extracts from replanted w oodland increased the growth of pathogenic fungi. The combination of s oil extracts and pathogenic fungi did not significantly reduce the gro wth of Chinese-fir seedlings when compared to the soil extracts alone. The combination of soil extracts with pathogenic and nonpathogenic fu ngi significantly increased the growth of Chinese-fir seedlings when c ompared to the combination of soil extracts and pathogenic fungi. The results suggest that the allelochemicals from soil extracts, rather th an pathogenic fungi, are the key factor regulating the productivity an d nitrogen cycling in repeated plantation woodlands.