No abstract

Long-term continuous growth of the same tree species in planted pure forest will lead to soil polarization and degradation. Mixed forestation or litter replacement between different needle-and broad-leaved forests are effective measures, except fertilization, to control soil polarization according to the mutual compensation principle of different tree species. Through a two-year leaf litter replacement experiment in 4 typical planted pure forests of Larix kaempferi, Pinus tabulaeformis, Catalpa fargesii and Quercus aliena var. acuteserrata in Qinling Mountains of China, influences of leaf litter replacement on soil biochemical characteristics and their interspecific relationships were studied and main conclusions were reached as follows.(1) Annual leaf litter decomposition rate of broadleaved forests was 33.70% higher than those of needleleaved forests and increased by 8.35% -12.15% when needle-leaved litter was replaced with broad-leaved forests, whereas it decreased by 5.38% -9.49% when broad-leaved litter was replaced with needle-leaved forests.(2) Leaf litter replacement between needle-and broad-leaved forests popularly raised the contents of organic C, available N, P and K in soil, whose content increments in the needle-leaved forests (8.70% -35.84%) were obviously more than those in the broad-leaved forests (3.73% -10.44%), and in the former, the content increments after replacement with the litter of Catalpa fargesii (24.63% -35.84%) were more than those after replacement with the litter of Quercus aliena var. acuteserrata (8.70% -28.15%). Furthermore, the litter replacement was found to make the soil pH of needle-leaved forests developed from light-acid to neutral. (3) Litter replacement of the needleleaved forests with the broad-leaved litter popularly raised enzyme activities, amounts of microorganisms and contents of micro-biomass C and N in soil, the increments of which after replacement with the litter of Catalpa fargesii were also more than those after replacement with the litter of Quercus aliena var. acuteserrata; while the litter replacement of broad-leaved forests with needle-leaved litter resulted differently depending upon the tree species. Among them, the soil enzyme activities and contents of micro-biomass C and N in the forest of Quercus aliena var. acuteserrata raised while they lowered in the forest of Catalpa fargesii.