Interspecific relationship of artificial forests on upper reach of Minjiang river of China

Long-term growth of artificial pure forest will lead to continuous planting obstacle. The best solution is to form mixed forest through introducing other regenerated tree species. In order to direct the option of mixed tree species and ratios on upper reach of Minjiang river, sltu incubations of soil mixture of depth O-lOcm （humus soil of coniferous with deciduous tbrest, in this way to model mixed-forest） of typical forests of Cercidiphyllum japonicum（L）, Betula utilis（H）, Pinus yunnansinsis（M） and Picea asperata（Y） were carried out and the interspecific relationships were studied through analyzing the influences of soil mixing on the biochemical characteristics of soil and Jitter decomposition. The results can be concluded as following： （1） In forestlands of C.japonicum, P.yunnansinsis amt P.asperata, enzyme activities of urease, invertase and catalase of soil were intensified after soil mixing. Whereas, in forestland of B.utilis, all the three enzyme activities of soil were decreased after mixing with soil of P.yunnansinsis, but after mixing with soil of P.asperata, enzyme activities of urease and catalase were intensified and enzyme activity of invertase was decreased （2） Litter decomposition were popularly advanced after soil mixing. In forestlands of C.japonieum, P.yunnansinsis, the contents of organic-C and total N in soil were increased after soil mixing. Whereas, in forestland of B.utilis and P.asperata, the contents of N in soil were increased while organic-C decreased after soil mixing. （3） The acidities or alkalinity of soil were neutralized and further intensified after soil mixing, which means that soil of deciduous forest develops toward acidity while soil of coniferous forest develops toward to alkalinity. （4） Mixed ratios of LM0.15-0.50 and LY0.15-0.35 in forestland of C.japonicum, HM0.15 and HY0.15-0.50 in forestland of B.utilis, MI.,0.15-0.50 and MH0.35-0.50 in forest/and of P.yunnansinsis, YL0.35-0.50 and YH0.35 in forestland of P.asperata are betterchoice for soil mixing relatively, which can be taken as reference in decision of introducing regenerated tree species and ratio of mixed forest in practice.

Impacts of Forest Gaps on Soil Properties After a Severe Ice Storm in a Cunninghamia lanceolata Stand

During January–February 2008, a severe ice storm caused significant damages to forests in southern China, creating canopy gaps and changing soil nutrient availability and enzyme activity. To understand the relationships between gap size, changes in the soil environment and the effects that these changes have on soil processes, we investigated the effects of gap size on soil chemical and biological properties in the forest gaps in a Cunninghamia lanceolata stand in northern Guangdong Province, southern China. Ten naturally created gaps, five large(80–100 m^2) and five small(30–40 m^2), were selected in the stand of C.lanceolata. The large gaps showed a significant increase in light transmission ratio and air and soil temperatures and a decline in soil moisture, organic matter,N and P compared with the small gaps and the adjacent canopy-covered plots in the 0–10 cm soil. The differences in organic matter and nutrient levels found between the large and small gaps and the canopy-covered plots may be related to changes in environmental conditions. This indicated rapid litter decomposition and increased nutrient leaching in the large gaps. Moreover, the lowest levels of catalase, acid phosphatase and urease activities occurred in large gaps because of the decline in their soil fertility. Large forest gaps may have a region of poor fertility, reducing soil nutrient availability and enzyme activity within the C.lanceolata stand.