[Relationships between initial chemical composition of forest leaf litters and their decomposition rates in degraded red soil hilly region of Southern China].

A pot experiment with litter bags was conducted to study the relationships between the initial chemical composition of 8 kind forest leaf litters and 4 kind mixed leaf litters and their decomposition rates in degraded red soil hilly region of Southern China. Comparing with needle-leaf litters, broad-leaf litters had significantly higher contents of N, P, K, and Mg, but significantly lower contents of lignin and C. The decomposition rates of test litters were significantly positively correlated with the litters initial contents of N, P, K, and Mg (P < 0.05), and negatively correlated with the initial contents of lignin and C as well as the lignin/N, lignin/P, and C/P ratios (P < 0. 05). The lignin content explained 54.3% of the variation in litter decomposition rates, being the key affecting factor. Litters C, N, and P contents also had close correlations with the decomposition rates, and together with lignin content, contributed 81.4% of the variation. It was suggested that in the process of vegetation restoration in degraded red soil hilly region of Southern China, introducing broad-leaf trees with lower lignin and higher N and P contents would benefit the acceleration of forest litters decomposition and the restoration of soil fertility.

[Effects of cadmium on rice seed germination].

With 319 rice varieties as test objects, this paper studied the effects of cadmium on their seed germination. The results showed that after treated with 10 mg x L(-1) of Cd2+, seed germination rate was less affected, but root growth was restrained evidently. Cadmium had more serious impact on root than on sprout. Different rice varieties had different germination responses to Cd2+, with the sequence of conventional rice (Japonica rice) > hybrid rice (Indianica rice) > conventional rice (Indianica rice). The root length and number of two-line sterilities were restrained more strongly than those of three-line sterilities. Based on their responses to Cd2+, the test 319 varieties were clustered into 3 types, i.e., endurant type, medium type, and sensitive type.

[Dynamics of soil water under Vernicia fordii plantation in hilly red soil region of Southern China].

By using time domain reflectometry (TDR) , a fixed-position monitoring was made on the dynamic characteristics of soil water under Vernicia fordii plantation in the hilly red soil region of Southern China. The results showed that there was a significant difference in the soil water storage among different months, and the dynamics of soil water could be described as the phases of accumulation, depletion, and stabilization. Soil water had a significant variation in its vertical distribution, and the variation pattern differed in different seasons. Significant correlations existed between soil water storage and meteorological factors such as relative humidity (RH) , air temperature (t) , vapor pressure deficit (VPD) and rainfall (R) (P < 0. 05). After rain, soil water loss had a significant hyperbolic correlation with drought duration, while soil water storage had a significant linear negative correlation with this duration (P < 0. 05). With the extension of drought duration after rain, soil water loss tended to vary gently with increasing soil depth.