Effects of litter removal on plant species diversity: a case study in tropical Eucalyptus forest ecosystems in South China

The removal of litterfall in the Eucalyptus plantations in South China affected the plant biodiversity in these ecosystems was found based on the field observation and lab analysis.The protection times of species diversity of three Eucalyptus communities were different (Community Ⅰ with no protection,Community Ⅱ with 7-year-protection,Community Ⅲ with 35-year-protection).The total numbers of species in these communities(from Community Ⅰ to Ⅱ to Ⅲ)are 1,6,and 17,respectively.The tesults showed that the protection of litterfall from being taken out of the ecosystem is important and can increase plant species diversity.This study ombined biomass data,the chemical and physical properties of the soil,and the diversity of microbes in the communities.It is concluded that the mechanism of the effects of litter removal on biodiversity includes three factors:removing the suitable habitat of microbe and animal,decreasing the soil mutrient, and changing the special habitat for the germination and growth of invading plants.These results should have important implications for managing these Eucalyptus forest ecosystems in South China.     

不同磷水平对不同种源尾叶桉的生长和养分吸收的影响

选定4个尾叶桉种源在不同的施P水平下盆栽，研究它们之间在生长和P、N吸收上的遗传差异．结果显示：施P肥对尾叶桉4个种源的生长高度、生物量积累、P及N吸收有着明显的作用，种源之间在上述指标上也有着明显的差异．在低P和高P施肥条件下，这种差异不明显，最大差异出现在土壤P的临界供给范围内（每kg土壤施15－20mg的P）．施P肥还会改变苗木地上部分和地下部分的干重之比、地上部分和地下部分的P、N吸收量之比．     

Constitutive or induced defences - how does <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> defend itself from larval feeding?

Summary. Following herbivory, induced responses involving plant secondary metabolites have been reported in a number of tree species. Although a wide range of plant secondary metabolites appear to operate as constitutive plant defences in trees belonging to the Eucalyptus genus, no induced responses have as yet been reported following foliar-chewing insect damage. We empirically tested whether branch defoliation (artificial and larval) of 2-year-old Eucalyptus globulus Labill. trees altered the abundance of specific plant secondary metabolites immediately (3 months after initial larval feeding) and 8 months after the cessation of larval feeding. Metabolites assayed, included essential oils, polyphenolic groups and foliar wax compounds and in all cases their abundance was not significantly altered by defoliation. However, the level of foliar tannins after 3 months of larval feeding did display a trend that suggested elevated levels as the result of defoliation, though this trend was not evident 8 months later, indicating that, if real, the response was a rapid and not a delayed induced response. The level of foliar tannins was also negatively correlated to both average larval survival and average percentage branch defoliation, suggesting that foliar tannins may operate as toxins and/or anti-feedants to M. privata larval feeding.     

The effect of temperature on leaching and subsequent decomposition of dissolved carbon from inundated floodplain litter: implications for the generation of hypoxic blackwater in lowland floodplain rivers

Dissolved organic carbon export from floodplain litter during flood events is an important energy subsidy for lowland rivers. Temperature affects both the release and decomposition of dissolved organic carbon from floodplain plant litter. Unseasonally warm flood conditions have resulted in the release and consumption of carbon at a rate so rapid that water column oxygen has been depleted, causing the death of aquatic organisms upon exposure to this ‘hypoxic blackwater’. To date, there has not been a systematic investigation of the role of temperature on hypoxic blackwater dynamics. In a series of laboratory experiments, we investigated the temperature dependence of both leaching and decomposition of carbon from a common floodplain litter component in south-eastern Australia – the leaves of the river red gum Eucalyptus camaldulensis. The leaching rate increased with temperature and approximated Arrhenius kinetics. Additionally, the solubility of the leaf carbon increased substantially at temperatures above ～25°C. The rate of organic carbon respiration also increased with temperature, and the relationship with temperature was approximately linear. These data can be used to improve models for the prediction of hypoxic blackwater risk.     

In vitro assessment of natural plant extracts Withania somnifera,Cassia fistula,Saraca asoca,and Eucalyptus tereticornis using primary chicken embryo fibroblast cell culture treated with urea or mercuric chloride (II)

The present investigation examined the detoxifying potential of methanolic herbal extracts, namely the leaf and bark extract of Eucalyptus tereticornis, bark extract of Saraca asoca, Cassia fistula and Withania somnifera in vitro using primary chicken embryo fibroblast (CEF) cells against damaging effects of urea and mercuric chloride (HgCl) (II). The influence of 20?mM urea and 10?µM?HgCl (II) was determined on cell viability or proliferation of cells after treatment with plant extracts. Higher survival rate of primary CEF cells treated with higher concentrations of plant extracts was observed due to their protective ability against urea and HgCl (II). Cassia fistula bark extract (10?mg?mL^?1) was found to be most effective against 20?mM urea as it protects 90% of CEF cells whereas W. somnifera protects 86% of the cells within 24?h. After treating cells with10?µM HgCl, W. somnifera and E. tereticornis leaf extracts were found to be more effective among all other extracts as they protect approximately 86% and 70% of CEF cells, respectively, within 24?h. These results indicate that C. fistula and W. somnifera has the highest potential amongst all the five plant extracts for protecting CEF cells against damaging effects of urea and HgCl (II), respectively.     

Soil physi-chemical properties,biomass and nutrient contents of forest litter in mixed plantations of Eucalyptus grandis and three tree species北大核心CSCD

In the present study, we compared the soil physical and chemical properties, biomass of forest litter and nutrient contents in three-and-half-year plantations of E. grandis mixed with Toona ciliate, Alnus formosana, Sassafras tzumu. The results indicated that mixing T. ciliate and A. formosana with E. grandis mitigated soil acidification. In E. grandis × S. tzumu plantations, the soil bulk density decreased, but the moisture capacity and porosity increased. The mixed plantations of E. grandis × S. tzumu significantly increased the soil total C, N, P and K content, by 64.7%, 41.9%, 28.6% and 7.7%, respectively. The mixed plantations of E. grandis × A. formosana also significantly increased the soil total C, N and P content, by 15.2%, 27.9% and 47.6%, respectively. Compared with the pure plantations, the mixed plantations had significantly lower soil hydrolysis N and higher available P content. Only the E. grandis × A. formosana plantations had higher soil available K content. Compared with that in pure plantations, the biomass of branch litter and leaf litter was significantly higher in E. grandis × A. formosana plantations but significantly lower in E. grandis × A. formosana and E. grandis × A. formosana plantations; the biomass of leaf litter and total biomass of litter of E. grandis × S. tzumu were 9.8% and 9.3% respectively lower. The litter C content in three kinds of mixed forest was significantly lower and the litter N content was significantly higher than that in the pure plantations. Only the mixed plantations of E. grandis × A. formosana plantations would increase the content of litter P. The mixed plantations of E. grandis × S. tzumu would increase the content of litter K. In general, S. tzumu is the optimal tree species to mix with E. grandis, followed by A. formosana, but T. ciliate is unsuitble for mixed plantation with E. grandis.