Interactive effects of understory removal and fertilization on soil respiration in subtropical Eucalyptus plantations

Aims It has been well recognized that understory vegetation plays an important role in driving forest ecosystem processes and functioning.In subtropical plantation forests,understory removal and fertiliza-tion have been widely applied;however,our understanding on how understory removal affects soil respiration and how the process is regulated by fertilization is limited.Here,we conducted an under-story removal experiment combined with fertilization to evaluate the effects of the two forest management practices and their inter-actions on soil respiration in subtropical forest in southern China.Methods The study was conducted in a split-plot design with fertilization as the whole-plot factor,understory removal as the subplot factor and block as the random factor in subtropical Eucalyptus plantations.In total,there were four treatments:control with unfertilized and intact understory(CK),understory removal but without fertilization(UR),with fertilization but without understory removal(FT)and with fertilization+understory removal(FT+UR).Eucalyptus above-and belowground biomass increment,fine root biomass,soil tempera-ture,soil moisture and soil respiration were measured in the present study.understory respiration(Ru)was quantified in different ways:Ru=RCK−Ru or Ru=RFT−R(FT+u);fertilization increased soil respiration(RFI)was also quantified in different ways:RFI=RFT−RCK or RFI=R(FT+u)−Ru.Important Findingsover a 2-year experiment,our data indicate that understory removal significantly decreased soil respiration,while fertilization increased soil respiration.understory removal decreased soil respiration by 28.8%under fertilization,but only 15.2%without fertilization.Fertilization significantly increased soil respiration by 23.6%with the presence of understory vegetation,and only increased by 3.7%when understory was removed,indicating that fertilization increased soil respiration mainly by increasing the contribution of the understory.our study advances our understanding of the interactive effects of understory management and fertilization on soil respiration in subtropical plantations.

Bird community comparisons of four plantations and conservation concerns in South China

Plantations of non-native,fast-growing trees are increasing in the tropics and subtropics,perhaps with negative consequences for the native avifauna.We studied bird diversity in 4 types of plantations in South China to deter-mine which plantation types are especially detrimental,and compared our findings with studies in nearby natu-ral forests to assess the magnitude of the negative impact.A total of 57 species was recorded.The mean capture rate of understory birds was 1.7 individuals 100-net-h-1.Bird richness and capture rate were lower in plantations than in nearby natural forests.Babblers(Timaliidae),primarily forest-dependent species in South China,were particularly under-represented in plantations.Species richness,composition and bird density,particularly of un-derstory birds,differed between plantation types.Plantations of Schima,which is native to South China,had the highest species richness according to point count data.Plantations of Acacia(non-native)supported the highest understory species richness and produced the highest capture rate of understory birds,probably because of their complex structure and high arthropod abundance.If bird diversity is to be considered,we strongly recommend that future re-afforestation projects in South China should,as far as possible,use mixed native tree species,and especially Schima,ahead of the other species.