Factors limiting the recruitment of Quercus schottkyana,a dominant evergreen oak in SW China

Quercus schottkyana is a dominant species of oak in the Asian evergreen broad-leaved forests in southwestern China but seedlings are uncommon and recruitment is rare. Annual acorn production by Q. schottkyana is variable and the acorns are exposed to a series of mortality risks. Understanding the factors that limit recruitment of the oak requires knowledge of the oak's life cycle from acorn production to germination and seedling establishment. In this study, we first tested the effects of acorn density on establishment of seedlings by placing batches of acorns at different densities throughout the study area.Second, we tested the effects of herbivores on seedling survival by erecting fences around both natural and transplanted seedling populations. Our results show that even though the rate of seedling establishment increases as acorn density increases(for 32-8000 acorns?m^(-2)), survival rates of seedlings in the field were generally low(0-0.6%). We show that seedling recruitment of Q. schottkyana is mainly limited to the acorn stage where 88% of the acorns died from the combined effects of desiccation and predation by weevils(Curculio) and bark beetles(Coccotrypes sp.). Herbivory results in the death of some seedlings and consequently also affects the recruitment of seedlings of Q. schottkyana.

An experimental approach to addressing ecological questions related to the conservation of plant biodiversity in China

We briefly introduce and describe seven questions related to community structure and biodiversity conservation that can be addressed using field experiments,and provide the context for using the vast geographic diversity,biodiversity,and network of Nature Reserves in China to perform these experiments.China is the world's third largest country,has a diverse topography,covers five climatic zones from cold-temperate to tropical,has 18 vegetation biomes ranging from Arctic / alpine tundra and desert to Tropical rain forest,and supports the richest biodiversity in the temperate northern hemisphere( > 10%of the world total). But this tremendous natural resource is under relentless assault that threatens to destroy biodiversity and negatively impact the services ecosystems provide. In an attempt to prevent the loss of biodiversity,China has established 2,729 nature reserves which cover 14.84% of the nation' s area. Unfortunately underfunding,mismanagement,illegal activities,invasive species and global climate change threaten the effectiveness of these protected areas. Attention has focused on protecting species and their habitats before degradation and loss of either species or habitats occur. Here we argue that we must move beyond the simple protection of ecosystems,beyond their description,and by using experiments,try to understand how ecosystems work. This new understanding will allow us to design conservation programs,perform restoration of damaged or degraded areas,and address resource management concerns( e.g.,agriculture,logging,mining,hunting) more effectively than with the current approach of ad hoc reactions to ecological and environmental problems. We argue that improving our understanding of nature can best be done using well designed,replicated,and typically manipulative field experiments.