Species richness and endemism pattern of Fagaceae in Southwest China and their environmental interpretation.

How to accurately model species macro-richness patterns and endemism centers is a key focus of biodiversity conservation efforts and a hot biogeographical topic. Southwest China is one of regions with high Fagaceae species richness, the species diversity patterns and driving mechanisms are unclear. In this study, the distribution pattern of species richness (SR), weighted endemism (WE), and corrected weighted endemism (CWE) indices were estimated based on 7258 occurrence points of 161 Fagaceae species in Southwest China using both occurrence-to grid method and species distribution model (SDM). We used the spatial autoregressive (SAR) model to analyze the relationship between diversity indices and environmental factors. Overall, the three SDM-simulated diversity indices were more continuous in values than that of the occurrence-to grid method, though the distributions of those indices obtained by the two methods were similar. The areas with high SR value were mainly distributed in the south edge of Yunnan, north Guangxi and southwest Guangxi (62-89 species). The maximum of WE concentrated in south Yunnan and west Guangxi (1.77-5.02). The highest CWE (0.07-0.17) was found in southeast Tibet, Qinling-Daba Mountains, southwest Guangxi, and southeast Yunnan. The SAR models showed significant effect of precipita-tion in the driest month, standard deviations of seasonal temperature, altitude range and soil organic carbon content on SR. The effects of precipitation in the driest month, standard deviations of seaso-nal temperature, potential evaporation and altitude range on the WE were significant. The precipitation in the driest month, standard deviations of seasonal temperature, historical temperature change, coefficient of variation of enhanced vegetation index and altitude variation had significant effects on the CWE. The R2 of SAR model for SR, WE and CWE was 0.857, 0.733, 0.593, respectively, being higher than that of ordinary least squares (OLS) (R2=0.689, 0.425, 0.422). In conclusion, water availability, climate seasonality, habitat heterogeneity, historical climate change and soil condition were the most important factors limiting the distribution of SR and WE of Fagaceae in Southwest China. The SR and WE centers of Fagaceae were located in south and southeast Yunnan, southwest Guangxi, west Guangxi, Qinling-Daba Mountains, and southeast Tibet, where should be adequately protected.

[Distribution changes and refugia of three spruce taxa since the last interglacial.] / 末次间冰期以来3种云杉属植物的历史分布变迁及避难所.

Based on the current distribution information and 19 environmental variables data, we used the maximum entropy model to simulate the suitable distribution of Picea likiangensis var. likiangensis, P. purpurea and P. wilsonii in the last interglacial, Last Glacial Maximum, Mid- Holocene and present. The results from such modelling were validated by pollen data. We analyzed the relationship between species distribution dynamics and climate change, and then speculated the cryptic refugia of those species. Both the areas under the receiver operating characteristic curves and the verification results from pollen data indicated high accuracy of the model results. Results showed that isothermality was the most important factor influencing the distribution of P. likiangensis var. likiangensis and mean temperature of the warmest quarter was the most important for the distribution of both P. purpurea and P. wilsonii. Temperature was more important than precipitation in driving species distributions. Three species expanded their distribution ranges in Last Glacial Maximum due to their cold-adapted ecological habitat and the deep canyon topography feature which benefited their migration. There might be refugia of both P. wilsonii and P. purpurea in last interglacial, and they respectively located in Shennongjia Mountain in Hubei and Erlang Mountain and its nearby mountains in Sichuan. Our results, to some extent, made accurate prediction of the suitable distribution of three spruce species in the key periods since last interglacial, and speculated refugia of P. purpurea and P. willsonii. Our findings provided reference for better understanding of the formation mechanism of the present distribution of Picea and prediction of distribution changes in the future and sustainable management and protection of three spruce species.

Photoprotective and antioxidative mechanisms against oxidative damage in Fargesia rufa subjected to drought and salinity.

Drought and salinity are the two most common and frequently co-occurring abiotic stresses limiting plant productivity worldwide, yet it remains unclear whether bamboo species possess effective mechanisms to protect against oxidative damage caused by drought and salinity, either alone or in combination. In this study, we utilised Fargesia rufa Yi, a species important to forest carbon sequestration and endangered giant pandas, to evaluate physiological, biochemical and ultrastructural responses to drought, salinity and their combination. Under drought alone, F. rufa exhibited reduced water loss from leaves, photochemistry inhibition, pigment degradation, reactive oxygen species accumulation, lipid peroxidation, and damage to organelles compared with salinity and combined stress treatments. The superior performance under drought alone was attributed to greater thermal dissipation and the water-water cycle capacities, increased SOD/AsA-GSH cycle enzymes activities, and a favourable redox balance of antioxidants. Therefore, relative to salinity alone and drought+salinity, F. rufa plants under drought exhibit highly efficient mechanisms to protect against oxidative damage, which most likely allow accelerated recovery of photosynthetic plasticity once the stress is removed.

[C and N allocation patterns in planted forests and their release patterns during leaf litter decomposition in subalpine area of west Sichuan].

With the planted forest ecosystems of Cercidiphyllum japonicum, Betula utilis, Pinus yunnansinsis, and Picea asperata in subalpine area of west Sichuan as test objects, their total biomass and the C and N contents in soils and tree organs were determined. The results showed that the allocation of C in tree organs had less correlation with the age of the organs, while that of N and C/N ratio had closer relationship with the age. The N content in young organs was higher than that in aged ones, whereas the C/N ratio was higher in aged organs than in young organs, and higher in the leaf litters of needle-leaved forests than in those of broad-leaved forests. There was an obvious enrichment of C and N in the topsoil of test forests. The accumulated amounts of C and N in the whole planted forest ecosystem, including tree, litter, and 0-40 cm soil layer, were 176.75-228.05 t x hm(-2) and 11.06-16.54 t x hm(-2), respectively, and the nutrients allocation ratio between soil-litter and tree was (1.9-3.3):1 for C and (15.6-41.5):1 for N. Needle-leaved forests functioned as a stronger "C-sink" than broad-leaved forests. The decomposition rate of the leaf litters in needle-leaved forests was larger than that in broad-leaved forests, with the turnover rate being 2.2-3.7 years and 3.9-4.2 years, respectively. During the decomposition of leaf litter, the C in all of the four forests released at super-speed, with the turnover rate being 1.9-3.4 years. As for N, it also released at super-speed in C. japonicum and B. utilis forests, with the turnover rate being 1.9-3.2 years, but released at low speed in P. yunnansinsis and P. asperata forests, with the turnover rate being 6.7-8.5 years.