Effects of vegetation patterns and environmental factors on woody regeneration in semi-arid oak-dominated forests of western Iran

This study assesses the effects of vegetation natural tree and shrub regeneration in semi-arid forests patterns and environmental factors on the abundance of of the Zagros Mountains, western Iran. We sampled 120 releves at different topographic positions in a protected area of the studied region. Floristic composition, slope, elevation and soil properties were recorded at each releve, and woody seedling density was measured. We have first discerned five floristic groups using two-way indicator species analysis （TWINSPAN）, detrended correspondence analysis （DCA）, and canonical correspondence analysis （CCA） and then explored the relationships among the floristic group compositions, environmental factors and seedling densities. The indicator species of the five groups were Quercus brangi, Acer monspessulanum, Cerasus microcarpa, Rhamnus arvensis and Astragalus licyoides. Our results indicated that these groups were significantly affected by elevation and soil properties and the soil properties refer to： EC （electrical conductivity）, N （nitrogen）, K （potassium）, OM （organic matter）, and bulk density. Woody regeneration was composed of Q. brangi, A. monqJessulanum, C microcarpa, Amygdalus scopada and Crataeguspongca seedlings. The highest density of seedlings was found for Q. brantii （97.14 （_＋48.00） plants/hm2） and the lowest for A. scoparia （2.28 （＋1.50） plants/hm2）. Quercus brantii was the dominant species and the seedling density was positively correlated with soil pH and P （phosphorus） values. Amygdalus scoparia regeneration was negatively correlated with elevation, and the seedling density peaked in C. microcarpa group. There was no significant variation in distribution of C. pongca seedlings among the groups, but the seedling density of this species was positively correlated with slope and K. Cerasus microcarpa seedlings were more abundant in the Q. brantii group than in other groups. This study showed that the regeneration of tree and shrub species was unequally distributed in different floristic groups for some species （A. scopada and C microcarpa） but not for other （Q. branlii and C. pongca） and was generally correlated with some environmental factors, particularly elevation, slope and soil nutrients （P and K）. These results are a first step to implement future management and restoration strategies for promoting forest regeneration.

Quantitative analysis of endangered Acanthopanax senticosus communities in Dongling Mountain of Beijing

Based on the survey of community plots,a quantitative analysis of endangered Acanthopanax senticosus communities in Dongling Mountain was performed with two way indicator species analysis(TWINSPAN),detrended correspondence analysis(DCA)and canonical correspondence analysis(CCA).The communities of A.senticosus were classified into 9 types by TWINSPAN and the results were validated by DCA.On the DCA graph,the first axis reflected the gradient of altitude and the second axis reflected the aspect and slope.Most of A.senticosus were distributed in the thick forests at a high altitude with little light.With the exception of being a dominant species of shrub layers in a few communities,A.senticosus has a relatively scarce distribution.In accordance with DCA,the results of CCA also show the trend that the distribution of A.senticosus communities varied along with the gradient change of environmental factors.Altitude and light are the main factors affecting A.senticosus growth.