An unprotected vulnerable relict subtropical conifer-Keteleeria evelyniana: Its forests, populations, growth and endangerment by invasive alien plant species in China

Relict subtropical coniferous forests in China face severe fragmentation,resulting in declining populations,and some are under significant threat from invasive alien species.Despite the crucial importance of understanding forest dynamics,knowledge gaps persist,particularly regarding the impact of invasive plants on vulnerable natives like Keteleeria evelyniana.In this study,we investigated the impact of invasive plants on the regeneration of forests dominated by K.evelyniana,a subtropical relict species in southwestern China.For this purpose,we characterized forest dynamics of 160 forest plots featuring K.evelyniana as the primary dominant species and determined whether the presence of invasive plants was correlated with regeneration of K.evelyniana.We identified four distinct forest types in which K.evelyniana was dominant.We found that radial growth of K.evelyniana trees is faster in younger ageclasses today than it was for older trees at the same age.The population structure of K.evelyniana in each forest type exhibited a multimodal age-class distribution.However,three forest types lacked established saplings younger than 10 years old,a situation attributed to the dense coverage of the invasive alien Ageratina adenophora.This invasive species resulted in a reduction of understory species diversity.Additionally,our analysis uncovered a significant negative correlation in phylogenetic relatedness(net relatedness index)between native and invasive alien plant species in eastern Yunnan.This suggests closely related invasive species face heightened competition,hindering successful invasion.Taken together,our findings indicate that successful establishment and habitat restoration of K.evelyniana seedling/saplings require effective measures to control invasive plants.

Forest characteristics and population structure of a threatened palm tree Caryota obtusa in the karst forest ecosystem of Yunnan,China

Caryota obtusa of Arecaceae is a fascinating palm tree native to southwestern China,India,Myanmar,Thailand,Laos and Vietnam.It is an economically important and threatened species and appears as a canopy dominant in some karst areas in Yunnan.We aim to clarify the forest structure,species diversity,population status and regeneration dynamics of C.obtusa in the karst forest ecosystem of Yunnan,China.We established 56 vegetation plots dominated by C.obtusa in 10 counties of southern Yunnan.Based on the plot data,we analyzed the community stratification,floristic composition and C.obtusa’s population structure.We used questionnaires to interview local people and recorded the human activity history in C.obtusa-dominated forests.Caryota obtusa palm forests were distributed on limestone mountain slopes and gullies.There were seven forest community types.The stratification of each community included arborous layer,shrub layer and understory.The communities had rich species composition.For all the plots as a whole of each community type,Shannon–Wiener diversity index of either woody or herbaceous species ranged from 2.1 to 3.8.The diameter at breast height(DBH)-class frequency distribution of C.obtusa was a multimodal type.The regeneration was sporadic and dependent on intermediate natural disturbances.In the current population structure,a number of C.obtusa trees with small DBHs consisted mainly of the forest communities with no or a slight degree of human disturbances.Intensive human activities terribly hindered recruitment of C.obtuse,followed by the medium intensity of human activities.