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 age-classes 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.

[Effects of nitrogen and sulfur combined application on nutritional components and active components of Isatis indigotica at seedling stage].

Using split plot design, a pot experiment with sand culture was conducted to investigate the effects ofnitrogen and sulfur combined application on nutritional components and active component of Isatis indigotica at seedling stage under different N (5，15，25 mmol·L⁻¹)and S(0.00，1.25，2.50，5.00，7.50 mmol·L⁻¹) levels. The results showed thatthe two elements had obvious effects and the leaf and root dry weights of I. indigotica seedlings increased greatly at N2 level. Under the same nitrogen concentration, the leaf and root dry weights increased firstly and decreased with the rising of sulfur concentrations in which S2 was conducive to the growth and biomass accumulation. Soluble sugar, soluble protein, soluble amino acids contents were the highest in N1, N2 and N3 treatments, respectively. The influence of sulfur concentrations on nutritional components was same as biomass, but the peak of different nutritional components was diversity in different nitrogen levels. The effects on secondary metabolites (total flavones, indigo, indriubin, epigotrin contents) were not obvious significantly, in which these indexes by N1S3，N1S2，N3S0，N3S1were the highest, respectively. In conclusion, the combination of nitrogen and sulfur of N2S2(N 15 mmol·L⁻¹ and S 2.5 mmol·L⁻¹) was beneficial to the growth and secondary metabolites accumulation of I. indigotica. These results could provide a theoretical basis for rational fertilization and cultivation of I. indigotica seedling.

[A preliminary study of epidemiology of sudden manhood death syndrome in the peasant derived workers in Dongguan city].

OBJECTIVE: To study the feature of sudden manhood death syndrome(SMDS) in Dongguan city. METHODS: The data of 284 cases of SMDS were analysized by retrospective study. RESULTS: The distribution of age, sex, the time of death and hometown of the dead in SMDS were described. The clinical or anatomical characters of SMDS were also discussed. CONCLUSION: These data will contribute to the late epidemical study.