The endangered Vatica mangachapoi,a longlived,tropical tree with economic and ecological importance found in Hainan,China,was used to assess the hypothesis that historical human activities in Hainan’s tropical rain forest could have negative effects on the genetic diversity of V.mangachapoi.Three hundred and twenty individuals from 11 natural populations—which were classified into three groups according to levels of disturbance—were sampled and analyzed with ISSRmarkers.Although genetic diversity of V.mangachapoi is high at the species level,it is relatively low within populations.A significant genetic differentiation occurs among different disturbance levels.Significant isolation-by-distance indicated relevant historical anthropogenic changes.Our findings showed that historical human disturbances significantly increase the genetic differentiation and slightly decrease the genetic diversity of long-lived tree V.mangachapoi.Relevant targeting conservation actions were recommended.
Zhicong DaiChuncan SiDeli ZhaiPing HuangShanshan QiYing LinRuiping WangQiongxin ZhongDaolin Du
The continuing increase in human activities is causing global changes such as increased deposition of atmospheric nitrogen. There is considerable interest in understanding the effects of increasing atmospheric nitrogen deposition on soil enzyme activities, specifically in terms of global nitrogen cycling and its potential future contribution to global climate change. This paper summarizes the ecological effects of atmospheric nitrogen deposition on soil enzyme activities, including size-effects, stage-effects, site-effects, and the effects of different levels and forms of atmospheric nitrogen deposition. We discuss needs for further research on the relationship between atmospheric nitrogen deposition and soil enzymes.
外来生物入侵引发了严重的生态环境安全问题,对其开展风险评估已经成为一个现实、紧要的研究课题。为了把握该领域的研究动态,在Web of Science引文数据库中,以生物入侵风险评估作为主题词,检索2003—2012年间收录的相关文献,并用HistCite软件进行引文计量研究。统计发现,美国、澳大利亚两国的发文量超过了检索文献的一半,发文量排名前20的机构共发表文章521篇,占总发文量的34.4%;并分析得到该领域的核心期刊和影响力较大的作者。根据本地引用次数的排序,绘制了知识图谱,并总结出4个主要研究热点:WRA系统适用性及改进研究、其他风险评估方法研究、生物生态学效应在生物入侵风险评估中的应用研究、各类模型在生态风险评估中的应用研究。
Aims Although many studies have reported net gains of soil organic carbon(SOC)after afforestation on croplands,this is uncertain for Chinese paddy rice croplands.Here,we aimed to evaluate the effects of affores-tation of paddy rice croplands on SOC sequestration and soil respiration(R).Such knowledge would improve our understanding of the efctive-ness of various land use options on greenhouse gas mitigation in China.Methods The investigation was conducted on the Chongming Island,north subtropical China.Field sites were reclaimed from coastal salt marshes in the 1960s,and soils were homogeneous with simple land use:histories.SOC stocks and R,levels were monitored over one year in a paddy rice cropland,an evergreen and a deciduous broad-leaved plantation established on previous paddy fields and a reference fal-low land site never cultivated.Laboratory incubation of soil under fast-changing temperatures was used to compare the temperature sensitivity(Q10)of SOC decomposition across land uses.Important Findings After 15-20 years of afforestation on paddy fields,SOC concentra-tion only slightly increased at the depth of 0--5 cm but decreased in deeper layers,which resulted in a net loss of SOC stock in the top 40cm.Seasonal increase of sOC was observed during the rice-growing period in croplands but not in afforested soils,suggest-ing a stronger SOC sequestration by paddy rice cropping.However,SOC sequestered under cropping was more labile,as indicated by its higher contents of dissolved organic carbon and microbial bio-mass.Also,paddy soils had higher annual R,than afforested soils;R,abruptly increased after paddy fields were drained and plowed and remained distinctively high throughout the dry farming period.Laboratory incubation revealed that paddy soils had a much higher Q10 of SOC decomposition than afforested soils.Given that tem-perature was the primary controller of R,in this region,it was con-cluded that despite the stronger SOC sequestration by paddy rice cropping,its SOC was less stable than in afforested s
Jun CuiRongjuan ZhangNaishun BuHuabin ZhangBoping TangZhaolei LiLifeng JiangJiakuan ChenChangming Fang
