Beijiang River Research Articles

Protecting China's rivers

Protecting China's rivers

Environmental impacts of surface mining on mined lands, affected streams and agricultural lands in the Dabaoshan Mine region, southern China

AbstractImpacts of surface mining on ecosystems were investigated in the Guangdong Dabaoshan Mine region, southern China. Significant soil acidification has been induced by mining activities which cause oxidation of metal sulfides contained in the mine spoils. Natural colonization of vegetation in the mine site has been impeded and this has resulted in severe soil erosion. Acid mine drainage from this mine site has caused the degradation of the downstream aquatic ecosystems. Mine water with pH< 3·5 has been continuously flowing into a first‐order tributary of the Beijiang River and has destroyed all the aquatic life to a distance of at least 25 km downstream of the discharge point, even when the pH rose to above 6 in the Hengshishui River (a third‐order tributary of the Beijiang River). Further downstream, macroinvertebrates first occurred at about 30 km from the discharge point, and only one species was found. This is in contrast to a reference site that was not affected by acid mine drainage, where 36 macroinvertebrate taxa were found. Acidic mine water also had marked impacts on the agricultural lands irrigated with it. Severe contamination of the soils by mine drainage is responsible for the extremely high concentrations of some heavy metals in the edible portions of a variety of food crops grown on the agricultural lands. Copyright © 2005 John Wiley & Sons, Ltd.

Population structure of wild bananas, Musa balbisiana, in China determined by SSR fingerprinting and cpDNA PCR‐RFLP

Both demographic history and dispersal mechanisms influence the apportionment of genetic diversity among plant populations across geographical regions. In this study, phylogeography and population structure of wild banana, Musa balbisiana, one of the progenitors of cultivated bananas and plantains in China were investigated by an analysis of genetic diversity of simple sequence repeat (SSR) fingerprint markers and cpDNA PCR-RFLP. A chloroplast DNA (cpDNA) genealogy of 21 haplotypes identified two major clades, which correspond to two geographical regions separated by the Beijiang and Xijiang rivers, suggesting a history of vicariance. Significant genetic differentiation was detected among populations with cpDNA markers, a result consistent with limited seed dispersal in wild banana mediated by foraging of rodents. Nuclear SSR data also revealed significant geographical structuring in banana populations. In western China, however, there was no detected phylogeograpahical pattern, possibly due to frequent pollen flow via fruit bats. In contrast, populations east of the Beijiang River and the population of Hainan Island, where long-range soaring pollinators are absent, are genetically distinct. Colonization-extinction processes may have influenced the evolution of Musa populations, which have a metapopulation structure and are connected by migrating individuals. Effective gene flow via pollen, estimated from the nuclear SSR data, is 3.65 times greater than gene flow via seed, estimated from cpDNA data. Chloroplast and nuclear DNAs provide different insights into phylogeographical patterns of wild banana populations and, taken together, can inform conservation practices.