Reproduction and community dynamics of staghorn sumac (Rhus typhina) in a coal-gangue area

Abstract

Coal mining has caused severe damages to local environment, such as vegetation destruction and decrease in species diversity, which poses a great challenge for sustainable development. Ecological restoration, aiming to increase plant coverage and soil nutrients in coal-mine areas, is of great significance for improving environment quality. The restoration effort at the mineral resource-rich Gujiao coal mine is an example of ecological reconstruction in Shanxi Province. Staghorn sumac (Rhus typhina) was used as one of the main plant species for the ecological restoration in Gujiao. We surveyed staghorn sumac communities at four different restoration stages in a coal-gangue area in 2008 and 2009. The relationship between species diversity index and various environmental factors was analyzed using Pearson correlation coefficient. Based on the investigation of vegetation and soil properties, the following parameters were analyzed: reproduction of staghorn sumac; dynamics of community structure; plant species diversity; and soil condition. The results showed that significant changes in community structure, species composition, and diversity occurred during a 12years of restoration period. Pioneer species such as Artemisia scoparia and Setaria viridis played dominant roles at the early stage of restoration. However, these pioneer species were replaced by neutral species such as Poa sphondylodes and Bothriochloa ischaemum 5–8years later. Community coverage increased quickly because of a high reproduction rate of staghorn sumac, leading to a vertical decrease in light intensity from the canopy to the forest floor. Meanwhile, species numbers in the herb layer decreased substantially. Due to vigorous sprouting reproduction, staghorn sumac colonized new habitats and expanded its population rapidly. Staghorn sumac became an exclusive edificator of the community 12years later, and other species were greatly suppressed and nearly disappeared. Although soil organic matter, total N content, and available P content increased slightly during the restoration period, soil nutrients were still at a low level according to the soil fertility classification standards of the Second National Soil Survey in the 1980s. Therefore, the improvement to the soil condition was very limited. Pearson correlation suggested that soil fertility was a main factor influencing species diversity at the early stage of restoration, while light intensity became a leading factor after the canopy was closed. The vigorous sprouting reproduction of staghorn sumac was beneficial for increasing vegetation coverage of the coal-gangue area during a short time period. However, in the long term, staghorn sumac suppressed not only other species but also its own sprouts, resulting in high risks of degradation to the plant community. Therefore, caution should be taken when staghorn sumac is extensively planted for ecological reconstruction. Vegetation coverage, species diversity, and succession tendency should be used as main indices in an evaluation of ecological restoration. Moreover, our results suggest that low nutrient content is a disadvantage for vegetation restoration. Therefore, it is necessary to increase soil nutrients in ecological reconstruction in coal-gangue areas.