Assessing environmental and plant community changes by phytolith characteristics in sediments from Nanjishan Nature Reserve, Lake Poyang

Abstract

To assess the impacts of increasing human disturbance, wetland degradation, and biodiversity loss, and to determine the main environmental factors affecting the spatial distribution of phytoliths in Nanjishan Nature Reserve, phytoliths from 17 topsoil samples and a sediment core sample were analyzed. Yellow-brown, silty, and gray-black clays were the main sedimentary constituents, and the total organic carbon content decreased with increasing depth. Lakes Zhanbei, Chang, and Sanniwan were located in an alluvial delta and characterized by intensive human activity and grass communities of Triarrhena lutarioriparia and Zizania latifolia, whereas Lakes Shangbeijia, Beishen, Nanshen and Baisha were characterized by a lower degree of disturbance and grass communities of T. lutarioriparia and Phragmites australis. A total of 11,942 phytoliths (4248 in topsoil and 7694 in core sediment) were isolated from 46 samples and 19 distinct morphological types were identified. Vesicular cells constituted 42%–51% of all samples, short cells 24%–32%, and elongate types 15%–26%. The phytolith assemblages at Lakes Zhanbei, Chang, and Sanniwan were mainly composed of fans, rectangles, points and elongates. While Lake Shangbeijia, Beishen, Nanshen and Baisha were dominated by fans, saddles and elongates. Based on phytolith analysis, we found that the typical communities in the study area were significantly degraded from 1986 to 2003. Sediment cores dated by 210Pb showed that the main plant communities were transformed from Carex and T. lutarioriparia to Z. latifolia, T. lutarioriparia and P. australis.