Trace metals of needles and litter in timberline forests in the Eastern of Tibetan Plateau, China

Abstract

Concentrations of six trace elements (Cr, Pb, Cd, Co, V and Ni) in needles and litter of the fir (Picea spinulosa) and spruce (Abies georgei var. smithii) collected respectively at 42 sites and 18 sites in timberline forests in Heng Duan mountains, China, are reported in the present study. Mean concentrations of trace metals (Cr, Co, Ni, V, Cd and Pb) were 3.07mgkg−1, 2.48mgkg−1, 39.81mgkg−1, 8.12mgkg−1, 0.13mgkg−1, 4.26mgkg−1 respectively in litter and 0.89mgkg−1, 0.38mgkg−1, 7.33mgkg−1, 0.38mgkg−1, 0.92mgkg−1 and 0.92mgkg−1 in needles. In contrast to needles, all of elements in both parts were significantly enriched in the litter. Translocation of trace metals in the needles senescence before falling off may be confirmed, but additional investigations should be performed. Geostatistical analysis of Arcgis 10.0 was carried out in order to present the spacial distribution of trace metals in needles. The mine areas had relatively high levels of trace metals according to our original data. Trace metal concentrations of three belt transects, which could be the results of responding to the effects of the monsoon, were different. We deduced that mineral resources and climatic factor (southeasterly and southwesterly monsoon) could be possible contributions regarding the distribution of trace metals in needles. Depending on the results, we proposed a simple and novel way of the bio-monitor of trace metal. This method maybe used as a preliminary judgment to the possible source of trace metals. This study also is the first report on the spatial distribution of needle trace metals in the timberline forests by geostatistical analysis. Such biological monitoring is needed to provide databases which will facilitate the next step of this kind of studies which would be to evaluate levels of trace metal accumulation. In order to better understand trace metals of our study area, more sampling sites, climate data, soil data of trace metal, back trajectory studies of air mass and the continuous monitor should be good choices.