Plant leaf and root N, P levels and their relationship to geographical and climate factors in a Chinese grassland transect

Abstract:

Nitrogen (N) and phosphorus (P) are generally considered the two most limiting and essential elements for the function of plants and ecosystems. Ecological stoichiometry of plant N and P provides the dominant means for investigating plant nutrient, and it may provide insights for fields as diverse as global carbon modeling, global climate change, and macroecology. Here we measured N and P contents and their ratios for 132 leaf samples and 120 root samples collected at 132 sites along the 5000km long China Grassland Transect (CGT) that traverses the Inner Mongolian and Qinghai-Tibet Plateaus. The aim was to explore the patterns of leaf N, P and root N, P and their ratio (N/P) respectively in relation to variability in geography, temperature and precipitation, and also the patterns of the relative N and P contents in leaf and root (leaf N(P)/ root N(P)). Results show that: 1) with decreasing longitude and latitude, increasing altitude and mean annual precipitation, leaf N and P increased, N/P decreased. 2) root N increased with increasing longitude, latitude, mean annual temperature, root P only increased with longitude. The patterns of root N,P were not in accord with the patterns of leaf N, P. 3) leaf and root relative N and P increased with increasing latitude and decreasing altitude, and relative N content also increased with decreasing mean annual temperature and increasing mean annual precipitation. Leaf and root relative N and P content reflected the distribution characteristics of the elements in relation to variability in geographical and climate factors. When there was more precipitation, or lower temperature, more N would be distributed to root. Lastly, we speculated that the ratio of leaf and root relative N and relative P content should be a fixed value, and our study was 0.81±0.51.