Warming Increased Nitrogen Availability and Tree Growth During the Last Five Decades as Revealed by Annual Ring Data of Pinus merkusii in Central Vietnam

The effects of climate change including warming on nitrogen (N) availability and growth of Pinus merkusii in central Vietnam were investigated using the relationship between climate variables (rainfall and temperature) and tree-ring parameters (ring width, density, basal area increment, and N concentration) for the last five decades. Rainfall was not correlated with any tree-ring parameters, indicating that water availability did not limit tree growth in the study site probably due to sufficient rainfall. Temperature was positively correlated with ring N concentration, basal area increment, and ring density, probably reflecting the positive effects of warming on soil N mineralization, net photosynthesis, and cell wall thickness, respectively. Therefore, this study suggested that global warming during the last five decades increased N availability and the increased N further helped warming-induced increases in the growth of P. merkusii in central Vietnam.