China is a big country in forest plantations. The acreage of artificial forest in China is 1/3 of all over the world and is 1/3 of all forest in China. The plantations have irreplaceable roles in lumber production and ecological safety of China. However, a  large area is covered by multi-generation plantations with uni-tree spacies, and the nutrient export of the plantations is bigger than import, the productivity has been low. Fertilization as a manage measurestep, effectively improved the soil nutritional conditions, enhanced the forest productivity and changed the below-ground carbon cycling. Huge research has been done on the responses of soil respiration to fertilization. However, the major concern was the changes in the entire respiration, but autotrophic respiration is not separated from heterotrophic respiration and so the effect of fertilization on carbon immobilization by soil is hard to precisely evaluate.

Prof WANG Qingkui in the research group of Forest Plantation IAE has been devoted to the related research. He took the long-term experimental plots in Cunninghamia lLanceolata plantation as subject, used root-cutting to separate autotrophic from heterotrophic respiration to investigate the effect of fertilization on soil respiration. The results of 2-years research showed that the total respiration, autotrophic respiration and heterotrophic respiration were decreased by 18.6%, 23.6% and 17.1% by fertilization. The reduction of total respiration came mainly from heterotrophic respiration. Phophoriusc fertilization enhanced this contribution. Fine root biomass was major factor in controlling heterotrophic and autotrophic respiration. The heterotrophic respiration was also affected by the composition of organic soil carbon and the availability of soil nitrogen. The research illustrated the important role of fertilization on soil carbon release and assessment of potential of forest plantations in carbon fixation.

The work was supported by 973 Program (2012CB416905), CAS Pilot program , (XDB15010301) and NNSFC (31570466). The results were published in Agricultural and Forest Meteorology 232 (2017) 66–73 entitled as N and P fertilization reduced soil autotrophic and heterotrophic respiration in a young Cunninghamia lanceolata forest.