Response of soil phytolith occluded organic carbon accumulation to long-term vegetation restoration in Southwest China karst

Aboveground vegetation can significantly affect soil PhytOC (phytolith occluded organic carbon) accumulation. To clarify the response of soil PhytOC accumulation to long-term vegetation restoration in Southwest China karst, the four typical vegetation restoration engineering types of tree, shrub, vine forest, and grassland construction including seven species planting measures carried out 28-31 years ago were selected as study objects. And studies on their effects on soil PhytOC content and storage were conducted. Results showed that long-term vegetation restorations obviously increased soil PhytOC accumulation and changed the proportion of soil PhytOC to total soil organic carbon. Among the different engineering types or species planting measures of vegetation restoration, there were significant or extremely significant differences in effects on soil PhytOC accumulation. Among the four types of restoration engineering, the tree forest construction had the best increase effect on soil PhytOC accumulation. And among the seven kinds of planting measures, the increased effect on soil PhytOC accumulation of Tectona grandis ('teak' an angiosperm tree species) planting was the highest. Vegetation biomass and litters were the key influencing factors on soil PhytOC accumulation. Soil C:P and N:P had significant effects on soil PhytOC accumulation by changing aboveground vegetation biomass and litters. Human activities could significantly change soil PhytOC content and storage, and reducing human activities of tilling and harvesting would be beneficial to soil PhytOC accumulation. The present results not only provided scientific bases for the vegetation rehabilitation of increasing soil PhytOC accumulation in outhwest China karst but also were great of significance in promoting stable soil C sequestration of the global terrestrial ecosystems.