Undergrowth clearing is an important process in artificial forest management in China. It is used to facilitate the forest managing practices, to reduce the nutrients competition from understory and to improve the growth of trees. As the ecological suitability of undergrowth clearing is still debatable, a field experiment by removing litter layer and understory plants was carried out to test the responses of fine root features for nutrient absorption in both understory and trees. The aims are to analyze the relations between the biomass of dominant trees and the understory plantation.
Results/Conclusions
The morphological traits of understory fine roots showed more plasticity and competitiveness in nutrients uptake than trees and affected the growth of trees in subtropical plantations. Understory species obviously improved the soil organic carbon content, soil pH and the biomass of soil microbes. These effects depended on the understory biomass rather than the biodiversity of species. Our field investigation indicated that the optimum biomass of understory is about 1.1 t C ha-1 in a 27-year-old plantation in this region. Although the understory may aggravate the competition on nutrients due to a stronger plasticity of morphological traits of fine roots than that of trees, they may also enhance the soil nutrients supply by accelerating the soil mineralization, thus to improve the growth of trees. Therefore, to keep a certain amount of understory is obviously beneficial to the growth of dominant trees. Several shrub species were suggested to maintain in understory when managing Chinese fir plantation based on the complementarities of fine root development between the understory species and dominant trees.