Fine roots (<2 mm of diameter) represent a relatively small part of total plant biomass, but they are the most dynamic component of the root systems with highest production and turnover rates ( Zhiyanski, 2014 Sun et al., 2015, 2018). The root biomass is an important part of the biosphere and it constitutes approximately 30% of the aboveground biomass ( Yuan and Chen, 2010 Zhiyanski, 2014). The conversion of degraded land to forest could improve the productivity of underground ecosystems and vegetation restoration projects in the fragile karst region should, therefore, continue. Moreover, there was a higher seasonal fluctuation and a greater vertical decreasing trend in late-successional stages than in the early-successional stages. Overall, our results suggested that fine roots show clear seasonal and vertical changes with vegetation succession. In addition, fine root production showed a similar vertical pattern of variation with biomass. Most of the fine roots were concentrated in the surface soil layer (0–10 cm), which accounted more than 57% root biomass, and decreased with increasing soil depth. In autumn, the fine root biomass was high, whereas the necromass was low. The fine root biomass and total fine root mass also showed a single peak with seasonal change. They showed a single peak across the vegetation restoration gradient. The total mass of fine roots and their production ranged from 187.00 to 303.11 g m −2 and 55.74 to 100.84 g m −2 year −1, respectively. The results showed that the fine root biomass and necromass ranged from 136.99 to 216.18 g m −2 and 47.34 to 86.94 g m −2, respectively. In this study, we investigated the seasonal and vertical variation in biomass, necromass, and total mass of fine roots using sequential soil coring under different stages of vegetation restoration (grassland, shrubland, secondary forest, and primary forest) in Southwest China. However, the spatial and temporal variations of fine root biomass in different vegetation types of the karst region remains poorly understood. In addition, fine roots (diameter < 2 mm) contribute to the regulation of nutrient cycles in terrestrial ecosystems.
In karst ecosystems, plants absorbing smaller amounts of nutrients, owing to shallow soil, show limited growth. 3Hunan Agricultural Biotechnology Research Institute, Changsha, China.2Huanjiang Observation and Research Station for Karst Ecosystems, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Huanjiang, China.1Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, China.Hu Du 1,2, Lu Liu 3, Liang Su 1,2, Fuping Zeng 1,2, Kelin Wang 1,2, Wanxia Peng 1,2, Hao Zhang 1,2 and Tongqing Song 1,2*
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