To detect the effects of thinning on the structural and compositional complexity, and carbon sequestration capacity in a Chinese fir plantation, to provide theoretical references for the management and conservation of forest ecosystems in the context of climate change.

Using a 19-year-old Cunninghamia lanceolata plantation at the Lishui forest farm in Nanjing as the research subject, four thinning intensities were randomly established (with 0%, 30%, 50%, and 70% of trees removed). Changes in structural and compositional diversity, as well as carbon storage and carbon sequestration rates, were measured three and six years after thinning.

Compared to the unthinned plots (0% reduction in trees), high intensity thinning (70% reduction in trees) reduced carbon storage of trees, and carbon storage of the shrubs and herbs significantly increased in the high intensity thinning and medium intensity thinning (50% reduction in trees). In contrast, aboveground carbon storage of stands was dependent on sampling time. With recovery time increasing after thinning, the carbon storage of trees, shrubs and herbs increased significantly. Carbon sequestration rate of the trees, shrubs, herbs and aboveground significantly increased with increasing thinning intensity. Effects of thinning on the structural and compositional complexity indices of Chinese fir plantation was dependent on the recovery time after thinning. Three years after thinning, DBH, Simpson index and species richness increased with thinning intensity, and both moderate and low intensity thinning significantly reduced Gini index of DBH and thinning had no significant effects on Shannon index and basal area of trees. Six years after thinning, DBH and Simpson indexes increased significantly with thinning intensity, and high intensity thinning decreased Gini_DBH index but increased Shannon index, while basal area and species richness did not change. Aboveground carbon sequestration rate was positively correlated with Simpson index, species richness and DBH, but negatively correlated with Gini index of DBH.

These results suggested that the relationship between the structural and compositional complexity and carbon sequestration capacity of Chinese fir plantation after thinning depends on the recovery time after thinning, so long-term research is necessary.

Air temperature affects absorptive root traits, which are closely related to species distribution. However, it is still unclear how air temperature regulates species distribution through changes in absorptive root traits. Seven functional traits of the absorptive roots of 240 individuals of 52 species, soil properties and air temperature were measured along an elevational gradient on Mt. Fanjingshan, Tongren City, Guizhou, and then the direct and indirect effects of these controls on species distribution were detected.

Absorptive roots adapted to air temperature with two strategies. The first strategy was positively associated with the specific root area (SRA) and specific root length (SRL) and was negatively associated with the root tissue density (RTD), representing the classic root economics spectrum (RES). The second strategy was represented by the trade-off between root diameter, mycorrhizal fungi colonization (MF) and SRL, representing the collaboration gradient with "do it yourself" resource uptake ranging from "outsourcing" to mycorrhizal resource uptake. Air temperature regulated species distribution in six ways: directly reducing species importance value; indirectly increasing the species importance value by reducing soil nitrogen content or increasing soil pH by reducing soil moisture inducing absorptive roots to change from "do it yourself" resource absorption to "outsourcing" resource absorption; indirectly decreasing the species importance value by decreasing soil moisture to change from "outsourcing" resource absorption to "do it yourself" resource absorption; indirectly increasing the species importance value with increasing soil pH by reducing soil moisture resulting in absorptive root traits turning into nutrient foraging traits; and indirectly decreasing the species importance value by promoting absorptive root traits to nutrient conservation traits.

Absorptive root traits play a crucial role in the regulation of species distribution through multi-approaches of air temperature.