Effects of thinning on the functional traits of understory Vitex negundo var. heterophylla in Quercus variabilis plantation

Abstract

Objective The objective of this study is to explore the effect of thinning on the functional traits of roots, stems and leaves of Vitex negundo var. heterophylla under Quercus variabilis plantation in order to provide theoretical basis for the optimization of plantation structure and the regeneration and protection of understory seedlings. Method The V. negundo var. heterophylla in the shrub layer of Q. variabilis plantation 3 years after thinning was taken as the research object, and the differences of leaf area, specific leaf area, leaf dry matter content, stem dry matter content, total root length, specific root length and other structural traits, as well as total nitrogen, total phosphorus, total potassium and total organic carbon content in various plant organs were compared. The relationship between plant functional traits and the understory light environment and soil physical and chemical characteristics was studied. Result After thinning, the aboveground functional traits of plants of V. negundo var. heterophylla such as total leaf organic carbon, leaf area, specific leaf area, leaf organic nitrogen, stem total organic carbon, and the underground functional traits of plants such as root length, root volume, root biomass, the total organic carbon content of roots were significantly higher than those of the control plot (P＜0.05). Correlation and stepwise regression analysis results showed that scattered radiation was the main factor affecting the structural properties of V. negundo var. heterophylla leaves. Direct radiation flux, photosynthetically active radiation and total solar radiation time were the key factors affecting leaf chemical properties, while stem functional properties were mainly affected by the direct radiation and scattered radiation under the forest. Total root length, specific root length and root organic carbon content were significantly correlated with soil non-capillary porosity, soil total porosity, soil organic carbon and soil total nitrogen (P＜0.05), among which soil organic matter content was the key factor affecting functional traits. Conclusion Thinning can significantly promote the development of the functional traits of leaves and roots of Q. variabilis plantation, and has a weak effect on stem functional traits. [Ch, 1 fig. 6 tab. 31 ref.]