Growth Rate and Leaf Functional Traits of Four Broad-Leaved Species Underplanted in Chinese Fir Plantations with Different Tree Density Levels

Abstract

The close-to-Nature management method of interplanting broad-leaved trees after thinning of monoculture plantations is an important mixed species restoration model to improve the ecological service and functions effectively as well as to reduce the productivity decline of the multi-generation continuous planting of monoculture. Thus, the selection of tree species for establishing mixed forest and its ecological adaptability are the key issues. In this study, we conducted thinning experiment in an 11-year-old Chinese fir plantation with retention density of 900 trees/ha, 1200 trees/ha and 1875 trees/ha, and then underplanted four broad-leaved species, Schima superba, Phoebe bournei, Tsoongiodendron odorum and Michelia macclurei. After three years, we analyzed the growth rate and leaf functional traits of the broad-leaved species and their correlations with stand characteristics. The results showed that growth rate of seedlings of the four broad-leaved species were significantly different (p < 0.05) among different tree density levels and species. Low tree density favored seedling growth compared with high tree density and seedlings of T. odorum and S. superba performed best. However, leaf functional traits varied significantly (p < 0.01) among species only, and T. odorum had the largest specific leaf area, the smallest leaf mass per unit area, the smallest leaf tissue density, relatively large leaf thickness, and relatively small dry matter content. The leaf C content varied significantly among tree density levels and species; leaf N content varied significantly among species only; and leaf p content varied among tree density levels only. Correlation analyses between growth characters and leaf functional traits showed that height growth was significantly correlated with leaf N content (r = 0.686; p = 0.041) and with C:N ratio (r = −0.682; p = 0.043). Root collar diameter growth was significantly correlated with specific leaf area (r = 0.820; p = 0.007), leaf N content (r = 0.685; p = 0.042), leaf thickness (r = −0.706; p = 0.034) and leaf mass per unit area (r = −0.812; p = 0.008). Thus, leaf functional traits possibly predict diameter growth better than height growth. As a whole, growth rate and leaf functional traits could be used as a guide for selection of species for under planting in thinned pure monoculture plantations to establish conifer-broadleaved mixed forests. Based on growth rate and leaf functional traits, T. odorum appeared to be suitable for planting under low tree density stands where the degree of shading is low.

Combo chloro-photosynthetic device and applications for greenhouse gas reduction campaign and smart agriculture

“…Adjustments in leaf area, thickness, and chlorophyll content enable plant leaves to adapt to different light intensities and qualities. For instance, under low-light conditions, the leaf area expands, facilitating better light capture and utilisation by the plant, thus promoting growth [ [59] , [60] , [61] ]. Furthermore, under drought conditions, plant leaves become smaller, thicker, and more densely packed.…”

Water-Light Interaction and its Effect on the Morphophysiology of <em>Cedrela fissilis</em> Vell Seedlings

“…In this sense, higher leaf area values for C. fissilis in 70% shading were also observed. Increasing leaf area is a strategy of the species to optimize the use of light, increasing the surface for capturing photons to maintain photosynthetic processes [37,38].…”

Environmental Drivers of Landscape Fragmentation Influence Intraspecific Leaf Traits in Forest Ecosystem

“…R. pseudoacacia individuals do not ultimately adapt to the environment by influencing their growth, reproduction, and establishment [25]. In the later stages, after the thinning of monoculture plantations, native species can be intercropped to avoid the key problem of single cultivation, reduce ecological adaptability, and effectively improve ecological services and functions [48].…”

“…In subsequent restorations, native species with strong resistance can be planted to form a mixed forest and enhance tolerance mechanisms [62]. Leaf functional traits and growth rate have been used as the basis for selecting native tree species for planting in thinned, pure monoculture R. pseudoacacia plantations [48]. These measures are beneficial for the effective management of the stable relationship between the environment and plant interspecific traits, which improves ecological benefits and ecosystem services [63].…”