Effects of Shading on the Growth and Photosynthetic Fluorescence Characteristics of Castanopsis hystrix Seedlings of Top Community-Building Species in Southern Subtropical China

Abstract

Castanopsis hystrix is a major community-building species in the top communities of southern subtropical China, with a high natural regeneration capacity. However, excessive logging and the introduction of exotic tree species have substantially reduced the area of natural forest patches of Castanopsis hystrix, and seedling regeneration is essential for the long-term continuation of Castanopsis hystrix populations. To explore the effects of light intensity on the seedling emergence and early growth of Castanopsis hystrix, shading experiments were conducted under four shading treatments (0%, 40%, 60%, and 80%). The growth, biomass accumulation, and distribution, the quality index of seedlings, the morphology and structure of the root systems of seedlings, and the leaf chlorophyll content and chlorophyll fluorescence properties of seedlings under different shading treatments were analyzed. The results displayed the following: (1) Shade intensity impacts growth of Castanopsis hystrix seedlings and biomass allocation, with optimal results observed at 60% shade, leading to the promotion of organic matter production in leaves and the limitation of stem growth. (2) Using a multi-indicator composite index, it was determined that seedling quality for Castanopsis hystrix peaks at 60% shade intensity. (3) Shade significantly impacts the morphology and structure of Castanopsis hystrix’s root system, with most root characteristics peaking at 60% shade, indicating a substantial increase in root development compared to no-shade conditions. (4) The D-values indicated the most suitable shade intensity for seedling growth to be 60%, suggesting that Castanopsis hystrix seedlings are sensitive to light and excessive light can be detrimental to their growth. (5) The 60% shade treatment showed the maximum values of chlorophyll fluorescence characteristics and photochemical activity, with variations in energy conversion efficiency and dissipation reflected in parameters like photochemical burst coefficient (qP), photochemical burst coefficient (qN), the actual photometric yield of PSII under light acclimation (YII), and the maximum photosynthetic electron transport rate in photoinhibition (ETR), thereby supporting seedling growth and maintaining the normal function of photosynthetic organs. In conclusion, 60% shade treatment can effectively improve the growth and photosynthetic characteristics of Castanopsis hystrix seedlings and promote the accumulation of nutrient elements, ultimately promoting their growth.

Adaptive Mechanisms of Tree Seedlings to Adapt to Stress

“…In another study, Xue et al [2] examined the effects of four levels of manipulated light intensity (0%, 40%, 60%, and 80%) on the seedling emergence and early growth of Castanopsis hystrix, a dominant tree species with a high natural regeneration capacity in southern subtropical China. Through various physiological and biochemical measurements, their results indicated that 60% light intensity promoted maximum growth and the photosynthetic characteristics of C. hystrix seedlings.…”

Effects of Different Altitudes on Castanopsis hystrix, the Top Community-Building Species in Southern Subtropical China: Rhizospheric Soil Chemical Properties and Soil Microbiota

“…C. hystrix wood is greatly esteemed for its long-lasting nature, decay resistance, the attractive light-red color of its heartwood, and its workability. These traits render it a preferred choice for timber in its native regions [28]. The potential for its application in interior decor, carpentry, and ship construction is quite promising.…”

The effect of shade and drought on the growth and proline content of Medinilla speciosa and Medinilla verrucosa plants

“…This shows a link between proline accumulation and resistance to drought stress. This accumulation of proline is a crucial factor in determining plant tolerance to extreme environmental conditions, such as drought [12].…”