Nitrogen deposition does not affect the impact of shade on Quercus acutissima seedlings

Abstract

Light and atmospheric nitrogen (N) deposition are among the important environmental factors influencing plant growth and forest regeneration. We used Quercus acutissima, a dominant broadleaf tree species native to the deciduous forests of Northern China, to study the combined effects of light exposure and N addition on leaf physiology and individual plant growth. In the greenhouse, we exposed Quercus acutissima seedlings to one of two light conditions (8% and 80% of full irradiation) and one of three N treatments (0, 6, and 12 g N m−2 y−1). After 87 d, we observed that nitrogen deposition had no significant effects on the seedlings regardless of light exposure. In addition, shade significantly reduced plant height, basal diameter, leaf number, total biomass, gas exchange capacity, and carbohydrate content. In contrast, however, shade significantly increased the amount of photosynthetic pigment, above-ground biomass allocation, and specific leaf area. There was also a hierarchical plasticity among the different seedling characteristics. Compared to traits of growth, biomass, biomass allocation and leaf morphology, the leaf physiology, including photosynthetic pigment, gas exchange, carbohydrate, and PUNE, is more sensitive to light conditions. Among the biomass allocation parameters, the leaf and root mass ratios had a relatively low phenotypic plasticity. The seedlings had high foliar physiological plasticity under various light conditions. Nevertheless, we recommend high irradiance to maintain vigorous seedling growth and, in turn, promote the restoration and reconstruction of vegetation.

Nitrogen deposition does not alleviate the adverse effects of shade on Camellia japonica (Naidong) seedlings

“…Some studies hold that shade can limit plant growth owing to the lower relative growth rate and biomass accumulation [ 16 , 35 – 38 ], whereas other studies indicate that there is a positive relationship between shade and plant growth [ 18 , 21 , 39 ]. In the present study, basal diameter and crown area were affected negatively by deep shade, which is in accordance with previous reports showing that low light intensity restricts seedlings growth and biomass accumulation [ 14 , 16 , 35 , 40 ]. But what’s interesting about Naidong seedlings is that the height was not affected by the light intensity.…”

“…Nitrogen supply affects plant reproduction, survival and biodiversity, which leads to both advantages and disadvantages. On one hand, elevated nitrogen deposition may stimulate seed germination, and facilitate plant growth and productivity [ 1 , 11 – 14 ]. On the other hand, excess nitrogen may cause many environmental problems, such as plant nutritional imbalance, plant growth depression, decline in biodiversity, and ecosystem function disorder [ 2 , 3 , 11 , 12 , 14 ].…”

“…Light heterogeneity in a forest increases as a result of natural disasters and human activities, and heterogeneity in the light environment might be important for expression of some plant traits [ 15 ]. Variation in irradiance has a fundamental effect on development, production and survival of plant, and excessively low or high incident light will prevent photosynthesis in the plant leaves [ 14 , 16 , 17 ]. A given species usually exhibits a variety of morphological and physiological characteristics under changeable light conditions.…”

“…Studies with respect to the effects of the interaction of nitrogen deposition and shading on plant physiological parameters have been reported [ 14 , 18 – 20 ]. Previous studies indicated that the efficiency of utilization nutrients is dissimilar in different light environments [ 18 , 19 ].…”

Combined Effects of Drought and Shading on Growth and Non-Structural Carbohydrates in Pinus massoniana Lamb. Seedlings

“…Water and light are important environmental factors that influence plant growth. The irregular distribution of precipitation and variable light conditions often cause drought and shading stress [1,2], thereby limiting growth [3][4][5][6][7]. Plants can alter their biomass distribution to improve their ability to capture resources and mitigate the damage caused by environmental stress [8][9][10].…”