Does soil nutrient heterogeneity affect the competition and adaptation of Vernicia montana?

Abstract

Plants respond to variations in soil nutrient distribution and the presence of neighboring plants, yet consensus is lacking on the impact of naturally heterogeneous soil nutrient environments on plant competition. This study employs pot experiments to simulate homogeneous and heterogeneous forest soil nutrient environments and designs neighbor competition experiments for Vernicia montana, Cunninghamia lanceolata, and Phoebe bournei, to assess the impact of neighbor competition on these seedlings from the perspective of root morphology and foraging ability in different nutrient environments. The results reveal that when faced with heterogeneous nutrient environments or competitive settings, V. montana primarily utilized morphological and physiological plasticity, such as increasing root morphological indicators and concentrating more nutrients in the underground part, to enhance its adaptability and achieve competitive advantages. C. lanceolata and P. bournei mainly depended on physiological plasticity, like increased root nutrient concentration, when they were co-planted with other species. Compared to interspecific competition, intraspecific competition had a significant inhibitory effect on V. montana, especially under heterogeneous nutrient conditions, with notable reductions in root morphological indicators and root N, P concentration in mono-culture. Nutrient heterogeneity also altered the effects of interspecific competition on C. lanceolata and P. bournei. When mixed-planted with C. lanceolata or P. bournei, V. montana exhibited stronger competitive ability in both nutrient environments. The effects of mixed planting on C. lanceolata and P. bournei were significantly different between the two nutrient environments, in that homogeneous nutrient environment favored the growth and nutrient absorption of C. lanceolata, while heterogeneous nutrients generally benefited P. bournei. Most research on seedling competition is conducted under homogenous nutrient environments, and the results may not accurately reflect in-situ competition, potentially obscuring the scientific implementation of forestry management. Taking into account competition under unevenly distributed soil resources will help in optimizing tree species selection and cultivation methods, thereby improving the adaptability and ecological benefits of forests.