Effects of defoliation modalities on plant growth, leaf traits, and carbohydrate allocation in Amorpha fruticosa L. and Robinia pseudoacacia L. seedlings

Abstract

Defoliation modality significantly affected leaf traits and carbon allocation especially in the early recovery period of two Leguminosae woody species . Robinia pseudoacacia L. recovered more quickly following defoliation than Amorpha fruticosa L. Defoliation resulting from anthropogenic disturbance, insects, and grazing animals affects plant growth and vegetation dynamics. Robinia pseudoacacia L. and Amorpha fruticosa L. with different susceptibility to biotic attack are commonly used for vegetation restoration in North China. However, plant responses to defoliation were not fully understood in the two Leguminosae woody species. We selected R. pseudoacacia and A. fruticosa to determine the effects of defoliation on individual plant growth, leaf traits, and carbohydrate allocation and compared the two species in terms of recovery strategies following defoliation for vegetation restoration. In a greenhouse experiment, A. fruticosa and R. pseudoacacia seedlings were subjected to three defoliation treatments: defoliation of the top down (TD) or bottom up (BU) 50% of the crown, and a control without defoliation (CK). The physiological and growth traits of seedlings were determined at 1, 3, 14, 30, and 60 days following defoliation. Plant growth in both species recovered after 2 months whatever defoliation modalities. Carbon allocation in both species was greatly affected by defoliation modalities during the early recovery period but had been fully recovered after 60 days of treatment. In the end of the experiment, defoliation modalities still had obvious impacts on leaf characteristics, especially in chlorophyll concentration and specific leaf area. R. pseudoacacia exhibited more evident compensatory mechanisms than A. fruticosa following defoliation. Defoliation modality treatments significantly affect most leaf traits and carbon allocation, especially in the early recovery period of both species. Considering the faster recovery ability of R. pseudoacacia than A. fruticosa after defoliation, R. pseudoacacia seedlings may be more suitable for vegetation restoration in North China.