Affiliation:
1. Center for Global Change and Complex Ecosystems, Zhejiang Tiantong Forest Ecosystem National Observation and Research Station, School of Ecological and Environmental Sciences East China Normal University Shanghai 200241 China
2. Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092 China
3. Administration of Guanshan National Nature Reserve Yichun 336300 China
4. Lushan Botanical Garden Chinese Academy of Sciences Jiujiang 332900 China
Abstract
AbstractPremiseTheories of plant–herbivore interactions hold that seedlings are more vulnerable to herbivory in warmer and more stable climates at lower elevations. Hypotheses of plant apparency, resource concentration, and resource availability have been proposed to explain variability in leaf herbivory. However, seasonal differences in the effects of these hypotheses on leaf herbivory on seedlings remain unclear.MethodsWe evaluated the three herbivory hypotheses by comparing the percentage and frequency of leaf herbivory in understory broadleaf seedlings in a subtropical forest in May (spring) and October (autumn) along an elevational gradient (290–1370 m a.s.l.). In total, we measured 2890 leaves across 696 seedlings belonging to 95 species and used beta regressions to test the effects of plant apparency (e.g., leaf area, seedling height), resource concentration (e.g., plant species diversity), and resource availability (e.g., canopy openness, soil available N and P) on leaf herbivory.ResultsSeedlings exhibited unimodal patterns of leaf herbivory along elevation, with drivers of leaf herbivory varying by the month. Variation in the frequency of leaf herbivory was best explained by the resource concentration hypothesis (e.g., plant species diversity) in both months, and herbivory was lower on seedlings in sites with higher plant diversity. Plant apparency hypothesis (e.g., leaf area, seedling height) was weakly supported only in spring, and the evidence for resource availability hypothesis (e.g., canopy openness, soil nutrients) was mixed.ConclusionsThis study supports the resource concentration hypothesis and reveals the importance of seasonal difference on understanding leaf herbivory patterns and the drivers of plant diversity in subtropical forests.