The intensity of heat waves and insect herbivory on campus plants and their relationship with leaf functional traits

Aims: In recent years, extreme weather events such as high-temperature heat waves have become increasingly frequent. In 2022, China experienced widespread and prolonged high temperatures, marking the most intense heatwave since comprehensive meteorological records began in 1961. These high-temperature heatwave events not only directly affect plant growth, but may also indirectly affect plant fitness by altering the intensity of herbivory. This study aims to clarify interspecies differences in the intensity of high-temperature heatwave damage and herbivory, investigate their relationships with leaf functional traits, and explore the interactions between high-temperature heatwave effects and the intensity of herbivory. Methods: This study focused on 11 common woody plant species on the campus of Northwestern Polytechnical University. Data were collected from 97 individuals, encompassing 2,358 leaves, to measure the intensity of sunburn damage and herbivory, alongside four leaf functional traits: leaf area, specific leaf area (SLA), leaf dry matter content (LDMC), and leaf thickness. One-way ANOVA was employed to assess interspecies differences in heatwave and herbivory intensity, while generalized in linear mixed models (GLMMs) were used to identify patterns relating these intensities to leaf traits. Correlations between heatwave damage and herbivory intensity were also analyzed. Results: The study revealed that: (1) Significant interspecies differences were observed in sunburn damage frequency, herbivory rate and herbivory frequency. (2) The frequency of sunburn damage was negatively correlated with leaf area but positively correlated with leaf thickness and LDMC. Both herbivory rate and herbivory frequency were positively correlated with LDMC but negatively correlated with leaf thickness, while herbivory frequency also exhibited a positively correlation with leaf area. (3) A negative correlation was detected between herbivory frequency and sunburn damage frequency. Conclusion: This study provides insights into responses of common woody plant species to extreme heatwave events and herbivory, identifying key leaf functional traits associated with these responses. Furthermore, it highlights the interplay between heatwave damage and herbivory intensity. The findings provides valuable guidance for understanding plant adaptation strategies under extreme climatic conditions and for selecting garden tree species that can withstand high-temperature heatwaves or herbivory.