Effects of Elevated Atmospheric CO2 Concentration on Insect Herbivory and Nutrient Fluxes in a Mature Temperate Forest

Abstract

Insect herbivory is one of the most important ecological processes affecting plant–soil feedbacks and overall forest ecosystem health. In this study, we assess how elevated carbon dioxide (eCO2) impacts (i) leaf level insect herbivory and (ii) the stand-level herbivore-mediated transfer of carbon (C) and nitrogen (N) from the canopy to the ground in a natural mature oak temperate forest community in central England at the Birmingham Institute of Forest Research Free Air CO2 Enrichment (BIFoR FACE) site. Recently abscised leaves were collected every two weeks through the growing season in August to December from 2017–2019, with the identification of four dominant species: Quercus robur (pedunculate oak), Acer pseudoplatanus (sycamore), Crataegus monogyna (common hawthorn) and Corylus avellana (hazel). The selected leaves were scanned and visually analyzed to quantify the leaf area loss from folivory monthly. Additionally, the herbivore-mediated transfer of C and N fluxes from the dominant tree species Q. robur was calculated from these leaf-level folivory estimates, the total foliar production and the foliar C and N contents. This study finds that the leaf-level herbivory at the BIFoR FACE has not changed significantly across the first 3 years of eCO2 treatment when assessed across all dominant tree species, although we detected significant changes under the eCO2 treatment for individual tree species and years. Despite the lack of any strong leaf-level herbivory response, the estimated stand-level foliar C and N transferred to the ground via herbivory was substantially higher under eCO2, mainly because there was a ~50% increase in the foliar production of Q. robur under eCO2. This result cautions against concluding much from either the presence or absence of leaf-level herbivory responses to any environmental effect, because their actual ecosystem effects are filtered through so many (usually unmeasured) factors.

Forecasting Dendrolimus sibiricus Outbreaks: Data Analysis and Genetic Programming-Based Predictive Modeling

“…Additionally, the presence of past outbreaks serves as a benchmark for anticipating future occurrences. Age, height, diameter, and density of trees within the plots offer insights into the maturity and health of the forest [20][21][22], influencing the susceptibility to moth infestations. Furthermore, factors such as volume and area of selected forest plots provide quantitative measures of forest coverage [23], influencing the scale of potential outbreaks.…”

Elevated CO2 does not improve seedling performance in a naturally regenerated oak woodland exposed to biotic stressors

“…The first-generation of FACE experiments were established in temperate and young monocultures (Nowak et al, 2004;DOE, 2020) and substantially improved our understanding of the capacity of forests to sequester carbon under elevated CO 2 (eCO 2 ) (Nowak et al, 2004;Ainsworth and Long, 2005;Norby et al, 2005;Norby and Zak, 2011;Medlyn et al, 2015). Second generation FACE experiments, the Eucalyptus free air carbon dioxide enrichment experiment facility (EucFACE) in Australia and the Birmingham Institute of Forest Research FACE Facility (BIFoR-FACE) in UK, have advanced this endeavour to include old-growth forests, allowing researchers to investigate whether eCO 2 alters a broader range of forest processes in the canopy, subcanopy, herb-and-regeneration layer (Gherlenda et al, 2016a;Jiang et al, 2020;Roberts et al, 2022), and soils (Martins et al, 2021). EucFACE was established in a eucalyptus forest (Duursma et al, 2016), whereas BIFoR-FACE, the site of the present study, is in a more complex and mixed canopy (Hart et al, 2020) dominated by English oak (Quercus robur L.) in the top canopy, and co-dominated in the understorey by other deciduous and evergreen broadleaves such as sycamore (Acer pseudoplatanus L.), hazel (Corylus avellana L.), hawthorn (Crataegus monogyna Jacq), and holly (Ilex aquifolium L.).…”