Insect herbivory dampens Subarctic birch forest C sink response to warming

Tarja Silfver,Juha Mikola,Juha-Pekka Tuovinen,Nele Meyer,Elina Oksanen,Kristiina Karhu,Mika Aurela,Kristiina Myller,Matti Rousi,Lauri Heiskanen

doi:10.1038/s41467-020-16404-4

Abstract

Climate warming is anticipated to make high latitude ecosystems stronger C sinks through increasing plant production. This effect might, however, be dampened by insect herbivores whose damage to plants at their background, non-outbreak densities may more than double under climate warming. Here, using an open-air warming experiment among Subarctic birch forest field layer vegetation, supplemented with birch plantlets, we show that a 2.3 °C air and 1.2 °C soil temperature increase can advance the growing season by 1–4 days, enhance soil N availability, leaf chlorophyll concentrations and plant growth up to 400%, 160% and 50% respectively, and lead up to 122% greater ecosystem CO2 uptake potential. However, comparable positive effects are also found when insect herbivory is reduced, and the effect of warming on C sink potential is intensified under reduced herbivory. Our results confirm the expected warming-induced increase in high latitude plant growth and CO2 uptake, but also reveal that herbivorous insects may significantly dampen the strengthening of the CO2 sink under climate warming.

Highlights

Climate warming is anticipated to make high latitude ecosystems stronger C sinks through increasing plant production
Supporting earlier studies with avian[7,8] and mammalian[10,11] herbivores, we found that shifts in NEE800 were mainly driven by shifts in GPP800 (Fig. 1a–f), ecosystem respiration (Re) was affected by the treatments (Table 2 and Fig. 1g–i)
In line with the 50% increase in plant growth with herbivory reduction (Fig. 2g), we found that the relative increase in GPP800, NEE800, and Re due to warming was higher when herbivore pressure was reduced (Fig. 4a), statistically significant warming × herbivory interaction effects were observed for Re only (Table 2 and Fig. 1g)

Summary

Introduction

Climate warming is anticipated to make high latitude ecosystems stronger C sinks through increasing plant production This effect might, be dampened by insect herbivores whose damage to plants at their background, non-outbreak densities may more than double under climate warming. While there are studies of the effects of insect herbivory on leaf chlorophyll fluorescence and photosynthesis rates at high latitudes[22,24], no study has yet examined how background insect herbivory influences ecosystem–atmosphere CO2 exchange in these areas Both paleontological data from past intervals of significant climate change[25] and observations along latitudinal[16,26,27,28,29] and elevational[30] gradients indicate increasing insect herbivory with warming. The CO2 uptake of high-latitude ecosystems in the future likely depends on the magnitude of temperature rise, and on the levels of insect herbivory

Methods

Results

Conclusion