Epidemiological Estimate of Growth Reduction by Ozone in Fagus sylvatica L. and Picea abies Karst.: Sensitivity Analysis and Comparison with Experimental Results.

Sabine Braun,Christian Schindler,Beat Rihm

doi:10.3390/plants11060777

Sabine Braun, Christian Schindler + Show 1 more

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https://doi.org/10.3390/plants11060777

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Abstract

The critical level of ozone flux for forest trees is based entirely on biomass data from fumigation experiments with saplings, mostly in open-top chambers. Extrapolation to mature forests asks, therefore, for validation, which may be performed by epidemiological data analysis. This requires a multivariable regression analysis with a number of covariates to account for potential confounding factors. The present paper analyses the ozone sensitivity of volume increments of mature European beech (Fagus sylvatica) and Norway spruce (Picea abies), with the addition, or removal, of covariates. The comparison of the epidemiological dose–response relationship with experimental data shows very good agreement in beech and a more sensitive relationship in the epidemiological analysis of Norway spruce compared to the experiments. In Norway spruce, there was also a strong interaction between the effects of ozone and temperature; at high July temperatures, the ozone effect was stronger. This interaction may explain the disagreement between the epidemiological study and the experiments, of which the majority were performed in Sweden.

Highlights

The critical level for tropospheric ozone is based on the dose–response relationships with biomass data from fumigation experiments with young trees in chambers [1]
A set of fumigation experiments, mostly in open-top chambers (OTC), was compiled, and the biomass response at a specific ozone flux was related to the biomass of the controls
Dose–response relationships were established for beech/birch and for Norway spruce [3], and critical levels were set to 5.2 (4% biomass reduction for beech and birch) and 9.2 mmol m−2 yr−1 (2% biomass reduction for Norway spruce) [4]

Summary

Introduction

The critical level for tropospheric ozone is based on the dose–response relationships with biomass data from fumigation experiments with young trees in chambers [1]. (2% biomass reduction for Norway spruce) [4] The drawbacks of these kinds of experiments are the use of young trees and a chamber effect on climate [5]. A more realistic estimate can be obtained by either free-air fumigation of larger trees [6,7] or by epidemiological analysis of forest data [8]. The latter was used by Karlsson [9], who showed a negative impact of ozone, as AOT40, on the stem basal area increment of mature Norway spruce in South Sweden. Paoletti [11] did not find an ozone effect on stand volume growth in 728 European beech sites across Italy in one five-year increment period

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