Effects of elevated ozone concentration and nitrogen addition on ammonia stomatal compensation point in a poplar clone

Xu, Wen; Shang, Bo; Xu, Yansen; Yuan, Xiangyang; Dore, Anthony J.; Zhao, Yuanhong; Massad, Raia-Silvia; Feng, Zhaozhong. 2018 Effects of elevated ozone concentration and nitrogen addition on ammonia stomatal compensation point in a poplar clone. Environmental Pollution, 238. 760-770. https://doi.org/10.1016/j.envpol.2018.03.089

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Abstract/Summary

The stomatal compensation point of ammonia (χs) is a key factor controlling plant-atmosphere NH3 exchange, which is dependent on the nitrogen (N) supply and varies among plant species. However, knowledge gaps remain concerning the effects of elevated atmospheric N deposition and ozone (O3) on χs for forest species, resulting in large uncertainties in the parameterizations of NH3 incorporated into atmospheric chemistry and transport models (CTMs). Here, we present leaf-scale measurements of χs for hybrid poplar clone ‘546’ (Populusdeltoides cv. 55/56 x P. deltoides cv. Imperial) growing in two N treatments (N0, no N added; N50, 50 kg N ha−1 yr−1 urea fertilizer added) and two O3 treatments (CF, charcoal-filtered air; E-O3, non-filtered air plus 40 ppb) for 105 days. Our results showed that χs was significantly reduced by E-O3 (41%) and elevated N (19%). The interaction of N and O3 was significant, and N can mitigate the negative effects of O3 on χs. Elevated O3 significantly reduced the light-saturated photosynthetic rate (Asat) and chlorophyll (Chl) content and significantly increased intercellular CO2 concentrations (Ci), but had no significant effect on stomatal conductance (gs). By contrast, elevated N did not significantly affect all measured photosynthetic parameters. Overall, χs was significantly and positively correlated with Asat, gs and Chl, whereas a significant and negative relationship was observed between χs and Ci. Our results suggest that O3-induced changes in Asat, Ci and Chl may affect χs. Our findings provide a scientific basis for optimizing parameterizations of χs in CTMs in response to environmental change factors (i.e., elevated N deposition and/or O3) in the future.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.envpol.2018.03.089
UKCEH and CEH Sections/Science Areas:	Atmospheric Chemistry and Effects (Science Area 2017-)
ISSN:	0269-7491
Additional Keywords:	ammonia, ozone, apoplast, compensation point, forest species
NORA Subject Terms:	Ecology and Environment
Date made live:	12 Apr 2018 11:58 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/519825

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