Compensation point of NO_x

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• 作者：Maarit Raivonen ; Timo Vesala ; Liisa Pirjola ; Nuria Altimir ; Petri Keronen ; Markku Kulmala ; Pertti Hari
• 关键词：Compensation point ; NO_x ; Stomatal control ; Ultraviolet radiation ; Shoot chamber
• 刊名：Agricultural and Forest Meteorology
• 出版年：2009
• 出版时间：15 June 2009
• 年：2009
• 卷：149
• 期：6-7
• 页码：1073-1081
• 全文大小：663 K

文摘

The compensation point of bidirectional NO_x fluxes of plants is often determined in chamber measurements by varying the NO_x concentration and searching for the point where the net flux is zero. We hypothesized that the compensation point can vary with changing conditions so much that one constant value is not sufficiently accurate. The compensation point for NO_x fluxes of Scots pine was analysed with a model describing the NO_x consumption and production processes. Consumption was assumed to occur via the stomata and on needle surfaces, with the rate depending on ambient concentration and degree of stomatal opening. Production was assumed to occur on the needle surfaces depending on solar UV-A irradiance. We used NO_y flux data measured with two gas-exchange chambers in southern Finland to parameterize the model. The estimated compensation points increased with increasing UV-A irradiance and decreased with increasing stomatal conductance. With open stomata, it varied several ppb even under field conditions.