Physiological ecology of lodgepole pine (Pinuscontorta) in an enriched CO₂ environment

Abstract

Relatively little work has been done to evaluate the effects of chronically high levels of carbon dioxide on growth and physiology of woody plants. In this study, seedlings of lodgepole pine (Pinuscontorta Dougl. var. latifoliaEngelm.) were grown for 5-month periods at 330, 1000, or 2000 μL CO2•L−1. Height growth; leaf area production; biomass of leaves, stems, and roots; and photosynthetic responses to changing light, moisture, and CO2 concentration were measured. Significant differences between treatments were found in mean seedling height on all measurement dates. Seedlings grown at 1000 μL CO2•L−1 were tallest, with seedlings grown in 2000 μL•L−1 intermediate between the control (330 μL•L−1) and 1000 μL•L−1 treatments. The same relationship was found in production of total leaf surface area. Increased leaf surface area yields a productive advantage to seedlings grown at concentrations of CO2 up to 2000 μL•L−1 even if no increase in net photosynthesis is assumed. Biomass of stems, roots, and secondary leaves was increased in both elevated CO2 conditions, with root biomass approximately 15 times greater in seedlings grown at 1000 μL•L−1 than in those grown at 330 μL•CO2•L−1. Stomatal resistances were essentially the same for all treatments, indicating no CO2-induced stomatal closure to at least 2000 μL•L−1. Photosynthetic Vmax (milligrams per square decimetre per hour) for light response curves varied with CO2 concentration. If results are extrapolated beyond a 5-month period and into field conditions, it appears that size of trees, interactions with competitors, and ecological role of the species might be altered.

Plant water relations and the effects of elevated CO2: a review and suggestions for future research

“…Beadle et al (1979) observed that stomatal response to short term increases in Ca depended on the degree of existing water stress (see below). Higginbotham et al (1985) observed no CO2 related change in gs of Pinus contorta foliage grown at Ca'S as high as 2,000 #mol mol -1, while Nijs et al (1988) report that in L. perenne grown at elevated Ca, E, and presumably g~, increased with increasing Ca.…”

“…These chambers can be placed outdoors to take advantage of natural light and temperature regimes (Jones et al 1984;Rogers et al 1984;Idso et al 1987;Szarek et al 1987), or closed chambers placed in greenhouses, where environmental factors are more readily controlled (Khan & Madsen 1986;Reekie & Bazzaz 1989;Arnone & Gordon 1990). Controlled environment rooms are frequently used to grow seedlings at enhanced Ca (e.g., Higginbotham 1985;Wray & Strain 1986). Growing conditions generally span normal terrestrial light and temperature ranges, but include Ca'S ranging from 350 to 675 #mol mol-1 (Oberbauer et al 1985;Idso 1988;Marks & Strain 1989;Nijs etal.…”

“…Growing conditions generally span normal terrestrial light and temperature ranges, but include Ca'S ranging from 350 to 675 #mol mol-1 (Oberbauer et al 1985;Idso 1988;Marks & Strain 1989;Nijs etal. 1989a), with some studies involving CO2 treatments of 800 to 1,000/~mol mol-1 (Tolley & Strain 1984a;Del Castillo et al 1989), and still others as high as 2000 #mol mol -1 (Higginbotham et al 1985) and 4,000 #mol mol-1 (Pallas 1965).…”

“…Both methods can be reliable if used with knowledge and caution, but serious errors can result when inappropriately used. The pressure bomb method has been used by a number of researchers studying effects of CO2 on plant water relations (Beadle et al 1979;Tolley & Strain, 1984b;Higginbotham et al 1985;Teskey et al 1986;Sasek & Strain 1989;Frederick et al 1990). Readers are referred to Tyree and Jarvis (1982) for an account of how this analysis is done and examples of possible sources of error (Cheung et 49 al.…”

“…The global average atmospheric CO2 concentration is currently thought to be around 350/~mol mol-1, an increase of circa 70 ~mol mol-~ since the mid 1800's (Leadley et al 1987;Arnone & Gordon 1990;Conroy et al 1990), and may nearly double by the mid-21 St century (Tolley & Strain 1984a;Leadley et al 1987). It has been hypothesized that this increase will impact plant growth (Higginbotham et al 1985;Idso 1988), competition (Carlson & Bazzaz 1980;Marks & Strain 1989), and water relations (Sionit et al 1981;Rogers et al 1984; Barr et al 1990). Aside from sun light, the one factor most basic to the continuance of plant metabolic processes and survival is water.…”