Diversity of an early successional plant community as influenced by ozone

Abstract

An early successional plant community was exposed to various ozone concentrations for two growing seasons (1994)(1995) in open-top chambers in Auburn, Alabama, USA. The ozone treatments were : AA, ambient air (open plots) ; CF, carbon-filtered air (c. 0n5iambient air), 1i, non-filtered air, and 2i, twice ambient air. Vegetative canopy cover exhibited a pattern of accumulation in the spring, with maximum canopy cover attained in summer, then senescence of foliage in the autumn 1994. This pattern was not observed in 1995 as a result of a drought during the spring and summer. Varying ozone exposures caused shifts in the competitive interactions between plants, thereby altering community structure. Higher canopy cover, vertical canopy density (layers of foliage), species richness, diversity, and evenness existed in the CF treatments than in the other treatments. In addition, winged sumac (Rhus copallina L.) became a major component of the CF treatments only during 1995. Surprisingly, blackberry (Rubus cuneifolius Pursh.), a species considered ozone-sensitive, based on visible injury, dominated canopy cover within the 2i treatments, 41 and 33 % of total canopy cover in 1994 and 1995, respectively. From these results it is concluded that plant communities existing in areas where lower ozone concentrations are prevalent might be more complex and diverse than those existing in areas with higher ozone concentrations.

Effects of ozone on wild plants

“…There is nothing known about the rate of recovery of sensitive species in low-ozone periods (Fuhrer, 1997). Duchelle et al, (1983), Evans & Ashmore (1992), Barbo et al (1994), Ashmore et al, (1995) and Barbo et al (1998) have all used OTCs placed over natural vegetation. Duchelle et al, (1983) determined the effects of ozone on the productivity of natural vegetation in a high meadow in the Shenandoah National Park, USA.…”

“…Unfortunately no data on species composition were reported. Working a little further south, Barbo et al, (1994), and Barbo et al (1998), exposed an early successional forest community to AA, CF, NF and 2iAA. They found changes in species performance, canopy structure, species richness, diversity index and evenness (Fig.…”

Impacts of ozone on trees and crops

“…The more ozone-sensitive species also tended to have a higher genetic multiplicity and diversity . Indeed, Barbo et al (1998) showed that in an early successional plant community, exposure to ozone led to a less complex community structure by affecting competitive interactions among plants.…”

Growth response to ozone of annual species from Mediterranean pastures

“…Semi-natural vegetation is frequently exposed to elevated ozone (0 3 ) concentrations throughout Europe (EMEP, 2002) which can adversely affect the most sensitive species, inducing changes in the floristic composition of plant communities (Ashmore and Ainsworth, 1995;Barbo et al, 1998;Fuhrer et al, 1994). However, limited information has been provided regarding the sensitivity of these ecosystems to 0 3 as has been recently reported in the last UN/ECE (United Nations Economic Commission for Europe) workshop held to define ozone critical levels for plant protection (Ashmore and Franzaring, 2003).…”