Document: LEA-3-34-48

A meta-analysis of reproductive responses to elevated CO₂ in native and crop species.

JABLONSKI, L.M.* ^1,2, M.H.JONES ¹, X.WANG ^1,3 and P.S.CURTIS ¹

The Ohio State University, Columbus, OH 43210-1293 USA ¹
Marianist Environmental Education Center, Dayton, OH 45430-1095 USA ²
Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964 USA ³

Abstract:
We examined the impact of elevated CO₂ on reproductive traits related to fitness or yield in native and crop species using meta-analytic techniques. We hypothesized that because of greater carbon storage capacity, perennials would be more responsive to CO₂ enrichment than annuals and that for all species reproductive responses would be greater than vegetative responses. The literature was searched from 1983 to 1998. All studies with reproductive trait data were included where a CO₂ level near doubling and less than 1000ppm was applied to the entire plant through the majority of its life cycle. We analyzed 170 publications with data on 94 different species: 63 native and 31 crop species. Studies were dominated by the crop species wheat, rice, soybeans, cotton, and barley which formed 42% of the database. The majority of studies were conducted in controlled environment growth chambers or glasshouses (58%), 27% were conducted in field open-top chambers, 4% in FACE systems, and 5% in temperature gradient tunnels. Interactions with treatments of temperature, water, nutrients and ozone were also examined. Growth environment did not significantly affect reproductive response to elevated CO₂. However, functional groups showed different yield responses to a CO₂ doubling. C₃ plants had a response ratio, RR, of 1.5 compared to a RR of 1.4 in C₄ plants. Forbs were more responsive than grasses (RR of 2.0 compared with RR 1.5) but crops did not respond differently than native species. Seed number showed a RR of 1.2, predominantly through an increase in inflorescence (RR of 1.2) and fruit number (RR of 1.7). In reproductively mature plants, response of total, above-ground and below-ground mass to elevated CO₂ were similar in magnitude to that of seed number. Biomass allocation to reproductive parts was greater under elevated CO₂ since both reproductive allocation and harvest index showed a RR of 1.18. Individual seed weight increased 6 % under elevated CO₂, and there was no significant impact on seed carbon, lipid or starch. However, seed nitrogen and protein decreased 5% under high CO₂. Results suggest that yield and relative fitness will increase under elevated CO₂, and that forbs will respond more than grasses.

Keywords: elevated CO₂, seed, reproductive, fitness, review, meta-analysis

This abstract is being presented at: 10:30 AM in session:
Poster Session #18: Elevated CO₂.