Blackwell Publishing Ltd Reproductive and physiological responses to simulated climate warming for

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Research

Blackwell Publishing Ltd Reproductive and physiological responses to simulated

climate warming for four subalpine species

Susan C. Lambrecht1,5, Michael E. Loik2,5, David W. Inouye3,5 and John Harte4,5

1

Department of Biological Sciences, San José State University, San José, CA 95192, USA; 2

Department of Environmental Studies, University of California,

Santa Cruz, CA 95064, USA; 3

Department of Biology, University of Maryland, College Park, MD 20742, USA; 4

Energy and Resources Group, University of

California, Berkeley, CA 94720, USA; 5

Rocky Mountain Biological Laboratory, PO Box 519, Crested Butte, CO 81224, USA

Summary

• The carbon costs of reproduction were examined in four subalpine herbaceous

plant species for which number and size of flowers respond differently under a long￾term infrared warming experiment.

• Instantaneous measurements of gas exchange and an integrative model were

used to calculate whole-plant carbon budgets and reproductive effort (RE).

• Of the two species for which flowering was reduced, only one (Delphinium

nuttallianum) exhibited higher RE under warming. The other species (Erythronium

grandiflorum) flowers earlier when freezing events under warming treatment could

have damaged floral buds. Of the two species for which flowering rates were not

reduced, one (Helianthella quinquenervis) had higher RE, while RE was unaffected

for the other (Erigeron speciosus). Each of these different responses was the result

of a different combination of changes in organ size and physiological rates in each

of the species.

• Results show that the magnitude and direction of responses to warming differ

greatly among species. Such results demonstrate the importance of examining

multiple species to understand the complex interactions among physiological and

reproductive responses to climate change.

Key words: climate change, Delphinium, Erigeron, Erythronium, Helianthella,

photosynthesis, reproduction, subalpine.

New Phytologist (2007) 173: 121–134

© The Authors (2006). Journal compilation © New Phytologist (2006)

doi: 10.1111/j.1469-8137.2006.01892.x

Author for correspondence:

S. C. Lambrecht

Tel: 408-924-4838

Fax: 408-924-4840

Email: [email protected]

Received: 6 June 2006

Accepted: 18 August 2006

Introduction

The impact of ongoing climate change on plant reproduction

in high-altitude environments has fundamental implications

for species persistence, dispersal, and migration. In high￾altitude environments, warmer temperatures advance the timing

and rate of snowmelt in the spring and lengthen midsummer

periods of low soil water availability (Harte et al., 1995;

Inouye et al., 2000). Snowmelt serves as a vital cue to initiate

flowering for high-altitude species that emerge and bloom

early in the growing season (Holway & Ward, 1965; Walker

et al., 1995; Price & Waser, 1998; Inouye et al., 2000; Dunne

et al., 2003). Furthermore, correlations between snowpack and

reproduction over temporal and spatial snowmelt gradients

and in manipulative experiments demonstrate that the timing

and abundance of flowering for some species are intimately

linked with snowpack depth (Inouye & McGuire, 1991;

Galen & Stanton, 1993; Walker et al., 1995; Molau, 1997;

Mølgaard & Christensen, 1997; Suzuki & Kudo, 1997; Starr

et al., 2000; Heegaard, 2002; Inouye et al., 2002; Dunne

et al., 2003; Saavedra et al., 2003; Stinson, 2004; Kudo

& Hirao, 2006). While these correlative studies reveal the

sensitivity of high-altitude plant reproduction to aspects of

climate change, no clear pattern emerges; the response

of reproduction to variables associated with climate change

is highly variable among species. The mechanisms that