|Brewer, T - OREGON STATE UNIVERSITY|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 4, 2001
Publication Date: November 30, 2001
Interpretive Summary: Wetland habitat restoration efforts frequently require the mandated use of native species. Understanding how introduced species invaded and became established in these landscapes may help us understand the best ways to successfully re-introduce natives where invasive weeds are in place. The effects of different growing temperatures on the relative competitiveness of two native wetland grasses (sloughgrass, Beckmannia syzigachne Steud. and tufted hairgrass, Deschampsia caespitosa L.) and tall fescue (Festuca arundinaceae Schreb. cv. Titan), a non-native grass species were investigated. We found that the native grasses were similarly competitive with tall fescue at the coolest temperature, but as the temperature increased, so did the competitiveness of tall fescue. These findings suggest these native species would be most competitive with tall fescue seedlings during cool temperature periods of the year and thus would improve the likelihood of successful re-introduction.
Technical Abstract: Successful reintroduction of native species into landscapes requires an understanding of how introduced species invaded and became established. This study was conducted to determine the effect of temperature on interspecific seedling interference of two native Pacific Northwest wetland grasses (sloughgrass, Beckmannia syzigachne Steud. and tufted hairgrass, Deschampsia caespitosa L.) and tall fescue (Festuca arundinaceae Schreb. cv. Titan), a non-native grass species. The relationships of species interference to the thermal response of photosystem II variable fluorescence reappearance ratio (FV/F0) and glutathione reductase (GR) thermal stability were also investigated. Two species replacement series experiments were conduced in growth chambers, planted in four proportions (0.0:1.0, 0.25:0.75, 0.5:0.5, 0.75:0.25, and 1.0:0.0), and grown at four temperatures (5C, 10C, 20C, and 30C). The FV/F0 and GR were measured at eight temperatures ranging from 5C to 40C. Tall fescue aggressiveness increased with increasing temperature. Sloughgrass and hairgrass ranked second and third, respectively, and were only more aggressive than tall fescue at 5C. Peak FV/F0 occurred at 15C, 20C, and, 22.5C for sloughgrass, hairgrass, and tall fescue, respectively. Species seedling dry mass was correlated with the stability of glutathione reductase and the average efficiency of the photosystem II apparatus over the range of growing temperatures (r = -1.00 and 0.96, respectively). Since tall fescue has greater photosystem II efficiency and glutathione reductase stability under elevated temperatures than sloughgrass and hairgrass, this may explain why tall fescue has been able to dominate some temperate western USA landscapes.