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Effects of N on Plant Response to Heat-wave: A Field Study with Prairie Vegetation
- Wang, Dan, Heckathorn, Scott A., Mainali, Kumar, Hamilton, E. William
- Journal of integrative plant biology 2008 v.50 no.11 pp. 1416-1425
- Andropogon gerardii, C3 plants, C4 plants, Solidago canadensis, aboveground biomass, air temperature, canopy, carbon, carbon dioxide, environmental impact, field experimentation, flowers, forbs, global warming, grasses, heat, heat shock response, leaf water potential, leaves, nitrogen, nutrient use efficiency, photosystem II, plant response, resorption, rhizosphere, soil respiration, soil temperature, stomatal conductance, terrestrial ecosystems, vegetation, warm season
- More intense, more frequent, and longer heat-waves are expected in the future due to global warming, which could have dramatic ecological impacts. Increasing nitrogen (N) availability and its dynamics will likely impact plant responses to heat stress and carbon (C) sequestration in terrestrial ecosystems. This field study examined the effects of N availability on plant response to heat-stress (HS) treatment in naturally-occurring vegetation. HS (5 d at ambient or 40.5 °C) and N treatments (±N) were applied to 16 1 m² plots in restored prairie vegetation dominated by Andropogon gerardii (warm-season C₄ grass) and Solidago canadensis (warm-season C₃ forb). Before, during, and after HS, air, canopy, and soil temperature were monitored; net CO₂ assimilation (Pn), quantum yield of photosystem II (ΦPSII), stomatal conductance (gs), and leaf water potential (Ψw) of the dominant species and soil respiration (Rsoil) of each plot were measured daily during HS. One week after HS, plots were harvested, and C% and N% were determined for rhizosphere and bulk soil, and above-ground tissue (green/senescent leaf, stem, and flower). Photosynthetic N-use efficiency (PNUE) and N resorption rate (NRR) were calculated. HS decreased Pn, gs, Ψw, and PNUE for both species, and +N treatment generally increased these variables (±HS), but often slowed their post-HS recovery. Aboveground biomass tended to decrease with HS in both species (and for green leaf mass in S. canadensis), but decrease with +N for A. gerardii and increase with +N for S. canadensis. For A. gerardii, HS tended to decrease N% in green tissues with +N, whereas in S. canadensis, HS increased N% in green leaves. Added N decreased NRR for A. gerardii and HS increased NRR for S. canadensis. These results suggest that heat waves, though transient, could have significant effects on plants, communities, and ecosystem N cycling, and N can influence the effect of heat waves.