Global warming might seem like a botanical boon. After all, milder temperatures and more carbon dioxide and nitrogen should feed flora. But a ten-year study has found that any initial positive effect on plant growth from climate change may soon disappear. The report is in the journal Nature Climate Change. [Sarah C. Elmendorf et al.,"Plot-scale evidence of tundra vegetation change and links to recent summer warming"]
Researchers transplanted vegetation from four grassland ecosystems to lower, warmer elevations. They also modified the precipitation at the transplant sites based on altered rainfall estimates. For the first year, the plants did great, producing more biomass and churning out more oxygen for us. But their productivity went down for the rest of the decade.
What happened? Warming did speed up the nitrogen cycle, which should have increased nitrogen’s availability as plant fertilizer. But a lot of the nitrogen left the soil through run-off or uptake into the atmosphere. In addition, productive native plants began to lose out to species that thrive at higher temperatures, but are less productive than the natives. Warmer temperatures may spur immediate growth, but in the long term, we can’t expect plants to like it hot.
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