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C-3 and C-4 plant responses to increased temperatures and altered monsoonal precipitation in a cool desert on the Colorado Plateau, USA

机译:在美国科罗拉多高原的一个凉爽沙漠中,C-3和C-4植物对温度升高和季风降水变化的反应

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Dryland ecosystems represent > 40 % of the terrestrial landscape and support over two billion people; consequently, it is vital to understand how drylands will respond to climatic change. However, while arid and semiarid ecosystems commonly experience extremely hot and dry conditions, our understanding of how further temperature increases or altered precipitation will affect dryland plant communities remains poor. To address this question, we assessed plant physiology and growth at a long-term (7-year) climate experiment on the Colorado Plateau, USA, where the community is a mix of shallow-rooted C-3 and C-4 grasses and deep-rooted C-4 shrubs. The experiment maintained elevated-temperature treatments (+2 or +4 A degrees C) in combination with altered summer monsoonal precipitation (+small frequent precipitation events or +large infrequent events). Increased temperature negatively affected photosynthesis and growth of the C-3 and C-4 grasses, but effects varied in their timing: +4 A degrees C treatments negatively affected the C-3 grass early in the growing season of both years, while the negative effects of temperature on the C-4 grass were seen in the +2 and +4 A degrees C treatments, but only during the late growing season of the drier year. Increased summer precipitation did not affect photosynthesis or biomass for any species, either in the year the precipitation was applied or the following year. Although previous research suggests dryland plants, and C-4 grasses in particular, may respond positively to elevated temperature, our findings from a cool desert show marked declines in C-3 and C-4 photosynthesis and growth, with temperature effects dependent on the degree of warming and growing-season precipitation.
机译:旱地生态系统占陆地景观的40%以上,为超过20亿人口提供支持;因此,了解干旱地区如何应对气候变化至关重要。然而,尽管干旱和半干旱的生态系统通常会经历极度炎热和干燥的状况,但我们对温度进一步升高或降水变化将如何影响旱地植物群落的理解仍然很薄。为了解决这个问题,我们在美国科罗拉多高原进行了长期(7年)气候实验,评估了植物的生理和生长情况,该群落由浅根的C-3和C-4草和深根的C-4灌木。该实验保持了高温处理(+2或+4 A摄氏度),并改变了夏季季风性降水(+较小的频繁降水事件或+较大的不频繁事件)。温度升高对C-3和C-4草的光合作用和生长产生负面影响,但影响的时间不同:+4 A摄氏度的处理在这两个生长季节的早期对C-3草产生负面影响,而对在+2和+4 A℃处理中,可以看到温度对C-4草的影响,但仅在较干燥的生长后期才出现。夏季降水增加对任何物种的光合作用或生物量都没有影响,无论是在应用降水的那一年还是在第二年。尽管以前的研究表明干旱地区的植物,尤其是C-4草可能对高温产生积极响应,但我们在凉爽沙漠中的发现显示C-3和C-4光合作用和生长显着下降,温度影响取决于程度和生长季节降水的变化。

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