Abstract
Abstract. Roots are key components of C cycling in terrestrial ecosystems and play an important role in the regulation of response of terrestrial ecosystems to global climate warming, which is predicted to occur with greater warming magnitudes at night than during daytime across different regions on the Earth. However, there has been no detailed study to investigate the effect of asymmetrical warming on root dynamics at the level of terrestrial ecosystems. To understand the effects of day and night warming on root lifespan in the semiarid temperate steppe in northern China, a field study with a full factorial design including control, day warming, night warming and continuous warming was conducted using modified rhizotron technique during three growing seasons in 2007–2009. Our results show that day, night and continuous warming had different effects on longevity of roots born in spring, summer and autumn, and that day warming significantly prolonged overall lifespan for the roots born in the three growing seasons, while night warning had no effect on overall lifespan. Day and night warming had different effects on root non-structural carbohydrate content, suggesting that allocation of photoassimilate may account for the differential responses of root lifespan to day and night warming. These results differ from other processes associated with ecosystems C cycle such as total ecosystem productivity, net ecosystem productivity and soil respiration. Our findings highlight that it is essential to incorporate the differential effects of day and night warming on root dynamics into simulating and predicting the responses and feedbacks of terrestrial ecosystems C cycling to global warming.
Highlights
Model projection and field experimental observations have demonstrated that global warming can have significant impact on the structure and function of terrestrial ecosystems in general, and carbon (C) cycle of terrestrial ecosystems in particular (Ciais et al, 2005; Luo, 2007; Piao et al, 2008; Wan et al, 2009; Bai et al, 2010)
We investigated the effects of day and night warming on root lifespan in semiarid temperate steppe in northern China
We addressed the following two questions: (1) Does root lifespan have a different response to day and night warming? (2) Is the response of root lifespan to day and night warming comparable to other C cycle process in ecosystems such as gross ecosystem productivity, net ecosystem productivity, ecosystem respiration and soil respiration?
Summary
Model projection and field experimental observations have demonstrated that global warming can have significant impact on the structure and function of terrestrial ecosystems in general, and carbon (C) cycle of terrestrial ecosystems in particular (Ciais et al, 2005; Luo, 2007; Piao et al, 2008; Wan et al, 2009; Bai et al, 2010). It has been reported that increased daily minimum and maximum temperatures have different effects on biomass and yield (Dhakhwa et al, 1998; Alward et al, 1999; Peng et al, 2004; Lobell, 2007; Lobell and OrtizMonasterio, 2007) as well as C cycling (Wan et al, 2009; Xia et al, 2009) in terrestrial ecosystems. The differential response of semi-arid steppe to day and night warning may result from stimulation of plant respiration by night warming, altering C allocation due to compensatory response of leaf photosynthesis
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