Influence of drought intensity on the response of six woody karst species subjected to successive cycles of drought and rewatering

Abstract

Tolerance to the effects of drought and subsequent recovery after a rainfall appear to be critical for plants in the karst regions of southwestern China, which are characterized by frequent but temporary drought events. This study investigated the effects of drought intensity and repetition on photosynthesis and photoprotection mechanisms of karst plants during successive cycles of drought and subsequent recovery. Leaf water potential, gas exchange, chlorophyll fluorescence and several associated metabolic processes were studied in six plant species, including Pyracantha fortuneana (PF), Rosa cymosa (RC), Broussonetia papyrifera (BP), Cinnamomum bodinieri (CB), Platycarya longipes (PL) and Pteroceltis tatarinowii (PT) during three cycles of drought treatments at four different intensities. The four treatments were: well-watered, mild drought, moderate drought and severe drought, each followed by rewatering events. We found that limitations to CO(2) diffusion accounted for photosynthetic declines under mild and moderate drought treatments, while metabolic limitations dominated the response to severe drought. Repetition of drought did not intensify the impairment of photosynthetic metabolism regardless of drought intensity in the six species studied. Repetition of severe drought delayed the photosynthetic recoveries in PF, RC and CB after rewatering. Repetition of drought increased thermal dissipation in PF, CB and BP, as well as superoxide dismutase (EC 1.15.1.1) activity in RC and CB. Enhanced photosynthetic performance, measured as increased intrinsic water use efficiency, photosynthetic performance per unit of photosynthetic pigment, maintenance of high thermal dissipation and high ratios of carotenoids to chlorophylls, was observed during the rewatering periods. This enhanced photosynthetic performance allowed for the complete recovery of the six karst species from successive intermittent drought events.

Daily dynamics of photosynthetic parameters in beech population under periodical drought conditions

“…Therefore excess of precipitation in May and June as well as accumulated water in deeper layers of soil caused high and stabile photosynthesis in July. The reduction of photosynthesis caused by drought occurrence in vegetation period was certainly expected and previously confirmed in many studies [15][16][17]. Comparing the monthly averages of photosynthesis, it could be seen that the highest photosynthetic production was found in July, when the average temperature was about 25.5°C.…”

Eco-physiological adaptation of dominant tree species at two contrasting karst habitats in southwestern China

“…It may also be due to the ample precipitation found in the studied areas (annually around 1000 mm, mainly occurring during the growth season). Liu et al 11 did find that soil water stress (withholding water) affected photosynthesis and growth, and re-watering could remove or alleviate these effects in potted tree seedlings from almost the same karst area as in our study. However, the water stress treatment (withholding water) period in Liu et al's experiment was as long as 20 days.…”

Do successive climate extremes weaken the resistance of plant communities? An experimental study using plant assemblages

“…drought events are repeated, as reported in Liu et al (2010). Evidence that repeated events can impair resilience or resistance was also given by Zavalloni et al (2009), who observed that frequent mild drought events evoked by simulated climate warming enhanced stress levels in grasslands and lowered the resistance to a severe drought event.…”

“…Lack of sufficient resilience (capacity of an ecosystem to reach pre-disturbance performance levels) can thus compromise resistance (ability of an ecosystem to withstand displacement from control levels) to a subsequent event. The ability to recover not only is species-specific (Gallé et al, 2011;Liu et al, 2010) but is also influenced by competitive interactions, plant age or size (Lloret et al, 2004), the intensity of the past drought (Miyashita et al, 2005), and the amount of stored carbon reserves (Galiano et al, 2011). Importantly, recovery can be delayed when Published by Copernicus Publications on behalf of the European Geosciences Union.…”