Responses of arid land plants to simulated changes in rain frequency and intensity.
Jankju Borzelabad, Mohammad1, 1 Yazd University, Yazd, Iran
ABSTRACT- In communities of arid land areas various plant growth forms coexist, which may respond differently to a shift in the dominant rainfall pattern. With the same rainfall input, annuals establishment are expected to promote by lighter and more frequent rainfall events, whereas perennials may be advantaged under heavier and low frequent rainfall patterns. Furthermore, a shift in plant-plant interaction is expected as a result of changes in rainfall intensity and frequency. Simulated rainfall events were applied on an arid rangeland. A total rainfall of 40 mm was delivered as 4 low volume-High Frequency (HF) or as 2 high volume-Low Frequency (LF) rain events. Unexpectedly both annuals and perennial plants responded similarly to the watering pulses. Total density of annuals and current year growth of the dominant perennial species (Artemisia aucheri) both were significantly higher where water had been applied as low frequent and heavy rains (LF) than under more frequent and lighter rains (HF). These results also suggest more significant influence of rain volume than rain frequency on plant performances. On the other hands different responses were found for effects of simulated rains on interaction between various growth forms. Whereas interaction between annuals and perennials shifted from facilitation (in control) into no significant relationship (under LF), interaction between perennial plants changed from none (in control) towards competitive relationships (under LF). These results suggest changes in plant strategy from stress tolerant to competitive, as a result of increasing "effective rainfalls" in arid lands.
Key words: arid land ecology, water pulses, competition, plant strategy
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