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Physiological Differences in Rhododendron Calophytum Seedlings Regenerated in Mineral Soil or on Fallen Dead Wood of Different Decaying Stages

Dec 23, 2010

Fallen dead wood is the main component of coarse woody debris (CWD) and known to be highly important for forest ecosystems. The amount, structure and dynamics of fallen dead wood and other CWD in forests can influence the species composition, nutrient cycling, productivity and geomorphology for centuries and millennia.

Due to its unique properties, the fallen dead wood is a habitat for many species, including both autotrophs and heterotrophs. “Nurse logs” are a widely recognized example of fallen dead wood acting as a habitat for autotrophs. Indeed, in some environments, logs are the major site of tree seedling establishment.

Chengdu Institute of Biology Prof. LI Chunyang’s team designed an experiment to demonstrate that regeneration substrates may differ in water and nutrient availability, and that may lead to differences in physiological traits among seedlings. This assumption was tested by investigating the effects of different regeneration substrates (fallen dead wood and soil) on physiological traits in seedlings of Rhododendron calophytum Franch in a subalpine conifer forest, southwest China.

In this research, CIB researchers divided the seedlings into three groups according to their regeneration substrates: moderately decayed dead wood (DWm), severely decayed dead wood (DWs) and soil (S).

The results showed that there were significant differences in leaf mass per area (LMA), photosynthetic capacity, non-structural carbohydrate composition (NSC), leaf phosphorus (P) concentration, carbon isotope composition (delta C-13) and ultrastructural morphology, not only between the seedlings regenerated in soil and on dead wood, but also between the seedlings regenerated on dead wood of different decaying stages.

Overall, Prof.LI’s team proved that the photosynthetic capacity of the seedlings increased in the order of DWm < S < DWs, and the long-term water use efficiency (WUE) of the seedlings increased in the order of DWm < DWs < S. Different nutrient and water availability in the substrates might be responsible for these differences. It is suggested that severely decomposed fallen dead wood is the most suitable substrate for the regeneration of R. calophytum.

LI's study was supported by the Key Program of the National Natural Science Foundation of China (No. 30930075) and the Program of “Knowledge Innovation Engineering” of the Chinese Academy of Sciences (No. KSCX2-YW-N-064).The paper has been published on line in Plant and Soil  in December 2010.

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