Effects of sap velocity on the daytime increase of stem CO2 efflux from stems of Schima superba trees |
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Authors: | L W Zhu P Zhao X A Cai X P Zeng G Y Ni J Y Zhang L L Zou T T Mei and M H Yu |
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Institution: | (1) South China Institute of Botany, Chinese Academy of Sciences, Guangzhou, 510650, People’s Republic of China; |
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Abstract: | Stem CO2 efflux (E
s) has been estimated from a temperature-related equation, but sap flux often affects measurements of E
s, which leads to misunderstanding real stem respiration. In order to observe the relationship between E
s and stem temperature and to analyze the effect of sap velocity on E
s, stem temperature, E
s and sap flux were measured from a subtropical Schima superba plantation in South China on three trees for consecutive 3 days in July and October 2009. Stem temperature, E
s and sap velocity were significantly higher in July than in October. Stem temperature could explain 17–41 and 54–75% variations
of E
s in July and October, respectively. A negative relationship between E
s and stem temperature was found during 1800–2300 hours in July. The daytime E
s was 9.2, 4.3 and 2.4% higher than the predicted for three trees in July, and this occurred only on Tree 1 in October. Sap
velocity was positively correlated with E
s for three trees in July, and the increase of E
s with the increase of sap velocity was only observed on Tree 1 in October. These results demonstrated that the occurrence
of sap flux could account for the increase of daytime E
s, and the effect of sap velocity on E
s varied with the seasons from the S. superba stem. |
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Keywords: | |
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