Publication Date:
2014-04-15
Description:
A larch forest in eastern Siberia was characterized by the presence of two distinct stories, the overstory with a small leaf area index ( LAI ) and a dense understory with a relatively large LAI . To understand the roles of the over- and understory in forest-atmosphere water exchange, canopy conductance ( G c ), a critical parameter used in determining the energy and mass exchange, was calculated based on latent heat flux above the overstory and understory, measured separately. Results showed that G c for the overstory ( G co ) and understory ( G cu ) experienced different seasonal fluctuations. G co was smaller than G cu during periods of leaf expansion and leaf fall and showed an increasing trend until one month after the onset of leaf expansion. In contrast, a sharp decrease in G co was observed immediately before onset of leaf fall. Furthermore, G co was slightly larger than G cu during the fully foliated period. A simple model using solar radiation and vapor pressure deficit ( D ) as inputs successfully reproduced the G c in fully foliated periods with acceptable accuracy. Furthermore, both the understory and overstory in this study have a large reference G c ( G c at D = 1 KPa) than their counterparts of other boreal forests and would not be able to sustain a constant leaf-soil water potential difference as D increases. We speculated that this confers the forest with an advantage allowing it to be able to sustain carbon assimilation during large D days and thus provides for the survival of the ecosystem during the short growing season at this site. This article is protected by copyright. All rights reserved.
Print ISSN:
0885-6087
Electronic ISSN:
1099-1085
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
Permalink