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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGEMENT OF AGRICULTURAL AND NATURAL RESOURCE SYSTEMS TO REDUCE ATMOSPHERIC EMISSIONS AND INCREASE RESILIENCE TO CLIMATE CHANGE Title: Effects of thinning on transpiration by riparian buffer trees in response to advection and solar radiation

item Hernandez-Santana, Virginia -
item Asbjornsen, Heidi -
item Sauer, Thomas
item Isenhart, Tom -
item Schilling, Keith -
item Schultz, Richard -

Submitted to: International Workshop on Sap Flow
Publication Type: Abstract Only
Publication Acceptance Date: February 17, 2011
Publication Date: N/A

Technical Abstract: Advective energy occurring in edge environments may increase tree water use (e.g., latent heat loss, LE > net radiation, Rn). In humid agricultural landscapes, advection-enhanced transpiration in riparian buffers may provide hydrologic regulation and flood control benefits; however, research in humid environments is lacking. The objectives of this study were to determine how water use by trees growing in a riparian buffer in central Iowa is influenced by 1) advective energy, 2) tree position, and 3) thinning (40% LAI reduction). We measured meteorological variables and sap flux density from July to Sept. in 16 trees (2009) and 12 trees (2010) in one thinned plot (TP, treated in Aug 2010) and one control plot (UP). Sapflow rates (F) for trees growing at the edge exposed to prevailing winds were 39% greater than interior trees (maximum F 3*10-7 m3 s-1). The difference in F between edge and interior trees was attributed to the advective energy at the buffer edge (LE/Rn>1 in 8 out of 25 days and higher than for inner trees, p<0.001). After thinning, maximum F was greater in TP compared to UP, explained primarily by solar radiation (R2=0.7, p<0.05), since meteorological conditions were not optimal for advection. However, the LAI reduction counteracted the increase in whole tree F, such that stand transpiration would be greater for the TP with the original LAI (1.6 mm day-1) compared to the TP with the LAI reduction due to the thinning (0.9 mm day-1). Future measurements will assess possible interactions between long-term changes in LAI, advective energy, and transpiration.

Last Modified: 8/28/2016
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