Sapwood hydraulic recovery following thinning in lodgepole pine

Abstract

-Sapflow in lodgepole pine (Pinus contorta) was measured over the summer of 2002 to assess the impact of reduced sapwood permeability (k) after thinning on tree water use. Lodgepole pine in recently thinned (RT), thinned five years prior (5T), and un-thinned (C) stands were instrumented with thermal dissipation sap flow sensors. Daily water use varied considerably (10.8-0.04 L Day −1 ), but trees in the thinned areas used more water. Despite lower k and leaf specific hydraulic capacity (Q L ) in both RT and 5T trees, leaf related sapflow rates (Q l ) were generally higher than for C trees. RT trees appeared to experience water stress immediately following thinning in June, but by mid August maintained higher Q l and canopy stomatal conductance than both 5T and C trees. Allocation to radial growth following thinning appears to maintain sufficient sapwood area, and may offset damage to conducting tissues enabling lodgepole pine trees to tolerate periodic water stress.

Thinning effects on pine-spruce forest transpiration in central Sweden

“…Stand transpiration of the thinned plot exceeded that in the reference plot from 4 July, except for a few days in October 1999, though the difference was only significant during the drought periods. Similar results were found for lodgepole pine (P. contorta) where the leaf area based transpiration increased from 80 to 200% of the reference during the first 3 months after thinning (Reid et al, 2006). In a loblolly pine (P. taeda) thinning experiment, the 50 and 75% removals of BA resulted in reductions of 29 and 43%, respectively, in stand transpiration, compared to the reference, during the first wet growing season.…”

Short‐term selective thinning effects on hydraulic functionality of a temperate pine forest in eastern Canada

“…Previous studies in forests of Oak (Bréda et al, ) and Lodgepole pine (Reid et al . , ) have found that forest thinning results in greater soil moisture availability and can lead to a higher rate of transpiration among the remaining trees. Without a paired study of a thinned and unthinned plot at our forest, it was not possible to directly conclude that thinning allowed greater soil moisture.…”

“…Furthermore, the remaining trees are exposed to greater radiation and wind loading, which can lead to water stress (Reid et al . , ). Ma, Concilio, Oakley, North, and Chen () found that the net effect of thinning upon soil moisture was positive across six thinning treatments of mixed‐conifer stands, when basal area was reduced by 12.4–66.0%.…”

“…Tree removal impacts a forest's water balance by reducing canopy interception, which increases the proportion of precipitation reaching the forest floor for soil recharge (Qiu, Bell, Hobbs, & McComb, ; Slodicak, Novak, & Dusek, ). Intertree competition for water is decreased, as more water for transpiration ( Et ) is available per tree (Reid, Silins, & Lieffers, ). Conversely, as thinning intensity (i.e., proportion of basal area removed) increases, the associated reduction in canopy cover exposes the soil to higher temperature fluctuations, wind, and radiation (Son, Yoon, Young, & Kim, ), thus increasing soil water evaporation.…”

Evaluation of sap flow density of Acacia melanoxylon R. Br. (blackwood) trees in overstocked stands in north-western Iberian Peninsula

“…The upper probe was continuously heated to constant power by the Joule effect whereas the lower one was not heated, remaining at trunk temperature (reference probe). In spite of some technical weaknesses (Köstner et al 1998), this method is one of the most widely used in ecophysiological research (Delzon et al 2004;Ford et al 2004;Reid et al 2006). When sap moves upwards, the temperature difference between heated and unheated probes decreases.…”