Concerns for water quantity, water quality and fisheries resources have raised questions about the impact of MPB on annual water yield and peak flows. Answers to these questions are urgently needed as BC moves towards a large scale timber harvest salvaging strategy that is supposed to minimize economic losses while reducing environmental impacts (Snetsinger 2005). There exists a great deal of literature about the effects of healthy forest and conventional timber harvesting on streamflows from process stand level (e.g. Troendle and Reuss 1997, Winkler et al. 2005), empirical paired watershed (e.g. Stednick 1996, Troendle et al. 2001) and watershed scale modelling (e.g. Schnorbus and Alila 2004, Whitaker et al. 2002, Bowling et al. 2000, Waichler et al. 2005) studies. In the pine forest of BC, the winter snow accumulation and spring melt drive the hydrologic regime, which in turn is controlled by processes such as canopy interception, evaporation, tree transpiration, melt and groundwater storage. The effects of beetle-kill on these processes, with or without salvage harvesting, is largely unknown and may or may not mimic that of conventional timber harvesting (Uunilla et al. 2006). Since dead trees do not transpire, the effects of beetle-killed and newly harvested stands on transpiration processes may be the same; however the effects of beetle-kill on interception and melt processes may be different. After beetle attack, trees retain their needles for 2-4 yrs and retain branches and stay standing for many more years. Beetle-killed stands may retain live understorey vegetation and are not necessarily impacted by road developments, unlike conventional harvested stands. Only few paired watershed studies on the effect of insect infestation (Mitchell and Love 1973, Bethlahmy 1975, Potts 1984) and two others on the effect of salvage harvesting (Cheng 1989 and Moore and Scott 2005) on streamflow characteristics have been reported in the literature. However, the level of disturbance reported in these studies does not exceed 35% of the whole watershed and therefore are not large enough to be of relevance to the larger scale disturbance questions raised in this study. Only one infested forest stand level investigation had been reported in the literature from the Rocky Mountain of Colorado by Schmid et al. (1991). Their findings indicated that net precipitation under recently infested stands (few years after infestation before trees loosing their needles, so called brown attack) is not significantly different from its respective controls. The authors explained the possible reasons for these findings by the needle retentions of beetle-killed trees and the presence of a young and live understorey that has the potential for mitigating the effects of the beetle-kill. They also suggested that analogues between conventional partial cuts of healthy and beetle-killed forests may be valid, but only in even-aged stands (i.e. without significant understorey) and only after beetle-killed trees have begun to lose their needles. It is tempting to draw analogues, albeit in an opportunistic ways, between infested (defoliated) conifer stands and healthy (leafless) deciduous stands to take advantage of the wealth of knowledge in the literature on stand level processes in deciduous forest (e.g. Hardy et al. 1998). However, while the forest canopy architecture (tree elements and gaps) of the two forest stands may lead to similar interception and melt processes they would certainly be different in transpiration and its subsequent effects on soil moisture. Over the last two years, several projects have been initiated to quantify the differences in processes between a clearcut and infested brown and grey (i.e. after the infested stands lose their needles) forest stands (e.g. MPBI 8.26 on soil moisture & MPBI 8.39 on snow processes). The challenging question related to these types of studies is how this stand level knowledge translates to an operationally use ...
Bewley, D.M., Alila, Younes; Teti, Patrick; Leech, Susan; Hafer, Mark. 2008. Peak flow and water yield responses to mountain pine beetle infested and salvage logged watersheds in the Kootenays. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2008MR191
Topic: FLNRORD Research Program
Keywords: Forest, Investment, Account, (FIA), British, Columbia
To copy the URL of a document, Right Click on the document title, select "Copy Shortcut/Copy Link", then paste as needed. Only documents available to the public have this feature enabled.