Investigation of underlying causes for early conelet abortion in lodgepole pine seed orchards in Alberta

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Lodgepole pine is one of the most economically important tree species in Western Canada, contributing the second highest harvest volume after spruce in Alberta, where it is also the provincial tree. At the same time, lodgepole pine is currently under severe pressure from changes in climate which has facilitated the large-scale infestations of mountain pine beetles and subsequent early death of thousands of hectares of trees. Alberta has five regional tree improvement programs for lodgepole pine which are designed to provide locally adapted, faster growing lodgepole pine seedlings for reforestation after harvesting. However, some of the lodgepole pine seed orchards associated with these tree improvement programs, are failing to meet their seed yield targets by as much as 80%. Ensuring there is enough seed for reforestation from these programs is a major concern. Loss of newly developing female cones (called conelet abortion) has been identified as a major contributor to this low seed yield. Preliminary research has revealed that the loss of conelets occurs early in the 2-year reproductive cycle and appears to be influenced both by genetics and site conditions where the seed orchards are located. Moreover, grafted trees seem to show higher conelet abortion rates that trees originating from seeds. However, the underlying causes for this abortion remain unclear. We propose to use a combined approach, consisting of remote-sensing, in-situ monitoring of environmental conditions, both at canopy height and within the root-zone, and physiological measurements to determine the mechanisms underlying the observed conelet abortion. We also intend to develop recommendations that should allow orchard managers to reliably identify trees likely to suffer high abortion rates, allowing seed yield targets to be met.