Lodgepole pine stocking standards need review; climate change poses problems say reports

With at least 80 per cent of the mature lodgepole pine in B.C. expected to be lost to the mountain pine beetle plague over the next few years, two recent studies show that juvenile pine plantations across the province are performing poorly and climate change is likely to make things worse.

The studies, presented at the Southern Interior Silviculture Committee (SISCO) spring conference in April, recommend a major review of current stocking standards for pine and the exercise of caution in the application of silviculture treatments, species selection and timber supply predictions. Although framed in the understated prose of bureaucratic and academic studies the two reports amount to a major shock to the assumptions that underly past and present silviculture practices and future timber supply estimates over a large part of B.C.

After noting that stocking standards have changed little in the past 20 years, in spite of the intentions of the Forest and Range Protection Act (FRPA) which meant to encourage new and innovative practices among licensees, the Forest Range Evaluation Program (FREP) Forest Stewarship Stocking Standards Report #19 drew particular attention to the condition of the province’s pine plantations. It identified that stands grown to current stocking standards appear prone to a high level of hard pine stem rust and poor formation. The simple inference from the this observation is that pine may be stocked at too low densities allowing, for instance, pathogens to migrate more freely between the trees and heavy snow and ice loads to damage limbs. The report identified the condition of the province’s pine plantations as a key concern given our reliance on these trees for future timber supply, their widespread use across the Interior at these densities and the apparent vulnerability of the young trees to destructive agents.

A yet to be published paper from the University of British Columbia has investigated the potential effects of climate change on juvenile pine plantations across B.C. It observed more than half the 15 to 30 year old trees in the extensive study were already suffering health effects due to bugs and various blights. Given what we understand about the destructive agents that affect young pines, including gall rust, snow and ice, mistletoe, needle cast, and insects; all these threats are likely to thrive and amplify as a result of climate change. The anticipated effects on forests due to global warming and the report’s projected consequences of destructive agents on lodgepole pine raise uncertainties about how many of today’s young stands will make it to productive maturity. Current stocking guidelines examine whether stands are well stocked and healthy at 12-15 years. But no mechanism is in place to monitor their ongoing condition through to maturity the study noted; the inference being our present free-growing threshold may not be a reliable indicator of the future of a stand of pine. The report also identified that some silviculture treatments such as spacing to too wide densities may actually contribute to the degeneration of pine plantations. The observations of the study indicate trends that could have a marked effect on future timber supply predictions as well as the general abundance and diversity of the forest estate well into the future. The study recommended these potential effects be considered in silviculture planning and future timber supply forecasts.

The two reports seem to confirm what has been widely observed anecdotally across the province regarding pine plantations. In response to the FREP report, government’s draft action plan refers to ongoing trials, working groups and monitoring. But ultimately any new principles and practices adopted, such as possibly doubling the planting density for pine, will be based on the pending silviculture framework resulting from the government’s Growing Opportunities discussion paper. The WSCA has been told by the ministry of forests and range executive that strategy will be released by next month.