By Zack Holden, USFS Scientist, Northern Region, Missoula, MT
The high late winter snowpack, warm spring temperatures and a warm, yet humid summer could have important consequences for berry production of several shrub species this summer in the region that are beloved by both people and bears.
In a study of interannual production of Huckleberry and Serviceberry in western Montana and Northern Idaho, we used data from several SNOTEL stations in western Montana to examine relationships between climate and huckleberry and serviceberry fruit production across the Cabinet-Yaak Grizzly Bear recovery zone. Recall that from a previous post and refereed publication, we have correlated berry productivity to maximum snow water equivalent, springtime growing degree days during and diurnal temperature range in July. Using data collected on those factors, we derive a forecast for huckleberry and serviceberry in Northern Idaho and Northwestern Montana for 2012.
Climate observations: Climate data from two SNOTEL stations in northwestern Montana, Hawkins Lake (6450 ft el) and Banfield Mountain (5600 ft el) used in our previous study have been updated through 2012. This year both sites experienced above average (1989-2012) maximum snow water equivalent due to the wet spring and the high elevations of these stations. Despite elevated snowpack, spring temperatures were slightly above average. And finally, as mentioned in the previous post, the moist air mass in the region for month of July contributed to some of the lowest diurnal temperature ranges at the lower elevation Banfield Mountain station seen in the 24 year record at this site with only the exceptionally wet summer of 1993 having a lower diurnal temperature range.
Minimum temperature at Banfield Mountain was above normal for 27 of the 31 days in July. This was primarily a consequence of high atmospheric humidity in July, which limited outgoing longwave radiation, resulting in relatively high nighttime minimum temperatures.
Anecdotally, in the Ninemile valley where I live in western Montana, we have experienced almost no cold air drainage so far this year. This has been a stark contrast to the last two years, where we experienced strong inversions and cold air flows on most nights in July and August when on calm, clear nights.
So, what does this all mean for berry productivity this year? Past huckleberry production has been highest during cool springs with high diurnal temperature ranges. This relationship may reflect earlier than optimal flowering timing in years with warm springs and better berry development associated with higher vapor pressure deficits and clear skies.
Because of the warmer spring temperatures and moist air this July, our model predicts Huckleberry production of 1.20 berries per plot, 70% of the 23 year average measured berry index. The story for Serviceberry should be a bit different. The relatively high snowpack and near average spring temperatures bode well for berry production in this lower elevation species. Our model for serviceberry predicts an average of 205 berries per plot, 160% of the 22 year measured average.
Wayne Kasworm of the US Fish and Wildlife Service continues to monitor berry productivity across this region and it will be interesting to see how well our simple statistical models predict his field-based estimates of berry production this year. In addition to being useful for the efficiency and success at collecting berries, these model predictions may be helpful in understanding late summer and fall bear behavior in the region. For 2012, the models suggest that the huckleberry production may be lower than average, while the lower elevation serviceberry production should be relatively high. This could be a recipe for more bears moving into lower elevation valleys in search of food. Rural dwellers living in bear country may want to keep an eye out for bears and perhaps keep the zucchini handy.