Green Hills at Dusk
I was up at our Green Hills Preserve last evening as the sun was setting. Denise and Owen hiked around while I added our Conservation Area signs to the many bluebird boxes that Force of Nature volunteer Jim Moffett had put up. I heard my first wood thrush of the year calling.
Green Hills is ahead of Crow’s Nest Preserve in the advancement of spring. I noticed on my last visit that the tree blooms were budding earlier. In addition to the wood thrush (which I have not heard at Crow’s Nest yet) the autumn olive (an invasive shrub) is starting to bloom at Green Hills (and there is quite a lot of it), but not at Crow’s Nest—where there is still some despite years of work to control it.
Green Hills is 15 miles north and west of Crow’s Nest, so in my mind I think it would be colder (north, and further from the urban heat island of Philadelphia). But there is also a smaller heat effect from the city of Reading, near Green Hills. But a quick check on Google Earth confirms a difference in altitude and topography that are likely a far greater influence. Crow’s Nest is in a valley that ranges from 430 – 600 feet in elevation surrounded by hills in French Creek State Park that rise to more than 900 feet above sea level. Green Hills is in open, rolling terrain that is up to 450′ in elevation at its highest. So cold air sinks and settles in our valley at Crow’s Nest but drains away from Green Hills. And if you don’t think there’s a temperature difference between 450 and 900′ in elevation, stop by sometime in winter when there is freezing rain in our valley and ice sticking to the trees in the hills above.
Posted by Daniel Barringer on May 1, 2013.