Dog Day Afternoon

On a hot, early September afternoon, in Iowa’s drought of 2012, eleven students in Grinnell’s BIO 368 (Ecology) class gathered infrared thermometers and GPS receivers and set out to characterize the thermal environment of the Grinnell College campus (above left). Each of three teams of four students devised their own sampling scheme for an assigned area of campus—south, central, or north.  We used interpolation in ArcMAP to transform the raw data—which consisted of point estimates of surface temperature, air temperature, and relative humidity—into contour maps (e.g., surface temperature, above right).

As I expected (but didn’t tell the students), the outcome revealed a range of sampling strategies. The “southern group” traveled from west to east, starting out with ambitions of sampling the whole area in a dense, regular grid. With enough time, this scheme would have been comprehensive and representative.  Time ran short, however, compelling them to abandon those plans. At the (SE) end, they collected data in a less dense, haphazard fashion. The sample points of the “central group” were not in a formal grid and not quite haphazard, but they were broadly and more or less regularly distributed throughout their area. “The northern group” took sample points in lines along walkways and, especially, along the peripheries and of their assigned area, as if they were looking for a way out of a box.

Had we been a social psychology (or primate behavior) course, we might have used this “finding” to analyze how group dynamics led to contrasting decisions. Being an ecology class, we used the experience to identify best-practice environmental sampling approaches. Then, acknowledging the limitations of the data set, we asked what the preliminary findings could tell us about the thermal properties of contrasting surfaces and of different campus areas.

Some highlights

·      In that summer’s severe drought, exposed, un-irrigated lawns near the east-campus dorms were almost as hot as pavement. “Weedy” areas of those lawns, however, were 5-10 degrees Celsius cooler than adjacent turfrass. It is likely that the relatively deep-rooted weeds (such as prostrate knotweed, Polygonum aviculare) had access to soil water (and in that way, created evaporative cooling by transpiration) that shallow-rooted turf grasses did not.

·      Paved areas south of the Bear Athletic Center were the hottest place on campus. Warmth that might have been welcome on chilly winter days was barely bearable.

·      With the exception of the east campus lawns, vegetated areas were distinctly cool. Irrigated athletic fields—presumably, again, because of evaporative cooling—and areas under dense tree cover (e.g., west of the south campus dorms) were coolest.

Temperature affects all the organisms that share Grinnell College, including us. For the sake of our summer comfort, does this pilot study mean that we ought to irrigate the whole campus? Cover all the open fields with shade trees? Let weeds take over the lawns? Re-vegetate the parking lots? Respectively: (1) no, that would be an expensive, environmentally unsustainable use of water; (2) no, we need some open lawns for recreation and views; (3) no, we wouldn’t want those “weeds,” anyway, but maybe we should consider replacing some areas of conventional turf grass with deeper-rooted, native alternatives; and (4) no, but maybe we should be wary about installing more parking lots. In any event, we should think about the kind of habitat we create when we put together a college campus.

BIO 368, 2012: Leslie Bean (class of 2013), Cory Brooke-DeBock (2012), Brendan Byrne (2014), Tayler Chicoine (204), Erik Dixon-Anderson (2014), Savannah Duby (2013), Carla Eckland (2013), Griffin Lentsch (2013), Kaya Matson (2014), Pavlo Nikolaidis (2014), and Jordan Young (2014)