I recently escaped from the heat of Tucson to the Catalina Mountains, five thousand feet above, and ecologically a world away. Our lab installed a set of new forest plots near the summit of Mt. Bigelow, and I was glad to help with the fieldwork.

Here we are carrying 100-meter measuring tapes up the slope. The forest is dominated by conifers, with an open understorey maintained by wildfire.

Brian taught John how to use a compass to sight bearing lines and lay out the plot on the landscape. It was an easy place to work – no snakes, no large obstacles, no tangle of vines anywhere.

The worst obstacles we encountered were a few large treefalls. Here Sean is tagging a sapling that was crushed by the larger tree but managed to survive, bending under the weight and sending out new branches into the light-filled gap.

All the trees received a metal tag – here Brian is marking a white fir, Abies concolor.

I was surprised how many species of trees there were on the mountaintop. I had expected only one or two – a pine and a fir – but we found a few types of each, as well as some other broadleaved species. It is a pleasure when a forest reveals its diversity, especially on a cool sunny morning when the hot desert lies far below and far out of mind.