It’s the last day of ESA 2012! The first talk for my day was by Sarah Mincey, investigating social factors that influence tree species diversity and basal area in Bloomington, Indiana. Species diversity increased with the diversity of the distribution of size classes, age of the land parcel, and resident age. It decreased with the degree of rule compliance, with the local laws dictating when trees are to be removed rather than when they are to be retained. The analysis of basal area was based on total basal area per land parcel rather than basal area per area of land, so the results are a little hard to interpret. I’ll leave it at that.
Caroline Wilson investigated correlates of night-flying insect biomass in urban areas. There were positive associations with air temperature and the number of trees, and negative associations with ambient light, local road density and distance to water. Differences between urban landform were apparent, with highest insect biomass in riparian and remnant areas, and lowest biomass in industrial areas. It was nice to see the effect sizes presented clearly rather than ignoring confidence intervals! Bat activity, as measured by the number of bat calls recorded, was higher in areas with greater insect biomass. Whether that reflects greater bat density or simply greater call frequency is unclear.
A long walk and a short break led to Carl Boettiger. In a lively presentation, he compared thinking about problems using decision theory and resilience thinking. He showed that the ideas of resilience thinking can in fact be incorporated into decision theory by modifying objectives, the state space and cost functions. He used harvesting a fishery as an example.
I had another long walk and short break to get to Brian Enquist’s talk on quantifying the distribution of commonness and rarity of plant species at continental scales (across the Americas), with an aim of assessing some prominent theories for explaining diversity. Quantifying aspects of species diversity is biased because of problems with inconsistent and unreliable taxonomy, bad data, and sampling heterogeneity. However, despite these difficulties, it seems that the majority of species are rare. Incidentally, this is something previously found in different systems by Kevin Gaston. Perhaps the most interesting aspect of this talk from my perspective was the impressively large database that has been developed, which should set a platform for a substantial body of future research
There was one final long walk and short break – I had lots of exercise for the last session of the conference! The destination was the fire session in which Luke Kelly was presenting. Luke and colleagues (including me!) built models of how birds, reptiles and mammals responded to time since fire in mallee vegetation, and then examined which distribution of age classes maximized the geometric mean abundance of these species in the landscape. The optimal age class distribution across these species was one with a relatively even mix of mid (10-35 years since fire) and old vegetation (>35 years since fire). Further work will include dynamic optimization, other aspects of the fire regime, and other vegetation types.
My last talk at the conference was by Morris Johnson, who showed how thinning of forest stands reduce the severity of fires, yet the effect of untreated areas extended several hundred metres into the treated stands. This has implications for how large treated areas need to be.
Well, that is all from ESA2012. Thanks to the organizers and the participants, particularly all the tweeps and bloggers! It has been a very interesting conference, but I’m looking forward to being home.