Field work - snapshots in ecological time

Only other field biologists can appreciate and sympathize with this problem. Studies done in the field cannot control for all the variations in nature, in particular normal variations in weather patterns, and so each study is actually a snapshot in ecological time. The trouble is that we try to extrapolate from these snapshots, and sometimes that doesn't work. And even worse you worry that the effects of weather can overwhelm your treatments.

The effort involved in field work makes the situation even worse. The steadfast effort involved in maintaining long term field studies is beyond most of us. For this reason I really admire Deborah and David Clark whose quarter century survey of tropical forest tree growth in Costa Rica is laudable just for its longevity, its contribution to understanding changes that may accompany global warming notwithstanding (Tropical rain forest tree growth and atmospheric
carbon dynamics linked to interannual temperature variation during 1984–2000. D. A. Clark, S. C. Piper, C. D. Keeling, and D. B. Clark. 2003. PNAS 100:5852-5857.). If you haven't read this paper and want to see good evidence of changes that accompany increases in carbon dioxide and temperature, I recommend it.

In just the 3d year of our field study on the effects of hemiparasitic plants on the prairie community, and already the year to year variation seems destined to swamp any treatment effects. Last year our plots had so many hemiparasite seedlings that we wondered if eradication was a feasible treatment. They just kept sprouting, and we just kept weeding. Those seeds were the product of the 2006 season. The spring of 2008 was very different. It was cold and wet, and this affected the number and/or activities of bumblebees because seeds of our hemiparasite are scarce even though it flowered like crazy. Last year I could collect seeds in huge numbers, nearly 250,000 in about 20 mins. But this year a similar investment in collecting produced a very small volume in comparison. Guess we won't have so many seedlings to remove next year.

But that's not all. Last year produced a bumper crop of seeds, but so far they have not been germinating like last year at all. In 2007 we could find hundreds per square meter, and this year when we decide to monitor seedling mortality, seedlings are hard to find. It makes for easier eradication, but is messing with out demographic study.

That's just how field work goes. And it's why those rare long term studies are so valuable. If we monitored pollination, and seed production, and seed germination for 25 or so years, we would probably understand many of the variables. But when something gives you a significant result, well, dang, you just know it's important and real because everything was working against you getting any results at all.