Temporal scale of field experiments in benthic ecology

The issue of scale in ecology is all-pervasive, with recognition that most ecological questions are scale dependent. Scaling up has become part of the lexicon of experimental ecology, and in marine benthic systems has resulted in numerous advances. While it is clear that manipulative experiments in benthic systems have been conducted over increasing spatial scales, it is less clear whether the notion of scaling up has been applied to temporal scales. Here, we examine the temporal scale at which experiments have been undertaken before reviewing longer-term studies to examine the insights gained from extending the duration of observation following perturbation. Field experiments which examined population/community responses to perturbations and studies which monitored the consequences of natural disturbances were identified over the period 1980 to 2013. The median length of study was 10 mo, and only 12% of studies were carried out over more than 3 yr. Neither the median study length nor the proportion of studies longer than 2 or 3 yr showed a trend over the 33 yr. Review of experiments with a duration of 3 yr or more revealed numerous benefits of a long-term approach. Some of these were unexpected, but others were predictable based on life-history traits of dominant organisms, slow successional patterns or response variables related to longer-term community-level responses, such as stability. The review suggests that modest investment in resources to extend the duration of experiments can bring substantial benefits; hence, consideration of experimental duration should be one of the primary decisions in planning field experiments.