Temporal variability within disturbance events regulates their effects on natural communities

Abstract

Disturbances are processes inherently variable in time and space. This variability comprises a key determinant of ecosystem responses to disturbance. Temporal patterns can, however, vary significantly both among and within individual disturbance events. While recent research has demonstrated an importance of the former, studies on the effects of variability within perturbations have consistently confounded temporal variability with other disturbance attributes (e.g. overall intensity or duration). We established a field experiment to test explicitly the hypothesis that the temporal pattern within perturbations can drive ecosystem responses independently of other disturbance traits. We examined the effects of two disturbance regimes comprising sediment pulses of contrasting temporal pattern (constant and temporally variable intensities) on the benthic invertebrate assemblage of a headwater stream. The overall intensity, duration, timing and frequency of the perturbations were, however, identical. Invertebrates drifting during the temporally variable pulses were more abundant and differed in taxonomic and trophic structure than those exposed to constant perturbations. Moreover, whereas temporal patterns of disturbance events had no immediate effect on benthic invertebrate assemblages in situ, assemblages exposed to the constant perturbations took longer to recover from sediment disturbances than those exposed to temporally variable perturbations. Our results demonstrate that variability in the temporal pattern of intensity within individual perturbations can regulate, independently of other disturbance attributes, the extent and type of ecosystem responses to, and recovery from, disturbances. Effective environmental management and policy therefore necessitate the explicit quantification of temporal patterns of intensity both within and among perturbations.

Interplay of experimental harvesting and climate-related disturbance on benthic assemblages of rocky seashores

“…The application of several disturbance events clustered in shorter periods of time could overwhelm such buffering ability, creating patches of available resources, mainly space, that allowed the colonization by organisms otherwise excluded as inferior competitors per se. This could logically explain the larger temporal heterogeneity in the structure of assemblages when subjected to the irregular disturbance treatment, in general in agreement with previous findings on freshwater benthic assemblages under constant vs. temporally variable sediment disturbance (Molinos & Donohue 2011). Such a mechanism has also been documented in terrestrial systems through a progressive reduction of the ability of organisms to resist or recover from increasingly stressful disturbance, leading to a destabilization of assemblages and to an increased variability of the system (Collins 2000, Fraterrigo & Rusak 2008.…”

“…However, climate change also implies alterations in temporal patterns of meteorological events, including their timing, frequency and variance (Muller & Stone 2001, Gutschick & BassiriRad 2003. While the traditional approach for experimentally examining the effects of temporal variability of disturbance focused on manipulating the frequency of events (Collins 2000, McCabe & Gotelli 2000, the consideration that the temporal variation and the total intensity of disturbance applied over the period of the experiment can be confounded (Benedetti-Cecchi 2003) led to temporal variance of disturbance being taken into account (Bertocci et al 2005, Benedetti-Cecchi et al 2006, Vaselli et al 2008, Molinos & Donohue 2011, Buckley & Kingsolver 2012. Few studies, however, specifically examined how variable regimes of disturbance can affect temporal fluctuations of assemblages (e.g.…”

Local versus regional intraspecific variability in regeneration traits

“…However, local processes like disturbances, species interaction and heterogeneity in resource availability generate trait variability at a local scale. This local trait variability determines the species response to biotic and abiotic Wlters, which in turn has implications on the population dynamics and the community structure (Prinzing et al 2008;Jung et al 2010;Pausas and Verdú 2010;Bolnick et al 2011;García Molinos and Donohue 2011). While there is an increasing bulk of information highlighting the important contribution of intraspeciWc variability to the overall trait variability (Boege and Dirzo 2004;Lecerf and Chauvet 2008;Cianciaruso et al 2009;Albert et al 2010), there is little information on the relative role of local versus regional processes in generating this variability.…”

Dominant Fish and Macroinvertebrate Response to Flow Changes of the Geum River in Korea

“…The change of the flow regime due to hydropeaking affected the aquatic ecosystems, in many previous reports, extending with a reach of hundreds of kilometers downstream [1,7,8]. That is, hydropeaking changes physical habitat variables, as well as the intensity, duration, timing, and frequency of the perturbations affect the habitat abundance (or availability) and diversity patterns [9][10][11]. Physical habitat simulations have been successfully used to solve various relevant problems.…”