Resource pulses in space and time: Introduction and overview.
Yang, Louie*,1, 1 University of California-Davis, Davis, CA, USA
ABSTRACT- In many systems, natural resource variability in space and time includes occasional episodes of ephemeral superabundance. The emerging concept of resource pulses seeks to identify general patterns among these diverse and extreme events of resource variation. The inherent variability of pulsed resource systems provides both an impetus and a challenge for synthesis. Resource pulses vary in magnitude, phenology, predictability, frequency, duration, character, spatial distribution, and spatial scale. Are there ecological generalizations within this diverse collection of uncommon and extraordinary events? Because of the diversity of pulsed systems in nature, the resource pulse concept necessarily describes a broad class of events, rather than a clearly delineated set. In this context, it may be less useful to ask whether a particular system is pulsed or not, than to ask how particular characteristics of pulsed resource dynamics influence natural systems. For example, the consequences of a highly ephemeral and patchy pulse of periodical cicada litter in the temperate spring are likely to be different from a less labile and widespread pulse of hurricane-caused foliage greenfall in the tropical wet season. Because both pulses represent sudden, large scale and large magnitude inputs of detrital matter, these events may also share some similar consequences. Are there predictable relationships between the characteristics of a resource pulse and its community effects? I suggest that some general patterns are emerging: for example, delayed numerical responses by trophic generalist consumers are a common consequence of several large magnitude and spatially widespread pulses. In many systems, the initial bottom-up effects of large, ephemeral resource pulses result in subsequent top-down effects during the period of resource decline. In systems characterized by spatially patchy pulses, mobile trophic specialists may be especially likely to show strong behavioral, as well as reproductive, responses. In many systems, aboveground resource pulses create secondary detrital pulses belowground. I suggest that further attempts to compare community dynamics across systems with common or different pulse characteristics may contribute greater synthesis to the study of resource pulses.
Key words: resource pulse, temporal variation, spatial variation, periodical cicadas
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