Data from: A test of the effects of timing of a pulsed resource subsidy on stream ecosystems

Spatial resource subsidies can alter bottom-up and top-down forces of
community regulation across ecosystem boundaries. Most subsidies are
temporally variable, and recent theory has suggested that
consumer-resource dynamics can be stabilized if the peak timing of a
subsidy is desynchronized with that of prey productivity in the recipient
ecosystem. However, magnitude of consumer responses per se could depend on
the subsidy timing, which may be a critical component for community
dynamics and ecosystem processes. The aim of this study was to test (1)
whether a recipient consumer (cutthroat trout) responds differently to a
resource subsidy occurring early in its growing season than to a subsidy
occurring late in the season, and, if this is the case, (2) whether the
timing-dependent consumer response has cascading effects on communities
and ecosystem functions in streams. To test those hypotheses, we conducted
a large-scale field experiment, in which we directly manipulated the
timing of augmentation of the terrestrial invertebrates that enter stream
(i.e., peak timing of June-August vs. August-October), keeping constant
the total amounts of the invertebrates entered. We found large increases
in the individual growth rate and population biomass of the cutthroat
trout, in response to the early resource pulse, but not to the late pulse.
This timing-dependent consumer response cascaded down to reduce benthic
invertebrates and leaf break-down rate, and increased water nutrient
concentrations. Furthermore, the early resource pulse resulted in higher
maturity rate of the cutthroat trout in the following spring,
demonstrating the importance of the subsidy timing on long-term community
dynamics via the consumer's numerical response. Our results emphasize
the need to acknowledge timing-dependent consumer responses in
understanding the effects of subsidies on communities and ecosystem
processes. Elucidating the mechanisms by which consumers effectively
exploit pulsed subsidies is an important avenue to better understand
community dynamics in spatially coupled ecosystems.