Disturbance structures canopy and understory productivity along an environmental gradient.

Disturbances often disproportionately impact different vegetation layers in forests and other vertically stratified ecosystems, shaping community structure and ecosystem function. However, disturbance-driven changes may be mediated by environmental conditions that affect habitat quality and species interactions. In a decade-long field experiment, we tested how kelp forest net primary productivity (NPP) responds to repeated canopy loss along a gradient in grazing and substrate suitability.

Improved estimates of net primary production, growth, and standing crop of Macrocystis pyrifera in Southern California.

The giant kelp Macrocystis pyrifera forms subtidal forests on shallow reefs in temperate regions of the world. It is one of the fastest-growing multicellular autotrophs on Earth and its high productivity supports diverse marine food webs. In 2008, we published a method for estimating biomass and net primary production (NPP) of giant kelp along with five years of data, to provide a more integrated measure of NPP than those yielded by previous methods.

Patterns and controls of the dynamics of net primary production by understory macroalgal assemblages in giant kelp forests.

Macroalgae are important primary producers in many subtidal habitats, yet little information exists on the temporal and spatial dynamics of net primary production (NPP) by entire subtidal assemblages. This knowledge gap reflects the logistical challenges in measuring NPP of diverse macroalgal assemblages in shallow marine habitats. Here, we couple a simple primary production model with nondestructive estimates of taxon-specific biomass on subtidal reefs off Santa Barbara, California to produce a 4-year time series of net primary production by intact assemblages of understory macroalgae in giant kelp forests off Santa Barbara, California, USA.