Abstract
Pulse disturbances and habitat patch size can determine community composition independently or in concert, and may be particularly influential on small spatial scales for organisms with low mobility. In a field experiment, we investigated whether the effects of a pulsed disturbance that simulated a grazing event varied with habitat patch size. We focused on the short-term responses of multiple co-occurring emergent salt marsh arthropods with differing levels of mobility and dispersal potential. As part of a marsh restoration project, two types of emergent marsh structures were created: small circular mounds (0.5 m diameter) separated by several meters of aquatic habitat, and larger, elongated terraces (>50 m long). Study plots (0.25 m2) were established on both structures; in a subset of plots, we simulated a pulsed grazing disturbance event by clipping the aboveground tissue of emergent plants, primarily Spartina alterniflora. At the end of the two-month recovery period, Ischnodemus (Hemiptera: Blissidae) density was over 50% lower in disturbed treatments within both large (terrace) and small (mound) patches. Predatory spider treatment responses were similar to Ischnodemus responses, suggesting a trophic relationship between those two arthropod groups. Alternatively, spiders may have been directly affected by the loss of shelter in the disturbed plots. Prokelisia (Homoptera: Delphacidae), which are generally more mobile than Ischnodemus, were not affected by disturbance treatment or by patch size, suggesting the potential for rapid recolonization following disturbance. Larval stem borers decreased by an order of magnitude in disturbed plots, but only in the large patches. In general, the disturbance effects of vegetation removal on arthropod density and community composition were stronger than patch size effects, and there were few interactions between pulsed disturbance and patch size. Rather, emergent marsh arthropod responses to disturbance and habitat area treatments were linked to the dispersal potential and mobility of each individual taxon.
Highlights
Spatial and temporal heterogeneity are widely recognized as important determinants of community assembly e.g. [1]
In a study timed to correspond with critical emergence and reproductive periods and at an appropriately small spatial scale, we investigated the recovery of marsh arthropod densities following a pulse disturbance in the form of vegetation removal that simulated severe grazing [7,8,11,22,27,28]
Our investigation is the first to our knowledge that evaluated the interactions between disturbance and patch size on fauna in coastal marshes, with a focus on multiple co-occurring arthropod species with varying dispersal abilities and degrees of mobility
Summary
Spatial and temporal heterogeneity are widely recognized as important determinants of community assembly e.g. [1]. Spatial and temporal heterogeneity are widely recognized as important determinants of community assembly e.g. Unpredictable disturbances can be influential drivers of ecosystem structure e.g. Pulse disturbances, defined as short-term, discrete physical or chemical disruption to a habitat [2], are frequently a result of episodic grazing events e.g. Community-level responses to grazing disturbances usually vary among sites and species. Moderate grazing can maintain heterogeneity within vegetation assemblages, which is generally considered an ecosystem benefit [6]. In other cases, grazing episodes can greatly reduce plant biomass [7] or completely denude areas [8,9], which in turn decreases the abundance of associated fauna [10,11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
