Seed Bank Changes with Time-Since-Fire In Florida Rosemary Scrub

The soil seed bank plays a central role in the regeneration of obligate seeding species in fire-prone habitats. We evaluated how seed density and species composition changed with time-since-fire in the Florida, USA, rosemary scrub community. Because fire affects habitat availability and plant demographic variation, we predicted that soil seed density would be low in recently burned and long-unburned stands and high at intermediate time-since-fire. Seed bank soil samples were collected from a chronosequence of time-since-fire composited from two trials conducted in 1992-1993 and 2008-2009: two sites each of 3, 6, 10, and 24 years post-fire, and 3 long-unburned (similar to 67 years) sites. The seedling emergence method was used to determine species composition of the seed bank. Across all time-since-fire age classes, herbaceous species dominated the seed bank, while long-lived subshrubs and shrubs were present in low densities. Seed banks from sites three years post-fire were distinct from the other sites. When species were sorted as functional groups, seed density was related with time-since-fire for subshrubs and ruderal herbs, but not for scrub herbs and graminoids. Subshrubs and ruderal herbs had highest seed densities in recently burned stands. Seed densities of Florida rosemary (Ceratiola ericoides Michx.) (the major obligate seeding shrub in this community) were associated with time-since-fire and showed highest densities at recently burned and long-unburned sites. The seed banks of two scrub herb species, paper nailwort (Paronychia chartacea Fernald) and nodding pinweed (Lechea cernua Small), were associated with time-since-fire. They reached peaks in density in the first ten years post-fire, corresponding with similar changes in their aboveground abundances with time-since-fire. Soil seed densities of several species and functional groups were associated with time-since-fire, but timing of peak seed density varied depending on species\u27 life span and age of reproductive maturity

Metacommunity Dynamics Over 16 Years In A Pyrogenic Shrubland

This article offers one potential response to Yancey\u27s (1999) call for a fourth wave of writing assessment able to capture writing development in all of its complexity. Based on an ecological perspective of literate development that situates students\u27 growth as writers across multiple engagements with writing, including those outside of school, the ecological model of writing assessment described in this article seeks to provide students, teachers, departments, and institutions with fuller, richer accounts of the breadth of students\u27 literate experiences and how those experiences impact their abilities to accomplish academic tasks throughout the undergraduate years and beyond. Using the University of Central Florida\u27s recent efforts to develop and employ an ecological assessment model as one of many potential examples, this article argues that an ecological model of writing assessment enables institutions to make visible the multiple sites where writing takes place, strengthen the affordances for student learning and writing in these sites, and also respond effectively to the multiple stakeholders invested in understanding writing development, what it involves, and how it might best be supported. © 2012 Elsevier Ltd