Processes of understory seedling recruitment 1 year after prescribed fire in an Arizona ponderosa pine community

Abstract

We monitored seed rain, buried seed germination, and vegetative reproduction to determine the processes of understory species seedling recruitment after prescribed fire in an Arizona ponderosa pine (Pinus ponderosa) stand. Stands were burned with both backing and strip head fires. These fires were restricted to surface fuels, with fuel consumption ranging from 25 to 95% and total heat yield ranging from 1 600 to 42 082 kJ/m². We identified seed rain from surviving plants the year after burning, as well as residual seeds surviving the burn, as being the major contributors of propagules for recruitment of herbaceous seedlings. Several seedlings were present in both the early-spring and late-fall inventory. We hypothesize that the early recruitment was mainly due to germination of seeds immediately after burning or early the next spring and that seed rain from surviving plants provided propagules for seedlings detected in the late-fall inventory. The pattern of seed rain reflected the phenologies of cool-season and warm-season plants. Buried seed populations were not found to be an important source of new seedlings. Ceanothus fendleri was the only species to sprout prolifically after burning.