Effect of fire on recruitment of two dominant perennial grasses with different palatability from semi-arid grasslands of NW Patagonia (Argentina)

Abstract

Fire is a non-selective disturbance that impacts equally plant species that could be selected differentially by livestock. Post-fire recruitment dynamics is an important ecological process that has been barely studied in Patagonian grass species. This work analyzes the effect of fire on seed germination, seedling growth, and survival of Pappostipa speciosa (ex Stipa speciosa) and Festuca pallescens, two dominant perennial grasses from NW Patagonia that differ in palatability. We hypothesized that physical and chemical factors derived from fire differentially affect recruitment of these species. We performed experiments in the field and under laboratory and greenhouse conditions to study the integral effect of fire and of related abiotic factors (i.e., smoke, heat, charcoal, and ash) on different phases of recruitment of both species. Experimental burning promoted P. speciosa emergence over time, but they did not affect F. pallescens total emergence. Experimental burning decreased P. speciosa seedling growth (i.e., few leaves and small size), but they did not affect seedling survival. Smoke from laboratory experiments stimulated P. speciosa germination. Exposing F. pallescens seeds to 120°C decreased germination and seedling growth. Fire might act as a selective force on recruitment of both species, as well as changing competitive interactions during postfire regeneration. The effect of fire on the recruitment dynamics of the studied species depended strongly on both intrinsic species characteristics and meteorological conditions.

Seed rain alteration related to fire and grazing history in a semiarid shrubland

“…Pappostipa speciosa seed rain, the only non palatable species included in the analysis, showed the same pattern observed by Peter et al (2013) in plant cover and by Franzese and Ghermandi (2012) in seedling emergence, increasing after fire occurrence in ungrazed situations. Poa spp.…”

Effects of volcanic ash deposition on the early recovery of gap vegetation in Northwestern Patagonian steppes

“…) and the ash layer could function as a filter that selectively retains larger seeds. Gaps constitute a safe site for the matrix species such as the perennial grasses (Franzese and Ghermandi, 2012b) where they could germinate.…”

“…Soil was covered by an average of 3 cm of tephra (Gait an et al, 2011;Ghermandi and Gonzalez, 2012) (Fig. 1), with particle size ranging from 0.001 to 0.025 mm.…”

“…The landscape originated from volcanic activity and presents a relief of smooth plains and hills with numerous rocky outcrops, eroded by the glaciers in the Pleistocene and covered by ash from volcanoes located in Chile during the Holocene (Anchorena et al, 1993;Anchorena and Cingolani, 2002). Dominant soils are moderately developed (Haploxerolls) with sandy-loam texture and superficial horizons containing moderate organic matter (Gait an et al, 2004). Vegetation cover is approximately 60% and consists of a matrix dominated by the tussock grasses Pappostipa speciosa ((Trin.…”

“…Complete burial by ash kills small annual species (Smith, 1913;Gal an de Mera et al, 1999;Tsuyuzaki and Hase, 2005), but, if the tephra layer is not too deep, plants with buds localized near volcanic ash surface can recover more easily than annual species (Kent et al, 2001;Voronkova et al, 2008). Persistent seed banks can survive under tephra.…”