Contrasting effects of fire frequency on plant traits of three dominant perennial herbs from Chaco Serrano.
Carbone, Lucas M.
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Fire frequencies are currently increasing in many regions a cross the world as a result of anthropic activities, affecting ecological processes and plant population dynamics. Fire can generate important changes in soil properties, altering nutrient dynamic sand there by plantg rowth. Here wean analyse fire frequency effects on soil quality and plant trait sof three native perennia lherbaceous plants (Cologania broussonetii, Desmodiumun cinatum and Rhynchosia edulis; Fabaceae) with the capacity for biological N2 fixation that resprouts and are abundant after fire in Chaco Serrano forests. Based on 22-year fire history, we assessed plant traits in sites with low and high fire frequencies along with unburned scenarios. We found significantly lower water content, nitrates and electrical conductivity in frequently burneds oils. As a result, the three species showed consistently lower leaf area and specific leaf area in both fire frequencies, implying lower growth rates in comparison to unburned sites. However, total leaf biomass was not affected by fire, leaf phosphorus concentration was higher in R. edulis in high fire frequency and leaf N concentration was twice as large in plants growing in sites of high fire frequencyi n C. broussonetii and R. edulis. Such an increase in N and phosphorus concentrations is likely a result of both their conservative use of resources and their biological N2 fixation capacity. To our knowledge, this is the first record of such contrasting fire effects observed consistently in three co-occurring species: while plant growth decreased with fire frequency, leaf nutritional traits remain unchanged or increased in frequently burned sites.Quality depleted and drier soils that result from in creased fire frequencies may not only affect trait variation at the intraspecific level but can also drive to a homogenization of the plant community, selecting species with particular combinations of morphologic a land functional traits.
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