Effects of Fire and Cattle Grazing on Amphibians and Lizards in Northeastern Argentina (Humid Chaco)

Eur J Wildl Res DOI 10.1007/s10344-009-0335-7 ORIGINAL PAPER Effects of fire and cattle grazing on amphibians and lizards in northeastern Argentina (Humid Chaco) Paula D. Cano & Gerardo C. Leynaud Received: 25 February 2009 /Revised: 21 September 2009 /Accepted: 1 October 2009 # Springer-Verlag 2009 Abstract Richness, diversity and abundance of amphibians and lizards, with a greater effect on amphibians. Also, fire and lizards were compared in four sites subjected to favoured the presence of some lizard species. different fire and grazing regimes in Mburucuyá National Park (Corrientes, Argentina). The surveys were performed Keywords Prescribed fire . Disturbance . Grasslands . using drift fence–pitfall traps randomly distributed in four Herpetofauna . Cattle . Argentina sites subjected to the following prescribed fire and grazing regimes: (A) no fire or grazing for the last 12 years (control), (B) 3 years since the last prescribed fire, (C) Introduction annual prescribed fire and (D) annual prescribed fire and grazing. Fourteen species of amphibians and six species of In several regions of Argentina, fire and grazing are lizards were captured during the study period (80 days). important disturbances that critically modify the landscape. The lowest values of amphibian richness and abundance In wild areas, fire reduces plant biomass, suppresses were found in sites C and D. The amphibian species development of woody vegetation and removes the upper Leptodactylus ocellatus and Leptodactylus podicipinus litter layer (Gibson and Hulbert 1987; Ensbey et al. 2000). were most abundant in the control site (A). In lizards, no At the same time, fire exposes soil where new individuals significant differences were found among sites, although can establish, leading to different successional stages of Kentropyx viridistriga and Teius oculatus were more plant and animal communities (Kunst et al. 2003). Grazing abundant in annually burnt sites (C and D). Vegetation by domestic cattle has a significant effect on grasslands variables were correlated with amphibian and lizard species through plant removal and compaction, erosion and loss of composition. The species differed in their preference for the soil biological properties (Braunack and Walker 1985; Abril differently managed sites. The combination of fire and and Bucher 1999; Ensbey et al. 2000). Grazing-induced grazing had a negative effect on diversity of amphibians changes modify availability of habitat and food resources for the grassland fauna (Ryder 1980). Communicated by H. Kierdorf Some species of amphibians and reptiles are highly sensitive to environmental changes induced by fire and P. D. Cano Programa de Maestría en Manejo de Vida Silvestre, grazing. Some particular characteristics of amphibians Centro de Zoología Aplicada, Facultad de Ciencias Exactas, (highly permeable skin, shell-less eggs) make them vulner- Físicas y Naturales, Universidad Nacional de Córdoba, able to drastic changes in environmental quality (Zug et al. Casilla de Correos 122, 2001). Reptile species are more tolerant to on-site moisture 5000 Córdoba, Argentina reductions than amphibian species mainly because reptiles’ G. C. Leynaud (*) skin is relatively impermeable, their eggs have a shell and Centro de Zoología Aplicada, Facultad de Ciencias Exactas, also because some aspects of their behaviour (use of Físicas y Naturales, Universidad Nacional de Córdoba, borrows and low mobility) help them overcome adverse Casilla de Correos 122, 5000 Córdoba, Argentina conditions. However, as reptiles are associated with e-mail: [email protected] particular biomes, some species are highly sensitive to Eur J Wildl Res subtle changes in the ecological communities where they Argentina, which provides a unique opportunity to evaluate belong (Zug et al. 2001). A species’ local distribution and the effects of fire and grazing, individually and combined, abundance may be restricted by fire-induced changes on local populations of amphibians and lizards. (James and M’Closkey 2003). Pianka (1996) mentioned fire as one of the most important factors determining lizard species diversity in the deserts of Australia. Materials and methods Mortality of individuals is one of the immediate effects of fire on animal populations (Heinrich and Kaufman 1985; Study area Whelan 1995). However, different authors mentioned that neither amphibians nor reptiles are usually directly affected The work was conducted in Mburucuyá National Park by fire or that they are only slightly affected (Mushinsky (17,682 ha; 57°59′ and 58°08′ W; 27°58′ and 28°05′ S), and Gibson 1991; Cunningham et al. 2002). Accordingly, located in the northwest of the province of Corrientes, studies conducted in other parts of the world indicate that northeastern Argentina (Fig. 1). The relief in the region is fire has a low effect on amphibians and reptiles (Cunning- slightly undulated, with deficient drainage due to the slight ham et al. 2002). Many species even take advantage of the slope; 65% of the area is covered by semi-permanent habitat mosaic generated by fire (Mushinsky and Gibson ponds, swamps and marshes (Saibene and Montanelli 1991) and of the increased availability of food and refuge, 1997). the latter one being provided by logs (Cunningham et al. Mean annual temperature ranges between 21°C and 23°C. 2002; James and M’Closkey 2003). Furthermore, the Maximum absolute temperatures can peak 46.5°C, and herpetofauna historically adapted to environments with minimum absolute values of up to −5.5°C are recorded in periodic natural fire regimes not only tolerates but also winter. Frosts are barely frequent, with up to 340 days free of takes advantage of this disturbance (Russell et al. 1999; frosts a year. Mean annual rainfall is 1,300 mm, concentrated Brisson et al. 2003). in spring and summer, with a dry season in winter. Prescribed burning, usually conducted during winter and The park lies in a wide ecotone among the Paranaense, early spring, is a management tool used to reduce Chaco and Espinal phytogeographic provinces (Cabrera hazardous fuel buildup, maintain or restore native ecosys- 1976). The area is included in the Ibera wetlands system, tems, increase water availability, control undesirable plant which is considered one of the most important wetlands in species and create clean seedbeds for seeding purposes Latin America (Canevari et al. 1998). The characteristic (Wright and Bailey 1982). Prescribed fire has also been physiognomy of the Park is of an open savannah, with indicated as an adequate management action to improve grasslands and inclusion of hygrophilous forests. The most pasture quality (Andersen et al. 2005) and restore historical common species of grasses during the study period were mosaics of successional stages, habitat structure and plant Andropogon lateralis, Andropogon selloanus, Schizachy- species composition (Russell et al. 1999). However, most rium paniculatum, Sorghastrum agrostoides, Elionurus authors suggest that the effects of fire on biodiversity are muticus and Paspalum notatum. complex, depend on the environment and species analysed and pose an important challenge to wildlife managers Experimental design (Mushinsky 1985; Penn et al. 2003). Grasslands in northeastern Argentina are heavily Four sampling sites (minimum of 400 ha each) with exploited for cattle production, the main economic activity different history of grazing and natural or prescribed fires in the region; fire is used as a management tool to promote were selected. The sites were defined as (A) site non- re-sprouting and remove barely palatable vegetation (Whelan burned and non-grazed since 1995, (B) site non-burned 1995). One of the main problems encountered in the study since 2003 and non-grazed, (C) site annually burned and of the effect of fire or overgrazing on animal communities non-grazed and (D) site annually burned and grazed or populations is the low availability of undisturbed sites (Fig. 1). relatively close to sites presenting a mosaic of disturban- Burns were conducted at the time of the year of greatest ces induced by fire and grazing. This study aims at accumulation of dry vegetation cover (August–September). examining the response of amphibians and lizards to the Fuel material was mostly fine (dried grasses), with an different management strategies implemented in an area approximate load of 5 t/ha and about 10–15% humidity. that presents a disturbance mosaic generated and main- Head fires were ignited with a hand-held drip torch. Fires tained for experimental purposes by means of prescribed reached a mean height of 3 to 5 m, with a maximum of burning and cattle grazing. 10 m. Prescribed burns were conducted under the following The study was conducted in Mburucuyá National Park, conditions: winds 10–15 kph, air temperature 15–22°C and one of the largest native grasslands of northeastern relative humidity 40–50%. Eur J Wildl Res Fig. 1 Location of Mburucuyá National Park (Corrientes, Argentina) and of the four sampling sites (A, B, C and D) Cattle carrying capacity in the grazed sites was 3.1 ha surface; the buckets were filled with a wet sponge, 1–2cm per cattle unit. Cattle used the plots all the year round. Five of water, and plant remains to prevent dehydration of to 7 days before the start of the start of burns, they were individuals (Greenberg et al. 1994). Thus, each array was a removed and were re-introduced in the burned plots sampling unit made up of three drift fences and four 2 months after the last burn. buckets (Leynaud and Bucher 2005). The four sites were simultaneously sampled to compare The sampling statistical design used is a completely richness, abundance and diversity of amphibians and lizards randomised model with one classification factor (Zar 1984). and the relationship of these parameters with vegetation In each of the four sampling sites (A, B, C and D), eight structure and composition in each site. Samplings were sampling units were randomly established. A total of 32 conducted uninterruptedly from January 12 to April 1, 2006 arrays (sampling units) were installed in the entire study (80 days).

Load more