Plant and soil responses to fire on a fern-covered landslide in Puerto Rico

Landslides are common in tropical mountains and occur in areas of high rainfall, steep slopes and unstable soils (Garwood et al. 1979). Landslides cover approximately 18 ha (0.1%) of the steep slopes of the Luquillo Experimental Forest (LEF) in eastern Puerto Rico (Guariguata 1990, Scatena & Larsen 1991) and are frequently associated with roads (Guariguata & Larsen 1989, Scatena & Larsen 1991). The annual precipitation in the LEF is 3450 mm and there is little seasonal variation (Brown et al. 1983). Ferns in the family Gleicheniaceae are the dominant vegetation on many landslides in the LEF, and Guariguata (1990) has suggested that these ferns may have a role in the development of vegetation on landslides. However, very little is known about the role of ferns in succession on landslides. Ferns form dense thickets in the LEF that are occasionally burned by road crews to maintain visibility along roadsides. This study examines plant and soil responses to a fire on a fern-covered landslide in Puerto Rico to determine their relative importance in maintaining the fern thicket. In April 1990, road crews burned one-half of a 650 m2 landslide (estimated age: 5-20 yr) on the western edge of the LEF. On 10 April 1990 (approximately 3-5 days after the fire), we sampled temperatures at noon at six randomly placed locations in the burned area and six adjacent unburned areas covered with two species of ferns in the Gleicheniaceae (Dicranopteris pectinata and Gleichenia bifida). Nomenclature follows Liogier and Martorell (1982). At each location, three measurements were taken from each of three levels: 5 cm depth, the