**2. Methods**

Our study took place at El Triunfo Biosphere Reserve (ETBR) in Chiapas, Mexico. El Triunfo lays on the Sierra Madre de Chiapas Mountain range (Figure 1), which runs parallel to the Pacific coast. ETBR has an extension of 119,177 ha and its altitudinal range goes from 450 to 3000 meters above sea level (Arreola-Muñoz et al., 2004). Along this range, several climates occur; from hot humid in the low parts to temperate humid in the high lands (García, 2004). Several vegetation types are present, but upper parts are dominated by Cloud Forest (Rzedowski, 1978).

Fig. 1. Map showing El Triunfo Biosphere Reserve boundaries in Chiapas, southern Mexico.

(20-25 years old, 30-35 years old, and mature forest), and to determine the floristic

Our study took place at El Triunfo Biosphere Reserve (ETBR) in Chiapas, Mexico. El Triunfo lays on the Sierra Madre de Chiapas Mountain range (Figure 1), which runs parallel to the Pacific coast. ETBR has an extension of 119,177 ha and its altitudinal range goes from 450 to 3000 meters above sea level (Arreola-Muñoz et al., 2004). Along this range, several climates occur; from hot humid in the low parts to temperate humid in the high lands (García, 2004). Several vegetation types are present, but upper parts are dominated by Cloud Forest

Fig. 1. Map showing El Triunfo Biosphere Reserve boundaries in Chiapas, southern Mexico.

composition, vegetation structure, and species replacement along this gradient.

**2. Methods** 

(Rzedowski, 1978).

We selected three study sites at ETBR, all localized in the core zone I, based on accessibility and disturbance history. We established sampling plots in three different successional stages according to the time elapsed since disturbance: 1.- Early growth, 20-25 years old (n = 10); 2. old growth 30-35 years old (n = 7); and 3.- Mature forest (n = 10).

We modified the method proposed by Ramírez-Marcial et al. (2001) to describe the physiognomy and structure of plant communities. We used 0.1 ha circular plots, with a radius of 17.8 m. Inside each circular plot we set smaller circular sub-plots (Figure 2). To avoid border effect, plots were placed at least 50 meters from the border. We randomly selected a point to be used as the center of the plot, and then we placed four straight lines 17.8 m long to each cardinal direction with marks at 5.6, 12.6 y 17.8 m. Then, beginning from the plot center, we traced a circle at the 5.6 m mark (circle "A"), another at the 12.6 m mark (circle "B"), and finally one at the 17.8 mark (circle "C"). Then we measured different vegetation features in each circle. Circle A: all trees with DBH ≥5 cm and ≤ 10 cm; circle B: all trees with a DBH >10 cm and ≤ 30 cm; circle C: all trees with a DBH > 30 cm.

Fig. 2. Plot sampling layout (modified from Ramírez-Marcial et al., 2001)
