**2.1 Data analysis**

*Dominance* (D): Due to the difficulty of measuring horizontal crown projection to estimate dominance (Lamprecht, 1990), we used basal area, expressed in m2, for each species to estimate Absolute Dominance (AD):

$$\mathbf{AD} = (\mathbf{n}/4) \times \mathbf{dbh^2}$$

Where: π = 3.1416, dbh = diameter at breast height

$$\mathbf{DR} = \frac{\text{Absolute Domain}}{\text{Total Absolute Dominance}} \times 100\tag{1}$$

$$\mathcal{D}\mathbf{e} = \frac{N}{a} \tag{2}$$

$$\mathbf{Der} = \frac{\text{Density of a given species}}{\text{Sum of the density of all species}} \times 100\tag{3}$$

$$FA = \frac{number\ of\ sub-plots\ where\ the\ species\ occurs}}{total\ number\ of\ sub-plots} \tag{4}$$

$$FR = \frac{absult\ frequency \ of \ a\ given\ species}{total\ absolute\ frequency} \times 100\tag{5}$$

$$\mathbf{IVI(F)} = (\mathbf{AR} + \mathbf{FR} + \mathbf{DR}) \;/\; \; \; \; \; \; \; \; \tag{6}$$

$$\mathcal{CC}\_l = \frac{c}{s\_1 + s\_2 - c} \tag{7}$$

$$t = \frac{{H'\_1} - {H'\_2}}{\left(Var \, H'\_1 + Var \, H'\_2\right)^{1/2}}\tag{8}$$

$$t = \frac{(Var \ H\_1' + Var \ H\_2')^2}{[(Var \ H\_1')^2/N\_1] + [(Var \ H\_2')^2/N\_2]} \tag{9}$$



Structure and Floristic Composition in

**3.3 Early growth** 

19.61 ind/ha.

DBH of 200 cm.

**3.4 Diversity patterns** 

a Successional Gradient in a Cloud Forest in Chiapas, Southern Mexico 141

A total of 43 species and above 50% of the total genera were found in the 20-25 years old successional stage. This stage presented the lowest basal area and a tree density of 16.96±50.75 ind/ha. The species with the highest importance values were *Saurauia madrensis, Crossopetalum parviflorum, Hedyosmum mexicanum, Heliocarpus donnellsmithii,* and *Cestrum elegantissimum*, which account for an added IVI of 162% (Table 3). Trees with a DBH > 400 cm were represented by *Saurauia madrensis, Crossopetalum parviflorum, Hedyosmum* 

*Saurauia* aff*. oreophila,* and *Liquidambar styraciflua;* arboreal elements with a DBH between 100 and 400 were *Saurauia kegeliana, Fuchsia paniculata, Verbesina apleura, Lepidaploa polypleura, Clethra lanata, Brunellia mexicana, Arachnothryx buddleioides, Wigandia urens* and *Comarostaphylis arbutoides*; finally, species with a DBH < 100 cm included *Pinus oocarpa, Ocotea acuminatissima, Citharexylum mocinoi, Clethra hondurensis, Clusia flava, Piper pseudolindenii, Trichillia havanensis, Matudaea trinervia, Prunus annularis, Myriocarpa longipes, Licaria excelsa, Cyathea sp, Conostegia volcanalis, Ardisia compressa, Pterocarpus* aff*. rohrii, Glossostipula concinna, Ostrya virginiana,* and *Dendropanax arboreus* (Table 3). Total tree density was 13.05 ±

The greates richnness and diversity were found in the intermediate successional stage (30-35 years growth). This stage presented species that are characteristic both of the mature forest and the early growth (Table 4). The nature of this intermediate state is supported by statistical differences in diversity between the early growth and mature forest (Δ = - 0.21 p = 0.01), while there were no differences between early growth and old growth (Δ = -0.56 p >

**Successional stage Mature forest Old growth Early growth** 

Table 4. Number of plots, total sampled area (ha), plant density and estimated values for species richness(S), Shannon-Wiener diversity index (H'), Simpson's diversity index (D) and

In all three successional stages there was a high abundance of plants in early development stages and a low abundance of bigger sizes, so, according to Peter (1996), the class of structure found in the system is Type I (Figure 3). In all three successional stages, short size individuals are predominant, while in the early successional stage, no individual reaches a

Similarity analysis results showed that mature forest has a higher similarity with the old growth (26%). Figure 4 shows dominant species of each successional stage and shared species between habitats. Eight species were found in all three stages, while mature forest
