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Trail I ran alongside several watercourses, at elevations of 800-1000 m a.s.l.

Compared to the vegetation density of the other trails I-IV inside the primary forest trail I was characterised by the second highest density (Ď = 17.4) of massive trees with a trunk diameter larger than 10 cm (average per plot). Massive trees stood significantly denser on trail I than trail II (Mann-Whitney U test; P<0.05). In contrast, trees with lianas (Ď = 31.3) as well as bushes (Ď = 115.4) were scarcest on trail I compared with the other three primary forest trails. The low density of trees with lianas and the low density of bushes was significant in comparison with trail II (Mann-Whitney U test; P<0.05). Some trapping sites along the trail were situated in boggy areas resulting from flooding by the numerous brooks and rivers. The tall massive trees such as the dragon trees (Dracaena spec.) characteristic for this forest as well as its situation in a valley made this trail an especially boggy, damp and shady habitat. Bamboo lianas and tree ferns as well as a water growing species of pandanus were quite common there.

Trail II led to the highest, often misty elevation of the study area, at altitudes of up to 1200 m a.s.l. Compared to all other trails, this one showed the highest density of trees with lianas (Ď = 96.9). Compared with trails I and IV trees with lianas stood significantly closer here (Mann-Whitney U test; P<0.05). Slender trees with a trunk diameter of 2-4.9 cm (Ď = 139.5) also occurred at a high density (significant in comparison with trail III; Mann-Whitney U Test; P<0.05). In comparison, trail II showed a significantly higher density of bushes than all other trails (Mann-Whitney U test; P<0.05). This trail was characterised by especially low and closed vegetation in the peak region. Mist and high amounts of precipitation as well as markedly lower temperatures during the day made this region a wet, cold and extremely windy habitat. Low vegetation, mosses and lichens abounded there.

Trail III ran along a mountain ridge at mid elevations (1100 m a.s.l.).

Compared to the other trails in the primary forest the lowest density of trees without lianas (Ď = 37.3), the lowest density of slender trees with a trunk diameter of 2-4.9 cm (Ď = 46.8) and the lowest density of trees with a trunk diameter of 5-10 cm (Ď = 34.8) were found. The low density of slender trees on trail III was significant compared to trail II and trail IV (Mann-Whitney U test; P<0.05). This trail was characterised by its drier slopes. Typical for this habitat was the thick undergrowth

consisting, for instance, of bamboo grass, with exposed roots forming a maze among dead wood, leaf litter and a springy humus layer.

Trail IV also ran along a mountain ridge at mid elevations (1100 m a.s.l.), similar to trail III. Here, however, the highest density of tree without lianas could be recorded (Ď = 139.5 / significant in comparison with trail I; Mann-Whitney U test;

P<0.05), as well as the highest density of slender trees with a trunk diameter of 2-4.9 cm (Ď = 139.5 / significant in comparison with III; Mann-Whitney U test; P<0.05) and the highest density of trees with a trunk diameter of 5-10 cm (Ď = 86.98 / significant in comparison with trails I and III; Mann-Whitney U test; P<0.05). Tall, massive trees with a trunk diameter of > 10 cm reached their highest density on trail IV (Ď = 20.76).

This habitat can be described as a particularly tree-rich region; slender, thin saplings as well as massive trunks stand closely together, forming a maze of twigs and roots.

Noticeable features of this habitat are the pandanus trees with their broad crowns (different from those standing in water).

Trail V was situated on a degraded agricultural site outside the primary forest, at an altitude of 800 m a.s.l. This habitat was dominated by numerous non-endemic plant species such as Clidemia hirta (Melastomataceae), Solanum mauritianum (Solanaceae), Lantana camara (Verbenaceae) and Passiflora edulis (Passifloraceae); furthermore, several non-endemic crops were cultivated there, among these: eucalyptus (for charcoal production), banana and plantain, manioc, sweet potato, corn, beans and taro (Colocasia esculenta). The area was cut-and-burned every year (this kind of fire clearance is called "tavy" in Malagasy) to create new open spaces for agriculture. Trail V was located on more or less open agricultural land dotted with bushes and a few trees. A small brook coming from the primary forest ran across the study site to the valley, flanked by grasses and bushes.

The vegetation along trail V merged with a thick, almost impenetrable vegetation belt consisting of Rubus moluccanus. This introduced species of Rosaceae is a strongly dominant plant which quickly overgrows all other vegetation at heights between 1-1.50 m. Adjacent to these bushy thickets around trail V the vegetation gave way to a more open secondary forest partly consisting of non-endemic eucalyptus and native tree species. This secondary forest was directly connected with the primary forest.

Except few tall endemic dragon trees (Dracaena spec.) were able to withstand the annual fire, no other endemic plant species could be found on the agricultural land.

Because of the scarcity of data only the trees (or non-endemic vegetation of

equivalent height, respectively) without lianas with a trunk diameter of 2-4.9 cm and the density of bushes could be compared statistically with the other trails in the primary forest. All three vegetation categories were present with the significantly lowest density on the agricultural area (Mann-Whitney U test; P<0.05), see Fig 9: for density of vegetation and see Tab. 5: for density of vegetation categories).

Vegetation density

0 50 100 150 200 250 300 350 400 450 500

Trail I Trail II Trail III Trail IV Trail V

Density <Ď>

1. trees with lianas 2. trees without lianas 3. trees [DBH 2 - 4,9 cm]

4. trees [DBH 5 - 10 cm]

5. trees [DBH > 10 cm]

6. shrubs [Ø > 50 cm]

Fig. 9: Density [Ď] of vegetation recorded at the sample trails.

Tab. 5: Density of vegetation categories 1-6

DBH: diameter at breast height, *: highest density of vegetation in this category