DO MICROHABITATS IN FOREST GAPS INFLUENCE TREE REGENERATION? A STUDY IN THE MONTANE FORESTS OF VENEZUELAN GUAYANA

作者：Duran Rangel Cristabel^*; Gaertner Stefanie; Hernandez Lionel; Reif Albert

来源：Ecotropica, 2012, 18(2): 93-103.

• microhabitat
• tree regeneration
• forest gap
• disturbance
• Sierra de Lema
• Guayana Shield
• tropical forest

One theory used to explain the high tree species richness in tropical forests involves niche partitioning, whereby species specialize according to the availability of environmental resources in microhabitats. We examined whether there were differences in microhabitats that could account for the composition and diversity of tree regeneration in natural small-scale montane forest canopy gaps found in the Sierra de Lema, Venezuela. Five microhabitats (fallen crown, fallen large branches, large lying trunk, undisturbed ground, and the gap border) were identified and sampled for species richness in 20-m(2) plots within gaps. Additionally, the cover of trees, large palm seedlings, shrubs, tree ferns, and small palms was estimated and gap age, size, and disturbance category were assessed. To test what was influencing tree species richness we developed four alternative models and used various combinations of explanatory variables: microhabitats, abiotic gap characteristics, and competition with other life forms. The importance of each variable was evaluated based on the model averages. The differences in composition were analyzed with permanova and mrpp, and an indicator species analysis was done. A total of 111 morphospecies was recorded. Species richness differed between microhabitats. Branch and crown areas had a negative impact, as did the most severe disturbance category Gap size, however, did not have any impact on species richness at either plot or gap level. Species composition differed between crown, undisturbed, and trunk microhabitats and the most severe disturbance category also had a differentiating impact. Sloanea sp. and Ocotea sp.1 were associated with undisturbed and trunk microhabitats. The palm Euterpe catinga was associated with an intermediate disturbance intensity, whereas Elaeagia maguirei, Ocotea sp.1, and Schefflera quinquesvlorum were associated with the severe disturbance category. We conclude that species richness and floristic composition of trees regenerating in the montane forest gaps of the Sierra de Lema were mainly affected by disturbance and advanced regeneration.

• 出版日期2012