Modelling spatial dynamics of vascular epiphytes(MODVE): modelling demography and spatial-temporal dynamics of vascular epiphytes, aiming their incorporation into forest dynamics' models.
Final Report Abstract
Vascular epiphytes constitute c. 9% of all vascular plants, but have been largely neglected in ecological modelling despite impeding global change. This may be partially due to the difficulties in accessing forest canopies, the epiphyte habitat. Recent works have started to gather valuable data that can support the inclusion of epiphytic plants into the ecological forecasts (e.g. model calibration and validation). Combining this data, forest models and models simulating vascular epiphytes would thus enable the inclusion of vascular epiphytes into mainstream ecological modeling. Hence, this project aimed at understanding and modeling the spatiotemporal dynamics of epiphytes. The findings are described according to the project’s four objectives, which also constituted the topics for a PhD thesis dissertation. Objective 1: Vascular epiphytes, which are plants growing non-parasitically on trees, are exposed to different environmental conditions within the forest canopy (e.g. light and humidity vertical gradients). Therefore, we analyzed the variation in leaf traits, which control the water and carbon balance, along height gradient and whether this variation is driven only by the environment or also by species and taxonomic group. For most traits, the average value changed with height. For example, leaf thickness increased and specific leaf area decreased with height. Such trends were similar for orchids, ferns, bromeliads and aroids. Species with higher trait variability occurred at a greater height range. These findings contribute to our understanding of the vertical distribution of epiphyte communities. Objective 2: Vascular epiphytes live in a three-dimensional, highly dynamic, and heterogeneous habitat that is the forest canopy, which is difficult to survey. Therefore, we proposed a forest floor-based sampling method, quantifying branchfall (a main cause of mortality) and vascular epiphytes on the forest floor. We surveyed 96 transects in two forests (Atlantic rainforest in Brazil and Caribbean rainforest in Panama). Epiphyte abundance and richness per branch and proportion of adults were positively correlated with branch diameter. Individuals found on the forest floor corresponded to >12% of all individuals on branches <10 cm in diameter, with abundance, richness and composition trends on forest floor reflecting canopy trends. We further confirmed branchfall as a main cause for epiphyte fall. Therefore, branchfall acts as demographic filter structuring epiphyte communities. Objective 3: We developed a carbon-based, long-term (~1000 years), dynamic forest stand model, in which each tree is simulated as three-dimensional functional-structural tree models (FSTMs). Long-term dynamics of natural tropical forests could be reproduced when this FSTM was coupled with a forest stand model in which demography and between-species competition for space and light were integrated. The model successfully reproduced multiple structural variables and long-term dynamics of Neotropical lowland forests. The proposed model offered the desired level of structure detail that can be used in epiphytes models. Objective 4: Once trait and demographic data were gathered and a suitable forest model was developed, we finally tackled the main goal of this project, namely to develop, validate and explore the first process-based framework for spatiotemporal dynamics of epiphytes. This framework included key demographic processes linked to environmental preferences, generating vertical distributions of individuals and species and rank-abundance distributions that were validated with field data. Thereafter, we assessed three human impacts. Higher forest dynamics (e.g. due to Global warming) had complex effects on epiphyte assemblages, with stable forests having generally high abundances, low extinction rates and highest saturation. Selective tree logging resulted in lower abundances, species numbers, and saturation levels of epiphytes. Increasing fragment size decreased species extinction rates.
Publications
- (2015) Branchfall as a demographic filter for epiphyte communities. PloS one 10: e0128019
Cabral, J.S., Petter, G., Mendieta-Leiva, G., Wagner, K., Zotz, G., Kreft, H.
(See online at https://doi.org/10.1371/journal.pone.0128019) - (2015). Chromosomal evolution in Pleurothallidinae (Orchidaceae: Epidendroideae) with emphasis on the genus Acianthera: chromosome numbers and heterochromatin. Botanical Journal of the Linnean Society 178: 102-120
de Oliveira, I.G., Moraes, A.P., de Almeida, E.M., de Assis, F.N.M., Cabral, J.S., de Barros, F., Felix, L.F.
(See online at https://doi.org/10.1111/boj.12273) - (2016) Functional leaf traits of vascular epiphytes: vertical trends within the forest, intraand interspecific trait variability, and taxonomic signals. Functional Ecology 30: 188-198
Petter, G., Wagner, K., Wanek, W., Sánchez Delgado, E.J., Zotz, G., Cabral, J.S., Kreft, H.
(See online at https://doi.org/10.1111/1365-2435.12490) - Effects of forest structure and dynamics on trait distribution and community dynamics of vascular epiphytes. PhD thesis, University of Göttingen
Petter, G.
