Effects of nutrient limitation on understory communities in a tropical forest

Ferns are the second most diverse group of vascular plants whose diversity and abundance peak in mid-elevation tropical forests. Soil nutrient limitation is an important factor influencing plant communities and yet little is known about the factors influencing fern floristic composition and functional traits in montane tropical forests. My dissertation compares composition variation and decay-rates between terrestrial ferns and understory palms, since the extent to which their resource needs overlap has not been determined. Furthermore, ferns and palms are two essential components of forest understories that differ widely in physiology and reproductive traits, while competing for the same limited resources. I found that soil factors impacted compositional similarity of both ferns and palms, with fern compositional variation related to total soil nitrogen to phosphorus ratio (soil N:P) and light conditions (red:far read – RFR) and palm compositional variation related to bulk density. Distance–decay rates in compositional similarity were slightly higher for palms than ferns. In addition, the abundance of understory palms and tree ferns showed opposite trends with soil N:P and RFR compared to herbaceous ferns. I also analyzed the responses of functional composition and functional dispersion to soil and precipitation gradients, to determine to what degree environmental factors influence trait distribution and diversity of fern communities across their phylogeny. The examination of functional composition and functional dispersion of fern communities along the soil fertility gradient demonstrated that functional composition was affected by soil variables and dry season rainfall. Leaf traits contributed to most of the variation among all trait variables evaluated. Functional dispersion decreased with soil N:P and manganese (Mn), and increased with dry season soil moisture. Trait and phylogenetic diversity showed clustered patterns. Due to field collections, the fern species list of Fortuna is expanded. I give floristic details of species occurrence and extend the discussion on habitat preference of herbaceous ferns and tree ferns. Several indicator taxa associated with soil nutrient conditions related to parent material type were identified. By contrasting compositional and abundance patterns of similar groups with differing dispersal strategies in highly diverse ecosystems, this dissertation uncovers how distinctly terrestrial ferns and understory palms respond to soil nutrient limitation gradient. Incorporating edaphic gradients with the phylogenetic framework of the fern communities, this research reinforces the importance of eco-evolutionary information to better understand the mechanisms of assembly that maintain diversity in tropical forests.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Plant Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2021

Author dc:creator

• Lira Viana, Jessica

Contributors dc:contributor

• Dalling, James W
• Yannarell, Anthony C
• Yang, Wendy H
• Fraterrigo, Jennifer M

• tropical rainforest
• nutrient limitation
• environmental gradients
• pteridophytes
• ferns
• understory palms
• floristics
• composition turnover
• functional traits Fortuna Forest Reserve
• Panama

Statement dc:rights

• Copyright 2020 Jéssica Lira Viana

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/109403

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/109403