Microhabitat variation affects the understory community assembly of a neotropical rainforest

Author(s)

Aranha, Bruno A. ; Maciel, Everton A. ; Cielo-Filho, Roque ; Martins, Fernando R.

• Document type: Journal article
• Source: FLORA; v. 306, p. 10-pg., 2023-09-01.

Abstract

Deterministic and stochastic processes combine with biotic interactions in community assembly. Stochasticity and biotic interactions are thought to operate on fine scales, and determinism on coarse scales. Would determinism be detected on a fine scale in an understory community of a tropical rainforest? We measured the altitude, index of convexity (IC), slope, and canopy openness, counted the individuals and species and calculated Simpson's dominance index of plants with height =30 cm and DBH < 5 cm for each of 50 randomly drawn 3 x 3 m plots from a one-hectare grid. We used redundancy analysis and spatial modeling with principal coordinates of neighbor matrices to assess how much of the community variation each variable explained. The same was done for each set of plots with 20%, 60%, and 20% respectively of the lower, intermediate, and higher values of the microrelief variables. Most of the community variation remained unexplained, but the effect of the microrelief variables was significant. IC had the highest contribution and was four times higher in the plots with 20% higher values, stressing the increasing importance of determinism towards the higher extremes of the variable's local range. Species richness decreased and dominance increased in convex plots (high IC), and the most abundant species differed between concave and convex plots. Microrelief variation can act as a local filter with a growing influence towards the extremes of the local range of microenvironmental variables in the community space. Niche-based processes rely on the strength of the environmental filter. (AU)

• FAPESP's process: 03/12595-7 - Floristic composition, structure and functioning of the Dense Rainforest nuclei of Picinguaba and Santa Virgínia of Parque Estadual da Serra do Mar, State of São Paulo, Brazil
• Grantee: Carlos Alfredo Joly
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants