Effect of Seasonal Rains and Floods on Seedling Recruitment and Compositional Similarity in Two Lowland Tropical Forests

Brayan S Polanía,Pablo R Stevenson,Francisco Castro-Lima,Adriana Sanchez,Diana M Cruz,Ana M Aldana,Marius Bottin

doi:10.3390/f11121297

Brayan S Polanía, Pablo R Stevenson + Show 5 more

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https://doi.org/10.3390/f11121297

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Journal: Forests	Publication Date: Dec 2, 2020
Citations: 3	License type: CC BY 4.0

Affiliation: Universidad de Los Andes, Universidad del Rosario

Abstract

Research Highlights: Seasonally flooded and terra firme forests are characteristic ecosystems of the Colombian Orinoco Basin and of great importance in the maintenance of regional biodiversity and ecosystem function. These forests have a unimodal precipitation regime that can cause a temporal effect on the seedling regeneration niche. This could partly explain the high diversity and coexistence of plant species in these forests, as well as the similarity in composition of seedlings and trees. Background and Objectives: Seedlings are a key factor in the assembly of plant communities. We evaluated the effect of flooding and rains on the dissimilarity and compositional affinity between trees and seedlings of seasonally flooded and terra firme forests. Materials and Methods: the tree community of these forests in San Martín (Meta, Colombia) was characterized and compared with their respective seedling communities before (June) and after (December) rain and flooding (during the rainy season). We evaluated plant species diversity and abundance (Shannon diversity and Pielou eveness index), as well as the compositional dissimilarities of each tree community with their corresponding seedling community sampled at the beginning and end of rains and flooding (Bray–Curtis dissimilarity). We also compared sampling site composition using a NMDS analysis. Results: We found that the terra firme forest had higher diversity compared to the flooded forest. Seedling density in the seasonally flooded forest decreased significantly after the flood but not in the terra firme forest at the end of the rainy season. The compositional dissimilarity between trees and seedlings in the seasonally inundated forest also decreased after the flood. However, this pattern was not evident in the terra firme forest. Conclusions: These results indicate that seasonal flooding generates a strong ecological filter that affects the realized niche of plants in these forests. Our results can contribute valuable information for the effective development of assisted restoration and conservation programs.

Highlights

Lowland tropical forests are divided into several forest types
In this study we found that seasonal flooding is an important filter on the temporal regeneration niche of seasonally flooded forest (SFF) seedlings
We found that at the end of the flood, the compositional affinity between seedlings and trees of the SFF increased with respect to the beginning of the flood

Summary

Introduction

Lowland tropical forests are divided into several forest types. These types are characterized by complex ecological dynamics and multiple interactions between biotic and abiotic factors, such as temperature, drought, and flooding [1]. One of these types are the floodplain forests, which are classified according to their seasonality (i.e., season or permanent) and to the river type that floods them (e.g., white-water or várzea, black-water or igapó). Flooded forests (SFF) perform key ecosystem functions such as water retention, cation exchange, the balance of nutrient cycle, and microclimate; these functions are associated with particular plant communities, which have a narrow regeneration niche [2]. Organic matter and sediments in the soil largely determine the ecological dynamics of their tree communities [1,3]

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