Spatial variation of seed rain in deciduous tropical forest

Cleide Brachtvogel,Sandro Menezes Silva,Zefa Valdivina Pereira

doi:10.33448/rsd-v9i9.7956

Cleide Brachtvogel, Sandro Menezes Silva + Show 1 more

Open Access

https://doi.org/10.33448/rsd-v9i9.7956

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Abstract

Seed rain is an ecological process and its functional attributes are essential for maintaining the dynamics of natural regeneration. The objective of this research was to evaluate the spatial variation of the seed rain in a toposequence of a Seasonal Deciduous Forest defined by three elevations: (Base 512 m; Slope: 534 m and Top: 559 m). 15 collectors of 1 m² were installed at each elevation level. Data were collected monthly from September / 2017 to February / 2019. The seeds were classified according to the dispersion syndrome, habit and size. Non-Metric Multidimensional Scaling (NMDS) was used to verify the variation in species composition and distribution. We identified 20,217 propagules, belonging to 65 species and 30 families, in addition to 4 morphospecies, which represents 449 seeds / m². The families with the highest species richness were Fabaceae, Sapindaceae and Euphorbiaceae. Of the 65 species sampled, 71% were arboreal. Zoochoric species predominated (78%) and very small seeds corresponded to 53% of the sample. We demonstrate that, on a small spatial scale, the relief represents an important source of heterogeneity in the vegetation component, since the topographic gradient influenced the composition and distribution of the functional attributes of the seed rain.

Highlights

Forests cover 31 percent of the global land area but are not distributed around the globe. (FAO & UNEP, 2020)
The goal of this research was to evaluate the spatial variation of the seed rain in a toposequence of a SDF, to answer the following questions: is there variation in the seed rain in relation to the position occupied in this toposequence? What environmental factors influence this variation, if any? Are the dispersion syndromes and the propagules size related to the patterns detected? 2
The differences in richness and abundance of the seed rain between the elevation levels can be a consequence of several factors, such as soil conditions, topography and microclimate characteristics, that change along the elevational quotas (Ferreira-Júnior et al, 2007; Ferreira-Júnior et al, 2012; Jones et al, 2011; Klein, 1980, 1984; Marangon et al, 2013; Veloso & Klein, 1959)

Summary

Introduction

Forests cover 31 percent of the global land area but are not distributed around the globe. (FAO & UNEP, 2020). Deciduous Tropical Forests, known as Dry Forests and Seasonal Deciduous Forests, (hereafter called SDFs), occur in ice-free areas, where the mean annual temperature is 17 °C, and the mean annual precipitation is less than 1600 mm, with less than 100 mm of rainfall over five months. The SDFs are usually a transition zone between semi-desert regions and/or savannas with humid forests (Murphy & Lugo, 1986). Leaf loss in these forests can exceed 50% of the vegetation cover, which may rise up to 100% of trees and shrubs defoliation during the drought (IBGE, 2012; Pereira et al, 2011). Mexico has the largest amount of SDFs (38%), followed by Bolivia (25%), Brazil (17%), Colombia (6.5%), and Venezuela (6.2%) respectively (Murphy & Lugo, 1986; Portillo -Quintero & Sánchez-Azofeifa, 2010)

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