Soil properties influence tree fall in a fragment of Atlantic Forest in Recife, Pernambuco, Brazil

Abstract

Trees falling in natural environments can be attributed to tree age, terrain topography, amount of rainfall, wind strength, root type and soil properties. Soil plays a role in nutrient cycling, water retention and distribution, and tree support, and can be a determining factor in tree falls in a forest fragment. The aim of this study was to investigate the relationship between tree falls and soil properties in an Atlantic Forest fragment in Recife, Pernambuco, Brazil. Fallen trees were identified, sampled and georeferenced using existing trails. Soil samples were collected in areas with higher incidence of falls. Soil chemical properties such as pH, Ca²⁺, Mg²⁺, K⁺, Na⁺, P and Al³⁺, and base saturation, aluminium saturation, effective cation exchange capacity and potential cation exchange capacity were determined. Soil physical properties such as texture, particle density, soil density, macro, meso, micro and cryptoporosity, total porosity, field capacity, permanent wilting point, saturated hydraulic conductivity and available water were also determined. The data were subjected to multivariate analysis to investigate the relationship between tree falls and soil properties. A total of 98 fallen trees were found on the trails, with only 52 identified at the species level. Tapirira guianensis and Sacoglottis mattogrossensis had the highest number of fallen trees. The incidence of tree falls was influenced by both chemical and physical soil properties. Al³⁺ and (H+Al) were the most discriminating soil chemical properties; porosity, hydraulic conductivity and clay content were the physical properties that most influenced tree falls. Creation of a database of factors influencing tree falls is recommended, to support future studies. Additionally, it is suggested that species most vulnerable to falls and opening soil profiles are monitored, to understand the dynamics of root growth in soils with high Al⁺³ content.