Recovery of Forest Structure Following Large-Scale Windthrows in the Northwestern Amazon

J David Urquiza Muñoz,Rodil Tello-Espinoza,Daniel Magnabosco Marra,Alexander Brenning,Tedi Pacheco-Gómez,Sami W Rifai,Hillary S Jenkins,Waldemar Alegría-Muñoz,Susan E Trumbore,Jeffrey Q Chambers,Robinson I Negrón-Juarez

doi:10.3390/f12060667

Abstract

The dynamics of forest recovery after windthrows (i.e., broken or uprooted trees by wind) are poorly understood in tropical forests. The Northwestern Amazon (NWA) is characterized by a higher occurrence of windthrows, greater rainfall, and higher annual tree mortality rates (~2%) than the Central Amazon (CA). We combined forest inventory data from three sites in the Iquitos region of Peru, with recovery periods spanning 2, 12, and 22 years following windthrow events. Study sites and sampling areas were selected by assessing the windthrow severity using remote sensing. At each site, we recorded all trees with a diameter at breast height (DBH) ≥ 10 cm along transects, capturing the range of windthrow severity from old-growth to highly disturbed (mortality > 60%) forest. Across all damage classes, tree density and basal area recovered to >90% of the old-growth values after 20 years. Aboveground biomass (AGB) in old-growth forest was 380 (±156) Mg ha−1. In extremely disturbed areas, AGB was still reduced to 163 (±68) Mg ha−1 after 2 years and 323 (± 139) Mg ha−1 after 12 years. This recovery rate is ~50% faster than that reported for Central Amazon forests. The faster recovery of forest structure in our study region may be a function of its higher productivity and adaptability to more frequent and severe windthrows. These varying rates of recovery highlight the importance of extreme wind and rainfall on shaping gradients of forest structure in the Amazon, and the different vulnerabilities of these forests to natural disturbances whose severity and frequency are being altered by climate change.

Highlights

Windthrows are associated with strong downdrafts produced during severe convective storms [1,2,3,4]
Understanding the drivers of structural and compositional change in tropical forests is important for predicting the future composition of these ecosystems [18,19], especially since the frequency and intensity of convective storms are being affected by climate change [7,12]
We address the following questions: (a) Which forest structural attributes are most affected following windthrows? and (b) How rapidly do these attributes recover to old-growth conditions? This is the first assessment of forest recovery after windthrow events in the Northwestern Amazon, and provides insight into the different regional patterns of forest dynamics and vulnerability to natural disturbances

Summary

Introduction

Windthrows are associated with strong downdrafts produced during severe convective storms [1,2,3,4]. Understanding the drivers of structural and compositional change in tropical forests is important for predicting the future composition of these ecosystems [18,19], especially since the frequency and intensity of convective storms are being affected by climate change [7,12]. This knowledge is crucial for better planning initiatives of forest management and climate adaptation [20]. Understanding how wind disturbances impact standing biomass and influence subsequent succession through tree establishment, growth, and mortality is an enduring task in forest ecology [28]

Methods

Results

Conclusion