Understanding and predicting frost‐induced tropical tree mortality patterns

Abstract

Extreme climatic and weather events are increasing in frequency and intensity across the world causing episodes of widespread tree mortality in many forested ecosystems. However, we have a limited understanding about which local factors influence tree mortality patterns, restricting our ability to predict tree mortality, especially within topographically complex tropical landscapes with a matrix of mature and secondary forests. We investigated the effects of two major local factors, topography and forest successional type, on climate‐induced tropical tree mortality patterns using an observational and modeling approach. The northernmost Neotropical dry forest endured an unprecedented episode of frost‐induced tree mortality after the historic February 2011 cold wave hit northwestern Mexico. In a moderately hilly landscape covering mature and secondary tropical dry forests, we surveyed 454 sites for the presence or absence of frost‐induced tree mortality. In addition, across forty‐eight 1 ha plots equally split into the two forest types, we examined 6,981 woody plants to estimate a frost‐disturbance severity metric using the density of frost‐killed trees. Elevation is the main factor modulating frost effects regardless of forest type. Higher occurrence probabilities of frost‐induced tree mortality at lowland forests can be explained by the strong influence of elevation on temperature distribution since heavier cold air masses move downhill during advective frosts. Holding elevation constant, the probability of frost‐induced tree mortality in mature forests was twice that of secondary forests but severity showed the opposite pattern, suggesting a cautious use of occurrence probabilities of tree mortality to infer severity of climate‐driven disturbances. Extreme frost events, in addition to altering forest successional pathways and ecosystem services, likely maintain and could ultimately shift latitudinal and altitudinal range margins of Neotropical dry forests.

Toward a more temporally explicit framework for community ecology

“…Jentsch et al () advocated for new generation of climate‐change experiments focused specifically on the study of climatic events, not trends. Since then, the number of studies focused on climatic events has continued to increase, with recent studies focused on heat waves (e.g., McKechnie & Wolf, ; Siegle, Taylor, & O'Connor, ), cold snaps (e.g, Bojorquez, Alvarez‐Yepiz, Burquez, & Martinez‐Yrizar, ; Leriorato & Nakamura, ), drought (e.g, Jentsch et al, ; Sankaran, ), flooding (e.g., Rivas, Spinola, Arrieta, & Faife‐Cabrera, ; Ujvari, Brown, Shine, & Madsen, ; Woodward, Bonada, Feeley, & Giller, ) and wildfire events (e.g., Cooper et al, ; Hale et al, ), among many others. However, while this emphasis has emerged recently in the context of climate change, these questions have deep roots in the study of event‐driven dynamics more generally.…”

Restoration ecology in the Anthropocene: learning from responses of tropical forests to extreme disturbance events

“…The most common type of damage was incline/bent trunks and broken branches and almost half of damaged individuals resprouted (Jimenez‐Rodríguez et al ). In comparison, the extreme frost in 2011 caused more than 90% of trees to die at severely affected sites in the Alamos forest, where only a few scattered trees resprouted (Bojórquez et al ). Most forests worldwide have an average background mortality of 5.5% (Zhang et al ), reinforcing the notion that effects of extreme events are highly context dependent.…”

“…In the following section, I present two examples of well-studied lowland tropical dry forests (e.g. Alvarez-Yépiz et al 2008, 2018Bojórquez et al 2019), subjected to similar land-use change but exposed to different recent climatic disturbances, to demonstrate how we could capitalize on their responses to extreme events to facilitate their restoration.…”

“…For ecosystems subjected to similar regional socioeconomic status and management schemes, the disturbance regime largely depends on latitude, topography, and distance to the coast. For example, hurricanes primarily disturb coastal tropical forests at low latitudes such as those in the Caribbean and Pacific (Álvarez‐Yépiz et al ; Lugo ), whereas frosts only disturb marginal tropical forests at high latitudes and elevations (Bojórquez et al ; Hoffmann et al ). In terms of anthropogenic disturbance, land‐use changes mainly occur in lowland forests (defined here as areas below 600 m), where a characteristic set of natural and anthropogenic processes modify the landscape owing to the gentle topography.…”

Different ways to die in a changing world: Consequences of climate change for tree species performance and survival through an ecophysiological perspective

“…Moreover, it is important to note that these events of frost mortality are observed not only in temperate regions, but also in tropical forests. In a recent study, it was shown that a widespread mortality event in a tropical dry forest from Mexico was related to an unusual combination of duration, intensity, and timing of a frost event (Bojórquez, Álvarez‐Yépiz, Búrquez, & Martínez‐Yrízar, ). Similarly, dieback events related to frost injury were also reported for species from the Mediterranean region (Jalili et al, ; Matusick, Ruthrof, Brouwers, & Hardy, ).…”