Ecological consequences of compound disturbances in forest ecosystems: a systematic review

Investigations of compound disturbances that alter forest resilience (i.e., recovery time or trajectory) have escalated over the past two decades. We used a systematic approach to identify and describe the ecological consequences of discrete forest disturbance events involved in compound interactions. Fire, wind disturbance, and salvage logging were the most common disturbance types investigated. Most compound interactions occurred in North America and involved five or fewer years between disturbances. Common and interrelated disturbance legacies that facilitated compound interactions included reduced seed source availability, deadwood deposition and extraction, and increased light and growing space availability. Forest recovery was assessed with a diversity of metrics including woody and herbaceous plants, soil properties, and carbon stocks, which sometimes determined whether and what kind of compound interaction was detected. Distinctions between recovery time and trajectory, forest succession and development, and species‐specific and community‐level responses also influenced the detection and direction of compound interactions. Moving forward, we advocate a more holistic approach to quantify ecosystem recovery that considers multiple response variables. Other opportunities to improve compound disturbance ecology include increased emphasis on understudied disturbance types, regions, and forest types. We also encourage more research on buffering interactions that increase forest resilience, which were underrepresented in this review. Disturbances modify forest composition, structure, and function, and leave legacies that impact the rate and trajectory of forest recovery (Oliver and Larson 1996, Franklin et al. 2002). Natural disturbances include biotic events, such as insect outbreaks and invasive pathogens, and abiotic events, such as fires, floods, ice storms, and damaging wind events. Forest succession and development are also directed by human impacts that range from exploitative logging and land‐use change to deliberate silvicultural entries designed to achieve desired conditions. The widespread occurrence of more frequent and severe natural disturbances has been attributed, in part, to precipitation and temperature anomalies associated with global change (Dale et al. 2001, Seidl et al. 2017, Sommerfeld et al. 2018). Coupled with growing human demands, recognition of altered disturbance regimes has motivated interest in multiple interacting disturbances (Turner 2010, Buma 2015). Interacting disturbances may cause unexpected rates and trajectories