Pollen cone production in jack pine: spatial and temporal patterns subject to natural disturbance by the jack pine budworm

Abstract

Patterns of jack pine (Pinus banksiana Lambert) pollen cone production are of interest because they may help explain jack pine budworm (Choristoneura pinus pinus Freeman) outbreak patterns. We used generalized linear mixed models to analyze pollen cone production in 180 permanent plots in Ontario, Canada between 1992 and 2008. Pollen cone production increased with stand age, and large trees in sparsely-populated stands produced more pollen cones. Defoliation decreased the propensity of trees to produce pollen cones for at least two years. We also identified important patterns that are not explained by defoliation and stand characteristics. Pollen cone production is spatially synchronized among years, trees in central Ontario produced more pollen cones than trees in northwestern Ontario, and background cone production increased over time in the central region but not in more northwestern plots. Synchronized reproduction is common among tree species, but has not previously been noted for jack pine pollen cones. Increasing cone production in central Ontario may be evidence of changing forest and (or) climatic conditions and deserves further investigation. Our model can be used to quantitatively predict pollen cone production and assess the risk of jack pine budworm defoliation.Résumé : Les profils de production de cônes mâles chez le pin gris (Pinus banksiana Lambert) présentent un intérêt parce qu'ils pourraient contribuer à expliquer le comportement des épidémies de tordeuse du pin gris (Choristoneura pinus pinus Freeman). Nous avons utilisé des modèles linéaires mixtes généralisés pour analyser la production de cônes mâles dans 180 placettes permanentes en Ontario, au Canada, entre 1992 et 2008. La production de cônes mâles augmentait avec l'âge du peuplement et les gros arbres dans les peuplements clairsemés produisaient plus de cônes mâles. La défoliation réduisait la propension des arbres à produire des cônes mâles pendant au moins deux ans. Nous avons aussi identifié des profils importants qui ne sont pas expliqués par la défoliation ni par les caractéristiques du peuplement. La production de cônes mâles est spatialement synchronisée d'une année à l'autre : les arbres produisaient plus de cônes mâles dans le centre que dans le nord-ouest de l'Ontario, et la production historique de cônes mâles a augmenté avec le temps dans la région centrale mais pas dans les placettes les plus éloignées vers le nord-ouest. La reproduction synchrone est courante parmi les espèces d'arbre mais n'avait pas jusqu'ici été observée chez les cônes mâles du pin gris. La production accrue de cônes mâles dans le centre de l'Ontario pourrait être un indice que les conditions climatiques et la forêt changent et mérite d'être davantage étudiée. Notre modèle peut être utilisé pour prédire de façon qualitative la production de cônes mâles et évaluer le risque de défoliation par la tordeuse du pin gris. [Traduit par la Rédaction] Mots-clés : Choristoneura pinus, Pinus banksiana, dynamique des populations, synchronisme spatial, interactions ...

Comparative ecology of conifer-feeding spruce budworms (Lepidoptera: Tortricidae)

“…Volney (1988) proposed a 10-year periodicity for jack pine budworm outbreaks in the Prairie Provinces of Canada but this was confounded with the periodicity of forest fires, which influence this system significantly. Regardless, this apparent historical pattern has changed because outbreaks of jack pine budworm have been essentially absent from the prairie region since Volney’s analysis and have become recurrent, if not yet periodic, more than 1000 km east in Ontario, Canada (Scarr et al 2012; Hughes et al 2014). Surveys from Wisconsin, United States of America, revealed highly variable periodicities averaging from five to 12 years depending on specific site conditions (Volney and McCullough 1994).…”

“…Jack pine budworm, however, is unable to mine the needles of jack pine and so pollen cones are critical during its spring dispersal period (Nealis and Lomic 1994). Fortunately for jack pine budworm, jack pine has a high propensity to produce pollen cones (Nealis et al 2003; Hughes et al 2014). So an adaptive syndrome for all budworm species that mitigates the problems of precocious emergence is the temporary use of previous years’ needles and pollen cones when available.…”

“…What happens to these early-season feeding sites during outbreaks emphasises the differences among host tree species and consequent dynamics of their associated budworms. When defoliated, conifers reduce pollen cone production abruptly (Blais 1952; Nealis et al 2003; Hughes et al 2014). This has an immediate impact on jack pine budworm that now must forage more extensively for scarce resources critical to its survival (Nealis and Lomic 1994).…”

Oviposition and feeding on red pine by jack pine budworm at a previously unrecorded scale

“…Pollen cone production and abundance can be highly variable from year to year for both jack and red pine. The production of pollen cones is affected by a variety of factors, including tree size and age (McCullough, ; Hughes et al , ), tree vigor (Hodson & Zehngraff, ), nitrogen (McCullough & Kulman, ), stand density (Kulman et al , ; Batzer & Jennings, ) and prior defoliation (Nealis & Lomic, ). Thus, forecasting peak years of pollen cone production by jack pine and red pine or how larvae of jack pine budworm will respond to pollen cone dynamics remains challenging, as well as unexplored for red pine.…”

Landscape Features and Processes Influencing Forest Pest Dynamics

“…In this case, the distribution of pine tree phenotypes that are preferred by budworms are not randomly distributed within forest stands during or after jack pine budworm outbreaks. Instead, pines are found structured within stands in relation to the interactions among insect outbreak history, stand age (older trees produce more pollen cones), and synchronized spatial patterns of pollen cone production across the landscape [95].…”