Seed Dispersal in Pines (Pinus) (Journal Article)

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Abstract: Pines (n = 121 species) are important elements of forest ecosystems. They are economically and ecologically valuable and are often at the center of efforts to manage forests to reduce the risk of wildland fires. The pattern and process of pine seed dispersal and seedling establishment have important implications for maintaining healthy forests. 75% of pines are dispersed by wind, and 25% are dispersed by scatter-hoarding birds and rodents. Among the wind-dispersed pines, there are about 20 species that attract the attention of seed-caching animals that gather seeds and cache them in soil, so these species are dispersed by a combination of wind and animals. Animal-dispersed pines often occur in semi-arid ecosystems. The seeds cached by animals are a dynamic resource. Animals pilfer each other’s caches, move them to new sites and recache them. Some seed reside in dozens of different cache sites between seed maturation and seed germination. Many pines are adapted to fire. This involves serotinous cones (about 24 species), which are dense, woody, and lignified and remain closed at maturity. Serotiny establishes a canopy seed bank that can persist for several decades. Shortly after fire, these cones open and shed seeds onto the burned landscape. Pines often mast, producing large crops of seeds at intervals of several years. These large cone crops satiate the appetites of specialist seed predators, resulting in increased seedling establishment and also increases the effectiveness of seed dispersal. In the past, pines have responded to climate change by shifting geographic ranges, and some pines appear to be responding to warming climates in a similar way.