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Title: Population Dynamics of the Island Torrey pine (Pinus torreyana insluaris) on Santa Rosa Island, CA

Hypothesis:

What effect does precipitation and leaf litter have on the germination (time and probability) of Pinus torreyana insluaris?

Abstract:

The Torrey pine (Pinus torreyana and ssp. Pinus torreyana insularis) is the rarest pine species in North America, with populations limited to San Diego and Santa Rosa Island (SRI), CA. Over the past century, non-native ungulate grazing and erosion reduced recruitment and distribution of P. torreyana insularis. To aid this recovery, all non-native ungulates were removed from SRI in 2012. We began censusing this population in 2013 to determine: (a) population size and any recovery trajectory; (b) spatial variation in population structure; (c) spatial pattern of distinct age classes; (d) environmental factors correlating with seed germination and seedling survival; and (e) conservation gains associated with non-native ungulate removal. 24,192 individuals make up the SRI population, of which 3,068 are sexually mature. Using a point density calculation within ArcMap, we isolated six distinct groves on SRI. Groves were further characterized by collecting tree cores to determine relative age and permanent plots were established to monitor seedling and sapling survival. It was determined that smaller, younger individuals are frequently located on the edges of the groves, while larger, older individuals tend to dominate grove centers. To understand this recent recruitment and ideal reproductive habitat, a common garden study was performed to evaluate germination (time and success) under the presence or absence of leaf litter and historical precipitation since 1999. Data from this study is imperative for resource managers quantifying the ongoing recovery of the SRI Torrey pine.

Data Figure:

Test from the field!