The differential contribution of coyotes and passerines on future biotic carbon storage through juniper seed dispersal

Abstract

Differences in seed dispersal patterns can alter plant distributions, species persistence, plant community composition, and biotic carbon sequestered within a landscape. Though carnivorans are known to be frugivorous, their contribution to seed dispersal is marginally studied, especially compared to other sympatric dispersers such as passerines. This gap is important to understand because carnivorans may be better suited to assist plant dispersal in disturbed habitats and the longer distances necessary for climate migration. In this study, we evaluated how seed dispersal by a particular carnivoran, coyote Canis latrans, differed from passerines Passeriformes for juniper Juniperus sp. in the conterminous United States under future climate change. We modeled changes in juniper niche suitability starting in 2021 through the next 80 years of climate change by estimating the current niche with Maxent, and then using climate predictions to define spatial changes in suitable niches. Seed dispersal by both coyote and passerine dispersers was simulated to estimate total juniper dispersal, juniper encroachment into grasslands, and finally changes in above‐ground biotic carbon storage due to juniper encroachment. Our models indicate that over the next 80 years, suitable conditions for juniper will contract, but losses from the current range will be minimal. Our model suggests that coyote dispersal of juniper will result in a 54–59% increase in range, which is 2.5 times as much as the estimated increase provided by passerines. We estimate that coyotes will facilitate juniper encroachment into 170 000–185 000 km2 of current grasslands, 3.4 times as much as passerines. Modeling the effect of coyote‐mediated juniper encroachment of grasslands, we forecast that the addition of woody aboveground biomass will provide between 1.1 and 1.2 Pg of additional carbon storage over the next 80 years. Results highlight how coyotes and passerines provide different outcomes for changes in juniper ranges, plant community composition, and landscape carbon storage. Understanding the differences in outcomes provided by different seed dispersers is important for modeling plant species distributions and carbon storage.