The long-term stability and resilience of our forests depends on tree reproduction. Understanding and predicting demography is critical to determine whether reproduction can balance increasing mortality and facilitate range shifts to track suitable habitats. This is particularly challenging for plant species with highly variable reproduction, known as “mast seeding.” Using a 27-year reproduction dataset on Pinus edulis data from the Sevilleta Long Term Ecological Research (LTER) and newly germinated seedlings data, we examined the plant seed to seedling transition. Specifically, we asked (1) Are seedling hotspots spatially distributed near super seed producers? (2) Which micro-conditions are important for seedling survivorship? In September 2021, we established eight permanent 100 m transects (four east to west transects and four north to south transects) on a 1-hectare plot. Together, we tagged 1st year P.edulis seedlings and measured plant height and stem diameter. Additionally, we selected and measured three microhabitat variables that were expected to affect seedling survival, including canopy openness, litter thickness, herb coverage for each seedling. The labeled seedlings that were still alive were censused bi-monthly.
Results/Conclusions
A total of four-hundred seedlings were tagged, measured, and censused from September 2021 until present. We find that seedlings are spatially aggregated near super seed producers but seedling survival is trait and micro-environment dependent. For example, seedlings in environments with greater litter cover and moderate canopy openness have a higher survival rate than seedlings with less litter cover and either extensive or minimal canopy openness In addition, we find that the seedlings that died had smaller heights and smaller diameters during the initial survey in September 2021 suggesting that these seedlings were showing early signs of stress. In a changing climate plant reproduction is expected to become more variable and less predictable. For plant species that already have episodic reproduction such as “mast seeders” this means even smaller seed crops spaced over multiple years. Tracking the fate of seedlings allows researchers to understand the benefits of masting on seedling recruitment and make predictions of how a changing climate will affect the long-term stability of forests.
