Plants’ immobility poses challenges for key processes such as resource acquisition, growth, and fecundity that make plants vulnerable to a heterogeneous landscape. In harsh environments, like the semi-arid Southwestern US, environmental conditions further exacerbate plants’ limitations. Low precipitation, warm temperature, and a high vapor pressure deficit result in soil infertility and a drought prone environment. A common strategy in these ecosystems, with low plant productivity and low species diversity, is mast seeding (synchronous and episodic reproduction). Mast seeding benefits individuals by increasing plant fitness through economies of scale including predator satiation, improved seed-dispersal efficiency, and increased pollination success. Yet, the proximate cause of mast seeding remains unknown despite various hypotheses proposed in the literature. This research takes advantage of an ongoing long-term monitoring study for piñon pine (Pinus edulis) in semi-arid New Mexico to evaluate different resource availability hypotheses. We sampled over 50 piñon pines that varied from low mast seeding trees to high mast seeding trees. After correcting for age differences, we developed a model to test for trade-offs between basal area growth and cone production.
Results/Conclusions
We found a weak relationship between cone production and basal area growth. We had hypothesized that piñon pines with large cone production (high mast seeding) would have lower basal growth and that piñon pines with low minimum cone production (low mast seeding) would have higher basal growth following a resource allocation trade-off. We did not find support for differences in resource allocation between high and low mast seeding pines. Despite different cone production there was a high degree of synchrony across the trees which suggests that the pines are cueing in on a common weather signal and must have a baseline level of resources for cone production. Further work is needed to elucidate carbon partitioning between different sinks to evaluate what drives cone production and how this sink strength may change in response to warmer and drier conditions. Together these results suggest that mast seeding variability may not be driven by trade-offs.