Ecological drivers of plant life-history traits: Assessment of seed mass and germination variation using climate cues and nitrogen resources in conifers

摘要

Understanding plant-environment interactions is an important link to studying the impact of climate change on community assemblies and population dynamics, especially for tree species that define the ecosystem they occupy. Based on seed mass and germination data of three conifers over six decades (1955-2015) across British Columbia, Canada, we performed pairwise correlation analysis between focal traits and the environment (climates in crop year and four prior-years and nitrogen resources). Using key environmental correlates, we constructed a linear mixed model to assess both traits and performed linear discrimination analysis to predict trait tendencies under future climate scenarios. Findings showed that seed mass variation was considerably ascribed to nitrogen deposition and climate in prior-years preceding seed crop. Climate in crop year had higher correlations with seed germination than in prior-years, but germination-climate correlations were much weaker than seed mass-climate counterparts. Both seed mass and germination had high correlations with temperature-based climate variables, such as evapotranspiration, degree-days above 5 degrees C (positive) and below 18 degrees C (negative); however, some climate variables had high but opposite correlations with the same trait between species. Across the study region, ecological trade-offs between species were similar for the aspect of temperature but differed between precipitation-based variables, indicating the important role of precipitation in ecological constraints. Finally, we predicted that climate change would result in more spatially homogeneous traits and make them shift towards intermediate or low levels. These results have important implications for the natural seedling regeneration of forest trees under climate change, which potentially cascades to influence trait expression, plant fitness and population persistence.