Do key dimensions of seed and seedling functional trait variation capture variation in recruitment probability?
Seedling recruitment is a critical driver of population dynamics and community assembly, yet we know little about functional traits that define different recruitment strategies. For the first time, we examined whether trait relatedness across germination and seedling stages allows the identification of general recruitment strategies which share core functional attributes and also correspond to recruitment outcomes in applied settings. We measured six seed and eight seedling traits (lab- and field-collected, respectively) for 47 varieties of dryland grasses and used principal component analysis (PCA) and cluster analysis to identify major dimensions of trait variation and to isolate trait-based recruitment groups, respectively. PCA highlighted some links between seed and seedling traits, suggesting that relative growth rate and root elongation rate are simultaneously but independently associated with seed mass and initial root mass (first axis), and with leaf dry matter content, specific leaf area, coleoptile tissue density and germination rate (second axis). Third and fourth axes captured separate tradeoffs between hydrothermal time and base water potential for germination, and between specific root length and root mass ratio, respectively. Cluster analysis separated six recruitment types along dimensions of germination and growth rates, but classifications did not correspond to patterns of germination, emergence or recruitment in the field under either of two watering treatments. Thus, while we have begun to identify major threads of functional variation across seed and seedling stages, our understanding of how this variation influences demographic processes-particularly germination and emergence-remains a key gap in functional ecology.
Environmental Sciences Graduate Program, Oregon State University, Corvallis, OR, 97330, USA. jlarson@chapman.edu.|Schmid College of Science and Technology, Chapman University, Orange, CA, 92866, USA. jlarson@chapman.edu.
Julie E
JE
Larson
United States Department of Agriculture-Agricultural Research Service, Burns, OR, 97720, USA.
Roger L
RL
Sheley
United States Department of Agriculture-Agricultural Research Service, Boise, ID, 83712, USA.
Stuart P
SP
Hardegree
College of Forestry, Oregon State University, Corvallis, OR, 97330, USA.
Paul S
PS
Doescher
Sierra Foothills Research and Extension Center, University of California Division of Agriculture and Natural Resources, Browns Valley, CA, 95918, USA.
Jeremy J
JJ
James
D018525:Germination; D010641:Phenotype; D018515:Plant Leaves / Q000502:physiology*; D018517:Plant Roots / Q000502:physiology*; D006109:Poaceae / Q000254:growth & development / Q000502:physiology*; D011336:Probability; D036226:Seedlings / Q000254:growth & development / Q000502:physiology*; D012639:Seeds / Q000254:growth & development / Q000502:physiology*; D014867:Water
D014867:Water
Emergence; Germination; Plant functional type; Roots; Survival