COS 22-9 - Resource acquisition strategies of tropical dry forest tree species predict seedling performance in a large-scale restoration experiment

Monday, August 7, 2017: 4:20 PM
B115, Oregon Convention Center
Leland K. Werden, Plant and Microbial Biology, University of Minnesota - Twin Cities, St. Paul, MN and Jennifer S. Powers, Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN

Successional trajectories of tropical dry forests (TDFs) are not well understood, but recent observational studies have found TDFs transition from tree communities with conservative traits to communities with acquisitive traits, the opposite of tropical wet forests. Considering successional and resource use theory when designing TDF restorations could therefore increase restoration effectiveness. To determine if the presence or absence of remnant vegetation controls the performance of tree species with different resource acquisition strategies, we planted a 6-hectare restoration experiment with communities of seedlings that have conservative or acquisitive trait syndromes into plots with different management treatments: (1) fully clearing existing vegetation to simulate early succession, or (2) interplanting seedlings into existing vegetation to simulate later succession. Twelve native species were assigned to acquisitive or conservative groups based on hierarchical cluster analysis of multiple traits, resulting in communities of six species for each trait syndrome. In September 2015, we fully cleared three 1 ha plots, and three 1 ha plots were left with scattered trees. Each 1 ha plot was divided into four 50x50 m split plots, and two replicates each of the species mixes (acquisitive or conservative) were assigned randomly to those plots. To quantify seedling performance we measured seedling survival seasonally for one year.


Environmental conditions differed between management treatments with dry season soil moisture in the interplanted plots 3% higher, and mid-day soil temperature 5.2 °C lower, than the fully cleared plots. We therefore hypothesized conservative species would have higher survival than acquisitive species in the cleared treatment because conservative TDF species are theoretically more adapted to early successional conditions. Our data were consistent with this hypothesis, as conservative species had 9.3% higher survival in the cleared treatments than acquisitive species (p<0.05). By contrast, we hypothesized that acquisitive species would have higher survival than conservative species when interplanted into existing vegetation. However, we found that conservative species had higher survivorship than acquisitive species in the interplanted treatment (p<0.05), but the difference was only 4.0%. Our initial results show that species with conservative traits have higher survivorship than species with acquisitive traits at early successional stages, which aligns with recent advances in TDF successional theory. Furthermore, while we did not find any differences in overall survival between the cleared (30.3%) and interplanted (30.4%) management treatments, conservative species had 6.7% higher survival overall (p<0.05), indicating that successional and functional trait theory can aid in the design of TDF restoration projects.