A key challenge of the 21st century is restoring habitats damaged by anthropogenic change. A promising avenue for improving restoration is the inclusion of microbial communities in management. Plant-associated microbiomes, for example, can improve plant fitness by ameliorating environmental stresses, yet their importance for restoration remains unresolved for many imperiled ecosystems. One such habitat, Everglades tree islands, has declined by up to 54% in some areas, releasing excess nutrients into surrounding wetlands and exacerbating nutrient pollution. We conducted a growth room experiment manipulating the soil microbiome and hydrological regime experienced by a declining tree Ficus aurea, to determine how microbiomes impact germination and growth under two recently proposed hydrological management plans. All treatments were watered at levels simulating natural precipitation, but plants in the “unconstrained” management treatment were allowed to accumulate water above the soil surface in the simulated wettest months of the year, while the “constrained” treatment had a reduced stage to avoid soil surface submersion. We measured germination and leaf growth throughout the experiment as well as above and belowground biomass and specific leaf area at harvest. We are currently sequencing the composition of the initial and final microbiomes to determine how hydrological treatment altered the microbial community.
Results/Conclusions
In general, the microbiome and changes in hydrology had substantial effects on tree performance. For example, tree germination was 19% greater in the microbial treatment (z1,175=2.98, p=0.0029) indicating a beneficial effect of the microbiome at this early developmental stage. We also found that the microbiome impacted functional traits of F. aurea with specific leaf area reduced by 31% compared to plants grown in the absence of microbes (F1,33=5.6, p=0.0200). Both microbial treatment and hydrology significantly affected biomass metrics, including root:shoot ratio, root mass, and shoot mass. Root and shoot length were also 47% and 37% smaller (respectively) in unconstrained watering treatments (Root: F1,33,=15.60, p=0.0003; Shoot:F1,33, =19.23, p= 0.0001) indicating that an excess of water acts as a stressor for F.aurea. Overall, our results suggest that use of a microbiome could enhance germination of a declining tree, while flooding in these early stages hinders growth. These data will be used to inform future restoration and management decisions in one of the world’s most iconic and ecologically-important ecosystems.