Factors affecting primary production and respiration in small forested pools

Background/Question/Methods

Small temporary and permanent wetland pools were once a common feature of northern temperate forests, but a legacy of deforestation, tillage and erosion has reduced their numbers substantially.  These pools are often hydrologically isolated and underweak regulatoryprotection, but increasingly studied as vital amphibian habitat.  Construction of vernal pools is becoming more common to replace those lost and help conserve both abundant and endangered amphibian species requiring this specialized habitat for breeding.  Despite the proliferation of studies on woodland pool use and construction, there is still little understanding of these aquatic ecosystems.  In particular, factors regulating ecosystem processes such as primary production and respiration are generally uninvestigated, although they may contribute to success of amphibians and other species in both natural and constructed forested pools.

Here we report on a study conducted in summer 2012 in which we measured pelagic primary productivity (GPP, NPP) and respiration in a subset (26 ) of constructed small pools (72 total) in a mixed second growth forest (Heiberg Forest, Tully, NY), and correlated these rates with potential influencing factors including canopy cover, light extinction coefficients, chlorophyll a, DOC, and turbidity.  We used light/dark bottle incubation and oxygen change to estimate production and respiration.

Results/Conclusions

Even within this set of recently constructed pools in the same forest there were substantial differences in light climate among pools.  These include large differences in (1) light reaching the pools due to variable amount of canopy cover (range of 31-97% initially) and (2) order of magnitude differences in light extinction coefficients among the pools.  The factors contributing to light extinction also differed among pools, again including order of magnitude variation in both turbidity and DOC.  Chlorophyll a was also extremely variable (all pools' mean 21 +69 ug/L).  Current results highlight the importance of total light availability for chlorophyll a and primary production in the pools.  Further analyses will be conducted to determine the contribution of each component of light climate (canopy cover, turbidity, chlorophyll and DOC) to primary production and respiration.  The relative importance of autochthonous (in pool) production versus supply of allochthonous (leaf litter) material to a pool is thought to be important not only for understanding the pool ecosystem, but also potentially for amphibian success. These results will contribute to knowledge of how pool construction micro-site choice affects autochthonous pelagic production, leading to increased functionality of small constructed forested pool systems.