Pine Barrens field station

Field Studies of the Chemistry of Weathering Plant Material:
Pine Barrens Field Station

In order to monitor the chemistry in decaying leaves systematically over time in a natural setting, we have established a field station in the Lebanon State Forest in the Pine Barrens of New Jersey. Oak leaves and pine needles collected from the trees at the onset of senescence are encased in mesh and suspended in trays, where they are allowed to weather in the natural environment with full exposure to the elements. The leachate resulting from the interaction of rainwater with the plant matter is routed from the trays into collection carboys.

The field station entails guided management of different environmental parameters to investigate their effects on the chemical properties of decaying plant material. The degree of exposure of degrading plant matter to the biological and mineral content of the soil milieu is one major focal point of our field studies. Keeping trays of weathering plant material five feet above the ground prevents contact with soil minerals and minimizes interactions with mulch microbes. By controlling these factors, we can assess their role in certain chemical transformations during the decay of plant material.

Figure 1a

Figure 1b

Figure 1c

Figure 1: Above-ground leaf containment and leachate collection system.

 

Another set of sample trays sits embedded in the soil surface, with carboys for leachate collection buried a few feet underground. These below-ground sampling trays allow examination over time of leaves decaying under conditions that most resemble the natural degradation environment, fully exposed to the microbes and mineral dust of the surrounding mulch.

 

Figure 2b

Figure 2: Above-ground leaf containment and leachate collection system.

 

Figure 2a

 

Both the solid plant detritus and the liquid leachate are the focus of elemental and molecular analyses, including total organic carbon measurement, trace metal analysis, and spectroscopic studies. Material from the field station will be screened continually over the course of the next several years, with new experiments incorporated periodically (the next slated experiment will test the effect of exposure to sunlight on degradative processes). Meanwhile, laboratory experiments with model systems will supplement the field experiments with more precise mechanistic information.