1999 Progress Report: Foliar Chemistry as an Indicator of Forest Ecosystem Status, Primary Production and Stream Water ChemistryEPA Grant Number: R825865
Title: Foliar Chemistry as an Indicator of Forest Ecosystem Status, Primary Production and Stream Water Chemistry
Investigators: Aber, John , Bailey, Scott , Driscoll, Charles T. , Hallett, Richard , Martin, Mary , Ollinger, Scott , Smith, Marie-Louise
Current Investigators: Aber, John , Bailey, Scott , Hallett, Richard , Martin, Mary , Ollinger, Scott , Smith, Marie-Louise
Institution: University of New Hampshire - Main Campus
EPA Project Officer: Hahn, Intaek
Project Period: June 1, 1998 through May 31, 2001
Project Period Covered by this Report: June 1, 1998 through May 31, 1999
Project Amount: $850,000
RFA: Ecosystem Indicators (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Ecosystems
The study area is the White Mountain National Forest (WMNF), a 300,000 ha area in northern New Hampshire (Figure 1). Monitoring the biogeochemical status of forest and stream ecosystems is a key component of assessing environmental quality in the northeastern United States. Any monitoring system requiring spatially-continuous capabilities will need to use some form of remote sensing. Forest canopies are the only portion of the system accessible to optical reflectance remote sensing instruments, and so offer the most likely target surface for monitoring forest health in this spatial mode.
Forest productivity, soil chemistry, and foliar chemistry at the whole stand level are tightly linked to the biogeochemical status of the forest ecosystem and so to each other. If true, then streamwater chemistry, averaged over some time period, can be predicted from foliar chemistry.
Hypothesis 1. Foliar chemistry parameters will show predictable interannual variation in response to interannual variation in climate and hydrology. We have collected multiple years of foliar chemistry data from an intensive network of 50 plots at the Bartlett Experimental Forest (Figure 2). These data are in the process of being analyzed for statistically significant interannual variation.
Hypothesis 2. Mean, species-weighted foliar chemistry at the whole stand level will reflect both nitrogen (N) and cation status of a stand/watershed, and thus both forest productivity within a climatic zone and the time averaged chemistry of the drainage water.
Strong relationships among whole stand level foliar canopy N, net primary productivity (NPP), and forest floor carbon:nitrogen (C:N) ratios exist (Figure 3).
Figure 2. Bartlett Experimental Forest with permanent plot grid superimposed. Red plots are foliar chemistry and productivity plots in this study.
Figure 3. Canopy-soil-stand interactions at the Bartlett Experimental Forest showing a) foliar nitrogen concentration in relation to forest floor C:N ratio, b) foliar nitrogen concentration in relation to aboveground net primary production, c) forest floor C:N ratio in relation to aboveground net primary production, and d) forest floor C:N ratio in relation to annual net nitrification in soils.
Further analysis will determine if foliar cation concentrations are correlated with forest productivity. Streamwater sampling was initiated (November 1999) from 50 streams in the WMNF covering a range in estimated mineralogical richness. The sampling schedule involves quarterly sampling through August 2000. A nested approach was used to allow us to test the optimum scale at which streamwater chemistry may be predicted.
Hypothesis 3. Foliar chemistry can be measured and mapped, and forest productivity and streamwater chemistry predicted, over larger landscape areas using high spectral resolution remote sensing. We have established that foliar N and calcium (Ca) can be mapped across the WMNF (300,000 ha) using remote sensing technology (Figures 4 a, b). Foliar N is a good predictor of forest productivity. The relationship between foliar Ca and productivity needs to be examined. Streamwater data are not ready for analysis.
Hypothesis 4. Spatial patterns in soil mineralogy and chemistry for soils developed in glacial till can be predicted using a simple geometric model that examines bedrock geology and glacial processes.
A geographic information system (GIS) model has been developed for the WMNF that predicts the element content of the glacial till (Figure 5). The predications for till Ca have been compared to plot level foliar Ca data and a significant relationship exists (Figure 6).
The following activities are anticipated:
1. Continue collection and analysis of streamwater from 50 streams across the WMNF.
2. Process and analyze new AVIRIS imagery from low altitude platform for selected watersheds. AVIRIS low altitude data (3?4 m resolution) for summer 2000 has been requested through the NASA Airborne Science Program.
3. Collect data from new plots across the WMNF to validate foliar and glacial till element concentration maps.
4. Use soil and foliar element coverages to develop relationships with measured streamwater chemistry and forest productivity.
The proposed research will establish the linkage between foliar chemistry and the process of controlling forest growth, element loss, and streamwater chemistry, and the methods by which remote sensing can be used to predict canopy chemistry. This program then would establish the scientific basis for developing a satellite or aircraft based remote sensing program for monitoring forest health and streamwater quality.