Study Number: 

1107

Project Title:

CWT 15N -protein-tannin-complex field tracer study.

Investigator(s):

Ronald Hendrick | Biographical Sketch | E-Mail | Tel. 706.542.1385 | Fax. 706.542.8356
Nina Wurzburger | E-Mail | Tel. 706.542.1385
Affiliated Institution(s): University of Georgia
Address: School of Forest Resources
University of Georgia
Athens, Georgia 30602
Study Type: Terrestrial
Project Type: Type 1
Study Period:

07/2005 - 08/2006.
Status/Notes:

Related to project 1088.
Funding Sources:

National Science Foundation, Grants DEB-9632854 (Text Version) and DEB-0218001 (Text Version) to Coweeta LTER.
Abstract: In the southern Appalachians, Rhododendron maximum (Rm) thickets suppress overstory regeneration. While there has been research on the effects of Rm thickets on physical and chemical environment, to this point, the functioning of Rm litter and ericoid mycorrhizas (ERM) has been unexplored. We examined the possibility of a N feedback between litter and ERM fungi in high elevation hardwood forests at the Coweeta hydrologic lab. Rm thickets increase leaf and root litter inputs and Rm soils contain two times as much C and eight times as much N in the organic horizons, compared to hardwood soils. Rm litter also has a greater capacity to create protein- tannin (P-T) complexes in laboratory assays. Together, these results suggest that the greater amount of organic matter and organic N under Rm is a function of litter quality and the formation of P-T complexes. While P-T complexes are recalcitrant, the mycorrhizal fungi of ericaceous plants, ERM fungi, have the ability to access this sequestered N via extra-cellular polyphenol oxidases (PPO). We found soil PPO activity to be significantly greater under Rm in the O horizons compared to hardwood soils. Rm litter polyphenols may create a pool of organic N that is recalcitrant to ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) overstory recruits, yet remains available to Rm itself. However, an examination of the movement of N from P-T complexes into Rm biomass, compared on a relative basis with N movement into ECM and AM overstory trees is necessary to provide closure of this proposed positive feedback between Rm litter and ERM fungi. We propose a field tracer study using 15N labeled P-T complexes to quantify movement of 15N into soil pools and root biomass. Conducting this study in the field provides clear relevance to the research question as 1) microbial and mycorrhizal fungal communities will be unaltered, 2) ERM, ECM and AM roots coexist under Rm, and ECM and AM coexist in hardwood stands, 3) N inputs from the tracer in our plots can be placed into the context of N budgets estimated from our previous work.
Location(s), Described: Research will be conducted near the Coweeta Hydrologic Lab/Nantahala NF boundary at ~4800’ (west of the watershed 28 boundary on the NW-facing slope of Big Butt, and east of road 83).
Location(s):
Elevation
Decimal Degrees
UTM, Zone 17, NAD83		 Requested GPS Points from  Brian Kloeppel, February 2006.
Location(s), Download GPS: ArcView Shape Files (shp.):  UTM, NAD83, Zone 17 |  Lat/Lon
 
Location(s), Online Maps: Online map
Methods/Experimental Design: Four types of P-T complexes will represent four treatments: 15N-protein + hardwood tannin, 15N-protein + Rm tannin, 14N-protein + hardwood tannin, and 14N-protein + Rm tannin (with the latter two being control treatments of the previous two). Four treatments will be replicated 4 times and sampled on 2 dates (2 and 10 months) (4 x 4 x 2 x 2 = 64). Treatments will be replicated once in each of 4 sets of paired plots (Rm thicket and hardwood stand). P-T complexes will be suspended in deionized water and applied at a rate of 0.5 g N m-2 over an area enclosed by a 2” pvc ring (area = 0.00204 m2). This N application rate is similar to the estimated annual N inputs from Rm leaf fall. The 15N enrichment of the P-T complexes will be between ~50 atom percent. Soils will be sampled with a corer of the same diameter as the pvc ring (2”) to 10 cm depth. Because of the recalcitrance of P-T complexes, we expect to recover 80-90% of the applied 15N within a core. At sampling, each core will be processed for root and soil samples. Mycorrhizal roots will be sorted into 2 or 3 classes depending on location (ERM, ECM and AM). Soils will be extracted for inorganic N, DON, microbial N and total soil N. Roots will be cleaned, dried, weighed and analyzed for %N and 15N. Soil pools will be analyzed for N concentrations and 15N at the Stable Isotope Facility at the Institute of Ecology, UGA.
Sampling Frequency: Six weeks, yearly.
Data Columns: None Available.

Missing Data Codes: . (Period)
Publications: Wurzburger, Nina; Hendrick, Ronald L. 2007 Rhododendron thickets alter N cycling and soil extracellular enzyme activities in southern Appalachian hardwood forests. Pedobiologia. 50: 563-576.
Data Restrictions: Users must adhere to the Coweeta LTER Data Policy.
Metadata: EML Format (XML Schema) | Information about EML
Data Downloads: Project is new and still in the data collection phase.