Aboveground Growth 2001
PI: 	Jeff Welker
Natural Resource Ecology Laboratory
Natural and Environmental Science Building
Fort Collins, CO 80523
Office Phone: (970) 491-1796
E-Mail: jwelker@nrel.colostate.edu
co-PI:	Jace Fahnestock
Natural Resource Ecology Laboratory
Natural and Environmental Science Building
Fort Collins, CO 80523
Office Phone: (970) 491-5262
E-Mail: jace@nrel.colostate.edu
Contact: Paddy Sullivan
Natural Resource Ecology Laboratory
Natural and Environmental Science Building
Fort Collins, CO 80523
Office Phone: (970) 491-5630
E-Mail: paddy@nrel.colostate.edu
Funding Source
	NSF (OPP-019643)
Overview
	Above-ground growth data were collected from June 5-August 13, 2001 for
Betula nana and Eriophorum vaginatum at the Toolik Lake LTER (68º 38'N, 149º 
43'W) ITEX moist tussock snowfence site.  Measurements were taken at a mean 
interval of 7.58 days in plots treated with elevated winter snow (7th year of 
treatment - ~3m drift), warming (1st year of treatment - ITEX open-top chambers) 
and fertilization (1st year of treatment - 2 applications: June 5 and July 9, 
2001, each @ 15g N m-2).

Instrument Description
	Successive measurements of the same leaf/woody stem were taken with a 
metric ruler and growth was identified as the difference between the current 
measure and that of the previous sampling date.  Betula nana woody stems were 
marked with white-out to distinguish between 2000 and 2001 growth.

Data Collection and Processing
	Measurements were taken from 5 E. vaginatum new leaves, 5 E. vaginatum 
over-wintering leaves and 5 B. nana woody stems per plot.  7 plots were treated 
with elevated snow, 8 plots were treated with N fertilizer, 6 plots were warmed 
and 8 plots served as controls.  All of the measurements were taken by the same 
individual and measurements were taken blind (i.e., no knowledge of the leaf/stem 
length on the previous sampling date).  Daily growth rates of each species/cohort 
were calculated for each sampling interval. 

Data Format 
	Missing data: "."
	Negative values for interval growth were changed to "0"
	Column Headers 
		Julian Date
		Plot
		Replication
	E_O Daily (Overwintered E. vaginatum leaf interval growth/days in 
interval)
		E_N Daily (New E. vaginatum leaf interval growth/days in interval)
		B Daily (B. nana woody stem interval growth/days in interval)

Data Remarks
	Taking these above-ground measurements blind (i.e., no knowledge of the 
leaf/stem length on the previous sampling date) reduced potential subjectivity, 
but increased the occurrence of intervals with negative growth and increased the 
variance in our measurements.  There are instances in the data sets where the wrong 
leave or stem was measured for one or more sampling dates.  These measurements are 
considered missing until successive samples of the same leaf/stem are resumed.