Plant available NH4, NO3, and PO4 was determined at sites near ARC LTER Toolik acidic tundra and at a toposequence along the floodplain of the Sagavanirktuk River using 2 N KCL and weak HCL extracts. This file complies data collected at different times from 1987 through 2001 and includes initial extracts taken for buried bag method of net nitrogen mineralization.
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Cores (5.95cm diameter) were taken at various communities near Toolik Lake and at the toposequence at the Sagavanirktuk River. Some cores were from experimental plots: i.e. plots treated with annual fertilization treatments of 10 g/m2 Nitrogen (as NH4NO3) and 5 g/m2 Phosphorous (as triple superphosphate) and with greenhouses and shadehouses, annually set up in late May or early June and removed at the end of August or early September.. Cores from the tussock communities were taken in moss dominated intertussock spaces. The cores were separated into organic (O) and mineral horizons (B), with corresponding lengths recorded directly from the core hole. For NH4-N and NO3-N extractions 100mls of 2N KCl was added to approximately 20g wet set homogenized soil. A 0.025N HCl solution was used to access plant available PO4-P. KCl extracts were shaken for 2 hours and weak HCl extracts for 5 minutes. All extracts were immediately filtered through Whatman No. 42 filter paper. PO4-P and NH4-N extractions were hand run on a spectrophotometer (following LTER protocol) using an 5 or 1cm cell or were run on an autoanalyzer at Toolik. NO3-N extractions were either run on an autoanalyzer at Toolik or frozen and run on an autoanalyzer following LTER protocol in the fall at Woods Hole, MA.
Notes: This file contains all data from the analysis, including bulk density and soil moisture calculations. See variable comments for notes on the different extractions.
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