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The DIRT Project (Detritus Input, Removal, & Transfer) |
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HISTORY OF FIELD INSTALLATIONS AND SAMPLING 1990: Plots for all treatments except O/A-less were established by September. Soil samples were taken from two pits in April and from several plots in October. Above-ground litter manipulations began in September and continued into November, the period in which 95% of all litterfall occurs. Litterfall manipulations have been carried out every fall thereafter. 1991: Soil respiration was measured using the soda lime method, from June through August (Bowden et al. 1993). O/A-less plots were established in July. Soils sampled in November were incubated for several months in the laboratory and were monitored for CO2 efflux, NH4+ and NO3- release. Soils were also analyzed for 13C and 15N content. 1992: Soil respiration was measured with the soda lime method from June through November. In October, Prenartâ tension lysimeters (TLs) were installed in all plots at 60 cm depth in the mineral soil. Conducted first tree inventory. 1993: Soda lime measurements of soil respiration were made from April through November. TDR (Time Domain Reflectometry) probes were installed in all plots at 15 cm depth in the mineral soil during the summer for the purpose of collecting soil moisture data in conjunction with soil respiration measurements. Zero-tension lysimeters (ZTL) were installed at in all plots at the organic-mineral soil interface to collect soil water percolating through the O horizon only. Soil solution was collected from ZTLs and TLs between June and December and analyzed for NO3-. Throughfall samples were also collected and analyzed for NO3-. 1994: Soil respiration was measured from April to November with both the soda lime method and by IRGA (infra-red gas analyzer). Continuous collection of soil temperature data at 5 and 15 cm in the mineral soil in all plots using a Campbell Scientific datalogger system began in June. Leaf litterfall collection and quantification began, using plastic laundry baskets located near each of the 21 plots. Soil solution was collected from April to December and analyzed for NH4+ and NO3-. 1995: Soil respiration was measured from March through October with the IRGA. All subsequent soil respiration measurements are made with the IRGA method only. Leaf litterfall was quantified. Soils were sampled from all treatments for physical and chemical analysis. Laboratory incubation was initiated on one subset of soils, with CO2, DOC, NH4+, and NO3- release monitored for several months. Another subset of soils was analyzed for microbial and microfaunal properties. 1997: Collection of coarse woody debris input (CWD) was begun on NO INPUTS plots (TOX) in order to quantify annual input of this litterfall fraction. CWD is defined as woody material between 0.8 to 2.5 cm diameter. TLs and ZTLs were sampled in all plots between May and November for analysis of soil solution DOC, DON, TDN, cations and anions. 1998: Soil respiration was measured from July through August. Leaf litterfall and CWD were quantified. 1999: Because it was previously determined that tree roots had grown into the root-excluded soils, trenches were redug around all NO ROOTS and NO INPUTS plots and relined with Griffolynâ and polyethylene sheeting. ZTL soil solution was collected from CONTROL, DOUBLE LITTER, and NO LITTER plots between May and November for DOC and DON analysis. Soil respiration was measured in the CONTROL, DOUBLE LITTER, and NO LITTER plots from June to November. Leaf litter fall and CWD were quantified. 2000: Soil respiration was measured from May - August. Litterfall and CWD were quantified. Soil solution was collected from ZTLs and TLs for DOC and DON analysis. Soils were collected from all plots in June for C and N analysis. 2001: Shadecloth was installed from May - November over all NO LITTER and NO INPUTS plots to kill moss growth. Dead moss was manually removed in December. Soil respiration was measured from May - October and soil solution was collected from TLs and ZTLs for DOC and DON analysis. Leaf litter and CWD were quantified. Onset Optic Stowawayâ dataloggers were installed in all 21 plots at a depth of 12 cm in the mineral soil in October. Soil temperature data are henceforth collected at 5, 12, and 15 cm with the exception of most NO ROOTS and NO INPUTS plots and several non-working 5 and 15 cm Campbell Scientificâ temperature probes. Completed tree reinventory. |