Ecosystem Function Components, Blandy Experimental Farm
These data were collected during the 2017 and 2018 growing seasons and are components of 5 ecosystem functions: primary productivity, net N mineralization, decomposition, leaching, and respiration. These were measured in 5 plots within 3 different land-use types: an agricultural field, a restored Virginia native plant meadow, and an unmanaged early successional field. The data were used in conjunction with a framework to quantify ecosystem functions in order to estimate supporting ecosystem services, which are difficult to quantify. Supporting ecosystem services that were estimated using these functions were: primary production, nutrient cycling, and soil production. We acknowledged that not all ecosystem functions are necessarily beneficial and therefore should not always be equated to services in and of themselves. For example, we acknowledge that leaching results in a loss of N from systems and that respiration, while associated with decomposition and soil formation, also results in a loss of C from systems.
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Biomass was harvested from three 0.25 m2 subplots within each plot in the early successional field and native prairie. Dry weights were recorded for the total standing dead and live material of each plant functional type for each of the three replicate subsamples from each plot in these fields. Given the spatially uniform nature of the agricultural field, two millet plants were sampled from each plot in this field. The number of plants within multiple 1 m2 areas were counted and multiplied by the mean mass of the two harvested individuals. In situ soil CO2 efflux was measured with a portable infrared gas analyzer with attached soil respiration chamber (EGM-4; PP Systems, Amesbury, MA), to serve as a proxy for soil respiration. Measurements were taken mid-day between 10h and 14h once per week during May and June in the three replicate subplots within the five plots of both the native prairie and early successional field. Litter was collected from an undisturbed 0.25 m2 corner of each of the three 1-m2 subplots in each plot at the beginning of the 2018 growing season. Each sample was oven-dried and weighed to estimate the litter pool, established from litter fall of multiple previous growing seasons. Seasonal litter inputs were estimated based on the amount of live foliar biomass (no evergreen species were present in plots used in this study). The maximum possible seasonal litter inputs were also estimated by adding the standing dead biomass to the total foliar biomass. The leaf litter pool, sampled at the beginning of the growing season, when compared to the estimated seasonal litter input, provided insight into the rate of aboveground litter decomposition. Three 1-month NNM in situ resin-core incubations were conducted in three replicate subplots of the five plots in each land-use type using the resin-core method of DiStefano and Gholz (1986). The resin bag acted to capture any NO3- or NH4+ that leached from the soil core, which also gives an estimate of vertical N flux. Resin bags were constructed of nylon and contained a mixture of 1-tablespoon each of cation (USF C-211 resin cation, Na form) and anion (USF A-464 resin, Type I anion, Cl form) resins. Soil samples and resin bags were retrieved after one month in the field and immediately frozen to minimize further microbial activity. NO3- and NH4+ were extracted from samples using KCl extraction methods (Baer and Blair, 2008) and run through an autoanalyzer (Lachat QuikChem 8500; Hach Company, Loveland, CO) for detection of NO3- and NH4+. All samples were diluted with 2 M KCl to fall in the range of response curves. NNM was calculated as change in NO3 and NH4 in cores after the one-month incubation, plus any detected in the resin bags. Soil samples were collected from each plot across 10 cm increments to a 30 cm depth. Samples were collected mid-July and mid-October during 2018. Samples were treated in the laboratory in the same manner as in the NNM analysis.