Ecological Archives E093-133-A3

Madeleine M. Mineau, Colden V. Baxter, Amy M. Marcarelli, and G. Wayne Minshall. 2012. An invasive riparian tree reduces stream ecosystem efficiency via a recalcitrant organic matter subsidy. Ecology 93:1501–1508.

Appendix C. Additional OM budget methodology and data.

We used data on organic matter fluxes and pools collected at Deep Creek to compile the partial annual organic matter budgets presented in Fig. 1. For GPP, ER, and P:R, we used the measurements described in the methods to estimate monthly values for each of these metrics. If no data were recorded in a given month, the nearest measurement in the same season was used. For example the value for February was also used as the estimate for January at the invaded reach. If multiple measurements were made in the same month, either the same or different years, these values were averaged. Values were scaled from per day to monthly estimates by multiplying by the number of days per month and the monthly values were then summed to produce annual estimates. For the IBP study, published annual estimates were used (Minshall 1978). Annual flux of litter inputs from the IBP study and our study were calculated by scaling daily values measured in June - December to monthly values as described above. The value for May was assumed to be half that for June and values for January–April was assumed to be negligible and assigned a value of zero. We determined that scaling CPOM fluxes in the same manner as other fluxes was not appropriate because this is one of the most variable components of stream organic matter budgets. Estimates of CPOM flux ranged from net import to net export for each site, time period, and CPOM type (Table C1). Furthermore, we judged that scaling measurements made in 15 minute intervals to monthly values would likely not be representative. Rather, individual measurements were scaled to a daily value from water volume passing though the drift net to daily discharge. We then used the median of all daily estimates made for each CPOM type at each site and scaled these to an annual estimate by multiplying by 365. BOM standing stock was measured in pool and riffle habitats and the mean of these two values are used as the whole stream value in Fig. 1. In order to present a better understanding of the variability of the measurements made for the fluxes and pools included in the partial organic matter budget (Fig. 1), we present the mean and range for each component in Table C1.

Though we were unable to include dissolved organic carbon (DOC) in the organic matter budget, we include here all DOC data collected at Deep Creek from March 2008–February 2009 (Table C2). DOM data from the IBP study is unreliable and cannot be compared to recent measurements. Suspicious of values in the annual reports, we re-calculated DOC concentrations based on raw data of O2 consumption from the dichromate oxidation method used and obtained the same impossibly large values of DOC concentration (> 100 mg·L-1). We determined that these data are flawed and therefore a before-after comparison similar to the other fluxes included in the budget was not possible. The values presented in Table C2 reflect concentration at the downstream end of the study reach for each date. A grab sample was collected from the thalweg and placed on ice until it was frozen the same day. Samples were later thawed, filtered using ashed GFF filters, and analyzed using the UV oxidation method on a Sievers 900 series total carbon analyzer (GE Analytical, Boulder CO).

Table C1. Mean and range for each OM flux and pool presented in the partial OM budget in Fig. 1.

  Units Mean (range)
reference reach
IBP pre-invasion
Invaded reach
IBP pre-invasion
Litter input mg AFDM m-2day-1 2
GPP g C m-2 day-1 0.75
ER g C m-2 day-1 0.69
P:R   0.90
CPOM AL mg AFDM day-1 -1.18
CPOM AT mg AFDM day-1 -3.62
BOM g AFDM m-2 571 1459
487 2058

Abbreviations are defined in the main text.

Table C2. Dissolved organic carbon concentrations in Deep Creek in mg L-1. NM = not measured.

Date Reference Invaded
19 March 2008 1.1 0.7
21 April 2008 1.2 0.6
7 May 2008 3.1 0.6
13 June 2008 2.2 1.1
23 June 2008 NM 0.5
2 July 2008 NM 1.3
28 July 2008 1.4 1.3
3 September 2008 1.6 1.1
29 October 2008 1.6 1.5
20 February 2009 1.8 0.9
Mean 1.7 1.0
SE 0.2 0.1

Literature Cited

Minshall, G. W. 1978. Autotrophy in stream ecosystems. Bioscience 28:767–771.

Webster, J. R., and J. L. Meyer. 1997. Organic matter budgets for streams: A synthesis. Journal of the North American Benthological Society 16:141–161.

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