Research ArticleECOLOGY

Precipitation and temperature drive continental-scale patterns in stream invertebrate production

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Science Advances  17 Apr 2019:
Vol. 5, no. 4, eaav2348
DOI: 10.1126/sciadv.aav2348
  • Fig. 1 Conceptual diagram or metamodel of major hypothesized influences on ACSP.

    Covariates that are external to stream ecosystems (i.e., exogenous variables) are indicated by rectangles. Covariates that are direct measures of in-stream conditions or processes (i.e., endogenous variables) are indicated by ovals. Each covariate is also recognized as one of five color-coded types (see inset key): biogeography, climate, terrestrial habitat, in-stream habitat, and community. Solid black arrows depict known causal effects among covariates. Arrow labels correspond to exemplar references [A (23, 25), B (26, 27), C (35, 94), D (22, 95), E (36, 96), F (7, 28), G (29, 33), H (34, 97)]. Parenthetic signs next to black arrow labels indicate that the relationship is expected to be positive (+), negative (−), or variable (+/−). Solid green arrows depict fundamental relationships that are expected but not explicitly documented here (e.g., the negative relationship between latitude and air temperature). Dashed arrows depict hypothesized covariation among variables.

  • Fig. 2 SEMs of ACSP in streams and rivers.

    Models include an SEM for the U.S. (A) and for global streams and rivers (B). Exogenous variables are indicated by rectangles, and endogenous variables are represented by ovals. Coefficients of determination (r2) are shown for all endogenous variables, and standardized path coefficients are shown for all modeled relationships. Positive and negative effects among variables are depicted by black and red arrows, respectively, with arrow widths proportional to effect sizes (i.e., path coefficients). In the U.S. model, significant covariance between mean annual water temperature (“Water temperature”) and the minimum average discharge that persists for 30 consecutive days (“30-day consec. flow”) is depicted by a dashed double-headed arrow. In the global model, the dashed arrow between mean annual precipitation (“Precipitation”) and mean annual water temperature indicates a nominally significant (P = 0.09) effect; all other relationships in the U.S. and global models are significant at P = 0.05. Both the U.S. and global models satisfied each of the three model fit criteria, with significant χ2 P values (U.S. = 0.06; global = 0.63), standardized root mean squared residuals (U.S. = 0.06; global = 0.02), and comparative fit index values (U.S. = 0.97; global > 0.99). Inset histograms show the distribution of natural log (ln)–transformed ACSP at U.S. and global scales. Covariate types are as shown in Fig. 1.

  • Table 1 Comparison of effect sizes in univariate regression models of ACSP in U.S. streams.

    Unstandardized regression slopes (b) and standardized slopes (β) are each reported with 95% confidence intervals (shown in parentheses) as well as sample sizes (n) and coefficients of determination (r2). Covariates shown in bold text have slopes (95% confidence intervals) that exclude zero and are therefore considered statistically significant.

    Hypothesized effectCovariatenbβr2
    TemperatureMean annual air
    temperature
    1281.32 (−0.11 to 2.75)0.16 (−0.01 to 0.34)0.02
    Mean annual water
    temperature
    1071.32 (0.74 to 1.90)0.39 (0.22 to 0.57)0.15
    Canopy shading% Forest cover in
    catchment
    128−0.56 (−1.06 to −0.06)−0.19 (−0.37 to −0.02)0.03
    Stream sizeBasin area1280.10 (0.02 to 0.19)0.21 (0.03 to 0.38)0.03
    Mean annual discharge1020.04 (−0.03 to 0.11)0.10 (−0.08 to 0.27)<0.01
    HydrologyFlashiness124−0.23 (−0.64 to 0.19)−0.10 (−0.27 to 0.08)<0.01
    CV discharge124−0.20 (−0.86 to 0.45)−0.06 (−0.24 to 0.13)0.01
    Minimum 30-day
    consecutive flow
    1241.36 (0.39 to 2.33)0.24 (0.07 to 0.42)0.05
    Channel substrateAverage sediment size
    (unweighted)
    88−0.10 (−0.22 to 0.02)−0.17 (−0.38 to 0.04)0.02
    Average sediment size
    (weighted)
    88−0.12 (−0.24 to 0.00)−0.20 (−0.41 to 0.01)0.03
    Land coverImpervious surface in
    basin
    1243.24 (−0.19 to 6.67)0.16 (−0.01 to 0.34)0.02
    % Medium density
    urbanization in
    catchment
    1283.39 (1.11 to 5.68)0.25 (0.08 to 0.42)0.06
    % Crop cover in
    catchment
    1280.86 (−0.46 to 2.18)0.11 (−0.06 to 0.29)0.01
  • Table 2 Direct and total effects of each driver on ACSP in the U.S. and global models.

    Total effects are calculated as the sum of the direct and indirect effects of the predictor on the response variable.

    SEM modelPredictorResponseDirectTotal effect
    U.S. modelWater temperatureACSP0.390.39
    30-day consecutive flowACSP0.280.28
    PrecipitationACSP0.18
    Air temperatureACSP0.36
    Impervious coverACSP0.02
    Watershed areaACSP0.16
    Mean elevationACSP−0.10
    Absolute latitudeACSP−0.01
    Forest coverACSP−0.08
    Global modelAbsolute latitudeACSP0.350.19
    Air temperatureACSP0.38
    Mean elevationACSP−0.19
    PrecipitationACSP0.05
    Water temperatureACSP0.470.47

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/4/eaav2348/DC1

    Supplementary Materials and Methods

    Fig. S1. Maps of study sites included in the ACSP database.

    Table S1. Data dictionary for variables included in the secondary production database for U.S. streams.

    Data file S1. Citation records for all studies included in the ACSP database.

    Data file S2. Complete secondary production and covariate data for all U.S. streams.

    Data file S3. Secondary production and covariate data for the global streams database.

    Data file S4. R code to build the U.S and global SEM models.

    References (98102)

  • Supplementary Materials

    The PDF file includes:

    • Supplementary Materials and Methods
    • Fig. S1. Maps of study sites included in the ACSP database.
    • Table S1. Data dictionary for variables included in the secondary production database for U.S. streams.
    • References (98102)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Data file S1 (.csv format). Citation records for all studies included in the ACSP database.
    • Data file S2 (.csv format). Complete secondary production and covariate data for all U.S. streams.
    • Data file S3 (.csv format). Secondary production and covariate data for the global streams database.
    • Data file S4 (.txt format). R code to build the U.S and global SEM models.

    Files in this Data Supplement:

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