Table 1 Description model structures considered in the MARSS time series models.

From: Climate and landform interact to control the source and transport of nitrate in Pacific Northwest rivers

Model name

Model descriptions

# of state processes

Basin

All rivers in the Puget Sound basin follow the same hidden state or trend through time

1

Mountain

There are two hidden states defined by mountain range, one for rivers located in the Cascade Range, and one for rivers located in Olympic Mountains

2

Land use

Rivers that share similar watershed land use and degree of human disturbance follow the same hidden state (i.e., urban vs. agriculture vs. forest)

3

Geomorphology

Rivers that share similar watershed topographic and soil characteristics follow the same hidden state.

Groupings as follows: (1) Small watershed area, high slope and elevation, lower soil depths and organic matter (OM), (2) Large watershed area, high slope and elevation, lower soil depths and OM, (3) Intermediate watershed area, lower slope and elevation, and higher soil depths and OM

3

Watershed

Each river follows its own independent state or trend through time

13

  1. Models compared groupings of NO3– concentration, NO3– yield, δ15N, and δ18O of NO3– time series and the effects of hydroclimate on state processes at different spatial and functional scales (see “Methods” for details).
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