Landscape filtering of hydrologic and biogeochemical responses in managed catchments

• Published in: Landscape ecology Vol. 28; no. 4; pp. 651 - 664
• Main Authors: Gall, Heather E., Park, Jeryang, Harman, Ciaran J., Jawitz, James W., Rao, P. Suresh C.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-04-2013; Springer; Springer Nature B.V
• Subjects: Animal, plant and microbial ecology; Anthropogenic factors; Applied ecology; Biogeochemistry; Biological and medical sciences; Biomedical and Life Sciences; Catchments; Ecology; Environmental Management; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Human influences; Hydrology; Landscape Ecology; Landscape/Regional and Urban Planning; Life Sciences; Nature Conservation; Nutrient dynamics; Nutrients; Probability distribution; Research Article; Spectral analysis; Statistical analysis; Sustainable Development; Urban areas; Wet deposition; Urban catchments; Anthropogenic drivers; Nutrient export; Agricultural catchments; Hydro-climatic drivers; Catchment responses; Wet deposition; Climate; Filtering; Landscape; Environmental factor; Urban area; Climatic condition; Biogeochemistry; Agricultural region; Watershed; Nutrient; Anthropogenic factor
• ISSN: 0921-2973; 1572-9761
• DOI: 10.1007/s10980-012-9829-x

Here, we examine hydrologic and biogeochemical responses of managed catchments regarding the degree of
stochastic, nonlinear filtering
of hydro-climatic and anthropogenic drivers. We utilize three types of analyses to examine the time-series records of catchment responses: (1) statistical analysis, based on probability distribution functions (
pdf
s); (2) temporal Lorenz inequality, based on Gini coefficients, and (3) contingency or memory assessment, based on spectral analysis. We present analytical expressions for
pdf
s and statistical moments for several catchment responses, explicitly linking stochasticity of drivers and catchment filtering properties. We also examine
relative temporal inequality
of two catchment signals: Φ
G
 = 
G
2
/
G
1
, where
G
i
is the Gini coefficient of each signal. We use
spectral analysis
to evaluate the
relative memory
of two signals: Φ
α
 = 
α
2
/
α
1
, where
α
i
is the slope of spectral power versus frequency of each signal in log–log plots. We use these metrics to evaluate: (1) filtering of precipitation (
P
) inputs to discharge (
Q
) outputs from four locations in different moisture regimes in the US, and identify human impacts on catchment hydrology; and (2) dominance of hydrologic variability for nitrate wet deposition flux (Ω) patterns for nine US urban sites, and in the patterns of exported solute loads in intensively managed catchments. Our analyses of long-term monitoring in selected managed catchments suggests that increasing human impacts on landscapes: (1) cause hydrologic and biogeochemical processes to exhibit increasing functional homogeneity; (2) contribute to shifts in memory between catchment drivers and responses; and (3) decrease the temporal inequality of nutrient export dynamics.