Exam 2
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Role of “movement” in biogeochemical cycles? What affects “movement”?
Biological vectors can move materials against chemical or physical gradients.
Role of “sticking” in biogeochemical cycles? What affects “sticking”?
-determines retention -impacts how available a material is (more stuck less available) -chemical properties (solubility, charge, size) influence stickiness.
Role of “change” in biogeochemical cycles? What affects “change”?
-phase changes, changes in bonds -often coupled with changes in mobility -storage and release of energy
Cycling takes place via _________.
Redox reactions
Major pools and fluxes in N cycle?
pool - atmosphere flux - internal cycling
Chemical/physical processes in N cycle?
-Biological nitrogen fixation makes N bioavailable -plants and marine biomass have shortest turnover time -atmosphere has longest turnover time
What are anthropogenic fluxes like in the N cycle?
similar in size to nitrogen fixation fluxes because we have doubled the N input from using/making fertilizers
Major pools and fluxes in P cycle?
pool - sediments flux - internal cycling
Chemical/physical processes in P cycle?
• weathering (physical) makes P bioavailable • internal cycling has shortest turnover • belowground pools have longest turnover
What are anthropogenic fluxes like in the P cycle?
more than doubled the rate at which P has changed from non-bioavailable to available (increased weathering and increased mining of P for fertilizers)
Similarities between P and N cycles?
• abiotic pools are larger than biotic pools • humans have doubled the rate at which N and P become bioavailable
Differences between P and N cycles?
• P cycle is more linear than N cycle • No atmosphere component in P cycle • N cycle has a lot more biological processes involving organisms
Watershed
topographic area that is drained by a stream / total land area above some point on a stream or river that drains past that point and that is enclosed by a continuous hydraulic drainage divide
Hydrologic Unit Code (HUC)
code used to classify and divide a land area based on hydrologic features
What are some of the different HUC orders?
HUC 2 : 21 - regions HUC 4 : 221 - subregions HUC 6 : 352 - basin HUC 8 : 2149 - subbasin HUC 10 : 22000 - watershed HUC 12 : 160000 - sub watershed (ALLEN CREEK)
Why take a watershed approach?
• limits are defined clearly by topography and runoff patterns • entire area is physically linked by water flow • upstream processes/activities directly impact downstream areas • shows how the surrounding land-use can impact water
What factors control stream flow?
topography vegetation climate geology
Watershed drawbacks?
watersheds provide boundaries for management, but do not comply with “political” boundaries
What factors control watershed water quality?
sediments nutrients organic matter other contaminants
Infiltration
water soaks into the ground - depends on: - soil characteristics (clay vs sand) - soil saturation (saturated soil cant absorb more water) - land cover (impervious “fast lane” and vegetation allows water to seep into ground and slows runoff) - slope
Evapotranspiration
evaporation - depends on temperature and wind transpiration - depends on land cover and primary production
water balance equation
P - R - Et = ^S
P = precipitation
varies most over time and is sensitive to climate change
Et = evapotranspiration
most sensitive to land use change - less vegetation cover - pavement does not infiltrate, so water accumulates and evaporates sensitive to climate change