Ecotone Rodent 1st Capture Metrics (abundance, biomass, energy, species richness)

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   OBJECTIVE:  The purpose of the study is to investigate how pulses of precipitation translate
   into pulses of plant above ground net primary productivity (NPP) and how the small mammal
   community responds to such changes also in relation to shrub gradient across the landscape.
   Particularly we are interested in how the energy flows through the ecosystem in response to
   pulses of rain.

   1) Small mammal abundance should respond positively to precipitation and NPP.
   2) On a temporal scale, the small mammal energy use should show parallel fluxes along the
      shrub gradient.

   Variables measured:  Rodent abundance expressed as Minimum Number Known Alive (MNKA),
                        rodent biomas, rodent energy, and rodent species richness.

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Digital voice recorders and data sheets

At each site, three rectangular trapping grids (300m X 100m, 16 X 6 traps, 20m apart) were permanently marked in each of the three habitat types characterizing the ecotone (shrubland, grassland, and the transition zone between them) where small mammal trapping took place. Trapping occurred for 4 consecutive nights using Sherman-type live traps (one at each station) baited with a seed mix. Traps were checked every morning and rodents were uniquely marked with ear tags or individual colored numbers with permanent markers and released unharmed at the point of capture. Small mammal metrics of interest were abundance, expressed as Minimum Number Known Alive (MNKA), biomass expressed in grams (gramPerGridPerYear), energy expressed in watts (WattsPerGridPerYear), and species richness. Total community biomass and energy were estimated as M(tot) = N(tot) x mean of M where M(tot) = total community mass N(tot) = total number of rodents in the community mean of M = average mass of an individual E(tot) = b(o) * N(tot) * M(mean3/4) where E(tot) = total community energy b(o) = normalization constant with a fixed value of 5.69 N(tot) = total number of rodents in the community M(mean3/4) = mean of (M raised to the 3/4 power) b(o) x M(mean3/4) = estimated average metabolic rate from metabolic allometry of a rodent total energy = (estimated average metabolic rate from metabolic allometry of a rodent) x (total number of rodents in the community)(White et al., 2004))

Quality Assurance: 

QA/QC: Visual verification Preliminary treatment of data: Data has been extracted from the rodents_ecotonesonly1.xls using the formulas mentioned in the methodology.

Additional information: 

The 3 sites are located in JER Pastures 9, 12 and in CDRRC Pastures 3.



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