[BoulderCouncilHotline] Re: PDs, tilling, and soil jpg

[Potter, John]

Good Afternoon Everyone:


Thank you for your interest in the preliminary soil carbon data collected by OSMP on land with current or past prairie dog colonies. All three graphs copied in the emails below are correct, but show different results from considering different groupings of plots.


Additional information on the x-axis labels may be helpful:

  1.  The May 8th slide below compares soil carbon data from plots that were in mixed grass prairie communities only and where there has ever been a prairie dog colony recorded (maximum extent) v. areas in mixed grass prairie and where staff have never observed a prairie dog colony.
  2.  The May 6th slide compares soil carbon in all areas where there were prairie dog colonies present in 2017 (the fall prior to soil sampling) v. all areas where they were not present in 2017.
  3.  The final slide compares soil carbon in all areas that are known to have ever been tilled v. those that are not.


A quick reading of the data could lead me to think that the preliminary results from the second and third slide are the same, however they differ as indicated in the summary table below (error bars shown in the slides were constructed using 1 standard error from the mean, not standard deviation):



Slide

Landuse

Mean (OrgC_pct)

Std Error (OrgC_pct)

N =

1

In Prairie Dog Max Extent (Mixed Grass Prairie only) = No

2.340

0.169

33

1

In Prairie Dog Max Extent (Mixed Grass Prairie only) = Yes

1.834

0.197

17

2

In Prairie Dog Colony (2017) = No

2.807

0.115

77

2

In Prairie Dog Colony (2017) = Yes

1.564

0.173

11

3

Ever Tilled = No

2.835

0.111

75

3

Ever Tilled = Yes

1.505

0.220

13



While the magnitude of how much less soil carbon there is in prairie dog occupied areas is sensitive to the comparison being made, OSMP has no evidence to date that prairie dog presence increases soil carbon. The preliminary data instead suggest that soil carbon building efforts on OSMP lands might best be focused on areas that have been historically tilled, particularly where prairie dog colonies are also currently active. This is what staff have been doing for example on the Bennett property -- trying to build soil carbon (in the presence of prairie dogs) to hopefully reverse this trend.



Attached is the staff report that accompanied the May 8th presentation. If any council or board members would like to discuss this information further, please let me know. Thank you for your patience and support as staff try to provide early results to best inform land management around a complex situation.


--John


John Potter

Resource and Stewardship Manager

[1465493373704_logoosmp.png]

(O/C) 303-579-7254

potterj at bouldercolorado.gov<mailto:potterj at bouldercolorado.gov>


Boulder Open Space & Mountain Parks

2520 55th St. | Boulder, CO  80301

https://bouldercolorado.gov/osmp

________________________________
From: Morzel, Lisa <MorzelL at bouldercolorado.gov>
Sent: Tuesday, May 21, 2019 5:15 PM
To: Council; Burke, Dan; HOTLINE
Subject: [BoulderCouncilHotline] PDs, tilling, and soil jpg

Please see images and captions below.

In reviewing slides presented by OSMP staff to the OSBT on May 8th and comparing  a slide sent to City Council on May 6th by OSBT member Hollweg, it appears as if Hollweg used the wrong slide to make her point regarding prairie dogs’ impact/contributions to %C in soil.  It looks as if Hollweg (middle image) incorrectly used the slide showing that soil carbon is depleted in historically tilled land (bottom image) instead of the correct image regarding soil carbon in prairie dog colonies (top image).

Would OSMP staff please explain whether the standard deviations shown in their slides are at 1 or 2 sigma? Also I would like to see the OSMP staff report from the May 8 OSBT meeting.

A number of peer-reviewed papers conclude that prairie dogs actually add, not deplete,  carbon to the soil.

Thanks. I’ll forward those peer-reviewed papers in the next few days.

Lisa

Lisa Morzel
Member, Boulder City Council

[cid:f_jvye6i1g0]
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