Parks inventory in Merida

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hdelaconcha
Posts: 49
Joined: Mon Jul 11, 2016 8:10 pm

Parks inventory in Merida

Post by hdelaconcha » Mon Jan 08, 2018 8:15 pm

After the city tree inventory through plots, in MERIDA, YUC., they are interested now, in a full inventory of trees in the parks that will help the city better plan their management. The situation is that there are around 500 parks, or at least "public spaces", with a total of 236 hectares. OF course I do not know how many trees in total but in order to keep it doable, I am proposing to eliminate those smaller than 1500 m2 since are too small, and the really big ones (around 20) which are above 1.8 ha all the way to one that is 14.5 ha, do them with plots. My questions are: (1) I read somewhere that at least 20 plots are needed for good statistical results is this correct? and if so (2) this will mean surveying 0.8 ha which in the case of a 2 ha park is about 40% so basically I will like to know if there is a practical, (from experience) minimum number of plots per ha to get fairly good results. Or in other words in parks between the sizes mentioned what is the minimum plots/ha that will yield good results. After reducing the number of parks with this 2 reason I still have 165 ha and 300 parks to sample which I am afraid will end up being a lot of trees.

thanks
Horacio de la Concha
AGRINET SA de CV
Cuernavaca MEXICO
hdelaconcha@agrinet.com.mx
azelaya
i-Tree Team
Posts: 320
Joined: Fri Jun 27, 2008 10:50 am

Re: Parks inventory in Merida

Post by azelaya » Thu Jan 11, 2018 10:58 pm

The 20 plot number recommendation may be from the i-Tree User manual https://www.itreetools.org/resources/ma ... Manual.pdf page 9 which is a general guideline for the minimum number of plots recommended for each stratum of a plot-based sample project. Again, this is only a general guideline and may be more applicable for typical cities but may not be well suited for park systems with different individual park sizes, land uses such as golf courses, natural areas, managed turf, picnic areas, etc.

We are not aware of many park system Eco projects that have used sampling, or a combination of sampling for large parks and complete inventories for smaller parks. Most park projects typically use the Eco complete inventory option, and may limit the trees collected to managed areas for larger parks to focus on areas more important to park managers for risk management, maintenance, etc. I can only think of a couple Cleveland Metro Parks and Three Rivers Parks in MN which used sampling for the entire park system. The MN project was only partially completed because of the time involved in collecting data in heavily wooded plots. The Cleveland metro parks project was completed by a consultant and the report, which is a combined UTC & Eco analysis, can be accessed online at the following link https://www.clevelandmetroparks.com/get ... r.pdf.ashx . Both of these were park system wide sampling projects and not stratified by individual park units within the system.

Eco users frequently ask us for a plot per ha or acre for smaller scale or non-traditional projects such as for parks and park systems, but it is difficult to provide a general rule that can apply to all projects and situations… without knowing something about the characteristics of each project because of the variability between vegetation diversity, vegetation distribution, land uses, etc. For this reason, we recommend considering doing pre or pliot sampling, or working directly with a local statistician who can assist with sampling design beyond our general recommendations.

If interested, there is a post which discusses options for using pilot plots to determine optimal plot sampling for a project. viewtopic.php?f=19&t=1210
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