A. for a planting density of 1667 trees (2 x 3 m) is indicated the harvesting after a period of 5 or 10 years? and what growth we can achieve in these periods?
B. after 5 years of growth (2 x 3 m density), is indicated to reduce the density to 3 x 4 m? and keeping the culture another 5 years in the field (up to 10 years)?
C. is indicate to use for a period of 10 years for a SRF (short rotation forestry) a density of 3 x 4 m or 4 x 4 m?
D. What do you recommend for maximum yield for crops of hybrid poplar?
Thanks.
Hi Iulian,
Thanks for your good questions. I work with hybrid poplars too. The answers to your questions will depend on some factors such as: 1) what is the desired product (wood, or pulp chips, etc.); 2) who will be doing the thinning/harvesting (you or a contractor); 3) what type of watering system do you have (just rainfall or drip irrigation or other), as poplars respond well to routine irrigation.
In our experience, a good spacing for a mature poplar stand is ~4m x 4m. This allows for our truck and other vehicles to drive through the trees without problem. Trees can grow much closer together if the goal is short rotation (for example, 2m x 2m). Hybrid poplars, as you know, grow very fast. They can reach over 20 m in 10 years.
For maximum yield, you need to make sure you are selecting the most appropriate clones/varieties for your area. The ideal clone will not just be high yielding, but should be able to survive and thrive in your local growing conditions, soil type, winter months, etc. It should not "break bud" too early (i.e., it should break bud after the last major frost in the springtime).
These are just some thoughts. Hope this is helpful. Best wishes with your research. - Sam Allen
Thanks Sam for your replay,
i use a part of the crops for wood (trunk with dbh great to 8 cm), i know that the poplars have a good response to the amount of water (from precipitation), but i use just rainfall in a continental temperate conditions, with approx. 550-600 mm per year. In this conditions i have after 5 years aprox. 40 t/ha (1667 density per hectar). what do to for more biomass (in the terms of my question)?
Iulian
Hi all,
I would like to know if poplar short rotation cycles are/or if not can be installed in city areas and rooftops? Also I would look forward to a regional or peri-urban cooperative that implies only necessary stakeholders and participants! Any suggestions/projects known?
Hi Iulian,
Here are some ideas for increasing poplar biomass, based on my observations (we have not yet harvested trees):
1) In general, I think a N/S stand orientation takes more advantage of available sun, but some people plant E/W, or parallel to prevailing wind, or on the contour of the site (it depends on the site, really).
2) if your past research indicates that your poplar variety has good survival (>95%), then you can probably expect good survival at various spacings.
3) Need to think about how the poplars will be maintained (trimmed or not trimmed during growth), and how they will be harvested (chainsaw or small/large mechanical harvester). We trim our trees by hand up to head height for most of our trees (to get a single large stem), but we do have a close-spaced trial which is not trimmed. Survival and health was lower in close-spaced trees. It is difficult to walk through/access the trees when they are 2m x 2m and not trimmed.
4) Do the trees need any type of fertilizer (such as urea nitrogen, or iron)? This will depend on the soil type and soil pH. This is best delivered through a drip irrigation system, which is not expensive (at least for the water driplines).
5) Maybe consider an understory grass or legume, to enhance soil fertility.
6) Also consider WHO will be harvesting the trees. If a contractor logging company, then it will be good to check with them, to see what size/form they need in order for the material to fit on their trucks and for them to make a profit.
7) In my view, I think it's best to plant small cuttings that have a few buds.
8) All in all, I think you will have success at whichever spacing you choose, if you have a site-appropriate variety.
See p. 143 in our Annual Report, for info on planting techniques and data on biomass yield of trees planted at 10 ft or 12 feet apart (some were planted in 2002, 2005 and 2007). I think we also have older data on close-planted trees planted in 2003. Here is the link on our reports:
http://farmingtonsc.nmsu.edu/documents/nmsu-annrpt-2014-final-all.pdf
These are some ideas. Hope this helps. Will be glad to hear more about your project.
Best,
Sam
Thanks again Sam for everything. I will response here with news!
All the best,
Iulian
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