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Toby Marthews

I am a postdoc in the Oxford Ecosystems Lab. See http://www.tobymarthews.com/ for me and what I do.

Recent Posts

  • One more thing: I know that the difference between 39% and 31% is small and less than the natural variability between forests for this factor. The reason why I'm suggesting rather to use Jackson's 31% is because that paper also suggested estimates for other biomes (which I copied into the manual) so this factor becomes biome-specific if you follow that. For me, this is much more ecological. Toby

  • Hi Jhon,

    There is the following rule of thumb in Malhi et al. ("The productivity, metabolism and carbon cycle of two lowland tropical forest plots in south-western Amazonia, Peru", Plant Ecol & Diversity). I imagine the Galbraith paper is referring to this '39% rule':
    "We also estimated that there is an additional 39% fine root NPP beneath our 30 cm ingrowth core, by extrapolating to 1 m depth assuming an exponential decay of root biomass and productivity with depth"
    this rule is equivalent to assuming 61% of all roots occur in the top 30 cm of the soil profile and... More

  • Soil depth profileDendrometer bandsCoarse litter fallRAINFOR methodologiesGround coarse litter massStem respirationCensusIngrowth coresFine litter fallSoil respiration partitionningSoil respirationRhizotrons

    Dear All,

    A new version of the RAINFOR-GEM manual is now out and here is the link: http://www.tobymarthews.com/rainfor-gem-manual-v30.html (it'll move across to the permanent URL at http://gem.tropicalforests.ox.ac.uk/page/resources very soon).

    I hope this is useful!

    Best regards,
    Toby

  • Hi Erika,
    Basically: it's a cost issue. Also, clipping the metallic band is much more difficult than the plastic band and often has to be done back at the lab rather than in the field.
    Toby

  • Dear Jhon,

    Apologies for taking a while to reply: I had to check on a few things. Some answers:

    1. "stemlength" is clearly described in the RAINFOR-GEM manual section 1.5 where I put a photo I took of a tree at Wayqecha: it is the length from the base to point A (not B or C) on that photo.

    2. How to calculate aboveground NPP: this is not described in the manual, but briefly described either in Yadvinder's 2009 paper http://www.geog.ox.ac.uk/~ymalhi/publications/Publications2009/2009-gcb-comp-assess-of-carbon-product.pdf or in the Plant Ecology & Diversity papers coming out just now (which I'm sure will be posted on GEM within... More

  • Hi Jhon,

    Thanks for your feedback: this is all a bit of a tricky area. Just to be 100% clear, let's define some terms:

    RHEIGHT = "Height" as measured in the RAINFOR protocols, which is really stemlength because that is what is most relevant for biomass estimation.

    VHEIGHT = Vertical height to crown top, which for a leaning tree will be less than RHEIGHT. Chave's papers talk about "total tree height" so his H is technically VHEIGHT (and for Larjavaara and Muller-Landau too).

    AGLB = AboveGround Live Biomass INCLUDING both stem and branches.
    In most papers this is the same... More

  • RAINFOR methodologies

    Dear All,

    Measuring tree heights. About a week ago a CTFS paper came out about measuring tree heights by Markku Larjavaara and Helene Muller-Landau (see http://ctfs.arnarb.harvard.edu/Public/pdfs/Measuring%20tree%20height,%20a%20quantitative%20comparison%20of%20two.pdf ).

    Apologies if other people have seen this before me, but I think it is important to stress that in RAINFOR we measure STEMLENGTH for our tree heights (see section 1.5 of the GEM manual) but in CTFS they measure vertical height to crown top. For leaning trees these are not the same so please don't use the methods proposed in that paper in RAINFOR-GEM plots (neither their tangent method nor their sine method).

    ... More

  • RAINFOR methodologiesStem respirationSoil respiration partitionningSoil respiration

    Hi Jhon,
    I put a schematic of the adapter ring in Appx. II of the RAINFOR-GEM manual (footnote, p.72). If you extract that image and blow it up, you get the attached. With that, you should be able to get an adapter ring made up in any workshop (best to take an SRC-1 with you to the workshop so that they can make it fit exactly).
    Saludos,
    Toby

    Thumb_srcadapterringspec
  • Dendrometer bands

    Dear All Who Have Worked With Dendrometer Bands,

    I have a question: what is the minimum diameter of stem on which you have attached a dendrometer? Below a certain cut-off diameter the dendroband doesn't fit snugly against the tree (because of the spring and the clips it becomes 'square' and sticks out even if the stem isn't irregular) and also below a certain cut-off the spring can't exert enough tension for the band to work as it should. At the moment, the RAINFOR-GEM manual doesn't specify what this cut-off is.

    I always thought that the cut-off was at about 20... More

  • RAINFOR methodologiesIngrowth cores

    After a meeting yesterday at the OUCE in Oxford, we all suggest to add a Replacement Rotation to the in-growth core protocol in the manual:

    As has been discussed here before (Terhi, Chris and Dan Aug/Sep 2012: http://gem.tropicalforests.ox.ac.uk/postings?resource=ingrowth-cores ), over the course of time, in-growth cores become degraded: some soil is lost at each excavation and repeated searching through the core fragments the soil structure. So, we suggest to arrange a rotation so that 25% (i.e. 4 under the standard protocol) of the in-growth cores are replaced with new cores (at least 1 m away) every three months. At changeover,... More

Photos and images

Medium_srcadapterringspec
Uploaded 20 Mar 2013 by Toby Marthews. Copyright © 2017.

Hi Jhon,
I put a schematic of the adapter ring in Appx. II of the RAINFOR-GEM manual (footnote, p.72). If you extract that image and blow it up, you get the attached. With that, you should be able to get an adapter ring made up in any workshop (best to take an SRC-1 with you to the workshop so that they can make it fit exactly).
Saludos,
Toby

  • Thumb_srcadapterringspec
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