Indeed the elusive holy grail of RS. We have tried by additionally measuring tree crown projection (inaccurate) and tree height (accurate) with high-density, airborne  Lidar. No luck, not even for the rather simple crown and trunk architecture of conifers.  Even ground-measurement of woody biomass in the savanna is daunting. My practitioner side would therefore approach the issue from a different angle. Who is the client for actual or potential woody biomass data of the savanna for what purpose? For some questions, a customized LULC map (with RS of course) may provide a doable answer.

Hi Marcos,

some ecological considerations in addition to the comments on the technology made by Hein van Gils.

What is the area that you are working in? The development of the woody vegetation is very much dependent on species and rainfall, but also on competition with the grasses in the area. (and the establishment of Acacias is often episodic, in response to multiple consecutive years of high rainfall.)

What fallow period are you referring to? Are you looking at agricultural lands? Here you will find that the duration of use and the equipment used to till the soil affects regrowth substantially. The thesis by Stephen Syampungani is also quite instructive.

Regards,

Syampungani, S. “Vegetation Change Analysis and Ecological Recovery of the Copperbelt Miombo Woodland of Zambia.” Ph.D., University of Stellenbosch, 2008.

Hello,

Very helpful contributions indeed.

Regarding technology, I can only afford 5m pixelsize images and land use maps.

I aim to develop growth tables for a wide range of woody land use types, which further include an estimation of the annual sustainable harvestable yield. These tables will be used for testing land use pattern and management scenarios.

Data on standing stocks exists, either from studies on-the-field or remote sensing. More tricky is to move from data on standing stocks to growth models, because many factors come into play. Here, maybe the most sensible issue is the definition and selection of a value for "sustainable" wood extraction rates (or merchantable volume in forest economics) at the different stages of the stand age. The fallow-lenght periods I am looking range between 5 and 20 years.

I have also agricultural yield tables, because the aim is to perform a landscape assessment of biomass provision. But so far, I cannot deepen much into process-based-ecological/agroforestry models.

Thanks,

Marcos

Hi Marcos - it seems that you have your work cut out...

With the development of growth models you might want to follow up on authors in forestry: van Laar (older lit), von Gadow (also here in Research Gate), Seifert and Saborowski.

From the rangeland management side (browse trees) you might want to look up BECVOL from N. Smit.

From dry woodland savanna management you might search for Chidomayo, Geldenhuys, Shackleton and Chirwa. The work of Coert Geldenhuys will be of particular interest to you when you look at stand composition in relation to regrowth on agricultural fields. If you can contact him directly, so much the better. Also, there is a M.Sc. study going on in Namibia, looking at regeneration of woody plants on abandoned agricultural lands.

Another thought... When you look at harvest-able volume keep in mind that in many  parts of southern Africa large timber trees are not nearly as important as poles, i.e. up to maybe 15cm and fire-wood. The sawtimber trees are more for export to "developed" countries.

Got to go.