I'm just checking into the conversation, because I map vegetation in Arizona, and have long dealt with the issue of boundaries. Some are discrete and most are diffuse. This is simply because the rules used to create the boundaries vary tremendously. Where I work, for instance, everyone agrees that the boundary between ecosystems depends on soils, regional and local climate, slope and aspect, bedrock geology, and the characteristic vegetation and fire regime. Trouble is, nobody agrees on which of these is the most important, so we end up with many different maps. (Of course they agree on some things: the seashore, for instance.)

I think the important thing is to recognize that they may all be right, and serving the purpose for which they were created. If your purpose is explaining biome boundaries, you'll have to explore the reasons the boundaries were made. Unfortunately, most biome descriptions focus on the typical characters of that biome – one snapshot of what would be the center of that biome. I'm more interested in the edges, and what were the specific rules for that boundary. Karst topography? Summer rain under 100mm? Species X at a density greater than 10/hectare? The other contributors to this conversation have given you links to just the resources you'll need, so…Good luck!

Dear friend, 

I have been trying for years to use animals and plants for freshwater 'biome-style" boundary justification and interpretation. Have you seen the notion of "ecoregion". NOT easy.

Look at climate carefully; look at geo-history and steady boundaries - so-called breaks.

 In Europe there is a policy-relevant glitch as well. See our older paper: Ecoregions in the Southern Balkans: Should their boundaries be revised.

 http://www.researchgate.net/profile/Stamatis_Zogaris/publication/23789456_Ecoregions_in_the_southern_balkans_should_their_boundaries_be_revised/links/0f317530595ec5ecd8000000.

Best of luck on your research, 

Stam

Article Ecoregions in the Southern Balkans: Should Their Boundaries ...

Thank you Stamatis, I will have a look on that paper. I personally look more on the combination of the Geology, secondly the pressure cells that influence our climate and the other aspect ofcourse is the influence of fauna and flora. Coming to think of it again is the possibility of evolutionary history of each area but that seems a futile hypothesis.

There is a great deal of work on explaining the deliminations of the boundaries. Start with Acocks and Mucina and Rutherford and work from there. Then look into the recent work on bush encroachment and invasion into grasslands (and the reasons for the absence of trees in grasslands) by people like Tim O'Connor, William Bond, David Ward. Evolutionary history is pretty important as ancient climate patterns and geomorphology influenced the spread of species through Africa. The distribution of montane forests is a good example. One of the key things to look for is how the boundaries have changed over time in response to changing conditions. Acocks famously had maps of the assumed former distribution of boundaries (particularly the distribution of the karoo) and the predicted future distribution, and his hypotheses have been tested recently by Timm Hoffman and colleagues.

Thank you very much Alan. This answer is cery descriptive and I am very greatful for the time you took to guide me through. I like the straightforwardness of the answer. Thanks once again. I did consider Acocks and I will definitely look through Mucina and Rutherford

Dear colleague: attached you will find a paper of our authorship, regarding the subject. May be you will find it useful.  It is a case study on the Seasonally Dry Tropical Forest (SDTF) biome using herbarium data of habitat specialist species. We based our approach on the Biome Distribution Modelling (BDM) approach, where

georeferenced herbarium data is used in conjunction with bioclimatic data. A new refined working map of South American SDTF biome was proposed. Our study showed that herbarium data could be used as a way of ground-truthing biome maps in silico. Herbarium data can be used to model vegetation maps through predictive modelling, and could be particularly useful for mapping poorly known,

fragmented, or degraded vegetation.

Good reading and good luck! Cheers, Darién

Article Forgotten forests - issues and prospects in biome mapping us...

Hi Thamsanqa

Here are some random articles from my collection which may help get you started. I have all of the full-text articles; if you can't find them, just contact me. As you can see, these are biased towards southern Africa. You need to read more global literature to get a bigger picture, but I think many of the articles will have references to point you in the right direction.

O’Connor, T. G., J. R. Puttick, and M. T. Hoffman. 2014. Bush encroachment in southern Africa : changes and causes. African Journal of Range and Forage Science 31:67–88.

Hoffman, M. T., P. J. Carrick, L. Gillson, and A. G. West. 2009. Drought , climate change and vegetation response in the succulent karoo , South Africa. South African Journal of Science, 105:54–60.

Bond, W. J., G. F. Midgley, and F. I. Woodward. 2003. What controls South African vegetation — climate or fire? South African Journal of Botany 69:79–91.

Higgins, S. I., W. J. Bond, and W. S. W. Trollope. 2000. Fire, resprouting and variability: a recipe for grass-tree coexistence in savanna. Journal of Ecology 88:213–229.

Manry, D. E., and R. S. Knight. 1986. Lightning density and burning frequency in South African vegetation. Vegetatio 66:67–76.

Rethman, N. F. G. 2001. Cenozoic expansion of grasslands and climatic cooling. The Journal of Geology 109:407–426.

Lawes, M. J., H. a. C. Eeley, N. J. Findlay, and D. Forbes. 2007. Resilient forest faunal communities in South Africa: a legacy of palaeoclimatic change and extinction filtering? Journal of Biogeography 34:1246–1264.

Dean, W. R. J., M. T. Hoffman, M. E. Meadows, and S. J. Milton. 1995. Desertification in the semi-arid Karoo, South Africa: review and reassessment. Journal of Arid Environments 30:247–264.

I'm just checking into the conversation, because I map vegetation in Arizona, and have long dealt with the issue of boundaries. Some are discrete and most are diffuse. This is simply because the rules used to create the boundaries vary tremendously. Where I work, for instance, everyone agrees that the boundary between ecosystems depends on soils, regional and local climate, slope and aspect, bedrock geology, and the characteristic vegetation and fire regime. Trouble is, nobody agrees on which of these is the most important, so we end up with many different maps. (Of course they agree on some things: the seashore, for instance.)

I think the important thing is to recognize that they may all be right, and serving the purpose for which they were created. If your purpose is explaining biome boundaries, you'll have to explore the reasons the boundaries were made. Unfortunately, most biome descriptions focus on the typical characters of that biome – one snapshot of what would be the center of that biome. I'm more interested in the edges, and what were the specific rules for that boundary. Karst topography? Summer rain under 100mm? Species X at a density greater than 10/hectare? The other contributors to this conversation have given you links to just the resources you'll need, so…Good luck!

Hi Thamsanqa

Two more references for you:

Article: Boundary of treeless grassland in relation to nutrient content of soils on the Highveld of South Africa. Anthony J. Mills, Antoni V. Milewski, Kevin H. Rogers, Ed T.F. Witkowski, Marc Stalmans. Geoderma s 200–201:165–171.

Article: Mills, A.J., Rogers, KH, Stalmans, M. & Witkowski, ETF. (2006). A framework for exploring the determinants of savanna and grassland distribution. Bioscience 56, 579-589. Mills AJ, Rogers KH, Stalmans M, Witkowski ETF BioScience 01/2006; 56:579-589.

Briliant!

Thank you very much to Alan and Jim. Your contribution is valueable and I highly appreciate it. I thank Research gate for this community of practice.

Jim:

Could you please share with me some of your published material if you do not mind?

Hello, Thamsanqa,

You are welcome.  You can download published materials from my page on Research Gate, by clicking on my photo/name above.  Most relevant to your question would be my paper titled:

Malusa, J., L. Laing, D. Falk, and B. Gebow, 2013. Mapping Ecological Systems in Southeastern Arizona.

I wish you well.

Another facet of the issue of biome boundaries is species' ranges. A couple of good introductions are

Gaston, K.J. 2003. The structure and dynamics of geographic ranges. Oxford University Press, Oxford.

Peterson, A.T., J. Soberon, R.G. Pearson, R.P. Anderson, E. Martinez-Meyer, M. Nakamura, and M.B. Araujo. 2011. Ecological niches and geographic distributions. Princeton University Press, Princeton, NJ.

I've always liked the perspective of Whittaker & Niering (1968:442) in one of their papers on the Santa Catalina Mountains in Arizona:

"The vegetation of the mountains should be conceived as a complex population continuum, a single pattern of continuously intergrading communities. The community-types and their boundaries are products of classification, of essentially arbitrary division of the pattern by particular combinations of growth forms and species dominance."

The same can be said of biomes.

The reason there is variation in setting biome boundaries (as geographic lines I assume) is because biome units are artificial constructions that impose borders or demarkations on a continuum. One may delimit a boundary or boarder based on any one organism or geographic feature, but this is not to say that such lines have any natural significance for defining a 'biome' area.

See chapters 2 and 3 of The Vegetation of South Africa, Lesotho and Swaziland by Mucina, L. and Rutherford, M.C. 2006.