Since it appears not to have been mentioned=20 (unless I missed it), the "corollary" effects of=20 cattle on ecosystems should be a part of any=20 study. Trampling, for example, can have=20 significant effects, more so than grazing in some=20 systems, and feces distribute plant propagules=20 and other organisms, such as parasites and=20 pathogens. Both direct and indirect effects=20 "flow" through the system in both profound and subtle ways.
In habitats that did not evolve with cattle,=20 grazing and other effects can be more=20 pronounced. Of course, such effects can be=20 changed in degree and rate with cattle populations. Unfortunately, much of "the literature" is=20 focused on agronomics, not ecosystem function and=20 characteristics. Should there be at least an=20 unwritten "law" like "truth in labeling" such=20 that agronomy is distinguished from ecosystem studies? WT At 04:56 AM 4/12/2006, Alexandre Souza wrote: >Dear friends, > > I am posting a digest on the following=20 > question I asked to the list a few days ago. > > Thank you very much to all who read and answered it. > > Alexandre > >ORIGINAL QUESTION > > >Dear friends, > > > I am preparing an article about the=20 > effects of cattle grazing on the structure of=20 > subtropical riparian forests, and I want to=20 > depart from the ecological foundations of the=20 > issue: what kind of predators are cows and what=20 > kind of effects one could expect them to have=20 > on forest communities, based on ecological theory? > > Do anyone knows of key references on=20 > cattle foraging behaviour regarding forest=20 > seedlings and saplings? Are they specialists or=20 > generalists? Do they impact forest communities more by trampling or by= grazing? > > I have found mainly descriptive articles=20 > on net effects on forest strucuture, but I am=20 > finding it somewhat hard to find the=20 > above-mentioned questions addressed in the ecological literature. > > Thanks in advance, > > All the best, > > Alexandre > >ANSWERS I HAVE RECEIVED > >* The Konza Prairie LTER in Manhattan,=20 >Kansas, USA has done a number of=20 >studies comparing foaging impacts of domestic=20 >cattle and buffalo. You might try to do a=20 >search for Konza and buffalo and see what you get; > >* A researcher at Texas Tech was modelling=20 >the grazing behavior of cattle back around 1994.=20 >I don't recall his name but he was in the=20 >department of range scienes and was applying the=20 >disc equation to cattle feeding. Back in my=20 >undergrad days I took some ag classes and recall=20 >that in comparing goats, sheep, cattle, and=20 >bison that bison tended to clip grasses and=20 >preferred the fresh grass (in fact native=20 >americans would use fire to keep bison in their=20 >area). Cattle tend to prefer forbes, althought=20 >they do eat the grasses. Cattle will pick clean=20 >all the forbes out of a pasture over time. They=20 >also pull vegetation rather than clip it,=20 >leading to a different kind of grazing pressure=20 >on the vegetation. Sheep tend to pull as well,=20 >but also tend to leave much shorter grazing=20 >pastures. Sheep will feed on much "rougher"=20 >pasture than cattle and are better converters of=20 >rough forage. Goats tend to be browsers and=20 >will reportedly starve on a grass field if no forbes are present. B! > y no means am I a ruminant biologist, but I=20 > think I recall this info accurately. I=20 > recommend you contact the folks at Texas Tech=20 > as they will probably have good info for=20 > you. If I remember the Prof's name I will=20 > email it to you, but its been so long! Another=20 > good source of information is to look into some=20 > animal science departments or textbooks. There=20 > are various papers and books on ruminant=20 > biology, forage management, pasture management,=20 > and range management that might provide you=20 > with the information that you are seeking. > >* Dear Alexandre, our group works on=20 >ruminant foraging behaviour in (sub)tropical=20 >environments. Check our website for articles and=20 >staff who might help you find the information=20 >you're looking for. Jasja Dekker, PhD=20 >student, Resource Ecology Group, Dept.=20 >Environmental Sciences, Wageningen University.=20 >Bornsesteeg 69 6708 PB Wageningen The=20 >Netherlands http://www.reg.wur.nl/UK/Staff/ > >* I am currently thinking a lot about classification of consumers in >consumer-resource systems. I work with predator-prey models but have >recently become interested in the larger issue of "what if any discrete >categories of consumers are there?". Cows are=20 >tough... by one definition they are parasites=20 >(eat only part of their host), by another they=20 >are predators (larger than their host), by=20 >another they are parasitoids (generation time is about the same as their >hosts [?Maybe?]). Cows are the best example of how little these categories >actually mean. > > > >Dr. Alexandre F. Souza >Programa de P=F3s-Gradua=E7=E3o em Biologia: Diversidade e Manejo da Vida= Silvestre >Universidade do Vale do Rio dos Sinos >Av. UNISINOS 950 - C.P. 275 >S=E3o Leopoldo 93022-000 >RS - Brasil >Telefone: (051)3590-8477 ramal 1263 >Skype: alexfadigas >[EMAIL PROTECTED] >http://www.unisinos.br/laboratorios/lecopop
