Abraham, I'll jump in. I would argue that both statements are false, given there will exceptions and nuanced responses relative to resource availability. Early successional forests would typically fix more carbon in the ecosystem than would be respired by the heterotrophic community. There will be an asymtope in the system, if undisturbed, that will approach equilibrium as the vegetation matures. For grasslands, grazing impacts are related to precipitation and stocking rate where precipitation resources are limiting, and possibly more related to management where they are not, i.e., timing, frequency, and intensity of defoliations. So in a nutshell, one cannot paint with a broad brush for either system. A simple way to think about C sequestration; are the C inputs (NPP + imports) greater than the C outputs (heterotrophic resipration + exports) in a well delineated system? You need to define the boundaries of the system in which you are interested, because to get at whether that! system is actually sequestering C, you will have to account for all C fixed by the vegetation, heterotrophically respired by microbial communities, and all C moved into, or out of, the system as you define it.
Gary Oates PhD Candidate - Jackson Lab Environment and Resources Program The Nelson Institute for Environmental Studies University of Wisconsin-Madison 1575 Linden Drive - Madison, WI 53706-1597 Email - [email protected] Web - http://agronomy.wisc.edu/jackson/ "There is not a sprig of grass that grows uninteresting to me" Thomas Jefferson 1786 ----- Original Message ----- From: "Abraham de Alba A." <[email protected]> Date: Thursday, September 3, 2009 3:26 pm Subject: [ECOLOG-L] C Seq Grass vs Wood To: [email protected] > I am trying to settle an interesting argument and my > dear ecologgers: > > I am trying to settle an interesting argument and my library resources > are quite limited, I hope you can direct me to reputable references. > > There is the general belief (even academic) that forests or woodlands > in general can be a Carbon net sink, I am told that is not totally > true, since an early successional woodland, would probably be growing > fast, respiring also (so producing more C than sequestrating). > > Now grasslands, if grazed properly (enough time given for > recuperation) is is argued that the root loss due to grazing can > increase the net C content in the soil (which is more stable than the > above ground wood), even better if high density grazing can topple > residue and mix it with urine and feaces. > > What do you think ? > > Abraham de Alba Avila > Terrestrial Plant Ecology > INIFAP-Ags > Ap. postal 20, > Pabellón Arteaga, 20660 > Aguascalientes, MEXICO > > SKYPE: adealba55 > Tel: (465) 95-801-67, & 801-86 ext. 126, FAX ext 102 > alternate: [email protected] > cel: 449-157-7070 > > >
