[Note: I have concocted a revised (and ridiculously convoluted) subject-line for this line of slight digression (it is still relevant, but specialized), but feel free to go back to the old one if anyone thinks that the better path.]
Warren, we need to have another beerhall colloquium (in one of those fancy ones again that serve coffee--no decaf, as I've been taken off coffee and beer). It would, indeed, seem simple, but is the standard explanation too simple? How about the following scenario? Again, I have to agree that "a stand of junipers has greater biomass and a deeper root system," but I suggest that said biomass was accumulated over time, doubtless due to the fact that the deeper root system allows it to avoid the seasonal vagaries of weather, continuing to transpire but not produce additional biomass, through dry periods in the upper profile, the annual increase in biomass being limited by said dryness (perhaps because of nutrient limitations in the deeper rhizosphere, a net reduction in water uptake [and transpiration], or a combination of these and other factors. If my observations from other areas are closer to reality than farther away from it, would I be safe in saying that juniper roots are less efficient at capturing water from percolation because there are effective "holes" in the pattern of water-absorbing roots (as mentally-pictured in plan view) than the much tighter maze of roots formed by the grasses, forbs, and shrubs. Some percolating water escapes "capture" by the former, but little, if any by the latter. Water from infrequent, light precipitation events during periods of active transpiration, never makes it to the water table (except, perhaps, getting past the juniper root-maze). Deeper percolation occurs only after a short-interval, longer sequence of lighter precipitation events or prolonged ones. The depth of penetration can be calculated/modeled through a combination of available water capacity and percolation rate obtained through adequate and actual field work. Once the "wetted front" gets past the shallower root systems (after a peak at shallower depths the interception efficiency falls off as the fibrous root systems "thin out) it is then free to percolate to depth until it is stopped by surface tension, leaving behind, as it were, a "layer" of subsoil at "field capacity." Of course, discontinuities within the soil profile like big, non-absorbing living and dead roots, rocks, rodent holes, fissures, etc., all "conspire" to produce a heterogeneous penetration profile very unlike that to be found in every textbook I have ever seen. (See: Kramer and ?: Water Relations of Plants and Soils for the best treatment I have seen). Junipers and other deep-rooted woody plants can mine this water by penetrating the interfaces along the discontinuities, but where free water flows, it escapes even their clutches, ending up either draining out at lower elevation through springs and streams or some kind of water table. And, not all fissures are equally exploited by roots, as the root tips are the primary and specialized absorbing organs. The bottom line here is that there are ups and downs with respect to the whole picture of soil water relations and groundwater on its way to springs that certainly involve junipers, but perhaps not to the degree presumed by a long and persistent history that might do with some reexamination. WT ----- Original Message ----- From: Warren W. Aney To: 'Wayne Tyson' ; [email protected] Sent: Monday, September 12, 2011 11:11 PM Subject: RE: [ECOLOG-L] a non Ivory Tower view of invasive species Wayne, it would seem to be as simple as this: a stand of junipers has greater biomass and a deeper root system than a flora composed of grasses, forbs and scattered shrubs. As a result the stand of juniper transpires more water from more levels than its counterpart biota. However, the observed effect of juniper removal on springs and streams is primarily anecdotal, as you said. Oregon's Great Basin ranges were heavily overgrazed starting way back in the late 19th century. The increase in juniper cover has occurred since then, primarily as a result of reduced fire carrying forage species. You can find out much more than you probably want to know about this in the 2005 Oregon State University Technical Bulletin 152, Biology, Ecology, and Management of Western Juniper. http://www.sagebrushsea.org/pdf/Miller_et_al_Juniper_Tech_Bulletin..pdf This publication will answer your questions about pre-fire-exclusion stand characteristics, management practices, and causes for increased juniper recruitment. It will informs us that cow pies have little or no effect - juniper seeds spread by birds, not cattle. Warren W. Aney Tigard, Oregon -----Original Message----- From: Wayne Tyson [mailto:[email protected]] Sent: Monday, 12 September, 2011 19:28 To: Warren W. Aney; [email protected] Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species Warren and Ecolog: Well, Warren, I guess I'll have to take your word for it. You've got more experience with that area than I do, but I would still like to know more about the theoretical foundations and evidence to justify some of those conclusions. And, I'm concerned about the actual costs and benefits to wildlife as well as cows. To me, that area shouldn't have a cow on it, but certainly not a subsidized cow on a subsidized "range." And I come from a cow background, so I'm not prejudiced; I had a Hereford bull for a 4-H project, so I'm not insensitive to "ranchers" either. But I have seen plenty of cow-burnt "range" in the Intermountain West. I've heard the same "water-hog" story about pinyon pines and other "brush" all over the western US. I've heard the restored spring and streamflow stories too, but haven't seen evidence beyond anecdotal stuff. However, you know me, I think that anecdote is the singular of data. But correlation, again, is not necessarily causation. I'm still skeptical, but holding any "final" judgment in reserve. I do agree that "nothing" grows under junipers, but out beyond the drip line it's a different story, at least where I've observed it elsewhere (I wasn't that carefully-observant at Steen's). I don't doubt the stemflow part either, but it's not uncommon for plants to shade out other plants; this doesn't mean that said "parched mini-desert" is a serious problem in the context of the ecosystem--or does it? But the channeling down into the ground works to the benefit of the juniper--ain't that the way it's supposed to work? What is the penetration profile like in the absence of the juniper? What's the ratio of annual unit biomass production to water consumption for junipers? For the "replacement" vegetation? Has it been demonstrated that groundwater recharge is more effectively intercepted by junipers than, say, grasses. The former have deeper, ropier root systems than grasses that mine the capillary fringe and other water on its way down, but enough to shut off springs and stop streamflow? It seems to me that any given site has a given effective carrying capacity that is going to limit vegetation growth accordingly, no matter what the (natural) vegetation is. The water may have a better chance of percolating past the junipers than the grass, no? The junipers have a limited capacity (and a limited need) for water; the grasses will increase transpiration surfaces much faster in response to water. What were pre-fire-exclusion stand characteristics? Are management practices aiming for that, or for some other target? How much increased juniper recruitment occurred as a result of fire exclusion rather than some other cause, such as livestock-induced soil disturbance? Do cow pies have any effect, etc? Now I guess we have to add "intrusive" to our list of terms? But really, Warren--crying cowboys? Is that fair? WT ----- Original Message ----- From: "Warren W. Aney" <[email protected]> To: "'Wayne Tyson'" <[email protected]>; <[email protected]> Sent: Monday, September 12, 2011 3:44 PM Subject: RE: [ECOLOG-L] a non Ivory Tower view of invasive species Yes, Wayne, the BLM is cutting down "big junipers" as you saw -- 100 years of fire protection means we now have some pretty good-sized junipers in the areas that once burnt over. However, the BLM is not cutting down the really big "grandfather" junipers growing on rims and rocky ridges where wildfires did not reach or burn hot enough to kill these old junipers. Regarding water and vegetation effects, junipers are water hogs and vegetation excluders. The ground under a big juniper tends to be void of grasses, forbs and shrubs. That's because the juniper not only mines the deep water, its canopy also collects rainwater and channels it down the trunk into the ground, creating a parched mini-desert where other species are inhibited from growing. My son tells an anecdote from when he was a Forest Service district ranger on the east (Great Basin) side of the Fremont-Winema National Forest: He took a senior rancher to see an area adjacent to his ranch property where they had been removing intrusive juniper from a draw leading into the Chewaucan River. When the rancher saw rejuvenated springs he teared up, saying "I remember seeing those springs go away many years ago and I thought I'd never see them flowing again." Warren W. Aney Tigard, Oregon -----Original Message----- From: Ecological Society of America: grants, jobs, news [mailto:[email protected]] On Behalf Of Wayne Tyson Sent: Monday, 12 September, 2011 13:08 To: [email protected] Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species All: The BLM has a "demonstration" project on Steen's mountain, complete with plasticized photos and text explaining that fire suppression was the culprit in the juniper "invasion," but my bias tends to line up more with Hohn's. However, I suspect trampling and hoof-dragging (soil disturbances) are more likely to be primary factor, borne more of gut feelings than evidence. The BLM PR discusses the comparative effects of various treatments, but the bias seems to be pretty much as Hohn describes. Back in 1980, I used the field-trial approach to "test" various treatments for grassland restoration. One of the results showed that evaporative losses went up, apparently drastically, as the clayey soil developed large desiccation cracks quickly, while the uncleared plots did not crack until much later in the dry season. If the cracks are deep enough and swelling doesn't close them too fast, there might be an advantage to the cracks as a means of depositing free water (especially in low-volume precipitation events) at depth rather than depending upon percolation alone. This sort of thing cries out for more and better research than we had the budget to do. Based on what I have read and heard over the years, I suspect that plant-soil-water relations, especially in wildland soils, is not well-understood by most researchers. The more certain a researcher is concerning such conclusions, the more I tend to consider them suspect. I think that a lot of range managers are shooting themselves in the foot by cutting down big junipers (as has been done at Steen's Mountain). First, interception of solar radiation tends to reduce evaporative loss. Second, junipers and other woody plants of semi-arid and arid regions tend to be fairly efficient in terms of "water use." Third, grasses tend to mine water from shallow depths and transpire more (higher ET?) from the first, say, meter or less of soil, thus intercepting percolating water, especially in heavier soils, possibly or probably reducing rather than enhancing groundwater recharge. Fourth, I suspect that the marginal "improvement" in forage production is a snare and a delusion; nobody seems to check the alternative of a mixed stand, so there is no comparative basis for any such conclusions apart from intuitive inference. Fifth, heterogeneous sites are more resilient than more homogeneous ones; the big, old junipers (ironically far older than the acknowledged beginning of fire suppression) shade areas where grasses tend to remain active longer as the season advances, providing more palatable forage as well as providing for wider reproduction potential via zones of seed production when the more open areas die or go dormant, resulting in diminished seed production or "crop" failure (provided the stock has been taken off soon enough to keep the seeds from being eaten before maturity). Sixth, the old junipers provide stock shade and wildlife cover. There may be more, but that's what comes to mind at the moment. If managers want to control the juniper invasion, why not kill the trees that truly represent the invasion, i.e., the younger seedlings, saplings, and smaller trees rather than the ones they must acknowledge existed prior to the "invasion?" As usual, I look forward to alternative evaluations of the evidence, including speculation with a sound theoretical foundation. WT PS: I'd like to see some conclusive evidence that, in the long-term, exclusion of livestock from cheatgrass areas would not result in reduced cheatgrass populations. The restoration process could be speeded up by planting colonies of indigenous grasses and perhaps other species (as propagule-generators and for site heterogeneity) consistent with comparable sites without heavy cheatgrass populations. ----- Original Message ----- From: Charlie Hohn To: Wayne Tyson Cc: [email protected] Sent: Monday, September 12, 2011 10:06 AM Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species Native invasives are an important thing to acknowledge, because again the issue is not where plants are native to, but if they are invasive. Native invasives are necessarily behaving in this way due to changes in their environment (I think in the juniper's case it has to do with grazing, right?)... and in these cases - as well as with many non-native invasives, it makes sense to deal with the problem by addressing the changes in the environment (adopt better grazing practices, fire management practices, or whatever the case may be). However, I do think there are some invasive organisms that would be a problem even WITHOUT all these other human disturbances (for instance, cheatgrass)... that invade undisturbed areas and 'crash' ecosystems without being caused by environmental changes. I think that is the main reason to differentiate native invasives from introduced ones. On Mon, Sep 12, 2011 at 9:41 AM, Wayne Tyson <[email protected]> wrote: Warren (and others), how might the juniper "invasion" on Steen's Mountain (or other "invasions" of indigenous species, particularly dominant, long-lived indicators) fit into this discussion? WT ----- Original Message ----- From: "Warren W. Aney" <[email protected]> To: <[email protected]> Sent: Sunday, September 11, 2011 9:08 PM Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species I was speaking from a contemporary perspective, Manuel. From a very long term perspective perhaps we can say that a species that somehow translocated into another ecosystem may have initially disrupted that ecosystem but after a few thousand generations the species and the ecosystem evolved together to form a coherent and mutually productive stability. There is a hypothesis that Native Americans disrupted the American ecosystems resulting in the extinction of several large mammal species shortly after their arrival. But after a few thousand generations it appears that they became a component of the American ecosystems, sometimes managing certain ecosystem elements to their benefit but certainly not disrupting and degrading these systems to the extent that Euro-Americans did (and continue to do so). Taking your island fauna example, consider the Galapagos finches. Charles Darwin concluded that there was probably a single invasion of a finch species eons ago, but these finches evolved into different species so as to fill various ecological niches, resulting in a diverse and stable set of finch-inhabited ecosystems. Certainly introduced rats could also eventually evolve along with the ecosystems to become a stable component. But in the short term that ecosystem is going to be disrupted, and in the long term that ecosystem is going to be a somewhat different system. We humans, as "overseers" have the ability and duty to evaluate that current disruption and that future potential. There are those of us who say "let nature take its course" and there are those who say "manage for human values" - I say we should be following the axiom of Aldo Leopold: "A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise." We need to evaluate and manage invaders with that axiom as our beacon. Warren W. Aney Tigard, Oregon _____ From: Manuel Spínola [mailto:[email protected]] Sent: Sunday, 11 September, 2011 04:54 To: Warren W. Aney Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species Hi Warren, Take an island, you have "native" birds and later in time you have black rats that you consider invaders, but why those "native" birds are in the island, they needed to be invaders at some point in time. If Homo sapiens originated in Africa, from where the native Americans are from? Best, Manuel 2011/9/10 Warren W. Aney <[email protected]> There can be a meaningful ecological difference between an organism that evolved with an ecosystem and an organism that evolved outside of but spread, migrated or was otherwise introduced into that ecosystem. An organism that evolved with an ecosystem is considered a component that characterizes that ecosystem. An introduced organism that did not evolve with that ecosystem should at least be evaluated for its potential modifying effects on that ecosystem. Am I being too simplistic? Warren W. Aney Senior Wildlife Ecologist Tigard, OR -----Original Message----- From: Ecological Society of America: grants, jobs, news [mailto:[email protected]] On Behalf Of Manuel Spínola Sent: Saturday, 10 September, 2011 12:22 To: [email protected] Subject: Re: [ECOLOG-L] a non Ivory Tower view of invasive species With all due respect, are not we all invaders at some point in time? Best, Manuel Spínola 2011/9/10 David L. McNeely <[email protected]> ---- Matt Chew <[email protected]> wrote: > We can compose effectively endless lists of cases where human agency has > redistributed biota and thereby affected pre-existing populations, > ecological relationships and traditional or potential economic > opportunities. Those are indisputable facts. The House Sparrow is in North America by human hand. > But what those facts mean is disputable. House sparrows are in serious decline in Europe, probably as an unintended consequence due to human actions. > > I see effects; they see impacts. > I see change; they see damage. Many people see a need to eradicate non-natives. At the same time, many people see a need to preserve natives. With regard to the house sparrow ------ hmmm......... . Where does the "arms race" that Matt mentioned further along in his post lead? mcneely > -- *Manuel Spínola, Ph.D.* Instituto Internacional en Conservación y Manejo de Vida Silvestre Universidad Nacional Apartado 1350-3000 Heredia COSTA RICA [email protected] [email protected] Teléfono: (506) 2277-3598 Fax: (506) 2237-7036 Personal website: Lobito de río <https://sites.google.com/site/lobitoderio/> Institutional website: ICOMVIS <http://www.icomvis.una.ac.cr/> -- Manuel Spínola, Ph.D. Instituto Internacional en Conservación y Manejo de Vida Silvestre Universidad Nacional Apartado 1350-3000 Heredia COSTA RICA [email protected] [email protected] Teléfono: (506) 2277-3598 Fax: (506) 2237-7036 Personal website: Lobito de río <https://sites.google.com/site/lobitoderio/> Institutional website: ICOMVIS <http://www.icomvis.una.ac.cr/> ----- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1392 / Virus Database: 1520/3890 - Release Date: 09/11/11 -- -- ============================ Charlie Hohn Recent Graduate Field Naturalist Program, Department of Plant Biology University of Vermont [email protected] slowwatermovement.blogspot.com ---------------------------------------------------------------------------- -- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1392 / Virus Database: 1520/3892 - Release Date: 09/12/11 ----- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1392 / Virus Database: 1520/3892 - Release Date: 09/12/11 ------------------------------------------------------------------------------ No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1392 / Virus Database: 1520/3892 - Release Date: 09/12/11
