Aldo Leopold (1933), Game Management.

 In short, twenty centuries of progress have brought the average citizen a vote, a national anthem, a Ford, a bank account, and a high opinion of himself, but not the capacity to live in high density without befouling and denuding his environment...Nor a conviction that such capacity, rather than such density, is the true test of whether he is civilized.


Aldo Leopold, ardent environmentalist, poses with his blushing bride Estella and their dog Flick.

What would Aldo do?  Aldo ignored horse impacts and thought shooting coyotes was OK.  Even he had a conflict between what he wanted and what was real awareness. 


"People usually don't do what they believe in. They do what they want and then they repent" (Bob Dylan in Brownsville Girl).


Other Similar Literature Surveys



A LITERATURE REVIEW  - Marilyn Jordan Ph.D. (

The Nature Conservancy, May 4, 2000

Nitrogen and Weeds


Fargione, J., Brown, C.S., Tilman, D. 2003.  Community assembly and invasion: An experimental test of neutral versus niche processes. Colorado State University, Fort Collins, CO 80523


Weeds can target areas of high diversity which may also have elevated N.

Stohlgren T.J., Binkley D., Chong G.W., Kalkhan M.A., Schell L.D., Bull K.A., Otsuki Y., Newman G., Bashkin M., Son Y.  1999.  Exotic plant species invade hot spots of native plant diversity.  Ecological Monographs 69 (1): 25-46.


Tilman, D. 1982. Resource competition and community

structure, Monographs in population biology. Princeton

University Press, Princeton, New Jersey, USA.


Tilman, D. 1987. Secondary succession and the pattern of plant

dominance along experimental nitrogen gradients. Ecological

Monographs 57:189–214.


Tilman, D. 1988. Plant strategies and the dynamics and structure

of plant communities. Monographs in population biology.

Princeton University Press, Princeton, New Jersey, USA.


Tilman, D. 1989. Competition, nutrient reduction, and the competitive

neighborhood of a bunchgrass. Functional Ecology



Tilman, D. 1990. Constraints and tradeoffs: toward a predictive

theory of competition and succession. Oikos 58:3–15.


Tilman, D. 1994. Competition and biodiversity in spatially

structured habitats. Ecology 75:2–16.


Tilman, D., May, R. M. , Lehman, C.L., Nowak, M.A.

1994. Habitat destruction and the extinction debt. Nature



Habitat destruction is the major cause of species extinctions1?3. Dominant species often are considered to be free of this threat because they are abundant in the undisturbed fragments that remain after destruction. Here we describe a model that explains multispecies coexistence in patchy habitats4 and which predicts that their abundance may be fleeting. Even moderate habitat destruction is predicted to cause time-delayed but deterministic extinction of the dominant competitor in remnant patches. Further species are predicted to become extinct, in order from the best to the poorest competitors, as habitat destruction increases. More-over, the more fragmented a habitat already is, the greater is the number of extinctions caused by added destruction. Because such extinctions occur generations after fragmentation, they represent a debt?a future ecological cost of current habitat destruction.




Ehrlich, P. & Ehrlich, A. Extinction (Ballantine Books, New York, 1981).


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Simberloff, D. Zh. Obshch. Biol. 45, 767?778 (1984).


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Hanski, I. in Living in a Patchy Environment (eds Shorrocks, B. & Swingland, I. R.) 127?145 (Oxford Univ. Press, UK, 1990).


Shorrocks, B. Biol. J. Linn. Soc. 43, 211?220 (1991).


Sale, P. F. The Ecology of Fishes on Coral Reefs (Academic, New York, 1991).


Doherty, P. & Fowler, T. Science 263, 935?939 (1994).


Werner, P. A. & Platt, W. J. Am. Nat. 110, 959?971 (1976). | Article | ISI |


Shmida, A. & Ellner, S. Vegetatio 58, 29?55 (1984). | ISI |


Grubb, P. J. in Community Ecology (eds Diamond, J. & Case, T.) 207?226 (Harper & Row, New York, 1986).


Nee, S. & May, R. M. J. Anim. Ecol. 61, 37?40 (1992). | ISI |


May, R. M. in Ecology and Evolution of Communities (eds Cody, M. L. & Diamond, J. M.) 81?120 (Harvard Univ. Press, Cambridge, MA, 1975).


Diamond, J. M. Proc. natn. Acad. Sci. U.S.A. 69, 3199?3203 (1972).


Terborgh, J. BioScience 24, 715?722 (1974). | ISI |


Case, T. J., Bolger, D. T. & Richman, A. D. in Conservat. Biology (eds Fielder, P. L. & Jain, S. K.) 91?125 (Chapman & Hall, New York, 1992).


Lovejoy, T. E. et al. in Extinctions (ed. Nitecki, M. H.) 295?325 (Univ. of Chicago Press, Chicago, 1984).


Bucher, E. H. Curr. Ornithol. 9, 1?36 (1992).


Chapin, F. S. A. Rev. Ecol. System. 11, 233?260 (1980). | ChemPort |


Pastor, J., Aber, J. D., McClaugherty, C. A. & Melillo, J. M. Am. Mid. Nat. 108, 266?277 (1982).


Tilman, D. & Downing, J. A. Nature 367, 363?365 (1994). | Article | ISI |


Naeem, S., Thompson, L., Lawler, S., Lawton, J. H. & Woodfin, R. Nature 368, 734?737 (1994). | Article | ISI |





Tilman, D., and D. Wedin. 1991a. Plant traits and resource

reduction for five grasses growing on a nitrogen gradient.

Ecology 72:685–700.


Tilman, D., and D. Wedin. 1991b. Dynamics of nitrogen

competition between successional grasses. Ecology 72:



Wedin, D. A. and D. Tilman.  1996.  Influence of nitrogen loading and species composition on the carbon balance of grasslands.  Science 274: 1720-1723.


Tilman, D., D. Wedin, and J. Knops. 1996. Productivity and

sustainability influenced by biodiversity in grassland ecosystems.

Nature 379:718–720.


The functioning and sustainability of ecosystems may depend on their biological diversity1?8. Elton's9 hypothesis that more diverse ecosystems are more stable has received much attention1,3,6,7,10?14, but Darwin's proposal6,15 that more diverse plant communities are more productive, and the related conjectures4,5,16,17 that they have lower nutrient losses and more sustainable soils, are less well studied4?6,8,17,18. Here we use a well-replicated field experiment, in which species diversity was directly controlled, to show that ecosystem productivity in 147 grassland plots increased significantly with plant biodiversity. Moreover, the main limiting nutrient, soil mineral nitrogen, was utilized more completely when there was a greater diversity of species, leading to lower leaching loss of nitrogen from these ecosystems. Similarly, in nearby native grassland, plant productivity and soil nitrogen utilization increased with increasing plant species richness. This supports the diversity?productivity and diversity?sustainability hypotheses. Our results demonstrate that the loss of species threatens ecosystem functioning and sustainability.




Ehrlich, P. & Ehrlich, A. Extinction (Random House, New York, 1981).


Wilson, E. O. The Diversity of Life (Belknap, Cambridge, Massachusetts, 1992).


McNaughton, S. J. Am. Nat. 111, 515?525 (1977). | Article | ISI |


Ewel, J. J., Mazzarino, M. J. & Berish, C. W. Ecol. Applic. 1, 289?302 (1991).


Vitousek, P. M. & Hooper, D. U. in Biodiversity and Ecosystem Function (eds Schulze, E. D. & Mooney, H. A.) 3?14 (Springer, Berlin, 1993).


McNaughton, S. J. in Biodiversity and Ecosystem Function (eds Schulze, E. D. & Mooney, H. A.) 361?384 (Springer, Berlin, 1993).


Tilman, D. & Downing, J. A. Nature 367, 363?365 (1994). | Article | ISI |


Naeem, S., Thompson, L. J., Lawler, S. P., Lawton, J. H. & Woodfin, R. M. Nature 368, 734?737 (1994). | Article | ISI |


Elton, C. S. The Ecology of Invasion by Animals and Plants (Chapman and Hall, London, 1958).


May, R. M. Stability and Complexity in Model Ecosystems (Princeton Univ. Press, 1973).


Goodman, D. Q. Rev. Biol. 50, 237?266 (1975). | Article | ISI |


King, A. W. & Pimm, S. L. Am. Nat. 122, 229?239 (1983). | Article |


Pimm, S. L. Nature 307, 321?326 (1984). | Article | ISI |


Tilman, D. Ecology (in the press).


Darwin, C. The Origin of Species by Means of Natural Selection (Murray, London, 1859).


Ehrlich, P. R. & Mooney, H. A. BioScience 33, 248?254 (1983).


Swift, M. J. & Anderson, J. M. in Biodiversity and Ecosystem Function (eds Schulze, E. D. & Mooney, H. A.) 15?41 (Springer, Berlin, 1993).


Naeem, S., Thompson, L. J., Lawler, S. P., Lawton, J. H. & Woodfin, R. M. Phil. Trans. R. Soc. Lond. B347, 249?262 (1995). | ISI |


Lawton, J. H. & Brown, V. K. in Biodiversity and Ecosystem Function (eds Schulze, E. D. & Mooney, H. A.) 255?270 (Springer, Berlin, 1993).


Givnish, T. J. Nature 371, 113?114 (1994). | Article | PubMed | ISI |


Tilman, D., Downing, J. & Wedin, D. Nature 371, 114 (1994). | Article |


Andre, M., Brechignac, P. & Thibault, P. Nature 371, 565 (1994). | Article | ChemPort |


Naeem, S., Thompson, L. J., Lawler, S. P., Lawton, J. H. & Woodfin, R. M. Nature 371, 565 (1994). | Article |


Tilman, D. Oikos 58, 3?15 (1990).


McKane, R. B., Grigal, D. F. & Russelle, M. P. Ecology 71, 1126?1132 (1990). | ISI |


Chabot, B. F. & Mooney, H. A. (eds) Physiological Ecology of North American Plant Communities (Chapman and Hall, New York, 1985).


Givnish, T. J. (ed.) On the Economy of Plant Form and Function (Cambridge Univ. Press, 1986).


Grime, J. P. Nature 242, 344?347 (1973). | Article | ISI |


Tilman, D. & Pacala, S. in Species Diversity in Ecological Communities (eds Ricklefs, R. & Schluter, D.) 13?25 (Univ. of Chicago Press, 1993).


Pimm, S. L., Russell, G. J., Gittleman, J. L. & Brooks, T. M. Science 269, 347?350 (1995). | ISI | ChemPort |




Turelli, M. 1981. Niche overlap and invasion of competitors

in random environments. 1. Models without demographic

stochasticity. Theoretical Population Biology 20:1–56.


The relationship between persistent, small to moderate levels of random environmental fluctuations and limits to the similarity of competing species is studied. The analytical theory hinges on deriving conditions under which a rare invading species will tend to increase when faced with an array of resident competitors in a fluctuating environment. A general approximation scheme predicts that the effects of low levels of stochasticity will typically be small. The technique is applied explicitly to a class of symmetric, discrete-time stochastic analogs of the Lotka-Volterra equations that incorporate cross-correlation but no autocorrelation. The random environment limits to similarity are always very close to the corresponding constant environment limits. However, stochasticity can either facilitate or hinder invasion. The exact limits to similarity are extremely model-dependent. In addition to the symmetric models, an analytically tractable class of models is presented that incorporates both auto- and cross-correlation and no symmetry assumptions. For all of the models investigated, the analytical theory predicts that small-scale stochasticity does little, if anything, to limit similarity. Extensive Monte Carlo results are presented that confirm the analytical results whenever the dynamics of the discrete time models are biologically reasonable in the sense that trajectories do not exhibit unrealistic crashes. Interestingly, the class of stochastic models that is well behaved in this sense includes models whose deterministic analogs are chaotic. The qualitative conclusion, supported by both the analytical and simulation results, is that for competitive guilds adequately modeled by Lotka-Volterra equations including small to moderate levels of random fluctuations, practical limits to similarity can be obtained by ignoring the stochastic terms and performing a deterministic analysis. The mathematical and biological robustness of this conclusion is discussed.


Usher, M. B. 1988. Biological invasions of nature reserves: A search for generalizations.

Biological Conservation.  44:(1-2) 119-135


Each one of the 24 nature reserves in the preceding case studies has received introduced species of plants and vertebrates (and invertebrates where the data exist). Some of these have become invasive, although the probability that an island nature reserve is invaded is greater than a savanna or dry woodland. Arid lands and Mediterranean-type reserves showed a negative relationship between the proportion of species that are introduced and the reserve's area. Examples demonstrate that after a period of about 1000 years it is difficult to distinguish between native and introduced species.

Invasive species affect both the structure and function of an ecosystem. Management priority has to be given both to invasive species that threaten endemic species with extinction and to species that have a strong landscape effect. The cost of controlling invasive species can utilise a large proportion of a reserve manager's recurrent budget. Tourism poses dangers for reserves since there is a positive correlation between visitation rate and the number of introduced species.

The most important generalisation is that all nature reserves, except those in Antarctica, appear to have invasive species. Managers face the problem of how best to conserve ecological variety.


Badgery, W.B., Kemp, D.R., Michalk, D.L., King, W.M.C.G. 2005.

Competition for Nitrogen between Australian Native Grasses and the Introduced Weed Nassella trichotoma (summary not full paper)

Annals of Botany 2005 96(5):799-809;

• Background and Aims Nassella trichotoma is an unpalatable perennial grass weed that invades disturbed native grasslands in temperate regions of south-eastern Australia. This experiment investigated whether elevated N levels, often associated with disturbance, increases the competitiveness of N. trichotoma relative to C3 and C4 native Australian grasses.

• Methods A pot experiment investigated competitive interactions between four native grasses, two C3 species (Microlaena stipoides and Austrodanthonia racemosa) and two C4 species (Themeda australis and Bothriochloa macra), and N. trichotoma at three different N levels (equivalent to 0, 60 and 120 kg ha–1) and three competing densities (zero, one and eight neighbouring plants), using an additive design.

• Key Results All native grasses were competitive with N. trichotoma at low N levels, but only M. stipoides was competitive at high N. High densities of native grasses (8 : 1) had a major competitive effect on N. trichotoma at all N levels. The competitive ranking of native grasses, across all N levels, on N. trichotoma was: M. stipoides > A. racemosa > B. macra > T. australis. The C3 species were generally more competitive than the C4 species and C4 grasses were not inherently more productive at low N levels, in contrast to the results of other studies.

• Conclusion To resist invasion from N. trichotoma, these native grasses need to be maintained at a high density and/or biomass. The results do not support the theory that species such as N. trichotoma, with high tissues density, are always less competitive than those of low tissue density; in this case competitiveness depended on N levels. The ability of N. trichotoma to accumulate biomass at a higher rate than these native grasses, helps to explain why it is a major weed in disturbed Australian native grasslands.




This references numerous other studies related to weeds and nitrogen.

Hobbs, R.J., Huenneke, L.F. 1992. Disturbance, Diversity, and Invasion: Implications for Conservation. Conservation Biology, 6:(3) 324-337.


Abstract: Disturbance is an important component of many ecosystems and variations in disturbance regime can affect ecosystem and community structure and functioning. The "'intermediate disturbance hypothesis" suggests that species diversity should be highest at moderate levels of disturbance. However, disturbance is also known to increase the invasibility of communities. Disturbance therefore poses an important problem for conservation management Here we review the effects of disturbances such as fire, grazing soil disturbance and nutrient addition on plant species diversity and invasion, with particular emphasis on grassland vegetation Individual components of the disturbance regime can have marked effects on species diversity, but it is often modifications of the existing regime that have the largest influence. Similarly, disturbance can enhance invasion of natural communities, but frequently it is the interaction between different disturbances that has the largest effect. The natural disturbance regime is now unlikely to persist within conservation areas since fragmentation and human intervention have usually modified physical and biotic conditions. Active management decisions must now be made on what disturbance regime is required and this requires decisions on what species are to be encouraged or discouraged


Wolf, J.J., Beatty, S. W., Seastedt, T. R.. 2004. Soil characteristics of Rocky Mountain National Park grasslands invaded by Melilotus officinalis and M. alba. Journal of Biogeography 31:1-10.


Luken, J.O., Seastedt, T.R.. 2004. Plant invasions, management, and the conflict of perspective. Weed Technology 18:1514 -1517.


Suding, K.N., LeJeune, K.D., Seastedt, T.R. 2004 Competitive interactions and responses of an invasive weed: dependencies on nitrogen and phosphorus availability. Oecologia 141: 526-535.


LeJeune, K.D., Suding, K.N., Seastedt, T.R. in press. Nutrient availability does not explain invasion and dominance of a mixed grass prairie by the exotic forb Centaurea diffusa Lam. Applied Soil Biology.


LeJeune, K D., KN. Suding, S. Sturgis, A. Scott and T.R. Seastedt. in press. Biocontrol insect use of fertilized and unfertilized diffuse knapweed (Centaurea diffusa Lamarck) in a Colorado grassland. Environmental Entomology.


Heather E. Reed, Timothy R. Seastedt, and John M. Blair. In press. Ecological consequences of C4 grass invasion of a C4 grassland: A dilemma for management. Ecological Applications.


Seastedt, T.R., K.N. Suding and K.D. LeJeune. In press. Understanding Invasions: The rise and fall of diffuse knapweed (Centaurea diffusa) in North America. In: Inderjit (Ed.) Invasive plants: ecological and agricultural aspects. Basal, Switzerland: Birkhauser-Verlag AG.


Seastedt, T. R., J. M. Briggs and D. J. Gibson. 1991.  Controls of nitrogen

limitation in tallgrass prairie.  Oecologia 87: 72-79.


Seastedt, T.R., P. Duffy and J. Knight. 1996.  Reverse fertilization experiment

produces mixed results.  Restoration and Management Notes 14:64.



Reever-Morghan, K.J. and T.R. Seastedt. 1999. Effects of soil nitrogen on non-native

plants in disturbed grasslands.  Restoration Ecology 7: 51-55.



Holford, I. C. R. (1980). Effect of duration of grazed lucerne on long-term yields and nitrogen uptake of subsequent wheat. Aust. J. Agric. Res. 31, 239-50.


Holford, I.C.R. 1981. Changes in nitrogen and organic carbon of wheat growing soils after various periods of grazed lucerne, extended fallowing and continuous wheat

Australian Journal of Soil Research 19(3) 239 - 249

“Extremely high rainfall for three months (534 mm) following harvest in 1975 prevented normal fallow cultivation in early 1976, with resultant heavy growth of weeds and volunteer wheat on the black earth but not on the red-brown earth; less growth on the latter soil was apparently caused by leaching of nitrogen (Holford 1980).”


Changes in total and mineral nitrogen and organic carbon were measured over a nine year period in two contrasting soils of northern New South Wales after various durations of grazed lucerne, extended fallowing and continuous wheat growing. At least 2 1/2 years of lucerne ley were required to raise the total soil nitrogen above the original level on both soil types. For each year of lucerne growth the average increase (above the control treatments) in total soil nitrogen (0-15 cm) was equivalent to about 140 kg nitrogen ha-1 in the black earth and about 110 kg nitrogen ha-1 in the red-brown earth. Significantly higher levels of soil nitrogen were maintained after the lucerne treatments throughout the 9 years of measurement on the black earth and for 5 years on the red-brown earth. Lucerne had a much larger effect on nitrogen than on organic carbon, which was significantly increased only in the black earth. There were very large increases in mineral nitrogen (0-15 cm) in the first year of measurement after lucerne. Levels remained greater than they were originally for the first 4 years, and they were greater for 7 years in the black earth and 4 years in the red-brown earth following lucerne than following continuous wheat or extended fallow. The decline in mineral nitrogen during wheat cropping after lucerne was greatly increased by excessive rainfall (574 mm or more) during the fallow. Leaching was greater in the red-brown earth than in the black earth, and this explained occasional differences in nitrogen uptake by wheat between the two soil types. Some evidence suggested that under moderately moist conditions nitrogen mineralization from lucerne-fixed nitrogen was greater in the red-brown earth than in the black earth but under drier conditions it was less.

Weeds in Ecosystem


Stohlgren, T.J.; Chong, G.W.; Schell, L.D.; Rimar, K.A.; Otsuki, Y.; Lee, M.; Kalkhan, M.A.; Villa, C.A. 2002. Assessing vulnerability to invasion by nonnative plant species at multiple scales. Environmental Management 29:566-577.


Stohlgren, T.J.; Otsuki, Y.; Villa, C.; Lee, M.; Belnap, J. 2001. Patterns of plant invasions: a case example in native species hotspots and rare habitats. Biological Invasions 3:37-50.


Weeds can target areas of high diversity which may also have elevated N.

Stohlgren T.J., Binkley D., Chong G.W., Kalkhan M.A., Schell L.D., Bull K.A., Otsuki Y., Newman G., Bashkin M., Son Y.  1999.  Exotic plant species invade hot spots of native plant diversity.  Ecological Monographs 69 (1): 25-46.


Stohlgren, T.J., Bull, K.A., Otsuk, Y.i, Villa, C.A., Lee, M. 1998. Riparian zones as havens for exotic plant species in the central grasslands. Plant Ecology 138:(1) 113-125.


 In the Central Grasslands of the United States, we hypothesized that riparian zones high in soil fertility would contain more exotic plant species than upland areas of low soil fertility. Our alternate hypothesis was that riparian zones high in native plant species richness and cover would monopolize available resources and resist invasion by exotic species. We gathered nested-scale vegetation data from 40 1 m2subplots (nested in four 1000 m2 plots) in both riparian and upland sites at four study areas in Colorado, Wyoming, and South Dakota (a total of 320 1 m2 subplots and 32 1000 m2 plots). At the 1 m2 scale, mean foliar cover of native species was significantly greater (P<0.001) in riparian zones (36.3% ± 1.7%) compared to upland sites (28.7% ± 1.5%), but at this small scale there were no consistent patterns of native and exotic species richness among the four management areas. Mean exotic species cover was slightly higher in upland sites compared to riparian sites (9.0% ± 3.8% versus 8.2% ± 3.0% cover). However, mean exotic species richness and cover were greater in the riparian zones than upland sites in three of four management areas. At the 1000 m2 scale, mean exotic species richness was also significantly greater (P<0.05) in riparian zones (7.8 ± 1.0 species) compared to upland sites (4.8 ± 1.0 species) despite the heavy invasion of one upland site. For all 32 plots combined, 21% of the variance in exotic species richness was explained by positive relationships with soil % silt (t =1.7, P=0.09) and total foliar cover (t = 2.4, P=0.02). Likewise, 26% of the variance in exotic species cover (log10 cover) was explained by positive relationships with soil % silt (t =2.3, P=0.03) and total plant species richness (t = 2.5, P=0.02). At landscape scales (four 1000 m2 plots per type combined), total foliar cover was significantly and positively correlated with exotic species richness (r=0.73, P<0.05) and cover (r=0.74, P<0.05). Exotic species cover (log10 cover) was positively correlated with log10% N in the soil (r=0.61, P=0.11) at landscape scales. On average, we found that 85% (±5%) of the total number of exotic species in the sampling plots of a given management area could be found in riparian zones, while only 50% (±8%) were found in upland plots. We conclude that: (1) species-rich and productive riparian zones are particularly invasible in grassland ecosystems; and (2) riparian zones may act as havens, corridors, and sources of exotic plant invasions for upland sites and pose a significant challenge to land managers and conservation biologists.


Hobbs, R.J.; Huenneke, L.F. 1992. Disturbance, diversity, and invasion: implications for conservation. Conservation Biology 6:324-337


Dog Feces/Urine Characteristics and Effects


Animal waste collection survey.


Toxins and concentration in Dog feces -just a component of the full article


Watershed effects of dog feces and public compliance with poop pick up -just a component of the full article


North Virginia dog park proposed study and summary of watershed data from the literature.


Results of the North Virginia study to determine dog feces contribution to stream fecal coliform.  Values could range from about 9% to 25%, and wildlife was the primary contributor of the other 75%

Simmons, G.M. Jr., Waye, D.F., Herbein, S., Myers, S., Walker, E. 2000. Estimating Nonpoint Fecal Coliform Sources in Northern Virginia's Four Mile Run Watershed. The Northern Virginia Regional Commission (NVRC) Fairfax, VA



Referenced as a source of public behaviour and attitudes Re: dog feces.  This is a summary , and partial report (52 pages) not the full report.

Swann, C. 1999. A Survey of Residential Nutrient Behaviors in the Chesapeake Bay. Widener-Burrows, Inc. Chesapeake Research Consortium. Center for Watershed Protection. Ellicott City, MD. 112 pp. 




Dog Urine effects on grass.

Speculation on the actual cause of the lawn burn has resulted in numerous theories on what else in the urine may be contributing to the damage. Dr. A.W. Allard, a Colorado veterinarian, examined numerous variations in dog urine and the effects on several common lawn grasses1. His results support the fact that volume of urine (nitrogen content) and urine concentration had the most deleterious effects on lawns. The pH of the urine did not have any variable effect nor did common additives designed to alter the urine pH. Of the four grasses tested, Festuca sp. var. Kentucky 31 (fescue) and Lolium perrene (perennial ryegrass) were the most resistant to urine effects. In fact, the urine routinely produced a fertilizer effect on these grasses at diluted concentrations. Poa pratensis (Kentucky bluegrass) and Cynodon sp. var. Fairway (bermudagrass) were very sensitive to any urine concentration and severe burns resulted, persisting greater than 30 days after initial exposure to even four ounces of diluted urine. Even on the most urine resistant grass tested (fescue) urine concentration was a bigger problem than urine volume. Concentrated urine with volumes as little as 30cc (one ounce) caused lawn burn even on fescue grasses.


Allard, A.W. 1981. Lawn burn and dog urine, Canine Practice, March/April 1981;8;(2);26-32.


CDC (Center for Disease Control).  Guidelines for Veterinarians: Prevention of Zoonotic Transmission of Ascarids and Hookworms of Dogs and Cats. Web Site Reference


Finkel, A.J. 1972. Dog feces as vector of human disease.
JAMA  1972 Sep 4;221(10):1172

No Abstract


Beaver, P.C. 1975. Biology of soil-transmitted helminths: the massive infection.

Health Lab Sci. 1975 Apr;12(2):116-25.


Soil-transmitted helminth infections when invariably cause disease. A massive

infection with Ascaris lumbricoides may cause intestinal obstruction, liver

abscess, or some other condition requiring surgical treatment; more regularly,

however, ascaris disease is a form of malnutrition. Trichuris trichiura causes

diarrhea and dysentery and, at times, rectal prolapse. The hookworms, Necator

americanus and Ancylostoma duodenale, cause blood-loss from the intestine

resulting in anemia. Necator infection is acquired percutaneously, and is more

frequently massive than is that of Ancylostoma which may be acquired

percutaneously or orally. Estimates of egg output in the feces, based on

egg-counts by dilution, direct smear, or thick-film techniques, provide a

reliable index of light, medium, or heavy infection. Acquisition of heavy

infection with Ascaris and Trichuris depends on favorable qualities of the soil,

and on the sorting action of rain which transports and concentrates the eggs of

helminths in locations where survival and transmission are favored. The high

frequency of heavy hookworm infection in southeastern United States and probably

elsewhere may depend largely on the presence of feces-burying dung beetles.

Human infection with soil-transmitted helminths of dogs and cats has become a

serious public health problem attributable to the persistence of rural mores in

the urban setting.

PMID: 1052507 [PubMed - indexed for MEDLINE]


Diseases that can be Spread Through Feces. Drs. Foster & Smith Educational Staff Web site.


Basso, W., Venturini, L., Venturini, M. C., Hill, D. E., Kwok, O. C. H., Shen, S. K., Dubey, J. P. 2001.  First Isolation of Neospora caninum From the Feces of a Naturally Infected Dog.  Journal of Parasitology Volume: 87 Issue: 3 Pages: 612-618

Neospora caninum is a major cause of abortion in cattle worldwide. Cattle become infected with N. caninum by ingesting oocysts from the environment or transplacentally from dam to fetus. Experimentally, dogs can act as definitive hosts, but dogs excrete few oocysts after ingesting tissue cysts. A natural definitive host was unknown until now. In the present study, N. caninum was isolated from the feces of a dog. Gerbils (Meriones unguiculatus) fed feces from the dog developed antibodies to N. caninum in the Neospora caninum agglutination test, and tissue cysts were found in their brains. Neospora caninum was isolated in cell culture and in gamma-interferon gene knockout mice inoculated with brain homogenates of infected gerbils. The DNA obtained from fecal oocysts of the dog, from the brains of gerbils fed dog feces, and from organisms isolated in cell cultures inoculated with gerbil brains was confirmed as N. caninum. The identification of N. caninum oocyst by bioassay and polymerase chain reaction demonstrates that the dog is a natural definitive host for N. caninum.


Johnson, J.R., Stell, A.L., Delavari, P. 2000.  Canine Feces as a Reservoir of Extraintestinal Pathogenic Escherichia coli. VA Medical Center and Department of Medicine, University of Minnesota, Minneapolis, Minnesota.




Horse Manure/Urine Characteristics and Weed Seed


Horse manure nitrogen % from Cornell composting Manual – Average 1.6% dry weight



Amount and N-P-K content of horse manure from CSU 

Horse Manure Management

J.G. Davis and A.M. Swinker – 2002


50 pounds manure/day/horse


Table 1: Average fertilizer content in horse manure (as-is basis).



19 lb


14 lb


36 lb

Per day basis     N       = 0.475 lbs

                          P2O5   = 0.35 lbs

                          K2O   = 0.9 lbs



This is the reference that shows seed germination from horse manure at RMNP.

Benninger, M. C. 1989. Trail as conduits of movement for plant

species in coniferous forests of Rocky Mountain National Park,

Colorado. M.S. Thesis, Miami University.


Benninger-Truax, M. C., Vankat, J. L. & Schaefer, R. L. 1992. Trail

corridors as habitat and conduits for movement of plant species

in Rocky Mountain National Park, Colorado, USA. Landscape

Ecology. 6: 269–278.





I tracked down the primary investigator for the following horse manure/weed item:

Dr. Sibdas Ghosh

Dominican Univeristy

San Rafael, CA 94901


The NPS contact is:

Mietek Kolipinski



By The Associated Press Mon Nov 21, 2005 8:30 PM ET


SAN RAFAEL, Calif. - Researchers are looking to horse manure to study the spread of invasive weeds. Dominican University has received a $100,000 National Park Service grant to study how to slow the spread of nonnative plants and weeds in state parks, school officials said.  Horse manure might be part of the problem, according to scientists.

Researchers began collecting horse manure samples from trails and pastures this summer. They want to test an assumption that seeds can pass through horses, leading to sprouts of invasive weeds.


"We need to know through scientific research if horses do or do not spread weeds and if they do, what is the impact on the parks," said Sibdas Ghosh, chair of Dominican's Department of Natural Sciences and Mathematics.

Colorado, Nevada and Montana require horse owners to give their animals feed that has been certified as weed free.


A.         Preliminary Findings of DU of C:


The preliminary study of forty five samples collected from selected locations throughout the Northern California including Bay Area and Central California were transported to DU of C and placed in a refrigerator.  Utilizing sterile procedures, each bag was opened and split into two samples: one dry and one wet.  Samples to be dried were weighed and placed on paper towels and then transferred on to paper plates.  Whole sample was covered and placed on counters to air dry.  The remaining samples were placed back into individual bags to maintain the original integrity of the horse manure.  Sterile gloves were used at each separation process to avoid cross contamination. Gloves were then counted after procedure was complete to ensure that all gloves were used only once.

After one week, both dry and wet samples were weighed and planted individually in sterile 4 inch pots containing weed free soil.   Vinyl gloves were used for each sample.  Once samples were potted, they were randomly numbered “1 through 45” for wet samples and “1A through 45A” for dry samples.  A random number selection process for pot locations in trays was computer generated along with 10 control samples which contained no horse manure.

After numbering and placing pots into trays, samples were covered and transported to racks which were completely enclosed in a netted, potting shed located three feet off ground. This prevented wind or animal based seed contaminations.  A self-timed watering system within the enclosure was used to evenly water the samples.  Plants were monitored daily for comment notes, growth, photos.

Of ninety pots, 34 plants germinated in 21 pots of which 12 represent dry and 9 represents wet samples respectively.  All plants were identified by Ms. Doreen Smith, California Native Plant Society, Marin Chapter, CA. NONE of the plants identified are listed as Noxious Weeds on the CDFA site.  We report that 2 toad rush (Juncus bufonius), 25 Italian ryegrass (Lolium multiflorum), 1 bur-clover (Medicago polymorpha), 1 summer mustard (Hirschfeldia incana), 1 cudweed (Gnaphalium luteoalbum), 1 purslane (Portulaca oleracea), 1 dooryard knotweed (Polygonum aviculare), 2 cheeseweed (Malva niceaeensis).  Only toad rush (Juncus bufonius) is a native California while the rest are non-native to USA.  However we have found that none of these plants are listed as CDFA (California Department of Food and Agriculture) Noxious Weeds. 

Currently we have additional 90 horse manure samples collected mainly from the National Parks of Northern California.  We are in the process of daily monitoring of plants species germinated from the samples. The anticipated identification of these plant species will be completed by March 31, 2006.


Campbell, J.E., Gibson, D.J. 2001. The effect of seeds of exotic species transported via horse dung on vegetation along trail corridors. Plant Ecology 157(1): 23-25



Landsberg, J., Logan, B., Shorthouse, D.  2001. Horse riding in urban conservation areas: Reviewing scientific evidence to guide management. Ecological Management and Restoration.  2: 36-46.


 We undertook a literature review of the impacts of horse riding in conservation areas, and used it to guide management of horse riding in Canberra Nature Park (CNP), a large, fragmented semi-natural park in and around the city of Canberra in the Australian Capital Territory. The literature review established that, because of their relatively large weight and small area in contact with the ground, horses have a relatively high potential for doing environmental damage. Impacts tend to be generally lowest for hikers, followed by motorcycles, horses and four-wheeled vehicles. One study showed horse traffic caused more damage on established trails than motorcycles, off-road bicycles or hikers. Most published studies of horse-riding impacts in Australia have been conducted in alpine and subalpine environments, and in temperate woodlands and forests on sandstone near Sydney. They have shown that impacts are generally highest in previously untracked areas. Impacts on established trails are generally most marked on sections of trail that are wet, boggy or steep, and on unplanned and unmaintained trails. Impacts are lowest on constructed and maintained trails. Trail proliferation, associated with avoidance of untrafficable sections and short-cutting, can be a major problem. Horses also have potential to spread weeds, because pastures and dried stock feeds contain large numbers of weed seeds that retain high levels of viability in horse manure. The risk of weed establishment is highest when manure is deposited in disturbed, damp sites, particularly when riding off-track. Much less weed establishment is apparent when horse riders remain on-track. Horse riding is a popular activity, but one that is relatively expensive to provide for, and one that may reduce opportunities for lower-impact recreational park users. For all these reasons it appears socially equitable that provision is made for lower numbers of horse riders compared to numbers of park users involved in lower impact, more passive, recreational activities. We conclude by describing how this information was used to develop principles to guide management of horse riding and assess risk at individual sites in Canberra Nature Park.


Harmon GW and FD (1934) The percentage and viability of weed seeds recovered in the feces of farm animals and their longevity when buried manure.  Journal American Society Agronomy.  26: 762-767




Soil Compaction/Disturbance


Cole, D. N.; Spildie, D. R. 1998. Hiker, horse and llama trampling effects on native vegetation in Montana, USA. Journal of Environmental Management 53: 61-71.

Leopold Publication Number 332
     Intensity of trampling disturbance varies with type of recreation traffic. The purpose of this study was to assess the relative impact of hiker, horse, and llama traffic on vegetation and groundcover conditions. Hiker, horse, and llama traffic were applied at two trampling intensities to two previously undisturbed forested vegetation types. Trampling effects were assessed immediately after traffic application and 1 year later. For most impact parameters, intensity of trampling impact varied with type of user. For all parameters that varied with type of user: (1) horse traffic caused the most disturbance; and (2) hiker and llama impacts could not be differentiated statistically. The forb-dominated vegetation type was highly vulnerable to vegetation impact but recovered rapidly. The shrub-dominated type was more resistant but lacked resilience. Higher trampling intensities caused more disturbance but the relationship between trampling intensity and disturbance intensity was non-linear.



DeLuca, T. H.; Patterson, W. A., IV; Freimund, W. A.; Cole, D. N. 1998. Influence of llamas, horses, and hikers on soil erosion from established recreation trails in western Montana, USA. Environmental Management 22(2): 255-262
Leopold Publication Number 319
     Various types of recreational traffic impact hiking trails uniquely and cause different levels of trail degradation; however, trailhead restrictions are applied similarly across all types of packstock. The purpose of this study was to assess the relative physical impact of hikers, llamas, and horses on recreational trails. Horse, llama, and hiker traffic were applied to 56 separate plots on an existing trail at Lubrecht Experimental Forest in western Montana. The traffic was applied to plots at intensities of 250 and 1000 passes along with a no-traffic control under both prewetted and dry trail conditions. Soil erosion potential was assessed by sediment yield and runoff (using a Meeuwig type rainfall simulator), changes in soil bulk density, and changes in soil surface roughness. Soil moisture, slope, and rainfall intensity were recorded as independent variables in order to evaluate the extent that they were held constant by the experimental design. Horse traffic consistently made more sediment available for erosion from trails than llama, hiker, or no traffic when analyzed across wet and dry trail plots and high and low intensity traffic plots. Although total runoff was not significantly affected by trail user, wet trail traffic caused significantly greater runoff than dry trail traffic. Llama traffic caused a significant


Soil compaction comparison (in gm/ of pedestrian, horses, bikes etc.


Eckert, R.E. Jr, Wood, M.K., Blackburn, W.H., & Petersen, F.F.. 1979. Impacts of Off-Road

Vehicles on Infiltration & Sediment Production of Two Desert Soils. Journal of Range

Management. Vol. 32. Pages 397-397.


Liddle, M. & Grieg-Smith., 1975. A Survey of Tracks & Paths in a Sand Dune Ecosystem.

Journal of Applied Ecology Vol. 12 Pages 909-930.


Liddle, M. & Scorgie, H.R.A. 1980. The Effects of Recreation on Freshwater Plants and

Animals: A Review. In Biological Conservation 17.


This paper reviews the impacts of recreation on freshwater plants and animals. A distinction is made between water- and shore-based activities, and between physical and chemical effects. The impacts of water-based recreation, which result mainly from boating, are discussed in terms of wash, turbulence and turbidity, propeller action, direct contact, disturbance to animals, pollution from outboard motors and sewage. Those resulting from shore-based activities, such as angling and swimming, include trampling and associated effects, as well as sewage and other chemical impacts. The effects of management for recreation are also considered. There is relatively more information on the effects of recreational activities on plants than on animals, but the authors consider that further research is required in both fields. Some possible approaches are presented.

Liddle, M., 1997. Recreation Ecology. Chapman & Hall, London.


Godwin, I.C.P. 2000. Physiographic Components of Trail Erosion. M.S. Thesis, Montana State University, Bozeman MT.


No previous study has sought to discriminate between soil erosion and soil compaction when explaining the “missing” cross-sectional areas of incised trails, assuming instead that erosion was the dominant process. Separating the two processes of erosion and compaction is critical to understanding the relationship between physiographic variables and the structure of trails.


The purposes of this project are to estimate the relative effects of compaction and erosion on trail cross sectional area along the New World Gulch Trail, Montana, and to better understand the relationship between erosion, compaction, local topography, vegetation, soil bulk density, and soil texture. The following hypotheses were addressed: 1) adjusting the incised cross sectional area of a trail, by removing the effects of soil compaction, will increase the amount of variance in erosion explained by collected physiographic variables; and 2) inclusion of soil bulk density and soil texture as physiographic variables will increase the amount of variance in cross-sectional area explained along the trail.


The goals of this study required the collection of field data, analysis of soil samples, and statistical analysis of data. Soil samples and other field measurements were collected over several months during the summer and fall of 1994. Some of the topographic information used in the statistical analysis originated in Urie's (1994) studyof recreational trails.


The determination of trail slope as one of the primary components of trail incision is consistent with previous studies. Soil water content is the second most significant independent variable when the percentage of particle sizes are not considered. Percent vegetative cover is also significant in the stepwise regression, although it is not significantly correlated to cross-sectional area.


The most significant variable added to those already studied was soil bulk density. When individual variables were regressed against the measured cross-sectional area, off trail soil bulk density accounted for the second greatest amount of variance (r2 = 0.12) after trail slope (r2 = 0.35). The ratio of on-trail soil bulk density to off-trail soil bulk density, which could be considered a measure of compaction, accounted for even more variance (r2 = 0.18) than soil bulk density.










General Understanding of Dog Impacts


Recommendations and brief discussion of dog impacts. - Canada


Urban problems with dogs and cats. – Australia


Not the exact article, but by the same author - Murray

Murray, R. W. and Penridge, H. 1992. Dogs in the Urban Environment: a handbook of municipal management, Chiron Media, Mackay.

Cameron, D. 1993. 'The impact on rural production of irresponsibly owned pets', Proceedings of the UAM Integration Symposium, November 1993.

Faecal litter management - a local government priority for reasons of community health and environmental amenity.  Virginia Jackson

Proceedings of the UAM Integration Symposium, 2000.


Many local authorities around Australia have introduced laws that require dog owners to pick up after their dog in public places. In New South Wales, this requirement is contained in the Companion Animals' Act.

A range of products and facilities has been developed and are in use around the world to address this issue. However the expense involved can be extremely high and local authorities need to decide carefully whether this is the best allocation of resources relative to other priorities. Virginia will outline the results of recent research on the options available for removing dog faeces. She will also report on a recent nationwide telephone survey that sought to uncover the importance of unremoved dog faeces vis-a-vis other animal management issues.






Dog Issues/Regulations at Other Locations


Juneau Alaska


SanFrancisco California


Australian Urban Animal Management Proceedings 1992-2000


OffLeash1 - Australia

OffLeash2 – Australia

OffLeash3 - Australia


Open space for dogs – Australia


Regulations – Australia


Dog bite data – Australia


Dog bite data – Colorado – About 116 reported bites/year in Colorado over the last 10 years – these are hospitalizations.

Dogs and Wildlife


Environmental Impacts:The Dark Side of Outdoor Recreation. by Scott G. Miller


Dogs and Vegetation


Dog Issue in Boulder





Murphy comments to Boulder City Council re: Mt. Sanitas


Letter to Boulder City Council 2005.

I am a plant ecologist in Boulder Colorado.  For years I have observed the accelerated degradation of the local hiking trails due to off-leash dogs.  Because of the powerful stigma against saying anything negative about dogs, few studies exist that demonstrate even the most obvious impacts of dogs.  Those impacts include compacted ground, poop and urine that create prime weed invasion sites (we have had continuaous new weed invasions along the trails especially the parallel dog trails that humans dont use), wildlife impacts (we have had deer killed while hikers watched, I have observed that the towhee that was once abundant is now uncommon, there are dog trail rings around the shrubs where the birds used to be), Children have been mauled, and adults have been injured, and the list goes on and on.  I hope that a conscerted effort is made to maintain the strict regulations until the studies can be conducted that test/prove the obvious.  When dogs go off trail they accelerate the negative impacts of recreation in a disproportionate rate.  I have had three dogs in my life an I love dogs.  Why must I continue to watch the degradation caused by dogs because there is no science that proves the obvious.  If I had enough resources and was willing to sacrifice perfectly good habitat I could easily prove that dogs have a negative impact that is not necessary and not justified.  Dog owners can be fierce and will never accept the obvious even when the science does exist, that is why you need to be conservative and protect the environment until the science can be completed. 


Please kick start the research that will demonstrate the impacts of dogs.  I know it is almost sinfully wasteful to spend the money necessary to do this, since I feel that it will only prove the obvious, but to let the slow/fast degradation continue is far worse and far more costly in the long run.  Restoration is far more expensive that protection, and total loss is tragic.


There is selfishness in the attitudes of many that say that when it comes to public land, we own it, so we should be allowed to consume it, and we have no significant impacts.  Don't let selfishness be the foundation upon which management is based.


Thank you.