Thoughts
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).
Contents:
- Other Similar Literature Surveys
- Dog Feces/Urine
Characteristics and Effects
- Horse
Manure/Urine Characteristics and Weed Seed
- General
Understanding of Dog Impacts
- Dog
Issues/Regulations at Other Locations
Other Similar Literature Surveys
ECOLOGICAL IMPACTS OF RECREATIONAL USE OF
TRAILS:
A LITERATURE REVIEW - Marilyn Jordan Ph.D. (mjordan@tnc.org)
Weeds can
target areas of high diversity which may also have elevated N.
Tilman,
D. 1982. Resource competition and community
structure,
Monographs in population biology.
University Press,
Tilman, D. 1987. Secondary
succession and the pattern of plant
dominance
along experimental nitrogen gradients. Ecological
Tilman,
D. 1988. Plant strategies and the dynamics and structure
of plant
communities. Monographs in population biology.
Tilman,
D. 1989. Competition, nutrient reduction, and the competitive
neighborhood of a bunchgrass. Functional Ecology
3:215–219.
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
371:65–66.
Abstract
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.
References
|
1. |
Ehrlich, P. & Ehrlich, A. Extinction (Ballantine Books, New York, 1981). |
|
2. |
Wilson, E. O. Biodiversity (National Academy, Washington
DC, 1988). |
|
3. |
Simberloff, D. Zh. Obshch. Biol.
45, 767?778 (1984). |
|
4. |
Tilman, D. Ecology 75, 2?16 (1994). | ISI | |
|
5. |
Levins, R. & Culver, D. Proc. natn. Acad. Sci. U.S.A. 68,
1246?1248 (1971). |
|
6. |
Horn, H. S. & MacArthur, R. H. Ecology 53, 749?752 (1972). | ISI | |
|
7. |
Cohen, D. & Levin, S. A. Theo. Pop. Bio. 39,
63?99 (1991). |
|
8. |
Hastings, A. Theo. Pop. Bio. 18, 363?373 (1980). |
|
9. |
Hanski, |
|
10. |
Levin, S. A. & Paine, R. T. Proc. natn.
Acad. Sci. U.S.A. 71, 2744?2747 (1974). | ChemPort | |
|
11. |
Gaines, S. & Roughgarden, J. Proc.
natn. Acad. Sci. U.S.A.
82, 3707?3711 (1985). |
|
12. |
Harrison, S., Murphy, |
|
13. |
Hanski, |
|
14. |
Shorrocks, B. Biol. J. Linn. Soc. 43,
211?220 (1991). |
|
15. |
Sale, P. F. The Ecology of Fishes on Coral Reefs
(Academic, New York, 1991). |
|
16. |
Doherty, P. & Fowler, T. Science 263, 935?939 (1994). |
|
17. |
Werner, P. A. & Platt, W. J. Am. Nat. 110, 959?971 (1976). | Article | ISI | |
|
18. |
Shmida, A. & Ellner,
|
|
19. |
Grubb, P. J. in Community Ecology (eds
Diamond, J. & Case, T.) 207?226 (Harper &
Row, New York, 1986). |
|
20. |
Nee, S. & May, R. M. J. Anim.
Ecol. 61, 37?40 (1992). | ISI | |
|
21. |
May, R. M. in Ecology and Evolution of Communities (eds Cody, M. L. & Diamond, J. M.) 81?120 (Harvard Univ. Press, Cambridge, MA, 1975). |
|
22. |
Diamond, J. M. Proc. natn. Acad. Sci. U.S.A. 69, 3199?3203
(1972). |
|
23. |
Terborgh, J. BioScience
24, 715?722 (1974). | ISI | |
|
24. |
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). |
|
25. |
Lovejoy, T. E. et al. in Extinctions (ed. Nitecki, M. H.) 295?325 (Univ.
of Chicago Press, Chicago, 1984). |
|
26. |
Bucher, E. H. Curr. Ornithol. 9, 1?36
(1992). |
|
27. |
Chapin, F. S. A. Rev. Ecol. System. 11, 233?260 (1980). | ChemPort | |
|
28. |
Pastor, J., Aber, J. D., McClaugherty, C. A. & Melillo,
J. M. Am. Mid. Nat. 108, 266?277 (1982). |
|
29. |
Tilman, D. & Downing, J. A. Nature
367, 363?365 (1994). | Article | ISI | |
|
30. |
Naeem, S., Thompson, L., Lawler, S., |
Tilman, D., and D. Wedin. 1991a. Plant
traits and resource
reduction
for five grasses growing on a nitrogen gradient.
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.
Abstract
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.
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References
|
1. |
Ehrlich, P. & Ehrlich, A. Extinction (Random House,
New York, 1981). |
|
2. |
Wilson, E. O. The Diversity of Life (Belknap, Cambridge,
Massachusetts, 1992). |
|
3. |
McNaughton, S. J. Am. Nat. 111, 515?525 (1977). | Article | ISI | |
|
4. |
Ewel, J. J., Mazzarino,
M. J. & Berish, C. W. Ecol. Applic. 1, 289?302
(1991). |
|
5. |
Vitousek, P. M. & Hooper, |
|
6. |
McNaughton, S. J. in Biodiversity and Ecosystem Function
(eds Schulze, E. D. & Mooney, H. A.) 361?384 (Springer, Berlin, 1993). |
|
7. |
Tilman, D. & Downing, J. A. Nature
367, 363?365 (1994). | Article | ISI | |
|
8. |
Naeem, S., Thompson, L. J., Lawler, S. P.,
Lawton, J. H. & Woodfin, R. M. Nature 368,
734?737 (1994). | Article | ISI | |
|
9. |
Elton, C. S. The Ecology of Invasion by Animals and Plants
(Chapman and Hall, London, 1958). |
|
10. |
May, R. M. Stability and Complexity in Model Ecosystems
(Princeton Univ. Press, 1973). |
|
11. |
Goodman, D. Q. Rev. Biol. 50, 237?266 (1975). | Article | ISI | |
|
12. |
King, A. W. & Pimm, S. L. Am.
Nat. 122, 229?239 (1983). | Article | |
|
13. |
|
|
14. |
Tilman, D. Ecology (in the press). |
|
15. |
Darwin, C. The Origin of Species by Means of Natural
Selection (Murray, London, 1859). |
|
16. |
Ehrlich, P. R. & Mooney, H. A. BioScience
33, 248?254 (1983). |
|
17. |
Swift, M. J. & Anderson, J. M. in Biodiversity and
Ecosystem Function (eds Schulze, E. D. &
Mooney, H. A.) 15?41 (Springer, Berlin, 1993). |
|
18. |
Naeem, S., Thompson, L. J., Lawler, S. P.,
Lawton, J. H. & Woodfin, R. M. Phil. Trans.
R. Soc. Lond. B347, 249?262 (1995). | ISI | |
|
19. |
|
|
20. |
Givnish, T. J. Nature 371, 113?114 (1994). | Article | PubMed | ISI | |
|
21. |
Tilman, D., Downing, J. & Wedin, D. Nature 371, 114
(1994). | Article | |
|
22. |
Andre, M., Brechignac, P. & Thibault, P. Nature 371, 565
(1994). | Article | ChemPort | |
|
23. |
Naeem, S., Thompson, L. J., Lawler, S. P.,
Lawton, J. H. & Woodfin, R. M. Nature 371,
565 (1994). | Article | |
|
24. |
Tilman, D. Oikos
58, 3?15 (1990). |
|
25. |
McKane, R. B., Grigal,
D. F. & Russelle, M. P. Ecology 71,
1126?1132 (1990). | ISI | |
|
26. |
Chabot, B. F. & Mooney, H. A. (eds)
Physiological Ecology of North American Plant Communities (Chapman and
Hall, New York, 1985). |
|
27. |
Givnish, T. J. (ed.) On the Economy of
Plant Form and Function (Cambridge Univ. Press, 1986). |
|
28. |
|
|
29. |
Tilman, D. & Pacala,
S. in Species Diversity in Ecological Communities (eds
Ricklefs, R. & Schluter,
D.) 13?25 (Univ. of Chicago Press, 1993). |
|
30. |
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.
Abstract
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
Abstract
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
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
• 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.