Our Lirini^ Rcstmrccs — Terrestrial Ecosystems 



227 



severe damage was probably done by intensive 

 sheep grazing during the late ISOO's when the 

 entire region was negatively affected by open- 

 land sheep ranching. We cannot yet demonstrate 

 whether the grazing effects are continuing or if 

 the site is improving, although reinvasion of 

 palatable species is unlikely in the face of even 

 light grazing. Severe overgrazing is required to 

 eliminate abundant palatable species, but once 

 they are eliminated. e\en light grazing can pre- 

 vent their restoration. 



Implications 



Wise land management decisions are more 

 likely to be made if land managers understand a 

 site and are able to place the status quo into a 

 historical perspective. Because most of the 

 damage to these four sites occurred before the 

 20th century, land managers might not even be 

 aware of the tremendous changes that have 

 occurred were it not for these fossil records. 

 Since the ultimate goal for the management of 

 many areas is to mitigate settlement impacts 

 and return the land to its presettlement status, 

 detailed knowledge of the effects of settlement 

 is imperative. 



In all study areas, postsettlement rates of 

 change were at least 10 times higher than the 

 presettlement rates of change. Thus, the changes 

 now being observed in even remote natural 

 ecosystems are unlike former natural changes. 

 Some areas are continuing to change at rapid 

 rates, while other areas, which have not been 

 disturbed as recently, are stabilizing. The climat- 

 ic warming projected for the next 50 years may 

 exacerbate these ongoing changes, but will be 

 only one of many variables operating in the 



unplanned redesign of our natural ecosystems. 

 Land managers need to understand the nature 

 and severity of the effects of settlement to return 

 the land to its presettlement condition. 



References 



Betancuurt. J.L.. T.R. Van Devender. and PS. Martin, eds. 

 1990. Packrat middens: the last 40.0(10 years of biolic 

 change. The University of Arizona Press. Tucson. 467 pp. 



Cole. K.L. 1995. A survey of the fossil packrat middens and 

 reconstruction of the pregrazing vegetation of Capitol 

 Reef National Park. National Park Sei-vice Res. Rep. In 

 press. 



Cole. K.L.. D.R. Engstrom. R.P Futyma. and R. 

 Stottlemyer. 1990. Past atmospheric deposition of metals 

 in northern Indiana measured in a peat core from Cowles 

 Bog. Environmental Science and Technology 24:.'i4,^- 

 .549. 



Cole, K.L.. and G. Liu. 1994. Holocene paleoecology of an 

 estuary on Santa Rosa Island, California. Quaternary 

 Res. 41:.^26-3.VS 



Faegri. K., and J. Iversen. 1989. Textbook of pollen analy- 

 sis. Wiley and Sons, New York. 328 pp. 



Jacobson. G.L., Jr.. and E.G. Grimm. 1986. A numerical 

 analysis of Holocene forest and prairie vegetation in cen- 

 tral Minnesota. Ecology 67:958-966. 



Wilhelm. G.S. 1990. Special vegetation of the Indiana 

 Dunes National Lakeshore. Indiana Dunes National 

 Lakeshore Research Program. Rep. 90-02, Porter. IN. 



Twenty-eight thousand-year-old 

 packrat midden at Capitol Reef 

 National Park; orange notebook is 

 6 inches high. 



For further information: 



Kenneth L. Cole 



National Biological Service 



Cooperative Park Studies Unit 



University of Minnesota 



Department of Forest Resources 



115 Green Hall 



St. Paul, MN 55108 



Air pollution poses a threat to forest 

 ecosystems in several regions of North 

 America. Although there are isolated 

 impacts downwind from point sources such 

 as industrial operations, the major impacts 

 are from regional-scale exposure to ambient 

 ozone and acid precipitation. Acidic deposi- 

 tion (including sulfur and nitrogen deposi- 

 tion) is fairly high in the northeastern United 

 States and southeastern Canada, although 

 symptomatic injury and changes in forest 

 growth have not been clearly linked to a par- 

 ticular pollutant. Recent evidence, however, 

 indicates that long-term inputs of acid pre- 

 cipitation may be altering the chemical equi- 

 librium of some soils, which could result in 

 a nutritional imbalance in trees. 



Elevated levels of ozone have resulted in 

 stress in several forest ecosystems of North 

 America: ( 1 ) those adjacent to Mexico City 

 (extensive mortality and reduced growth): 



Air Pollution Effects on 



Forest Ecosystems in 



North America 



by 



David L. Peterson 



National Biological Service 



(2) those in mountains of the Los Angeles 

 Basin in California (mortality and growth 

 reductions); (3) those in the central and 

 southern Sierra Nevada (some reduced 

 growth and widespread symptomatic 

 injury); (4) those in the Rincon Mountains of 

 Arizona (some symptomatic injury); and (5) 

 those in the Great Smoky Mountains (some 

 symptomatic injury). 



Recent growth reductions and changes in 



forest health have been reported for several 

 locations in North America although the role 

 of air pollution in these "declines" must be 

 evaluated in the context of a stress complex 

 that includes climate, stand dynamics, and 

 site factors. Although some lichens are 

 known to be sensitive to air pollution, there 

 is relatively little information on the effects 

 of air pollutants on forest species other than 

 trees. Only if monitoring programs are 

 implemented soon will it be possible to 

 detect how long-term pollutant deposition 

 affects forest health and productivity. 



For furtlier information: 



Da\ id L. Peterson 



National Biological Service 



Cooperative Park Studies Unit 



University of Washington 



AR-10 



Seattle. WA 98195 



