F. H. Bormann

Nutrient loss accelerated by clear-cutting of a forest ecosystem.

The forest of a small watershed-ecosystem was cut in order to determine the effects of removal of vegetation on nutrient cycles. Relative to undisturbed ecosystems, the cut ecosystem exhibited accelerated loss of nutrients: nitrogen lost during the first year after cutting was equivalent to the amount annually turned over in an undisturbed system, and losses of cations were 3 to 20 times greater than from comparable undisturbed systems. Possible causes of the pattern of nutrient loss from the cut ecosystem are discussed.

Phosphorus Cycling in a Northern Hardwood Forest: Biological and Chemical Control

Phosphorus is tightly conserved within the northern hardwood forest ecosystems at Hubbard Brook, New Hampshire. Detailed analyses of the soil system indicate that biological and geochemical processes, stratified within the profile, regulate phosphorus retention.

Nitrification: Importance to Nutrient Losses from a Cutover Forested Ecosystem

The nitrate concentration (weighted average) in stream water from an experimentally deforested watershed increased from 0.9 milligram per liter before removal of the vegetation to 53 milligrams per liter 2 years later. This nitrate mobilization, presumably due to increased microbial nitrification, was equivalent to all of the other net cationic increases and anionic decreases observed in tae drainage water.

Nitrogen budget for an aggrading northern hardwood forest ecosystem

Long-term analyses of the structure and function of a northern hardwood ecosystem have resulted in measurement of the salient features of the nitrogen cycle. These data allow an evaluation of the importance of the various components and provide a framework for more efficient forest management.

Natural root grafts

Introduction 255 Formation of grafts .... . . . . . . . . . . . . . . . . . . . . . . 256 Types of grafts 258 Self-grafting 258 Intraspecific grafting 258 Interspecific grafting 260 Living stumps .. ........ 260 Prevalence of root-grafting 263 Implications 264 Ecology 264 Stand development 264 Response to thinning. 266 Forest Management 268 Pathology .... . . . . . . . . . . . . . . . . . . . . .. 268 Resistance to windthrow 270 Girdling 270 Silvicides 270 Nest plantings 273 Summary ... 274

LONG-TERM TRENDS IN PRECIPITATION CHEMISTRY AT HUBBARD BROOK, NEW HAMPSHIRE

Abstract A continuous, 19-year record (1963–1982) of weekly, bulk precipitation chemistry at the Hubbard Brook Experimental Forest in West Thornton, New Hampshire shows no statistically significant trend in annual volume-weighted concentrations of hydrogen ion and nitrate, but a 34% decrease in sulfate, a 34% decrease in ammonium, a 63% decrease in chloride, a 79% decrease in magnesium and an 86% decrease in calcium during the period. Nitrate concentrations increased from 1964 to 1971 and H-ion concentrations decreased after 1970. Frequency distributions of the concentrations of the chemical components of precipitation are skewed. The range of H-ion concentrations in weekly samples has narrowed, and the frequency distribution has shifted toward higher concentrations (lower pH) during the last 19 years. Highest concentrations generally occur with lowest amounts of precipitation for most ions, but low concentrations can occur with either low or high amounts of precipitation. Time trends in deposition generally parallel trends in concentration over the 19-year period. Chemical deposition generally increases with increasing amount of precipitation in weekly samples.

Air Pollution and Forests: An Ecosystem Perspective

tree species and the processes by which they may be damaged by specific air pollutants (Lindhurst 1984, Tamm 1984, Ulrich and Pankrath 1983). This paper looks at the problem from the view of the ecosystem as a whole. Questions that arise from this analysis are: Is it possible to quantify ecosystem damage resulting from specific air pollutants? Can we quantitatively relate forest damage to emissions of air pollutants? Can we wait for quantification of the relationship between emissions and damage to write air quality standards? Finally, what role can ecological scientists play? What is their responsibility in establishing air quality standards?

Changes in the Growth Pattern of White Pine Trees Undergoing Suppression

The phenotypic responses of suppressed trees were studied in a 60—year—old white pine stand. The first evidence of suppression is a tree—wide decrease in the production of secondary xylem. Height growth is relatively insensitive. During the latter 30 years of life suppressed trees made 50.7% of their total height growth but only 19.1% of their total diameter growth. Eventually the cambium fails to cut off xylem at the base of the tree. With time, the sheath of new—formed xylem retreats from the based giving rise to an increasingly large zone of missing rings. Girdling experiments indicate that diminished supplies of food and growth regulators move through the zone of missing rings to support primary root growth. Apparently the phloem remains functional in the zone of missing rings. Either the phloem can function for periods greater than 1 or 2 years, or the cambium cuts off phloem alone in the missing ring zone. In the normal cambial cycle, phloem alone is produced during the last part of the growing seas...

A METEOROLOGICAL ANALYSIS OF THE PRECIPITATION CHEMISTRY EVENT SAMPLES AT HUBBARD BROOK (N.H.)

Abstract On 100 occasions over a 3-y period ( June 1975 to July 1978 inclusive), precipitation collected at the Hubbard Brook Experimental Forest was analyzed for its chemical constituents. The present paper is a meteorological examination of the data, using back trajectories based on a quasi-geostrophic method. Some of the trajectories are complex and difficult to interpret. When these are excluded, the remaining 69 events show the influence of meteorology on wet deposition at Hubbard Brook. Highest values of H+, SO4 and NO3 are associated with winds from the SSE through SSW, and with looping trajectories over New England. In contrast, air that has come from the NNW-NE-ESE sector is relatively clean. These results are confirmed using a crossing-trajectory analysis. A method of trend analysis for SO4 concentrations is suggested, using crossing-trajectory statistics and a simple linear chemistry model. The sample period (3 y) is too short to provide a fair test of the method. Nevertheless, the results obtained are not unreasonable, namely a downward trend of 7% in SO4 concentrations, when the data are normalized for meteorological factors, as compared with a decrease of 5 % in regional emissions of SO2 over the same period.

Unlimited Growth: Growing, Growing, Gone?

During the past decade, ecologists like LaMont Cole, Rachel Carson, Paul Ehrlich, Garrett Hardin, George Woodwell, Eugene Odum, and others too numerous to mention have helped to create a new and extremely powerful force in our political lives. That force is public awareness of an environmental crisis-an awareness that senses a decline in the quality of life and a threat to the very basis of life. The intense days of the late 1960s are past, and a growing complacency has settled over the nation. The environmental issue has been largely captured by expert linear thinkers, engineers, economists, politicians, biologists, and even some ecologists who tell us that they know the problems and that the cure merely requires the application of more money and technology. Their efforts, marked by faith in the power of Adam Smiths invisible hand and by a reluctance to question assumptions underlying the modern industrial state, have shaped and continue to shape governmental policy vis-a-vis the environmental crisis, everywhere in the world. The multifactorial nature of our environmental problem has often been obscured by ecologists who have tended to cast the environmental crisis in terms of