Scholars@Duke
Norman L. Christensen

Norman L. Christensen

Professor Emeritus in the Division of Environmental Natural Sciences
Environmental Natural Science
normc@duke.edu
Box 90329, Durham, NC 27708-0329
A316 LSRC, Durham, NC 27708

Scholarly Works - Journal articles

Ecosystem-based management for military training, biodiversity, carbon storage and climate resiliency on a complex coastal land/water-scape.

Journal article Journal of environmental management · February 2021 The Defense Coastal/Estuarine Research Program (DCERP) was a 10-year multi-investigator project funded by the Department of Defense to improve understanding of ecosystem processes and their interactions with natural and anthropogenic stressors at the Marin ... Full text Cite

White-sand Ecosystems in Amazonia

Journal article Biotropica · January 1, 2016 Vegetation on sandy soils, ranging from open grasslands and shrublands to closed-canopy, thin-trunked forests, can be found in patches throughout the Amazon. Despite variation in names, appearance, ecological correlates, and suggested origins, these 'white ... Full text Cite

Patterns of vegetation composition and diversity in pine-dominated ecosystems of the Outer Coastal Plain of North Carolina: Implications for ecosystem restoration

Journal article Forest Ecology and Management · November 15, 2015 Terrestrial ecosystems of the Atlantic coastal plain have experienced considerable change over the past two centuries, largely due to agricultural activities and fire suppression and exclusion. Many areas that were once dominated by open longleaf pine (Pin ... Full text Cite

Clarifying the role of fire in the deciduous forests of eastern North America: reply to Matlack.

Journal article Conservation biology : the journal of the Society for Conservation Biology · June 2015 Full text Cite

An historical perspective on forest succession and its relevance to ecosystem restoration and conservation practice in North America

Journal article Forest Ecology and Management · October 15, 2014 Eugene Odum's 1969 paper, The Strategy of Ecosystem Development, marks a watershed moment in approaches to the study of succession, ecosystem change caused by discrete disturbances. He argued that succession is unique from other kinds of change with regard ... Full text Cite

Three-dimensional characterization of pine forest type and red-cockaded woodpecker habitat by small-footprint, discrete-return lidar

Journal article Forest Ecology and Management. · October 2012 Accurate measurement of forest canopy structure is critical for understanding forest-wildlife habitat relationships. Although most theory and application have been based on in situ measurements, imaging technologies such as Light Detection and Ranging (lid ... Full text Cite

The road to sustainable development and conservation

Journal article Frontiers in Ecology and the Environment · March 1, 2011 Ecologists visit some of the most interesting places on Earth, and many have fascinating tales to tell. These encounters can highlight important scientific concepts or lead to a better understanding of organisms or systems. In the new series, Trails and Tr ... Full text Cite

Sex matters: Modeling male and female habitat differences for jaguar conservation

Journal article Biological Conservation · September 1, 2010 Competition for mates, cub rearing, and other behaviors differ between males and females in large carnivores. Although these differences can be reflected in patterns of habitat use, gender has rarely been incorporated into habitat models. We evaluated diff ... Full text Cite

The shrinking ark: patterns of large mammal extinctions in India.

Journal article Proceedings. Biological sciences · July 2010 Mammal extinctions are widespread globally, with South Asian species being most threatened. We examine local extinctions of 25 mammals in India. We use historical records to obtain a set of locations at which each species was known to have been present at ... Full text Cite

Reconstructing Holocene fire history in a southern Appalachian forest using soil charcoal.

Journal article Ecology · March 2010 Lacking long-term dendrochronological and lake sediment data, little is known regarding the history of fire in southern Appalachian forests through the Holocene. Here we used 82 radiocarbon ages for soil charcoal collected from local depositional sites alo ... Full text Cite

Patterns and determinants of mammal species occurrence in India

Journal article Journal of Applied Ecology · December 1, 2009 Many Indian mammals face range contraction and extinction, but assessments of their population status are hindered by the lack of reliable distribution data and range maps. 2. We estimated the current geographical ranges of 20 species of large mammals by a ... Full text Cite

Determinants of coastal treeline and the role of abiotic and biotic interactions

Journal article Plant Ecology · May 1, 2009 Recent die-off of coastal forests has been attributed primarily to the effects of sea level rise by correlation with tide-gage records. Due to the temporal and spatial scales involved, direct monitoring of sea level rise impacts is challenging and its attr ... Full text Cite

Evaluating the Conservation Status of Illinois Snakes

Journal article Journal of Herpetology · 2009 Cite

Ecological Foundations of Fire Management

Journal article U.S.D.A. Forest Service General Technical Report · 2009 Cite

Future Forests, Future Fires

Journal article Yellowstone Science · 2009 Cite

Reserves protect against deforestation fires in the Amazon.

Journal article PloS one · January 2009 BackgroundReserves are the principal means to conserve forests and biodiversity, but the question of whether reserves work is still debated. In the Amazon, fires are closely linked to deforestation, and thus can be used as a proxy for reserve effe ... Full text Cite

Sustaining America's forest legacy.

Journal article Conservation biology : the journal of the Society for Conservation Biology · December 2008 Full text Cite

Embracing diversity, embracing change

Journal article Frontiers in Ecology and the Environment · October 1, 2008 Full text Cite

Examining conservation attitudes, perspectives, and challenges in India

Journal article Biological Conservation. · September 2008 Biodiversity conservation issues are often contentious and complex. Polarized debates on the effectiveness of protected areas and role of people inside them, charismatic species as conservation foci, and on specific policy initiatives are common among Indi ... Full text Open Access Cite

Examining conservation attitudes, perspectives, and

Journal article Biological Conservation · August 2008 Biodiversity conservation issues are often contentious and complex. Polarized debates on the effectiveness of protected areas and role of people inside them, charismatic species as conservation foci, and on specific policy initiatives are common among Indi ... Cite

Tolerance of Pinus taeda and Pinus serotina to low salinity and flooding: Implications for equilibrium vegetation dynamics

Journal article Journal of Vegetation Science · February 1, 2008 Questions: 1. Do pine seedlings in estuarine environments display discrete or continuous ranges of physiological tolerance to flooding and salinity? 2. What is the tolerance of Pinus taeda and P. serotina to low salinity and varying hydrologic conditions? ... Full text Cite

Faculty response

Journal article Frontiers in Ecology and the Environment · October 1, 2007 Cite

Making the most of your teaching assistantship experience - Response

Journal article FRONTIERS IN ECOLOGY AND THE ENVIRONMENT · October 1, 2007 Link to item Cite

Environmental leadership equals essential leadership redefining who leads and how

Journal article Environmental Leadership Equals Essential Leadership Redefining Who Leads and how · December 1, 2006 The important new approach to leadership that John Gordon and Joyce Berry explain in this book is built upon the experiences of environmental and natural resource organizations as they contend with complex, long-term problems. But the lessons learned apply ... Cite

Carbon emissions from a temperate peat fire and its relevance to interannual variability of trace atmospheric greenhouse gases

Journal article Journal of Geophysical Research Atmospheres · March 27, 2006 The contribution of wildfire in peatlands outside of boreal and tropical regions to interannual variability of global carbon emissions has been relatively little studied. There are 0.19 to 0.88 million km2 of localized peat deposits in the tempe ... Full text Cite

Epilogue: After the fires. what have we learned

Journal article · December 1, 2004 Cite

Uses and limitations of historical variability concepts in managing ecosystems

Journal article Ecological Applications · January 1, 1999 Full text Cite

Evaluation of approaches to estimating aboveground biomass in southern pine forests using SIR-C data

Journal article Remote Sensing of Environment · February 1, 1997 A study was performed to evaluate various techniques for estimating aboveground, woody plant biomass in pine stands found in the southeastern United States, using C- and L- band multiple polarization radar imagery collected by the Shuttle Imaging Radar-C ( ... Full text Cite

The scientific basis for ecosystem management

Journal article Ecological Applications · 1996 Cite

The report of the ecological society of america committee on the scientific basis for ecosystem management

Journal article Ecological Applications · January 1, 1996 Ecosystem management is management driven by explicit goals, executed by policies, protocols, and practices, and made adaptable by monitoring and research based on our best understanding of the ecological interactions and processes necessary to sustain eco ... Full text Cite

Correlating Radar Backscatter with Components of Biomass in Loblolly Pine Forests

Journal article IEEE Transactions on Geoscience and Remote Sensing · January 1, 1995 A multifrequency, multipolarization airborne SAR data set was utilized to examine the relationship between radar backscatter and the aboveground biomass in loblolly pine forests. This data set was also used to examine the potential of SAR to estimate above ... Full text Cite

The effects of changes in forest biomass on radar backscatter from tree canopies

Journal article International Journal of Remote Sensing · January 1, 1995 We validated a canopy backscatter model for loblolly pine forest stands at the Duke Forest, North Carolina, by comparing the observed and modelled SAR backscatter from the stands. Given the SAR backscatter data calibration uncertainty, the model made good ... Full text Cite

Fire, global warming, and the carbon balance of boreal forests

Journal article Ecological Applications · January 1, 1995 Full text Cite

Sensitivity of ERS-1 and JERS-1 radar data to biomass and stand structure in Alaskan boreal forest

Journal article Remote Sensing of Environment · January 1, 1995 Thirty-two boreal forest sites were identified and sampled in the central region of Alaska to evaluate the sensitivity of the C-band ERS-1 and the L-band JERS-1 radar platforms to site biophysical properties. A growing body of research has shown a signific ... Full text Cite

Estimating release of carbon from 1990 and 1991 forest fires in Alaska

Journal article Journal of Geophysical Research · January 1, 1995 The location and areal extent of fires in this region for 1990 and 1991 were based on both field observations and analysis of satellite (advanced very high resolution radiometer (AVHRR)) data sets. Estimates of average carbon release for the two study year ... Full text Cite

Estimating release of carbon from forest fires in Alaska using satellite remote sensing data

Journal article International Geoscience and Remote Sensing Symposium IGARSS · December 1, 1994 A ground-based model of biomass levels and carbon-release during fires in Alaskan boreal forests is developed to estimate the amounts of carbon released during fire in the region for 1990 and 1991. The models gave significantly higher estimates of carbon r ... Cite

Relating soil water measurements at fire disturbed sites in Alaska to ERS-1 SAR image signature

Journal article International Geoscience and Remote Sensing Symposium IGARSS · December 1, 1994 Studies of ERS-1 imagery have shown that fire scars in the Alaskan boreal forest are significantly (3-6 dB) brighter than surrounding unburned forest. Additionally, studies have shown that soil moisture increases in black spruce (Picea mariana [Mill.] B.S. ... Cite

The effects of changes in loblolly pine biomass and soil moisture on ERS-1 SAR backscatter

Journal article Remote Sensing of Environment · January 1, 1994 For young (< 15 years old) loblolly pine stands at Duke Forest (North Carolina, USA), when the ground was wet, the observed ERS-1 SAR backscatter from short-grass fields of 0.05 kg/m2 biomass was ≥ the backscatter from the stands, and there was ... Full text Cite

Modeling of Geometric Properties of Loblolly Pine Tree and Stand Characteristics for Use in Radar Backscatter Studies

Journal article IEEE Transactions on Geoscience and Remote Sensing · January 1, 1994 An approach is presented to physically describe the tree and canopy components within loblolly pine forests in studies of microwave backscattering from forested canopies. The approach is based on a set of algorithms which describe the biomass characteristi ... Full text Cite

Observations on the sensitivity of ers-1 sar image intensity to changes in aboveground biomass in young loblolly pine forests

Journal article International Journal of Remote Sensing · January 1, 1994 A study was conducted to evaluate the sensitivity of the microwave return recorded by the ERS-1 C-band synthetic aperture radar (SAR) to changes in above-ground woody biomass in young loblolly pine forests (dry weight biomass <6kgm-2). Radar bac ... Full text Cite

Monitoring of wildfires in Boreal Forests using large area AVHRR NDVI composite image data

Journal article Remote Sensing of Environment · January 1, 1993 Normalized difference vegetation index (NDVI) composite image data, produced from AVHRR data collected in 1990, were evaluated for locating and mapping the areal extent of wildfires in the boreal forests of Alaska during that year. A technique was develope ... Full text Cite

Dependence of Radar Backscatter on Coniferous Forest Biomass

Journal article IEEE Transactions on Geoscience and Remote Sensing · January 1, 1992 Two independent experimental efforts have examined the dependence of radar backscatter on aboveground biomass of mono specie conifer forests using polarimetric airborne SAR data at P-, L-and C-bands. Plantations of maritime pines near Landes, France range ... Full text Cite

Initial observations on using SAR to monitor wildfire scars in boreal forests

Journal article International Journal of Remote Sensing · January 1, 1992 Initial observations on the effects of wildfires in black spruce forests on radar backscatter are presented. Airborne and spaceborne SAR imagery are utilized to illustrate two distinct fire signatures. A theory is presented lo explain these differences. © ... Full text Cite

Spatial and temporal variation of the microwave dielectric properties of loblolly pine trunks

Journal article Digest International Geoscience and Remote Sensing Symposium IGARSS · December 1, 1991 The dielectric properties of loblolly pine trunks are found to be seasonally and diurnally variant. In addition, the dielectric constant is found to vary both with depth into the trunk for different tissue regions (i.e., phloem, cambial zone, and xylem) an ... Cite

Ecosystem monitoring with the Eos SAR

Journal article Digest International Geoscience and Remote Sensing Symposium IGARSS · December 1, 1990 The expected requirements for the Earth Observing System synthetic aperture radar (Eos SAR) system as defined by the Eos interdisciplinary investigations for terrestrial ecosystem analysis are presented. The potential of the SAR meeting these requirements ... Cite

SAR-derived estimates of aboveground biomass in forested landscapes

Journal article Digest International Geoscience and Remote Sensing Symposium IGARSS · December 1, 1990 The preliminary results of an experiment designed to study the relationship between total above-ground biomass in southern US pine forests and the radar signature observed on SAR imagery are presented. Model results which illustrate the relationship betwee ... Cite

Monitoring forest freeze-thaw: The March '88 Alaskan aircraft SAR experiment

Journal article Digest International Geoscience and Remote Sensing Symposium IGARSS · December 1, 1990 In preparation for the first European Earth Remote Sensing (ERS-1) mission, a series of multitemporal, multifrequency, multipolarization aircraft synthetic aperture radar (SAR) data sets were acquired over the Bonanza Creek Experimental Forest near Fairban ... Cite

The effect of changing environmental conditions on microwave signatures of forest ecosystems: Preliminary results of the March 1988 Alaskan aircraft SAR experiment

Journal article International Journal of Remote Sensing · January 1, 1990 In preparation for the first European Space Agency (ESA) Remote Sensing (ERS-1) mission, a series of multitemporal, multifrequency, multipolariz-ation aircraft synthetic aperture radar (SAR) data sets were acquired over the Bonanza Creek Experimental Fores ... Full text Cite

Connecting forest ecosystem and microwave backscatter models

Journal article International Journal of Remote Sensing · January 1, 1990 A procedure is outlined to connect data obtained from active microwave remote sensing systems with forest ecosystem models. The hierarchy of forest ecosystem models is discussed, and the levels at which microwave remote sensing data can be used as inputs a ... Full text Cite

Interpreting the Yellowstone Fires of 1988

Journal article BioScience · November 1989 Full text Cite

Population dynamics in loblolly pine stands: changes in skewness and size inequality

Journal article Ecology · January 1, 1989 Determined the changes in size inequality and asymmetry that occurred over 50 yr period in 16 even-aged, naturally seeded populations of Pinus taeda. Initial densities ranged from 618-28 861 stems/ha. In young stands size inequality was greater at higher p ... Full text Cite

Wilderness and natural disturbance

Journal article Forum for Applied Research Public Policy · January 1, 1989 Research during the past two decades has dramatically changed man's understanding of wilderness ecosystems and, consequently, the way in which such systems should be managed. Rather than simple, highly stable, and homogeneous, such systems are in fact comp ... Cite

Malaysian dipterocarp forest: tree seedling and sapling species composition and small-scale disturbance patterns

Journal article National Geographic Research · January 1, 1989 The authors tallied all tree and shrub seedlings and saplings ≤5 cm dbh in 39 hexagonal, 20-m2 plots in coastal hill dipterocarp forest of Penang. Ten plots were located in a closed-canopy forest; the rest were located in 21 natural tree-fall ga ... Cite

Vegetation variation among mesic successional forest stands in northern lower Michigan

Journal article Canadian Journal of Botany · January 1, 1988 Successional aspen Populus tremuloides and P. grandidentata stands of different ages (1-90 yr) were examined on a variety of sites. Sandy dry-mesic soils support forests of Acer rubrum, Quercus rubra, Pinus resinosa and P. strobus. On lowland sandy soils w ... Full text Cite

Vegetation of the southeastern Coastal Plain

Journal article North American Terrestrial Vegetation · January 1, 1988 Plant communities vary from grassland and savanna through shrubland to needle- and broadleaved sclerophyllous woodland and rich mesophytic forest, differences which can occur within a few hundred metres and an elevational shift of only 10m. Dramatic gradie ... Cite

Competition and Tree Death

Journal article BioScience · September 1987 Full text Cite

USE OF OLD-FIELD STANDS OF LOBLOLLY PINE IN STUDIES OF THE POTENTIAL USE OF ACTIVE MICROWAVE REMOTE SENSORS FOR MONITORING FOREST ECOSYSTEMS.

Journal article Digest International Geoscience and Remote Sensing Symposium IGARSS · January 1, 1987 The potential utility of active microwave remote sensors, such as scatterometers and imaging radars, for forest ecology studies is discussed. Secondary-growth loblolly pine forests are used to explore how such studies may be useful for determining the ulti ... Cite

Vegetational Variation Among Old Fields in Piedmont North Carolina

Journal article Bulletin of the Torrey Botanical Club · October 1986 Full text Cite

Intraseasonal variation in seed production among flowers and plants of Thalictrum thalictroides ( Ranunculaceae).

Journal article American Journal of Botany · January 1, 1986 Mean seed number and percent seed set were lower in flowers open late in the season than in those open earlier. The lower percent seed set occurs primarily in flowers that are positioned laterally on the inflorescence and which open later than center flowe ... Full text Cite

Herb-layer response to burning in pine flatwoods of the lower coastal plain of South Carolina.

Journal article Bulletin Torrey Botanical Club · January 1, 1986 Cover and species richness were significantly higher in winter-burned areas compared to either unburned or summer-burned areas. Causes of these differences appeared to be related to seasonal differences in post-burn soil nutrient status. -from Authors ... Full text Cite

Soil mineral nitrogen transformations during succession in the piedmont of north carolina

Journal article Soil Biology and Biochemistry · January 1, 1985 Variations in patterns of ammonification and nitrification among and within four sites at each of three stages of old field succession (old field to pine to deciduous hardwoods) were evaluated by laboratory incubations in May and August 1979. Each experime ... Full text Cite

Shrubland fire regimes and their evolutionary consequences.

Journal article Ecology of Natural Disturbance and Patch Dynamics · January 1, 1985 In most shrublands, fires play a significant role in the maintenance of community structure and function, and have been important selective forces in the evolution of plant form and life history. Fires are patchy phenomena, and contribute greatly to tempor ... Cite

THIS LAND, THIS SOUTH - AN ENVIRONMENTAL HISTORY - COWDREY,AE

Journal article SOUTH ATLANTIC QUARTERLY · 1985 Link to item Cite

Basic and Applied Fire Ecology

Journal article Ecology · June 1984 Full text Cite

Convergence during secondary forest succession.

Journal article Journal of Ecology · January 1, 1984 Successional convergence in community composition was examined in terms of 3 questions: 1) for a given site is there a continuous shift in composition toward that characteristic of climax? 2) does variation in community composition along an environmental g ... Full text Cite

FIRE REGIMES IN SOUTHEASTERN ECOSYSTEMS.

Journal article undefined · December 1, 1981 Cite

Seasonal patterns of growth, tissue acid fluctuations, and 14CO2 uptake in the crassulacean acid metabolism epiphyte Tjllandsia usneoides L. (Spanish moss).

Journal article Oecologia · July 1981 Seasonal patterns of growth, 14CO2 uptake, and fluctuations in tissue titratable acidity were studied over the course of a year at a study site in the coastal plain of North Carolina.Elongation rates of Spanish moss strands were maxim ... Full text Cite

Succession: A population process

Journal article Vegetatio · December 1, 1980 Recent critical reviews suggest the need for a reductionistic approach to the study of secondary plant succession. We propose viewing succession as the result of the underlying plant population dynamics. This approach is being developed using nearly 50 yea ... Full text Cite

NITRIFICATION AND SUCCESSION IN THE PIEDMONT OF NORTH-CAROLINA

Journal article FOREST SCIENCE · January 1, 1979 Link to item Cite

Fire and soil-plant nutrient relations in a pine-wiregrass savanna on the coastal plain of North Carolina.

Journal article Oecologia · January 1977 Changes in soil and plant nutrient conditions were evaluated following various burn and clip treatments in a longleaf pine-wiregrass savanna in Bladen Co., N.C., USA. Ground fires were found to add substantial quantities of N, P, K, Ca, and Mg to the soil, ... Full text Cite

ROLE OF CARNIVORY IN SARRACENIA-FLAVA L WITH REGARD TO SPECIFIC NUTRIENT DEFICIENCIES

Journal article JOURNAL OF THE ELISHA MITCHELL SCIENTIFIC SOCIETY · January 1, 1976 Link to item Cite

Fire and the nitrogen cycle in California chaparral

Journal article Science · January 1, 1973 Analysis of soils from burned and unburned chaparral indicates that high nitrate concentrations following fire are due to the addition of ammonium and organic nitrogen in the ash. Inhibition of mineralization in unburned chaparral results in low nitrate co ... Full text Cite