Spatial and temporal variation in the prevalence of growth decline in red spruce populations of the northeastern United States: Discussion

1993 ◽  
Vol 23 (7) ◽  
pp. 1492-1493
Author(s):  
Gregory A. Reams ◽  
Paul C. Van Deusen ◽  
Edward R. Cook
Keyword(s):  
United States ◽  
Temporal Variation ◽  
Red Spruce ◽  
Spatial And Temporal Variation ◽  
Northeastern United States ◽  
Growth Decline

not available

Spatial and temporal variation in the prevalence of growth decline in red spruce populations of the northeastern United States

1992 ◽  
Vol 22 (9) ◽  
pp. 1351-1363 ◽  
Author(s):  
David C. LeBlanc
Keyword(s):  
United States ◽  
Tree Size ◽  
Red Spruce ◽  
Tree Age ◽  
Spatial And Temporal Variation ◽  
Northeastern United States ◽  
Data Bases ◽  
Growth Decline ◽  
Individual Trees ◽  
Historical Levels

An analysis of the prevalence of individual-tree growth decline, based on reconstructed annual stemwood volume increment (AVI), was implemented on three data bases that have been used in past dendrochronological analyses of red spruce (Picearubens Sarg.) decline in the northeastern United States. This analysis focused on the proportion of individual trees that exhibited a decrease in periodic mean AVI, a decrease in the linear trend of AVI, and (or) a negative AVI trend during the most recent 20-year period. Various subpopulations within the data bases were identified by site location, elevation, and aspect, and tree size, age, and competitive status, and the proportion of individual trees exhibiting growth decline was compared among these subpopulations. Also, the prevalence of growth decline after 1960 was compared with historical levels of growth decline. Differences in prevalence of growth decline were found among the three data bases and among locations within data bases. The proportion of red spruce that exhibited growth decline after 1960 exceeded historical levels of decline for populations in New York, Vermont, and New Hampshire, but not in the northern Maine population. Weak positive associations were found between prevalence of growth decline and tree size (DBH) and elevation. No consistent relationship was found between growth decline and tree age, competitive status, or stand density. Contrary to a previous report, growth decline was not more common among trees that exhibited evidence of competitive release in the 1940s than among unreleased trees.

Stand dynamics and red spruce decline

1990 ◽  
Vol 20 (6) ◽  
pp. 743-749 ◽  
Author(s):  
Paul C. Van Deusen
Keyword(s):  
United States ◽  
Red Spruce ◽  
Model Fit ◽  
Stand Dynamics ◽  
Data Sets ◽  
Northeastern United States ◽  
Improve Model ◽  
Growth Increase ◽  
Tree Ring Data ◽  
Growth Decline

The red spruce (Picearubens Sarg.) growth decline in the northeastern United States does not appear to be ubiquitous. Some selected tree-ring data sets are compared graphically and with two models that tend to support the notion that differences exist between stands as to the presence and degree of decline. It appears that the degree of post-1960 decline is related to the proportion of trees showing a pre-1950 growth increase, and stratifying the data into as few as two classes can improve model fit substantially. The models used in the comparisons are of interest in themselves, because they are capable of exhibiting the mathematical phenomenon of chaos.

Red spruce decline on Whiteface Mountain, New York. II. Relationships between apical and radial growth decline

1990 ◽  
Vol 20 (9) ◽  
pp. 1415-1421 ◽  
Author(s):  
David C. LeBlanc ◽  
Dudley J. Raynal
Keyword(s):  
New York ◽  
Radial Growth ◽  
Red Spruce ◽  
Northeastern United States ◽  
Spruce Decline ◽  
Growth Decline ◽  
Whiteface Mountain ◽  
The 1960S ◽  
Crown Dieback ◽  
The Relationship

Understanding the relationship between apical and radial growth decline can contribute toward the evaluation of hypotheses regarding causal mechanisms of red spruce decline. The etiology of red spruce decline in montane spruce-fir forests of the northeastern United States includes loss of foliage at branch apices, crown dieback, and unreversed radial growth decline since the 1960s. Demographic analyses of crown damage and radial growth decline for red spruce on Whiteface Mountain, New York, indicate that large, canopy-emergent trees with exposed crowns exhibit greater decline than codominant trees within an intact canopy. In this paper, radial growth decline is shown to have been coincident with decreased apical growth and increased incidence of injury to terminal leaders. Incidence of leader mortality is greatest for canopy-emergent red spruce or trees with exposed crowns, similar to patterns described for radial growth. This relationship suggests that the post-1960 decline of red spruce on Whiteface Mountain is caused, at least in part, by stresses that act directly on the crown.

Vitality and chemistry of roots of red spruce in forest floors of stands with a gradient of soil Al/Ca ratios in the northeastern United States

2003 ◽  
Vol 33 (4) ◽  
pp. 635-652 ◽  
Author(s):  
Philip M Wargo ◽  
Kristiina Vogt ◽  
Daniel Vogt ◽  
Quintaniay Holifield ◽  
Joel Tilley ◽  
...  
Keyword(s):  
United States ◽  
Soluble Sugars ◽  
Red Spruce ◽  
Northeastern United States ◽  
Root Tips ◽  
Exchangeable Al ◽  
Crown Health ◽  
Living Root ◽  
C And N ◽  
Forest Floors

Number of living root tips per branch, percent dead roots, percent mycorrhizae and mycorrhizal morphotype, response of woody roots to wounding and colonization by fungi, and concentrations of starch, soluble sugars, phenols, percent C and N and C/N ratio, and Al, Ca, Fe, K, Mg, Mn, and P were measured for 2 consecutive years in roots of red spruce (Picea rubens Sarg.) in stands in the northeastern United States (nine in 1993 and two additional in 1994) dominated by red spruce and with a gradient of forest floor exchangeable Al/Ca ratios. Root vitality was measured for nonwoody and coarse woody roots; chemical variables were measured for nonwoody (<1 mm), fine woody (1 to <2 mm), and coarse woody (2 to <5 mm) roots. There were significant differences among sites for all variables, particularly in 1993, although few were related to the Al/Ca ratio gradient. Percent mycorrhizae decreased, while some morphotypes increased or decreased as the Al/Ca ratio increased. In nonwoody roots, N increased as the Al/Ca ratio increased. Most sampled trees appeared to be in good or fair health, suggesting that an adverse response of these root variables to high Al concentrations may be apparent only after a significant change in crown health.

scholarly journals Spatial and Temporal Variation in PM 2.5 Chemical Composition in the United States for Health Effects Studies

2007 ◽  
Vol 115 (7) ◽  
pp. 989-995 ◽  
Author(s):  
Michelle L. Bell ◽  
Francesca Dominici ◽  
Keita Ebisu ◽  
Scott L. Zeger ◽  
Jonathan M. Samet
Keyword(s):  
United States ◽  
Chemical Composition ◽  
Temporal Variation ◽  
Health Effects ◽  
The United States ◽  
Spatial And Temporal Variation ◽  
Pm 2.5

scholarly journals The Effect of Stay-at-Home Orders on COVID-19 Infections in the United States

2020 ◽  
Author(s):  
James H. Fowler ◽  
Seth J. Hill ◽  
Remy Levin ◽  
Nick Obradovich
Keyword(s):  
United States ◽  
Temporal Variation ◽  
Fixed Effects ◽  
National Level ◽  
The United States ◽  
Spatial And Temporal Variation ◽  
Full Potential ◽  
County Level ◽  
Fixed Effects Model ◽  
At Home

SummaryBackgroundIn March and April 2020, public health authorities in the United States acted to mitigate transmission of and hospitalizations from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19). These actions were not coordinated at the national level, which raises the question of what might have happened if they were. It also creates an opportunity to use spatial and temporal variation to measure their effect with greater accuracy.MethodsWe combine publicly available data sources on the timing of stay-at-home orders and daily confirmed COVID-19 cases at the county level in the United States (N = 124,027). We then derive from the classic SIR model a two-way fixed-effects model and apply it to the data with controls for unmeasured differences between counties and over time. This enables us to estimate the effect of stay-at-home orders while accounting for local variation in factors like health systems and demographics, and temporal variation in national mitigation actions, access to tests, or exposure to media reports that could influence the course of the disease.FindingsMean county-level daily growth in COVID-19 infections peaked at 17.2% just before stay-at-home orders were issued. Two way fixed-effects regression estimates suggest that orders were associated with a 3.9 percentage point (95% CI 1.2 to 6.6) reduction in the growth rate after one week and a 6.9 percentage point (2.4 to 11.5) reduction after two weeks. By day 27 the reduction (22.6 percentage points, 14.8 to 30.5) had surpassed the growth at the peak, indicating that growth had turned negative and the number of new daily infections was beginning to decline. A hypothetical national stay-at-home order issued on March 13, 2020 when a national emergency was declared might have reduced cumulative infections by 63.3%, and might have helped to reverse exponential growth in the disease by April 10.InterpretationAlthough stay-at-home orders impose great costs to society, delayed responses and piecemeal application of these orders generate similar costs without obtaining the full potential benefits suggested by this analysis. The results here suggest that a coordinated nationwide stay-at-home order might have reduced by hundreds of thousands the current number of infections and by tens of thousands the total number of deaths from COVID-19. Future efforts in the United States and elsewhere to control pandemics should coordinate stay-at-home orders at the national level, especially for diseases for which local spread has already occurred and testing availability is delayed. Since stay-at-home orders reduce infection growth rates, early implementation when infection counts are still low would be most beneficial.FundingNone.

Sign in / Sign up

Export Citation Format

Share Document