Evaluating Black Ash (Fraxinus nigra) Decline in the Upper Midwest
K. Ward1, E. Abdela2, M. Ostry1, R. Venette1, B. Palik2; USDA Forest Service,
Northern Research Station, 1St. Paul, MN and 2Grand Rapids, MN
The Problem:
Objectives:
Results: FIA public data
Discussion:
Black ash (Fraxinus nigra) decline has been
noted with increasing frequency. Over 27,000
acres were affected in Minnesota in 2004.
• Use Forest Inventory & Analysis (FIA) and
Forest Health Monitoring (FHM) data to assess
the distribution of decline in Minnesota.
• Survival and mean DBH decreased over time.
Roads contribute to decline of black ash,
potentially due to changes in hydrology or
accumulation of de-icing agents. Trees were often
old (>100 years) and older trees may be more
vulnerable to biotic and abiotic stresses.
• Relate decline occurrence and variation to
mapped landscape-scale climatic, physiographic,
and edaphic data.
• Conduct field evaluations of decline and
mortality within selected ecosystems.
• Survival differed greatly among counties
(44% to 94%).
• Mean DBH and survival were greater on moist
slopes than on flat, wet sites.
• Most declining and non-declining trees (~80%)
and the oldest trees were growing on sites with
the poorest productivity.
• Quantify relationships between field
observations and cultural features.
• Dead terminals and conks or decay were the most
common damage types.
Data Sources:
• FHM aerial sketchmapping data, Minnesota,
2004.
• FIA public data (1977 to 2005) and FIA truecoordinate data (1990 and 2003).
Black ash is an important component of
wetland forests throughout the Upper
Midwest and northeastern USA, and is highly
valued for paneling, veneer, furniture, and
Native American basketmaking.
• National Hydrography Dataset, National
Wetlands Inventory, STATSGO soils (Fig. 1),
PRISM climate, and roads data.
• Change in DBH was greater on drier than on
wetter sites.
• Levels of mortality differed among counties,
climate divisions, and ecological subsections.
• Soils, temperature, and precipitation data were
associated with mortality and change in DBH, but
explained little of the variation.
• Field observations of 2,116 trees – mortality,
condition, DBH, age, soil moisture, and
regeneration.
Analyses:
• Linear regression and categorical data analyses.
Figure 1. (A) Hydrography, (B) wetlands, and (C)
soils data.
B
A
SCHULTZ
FLOWAGE
JACOBS
C
274
ISLAND W
SCHULTZ
FLOWAGE
249
UNNAMED
DEEPWATER
UNNAMED
CLEAR
DEEPWATER
MIRROR
Results: Field evaluations
• Trees growing on wetter plots had greater decline
symptoms than trees growing on drier plots (Fig.
2).
• Severity of decline was greater in older trees than
in younger trees.
CLEAR
MIRROR
Decline Hypotheses Tested:
FISH RES
FISH RES
473
FISH RES
255
473
WILD RICE W
WILD RICE
473
251
Results: FHM sketchmapping
• Trees growing closer to roads had more decline
symptoms than those farther from roads.
Decline/dieback
60
100
80
40
20
A
60
40
20
Counties
r ²=0.2835
0
250 500 750 1000 1250 1500 1750 2000 2250
Distance from County/State Roads (ft)
80
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Wetness Mean
Continuing Research:
30
• Relate regeneration to hydrology, stand history,
and adjacency to roads.
C
25
40
0
35
B
60
Acknowledgement:
20
15
10
5
20
0
0
100
Trees (%)
Black Ash
Figure 2.
2. Relationship between (A) healthy, (B)
dying, and (C) dead trees and field plot wetness.
Trees (%)
Random
Declining
Ward, K., M. Ostry, R. Venette, B. Palik, M. Hansen, and M.
Hatfield. 2007. Assessment of black ash (Fraxinus nigra) decline
in Minnesota. In: Proceedings of the Eighth Annual Forest
Inventory and Analysis Symposium. October 16-18, 2006.
Monterey Bay, CA, USDA Forest Service, Northern Research
Station (In Press).
• Use dendrochronology to identify periods of
reduced growth associated with drought,
flooding, or changing land use.
• Declining stands were significantly closer to
city, county, and state roads.
80
For additional details see:
• Conduct additional field evaluations of black ash
decline and mortality within selected sites
varying in hydrology, stand age, and
management history.
• No biotic agent was found to be responsible for
the decline.
• Decline was concentrated spatially.
Trees (%)
Hydrography
Adjacency to roads
Tree age
Temperature and precipitation
Soil characteristics
• Black ash regeneration (seedling and sapling size
classes) varied widely across sites but was
generally greater on better drained plots (Fig. 3).
249
Number of Sites
•
•
•
•
•
473
W FISH RES
FISH RES
ES
Figure 3. Vigorously growing black ash trees (left)
and thriving regeneration (right) on a rich mesic
site.
Results: FIA true coordinate data
Importance:
ISLAND
FIA growth and mortality data proved valuable for
discriminating among several factors that could be
associated with black ash decline but the data
were limited in revealing factors that could have
caused the decline, such as damage from biotic
and abiotic agents.
r ²=0.2254
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Wetness Mean
0
r ²=0.3311
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Wetness Mean
The authors thank Manfred Mielke and the Forest
Health Monitoring Program for partial funding of
the study.