Transcript PACIFIC MADRONE DISEASES AND GLACIAL SOILS OF THE …

NATURAL HISTORY OF PACIFIC MADRONE,
ITS DISEASES AND INTERACTION WITH
GLACIAL SOILS OF THE PUGET SOUND
A.B. ADAMS
POSSIBLE ESC 110 PROJECT
BACKGROUND
Pacific madrone (Arbutus menziesii) is in decline in urban
areas of the Puget Trough.
This Puget Sound region
is
characterized by young glacial soils of mixed mineralology and
texture. Associated with the decline of madrones is infestation by
fungal pathogens that most likely are of native origin. The slow
demise or death of the madrones occurs over a time period of years
or even decades suggesting that plant nutrition, habitat or root
function may play a role in the pathology of this plant. In other
well-known tree/fungal pathogen interactions, death of the tree host
is abrupt and certain. Such is the case with the American chestnut,
Dutch elm and more recently oak infestations California.
From the standpoint of pathology and co-evolution this tree
is most interesting to study. This is especially true when soils are
considered as a factor in pathology. Phytophthora (root rot) seems
to infect roots in soil of poor drainage. Fungal hyphae move
rapidly into the vascular tissue of the plant and young saplings at
least die within weeks of the infection. Death occurs for the top of
the plant downward. This sudden death results in leaves remaining
on the plant after death, thus providing a field method for
identifying the disease. Soils with poor drainage are more likely to
have trees that die young with Phytophthora.
Nattrassia mangiferia, on the other hand, infects the stem as a
surficial depression of the bark. The fungus grows actively from
the circumference of the depression leaving a black hollow hole
behind. Although this fungus directly takes nutrients from the
plant, it also damages its host indirectly by girdling branches thus
denying transport of water and soil nutrients to the leaves and sugar
products of photosynthesis from the leaves to the roots. Unlike
Phytophthora, madrone trees often coexist with Natrassia cankers;
in some cases, they even reverse the spread of disease. On many
urban soils and natural soils in which topsoil has been removed or
modified, nonetheless, the Nattrassia fungus has slowly decimated
some madrone populations.
HYPOTHESES
• Madrone diseases are related to soil type
– Soil structure and function (for instance, drainage)
– Soil chemistry (for example, pH and nutrients)
• Madrone diseases are related to community
physical structure
• Madrone diseases are related to disturbances (fire)
• Madrone fruits provide a scarce resource for
migratory and resident birds during a critical time
period (late fall) in Puget Sound
Pure Broadleaf Evergreen Forest of Pacific Madrone
SAND QUARRIES ALLOW FOR STUDY OF BASAL ROOTS IMPORTANT FOR
WATER UPTAKE , SLOPE STABILITY AND ANCHORING PLANT
PIT SHOWING ESPERENT SAND WITH Bw/Bs?
Hypothesis: natural soil series supports healthy madrones
• Lower left - Nattrassia induced branch
cankers produced black sunken centers
with areas of active pathogen growth on
the borders
• Upper right - Cankers may completely
girdle branches
• Lower right - Competition for nutrients
between the tree and fungus and girdling
of vascular tissue ultimately may cause
death in major branches or trunks of large
trees. Here the two madrone trunks to the
right (one dead with leaves, the other
alive) are from the same tree; the dead
trunk was girdled by Nattrassia.
A TYPE OF ROOT ROT (PHYTOPHTHORA) INFECTS POTTED
AND FIELD PLANTS THAT ARE PERIODICALLY FLOODED.
BELOW SHOWS THE PROGRESSION OF PHYTOPHTHORA
SYMPTOMS IN OVERWATERED POTTED PLANTS. FLOODING
IS COMMON IN URBIC (CONSTRUCTION FILL) SOILS
• Left most plant showed initial
signs of infection, but the
watering regime was made drier
and it recovered
• Second from left - fungus
spreads from root clogging
vascular system killing plant
from top down.
• Middle - the rapidity of death
caused by root rot aids in
identifying it because the leaves
remain on the plant at the time
of death.
• Far right - all leaves eventually
abscise.
LAWTON CLAY FOUND BELOW LAWN AT LAURELHURST PARK,
SEATTLE. IS THIS IMPERMEABLE STRATA RESPONSIBLE FOR
DISEASED MADRONES GROWING HERE?
MAGNOLIA BLUFFS HAS A COMPACTED CAP OF GLACIAL TILL.
MADRONES ARE BELIEVED TO PLAY A ROLE IN STABILIZING
THESE SLOPES WITH THEIR ROOTS, BUT THE SHALLOW HARDPAN
MAY CAUSE MADRONES TO BECOME SICK?
• Undisturbed, natural
soils with madrones
are very uncommon
in the urban areas.
• Compaction and
erosion destroy
upper soil surfaces
crucial for ion
exchange and plant
nutrient uptake
SOME POSSIBLE PROJECT TOPICS
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Help in field work to determine the
relationship of depth to hardpan to
madrone health at Magnolia Bluffs
Characterize construction fill
material (urbic soil) at Warren
Magnunson and NorthSeattle
Community College wetland fill
Characterize soil profiles beneath
sick madrone trees at Laurelhurst
Park.
Take part in a soil and leaf
sampling project at a natural,
healthy madrone site.
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Conduct literature research on
Phytophthora infestations at other places
and on other plants (for instance,
California oaks) and relate it to Pacific
madrone problems.
Conduct literature research on Nattrassia
(stem cankers) infections at other places
and on other plants and relate it to
Pacific madrone problems
Analyze results of studies on previous
bird frugivore studies, develop
hypothesis and design your on bird
study.
Plant/pathogen coevolution