Transcript Document

Winter stresses to crops and native plants during
climate change
Bjarni E. Guðleifsson
Agricultural University of Iceland, Modruvellir, 601 Akureyri, Iceland
ABSTRACT
The main winter stresses to plants are frost, ice encasement and low temperature parasitic fungi. In
Iceland, ice cover mainly damages herbage crops whereas frost causes damage to woody plants. Wild
alpine plants are better adapted to these winter stresses than crops, some are frost tolerant, others are ice
tolerant, depending on their growing site. The expected increase in winter temperatures, caused by
climate change, will reduce winter damages to crops cultivated at low altitudes. Decrease in snow cover at
higher altitudes might on the other hand increase frost and ice
cover stress to alpine plants which might be damaged.
Type of stress
In
In
Icelandic
hayfields,
%
1
Icelandic
forests, %
Drought
2
5
Frost
5
85
Energy starvation
+
?
Flooding
+
?
Ice encasement
90
-
Snow molds
2
2
INTRODUCTION
Perennial plants are subject to many kinds of winter stresses.
Plants are damaged or killed if the environmental stress passes
the tolerance of the plant. The tolerance to winter stresses is
much more studied in crops than in wild native plants. Crops are
often introduced species or cultivars, not always adapted to the
local climate. On the other hand iIndigenious plants are adapted
to the local winter stresses and prevailing climate. The proportion
of different stresses in damage to hayfields and trees in Iceland
has been estimated. Ice damage dominates in herbage crops and
frost in wooddy plants.
Frost heaving
Species
TOLERANCE TESTS
Wild indigenious plants are distributed to
localities where the stress intensity is lower than
the plant tolerance to that particular stress.
Preliminary test of a few alpine plant species,
indicates that plants living in snow patches (e.g.
Sibbaldia) possess fairly low frost tolerance,
whereas plants living in dry location (e.g. Threeleaved rush) are tolerant to both frost and ice.
8
Frost
tolerance
LT50,
°C
Ice
tolerance
LD50,
Days
Winter wheat
Triticum aestivum
- 19
15
Timothy
Phleum pratense
-20
37
Sibbaldia
Sibbaldia procumbens
-11
35
Three-laved rush
Juncus trifidus
-20
49
FUNGI
FROST
FROST
ICE
FROST
Year 2000
ICE
ICE
FROST
ICE
FROST
ICE
Temperatures are expected to rise dramatically
In futural climate change. During the next 50
years the mean temperature in Iceland is
expected to rise 1,5 °C during summer and 3,0
°C during winter. Winter stresses to crops and
plants at lower altitudes will decrease and
winter damages might disappear. However,
warm winter thaws might promote premature
plant dehardening and growth, resulting in
damages caused by subsequent stresses. The
high rise in winter temperature will result in
decreased snow cover at higher altitudes, and
this might result in increase or change in winter
stresses at higher altitudes. Plants adapted to
snow mold stress might therefore in the future
experience frost or ice encasement to which
they are not well adapted. Therefore winter
damages at higher altitudes might increase and
influence distribution of alpine plants.
FUNGI
IMPACT OF CLIMATE CHANGE
Year 2050