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<p>This story has another Dal connection: Barry Goldsmith, forest ecologist who worked at Dal before Bill Freedman. Barry (FB Goldsmith, we have
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Hi Nick, David P. & All, Jan 6, 2016
Before getting bogged down in details and side reactions it may help =
to sketch in the general context as I view it.=20
LEACHING OF NUTRIENTS FROM FOLIAGE DAMAGED BY AIR POLLUTANTS OR WIND:
When I noticed about 1990 that Spruce trees in the Valley were dying =
in what should have been the prime of life I became alarmed and =
attributed this to air pollution; acid ppt. and ozone. This resembled =
Waldsterben of Germany and Austria and based on extensive studies there =
involving also motor vehicle exhaust (I think) it seemed logical that =
excessive leaching of nutrients from foliage which had been damaged by =
air pollution was the probable mode of action. In the early 80s (?)I =
reviewed a long preliminary report on decline of Sugar Maple in Ontario =
and Quebec and suggested that leaching loss from leaves and responses to =
application of fertilizers should be examined in follow-up studies. The =
editor (Rennie I think), who had solicited reviews, was keen on this =
idea because naturally a tree will decline if it has to do the same job =
many times. He died shortly after of a heart attack and so far as I am =
aware this possible effect of leaching was not investigated.
Potassium is of particular interest in this context because it is =
more readily leached from leaves than other cations, tends to be most =
abundant in uppermost soil and as the season advances will become less =
available as upper layers dry and, being relatively immobile in soil, =
requires extension of roots and root hairs into soil volumes that =
contain K before absorption can take place. The behavior of P in soil =
resembles K but is less subject to leaching from foliage.=20
Absorption and transport of all nutrients requires metabolic energy =
and doing this a second time will double the cost and growing into fresh =
soil to exploit localized K or P uses even more energy.=20
From the late 90s onward, tree death seemed related to unusually dry =
periods, but I now notice that dry periods would be especially damaging =
if prior K leaching from foliage had been excessive because K uptake =
would tend to be limited to K-poor horizons.
=20
WIND and WEATHER EXTREMES:
Based on my limited recent field of vision; (mostly North Alton =
woods and two other woodlots) we have had more windthrow since Dec 2010 =
than in the previous century. At one time I walked much cross-country, =
hunting or just walking, and encountered evidence of widespread =
windthrow only as localized exceptions, such as Old Field Spruce killed =
by Budworm and Fir topped by an ice storm. These recent wind events may =
prove to be a blip as opposed to a trend but in view of other recent =
extreme weather here and elsewhere I reluctantly bet on trend.
I recall warnings about the greenhouse effect, as climate change was =
initially called, back about 1965. Now, 50 years later, I am reasonably =
sure our forests are being affected and began to be affected about 15 =
years ago. Unless we can make an abrupt change in course with respect =
to carbon emissions then I think forests here, their dependents and much =
else will be "gone with the wind".
Biomass, from forest or otherwise, is one potential way to reduce =
carbon footprint so I think every effort should be made to foster and =
expand this as quickly as possible. =20
With climate change in Federal crosshairs and the world economy =
sputtering the time is right, I think, for a Federally sponsored =
research program run under the auspices of some hopefully permanent =
agency to provide continuity, such as Environment Canada, with =
Provincial Departments, such as Natural Resources and Agriculture acting =
in an advisory capacity and/or providing analytical services and =
Universties, at least initially, acting as incubators to launch some =
relevant research experiments and grow a core of potential researchers =
for the long haul.=20
This might never become the northern chapter of the Tennessee Valley =
Authority but sometimes mighty oaks from little acorns grow. If the =
overall aim were to conduct top quality research with an eye for =
practical results then I see no way it could fail to result in both =
fundamental and practical advances. Sadly, unless matters have changed =
in the last two decades, we are still dependent upon US sources of =
reference samples and without such guides, analytical results may be =
wildly inaccurate.
CALCIUM AND pH:
Many I think suppose soil Ca and soil pH are two sides of the same =
coin when in fact they are entirely distinct. If for example gypsum is =
applied to the soil surface there can be a dramatic increase in soil Ca =
and little or no change in pH.=20
In one of my orchard trials e.g. (Ag. Can. Tech Pub. 99-02), both =
coarse Anhydrate and fine gypsum significantly increased soil Ca in each =
of seven depths between 0 and 100 cm and significantly decreased pH from =
5.84 to 5.57 (coarse) and 5.49 (fine) with no depth interaction. At most =
depths Ca was doubled or more than doubled; 80-100 cm, Control 250, =
Coarse 642 and Fine 590 Kg/ha 15 cm. Both Gypsum sources decreased trunk =
growth, decreased yield in two years and (drawing on memory) decreased =
fruit size.
Clearly any field trial which attempts to demonstrate that Ca =
affects tree growth should use some form of Gypsum. Anhydrate, although =
useless for wallboard purposes, ie equivalent to Gypsum once dissolved =
and is likely still available here. But nothing is simple in soil trials =
because Ca induces downward movement of K and Mg. And an apparent =
positive response to Ca might in fact be a response to higher amounts of =
K at greater depth.=20
Soil Ca and pH naturally both increase in tandem if limestone is =
applied because the CO3 in limestone reacts with H+ to form CO2 and =
water but this is a consequence of the anion applied not an effect of =
Ca.=20
ACIDIC PRECIPITATION AND Ca LEACHING FROM SOIL
Based on historical averages of pH 4.5 in ppt. and 100 cm annual =
ppt. I get a value of 3.2 x 10^-6 H+ equiv/cm^2 > 316.2 eq H+/ha and =
assuming no other constituents in ppt. [impossible but for worst case =
numbers] and further assuming all of this goes to Ca leaching; a loss of =
6.3 kg Ca/ha. In an agricultural context this is tiny but apparently not =
in a forest context.
This is that same order of magnitude as Ca leaching observed in =
woodland (Table 2; Lawrence & Huntington) reached =
by--http://ny.water.usgs.gov/pubs/wri/wri984267/
[I finally got around