Yes. Losing the trees is very disturbing
but it is a powerful reminder of municipal neglect in continuous planting, tree
care and good arboriculture over the last 60 yrs when municipalities lost
interest in tree planting and tree care. And there’s more to come. Surviving
trees are still very distressed and more will die over the next 5 – 10 yrs
even if the rainfall patterns are restored and tree watering is resumed.
The drought – if that is what it is
has been on-going for up to 9 yrs in some places, 5 yrs in other. There have
been other periods of long drought but like the US we have very short periods of
historical records so who knows what the long term pattern is over a 1,000 yrs
or more? One figure did impress me from US research and that is that there was
a 100 + yr drought in the SW that resulted in the cliff-dwelling tribes of the
SW deserting their settlements because they couldn’t farm their cliff top
corn and squash any longer.
We have much to learn.
Cheers
Trevor N
From:
Ben Wiswall [mailto:benwiswall@pacbell.net]
Sent: Monday, 20 July 2009 2:54 PM
To: margn@internode.on.net
Cc: medit plants forum
Subject: Re: watering time
I don't know how dry it will have to get before our urban forests begin
to die off, but it sounds like you and your fellow citizens are finding out
now. Losing 120-year-old trees by the hundreds in parks (and 30,000 on
streets) is very disturbing!
How long and how severe is the current drought in Australia?
I've heard from another Australian on this forum, and the situation
sounds extreme: is the drought continent-wide? Does it have historical
precedent?
By analyzing tree rings, scientists have determined that cyclical
drought is typical for California
over the past few hundred years, with periodic prolonged droughts. The
most recent of these was from around 1760-1820, when rainfall was about 25-30%
below the the 20th century average.
We don't know precisely how increased atmospheric carbon dioxide will
effect weather patterns, but it's a safe bet conditions here will be drier than
they have been. Let's hope it doesn't become so dry our young
civilization will just dry up and blow away!
Simi Valley, inland southern
California
From: Margaret Nottle <margn@internode.on.net>
To: pkssreid@comcast.net;
medit plants forum <medit-plants@ucdavis.edu>
Sent: Sunday, July 19, 2009
8:11:58 PM
Subject: RE: watering time
Another quick note. We are not allowed to water by any other means than
sub-surface or dripper system for a total of 3 hrs a week - either all in
one go on Saturday or Sunday according top odds and evens letter box
numbers, or for 1.5hrs at a time either Saturday and Tuesday, or Sunday and
Wednesday. No sprinklers at all; no misters, no hoses, no car washing, no
hosing of driveways, swimming pool top-ups by permit, same for new pools; no
fountains, ponds, garden pools, water features. All watering is from 6.00AM
to 9.00AM whatever day. If you are disabled and also old you can get a
permit to water using a hose with trigger nozzle at anytime but still for
only 3 hrs. Bucketting water from a tap (faucet) is allowed any-time or
until your back breaks!!!
Our gardens are changing in appearance but still nothing like Santa Fe.
Plenty of old established stressed trees are past recovery........ Last yr
our biggest park lost over 800 mature trees - up to about 120 yrs old, and
over 30,000 street trees died. Things are changing.
Cheers
Trevor N
_____________________________________________
From: o*@ucdavis.edu
[mailto:o*@ucdavis.edu]
On Behalf Of pkssreid
Sent: Monday, 20 July 2009 11:35 AM
To: 'medit plants forum'
Subject: watering time
Just a quick note: University
of California guidelines
recommend landscape
irrigation between 2 am and 6 am, for all the reasons mentioned previously,
including best water pressure, less loss to wind and evaporation, and in the
case of sprinklers, less time for fungal organisms to grow before foliage
dries. An additional note about night watering has to do with the fate of
the water in the soil: since the main cause of water movement in soil is
gravity (down) or evapotranspiration (up), unused water in the evening may
actually move below the zone of most water uptake (top 18") if it isn't
being used by the plant. Since most plants won't be as active in water
uptake in the evening as they will be in the morning, some of the applied
water may actually be wasted in the case of more shallowly rooted plants.
Now, I know that many mediterranean plants survive drought with very deep
roots, like Quercus lobata to name one prime example, but they also survive
it by having widespread roots with lots of root hairs in those top 18" to
make rapid use of any shallowly available water as well, including those
brief flash rains prevalent in med climates other than California
and Chile.
For those of us without shallow water tables, very deep, infrequent watering
of large specimens may be necessary, but in that case, research shows that
time of day has very little to do with it from the plant's perspective, and
usually isn't accomplished by sprinklers. And any oxygen that might be
carried in a sprinkler drop isn't going to get very far in the soil anyway.
Significant soil aeration isn't accomplished that way. Over-watering too
often leads to anaerobic conditions and can be accomplished just as easily
with sprinklers as it can be with drip or a hose or a bucket.
If one has to water by hose, then getting up at 2 am isn't feasible, but
certainly 6 am would be.
Karrie Reid
|
