Importance of Old Trees

I have posted many times on theneed for forest refugia.  Here we getanother lesson.  The older trees grow mossesand these mosses actually fix nitrogen which is then dropped onto the forestfloor.

In fact, proper forest husbandrymust include refugia in various shapes and sizes, but most likely best set innarrow strips that perhaps go for miles. Such strips also cater to the needs of wildlife.  Such strips are usually best set right alongthe valley drainage to protect the fishery as well.  Yet hillside strips are also called for. 

This way planned timberharvesting can follow decadal programs rather easily while also preserving a lotof natural fertility and diversity.

Even better will be the day wesimply practice selective logging from time to time that includes extensivebrush clearing through burning.

I personally think that mostforestry needs to be privately owned with a quota system put in place anddesignated refugia that is deliberately preserved. 

This shows us another controlthat can be put in place.  Just licensethe allowable cut on the basis of the number of healthy refugia trees whose ageexceeds a certain standard.  Unhealthytrees would be removed posthaste but then one would wait for their replacementsto reach the proper age before new cutting was allowed.  That should motivate everyone to be good andalso careful.

Old trees 'important for forests'

Mar 15, 2011

Bacteria living in mosses on tree branches are twice as effective at'fixing' nitrogen as those on the ground, say researchers from McGill University, Canada.

A new study by McGill's Zoë Lindo and Jonathan Whiteley shows thatlarge, ancient trees may be very important in helping forests grow.

These findings highlight the importance of maintaining the largeold-growth trees in the coastal temperate rainforests that stretch fromSouthern Alaska to Northern California.Lindo's findings suggest that interactions between old trees, mosses andcyanobacteria contribute to nutrient dynamics in a way that may actuallysustain the long-term productivity of these forests.

"What we're doing is putting large, old trees into a context wherethey're an integral part of what a forest is," says Lindo. "Theselarge old trees are doing something: they're providing habitat for somethingthat provides habitat for something else that's fertilizing the forest. It'slike a domino effect; it's indirect but without the first step, without thetrees, none of it could happen."

There are three players in this story: large, old trees; mosses thatgrow along their branches; and cyanobacteria associated with the mosses. Thecyanobacteria take nitrogen from the atmosphere and make it available to plants– a process called "nitrogen fixation" that very few organisms cando.

The growth and development of many forests is thought to be limited bythe availability of nitrogen. Cyanobacteria in mosses on the ground wererecently shown to supply nitrogen to boreal forest, but until now cyanobacteriahave not been studied in coastal forests or in canopies (tree-tops). Bycollecting mosses on the forest floor and then at 15 and 30 metres upinto the forest canopy, Lindo was able to show both that the cyanobacteria aremore abundant in mosses high above the ground, and that they "fix"twice as much nitrogen as those associated with mosses on the forest floor.

It seems moss is the crucial element; the amount of nitrogen comingfrom the canopy depends on trees having mosses.

"You need trees that are large enough and old enough to startaccumulating mosses before you can have the cyanobacteria that are associatedwith the mosses," says Lindo. "Many trees don't start to accumulatemosses until they're more than 100 years old. So it's really the densityof very large, old trees that are draped in moss that is important at a foreststand level. We surveyed trees that are estimated as being between500 and 800 years old."

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