Agronomy 101 - Air circulation vs. tree roots for turf drying

[John Connolly]

I think it's well-accepted that enhanced air circulation via tree removal promotes drier and firmer turf. I'm assuming that an elaborate, water wicking, tree root system doesn't achieve the same turf drying effect because of the associated shade and wind-negating effect that comes with the leaves and branches of large, root-bearing trees. What is the rest of the story of air circulation vs. tree roots in the eternal quest for firm turf.

[Jeff_Brauer]

John,


Probably too site specific to discuss, but yes, in general, no trees is better.  I have seen a few situations where planting a willow helps a bit in drying out soil, but because they are trash trees, you would never want to plant them too close to greens, tees, or fairways where they would block shots, etc.


Besides, French drains probably are a better wet soil solution (or surface drains) than the willows.  And, come to think of it, how many times have we seen willows or other water loving trees break through pipes and clog them in search of water?


Lastly, water loving trees tend to be shallow rooted, causing the same problem Sergio faced at Medinah (yes, he was upland) so they can break wrists, mowers, etc.

[Steve Okula]

Shade and any wind-negating effect does not begin to compensate for the water trees such out of the soil.

[Duncan Cheslett]

Shade and any wind-negating effect does not begin to compensate for the water trees such out of the soil.

Is that a statement of fact or the perpetuation of a popular myth?


Our greenkeeper is of the opinion that this is nonsense  and wants to remove trees in the furtherance of drier soil.

[Jeff_Brauer]

Texas A and M did a study, and its true.  Trees take far more water out of the soil than turf, at least in this region.

[Steve Okula]

Shade and any wind-negating effect does not begin to compensate for the water trees such out of the soil.

Is that a statement of fact or the perpetuation of a popular myth?


Our greenkeeper is of the opinion that this is nonsense  and wants to remove trees in the furtherance of drier soil.

It is a conclusion I have drawn from four decades of observation as a greenkeeper.

[Terry Lavin]

Shade and any wind-negating effect does not begin to compensate for the water trees such out of the soil.

Is that a statement of fact or the perpetuation of a popular myth?


Our greenkeeper is of the opinion that this is nonsense  and wants to remove trees in the furtherance of drier soil.

It is a conclusion I have drawn from four decades of observation as a greenkeeper.

Makes sense. I'm guessing there are studies to confirm this?

[Steve Okula]

Shade and any wind-negating effect does not begin to compensate for the water trees such out of the soil.

Is that a statement of fact or the perpetuation of a popular myth?


Our greenkeeper is of the opinion that this is nonsense  and wants to remove trees in the furtherance of drier soil.

It is a conclusion I have drawn from four decades of observation as a greenkeeper.

Makes sense. I'm guessing there are studies to confirm this?

None that I am aware of.

[Duncan Cheslett]

I'm guessing that it depends on local factors and conditions.


Here in the rainy north west of England, our inland golf courses generally sit on clay soil and become waterlogged in winter - indeed at any time of year if the water table remains high, as it has done for the last couple of years. No amount of trees is ever going to lower the water table.


I see no evidence whatsoever that areas with trees have dryer soil than areas without; indeed some of the wettest parts of courses seem to be the most heavily wooded. 


Despite our climate and soil conditions however, a rain-free week in spring and a bit of wind can make a phenomenal difference to a wet course  - provided the wind and sun can get to the turf.


Another thing...


Our courses still rely to a large extent on the clay drainage pipes installed 100 years ago when the golf boom happened. Many drains still function well, but the ones that fail are generally victims to the same culprit  -  tree roots!


This alone is a good reason to keep trees off our golf courses.

[Jon Wiggett]

Duncan,


it is generally accepted that trees use a lot more water than grass and so people draw the conclusion that trees will dry the soil out. This is correct when looking at the whole soil profile but completely wrong when looking at it from a golfing point of view. Trees have the vast majority of their roots in the upper few inches of the soil profile. This means that the tree needs to keep the top part of the profile wet in order for the roots to provide the tree with moisture. Trees will dry out the deeper soil profile but keep the top part wet which is bad for golf. Your greenkeepr is correct so let him cut down all the trees he needs.


Jon

[Duncan Cheslett]

Jon,


Makes sense.


The other thing that our greenkeeper wants to do is to encourage the heathland grasses and heathers which are native to our course. He tells me that the trees which have been allowed to prolifirate over the last 50 years  have put these under threat.


Does this also make sense?

[James Bennett]

yes - the native grasses can't get the native light, air or water because of the trees

[Jon Wiggett]

Duncan,


absolutely. I have cleared area of scrub woodland and gorse that are now showing signs of heather regeneration. It is an on going program to keep on top of any regrowth of trees and especially gorse which is maybe something the club membership could help with in once yearly 'help the greenkeeper days'.


Jon

[Steve Okula]

Duncan,


it is generally accepted that trees use a lot more water than grass and so people draw the conclusion that trees will dry the soil out. This is correct when looking at the whole soil profile but completely wrong when looking at it from a golfing point of view. Trees have the vast majority of their roots in the upper few inches of the soil profile. This means that the tree needs to keep the top part of the profile wet in order for the roots to provide the tree with moisture. Trees will dry out the deeper soil profile but keep the top part wet which is bad for golf. Your greenkeepr is correct so let him cut down all the trees he needs.


Jon

I'm trying to make sense of this post. How do trees dry out dry out the deeper soil if they have no roots down there? What actions do trees take to maintain moisture in the upper soil levels?

[Jon Wiggett]

Steve,


the tree roots act almost like a membrane keeping moisture in the top layers of the soil profile meaning that much of the moisture never gets to the lower soil profile.


Jon

[Steve Lang]

 
     So, how do trees grow?  … A quick investigation could lead one to this reference:
http://woodlandsteward.squarespace.com/storage/past-issues/how%20trees%20grow.htm
“THE ROOT SYSTEM
The root system develops from the embryonic root within the seed. As cells in the apicalmeristem of the root divide and elongate, they push the root tip into the soil. Roots lengthen in this manner. The rootcap, whose cells are constantly being sloughed off, protects the tender cells in the apical meristem and lubricates the root as it is rammed into the soil. Expanded root cells differentiate to carry out functions of uptake and transport of water and nutrients to above ground parts of the tree.
Lateral roots do not grow from a bud like lateral shoots. They grow from internal root tissue. Some internal root cells, in response to the right balance and mixture of hormones, produce a new root meristem. These cells divide and elongate and are forced between and around cells in the root, rupturing root tissue and emerging us a lateral root. This creates a pathway for easy movement from the soil into roots that avoids entering living cells. If fertilizers or any other chemicals are appliced in close contact with branced roots, or even at the base of a tree, uptake will occur. Fine feeder roots are not essential to have uptake. However, water and nutrients move through soil very slowly and for only short distances. Anything near a stationary root is quickly depleted from the soil around the root. Hence, to be healthy, a tree must have existing and new roots growing in length to explore the soil for water and nutrients.
Tree roots are not very deep. Basic tree biology education should convey that most of the root system is quite shallow and can extend far from a tree, even for beyond the drip line. Much of this is genetically controlled, but the principal reason for shallow rooting is the very stressful environment, particularly poor soil conditions. Low oxygen content and soil compaction predispose trees to many other problems.
To survive, roots need 3 percent oxygen in the soil. If they are to grow, existing apical meristems require 5-10 percent oxygen. And, for new roots to form, soil oxygen content must be at least 12 percent. Our atmosphere is about 21 percent oxygen. In an undisturbed loom soil six inches below the surface, the percent oxygen is only slightly less than that in the air. A compacted loom will have about 5 percent oxygen 15 inches deep into the soil. Tree roots would survive at this depth, but new roots would be stressed. A clay loom soil at three feet has an insufficient oxygen level to support new root growth. In a sandy soil, even at five feet, the oxygen content is about 15 percent, where roots can survive and grow.”
Or…  http://www.treemail.nl/download/treebook7/soil/chapt6.htm
Makes sense, if there’s tight clayey soils, water and air don’t infiltrate very deep and roots stay close to surface, contributing to primary porosity or pore spaces which can hold water but probably not doing much capillary type action via small pore structures that could draw moisture out of deeper soils.  This is in contrast to looser soils where one never really sees much surface saturation…  classic water balance issues.
Duncan, you know that the River Tame you see represents the water table running through Reddish Vale, and probably most slopes down to it all carry subsurface water to discharge into the river… on which holes are trees are targeted?
 

[Duncan Cheslett]

I've taken the liberty of blowing up Steve's post above to make it legible;


So, how do trees grow?  … A quick investigation could lead one to this reference:
http://woodlandsteward.squarespace.com/storage/past-issues/how%20trees%20grow.htm

“THE ROOT SYSTEM
The root system develops from the embryonic root within the seed. As cells in the apicalmeristem of the root divide and elongate, they push the root tip into the soil. Roots lengthen in this manner. The rootcap, whose cells are constantly being sloughed off, protects the tender cells in the apical meristem and lubricates the root as it is rammed into the soil. Expanded root cells differentiate to carry out functions of uptake and transport of water and nutrients to above ground parts of the tree.
Lateral roots do not grow from a bud like lateral shoots. They grow from internal root tissue. Some internal root cells, in response to the right balance and mixture of hormones, produce a new root meristem. These cells divide and elongate and are forced between and around cells in the root, rupturing root tissue and emerging us a lateral root. This creates a pathway for easy movement from the soil into roots that avoids entering living cells. If fertilizers or any other chemicals are appliced in close contact with branced roots, or even at the base of a tree, uptake will occur. Fine feeder roots are not essential to have uptake. However, water and nutrients move through soil very slowly and for only short distances. Anything near a stationary root is quickly depleted from the soil around the root. Hence, to be healthy, a tree must have existing and new roots growing in length to explore the soil for water and nutrients.
Tree roots are not very deep. Basic tree biology education should convey that most of the root system is quite shallow and can extend far from a tree, even for beyond the drip line. Much of this is genetically controlled, but the principal reason for shallow rooting is the very stressful environment, particularly poor soil conditions. Low oxygen content and soil compaction predispose trees to many other problems.
To survive, roots need 3 percent oxygen in the soil. If they are to grow, existing apical meristems require 5-10 percent oxygen. And, for new roots to form, soil oxygen content must be at least 12 percent. Our atmosphere is about 21 percent oxygen. In an undisturbed loom soil six inches below the surface, the percent oxygen is only slightly less than that in the air. A compacted loom will have about 5 percent oxygen 15 inches deep into the soil. Tree roots would survive at this depth, but new roots would be stressed. A clay loom soil at three feet has an insufficient oxygen level to support new root growth. In a sandy soil, even at five feet, the oxygen content is about 15 percent, where roots can survive and grow.”
Or…  http://www.treemail.nl/download/treebook7/soil/chapt6.htm
Makes sense, if there’s tight clayey soils, water and air don’t infiltrate very deep and roots stay close to surface, contributing to primary porosity or pore spaces which can hold water but probably not doing much capillary type action via small pore structures that could draw moisture out of deeper soils.  This is in contrast to looser soils where one never really sees much surface saturation…  classic water balance issues.

Duncan, you know that the River Tame you see represents the water table running through Reddish Vale, and probably most slopes down to it all carry subsurface water to discharge into the river… on which holes are trees are targeted?

[Duncan Cheslett]

Duncan, you know that the River Tame you see represents the water table running through Reddish Vale, and probably most slopes down to it all carry subsurface water to discharge into the river… on which holes are trees are targeted?

Steve,


Yes, as you will recall at Reddish Vale we are blessed with undulating land draining naturally into the River Tame, which meanders through the golf course. Our greens are generally raised above fairway level to aid drainage and mostly give few problems, but one or two are perennially damp and accumulate surface water in wet periods. Coincidentally, (or not) these are the greens surrounded by tall trees.


Anecdotal evidence from older members suggests that playing conditions on the course 40-50 years ago were rather different to those today. Wind was far more of a factor on more holes, and fairways drier. Climate change apart, the big difference over the intervening period has been the growth of self-seeding trees all around the perimeter of the course, in pockets within the course, and the planting of silver birches behind greens to add "definition".


The only part of the soil profile of real interest to golfers is the top half inch or so. It seems to me intuitive that on poorly draining soils such as clay the retention of water on the surface is alleviated principally by evaporation, which requires warmth and air flow. Anything that acts to shade the turf from sunlight or to prevent airflow must slow down the evaporation process.


Can there really be an argument that more trees can mean less accumulation of surface water?

[Steve Okula]

How much oxygen tree roots need depends on the species. To take an extreme example, the bald cypress (or swamp cypress) grows in standing water. I don't know what the oxygen content is in their root zone, but we can be reasonably sure that it's less than 3%. An eastern white pine, on the other hand, requires sandy, airy soils.

Trees roots go down much further than, "a few inches" as stated above. A mature hardwood like an oak will have roots down several feet. We've all seen root balls of trees blown over by the wind and they are thicker than a few inches. You could just google "tree roots/ images" and see for yourself.

I have seen trees growing near tees and greens where the roots dried out the soil to the point where turfgrass does not survive, regardless of how much irrigation is applied, and this is on the south side of the trees with good sun exposure. It's not the shade or lack of air circulation causing the problem, probing the soil it is chronically dry.  Upon removal of the tree and resowing or sodding the area it does just fine. Another solution is root pruning, where I know to cut all the roots you need to go down at least three feet. I have done it and seen the roots down there myself.

[JohnH]

I have seen trees growing near tees and greens where the roots dried out the soil to the point where turfgrass does not survive, regardless of how much irrigation is applied, and this is on the south side of the trees with good sun exposure. It's not the shade or lack of air circulation causing the problem, probing the soil it is chronically dry.  Upon removal of the tree and resowing or sodding the area it does just fine. Another solution is root pruning, where I know to cut all the roots you need to go down at least three feet. I have done it and seen the roots down there myself.

I could not agree more with this paragraph. I have a putting surface that's within 30 feet of the south side of mature, grand hardwoods. It has no issue with shade or air circulation. The rear quarter of the surface has always been the most difficult on the course to keep adequate moisture for healthy turf. Easily one of my biggest challenges to achieve consistent playability as the area undergoes mulitiple core/wetting agent apps throughout the season. Couple that with irrigation/hand watering practices and the result is not always ideal for the golfer who desires consistency.


Ultimately, root pruning has been the mode of action over the removal of the old giant trees.

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