Permaculture: A Designers' Manual - Chapter 6 TREES AND THEIR ENERGY TRANSACTIONS

Chapter 6 TREES AND THEIR ENERGY TRANSACTIONS

6.1 Introduction
6.2 The biomass of the tree
6.3 Wind effects
6.4 Temperature effects
6.5 Trees and precipitation
6.6 How a tree interacts with rain
6.7 Summary
6.8 References

I started reading Ch. 6 and started thinking maybe my wind pictures of trees should be here instead? Oh well.

I thought it was interesting about the rain nuclei effect of materials from forests being better than 'industrial' cloud-seeding materials. Also, very interesting how much the throughfall water is enhanced by the canopy.

Mollison mentions Kaho'olawe and I just happened to see it recently on a TV show. It sounds like the restoration going on there are some of the same principles practiced by permies. Plant guilds, native species, soil retention/building, and water-catchment.

If Chapter 5 had "news you can use," this chapter has a specific call to action: plant windbreaks. This chapter is going to cost me a ton of money. Or accelerate planned expenditures.

Mollison's numbers about 50% of the forest's water used to transpiration make sense, but how much more do trees transpire in a windy, dry climate? How much more water could I retain in the soil if I cut that wind in half? Enough to make a huge difference.

Over half of our moisture comes as snow. Much of our snow does evaporate rather than melt into the soil. The snow can be so dry you can sweep it with a broom. I see just what he's talking about, where it does accumulate in clumps of grass and at the base of plantings, and that it is more likely to melt in the shade. It's happening now in the swales I had cut in October. But can I do more? Maybe every new tree needs a small boulder at its base to catch the snow. My neighbors have plenty they'd like to get rid of.

I have been planning a windbreak to shield the prevailing wind on the new orchard planting. This chapter reinforces the need to get this done at all costs to help drought-proof the new crop trees. Just last night I placed my first order for 20 hazelnuts. I have 200' to start with, so I'm going to need a lot more trees yet.

USDA actually has a program on agroforestry. One of their sub-areas is shelter belts.

An interesting old thread with some discussion on the mathematics of windbreaks/shelterbelts/hedges/fedges (how's that for optimizing the search engines!).

My favorite permies.com thread on fedges. I am inspired by what Tom Southwell is doing at ABCacres with hedges.

If the rest of the book goes like this, it's going to be worth it to finish.

I spend a lot of my time thinking through regional ecosystem policy. A lot of goals in the PNW, from mgmt of summer base stream flow, to in channel habitat for salmonids, to stormwater managment, to habitat corridors for terrestrial diversity, all come down to forest and tree management. This chapter does a nice job of summarizing the mechanisms, but leaves us to implement. PC design has a lot of value for ecosystem management.

I wanted to share one idea of how to extend these ideas into the invisible structures that affect landscape management.

Modified watersheds have surplus water. Until we reforest the landscape (in other words,learn how to make a living amongst woody vegetation), we have surplus runoff to manage. This surplus is the imperative to capture and store for summer use because the trees no longer intercept, evaporate and transpire. Stream ecosystems are unraveling because they are trying to pass more water than they are evolved to do, and so are thrown into erosional disequilibrium that will take a millenia to resolve. In addition to the compression of time from rainfall to entering stream flow--our landscapes shed water faster during rain--there is the proportion of rainfall that is intercepted or transpired by forest and passed back up the mountains (and stored as snowpack). In our massive forests, interception/evaporation alone can account for 30% of annual rainfall (more in the shoulder seasons, less in the rainy season).

The historical function of trees in the water cycle is only beginning to be part of our water management policy. If you capture runoff, store it in a pond, and feed it to an orchard over time, simulating the natural process and proportion of water going through interception and transpiration and evaporation, you are exercising a water right. This water right is considered along with all the other water rights, in the legal morass of water rights law. However this kind of water use can be evaluated outside the stream diversion and groundwater pumping water rights that exacerbate our summer base stream flow.

If we change this model, to where a portion of surface stormwater has a different legal status as water, farmers can provide a public service by capturing storing and using water in surface catchment. Right now, most bureaucratic systems are designed to limit this practice. This is a huge opportunity for permaculture design to reform water management practices, and thereby increase scale and fluidity and subsidy for permaculture installations.

This reform will require permaculturists to become fluent in basin hydrologic analysis and bureaucratese, to create basin scale water planning analyses, that allow farmers and their allies to efficiently provide this service, and be compensated by the forest clearing public for doing so.

I think the "news to use" is cool. I think the challenge for us living in communities and on the landscape is to connect these concepts both to site management, and to how we collectively create the rule systems and economic feedback loops that drive site management in our communities.

In other words, either we "up our game" or the bastards are going to ruin it all.

Previous depressing conversation about frakking ... definitely, ruin it all is a distinct possibility. Or at least, the portion of the planet's surface that can be considered habitable by humans diminishes when rainwater, groundwater, and subsurface waters are all rendered less available or more toxic.

I definitely noticed the frost-collecting cloud forest aspect of our woodlands this winter, when actual snow and precipitation has been at a scary low / almost entirely absent the first half of the winter.
The climate geeks are speculating about whether we can expect more of this type of weird winter weather systems that just squat in one place for weeks, rather than the skirling alternations and briefer cold snaps of recent history.
Not something I like to think about - the possibility of annual precipitation that differs by 100% or 150% from the "average," instead of just a few inches (30-50%), is pretty scary.

But trees are definitely awesome.
The shape that snowflakes make by themselves due to certain points' preferential accumulation of moisture, our conifers seem to emulate for deliberate (evolved) entrapment of moisture and other useful atmospheric gases.
I still wonder about the details of how they "decide" to be deciduous or not.. what's the energy benefit to dropping leaves for the winter vs. retaining them? Larch especially.
What are the cues that let sometimes-evergreen and sometimes-deciduous trees decide?

Are most areas of the world prone to wet winters and dry summers like our Western states, or are we an anomaly?
Is there anything we could potentially do to increase summer rainfall, or extend the frost-free growing season into the wetter spring and fall?

How reliable is this data he's citing, with the proportions of rainfall and water processing? It all sounds plausible, but the one little graph of data that he offers from a particular Australian site is widely variable, and pretty scanty.
Also, the Scandinavian data about wooded hills "only" 9,500 feet tall seems like it might not apply directly to a little shelterbelt that is only 30 to 100 feet tall. Might have been the hills, more than the woods, affecting the rain. Our hills do the same thing, for sure, but so do mountains above the treeline; lenticular clouds even without rain, and rain and mist-deposition definitely more abundant on the weather side of mountains. On the lee side, we have 'rain shadows,' and I've seen this effect even for fairly small hills, or from one side to the other of foothills (e.g. 1000 feet tall or so, along the valleys from OR/WA to MT). Sometimes you can see tree patterns at certain times of year, just like you do in valleys or washes, indicating significant weather differences from west-facing to east-facing hills, or north-to-south.

I suspect the height of the weather systems you want to 'catch' is a big factor too.
In areas where the cloud cover has 'lifted off,' or like at the edges of the Sahara where there is not enough moisture or labor available for planted trees to survive, there are intermediate steps to reafforestation that seem pretty critical, technically, and sometimes different from place to place.

In general, reforesting and learning to live in forested areas seems pretty obviously beneficial.

Learning to make a living amongst intact trees seems to be a critical step. If people can't learn to thrive and to credit the trees with their benefits; or to angrily protect the trees the way they currently protect their right to build burn-piles or clear gardens .... how do we get there?
I remember the story about that primitive coffee plant that had to be triple-fenced to keep people from stripping off a piece of it for personal luck; the locals realized it was special, but don't have any concept that it's most special if it remains intact and alive.
By contrast, you get very old groves... where....
- Sacred: where people developed a sense of them as sacred, e.g. NW cedars, Indian sacred groves. Western civilization has a long history of felling sacred groves and demonizing people who venerate them. There's some evidence that India's sacred groves serve as a biological reserve; in times of severe famine or drought, they may be opened to the neighborhood for fodder by special decree, but ordinarily are kept protected from use and abuse.
- Private or privileged: where societies reserved specific forests to a privileged class, purpose, or contract; the 300-year-old English oak forests purpose-grown by contract for specific ships or collegiate halls, for example. Widespread European practice of reserving the game (wildlife) of the forest for nobility to hunt; presumably not only poachers but clear-cutters would have been prosecuted for interfering with the hunt.
- Vast: where societies remain small enough, or mobile enough, or humble enough, not to have the appetite or means to destroy forests faster than they arise (almost everywhere, with the exception of European, Chinese, Middle Eastern, and specific island periods of deforestation)
- Inclement: where cold winters, steep terrain, or other inaccessibility limits population compared to nearby areas (east cascades vs. west coast / I-5 corridor).

I note increased deforestation:
- economic / population boom: in Europe in the industrial and population booms following the Black Plagues; where fossil fuels or industrial ambitions drive demand up and prices down; where economics favors mechanized short-term harvest by distant interests rather than long-term management by local interests.
- settlements: around villages that use firewood, including native american villages of settled rather than nomadic peoples; and around villages that use timber for building, shipping, and other industries
- empires: where monumental architecture, political ambitions, and distant management leads to large-scale mobilization of timber-eaters
- annual agriculture: permanent deforestation in many climates must be maintained over years or decades before tree seeds and regrowth are thoroughly suppressed; tillage agriculture using shade-intolerant crops is one way to accomplish this.
- fires, volcanic eruptions: esp. where poor management leaves forests vulnerable to large-scale wildfires (less permanent than the above; forests re-establish with or without much help).
- stressed edges of existing deserts; arid and semi-arid regions.

Our own lifestyle choices:
For example, we located a building in the spot with adequate road access where we had to remove the least number of established trees, even though it's not the passive-solar aspect I preferred.
The frost-shelter ideas, and the solar possibilities using the roof of the building, makes me happier with this choice.
In general, the idea of 'settling' a site still seems to involve finding or clearing sunny spots for annual gardening. Even though our area is hardly sun-limited for planting.
Shady gardening, and shade-preserving industries (like heating methods that don't require either large firewood harvests or massive solar exposure) seem like important areas for development and research.

Thanks for the links, will check them out.

-Erica W

I still wonder about the details of how they "decide" to be deciduous or not.. what's the energy benefit to dropping leaves for the winter vs. retaining them? Larch especially.
What are the cues that let sometimes-evergreen and sometimes-deciduous trees decide?

The best stories are heard were told between two elders... Linda Brubaker, and Philip Grime. Linda told me that it had to do with when resources were available. In our climate, much of the photosynthetic opportunity (simultaneous presence of light and soil moisture) occurs in the shoulder seasons. This gives a tree with leaves already unfurled a head start over some poor bloke in the cold with proto-leaves buried in buds.

Grime approached it from a nutrient perspective. A certain proportion of nutrients cannot be pulled back from the leaf before senescence. If nutrients are scarce and tightly cycled (as in an old forest) to make a leaf, and only use it for 9 months and then discard it, is a sloppy and dangerous way to live. Far better to build a conservative but durable leaf with two or three years of function, before that little nutrient packet is reluctantly let go to the litter layer. Even better to have new leaves ready to start pulling the first flush of water and whatever nutrient packets have been left lying around in the cold months.

Larch if I recall is a early succession species, shade intolerant, and often indicating fire. Perhaps following on the death partial immolation of its predecessors, it is less concerned with nutrients. I suspect your new home is all about fire... particularly in those drier than usual years. I won't bother encouraging you to get fire training .

In the brief time that I actually collected field vegetation data on the east-side (I think it was 2 days...) We found clear shift in species composition based on solar aspect, with species typical of wetter sites on shadier slopes at the same elevation.