I live in Tulare County, CA, the top ag county in the world by most measures, where annual rainfall is 9" on a good year (which we haven't had too many of lately). I'm in the process of designing a model food forest for an awesome organization. As a primary strategy, I've envisioned planting key food trees in large (15' diameter), wood-chip mulched circular depressions that will act as watersheds for the tree in the middle. What I'm wondering is whether and which plants could function as "condenser plants." Of course, the hope would be to also stack functions: nurse plant (initially), nutrient/mulch accumulator, food production (human/chicken/wildlife), etc.
Thoughts on this strategy and suitable plants? Thanks
Let us now be clear about how trees affect total precipitation. The case taken is where winds blow inland from an ocean or large lake:
1. The water in the air is that evaporated from the surface of the sea or lake. In contains a few salt particles but is 'clean'. A small proportion may fall as rain (1520%), but most of this water is CONDENSED out of clear night air or fogs by the cool surfaces of leaves (8085%). Of this condensate, 15% evaporates by day and 50% is transpired. The rest enters the groundwater. Thus trees are responsible for more water in streams than the rainfall alone provides.
2. Of the rain that falls, 25% again re-evaporates from crown leaves, and 50% is transpired. This moisture is added to clouds, which are now at least 50% 'tree water'. These clouds travel on inland to rain again. Thus trees may double or multiply rainfall itself by this process, which can be repeated many times over extensive forested plains or foothills.
3. As the air rises inland, the precipitation and condensation increases, and moss forests plus standing cluods may form in mountains, adding considerably to total precipitation and infiltration to the slower slopes and streams.
4. Whenever winds pass over tree lines or forest edges of 12 metres (40 feet) or more in height, Eckman spirals develop, adding 40% or so to rainfall in bands which roughly parallel the tree lines.
5. Within the forest, 40% of the incident air mass may enter and either lose water or be rehumidified.
6. And in every case, rain is more likely to fall as a result of organic particles forming nucleii for condensation, whereas industrial aerosols are too small to cause rain and instead produce dry, cloudy conditions.
Thus, if we clear the forest, what is left but dust?
By this it would seem the greater the overall surface area of leaves in your forest the more water would condense, so any broadleaf will be good.
Where I live is sooo arid that I don't really ever see dew so I don't think any condensation trap method would yield anything at all.
Rebecca, while my climate would NOT be classified as humid for the most part, our winter months do provide dew accumulation on lawns and leaves in the mornings (like now in March) and we're known for having serious fogs during the winter as well. I'm not really sure how late into the spring/summer I can expect this humidity to extend, but I'm sure there's someone in my area I could ask who would know. In my mind, given the fogs and dew, it's a question of whether this strategy can yield more benefits during the winter months than input demands during the periods of long drought.
from wikipedia. "The tree's extremely long needles make a significant contribution to the islands water supply, trapping large amounts of condensation from the moist air coming off the Atlantic with the prevailing north eastern wind (locally called "alisios"). The condensation then drops to the ground and is quickly absorbed by the soil, eventually percolating down to the underground aquifers."
That sounds like the tree to me. One day I will go back and listen to all of those lectures and find the one where he talks about that and I will post back, but for now I recommend that everyone else do that because those lectures are full of extremely valuable information.