Trees bring rain they say and i believe it is something observable, you grow a lot of trees in some place and you start to get more rain. Water also brings rain, I think both increase the humidity in the air and so the possibility that the humidity will reach saturation point. I wrote to NASA about leaving
land fallow and the potential of bare earth to heat the world whose cooling system is done for and they answered back which is unusual, I write letters no one answers and among other things said that when bit of Florida was drained it rained less, so they thought that changes in the landscape change the clamate.
I wanted to give an explanation to the trees rain factor, so I have broken down the possible advantages they could bring as far as increasing the
local humidity is concerned.
They probably increase air humidity so that when some humid air comes in there is a greater likely hood that the saturation of humidity in the air is such as for it to condense and fall as rain. Mind you a great deal of humidity in the air makes a difference to plants even when it does not rain it reduces their water loss and that of the land both because the air dries the land less and because the plants take up less water from the soil. Humidity on leaves can also form into drops of water and drop off the leaves onto the ground as happens in some canary island where there are always mists because of the winds that come in from the sea and a great deal of the moisture comes in this form.
I speculate that trees absorb humidity from the air through their leaves so if the air is more humid the leaves of trees can get more water than they would be able to from dryer air and if trees take water from the air their leaves absorbing it then leaves will stop the humidity of the locality being lost in the air and hold on to it.
I can’t find much mention of leaves absorbing water. James Churchill book “Survival.” says that if you tie a bag round a sprig of leaves on a tree the water that evaporates from the leaves will be caught in the bag and you can collect it at night and drink it, but he says, don’t leave the bag on all night, the leaves will reabsorb the water!
Foliar feeding would seem to be evidence that leaves absorb water. They use foliar feeding to fertilize crops. Foliar feeding serves when it is not advisable to fertilize the ground, like when the ground is dry and fertilizer applied round roots might burn them, or when you have just planted a plant and the roots aren’t established yet. The leaves take up the nutrients sprayed on when the leaf is wet, when the spray is applied and on dewy nights afterwards, so i suppose they absorb the dew as well as the fertilizer.
Plants like trandescantia or brazil sticks live for ages when you don’t water them, I think they would be good plants to use to find out how much humidity plants can absorb from the air though we need to find out how much humidity the leaves all plants can absorb not just of the ones that are specially good at it.
On trees remediating deserts, they are not the only important factor, a book i like a lot that i think contains a lot of the ideas of that American great ecologist Hugh Hammond Bennett, who wrote the prologue, who says that far too few people think of preserving soils, only those directly involved with soils and even too few farmers think of it. The book said that grass renews soils faster than trees do and as deserts suffer from poor soils as well as too little rain you have to think of how to better their soils as well as of planting trees.
The book was a compilation of articles of anonymous agricultural experts, the one who claimed that grass bettered soil faster than trees and had planted a piece of his land that had been a road with grass and clover to prove the efficiency of small plants to better earth and had also put in currant bushes to feed the fauna.
Another reason plants trees and bushes and herbaceous plants keep things humid is that they and their fallen leaves isolate the ground from the sun.
Trees and bushes shade the ground and grass and dead leaves of trees and bushes isolates the ground grass is the first level isolator of the the soil and it isolates the soil whether grass is green or dry. Grass dries in the dry season of hot countries, to regrow in the wet season. It self mulches in the dry season and as earth. Soil is a good accumulator of heat, it is important to isolate it from the sun if the ground heats less it will heat the air less and less water will evaporate from it the ground and the cooler air and with more humidity, the humidity in the air is more likely to reach saturation point, hot air holds much more moisture than cooler air will, so it is good to have the soil covered with grass be it only dry grass and shaded by bushes and trees.
Tarmac is the best accumulator of heat though.
Plants or fallen or dead leaves on the ground also tap the ground put a lid on it, cover it, making the escape of humidity from the soil harder.
I should think many layers of foliage in the air also hold in the air under them, air that might be more humid than the air surrounding the
wood or undergrowth, unless there is a good breeze.
Any hot currants of rising hot where there are trees or bushes, are likely to hit leaves and cool. I think that leaves must work as the radiator of cars work. Leaves are cool though hot country trees less so having a thicker epidermis, which is to say skin. As leaves are cool even though some are less so than others, leaves and must cool the air.
Also plants are humidifiers though many, dry country plants, shut their stomata at mid day when the water stress get too big. I suppose water stress is when the roots can’t find enough water to replace the water lost in evaporotranspiration. So where there are trees there will be more humidity in the air and a greater likelihood of the water in the air reaching saturation point and raining.
When there are bodies of water swamps and lakes there will also be more water in the air and so more likelihood of the water in the air reaching saturation point and it raining. That is why if you take the water from a wet area to a dry one you may dry the wet area, and end up with have two areas of little rainfall, so the equation, “you have a lot of water give it to me,” is not as simple as it seems. Agri rose macaskie.