Hydraulic Descent

An Ecosystem's Tool for Filling Vast Underground Reservoirs

The above picture shows a pristine scene from a sink hole in a clean healthy environment, probably some southeastern Asian rainforest where monsoonal rains are emptying into a sink hole in some limestone underground cave network. Beautiful yes. Most efficient way Nature has programmed for getting water into it's subsoil layers, No! Continuing along the same subject line of the brilliant purpose driven mechanism schematics & blueprints encoded into the natural world's health and maintenance information driven tools of 'Hydraulic Lift & Redistribution' , there is yet another one of those terminologies closely associated with those terms and it is called 'Hydraulic Descent'. There seems to be less public info on this fantastic phenomena outside of the usual hidden info, with the exception of privilege found only within the scientific researcher's world.  Joe/Jane Gardener/Landscaper/Ecosystem Restoration Volunteer as usual has very little in the way of this amazing info to not only help them understand the basics of how vegetative systems work, but how to use such information in terms of practical applications in their organic garden, urban landscape or ecosystem restoration projects. And I highly doubt that many nature volunteers who donate time to such restoration projects actually know and understand the deeper mechanisms and forces which run, work and function, other than their own personal "I'm a green loving eco person and I love Nature things, so I'm doing my part as a volunteer." That's certainly a great motivation and attitude, but more is needed to actually make it a part of you. Learning how nature really works is a great enhancer that will always be imprinted on your mind.

When I was a kid in the 1960s, I was in a number of nature conservation programs and clubs like something called "Indian Guides" , Summer Nature Kamps up in the mountains and of course one of the most popular Groups of the times, the Boy Scouts of America. These organizations today are either extinct or heading that way as young minds are being trained and entertained by the modern worlds electronics technology booms. Especially in the Industrialized Technologically Advanced Countries are children less interested in nature(anything outdoors) than at anytime before, In times past it was always the norm for young boys to be curious about the natural world around them. Remember the old time favourite description of boys being "Sticks and Snails and Puppy Dog Tails" ? If updated today it may read something like "Cellphones, Dames and Internet Games".  Most young people don't have a real life in the outdoors world anymore and the 3rd world developing Nations are catching up with their industrialized cousin counterparts.

In the middle 1960s, I remember being either on a school field trip or Boy Scouts outing and listening to a Forest Ranger explain how important forests were to our environment. He said something that at the time didn't seem to make much sense, or rather no doubt because of my ignorance I couldn't relate to it at the time. But today with newer discoveries and my own personal deeper appreciation it makes a ton of sense. He said that healthy old growth tree and shrub forested slopes of mountains, hills and valleys were better water reservoirs than any of those concrete Dams built by humans to hold back seasonal rainfall in some remote valley outside the city. At the time and even many years later I had always assumed water percolating into the ground filling the water table was simply a matter of rainfall eventually saturating it's way all by itself through the soil to eventually after some decades later make it's way to the deep underground Aquifers. Part of that is true, water certainly does saturate the earth and percolate downwards, but under the best circumstances it requires the perfect soil structure to do so efficiently. Sandy loam soils are great soils, yet how does water get through clay, hardpan soils or even down past bedrocks ?

The answer of course is certain plants found in any ecosystem around the globe who we've briefly mentioned in the previous post as having the amazing ability to bring water from deeper layers of the earth and share it with their plant friends around them through the amazing "Mycorrhizal Networking Grid". But how many of you knew that these same plants have the ability to reverse this hydrological cycle and absorb the saturated soil on the surface during rainy seasons and actually pump it into the deeper subsoil layers ? How many really knew that not only can they perform this task, but even do so when they are in their winter/rainy season dormancy sleep-like state ? It's true and that is what the phenomena scientist's now call "Hydraulic Descent". But again, there still is some limited info on this for the public benefit. Let me take the example of the southwestern USA desert Mesquite Tree (Prosopis). For any readers from Asia, Africa, Australia or South America, you will likely identify with other familiar trees like Acacia and so forth which accomplish these same tasks on subsoil water injection.

Image - Johnathan DuHamel - Arizona Daily Independent

Velvet Mesquite (Prosopis velutina)

Here is a link to an article written on the subject of not only 'Hydraulic Lift & Redistribution' but also the observance of the third phenomena of 'Hydraulic Descent' from the dormant desert tree of Velvet Mesquite (Prosopis velutina) (As a special mental note for those of other parts of the world, substitute Acacia when reading the effect of this phenomena)

Blackwell Publishing, Ltd. - "Hydraulic redistribution by a dominant, warm-desert phreatophyte: seasonal patterns and response to precipitation pulses"

Functional Ecology 2004

While referring to the already understood phenomena of 'Hydraulic Lift & Redistribution' here is a quote of the article in the Discussion section where they make special note of the  rainy season dormancy state where the mechanical function of "Hydraulic Descent" is not only acknowledged, but it's possible important implications and importance to the ecosystem are alluded to, though more research is recommended.

Here is the quote:

"After adjusting for differences in sapwood area among the tap-roots of the three trees, maximum rates of reverse flow (l day−1) in the two trees instrumented during the dormant period were 69 and 73% of the maximum nightly rate of reverse flow observed in the tap-root of a third tree during the summer, while nocturnal reverse flow in the tap-root of the third tree was 25–50% of daytime positive flow during transpiration (cluster not shown). Based on these observations, 3–6 days’ reverse flow during the dormant season potentially could supply the tap-root with enough moisture to meet the transpiration for 1 day during the growing season. We caution against strict conclusions based on a few individual trees. Nevertheless, given that crown dormancy in Prosopis velutina at this site typically lasts about 5 months, hydraulic descent during wet winters could supply the tap-root with several days, or even several weeks, of water for growing-season consumption as long as a water-potential gradient is maintained within the root zone."

"The relative importance of hydraulic descent to plant water balance depends on the fate of shallow soil water if it is not otherwise redistributed by the root system. Soil water from winter precipitation apparently does not recharge deep soil layers along the alluvial river terrace (Scott et al. 2004), nor at other upland sites in this region (Scott et al. 2000). Thus much of the water that remains in shallow soil layers is either taken up early in the growing season by co-occurring shallow-rooted plants such as the perennial tussock grass Sporobolus wrightii, or is potentially lost to evaporation, as potential evapotranspiration during the winter and early spring remains relatively high in semiarid climates. The ability to ‘bank’ water during winter dormancy for later consumption presents a win–win scenario for deep rooted plants, as there is a very small carbon investment to maintain the fine-root systems that act as conduits for redistribution during winter dormancy (Widen & Majdi 2001; Burton et al. 2002). Nevertheless, the significance of hydraulic descent to the water balance of mature mesquite plants in floodplain ecosystems is an open question, as mature plants have access to groundwater throughout the growing season (Scott et al. 2003). Fig. 5. (a) Total daily nocturnal sap flow of the stem, taproot and lateral root of Tree 3 calculated from half-hourly measurements from 20.00 h to 05.30 h during the 2002 growing season. Negative values represent reverse flow (away from the crown). (b) Daily precipitation totals (mm day−1) at the field site during the study. Fig. 6. Relative change in soil-water content after initial measurements on 17 June 2002. Measurements were conducted with cross-borehole ground-penetrating radar. Values are the mean from two adjacent vertical transects." 

K. R. Hultine et al. © 2004 British Ecological Society, Functional Ecology

Dormant-season hydraulic descent may play a much greater role in the water balance of mesquite growing in upland habitats where groundwater is not available within the rooting zone, or in young plants in the floodplain that have not yet grown roots into groundwater.

During years of little or no winter precipitation, the balance of redistribution is towards the upper soil layers (hydraulic lift). Hydraulic lift during extended periods of the dormant season provides water storage in the upper soil layers that can be rapidly extracted during spring leaf flush, as the upper soil layers generally contain the highest root-length densities (Jackson et al. 1996). However much of the water that is deposited from deep soil layers to shallow soils may be lost to evapotranspiration before leaf flush, or to other co-occurring plants. Further work is needed to establish a clear connection between dormant-season hydraulic lift and whole-plant water balance.

Regardless of its role in plant and ecosystem water balance, dormant-season hydraulic redistribution has several potentially important implications for plant nutrient balance (Richards & Caldwell 1987). Mineral nutrients are generally most abundant in the upper soil layers. However, the early growing season in most of the south-western USA is characterized by warm daytime temperatures with little or no precipitation until the onset of the monsoon (usually mid-July). For P. velutina trees at our field site, this represents between 80 and 120 days between spring leaf flush and the onset of the monsoon. Thus the mobility of nutrients in the dry shallow soils is potentially low before the monsoon, and diffusion to roots is inhibited. Hydraulic lift during the dormant season can prolong the life span of fine roots and micro-organisms and thereby enhance nutrient ion mobility and uptake during the dry periods of the growing season. Likewise, the dormant-season transfer of mineral nutrients with hydraulic descent to deeper soil layers can potentially smooth the spatial heterogeneity of nutrients, and therefore, enhance plant nutrient uptake during the early growing season when water extraction is primarily from deep soils (Emerman 1996; Burgess et al. 2001a). 

For plant roots to redistribute water between soil layers, they must maintain axial (xylem) hydraulic conductivity (Kx). In many regions xylem conduits in above-ground tissues typically become dysfunctional during the winter due to freeze–thaw cavitation (Cochard & Tyree 1990; Sperry 1993; Pockman & Sperry 1997). Conversely, xylem conduits in roots may not completely embolize where soils insulate roots from freezing temperatures. 

In the present study, P. velutina roots in the upper 50 cm of soil maintained 35% of maximum conductivity during winter, and 70% during summer before the onset of the monsoon (data unpublished). The relatively high xylem conductivities in winter are not surprising considering soil temperatures at 15 cm never reached freezing, despite the fact that minimum air temperatures at mid-canopy reached −15 °C during the winter. Prosopis velutina roots at the site are rarely found near the soil surface above 15 cm depth, particularly in the intercanopy spaces where high temperatures in the upper top few centimetres of soil during the growing season are lethal to living root tissues. 

Soil moisture levels in deep soil layers (−1·5 to −9·5 m) increased during the monsoon. Observed soil moisture changes were probably due to hydraulic redistribution; moisture throughout the vertical transect increased 318 mm between 17 June and 25 September (DOY 168–268). Calculated values of capillary rise from groundwater fluctuations and direct infiltration from summer precipitation could account for only 45 mm of moisture within the GPR profile (R.L.S. and co-workers, unpublished data). Even if all precipitation inputs (248 mm) were transferred below −1·5 m (highly unlikely), the combined inputs from capillary rise and direct infiltration still would not explain the observed change in moisture in the deep soil layers. Moreover, Scott et al. (2004), using profiles of soil moisture probes in the upper 1·0 m of soil at this site, report that infiltration of precipitation below 0·5 m rarely occurred during 2001 and 2002. Only one infiltration event was observed below 0·5 m, and this resulted in only a 2% change in soil moisture content at 0·7 m. 

The above argument requires reasonably accurate estimates of vadose zone θ. Although a site-specific calibration of apparent dielectric constant vs soil moisture content has not yet been established, Alumbaugh et al. (2002) argued that the precision error for this type of cross-borehole GPR measurement is ≈0·5% in moisture content estimation. Therefore the changes seen in the profile are arguably significant. Water content changes between ≈5·75–7·25 m depth could not be estimated as there was too much attenuation of the waveform for an accurate estimation of the travel time. At this depth interval, well logs reveal a thick layer of clayey material.

After the onset of the monsoon, nocturnal reverse flow in the tap-root was typically lower in magnitude than its daytime flow towards the stem, suggesting that the water content of deep soil layers should still be depleted (although at a lower rate) after precipitation wetted the upper soil layers. However, water content increased during the monsoon in the deep soil layers despite the absence of direct recharge of precipitation below 1 m. It is likely that lateral roots, fine roots and root hairs extend from the tap-root in relatively dry soil layers as well as the shallow groundwater table or capillary fringe. Thus the bulk of daytime positive flow in the tap-root was probably derived from the extraction of groundwater, and nocturnal reverse flow was a consequence of redistribution to the dry soil layers above the water table. Unfortunately, measurements of root sap flow alone cannot detect the source or fate of water that moves through woody roots. There were substantial differences between Trees 1 and 2 in the pattern and direction of root sap flow during the dormant season prior to irrigation. Sap in the tap-root

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Here is yet another article specifically dealing with the exact same mechanisms referenced above, with the quote 

Abstract: & Link:

 http://adsabs.harvard.edu/abs/2003AGUFM.B51A..06S

The Ecohydrological Interactions Between Mesquite and its Water Sources

Abstract:

"Velvet mesquite (Prosopis velutina), a native woody plant to southern Arizona, USA and Sonora, Mexico, has successfully expanded its range and encroached into both upland and riparian grasslands during the 20th century. In this study, we examined the interactions between mesquite and its water sources in order to determine how the trees responded to moisture availability. This study took place in a riparian area and because the trees had access to both deep groundwater and surface water, these interactions resulted in important hydrological and ecological consequences. Surprisingly, we found that the mesquite responded to and even manipulated both surface and deep soil moisture even though they apparently had access to a stable groundwater source throughout the growing season. During dry season nights, observations of root sap flow showed that the trees moved moisture upwards in the taproot and out into the surface soils in lateral roots. As a consequence of this "hydraulic lift", diurnal soil respiration measurements showed that the soil microbes were stimulated following the nocturnal release of moisture into the near-surface regions. During rainy season nights, there was sap flow movement toward the tree in the surface lateral roots and downwards in the taproot indicating "hydraulic descent". Borehole GPR measurements of the deeper, 2 - 10 m, vadose zone moisture content increased apparently as a result of this tree-facilitated water movement. Also, hydraulic descent influenced water table elevations indicating direct groundwater recharge via plant pathways."

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Now while acknowledging the benefits of reverse flow descent into the deeper layers of the Earth during it's period of cold winter rainy season dormancy, they advise caution as they do not understand the full impact of this on the environment without further studies. Keep in mind that this particular study was in 2004. Today much more has been learned since. We also lack many of the old growth  Mesquite Bosques (Ancient Old Growth Mesquite Forests) that were originally observed by the early pioneers who conquered the West and brought in European Agricultural practices which ruined the pristine landscape. In many ways, we can only assume what and how such systems must have functioned and maintained like in the good old days. Though there are very few old growth Mesquite examples today, can you imagine the potential 'Hydraulic Descent' capabilities of an old growth tree like this South American Huarango tree pictured along side men to give it scale in my previous article:

Now that's what I would call a natural industrial sized pump as opposed to the average sized Mesquite which by comparison would be nothing more than a Honda Generator by comparison. Below I'm going to close with a large linked list for online viewing regarding this natural phenomena. As per the norm, the articles are not meant for Joe/Jane Q-Public, but rather for other researchers. Nevertheless, they are condensed important resources collected for the benefit of others. Hopefully my story line above gives some sensibility to an interesting natural mechanized phenomena. I'm also adding links to African Acacia tree studies dealing with such species as Acacia tortilis.

Further References:

Influence of soil texture on hydraulic properties and water relations of a dominant warm-desert phreatophyte 

New study finds 400,000 farmers in southern Africa using 'fertilizer trees' to improve food security As World Food Day puts focus on food crises, research shows potential for rapid, radical transformation on smallholder farms

Impact of Fertilizer Tree Fallows in Eastern Zambia:  A study on Impacts of Agroforestry

Quantifying Riparian Evapotranspiration: - "The Water-Banking Mesquites"

http://ddr.nal.usda.gov/bitstream/10113/21015/1/IND44045056.pdf

Ludwig F. (2001). Tree-grass interaction on an East African Savanna: The effects of competition, facilitation and hydraulic lift.

Hydraulic redistribution by deep roots of a Chihuahuan Desert phreatophyte

 Modeling Water and Nutrient Transport through the Soil-Root-Canopy Continuum: Explicitly Linking the Below- and Above-Ground Processes

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Some Conclusions: 

So what do we get from all of this other than some often times academic observational takes by some University researchers on one of their field trips to study how nature works ? 

Quite simply this. Humans for centuries have in ignorance bastardized our planet's natural resources. The have often taken and never put back. Rather than work with nature, they have insisted they knew better than nature and bulled ahead with their own purpose driven goals often motivated by greed and selfishness. Our present generation is paying the price for our ancestors ignorance and stupidity. 

Let us see what we've learned about Hydraulic 'Lift' - 'Redistribution' & 'Descent' which are three major components of the plant world that are brilliantly engineered into the system for constant recycling & renewal. Human science-based technologies when it comes to managing water is to straight channel it on it's way to the sea. Straight channeling also allows for that ever important commercial trafficking of goods from various parts of the earth to other parts to be used in an economic philosophy where consume, consume, consume is the only way our world's global economy is able to survive. Any disruption of the status-quo causes chaos to enter the economic system and sends vibrational upset across the globe which results in some countries civil unrest. So nothing changes and still the environment pays the cost, which eventual leads to our wallet.

It is hoped that readers here will understand that the Earth's Network is engineered to slow water down. The idea when it comes to technology is that once that raindrop hits the Earth, we want to slow it down before it goes out to sea. It's not the aim or goal to prevent it from doing so, but merely to slow down the process. Viktor Schauberger had much to say about ecological river custodialship. He saw the way nature handled water in streams and rivers by a slowed down process of allowing water to meander back and forth in a zig-zagged cris-cross motion aided by rocks, log jam debris, streamside vegetation, etc. The benefit is that the water table rises and saturates the subsoils in the surrounding landscape. 

The cooperative association of the fungal networks assisting the hydrological processes carried on by the plant's internal structure which employ this hydrological functions in ant plant community system for which hydration of the deeper layers is possible even under the poorest soil structural conditions. Science based Reservoir systems want to halt water and store it in inundated valleys which no longer support life and have long ago replaced it. Nature's way was to pump it deep inside the Earth and thereafter allow slow release of that stored water through springs and seeps which then turn into streams, then to rivers and finally making their way to the sea to start the cycle all over again, but in an orderly non-destructive fashion. All the while humans could be allowed to draw off some of this precious gift from wells and other sources, yet using it responsibly and efficiently. 

From the patterns of historical behavior, it is clear that human governments and big business institutions (this includes much of conventional old school thinking of science) will never get the sense of the important discoveries and benefits that some responsible researchers are bringing to light. It is mostly hoped that individual readers here will share the positive discoveries and make their own personal practical applications and share them with others. In a way, it's a sort or type of positive genomic imprinting or educational epigenetics that can be passed on to future generations. We unfortunately don't live in that kind of world presently where positives push forward without the proverbial price tag attached to it. I'm not so blind as to believe that humans will necessarily do this on their own. At any one time in the history of mankind's existence on this globe, there has only been a small minority(when compared to the globe's entire population) who have ever done the right thing in any one generation. But humans have accelerated things to a point where something has to change. 

Though this particular blog is not necessarily pushing a spiritual viewpoint, there are never the less some scriptural references which apply here. For example, on the point of genomic imprinting, most of the research shows the consequences of negative experiences lived by one generation can have negative impacts on descendants even generations removed. If that is true, then a reverse of what this scripture says could be true also if we work at applying the positives in our lives. It goes something like this:

Jeremiah 31:29 (NW)

“In those days they will no more say, ‘The fathers were the ones that ate the unripe grape, but it was the teeth of the sons that got set on edge*.’

* footnote: got blunted or dulled

Here's a cross reference scripture - Lamentations 5:7 (NW) 

"Our forefathers are the ones that have sinned. They are no more. As for us, it is their errors that we have had to bear."

Those scriptural references have great practical application not only when it comes to living life properly when it comes to the way we treat our fellow man, neighbour, stranger, child, parent, husband or wife, but also the responsible or irresponsible choices we make when it comes to proper or improper decision making when it comes to custodianship of our wonderful planet earth. If it's true that negatives can have great impacts on later generations, then most certainly positives can have a healing effect to reverse those negatives. It's up to all individuals to make the right choices and decisions in their personal lives. There are consequences to present generations making bad choices on an ecological level which effect future generations. We all now experience the stupid choices and decision making by the early European pioneers who by means of ambitious conquering of other lands in Empire building and it's indigenous peoples and exploiting their natural resources for their own economic greed have left all of us with a number of badly broken down functional systems, some being destroyed altogether. Since 1990 with the failure and fall of communism, those country's various attempts at creating their own capitalistic machines for wealth infusion into their economies and promoting a consumerism mindset, have almost surely doubled and tripled the rapid search and exploitation of Earth's raw materials. Various charts & graphs of historic deforestation, CO2s, Temps, etc are a testament to this truth. Keep one thing in mind, the rise in destruction of forests and other various vegetative ecosystems around the globe ALWAYS precedes the rise in other damaging components referenced on those climate charts. Incredible, NONE of the climate scientists ever bring this to the public's attention. Question now is, WHY ?

Can You Imagine the restoration possibilities with recognizing a Forest Mechanism ?   

Future articles will be posted on the hydrological processes mentioned as I will news update from time to time.

 Thanks for reading.