Tree root depths

Trees. Phreatophyte roots will tend to extend deeper than other tree roots. Phreatophytic tree roots can reach as deep as 24 m (80 ft). Two examples are mesquite tap roots, which range from 12 to 30 m (40 to 100 ft), and river birch tap roots, which go to a depth of 27 to 30 m (90 to 100 ft). 

There are many types of roots, including thick fibrous, deep tap, shallow, and tubers, all in one plant community. Some roots explore the soil to significant depth (i.e., as much as 250 cm deep), while others are shallow (i.e., only 25 cm deep). Different rooting depths are found in all plant types grasses, legumes, shrubs, and trees. Each root type will contribute its own unique exudates and characteristics to its unique volume of soil and the associated soil solution. 

The significant investment made in superficial roots by trees of Amazon forests is a clear indication of the importance of nutrient recycling from organic pools at the soil surface. However, research from the central and eastern Amazon has shown that trees in seasonally dry forests also have roots extending to at least 18 m depth (Nepstad et al. 1994). While the main function of these roots appears to be the uptake of deep soil water and groundwater, there is also potential for these roots to access deeper nutrient pools in the soil column. Nepstad et al. (this volume) elaborate on this issue by demonstrating that secondary forests growing in the eastern Amazon have P and K nutrient needs that cannot be satisfied by available stocks in the... 

Mobilization of water from the soil is closely related to root depth and root density in each layer of soil. Fine roots of active B. brizantha pastures, established in deeply weathered clayey soils in eastern Amazonia, reach depths of 8 m or more (Nepstad et al. 1994). In abandoned pastures (50% B. humidicola and P. maximum cover and 50% invading shrubs and small trees), fine roots ( < 1 mm in diameter) were found at depths of 12 m (Nepstad et al. 1994). Fine-root biomass in the superficial soil layers of an active pasture in Paragominas, eastern Amazonia, was 3 times higher than that found in an adjacent primary forest area. Fine root biomass in the active pasture decreased by a factor of 100 between the surface and 6 m depth. In an abandoned pasture area, the distribution pattern of fine-root biomass was similar to that observed in the deeper soil layers of the forest ecosystem. This pattern is associated with the fine roots of the existing dicotyledonous invading species. 

Figure 2 Deep rooting of trees in tropical weathering (in Hawaii). The depth of the roots, based on the figure for scale, is 7 m (photo by C. Bowser).

The secondary fine-crystal and amorphons qnartz material is deposited around living fine roots of trees, forming silicon powder as the spots, nets or bunch at the depth of 20-80-100 cm (Fignre 37)... 

Consider, for definiteness, a set of otherwise identical lowest-level components of a system, so that the hierarchy is a tree of constant depth. Since we assume that the components are all identical, the only distinction among the various nodes of the hierarchy consists of the structure of the subtrees. Now suppose we have a tree T that consists of /3 subtrees branching out from the root at the top level. We need to determine the number of different interactions that can occur on each level, independent of the structure of each subtree i.e. isomorphic copies of trees do not contribute to our count. We therefore need to find the number of nonisomorphic subtrees. We can do this recursively. 

These maximum depths are not likely to occur in most cases. The effective depth for phytoremediation using most nonwoody plant species is likely to be only 30 or 61 cm (1 or 2 ft). Most accumulators have root zones limited to the top foot of soil, which restricts the use of phytoextraction to shallow soils. The effective depth of tree roots is likely to be in the few tens of feet or less, with one optimistic estimate that trees will be useful for extraction of groundwater up to 9 m (30 ft) deep.41-58... 

One way of thinking of this situation is to visualize a game, with a binary tree of depth N as a "board" and k markers or "pieces" (representing locations in a program scheme). Any marker can be placed on a leaf. Each node is either a leaf or has two "sons". If both sons of a node are covered with markers, then one marker can be moved up to that node and markers removed from the two sons. The object is to eventually place a marker on the root, using as few markers as possible. How many markers are needed in the worst case ... 

The answer is that if the tree is a full binary tree of depth N, then N+l markers are necessary and sufficient. The proof is by induction on N. The case N - 1 is obvious, for then there are just two leaves and both must be covered before the root can be covered. Suppose this is true for depth N-l. The root has two sons each of which can be regarded as the root of a full binary subtree of depth N-l call these nodes n and n. The root can be covered when and only... 

It should be stressed that PROFILE needs the nutrient uptake limited to PROFlLE-acceptable layer (0.5-1 m depth) for simplicity, whereas the real nutrient uptake takes place down to the 3-5-7-10 m depth corresponding to the distribution of tree roots. So, the nutrient uptake in a PROFlLE-acceptable layer is always less than the whole nutrient uptake. This might be a source of uncertainty in critical load calculations. 

The latest development in the field of citrus pests involves nematodes. The citrus nematode (Tylenchulus semipenetrans Cobb) has been known for many years in California, Florida, and Argentina and probably exists in most other areas. Whether it could do much damage to healthy citrus trees is a moot point. In recent years, however, more and more workers in California have been inclined to blame it for poor tree condition and their inability to replant citrus with citrus satisfactorily. The idea that nematodes are of importance has been stimulated by the finding in Florida that the cause of spreading decline is the burrowing nematode, Radopholus similis (Cobb) Thorne. This nematode, hitherto unknown as a citrus pest, destroys the feeder roots particularly below a depth of about 2 feet and has been found to a depth of 14 feet. In the course of this work a number of other nematodes, hitherto unreported on citrus, have been found and at least some of these appear to damage citrus roots. The indications are that nematodes are going to be one of the real citrus problems of the future. 

The nematode problem in citrus is very different from the problem in vegetables and other annuals, where the soil can be fumigated between crops. The final solution of this problem will require either a resistant rootstock or a treatment which will tip the balance in favor of the tree. This latter might be either a systemic which will move downward in the tree and make the roots either poisonous or distasteful to nematodes or a soil treatment which will penetrate to great depths and destroy the nematodes without seriously injuring the trees. Either type of control is a big order. Standard known rootstocks are all attacked and an entirely new rootstock might require 25 years to test thoroughly, while in the chemical field there is no precedent in other crops. 

Biogeochemistry has been developed for uranium exploration during the 1980s (Dunn 2007). For example, spruce twigs indicate that tree roots can extract anomalous U from ground water and reflect deposits at 300m depth. 

Method A involves a deductive search for all credible ways an occurrence could arise using timeline construction and a simplified fault tree approach. It can be viewed as an integrated method for systematically searching for all underlying root causes. The structured framework helps the investigator to keep on track, reach sufficient depth, and not stop prematurely at the symptoms or apparent causes. 

There are a number of mechanisms of selectivity that are found in the herbicides that are used today. Diuron is used as a residual broad-spectrum herbicide in a number of situations such as plantations and forests. It is, however, phytotoxic to most perennial species and the selectivity shown by the established trees is because the compound does not move within the soil profile to a depth where established tree roots will absorb the compound in sufficiently high concentrations to exert an effect. This is selectivity by placement. 

Using the depth first search with backtracking, we obtain the optimal solution in node 5 as shown in Figure 5.2, and we need to consider 6 nodes plus the root node of the tree. 

Rowe, E.C. Hairiah, K. Giller, K.E. van Noordwijk, M. and G. Cadisch (1999) Testing the safety-net role of hedgerow tree roots by 15N placement at different soil depths.- Agroforestry Systems 43, 81-93. 

The use of soil tillage equipment before planting depends on the results of the soil tests. If there are layers in the soil which are difficult for the roots of the fruit trees to penetrate, the soil needs to be loosened and then enriched with green manure. The depth of tillage is critical for successful loosening of the soil and should be only slightly (about 5 cm)... 

Fig. 7.4 Aboveground biomass and roots (0-15 cm soil depth) of 3-year-old stands of 4 indigenous tree species Terminalia amazonia, Hieronyma alchomeoides, Albizia guachapele, and Virola koschnyi, grown in pure plots, and a mixture of the 4 species at La Selva Biological Station, Costa Rica.

The availability of scarce plant nutrients in deep soil is only relevant to our understanding of secondary forest nutrient acquisition if plants are able to absorb these nutrients with deeply penetrating root systems. Enticing evidence for such an extensive approach to nutrient acquisition is supported by the distribution of fine-root biomass (diameter = 0-1 mm) in the secondary forest, as compared to that in the neighboring mature forest and active cattle pasture (Fig. 9.2). Fine root biomass to 6 m depth is virtually identical in mature and secondary forests, and is > 10 times greater at depth than in the active cattle pasture. Hence, after 16 years of recovery, some of the trees, lianas and palms of the secondary forest had re-established root systems to at least 6 m depth. 

The recovery of deep soil water uptake in the Paragominas secondary forest was possible because of the re-establishment of deep root systems following pasture abandonment (Fig. 9.2). The root systems of secondary forest trees, vines, and palms rapidly penetrate to at least 8 m depth during the first 15 years of regrowth. We identified one third as many morphos-pecies of roots to 8 m depth in the secondary forest as in the neighboring mature forest, with a prevalence of vine and palm roots in the secondary forest. The vine Davilla kunthii, for example, penetrates to at least 8 m depth by the time its stem has attained 1 m height (Restom 1998). Vines in... 

However, even in such areas tree roots can penetrate great distances (25-30 ft (lft = 0.3048 m)) below the surface (Nepstad et al., 1994) and reach bedrock (see also Figure 2). If there is a change in the plant cover due to drought, flood, disease, storms, or forest fires, so that the depth of root penetration changes, rate of weathering in low relief areas can change. Also, there... 

Soil samples are collected at depths of at least 40-50 cm and below any stone debris, tree roots and the cultivated layer. Samples are air dried, and then sieved and bagged immediately. Mechanical grinding must be avoided or Hg may be thermally released during the resulting heating. Prolonged storage of samples may result in loss of Hg by vaporisation or in sample contamination. 

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