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Hillslope Degradation by Trees in Central Kentucky
Abstract and Figures
I am at the age & stage of career where I have to choose my battles, and this is one I don't really have time for. This paper was submitted to Catena in February, 2015, and received two reviews recommending minor revision. A revised version was submitted June 1, 2015, but a third reviewer was strongly critical and Catena’s editor decided to reject it. Some of the referee’s objections & suggestions are reasonable, but for various reasons I am not able or willing to accommodate them. Some are demonstrably off-base—for example, he/she complains some things are missing from the paper that are unquestionably there. Some—well, you can be the judge if you decide to read this, as the reviewer complains that the paper is “quite poorly written, hard to follow,” and “simply a mishmash of various statements.” I don’t think it’s THAT bad, but consider yourself fairly warned. I have cleaned up a
typo or two in formatting the paper for posting, but what you see is pretty much what the 3rd referee didn’t like.
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... The roots inevitably increase in length and girth and split the rocks apart slowly (Matthes-Sears and Larson, 1995). Phillips (2015) showed that about 90% of the examined trees of his study conducted on limestone bedrock hillslopes exhibited evidence of: i) joint widening both horizontally and vertically by root penetration; ii) mechanical displacement of bedrock along bedding planes; and iii) root exposure indicating the removal of material at the tree base (Table 3). Phillips (2016) further explained how the widening of joints can promote chemical weathering in such karst-associated bedrock environments. ...
... Phillips (2016) further explained how the widening of joints can promote chemical weathering in such karst-associated bedrock environments. A combination of root growth in joints, trunk expansion, and the development of basal flares near the tree-ground interface can displace rock fragments both vertically and horizontally (Phillips, 2015). Thus, trees can promote weathering of bedrock and displace mass via root and trunk growth (Gabet and Mudd, 2010;Lutz and Griswold, 1939) (Table 3). ...
... Finally, the infilling of stump holes and trapping of sediments from upslope are distinctive BGIs within rocky hillslopes (Pawlik, 2013;Phillips, 2015;Shouse and Phillips, 2016) as bedrock stream environments have limited potential to display such impacts. Additionally, within hillslope environments, tree growth may enclose (or partly enclose) rock fragments and prevent the downslope movement of sediments until the death of the tree and wood decomposition (Phillips, 2015). ...
The dynamic interactions between fluvial processes and vegetation vary in different environments and are uncertain in bedrock settings. Bedrock streams are much less studied than alluvial in all aspects, and in many respects act in qualitatively different ways. This research seeks to fill this lacuna by studying bedrock streams from a biogeomorphic perspective. It aims to identify the impacts of woody vegetation that may be common to fluvial systems and rocky hillslopes in general, or that may be unique to bedrock channels. A review of the existing literature on biogeomorphology – mostly fluvial and rocky hillslope environments – was carried out, and field examples of biogeomorphic impacts (BGIs) associated with fluvial systems of various bedrock environments were then examined to complement the review. Results indicate that bedrock streams exhibit both shared and highly concentrated BGIs in relation to alluvial streams and rocky hillslopes. Bedrock streams display a bioprotective geomorphic form – root banks (when the root itself forms the stream bank) – which is distinctive, but not exclusive to this setting. On the other hand, shared biogeomorphic impacts with alluvial streams include sediment and wood trapping, and bar and island development and stabilization (i.e. bioconstruction/modification and protection). Shared impacts with rocky hillslopes also include bioprotection, as well as displacement of bedrock due to root and trunk growth, and bedrock mining caused by tree uprooting (i.e. bioweathering and erosion). Two BGI triangles were developed to graphically display these relationships. Finally, this paper concludes that bedrock streams exhibit some BGIs that also occur in either alluvial channels or on rocky hillslopes. Therefore, no BGIs were identified that are absolutely unique to bedrock fluvial environments.
Complex nonlinear dynamics in pedogenesis, and in the interactions among soils, landforms, biota and climate, often results in dynamical instabilities and deterministic chaos. This means that the effects of small disturbances, or of variations in initial conditions, can persist and grow over time, leading to divergent pedogenesis. Where divergent pedogenesis occurs, it results in increasing pedodiversity over time, and to soil variations that are large relative to those of soil forming factors.
Neither divergent or convergent pedogenesis can continue indefinitely and the appearance of either can vary not only with the environmental situation, but also with spatial or temporal scale or intensity of survey. Two phenomena are common in this regard. One is a tendency toward instability and divergence when interactions among Earth surface system components dominate system dynamics, which is often more common in earlier stages of development. As external controls or self-limitations on development of system components come into play, stable, convergent development ensues. The second is a tendency for convergence at a regional (soil landscape or broader) scale, as the range of variation of soil forming factors constrains pedodiversity to a finite set of outcomes. This is coupled with a tendency for divergence to be noted at a more local scale, where pedological variation within the set of possible outcomes is often disproportionately large relative to that of soil forming factors.
: Despite the important functional role of deep roots in withdrawing water during drought, direct measurements of root distribution are very rare in tropical rain forests. The aim of this study was to investigate the root distribution of Entandrophragma cylindricum, a common tree species in the Central African semi-deciduous rain forest, in Ferralsols and Arenosols. We dug two pits to a depth of 6 m in Ferralsols and two pits to a depth of 3 m in Arenosols, close to E. cylindricum trees. The vertical soil profiles were divided into 10 × 10-cm grid cells and the roots counted were distributed in three diameter classes. We fitted a root distribution model to our dataset. We found that vertical root distribution was shallower in Arenosols than in Ferralsols. Root penetration was not stopped even by a Ferralsol with high gravel content in its subsoil. Overall, our measurements showed that 95% of all roots were distributed to depths of between 258 and 564 cm from the soil surface, which is much deeper than
A series of studies claimed that deep root development of plant established in karst regions was facilitated by fractured bedrock beneath the shallow soils; however, bedrock is not a uniform medium for root proliferation. We hypothesized plant species that survived in different karst habitats had some other rooting characteristics rather than deep penetration. To test the hypothesis, coarse root systems of two widely distributed woody species (one tree and one shrub) growing in three typical rocky karst habitats (shallow soil, loose rocky soil and exposed rock) were excavated in karst region of southwest China. Root systems were investigated based on four parameters: maximum rooting depth, maximum radial extent, root tapering pattern and root curvature. In all the three habitats, maximum rooting depths were no deeper than 120 and 40 cm for the tree and shrub species, respectively. Maximum radial extents were extremely large compared with maximum rooting depth, indicating that rooting characteristics were dominated by horizontal extension rather than deep penetration. Roots of both species growing in shallow soil habitat tapered gradually and curved slightly, which was consistent with the specific characteristics of this habitat. On the contrary, roots of the tree species growing in the other two habitats tapered rapidly but curved slightly, while roots of the shrub species tapered gradually but curved strongly. It was speculated that limited depths and rapid tapering rates of the tree roots were likely compensated by their utmost radial extensions, while the shrub species might benefit from its root curvature as the associated root tropisms may increase the ability of root to encounter more water and contribute to potentially high resource absorption efficiency. Our results highlight the importance of taking shallow-rooted species into account in understanding the distribution of natural plant communities and predicting future vegetation dynamics in karst regions.
Light oriented pinnacles (phytokarst) developed on the surface of limestone strata and boulders in cave entrances in Sarawak, are reported. These pinnacles are erosional forms produced by boring and, or, solutional action of red and blue-green algae which colonize the rock surfaces.-from Authors
The impacts on slope stability of Cyclone Bola in 1988 and the February storms in Wanganui-Manawatu in February 2004 provided strong evidence that treeless steepland is very vulnerable to mass wasting during large cyclonic storms whereas forested slopes are relatively resistant to failure. The evidence from numerous studies indicates it is the tree root systems which provide most of the additional resistance. This paper briefly reviews the influence of trees on shallow landslides with most of the emphasis on radiata pine. The relatively rapid development of radiata pine root systems enables this species to provide good soil reinforcement after about 10 years of growth but within a few years after harvesting, most of the root reinforcement is lost. The various approaches that can be adopted to manage forests for soil protection, and identify where the most landslide-vulnerable slopes or parts of slopes are located, are outlined. Modern computer models, in combination with GIS, provide very useful predictions of instability.
Boles of tall trees with large diameters behave as cantilever beams possessing great strength and the capacity for exerting tremendous leverage at the point of support or fulcrum. When trees are uprooted by wind they may move, both vertically and horizontally, rocks having a volume of as much as 50 cu. ft. and a weight of around 4 1/4 tons. Uprooting of trees contributes to downslope movement of the soil and rock mantle and locally may initiate erosion of the gully type. Some of the effects of soil and rock movement by uprooting trees are similar to those resulting from periglacial frost heaving.