The research projects that funded this research were: MARCoNI (CGL2013-42728-R); Dendro-Avenidas (CGL2007-62063); MAS Dendro-Avenidas (CGL2010-19274) of the Spanish Ministry of Science and Technology and the project IDEA-GESPPNN (OAPN 163/2010), which was funded by the Environmental Ministry of Spain.

1. Sampling Strategy
<ol>
	<li>Geomorphic process identification
	<ol>
		<li>Implement the Hydrologic Response Units approach (HRU)21. To this end, identify homogenous areas within the study site, comprising lithology and surface deposits, canopy cover, vegetative residue in contact with the soil surface and slope. Select among all the HRUs those in which the sheet erosion process is predominant.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57987/57987fig1.jpg" /> 
Figure 1: Example of HRUs associated to a sandy gully. Regarding the protocol proposed here, the sampling of exposed roots must be conducted in an HRU in which the effective erosive process is sheet erosion (in this figure legend corresponding to exposed sand with moderate slopes). This figure has been modified from Bodoque et al.21. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Sampling of exposed roots
	<ol>
		<li>Locate in the study site exposed roots corresponding to tree species useful for tree-ring dating (preferably coniferous)20.</li>
		<li>Provide a detailed description of the spatial and morphological characteristics of the surroundings of the exposed roots to be sampled. Collect the following information: geographical location (UTM coordinates); altitude; aspect in sexagesimal degrees, both for the hillside and for the particular root location (local aspect); distance of the root section to the tree trunk; hillside slope and slope of the specific root location (both expressed in degrees); orientation of the exposed root with regard to the runoff path.</li>
		<li>Take one soil sample of about 1 kg from the area surrounding each exposed root. The parameters to characterize are texture, percentage of organic matter and soil structure.</li>
		<li>Measure in situ hydraulic conductivity using a single ring infiltrometer under constant head. 
		Note: Implement steps 1.2.2 and 1.2.3 to characterize soil erodibility.</li>
		<li>Locate exposed roots that are farther than 1.5 m from the trunk. At lesser distances the exposure could be related to tree growth.</li>
		<li>Cut with a handsaw at least 30 exposed roots, with a diameter greater than 5 cm, into 15 cm-long sections. Subsequently, take two slices of approximately 1.5 cm thick.</li>
		<li>By using a gauging trowel, a handsaw and a measuring tape, sample a subset of buried roots (at least one-third of the total exposed roots sampled) at different soil depths (maximum 20 cm) to establish the minimum soil thickness below which roots begin to have an anatomical response due to exposure.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57987/57987fig2.jpg" /> 
Figure 2: Example of how to conduct field sampling. At least 30 exposed roots are selected and, subsequently, cut with a handsaw. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Microtopographic Characterization of Ground Surface and Exposed Roots at Easily Accessible Locations
<ol>
	<li>Use a Terrestrial Laser Scanning device that can measure up to 50,000 points per second with a precision of 1 mm at a scanning distance of &#60; 120 m.</li>
	<li>Consider at least two different conventional TLS locations to avoid shadow zones.</li>
	<li>Merge the different locations by using a minimum of four high-definition surveying (HDS) targets positioned to cover the entire area.</li>
	<li>In order to obtain highly accurate topographic data, scan an average area of 300 cm2 from the selected locations using a spatial resolution of 1 mm. Include the exposed roots and the surrounding area that is representative of the ground surface.</li>
</ol>
3. Microtopographic Characterization of Ground Surface And Exposed Roots, at Locations with Difficult and Steep Terrain (Mountain Environments)
<ol>
	<li>Place a microtopographic profile gauge perpendicular to the exposed root and, subsequently, level horizontally for all measurements in such a way that different datasets can be compared.</li>
	<li>Draw the profile obtained in step 3.1 on graph paper to be able to infer the amount of eroded soil along the profile with sub-millimeter precision.</li>
</ol>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57987/57987fig3.jpg" /> 
Figure 3: Example of characterization of ground microtopography using a microtopographic profile gauge. (A) Illustration of exposed roots as observed along a hiking trail; (B) measurements of soil microtopography using a microtopographic pro&#64257;le gauge; (C) estimation of Ex through the acquisition of microtopographic pro&#64257;les by drawing them on a graph paper to allow inference of the amount of eroded soil along the pro&#64257;le and with sub-millimeter precision. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
4. Determination of the Timing of Root Exposure
<ol>
	<li>Macroscopic analysis
	<ol>
		<li>Air dry the sections obtained in step 1.2.6 for 2 months.</li>
		<li>Obtain from the initial sections two slices that are each approximately 2 cm thick.</li>
		<li>Sand and polish the slices with sandpaper (up to 400 grit) to facilitate recognition of growth rings.</li>
		<li>Scan slices at a minimum resolution of 2,800 dpi so that they can be accurately analyzed even when rings are particularly thin.</li>
		<li>Use the increase in latewood percentage and larger growth-ring widths as indicators of stress induced by exposure.</li>
		<li>Mark at least 4-5 radii along the diameters of the slices that show the highest variability in growth-ring widths.</li>
		<li>Use an image analysis system or a measuring table to measure tree-ring width.</li>
		<li>Apply visual cross-dating procedures by comparing variability in growth-ring widths between the different radii, to both improve the dating precision for the first year of exposure to soil erosion and to correctly date subsequent rings and recognize the presence of multiple or discontinuous rings.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57987/57987fig4.jpg" /> 
Figure 4: Example of how to prepare a section of an exposed root to accomplish dendrochronological dating of growth ring series. In each section, four or five radii are marked along the directions that show the highest variability regarding tree-ring width. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Microscopic analysis
	<ol>
		<li>For both exposed and non-exposed root samples, use a sliding microtome to obtain radial cross-sections of approximately 1 cm in width and 20 microns thick.</li>
		<li>Stain cross-sections with safranin (i.e., 1 g of safranin + 50 g of water + 50 g of 96% ethanol) and dehydrate with increasingly richer ethanol-water solution up to 96% ethanol (e.g., 50% and 96% ethanol) until the ethanol runs clear. Soak the samples in xylol or a citrus oil clearing agent (e.g., Histoclear).</li>
		<li>Mount cross-sections on coated slides, cover-slip with a hardening epoxy (e.g., Eukitt, Canada balsam and dry at ambient temperature (i.e., about 5-8 h for Eukitt, at least 24 h for Canada balsam).</li>
		<li>Observe (under 125X magnification) and photograph samples with a digital imaging system under optical microscopy.</li>
		<li>Compare under an optical microscope the anatomical footprint of both exposed and non-exposed root samples (steps 1.2.5 and 1.2.6).</li>
		<li>Take microscopic measurements using an image analyzer on the digital photographs of the ensuing parameters: a) width of the growth ring; b) number of cells per ring; c) percentage of latewood; and d) lumen area in earlywood.</li>
		<li>Test with the image analyzer (step 4.2.6) the occurrence of resin ducts and take measurements for each growth ring.</li>
		<li>Perform a one-way analysis ANOVA with multiple range tests (method: 95% LSD &#8211;Least Significant Difference) for the anatomical variables considered (step 4.2.6) to verify the existence of statistically significant differences between the two groups of measurements (pre-exposed vs exposed roots).</li>
	</ol>
	</li>
</ol>
5. Estimation of the Thickness of the Soil Layer Eroded Since Initial Exposure (Ex)
<ol>
	<li>Scenario 1: exposed roots that run parallel to the runoff path.
	<ol>
		<li>Based on the data obtained in step 2.4, use inverse distance weighting as the interpolation method to obtain highly accurate digital elevation models (DEMs) with a spatial resolution of 3 mm.</li>
		<li>Use GIS tools to extract from the DEM perpendicular profiles of the exposed root with a rough distance of 150 cm.</li>
		<li>Perform steps 5.1.1 and 5.1.2 at easily accessible locations (step 2).</li>
		<li>Use the perpendicular profiles of the exposed root obtained in step 3.2 when the study site is located in areas where the terrain is difficult and steep (mountain environments) (step 3).</li>
		<li>In the profiles obtained in steps 5.1.2 and 5.1.3 use visual interpretation to locate the threshold distance (TD), defined as the distance between the root and the knickpoint at the ground surface. This establishes the lowering of ground surface for the profiles due to sheet erosion.</li>
		<li>Estimate the thickness of the soil layer eroded, by measuring the height between the top of the root and the knickpoint at the ground surface estimated in step 5.1.5.</li>
		<li>Correct the measurement obtained in step 5.1.6 by subtracting it from the ongoing secondary growth (i.e., growth of the root since the year of exposure) and the bark thickness on the upper/lower side of the root. See Corona et al. 30 for a detailed description.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57987/57987fig5.jpg" /> 
Figure 5: Example is illustrating how to place TD when the exposed roots sampled are orientated according to the runoff path. This figure shows a common microtopographic transversal profile of uncovered root and its immediate vicinity. Ex1 is the location applied to the traditional dendrogeomorphical approach to determine the eroded soil thickness; Ex2 belongs to the position where this parameter needs to be assessed. TD is taken as a guide position from which the ground surface is changed by sheet erosion only. This figure has been modified from Bodoque et al.34 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Scenario 2: exposed roots that run perpendicular to the runoff path
	<ol>
		<li>Implement steps 5.1.1 to 5.1.4 as stated under step 5.1.</li>
		<li>Using the raster calculator available in any Geographic Information System (GIS) software, for each perpendicular profile measure the height between the top of the root and the ground surface using the knickpoint at the ground surface as a reference. At this point measurements of Ex are not influenced by sedimentation and/or scour erosion and, therefore, it is possible to measure soil erosion.</li>
		<li>Correct the measurement obtained in step 5.2.2 using the procedure in step 5.1.7.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/57987/57987fig6.jpg" /> 
Figure 6: Example drawing how to proceed when the exposed roots sampled are orientated according to the perpendicular to the runoff path. This figure shows a schematic view of a ground surface profile related to an exposed perpendicular root concerning the runoff path. Eroded soil thickness (Ex) is quantified at the knickpoint coinciding to prevailing sedimentation and scour erosion processes nearby the root. This figure has been modified from Ballesteros-C&#225;novas et al.35 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
6. Sheet Erosion Rate Estimation
<ol>
	<li>Depending on the soil mechanic characteristics of the study site, apply equation 1 (i.e., hypothesizes that the radial growth pressure applied by the root is lower than shear strength of the soil), or equation 2 (i.e., supposes stability of the root axis through time)30: 
	<img alt="Equation 1" src="/files/ftp_upload/57987/57987eq1.jpg" />(1) 
	<img alt="Equation 2" src="/files/ftp_upload/57987/57987eq2.jpg" />(2) 
	Where: 
	ER (mm&#8729;yr-1), is the sheet erosion rate to be estimated. 
	EX (mm), is the thickness of the soil layer eroded since initial exposure. This is obtained by performing steps 5.1.1 to 5.2.3. 
	Gr1 and Gr2 (mm) represent the secondary (subsequent) growth on the upward/downward part of the root after exposure. It is obtained after performing step 5.1.7. 
	B1 and B2 (mm) are the bark thickness on the upper/Lower part of the root. It is obtained with the procedure in step 5.1.7. 
	&#949; (mm), is defined as the minimal depth of soil below which root begin to change its anatomical configuration. 
	NRex (yr), is the number of tree-rings developed after the year of exposure. It is obtained using steps 4.1.1 to 4.2.8.</li>
</ol>

The authors have nothing to disclose.

The protocol deployed demonstrates the value of detailed and proper characterization of ground surface microtopography, as it enables to measure trustworthy sheet erosion rates from dendrogeomorphology. Our methodological approach focuses on the importance of characterizing the microtopography in the surroundings of exposure roots to improve erosion rate estimation. This factor has been largely ignored in previous studies, resulting in a misinterpretation of soil erosion rates derived from dendrogeomorphology34.The inclusion of microtopography allows erosion rates to be estimated regardless of root orientation, which favors the replicability of the methods35. The acquisition of microtopography may be performed using different techniques. Therefore, we recognize differences between the DEM produced from microtopographic profiles (step 5.2.1) and TLS (steps 5.1.1 to 5.1.2). Despite these differences sometimes being even within the order of up to 50% of the variance of the measures36, we highlight that the reliability of our protocol based on microtopographic profiles (step 5.2.1) is comparable to that achieved with TLS (~mm).
This study also demonstrates that the protocol deployed here can be used in mountainous areas as an alternative approach to TLS. The use of TLS in this specific geographic context is not practical due to the size and weight of the device, which hinder its transport through inaccessible areas. The application of the TD criteria as an indication of the distance at which ground surface is not changing as a result of axial and radial pressures exerted by the root37,38, or where there is no sedimentation (upslope of the root) or scour erosion (downslope of the root)35 is illustrated as well (steps 5.1.5 and 5.2.2). We determined that this particular distance must be utilized in future work involving the definition on the point at which Ex shall be measured.
Macroscopic and microscopic observations (steps 4.1 and 4.2) are essential to decipher the environmental signal in tree-ring records. The only use of tree-ring width measurements might not be enough to determine the moment of exposure, since anatomical changes are more sensitive39 and could even be produced when root are still buried by a thin soil layer30. Thus, existing studies suggest that the coniferous tree species used in this paper (i.e., Pinus uncinata Ramond ex DC, Pinus pinaster Ait. and Pinus sylvestris) react to exposure with eccentric growth and a significant development of latewood tracheids, which is congruent with former findings on other conifer species21,27,29,30. Reactions start happening when the soil coverage of the root declines below 2.3 1.1 cmand therefore agrees with the observation from marly badlands in France in which the analysis was focused on Pinus sylvestris and Pinusnigra30.
The first exposure reaction is translated as a reaction to boosting temperature variability as well as drought stress that will happen more quickly in the top of the detrital level of loose sediment close to the soil surface29,30,40,41. This anatomical modification may also be viewed as a predictable response of the root to lessen the chance of dysfunctional tracheids due to cavitation, caused by the development of ice crystals in the sap42, or even due to mobile embolism associated with water stress43. Our observations, consequently, verify the hypothesis of Corona et al.30 and also propose that previous assessments that did not consider this bias could have undervalued erosion rates. In the case of Fagus sylvatica L., we can confirm similarities in the patterns and reactions between this particular species and other deciduous species discussed in the literature26,28,29.
Dendrogeomorphology has competitive advantages compared to other methods of direct estimation. So, the analysis based on exposed roots enables to be ambitious in terms of characterizing soil erosion even at the basin scale, providing representative erosion rates of the last decades. In contrast, the use of direct methods, as Gerlach troughs2, water collectors3 or gauging stations44, is usually limited to a few years and to the use at the hillslope scale, due to the high cost of maintenance and operation of these devices21. Similar thinking could also be applied to models aimed at estimating soil erosion45, since they require gauges located in the field to allow their validation and calibration46. Concerning the analysis of soil erosion in recreation trails, our protocol is much more easily applied than standard protocols, i.e., cross-sectional area (CSA), variable CSA, maximum incision to the trail or topographic surveys47,48,49, particularly if the trail is positioned in mountainous areas. In this particular geographic context, it is a challenge to use the protocols above owing to the heavy equipment required, which is difficult to move in such environments. This limitation can restrict the number of transects collected and can consequently impact spatiotemporal estimates of soil erosion50. Furthermore, it is a challenge to accurately determine the horizontal position and guarantee that the same height above the fixed points is considered, as soil creep tends to play a role in such environments49.
The limitations of erosion rates derived from dendrogeomorphology are related to the fact that the age of exposed roots is usually limited to a few decades. Nevertheless, this time window is usually larger than the one defined by erosion rates obtained from direct techniques. Cross-dating, the basic principle of dendrochronology, also has proven difficult to be implemented in roots, even though they pertain to the same tree51,52. Besides, the consistency of root-based estimation of erosion rates is probable to be affected by restrictions similar to those noted for documentary sources or approaches based on radioisotopes53. Concerning the above, soil erosion will be a consequence of a non-linear response to rainfall. Average erosion rates obtained from dendrogeomorphology might be, therefore, less reliable to characterize soil erosion in areas where this process is mostly due to a few heavy rainfall events, since under this circumstance erosion rates could be skewed55. Additionally, the sampling of large exposed roots may lead to underestimate erosion rates since it has been demonstrated that erosion rates and root thickness has an inversed proportional relationship19.
The results produced from the protocol deployed here offer useful information on soil degradation. In that sense, dendrogeomorphology may aid decision makers to design long-term management plans, due to the spatiotemporal representativeness of erosion rates derived from exposed roots.

Both economic and environmental impacts produced by sheet erosion makes this topic in a worldwide concern1. Several methods, from direct techniques to physical-based and empirical approaches, are used to calculate soil erosion rates on a variety of temporal and spatial scales. Direct techniques use field measurements under natural conditions and are mainly based on the use of Gerlach troughs2, water collectors3, erosion pins4 and profilometers5. Furthermore, models of soil erosion have been increasingly focused on representing in detail the real physical processes responsible for erosion6.
Dendrogeomorphology7 is a subdivision of dendrochronology8 that it is successful in characterizing frequency and magnitude of geomorphic processes9,10,11,12,13,14,15,16,17. Regarding sheet erosion, dendrogeomorphology is usually employed to enhance or replace the methodologies mentioned above, particularly in areas where erosion rates derived from direct techniques are either scarce or unavailable. Dendrogeomorphology is a very flexible method for assessing soil erosion and can be utilized to calibrate physical-based and empirical models, or perhaps as a data source to enhance the reliability of direct estimation techniques18,19. Dendrogeomorphology enables soil erosion to be established over large areas where exposed roots are available. These exposed roots should show clear tree rings limits and respond to annual growth patterns to be considered as optimum to apply dendrogeomorphological techniques20. Further, exposed roots to be sampled should be preferably located in homogenous units based on their reaction to soil erosion21.
The conventional dendrogeomorphical way of estimating sheet erosion is grounded on measuring in situ the eroded soil thickness (Ex) from the time of the very first exposure to the present22,23,24. The ratio between these two variables is utilized to calculate an erosion value in mm&#8729;yr1. Much of the research conducted to date has focused entirely on efficiently identifying the initial year of exposure. As an outcome, modifications in the root due to exposure are analyzed at the macroscopic level25, or at the tissue and cellular levels26,27,28. The principal anatomical change present in the exposed roots of conifers is increasing growth ring thickness, as a consequence of a significant number of cells within the earlywood (EW)26. A cutback has similarly been found within the lumen area of EW tracheids along with an increased cell wall structure thickness of latewood (LW) tracheids24,27,29. These modifications have been described and quantified as beginning when erosion lowers the ground surface over the root to roughly three cm30. Less attention was granted to the adequate determination of the Ex parameter. The age of exposed roots was typically connected with the height of the root&#39;s center axis of growth over the ground surface31,32. The estimation of Ex was consequently corrected considering ongoing secondary growth30,33. More recently, these methodological approaches have also integrated the characterization of soil microtopography to obtain reliable erosion rates34,35,36.
We present a laboratory and field protocol to estimate more accurate and reliable sheet erosion rates from dendrogeomorphology. In this particular protocol, we examine the hypothesis that sampling all exposed roots, regardless of orientation relative to runoff path and in conjunction with microtopographical analysis, enables erosion rates to be precisely reconstructed and quantified. Our objective, therefore, is to provide a protocol to estimate erosion rates from maximizing the sample size of exposed roots, using macroscopic and microscopic information found in growth tree-ring series and also high-resolution topographic data.

<table><tbody><tr><td>Topographic map, soil map, land cover map</td><td></td><td></td><td>To be obtained from public institutions or generate at the first phase of research</td></tr><tr><td>Single ring infiltometer</td><td>Turf-Tec International</td><td>IN16-W</td><td>http://www.turf-tec.com/IN16Lit.html</td></tr><tr><td>Handsaw</td><td></td><td></td><td>There is noy any specific characteristics to be considered regarding the model</td></tr><tr><td>Measuring tape</td><td></td><td></td><td>With accuracy of 1 mm</td></tr><tr><td>Terrestrial Laser Scanning (TLS)</td><td>Leica-Geosystems</td><td>Leica ScanStation P16</td><td>https://leica-geosystems.com/products/laser-scanners/scanners/leica-scanstation-p16</td></tr><tr><td>Microtopographic Profile Gauge</td><td>RS Online</td><td>Facom, 19</td><td>https://www.classic-conservation.com/es/herramientas-para-talla-y-escultura-en-madera/511-galga-medidora-de-perfiles.html</td></tr><tr><td>Sandpaper</td><td></td><td></td><td>from 80 to 400 grit</td></tr><tr><td>Scanner</td><td>EPSON</td><td>Perfection V800 Photo</td><td>https://www.epson.co.uk/products/scanners/consumer-scanners/perfection-v800-photo</td></tr><tr><td>Image analysis system</td><td>Regent Instruments Inc.</td><td>WinDENDRO</td><td>http://www.regentinstruments.com/assets/windendro_analysisprocess.html</td></tr><tr><td>Measuring table</td><td>IML</td><td></td><td>https://www.iml-service.com/product/iml-measuringtable/</td></tr><tr><td>Sliding microtome</td><td>Thermo Fisher SCIENTIFIC</td><td>Microm HM 450-387760</td><td>http://www.thermofisher.com/order/catalog/product/910020</td></tr><tr><td>Optical microscope</td><td>OLYMPUS</td><td>MX63/MX63L</td><td>https://www.olympus-ims.com/en/microscope/mx63l/</td></tr><tr><td>Digital camera for microscope</td><td>OLYMPUS</td><td>DP74</td><td>https://www.olympus-ims.com/en/microscope/dc/</td></tr><tr><td>Safranin</td><td></td><td></td><td>Empirical Formula (Hill Notation) C20H19ClN4&amp;nbsp;</td></tr><tr><td>Astrablue</td><td></td><td></td><td>Empirical Formula C&lt;sub&gt;47&lt;/sub&gt;H&lt;sub&gt;52&lt;/sub&gt;CuN&lt;sub&gt;14&lt;/sub&gt;O&lt;sub&gt;6&lt;/sub&gt;S&lt;sub&gt;3&lt;/sub&gt;</td></tr><tr><td>Alcohol</td><td></td><td></td><td>Alcohol by volume (50%, 75% and 100%)</td></tr><tr><td>Distilled water</td><td></td><td></td><td>H&lt;sub&gt;2&lt;/sub&gt;O</td></tr><tr><td>Citrus oil clearing agent</td><td></td><td></td><td>https://www.nationaldiagnostics.com/histology/product/histo-clear</td></tr><tr><td>Coated slides</td><td>Thermo Fisher SCIENTIFIC</td><td></td><td>https://www.fishersci.com/us/en/products/I9C8JXMT/coated-glass-microscope-slides.html</td></tr><tr><td>Hardening epoxy</td><td>MERCK</td><td></td><td>https://www.sigmaaldrich.com/catalog/product/sial/03989?lang=es&amp;amp;region=ES</td></tr></tbody></table>

laboratory and field protocol for estimating sheet erosion rates from dendrogeomorphology

Sheet erosion is among the crucial drivers of soil degradation. Erosion is controlled by environmental factors and human activities, which often lead to severe environmental impacts. The understanding of sheet erosion is, consequently, a worldwide issue with implications for both environment and economies. However, the knowledge on how erosion evolves in space and time is still limited, as well as its effects on the environment. Below, we explain a new dendrogeomorphological protocol for deriving eroded soil thickness (Ex) by acquiring accurate microtopographic data using both terrestrial laser scanning (TLS) and microtopographic profile gauges. Additionally, standard dendrogeomorphic procedures, dependent on anatomical variations in root rings, are utilized to establish the timing of exposure. Both TLS and microtopographic profile gauges are used to obtain ground surface pro&#64257;les, from which Ex is estimated after the threshold distance (TD) is determined, i.e., the distance between the root and the sediment knickpoint, which allows de&#64257;ning the lowering of the ground surface caused by sheet erosion. For each profile, we measured the height between the topside of the root and a virtual plane tangential to the ground surface. In this way, we intended to avoid small-scale impacts of soil deformation, which may be due to pressures exerted by the root system, or by the arrangement of exposed roots. This may provoke small amounts of soil sedimentation or erosion depending on how they physically affect the surface runoff. We demonstrate that an adequate microtopographic characterization of exposed roots and their associated ground surface is very valuable to obtain accurate erosion rates. This finding could be utilized to develop the best management practices designed to eventually halt or perhaps, at least, lessen soil erosion, so that more sustainable management policies can be put into practice.

Samples of exposed roots suffer serious cambial deterioration due to the impact of exposure (e.g., modifications in temperature, incidence of light) plus the physical stress, due to trampling by hikers or animal grazing and browsing that the roots undergo after they are exposed. Determining the existence of discontinuous rings, as well as precisely dating the first year of response to exposure was accomplished in the lab as in Protocol 4 (steps 4.1.6 to 4.1.8). We chose the increase of latewood percentage and the presence of tree-ring significantly wider than the average as indicators of first exposure.
114 sections of exposed Pinus uncinata Ramond ex DC, Fagus sylvatica L., Pinus pinaster Ait. and Pinus sylvestris roots were used for this purpose. As a result of the death of the cambium on the top part of the root, we found severe changes in the tree-ring growth pattern, which shifted from concentric to eccentric growth (Figure 7), as well as discontinuous tree-rings or even some that had been completely destroyed in the outer tree-rings. The above suggests that the approach we implemented was successful in determining with enough accuracy the age of the roots and the particular year in which the first exposure ring was formed.
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/57987/57987fig7.jpg" /> 
Figure 7: Examples of eccentric tree-ring pattern in roots due to exposure. This figure shows a view of a polished section of a root exposed in the absence scars (A) and with scars (B). In both cases, it is feasible to observe the pattern of eccentric tree-rings as a clear reaction to soil erosion. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
A lab experiment was conducted as in protocol 4 (steps from 4.2.1 to 4.2.8) to determine how roots anatomically respond to exposure. To this end, the same exposed roots sample described above was used. Samples were examined below optical microscopy and photographed with a digital imaging system. Microscopic images were analyzed at 50&#215; magnification with an accuracy of 1 &#956;m in the measurements. The first time of exposure can be seen in the characteristic anatomical changes. Tree-rings show evident increased growth (particularly recognizable in two or three succeeding rings), which is as a result of an increase in both tracheid number and their size. An increase in the number of vessels was also noticeable. Resin ducts usually appear in tangential rows in earlywood. Latewood is readily observable as it has several rows of thick-walled tracheids. A significant decline in the tracheid lumen of earlywood once root is exposed also occurs. With respect to the anatomical footprint of the ten buried roots sampled, results indicate that this sample group starts to react according to the behavior described above when the edaphic cover fall below 3 cm (Figure 8).
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/57987/57987fig8.jpg" /> 
Figure 8: Example of anatomical response of roots to exposure. Wood anatomy of Pinus uncinata Ramond ex DC roots: (A) anatomy of buried roots (200 &#956;m); (B) anatomy of exposed wood (500 &#956;m). Wood anatomy from roots of Fagus sylvatica L.: (C) anatomy of a buried root (500 &#956;m); (D) anatomy of exposed wood (500 &#956;m). This figure has been modified from Bodoque et al.36 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Characterization of surface microtopography variability plays a critical role in obtaining reliable sheet erosion rates derived from dendrogeomorphology (Figure 9). To this end, we designed an experimental and field experiment aimed at capturing highly accurate microtopographic surface profiles to be analyzed using protocol 5 on 114 samples of exposed roots. We utilized the distance between the root and the knickpoint, from which the profile defines the lowering of ground surface due to sheet erosion as a criterion to estimate the thickness of the soil layer eroded since initial exposure (Ex). Concerning sampled exposed roots running parallel to the runoff path, all profiles analyzed showed a concave configuration on both sides of the exposed roots that were characterized. This morphological pattern ends at a specific distance (TD), from which ground surface is only shaped by sheet erosion, determining, therefore, the location where Ex has to be measured. Concerning exposed roots that run perpendicular to the runoff path, our procedure made it possible to systematically determine the height between the topside of the root and a virtual plane tangential to the ground surface. It also allowed locating small-scale impacts of sedimentation and scour erosion and, hence, ensuring that sheet erosion is accurately estimated.
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/57987/57987fig9.jpg" /> 
Figure 9: Example of outputs of ground surface microtopography characterization obtained from TLS and a microtopographic profile gauge. (A) Hillshade model achieved using microtopographic profiles and (B) raster of slopes derived from the hillshade model; (C) hillshade model obtained from TLS and (D) resulting raster of slopes. Slopes are expressed in sexagesimal degrees. In plots B and D, dashed lines indicate the TD at which Ex must be measured. This figure has been modified from Bodoque et al.36 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig9large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Estimates of sheet erosion rates have been obtained according to the equation included in protocol 6 (Figure 10). As regards the 114 samples analyzed, the year of very first root exposure fluctuates from 1900-2012, which enables the medium-term (multidecadal) characterization of the erosion rates. Additionally, we examined ten buried roots, which were still protected by a thin soil cover. Results showed that buried roots began to anatomically respond to the exposure effects when they were 2.3 1.1 cm below the ground surface (Figure 11). We considered this specific soil level as a value to be added to the thickness of the soil layereroded (Ex).
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/57987/57987fig10.jpg" /> 
Figure 10: Example of sheet erosion rates estimated from dendrogeomorphology. Graph linking erosion rates and years of exposure of the exposed roots. Erosion rates inside the square are those used for quantification purposes. This figure has been modified from Bodoque et al.21 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig10large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/57987/57987fig11.jpg" /> 
Figure 11: Example of anatomical response in buried root sections. Dark grey circles show buried roots with exposure evidence. The size of circles shows root diameter, whereas the numbers indicate root depths. This figure has been modified from Ballesteros-C&#225;novas et al.35 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/57987/57987fig11large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Laboratory and Field Protocol for Estimating Sheet Erosion Rates from Dendrogeomorphology at JoVE.com

Laboratory and Field Protocol for Estimating Sheet Erosion Rates from Dendrogeomorphology

Characterizing erosion from dendrogeomorphology has usually focused on accurately finding the starting time of root exposure, by examining macroscopic or cell level changes caused by exposure. Here, we offer a detailed description of different novel techniques to obtain more precise erosion rates from highly accurate microtopographic data.

Sheet erosion is among the crucial drivers of soil degradation. Erosion is controlled by environmental factors and human activities, which often lead to ...

laboratory-field-protocol-for-estimating-sheet-erosion-rates-from

Nanyang Technological University

Research

JoVE Journal

Environment

7.7K Views.  University of Castilla-La Mancha (UCLM). Deze methode kan helpen bij het beantwoorden van belangrijke vragen in het veld voor de dendrogeomorfologie over het belang van grondmicropografische karakterisering voor het verkrijgen van betrouwbare plaaterosie tarieven. Het belangrijkste voordeel van deze techniek is dat het aanvaardbare schattingen van bodemerosie oplevert over vergelijkbare grote gebieden op een redelijke plaats. De implicatie van deze technieken strekt zich uit tot het verbeteren van de replibiliteit en het nut van den...

Video: Laboratory and Field Protocol for Estimating Sheet Erosion Rates from Dendrogeomorphology

Surface Renewal: An Advanced Micrometeorological Method for Measuring and Processing Field-Scale Energy Flux Density Data

Advanced micrometeorological methods have become increasingly important in soil, crop, and environmental sciences. For many scientists without formal training in atmospheric science, these techniques are relatively inaccessible. Surface renewal and other flux measurement methods require an understanding of boundary layer meteorology and extensive training in instrumentation and multiple data management programs. To improve accessibility of these techniques, we describe the underlying theory of surface renewal measurements, demonstrate how to set up a field station for surface renewal with eddy covariance calibration, and utilize our open-source turnkey data logger program to perform flux data acquisition and processing. The new turnkey program returns to the user a simple data table with the corrected fluxes and quality control parameters, and eliminates the need for researchers to shuttle between multiple processing programs to obtain the final flux data. An example of data generated from these measurements demonstrates how crop water use is measured with this technique. The output information is useful to growers for making irrigation decisions in a variety of agricultural ecosystems. These stations are currently deployed in numerous field experiments by researchers in our group and the California Department of Water Resources in the following crops: rice, wine and raisin grape vineyards, alfalfa, almond, walnut, peach, lemon, avocado, and corn.

Surface renewal is a micrometeorological method that is being used increasingly to determine energy fluxes, but its technical complexity makes it inaccessible to a broad audience. We describe the steps needed to set up and calibrate a surface renewal field station, to acquire and process data, and to correctly interpret results.

Advanced micrometeorological methods have become  increasingly important in soil, crop, and environmental sciences.  For many scientists without formal ...

Modifying the Bank Erosion Hazard Index (BEHI) Protocol for Rapid Assessment of Streambank Erosion in Northeastern Ohio

Understanding the source of pollution in a stream is vital to preserving, restoring, and maintaining the stream&#8217;s function and habitat it provides. Sediments from highly eroding streambanks are a major source of pollution in a stream system and have the potential to jeopardize habitat, infrastructure, and stream function. Watershed management practices throughout the Cleveland Metroparks attempt to locate and inventory the source and rate the risk of potential streambank erosion to assist in formulating effect stream, riparian, and habitat management recommendations. The Bank Erosion Hazard Index (BEHI), developed by David Rosgen of Wildland Hydrology is a fluvial geomorphic assessment procedure used to evaluate the susceptibility of potential streambank erosion based on a combination of several variables that are sensitive to various processes of erosion. This protocol can be time consuming, difficult for non-professionals, and confined to specific geomorphic regions. To address these constraints and assist in maintaining consistency and reducing user bias, modifications to this protocol include a &#8220;Pre-Screening Questionnaire&#8221;, elimination of the Study Bank-Height Ratio metric including the bankfull determination, and an adjusted scoring system. This modified protocol was used to assess several high priority streams within the Cleveland Metroparks. The original BEHI protocol was also used to confirm the results of the modified BEHI protocol. After using the modified assessment in the field, and comparing it to the original BEHI method, the two were found to produce comparable BEHI ratings of the streambanks, while significantly reducing the amount of time and resources needed to complete the modified protocol.

Modifying the Bank Erosion Hazard Index BEHI Protocol for Rapid Assessment of Streambank Erosion in Northeastern Ohio

Streambank erosion potential can be evaluated and ranked using David Rosgen&#8217;s Bank Erosion Hazard Index (BEHI), however this protocol has significant limitations. Here we present protocol modifications to address time constraints, allow nonprofessionals to complete accurate assessments, and account for non-alluvial stream conditions in Northeast Ohio.

Understanding the source of pollution in a stream is vital to preserving, restoring, and maintaining the stream&#8217;s function and habitat it provides. ...

Watershed Planning within a Quantitative Scenario Analysis Framework

There is a critical need for tools and methodologies capable of managing aquatic systems within heavily impacted watersheds. Current efforts often fall short as a result of an inability to quantify and predict complex cumulative effects of current and future land use scenarios at relevant spatial scales. The goal of this manuscript is to provide methods for conducting a targeted watershed assessment that enables resource managers to produce landscape-based cumulative effects models for use within a scenario analysis management framework. Sites are first selected for inclusion within the watershed assessment by identifying sites that fall along independent gradients and combinations of known stressors. Field and laboratory techniques are then used to obtain data on the physical, chemical, and biological effects of multiple land use activities. Multiple linear regression analysis is then used to produce landscape-based cumulative effects models for predicting aquatic conditions. Lastly, methods for incorporating cumulative effects models within a scenario analysis framework for guiding management and regulatory decisions (e.g., permitting and mitigation) within actively developing watersheds are discussed and demonstrated for 2 sub-watersheds within the mountaintop mining region of central Appalachia. The watershed assessment and management approach provided herein enables resource managers to facilitate economic and development activity while protecting aquatic resources and producing opportunity for net ecological benefits through targeted remediation.

There is a critical need for tools and methodologies capable of managing aquatic systems in the face of uncertain future conditions. We provide methods for conducting a targeted watershed assessment that enables resource managers to produce landscape-based cumulative effects models for use within a scenario analysis management framework.

There is a critical need for tools and methodologies capable of managing aquatic systems within heavily impacted watersheds. Current efforts often fall ...

Methods of Soil Resampling to Monitor Changes in the Chemical Concentrations of Forest Soils

Recent soils research has shown that important chemical soil characteristics can change in less than a decade, often the result of broad environmental changes. Repeated sampling to monitor these changes in forest soils is a relatively new practice that is not well documented in the literature and has only recently been broadly embraced by the scientific community. The objective of this protocol is therefore to synthesize the latest information on methods of soil resampling in a format that can be used to design and implement a soil monitoring program. Successful monitoring of forest soils requires that a study unit be defined within an area of forested land that can be characterized with replicate sampling locations. A resampling interval of 5 years is recommended, but if monitoring is done to evaluate a specific environmental driver, the rate of change expected in that driver should be taken into consideration. Here, we show that the sampling of the profile can be done by horizon where boundaries can be clearly identified and horizons are sufficiently thick to remove soil without contamination from horizons above or below. Otherwise, sampling can be done by depth interval. Archiving of sample for future reanalysis is a key step in avoiding analytical bias and providing the opportunity for additional analyses as new questions arise.

Repeated soil sampling has recently been shown to be an effective way to monitor forest soil change over years and decades. To support its use, a protocol is presented that synthesizes the latest information on soil resampling methods to aid in the design and implementation of successful soil monitoring programs.

Recent soils research has shown that important chemical soil characteristics can change in less than a decade, often the result of broad environmental ...

Measuring and Mapping Patterns of Soil Erosion and Deposition Related to Soil Carbonate Concentrations Under Agricultural Management

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonate (CaCO3) profiles. The objective is to describe a simple conceptual model and detailed protocol for repeatable field and laboratory measurements of these quantities. Here, accurate elevation is measured using a ground-based differential global positioning system (GPS); other data acquisition methods could be applied to the same basic method. Soil samples are collected from prescribed depth intervals and analyzed in the lab using an efficient and precise modified pressure-calcimeter method for quantitative analysis of inorganic carbon concentration. Standard statistical methods are applied to point data, and representative results show significant correlations between changes in soil surface layer CaCO3 and changes in elevation consistent with the conceptual model; CaCO3 generally decreased in depositional areas and increased in erosional areas. Maps are derived from point measurements of elevation and soil CaCO3 to aid analyses. A map of erosional and depositional patterns at the study site, a rain-fed winter wheat field cropped in alternating wheat-fallow strips, shows the interacting effects of water and wind erosion affected by management and topography. Alternative sampling methods and depth intervals are discussed and recommended for future work relating soil erosion and deposition to soil CaCO3.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonates. Repeatable methods for field and laboratory measurements of these quantities and data analysis methods are described here.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes ...

Leaf Area Index Estimation Using Three Distinct Methods in Pure Deciduous Stands

Accurate estimations of leaf area index (LAI), defined as half of the total leaf surface area per unit of horizontal ground surface area, are crucial for describing the vegetation structure in the fields of ecology, forestry, and agriculture. Therefore, procedures of three commercially used methods (litter traps, needle technique, and a plant canopy analyzer) for performing LAI estimation were presented step-by-step. Specific methodological approaches were compared, and their current advantages, controversies, challenges, and future perspectives were discussed in this protocol. Litter traps are usually deemed as the reference level. Both the needle technique and the plant canopy analyzer (e.g., LAI-2000) frequently underestimate LAI values in comparison with the reference. The needle technique is easy to use in deciduous stands where the litter completely decomposes each year (e.g., oak and beech stands). However, calibration based on litter traps or direct destructive methods is necessary. The plant canopy analyzer is a commonly used device for performing LAI estimation in ecology, forestry, and agriculture, but is subject to potential error due to foliage clumping and the contribution of woody elements in the field of view (FOV) of the sensor. Eliminating these potential error sources was discussed. The plant canopy analyzer is a very suitable device for performing LAI estimations at the high spatial level, observing a seasonal LAI dynamic, and for long-term monitoring of LAI.

An accurate estimation of leaf area index (LAI) is crucial for many models of material and energy fluxes within plant ecosystems and between an ecosystem and the atmospheric boundary layer. Therefore, three methods (litter traps, needle technique, and PCA) for taking precise LAI measurements were in the presented protocol.

Accurate estimations of leaf area index (LAI), defined as half of the total leaf surface area per unit of horizontal ground surface area, are crucial for ...

A Method for Quantifying Foliage-Dwelling Arthropods

Terrestrial arthropods play an important role in our environment. Quantifying arthropods in a way that allows for a precise index or estimates of density requires a method with high detection probability and a known sampling area. While most described methods provide a qualitative or semi-quantitative estimate adequate for describing species presence, richness, and diversity, few provide an adequately consistent detection probability and known or consistent sampling areas to provide an index or estimate with adequate precision to detect differences in abundance across environmental, spatial, or temporal variables. We describe how to quantify leaf-dwelling arthropods by sealing the leaves and end of branches in a bag, clipping and freezing the bagged material, and rinsing the previously frozen material in water to separate arthropods from the substrate and quantify them. As we demonstrate, this method can be used at a landscape scale to quantify leaf-dwelling arthropods with adequate precision to test for and describe how spatial, temporal, environmental, and ecological variables influence arthropod richness and abundance. This method allowed us to detect differences in density, richness, and diversity of leaf-dwelling arthropods among 5 genera of trees commonly found in southeastern deciduous forests.

We describe how to quantify leaf dwelling arthropods by sealing the leaves and end of branches in a bag, clipping and freezing the bagged material, and rinsing the previously frozen material in water to separate arthropods from the substrate for quantification.

Terrestrial arthropods play an important role in our environment. Quantifying arthropods in a way that allows for a precise index or estimates of density ...

Using Tree-Rings to Reconstruct Fire History Information from Forested Areas

Annual tree-ring patterns are a source of ecological and environmental information including the history of fires in forested areas. Tree-ring based fire histories include three fundamental phases: field collection, laboratory methods (preparation and dating), and data analysis. Here we provide step-by-step instructions and issues to consider, including the process for selecting the study area, sampling sites, plus how and which fire-scarred trees to sample. In addition, we describe fire-scar sample preparation and dating which are done in the laboratory. Finally, we describe basic analysis and relevant results, including examples from studies that have reconstructed fire history patterns. These studies allow us to understand the historical fire frequency, changes in those frequencies related to anthropogenic factors, and analyzes of how climate influences fire occurrence over time. The description of these methods and techniques should provide a greater understanding of fire history studies that will benefit researchers, educators, technicians, and students interested in this field. These detailed methods will allow new researchers to this field, a resource to start their own work and achieve greater success. This resource will provide a greater integration of tree-ring aspects within other studies and lead to a better understanding of natural processes with forested ecosystems.

This work explains the most appropriate techniques and methods for conducting a fire history study from beginning site selection to final analysis of fire-climate relationship.

Annual tree-ring patterns are a source of ecological and environmental information including the history of fires in forested areas. Tree-ring based fire ...

Monitoring Pedogenic Inorganic Carbon Accumulation Due to Weathering of Amended Silicate Minerals in Agricultural Soils.

The present study aims to demonstrate a systematic procedure for monitoring inorganic carbon induced by enhanced weathering of comminuted rocks in agricultural soils. To this end, the core soil samples taken at different depth (including 0-15 cm, 15-30 cm, and 30-60 cm profiles) are collected from an agriculture field, the topsoil of which has already been enriched with an alkaline earth metal silicate containing mineral (such as wollastonite). After transporting to the laboratory, the soil samples are air-dried and sieved. Then, the inorganic carbon content of the samples is determined by a volumetric method called calcimetry. The representative results presented herein showed five folded increments of inorganic carbon content in the soils amended with the Ca-silicate compared to control soils. This compositional change was accompanied by more than 1 unit of pH increase in the amended soils, implying high dissolution of the silicate. Mineralogical and morphological analyses, as well as elemental composition, further corroborate the increase in the inorganic carbon content of silicate-amended soils. The sampling and analysis methods presented in this study can be adopted by researchers and professionals looking to trace pedogenic inorganic carbon changes in soils and subsoils, including those amended with other suitable silicate rocks such as basalt and olivine. These methods can also be exploited as tools for verifying soil inorganic carbon sequestration by private and governmental entities to certify and award carbon credits.

The verification method described here is adaptable for monitoring pedogenic inorganic carbon sequestration in various agricultural soils amended with alkaline earth metal silicate-containing rocks, such as wollastonite, basalt, and olivine. This type of validation is essential for carbon credit programs, which can benefit farmers that sequester carbon in their fields.

The present study aims to demonstrate a systematic procedure for monitoring inorganic carbon induced by enhanced weathering of comminuted rocks in ...

How to Extract Climate Variability from Tree-Rings

Tree rings have been used to reconstruct climatological variables in many locations around the world. Moreover, tree-rings can provide valuable insights into climatic variability of the last few centuries and, in some areas, several millennia. Despite the important development, that dendrochronology has had in recent decades to study the dendroclimatic potential of a large number of species present in different ecosystems, much remains to be done and explored. In addition to this, in the last few years more people (students, teachers and researchers) around the world are interested in implementing this science to extend the timeline of climate information backwards and understand how climate has changed on scales of decades, centuries or millennia. Therefore, the objective of this work is to describe the general aspects and basic steps needed to conduct a tree-ring climate reconstruction, from site selection and field sampling to laboratory methods and data analysis. In this method's video and manuscript, the general basis in tree-ring climatic reconstructions is explained so newcomers and students can use it as an available guide into this field of research.

Tree-ring climate reconstructions can be helpful to better understand past climate variability beyond instrumental records. This protocol shows how to reconstruct past climate using tree rings and meteorological instrumental records.

Tree rings have been used to reconstruct climatological variables in many locations around the world. Moreover, tree-rings can provide valuable insights ...

Laboratory and Field Protocol for Estimating Sheet Erosion Rates from Dendrogeomorphology

Samenvatting

Meer video's verkennen

Hoofdstukken in deze video