Exposed Tree Roots Research Articles

Dendrogeomorphic possibilities for spatio-temporal reconstruction of the relationship between lateral river erosion and movements of destabilized river banks

Destruction of river banks and gradual lateral fluvial erosion can be closely related processes. This study presents the potential of a unique combination of two dendrogeomorphological (tree-ring and root-ring based) approaches to reconstruct the intensity of lateral river erosion and reconstruct subsequent bank movements. The data on anatomical changes in exposed tree roots and the analysis of the tree-rings eccentricity in tilted trees on the bank allowed to reconstruct seven erosion events over the last 15 years and 17 bank movement events over the last ca. 70 years. The frequency of erosion events was higher compared to bank movement events and, in addition, they occurred in less extreme discharge years. This can be attributed to the high erodibility of the banks, whose sediments contain minimal amounts of clay (demonstrated by grain size analysis). On the contrary, bank movement events were less frequent but occurred almost exclusively during the most extreme flood years. Thus, bank destruction appears to occur after the critical value of bank undercutting by lateral fluvial erosion is exceeded. The findings suggest the possible use of tree rings as a potential indicator of an increased risk of bank destruction.

Recent gully erosion intensity in an agricultural landscape underlain by fluvioglacial sediments (NE Czechia)

AbstractInappropriate agricultural management practices combined with intense rainfall often lead to gully erosion. Knowledge of the causes and consequences of past erosion pulses is essential not only for farmers to improve land management, but also for municipalities to define infrastructure threats associated with material transport. This study comprehensively evaluates accelerated gully erosion and estimates gully transport capacity in fluvioglacial sediments left by a Pleistocene ice sheet in northeastern Czechia. Geomorphic mapping of an area of approximately 2 km2 revealed gullies up to 3.5 m wide and deep, with their heads starting at the boundaries of fields and pastures. The ground‐penetrating radar survey confirmed the presence of soil pipes contributing to gully formation due to unmaintained field drainage combined with the natural occurrence of soil pipes. Microscopic analysis and dendrogeomorphic dating of 102 cross‐sections from 28 exposed tree roots revealed 18 years of gully incision since 1985, with increased activity from 2007 to 2014. The mean incision rates ranged between 1–20 cm/year, but could reach 1 m during individual events. More intensive incisions were typical for soils with higher smectite content. The last severe erosion event in 2014 caused clogging of culverts and damage to infrastructure by transporting boulders up to 34 cm in diameter at critical flow velocities of 2.4–2.8 ms−1. Considering the predominance of human‐induced factors (e.g., current soil compaction due to grazing and failure to maintain the drainage pipe outlets), ongoing gully erosion can be expected during intense rainfall events unless appropriate agricultural or stabilization measures are addressed.

Combining exposed tree roots and UAV imagery to quantify land denudation in central Mexico

Approximately 42 % of Mexico is affected by soil denudation resulting from moderate to severe sheet erosion and gullying processes. At Huasca de Ocampo (central Mexico), soil degradation has been linked to intense land use dating back to pre-Hispanic times as well as to unfavorable geological, geomorphic, and climatic conditions. Here, we quantify erosion rates with high precision at annual to multi-decadal timescales by combining, for the first time, dendrogeomorphic reconstructions and UAV-based remote sensing. To assess rates of sheet erosion and gullying processes over the longer-term erosion rates (10–60 yrs), we assessed the age and first exposure of 159 roots to determine sheet erosion rates and gullying processes. At shorter timescales (<3 yrs), we employed an Unmanned Aerial Vehicle (UAV) to develop digital surface models (DSMs) for February 2020 and September 2022. Exposed roots provided evidence of sheet erosion ranging between 2.8 and 43.6 mm yr−1 and channel widening ranging between 11 and 270 mm yr−1, with highest erosion rates found along gully slopes. The UAV-based approach pointed to intense gully headcut retreat with rates between 164.8 and 870.4 mm yr−1; within gullies, channel widening rates ranged between 88.7 and 213.6 mm yr−1 and gully incision rates were between 11.8 and 109.8 mm yr−1. The two approaches yielded very comparable results regarding gully erosion and channel widening; this underlines the potential of using exposed roots to quantifying soil degradation processes retrospectively and considerably beyond the period covered by UAV imagery.

Reconstruction of gully erosion based on exposed tree roots in a recent landform of Paricutin Volcano, Mexico

AbstractGullies in volcanic deposits are among the first signs of erosion that can be observed during or immediately after the volcanic activity and reflective of unstable conditions of newly formed deposits. Gully formation and erosion pulses may well continue to occur long after the initial landform was created, mostly as a result of torrential rainfall and/or land‐use changes. Yet, proper understanding of erosion dynamics and its relations with environmental drivers remains challenging as long‐term observations are, especially in volcanic terrain. Here we applied dendrogeomorphic approaches to (i) analyse both microscopic and macroscopic disturbances in tree roots exposed by gully erosion in a young volcanic landform of central Mexico and to (ii) quantify the evolution of erosion in the volcanic deposits of Paricutin Volcano. To this end we analysed 154 cross‐sections of 30 living, exposed roots of Pinus pseudoestrobus Lindl., of which 25 were used for anatomical and 129 for macroscopic analysis. Wood anatomical – or microscopic – disturbances were mostly in the form of strong growth reductions (~50%) in lumen area of earlywood tracheids, substantial increases in ring widths (mostly stemming from eccentric growth) and the increased formation of latewood cells. We observe major erosion pulses in 2010, 2012, 2015, 2016, 2017 and 2018, triggered primarily by torrential rainfall (with &gt;100 mm 24 h−1 for the maximum intensity event: standard precipitation index values ≥ 2). Along the gully, the lower sector formed between 2009 and 2017, whereas the central sector exhibited important phases of exposure from 2012 to 2018. In the upper, most recent sector of the gully, erosion started only in 2017. Erosion rates in the lower and upper sectors are smaller with a channel widening rate of 6 to 16 cm yr−1. Around the main knickpoint found in the central part of the gully, retreat rates are up to 60 cm yr−1 and gully incision is 30 cm yr−1. The methods applied in this research are novel and can be applied to other volcanic environments with intense gully erosion, so as to provide baseline data for land‐use and environmental management plans.

Carrying capacity and impact indicators: analysis and suggestions for sustainable tourism in protected areas – Brazil

ABSTRACT Protected Areas (PA) are widely studied, especially related to effectiveness strategies for environmental conservation and ecotourism management. Research on tourism planning and management in natural environments is fundamental. Several methodologies have been created to obtain data for indicating guidelines for the management and planning of PA. This paper analyzes, discusses and makes complementary suggestions to the carrying capacity methodology developed by Cifuentes et al. (1999). Our aim was to lower the subjectivity content of Carrying Capacity (Cifuentes et al. 1999), and to incorporate several impact indicators in the monitoring process. Data were collected on Ibitipoca State Park trails in August 2018 and April 2019. Results demonstrated that flooding, soil surface degradation, exposed tree roots and canopy layer are core for carrying capacity visitors, totaling 959 tourists per day. Water quality was altered through the parameters: Specific Conductivity (966 mS/cm) and Total Dissolved Solids (624 mg/L) and Conductivity (173 mS/cm) and pH (3.69). The discussions and results highlight the need for a broader approach to the physical parameters, the adoption of qualitative variables, the increase of biological and ecological factors. Therefore, the analysis of the carrying capacity methodology aims to assist more comprehensive strategies integrated with planning and monitoring of PA.

Quantification of cliff retreat in coastal Quaternary sediments using anatomical changes in exposed tree roots

AbstractSea cliffs represent 80% of the world's coasts and can be found virtually in all types of morphogenetic environments. Most studies on rocky environments focused on the impacts of modern sea level rise on cliff stability derived from sequential surveys, direct measurements or erosional features in anthropogenic structures. In this study, we explore the potential of dendrogeomorphic techniques to quantify multidecadal changes in coastal environments on Porquerolles Island (France). We sampled a total of 56 cross‐sections from 16 Pinus halepensis Mill. roots growing on former alluvial deposits and on sandy‐gravelly cliffs to quantify mean annual cliff retreat rates as well as changes in cliff geometry. Anatomical changes in roots have been used successfully in the past to quantify continuous denudation rates on slopes, channel incision and gullying processes but the approach has not been used so far in a coastal cliff context. At Porquerolles Island, reconstructed rates of cliff retreat cover 30–40 years and show average erosion rates between 0.6 and 3.9 cm yr−1 (average: 2.1 cm yr−1). Highest rates are observed at Pointe de la Tufière (2.6–3.9 cm yr−1), a small rock promontory that is more exposed to wave and storm surges than the remainder of the study area. By contrast, lower erosion rates are recorded at cliffs protected by the La Courtade pocket beach (0.6–1.9 cm yr−1). This contribution demonstrates that dendrogeomorphic analyses of roots clearly have a significant potential and that they are a powerful tool for the quantification of multidecadal rates of cliff retreat in areas where measurements of past erosion are lacking. More specifically, the approach also has clear advantages over the shorter time series obtained with repeat monitoring (e.g. terrestrial laser scanning, sensors, erosion pins) or over longer, but more coarsely resolved records obtained from aerial photographs or radio‐nuclides. © 2018 John Wiley &amp; Sons, Ltd.

Increased gully activity induced by short-term human interventions – Dendrogeomorphic research based on exposed tree roots

The recent acceleration of gully erosion caused by environmental factors and human impacts has led to an enhanced demand for applied research in risk-prone areas worldwide. We investigated the dynamics of gullies that have recently threatened dwellings and railways in the foreland of the Eastern Sudetes (340–390 m a.s.l. in the NE part of Czechia). Flood countermeasures in a residential area above the study site created conditions conducive to accelerated erosion in the gullies; thus, the main aim of this study was to determine how human interventions changed the spatio-temporal dynamics of the gullies during a short period. Twenty two gullies (with a mean length 48.5 m) have developed on a 1-km-wide escarpment (with a mean slope 25°) composed of glaciogenic sediments of various sizes. Dendrogeomorphic techniques were applied on 23 exposed roots of Tilia cordata Mill. (a tree species that has never been used to detect root exposure). Microsections were prepared using a G.S.L.1 sledge microtome and analysed using the WinCELL Reg software to determine the timing of root exposure.Approximately 90% of the eroded sediments (1287.4 m3) were transported across the railway onto the floodplain and caused damage to dwellings, while approximately 10% created bare accumulations at the gully floors. The most significant pulses of gully erosion occurred during the last 10 years (2007, 2009, 2010, and 2014). The maximum identified gully erosion occurred in 2014 (max. incision: 154 cm; maximum widening: 160 cm). In contrast, the development of the bank failures has been slowly progressing since the early 1990s, with a mean bank eroded area between 0.07 and 0.12 m2 year−1. The analysis of the precipitation characteristics (1963–2016) with the Mann-Kendal trend test revealed no significant trend. However, the last strong erosion event, in May of 2014, was triggered by an extraordinary rainstorm with an hourly intensity of 41.3 mm h−1 (maximum intensity of 2.8 mm min−1). Therefore, the recent increase in gully erosion is the consequence of extreme precipitation and human interventions that have been performed in the study site since 2007 (i.e., damming of the ditches and building of new culverts). The dendrogeomorphic research of exposed T. cordata roots significantly contributed to the identification of the gully erosion pulses and thus can be further applied in other localities.

Detailed reconstruction of gully headcut retreat using exposed tree roots: a case study from the Vsetínské vrchy Mts. (Outer Western Carpathians)

Gully erosion is a widespread natural hazard that causes substantial financial losses every year. Dendrogeomorphic (tree ring-based) methods are a good alternative approach for assessing gully development in forested areas. The majority of previous dendrogeomorphic studies dealing with erosion focused on sheet erosion or erosion rates in the active channels of old, stabilized gullies. This study aims to asses newly originated gully development based on an analysis of exposed tree roots. Moreover, the root exposure data were used to calculate rates of linear and areal gully headcut retreat (GHR). In total, 81 samples (microcuts) from common spruce (Picea abies(L.) Karst) were analyzed for anatomical responses to root exposure. The existence of the shallow channel preceding the gully itself was identified. This GHR reconstruction (for a limited time period of eight years) provides evidence of highly active gully development in the forested area of the Flysch Carpathians that is comparable with results from semi-arid regions.

Impacts of artisanal gold mining systems on soil and woody vegetation in the semi‐arid environment of northern Ethiopia

Gold mining is a tremendously important economic activity in rural districts of Ethiopia. We assessed the impacts of artisanal gold mining on soil and woody vegetation in northern Ethiopia. Estimation of soil loss, plant inventory, group discussions and transect studies were used to address the research questions. We employed t‐test to compare woody species and soil loss between mined and unmined sites. Moreover, we ran one‐way ANOVA to compare the average volume of soil loss among the mining sites. The study shows that gold mining removed colossal volumes of soil from the mining landscape with a significant difference among gold mining sites (P ≤ 0.05). Soil loss between the mined and unmined sites was also significant (P ≤ 0.05). Moreover, gold mining destroyed massive tracts of vegetation. Woody species encountered at plot level decreased from artisanal gold mined to unmined sites (P ≤ 0.05). Moreover, dead trees and exposed tree roots were higher in mined than the unmined areas (P ≤ 0.05). This discouraged regeneration and recruitment of woody vegetation. To conclude, gold mining system converted vegetated sites and farmlands into dysfunctional landscape. Therefore, we suggest that combined rehabilitation efforts are required to overcome the challenges of artisanal gold mining on sustainable land management in northern Ethiopia.

Comparison of two methodologies used to estimate erosion rates in Mediterranean ecosystems: 137Cs and exposed tree roots

The 137Cs deposited in soil and exposed tree roots have been widely applied to estimate medium-term soil erosion rates. However, comparative studies between these methods are scarce. For this purpose, three hillsides in two Mediterranean dehesas (rangeland with disperse tree cover) were selected. Regarding the 137Cs technique, a reference site close to the study areas and with similar altitude and rainfall was selected. In order to reduce uncertainties related to the use of point soil profiles, all those collected in an area were combined to form a representative composite profile. The total inventory was 2790±50Bq/m2, and the relaxation coefficient indicated it was an undisturbed soil. The radiocaesium inventory in the study areas was 14–23% lower than in the reference area. The erosion rates for 137Cs were in the range 20.9–38.1tha−1y−1. The exposed root technique was applied to holm oak trees (age about 90years), and the erosion rates were in the range 22–34tha−1y−1. The ratio between exposed root and 137Cs techniques was 1.02±0.11 (S.D.) within the range 0.89–1.2. Both methods produced very similar results equally with respect to the mean erosion rate as well as the relative difference between the hillslope sections, i.e. displaying the same spatial variation in the study areas. As the accounting time for these two techniques is different, 50 and 90y for 137Cs and exposed roots respectively, results suggest that no change in mid-term erosion rates was implied for these areas for almost a century. The use of 137Cs and exposed roots methodology for the determination of mean erosion rates can be reproduced in other ecosystems, but a careful selection of the reference site for 137Cs is essential.

The geomorphic impacts of culverts at paved forest roads: Examples from Carpathian headwater channels, Czech Republic

Road-stream crossings constructed with culverts have the potential to alter geomorphic processes in adjacent stream channels. We examined changes in channel geometry and bed sediments in longitudinal profiles related to culverts at five paved forest road crossings with perennial headwater streams and two gullies initiated by point releases of water through ditches. A dendrogeomorphic approach was used for dating of exposed tree roots and estimation of bank erosion rates in incised cross-sections downstream of road crossings. The studied forest road crossings concentrate surface runoff from the road net, act as stabilizing elements in stream longitudinal profiles and decelerate bedload transport in the case of culvert clogging, which caused notable upstream and downstream changes in fluvial processes. Notable fining of the coarsest fraction in upstream cross-sections was observed only for two culverts with the highest depositional tendencies. Much lower width-depth ratios (<4) and typically higher channel slopes were measured in channel reaches downstream of the culverts, compared with upstream cross-sections. Two road-induced gullies typically had very low width/depth ratios close to 2. At five of a total of seven studied culverts, the highest documented erosion rates occurred immediately downstream of these structures. The mean annual erosion rates reconstructed from cross-sections at the positions of individual tree root samples ranged from 0.2 to 6.5cm·year−1, and the erosion occurred over 2–5year intervals, depending on the studied location. The highest number of observed changes in cross-sectional geometry caused by channel erosion were connected with relatively high-magnitude flow events (with recurrence intervals >10years; specific discharge >1500l·s·km−2), whereas more frequent flows (with recurrence intervals of 2–10years) were not always recorded by exposed tree roots.

Soil Erosion Characteristics According to Tree-rings in a Karst Area

Abstract: Dendrogeomorphological method was used to study soil erosion in two typical karst sites (Puding and Zhengfeng) in Guizhou Province, China. Eleven pairs of exposed and unexposed tree roots were measured in the field and sampled for anatomical characteristics. The results showed that the exposed roots recorded karst soil erosion. Significant changes were shown in the anatomical characteristics of the exposed tree roots when soil erosion occurred, such as suddenly narrower tree rings, smaller cells, and fewer earlywood cells. Meanwhile, the fabre lumen and vessel lumen areas markedly declined to the range of 39.20% to 70.66%, which only slightly implies soil erosion. The accurate time period during which soil erosion occurred was identified and combined with the age of the tree roots. Dynamics of soil erosion were calculated and soil erosion recorded by the exposed roots from 2002 to 2007 at an average rate of 0.484 t y-1 at Puding, and from 2005 to 2007 at an average rate of 0.051 t y-1 at Zhenfen...

Exposed tree root analysis as a dendrogeomorphic approach to estimating bank retreat at the South River, Virginia

We use a biometric approach based on anatomical changes in the wood of exposed tree roots to quantify riverbank erosion along South River, Virginia, a site where commonly applied techniques for determining bank erosion rates are either not appropriate because of the required spatial scale of analysis (i.e., erosion pins, traditional surveys, LiDAR analysis) or have failed to detect obvious erosion (i.e., photogrammetric techniques). We sampled 73 exposed roots from 22 study reaches and identified the year of exposure macroscopically (2 to 20 times magnification) and microscopically (20 to 100 times magnification), comparing the estimated erosion rates between levels of magnification and to those obtained with photogrammetric techniques. We found no statistical differences between the results of macroscopic and microscopic analyses (t-test, α=0.01) but encountered difficulty in identifying the year of root exhumation in some samples. When comparing exposed root analysis to photogrammetric techniques, the results indicate that the exposed root approach is a feasible and effective method for estimating annual- to decadal-scale bank erosion. In addition to producing erosion rates statistically indistinguishable from photogrammetric techniques at sites with erosion rates large enough for detection using historical aerial photographs (regression analysis and t-test, α=0.01), exposed root analysis was able to estimate erosion rates at sites where photogrammetric techniques failed. We also identify deciduous species well suited for this approach (Fraxinus pennsylvanica) and others that prove more problematic (e.g., Acer negundo, Celtis occidentalis, Acer saccharinum). This study is significant because it describes a robust tool that provides insights into annual- to decadal-scale erosion where other commonly applied techniques may not be appropriate or easily applied.

ESTIMATING ANNUAL RIVERBANK EROSION RATES—A DENDROGEOMORPHIC METHOD

ABSTRACTAn accurate estimation of riverbank erosion rates is critical for the evaluation of the past, present, and future sediment regime of river systems. Understanding these relationships allows watershed managers and regulators to prioritize river restoration and contaminated site remediation projects. In this dendrogeomorphic study, changes in the anatomy of tree roots exposed between 1 and 31 years were used to estimate the average annual erosion rates of riverbank sediments on a large river in Michigan, USA. Exposed root samples from diffuse and ring‐porous hardwoods, together with buried ones as controls, were analyzed. Differences in the arrangement, size and frequency of vessels, fiber diameter, cell wall thickness, growth ring width, and scarring between the exposed and the buried samples were used to identify the first year of root exposure. Results of the regression analysis between the average annual erosion rate and the Bank Erosion Hazard Index (BEHI) indicated that the more recently exposed roots (less than 7 years in this study) explained more of the variance (R2 = 0.67) than when all samples were included (R2 = 0.38). Although the average erosion rates for long periods can be accurately determined from the dating of exposed tree roots, attempts to relate these rates using the BEHI for longer periods are less successful, as BEHI values can vary considerably over time as the riverbank erodes. Consequently, when using exposed tree roots to develop regression equations and erosion rate curves for the estimation of erosion rates based on BEHI scores, it is necessary to use roots that were recently exposed. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Spatiotemporal analysis of channel wall erosion in ephemeral torrents using tree roots—An example from the Patagonian Andes

This paper presents absolute ages for fl ash fl oods and related sediment entrainment in headwater catchments to construct a spatiotemporal framework of process dynamics and locations of major areas of channel wall erosion. The most reliable method for dating erosion is through dendrogeomorphic studies of exposed tree roots. Based on the analysis of erosion signals in root-ring records we documented a time series of channel wall erosion and successfully dated 21 erosive fl ash fl ood events since A.D. 1870 in an ephemeral gully in the Patagonian Andes. The study was performed with roots from Austrocedrus chilensis, Nothofagus dombeyi, and Pseudotsuga menziesii. Results demonstrate the potential of root analyses for the determination of major areas of sediment entrainment. In addition, we show that the position of damage within individual root rings allows inferences about the seasonal timing of fl ash fl ood effects and thus an assessment of possible meteorological triggers of erosive events, short intense storms occurring primarily in austral fall and late winter in this case. The approach presented adds signifi cantly to the documentation of sediment entrainment and facilitates identifi cation of areas of rapid erosion in small, remote headwater catchments with ephemeral fl ash fl ood activity.

The zoogeomorphic characteristics of burrows and burrowing by nine-banded armadillos (Dasypus novemcinctus)

Burrowing animals act like a geomorphic disturbance, changing the environment through soil excavation, landform creation and bioturbation. The potential zoogeomorphic effects of these actions include modification of surficial features, increased soil erosion, changes in the growth and distribution of vegetation, and modifications to soil fertility. The burrowing ninebanded armadillo (Dasypus novemcinctus) migrated to North America prior to the 1850s and has since continued to expand its habitat to the American Southeast and parts of the Midwest. Little data are available on the zoogeomorphic impact of the burrowing nature of this species, making it difficult to predict future implications of this animal as it continues to migrate into new regions. On the University of South Alabama campus, in Mobile, Alabama, armadillos are present on a 35-hectare unprotected forested preserve used by the university community for outdoor activities and research. To understand the potential zoogeomorphic impact of armadillo burrows on the local environment, morphometric measurements were recorded on 187 burrows located in the study area. Using dimensions of burrow entrances and minimum lengths of tunnels in calculations, armadillos excavated approximately 0.029m3 to 0.04m3 of soil from each burrow. The entrances to burrows averaged 33.5° in slope and tended to be located in a microhabitat of a fallen tree, exposed tree roots, or a sideslope. Persistent fall of forest litter and anthropogenic modifications makes positive identification of spoil mounds possible in approximately half of the burrow sites. Surface modification by armadillos is ongoing in the study area with over half of the burrows classified as active during the four-month project. We concluded that, for southern Alabama, armadillos prefer to excavate burrows into sideslopes, and that given the lack of ground cover, sandy soil, and humid climate, armadillos are an important zoogeomorphic agent in the region.

Measuring medium-term sheet erosion in gullies from trees: A case study using dendrogeomorphological analysis of exposed pine roots in central Iberia

The assessment of gully erosion poses a great challenge because of the complexity and connectivity of the geomorphic processes involved. This study focuses on the quantification of sheet erosion rates in a set of slope gullies located on the northern piedmont of the Guadarrama Mountains (Spanish Central System). In order to delineate accurately the gully areas in which sheet erosion was predominant, the Hydrologic/Erosion Response Unit (HRU/ERU) approach was used and a dendrogeomorphological analysis of exposed tree roots was carried out to quantify sheet erosion rates in one selected HRU/ERU. Identification of the first year of exposure by erosion from anatomical criteria was therefore critical. The 29 samples taken were prepared for anatomical analysis and cross-dated. Anatomical analysis of the samples showed a reduction in the lumen area of earlywood tracheids following root exposure and also, in most cases, a slight increase in growth rings. Moreover, at the end of the ring, latewood tissue and visible annual borders were very clearly defined by several rows of thick-walled tracheids. A non-parametric test was used on the findings derived from this qualitative analysis to objectify determination of the first year of exposure. Estimates of sheet erosion were obtained by dividing the height of eroded soil by the number of years that each root was exposed. The mean value of soil erosion for the entire study site was then determined from statistical inference. Using this procedure, a range of sheet erosion rates between 6.2 and 8.8 mm y −1 (125.2 and 177.8 t ha −1 year −1) was obtained for the dominant HRU/ERU of these gullies in central Iberia. These estimates of eroded soil thickness were adjusted based on the recent finding that root anatomical changes occur prior to their exposure by erosion.

Reproductive Role of Infrared Radiation Sensors ofMelanophila acuminata(Coleoptera: Buprestidae) at Forest Fires

AbstractBased on the original experimental results from stimulating the infrared radiation sensors of Melanophila acuminata (DeGeer) (Coleoptera: Buprestidae), it has been concluded that the sensors function at forest fires by protecting beetles from hazardous conditions associated with a flaming environment while swarming, mating, and ovipositing on heated, exposed tree roots. The beetles are renowned for their rapid flight and for their exceptional dispersal capacity resulting in such a wide distribution that they come upon fires randomly. Thus, a case is made here that the infrared radiation sensors of M. acuminata and, presumably, other species in the genus, evolved not for distance perception of fires but for enhanced reproductive activities at them. An examination of the literature has revealed a long-standing interest in distances of perception of forest fires by the sensors, during which time increasingly longer distances have been claimed in various publications. These distances, however, cannot be accepted because there are no calculations supporting them, but just as important is that all of them, ranging up to 100 km in length, far exceed distances obtained by application of the inverse square law of physics where the intensity of radiation of a fire is inversely proportional to distance.

Response of &amp;lt;i&amp;gt;Pinus sylvestris&amp;lt;/i&amp;gt; roots to sheet-erosion exposure: an anatomical approach

Abstract. Anatomical changes of exposed tree roots are valuable tools to date erosion events, but the responses of diverse species under different types of erosion need still to be studied in detail. In this paper we analyze the histological changes that occur in roots of Scots pine (Pinus sylvestris L.) subjected to continuous denudation. A descriptive and quantitative study was conducted in the Senda Schmidt, a popular trail located on the northern slope of the Sierra de Guadarrama (Central Iberian System, Spain). Measurement of significant parameters allowed the moment of exposure of the roots to be identified. These parameters were: a) width of the growth ring; b) number of cells per ring; c) percentage of latewood and d) diameter of cellular light in earlywood. A one-way analysis ANOVA was also carried out in order to establish statistically significant differences between homogeneous groups of measurements in pre-exposed and exposed roots. Based on these analyses, Scots pine roots show a remarkable anatomical response to sheet-erosion exposure. Increased growth in the ring is accompanied by a slight reduction of the cell lumina of the earlywood tracheids. At the end of the ring, several rows of thick-walled tracheids define latewood tissue and visible annual borders very clearly. Furthermore, resin ducts often appear in tangential rows, increasing resin density in the tissue. All of these indicators made it possible to determine with precision the first year of exposure and to estimate precisely sheet erosion rates.

Application of ash (Fraxinus excelsior L.) roots to determine erosion rates in mountain torrents

Abstract Due to the effect of global change, the potential risk of natural hazards occurring in alpine areas is expected to increase to an even higher risk-level than has been recorded during the last century. These global changes potentially also have distinct influences on fluvial processes in torrents causing erosion on slopes and riverbanks in forested areas. Dating the time of root exposure along riverbanks combined with common dendrogeomorphic analysis applied to tree trunks helps to reconstruct the erosion dynamics leading to a potential destabilization of adjoining trees. The advantage of using exposed roots compared to common erosion measurement techniques is that the erosion rates can be quantified with annual resolution. The first year of exposure can be determined precisely by the characterization of the wood anatomical changes in the microscopic structure of the root. This study is the first to concentrate on the analysis of wood anatomical features of exposed roots of angiosperm trees aiming to reconstruct erosional processes. Two mountain torrents were selected as study sites based on a preliminary evaluation of various Swiss alpine areas. Sites of special interest concerning erosive processes were classified and examined in five different geomorphological groups representing different processes. The analysis comprised the examination of the exposed tree roots in each group. The project shows the potential of roots in general and in particular roots of deciduous angiosperm trees for geomorphological research, especially concerning erosion studies.