Root strength comparison between early and late successional trees in a subtropical forest

2020 ◽  
Author(s):  
Cang-Wei Chen ◽  
Guo-Zhang M. Song ◽  
Li-Wan Chang ◽  
Chien-Jui Ko ◽  
Hsin-Tien Lee ◽  
...  
Keyword(s):  
Slope Stability ◽  
Tree Species ◽  
Survival Function ◽  
Root Diameter ◽  
Single Root ◽  
Pull Out ◽  
Daunting Task ◽  
Root Strength ◽  
Successional Species ◽  
Central Taiwan

<p><strong>ABSTRACT    </strong></p><p>Slope stability of forested areas is often determined by tree root strength. After landslides, the early successional species emerged first, followed by the late successional species. This study aimed to examine whether tree root strength varies as tree species change along with the succession sequence. The study site is in the Lienhuachi Experimental Forest in central Taiwan, where multiple landslides happened in 2008. Three dominant early (Mallotus paniculatus, Sapium discolor, and Schefflera octophylla) and three late successional species (Cryptocarya chinensis, Engelhardtia roxburghiana, and Randia cochinchinensis) were sampled to conduct the single-root-pull-out tests in the field. Root strength which varies with root diameters was estimated with the Root Bundle Model with the root-failure Weibull survival function (RBMw). Results showed that the overall root strength of the early successional tree species were higher than that of late successional species only when root diameter was lower than 5.44 mm. However, among the six species, the root strength of Sapium discolor, an early successional species, was highest and the species with the lowest root strength was a late successional species (Engelhardtia roxburghiana). To precisely estimate tree effects on slope stability, our results highlighted the need to collect root strength data specifically for each species, even though it will be a daunting task for areas rich in tree diversity.</p><p><strong>Keyword: landslide, Root Bundle Model, vegetation succession </strong></p>

scholarly journals Modeling root reinforcement using a root-failure Weibull survival function

2013 ◽  
Vol 17 (11) ◽  
pp. 4367-4377 ◽  
Author(s):  
M. Schwarz ◽  
F. Giadrossich ◽  
D. Cohen
Keyword(s):  
Mechanical Properties ◽  
Slope Stability ◽  
Root Distribution ◽  
Survival Function ◽  
Root Diameter ◽  
Root Turnover ◽  
Diameter Class ◽  
Root Reinforcement ◽  
Root Strength ◽  
Steep Slopes

Abstract. Root networks contribute to slope stability through complex interactions with soil that include mechanical compression and tension. Due to the spatial heterogeneity of root distribution and the dynamics of root turnover, the quantification of root reinforcement on steep slopes is challenging and consequently the calculation of slope stability also. Although considerable progress has been made, some important aspects of root mechanics remain neglected. In this study we address specifically the role of root-strength variability on the mechanical behavior of a root bundle. Many factors contribute to the variability of root mechanical properties even within a single class of diameter. This work presents a new approach for quantifying root reinforcement that considers the variability of mechanical properties of each root diameter class. Using the data of laboratory tensile tests and field pullout tests, we calibrate the parameters of the Weibull survival function to implement the variability of root strength in a numerical model for the calculation of root reinforcement (RBMw). The results show that, for both laboratory and field data sets, the parameters of the Weibull distribution may be considered constant with the exponent equal to 2 and the normalized failure displacement equal to 1. Moreover, the results show that the variability of root strength in each root diameter class has a major influence on the behavior of a root bundle with important implications when considering different approaches in slope stability calculation. Sensitivity analysis shows that the calibration of the equations of the tensile force, the elasticity of the roots, and the root distribution are the most important steps. The new model allows the characterization of root reinforcement in terms of maximum pullout force, stiffness, and energy. Moreover, it simplifies the implementation of root reinforcement in slope stability models. The realistic quantification of root reinforcement for tensile, shear and compression behavior allows for the consideration of the stabilization effects of root networks on steep slopes and the influence that this has on the triggering of shallow landslides.

scholarly journals Modeling root reinforcement using root-failure Weibull survival function

2013 ◽  
Vol 10 (3) ◽  
pp. 3843-3868 ◽  
Author(s):  
M. Schwarz ◽  
F. Giadrossich ◽  
D. Cohen
Keyword(s):  
Mechanical Properties ◽  
Slope Stability ◽  
Root Distribution ◽  
Survival Function ◽  
Root Diameter ◽  
Root Turnover ◽  
Diameter Class ◽  
Stability Calculation ◽  
Root Reinforcement ◽  
Root Strength

Abstract. Root networks contribute to slope stability through complicated interactions that include mechanical compression and tension. Due to the spatial heterogeneity of root distribution and the dynamic of root turnover, the quantification of root reinforcement on steep slope is challenging and consequently the calculation of slope stability as well. Although the considerable advances in root reinforcement modeling, some important aspect remain neglected. In this study we address in particular to the role of root strength variability on the mechanical behaviors of a root bundle. Many factors may contribute to the variability of root mechanical properties even considering a single class of diameter. This work presents a new approach for quantifying root reinforcement that considers the variability of mechanical properties of each root diameter class. Using the data of laboratory tensile tests and field pullout tests, we calibrate the parameters of the Weibull survival function to implement the variability of root strength in a numerical model for the calculation of root reinforcement (RBMw). The results show that, for both laboratory and field datasets, the parameters of the Weibull distribution may be considered constant with the exponent equal to 2 and the normalized failure displacement equal to 1. Moreover, the results show that the variability of root strength in each root diameter class has a major influence on the behavior of a root bundle with important implications when considering different approaches in slope stability calculation. Sensitivity analysis shows that the calibration of the tensile force and the elasticity of the roots are the most important equations, as well as the root distribution. The new model allows the characterization of root reinforcement in terms of maximum pullout force, stiffness, and energy. Moreover, it simplifies the implementation of root reinforcement in slope stability models. The realistic quantification of root reinforcement for tensile, shear and compression behavior allows the consideration of the stabilization effects of root networks on steep slopes and the influence that this has on the triggering of shallow landslides.

Building regression models to estimate tree traits influential to slope stability

2020 ◽  
Author(s):  
Hsin-Tien Lee ◽  
Guo-Zhang M. Song ◽  
Li-Wan Chang ◽  
Cang-wei Chen ◽  
Hung-Yen Hu
Keyword(s):  
Slope Stability ◽  
Tree Species ◽  
Regression Models ◽  
Model Performance ◽  
Poor Performance ◽  
Wind Loading ◽  
Breast Height ◽  
Stem Flow ◽  
Forest Dynamics Plot ◽  
Central Taiwan

<p><strong>ABSTRACT    </strong> The above-ground (shoot) system of trees can affect slope stability through effects of infiltration facilitation, surcharge and wind loading. The amount of stem flow that infiltrates into soils is determined by diameter at root collar (DRC) of trees. Tree weight (surcharge) is a function of their heights (H) and diameters at breast height (DBH). Wind loading is related to crown area (CA) of trees. To save efforts for measuring all of these traits, we aimed to build regression models which allow researchers to estimate the other three traits with DBH. The study site was located in the Lienhuachih Forest Dynamics Plot, central Taiwan. DBH, DRC, CA and H of 20-30 individuals for the 18 most dominant tree species were measures. Trees which have been snapped off were excluded. Results showed that the regression models between DRC and DBH were linear. The models of CA against DBH and H against DBH was best built with allometric models, indicating that CA and H stop to increase with DBH once DBH reach to a certain size. In terms of model performance, the models of DRC against DBH was best (r<sup>2</sup>= 0.48- 0.97), followed by those of H against DBH (r<sup>2</sup>= 0.32- 0.89). The relatively poor performance of CA against DBH models (r<sup>2</sup>= 0.15- 0.93), especially for light-demanding tree species, indicated the need of incorporating light environment (i.e. crown illumination index) into regression analysis.</p><p> </p><p>Key word：allomeric model, broad-leaved forest, diameters at breast height, landslide, Lienhuachih</p>

Mechanical Characteristics of Peanut Root System and its Tribological Properties against Soil

2012 ◽  
Vol 209-211 ◽  
pp. 1177-1182
Author(s):  
Xiao Ming Zhang ◽  
Qian Jin Liu ◽  
Xing Xiu Yu
Keyword(s):  
Applied Stress ◽  
Mechanical Characteristics ◽  
Root Diameter ◽  
Soil Resistance ◽  
Reinforcement Effect ◽  
Root Reinforcement ◽  
Single Root ◽  
Pull Out ◽  
The Relationship ◽  
Diameter Classes

Peanut root of crop lands in Menglianggu watershed in the upper reaches of Yi River were classified into different diameter classes by root diameter. The results show that (1) the relationship between force of pullout or breaking and root diameter is approximately linearity, and more significant linear for the latter; (2) Laboratory tests confirm the presence of a threshold or range of root diameter. When the diameter within the range (1.80-3.01mm), both root breaking and pullout occurred; when the diameter above 3.01mm, all roots broke under applied stress. While below 1.80mm, only roots were pulled out under applied stress. Root-soil resistance characteristic and root reinforcement effect were analyzed for different root classes: (3) pull out force of root-soil resistance is stronger than that of single root of the same root classes with the range from 6.03% to 39.39%.

scholarly journals Diurnal and seasonal carbon balance of four tropical tree species differing in successional status

2008 ◽  
Vol 68 (4) ◽  
pp. 781-793 ◽  
Author(s):  
GM. Souza ◽  
RV. Ribeiro ◽  
AM. Sato ◽  
MS. Oliveira
Keyword(s):  
Functional Groups ◽  
Tree Species ◽  
Carbon Balance ◽  
Dark Respiration ◽  
Tropical Tree ◽  
Pioneer Species ◽  
Wet Season ◽  
Gross Photosynthesis ◽  
Tropical Tree Species ◽  
Successional Species

This study addressed some questions about how a suitable leaf carbon balance can be attained for different functional groups of tropical tree species under contrasting forest light environments. The study was carried out in a fragment of semi-deciduous seasonal forest in Narandiba county, São Paulo Estate, Brazil. 10-month-old seedlings of four tropical tree species, Bauhinia forficata Link (Caesalpinioideae) and Guazuma ulmifolia Lam. (Sterculiaceae) as light-demanding pioneer species, and Hymenaea courbaril L. (Caesalpinioideae) and Esenbeckia leiocarpa Engl. (Rutaceae) as late successional species, were grown under gap and understorey conditions. Diurnal courses of net photosynthesis (Pn) and transpiration were recorded with an open system portable infrared gas analyzer in two different seasons. Dark respiration and photorespiration were also evaluated in the same leaves used for Pn measurements after dark adaptation. Our results showed that diurnal-integrated dark respiration (Rdi) of late successional species were similar to pioneer species. On the other hand, photorespiration rates were often higher in pioneer than in late successional species in the gap. However, the relative contribution of these parameters to leaf carbon balance was similar in all species in both environmental conditions. Considering diurnal-integrated values, gross photosynthesis (Pgi) was dramatically higher in gap than in understorey, regardless of species. In both evaluated months, there were no differences among species of different functional groups under shade conditions. The same was observed in May (dry season) under gap conditions. In such light environment, pioneers were distinguished from late successional species in November (wet season), showing that ecophysiological performance can have a straightforward relation to seasonality.

scholarly journals The contribution of chestnut coppice forests on slope stability in abandoned territory: a case study

2013 ◽  
Vol 44 (2s) ◽  
Author(s):  
Chiara Bassanelli ◽  
Gian Battista Bischetti ◽  
Enrico Antonio Chiaradia ◽  
Lorenzo Rossi ◽  
Chiara Vergani
Keyword(s):  
Slope Stability ◽  
Root Diameter ◽  
Slope Instability ◽  
Economic Changes ◽  
Sweet Chestnut ◽  
Forestry Practices ◽  
Short Rotation ◽  
Root Cohesion ◽  
Chestnut Coppice ◽  
High Level

Sweet chestnut has been for many centuries fundamental for the Italian mountainous economies, where this kind of forest was traditionally managed in short rotation to rapidly produce wood biomass. Due to the social and economic changes, which made such management scheme unprofitable especially on the steep and remote slopes, such practice has been mainly abandoned and most of chestnut forests became over-aged and very dense, causing an increase of localized slope instability. In this work the effect of over-aged chestnut coppice forests on shallow landslides was analysed by evaluating and comparing mechanical contribution to soil shear strength provided by root systems in differently managed chestnut stands. The study area is located in Valcuvia (Lombardy Prealps) where three different stands, one managed and the others abandoned (over 40 year aged), established on cohesionless slopes (quaternary moraine deposits) were chosen having care to select homogeneous conditions in terms of substrate, aspect and elevation. As slope steepness strongly affects forestry practices and steeper stands are more frequently abandoned, the considered stands have different terrain inclination, 30-35° in abandoned stands and 13° in the managed one. Slope stability of the three sites was evaluated by applying the infinite slope approach accounting for additional root cohesion and tree surcharge. Additional root cohesion was estimated through the Fiber Boundle Model approach by collecting roots in the field and measuring their resistance in laboratory, and by measuring root diameter and density distribution with depth by the wall technique method. The results, as expected, showed that over-aging does not affect root mechanical properties, whereas it significantly affects root distribution within the soil. In terms of slope stability, when steepness exceeds 35°, instability phenomena can be triggered by high level of soil saturation in the case of over-aged forests, whereas for less extreme cases chestnut forests, although over-aged, are able and fundamental to guarantee safe conditions.

scholarly journals Leaf and Crown Optical Properties of Five Early-, Mid- and Late-Successional Temperate Tree Species and Their Relation to Sapling Light Demand

Forests ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 925 ◽  
Author(s):  
Marc Hagemeier ◽  
Christoph Leuschner
Keyword(s):  
Optical Properties ◽  
Leaf Area ◽  
Tree Species ◽  
Forest Floor ◽  
The Sun ◽  
Area Index ◽  
Minimum Light ◽  
Tree Canopies ◽  
Successional Species ◽  
Shade Leaves

The optical properties of leaves and canopies determine the availability of radiation for photosynthesis and the penetration of light through tree canopies. How leaf absorptance, reflectance and transmittance and radiation transmission through tree canopies change with forest succession is not well understood. We measured the leaf optical properties in the photosynthetically active radiation (PAR) range of five Central European early-, mid- and late-successional temperate broadleaf tree species and studied the minimum light demand of the lowermost shade leaves and of the species’ offspring. Leaf absorptance in the 350–720 nm range varied between c. 70% and 77% in the crown of all five species with only a minor variation from the sun to the shade crown and between species. However, specific absorptance (absorptance normalized by mass per leaf area) increased about threefold from sun to shade leaves with decreasing leaf mass area (LMA) in the late-successional species (Carpinus betulus L., Tilia cordata Mill., Fagus sylvatica L.), while it was generally lower in the early- to mid-successional species (Betula pendula Roth, Quercus petraea (Matt.)Liebl.), where it changed only a little from sun to shade crown. Due to a significant increase in leaf area index, canopy PAR transmittance to the forest floor decreased from early- to late-successional species from ~15% to 1%–3% of incident PAR, linked to a decrease in the minimum light demand of the lowermost shade leaves (from ~20 to 1%–2%) and of the species’ saplings (from ~20 to 3%–4%). The median light intensity on the forest floor under a closed canopy was in all species lower than the saplings’ minimum light demand. We conclude that the optical properties of the sun leaves are very similar among early-, mid- and late-successional tree species, while the shade leaves of these groups differ not only morphologically, but also in terms of the resource investment needed to achieve high PAR absorptance.

scholarly journals Root diameter variations explained by anatomy and phylogeny of 50 tropical and temperate tree species

2014 ◽  
Vol 34 (4) ◽  
pp. 415-425 ◽  
Author(s):  
J. Gu ◽  
Y. Xu ◽  
X. Dong ◽  
H. Wang ◽  
Z. Wang
Keyword(s):  
Tree Species ◽  
Root Diameter

scholarly journals Tensile strength and cellulose content of Persian ironwood (Parrotia persica) roots as bioengineering material

2014 ◽  
Vol 60 (No. 10) ◽  
pp. 425-430 ◽  
Author(s):  
E. Abdi ◽  
F. Azhdari ◽  
A. Abdulkhani ◽  
H. Soofi Mariv
Keyword(s):  
Tensile Strength ◽  
Tensile Force ◽  
Root Diameter ◽  
Cellulose Content ◽  
The Road ◽  
Diameter Range ◽  
Lack Of Information ◽  
Root Strength ◽  
The Mean ◽  
Biotechnical Properties

Unstable slopes create numerous problems for forest management and may destroy the road network and disturb access to forest. Soil bioengineering is a solution that can prevent these problems and reinforce the hillslope. Persian ironwood is considered as a good protective species for hillslope stability in Iran with an extensive lack of information about biotechnical properties. In this research the root strength of this species and also the relation between root diameter and cellulose content were investigated. The results showed that the mean tensile force and tensile strength were 99.70 ± 2.01 N and 173.23 ± 4.94 MPa, respectively, for the root diameter range between 0.22 and 3.78 mm. The results of ANOVA showed that the power models between root diameter and tensile force and tensile strength were statistically significant and the results of t-test showed that coefficients and constants of the models are also significant. The values of the parameters of the power law (α and β) obtained for Persian ironwood do not fall in the range that has already been suggested for hardwood roots, which may be due to a narrow diameter range. The mean cellulose content was 56.87 ± 5.79% and the relationship between root diameter and cellulose content was not statistically significant. The data presented in this study expand the knowledge of biotechnical properties of Persian ironwood and support the idea that there is still an extensive lack of information about plant roots as a bioengineering material.    

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