06-04
Influence of the root strength of herbaceous vegetation inforest slopes of Mexico○Laura Sanchez Castillo, Graduate School of Bioresources and Bioenvironmental Sciences,Kyushu University
Tetsuya Kubota, Faculty of Agriculture, Kyushu University
Israel Cantú Silva, Universidad Autónoma de Nuevo León, México

1. Introduction
Soil erosion is one of the major environmental issues of Mountainous countries like Mexico. The mountainous
regions are inherently unstable and prone to different types of erosion causing natural geo-hazards. The surfaceerosion and landslides has been major environmental problems in the forest slopes of many countries. For
several years the problem of landslides processes and their interaction with erosion and deforestation have been
occurring in the forest slopes of Mexico causing a considerable sum of material damages, and human lives. The
application of vegetative techniques and the scientific study in erosion mitigation can be applied for road slope
stabilization but the systematic study on the relationships between vegetation and erosion is very limited. The
preparation and knowledge of this matter would make a great benefit for the making of decisions in thestabilization of slopes. The aim of this study is to find the pull out resistance force from herbaceous vegetation
species of the forest slopes of Mexico and find which species are more suitable for erosion control.
2.

Methodology and Study Area.
The study was conducted in two different sites of Mexico: 1) Iturbide, Nuevo Leon, 2) Linares, Nuevo Leon
(Figure 1). In order to investigate the influence of the root strength of herbaceous vegetation the sites weredelimitated with parcels of 25 m2. For carry out the pull out resistance force test, 30 herbaceous plants withdifferent sizes were randomly chosen per parcel. Before carrying pull out test, soil surface around the plant wascarefully cleared from litter exposing stem base. One end of a strong fine wire was tied around the stem base of
the plant and another end was connected to a hand-held portable Push Pull Digital Gage AIKOH Model
RX-100. The vertical force was loaded manually till plant was uprooted without mechanical damage to the rootsystems. In some tests, where roots were cut during extraction, tests were repeated. The peak force, at whichplants were just started to break off from the soil were recorded from the digital pulling gage (Figure 2). During
uprooting, it was revealed that the pull out resistive force was influenced by morphological characteristics, suchas shoot height, total numbers of roots present and root sizes of an individual species.

Fig 1. Location of Study Sites in Nuevo Leon,Fig 2. Schematic view of pullout experiment andMexico.

instrument used. A) illustration of pull out test, B)
instrument used for uprooting a plant.

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3. Results and Discussion
The relationships of the morphological characteristics such as shoot height and uprooting peak resistive force
were analyzed. As example the relationships between them are shown in the Figure 3. In the Site 1 (Iturbide)with species Abutilon incanum the maximum Pull Out Strength force of the herbaceous plants observed in thestudy sites ranged from 11.1 N to 115 N with a height of 15 cm and 55 cm respectively. Species Decatropis
bicolor ranged from 13.2 N to 79.8 N with height of 38 cm and 37 cm respectively. In the Site 2 for the specieMelochia tormentosa the Pullout Strength Force ranged from 49.5 N to 68.7 N with a height of 43.18 cm and40 cm. The Pull Out Strength force of the specie Turnera difusa ranged from 40.5 N to 90.8 N, with a height of
12.5 cm to 25 cm. The specie Croton cortesianus shown a range in Pull Out Strength Force of 54.5 N to 60.4 N,and a height of shoot of 35.5 cm and 39.37 cm. Gochnatia hypoleuca shown a range of Pull Out Strength Forceof 15 N to 22 N with a height of 13 cm and 16.5 cm respectively. The specie Salvia filipes show a range of Pull
Out Strenght Force of 33.8 N to 32.5 N with a height of 24.13 to 20.5 cm. Hibiscus cardiophyllus shown arange of 14.1 N to 91.1 and a height of 17.89 cm and 35.56 cm respectively.

Figure 3. Relationship between Height (cm) and Pull Out Resistance Force (N). A) Site 1:
Iturbide, Nuevo Leon. B) Site 2: Linares, Nuevo Leon.

4. Conclusion
The study of the herbaceous vegetation root systems might be a good indicator to know the site quality ineroded area, subsequent erosion state and to examine the relationships between plant and soil. The
understanding of this matter can be very useful for erosion control and to decrease the negative impacts onforest slopes, such as surface erosion or landslides. This study evaluated the Pull Out Strength force of
herbaceous plants of the forest slopes of Mexico and the data obtained from it revealed that Pull Out Strength
Force was determined by the combined morphological features of the plants like height, root morphology. The
maximum species observed in Iturbide Nuevo Leon (site 1) was Abutilon incanum with 115.8 N and in the site
2: Linares, Nuevo Leon the maximum Pull out resistance force observed was of 91.3 N with the specie
Hibiscus cardiophyllus. The pullout resistive strength of the plants is an important step in examining strengthof an individual species in erosion processes.
Reference
Devkota B. et al. 2006. Revegetation Condition and Morphological Characteristics of Grass Species Observedin Landslide Scars, Fukuoka, Japan. Journal of Applied Sciences, pp 2238-224.

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