A comparison of root distribution of three hardwood species grown on a hillside in the Caspian forest, Iran

Abstract

Slope is a complex environmental factor that can subject plants to a number of mechanical stresses. The anchorage of roots and improvement of slope stability mainly depend on specific properties of root systems, such as root distribution. In the present study, 24 trees (from three species) growing on gentle slopes (10-20°) were randomly chosen for root distribution analysis. The profile trenching method was used to obtain root characteristics. The findings indicated that root area ratio (RAR) decreased with depth and that maximum RAR values were observed in the upper layers; RAR values were between 0.0004% and 6.6444%. Average RAR values were not statistically different in upslope and downslope layers except in one case. The dot grid method (100 9 150 mm) usually overestimated the RAR values. The amount of roots decreased with depth following a power law. About 50% and 90% of roots were located in the first 30 and 60 cm depths, respectively. Results of analysis of covariance (ANCOVA) showed a significant effect of diameter at breast height (DBH) on total RAR but not on the total number of roots. About 70% of roots had diameter of less than 10 mm. Spearman's correlation showed significant negative correlation between the total number of roots and the amount of N, P, and K elements, and a positive correlation between DBH and RAR. The results serve to develop understanding of the biotechnical characteristics of root systems of Caspian species.

Investigation of Root Distribution and Tensile Strength of Acacia mangium Willd (Fabaceae) in the Rainforest

“…This study indicates that, RAR values decreased with soil depth which is in agreement with the result of earlier authors such as (Abdi et al, 2010 a, b;Bischetti et al, 2005;Burylo et al, 2011). Furthermore study shows that the highest RAR values are located in the second soil depth as indicated by the other authors (Burylo et al, 2011), and third soil layers Abdi et al, 2010b). The decline of RAR with soil depth is due to the reduction of nutrition and aeration in lower levels and presence of bedrock and compacted soil layers Chiaradia et al, 2012).…”

“…On the other hand, environmental conditions affect root cellulose content (Genet et al, 2005;Hales et al, 2009). The mean tensile strength of this study is 44.11 MPa which compared with other hardwood species, including Persian Ironwood 31.34 MPafor downhill and 25.20 for uphill (Abdi et al, 2010b), Quercus robur 32 MPa (Greenway, 1987), Alnussubcor data16.29 MPa (Naghdi et al, 2013). Therefore tensile strength is influenced by plant species and root diameter.…”

“…Values of root tensile strength decrease with increasing root diameters as studied by many other authors and can be well described by power law equation (Mattia et al, 2005;Tosi, 2007;Abdi et al, 2010b;Burylo et al, 2011). In the power law equation, the parameters depend on the plant species and environmental conditions.…”

“…In contrast, the highest RAR values were found to be in the first soil layer in the research conducted by Comino and Marengo (2010) in three different shrubs in Northern Italy. The maximum RAR values for beech was in the fourth layer in downslope and in the third soil depth for upslope as indicated by Abdi et al (2010b stressed that the general trend of RAR value decreased with soil depth, but in most cases the highest RAR values are in the first 30 cm soil profile. In Burylo et al (2011) research, RAR values significantly decreased with soil depth and the highest root distribution were in the upper 200 mm soil depth.…”

“…Four trees of A. mangium were selected along East-West highway, then one trench with a distance of 1 meter was dug (Abdi et al, 2010b). The dimension of profiles were 50 cm long × 70 cm depth.…”