Impact of the different duration years of grazing prohibition on the mechanical strength characteristics of Elymus nutans roots and its composite systems in the Yellow River source region

doi:10.11686/cyxb2022351

Abstract

Abstract:

The aim of this research was to investigate how the duration years of grazing prohibition affects the mechanical properties of Elymus nutans roots and its root-soil composite systems. The study sites were the grassland with no grazing prohibition （CK） and the grasslands with 1， 4， or 10 years of grazing prohibition in Henan County， which is located in the Yellow River source region. The researchers conducted a set of laboratory-based tests on the tensile properties of roots of E. nutans and direct shear tests on the root-soil composite systemsto quantify the effect of the duration years of grazing prohibition on the mechanical properties of soil. The results showed that a shorter period of grazing prohibition positively affected the growth of E. nutans with the increased growth index， but a longer period had the negative effect with the decreased growth index. With prolonged grazing prohibition， the tensile resistance of the roots initially increased and then decreased， with root tensile resistance increased by 15.9% after 1 year and 14.8% after 4 years of grazing prohibition. Meanwhile， the tensile strength of single roots and the cohesion of root-soil composite systems decreased gradually with prolonged grazing inhibition. The tensile strength and cohesion decreased by 57.3% and 63.5%， respectively， after 10 years of grazing prohibition compared with CK. The cohesion of root-soil composite systems was positively correlated with root diameter and soil natural density and negatively correlated with the soil moisture content. The relationship between cohesion and root content initially became stronger and then weakened with prolonged prohibition of grazing. These results provide theoretical support and practical guidance for the effective prevention and control of grassland degradation， soil erosion， and other forms of environment damage in alpine regions.

Key words: the Yellow River source region, different duration years of grazing prohibition, Elymus nutans, tensile strength of single root, root-soil composite systems, shear strength

Wei-peng HE, Xia-song HU, Chang-yi LIU, Xuan LI, Xi-lai LI, Jiang-tao FU, Hai-jing LU, Fu-cheng YANG, Guo-rong LI. Impact of the different duration years of grazing prohibition on the mechanical strength characteristics of Elymus nutans roots and its composite systems in the Yellow River source region[J]. Acta Prataculturae Sinica, 2023, 32(5): 106-117.

Figures/Tables 11

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工况类型 Working conditions	平均株高 Average plant height （cm）	平均地径 Average plant diameter at ground surface （mm）
未禁牧No grazing prohibition	50.99±9.86c	1.45±0.37ab
1 a禁牧1 a grazing prohibition	52.67±10.84b	1.64±0.40a
4 a禁牧4 a grazing prohibition	66.65±18.23a	1.68±0.60a
10 a禁牧10 a grazing prohibition	34.65±9.62d	1.18±0.42b

工况类型 Working conditions	平均株高 Average plant height （cm）	平均地径 Average plant diameter at ground surface （mm）
未禁牧No grazing prohibition	50.99±9.86c	1.45±0.37ab
1 a禁牧1 a grazing prohibition	52.67±10.84b	1.64±0.40a
4 a禁牧4 a grazing prohibition	66.65±18.23a	1.68±0.60a
10 a禁牧10 a grazing prohibition	34.65±9.62d	1.18±0.42b

工况类型 Working conditions	平均根数Average root number （No.）		平均含根量Average root content （mg·cm^-3）
工况类型 Working conditions	0~10 cm	10~20 cm	0~10 cm	10~20 cm
未禁牧No grazing prohibition	942±538c	476±311b	11.70±6.98b	4.90±1.19b
1 a禁牧1 a grazing prohibition	1428±778a	996±581a	18.51±7.91a	11.71±5.16a
4 a禁牧4 a grazing prohibition	1199±974ab	861±392a	11.41±6.12b	9.10±5.93ab
10 a禁牧10 a grazing prohibition	900±251c	435±151b	6.10±2.00c	4.30±2.10b

工况类型 Working conditions	平均根数Average root number （No.）		平均含根量Average root content （mg·cm^-3）
工况类型 Working conditions	0~10 cm	10~20 cm	0~10 cm	10~20 cm
未禁牧No grazing prohibition	942±538c	476±311b	11.70±6.98b	4.90±1.19b
1 a禁牧1 a grazing prohibition	1428±778a	996±581a	18.51±7.91a	11.71±5.16a
4 a禁牧4 a grazing prohibition	1199±974ab	861±392a	11.41±6.12b	9.10±5.93ab
10 a禁牧10 a grazing prohibition	900±251c	435±151b	6.10±2.00c	4.30±2.10b

工况类型 Working conditions	平均根径 Average root diameter （D， mm）	单根抗拉力Tensile resistance of single root			单根抗拉强度Tensile strength of single root
工况类型 Working conditions	平均根径 Average root diameter （D， mm）	平均抗拉力 Average tensile resistance （F， N）	回归方程 Regression equation	拟合优度R² Goodness of fit R²	平均抗拉强度 Average tensile strength （T_N， MPa）	回归方程 Regression equation	拟合优度R² Goodness of fit R²
未禁牧No grazing prohibition	0.19±0.05	2.63±1.20ab	F=38.238D^1.646	0.9707	88.21±11.06a	T_N=48.684D^-0.354	0.6049
1 a禁牧1 a grazing prohibition	0.23±0.04	3.05±1.32a	F=19.388D^1.768	0.8740	78.36±23.59a	T_N=24.280D^-0.740	0.7016
4 a禁牧4 a grazing prohibition	0.26±0.11	3.02±1.74a	F=14.107D^1.564	0.8768	63.91±24.18b	T_N=17.963D^-0.836	0.7862
10 a禁牧10 a grazing prohibition	0.28±0.09	2.26±1.06b	F=14.152D^1.463	0.9566	37.63±7.71c	T_N=18.020D^-0.537	0.7478