Effects Of Agroforestry Models On Roots Of Some Trees And Crops In Northern Wei River

Distribution patterns and morphological variations of fine roots in walnut (Juglans regia)-wheat (Triticum aestivum), walnut-rape (Brassica campestris) and walnut-soybean (Glycine max) agroforestry systems were studied, which provided theoretical basis for the interspecific relationship research and management of agroforestry ecosystem. Samples were collected by soil coring method. WinRHIZO root analysis system was conducted to measure root morphology parameters. Moreover, differences of the fine roots spatial distribution and morphological variations between the agroforestry ecosystem and monocropping ecosystem were analyzed. The main results were below:1. In walnut-wheat agroforestry ecosystem, the mean fine root length density of walnuts in agroforestry ecosystem is 83.6 cm/dm3, less than in walnut monocropping ecosystem (135.6 cm/dm3), reduced by 38%. The mean fine root length density of wheat in agroforestry ecosystem is 1 736.7 cm/dm3, more than in wheat monocropping ecosystem (1 223.3 cm/dm3), increased by 42%. In walnut-rape agroforestry ecosystem, the mean fine root length density of walnuts in agroforestry ecosystem is 95.67 cm/dm3, less than in walnut monocropping ecosystem (113.43 cm/dm3), reduced by 15.7%. The mean fine root length density of rape in agroforestry ecosystem is 321.33 cm/dm3, more than in rape monocropping ecosystem (316.39 cm/dm3), increased by 1.6%. In walnut-soybean agroforestry ecosystem, the mean fine root length density of walnuts in agroforestry ecosystem is 120.67 cm/dm3, more than in walnut monocropping ecosystem (118.57 cm/dm3). The mean fine root length density of soybean in agroforestry ecosystem is 275.09 cm/dm3, less than in soybean monocropping ecosystem (378.66 cm/dm3), reduced by 27.3%.2. In walnut-wheat agroforestry ecosystem, the vertical gravity center of walnut fine root length in agroforestry ecosystem is 35.49 cm, compared with that in walnut monocropping ecosystem(29.97 cm), move down 5.52 cm. The distance between the radial gravity centers of walnut fine root length and the tree in agroforestry ecosystem is 0.91 m, which is closer 0.08 m to the tree than that walnut monocropping ecosystem(0.99 m). The veridical gravity center of wheat root length in agroforestry ecosystem is 18.46 cm, compared with that in wheat monocropping ecosystem(26.04 cm), move up 7.58 cm. In walnut-rape agroforestry ecosystem, the vertical gravity center of walnut fine root length in agroforestry ecosystem is 36.50 cm, compared with that in walnut monocropping ecosystem(31.90 cm), move down 4.60 cm. The distance between the radial gravity centers of walnut fine root length and the tree in agroforestry ecosystem is 0.86 m, which is closer 0.11 m to the tree than that walnut monocropping ecosystem(0.97 m). The veridical gravity center of rape root length in agroforestry ecosystem is 19.90 cm, compared with that in rape monocropping ecosystem(25.10 cm), move up 5.2 cm. In walnut-soybean agroforestry ecosystem, the vertical gravity center of walnut fine root length in agroforestry ecosystem is 31.7 cm, compared with that in walnut monocropping ecosystem(25.55 cm), move down 6.2 cm. The distance between the radial gravity centers of walnut fine root length and the tree in agroforestry ecosystem is 0.96 m, which is away 0.03 m from the tree than that walnut monocropping ecosystem(0.93 m). The veridical gravity center of soybean root length in agroforestry ecosystem is 19.50 cm, compared with that in soybean monocropping ecosystem(15.00 cm), move down 5.5 cm.3. In walnut-wheat agroforestry ecosystem, the mean fine root diameter of walnut in the 0 ~ 30 cm soil layer was 0.314 5 mm in agroforestry ecosystem, is smaller than 0.356 7 mm in walnut monocropping ecosystem. In 0～30 cm soil layer, the specific root length of walnut is 51.49 m/g in agroforestry ecosystem, is greatter than the 36.23 m/g in walnut monocropping ecosystem, but in 30～100 cm soil layer, the specific root length of walnut is 26.27 m/g in agroforestry ecosystem, is smaller than the 39.07 m/g in walnut monocropping ecosystem.The mean fine root diameter of wheat in the 0 ~ 50 cm soil layer was 0.295 5 mm in agroforestry ecosystem, is greater than 0.272 0 mm. in wheat monocropping ecosystem.In 0～50 cm soil layer, the specific root length of wheat is 100.20 m/g in agroforestry ecosystem, is smaller than the 118 12 m/g in wheat monocropping ecosystem. In 50～100 cm soil layer, the specific root length of wheat is 143.29 m/g in agroforestry ecosystem, is greatter than the 133.90 m/g in wheat monocropping ecosystem.In walnut-rape agroforestry ecosystem, the mean fine root diameter of walnut in agroforestry ecosystem is 0.355 9 mm, smaller than 0.372 2 mm in walnut monocropping ecosystem. The specific root length of walnut in agroforestry ecosystem is 40.90 m/g, is greatter than the 37.67 m/g in walnut monocropping ecosystem. The mean fine root diameter of rape in agroforestry ecosystem is 0.205 9 mm, greater than 0.183 3 mm in rape monocropping ecosystem. The specific root length of rape in agroforestry ecosystem is 156.98 m/g, is smaller than the 211.95 m/g in rape monocropping ecosystem.In walnut-soybean agroforestry ecosystem, the mean fine root diameter of walnut in agroforestry ecosystem is 0.316 8 mm, greatter than 0.265 8 mm in walnut monocropping ecosystem. The specific root length of walnut in agroforestry ecosystem is 48.98 m/g, is smaller than the 68.97 m/g in walnut monocropping ecosystem. The mean fine root diameter of soybean in agroforestry ecosystem is 0.254 9 mm, greater than 0.222 0 mm in soybean monocropping ecosystem. The specific root length of soybean in agroforestry ecosystem is 102.98 m/g, is smaller than the 135.06 m/g in soybean monocropping ecosystem.4. Walnut - wheat, walnut - rape, walnut -soybean three agroforestry ecosystem, are all decreased soil water content, comparing the three agroforestry ecosystem water conditions: walnut - soybean> walnut - rape> walnut - wheat.In summary, root competition in agroforestry ecosystem, the strong competitors depend on increase the fine root diameter and decreased specific root length to adapt to competition in the highly competitive area. On the contrary, the weak competitors tendency to decreased fine root diameter and increased specific root length to adapt to competition. In agroforestry ecosystem, most of the root competitions appeared in 0～30 cm soil layer and radial distance 1.5～2.0 m from the tree. As responses to adapt to the competition and maximize to access to resources in soils in agroforestry systems, the spatial distribution and morphology in fine roots might have a high plasticity during the growth of walnut and wheat.