不同林农复合模式对造林1年后毛白杨幼林根系的影响

Effects of different agro-forestry models on seedling root system of Populus tomentosa after one year of afforestation

【目的】林农复合经营是解决林农争地的有效途径,本文为探究新品种毛白杨幼林根系在造林1年后不同林农复合模式下的分布情况,研究了毛白杨幼林间作条件下细根根长密度(FRLD)和细根根质量密度(FRBD)在不同造林密度和间作模式下的空间分布,旨在筛选较佳的林农复合模式,为毛白杨幼林林下物种合理配置提供理论依据。【方法】本研究以1年生‘北林雄株1号’为试验材料,采用裂区试验设计,主区设置2个毛白杨常见造林密度:2 m×3 m和3 m×4 m,副区设置2个当地常见的林下间作模式:毛白杨+花生+菠菜(花生、菠菜轮作)、毛白杨+花生,以幼林常规抚育模式作为对照,共6个处理,每个处理设3次重复。造林1年后,每个处理及对照组选取3株标准木,沿树体行间水平方向每隔30 cm取根样,取到150 cm处;垂直方向从地表向下每20 cm取根样,取到80 cm处,共取根样1 080个。通过对毛白杨FRLD和FRBD的分析,研究不同林农复合模式对2年生毛白杨幼林根系的影响。【结果】造林1年后,不同造林密度对2年生毛白杨单株的FRLD和FRBD未表现出显著影响(P> 0. 05),后期还需继续观测;造林1年后的不同间作模式对2年生毛白杨FRLD和FRBD均有显著影响(P <0. 05),两者的交互作用对毛白杨的FRLD和FRBD无显著影响。不同林农复合模式在水平和垂直方向的细根集中分布区相同。水平方向上,毛白杨+花生+菠菜、毛白杨+花生、常规抚育3种不同模式下有超过56. 36%的FRLD和FRBD分布于0～30 cm土层范围内;垂直方向上,在0～20 cm和20～40 cm土层范围内FRLD和FRBD约占测量总体的78. 95%以上。对3种模式在水平和垂直方向上的FRLD和FRBD进行多重比较,发现毛白杨+花生+菠菜和毛白杨+花生2种模式在水平和垂直方向的FRLD和FRBD均高于毛白杨幼林常规抚育模式。【结论】不同林农复合模式下,2年生毛白杨幼林根系水平方向主要分布于0～30 cm,垂直方向主要分布于0～20 cm和20～40 cm,毛白杨幼林间作农作物在造林1年后可以促进林木根系的生长。

[Objective] Agro-forestry is an effective way to solve the dispute between forest land and agricultural land. In order to explore the distribution of the new roots of Populus tomentosa in the forestagricultural compound model after one year of afforestation,the spatial distribution of fine root length density ( FRLD) and fine root biomass density ( FRBD) under different afforestation densities and intercropping patterns under intercropping conditions of P. tomentosa were studied. The purpose of this study was to screen a better intercropping pattern and provide a theoretical basis for the rational allocation of species under young P. tomentosa forests. [Method] 1-year-old‘Beilin Xiongzhu No 1’,a new variety of P. tomentosa was used as the experimental material. The split-plot experimental design was used,the main area was set with two common plantation space of 2 m × 3 m and 3 m × 4 m,two common intercropping modes were set in the sub-zone,P. tomentosa + peanut + spinach ( peanut,spinach rotation) ,P. tomentosa + peanut,with one conventional tending of plantation as control,a total of 6 treatments,repeated 3 times. After 1 year of outplanting,three standard saplings were selected for each treatment,root samples were taken at intervals of 30 cm along the horizontal direction between rows of trees,both planting densities were taken at 150 cm,root samples were taken at intervals of 20 cm from the surface to 80 cm in the vertical direction,a total of 1 080 root samples were taken. By analyzing the FRLD and FRBD of P. tomentosa saplings,the effects of different agro-forestry patterns on the root system of P. tomentosa saplings were studied. [Result]The planting space had no significant effects on the total average fine root length density ( FRLD) and fine root biomass density ( FRBD) after one year of afforestation,need to continue observation later. However,different intercropping patterns had significant effects on the FRLD and FRBD of 2-year-old P. tomentosa saplings( P < 0. 05) ,the interaction between them had no significant effects on FRLD and FRBD. Different agro-forestry patterns were similar in the fine root distribution areas in horizontal and vertical directions. In the horizontal direction,more than 56. 36% of the FRLD and FRBD of P. tomentosa + peanut + spinach,P. tomentosa + peanut and conventional tending accounted for 0 - 30 cm. FRLD and FRBD in vertical direction accounted for more than 78. 95% of 0 - 80 cm in 0 - 20 cm and 20 - 40 cm soil layer. After comparing the three models in horizontal and vertical directions,The FRLD and FRBD in both the horizontal and vertical directions of P. tomentosa + peanut + spinach and P. tomentosa + peanut were higher than the conventional tending of P. tomentosa saplings. [Conclusion] It is concluded that under the different intercropping patterns,the horizontal distribution of FRLD and FRBD was mainly in 0 - 30 cm,and the vertical distribution is mainly in 0 - 20 cm and 20 - 40 cm,the intercropping of agricultural crops after planting could promote the root growth of P. tomentosa trees after one year of afforestation.