菌根菌剂对科尔沁沙地3种常见造林绿化树种幼苗生长的影响

Effects of mycorrhizal inoculants on seedling growth of three common afforestation tree species in Horqin Sand Land

如何在沙地成功造林并使其快速生长是沙地生态环境建设面临的一个重大挑战。菌根菌剂具有改善造林树种生存环境、调节植物生长的作用,但菌根菌剂对不同植物的影响有何差异,以及如何依据不同生境条件和目标施用合适的菌根菌剂尚缺乏清晰认知。本研究以科尔沁沙地3种常见造林绿化树种樟子松(Pinus sylvestris var.mongolica)、紫穗槐(Amorpha fruticosa)和水蜡(Ligustrum obtusifolium)为对象,采用穴施方法按0、100、200和300 g·m^(-2)剂量,对紫穗槐和水蜡接种内生菌根菌剂(根内根孢囊霉,Rhizophagus intraradices),对樟子松接种外生菌根菌剂(彩色豆马勃,Pisolithus tinctorius)。在幼苗生长1年后,测定菌根侵染率及生长指标。结果表明:樟子松菌根侵染率随菌剂用量增加而显著增加,在300 g·m^(-2)处理下侵染率最高(17.8%);紫穗槐菌根侵染率随菌剂用量变化不显著;水蜡菌根侵染率随菌剂用量增加而显著减少,在100 g·m^(-2)处理下侵染率最高(19.3%);3种植物菌根依赖性平均大小为水蜡>樟子松>紫穗槐。添加菌剂后,樟子松除株高(200 g·m^(-2):26%)和吸收根质量(100 g·m^(-2):79.2%)外,各生长指标均降低;紫穗槐株高、地上生物量和总生物量在300 g·m^(-2)处理下平均显著增加21.7%;水蜡的基径、输导根质量、地上生物量、根系生物量和总生物量显著增加,最大增长均在100 g·m^(-2)处理下,分别提高47.0%、156.3%、207.6%、154.7%和186.6%。在100和200 g·m^(-2)处理下,水蜡生长指标增长率大多显著大于其他两树种;在300 g·m^(-2)处理下,紫穗槐主根长(38.5%)、输导根质量(45.5%)、根系生物量(45.3%)的增长率均显著大于其他两种树种。因此,菌剂对幼苗株高、吸收根质量、地上生物量、总生物量和根冠比增长率产生极显著影响,菌根菌剂促进水蜡地上部分生长但限制樟子松地下部分生长;高菌剂用量才能够促进紫穗槐生长。本研究为沙地造林合理施用菌根菌剂、加速植被恢复提供了依据。

It is a challenge for ecologists to afforest successfully and to accelerate plant growth in sand dune. Mycorrhizal inoculants play a role in improving habitat and regulating plant growth. However, it’s still unknown whether the effects of mycorrhizal inoculants depend on plant species identity and how to apply mycorrhizal inoculants to plants based on different habitat conditions and goals. We examined the effects of mycorrhizal inoculants on seedling growth of three woody species commonly used for afforestation in Horqin Sand Land. The arbuscular mycorrhizal inoculants(Rhizophagus intraradices) were applied to Amorpha fruticosa and Ligustrum obtusifolium, while the ectomycorrhizal inoculants(Pisolithus tinctorius) were applied to Pinus sylvestris var. mongolica at doses of 0, 100, 200, and 300 g·m^(-2)through adding into holes around the plant. The mycorrhizal colonization rate and seedling growth indices were measured after one year treatment. The colonization rate of P. sylvestris var. mongolica increased significantly with increasing doses of ectomycorrhizal inoculants, and was the highest at the dose of 300 g·m^(-2)(17.8%). The colonization rate of A. fruticosa did not change with the mycorrhizal amounts. The mycorrhizal colonization rate of L. obtusifolium decreased significantly with the mycorrhizal amounts, and was the highest at 100 g·m^(-2)(19.3%). L. obtusifolium had the highest mycorrhizal dependency and A. fruticosa had the lowest mycorrhizal dependency. Except for plant height(200 g·m^(-2): 26%) and absorptive root mass(100 g·m^(-2): 79.2%), all the other indices of P. sylvestris var. mongolica decreased after the application of ectomycorrhizal inoculants. Plant height, aboveground biomass, and total biomass of A. fruticosa increased significantly by 21.7% on average at the treatment of 300 g·m^(-2). The basal diameter, transport root mass, aboveground biomass, root biomass and total biomass of L. obtusifolium increased significantly compared with the control, with the maximum increase rates as 47%, 156.3%, 207.6%, 154.7% and 186.6% at 100 g·m^(-2), respectively. At the treatments of 100 and 200 g·m^(-2), all growth indices of L. obtusifolium were significantly increased compared to the other two species. At 300 g·m^(-2), main root length(38.5%), transporter root mass(45.5%), and root biomass(45.3%) of A. fruticosa were significantly increased compared to the other two species. Our results indicated that mycorrhizal inoculants have a significant effect on plant height, absorptive root mass, aboveground biomass, total biomass, and root-shoot ratio. Mycorrhizal inoculants can promote the aboveground growth of L. obtusifolium but restrict underground growth of P. sylvestris var. mongolica. Only high amount of mycorrhizal inoculants can promote the belowground growth of A. fruticosa. This study provides evidence for the rational application of mycorrhizal inoculants for afforestation in sand land to accelerate vegetation restoration.