坝上地区不同退化程度小叶杨细根分布特征

为了研究坝上地区不同退化程度小叶杨的细根分布特征,使用土柱法对比了未退化、中度退化和重度退化小叶杨的细根在水平和垂直方向的根系参数的分布规律以及差异,并分析了根系参数在不同土层中的占比。结果表明:(1)随着林地土壤含水率逐渐减小,小叶杨的退化程度加重,细根在表层的占比逐渐增加,在深层的占比逐渐减小。(2)在垂直方向上,3种退化程度小叶杨的细根生物量在0—20 cm土层显著高于其他土层(P0.05),并随土层加深而出现细根的根长密度、根表面积密度、根体积密度的较明显下降趋势。在0—20,20—40,40—60,60—80,80—100 cm土层,细根的根表面积密度和根体积密度均表现为未退化中度退化重度退化。(3)在离开树干的水平方向上,未退化和中度退化小叶杨的细根的根长密度呈现出先增加后减小的变化趋势,而重度退化在0—50,50—100,100—150 cm处相差不大,在150—200 cm处显著增加并达到最大(0.465 7 cm/cm~3)(P0.05)。细根的根表面积密度和根体积密度在4个水平距离上均表现为未退化中度退化重度退化,未退化小叶杨的细根生物量均为最大(19.53,15.74,14.17,14.20 g)。根体积密度整体上随水平距离增加而逐渐减小。研究结果可为探索防护林的细根分布格局和退化原因以及为指导坝上高原地区的植被恢复与重建提供科学参考。

Fine Roots Distribution Characteristics of Populus simonii with Different Degradation Degrees in Bashang Area

In order to study the distribution characteristics of the fine roots of Populus simonii with different degradation degrees in Bashang area, this paper used soil column method to compare the distribution rules and difference of fine root parameters in horizontal and vertical directions in P. simonii stands with different degradation degrees (no degradation, moderate degradation and severe degradation), and analyzed the proportion of root parameters in different soil layers. The results showed that:(1) With the decreasing of soil moisture content, the degradation degree of P. simonii increased, the proportion of fine roots in the surface layer increased, and its proportion in the deep layer decreased. (2) In the vertical direction, the fine root biomass of P. simonii in 0-20 cm soil layer was significantly higher than that in other soil layers (P < 0.05), and the root length density, root surface area density and root volume density decreased significantly with the deepening of soil layer. In 0-20, 20-40, 40-60, 60-80 and 80-100 cm soil layers, the root surface area density and root volume density of fine roots followed the order of no degradation>moderately degradation>severely degradation. (3) In the horizontal direction away from the trunk, the root length density of fine roots increased at first and then decreased in no degeneration and moderately degeneration stands, while there was no significant difference among 0-50, 50-100 and 100-150 cm soil layers in severely degenerated P. simonii stand, and that increased significantly in 150-200 cm soli layer and reached the maximum (0.465 7 cm/cm³) (P < 0.05). The root surface area density and root volume density of fine roots all followed the order of no degradation>moderately degradation>severely degradation at four horizontal distances. The fine root biomasses of no degraded P. simonii were all the largest (19.53, 15.74, 14.17 and 14.20 g). The root volume density decreased with the increasing of horizontal distance. The results of this study could provide a scientific reference for exploring the fine root distribution pattern and degradation reasons of shelterbelts, and for guiding the vegetation restoration and reconstruction in Bashang plateau.