【摘要】 [目的]探究不同林分密度、坡度和坡向条件下油松人工林细根(≤2 mm)生物量和细根形态的垂直分布规律,为晋西黄土区植被管理和生态建设评价提供依据。[方法]以油松人工林为研究对象,选择不同林分密度M1(<2 000株/hm~2)、M2(2 000～3 000株/hm~2)、M3(3 000～4 000株/hm~2)、M4(4 000～5 000株/hm~2)、M5(> 5 000株/hm~2),不同坡度(≤20°、20°～30°、30°～40°)和坡向(阴坡和阳坡)的样地,采用根钻法分层获取0～100 cm土层中的细根,对细根生物量密度、根长密度、组织密度、比根长和比表面积的垂直分布特征及其影响因素进行研究。[结果](1)0～100 cm土层的细根生物量密度随林分密度增大呈单峰变化趋势(M4密度条件下达到最大值606.19 g/m~3),不同坡度和坡向条件下细根生物量密度及其垂直分布没有明显变化趋势。细根生物量密度随土层深度增加呈显著递减趋势(P<0.05),主要集中在0～20 cm土层中,占比38%以上。(2)随着林分密度增加,0～100 cm土层的细根根长密度呈单峰变化趋势(M4密度下达到最高值3 639.73 m/m~2),比根长和比表面积呈先减小后增加的趋势(在M4密度下达到最低值:比根长601 cm/g,比表面积101.09 cm~2/g)。坡度和坡向对细根形态及其垂直分布的影响均不显著。垂直方向上,各林分密度0～40 cm土层的细根根长密度占比均在60%以上。在0～20 cm土层,比根长和比表面积随林分密度的增加先减少后增加(P<0.05)。(3)相关性分析显示,林分密度和土层深度对细根生物量密度和细根形态有显著影响。细根生物量密度和根长密度与林分密度、土壤全碳、全氮以及有机碳显著正相关,与土壤深度和C:N显著负相关。比根长、比表面积与林分密度和土壤有机碳显著负相关,与土壤深度显著正相关(P<0.05)。[结论]林分密度是油松人工林细根特征的关键调控因子,可通过林分管理措施来调整人工林林分密度以及细根生存策略,以此提高油松人工林应对环境胁迫的适应性,为半干旱区人工林可持续经营提供理论支持。更多还原

【Abstract】 [Objective] This paper explores the vertical distribution of fine root biomass(≤ 2 mm) and fine root morphology of P. tabuliformis plantations under different stand densities, slopes and aspects, so as to provide a basis for vegetation management and ecological construction evaluation in the loess region of western Shanxi Province of northern China. [Method] We investigated the vertical distribution and influencing factors of fine root characteristics, including fine root biomass density, length density, tissue density, specific root length and specific surface area in 0-100 cm soil layer of P. tabuliformis under five stand densities(M1(< 2 000 tree/ha), M2(2 000-3 000 tree/ha), M3(3 000-4 000 tree/ha), M4(4 000-5 000 tree/ha), M5(> 5 000 tree/ha)), three slopes(≤ 20°, 20°-30°, 30°-40°) and two aspects(shady slope and sunny slope). [Result](1) The fine root biomass density in 0-100 cm soil layer exhibited a unimodal pattern with the increase in stand density, reaching its peak at 606.19 g/m~3 with M4 density. The slope and aspect showed no significant impact on fine root biomass density. The density of fine root biomass decreased significantly with the increase of soil depth(P < 0.05), mainly concentrated in 0-20 cm soil layer,accounting for more than 38%.(2) With the increase of stand density, the fine root length density of 0-100 cm soil layer showed a unimodal pattern(the maximum value with 3 639.73 m/m~2 at M4 density), and the specific root length and specific surface area showed a trend of decreasing first and then increasing(the minimum values with 601 cm/g and 101.09 cm~2/g, respectively). While slope and aspect had no significant effects on the morphology and vertical distribution of fine roots. In the vertical direction, the ratio of fine root length density in 0-40 cm soil layer of each stand density was more than 60%. The specific root length and specific surface area of the 0-20 cm soil layer initially decreased and then increased as stand density increased(P<0.05).(3) Correlation analysis showed that stand density and soil depth significantly influenced fine root biomass density and morphology. Fine root biomass density and root length density were significantly positively correlated with stand density, soil total carbon, total nitrogen and organic carbon,significantly negatively correlated with soil depth and C∶N. Specific root length and specific surface area were significantly negatively correlated with stand density and soil organic carbon, and significantly positively correlated with soil depth(P < 0.05). [Conclusion] Stand density is a key regulatory factor for fine root characteristics of P. tabuliformis plantations. Stand management measures can be used to adjust stand density and fine root survival strategies, so as to improve the adaptability of P. tabuliformis plantations to cope with environmental stress, and provide theoretical support for sustainable management of artificial forest in semi-arid regions.更多还原