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合理高效的水肥集约经营是有效地提高速生丰产林生产力的重要途径。细根是植物吸收水肥和维持生长的主要器官,了解细根形态及其分布对水肥耦合措施的响应机制有助于解释树木生长和吸收水肥能力的差异性。该文基于水氮耦合措施对欧美108杨(Populus×euramericana‘Guariento’)幼林表土层(0–30 cm)细根形态及分布的影响研究,在连续两年的水氮管理后,开展了欧美108杨0–60 cm土层细根形态及垂直分布对水氮耦合响应的研究。田间设计3个灌溉水平(灌溉土壤水势起始阈值为–75 k Pa、–50 k Pa、–25 k Pa)和3个养分水平(施N 150 g·tree–1·a–1、300 g·tree–1·a–1、450 g·tree–1·a–1),组合成9个水氮耦合处理,另设1个对照处理(CK)。研究结果表明:(1)垂直方向上,各处理细根生物量密度、表面积和平均直径均表现为10–20 cm土层最大(该层生物量密度占0–60 cm土层总生物量的27%–37%),随后在30–60 cm土层逐层递减;根长密度则随土壤深度的加深而逐层递减,0–10 cm土层显著大于其他土层(该层根长密度占0–60 cm土层总根长密度的33%–45%)。(2)6个土层的细根生物量密度、根长密度和平均直径均表现为高水高氮(D3F3)和中水高氮(D2F3)2个处理间差异不显著,但均显著高于其他处理,其中,D3F3处理6个土层生物量密度是对照的3.12–47.74倍;细根表面积则是D3F3处理显著高于其他处理,是CK的4.36–30.57倍。(3)连续的水氮耦合管理措施不会改变细根的垂直分布格局(各处理均具有与CK一致的分布格局),但在第二个生长季,欧美108杨细根的整体分布随着林龄的增加趋于深层化;另外,中水高氮的耦合处理也可有效地促进细根的生长,这种水氮需求水平与第一个生长季内需高水高氮才可显著促进其生长的特性不同。欧美108杨细根在第2个生长季主要分布于0–20 cm土层,9个水氮耦合处理中,除低水低氮处理外,其他处理各细根形态指标值均显著高于CK,这种差异性在浅土层更为显著,而在深土层表现出相对较小的差异。当灌溉量一定时(尤其中、高灌溉水平),增加施氮量可显著促进细根生长,但当施氮量一定时(尤其低、中氮水平),增加灌溉量对细根生长的促进效果不显著,即欧美108杨细根生长趋肥性强于向水性。
Reasonable and efficient intensive management of water and fertilizer is an important way to effectively improve the productivity of fast-growing and high-yield forests. Fine roots are the main organs that plants absorb water and fertilize and maintain growth. Understanding the response mechanism of root morphology and its distribution to water and fertilizer coupling helps to explain the differences in tree growth and water and fertilizer absorption. Based on the study of the effect of water and nitrogen coupling on the fine root morphology and distribution of the topsoil (0-30 cm) in Populus × euramericana’Guariento ’young adults, after two consecutive years of water and nitrogen management, Study on Response of Fine Roots and Vertical Distribution to Coupling Water and Nitrogen in 0-60 cm Layer of Populus. Three irrigation levels (three thresholds of -75 kPa, -50 kPa, -25 kPa) and three nutrient levels (N 150 g · tree-1 · a-1,300 g · Tree-1 · a-1,450 g · tree-1 · a-1) were combined into nine water-nitrogen coupling treatments and another CK treatment was used. The results showed that: (1) In the vertical direction, the fine root biomass density, surface area and average diameter of the treatments showed the largest in 10-20 cm soil layer (biomass density of 0-60 cm soil layers 27% -37%), then decreased gradually in the layer of 30-60 cm. The root length decreased with the deepening of soil depth, and the layer of 0-10 cm was significantly larger than the other soil layers Accounting for 33% -45% of the total root length of 0-60 cm soil layer). (2) The fine root biomass density, root length density and average diameter of 6 soil layers showed no significant difference between the two treatments of high water and high nitrogen (D3F3) and medium water and high nitrogen (D2F3), but both were significantly higher Among other treatments, the biomass density of D3F3 was 3.12-47.74 times of that of the control. The fine root surface area of D3F3 was significantly higher than that of other treatments, which was 4.36-30.57 times of that of CK. (3) The continuous management of water and nitrogen coupling will not change the vertical distribution pattern of fine roots (all treatments have the same distribution pattern with CK). However, in the second growth season, In addition, the coupled treatment of high-N and high-N could also effectively promote the growth of fine roots. This requirement of water and nitrogen could be significantly enhanced by high-N and N-N during the first growing season Different characteristics. The fine roots of 108 European and American poplars were mainly distributed in the 0-20 cm soil layer in the second growing season. Among the 9 water-nitrogen coupled treatments, except the low water and low nitrogen treatments, the fine root morphological indexes of other treatments were significantly higher than CK Species diversity is more pronounced in shallow soil and relatively less in deep soil. When the amount of irrigation is a certain amount (especially in middle and high irrigation levels), increasing the amount of nitrogen fertilizer can significantly promote the fine root growth, but when the amount of nitrogen is constant (especially low and medium nitrogen levels), increasing the amount of irrigation on fine root growth promotion The effect is not significant, that is, Europe and the United States 108 Yang fine root growth stronger than water-based fertilizer.