不同密度下2种杨树短轮伐期矮林生长及生物量

Growth and biomass of two poplar clones in short rotation coppice under different densities

【目的】在培育能源林的过程中,短轮伐期矮林(SRC)培育模式在生产力及环境上有着优良表现,并正受到各国关注,但不同栽植密度及经营方式对其生长及生产力的影响尚有许多值得深入探讨的方面。本研究旨在探究在不进行后期人工水肥管理的情况下,2种杨树短轮伐期矮林的生长和生物量差异及其可持续性。【方法】本研究以种植在山东省高唐县的三倍体毛白杨B301(以下简称“B301”)和欧美杨107(以下简称“107”)为试验材料,以3种栽植密度(5 000、10 000、20 000株/hm^(2))和3种不同轮伐期(2、3、4年)为处理,历时6年,研究其存活率、离地22 cm处萌条直径(D_(22))、单株萌条数及各周期和6年间单位面积的生物量。【结果】(1)2树种的存活率在2年轮伐期中较高,在栽植密度为20 000株/hm^(2)时较低。存活率最高可达98.89%,处于B301中的2年轮伐期、10 000株/hm^(2)栽植密度的第2次轮伐。经过6年的短轮伐管理后,2年与3年轮伐期所有处理的存活率均显著下降,B301的存活率保持在66%以上,107在58%以上。(2)2树种的D_(22)与单株萌条数均在较小栽植密度下得到较大值,D_(22)在较长的轮伐周期及第1次轮伐中较大,而单株萌条数在2年和3年的轮伐周期及后2次轮伐中较大。2树种D_(22)均在4年轮伐期、5 000株/hm^(2)、第1次轮伐的处理下最大,B301可达到5.83 cm,而107可达到7.32 cm。B301平均单株萌条数为1.10~5.52枝,107为1.14~9.55枝。107有更强的萌蘖能力。(3)华北地区以本试验条件所栽植短轮伐期矮林的生产力:单个轮伐周期内B301的年均单位面积生物量为3.36~13.42 t/(hm^(2)·a),107为4.58~14.45 t/(hm^(2)·a)。在6年时间内B301的单位面积年均生物量为5.10~9.95t/(hm^(2)·a),107则为6.22~10.69 t/(hm^(2)·a);B301单位面积总生物量为30.63~59.68 t/hm^(2),107为37.32~64.17 t/hm^(2)。【结论】(1)在未进行人工水养管理的情况下,2种杨树短轮伐期矮林在第1次轮伐时生产力最高,之后随轮伐次数增加生产力下降。(2)在该地区培育短轮伐期矮林,若要取得较高生产力,107整体上优于B301。(3)考虑到实际经营中栽植和管理成本,3年轮伐期、10 000株/hm^(2)是这2种杨树较为适宜的轮伐期与栽植密度。

[Objective] In the cultivation process of energy forest, the cultivation pattern of short rotation coppice(SRC) has attracted attention from various countries due to its excellent performance in productivity and environment. However, the influence of different planting densities and management modes on its growth and productivity still needs further discussion. The purpose of this study was to investigate the difference in growth, productivity, and sustainability of two poplar clones’ short rotation coppice without later artificial water and fertilizer management. [Method](P. tomentosa × P. bolleana) × P. tomentosa(hereinafter referred to as “B301”) and Populus × euramericana cv. ‘74/76’(hereinafter referred to as“107”) planted in Gaotang County, Shandong Province of eastern China were used as experimental materials, with three planting densities(5 000, 10 000, 20 000 plant/ha) and three different rotation cycles(2,3, 4 years). It took 6 years to study the survival rate, shoot diameter(D_(22)) at 22 cm aboveground, number of shoots per plant, and biomass per unit area during each cycle and during 6 years. [Result](1) The survival rate of the two species was higher in two-year rotation cycle, and lower in the planting density of 20 000plant/ha. The maximum value of survival rate was 98.89%, which appeared in the second round of B301 of 2-year rotation and the planting density of 10 000 plant/ha. After six years of short-rotation management, the survival rate decreased significantly in all treatments of two-and three-year rotation cycle, with the survival rate of B301 remained above 66%, and that of 107 above 58%.(2) Both the average D_(22) and the average stoop per stump of the two clones were larger in the lower planting density. The average D_(22) was larger in the longer rotation and the first rotation, while the average stoop per stump was larger in the 2-and 3-year rotation and the last two rotations. The largest average D_(22) of the two clones appeared in the first rotation of the four-year rotation and the planting density of 5 000 plant/ha. It could reach 5.83 cm in B301, while it could reach 7.32 cm in 107. The average stoop per stump of B301 ranged from 1.10 to 5.52, and that of 107ranged from 1.14 to 9.55, and 107 has better resprout capacity.(3) Productivity of short-rotation coppice planted under this experimental conditions in North China: in a single rotation cycle, the average annual biomass per unit area was 3.36-13.42 t/(ha·year) for B301 and 4.58-14.45 t/(ha·year) for 107. During 6years, the average annual biomass per unit area of B301 ranged from 5.10 to 9.95 t/(ha·year), while that of 107 ranged from 6.22 to 10.69 t/(ha·year). The total biomass per unit area was 30.63-59.68 t/ha for B301 and 37.32-64.17 t/ha for 107. [Conclusion](1) Without artificial water and fertilizer management, the productivity of 2 species of short-rotation poplar coppice is the highest at the first rotation, and declines with the increase of the number of rotations.(2) To build SRC in this region, 107 is superior to B301 on the whole in order to obtain higher productivity.(3) Considering the actual planting and management costs in operation, the rotation period of 3 years and the plant density of 10 000 plant/ha are the more suitable rotation and planting density for these two poplar clones.