【作者】 杨超；

【导师】 田大伦；

【作者基本信息】 中南林业科技大学 ， 生态学， 2011， 博士

【摘要】 杉木是我国特有的优良速生用材树种,已有一千多年的栽培历史,因其易繁殖、生长快、材质优、产量高、好管理而深受群众的钟爱。杉木林是我国南方集体林区主要经营的森林类型之一,其栽培范围遍及我国整个亚热带多个省(区),栽培面积约占全国人工林面积的1/4。但由于多代连栽,出现了杉木人工林地力衰退,生产力下降等生态问题,为此,对杉木人工林生物量和生产力变化过程的研究,可为杉木林的长期生产力的维持和可持续发展,提供科学依据,对杉木林的长期经营具有实践指导意义本文采用空间一致和时间连续的定位研究方法,利用湖南会同杉木林生态系统国家野外科学观测研究站20多年的实测数据,对两个世代杉木人工林速生阶段(7—11a生)、杆材阶段(14—18a生)和成熟阶段(20a生)的生物量和生产力、林下植被、死地被物层和凋落物生物产量进行了对比研究,揭示了杉木连栽两代的代际效应,主要研究结果如下：1.7a生第2代杉木林的平均单株生物量为13.17 kg,变动范围为11.75—14.69 kg；林分生物量平均为31.10 t·hm-2,变动范围为27.03—38.48 t·hm-2；年平均净生产力为4.44 t·hm-2·a-1,变动范围为3.86—5.50 t·hm-2·a-1。与相同环境同龄第1代杉木林比较,其平均单株生物量下降2.46 kg,下降幅度为15.74%,林分生物量第2代较第1代下降14.18 t·hm-2,净生产力下降2.04 t·hm-2·a-1,下降幅度均达31.47%,干材经济系数下降幅度达40%。2.11a生第1代杉木林单株生物量为37.54 kg,第2代为34.73 kg,下降了7.49%。第1、2代杉木林分生物量分别为85.60和71.45 t·hm-2,第2代比第1代减少了16.53%。第1代杉木林的平均生产力为7.78t·hm-2·a-1,第2代为6.49 t·hm-2·a-1,下降1.29 t-hm-2·a-1。两代杉木林生物量均以树干最大,分别占林分生物量61.09%和58.22%,其他组分生物量排列顺序依次为树根>树叶>树枝。3.14a生第2代杉木林单株生物量、林分生物量和生产力分别为42.07 kg、97.18 t-hm-2和6.95 t·hm-2·a-1,第1代则分别为45.22 kg、104.45t·hm-2和7.47 t·hm-2·a-1,第2代比第1代分别下降3.15 kg、7.27 t·hm-2和0.52 t·hm-2·a-1。4.18a生第1代杉木单株生物量为63.51 kg,第2代为62.75 kg,第2代较第1代下降1.20%；第1代林分生物量和生产力分别为146.70 t·hm-2和11.88 t·hm-2·a-1,第2代为144.96 t·hm-2和9.49 t·hm-2·a-1,第2代较第1代下降1.19%和20.1%。5.20a生杉木单株生物量第1代为90.69 kg,林分生物量为209.50t·hm-2,生产力为10.78 t·hm-2·a-1,第2代分别为86.56 kg、199.94 t.hm-2、9.21 t·hm-2·a-1,第2代较第1代分别下降4.55%、4.56%、14.56%。干材经济系数第2代较第1代下降17.12%。6.杉木连栽生物量和生产力的代际效应：7a生第1、2代单株和林分生物量分别为15.63、13.06kg和45.38、37.90 t·hm-2,第2代比第1代下降16.44%和16.48%；11a生第1、2代分别为37.45、31.11 kg和108.73、90.31 t·hm-2,第2代比第1代下降16.93%和16.94%；14a生第1、2代分别为45.22、42.07kg和104.45、97.18 t·hm-2,第2代比第1代下降7.0%和6.96%；18a生第1、2代分别为63.51、62.75kg和146.70、144.96 t·hm-2,第2代比第1代下降1.20%和1.19%。20a生第1、2代分别为90.69、86.56kg和209.50、199.94 t·hm-2,第2代比第1代下降了4.55%和4.56%。7-11a生第1代杉木林的生产力是第2代的1.15倍；14-18a生第1代是第2代的1.25倍；18-20a生第1代是第2代的1.17倍。林分生物量分配格局虽然有波动,但总体上为第2代杉木林的枝、叶、树皮生物量高于第1代林,尤其是根的生物量是第1代林的2-4倍,而树干材第2代林比第1代少20%,表明第2代杉木林的干材经济利用系数小于第1代。7.两代杉木林从生长发育的速生阶段(7a-11a生)到杆材阶段(14a—18a生)过程中,林下植被生物量均呈现出波动性的变化状态,且规律不一致。在速生阶段,林下植被生物量第1代随林龄的加大而增加,第2代则随林龄的加大而减少；林分在杆材阶段,林下植被生物量第1代随林龄的加大而减少,第2代则随林龄的加大而增加。杉木林下死地被物层生物量,两代杉木林均表现出随林龄的加大而增加。代际间的表现为：7a生林分的死地被物层生物量第2代较第1代低,但11a、14a、18a生的林分,却为第2代高于第1代的2—3倍。杉木林凋落物的平均生物量第1代为4479.31 kg·hm-2,第2代为1109.86 kg·hm-2,,第1代为第2代的4倍,这主要是与两代杉木林生长差异有关外,还与同一林龄的连栽林分密度紧密相连,第2代杉木林的密度低于第1代,林木个体间竞争相对较弱,自然整枝没有第1代强烈。8.在连栽两代杉木人工林生态系统中,生物量均以林木层(杉木层)占据绝对优势地位,第1代杉木层生物量可占系统总生物量的97.21%—97.90%,第2代占91.76%—96.02%；林下植被层第1代占0.28%—0.55%,第2代占1.21%—2.88%；死地被物层第1代占1.55%—2.27%,第2代占0.18%—5.92%。表明林地空间位置为经营目的树种所有。更多还原

【Abstract】 Chinese fir (Cunninghamia lanceolata (lamb.) Hook) is a native fast-growing timber species in China with the characteristics of easy to breeding, fast-growth, excellent timber quality and high productivity, and has been planted and cultivated for more than 1000 years. Chinese fir plantation is one of the most managed forest types in Southern China and is cultivated almost subtropical regions in the country. The planted area of this species accounts for about one fourth of the total plantation areas in the nation. Because of over successive rotations of this species with multiple generations on the same sites in the past years, many studies have reported apparent yield decline and soil fertility degradation in Chinese fir plantations. Thus, it is necessary and important to study the changes of biomass production and net primary productivity (NPP) of Chinese fir plantations over successive rotations. The results from such projects will provide valuable information and references for sustainable management of the Chinese fir plantations in order to maintain long-term soil fertility and stand productivity for the forest ecosystems.In the present study, the biomass and NPP of two successive rotation generations of Chinese fir plantations were examined at Huitong Ecosystem Research Station of the Central South University of Forestry and Technology in Huitong County, Hunan Province, one of the National Field Stations for Scientific Observation and Experiment in China, using a chronosequence approach on the same forested small watersheds. Additionally, biomass partitioning in Chinese fir tree, understory vegetation ground dead vegetation, and little-fall layers was investigated and compared at fast-growing stage (7-11 year-old), timbering stage (14-18 year-old) and mature stage (20 year-old) in the two rotation stands. The major results showed:1. The mean individual tree biomass, stand biomass and NPP of a 7-year-old stand in second rotation of Chinese fir plantations were 13.17 kg (ranging 11.75-14.69 kg),31.10 t·hm-2 (ranging 27.03-38.48 t·hm-2), and 4.44 t·hm-2·a-1 (ranging 3.86-5.50 t·hm-2·a-1), respectively. The mean individual tree biomass, stand biomass and NPP was lower 2.46 kg (reduced by 15.74%),14.18 t·hm-2 (31.47%), and 2.04 t·hm-2·a-1 (31.47%) in the second rotation when compared to first rotation. In addition, the wood economic coefficient (wood biomass/total tree biomass) was reduced by 40% in the second rotation compared to the first rotation.2. For a 11-year-old stand, the mean individual tree biomass was declined by 7.49% in second rotation (34.73 kg) than first rotation (37.54 kg). The stand biomass and NPP were reduced by 16.5 and 16.6% in the second rotation (71.45 t·hm-2 and 6.49 t·hm-2·a-1) than the first rotation (85.60 t·hm-2 and 7.78 t·hm-2·a-1). The stem had the highest proportion of the total stand biomass, and it accounted for 61.1 and 58.2% of the total stand biomass in the two rotations, respectively. The biomass of other organs was in an order:root> leaf> branch.3. The mean individual tree biomass, stand biomass and NPP of a 14-year-old stand of the first and second successive rotations were 45.22 kg, 104.45 t·hm-2 and 7.47 t·hm-2·a-1, and 42.07 kg,97.18 t·hm-2 and 6.95 t·hm-2·a1, respectively. It meant the mean individual tree biomass, stand biomass and NPP decreased 3.15 kg,7.27 t·hm-2 and 0.52 t·hm-2·a-1 in second rotation compared to first rotation, respectively.4. The mean individual tree biomass of a 18-year-old stand was reduced by 1.2% in second rotation (62.75 kg) compared to first rotation (63.51 kg). The stand biomass and NPP were reduced 1.19%(144.96 and 146.70 t·hm-2) and 20.1%(9.49 and 11.88 t·hm-2·a-1), respectively, in second rotation when compared to first rotations.5. The mean individual tree biomass, stand biomass and NPP of a 20-year-old stand were declined by 4.55,4.56 and 14.56% in second rotation (86.56 kg,199.94 t·hm-2,9.21 t·hm-2·a-1) compared to first rotation (90.69 kg,209.50 t·hm-2 and 10.78 t·hm-2·a-1). The wood economic coefficient was lower by 17.12% in the second rotation stands than the first rotation stands. 6. The generation effects of biomass production between the two successive rotations showed that mean individual tree biomass and stand biomass of a 7-year-old stand were declined by 16.44%(13.06 and 15.63kg) and 16.48%(37.90 and 45.38t·hm-2) in second rotation compared to the first rotation; by 16.93 and 16.94%(31.11 and 37.45 kg, and 90.31 and 108.73 t·hm-2) of a 11-year-old stand; by 7.0 and 6.96%(42.07 and 45.22kg, and 97.18 and 104.45t·hm-2) of a 14-year-old stand; by 1.20 and 1.19%(62.75 and 63.51kg, and 144.96 and 146.70t·hm-2) of a 18-year-old stand; and by 4.55% and 4.56%(86.56 and 90.69kg, and 199.94 and 209.50t·hm-2) of a 20-year-old stand.The generation effects of NPP between the two successive rotations showed that NPP was 1.15 times higher in first rotation than in second rotation for 7-11 year-old stands, and 1.25 times and 1.17 times higher for 14-18 and 18-20 year-old stands, respectively.Generally speaking, the proportion of branch, leaf and bark components in the total stand biomass was slightly higher in second rotation than first rotation stands. Particularly, the percentage of root biomass in the total stand biomass was 2-4 times higher in second rotation than first rotation stands. But the ratio of wood biomass in the total stand biomass in second rotation was 20% less than that in first rotation stands, meaning the wood economic coefficient was lower in second rotation than first rotation of Chinese fir plantations.7. Different dynamic patterns of understory vegetation biomass were found in the fast-growing stage (7-11 years) and timbering stage (14-18 years) for the two successive rotations. Understory vegetation biomass increased with stand aged in first rotation, but decreased in send rotation during the fast-growing stage. In contrast, understory vegetation biomass decreased with increasing stand ages in first rotation, but increased in send rotation during the timbering stage.The dead vegetation biomass on the forest floor increased with increasing stand ages in the two successive rotations of Chinese fir plantations. The ground dead vegetation biomass of a 7-year-old stand was lower in second rotation than that in first rotation. However, the ground dead vegetation biomass in 11-,14-, and 18-year-old stands was higher in second rotation than that in first rotation stands.The average amount of little-fall was 4479.31 kg·hm-2 in first rotation, which was about 4 times as that in second rotation (1109.86 kg·hm-2). The difference was mainly derived from the dissimilar growth rate between the two rotation stands. In addition, the difference of stand density between the two rotation stands also made contribution to the difference of little-fall amount between the two rotation stands. The stand density was lower in second rotation stands was lower than that in first rotation. As a consequence, the competition of resources (such as light, water and nutrient elements) among the individual tree was weaker in second rotation compared to first rotation, and the natural pruning phenomenon was less in second rotation than first rotation stands.8. The biomass of tree stratum had the highest proportion of the total biomass in the two successive rotations of Chinese fir plantation ecosystem. The Chinese fir tree stratum accounted for 97.2-97.9% of the total biomass in first rotation, and 91.8-96.0% in second rotation. Understory vegetation stratum accounted for 0.28-0.55% and 1.21-2.88% in first and second rotations. The ground dead vegetation stratum accounted for 1.55-2.27% and 0.18-5.92% in first and second rotations, respectively. The results indicated that the Chinese fir as the planted tree species occupied almost spatial area in the forests.更多还原