共查询到20条相似文献，搜索用时 31 毫秒
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The competition–density (C–D) effect for non-self-thinning Populus deltoides and Populus × euramericana plantations from 3 to 9 years was analyzed using the reciprocal equation of the C–D effect. The C–D effect was well described
by the reciprocal equation, and with the progress of time the C–D curve, on logarithmic coordinates, of the P. × euramericana plantations shifted upward faster than that of the P. deltoides plantations. With increasing physical time t, the biological time τ, i.e. the integral from zero to t of the coefficient of growth λ(t) in the general logistic curve with respect to t, increased rapidly during early growth stages and the increases in τ gradually became slow during later growth stages. This trend was more evident in the P. deltoides plantations than in the P. × euramericana plantations. The coefficients A and B included in the reciprocal equation were calculated at each growth stage. With increasing τ, the coefficient A, the reciprocal of which means the asymptote of yield (=wρ) at a given growth stage, increased abruptly to a maximum value and then tended to decrease gradually to a constant level.
On the other hand, the coefficient B, the reciprocal of which means the asymptote of mean stem volume at a given growth stage, decreased exponentially and tended
to be close to zero with increasing τ. The λ(t) decreased with increasing stand age, whereas the final yield Y(t) defined as W(t) ρ, where W(t) is the asymptote of w in the general logistic growth curve, increased gradually with increasing stand age. The differences in coefficients A, B, and λ(t) between the two species were reported. 相似文献
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Many plantation tree species are cloned to achieve the growth, disease resistance and wood quality characteristics required
for a successful economic venture. However, clonal propagation is limited by declines in adventitious root formation with
increasing stock plant age. We examined the effects of immediate or delayed IBA application on adventitious root formation
and subsequent root and shoot development of cuttings harvested from 8-year-old clonal hedge plants of Pinus elliottii var. elliottii × P. caribaea var. hondurensis. IBA applied at the time of setting accelerated root formation, elevating the percentage of cuttings with roots at 13 weeks
post-setting from 45 to 78% and from 83 to 93% for a low- and a high-rooting clone, respectively. Final rooting percentages
for the same treatments and clones (78 and 85%, and 88 and 100%, respectively, at 20 weeks post-setting) were not significantly
affected by IBA application. IBA increased the root:shoot ratio of rooted cuttings by decreasing shoot weight compared with
untreated cuttings, without affecting root weight, root length, root surface area or root volume. IBA was only effective when
applied at the time of setting. A simple IBA treatment for cuttings from 8-year-old clonal hedges, by accelerating root production,
has potential for reducing nursery costs and increasing the root system quality of containerised pine cuttings. 相似文献
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Masahiko Nakagawa Jun Hamatsu Makoto Kuromaru Kazuhito Kita Kazuko Uchiyama 《Journal of Forest Research》2008,13(4):255-260
The efficiency of planting a hybrid larch F1 at two planting densities and of using seedlings of hybrid larch F1 or rooted cuttings of Gream, the registered variety, was investigated. Significantly more time was required to move from
one planting spot to the next in plots with 625 seedlings/ha than in plots with 1,333 seedlings/ha, but there was no significant
difference between seedlings and rooted cuttings. Approximately 18% more time was needed to plant a single planting stock
at the low planting density than at the high density. The need to prune roots or enlarge a planting hole occurred more often
for rooted cuttings than for seedlings, and 17% more time was needed to plant rooted cuttings of Gream than seedlings. 相似文献
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GhCesA2 is a cotton (Gossypium hirsutum) homologue of the bacterial cellulose synthase gene that encodes cellulose 4--glucosyltransferase. The central catalytic region of GhCesA2 was expressed as a soluble protein in the methylotrophic yeastPichia pastoris. The molecular size of the recombinant protein was 100kDa, which decreased to 85 kDa after treatment with endoglycosidase H. The recombinant GhCesA2 catalyzed transfer of glucose from UDP-glucose into unknown products in the presence of an extract of cotton hypocotyls, but the products were not-1,4-glucan. 相似文献
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大腹异木棉Ceiba insignis是近年来应用广泛的景观树种。通过对其实生苗株高、地径的年生长节律进行调查,并利用Logistic模型进行拟合,进而划分生长时期。调查发现,一年中苗木株高存在2次生长高峰,分别在6月和8月,地径于8月出现1次生长高峰。Logistic方程拟合度高,根据该曲线模型的特点,将苗木一年中生长阶段划分为生长初期(1—3月)、速生期(4—10月)、生长后期(11—12月)3个阶段,与其生物学特性相似且易混淆的同属植物美丽异木棉Ceiba speciosa生长过程也可划分为3个阶段,各阶段时间存在差异。并根据其生长规律研究成果及广州市气候环境提出相应栽培养护方案。 相似文献
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榕树Ficus microcarpa是华南地区的乡土树种,在广州栽植历史久远,形成了具有地方特色的榕树景观,但在适地适树栽植方面存在较多问题,破坏或影响了一些市政设施的使用功能。梳理榕树在广州城市园林绿化的应用,指出其中存在的突出问题——榕树生长空间严重受限,支柱根和板根破坏力强,以及修枝整型不规范。基于适地适树原则,提出解决突出问题的相应技术措施:从根据特性选择合适栽植地、合理规划设计榕树生长空间、选择适合的栽植土壤、科学规范的适养措施。 相似文献
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