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71.
Richard Waring Alan Nordmeyer David Whitehead John Hunt Michael Newton Christoph Thomas James Irvine 《Forest Ecology and Management》2008,255(12):4040-4046
Douglas-fir (Pseudotusga menziesii (Mirb.) Franco), a native to the Pacific Coast Range in North America, is recognized as a tree that is long-lived and can grow rapidly to standing volumes that approach the highest recorded for temperate conifers. Managed plantations in western Oregon register maximum periodic annual increments (PAI) at ages between 20 and 40 years of ∼30 m3 ha−1 year−1. The same seed source, when planted in New Zealand and elsewhere in the Southern Hemisphere, may attain a PAI of ∼50 m3 ha−1 year−1. Is this higher productivity mainly related to climate or to isolation from native pests? To evaluate the role of climate, we obtained meteorological data from plantation sites in New Zealand and Oregon, from which we established relationships between mean monthly temperature extremes and solar irradiance, air humidity deficits, and frost frequency. Using these empirical relationships, long-term weather records were converted to the meteorological variables required to drive a process-based forest growth model, 3-PG, for sites approaching the most productive in New Zealand and in Oregon. Annual precipitation is similar in both areas, but sites in Oregon receive only 10% during the growing season, resulting in humidity deficits 30% larger than those recorded in New Zealand. According to sensitivity analyses and direct measurements, the more productive Douglas-fir forests in Oregon avoid the limiting effects of summer drought by obtaining water from the subsoil and fractured bedrock. If such forests were under a reduced evaporative demand similar to that in New Zealand, we show that they would exhibit comparable productivity. 相似文献
72.
Herb-layer diversity in deciduous forests: Raised by tree richness or beaten by beech? 总被引:3,自引:0,他引:3
Andreas Mlder Markus Bernhardt-Rmermann Wolfgang Schmidt 《Forest Ecology and Management》2008,256(3):272
Where natural production capacity permits, modern silvicultural management in Central Europe frequently aims at the development of mixed broadleaved stands, instead of pure European beech (Fagus sylvatica) stands. It is crucial to study the effects of these tree-layer diversity variations on herb-layer vegetation, since herb-layer vegetation contributes significantly to ecosystem functioning in forests. In Hainich National Park (Thuringia, Germany), we conducted observational research in deciduous stands to investigate whether herb-layer diversity was related to canopy-layer diversity, and to ascertain possible causal mechanisms. We found that herb-layer vegetation of deciduous forest stands rich in canopy species appeared to be more diverse than herb-layer vegetation of beech-dominated stands. We surmise that herbaceous understorey diversity was indirectly influenced by canopy tree species through the medium of the altered environmental factors soil pH and litter layer thickness. Apparently, lower beech proportion had a more profound effect than the number of secondary tree species. There were no correlations between herb-layer diversity and light transmissibility of the canopy layer, indicating that the light factor was not crucial for herb-layer diversity. At least for the Hainich research sites, our results indicated that small-scale light and soil heterogeneity is insignificant for herb-layer diversity. We found several herb-layer species whose occurrence was particularly correlated with tree-layer diversity and environmental factors. Remarkably, all species positively correlated with soil pH were important for the phytosociological classification of the research sites. Beech-dominated research sites showed high tree-layer volumes, whereas research sites with high tree-layer diversity tended to feature lower tree-layer volumes. These findings could be the result of differing former silvicultural systems and varying soil clay contents affecting tree species composition. In contrast, herb-layer biomass was positively correlated with tree-layer diversity. Herb-layer productivity might be promoted in more diverse research sites by increased nutrient supply and base saturation. It is also possible that greater beech proportion interfered with herb-layer productivity. However, herb-layer biomass was also positively correlated with herb-layer diversity. Hence, our study hints that positive diversity-functioning relationships might occur in the herb-layer of the deciduous forest under investigation. 相似文献
73.
杜湖杂交猪生产性能的测定 总被引:1,自引:0,他引:1
以杜洛克为父本、湖北白猪二元配套系为母本所生产的杜湖猪、育肥期平均日增重为700g,料肉比3.0,屠宰率73.1%,瘦肉率65.6%。与原杜湖猪相比,综合生产性能有了很大提高。 相似文献
74.
红锥天然林生长规律与生物量的调查研究 总被引:12,自引:1,他引:12
华安金山林场红锥天然林调查表明,红锥生长快,34~38年生树高可达21.9~23.7m、胸径可达20~30cm。全林保存密度572株/hm2,蓄积量366m3/hm2;Ⅱ级立地级保存红锥600株/hm2,蓄积量高达483m3/hm2,生物量500.87t/hm2,材积年生长量可达13.4m3/hm2;Ⅲ级立地红锥蓄积量342m3/hm2,生物量354.65t/hm2。林分生产力很高,树高速生期为4~18年生。胸径速生期为6~14年生,材积速生期为10~27年生,34~38年生的红锥尚未达到数量成熟。表明红锥适应性强,不苛求立地,生长潜力大,极有发展前途。 相似文献
75.
高寒地区不同建植期人工草地群落垂直结构和生产力变化的研究 总被引:4,自引:0,他引:4
对高寒地区不同建植期人工草地群落垂直结构和生产力的变化研究结果表明:(1)随着人工草地建植时间的延长,人工草地群落垂穗披碱草高度异质性逐渐减小.(2) 不同建植期(1999、1998、1997年建植)人工草地垂穗披碱草和群落平均地上生物量均主要分布在0 ~20cm冠层中,约占平均地上生物量的61.03%、90.64%、84.55%和67.47%、92.54%、86.08%.(3) 不同建植期 (1999、1998、1997年建植)人工草地群落平均地下生物量均主要分布在0~10cm土层中,约占地下总生物量的85.97%、81.73%和78.47%.(4) 建植的人工草地如果其组分单一,即物种的丰富度很低时,均匀度增加,物种对环境资源的竞争力和利用率提高,导致土壤资源库中某些营养成分缺乏,草地群落初级生产力因此而降低。 相似文献
76.
野生细鳞鱼的生物学特性及繁殖力 总被引:1,自引:0,他引:1
本文对采捕的野生细鳞鱼的生物学特性及繁殖力进行了测定,结果表明:细鳞鱼可量比例性状为:全长/体长1.13±0.02,体长/体高4.86±0.30,体长/头长4.41±0.19,体长/尾柄长6.94±0.72,体长/尾柄高12.53±0.59,尾柄长/尾柄高1.82±0.17,头长/吻长3.36±0.31,头长/眼径5.41±0.52,头长/眼间距2.89±0.26;可数性状为:背鳍鳍式:II,11~13,胸鳍鳍式:I,15~19,腹鳍鳍式:I,9~12,臀鳍鳍式:II,10~14,侧线鳞:108~163,侧线上鳞:24~37,侧线下鳞:23~36,第一鳃弓鳃耙数:15~29,脊椎骨:57~61,肋骨:28~31,幽门垂:70~121。绝对繁殖力2823.25±1237.01,相对繁殖力3.20±1.79。 相似文献
77.
78.
79.
[目的]为金藻(Isochrysis galbana Parke)的大规模培养、药用研究及开发利用提供参考。[方法]在不同光径平板生物反应器中培养金藻,并对藻细胞的生长状况和细胞内的有机物质含量进行了分析。[结果]藻细胞的生长速率及单位体积产量随光径的减小而增大;单位面积产量随光径的增大而增大;光径越小的生物反应器中培养的金藻藻细胞内的总脂、蛋白质及多糖占细胞干重的总量越高。[结论]根据生产需要选择合适的生物反应器,可有效提高生产效率、降低生产成本。 相似文献
80.
山西三道川林场主要森林生态系统生物量和生产力研究 总被引:1,自引:1,他引:1
基于森林生态系统对区域碳库的杰出贡献,对维持生态平衡和减缓气候变化的巨大作用,以关帝山林区的油松林、白桦林、山杨林、落叶松人工林、油松封育林、灌木林和裸露荒坡地等主要生态系统为研究对象,对其生物量和生产力进行了初步探讨,并在生物量和生产力分析的基础上对该区森林经营提出了森林生物量和生产力的分类区划经营意见。结果表明:(1)不同生态系统具有不同的总生物量,其基本排序如下:白桦林>油松林>油松封育林>落叶松人工林>山杨林>灌木林>荒山坡;(2)不同生态系统具有不同的生物量分布格局;(3)不同森林群落具有不同的生产力,采用方精云的生物量与生产力的推算方法得到各林分生产力排序如下:山杨林>落叶松人工林>油松林>油松封育林>白桦林;(4)采用刘世荣等提出的森林生产力与主要气候因子之间的关系公式得到限制该区森林生产力的主导因素是降水,而非温度。 相似文献