延河流域自然与人工植被地上生物量差异及其土壤水分效应的比较

【目的】针对延河流域人工植被建造存在植被退化的问题,比较了自然植被与人工植被地上生物量的差异及其土壤水分效应,探寻人工植被退化的原因,为延河流域植被恢复重建提供理论支持。【方法】共采集57个气象站点1980-2000年的气候数据,并根据降雨和温度变化,将延河流域划分为17个环境梯度单元,测定了自然植被地上生物量及0～500cm土层土壤含水量,分析自然植被的空间变化及其影响因素,对自然植被与人工植被地上生物量及相应的土壤水分变化进行比较分析。【结果】延河流域自然植被地上生物量在空间上存在明显差异,从西北向东南呈现逐渐递增的变化趋势。自然植被地上生物量与年均总降雨量呈正相关关系,与年均生长季温度呈负相关关系;相同气候区的自然植被地上生物量随坡位和坡向的变化差异均很大。以自然植被为参照,人工植被地上生物量最大超载可达30 425.83g/m2,最小超载为118.93g/m2,平均为6 668.00g/m2,说明人工植被地上生物量明显超出了自然状态下所能承载的范围。与自然植被相比,人工植被土壤水分最大亏缺量可达80.5g/kg,说明人工植被地上生物量的超载引起平均土壤含水量显著低于自然植被,出现了不同程度的土壤干层,进而导致人工植被群落的衰退或死亡。【结论】生物量超载是引起土壤水分耗竭、植被退化的主要原因。植被恢复重建规划时,必须充分考虑特定立地环境条件下潜在生物量的制约,而不是盲目地选择不适宜的物种。     

Natural bixin as a potential carotenoid for enhancing pigmentation and colour in goldfish (Carassius auratus)

Discovering natural carotenoids for colour enhancement and health benefits of fish is important to develop new feed formulations. We have purified natural bixin from achiote seeds and evaluated the effect of colour enhancing and pigmentation in goldfish. Varying levels of bixin‐based diets were prepared with 420 g kg^?1 of crude protein and 120 g kg^?1 of lipid content. Our results clearly showed that bixin (0.05, 0.10, 0.20 and 0.60 g kg^?1) based diets significantly (P < 0.05) enhanced the skin and fin colour at 30 and 60 days compared to diet without bixin. Interestingly, diet which contains 0.20 g kg^?1 bixin and commercial feed (with astaxanthin) had similar effect on carotenoid deposition in skin. Moreover, total carotenoid deposition in fin was higher than in skin of all bixin‐containing diets. However, 0.60 g kg^?1 bixin‐containing diet had lower specific growth rate (1.01 ± 0.01) and higher feed conversion ratio (2.05 ± 0.19) compared to the control group. The present results demonstrate that achiote bixin can be successfully used as an alternative natural carotenoid source against synthetic astaxanthin in fish feed. Our data indicate that 0.20 g kg^?1 is a suitable dietary level of bixin to ensure strong pigmentation, acceptable growth and feed utilization in goldfish.     

Development and application of a PCR-based 'molecular tool box' for the identification of Phytophthora species damaging forests and natural ecosystems

A PCR-based 'molecular tool box', based on a region of the ras-related protein gene Ypt 1, was developed for the identification of 15 Phytophthora species that damage forests and trees: P. cactorum , P. cambivora , P. cinnamomi , P. citricola , P. europaea , P. inundata , P. lateralis , P. megasperma , P. nemorosa , P. kernoviae , P. pseudosyringae , P. psychrophila , P. quercina , P. ramorum and P. ilicis . Most primers proved highly specific in blast analyses and in tests with DNA from 72 isolates of 35 species of Phytophthora and nine species representative of Pythium . Exceptions were primers designed for P. cactorum and P. ilicis , which cross-reacted with P. idaei and P. nemorosa , respectively. Amplification with Phytophthora -genus-specific primers before amplification with the various species-specific primers (nested PCR) increased the sensitivity of detection over amplification with species-specific primers only: detection limits ranged between 100 and 10 pg target DNA µ L⁻¹ in the latter, compared with 100 fg µ L⁻¹ in nested PCR. Using existing methods for rapid extraction and purification of DNA, single-round amplification was appropriate for detection of target Phytophthora species in leaves, but nested PCR was required for soil and water samples. The quarantine pathogens P. ramorum and P. kernoviae were detected in a number of naturally infected leaves collected in England and Wales, whereas P. citricola was commonest in water and soil samples from natural Scottish ecosystems.     

浅谈内蒙古大兴安岭林区一期天保工程实施效果

文章对内蒙古大兴安岭林区一期天保工程实施效果进行了分析、评价,剖析了其存在的主要问题,并对今后经营提出了相应的建议。     

富源县竹园镇森林抚育现状及对策初探

文章通过对富源县竹园镇森林抚育的现状进行总结,系统分析存在问题,结合森林培育学等相关林学理论知识,提出开展森林抚育工作的6个具体对策。     

室温干燥贮藏和天然高寒草甸层积对草玉梅种子萌发的影响

明晰草玉梅种子休眠的释放,为草地管理和草玉梅的栽培提供基础,研究了室温干燥贮藏和高寒草甸层积对草玉梅种子萌发特征的影响。结果表明,室温干燥贮藏天数不同、是否去掉果皮和是否光照影响了草玉梅种子的初始发芽天数、发芽率和发芽指数。随着贮藏天数的增加,去掉果皮草玉梅种子的初始发芽天数呈不同程度的减小,发芽率和发芽指数呈不同程度的增加。室温贮藏40~180 d的草玉梅种子,去掉或未去掉果皮后光照条件下的初次发芽天数显著低于贮藏0 d处理(P<0.05)。室温贮藏40,80,150和180 d的草玉梅种子在去掉果皮光照处理下,其发芽率间的差异不显著(P>0.05),但皆显著高于贮藏0 d处理(P<0.05)。室温贮藏180 d的草玉梅种子未去掉果皮光照下的发芽率显著高于贮藏80和150 d处理(P<0.05),后两者显著高于贮藏40 d处理(P<0.05),贮藏40 d 处理又显著高于贮藏0 d处理(P<0.05)。光照不同程度地降低了草玉梅种子的初始发芽天数,提高了草玉梅种子的发芽率和发芽指数。高寒草甸土壤中冷季层积处理不同程度地降低了草玉梅种子的初次发芽天数,提高了发芽率和发芽指数。践踏层积的草玉梅种子在30/20℃和20/10℃变温条件下的初次发芽天数分别显著低于层积不践踏处理(P<0.05)。践踏层积的草玉梅种子在25/15℃和20/10℃变温条件下的发芽率(分别为38.0%和35.3%),显著高于层积不践踏处理(22.7%和14.0%);室温贮藏同期(11月-4月)未去掉果皮的草玉梅种子未能发芽。当年10月成熟后层积于天祝高寒草甸放牧地的草玉梅种子,至次年8月底有40.2%的发芽;未发芽的草玉梅种子在培养箱30/20℃到20/5℃的温度范围均能发芽,在30/20℃最高,仅为15.3%,绝大多数种子处于休眠。     

长三角城市乡土树种的天然林木群落分析与应用

长三角城市群园林绿化程度很高,但一些城市仍缺少乡土树种特色,危及生态系统稳定。长三角地跨北、中两个亚热带,有三类林木群落组成,即含有常绿阔叶树种的落叶阔叶林、落叶常绿阔叶混交林、常绿阔叶林。长三角范围乡土树种丰富,城市绿化以乡土树种为主,应大力推广应用。     

黄土丘陵沟壑区人工林地的土壤抗蚀性评价

以延安、安塞、吴旗的人工刺槐林、柠条林为研究对象,选取同一地区的自然恢复草地和坡耕地为对照,通过对5个表征土壤抗蚀性的指标即>0.25 mm水稳性团粒含量、>0.5 mm水稳性团粒含量、平均重量直径、团聚状况和团聚度的比较分析,对人工刺槐林、人工柠条林相对于自然恢复草地和坡耕地改善土壤抗蚀性的效果进行了评价,同时分析了不同林龄人工林土壤抗蚀性的变化.研究表明,人工林地相对于坡耕地,显著提高了土壤抗蚀性,但不及自然恢复草地,尤其在安塞和吴旗表现更明显;随着林龄的增长,人工林地土壤抗蚀性能增强,并趋于稳定.并通过对样地的聚类分析,也得出与上述相似的结果.综合分析表明,封禁条件下的植被自然恢复是黄土丘陵沟壑区比较适宜的植被恢复方式和控制土壤侵蚀的有效措施.     

Analysis of the change in the original Metasequoia glyptostroboides population and its environment in Lichuan, Hubei from 1948 to 2003

Lichuan, located at the foot of the Wuling Mountain in southwest Hubei Province of central China, is well known in the world for the discovery of the living fossil Metasequoia glyptostroboides Hu & Cheng in the 1940s. Its natural habitat has been well protected by the Chinese government. In order to provide a scientific foundation for the protection of the Metasequoia resource, it has become necessary to analyze the changes in the original, natural Metasequoia mother trees (ONMMT) and their environment from 1948 to 2003. The results and countermeasures are as follows: First, the distribution areas have little changed, involving four towns/farmland, 45 villages, 5,746 individual trees in 1983 and 5,388 trees in 2003, covering nearly 600 km², with an average density of less than 0.1 tree/hm². The Metasequoia distribution consists of two main types: a scattered distribution type found mainly at the foothills or near houses, roads, villages and rivers while the population distribution type is found mainly at the mountains and valleys with a minority at low elevations in the mountains and basins. The largest Metasequoia populations have 105 and 123 trees. Second, in the past, attention was only paid to the protection of individual trees while the protection of the Metasequoia population and environment was neglected. This led to a shift from the past mixed forests to pure Metasequoia forests, with a simpler structure, reduced biodiversity and conditions non-conducive for natural renewal. From 1983 to 2003, 386 original Metasequoia mother trees died. So it is vital to enhance the protection of the only original Metasequoia population in the world and its habitat. Third, modern ecological means should be taken to protect the original Metasequoia population and its habitat. Research on the restoration and rehabilitation of Metasequoia vegetation should be carried out. Restoration and rehabilitation should be put into practice in the Xiaohe Valley, where the highest concentration of Metasequoia is found. Fourth, efficient measures should be taken to stop human activities that are harmful to Metasequoia and to improve the environment of ONMMT in order to promote the protection of the ONMMT population and its ecosystem. Eco-emigration and the return of marginal agricultural land to forestry can be practiced. __________ Translated from Acta Ecologica Sinica, 2005, 25(5): 972–977 [译自: 生态学报, 2005, 25(5): 972–977]     

新疆棉区转Bt基因棉对棉田主要害虫及其天敌种群数量的影响

20 0 0～ 2 0 0 1年 ,在新疆棉区系统地研究了转Bt基因棉田主要害虫及其天敌的发生规律。结果表明 :转Bt基因棉对棉铃虫有良好的控制作用 ,发生高峰期百株落卵量和百株幼虫数量都显著低于常规对照 ,转Bt自控田和转Bt化防田棉蚜和棉盲蝽发生数量则显著高于常规棉对照田。在天敌方面 ,转Bt自控田和转Bt化防田较常规棉对照田 ,丽草蛉种群数量有所增加 ,而小花蝽和黑食蚜盲蝽等 5种捕食性和几种寄生性天敌数量都有所下降。转Bt基因棉田棉蚜和棉盲蝽等刺吸性害虫发生数量加重而多种天敌数量减少的趋势值得引起重视。鉴于新疆地区棉铃虫发生数量较低目前无需专门防治的特点 ,作者建议 :可以考虑推广农艺性状较好的常规棉品种并保护天敌 ,以达到控制害虫、丰产丰收的目的。