湖北神农架巴山冷杉径向生长对气候的响应

利用湖北神农架巴山冷杉树轮宽度标准年表,研究其径向生长对气候要素(月平均气温和月降水量)和生长期其他参数(活动积温、持续天数、初日和终日)的响应.结果表明:神农架地区巴山冷杉径向生长与当年2、4和9月平均气温呈显著正相关,与上年和当年9月降水量呈显著负相关,与上年12月降水量呈显著负相关.巴山冷杉径向生长与生长期活动积温和持续天数呈正相关,且与以9.0℃为阈值定义的活动积温和持续天数的相关最高.其生长期从5月下旬开始,到9月中旬结束,大约120 d.树轮宽度标准年表与以9.0和9.3℃定义的生长期初日和终日序列相关最高,相关系数分别为-0.25(接近0.05显著性水平)和0.33(P<0.05),所以9.0℃是其进行光合作用的敏感温度.生长期开始得早或结束得晚,即生长期延长,均有利于巴山冷杉的生长.与我国气候突变年(1978年)前相比,1978年以后神农架地区气温开始上升,生长期活动积温和持续天数开始增加,生长期初日提前,终日延迟,使得生长期延长,进而促进了巴山冷杉的径向生长.     

北亚热带生长期温度对马尾松径向生长的影响

近几十年由于温度升高导致的植物生长期的延长已经得到了证实,虽然生长期的长短变化会引起树木生产力变化,但不同起始温度的生长期对树木径向生长的影响尚不明确.为了探索不同起始温度的生长期变化对马尾松生长的影响,找出马尾松生长的敏感温度,本研究选择北亚热带西北边缘汉中地区的老龄马尾松为对象,应用树木年轮学的方法得到了马尾松从1945年到2009年的年轮宽度指数;同时利用汉中气象站的日均温度,计算每一年不同温度的初日、终日、持续时间以及生长期活动积温;分析生长期的变化规律和不同温度生长期对马尾松生长的影响.结果表明:6.0℃-7.5℃的开始时间对年轮宽度有负影响,6.0℃的初日对马尾松的生长最明显,10.5℃的终日时间对生长有显著促进作用;10.0℃和10.5℃的生长期与马尾松生长正相关最为显著,生长期活动积温对生长的影响也较为显著.这些敏感温度分别对应马尾松春季开始萌动、针叶出现以及秋季形成层活动停止时的温度,说明温度的变化导致物候期的变化进而影响植物的年生长量.     

川西亚高山林线岷江冷杉和红杉对气候变化的响应

为揭示川西亚高山林线优势树种岷江冷杉（Abies fargesii var.faxoniana）和红杉（Larix potaninii）径向生长对气候变化的响应差异。通过树木年轮生态学的方法,研究了岷江冷杉和红杉径向生长与年均温的分异现象、生长衰退以及应对严重干旱事件的抵抗力和恢复力稳定性,并结合限制岷江冷杉和红杉径向生长的主要气候因素进行了分析。结果表明：（1）温度是限制林线岷江冷杉径向生长的主要气候因素,而限制红杉径向生长的主要气候因素是降水;（2）岷江冷杉的径向生长与年平均温度的变化趋势一致,红杉在20世纪90年代后径向生长呈现出下降的趋势,与年均温的升高出现分异;（3）1800-2019年间,岷江冷杉出现生长衰退2次,红杉出现生长衰退5次,相同的时间内,红杉的衰退频率高于岷江冷杉;（4）岷江冷杉对严重干旱事件的恢复力相比升温前有所增强,抵抗力相比升温前下降明显,红杉对严重干旱事件的抵抗力和恢复力相比升温前均呈现出下降的趋势。可为川西亚高山林线的植被动态变化预测和历史区域气候重建提供参考。     

川西米亚罗林区不同海拔岷江冷杉生长对气候变化的响应

为分析青藏高原东缘半湿润区树木生长与气候关系随海拔变化的规律,于川西米亚罗林区分别在高、中、低海拔选取3个采样点,共采集132棵岷江冷杉年轮样芯,建立了最长达170a(1842-2011年)3个海拔高度的差值年表.岷江冷杉年轮指数与气候因子的相关分析表明:随海拔高度降低,温度与生长的负相关呈增加趋势.高海拔岷江冷杉径向生长与前—年冬季最低温呈显著正相关,中低海拔与当年春季均温、最高温和年均最高温呈显著负相关.低海拔岷江冷杉与当年4月降水呈显著正相关,随海拔升高降水与岷江冷杉生长的相关性降低.中低海拔岷江冷杉年表与4、5月帕尔默干旱指数(P DSI)呈显著正相关,表明在中低海拔存在春季干旱胁迫,抑制了岷江冷杉的生长.另外,大龄树木比小龄树木对气候变化的响应更敏感.     

升温突变对川西不同坡向和海拔岷江冷杉径向生长的影响

坡向和海拔作为重要的地形因子决定着林木立地条件的水热分配，为揭示川西地区升温突变前后制约岷江冷杉(Abies fargesii var.faxoniana)径向生长的气候因子变化及其在坡向和海拔上的响应格局，通过树木年轮学方法构建了4个坡向(NE、N、NW和W)的3个海拔梯度(≥3650 m)共12个岷江冷杉的标准年表，采用皮尔逊相关分析和回归分析的方法分析了升温突变前后(1980年)限制岷江冷杉径向生长主要气候因子的变化及径向生长的变化趋势。结果表明：升温前，生长季(7月)低温和降水、前一年冬季(10—11月)最高温和平均温制约岷江冷杉的生长，而当年春季(3月)温度的升高和生长季前(5月)较多的降水不利于其生长。升温后，4个坡向的林线、东北坡中海拔，西坡中、低海拔岷江冷杉的径向生长与大部分月温度表现为正相关关系，且上述样点树木径向生长明显加速。1980年升温前，制约不同样点岷江冷杉径向生长的气候因子具有一致性——坡向和海拔对其径向生长与温度相关关系的干扰和影响较小。增温促进了各坡向林线岷江冷杉的径向生长，且偏阳坡在更大的海拔范围内对增温表现出正反馈。研究对未来气候变化背景下川西不同坡...     

川西亚高山不同海拔岷江冷杉树轮碳稳定同位素对气候的响应

树木年轮(简称树轮)碳稳定同位素技术是研究树轮气候学的一种有效方法。利用四川卧龙亚高山暗针叶林不同海拔高度岷江冷杉树轮样本资料,提取该树轮稳定碳同位素(δ13C)和去趋势序列(DS),研究其树轮碳稳定同位素序列对气候要素(降水、月平均温度和月平均相对湿度)的响应关系,初步揭示了在全球气候变化背景下,川西亚高山森林岷江冷杉树木生长对气候因子变化(气候变暖、降水减少等)的响应方式。主要结论有:(1)岷江冷杉树轮δ13C组成变化范围为-23.33‰—-26.31‰,平均值为-24.91‰,变异系数为-0.011—-0.038,并表现出较强的一阶自相关;其对环境变化有较好的指示作用,表明岷江冷杉树轮δ13C组成在年际变化中较为稳定。(2)低海拔的岷江冷杉树轮δ13C分馏主要与当年8月月平均相对湿度和当年12月月平均温度相关性显著(P0.05);高海拔岷江冷杉树轮δ13C分馏主要与上一年8月月平均相对湿度和当年4月月平均温度相关性显著(P0.05);中海拔的岷江冷杉树轮δ13C分馏主要与上一年1、11月月平均温度和当年2、11月月平均温度相关性显著(P0.05),冬季温度是中海拔区岷江冷杉树木生长的限制因子,且具有明显的"滞后效应"。川西卧龙亚高山暗针叶林岷江冷杉树木径向生长主要受到气温的制约,从生物学基础上阐明了树木生长与环境的关系,冬季温度的升高,有利于植物生长期的提前,植物生长旺盛,抗旱能力减弱;同时证明了建群种岷江冷杉对雨水的依赖很小,这有利于植物生存,且维持了该植物群落的稳定性。该研究弥补了我国青藏高原高海拔地区气象台站稀少、观测资料时间短缺,为预测未来气候变化对岷江冷杉树木径向生长变化提供了科学的依据。     

植物群落类型和围栏封育对高山林线岷江冷杉幼苗成活的影响

林线树种幼苗的生长紧密关系着高山林线的形成。通过室内发芽实验测定了岷江冷杉种子萌发能力。2015年春,在川西巴郎山岷江冷杉林线之上的高山林线交错带,通过播种处理(播种和不播种),研究了不同植物群落类型(灌木和草地群落)和围栏处理(围栏和不围栏)对岷江冷杉幼苗成活率的影响,以期为进一步探讨高山林线形成机制提供科学参考。结果表明:(1)岷江冷杉室内发芽率31.4%,成活率随时间下降。(2)灌木群落的全年日平均空气温湿度显著高于草本群落,而两群落的全年日平均土壤温度无显著差异。(3)未播种样地没有发现岷江冷杉幼苗,说明林线交错带缺乏岷江冷杉种子。(4)与不围栏样地相比,围栏封育分别显著提高了岷江冷杉幼苗成活率2.0%(2015年)和2.2%(2016年);与灌木群落相比,草本群落中岷江冷杉幼苗成活率显著提高0.8%(2015年)和1.2%(2016年),说明灌木对林线交错带幼苗更新具有更强的竞争作用。围栏处理下,草本群落中岷江冷杉幼苗成活率显著高于灌木群落;不围栏处理下,草本群落中岷江冷杉幼苗成活率显著低于灌木群落,2017年在不围栏样地没有幼苗存活,说明动物干扰对林线交错带森林更新有阻碍作用。研究表明,高山林线交错带森林更新,受种子、植物竞争和动物干扰(例如,放牧)等多方面因素的共同影响,可以通过播种、植物剔除(去除竞争)和围栏等促进幼苗更新和成活。     

川西米亚罗林区主要树木生长对气候响应的差异

为分析青藏高原东缘半湿润区不同树种树木生长对气候变化的响应规律,于川西米亚罗林区海拔3000 m左右(低海拔)采集铁杉、岷江冷杉、紫果云杉,海拔4000 m左右林线位置(高海拔)采集岷江冷杉、四川红杉,共计182棵树木年轮样芯,建立了不同树种的树轮宽度年表,对不同树种的年轮指数与各月气候因子进行相关分析.结果表明： 在低海拔处,树木生长与4、5月气温呈负相关,与4、5月降雨呈正相关,受到春季干旱胁迫的影响;但树种之间存在显著差异： 铁杉的生长受春季干旱胁迫影响最严重,岷江冷杉次之,紫果云杉所受影响很小.在高海拔处,树木生长主要受生长季温度的影响,岷江冷杉年轮指数与当年2、7月最低气温呈显著正相关,与上一年10月最高气温亦呈正相关;四川红杉年轮指数与5月最高气温呈显著正相关,但与2月均温、3月最低气温呈显著负相关.近几十年青藏高原东北缘气候有干暖化趋势,如果这种趋势持续发生,低海拔紫果云杉长势将超过铁杉和岷江冷杉;高海拔处的升温更有利于岷江冷杉的生长.     

藏东南色季拉山急尖长苞冷杉(Abies georgei var. smithii)林线的生态气候特征

高山林线因其对气候因子的敏感性和自身结构的不稳定性而被视为气候变化的"监视器",通过自动微气象站对藏东南色季拉山急尖长苞冷杉(Abies georgei var. smithii)林线气象因子的连续监测,探讨了色季拉山高山林线的生态气候特征.结果表明:在色季拉山急尖长苞冷杉林线处,年平均温度为1.3℃,年平均相对湿度为79.4%,全年降水量为892.6 mm,主要集中在6、7、8、9月4个月份.林线最热月平均温度为9.4℃,最冷月平均温度为-6.4℃,年生物温度为3.1℃,温暖指数是11.6℃月,寒冷指数是-55.9℃月,生长季内平均温度为7.7℃,生长季长度为133d,大陆度指数为34.0,湿润指数为217.5.其温暖指数与我国两种山地森林树种祁连圆柏和喜马拉雅冷杉的分布上限较为接近.林线的最热月温度、年生物学温度和生长季平均温度与全国高山林线的平均值十分接近.从全球范围来看,色季拉山林线最热月平均温度9.4℃与全球均值10℃很接近.生长季内10cm深度的土壤均温为6.22℃,接近Krner观测的(6.7±0.8)℃全球均值.     

贡嘎山地区不同海拔冷杉比叶质量和非结构性碳水化合物含量变化

以贡嘎山地区磨西山谷东北坡和康定山谷西南坡为样地,研究了高山林线和低海拔冷杉休眠期和生长旺盛期针叶比叶质量和组织非结构性碳水化合物含量.结果表明:生长在温暖湿润的磨西山谷东北坡的冷杉针叶比叶质量和组织非结构性碳水化合物含量均高于炎热干燥的康定山谷西南坡;高山林线冷杉比叶质量大于低海拔冷杉;高山林线冷杉组织非结构性碳水化合物含量总体高于低海拔冷杉,且生长期比休眠期更为显著.研究结果不支持"碳供应不足导致高山林线形成"的假说.     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Hectorella: A member of the betalain-suborderChenopodiineae of the orderCentrospermae

Roots ofHectorella caespitosa Hook. f. were induced to produce a red pigment which was shown to be a betalain and not an anthocyanin. These data indicate thatHectorella belongs to theChenopodiineae, the betalain suborder of theCentrospermae, and excludes alignment with the anthocyanin family theCaryophyllaceae.     

Succession in the southern part of the Canadian boreal forest

Forest succession following fire in a forest mosaic of northwestern Quebec has been studied in order to: (1) describe the successional pathways using communities of different ages and (2) evaluate convergence of successional pathways and possible effect of fire suppression on the establishment of steady-state communities. As a first step, ordination and classification techniques were used in order to remove changes in forest composition which are related to abiotic conditions. Then, ordinations based on tree diameter distributions were used to study shifts in species composition in relation to time since the last fire.Even under similar abiotic conditions, successional pathways are numerous. However, regardless of forest composition after fire, most stands show convergence toward dominance of Thuja occidentalis and Picea mariana on xeric sites and dominance of Abies balsamea and Thuja occidentalis on more mesic sites. Stable communities of >300 yr occur on xeric sites while on mesic sites directional succession still occurs after 224 yr. Nearly all species involved in succession are present in the first 50 yr following fire. Only Abies balsamea and Thuja occidentalis increase significantly in frequency during succession. Following initial establishment, successional processes can generally be explained by species longevity and shade tolerance. Early successional species may be abundant in the canopy for more than 200 yr while the rapid decrease of Picea glauca, a late successional species could be related to spruce budworm outbreaks. Considering the short fire rotation observed (about 150 yr), a steady-state forest is unlikely to occur under natural conditions, though it may be possible if fire is controlled.     

Analysis of the genes of the OEE1 and OEE3 proteins of the photosystem II complex from Chlamydomonas reinhardtii

The sequences of the nuclear genes of the 33 kDa (OEE1) and the 16 kDa (OEE3) polypeptides of the oxygen evolving complex of Chlamydomonas reinhardtii have been established. Comparison between the OEE1 protein sequences of C. reinhardtii and higher plants and cyanobacteria reveals 67 and 47% homology. In contrast, C. reinhardtii and higher plants have only 28% overall homology for OEE3 which is mostly limited to the central portion of the protein. The transit peptides of the C. reinhardtii proteins consist of 52 (OEE1) and, most likely, 51 (OEE1) amino acids. They have a basic amino terminal region and, at least in the case of OEE1, a hydrophobic segment at their carboxy terminal end typical of thylakoid lumen proteins. Comparison of the genomic and cDNA clones indicates that the OEE1 and OEE3 genes contain five and four introns, respectively, some of which are located within the coding sequences of the transit peptides.     

The purification of the three trimannosyl-N-acetylchitobiose pentasaccharides from the urine of swainsonine-intoxicated sheep

A simple method for the preparative resolution of three Man₃GlcNAc₂ isomers called Ia, Ib and II has been designed. It consists mainly of the use of concanavalin A-Sepharose which allowed the total purification of Man₃GlcNAc₂-Ia, and then of anion-exchange resin in borate buffer-gradient to separate the Ib and II isomers. The purity of each oligosaccharide was checked by two HPLC methods. The use of these oligosaccharides for different analytical and biosynthetic purposes is discussed, and the unexpected resistance of one of the Man₃GlcNAc₂ alditols to the action of endo--N-acetylglucosaminidase H is noted.     

Evaluation of the Pro-Lab ID ring system for the identification of medically important yeasts

We evaluated 151 coded isolates of medically important yeast species belonging to the genera Candida, Cryptococcus, Geotrichum, Rhodoturula, Saccharomyces and Torulopsis using the newly developed rapid Pro-Lab Identification Ring, PL 960 system (PLID-Ring). All isolates were concurrently identified by the API 20C and conventional procedures comprising macro- and micromorphology, assimilation and fermentation of various carbon and nitrogen compounds. The PLID-Ring system identified isolates of Candida albicans, C. kefyr, C. krusei, C. lusitaniae, C. parapsilosis, Rhodotorula rubra, and Torulopsis glabrata with 100% accuracy in 24 h. This system identified C guilliermondii and S. cerevisiae isolates with an accuracy of 90% and 86%, respectively, while those belonging to Cr. neoformans, T. candida (= C. famata), C. rugosa and C. tropicalis were identified with 38.4%, 50%, 12.5% and 50% accuracy, respectively. Three isolates of Cr. laurentii were not identified by the PLID-Ring system. The overall accuracy of the PLID-Ring system was 81.45% (123 of 151 isolates). However, the system does not include species such as Cr. laurentii in its data base. When these three Cr. laurentii isolates were excluded from the evaluation, the accuracy of the PLID-Ring system increased from 81.45% to 83.1%.     

The history of the genusHomo

The genusHomo was established by Carolus Linnaeus in 1758. During the course of the past 150 years, the addition of fossil species to the genusHomo has resulted in a genus that, according to the taxonomic interpretation, could span as much time as 2.5 Myr, and include as many as ten species. This paper reviews the fossil evidence for each of the species involved, and sets out the case for their inclusion inHomo. It suggests that while the case for the inclusion of some species in the genus (e.g.Homo erectus) is well-supported, in the case of two of the species,Homo habilis andHomo rudolfensis, the case for their inclusion is much weaker. Neither the cladistic evidence, nor evidence about adaptation suggest a particularly close relationship with laterHomo.     

Comparative analysis of the Kekkon molecules,related members of the LIG superfamily

Leucine-rich repeats (LRRs) and immunoglobulin (Ig) domains represent two of the most abundant sequence elements in metazoan proteomes. Despite this prevalence, comparatively few molecules containing both LRR and Ig (LIG) modules exist, and fewer still have been functionally defined. One LIG whose function has been investigated is the Drosophila protein Kekkon1 (Kek1). In vivo studies have demonstrated a role for Kek1 in Epidermal Growth Factor Receptor (EGFR) signaling and have suggested a role in neuronal pathfinding. Kek1 is the founding member of the Kek family, a group of six Drosophila transmembrane proteins that contain seven LRRs and a single Ig in their extracellular domains. While this arrangement of domains predicts a possible role as cell adhesion molecules (CAMs), to date little is known about the function or evolutionary relationship of these additional Kek molecules. Here we report that orthologs of Kek1, Kek2, Kek5, and Kek6 exist in the mosquito, Anopheles gambiae, and the honeybee, Apis mellifera, indicating that this family has been conserved for ~300 million years of evolutionary time. Comparative sequence analyses reveal remarkable identity among these orthologs, primarily in their extracellular regions. In contrast, the intracellular regions are more divergent, exhibiting only small pockets of conservation. In addition, we provide support for the general notion that these molecules may share common functions as CAMs, by demonstrating that Kek family members can form homotypic and heterotypic complexes.Edited by D. TautzChristina M. MacLaren, Timothy A. Evans and Diego Alvarado contributed equally to this work     

Comparison of the Influence of Carbon Substrates on the Fibrolytic Activities of Anaerobic Rumen Fungi

Cellulolytic and xylanolytic activities among genera of anaerobic fungi when grown on glucose, xylan and the cellulosic substrates, filter paper and Avicel were compared. All the fungi had basal extracellular fibrolytic activities that could be enhanced by growth on xylan or the cellulosic substrates. However,Piromyces communisstrain 22 andNeocallimastix patriciarumstrain 27 had substantially greater levels of fibrolytic activity thanOrpinomyces joyoniistrain 19-2 orNeocallimastix frontalisstrain RE1. Zymogram analysis suggested both structural and regulatory differences amongst the enzyme systems of the fungi. Numerous and varied enzyme bands were evidenced for all the fungi, with substantial substrate influences seen in the xylanase activities. Most commonly the smaller molecular weight bands, found exclusively extracellularly, appeared under the greatest regulatory control. Endoglucanase activities ofP. communisandO. joyoniidemonstrated similar regulatory control, while those of the twoNeocallimastixstrains did not appear to exert such control. These results suggest that while the enzymatic activities are functionally similar, there are likely significant variations in the enzyme systems of the anaerobic fungi.     

Evaluation of antiprotozoal and antimycobacterial activities of the resin glycosides and the other metabolites of Scrophularia cryptophila

Resin glycosides are secondary metabolites exclusive to the convolvulaceous plants. In this study, crypthophilic acids A–C (1–3), the first resin glycosides occurring in another family (Scrophulariaceae), and the other constituents of Scrophularia cryptophila were examined for in vitro antiprotozoal and antimycobacterial potentials. Except for crypthophilic acid B (2), all tested compounds exhibited growth-inhibitory effect against Trypanosoma brucei rhodesiense, with l-tryptophan (6) and buddlejasaponin III (7) being the most potent ones (IC₅₀'s 4.1 and 9.7 μg/ml). In contrast, the activity towards Trypanosoma cruzi was poor, and only crypthophilic acid C (3), 6 and 7 were trypanocidal at concentrations above 40 μg/ml. With the exception of 2 and 6, all compounds were active against Leishmania donovani. Harpagide (4) and 3 emerged as the best leishmanicidal agents (IC₅₀'s 2.0 and 5.8 μg/ml). Only compounds 3, 6 and 7 showed antimalarial activity against Plasmodium falciparum with IC₅₀ values of 4.2, 16.6 and 22.4 μg/ml. Overall the best and broadest spectrum activity was presented by compounds 3 and 7, as they inhibited all four parasitic protozoa. None of the isolates had significant activity against Mycobacterium tuberculosis (MICs >100 μg/ml) or were toxic towards mammalian (L6) cells. This is the first report of antiprotozoal activity for natural resin glycosides, as well as for harpagide (4), acetylharpagide (5), tryptophan (6) and buddlejasaponin III (7).