Unusual abundance–range size relationship in an Afromontane bird community: the effect of geographical isolation?

Aim To show that the frequently reported positive trend in the abundance–range‐size relationship does not hold true within a montane bird community of Afrotropical highlands; to test possible explanations of the extraordinary shape of this relationship; and to discuss the influence of island effects on patterns of bird abundance in the Cameroon Mountains. Location Bamenda Highlands, Cameroon, Western Africa. Methods We censused birds during the breeding season in November and December 2003 using a point‐count method and mapped habitat structure at these census points. Local habitat requirements of each species detected by point counts were quantified using canonical correspondence analysis, and the size of geographical ranges of species was measured from their distribution maps for sub‐Saharan Africa. We tested differences in abundance, niche breadth and niche position between three species groups: endemic bird species of the Cameroon Mountains, non‐endemic Afromontane species, and widespread species. Results We detected neither a positive nor negative abundance–range‐size relationship in the bird community studied. This pattern was caused by the similar abundance of widespread, endemic and non‐endemic montane bird species. Moreover, endemic and non‐endemic montane species had broader local niches than widespread species. The widespread species also used more atypical habitats, as indicated by the slightly larger values of their niche positions. Main conclusions The relationship detected between abundance and range size does not correspond with that inferred from contemporary macroecological theory. We suggest that island effects are responsible for the observed pattern. Relatively high abundances of montane species are probably caused by their adaptation to local environmental conditions, which was enabled by climatic stability and the isolation of montane forest in the Cameroon Mountains. Such a unique environment provides a less suitable habitat for widespread species. Montane species, which are abundant at present, may also have had large ranges in glacial periods, but their post‐glacial distribution may have become restricted after the retreat of the montane forest. On the basis of comparison of our results with studies describing the abundance structure of bird communities in other montane areas in the Afrotropics, we suggest that the detected patterns may be universal throughout Afromontane forests.     

Impact of soil mesofauna on the decomposition of two main species litters in a Pinus koraiensis mixed broad-leaved forest of the Changbai Mountains

In most terrestrial ecosystems, the majority of aboveground net primary productivity enters the decomposition system as plant litter. The decomposition of plant litter plays a critical role in regulating build up of the forest soil organic matter, releasing of nutrients for plant growth, and influencing the carbon cycling. Soil fauna are considered to be an important factor in the acceleration litter decomposition and nutrient transformations. Mechanisms of soil faunal contribution to litter decomposition include digestion of substrates, increase of surface area through fragmentation and acceleration of microbial inoculation into litter. The Pinus koraiensis mixed broad-leaved forest is one of the typical forest vegetation types in Changbai Mountain. Previously, major studies carried here were focused on climate, soil and vegetation; however, on litter decomposition and the role of soil fauna in this forest ecosystem were limited. In this paper, we conducted a litter decomposition experiment using litterbag method to explore the contribution of soil fauna on litter decomposition and provide a scientific basis for maintaining a balanced in P. koraiensis mixed broad-leaved forest in Changbai Mountains. During 2009 and 2010, we used litterbags with different mesh sizes to examine the decomposition of two dominant tree species (P. koraiensis, Fraxinus mandshurica) in studied site. The results showed that the process of litter decomposition can be separated into two apparent stages. The initial decomposition process at former six months was slow, while accelerated the final six months. The former six months (from October 2009 to April 2010) was winter and spring. There was low temperature and almost no activity of soil fauna and microbes. The final six months (from June to October 2010), decomposition rates increased. In summer and autumn, both temperature and moisture increases, abundance of soil fauna was much than before and was most active. The remaining mass of P. koraiensis was higher than that of F. mandshurica in two mesh size litterbags after 1 year decomposition, meanwhile litter in 2 mm mesh size litterbag had higher decomposition rate than that of 0.01 mm for two species litter. The Collembola, Acari, Enchytraeidae Lithobiomorpha and Diptera larvae were mainly fauna groups in the litterbags. The composition of soil fauna community was difference between P. koraiensis and F. mandshurica during litter decomposition. 24 different soil fauna groups and 1431 individual were obtained in P. koraiensis litterbags; Isotomidae, Tomoceridae and Oribatida were dominant groups; while 31 different soil fauna groups and 1255 individual were obtained in F. mandshurica litterbags; Isotomidae, Hypogastruridae Oribatida and Mesostigmata were dominant groups. The rate of litter decomposition was positively correlated with the individual and group density of soil fauna. Contribution rate to litter decomposition was 1.70% for P. koraiensis and 4.83% for F. mandshurica. Repeated measures ANOVA showed that litter species, time and soil fauna had a significant impact on the rate of litter decomposition (P < 0.05). Our results suggested that soil fauna could accelerate litter decomposition and, consequently, nutrient cycling in P. koraiensis mixed broad-leaved forest, Changbai Mountains.     

Chromosome counts and karyotypes in Chaetoseris and Stenoseris (Asteraceae‐Cichorieae) from the Hengduan Mountains of SW China

Abstract Chaetoseris and Stenoseris are two morphologically close genera from the tribe Cichorieae of the sunflower family and they are endemic in alpine eastern Himalayas to the Hengduan Mountains of SW China. Mitotic chromosome numbers and karyotypes are reported for 12 populations representing eight species of Chaetoseris and two species of Stenoseris from the Hengduan Mountains region. Eight species are new and the other two provide confirmation of previous reference. All Chaetoseris and Stenoseris taxa are diploidy with 2n= 16 and their basic number is tentatively suggested as x= 8. Karyotypes of Chaetoseris and Stenoseris are similar to each other with 2A and 2B for the former and 2A for the latter. Cytological data of chromosomal numbers and karyotypes support a close relationship of the two genera. Currently no polyploids are found for these two genera and it seems that polyploidization has played a minor role in their evolutionary speciation in the Hengduan Mountains region.     

Novel GFP expression using a short N-terminal polypeptide through the defined twin-arginine translocation (Tat) pathway

Escherichia coli is frequently used as a convenient host organism for soluble recombinant protein expression. However, additional strategies are needed for proteins with complex folding characteristics. Here, we suggested that the acidic, neutral, and alkaline isoelectric point (pI) range curves correspond to the channels of the E. coli type-II cytoplasmic membrane translocation (periplasmic translocation) pathways of twin-arginine translocation (Tat), Yid, and general secretory pathway (Sec), respectively, for unfolded and folded target proteins by examining the characteristic pI values of the N-termini of the signal sequences or the leader sequences, matching with the known diameter of the translocation channels, and analyzing the N-terminal pI value of the signal sequences of the Tat substrates. To confirm these proposed translocation pathways, we investigated the soluble expression of the folded green fluorescent protein (GFP) with short N-terminal polypeptides exhibiting pI and hydrophilicity separately or collectively. This, in turn, revealed the existence of an anchor function with a specific directionality based on the N-terminal pI value (termed as N-terminal pI-specific directionality) and distinguished the presence of the E. coli type-II cytoplasmic membrane translocation pathways of Tat, Yid, and Sec for the unfolded and folded target proteins. We concluded that the pI value and hydrophilicity of the short N-terminal polypeptide, and the total translational efficiency of the target proteins based on the ΔGRNA value of the N-terminal coding regions are important factors for promoting more efficient translocation (secretion) through the largest diameter of the Tat channel. These results show that the short N-terminal polypeptide could substitute for the Tat signal sequence with improved efficiency.     

长白山北坡林线灌木草本植物与岳桦的动态关系

本文以长白山北坡林线为研究区,调查125个样方内岳桦种群的径级结构与林线灌草植物的生态重要值。采用常规统计和聚类方法分析岳桦种群与8种常见灌草植物的动态特点,采用典型与单因子相关分析岳桦动态与林线灌草植物的变化关系。结果表明岳桦种群扩张带动林下灌草的相继移动,林线上侵不仅是单一乔木的变化,而是森林群落向苔原群落的入侵,从空间上挤占生态位的过程。另外,这种替代中各个成分变化也存在差异,由于各种植物在群落中的地位和生态竞争力的区别,在替代过程中不同植物变化也具有明显的异步性。     

中国传统菊花品种‘小林静’再生及转化体系的建立

以中国传统菊花品种‘小林静’叶片为外植体,建立了‘小林静’较好的再生体系及遗传转化体系.结果表明,‘小林静’叶盘最适不定芽分化培养基为MS+2.0 mg/L 6-BA+1.5 mg/L NAA,不定芽分化率为92.76％,平均再生不定芽数为2.3767个;试管苗最佳生根培养基为1/2MS,生根率达100％.移栽采用灭菌的蛭石,再生苗移栽成活率达90％以上.采用根癌农杆菌C58C1介导的叶盘转化法进行‘小林静’的遗传转化试验,农杆菌OD600=0.5-0.6,侵染10 min后,将叶片外植体接种到MS+2.0 mg/L 6-BA+1.5mg/L NAA的培养基中黑暗共培养2d,之后转接到附加10 mg/L硫酸卡那霉素和400 mg/L羧苄青霉素的分化筛选培养基中进行转化细胞的筛选,待长出抗性芽后转接至生根培养基中进行培养,最终建立了菊花品种‘小林静’的遗传转化体系.     

秦岭产9种野菜中矿质元素含量的比较

野生蔬菜是指自然生长且未经人工栽培的蔬菜,因其富含人体所需的矿质元素、氨基酸及多种维生素而备受人们青睐[1-3],被公认为天然绿色食品.近年来,随生活水平的提高,多样化的饮食结构驱使人们不断对各种食品进行开发,尤其在旅游业的发展带动下,食用野菜已成为一种时尚和保健的需要.     

樟子松树轮δ13C的年内变化特征及其对气候要素的响应

对大兴安岭北部两株樟子松(Pinus sylvestris var.mongolica)树轮样品的年内稳定碳同位素比率(δ13C)进行测定,结果表明:樟子松树轮年内δ13C值在不同生长阶段总体表现出每年生长季中期最高、早期次之、晚期最低的变化特征.δ13C的年内变化趋势在幼龄期至速生期变化剧烈,成熟期至衰老期相对平缓.从幼龄期至衰老期的整个生长阶段,同时期年内δ13C的变动幅度基本为晚材大于早材.幼龄期年内晚材的δ13C一直明显高于早材,而成熟期年内早晚材δ13C的差别逐渐减小,至衰老期年内晚材δ13C已低于早材且无显著差别.树轮δ13C的年内变化主要体现在生长季中后期,即早晚材之间的过渡段至晚材.年内不同时段的d13C序列与同时段的宽度去除生长趋势序列(去趋势序列)之间的相关性随生长季节的推移而逐渐降低.当年早材宽度与前一年晚材宽度显著正相关,当年早材δ13C序列与前一年晚材宽度和当年早材宽度的去趋势合并序列呈现较显著的负相关性,与前一年晚材δ13C序列或宽度去趋势序列之间均未表现出显著的相关性.分析结果表明:早材的形成很可能来源于前一年光合作用的产物,在利用树轮年内不同材质宽度或δ13C序列进行气候环境重建时需要考虑这一点.年内早材、过渡段和晚材三个时段的δ13C分别对应于4月下旬至6月中旬土壤湿度较大、温度上升较快的时期,6月下旬至7月中旬降水增加、温度达到最高而相对湿度降低的时期,以及7月下旬至9月中旬降水增加、温度下降而相对湿度较大的时期.     

吉安市野生地被植物资源及其园林应用综合评价

通过对吉安市典型山地野生地被植物资源进行实地调查,在初步确定具有良好观赏价值的87种野生地被植物基础上,采用线性加权综合法数学模型对吉安市野生地被植物作了综合评价,重点推荐在吉安地区具有园林应用价值的野生地被植物5种,为野生地被植物的合理开发应用提供科学依据。     

祁连山东段高寒草甸植物总酚和黄酮含量及抗氧化活性研究

采用Folin-Ciocalteu法和铝盐显色法对祁连山东段12种高寒植物(灌木嫩枝和草本植物叶片)进行总酚、黄酮含量的测定,并用FRAP法和ABTS法测定其总抗氧化能力。结果表明:(1)金露梅、山生柳、高山绣线菊、西藏沙棘、珠芽蓼的总酚和总黄酮含量较高且总抗氧化能力较强,其中山生柳的总酚含量最高为19.58%,高山绣线菊的黄酮含量最高为13.23%。(2)采用FRAP法测得西藏沙棘的抗氧化能力最强为49.58mmol/L,而用ABTS法测得金露梅的抗氧化能力最强为32.46mmol/L。(3)总酚、总黄酮与总抗氧化能力(FRAP法)具有极显著的相关性(相关系数分别为0.887 1和0.915 7)。分析认为,12种高寒植物的植株体内总酚和总黄酮含量越高,其抗氧化能力越强。