福州市居住区景观树木多样性分析

对福州市辖区内自1995年建成的36个居住区景观树木构成和物种多样性进行调查,并根据建成年代和相对城市环线位置进行分析。结果表明,36个居住区共有155种12 694株景观树木,隶属于42科和97属。在树种构成分析中,将树种按常见程度分为6个组,标志组有20种,共7560株,优势组、常见组、少见组、稀有组以及孤生组分别有17、19、49、38、12种和2383、1297、1269、173、12株。多样性分析表明,福州市居住区景观树木多样性与发达城市比较还存在差距,尤其是旧居住区的景观树木物种多样性更低,树种选择也更为单一。此外,取样居住区中部分安置房居住区的景观树种多样性低于同时期非安置房居住区。     

西藏昆仑针茅草原的基本特征

正昆仑针茅(Stipa roborowskyi)是青藏高原特有的寒旱生多年生密丛型禾草,广泛分布于藏南喜马拉雅山北坡和雅鲁藏布江谷地、阿里地区、羌塘高原中南部和昆仑山地,以及印度和克什米尔地区(Wu et al.,2006;中国科学院中国植被图编辑委员会,2007)。昆仑针茅草原是西藏重要的草原类型之一,但分布较为零散,没有像紫花针茅(S.purpurea)草     

Early environments drive diversity and floristic composition in Mediterranean old fields: Insights from a long-term experiment

While many studies have explored how previous and current environmental conditions affect the performance of individual organisms, their relative importance as drivers of current diversity and composition of communities is virtually unknown. We evaluated the response of herbaceous communities to previous (experienced during early establishment) and current environmental conditions by comparing their composition and diversity in an abandoned Mediterranean cropland planted with Quercus ilex subsp. ballota L. seedlings. These seedlings received different experimental treatments (summer irrigation and artificial shading) during the first three years after planting, and were interrupted from then on. We tested two complementary hypotheses: (i) the previous environments experienced by the herbaceous communities during their establishment have a long-term carry-over effect on diversity and composition of species assemblages and (ii) these communities are influenced by their current environment, particularly by the woody layer and the soil conditions. Overall, we observed an important contribution of initial environmental conditions in determining the current diversity and composition of herbaceous communities. Amelioration of environmental conditions, particularly water stress, during community establishment resulted in a decrease in alpha and beta diversity, possibly as a consequence of decreasing environmental heterogeneity. Previous environments accounted for 26.3% of the explained variance in current community composition. Annuals, legumes and forbs also responded significantly to previous environments, which explained 27.9%, 36.2% and 30.1%, respectively, of the variance in their composition. Our results suggest that those species present at a particular site early in succession pre-empt the site and influence vegetation dynamics on that site for a long time. This study provides important insights for understanding the mechanisms underlying the ecological effects of issues like cropland reforestation and woody vegetation encroachment.     

Plant Community Composition as a Predictor of Regional Soil Carbon Storage in Alaskan Boreal Black Spruce Ecosystems

The boreal forest is the largest terrestrial biome in North America and holds a large portion of the world’s reactive soil carbon. Therefore, understanding soil carbon accumulation on a landscape or regional scale across the boreal forest is useful for predicting future soil carbon storage. Here, we examined the relationship between floristic composition and ecosystem parameters, such as soil carbon pools, the carbon-to-nitrogen (C/N) ratio of live black spruce needles, and normalized basal area increment (NBAI) of trees in black spruce communities, the most widespread forest type in the boreal forest of Alaska. Variability in ecosystem properties among black spruce stands was as large as that which had previously been documented among all forest types in the central interior of Alaska; we found an eightfold range in NBAI and fivefold range in mineral soil carbon and nitrogen pools. Acidic black spruce communities had significantly more carbon in the organic soil horizon than did nonacidic black spruce communities, but did not differ in any other measured ecosystem parameter. We explained 48% of the variation in total soil carbon with a combination of plant community indices and abiotic and biotic factors. Plant community composition was at least as effective as any single environmental factor or stand characteristic in predicting soil C pools in Alaskan black spruce ecosystems. We conclude that among the community properties analyzed, the presence of key groups of species, overall species composition, and diversity of certain functional types, especially Sphagnum moss species, are important predictors of soil carbon sequestration in the black spruce forest type.     

How general are global trends in biotic homogenization? Floristic tracking in Chile,South America

Aim   To quantify the occurrence of floristic change in the vascular flora of Chile. We test whether continental areas have experienced floristic modification leading to either homogenization, differentiation or tracking.
Location   Continental Chile.
Methods   On the basis of the geographical distribution of native (1806 species) and naturalized plants (552 species) in continental Chile, we quantified change between two floristic stages: (1) pre-European flora, including native extant and extinct species; and (2) current flora, including native and naturalized species, but excluding extinct plants. We compared changes in compositional similarity (calculated by Jaccard's index, Δ J ) between pairs of regions, and similarity decay with respect to geographical distance. Additionally, by means of Whittaker's index, we examined species turnover, distinguishing between native and naturalized plants.
Results   Between floristic stages (pre-European vs. current flora) no significant changes in floristic similarity were noted at national or regional scales. Similarity decay showed no statistical differences between pre-European and current flora. Analysing patterns of geographical turnover, we found that species turnover of naturalized plants over their geographical range is similar to that of native plants.
Conclusions   The composition of the continental flora of Chile does not show significant modifications in similarity patterns after considering naturalized species, thus indicating floristic tracking. The causes of this phenomenon may be related to the current geographical distribution of naturalized plants, which closely parallels that of native plants. Our results differ from those obtained in Northern Hemisphere continents, thus indicating that trends of biotic change may differ between hemispheres.     

庐山蕨类植物区系研究

庐山共有蕨类植物39科87属247种(含变种、变型),其区系带有热带和温带双重性。其中鳞毛蕨科、水龙骨科、蹄盖蕨科、金星蕨科和铁角蕨科属种优势明显,共有38属160种,分别占总属数的43.7%和种数的64.8%,代表了该地区蕨类植物区系的一个重要特征。该区区系地理成分复杂,相互交错,其中热带性属占总属数的64.2%,温带性属占总属数的35.8%。东亚成分在该区系占有绝对优势,共有14属,占总属数的20.9%,中国特有属缺乏,特有种丰富,表明成分具有多样性并具有热带亲缘性,是亚热带向北温带的过渡地区。该区与井冈山、武夷山关系密切,与鼎湖山、秦岭和横断山关系疏远。     

不同环境下水稻谷粒重发育的杂种优势和遗传相关性分析

选用9个不同类型的水稻品种(系),按双列杂交设计(6×5)配成两套亲本和F12个世代的遗传材料,采用数量性状的加性、显性遗传模型、发育遗传模型比较分析了水稻谷粒重发育的杂种优势和遗传相关性。结果表明,早季在谷粒充实前期(1～12d)群体平均优势较小,中后期(13～28d)正向优势趋于明显,在谷粒充实的全过程均表现较小的负向群体超亲优势;晚季则在谷粒充实前中期(1～18d)表现正向群体平均优势。后期(19～28d)优势不明显,在谷粒充实前期(1～12d)表现正向群体超亲优势,之后转为明显的负向群体超亲优势,表明晚季谷粒发育的杂种优势表现较之早季更有利于提高籽粒充实质量,不同发育时期谷粒重之间以及与最终谷粒重之间的遗传相关分析表明,早季以显性相关为主,晚季以加性相关为主,随着发育进程的推进,相关趋于密切。     

多物种集合的种-多度关系模型研究进展

种 -多度关系是群落结构研究最基本的方面之一。Preston最早描述的物种“常见性和罕见性的分布”是群落中种 -多度关系的一般特性。自从 Motomura开创性地提出一个几何序列模型用于描述这种特性后 ,生态学家已建立了许多拟合种 -多度关系的经验模型和理论模型 ,主要包括对数序列分布、对数正态分布等统计模型 ,几何序列模型、分割线段模型等生态位模型以及反映群落动态和环境制约作用的动态模型 ,还有其中一些模型的扩展模型。近年来 ,种 -多度关系研究领域已大大拓宽 ,如“群落”的内涵已延伸为“多物种集合”,物种“多度”的测度推广到“广义多度”。尽管种 -多度关系研究已取得很大进展 ,仍有一些问题尚待解决 ,诸如多度指标选择、种 -多度分布时空变化规律及其机制以及种 -多度关系模型的选择、检验、解释与应用。     

广东阳春鹅凰嶂自然保护区种子植物区系研究

鹅凰嶂自然保护区位于广东省阳春市境内 (1 1 1°2 1′2 9″～ 1 1 1°3 6′0 3″E ,2 1°5 0′3 6″～ 2 1°5 8′40″N) ,为北热带地区。计有维管植物 2 1 0科 75 4属 1 5 80种 (包括亚种与变型 ) ,其中种子植物有 1 72科 681属 1 44 8种。研究分析和讨论了本区主要植被类型、种子植物区系及珍稀濒危植物 ,其种子植物区系特征是 :种类组成比较丰富 ,地理成分复杂 ,联系广泛 ,以热带成分占绝对优势 ,是典型的热带北缘区系性质 ;植被类型以山地雨林为主 ;区系起源古老 ,原始类群丰富 ;特有性比较高 ,珍稀濒危植物明显。建议对一些濒危物种采取有效的保护措施。     

青海湟水流域植物区系研究

湟水流域位于青海省的东部,约处于北纬35°56′～37°38′,东经100°35′～103°05′。属于青藏高原和黄土高原的过渡地带,海拔1650～4395m,全区面积约16600km~2,属于大陆性气候和高原大陆性气候类型。本区共有野生种子植物83科、400属、1234种。分别占本区所属的青藏高原植物亚区唐古特地区总科数的92.22％、总属数的78.74％、总种数的54.00％。研究表明,湟水流域植物区系特征为:①在唐古特地区中种类相对较丰富;②温带成分占92.80％,以绝对优势确定了本区系为明显的温带性质(属于以北温带成分,特别是欧亚大陆温、寒地带典型成分为优势的,兼具温性、寒温和高寒类型的温带区系性质,或可称为在温带区系中的过渡区系所具有的“复合型”区系特征);③木本类型少,大多数种类为多年生草本植物,缺乏古老和原始类群,一些中国特有种衍生于其广布的亲缘种中,表明本区系具有年轻和衍生的性质;④我国西南高山区系和华北区系对该区系具有双重影响;⑤为青藏高原植物亚区唐古特植物地区同华北植物地区相互过渡的代表区系之一;⑥特有属和特有种少。在中国种子植物区系分区中,本区属于青藏高原植物亚区中的唐古特地区。