Biomass allocation patterns of Loropetalum chinense

Aims Biomass is the most fundamental quantitative character of an ecosystem. Biomass allocation patterns reflect the strategies of plants to adapt various habitat conditions and play a vital role in evolution, biodiversity conservation and global carbon cycle. Loropetalum chinense shrub is one of the most dominant shrub types in subtropical China. The objectives of this study were to quantify the allometric relationships and the biomass allocation pattern among organs, and to investigate the effects of body size, shrub regeneration origin and site factors on allometry and biomass allocation.
Methods Individual samples of L. chinense were harvested from shrublands in subtropical China and were further divided into leaves, stems and roots. The allometric relationships between different organs were modeled with standard major axis (SMA) regression and the biomass allocation to different organs was quantified. The effects of body size, shrub regeneration origin and other habitat factors on allometry and allocation were examined using Pearson’s correlation analysis and multiple linear regressions.
Important findings The isometric scaling relationships between shoot and root changed to allometric relationships with increasing basal diameter. The scaling relationships between leaf and stem and between leaf and root were isometric for smaller diameter classes, while for larger diameter classes they were allometric. These relationships were significantly different among shrub regeneration origin types. The scaling relationships between different organs were not affected by habitat factors; while the coverage of shrub layer and slope affected biomass allocation due to their influences on the allometric relationships between different organs at the initial stage of growth. The mean dry mass ratios of leaf, stem, root and the mean root to shoot ratio were 0.11, 0.55, 0.34 and 0.65, respectively. With the increase of basal diameter class, stem mass ratio (0.50-0.64) increased, while leaf mass ratio (0.12-0.08) and root mass ratio (0.38-0.28) decreased, and consequently root to shoot ratio (0.91-0.43) also decreased. In secondary shrublands, the leaf mass ratio was 0.12 and the root mass ratio was 0.33, while these values were 0.07 and 0.36 respectively in natural shrublands. The ratio of aboveground allocation was significantly correlated to shrub layer coverage (r = 0.44, p < 0.05). Leaf mass ratio was significantly correlated to slope (r = -0.36, p < 0.05) and root mass ratio was significantly correlated to mean annual temperature (r = 0.34, p < 0.05). Results showed that with the increase of body size, the scaling relationships between different organs of L. chinense changed from isometric to allometric, and more biomass was allocated to aboveground part, and concretely, to stems. Human disturbance affected biomass allocation by its influences on the allometric relationships between different organs, and by increasing biomass allocation to leaves and decreasing allocation to roots. Reduced light resource promoted the biomass allocation to aboveground part, and higher slope resulted in decreased biomass allocation to leaves, while higher mean annual temperature promoted biomass allocation to roots. The variation in annual precipitation had no significant influences on biomass allocation. The biomass allocation strategies of L. chinense partially support the optimal partitioning theory.     

小叶锦鸡儿(Caragana microphylla)灌丛对草本群落特征的影响

基于干旱、半干旱草原灌丛化现象的发展，探究灌木与草本之间的关系对深刻理解灌丛化对草原植物群落特征的影响机制具有重要意义。然而，很少有研究考虑草地类型和灌丛斑块大小对灌木和草本植物之间关系的影响。在内蒙古典型草原和荒漠草原的自由放牧草地上选择了18个小叶锦鸡儿灌丛化样地进行野外采样，并调查了不同大小灌丛和周围草地的植物群落特征。运用单因素方差分析(one-way ANOVA)和最小显著差异法(LSD)来检验不同大小灌丛斑块内外的植被群落特征(高度、密度、地上生物量、凋落物量)和植物多样性指数(Shannon-Wiener指数、Pielou指数、丰富度指数、群落Sprensen相似性系数)的差异性。结果表明：(1)与草地相比，两种草原类型的灌丛产生、捕获了更多的凋落物，灌丛的保育作用显著提高了斑块内草本植物的高度，但灌丛占用了生存空间和资源，从而降低了斑块内草本植物的密度和地上生物量。(2)灌丛对多年生草本植物的地上生物量有明显的抑制作用，但对两种草原类型的一、二年生草本植物没有显著影响(典型草原中的小灌丛除外)。(3)两种草原类型的灌丛对草本植物多样性的影响存在差异。典型草原灌丛内多样性...     

草原灌丛化对生态系统多功能性的影响

草原灌丛化现象在干旱半干旱区广泛发生,影响了生态系统的结构、过程和功能。生态系统具有同时提供多种功能的能力,即生态系统多功能性。灌丛化是否会引起草原生态系统多功能性的减少,其内在的作用机制又是什么？这些问题仍有待明晰。理解草原灌丛化对生态系统多功能性的影响,对于促进草原地区"草-畜-人"平衡和实现区域可持续发展至关重要。从响应规律、影响路径和控制因素三个方面总结评述了草原灌丛化对生态系统多功能性影响的研究进展,主要包括:(1)阐明了单一生态系统功能和多种生态系统功能对草原灌丛化的响应特征;(2)从生物路径、非生物路径以及气候变化和人类活动的影响方面探讨了灌丛化对生态系统多功能性的影响路径;(3)从灌丛化物种、灌丛化阶段和草原类型三个方面明晰了草原灌丛化对生态系统多功能性影响的控制因素。在此基础上,针对灌丛化对生态系统多功能性的影响机制,对生产-生态功能权衡的影响等方面对未来研究进行了展望,并面向可持续发展目标探讨了灌丛化生态系统的可持续管理路径。研究可为我国灌丛化草原的恢复和管理提供支撑。     

荒漠草原灌丛引入过程中土壤氮矿化的季节动态及其影响因子

选取封育草地、放牧草地、不同年限(引入柠条3、12、22年)/密度(间距2、6、40 m)的灌丛地为对象，研究荒漠草原-退化-灌丛引入过程中生长季(4—10月)土壤氮矿化的季节动态及其影响因子。结果表明：0～10 cm表层土壤水分具有明显的季节特征，0～200 cm剖面土壤水分随灌丛年限和密度增加而加剧消耗；与放牧草地和封育草地相比，灌丛对土壤碳氮磷养分的促进作用随灌丛年限和密度的增加呈现先强后弱趋势；生长季动态和草地变化对土壤氮矿化过程产生显著影响，土壤NO₃^-、微生物生物量碳和氮在生长季中期(6—8月)显著升高，其中NO₃^-占总无机氮的比值由封育草地30.5%增至灌丛地69.5%。NH₄⁺受生长季动态影响大于草地变化，其含量在生长季后期(10月)升高。在草原-退化-灌丛引入过程中，灌丛年限和密度的增加显著增大荒漠草原土壤硝化和铵化作用的生长季动态差异，而对微生物生物量碳和氮的影响不显著；土壤NH₄⁺和NO     

黔西北地区不同杜鹃灌丛群落特征和物种多样性

为探明黔西北地区不同杜鹃灌丛群落特征和物种多样性变化，本研究以5个不同的杜鹃群落为研究对象，分析了物种组成、重要值和多样性指数。结果表明，5个群落共有33种植物，属16科23属，灌木层和草本层分别有27种和6种；优势种和共优势种植物分别为小果珍珠花、小果珍珠花+露珠杜鹃、小果珍珠花+露珠杜鹃、露珠杜鹃、露珠杜鹃+黄山杜鹃。5个杜鹃灌丛群落灌木层的α多样性指数差异明显，灌木层的Margalef丰富度指数、Simpson多样性指数均表现为露珠杜鹃+黄山杜鹃灌丛群落(V)最大，小果珍珠花灌丛群落(I)最小；Shannon-Wiener多样性指数和Pielou均匀度指数均表现为小果珍珠花+露珠杜鹃灌丛群落(II)最大，小果珍珠花灌丛群落(I)最小。露珠杜鹃+黄山杜鹃灌丛群落(V)有进一步演替为亚热带常绿阔叶林的趋势。杜鹃属植物覆盖度大的临近群落的Whittaker指数、Jaccard指数和Sorenson指数值均较覆盖度小的临近群落大。     

狭叶小金梅草组织培养与快速繁殖

以狭叶小金梅草(Hypoxis angustifolia)当年花苞为材料进行离体快速繁殖体系研究。结果表明,花苞的愈伤诱导适宜培养基为MS+6-BA 0.8 mg·L^-1+NAA 0.05 mg·L^-1+TDZ 0.1 mg·L^-1;诱导芽培养基为MS+6-BA 0.5 mg·L^-1+NAA 0.02 mg·L^-1+AC(活性碳)0.2 g·L^-1;芽继代增殖培养基为MS+6-BA 1.0 mg·L^-1+NAA 0.1 mg·L^-1+花宝1号1 g·L^-1+AC 0.2 g·L^-1,30 d为一个继代周期,增殖系数达10~20倍;壮苗生根培养基为1/2MS+IBA 0.5 mg·L^-1+NAA 0.02 mg·L^-1+AC 0.5 g·L^-1。将生根苗移栽至泥土:蛭石按3:1配制旳基质中,盖膜保湿,成活率达80%。     

我国特有珍稀濒危植物银缕梅(Parrotia subaequalis)的花粉形态研究

采用光学显微镜和扫描电镜对产自安徽省大别山金缕梅科银缕梅(Parrotia subaequalis)的花粉进行了观察和研究。银缕梅花粉粒近球形或长球形,P/E(极轴/赤道轴)=1.27(1.14-1.32),赤道面观椭圆形,极面观圆三角形或三裂圆形,大小为37.3(32.0～41.0)×29.4(25.0～36.0)μm。具3沟,沟狭长,几达两极。花粉外壁厚2.0～2.4μm,外层与内层近等厚,柱状层基柱发达。外壁纹饰在光镜下为细网状,在扫描电镜下为粗网状纹饰,网脊上有刺瘤。现生银缕梅具有鲜明的生境和分布格局特点,本研究为利用地层中银缕梅化石花粉重建古环境、古气候等提供了现代孢粉学参考依据,也为研究金缕梅科的起源、演化和现代地理分布提供了科学依据。     

云南省大理地区果梅资源调查

梅是古老果树,我国有3000多年的栽培历史。果为浓酸味的核果,可加工多种食品,具有独特的保健功能。云南西部的少数民族,在远古时以梅花记年,如不说3年,而说梅开3次。梅与人民生活关系密切,用梅作调味品有悠久的历史。