Relative contribution of edge and interior zones to patch size effect on species richness: An example for woody plants

In order to understand the capacity of habitats to conserve species, many authors have searched for a species–area relationship (SAR) to evaluate the effect of patch size on species richness in habitat fragments. However, a range of different processes may underlie or obscure this relationship. For woody plant species in forest fragments, as for other taxa, considering forest edges separately in the investigation of SAR is particularly relevant. The objective of our study was to evaluate edge influence on SAR in a fragmented forest landscape in south-western France. To achieve this objective, we considered SAR in two separate spatial portions of the forest fragment: the edge and the forest interior. We also considered SAR for different ecological groups of species based on their shade tolerance and their mode of dispersal, as species can respond differently to habitat reduction depending on their ecological characteristics. In 40 woodlands in an agricultural landscape, we observed the presence/absence of all woody species along parallel walking transects 20-m wide to inventory the total number of species in each woodlot. Vegetation surveys resulted in the identification of 53 woody species, with a total of 23 trees and 30 shrubs, and a number of species per woodlot ranging from 18 to 44. The species richness found in a given woodlot was significantly correlated with its area. When considering the edge and the interior parts of the woodlot separately we found a steeper increase in species richness with area for the part we considered as the edge, compared with the increase found in the interior part of the forest. Our results confirm the contribution of forest edge to forest fragment SAR. Results also underlined the importance of two additional processes that may contribute to SAR: a possible extinction debt of shade-tolerant species in forest edge zones and colonisation by light-demanding species in forest interior zones probably due to disturbances. This approach underlines the importance of taking the edge effect into account when studying the influence of patch size on species richness and the dynamic of species richness pattern.     

浦绿对高尔夫球道结缕草草坪耐荫性的影响

浦绿是一种环己酸类植物生长调节剂,不仅可以通过抑制赤霉素的生物合成而延缓植物的生长,还可提高植物的抗逆性。为探讨浦绿对高尔夫球道结缕草（Zosia japonica）草坪耐荫性的影响,本试验以湖南龙湖高尔夫俱乐部球场5号洞球道的‘兰引3号’结缕草（Z.japonica ‘Lanyin No.3’）草坪为试验材料,研究了浦绿（0.1 mL·m^-2）对人工摸拟不同遮荫率条件下（全光照：自然光;轻度：遮荫率25%±3%;中度：遮荫率50%±3%;重度：遮荫率75%±3%）球道草坪冠层高度、叶长和茎粗以及草坪盖度、草坪质量、绿色指数、可溶性蛋白、脯氨酸、可溶性糖和赤霉素含量等指标的影响。试验结果表明,随着遮荫率的提高,未喷施浦绿的‘兰引3号’结缕草草坪的盖度、茎粗、草坪质量、绿色指数、可溶性蛋白和可溶性糖含量呈下降趋势,而草坪冠层高度、叶长、脯氨酸含量和赤霉素含量则呈升高趋势;喷施浦绿显著（P<0.05）降低了不同遮荫率下的冠层高度、叶长和赤霉素含量,显著（P<0.05）提高了可溶性蛋白和可溶性糖含量以及草坪绿色指数。因此,本试验得出浦绿可有效增强草坪的耐荫性,提高高尔夫球道的草坪质量。     

Relative growth and photosynthetic response of water-seeded rice and Echinochloa oryzoides (Ard.) Fritsch to shade

Echinochloa oryzoides is a serious weed of rice worldwide and one of the most important weeds of water-seeded rice in California, USA, where resistance to most available herbicides has been detected. Developing new integrated weed management strategies that include rice suppression of E. oryzoides growth requires understanding their relative responses to resource limitation. The effects of shade on the growth, morphology and CO 2 exchange rates (CER) of E. oryzoides and rice (cv. M-202) were assessed in glasshouse and growth chamber experiments. Plants were grown at 100, 50 or 18% of full sunlight (glasshouse) or at 500 and 250 µmol PPFD m-2s-1 (growth chamber) within a completely randomized design with two factors and four replicates. Shade was imposed at 21 days after seeding (d.a.s.) (glasshouse) and at 14 d.a.s. (growth chamber). Height, leaf area, tillers, and leaf, stem, root and seed dry weights were determined for both species. CER were determined for plants in the growth chamber. Both species increased dry-matter allocation to leaves and maintained CER when subjected to low light. However, in contrast to rice, E. oryzoides maintained or increased leaf area, specific leaf area and leaf area ratio (LAR) in response to shade. E. oryzoides tiller number and seed output were reduced only at 18% sunlight. Rice lacked such adaptive ability and tiller number and seed were reduced at 50% sunlight. Shade alone may not prevent the seed production of E. oryzoides. However, E. oryzoides increased LAR at the expense of allocation to roots. Thus, for substantial E. oryzoides control, early nutrient deprivation by rice roots may be as relevant as improving rice ability to intercept light.     

不同耐阴性玉米雌穗幼穗分化对遮荫胁迫的反应差异

以易空秆和不易空秆的成对近等基因系沈农98A、沈农98B和易发生空秆的玉米杂交种D90、不易发生空秆的品种郑单958为试材,在田间种植条件下,通过人工遮荫方法进行不同强度的光照胁迫处理,研究不同耐阴性材料雌穗幼穗分化对光胁迫的反应差异。结果表明,不同耐阴性材料在遮荫胁迫下雌穗幼穗发育均受到很大影响,但不同耐阴性材料之间差异很大。易空秆的杂交种及自交系在轻度胁迫下,D90幼穗长度减少38.2%,结穗率减少17.0个百分点;沈农98A幼穗长度减少35.8%,结穗率降低78.7个百分点。与杂交种相比,自交系的反应更为敏感,在38%遮荫胁迫下,沈农98A与沈农98B的幼穗长、结穗率、穗行数、行粒数和败育率产生明显差异;郑单958与D90在60%遮荫胁迫下幼穗长和结穗率差异开始明显,其他性状在75%遮荫胁迫下才有明显区别。     

荫湿环境对玉米穗位叶面积及其叶绿素含量的影响

采用人工模拟荫湿环境,比较不同基因型玉米在荫湿环境与自然环境条件下穗位叶面积及其叶绿素含量的差异。结果表明,荫湿环境对玉米穗位叶面积、叶绿素及其组分含量具有明显影响,穗位叶面积及其叶绿素a/b值均呈下降趋势,叶绿素相对含量和叶绿素b含量呈明显上升趋势,这些性状的变化基因型间存在显著或极显著差异。用穗位叶面积及其叶绿素含量计算出18个杂交种的综合耐荫湿系数平均值为0.751 1,标准差为0.178 5,变异系数为23.76%;30个自交系的综合耐荫湿系数平均值为0.678 1,标准差为0.155 4,变异系数为22.91%。根据综合耐荫湿系数,采用t检验选出耐荫湿性强的杂交种有8个,自交系有12个;耐荫湿性中的杂交种有5个,自交系有9个;耐荫湿性弱的杂交种有5个,自交系有9个。     

玉米遮阳防治番茄病毒病的探讨

玉米遮阳防治番茄病毒病省工、省时，效果显著，1994～1995年连续2年的研究结果表明，防病效果在62．3％～85．57％，增产幅度在17．2％～41．9％。     

茶园的他感作用研究

本文研究了茶园常见遮荫树及茶树本身茶子萌发及茶幼苗生长的影响，结果表明，茶树根，茎，叶，果皮的水抽提液对茶子萌发及茶幼苗生长均有明显的抑制作用；多酚类，咖啡碱是茶树自毒作用的主要物质。参试的７个供体树种对茶树他感作用强弱的顺序为：凤凰木＞银合欢＞台湾相思＞柠檬桉＞南洋楹＞大叶相思＞大叶桉。文章讨论了防止茶树衰老的措施及合理设计茶园群落的依据。     

2 个品系木奶果幼苗叶绿素荧光参数日变化分析

为了给木奶果Baccaurea ramiflora幼苗的遮阴养护提供基础支撑,以木奶果红皮和黄皮2个品系的盆栽幼苗作为试验材料,置于室外和室内2种条件下,测定其叶绿素荧光参数的日变化,分析木奶果幼苗的光适应性。2个品系的最大光化学效率(Fv/Fm)、PS Ⅱ实际光合效率(Yield)和稳态光化学淬灭系数(qP)的日变化趋势基本一致,表现为在中午光照强度较高时数值较低,在早上和傍晚光照强度较低时数值较高;电子相对传递效率(ETR)和非光化学淬灭系数(NPQ)表现为在中午光照强度较高时数值较高,在早上和傍晚光照强度较低时数值较低。在不同条件下黄皮品系的各项参数比红皮更优,其光能利用率更高、热耗散更少和电子传递能力更强,对环境的适应能力更强。     

不同密度遮阳网覆盖对张良姜生长发育及产量的影响

为了确定平顶山地区张良姜合理的遮阳网密度，通过遮阳试验（0%遮阳、50%遮阳、70%遮阳）研究了不同密度遮阳网对张良姜在植物学性状、子姜数量、重量和主要物质含量的差异。结果表明，遮阳网处理均可提高张良姜的植物学性状、生姜仔姜性状指标和单株重，张良姜姜块的粗纤维在遮阳条件下较高，锌、镁0%遮阳下含量较高，50%遮阳处理钙含量高。综合各项指标50%遮阳网处理表现较优，可在平顶山地区推广，为指导生产提供良好的理论依据。     

单屋面温室光照环境的数值实验

建立了分析单屋面温室直射光透光率、反射率及室内阴影率的计算机数学模型,并且利用该数学模型对三折式温室举例计算了温室方位角及温室长度与直射光透光率、反射率、室内阴影率的日变化关系。