光强对两种入侵植物生物量分配、叶片形态和相对生长速率的影响

 比较研究了不同光强下生长的（透光率分别为12.5%、36%、50%、100%）两种入侵性不同的外来种——紫茎泽兰（Eupatorium adenophorum）和兰花菊三七（Gynura sp.）的生物量分配、叶片形态和生长特性。结果表明: 1）两种植物叶片形态对光环境的反应相似。弱光下比叶面积（SLA）、平均单叶面积（MLS）和叶面积比（LAR）较大,随着光强的升高,SLA、MLS、LAR和叶根比（LARMR）降低。2）100%光强下紫茎泽兰叶生物量比（LMR）、叶重分数（LMF）和叶面积指数高于低光强下的值,也高于兰花菊三七,支持结构生物量比（SBR）则相反。强光下紫茎泽兰叶片自遮荫严重,这可能是其表现入侵性的重要原因之一;兰花菊三七分枝较多,避免了叶片自遮荫,较多的分枝利于种子形成对其入侵有利。3）随生长环境光强的升高,两种植物的净同化速率（NAR）、相对生长速率（RGR）和生长对NAR的响应系数均升高（但100%光强下兰花菊三七RGR降低）,平均叶面积比（LARm）和生长对LARm的响应系数均降低,但不同光强下LARm对生长的影响始终大于NAR。4）随着光强的减弱,两种植物都增加高度以截获更多光能,但它们的生物量分配策略不同,紫茎泽兰根生物量比（RMR）降低,SBR增大,而兰花菊三七SBR降低,RMR增大。紫茎泽兰的生物量分配策略更好的反应了弱光环境中的资源变化情况。结论：紫茎泽兰对光环境的适应能力强于兰花菊三七。     

异质性光照生境下克隆整合对外来入侵植物薇甘菊生长的影响

薇甘菊(Mikania micrantha)原产中、南美洲,1919年薇甘菊作为杂草在中国香港出现,目前已广泛侵入中国广东、海南、云南等省区,是世界上最有害的100种外来入侵物种之一。本文以海南重要外来入侵植物薇甘菊(Mikania micrantha)为实验材料,通过温室盆栽实验,研究了克隆整合对异质性光照生境下薇甘菊克隆片段生长的影响。结果表明:在异质性光照下,克隆整合显著提高了低光斑块分株的生物量,但同时降低了高光斑块分株的生物量,对克隆片段总体的生物量积累无显著影响,且这一结果不受资源输送方向的影响;克隆整合降低了异质性光照下克隆分株间根冠比的差异,加大了克隆分株间净光合速率的差异,且倾向于提高生长在高光斑块分株的比叶面积;克隆整合虽然并不能促进薇甘菊匍匐茎克隆片段在异质性光照生境下总体的生长,但可以促进低光斑块下分株的生长,因而,克隆整合可促进薇甘菊从开阔生境向低光生境(森林、杂草群落等)的入侵能力,因此,克隆整合特性是薇甘菊对异质性光照环境的重要适应对策之一。     

外来入侵植物薇甘菊(Mikania micrantha)对温度升高的响应

为探讨全球变化温度升高对外来入侵植物薇甘菊(Mikania micrantha)化感作用和入侵能力的影响,研究不同温度(22、26和30℃)处理对其种子萌发、幼苗生长、生物量分配、挥发物成分和化感作用的影响。结果表明,薇甘菊种子在温度为22、26和30℃时的萌发率分别为29.2%、52.4%和75.2%。30℃条件下薇甘菊种子萌发率最高,萌发速度快。温度升高显著增加薇甘菊茎的生长、增加对茎的生物量分配。GC-MS和GC测定显示,温度升高改变了薇甘菊挥发物的化学成分。同时,生物测定表明,温度升高增强薇甘菊挥发物对萝卜(Raphanus sativus)和油菜(Brassica campestris)的化感作用。说明温度升高促进了薇甘菊种子的萌发和生长,同时增强了该植物的化感作用,温度升高可能加速薇甘菊的生物入侵。     

红薯对薇甘菊的竞争效应

在外来入侵生物的生态管理中,利用具有较高经济价值的本地植物或伴生的本地物种进行替代控制是治理入侵植物的有效途径之一。本研究以本地作物红薯(Ipamoea batas)和入侵植物薇甘菊(Mikania micrantha)为试验对象,田间试验条件下采用deWit取代法,研究了红薯对薇甘菊的竞争效应。结果表明:薇甘菊单种时,主茎长、分枝长、节间长和分枝数大于红薯,而主茎节数、不定根节数、叶柄长、叶面积均明显小于红薯,使薇甘菊在与红薯争夺养分和光照时处于劣势;在薇甘菊与红薯共存条件下,各个混种比例中薇甘菊的株高、分枝、叶、茎节不定根和生物量等均受到显著抑制,且受到的抑制率普遍高于其对红薯的抑制率;薇甘菊和红薯的相对产量(RY)、相对产量总和(RYT)均显著小于1.0,说明2物种的种间竞争大于种内竞争;红薯对薇甘菊的竞争平衡指数,只有在薇甘菊所占比例高时(1:3)竞争平衡指数显著小于0,其余各个混种比例下竞争平衡指数均显著大于0,说明红薯与薇甘菊之间存在很强的竞争作用,红薯对薇甘菊的竞争力强于薇甘菊。本研究表明,无论是从形态特征还是生物量来看,红薯都可以作为一种对薇甘菊进行替代控制的理想竞争植物。     

薇甘菊和飞机草抗氧化物和膜脂过氧化物对光照和土壤水分的响应

田间温室控制条件下研究入侵杂草薇甘菊(Mikania micrantha)和飞机草(Chromolaena odoratum)在不同光照(高、中、低光照)和土壤水分(高、中、低水分含量)交互作用下, 叶片超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性, 脯氨酸(Pro)、谷胱甘肽(GSH)以及膜脂过氧化物丙二醛(MDA)含量的变化, 探讨两种杂草对不同光照和土壤水分交互作用的生理适应性。结果表明: 高光下低水处理的两种杂草MDA含量均显著高于全水处理, 表现出明显的胁迫。此胁迫条件下薇甘菊通过迅速提高SOD和CAT活性, 提高Pro和GSH含量来清除活性氧, 维持代谢平衡, 但不能在干旱条件下维持较长时间; 飞机草的SOD活性、Pro和GSH含量也迅速提高, 在高光缺水的适应性响应中起了重要作用, CAT则未能发挥保护作用。相对于其他光照, 低光显著降低了薇甘菊的SOD、CAT活性和MDA含量, 而对飞机草上述指标的影响较小, 说明低光降低了两种杂草尤其是薇甘菊的抗氧化物代谢水平。     

模拟酸雨对3种菊科入侵植物光合特性的影响

研究了模拟酸雨(pH值分别为2.5、4.5和5.6)对3种菊科入侵植物--三裂叶蟛蜞菊(Wedelia trilobata)、薇甘菊(Mikania micrantha)和飞机草(Chromolaena odoratum)光合生理生态特性的影响。结果表明, 重度酸雨(pH值2.5)对3种入侵植物叶片均造成可见伤害, 其中飞机草受害最严重, 薇甘菊次之, 三裂叶蟛蜞菊受害最轻。同时, 3种入侵植物对酸雨胁迫表现出不同的光合响应, 随着酸雨pH值的降低, 飞机草和薇甘菊叶片叶绿素含量均有所下降, 其净光合速率(P_n)受到抑制, 而三裂叶蟛蜞菊叶片叶绿素含量变化不大, 其P_n值呈上升趋势。酸雨处理下, 3种入侵植物的细胞膜透性、丙二醛含量(MDA)及超氧化物歧化酶(SOD)和过氧化物酶(POD)活性均有不同程度的增加, 表明它们受到酸雨的胁迫并具有一定的抵抗力。其中, 经pH值2.5酸雨处理后的三裂叶蟛蜞菊叶片SOD活性增幅最大, 其对酸雨胁迫的反应最为迅速。上述研究结果表明, 三裂叶蟛蜞菊对酸雨胁迫的耐受性和适应性均高于飞机草和薇甘菊。在酸雨污染日趋严重的今天, 应对其危害予以高度重视。     

薇甘菊叶片对光反射、透射和利用效率及其与同群落植物之比较研究

该文对薇甘菊及其所在群落内19种植物(草本和木本)的叶片透射率、反射率和光合特征指标进行了测定, 结果表明:薇甘菊与其它植物透射和反射图谱的变化趋势都比较相近, 在各个光学特征指标与光合相关指标的相互关系中, 薇甘菊并没有表现出区别于同一群落内其它植物的特征。从平均值来看, 200-800 nm下叶片反射率和透射率由大到小依次为: 薇甘菊>草本植物>木本植物, 薇甘菊各光学植被指标(SR680、SR750和PRI)均低于其它植物的平均值, 但是其光合能力(光利用效率、水分利用效率、电子传递速率和净光合速率)与其它植物接近或稍高。而且, 薇甘菊夏季叶片反射和透射率明显高于冬季, 这有利于散失夏季过多光照和充分利用冬季短缺光照。薇甘菊叶片的上述光学特征, 可能是其生长于其它植物表面强光照环境的一种适应性表现, 有利于其在入侵地快速生长。     

薇甘菊叶片对光反射、透射和利用效率及其与同群落植物之比较研究

该文对薇甘菊及其所在群落内19种植物（草本和木本）的叶片透射率、反射率和光合特征指标进行了测定,结果表明：薇甘菊与其它植物透射和反射图谱的变化趋势都比较相近,在各个光学特征指标与光合相关指标的相互关系中,薇甘菊并没有表现出区别于同一群落内其它植物的特征。从平均值来看,200—800nm下叶片反射率和透射率由大到小依次为：薇甘菊〉草本植物〉木本植物,薇甘菊各光学植被指标（SR680、SR750和PRO均低于其它植物的平均值,但是其光合能力（光利用效率、水分利用效率、电子传递速率和净光合速率）与其它植物接近或稍高。而且,薇甘菊夏季叶片反射和透射率明显高于冬季,这有利于散失夏季过多光照和充分利用冬季短缺光照。薇甘菊叶片的上述光学特征,可能是其生长于其它植物表面强光照环境的一种适应性表现,有利于其在入侵地快速生长。     

光照强度与埋深对外来植物曼陀罗幼苗生长的影响

光照强度与埋深是诸多环境因素中影响外来植物幼苗出土与生长的主要因素。为了探查外来植物幼苗对光照强度与埋深的生长响应, 以曼陀罗(Datura stramonium L.)为实验材料, 分别研究两种光照强度 (100%光照和35%光照)和五种种子埋深 (1、3、5、7和9 cm)处理对曼陀罗幼苗生长特征的影响。结果表明: (1)100%光照强度处理下曼陀罗幼苗的叶片总生物量、根冠比(R/S)、相对生长速率(RGR)和总生物量显著高于35%光照强度处理。相反, 幼苗的总叶面积、比叶面积(SLA)和叶面积比(LAR)和叶片生物量比(LMR) 显著低于35%光照强度处理。(2)曼陀罗幼苗的出土率、首苗出土所需时间、株高、根长、总生物量及相对生长速率(RGR)等指标均在埋深3 cm处理获得最大值, 埋深大于或低于3 cm均导致上述指标下降, 埋深7 cm处理呈现最小值; 埋深对幼苗根冠比(R/S)无显著影响, 但显著增加地下下胚轴长度。这表明曼陀罗幼苗更偏好入侵光照强度较高和较低埋深(≤3 cm)的环境, 遮阴或过深的埋深不利于曼陀罗幼苗出土和生长。因此, 提出曼陀罗入侵农田的防控建议为: 1)在曼陀罗种子结实前进行铲除, 从源头控制曼陀罗蔓延; 2)早春作物播种前进行深耕, 将土壤里的曼陀罗种子翻耕到深层土壤中。     

外来入侵植物飞机草和本地植物异叶泽兰对大气CO_2浓度升高的响应

大气CO2浓度升高影响外来植物入侵,研究外来入侵植物和本地植物对大气CO2浓度升高响应的差异,有助于准确预测和管理外来植物入侵。基于封顶式CO2生长室,模拟大气CO2浓度变化(对照和700μmol/mol),比较研究了外来入侵植物飞机草(Chromolaena odorata)和本地植物异叶泽兰(Eupatorium heterophyllum)形态、生长、生物量分配和光合特性对大气CO2浓度升高响应的差异。结果表明:(1)在当前大气CO2浓度下,飞机草总生物量、株高、基径和总叶面积高于异叶泽兰,分枝数低于异叶泽兰;CO2浓度升高,飞机的总生物量、株高、基径、分枝数和总叶面积分别增加了92%、41%、60%、325%和148%,高于异叶泽兰的32%、14%、30%、64%和79%,飞机草生长优势进一步提高。(2)无论在高或低CO2浓度下,飞机草根生物量分数(RMF)都低于异叶泽兰,叶生物量分数(LMF)和茎生物量分数(SMF)都高于异叶泽兰;CO2倍增两种植物RMF均降低,LMF和SMF均升高,但这2个参数对CO2倍增响应的种间差异不显著。(3)无论在高或低CO2浓度下,飞机草和异叶泽兰的净光合速率差异均不显著,CO2倍增对两种植物的净光合速率的促进作用相似。上述结果表明,在未来大气CO2浓度升高的条件下,飞机草的入侵性可能提高,入侵危害将加剧。     

Changes in Soil Microbial Community Associated with Invasion of the Exotic Weed, Mikania micrantha H.B.K

Invasions of exotic plant species are among the most pervasive and important threats to natural ecosystems. However, the effects of plant invasions on soil processes and soil biota have not been adequately investigated. Changes were studied in soil microbial communities where Mikania micrantha was invading a native forest community in Neilingding Island, Shenzhen, China. The soil microbial community structure (assessed by phospholipid fatty acid [PLFA] profiles) and function (assessed by enzyme activities), as well as soil chemical properties were measured. The results showed that the invasion of M. micrantha into the evergreen broadleaved forests in South China changed most of the characteristics in studied soils. Microbial community structure and function differed significantly among the native, two ecotones, and exotic-derived soils. For PLFA profiles, we observed a significant increase in aerobic bacteria but a decrease in anaerobic bacteria in the M. micrantha monoculture as compared to the native and ecotones. The ratio of cy19:0 to18:1ω7 gradually declined but mono/sat PLFAs increased as M. micrantha became more dominant. Both ratios were significantly related to pH according to regression analysis, therefore, pH was a sensitive indicator reflecting the invaded soil subsystem succession. The microbial community composition clearly separated the native soil from the invaded soils by principal component analysis (PCA) and discriminant analysis (DA). For enzyme activities, 7 of 9 enzymes (β-glucosidase, invertase, protease, urease, acid phosphatase, alkaline phosphatase, and phenol oxidase) showed the similar trend that the activities were highest in the exotic, intermediate in the two ecotones, and lowest in the native community. In most cases, enzyme activities were influenced by soil chemical properties, especially by pH value and soil organic matter. Differences in the structural variables were well correlated to differences in the functional variables as demonstrated by canonical correlation analysis (CCA). It was concluded that M. micrantha invasion had profound effects on the soil subsystem, which must be taken into account when we try to control its invasions.     

紫茎泽兰和飞机草的形态、生物量分配和光合特性对氮营养的响应

比较研究了紫茎泽兰(Ageratina adenophora)和飞机草(Chromolaena odorata)的形态、生物量分配、生长和光合特性对氮营养的可塑性反应,探讨其与入侵性的关系。结果表明:1) 两种入侵植物对氮营养变化表现出很高的可塑性。随供氮量的增加,两种植物的根冠比、根生物量比降低,叶生物量比(LMR)、叶面积比和叶根比升高。低氮时,增加吸收器官的生物量分配,有利于养分吸收;高氮时,更多的生物量投入同化器官,有利于碳积累。相比之下紫茎泽兰对氮素的适应性更强。2) 两种入侵植物偏好较高的氮营养环境,土壤氮含量升高利于紫茎泽兰和飞机草的入侵。在较大的氮范围内,其相对生长速率(RGR)、总生物量、株高、分枝数、叶面积指数、最大净光合速率和光合色素含量都随供氮量的增加而显著增加,过量氮素对上述参数的抑制不显著。在本地种基本停止生长的干季,紫茎泽兰和飞机草仍维持较高的RGR,这与它们的入侵性密切相关。3) 在决定RGR对氮营养的响应过程中,平均叶面积比和净同化速率同等重要。LMR对两种植物的RGR有重要的影响,是决定处理间和种间RGR差异的重要因素。随氮素的增加,紫茎泽兰的比叶面积(SLA)降低,飞机草的SLA升高,但在所有氮水平下,前者的SLA都高于后者,紫茎泽兰SLA的变化规律更利于植物适应氮环境。     

Growth and gas exchange responses of Brazilian pepper (Schinus terebinthifolius) and native South Florida species to salinity

Schinus terebinthifolius Raddi (Schinus) is an invasive exotic species widely found in disturbed and native communities of Florida. This species has been shown to displace native species as well as alter community structure and function. The purpose of this study was to determine if the growth and gas exchange patterns of Schinus, under differing salinity conditions, were different from native species. Two native upland glycophytic species (Rapanea punctata and Randia aculeata) and two native mangrove species (Rhizophora mangle and Laguncularia racemosa) were compared with the exotic. Overall, the exotics morphologic changes and gas exchange patterns were most similar to R. mangle. Across treatments, increasing salinity decreased relative growth rate (RGR), leaf area ratio (LAR) and specific leaf area (SLA) but did not affect root/shoot ratios (R:S). Allocation patterns were however significantly different among species. The largest proportion of Schinus biomass was allocated to stems (47%), resulting in plants that were generally taller than the other species. Schinus also had the highest SLA and largest total leaf area of all species. This meant that the exotic, which was taller and had thinner leaves, was potentially able to maintain photosynthetic area comparable to native species. Schinus response patterns show that this exotic exhibits some physiological tolerance for saline conditions. Coupled with its biomass allocation patterns (more stem biomass and large area of thin leaves), the growth traits of this exotic potentially provide this species an advantage over native plants in terms of light acquisition in a brackish forested ecosystem.     

Nutrient addition does not increase the benefits of clonal integration in an invasive plant spreading from open patches into plant communities

• One benefit of clonal integration is that resource translocation between connected ramets enhances the growth of the ramets grown under stressful conditions, but whether such resource translocation reduces the performance of the ramets grown under favourable conditions has not produced consistent results. In this study, we tested the hypothesis that resource translocation to recipient ramets may reduce the performance of donor ramets when resources are limiting but not when resources are abundant.
• We grew Mikania micrantha stolon fragments (each consisting of two ramets, either connected or not connected) under spatially heterogeneous competition conditions such that the developmentally younger, distal ramets were grown in competition with a plant community and the developmentally older, proximal ramets were grown without competition. For half of the stolon fragments, slow‐release fertiliser pellets were applied to both the distal and proximal ramets.
• Under both the low and increased soil nutrient conditions, the biomass, leaf number and stolon length of the distal ramets were higher, and those of the proximal ramets were lower when the stolon internode was intact than when it was severed. For the whole clone, the biomass, leaf number and stolon length did not differ between the two connection treatments. Connection did not change the biomass of the plant communities competing with distal ramets of M. micrantha.
• Although clonal integration may promote the invasion of M. micrantha into plant communities, resource translocation to recipient ramets of M. micrantha will induce a cost to the donor ramets, even when resources are relatively abundant.

     

Inhibition of an invasive plant (<Emphasis Type="Italic">Mikania micrantha</Emphasis> H.B.K.) by soils of three different forests in lower subtropical China

Biological invasion represents one of the most serious threats to biodiversity, and invasion ecology research has become one of the central issues of contemporary environmental science. However, the relative role of soil development as correlated with succession in influencing variation in invasion resistance has seldom been examined. We hypothesized that the invasion potential of exotic plants depends on soil conditions. In this study, we explored variation among soils of three forest types in their resistance to invasion by Mikania micrantha H.B.K. in lower subtropical China; this species is one of the top ten most invasive weeds in the world. In model systems of soils from different forests, M. micrantha performed worst on undisturbed late-successional stage forest (monsoon evergreen broadleaf forest, MEBF) soils and did not appear to take advantage of abundant soil nutrients. These results could reflect that a potential inhibitory effect was driven by MEBF soil. Plant litter is an important component of soils, litter bioassay and addition experiments demonstrated native plant species from different forests differentially confer invasion resistance and affect the performance of exotic plants. Naturally, other factors such as the relative abundances of nutrients, microbial feedbacks, could have contributed to these results as well. Our results challenge the notion that forests are not immune to invasion and suggest that maintaining late-successional plant communities in lower subtropical China, which could be related to increased productivity and stability, should be a primary objective of land managers.     

Functional traits,growth patterns,and litter dynamics of invasive alien and co-occurring native shrub species of chir pine forest in the central Himalaya,India

Across the continents, plant invasion is identified as one of the main threats to ecosystem functioning and stability. The main objective of this research was to evaluate the differences in the functional traits between invasive alien (Ageratina adenophora (Spreng.) and Lantana camara L.) and native (Berberis asiatica Roxb. Ex DC., Pyracantha crenulata (D. Don.) M. Roemer and Rubus ellipticus Sm.) shrub species of chir pine (Pinus roxburghii Sarg.) forest in the central Himalaya. Three 0.5 hectare chir pine forest stands were selected and individuals of similar diameter were tagged for comparative studies of leaf traits, growth pattern, and biomass accumulation in structural organs of each invasive alien and native species. Our one-way ANOVA and Tukey’s post hoc test results showed that both the invasive alien species have significantly (p?<?0.05) higher SLA, LWC, total chlorophyll content, foliar nutrient (N and P), RGR, LMR, SMR, nutrient uptake, and nutrient use efficiencies than native species. Leaf litter decomposition rate and nutrient release were also significantly (p?<?0.05) higher in both the invasive alien species. Native species, R. ellipticus, shared some of the traits, such as leaf area, chlorophyll content, RGR, LAR, LMR, and nutrient uptake efficiency with invasive alien species. The majority of traits differed among invasive alien and native species, implying that the success of invasive alien species is best described by being functionally distinct from native species. These findings indicate that invasive alien species had advanced functional traits which may be playing an important role in a rapid spread in the central Himalaya.

     

光照强度驱动典型阴生植物三七的生理生态响应特征

为探究阴生植物三七(Panax notoginseng)对不同光照强度的生理生态响应特征,研究5种透光率(46.5% LT、21.8% LT、9.70% LT、5.10% LT、2.80% LT)下三七生理、形态和生长等各项指标的变化特征,并对其相关指标进行相关性、可塑性和主成分分析。结果表明:三七在高光(46.5% LT和21.8% LT)和低光(5.10% LT和2.80% LT)条件下各形态特征(株高、茎粗、单株叶面积)、生物量及相对生长速率(RGR)均有所降低;随着光照强度的降低,根生物量比(RMR)、最大净光合速率(P_n-max)、气孔导度(G_s)、光补偿点(LCP)和暗呼吸速率(R_d)都随之下降,而叶面积比(LAR)、比叶面积(SLA)、茎生物量比(SMR)和叶生物量比(LMR)却呈现升高的趋势。这些变化能够减少三七在高光下的光能捕获及消耗,而低光下的光能捕获和消耗则会得到加强。此外,阴生植物三七的形态特征表型可塑性指数均小于0.5,而光合生理(P_n-max、G_s、LCP、R_d)、LAR和根部生物量的表型可塑性指数则大于0.5,其可塑性较强,且P_n-max、G_s、LCP与RGR的相关系数分别高达0.581、0.558、0.574,这些结果表明光照强度驱动三七的响应特征主要为光合生理特性、LAR和根部生物量的变化。研究还发现三七在10%左右的透光率下生长发育较好。而在低光条件下,三七主要采取保守策略进行缓慢的碳获取和碳消耗,高光条件下则主要采取快速碳获取和碳消耗的冒险策略。研究阐明了三七对不同光照环境的响应策略,为三七的优质高效种植提供理论依据。     

New seed morphological features in Moehringia L. (Caryophyllaceae) and their taxonomic and ecological significance

Abstract

Relative growth rate (RGR) is a fundamental trait for comparative plant ecology but cannot be measured in situ, leading to problems in interpreting vegetation function. However, the components of RGR (net assimilation rate (NAR), leaf area ratio (LAR), leaf weight ratio (LWR), and specific leaf area (SLA)) can be calculated for wild plants from morphological measurements (leaf area, leaf dry mass, whole plant dry mass), which potentially reflect RGR. Seeds of 19 species from Italian prealpine calcareous grasslands were collected and seedlings were cultivated under controlled conditions. RGR, NAR, LAR, LWR and SLA were analysed. The results demonstrated that RGR was positively correlated with SLA and LAR (p < 0.01). Furthermore, LAR was positively correlated with LWR and negatively with NAR (p < 0.05). Monocotyledons showed significantly higher LAR, LWR and NAR than dicotyledons, as the latter allocated a greater proportion of biomass to stems, but RGR and SLA showed no such phylogenetic constraint. Therefore SLA is the most reliable indicator of RGR in ecological and functional surveys of prealpine calcareous grasslands, and has the additional advantage that it can be measured from leaf material alone. Lower mean RGR and SLA for calcareous grassland species suggests that this vegetation is less likely to recover from the effects of disturbance than meadows and dry meadows.     

Phenotypic plasticity of lianas in response to altered light environment

The growth, morphology and biomass allocation of 11 liana species (six light-demanding and five shade-tolerant) were investigated by growing plants in three contrasting light environments (i.e., field, forest edge and forest interior). Our objectives were to determine: (1) changes in plant traits at the species level; and (2) differences in light-demanding and shade-tolerant species in response to altered light environment. We found that all seedlings of liana species increased in total biomass, total leaf area, relative growth rate (RGR), net assimilation rate (NAR), height, basal diameter, root length, leaf number, root mass/total plant mass (RMR) and root-to-shoot dry biomass (R/S ratio), and decreased in leaf area ratio (LAR), specific leaf area (SLA), leaf size, stem mass-to-total plant mass ratio (SMR) and leaf mass-to-total plant mass ratio (LMR) with increasing light availability. Under the three light environments, the two types of species differed significantly in total biomass, total leaf area, RGR, NAR, LAR, SLA and leaf number, and not in leaf area. Only light-demanding species differed significantly in height, root length, basal diameter, RMR, SMR, LMR and R/S ratio. The mean plasticity index of growth and biomass allocation were relatively higher than the morphological variables, with significant differences between the two groups. Our results showed that liana species respond differently to changing light environments and that light-demanding species exhibit higher plasticity. Such differences may affect the relative success of liana species in forest dynamics.     

Plasticity in seedling morphology,biomass allocation and physiology among ten temperate tree species in response to shade is related to shade tolerance and not leaf habit

• Mechanisms of shade tolerance in tree seedlings, and thus growth in shade, may differ by leaf habit and vary with ontogeny following seed germination. To examine early responses of seedlings to shade in relation to morphological, physiological and biomass allocation traits, we compared seedlings of 10 temperate species, varying in their leaf habit (broadleaved versus needle‐leaved) and observed tolerance to shade, when growing in two contrasting light treatments – open (about 20% of full sunlight) and shade (about 5% of full sunlight).
• We analyzed biomass allocation and its response to shade using allometric relationships. We also measured leaf gas exchange rates and leaf N in the two light treatments.
• Compared to the open treatment, shading significantly increased traits typically associated with high relative growth rate (RGR) – leaf area ratio (LAR), specific leaf area (SLA), and allocation of biomass into leaves, and reduced seedling mass and allocation to roots, and net assimilation rate (NAR). Interestingly, RGR was not affected by light treatment, likely because of morphological and physiological adjustments in shaded plants that offset reductions of in situ net assimilation of carbon in shade. Leaf area‐based rates of light‐saturated leaf gas exchange differed among species groups, but not between light treatments, as leaf N concentration increased in concert with increased SLA in shade.
• We found little evidence to support the hypothesis of a increased plasticity of broadleaved species compared to needle‐leaved conifers in response to shade. However, an expectation of higher plasticity in shade‐intolerant species than in shade‐tolerant ones, and in leaf and plant morphology than in biomass allocation was supported across species of contrasting leaf habit.