Leaves of Lianas and Self-Supporting Plants Differ in Mass per Unit Area and in Nitrogen Content

Abstract: The aim of this study was to test the hypothesis that the reduction in supporting tissues in climbers compared to self-supporting plants is also true for their leaves, and that climbers generally require higher leaf nitrogen than self-supporting plants to accomplish fast growth. This hypothesis was tested using paired samples of both growth forms with assessment of leaf area index above the sampled plants (LAI_a) in a tropical rain forest in Gabon. The sampling protocol ensured that within a highly fluctuating low canopy environment, the growth conditions were identical for each pair sampled. The results confirmed the hypothesis. Lianas had significantly lower leaf mass per unit leaf area (LMA) than their supporters. Liana leaves also contained significantly more nitrogen than host tree leaves. The differences in nitrogen concentration between liana and tree leaves reversed for the most shaded sites, when nitrogen was expressed on a leaf area base (N_area). Significant regression between leaf nitrogen and LAI_a was found for the climbers on the shaded sites but not for their supporters. This indicated better acclimation of climbers to prevailing light conditions. Better nitrogen allocation at low LMA, together with lower carbon costs for building supporting tissues, makes lianas highly competitive, especially where high nitrogen availability is assured.     

Nutritional differences and leaf acclimation of climbing plants and the associated vegetation in different types of an Andean montane rainforest

Climbing plants are known to play an important role in tropical forest systems, but key features for their distribution are only partly understood. Investigation was carried out to find if climbers differ from self-supporting vegetation in their adjustment of leaf parameters over a wide variety of light regimes in different forest types along an altitudinal gradient. Relative photon flux density (PFD_rel) was assessed above 75 pairs of strictly linked climbers and supporting vegetation on seven plots between 2,020 and 2,700 m a.s.l. along a mountain range in South-Ecuador up to the Páramo vegetation. Leaf samples from both growth forms were analyzed for leaf area (LA), specific leaf mass (LMA), mass and area-based carbon and nitrogen concentration (C, C_area, N, and N_area) and concentrations of P, K, Ca, Mg, Mn and Al. Leaf size of climbers was independent of general light condition, whereas the leaf size of the self-supporting vegetation increased in shade. LMA increased as expected with altitude and irradiance for both growth forms, but climbers generally built smaller leaves with lower LMA. N, P, and K concentrations were higher in the leaves of climbers than in their supporters. Relationships of LMA and N_area to the light conditions were more pronounced within the climbers than within their supporters. Slope for the regression between climber’s N_area and LMA was twice as steep as for the supporter leaves. Al accumulators were only found within the self-supporting vegetation. The investigated traits indicate improved adjustment towards light supply within climbers compared to self-supporting vegetation. Thus climbing plants seem to have a higher potential trade off in resource-use efficiency regarding irradiance and nutrients.     

Inherent allocation patterns and potential growth rates of herbaceous climbing plants

We tested the hypothesis that herbaceous climbing plants, unlike non-climbing herbs, maximize height growth and leaf area, with minimal expenditure in support structures. The enhanced investment in leaf area was expected to result in high relative growth rates in terms of biomass increment. Four leguminous herbaceous climbers from nutrient-poor sites and four non-leguminous herbaceous climbers from nutrient-rich sites, were compared with non-climbing, self-supporting leguminous and non-leguminous herbaceous species from similar habitats. Plants were grown in hydroponic cultures in controlled environment chambers. All climbers had inherently taller shoots than self-supporting plants when compared at an equal amount of total plant dry weight, due to longer stems per unit of support biomass. In contrast to the hypothesis, the relative growth rates of all climbers were relatively low compared to the range found for self-supporting species. The biomass allocation patterns of the non-leguminous climbers were similar to those of the self-supporting species. Leguminous climbers allocated more biomass to support tissue and less biomass to leaves than non-climbers. As a result, height growth was even more emphasized in leguminous climbers than in non-leguminous climbers. Climbing legumes had high rates of net carbon gain, which partly compensated the lower relative leaf weight. We conclude that leguminous herbaceous climbers maximize height growth by a large investment in support biomass, enabling them to keep a large proportion of their leaves in the better illuminated environment at the top of the vegetation canopy.     

延河流域植物叶性状间关系及其在不同植被带的表达

以延河流域不同植被带的地带性植物群落为研究对象,对群落优势种和主要伴生种的6种叶片性状进行测定,分析这些性状及其关系随环境梯度的变化,以了解该区域植物对环境变化的适应策略.结果表明: 植物比叶面积(SLA)与叶组织密度(LTD)、叶片单位面积氮和磷含量均呈显著负相关,与单位质量叶片磷含量呈显著正相关;各性状间的尺度关系和生存对策在不同植被带不同,典型草原带和森林草原带植物LTD SLA的尺度依赖关系比森林带植物的强,而森林带植物叶片单位〖JP2〗面积N、P含量与SLA、LTD间的尺度关系较草原带更明显,植物对环境的适应策略发生了位移.在干旱贫瘠的草原带和森林草原带,植物以防御和抗胁迫策略为主,而在环境条件相对湿润、富养的森林带,植物以快速生长和资源优化配置策略为主.     

Climbing strategy in herbs does not necessarily lead to lower investments into stem biomass

Herbaceous climbers (vines) represent a growth strategy in which the stem lacks most of its supporting function. This has led to the hypothesis that herbaceous climbers are structural parasites that invest less into stems than self-supporting plants. So far, the support for this idea has been ambiguous, as woody and herbaceous plants have been discussed jointly and evidence is often based on young plants in pot experiments. We collected in wild fully grown temperate herbaceous climbers and self-supporting herbs to examine the idea. We made a phylogenetically informed comparison of biomass allocation into stems and leaves of 16 climber species and 74 self-supporting herbs. Furthermore, we compared our results with those published for woody climbers to gain insight into different biomass allocation between herbaceous and woody growth forms. We found that herbaceous climbers and self-supporting herbs do not differ in their proportion of stem biomass to leaf biomass. Herbaceous climbers reach much higher in the canopy thanks to their climbing habit and in average more than seven times longer stems, but contrary to the expectation and unlike their woody counterparts, they do not save on investment into the stem. Herbaceous climbers and self-supporting herbs represent a study system which provides insight into biomass scaling with versus without supporting function where both stems as well as leaves are seasonal.

     

Trait-based community assembly of understory palms along a soil nutrient gradient in a lower montane tropical forest

Two opposing niche processes have been shown to shape the relationship between ecological traits and species distribution patterns: habitat filtering and competitive exclusion. Habitat filtering is expected to select for similar traits among coexisting species that share similar habitat conditions, whereas competitive exclusion is expected to limit the ecological similarity of coexisting species leading to trait differentiation. Here, we explore how functional traits vary among 19 understory palm species that differ in their distribution across a gradient of soil resource availability in lower montane forest in western Panama. We found evidence that habitat filtering influences species distribution patterns and shifts community-wide and intraspecific trait values. Differences in trait values among sites were more strongly related to soil nutrient availability than to variation in light or rainfall. Soil nutrient availability explained a significant amount of variation in site mean trait values for 4 of 15 functional traits. Site mean values of leaf nitrogen and phosphorus increased 37 and 64%, respectively, leaf carbon:nitrogen decreased 38%, and specific leaf area increased 29% with increasing soil nutrient availability. For Geonoma cuneata, the only species occurring at all sites, leaf phosphorus increased 34% and nitrogen:phosphorus decreased 42% with increasing soil nutrients. In addition to among-site variation, most morphological and leaf nutrient traits differed among coexisting species within sites, suggesting these traits may be important for niche differentiation. Hence, a combination of habitat filtering due to turnover in species composition and intraspecific variation along a soil nutrient gradient and site-specific niche differentiation among co-occurring species influences understory palm community structure in this lower montane forest.     

Can Growth Form Classification Predict Litter Nutrient Dynamics and Decomposition Rates in Lowland Wet Forest?

This study investigates whether it is possible to simplify the complex influence of numerous species on leaf litter decomposition in a diverse tropical forest using functional classifications to predict litter quality, decomposition rate, and nutrient dynamics during decomposition, over a 2-yr period. Thirty-three lowland tropical forest plant species from contrasting growth forms (canopy trees, pioneer trees, lianas, palms, herbs) were studied. Twelve of 18 indices of litter quality varied significantly among growth forms, with canopy trees and palms showing lower litter quality than pioneer trees and herbs. Canopy leaves decomposed more slowly than understory leaves. Decomposition rate and mass loss trended greater ( P <0.1) in herbs and pioneer trees compared with other growth forms. There were no significant differences between monocots and dicots, and no phylogenetic signal for decomposition was observed. Significant correlations between continuous litter quality variables and decomposition rate were observed with correlation coefficients up to 0.72. Litter lignin:Mg, P concentration, and lignin:K, were the litter quality variables most related to decomposition rate. All elements showed significant negative correlations between initial litter concentration and percent remaining, but many elements showed significant correlation between percent element remaining and initial concentrations of other elements, indicating a stoichiometric balance between these elements during decomposition. The results show that although classification by growth form and canopy position are helpful for considering the ecosystem implications of changing community composition, litter quality traits provide additional predictive power for estimating the effects of species change on decomposition.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp     

The question of cotyledon homology in angiosperms

The flowering plants (Magnoliophyta) are separated into two large classes distinguished by the morphology of their embryos. The embryos of monocots (class Liliopsida) have a single terminal cotyledon, while the embryos of dicots (class Magnoliopsida) usually have two lateral cotyledons. The cotyledons of monocots and dicots also differ in form, and there are no true intermediates. In addition, the third leaf of Nymphaealean seedlings appears to be identical to the single cotyledon of monocots. From this it is concluded that the cotyledons of monocots and dicots are not homologous. In addition, dissimilarity of cotyledons and succeeding leaves in dicots, together with recent genetic studies, suggests that the two cotyledons of dicots are not homologous with the succeeding leaves of the same plant. This interpretation is consistent with the view that the Nymphaealean embryo’s third leaf is homologous to the first leaf (cotyledon) of monocots. Because dicotyledonous embryos are common among seed plants and are present in the Gnetopsids, the most likely scenario is that the dicots share a widespread seed plant symplesiomorphy and that the monocots have lost this character state. A less parsimonious hypothesis of monocotyledonous embryos as plesiomorphic for angiosperms is also discussed. Genetic analysis of early embryo development in a variety of vascular plants may be the only way to conclusively determine the evolutionary origin of the distinctive difference between monocot and dicot embryos.     

Monocot leaves are eaten less than dicot leaves in tropical lowland rain forests: correlations with toughness and leaf presentation

Background and Aims

In tropical lowland rain forest (TLRF) the leaves of most monocots differ from those of most dicots in two ways that may reduce attack by herbivores. Firstly, they are tougher. Secondly, the immature leaves are tightly folded or rolled until 50–100 % of their final length. It was hypothesized that (a) losses of leaf area to herbivorous invertebrates are generally greatest during leaf expansion and smaller for monocots than for dicots, and (b) where losses after expansion are appreciable any difference between monocots and dicots then is smaller than that found during expansion.

Methods

At six sites on four continents, estimates were made of lamina area loss from the four most recently mature leaves of focal monocots and of the nearest dicot shoot. Measurements of leaf mass per unit area, and the concentrations of water and nitrogen were made for many of the species. In Panama, the losses from monocots (palms) and dicots were also measured after placing fully expanded palm leaflets and whole dicot leaves on trails of leaf-cutter ants.

Key Results

At five of six sites monocots experienced significantly smaller leaf area loss than dicots. The results were not explicable in terms of leaf mass per unit area, or concentrations of water or nitrogen. At only one site was the increase in loss from first to fourth mature leaf significant (also large and the same in monocots and dicots), but the losses sustained during expansion were much smaller in the monocots. In the leaf-cutter ant experiment, losses were much smaller for palms than for dicots.

Conclusions

The relationship between toughness and herbivory is complex; despite the negative findings of some recent authors for dicots we hypothesize that either greater toughness or late folding can protect monocot leaves against herbivorous insects in tropical lowland rain forest, and that the relative importance varies widely with species. The difficulties of establishing unequivocally the roles of leaf toughness and leaf folding or rolling in a given case are discussed.Key words: anti-herbivore defences, dicots, herbivory, leaf folding, leaf rolling, leaf toughness, monocots, palms, tropical rain forest     

Phosphorus responses of C3 and C4 species

An hypothesis was formulated that phosphorus (P) partitioningin tissues of C₄ leaves would permit C₄ plants to resist P deficiencybetter than C₃ plants. To test this hypothesis, 12 C₃, C₄, andC₃–C₄ intermediate species were grown at adequate, deficient,and severely deficient P supply in a solid-phase-buffered sandculture system to characterize photosynthetic and growth responses.Species differed considerably in response to P stress. The growthof C₃ species was more sensitive to P supply than C₄ species,but C₃ and C₄ species had similar photosynthetic P use efficiency,and C₄ species did not have low leaf P content, contrary toour hypothesis. In fact, leaf photosynthetic rates were notcorrelated with growth responses. Moncots had lower leaf P contentand better maintenance of leaf production under P stress thandicots, because of greater inhibition of branching (dicots)than of tillering (monocots). The most P efficient species inthis survey was Brachiaria, a C₄ monocot that increased rootbiomass allocation under stress while maintaining P allocationto the shoot. It is concluded that C₄ species are not inherentlymore P efficient than C₃ species, but that monocots are moreP efficient than dicots, because of contrasting P and biomassallocation under stress. Key words: Phosphorus deficiency, C₃ plants, C₄ plants, growth response     

Rapid nutrient cycling in leaf litter from invasive plants in Hawai’i

Physiological traits that contribute to the establishment and spread of invasive plant species could also have impacts on ecosystem processes. The traits prevalent in many invasive plants, such as high specific leaf areas, rapid growth rates, and elevated leaf nutrient concentrations, improve litter quality and should increase rates of decomposition and nutrient cycling. To test for these ecosystem impacts, we measured initial leaf litter properties, decomposition rates, and nutrient dynamics in 11 understory plants from the Hawaiian islands in control and nitrogen + phosphorus fertilized plots. These included five common native species, four of which were ferns, and six aggressive invasive species, including five angiosperms and one fern. We found a 50-fold variation in leaf litter decay rates, with natives decaying at rates of 0.2–2.3 year^–1 and invaders at 1.4–9.3 year^–1. This difference was driven by very low decomposition rates in native fern litter. Fertilization significantly increased the decay rates of leaf litter from two native and two invasive species. Most invasive litter types lost nitrogen and phosphorus more rapidly and in larger quantities than comparable native litter types. All litter types except three native ferns lost nitrogen after 100 days of decomposition, and all litter types except the most recalcitrant native ferns lost >50% of initial phosphorus by the end of the experiment (204–735 days). If invasive understory plants displace native species, nutrient cycling rates could increase dramatically due to rapid decomposition and nutrient release from invasive litter. Such changes are likely to cause a positive feedback to invasion in Hawaii because many invasive plants thrive on nutrient-rich soils.     

Herbivory in canopy gaps created by a typhoon varies by understory plant leaf phenology

1. Availabilities of light and soil nitrogen for understory plants vary by extent of canopy gap formation through typhoon disturbance. We predicted that variation in resource availability and herbivore abundance in canopy gaps would affect herbivory through variation in leaf traits among plant species. We studied six understory species that expand their leaves before or after canopy closure in deciduous forests. We measured the availabilities of light, soil nitrogen, soil water content, and herbivore abundance in 20 canopy gaps (28.3–607.6 m²) formed by a typhoon and in four undisturbed stands. We also measured leaf traits and herbivory on understory plants. 2. The availabilities of light and soil nitrogen increased with increasing gap size. However, soil water content did not. The abundance of herbivorous insects (such as Lepidoptera and Orthoptera) increased with increasing gap size. 3. Concentrations of condensed tannins, total phenolics, and nitrogen in leaves and the leaf mass per area increased in late leaf expansion species with increasing gap size, whereas none of the leaf traits varied by gap size in early leaf expansion species. 4. Herbivory increased on early leaf expansion species with increasing gap size, but decreased on late leaf expansion species. In these late leaf expansion species, total phenolics and C : N ratio had negative relationships with herbivory. 5. These results suggested that after typhoon disturbance, increased herbivory on early leaf expansion species can be explained by increased herbivore abundance, whereas decreased herbivory on late leaf expansion species can be explained by variation in leaf traits.     

Climbing plants in a temperate rainforest understorey: searching for high light or coping with deep shade?

Background and Aims

While the climbing habit allows vines to reach well-lit canopy areas with a minimum investment in support biomass, many of them have to survive under the dim understorey light during certain stages of their life cycle. But, if the growth/survival trade-off widely reported for trees hold for climbing plants, they cannot maximize both light-interception efficiency and shade avoidance (i.e. escaping from the understorey). The seven most important woody climbers occurring in a Chilean temperate evergreen rainforest were studied with the hypothesis that light-capture efficiency of climbers would be positively associated with their abundance in the understorey.

Methods

Species abundance in the understorey was quantified from their relative frequency and density in field plots, the light environment was quantified by hemispherical photography, the photosynthetic response to light was measured with portable gas-exchange analyser, and the whole shoot light-interception efficiency and carbon gain was estimated with the 3-D computer model Y-plant.

Key Results

Species differed in specific leaf area, leaf mass fraction, above ground leaf area ratio, light-interception efficiency and potential carbon gain. Abundance of species in the understorey was related to whole shoot features but not to leaf level features such as specific leaf area. Potential carbon gain was inversely related to light-interception efficiency. Mutual shading among leaves within a shoot was very low (<20 %).

Conclusions

The abundance of climbing plants in this southern rainforest understorey was directly related to their capacity to intercept light efficiently but not to their potential carbon gain. The most abundant climbers in this ecosystem match well with a shade-tolerance syndrome in contrast to the pioneer-like nature of climbers observed in tropical studies. The climbers studied seem to sacrifice high-light searching for coping with the dim understorey light.     

模拟氮沉降对北京东灵山辽东栎群落林下植物物种多样性的影响

氮沉降是驱动生物多样性变化的重要因素之一。一般认为氮沉降会改变物种多样性, 而且在外源氮添加条件下, 禾草类植物和落叶灌木比杂类草和常绿灌木更具竞争优势。不过该结论更多是从高寒草甸和荒漠草原等生态系统中得到, 主要是针对同一生活型内植物之间的竞争关系, 不涉及不同生活型植物之间的相互作用, 并且由于草原和草甸等生态系统没有明显的垂直结构, 同一层次中植物的高度差异较小, 有可能高估了光照因素对植物的作用。因此从森林生态系统入手, 可以进一步阐述不同生活型植物对氮沉降的响应。本文以我国北方典型的落叶阔叶林——辽东栎(Quercus wutaishanica)林为研究对象, 设置CK (0 kg N·ha ^-1·yr ^-1)、N50 (50 kg N·ha ^-1·yr ^-1)和N100 (100 kg N·ha ^-1·yr ^-1) 3个梯度氮添加实验, 模拟氮沉降对温带森林生物多样性的影响。8年连续的氮添加实验结果显示: (1)氮添加显著降低了林下植物的物种丰富度和多样性, 改变了群落的物种组成; (2)氮添加提高了灌木植物的物种丰富度和多样性; 降低了草本植物的丰富度; (3)氮添加降低了禾草类植物的重要值, 提高了杂类草的重要值。该研究表明, 长期氮添加会显著改变林下植物的物种组成, 不同生活型植物对氮添加的响应亦有所差别。造成该现象的原因可能是由土壤环境变化(如养分含量提高, pH值下降)和植物获取光照能力强弱(如灌木植物获取光资源要多于草本植物)导致。     

Small tropical forest trees have a greater capacity to adjust carbon metabolism to long-term drought than large canopy trees

The response of small understory trees to long-term drought is vital in determining the future composition, carbon stocks and dynamics of tropical forests. Long-term drought is, however, also likely to expose understory trees to increased light availability driven by drought-induced mortality. Relatively little is known about the potential for understory trees to adjust their physiology to both decreasing water and increasing light availability. We analysed data on maximum photosynthetic capacity (J_max, V_cmax), leaf respiration (R_leaf), leaf mass per area (LMA), leaf thickness and leaf nitrogen and phosphorus concentrations from 66 small trees across 12 common genera at the world's longest running tropical rainfall exclusion experiment and compared responses to those from 61 surviving canopy trees. Small trees increased J_max, V_cmax, R_leaf and LMA (71, 29, 32, 15% respectively) in response to the drought treatment, but leaf thickness and leaf nutrient concentrations did not change. Small trees were significantly more responsive than large canopy trees to the drought treatment, suggesting greater phenotypic plasticity and resilience to prolonged drought, although differences among taxa were observed. Our results highlight that small tropical trees have greater capacity to respond to ecosystem level changes and have the potential to regenerate resilient forests following future droughts.     

Matter-economical roles of evergreen leaves inAucuba japonica,an understory shrub in the warm-temperate region of Japan

Seasonal dynamics in nitrogen and phosphorus content were examined for each component organ ofAucuba japonica, an evergreen understory shrub in the warmtemperate region of Japan. Evergreen foliage was the largest pool for each nutrient; nitrogen and phosphorus were accumulated and stored in autumn and then redistributed in the spring. For individual leaves, such seasonal accumulations and redistributions were repeated through two or three years and then at leaf fall, an additional amount was withdrawn. Rapid growth of new shoots and flowers during spring was supported by the massive redistribution of the nutrients from the old foliage. The redistribution accounted for 85% and 65% of the total nitrogen and phosphorus input to the new shoots, respectively. Such a high ratio of redistribution resulted in a conservative nutrient economy, and must be positively related to the photosynthetic production in the ligh-limited environment.     

南京地区落叶栎林主要木本植物的展叶动态研究

 植物的展叶过程是由自身遗传因子决定的,同时又受到多种生态因子的调节,反映了植物的生活史对策和群落物种多样性的维持机制。在2001和2002年的3～6月间,不定期记录了南京地区三个落叶栎(Quercus spp.)林中主要木本植物的展叶情况,包括被标记标准枝的叶数、叶的长度、宽度、叶面积、叶干重等参数。结果表明在所调查的落叶栎林中,林冠层物种的成熟叶面积和单位叶面积干重都显著大于林下层物种;最早展叶的物种为林下层物种,但林冠层展叶顺序与林下层无显著差异。叶面积越大、单位叶面积干重越小的物种展叶越晚;林冠层物种展叶较林下层快,物种成熟叶面积越大,展叶速率越大。最后对展叶顺序和展叶速度的生态学意义作了讨论。     

Wetland dicots and monocots differ in colonization by arbuscular mycorrhizal fungi and dark septate endophytes

As an initial step towards evaluating whether mycorrhizas influence composition and diversity in calcareous fen plant communities, we surveyed root colonization by arbuscular mycorrhizal fungi (AMF) and dark septate endophytic fungi (DSE) in 67 plant species in three different fens in central New York State (USA). We found colonization by AMF and DSE in most plant species at all three sites, with the type and extent of colonization differing between monocots and dicots. On average, AMF colonization was higher in dicots (58±3%, mean±SE) than in monocots (13±4%) but DSE colonization followed the opposite trend (24±3% in monocots and 9±1% in dicots). In sedges and cattails, two monocot families that are often abundant in fens and other wetlands, AMF colonization was usually very low (<10%) in five species and completely absent in seven others. However, DSE colonization in these species was frequently observed. Responses of wetland plants to AMF and DSE are poorly understood, but in the fen communities surveyed, dicots appear to be in a better position to respond to AMF than many of these more abundant monocots (e.g., sedges and cattails). In contrast, these monocots may be more likely to respond to DSE. Future work directed towards understanding the response of these wetland plants to AMF and DSE should provide insight into the roles these fungal symbionts play in influencing diversity in fen plant communities.     

典型阔叶红松林主要树种叶性状的垂直变异及经济策略

分析不同树种叶片性状的变化有助于了解植物群落结构。该文通过对典型阔叶红松(Pinus koraiensis)林15种阔叶树种的比叶质量、叶片厚度、叶干物质含量、叶绿素含量指数、叶片碳、氮、磷含量的测定, 分析了冠层高度对叶性状及叶性状间相关关系的影响。结果表明, 水曲柳(Fraxinus mandshurica)和大青杨(Populus ussuriensis)上层的比叶质量显著大于下层, 而其他树种冠层间的比叶质量无显著变化; 叶绿素含量指数在白桦(Betula platyphylla)和春榆(Ulmus japonica)冠层间的分布分别为上层显著大于下层和上层显著大于中层; 单位质量氮含量在水曲柳的中层显著大于上层。叶片性状间存在着广泛的相关性, 比叶质量与叶片厚度、干物质含量在三层间均呈显著正相关关系, 而有些性状, 只在一或二个冠层中存在一定的相关性。山杨(Populus davidiana)和大青杨的叶片倾向于选择光合能力较低、营养浓度较低、呼吸速率较慢的一端, 而黄檗(Phellodendron amurense)和山槐(Maackia amurensis)叶片更倾向于光合能力强、营养物质浓度高的一端。不同树种对光照响应的差异可能会改变不同冠层中叶片的形态和化学性状, 从而有助于群落构建和物种共存。     

Vertical variation and economic strategy of leaf trait of major tree species in a typical mixed broadleaved-Korean pine forest

分析不同树种叶片性状的变化有助于了解植物群落结构。该文通过对典型阔叶红松(Pinus koraiensis)林15种阔叶树种的比叶质量、叶片厚度、叶干物质含量、叶绿素含量指数、叶片碳、氮、磷含量的测定, 分析了冠层高度对叶性状及叶性状间相关关系的影响。结果表明, 水曲柳(Fraxinus mandshurica)和大青杨(Populus ussuriensis)上层的比叶质量显著大于下层, 而其他树种冠层间的比叶质量无显著变化; 叶绿素含量指数在白桦(Betula platyphylla)和春榆(Ulmus japonica)冠层间的分布分别为上层显著大于下层和上层显著大于中层; 单位质量氮含量在水曲柳的中层显著大于上层。叶片性状间存在着广泛的相关性, 比叶质量与叶片厚度、干物质含量在三层间均呈显著正相关关系, 而有些性状, 只在一或二个冠层中存在一定的相关性。山杨(Populus davidiana)和大青杨的叶片倾向于选择光合能力较低、营养浓度较低、呼吸速率较慢的一端, 而黄檗(Phellodendron amurense)和山槐(Maackia amurensis)叶片更倾向于光合能力强、营养物质浓度高的一端。不同树种对光照响应的差异可能会改变不同冠层中叶片的形态和化学性状, 从而有助于群落构建和物种共存。