氮添加对山西太岳山天然油松林主要植物叶片性状的影响

为探讨植物性状对大气氮沉降的响应与适应机制, 该文以中国特有的、在北方温性针叶林中广泛分布的天然油松(Pinus tabuliformis)林为研究对象, 在2009-2013年开展了氮添加对植物叶片性状影响的野外控制试验, 4个氮添加浓度分别为0 kg·hm^-2·a^-1 (CK)、50 kg·hm^-2·a^-1 (低氮)、100 kg·hm^-2·a^-1 (中氮)和150 kg·hm^-2·a^-1 (高氮)。试验过程中分别测定了油松、蒙古栎(Quercus mongolica)、茶条槭(Acer ginnala)、毛榛(Corylus mandshurica)、沙梾(Cornus bretschneideri)、绣线菊(Spiraea salicifolia)、金银忍冬(Lonicera maackii)、羊须草(Carex callitrichos)、龙常草(Diarrhena mandshurica)、大火草(Anemone tomentosa)和玉竹(Polygonatum odoratum)等11种主要植物的9种叶片性状, 包括叶厚度(LT)、比叶面积(SLA)、干物质含量(LDMC)、叶氮含量(LNC)、叶磷含量(LPC)等。结果表明: 1)在氮添加影响下, 玉竹等个别物种的LT和SLA、绣线菊等部分物种的叶面积(LA)和LDMC差异显著, 上述所有物种的LNC与大多数物种的叶绿素含量(CC)、LPC显著增加, 油松等9种植物叶片N:P发生显著变化, 不同年龄、不同类型的植物叶片对氮添加的响应不同。2)叶性状之间普遍存在显著相关性, 如SLA与LNC和LPC极显著正相关, LT与LNC和LPC极显著负相关, 且相关性随氮添加强度变化。3) 11种植物的叶片特征空间分布规律与叶经济谱的描述一致, 氮添加使植物在特征空间中的位置向叶片薄、生长快、叶寿命短的“快速投资-收益型”一端发生移动; 在垂直方向上, 阔叶乔木、灌木及草本的位置与针叶乔木的移动方向相反。当环境改变时, 植物会改变生存策略, 调整资源分配, 从而保证物种间相对位置和群落整体结构的稳定性。叶经济谱的形成不依赖于环境的变化, 而是植物一种固有的属性。     

Exploring the community assembly of subalpine meadow communities based on functional traits and community phylogeny

Aims The community assembly has been a prominent issue in community ecology. This work was intended to explore the mechanisms of the species coexistence and biodiversity in communities. Our objective was to explore the mechanisms of community assembly in subalpine meadow plant communities along slope gradients in Gannan Tibetan Autonomous Prefecture, Gansu Province, Northwest China.Methods We selected five slope-oriented plots to construct a super-tree representing the species pool. We surveyed the leaf functional traits and soil environmental factors in different slopes. Then we tested the phylogenetic signal of leaf dry matter content (LDMC), specific leaf area (SLA), leaf nitrogen content (LNC) and leaf phosphorus content (LPC).Important findings The changes of slope aspect had significant influence on soil water content (SWC) and soil nutrient content. Most of the plants leaf functional traits had significant difference along different slope aspects. The LDMC was higher in south and southwest slope than north slope, while SLA, LNC and LPC were relatively high in north and northwest slope. The LPC showed feeble phylogenetic signal, while LDMC, SLA, LNC did not have a significant phylogenetic signal. With changes in the slope aspect from south to north, community phylogenetic structure shifted from over-dispersion to clustered dispersion. In south and southwest slope, habitat filtering was the driving force for community assembly. Interspecific competition was the main driving factor for community assembly in north and northwest slope aspects. But in west slope, two indices showed contrary consequence. This means the process of community assembly in west slope was more complicated and its phylogenetic index may be the result of several mechanisms working together.     

浙江天童常绿植物当年生与往年生叶片性状的变异与关联

植物叶片性状随叶龄的变化是植物生活史策略的体现, 反映了植物叶片的物质投资和分配方式。该研究通过在个体和物种2个水平, 比较浙江天童1 hm ²样地内常绿阔叶树种的平均叶面积(MLA)、比叶面积(SLA)和叶片干物质含量(LDMC)在当年生和往年生叶片间的差异和关联, 探究叶片物质分配策略在异龄叶间的变化, 并分析叶龄对植物叶片性状, 特别是叶片面积建成消耗的影响。结果显示: 1)在个体和物种水平上, MLA变异系数最大(个体: 79.5%; 物种: 66.5%), SLA次之(个体: 28.1%; 物种: 24.7%), LDMC较低(个体: 17.0%, 物种: 14.1%); 当年生叶片MLA、LDMC和SLA的变异系数均高于往年生叶片; 2)往年生叶MLA显著大于当年生叶(t = -38.53, p < 0.001), 往年生叶SLA显著小于当年生叶(t = 45.30, p < 0.001), 往年生叶LDMC显著大于当年生叶(t = -9.71, p < 0.001); 3)在个体水平, 当年生叶片MLA、SLA和LDMC值分别解释了往年生叶片MLA、SLA和LDMC变异的86%、48%和41%; 在物种水平, 当年生叶片MLA、SLA和LDMC值分别解释了往年生叶片MLA、SLA和LDMC变异的97%、83%和85%; 4) SLA在异龄叶间的变化表明, 与往年生叶片相比, 投资相同干物质, 当年生叶片可形成较大的叶面积, 其叶片面积建成消耗较小。研究认为, 植物叶性状在异龄叶间具有较大的变异性和关联性, 叶面积形成过程中生物量建成与消耗的协调可能影响植物叶片的发育。     

Geostatistical analysis of spatial variations in leaf traits of woody plants in Tiantong,Zhejiang Province

AimsExploring spatial variations in leaf traits and their relationships with environmental properties is crucial for understanding plant adaptation strategies and community assembly. This study aimed to reveal how leaf traits varied spatially and the role of environmental factors.MethodsThe study was conducted in a 5-hm² forest plot in Tiantong, Zhejiang Province. Three leaf traits, including individual leaf area (ILA), specific leaf area (SLA), and leaf dry matter content (LDMC) were measured for 20253 individual trees with diameter at breast height (DBH) ≥1 cm. Soil properties measured included contents of soil total nitrogen, soil total phosphorus, soil total carbon, soil pH value, soil volumetric water content, bulk density, and humus depth. Topographic variables measured included elevation, slope and convexity. We used geostatistical analysis to reveal spatial variations of the three leaf traits. Relationships between leaf variability and environmental factors were analyzed using principal component analysis (PCA) and Pearson’s correlation.Important findings Spatial variability followed the order of ILA > SLA > LDMC. Spatial autocorrelation of three leaf traits was weak within a distance of 5.16 m. The optimal model of the semi-variogram function was Gaussian model for ILA, and exponential model for SLA and LDMC. ILA showed the largest variability at the direction of northeast-southwest, and smallest variability at the direction of northwest-southeast. In contrast, SLA and LDMC had the highest variability at the direction of northwest-southeast and least variability at the direction of northeast-southwest. There were significantly negative relationships between ILA and topographic factors (r = -0.12, p < 0.0001), and between SLA and soil nutrients (r = -0.16, p < 0.0001). In contrast, LDMC was positively correlated with soil nutrients (r = 0.13, p < 0.0001). Relative to soil nutrients, topographic factors affected much more variations in ILA, SLA and LDMC at the direction of northeast-southwest. Distinctly, at the direction of northwest-southeast, variability of ILA was affected mainly by topographic factors, while soil nutrients resulted in the most variability of SLA and LDMC. In conclusion, leaf traits varied considerably with spatial direction in the studied forest plot. Associations between leaf traits and topographic factors and soil nutrients indirectly indicated effects of environmental filtering on community assembly.     

黄土高原不同人工林叶片-凋落叶-土壤生态化学计量特征

为探究“退耕还林(牧)”工程对陕西省子午岭林区的影响,分析3种典型的人工林(刺槐林、油松林和侧柏林)叶片-凋落叶-土壤的C、N、P含量及其生态化学计量特征.结果表明: 3种人工林不同组分中C、N、P含量大小均为叶片>凋落叶>土壤,刺槐林叶片N、P含量显著高于油松林和侧柏林.刺槐林、油松林和侧柏林叶片N∶P分别为12.2、5.4和6.1,油松和侧柏较刺槐林存在N亏损,C∶N和C∶P大小均为凋落叶>叶片>土壤,N∶P为叶片>凋落叶>土壤.油松林叶片C∶N与凋落叶C∶N间存在显著正相关关系.刺槐叶片在生长周期内吸收利用的N和P存在比例关系,且其凋落叶在元素再吸收后N和P的残留量也存在比例关系.与油松和侧柏相比,刺槐是黄土高原南部森林带最适宜的造林树种.     

不同火烈度火烧迹地内油松叶功能性状的变化

叶功能性状对林火的响应是林火生态领域的研究热点之一,研究火后油松叶功能性状变化能够揭示油松为适应火环境形成的生长策略,为促进油松火后恢复提供参考。以山西省沁源县火烧迹地内油松为研究对象,选择当年生叶片分析叶功能性状在不同火烈度(未过火、轻度火烧、中度火烧)火烧迹地间的变化规律,并研究不同火烧迹地内叶经济谱的变化特征。结果表明: 除氮磷比外,叶功能性状在不同火烈度的火烧迹地间存在显著差异,其中,叶面积的差异最为明显,是最敏感的性状。随火烧迹地内火烈度的增加,叶面积、叶厚度、叶干物质含量、叶氮含量和叶磷含量升高,比叶面积、叶有机碳含量降低。部分叶功能性状间存在显著的相关关系,但其相关性在不同火烈度的火烧迹地间存在差异。叶经济谱沿着“未过火-轻度火烧-中度火烧”的火烧迹地环境总体向“快速投资-收益型”的资源权衡策略移动,低烈度火烧迹地内油松的生长恢复会加快。     

海拔对青海湖流域群落水平植物功能性状的影响

海拔变化会引起气压、温度、降水、土壤湿度和风速等环境因子发生急剧变化, 植物功能性状-海拔的相互关系对于预测全球变化背景下山地植物的适应方式具有重要意义。该研究在青海湖流域海拔3 400-4 200 m范围内布设了5个样地(海拔间隔约200 m), 通过植物群落调查, 测定植物功能性状和土壤理化性质, 结合气象数据, 探讨了海拔对青海湖流域群落水平植物功能性状的影响。结果如下: (1)群落加权平均植株高度(H)、叶片干物质含量(LDMC)、叶片碳氮比(C:N)和叶片氮磷比(N:P)随海拔升高显著降低, 比根表面积(SRA)随海拔升高波动下降, 比叶面积(SLA)、叶片氮含量(LNC)和叶片磷含量(LPC)随海拔升高显著升高, 叶片碳含量(LCC)、比根长(SRL)和根组织密度(RTD)随海拔未发生显著变化。(2)所有性状的变异来源以物种组成变化为主, N:P和LPC的种内性状变异与物种组成变化呈现正的协变效应, 其余性状为负的协变效应。(3)降水和0- 10 cm土层土壤养分含量对SLA变化的解释率较高, 温度和10-20 cm土层土壤养分含量对其余性状随海拔变化的解释率较高。以上结果表明青海湖流域植物群落主要通过物种更替来适应随海拔升高而剧烈变化的环境, 且各群落中的非优势种倾向于占据与优势种相反的性状空间来提高资源利用率, 随海拔变化的热量和深层土壤养分含量是群落水平植物功能性状变化的主要影响因子。     

Empirical relationship between specific leaf area and thermal dissipation of Phragmites australis in salt marshes of Qinwangchuan

Aims The correlation between specific leaf area (SLA) and thermal dissipation reflects not only the accumulation and dissipation of plant photosynthesis, but also plants’ adaptation to their habitats and changing environment. The objective of this study is to examine the correlation between SLA and thermal dissipation of reed (Phragmites australis) under different soil moisture conditions and salt contents.Methods Our study site was located in the National Wetland Park in Qinwangchuan, Gansu Province, China. Our sampling site extends from the edge to the central of a salt marsh where the reed was the single dominant species. The study site was divided into three zones based on the distance from the water. Within each zone, six 2 m × 2 m sampling plots were randomly located to select six reed individuals in each plot (total = 18). Vegetation height, aboveground biomass, soil moisture, and soil electrical conductivity (EC) were measured, with the six reed individuals taken to the laboratory to measure leaf thickness. Leaf net photosynthetic rate (P_n), transpiration rate (T_r), and other parameters of the reeds were also measured in each plot prior to harvesting. Quantitative measures of chlorophyll fluorescence were taken after 30-min dark adaptation. Quadrat survey method was used to model the empirical relationship between the transpiration rate and leaf characteristics.Important findings Vegetation height and aboveground biomass increased with soil moisture content, but EC and photosynthetically active radiation decreased. Leaf area, T_r and P_n increased along the gradient, leaf thickness showed decreasing, but the increasing trend of SLA switched to a decreasing trend, while leaf dry mass presented an opposite trend. From plot I to III, the quantum yield of regulated energy dissipation (Y(NPQ)) and non-photochemical quenching decreased, the actual photochemical efficiency of PSII and photochemical quenching increased, and quantum yield of non-regulated energy dissipation increased before decreasing. There appeared a highly significant negative correlation (p < 0.01) between SLA and Y(NPQ) at plot I and III, and a less significant negative correlation (p < 0.05) at plot II. Along the soil moisture gradient, reed seemed using light effectively by changing leaf thermal dissipation through adjusting their leaf size and SLA—A potential self-protection mechanism in light of adapting the habitat.     

Leaf hydraulic traits and their trade-offs for nine Chinese temperate tree species with different wood properties

Aims Trees with different wood properties display variations in xylem anatomy and leaf vein structure, which may influence tree water transport efficiency and water-use strategy, and consequently constrain tree survival, growth and distribution. However, the effects of wood properties on leaf hydraulic conductance and vulnerability and their potential trade-offs at leaf level are not well understood. Our aims were to examine variations in leaf hydraulic traits of trees with different wood properties and explore potential trade-offs between leaf hydraulic efficiency and safety.
Methods Nine tree species with different wood properties were selected for measuring the leaf hydraulic traits, including three diffuse-porous species (Populus davidiana, Tilia amurensis, Betula platyphylla), three ring-porous species (Quercus mongolica, Fraxinus mandshurica, Juglans mandshurica), and three non-porous species (Picea koraiensis, Pinus sylvestris var. mongolica, Pinus koraiensis). Four dominant and healthy trees per species were randomly selected. The hydraulic traits measured included leaf hydraulic conductance on leaf area (K_area) and dry mass (K_mass) basis, leaf hydraulic vulnerability (P₅₀), and leaf water potential at turgor loss point (TLP), while the leaf structural traits were leaf dry mass content (LDMC), leaf density (LD) and leaf mass per unit area (LMA).
Important findings The K_area, K_mass, and P₅₀ differed significantly among the tree species with different woody properties (p < 0.05). Both K_area and K_mass were the lowest for the non-porous trees, and did not differ significantly between the diffuse-porous and ring-porous trees. The ring-porous trees had the highest P₅₀ values, while the diffuse-porous and non-porous trees showed no significant differences in P₅₀. Both K_area and K_mass were negatively correlated with P₅₀ (p < 0.05) for all the trees, and the relationships for the diffuse-porous, ring-porous, and non-porous trees were fitted into linear, power, exponential functions, respectively. This indicates that significant trade-offs exist between leaf hydraulic efficiency and safety. The K_mass was correlated (p < 0.01) with TLP in a negative linear function for the diffuse- and ring-porous trees and in a negative exponential function for the non-porous trees. The P₅₀ increased with increasing TLP. These results suggest that apoplastic and symplastic drought resistance are strictly coordinated in order to protect living cells from approaching their critical water status under water stresses. The K_mass was negatively correlated (p < 0.01) with LDMC, LD, or LMA, while the P₅₀ was positively correlated with LDMC and LD; this suggests that variations in K_mass and P₅₀ are driven by similar changes in structural traits regardless of wood traits. We conclude that the tree tolerance to hydraulic dysfunction increases with increasing carbon investment in the leaf hydraulic system.     

Plant leaf traits,height and biomass partitioning in typical ephemerals under different levels of snow cover thickness in an alpine meadow

Aims In the cold life zones, snow cover is a comprehensive environmental factor that directly influences soil temperature, soil water content, light and nutrient availability. Plants in these zones develop a series of unique mechanisms involving phenological characteristics, reproductive strategies, physiology and morphology to adapt to environmental changes. This paper is focused on the responses of plant leaf traits, height and biomass partitioning to variations in snow cover thickness, in order to better understand the responses of plant functional traits and specific adaptation strategies under global climate change scenarios. Methods Three transects were established along a gradient of snow cover in an alpine meadow of Mt. Kaka, in the eastern Qinghai-Xizang Plateau. Primula purdomii, Pedicularis kansuensis and Ranunculus tanguticus, which are three widely distributed and dominant ephemerals, were sampled and studied, particularly at their blooming stages. Plant height, specific leaf area (SLA) and biomass partitioning were measured accordingly. Important findings The values of SLA in Pedicularis kansuensis and R. tanguticus were relatively greater under better soil conditions; it was smaller in Primula purdomii with thick snow cover. The relationship between aboveground biomass and belowground biomass in Primula purdomii was allometric at sites with both thick and thin snow cover. No significant relationships were found between aboveground biomass and belowground biomass in Pedicularis kansuensis and R. tanguticus at some individual sites. However, when samples of the three species were pooled, the relationships between aboveground biomass and belowground biomass were allometric at all sites, which did not support isometric scaling hypothesis. In addition, on sites with either thick or thin snow cover, aboveground biomass had greater rate of accumulation than belowground biomass; whereas on sites with medium snow cover, the rate of biomass accumulation was greater for belowground component than aboveground component. Functional traits and biomass variables were better correlated in Primula purdomii and Pedicularis kansuensis than in R. tanguticus.     

中亚热带植被恢复阶段植物叶片、凋落物、土壤碳氮磷化学计量特征

为揭示植被恢复过程中生态系统的养分循环机制及植物的生存策略, 根据亚热带森林群落演替过程, 采用空间代替时间方法, 以湘中丘陵区地域相邻、环境条件基本一致的檵木(Loropetalum chinensis) +南烛(Vaccinium bracteatu) +杜鹃(Rhododendron mariesii)灌草丛(LVR)、檵木+杉木(Cunninghamia lanceolata) +白栎(Quercus fabri)灌木林(LCQ)、马尾松(Pinus massoniana) +柯(Lithocarpus glaber) +檵木针阔混交林(PLL)、柯+红淡比(Cleyera japonica) +青冈(Cyclobalanopsis Glauca)常绿阔叶林(LCC)作为一个恢复系列, 设置固定样地, 采集植物叶片、未分解层凋落物和0-30 cm土壤样品, 测定有机碳(C)、全氮(N)、全磷(P)含量及其化学计量比, 运用异速生长关系、养分利用效率和再吸收效率分析植物对环境变化的响应和养分利用策略。结果表明: (1)随着植被恢复, 叶片C:N、C:P、N:P显著下降, 而叶片C、N、P含量和土壤C、N含量、C:P、N:P显著增加, 其中LCC植物叶片C、N含量, 土壤C、N含量及其N:P, PLL植物叶片P含量, 土壤C:P显著高于其他3个恢复阶段, 各恢复阶段植物叶片N:P > 20, 植物生长受P限制; 凋落物C、N、P含量及其化学计量比波动较大。(2)凋落物与叶片、土壤的化学计量特征之间的相关关系较弱, 叶片与土壤的化学计量特征之间具有显著相关关系, 其中叶片C、N、P含量与土壤C、N含量、C:N (除叶片C、N含量外)、C:P、N:P呈显著正相关关系; 叶片C:N与土壤C、N含量、C:P、N:P, 叶片C:P与土壤C含量、C:N、C:P, 叶片N:P与土壤C:N呈显著负相关关系。(3)植被恢复过程中, 叶片N、P之间具有显著异速生长关系, 异速生长指数为1.45, 叶片N、P的利用效率下降, 对N、P的再吸收效率增加, LCC叶片N利用效率最低, PLL叶片P利用效率最低而N、P再吸收效率最高。(4)叶片N含量内稳态弱, 而P含量具有较高的内稳态, 在土壤低P限制下植物能保持P平衡。植被恢复显著影响叶片、凋落物、土壤C、N、P含量及其化学计量比, 叶片与土壤之间C、N、P含量及化学计量比呈显著相关关系, 植物通过降低养分利用效率和提高养分再吸收效率适应土壤养分的变化, 叶片-凋落物-土壤系统的N、P循环随着植被恢复逐渐达到“化学计量平衡”。     

Morphological traits and physiological characteristics in drought tolerance in 20 shrub species on the Qinghai-Xizang Plateau

Aims Providing indispensably theoretical evidence for establishing indices of evaluation on drought tolerance in shrubs, and screening for tree species that are drought tolerant for afforestation in arid regions or for matching their characteristics with suitable habitat conditions are the key to vegetation restoration in the Qinghai-Xizang Plateau. However, these issues are not adequately addressed in recent research due to lack of systematic methods. Therefore, our objective was to make a comprehensive evaluation on drought tolerance in 20 shrub species collected from different areas in Qinghai-Xizang Plateau, and to study their underlying mechanisms in drought tolerance.
Methods We made measurements on variables depicting root characteristics, including the root length (TRL), surface area (TRSA), volume (TRV), and tips number (TRTN) of all roots, the root length (FRL), surface area (FRSA), volume (FRV), and tips number (FRTN) of fine roots (d≤2 mm), and derived plant characteristic indices including thickness of cuticle (CT), thickness of palisade tissue (TPT), thickness of spongy tissue (TST), TPT/TST, thickness of leaf (LT), palisable tissue cell density, and tissue structural tense ratio (CTR = TPT/LT × 100%) and spongy tissue loosened ratio (SR = TST/LT × 100%) of leaf anatomical structure, root to shoot ratio (RSR), leaf transpiration rate (T_r), instantaneous water use efficiency (WUE_i), and carbon isotopic composition (δ¹³C) of the 20 shrub species through field experiments. Correlation analysis and principal component analysis were performed on the 19 variables and indices.
Important findings Different shrubs had different mechanisms of drought tolerance. In this study, the character- istics of drought tolerance were mainly categorized into 6 types, involving modifications of (1) root systems, (2) leaf anatomical structure, (3) leaf pattern, and (4) biomass allocation, or via (5) low water-consumption and (6) high WUE_i. Different genera or different tree species within the same genus clearly differed in drought tolerance. The species of the genus Hippophae were relatively poorly tolerant to drought, whereas several shrubs including Potentilla fruticosa, Berberis julianae, Caragana arborescens, Spiraea salicifolia and Hippophae rhamnoides ssp. mongolica occurred to be more drought tolerant than other shrub species investigated in this study. On the other hand, there were highly significant correlations among the characteristics of root systems and among characteristics of leaf anatomical structure. The results of principal component analysis on 19 variables and indices showed that TRL, TRSA, TRV, TRTN, FRL, FRSA, FRV, FRTN, CT, TPT, TST and WUE_i could be effective indicators of drought tolerance of shrubs in the Qinghai-Xizang Plateau. In addition, the drought tolerance of shrubs had a close connection with their origin of collections; the shrubs collected from Xining prefecture in Qinghai Province were more drought tolerant than those from Tianshui Prefecture in Gansu and Lasa Prefecture in Xizang.     

Specific leaf area estimation model building based on leaf dry matter content of Cunninghamia lanceolata

随着叶片功能性状研究的不断深入, 通过简单易测量的叶片指标, 同时探究植物生活史权衡对策和估算林分生产力的研究需求日益增长, 例如叶干质量比(LDMC)和比叶面积(SLA)的相互转换。杉木(Cunninghamia lanceolata)是亚热带重要的常绿针叶树种, 基于LDMC对杉木SLA进行估算, 能够为核算SLA提供途径, 为机理解释和生产估算构建连接途径, 为小区域到大尺度、精算到估算搭建桥梁。该研究在湖南会同和河南信阳两个杉木生长区, 对处于不同小生境(坡向、坡位和冠层深度)以及不同生活史(林龄和叶龄)的叶片进行抽样和采集, 通过测得不同叶龄的单叶LDMC和SLA, 初步探究在不同因子下两个性状值的分布差异, 进一步基于LDMC构建SLA估算模型并讨论以叶龄为差分因子对模型的影响。结果表明: 1)杉木SLA平均值为(103.15 ± 69.54) cm ²·g ^-1, LDMC为0.39 ± 0.11; 2)杉木LDMC和SLA可用非线性模型进行估算, 模型符合估算要求; 3)其中一年生叶的拟合效果最好, 老叶(大于二年生叶)的拟合优度较低, 老叶较低的SLA (52.28-75.74 cm ²·g ^-1)可能暗示LDMC的变化保持相对独立性。该研究基于杉木LDMC的SLA估算模型可信且有效, 且不同叶龄对LDMC和SLA的影响可能预示着杉木叶片的响应敏感性和生活史权衡策略。     

亚热带不同树种凋落叶分解对氮添加的响应

为探究不同质量凋落物对氮(N)沉降的响应, 该研究采用尼龙网袋分解法, 在亚热带福建三明格氏栲(Castanopsis kawakamii)自然保护区的米槠(Castanopsis carlesii)天然林, 选取4种本区常见的具有不同初始化学性质的树种凋落叶进行模拟N沉降(N添加)分解实验(施N水平为对照0和50 kg·hm ^-2·a ^-1)。研究结果表明: 在2年的分解期内, 对照处理的各树种凋落叶的分解速率依次为观光木(Michelia odora, 0.557 a ^-1)、米槠(0.440 a ^-1)、台湾相思(Acacia confusa, 0.357 a ^-1)、杉木(Cunninghamia lanceolata, 0.354 a ^-1); N添加处理凋落叶分解速率依次为观光木(0.447 a ^-1)、米槠(0.354 a ^-1)、杉木(0.291 a ^-1)、台湾相思(0.230 a ^-1), 除杉木凋落叶外, N添加显著降低了其他3种凋落叶分解速率。N添加不仅使4种树木凋落叶分解过程中的N释放减慢, 同时还抑制凋落叶化学组成中木质素和纤维素的降解; N添加在凋落叶分解过程中总体上提高β-葡萄糖苷酶(βG)和酸性磷酸酶活性, 对纤维素水解酶的活性影响不一致, 而降低β-N-乙酰氨基葡萄糖苷酶活性和酚氧化酶活性。凋落叶分解速率与凋落叶中的碳获取酶(βG)活性以及其化学组分中的可萃取物含量极显著正相关, 与初始碳浓度、纤维素和木质素含量极显著负相关, 与初始N含量没有显著相关性。凋落物类型和N添加的交互作用虽未影响干质量损失速率, 但对木质素和纤维素的降解具有显著效应。综上所述, 化学组分比初始N含量能更好地预测凋落叶分解速率, 而N添加主要通过抑制分解木质素的氧化酶(如PHO)来降低凋落叶分解速率。     

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。     

Traits of shrubs in forests and bushes reveal different life strategies

灌木是森林和灌丛生态系统的重要组成部分, 探究森林与灌丛灌木功能性状的差异, 可揭示灌木在不同生境的适应策略。该研究以金华北山森林群落林下灌木层、低山灌丛和山顶灌丛共24个样地中的优势灌木为研究对象, 分析叶片和小枝9个功能性状在3种生境下的总体差异, 以及种间、种内变异和不同生活型的差异。结果表明: 1) 9个性状在3种不同生境下存在差异。林下灌木具有较大的叶面积和比叶面积, 较小的叶干物质含量、叶和小枝的组织密度, 低山灌丛相较于山顶灌丛具有较大的叶厚度、叶组织密度和较小的比叶面积、小枝干物质含量。2)林下灌木的比叶面积、小枝直径、小枝组织密度和小枝干物质含量的种内种间变异系数最大, 低山灌丛的比叶面积、叶和小枝的干物质含量、叶和小枝的组织密度的种内种间变异系数最小。3)不同生活型间, 林下常绿灌木的叶厚度、叶组织密度、叶干物质含量显著高于落叶灌木, 落叶灌木的比叶面积显著高于常绿灌木, 而山顶灌丛叶厚度和比叶面积的差异规律与林下灌木相同, 叶组织密度和叶干物质含量的差异与其相反。4)影响灌木性状的主要因素是物种以及物种和生境的交互作用。总之, 森林群落林下灌木形成较大叶面积和比叶面积, 较小叶和小枝组织密度、叶干物质含量的性状组合, 以快速生长而适应光照较弱、竞争作用强的林下环境, 是资源获取型策略; 低山灌丛和山顶灌丛具有较大叶厚度、组织密度、干物质含量和小枝组织密度和较小叶面积、比叶面积等一系列储存养分、慢速生长的性状组合, 属于资源保守型策略。灌木植物性状的不同组合及其所反映的不同生活策略, 对亚热带地区退化植被的生态恢复具有指导意义。     

黄土高原天然和人工油松林根际土壤解磷细菌群落特征及其功能

为了揭示油松-根系微生物的互作关系及其对油松林分稳定性的影响,本研究选择陕西省黄龙县天然和人工油松林,采集油松根际与非根际土壤,测定非根际土壤化学特性,分离纯化根际土壤解磷(有机磷和无机磷)细菌,通过DNA基因测序鉴定解磷细菌,并测定解磷细菌的解磷能力。结果表明: 天然油松林非根际土壤中全碳(TC)、全氮(TN)含量以及C/N、N/P极显著高于人工油松林。2种油松根际土壤中共鉴定出20属65种解磷细菌,其中以芽孢杆菌属、链霉菌属和假单胞菌属为优势菌群;天然油松林根际解磷细菌多样性、丰富度和均匀度指数均高于人工油松林,而优势度指数低于人工油松林。链霉菌属与非根际土壤TC、TN和C/N、N/P呈正相关,而芽孢杆菌属和假单胞菌属与非根际土壤硝态氮、铵态氮、有效磷及全磷含量呈正相关。2种油松林根际土壤不同解磷细菌的解磷能力存在差异,其中天然和人工油松林根际共有的解磷细菌为假单胞菌Pseudomonas sp.34-5,其对磷酸钙的解磷能力最高,为11.40 μg·mL^-1;天然油松林根际独有的解磷细菌蕈状芽胞杆菌BF1-5对卵磷脂的解磷能力最高,为4.58 μg·mL^-1。该林区2种油松林根际解磷细菌菌群结构存在显著差异。与人工油松林相比,天然油松林根际土壤解磷细菌群落多样性更丰富且分布更均匀,解磷能力普遍高于人工林。     

基于叶干质量比的杉木比叶面积估算模型的构建

随着叶片功能性状研究的不断深入, 通过简单易测量的叶片指标, 同时探究植物生活史权衡对策和估算林分生产力的研究需求日益增长, 例如叶干质量比(LDMC)和比叶面积(SLA)的相互转换。杉木(Cunninghamia lanceolata)是亚热带重要的常绿针叶树种, 基于LDMC对杉木SLA进行估算, 能够为核算SLA提供途径, 为机理解释和生产估算构建连接途径, 为小区域到大尺度、精算到估算搭建桥梁。该研究在湖南会同和河南信阳两个杉木生长区, 对处于不同小生境(坡向、坡位和冠层深度)以及不同生活史(林龄和叶龄)的叶片进行抽样和采集, 通过测得不同叶龄的单叶LDMC和SLA, 初步探究在不同因子下两个性状值的分布差异, 进一步基于LDMC构建SLA估算模型并讨论以叶龄为差分因子对模型的影响。结果表明: 1)杉木SLA平均值为(103.15 ± 69.54) cm ²·g ^-1, LDMC为0.39 ± 0.11; 2)杉木LDMC和SLA可用非线性模型进行估算, 模型符合估算要求; 3)其中一年生叶的拟合效果最好, 老叶(大于二年生叶)的拟合优度较低, 老叶较低的SLA (52.28-75.74 cm ²·g ^-1)可能暗示LDMC的变化保持相对独立性。该研究基于杉木LDMC的SLA估算模型可信且有效, 且不同叶龄对LDMC和SLA的影响可能预示着杉木叶片的响应敏感性和生活史权衡策略。     

毛乌素沙地油蒿叶建成成本及相关叶性状沿降水梯度的变化

干旱区植物在如何提高水分利用效率与降低叶建成成本之间可能存在一种权衡。我们假设: 与湿润区植物相比, 干旱区植物能通过调节叶功能性状之间的关系(如通过提高单位面积叶氮含量(N_area)), 实现在相同的叶建成成本下具有更高的水分利用效率。为了验证这一假设, 该研究以毛乌素沙地的广布物种油蒿(Artemisia ordosica)为研究对象, 分析了油蒿叶建成成本沿降水梯度的变化规律及其与比叶面积(SLA)、单位质量叶氮含量(N_mass)、N_area和叶碳稳定同位素比率(δ ¹³C)的关系。结果表明: 油蒿单位质量叶建成成本(CC_m)在不同降水条件下差异不显著, 而单位面积叶建成成本(CC_a)在不同降水条件下虽有显著差异, 但并未随降水减少而明显增加。油蒿CC_m与SLA无显著相关性, 与叶δ ¹³C值呈显著正相关关系。油蒿叶建成成本与N_area呈显著正相关关系, 但这种关系格局在低降水量(264 mm)区与高降水量(310-370 mm)区之间存在策略位移现象——即在相同叶建成成本下, 低降水量区植物比高降水量区植物具有更高的N_area。以上结果表明, 尽管高水分利用效率与高叶建成成本相关, 但与高降水量区植物相比, 低降水量区植物具有较高的N_area并没有导致其叶建成成本增加。     

高寒草甸不同演替阶段植物叶片功能性状研究

以甘南高寒草甸演替过程中5个阶段的典型群落为研究对象,对围封样地内不同演替阶段群落叶片功能性状进行比较,分析了围封地内各演替阶段群落水平上主要物种叶性状与环境因子的关系。结果显示:(1)此围封地形成了一个从草本到灌木的演替过程。随着演替的进行,Margalef指数显著增加,Shannon-Wiener指数呈先增加后降低的趋势。(2)从演替前期到演替后期,土壤有机碳(SOC)、土壤全氮(STN)、土壤含水量(SWC)逐渐升高,光照度(LI)、土壤温度(ST)逐渐降低,土壤全磷(STP)呈先降低后增加趋势;叶片有机碳(LCC)、全氮(LNC)、含水量(LWC)逐渐升高;比叶面积(SLA)、磷利用效率(PUPE)、稳定碳同位素(δ13C)逐渐下降,叶片全磷(LPC)先降低后升高,而氮利用效率(PUNE)先升高后降低。(3)RDA冗余分析表明,在此围封样地内,演替前期植物群落叶性状主要受到LI和ST的限制作用。而在演替的中后期SWC[WTBZ]是主要影响因子。此研究有助于我们认识高寒草甸生态系统的退化过程所导致的生态环境问题,进而寻求更好的草地恢复和重建方法。