野化培训大熊猫采食和人为砍伐对拐棍竹无性系种群更新的影响

亚高山竹类占据着野生大熊猫(Ailuropoda melanoleuca)食物组分的99%,竹子的生命周期与大熊猫的生活史密切相关,竹子的更新和生长直接影响着大熊猫的生存与保护.为了弄清大熊猫的采食利用和人为砍伐是否促进或制约竹子的繁殖更新,应用样方法、定位观察法,连续研究了卧龙自然保护区大熊猫栖息地内野化培训大熊猫采食、人为砍伐和对照样方中拐棍竹无性系种群的更新动态.结果表明,在相同种群数量和环境条件的基础上(p>0.05),被大熊猫采食竹子的比例为67.07%,致死率29.07%;人为砍伐竹子的比例为65.67%,致死率46.68%,可见与大熊猫采食相比,砍伐更为影响拐棍竹种群的生存.从出笋数量来看,不同处理方式有利于拐棍竹无性系种群的更新(p<0.05),尤其是人为砍伐措施大大提高了竹子的出笋率,但人为砍伐样方的竹笋质量(地径和株高生长)却远低于大熊猫采食和对照样方,未能达到大熊猫觅食的选择利用标准.不同年份之间,各种处理方式下的拐棍竹出笋数量波动较大(p=0.006～0.035),并随着恢复时间的延长,逐渐趋于相似(2007,p=0 825).不同处理方式之间,拐棍竹无性系种群的年补充率,各年份均具有显著性差异(p<0.05,除2007年外),年死亡率仅2003年和2004年有明显的差异(p<0.05),2005～2007年均不显著(p>0.05).拐棍竹无性系种群的年补充率与年死亡率之间表现出年补充率﹥年死亡率的格局(p<0.05),唯有大熊猫采食样方的2004年和2005年、人为砍伐和对照样方的2005年的年死亡率略高于年补充率(p>0.05),这表明拐棍竹无性系种群对大熊猫采食和人为砍伐具有无性系整合的补偿效应.     

密度对缺苞箭竹凋落物养分归还及养分利用效率的影响

在缺苞箭竹-紫果云杉原始林下,选取3个密度(D1、D2、D3)的缺苞箭竹,研究了密度对缺苞箭竹凋落物量、养分归还量及养分利用效率的影响.结果表明:3个密度缺苞箭竹的年凋落物量分别为793.2、1135.7和1458.5kg.hm-2,C归还量分别为370.7、516.2和671.5kg.hm-2,5种主要养分归还量分别为16.3、22.9和29.3kg.hm-2,均随密度的增大而增加.各密度养分年归还量中均以Ca最高(占总量的48%～58%),P和Mg最低(3%～5%),总体排序为Ca>N>K>Mg、P.除高密度(D3)缺苞箭竹在8月有一个凋落与养分归还小峰外,10月生长季末是各密度缺苞箭竹凋落及养分归还高峰期.不同密度缺苞箭竹叶N和K的再分配能力无显著差异,P的再分配能力随密度的增大而增强,Ca、Mg则显著积累.缺苞箭竹P的养分利用效率随密度的增大而增高,表明P可能是缺苞箭竹生长更新的限制因子.     

贵州雷公山秃杉林不同林冠环境下箭竹分株种群结构特征

通过对贵州雷公山秃杉林的4种林冠环境,即林下(FU)、中林窗(MG)、大林窗(LG)和林缘旷地(FEW)内的箭竹的分株种群结构（包括株高、基径、生物量、叶和分株数等）和年龄结构进行较系统对比研究。结果显示:（1)从林下→中林窗→大林窗,箭竹分株种群的株高(h)、基径（bd)与生物量显著增加。（2)在4种林窗环境中,箭竹各构件的生物量的百分比发生相应变化,枝和叶片生物量的百分比沿林下→中林窗→大林窗→林缘旷地的顺序显著减小,在林缘旷地,地下茎、粗根（d＞0.5 mm)和细根（d≤0.5 mm)生物量的百分比显著高于其他3种林冠环境。（3)箭竹分株单位叶面积叶重沿林下→中林窗→大林窗→林缘旷地的顺序显著增大,单叶生物量与叶面积以中林窗最大,林缘旷地次之,二者与大林窗或林下差异显著;大林窗的单株叶片数显著高于其余3种林冠环境。（4)在4种林冠环境中,箭竹分株种群死亡率以林下最低,但各种群平均年龄间无显著差异。研究表明,箭竹分株种群对林冠环境变化的响应主要体现在形态与生物量的分配上,而非种群的年龄。     

不同群落冠层环境下紫耳箭竹笋期生长发育研究

对金佛山国家级自然保护区内3个不同类型群落(落叶阔叶林、常绿落叶阔叶混交林、常绿阔叶林)下紫耳箭竹(Fargesia decurvata J. L. Lu)幼笋的生长发育进行研究。结果显示:(1)落叶阔叶林和常绿落叶阔叶混交林下的紫耳箭竹出笋期早而长,历时110 d,出笋量大,出笋率高;常绿阔叶林下的出笋期晚而短,历时88 d,出笋量少,出笋率低;常绿落叶阔叶混交林中出笋量最大。(2)出笋期分为3个阶段:初期、盛期和末期,各群落中的紫耳箭竹进入每个时期的时间有所差异,常绿落叶阔叶混交林中最早进入出笋盛期,落叶阔叶林次之,常绿阔叶林最迟。出笋盛期也是退笋的高峰期,退笋率的大小为:常绿落叶阔叶混交林落叶阔叶林常绿阔叶林。(3)同一群落冠层环境下,紫耳箭竹不同时期出土的幼笋地径无显著差异。在落叶阔叶林和常绿落叶阔叶混交林林冠环境中,各时期出土的幼笋地径间无显著差异,但均显著大于常绿阔叶林(P 0.05)。(4)紫耳箭竹幼笋出土后80 d左右完成高生长过程,且符合Logistic方程,呈"慢-快-慢"的生长趋势。高生长速率为:常绿落叶阔叶混交林落叶阔叶林常绿阔叶林,且差异显著(P 0.05)。(5)紫耳箭竹的克隆繁殖与分株密度间有密切关系。随着分株密度的增加,出笋数量增加,成竹数量降低。本研究表明不同群落冠层环境下紫耳箭竹生长发育存在显著差异,在常绿落叶阔叶混交林中发育最好,常绿阔叶林中发育最差,种群密度对竹类的更新发展起重要调节作用。     

林冠环境对亚高山针叶林下缺苞箭竹生物量分配和克隆形态的影响

通过对亚高山针叶林的林下、小林窗(130 m²)、中林窗(300 m²)和大林窗(500 m²) 4种林冠环境中缺苞箭竹(Fargesia denudata)分株种群特征进行调查, 研究其生物量分配格局和克隆形态可塑性。研究结果表明: (1)分株生物量、基径、高度以及分株各构件生物量随林冠郁闭度减小均表现为先增加后减小的趋势, 在小林窗中达到最大值; (2)大林窗中, 根生物量分配和数量显著高于其他林冠环境, 随林冠郁闭度增大, 分株不断增大叶生物量分配、比叶面积和分枝百分比等地上部分投资, 以适应低光环境; (3)比茎长和比地下茎长随林冠郁闭度增大表现为先减小后增加的趋势, 在小林窗值最低, 分枝强度在小林窗和中林窗中显著高于林下和大林窗环境。结果显示, 缺苞箭竹在不同林冠环境中具有生物量分配和克隆形态的可塑性, 以利于种群对光资源的有效利用。小林窗环境是缺苞箭竹较适宜的生境, 生物量积累最多, 长势最好。     

异质光环境下克隆整合对白夹竹光合氮分配格局的影响

采用盆栽试验,以单轴散生型竹类植物——白夹竹(Phyllostachys bissetii)克隆片段为对象,使近端分株处于自然光照环境,远端分株处于遮荫环境中,对根状茎作切断或不切断处理,研究克隆整合对远端分株和近端分株光合氮分配格局的影响。结果表明:(1)根状茎保持连接的远端分株较根状茎切断的远端分株具有更高的最大净光合速率、叶片氮含量、光合色素含量、叶片光合氮分配系数。(2)相对根状茎切断处理,根状茎保持连接的远端分株将更多的氮分配到光合系统的羧化系统、生物力能学组分,而分配至捕光系统组分的比例较小。(3)比较处于自然光照条件的近端分株,比叶重、叶片氮含量等并没有因根状茎切断与否表现出显著性差异,根状茎连接的近端分株部分指标甚至高于根状茎切断的近端分株。研究认为,克隆整合作用影响处于遮荫环境的白夹竹远端分株的光合氮分配格局,使得处于遮荫生境中的克隆分株依旧维持较高的光合能力,保证了处于逆境条件下克隆分株的生存与生长。     

光合产物传输方向对蓉城竹根际微生物过程的影响

分株间光合产物的整合作用对克隆植物适应生存环境具有重要作用, 但有关光合产物传输方向对克隆植物根际土壤微生物过程的影响尚不清楚。该研究以根状茎克隆植物蓉城竹(Phyllostachys bissetii)为研究对象, 通过剪除分株地上部分控制光合产物传输方向(顶向传输和基向传输), 研究光合产物传输方向对蓉城竹分株根际土壤微生物过程的影响, 其中顶向传输组是将远端分株地上部分剪除(保留地面以上20 cm), 近端分株自然生长; 基向传输组则是将近端分株地上部分剪除(保留地面以上20 cm), 远端分株自然生长。两组实验中保持根状茎连接或切断处理。测定了地上部分被剪除分株根际土壤中碳和氮有效性、微生物生物量参数以及氮转化相关土壤胞外酶活性等指标。结果表明: 光合产物顶向传输中, 根状茎保持连接的远端分株根际土壤总有机碳(TOC)、溶解性有机碳(DOC)、溶解性有机氮(DON)、铵态氮(NH₄ ⁺-N)、硝态氮(NO₃ ^--N)含量显著高于切断的远端分株, N-乙酰基-β-D-氨基葡萄糖苷酶(NAGase)、多酚氧化酶(POXase)和脲酶(Urease)活性显著升高, 光合产物的顶向传输对远端分株根际碳、氮有效性和根际微生物过程产生了显著性影响; 光合产物的基向传输中, 根状茎保持连接的近端分株根际与切断分株相比具有更高的微生物生物量氮(MBN)含量、Urease、POXase活性, 较低的NAGase活性和NH₄ ⁺-N、NO₃ ^--N含量, 但碳的有效性无显著性差异。蓉城竹分株间光合产物的非对称性传输对根际微生物过程的影响可能是对动物取食或人为砍伐等干扰的有益权衡, 这有助于理解克隆植物对生存环境的种群适应机制。     

Effects of transportation direction of photosynthate on soil microbial processes in the rhizosphere of Phyllostachys bissetii

分株间光合产物的整合作用对克隆植物适应生存环境具有重要作用, 但有关光合产物传输方向对克隆植物根际土壤微生物过程的影响尚不清楚。该研究以根状茎克隆植物蓉城竹(Phyllostachys bissetii)为研究对象, 通过剪除分株地上部分控制光合产物传输方向(顶向传输和基向传输), 研究光合产物传输方向对蓉城竹分株根际土壤微生物过程的影响, 其中顶向传输组是将远端分株地上部分剪除(保留地面以上20 cm), 近端分株自然生长; 基向传输组则是将近端分株地上部分剪除(保留地面以上20 cm), 远端分株自然生长。两组实验中保持根状茎连接或切断处理。测定了地上部分被剪除分株根际土壤中碳和氮有效性、微生物生物量参数以及氮转化相关土壤胞外酶活性等指标。结果表明: 光合产物顶向传输中, 根状茎保持连接的远端分株根际土壤总有机碳(TOC)、溶解性有机碳(DOC)、溶解性有机氮(DON)、铵态氮(NH₄ ⁺-N)、硝态氮(NO₃ ^--N)含量显著高于切断的远端分株, N-乙酰基-β-D-氨基葡萄糖苷酶(NAGase)、多酚氧化酶(POXase)和脲酶(Urease)活性显著升高, 光合产物的顶向传输对远端分株根际碳、氮有效性和根际微生物过程产生了显著性影响; 光合产物的基向传输中, 根状茎保持连接的近端分株根际与切断分株相比具有更高的微生物生物量氮(MBN)含量、Urease、POXase活性, 较低的NAGase活性和NH₄ ⁺-N、NO₃ ^--N含量, 但碳的有效性无显著性差异。蓉城竹分株间光合产物的非对称性传输对根际微生物过程的影响可能是对动物取食或人为砍伐等干扰的有益权衡, 这有助于理解克隆植物对生存环境的种群适应机制。     

四川王朗自然保护区缺苞箭竹（Fargesia denudate Yi.）总酚含量及变化规律

采用分光光度法对四川王朗自然保护区缺苞箭竹的总酚含量进行了分析,结果表明:在采集到的不同器官中均有酚类物质分布,总酚含量最高的为叶龄超过1a的老叶(2.05%),笋中的总酚含量最低(0.20%).海拔高度和日照强度在一定程度上影响其含量变化,在海拔高和光照强的条件下,幼嫩器官中的总酚含量有明显增加的趋势.研究分析了缺苞箭竹各器官总酚含量的变化规律,及其与环境因子和大熊猫采食量之间的关系.     

Aboveground biomass and its biotic and abiotic modulators of a main food bamboo of the giant panda in a subalpine spruce–fir forest in southwestern China

中国西南亚高山云冷杉林中大熊猫主食竹的地上生物量及其生物和非生物影响因子 作为大熊猫(Ailuropoda melanoleuca)的主食竹之一，缺苞箭竹(Fargesia denudate)广泛分布在中国西南山地云冷杉林的林下。然而，缺苞箭竹生物量及其分布的驱动因素仍不清楚。本研究基于对王朗大样地(25.2 ha) 209个样方(投影面积为20 m × 20 m)中的乔木层和灌木层(包括竹子等木质草本)的系统调查，探讨非生物因素(地形和土壤理化性质)和生物因素(乔木密度、乔木总胸高断面积(TBA)和灌木盖度等) 对缺苞箭竹地上生物量的影响。研究结果表明，样方缺苞箭竹地上生物量平均为1.17 ton/ha，在209 个 调查样方中差异很大(0–4.88 ton/ha，95%置信区间)。缺苞箭竹生物量随海拔、坡度和乔木平均胸径的增 加而显著增加，随乔木密度、灌木盖度和土壤pH的增加而显著降低，而与乔木TBA、坡向、土壤有机质或总氮含量无显著线性关系。随机森林模型表明，地形和生物因素对缺苞箭竹生物量的影响比土壤理化性质更大。具体来说，地形主要通过改变乔木密度和土壤理化性质来影响缺苞箭竹的生物量。本研究结果可为大熊猫的保护和亚高山云冷杉林的管理提供科学参考。     

Clonal integration improves compensatory growth in heavily grazed ramet populations of two inland-dune grasses

Herbaceous species possess several mechanisms to compensate for tissue loss. For clonal herbaceous species, clonal integration may be an additional mechanism. This may especially hold true when tissue loss is very high, because other compensatory mechanisms may be insufficient. On inland dunes in northern China, we subjected Bromus ircutensis and Psammochloa villosa ramets within 0.5 m×0.5 m plots to three clipping treatments, i.e., no clipping, moderate (50% shoot removal) and heavy clipping (90% shoot removal), and kept rhizomes at the plot edges connected or disconnected. Moderate clipping did not reduce ramet, leaf or biomass density of either species. Under moderate clipping, rhizome connection significantly improved the performance of Psammochloa, but not that of Bromus. Heavy clipping reduced ramet, leaf and biomass density in the disconnected plots of both species, but such negative effects were negated or greatly ameliorated when the rhizomes were connected. Therefore, clonal integration contributed greatly to the compensatory growth of both species. The results suggest that clonal integration is an additional compensatory mechanism for clonal plants and may be important for their long-term persistence in the heavily grazed regions in northern China.     

Trade-off relationship between vein density and vein diameter of Achnatherum splendens in response to habitat changes in Zhangye wetland

Aims The coevolution between vein traits has influences on water use strategies of plant and the formation of leaf economic spectrum, and therefore is important for understanding the trade-off between carbon input in leaf vein construction and the functional feedback from leaf veins. Our aim is to study the allometric relationship between vein density and vein diameter of Achnatherum splendens populations at three natural microhabitats (subcanopy, transitional and open areas) in Zhangye wetland. Methods According to the shade condition of the arbor canopy and the distance to arbor, the A. splendens community were divided into three microenvironments: subcanopy, transitional and open areas. We sampled 10 (4 m × 4 m) A. splendens plots from each microenvironment and investigate the biological characteristics of the plots and leaf traits of the plants within the plots. Then the soil physical and chemical properties, and community photosynthetically active radiation (PAR) were investigated at three gradients. Six individual of A. splendens were selected in each plot and the leaf length, leaf width, vein density and vein diameter of two or three healthy and complete leaves from four directions of each individual were measured in laboratory. The SMA estimation method and correlation analysis were then used to examine the allometric relationship between vein density and vein diameter. Important findings Along the gradient from subcanopy, transitional zone to open areas, soil moisture displayed a pattern of initial decrease of plant community, and soil electric conductivity displayed increase changing trends. Photosynthetically active radiation (PAR), vapor pressure deficit (VPD), vein density (1.28-1.59 mm·mm^-2), leaf width and water use efficiency (WUE) increase gradually, while the leaf length, vein diameter (0.21-0.16 mm) of A. splendens decrease. The average value of plasticity indexes of leaf characteristics was 0.19. Leaf net photosynthetic rate (P_n), transpiration rate (T_r) and bundle density increase first and them decrease. The vein density and vein diameter of A. splendens were negatively correlated with each other in subcanopy environment (p < 0.01), transitional and open areas (p < 0.05). The SMA (0.54-1.50) slope of regression equation in the scaling relationships between vein density and vein diameter decrease gradually from subcanopy to open areas.     

Do rhizome severing and shoot defoliation affect clonal growth of Leymus chinensis at ramet population level?

Leymus chinensis (Trin.) Tzvel. is a perennial species of Gramineae, usually subject to defoliation from grazing and mowing. We examined whether shoot defoliation and rhizome severing affected rhizome and ramet growth, and vegetative bud outgrowth of L. chinensis ramet populations. We also tested the hypothesis that clonal growth of the ramets subject to defoliation would benefit from clonal integration between interconnected ramets besides from possible compensatory growth. To 48 experimental plots, we applied six treatments resulting from interactions between two rhizome connection states (unsevered/severed) and three defoliation regimes (non-defoliated, mildly-defoliated and heavily-defoliated). Defoliation affected rhizome growth and bud outgrowth, but had little effect on shoot growth. Mild and heavy defoliation exerted similar effects on rhizome growth. Only heavy defoliation significantly reduced bud outgrowth while mild defoliation did not. The fact that shoot growth did not change after defoliation and that the bud numbers remained unchanged after mild defoliation suggest that the compensatory response enable the species to tolerate grazing to some extent. Neither rhizome severing nor the interaction of rhizome severing and defoliation had effect on any tested variables. Lack of the effect of rhizome severing falsified the first half of our hypothesis, that is, clonal integration was unimportant in our experiment. The probable reasons were suspected to be the short duration of the experiment and/or the buffer effect of carbohydrate reserves in rhizomes for shoot growth and bud production in time of defoliation.     

Plastic responses of stem and leaf functional traits in Leymus chinensis to long-term grazing in a meadow steppe

植物对不同功能性状进行权衡, 通过表型可塑性达到对异质生境的适应是植物的一种生态对策。羊草(Leymus chinensis)是欧亚温带草原东缘的主要优势植物, 研究其对放牧的表型反应对揭示草原生态系统的放牧响应机制具有代表意义。该文以内蒙古呼伦贝尔草甸草原为例, 通过设置不同放牧压力与围封的长期试验, 研究了羊草茎叶功能性状对放牧的可塑性响应模式。结果表明: 1)与长期围封相比, 长期放牧导致羊草茎叶性状显著小型化, 其中, 株高和个体地上生物量分别降低76.82%和89.88%, 但3年短期围封对茎性状影响不显著, 说明羊草表型矮小化现象具有一定的保守性; 2)通过排序构建羊草性状可塑性变化谱, 发现茎质量、总质量、茎高、株高、叶面积等为对放牧响应的敏感性状, 而叶片数、茎粗、叶宽等较为稳定, 为惰性性状; 3)放牧干扰下, 羊草性状可塑性程度与其变异性之间符合y = y₀ + ae^bx拟合关系, 随着植物性状的响应强度增大, 其变异性增强; 4)偏最小二乘法分析发现茎长、株高、叶面积、叶长等性状的投影重要性指标大于1, 对地上生物量变化的解释率为68.6%, 是导致长期放牧下羊草个体生物量降低的主要因子。研究认为, 矮化型变是羊草的避牧适应对策, 在亚稳态下, 通过不同性状的权衡, 充分利用环境资源完成其生活史。     

Effects of grazing intensity and grazing exclusion on litter decomposition in the temperate steppe of Nei Mongol,China

Aims Grazing intensity and grazing exclusion affect ecosystem carbon cycling by changing the plant community and soil micro-environment in grassland ecosystems. The aims of this study were: 1) to determine the effects of grazing intensity and grazing exclusion on litter decomposition in the temperate grasslands of Nei Mongol; 2) to compare the difference between above-ground and below-ground litter decomposition; 3) to identify the effects of precipitation on litter production and decomposition. Methods We measured litter production, quality, decomposition rates and soil nutrient contents during the growing season in 2011 and 2012 in four plots, i.e. light grazing, heavy grazing, light grazing exclusion and heavy grazing exclusion. Quadrate surveys and litter bags were used to measure litter production and decomposition rates. All data were analyzed with ANOVA and Pearson’s correlation procedures in SPSS. Important findings Litter production and decomposition rates differed greatly among four plots. During the two years of our study, above-ground litter production and decomposition in heavy-grazing plots were faster than those in light-grazing plots. In the dry year, below-ground litter production and decomposition in light-grazing plots were faster than those in heavy-grazing plots, which is opposite to the findings in the wet year. Short-term grazing exclusion could promote litter production, and the exclusion of light-grazing could increase litter decomposition and nutrient cycling. In contrast, heavy-grazing exclusion decreased litter decomposition. Thus, grazing exclusion is beneficial to the restoration of the light-grazing grasslands, and more human management measures are needed during the restoration of heavy-grazing grasslands. Precipitation increased litter production and decomposition, and below-ground litter was more vulnerable to the inter-annual change of precipitation than above-ground litter. Compared to the light-grazing grasslands, heavy-grazing grasslands had higher sensitivity to precipitation. The above-ground litter decomposition was strongly positively correlated with the litter N content (R² = 0.489, p < 0.01) and strongly negatively correlated with the soil total N content (R² = 0.450, p < 0.01), but it was not significantly correlated with C:N and lignin:N. Below-ground litter decomposition was negatively correlated with the litter C (R² = 0.263, p < 0.01), C:N (R² = 0.349, p < 0.01) and cellulose content (R² = 0.460, p < 0.01). Our results will provide a theoretical basis for ecosystem restoration and the research of carbon cycling.     

Effects of fertilization on the relations of diameter at breast height between different-aged ramets of Phyllostachys edulis population

克隆植物不同年龄分株间可以通过生理整合作用相互传递资源, 实现资源共享。施肥可以改变林地资源状况, 进而可能影响分株间的整合作用及不同年龄分株间的生长关系。该文采用标准主轴(SMA)估计法和多元回归分析, 对不同施肥管理下大型克隆植物毛竹(Phyllostachys edulis)种群不同年龄分株(1年生分株、3年生分株和5年生分株)间的胸径(DBH)关系进行了研究, 探讨毛竹不同年龄分株DBH大小关系对施肥的响应。结果表明: 连续5年施肥有效地增加了毛竹1年生分株的DBH, 而施肥1年处理下, 1年生分株DBH与3年生分株和5年生分株平均DBH差异不显著(p > 0.05)。1年生分株与3年生分株和5年生分株DBH之间的SMA斜率为0.88-1.10, 均与1.00不存在显著差异(p > 0.05), 表现为等速生长关系。施肥1年和连续施肥5年没有改变不同年龄分株DBH之间的SMA斜率, 但连续5年施肥导致SMA的y轴截距显著增大(p < 0.001), 即在3年生分株和5年生分株DBH相同的情况下, 连续5年施肥使1年生分株具有更大的DBH增长量。采用多元线性逐步回归分析发现, 毛竹1年生分株的DBH大小在很大程度上受3年生分株DBH大小的影响, 而连续5年施肥可增强5年生分株对1年生分株DBH大小的影响。     

Correlation between vein density and water use efficiency of Salix matsudana in Zhangye Wetland,China

Aims The correlation between vein density and water use efficiency (WUE) affects the balance between water supply and demand of plant leaves, which is significant for comprehending the ecological adaptation strategies of plants. The objective of this study was to study how Salix matsudana modulated vein density and WUE along a soil moisture gradient in Zhangye Wetland, China. Methods The study was conducted in floodplain wetland near Heihe River in Zhangye City, Gansu Province, China. Three sample plots, at a spatial interval of 70 m, were set up along a soil moisture gradient ordinally from the area near the water body to the wetland edge, plot I (69.23%), spot II (48.38%) and spot III (35.27%). Community traits were investigated by using diagonal method, and all individuals of S. matsudana were used for measurements of height and canopy. At each plot, 5 individuals of S. matsudana at 4 vertices and diagonal intersection were selected for measurements of vein density, WUE, net photosynthetic rate (P_n), transpiration rate (T_r), photosynthetically active radiation (PAR), saturated vapor pressure differences (VPD), specific leaf area, stomatal conductance (G_s) and intercellular CO₂ concentration (C_i). We used mathematical methods of correlation analysis and standardized major axis to investigate relationships between vein density and WUE. Important findings With decreasing soil moisture, the height, canopy, specific leaf area, G_s and C_i of S. matsudana decreased gradually, while the vein density, WUE, P_n, T_r, PAR and VPD increased gradually. The correlation between vein density and WUE was positive in all the three plots, but the relationship varied along the soil moisture plots gradient. There was a highly significant positive correlation (p < 0.01) between the vein density and WUE at plot I and III, whereas the correlation only reached a significant level (p < 0.05) at plot II; The correlation coefficient between vein density and WUE is significantly smaller than 1 at plot I (p < 0.05), while the correlation coefficient is significant greater than 1 at plot II and III (p < 0.05). We can conclude that varied relationships between vein density and WUE of S. matsudana along a soil moisture gradient could reflect plant acclimation.     

鄂西南亚高山湿地泥炭藓的生长与分解

泥炭藓(Sphagnum)是湿地土壤碳的重要来源, 在土壤碳累积过程中发挥着关键作用, 但有关亚热带湿地泥炭藓生长与分解的研究鲜有报道。该研究选择鄂西南亚高山泥炭藓湿地为研究区域, 原位开展不同微生境泥炭藓的生长及其凋落物的分解实验, 室内测试凋落物的化学成分, 探讨亚热带亚高山湿地泥炭藓的生长与分解规律。结果表明: 泥炭藓在自然状态生长12个月后, 丘上和丘间两种微生境下泥炭藓的平均高度增长量分别为2.9和2.7 cm, 对应的净生产量分别为270.94和370.88 g·m ^-2, 生长时间与微生境对泥炭藓的高度增长量及净生产量均有显著影响, 且两者之间存在交互作用, 但是两种微生境下泥炭藓的生长变化过程不同; 两种微生境下泥炭藓的平均生长速率(2017年7-10月)为0.33 mm·d ^-1, 其生长速率高于寒温带地区。另外, 分解时间对泥炭藓的分解量有显著影响, 其残留率随时间增加表现为先减少后增加的趋势。12个月后, 丘间、丘上和水坑3种微生境下最终残留率分别为100.67%、90.54%和85.63%。凋落物中碳含量、碳氮比和多酚含量相比初始值均有所下降, 氮含量则为增加。同时, 微生境对凋落物分解的影响取决于分解时间。分解3个月时, 微生境之间凋落物的分解量差异显著, 其他时间段差异不明显。     

Chemical composition of volatiles from the syconia of Ficus microcarpa and host recognition behavior of pollinating fig wasps

Aims Chemical communication plays a key role in host plant recognition of pollinators. There are two recognized types of chemical communication between syconia and their pollinating fig wasps: one is “generalization”, of which the wasps respond to the relative ratio of multiple compounds, and the other is “specialization”, of which the key signal is a single uncommon, possibly unique, compound. The aims of this study were to identify the chemical composition of volatiles from the syconia of Ficus microcarpa at different developmental phases, and to determine if the signaling between F. microcarpa and its pollinating fig wasp, Eupristina verticillata, is of generalized type, or of specialized type.Methods The volatiles from syconia of F. microcarpa were extracted using solid-phase micro extraction (SPME) at different developmental phases (pre-female, female (before and after pollination), interfloral, male and postfloral phases) and the chemical compounds were identified by gas chromatography mass spectrometry (GC-MS). We then tested the behavioral responses of E. verticillata to fresh syconia at different developmental phases using two-choice olfactometers.Important findings There were 21 volatile compounds identified from the syconia at different developmental phases, which were mainly fatty acid derivatives, terpenoids and aromatic compounds. The components of the volatiles apparently differed among the developmental stages. The contents of terpenoids declined, but the contents of fatty acid derivatives increased, from before the pollination to after the pollination. Especially, the characteristic compounds of 2-heptanone and 3-octanone before the pollination disappeared, D-limonene decreased after the pollination, but copanene, cyclohexane and 2-hexenal increased. The results of the two-choice olfactometer experiment showed that the pollinating fig wasps had higher selection ratio to chemicals found in the female phase syconia than those in other phases; whereas the volatile compounds from the male phase syconia had the function pushing the pollinating fig wasps to leave the natal syconia so that there existed the “push-pull” responses by fig wasps to volatiles released by their host syconia. We conclude that there are multiple chemical compounds playing the roles in host recognition of pollinating fig wasp E. verticillata. The mutualistic relationship between F. microcarpa and E. verticillata is maintained by the chemical communication of “generalization” strategy.