Seed germination and seedling growth ofCarex doenitzii growing on alpine zone of Mt. Fuji

Carex doenitzii on the upper timberline of Mt. Fuji were studied to determine the effect of thermal conditions on their seed germination and seedling growth. Mature seeds collected at the end of the growing season were divided into five test groups, and each was germinated at constant temperature, the temperatures being 15 C, 20 C, 25 C, 30 C and 35 C. Seed germination percentage was highest (93%) at 25 C. Seedlings germinated at 25 C were grown in chambers at 15/10 C, 25/20 C and 35/30 C. Growth of seedlings was greatest at 25/20 C. The data suggest that the seed germination and seedling growth ofC. doenitzii occur only under limited conditions in the field.     

高寒矮嵩草草甸两种主要植物耐牧性的比较

通过野外控制实验,研究了刈割(留茬3 cm、留茬1 cm及不刈割)、施肥(施肥、不施肥)和浇水(浇水、不浇水)处理对高寒草甸矮嵩草(Kobresia humilis)和垂穗披碱草(Elymus nutans)补偿高度、株高相对生长率、比叶面积、叶片净光合速率和地上总生物量的影响.结果表明:2物种的株高和地上总生物量在刈割后均为低补偿响应,但其株高相对生长率显著提高,并均随年份而增加;垂穗披碱草比叶面积、叶片净光合速率和地上总生物量对刈割损伤更加敏感;尽管施肥能显著提高2物种上述各项指标,但在不同处理条件下矮嵩草的耐牧性指数均小于垂穗披碱草;浇水的作用不显著.说明2物种的耐牧性依赖于土壤养分资源获得性,矮嵩草的耐牧性强于垂穗披碱草.     

高寒草甸生态系统牲畜种群结构和动态

本文用Leslie矩阵模型研究了高寒草甸生态系统牲畜种群结构及动态。模型考虑了更加精确的年龄组转移关系,出栏率是种群波动的主要因子。目前,牲畜种群结构不合理,种群数量不能保持平衡。     

Performance of two alpine plant species along environmental gradients in an alpine meadow ecosystem in central Tibet

Understanding how biotic interactions and abiotic conditions affect plant performance is important for predicting changes in ecosystem function and services in variable environments. We tested how performances of Astragalus rigidulus and Potentilla fruticosa change along gradients of biotic interactions (represented by plant species richness, abundance of the dominant plant species Kobresia pygmaea, and herbivory intensity) and abiotic conditions (represented by elevation, aspect, and slope steepness) across a semi-arid landscape in central Tibet. Redundancy analyses showed that the biotic variables explained 30 and 39 % of the variation in overall performance of A. rigidulus (P = 0.03) and P. fruticosa (P = 0.01), respectively. Abiotic variables did not contribute significantly to variation among A. rigidulus populations. Plant size decreased with species richness in both species and was larger on south- rather than north-facing slopes. Reproductive effort for both species was significantly negatively related to the abundance of K. pygmaea and both species had larger reproductive effort on south- rather than north- and west-facing slopes. The proportion of biomass allocated to sexual reproduction in P. fruticosa was negatively correlated with K. pygmaea abundance and herbivory intensity. The population density of P. fruticosa was positively related to elevation, species richness, and K. pygmaea abundance. We conclude that plant performance at a local scale was more strongly related to biotic than abiotic conditions, but different components of plant performance responded differently to predictor variables and the responses were species-specific. These findings have important implications for rangeland management under changing environmental conditions.     

高寒草甸地下根系生长动态对积雪变化的响应

2013年11月至2014年8月在青藏高原东缘红原县高寒草甸通过人工堆积的方法,进行了积雪量野外控制试验。以自然降雪的积雪量为对照(CK),设置了S1、S2和S3(积雪量分别为自然对照的2倍、3倍和4倍)3个处理,运用微根窗法追踪研究了积雪量改变后高寒草甸植被根系生长动态,并测定了积雪变化对土壤温度的影响。结果表明:高寒草甸植被根系生长存在明显的季节性变化,随着时间的推移,根系表面积、根尖数量及现存量逐渐增加并在8—9月达到最大值;当冬季积雪量达到143.4mm(S1),对根系生长最为有利(根系表面积、根尖数量、现存量及生产量最大),根系生长旺盛期(净生产速率较高)有所提前和延长,但随着积雪量进一步增加,积雪对根系生长的正效应逐渐降低,根系生长旺盛期逐渐推迟甚至消失;研究还发现,随着积雪量增加,0—10 cm土层土壤温度逐渐降低,相似的变化规律也出现在10—20 cm土层,但在时间上有所延迟;相关性分析表明,在不同土层中,根系生长与土壤温度均呈正相关。因此,积雪变化通过改变土壤温度影响高寒草甸植物根系的生长发育,最终可能会影响高寒草甸生态系统的碳分配与碳循环过程。     

Differentiation of vegetation zones and species strategies in the subalpine region of Mt. Fuji

The floristic and structural differentiation of vegetation along the altitudinal gradient in four subalpine forests of different developmental stages on Mt. Fuji has been studied. Near the forest limit a micropattern of vegetation corresponding to the altitudinal zonation has been observed which elucidated the mechanisms of development of the vegetation zonation. As to early stages of vegetation development only two types can be distinguished: the volcanic desert above 1500 m and the pioneer forests below. As to later stages a differentiation of subzones includes from higher to lower altitudes: the Alnus maximowiczii, Betula ermanii, Abies veitchii and Tsuga diversifolia forests. Larix leptolepis and Sorbus americana ssp. japonica, appear as co-dominants in ecotonal communities between the principal subzones and are also important pioneers in early stages. Similarity analyses reveal that the upper subalpine Alnus-Betula forests can be regarded as early successional phases of the climax Abies-Tsuga forests of the lower subalpine zone. The regular arrangement of A. maximowiczii-B. ermanii-A. veitchii is studied along the gradient from the margin to the interior of the forest growing near the forest limit where locally favourable conditions prevail. Growth form, height growth, photosynthetic activity, seed supply, and seedling distribution of the three principal species have been compared, as well as biomass and production relations in contiguous forests of these species. The marginal Alnus type community is productive and disturbance-tolerant, and has a wide ecological and sociological amplitude along the gradient, while the central Abies community is accumulative and disturbance-intolerant, and has a narrower tolerance range, but is superior in competition under stable habitat conditions. A vegetation organization, ‘temporal multi-storeyed structure’, is suggested which means that a zonal pattern of vegetation within a climax region develops by successive replacement of successional species along an environmental gradient.     

Ectomycorrhizal fungi associated with two species of Kobresia in an alpine meadow in the eastern Himalaya

The diversity of ectomycorrhizal fungi (EMF) on Kobresia filicina and Kobresia capillifolia in an alpine meadow in China’s southwestern mountains, one of the word’s hotspots of biodiversity, was estimated based on internal transcribed spacer rDNA sequence analysis of root tips. Seventy EMF operational taxonomical units (OTUs) were found in the two plant species. Dauciform roots with EMF were detected in species of Kobresia for the first time. OTU richness of EMF was high in Tomentella/Thelophora and Inocybe, followed by Cortinarius, Sebacina, the Cenococcum geophilum complex, and Russula. Tomentella/Thelophora and Inocybe were general and dominant mycobiont genera of the two sedges. Besides the C. geophilum complex, the ascomycete components Hymenoscyphus and Lachnum were also detected on the two plants. Alpine plants in different geographical regions share similar main genera and/or families of EMF while harboring predominantly different mycobiont species; most of the members detected by us have not been found elsewhere. Significant differences in the profile of EMF occurrences were not found between the two plant species and among the three sampling seasons in our sample size.     

Shoot growth dynamics and photosynthetic response to increased nitrogen availability in the alpine willow Salix glauca

Plants subjected to increases in the supply of resource(s) limiting growth may allocate more of those resources to existing leaves, increasing photosynthetic capacity, and/or to production of more leaves, increasing whole-plant photosynthesis. The responses of three populations of the alpine willow, Salix glauca, growing along an alpine topographic sequence representing a gradient in soil moisture and organic matter, and thus potential N supply, to N amendments, were measured over two growing seasons, to elucidate patterns of leaf versus shoot photosynthetic responses. Leaf-(foliar N, photosynthesis rates, photosynthetic N-use efficiency) and shoot-(leaf area per shoot, number of leaves per shoot, stem weight, N resorption efficiency) level measurements were made to examine the spatial and temporal variation in these potential responses to increased N availability. The predominant response of the willows to N fertilization was at the shoot-level, by production of greater leaf area per shoot. Greater leaf area occurred due to production of larger leaves in both years of the experiment and to production of more leaves during the second year of fertilization treatment. Significant leaflevel photosynthetic response occurred only during the first year of treatment, and only in the dry meadow population. Variation in photosynthesis rates was related more to variation in stomatal conductance than to foliar N concentration. Stomatal conductance in turn was significantly related to N fertilization. Differences among the populations in photosynthesis, foliar N, leaf production, and responses to N fertilization indicate N availability may be lowest in the dry meadow population, and highest in the ridge population. This result is contrary to the hypothesis that a gradient of plant available N corresponds with a snowpack/topographic gradient.     

Interactions of plant species mediated plant competition for inorganic nitrogen with soil microorganisms in an alpine meadow

The aim of the present work was to evaluate the effects of regulated deficit irrigation (RDI) applied in the post-harvest stage of peach trees. The 3-year trial was carried out in Italy (N 40°20′, E 16°48′) on mature peach plants (cv “Springcrest”) trained to transverse Y. From bud break to harvest, irrigation was carried out by applying 100% ET_c, while from harvest to early autumn, plants were separated into three groups and subjected to different irrigation treatments (100, 57 and 34% ET_c). The decrease in soil water content caused a reduction in the values of tissue water potential and gas exchange both in 57% ET_c and 34% ET_c treatments. RDI determined the reduction in the growth of waterspouts and lateral shoots but did not influence the growth of fruiting shoots. During the trial, no significant reductions in crop yield and quality were observed in the 57% ET_c treatment, whereas about 1,100, 1,800 and 2,500 m³ ha⁻¹ of water were saved in the first, the second and the third year, respectively. In the second year of the trial, the use of RDI in the post-harvest stage determined carbohydrate and nitrogen accumulation in roots, branches, shoots and floral buds. The results demonstrate that, under scarce water supply conditions, a clear benefit can be obtained through the use of RDI during the post-harvest stage. This confirms the possibility to reduce the irrigation water by applying RDI during phenological stages less sensitive to water deficit without negatively affecting peach growth and yield.     

土壤盐分对高寒草甸主要植物生态位的影响

采用Levins生态宽度指数和Cowell生态位相似性公式,计算了巴音布鲁克高寒草甸主要物种在4个盐分梯度上土壤水分、有机质、速效钾3个资源维的生态位宽度及生态位相似性.结果表明：在3个资源维上,随着土壤盐分含量的增加,主要建群种细果苔草的平均生态位由0.4433降至0.1740,伴生种鹅绒委陵菜的平均生态位由0.1263升至0.2215,说明耐盐性较差的物种生态位宽度逐渐减小,耐盐性较好的物种逐渐增大,可能成为重要的演替种.随土壤盐分含量的增加,耐盐性较差物种间的生态位相似性逐渐升高, 而耐盐性较好的物种则逐渐降低.细果苔草和线叶嵩草的生态位相似比例由0.701升至0.842, 而鹅绒委陵菜和山地蒲公英的生态位相似比例由1降至0.708.物种的生物学特性是物种对土壤盐分响应不同的主要原因.     

小五台山亚高山草甸物种分布与温度关系研究

通过转化糖方法、植物群落野外调查和实验室分析,分别测得生境效应温度、物种盖度和生物量,应用该数据分析小五台山亚高山草甸植物物种分布与温度的关系.结果表明,在记录到的97种维管植物中,约36%的物种分布受生境温度条件影响,约20%物种的相对盖度与温度变化呈显著相关.生物量或相对盖度与温度呈正相关的有11种植物,相对盖度与温度呈负相关的有8种植物.在物种分布与温度关系的研究中,对频度为90%～20%的物种,采用盖度指标进行分析通常可行,对频度大于90%的物种,采用生物量数据比盖度更为有效.     

Ecological studies on the timberline of Mt. Fuji

The distribution of the meadow above the timberline and the structure of the forest at and below the timberline were investigated on the southeast slope of Mt. Fuji. At the same time, soil profiles, water content and nutrients in the soil as related to change in the structure of the plant community were examined to obtain the data regarding soil development with the course of succession. In the course of change in structure of forest, the plant community was classified into three types:Salix/Alnus dwarf forest,Larix forest andAbies/Picea forest. The change in the soil profile, from immature to mature soil, was observed. At the timberline the water content increased rapidly from about 10% of bare land to about 25% of timberline. The nitrogen and carbon contents also increased at timberline as compared with bare land. Relationships between successional stage and soil development were clarified on the area from bare land to climax forest. The present state of the timberline at the investigated area is discussed with reference to the course of change in forest structure and soil development. It was concluded that the timberline of the investigated area is in the process of moving to a higher altitude. This conclusion was reasonable in view of the factor of air temperature.     

Warming and grazing interact to affect root dynamics in an alpine meadow

Plant and Soil - Arbuscular Mycorrhizal Fungi (AMF) are ubiquitous soil microorganisms playing a vital role in the functioning of agricultural ecosystems. Although AMF are generally considered to...     

Ecological studies on the timberline of Mt. Fuji

An ecological study of dry matter production was made in a dwarf forest dominated byAlnus maximowiczii at the timberline of Mt. Fuji. Annual gross production was estimated by two methods, namely the summation method using stem analysis and total photosynthesis calculated from leaf area and photosynthetic rate per leaf area. Seasonal changes in relative light intensity and in leaf area were measured in a quadrat. Photosynthesis and respiration rates of samples were measured in temperature-regulated assimilation chambers. The phytomass was 2,989 g d.w.m^?2, and those of stems and branches, leaves, and roots were 1,672 g, 293 g, and 1,024 g respectively. The growing period of this plant was about four months and this plant expanded leaves quickly. The maximum gross photosynthetic rate was 21 mg CO₂dm^?2 h^?1 on September 1. Annual net production estimated by examining the annual rings was 922 g d.w.m^?2 year^?1 and annual respiration was 735 g. Annual gross production estimated from photosynthetic rates was 1,747 g d.w.m^?2 year^?1. The sum of annual net production by stem analysis and respiration agree closely with gross production estimated from photosynthetic rate. Gross production of this dwarf forest is comparable to the beech forest of the upper cool temperate zone owing to the high photosynthetic rate ofAlnus maximowiczii.     

放牧强度对川西北高山草甸两个优势物种凋落物分解的影响

研究了川西北高山草甸两个优势物种垂穗鹅冠草(Roegneria nutans)和四川嵩草(Kobresia setchwanensis)凋落物在不同放牧强度下的分解及其碳氮损失率。经过一年的分解,放牧不同程度地加速了两种凋落物的分解。垂穗鹅冠草凋落物在不放牧、轻牧、中牧和重牧草地的失重率分别为26.0、27.2、29.6和32.8%;川嵩草凋落物的失重率分别为44.0,46.2,50.4和56.2%。不放牧、轻牧、中牧和重牧草地垂穗鹅冠草凋落物碳的损失率分别为26.1%、27.5%、29.4%和32.9%,氮的损失率分别为13.6%、14.4%、17.3%和19.1%;川嵩草凋落物碳的损失率分别为41.9%、44.3%、48.5%和54.4%,氮的损失率分别为39.4%、41.4%、46.4%和52.8%。研究表明,增加的放牧强度加快了两种凋落物的分解速率,加速了凋落物中碳氮的释放;同时也表明,川嵩草凋落物的分解速率要快与垂穗鹅冠草凋落物。     

Ecological studies on the timberline of Mt. Fuji

To compare the nutrient economy of woody plants at timberline of Mt. Fuji, seasonal changes in nitrogen content in leaves were examined. There was remarkable difference in seasonal changes in leaf nitrogen content betweenAlnus maximowiczii and other deciduous trees at same habitat.A. maximowiczii scarcely withdrew the leaf nitrogen to woody part during the shedding period, while the other species withdrew about half of the leaf nitrogen to woody part.     

刈割和施肥对高寒草甸物种多样性和功能多样性时间动态及其关系的影响

强烈扰动和环境胁迫对植物群落的物种多样性(SD)和功能多样性(FD)有重要影响, 但SD和FD随时间的变化模式及其关系至今少有研究。该研究通过对高寒矮生嵩草(Kobresia humilis)草甸为期7年(2007-2013年)的刈割(3个水平: 不刈割、留茬3 cm和留茬1 cm)和施肥(2个水平: 施肥和不施肥)控制实验探讨了SD和FD随时间的变化模式及其关系。研究结果显示: (1)刈割显著增加了SD和FD, 施肥处理则降低了SD, 对FD增加仅有微弱影响; (2)各处理群落的SD随着时间而下降, FD则随时间增加; (3)随着刈割强度的增加, SD(x)-FD(y)关系由正线性相关变为无相关, 斜率大小为slope_l ≥ slope_m > slope_h (下标l、m和h分别表示轻度、中度和重度扰动强度), 施肥并不会改变此关系形式和斜率; (4)刈割与施肥对SD和FD的互作效应都不显著, 且不施肥群落SD(x)-FD(y)关系的斜率也为slope_l ≥ slope_m > slope_h。上述结果说明, 刈割并不一定导致植物功能性状的趋同构建, 也能引发趋异构建, 而施肥引起的强烈种间竞争也并未显著增强趋异构建过程, 这与植物群落构建理论的预测不完全一致。与施肥相比, 刈割扰动是决定群落中SD-FD时间关系形式的主要因素, 并决定着SD-FD关系斜率的变化。     

高寒草甸不同生境粗喙薹草补偿生长研究

补偿生长反映了植物的耐牧性, 受采食和土壤养分资源获得性的共同影响。但何种条件易于引起植物发生超补偿是长期以来争论的问题。通过一项野外调查试验, 研究了高寒矮嵩草(Kobresia humilis)草甸3种生境(I. 畜圈, 富养, 放牧; II. 牧道, 低养, 放牧; III. 封育草地, 低养, 不放牧)中粗喙薹草(Carex scabrirostris)的补偿生长模式与机制, 以及采食率、土壤养分和水分因子对补偿生长的相对贡献。粗喙薹草补偿生长量和分株盖度、密度及高度在生境I显著高于生境II和生境III, 在生境I和生境II均发生超补偿生长, 在生境III为低补偿。分株生物量对生长器官的分配在生境I和生境II相同, 并都高于生境II; 生物量对储藏器官的分配在生境II最高, 生境III次之, 生境I最低。储藏分配与生长分配和克隆繁殖分配间, 生长分配与有性繁殖分配间均存在负偶联(trade-offs)关系。对补偿生长贡献最大的因子是相对生长率和6月份土壤有机质含量, 其次是8月份土壤氮素营养和采食率。研究结果表明, 粗喙薹草的补偿生长和生物量分配具有可塑性, 并决定着补偿生长模式随生境条件而变化。不论在富养环境或低养环境, 储藏分配高的粗喙薹草都容易发生超补偿, 富养生境条件能降低采食的负面效应, 增加植物的耐牧性。