Fungal and bacterial biomass in tundra soils along an arctic transect from Taimyr Peninsula, central Siberia

Microscopic analyses of tundra soils from northern central Siberia, Taimyr Peninsula (74.5°N, 98.5°E) were performed in order to investigate spatial variation of fungal and bacterial biomass. Biomass figures of fungi and bacteria (µg C g^-1 dry wt.) were measured from 11 permafrost soil pits. Fungal biovolume of up to 3.5 mm³ g^-1 dry wt. (median 0.19 mm³ g^-1 dry wt.) and a maximum hyphal length of 393 m g^-1 dry wt. (median 21 m g^-1 dry wt.) were determined. Fungal biomass was found up to 455 µg C g^-1 dry wt. (median 24 µg C g^-1 dry wt.). The amounts generally decreased with depth but increased within organic horizons. Little fungal biomass was found in the unvegetated soils or deep horizons above the permafrost table. Bacterial counts ranged from 0.16 to 7.38*10⁹ g^-1 dry wt. and bacterial biomass ranged from 0.68 to 20.38 µg C g^-1 dry wt. (median 6.19 µg C g^-1 dry wt.) because of small cell volume (median 0.04 µm³). Microbial biomass was generally dominated by fungi as shown by the ratio of fungal to bacterial biomass, which was between 0 and 174.1 (median 4.5). Plant cover and soil organic matter content were found to be the important keys in understanding microbial ecology in arctic tundra soils.     

Microplankton and primary production in the Sea of Okhotsk in summer 1994

Phytoplankton composition, density, vertical distribution andprimary production were investigated in the Sea of Okhotsk andin the adjacent northern north Pacific in July–August1994, together with measurements of density and distributionof planktonic microheterotrophs: bacteria, nanoheterotrophsand ciliates. Different phases of phytoplankton seasonal successionwere encountered during the period of investigation in variousregions of this sea. Primary production measured at 144 stationswas found to be greatest (1.5–4 g C m^-2day^-1) in areasof spring-phase succession along the Sakhalin shelf and theKashevarov bank. Periodic relapses of the spring blooms of ‘heavy’diatoms during the whole growth season were recorded over thisbank. The summer phase of the phytoplankton minimum prevailedin the central and eastern parts of the sea, manifested by thedominance of nanoflagellates in terms of phytoplankton biomass.Primary production was 0.5–1 g C m^-2 day^-1. The earlyautumn phase of succession was typical of the Kurile straitarea and the adjacent north Pacific. Primary production therevaried from 0.7 to 2 g C m^-2 day^-1. The integrated phytoplanktonbiomass in the water column varied from 9–12 g m^-2 inzones supporting the summer minimum assemblage to 15–20g m^-2 in zones of early autumn recovery of phytoplankton growth,and up to 40–70 g m^-2 in areas of remnant or relapseddiatom blooms. The numerical density of bacterioplankton wasbetween 1 x 10⁶ and 3 x 10⁶ cells ml^-1 and its wet biomass wasbetween 100 and 370 mg m^-3. In deep waters it was 8–15mg m^-3. The integrated bacterioplankton biomass in the upperwater column varied from 6 to 29 g m^-2. The numerical densityof zooflagellates varied in the upper layer between 0.8 x 10⁶and 4 x 10⁶ l^-1 and their biomass was between 20 and 50 mg m^-3.In deep waters they were still present at a density of 0.05x 10⁶ to 0.2 x 10⁶ cells l^-1. The biomass of planktonic ciliatesvaried between stations from 20 to 100 mg m^-3. The joint biomassof planktonic protozoa in the water column was between 3 and12 g m^-3 at most of the stations.     

The annual cycle of planktonic ciliates in nearshore waters at Signy Island, Antarctica

The abundance and biomass of marine planktonic ciliates in BorgeBay, Signy Island, were determined at monthly intervals betweenApril 1990 and June 1991. At least 24 different ciliate taxawere recorded from samples preserved in Lugol's iodine, includingthe tintinnids Codonellopsis balechi, Cymalocylis convallaria,Laackmaniella naviculaefera and Salpingella sp., and the aloricatetaxa Didinium sp. and Mesodinium rubrum. Ciliate abundance andbiomass exhibited a clear seasonal cycle with high values duringthe austral summer and low values in the austral winter. Abundanceranged from 0.3 10³l^–1 in September to 2.3 10³l^–1in January, while biomass ranged from 0.5 µg C l^–1in October to 12.6 µg C l^–1 in December. Small ciliatesdominated abundance throughout the year, and biomass duringwinter. Larger ciliates contributed most to biomass during summer.Aloricate ciliates were common throughout the year, while tintinnidscontributed substantially to abundance and biomass only duringsummer. Salpingella sp. was the commonest tintinnid, but C.convallariacontributed most to tintinnid biomass. The seasonal patternof ciliate abundance and biomass matched that of chlorophylla concentration and bacterial biomass, suggesting tight trophiccoupling between ciliates and other components of the pelagicmicrobial community. ¹Present address: Scott Polar Research Institute, Universityof Cambridge, Lensfield Road, Cambridge CB2 1ER, UK     

江西千烟洲人工针叶林下狗脊蕨群落生物量

 根据野外调查和实验分析研究了江西省千烟洲人工针叶林下狗脊蕨（Woodwardia japonica）群落的生物量、细根生物量、净初级生产力(Net primary productivity, NPP)、 比叶面积（Specific leaf area, SLA） 和叶面积指数（Leaf area index, LAI）等。通过叶片参数和地上生 物量的相关关系建立了狗脊蕨单株地上生物量估算模型,分别 为W1=0.021H^1.545（R²=0.790）和W1=2.518（D²H）^{0 .616}（R²=0.894;H为株高 ,D为地径）。人工针叶林下灌草层地上生物量为367.8 g&;#8226;m^－2（52～932 g&;#8226;m^－2）,凋落物为1 631 g&;#8226;m^－2（672～2 763 g&;#8226;m^－2）,分别占 乔木层地上生物量的4.7%（1.55%～13.2%）和20.7%（7.6%～32.1%）。狗脊蕨群落地上生物量和NPP分别为266.6 g&;#8226;m^－2和88.67 g&;#8226;m^－2&;#8226;a ^-1 ,其中狗脊蕨种群占73.7%;地下生物量为212.6 g&;#8226;m^－2。狗脊蕨的SLA和叶干物质含量（Leaves day mutter content, LDMC）分别为144.0 cm²&;#8226;g^-1和31.99%,二者之间呈显著负相关;最佳叶面积估算模型为S=21.922 6-0.152L²+0.000 9L³（9.0≤L（叶片长度）≤23.5;1.4≤W （ 叶片宽度）≤5.9）。狗脊蕨种群的LAI为1.8。土壤含水量对狗脊蕨生物量有显著影响。群落生物量与土壤有机质和全氮含量正相关     

Abundance and productivity of heterotrophic nanoplankton in Georgia coastal waters

The population abundances and rates of biomass production ofheterotrophic nanoplankton (HNAN) in Georgia coastal waterswere evaluated by epifluorescence microscopy. HNAN populations(mostly non-pigmented microflagellates <10 µm in diameter)ranged from 0.3 x 10³ cells ml^–1 in shelf waters 15 kmoffshore to 6.3 x 10³ cells ml^–1 in waters 0.25 km fromthe coast. There was a strong correlation (r = 0.83) betweenHNAN and free bacterioplankton population abundances, but noapparent relation (r = 0.38) between HNAN and phototrophic nanopLankton(PNAN) abundances. HNAN biomass production in estuarine andnearshore shelf waters, as estimated from increases in HNANpopulations during laboratory incubations of natural water samples,ranged from 0.10 to 0.79 mg C m^–3 h^–3, with populationgeneration times of 9.7 to 26.5 h. There was a significant linearrelation (r = 0.95) between HNAN biomass and HNAN productivity.We calculated that HNAN may graze at least 30% to 50% of dailybacterioplankton production in Georgia coastal waters.     

Density and distribution of bacterioplankton and planktonic ciliates in the Bering Sea and North Pacific

The total number of planktonic bacteria in the upper mixed layerof the Bering Sea during the late spring-early summer periodranged between 1 and {small tilde}4 x 10⁶ ml^–1 (biomass10–40mg C m^–3). In the northern Pacific, along 47–52⁶N,the corresponding characteristics of the bacterioplankton densityin the upper mixed water layer were: total number 1–2x 10⁶ cells ml^–1 and biomass 15–46mg C m^–3Below the thermocline at 50–100 m, the density of bacterioplanktonrapidly decreased. At 300 m depth, it stabilized at 0.1–0.2x 106 cells ml^–1. The integrated biomass of bacterioplanktonin the open Bering Sea ranged between 1.2 and 3.6 g C m^–2(wet biomass 6–18 g m^–2) Its production per dayvaried from 2 to 23 mg C m^–3 days^–1 in the upper0–100 m. The numerical abundance of planktonic ciliatesin this layer was estimated to be from 3 to l0 x 10³ cells l^–1,and in the northern Pacific from 0.4 to 4.5 x 10³ l^–2.Their populations were dominated by naked forms of Strombidium,Strombilidium and Tontonia. In some shelf areas, up to 40% ofthe total ciliate population was represented by the symbioticciliate Mesodinium rubrum. The data on the integrated biomassof basic groups of planktonic microheterotrophs are also presented,and their importance in the trophic relationships in pelagiccommunities of subarctic seas is discussed.     

测定潜流人工湿地根系生物量的新方法

设计了一种新方法研究潜流人工湿地植物根系的分布和生物量。采用自制的圆柱形的不锈钢网柱,安放在潜流湿地的碎石基质中,定期分层取出网柱内的碎石,可观察根系的分布特点;收获网柱内的根,可测定根系的生物量和生长量。网柱的直径20cm,高50cm,网孔直径1．80cm,不锈钢丝粗1．38mm。安装时,使网柱垂直,上端达碎石表面,下端靠近湿地床底。安装好后,装入碎石基质,观察测定时,把基质取出,观察完后,再把基质放回。用该方法,对碎石基质的潜流人工湿地中植物根系的分布和生物量进行了1a的实验测定,认为该方法是测定潜流人工湿地根系生长和分布的有效方法,它易于安装、测定方便、准确。7月和12月份两次测定的湿地根系生物量之和为331．8gm^-2,其中分布于0—5cm的根生物量为174．4gm^-2,5～15cm为142．1gm^-2,15cm以下为15．3gm^-2。种问根系生物量的差异很大,根系生物量最大的是美人蕉,为182．4gm^-2,最小的是水鬼蕉,为1．38gm^-2。根生物量似乎呈不同的季节格局,象草7月份根系生物量较大,而其他种12月份的较大。不同种根系生物量的垂直分布也有显著的差异,具根状茎的芦苇和较粗根的水鬼蕉以直径大于1mm的根为主,它们的根分布较深,而浅层根较少;象草、美人蕉和风车草,直径1mm以内的根占根生物量的80％以上甚至100％,它们的根分布较浅。     

松嫩盐碱草地西部的植物群落特征与土壤因子动态关系分析

应用逐步回归法,分析了5~9月松嫩盐碱草地植物群落的生物量、丰富度、多样性和均匀度与同月土壤因子间的关系。松嫩盐碱草地植物群落特征受若干土壤因子的共同影响,不同月份影响因子的变化较复杂。5~7月土壤盐分和养分共同影响着松嫩盐碱草地植物群落生物量,但是土壤盐分因子与群落生物量的相关性更明显（5月的Ca²⁺质量分数,6月和7月的Mg²⁺质量分数）。土壤盐分因子在整个生长季内对松嫩盐碱草地植物群落生物量的直接作用都大于土壤养分因子的。6月时影响松嫩盐碱草地植物群落丰富度、Simpson指数和Shannon指数的土壤养分因子增加,其中土壤全氮质量分数的直接作用是所有土壤因子中最大的。8月植物群落生物量、Simpson指数和Shannon指数仅受土壤盐分因子影响,其中生物量与土壤pH值以及Simpson指数与土壤碱化度都是极显著负相关,Shannon指数与土壤含盐量显著负相关。6~9月的松嫩盐碱草地植物群落均匀度也同时受土壤养分和盐分因子的作用,其中6月和9月时土壤盐分因子对群落均匀度的直接作用更突出。生长末期（9月）松嫩盐碱草地植物群落生物量与土壤因子间的关系以及生长初期（5月）植物群落均匀度与土壤因子间的关系都不明显。     

川中丘陵区水稻田土壤呼吸及其影响因素

基于川中丘陵区2003年4~9月水稻田土壤呼吸、土壤温度和水稻(Oryza sativa)生物量的测定,研究了水稻田土壤呼吸日变化和季节变化特征以及影响稻田土壤呼吸的主要因素。结果表明,水稻田土壤CO₂排放通量的日变化为单峰型,其最小值和最大值分别出现在当地时间7∶00和15∶00;在水稻生长期内,稻田土壤CO₂排放通量在18.00~269.69 mg·m^-2·h^-1之间波动,平均排放通量为121.76 mg·m^-2·h^-1。在日的时间尺度上,水稻田土壤CO₂排放通量与5 cm土壤温度存在显著的指数函数关系;而从整个生长期时间尺度上看,水稻田土壤CO₂的排放通量主要受到5 cm土壤温度和水稻地下生物量的影响。在水稻生长初期,水稻地下生物量与稻田土壤CO₂排放通量之间存在着显著的相关关系;水稻拔节中后期到成熟期,土壤温度则是制约稻田土壤CO₂排放的关键因素。CO₂排放通量与稻田地表水层深度的相关关系不显著。     

千烟洲针叶林的比叶面积及叶面积指数

根据实测数据计算了湿地松(Pinus elliotii)、马尾松(P. massoniana) 和杉木(Cunninghamia lanceolata)不同年龄、不同类型叶片的生物量和比叶面积,并结合样地调查数据和相对生长方程计算了中国科学院千烟洲试验站20年生湿地松林、马尾松林、杉木林和针叶混交林的叶面积指数。根据拟合结果,选择如下方程计算3个树种的叶生物量:湿地松W=12.074 1D^{2.151 5}、马尾松W=6.972 7D^{2.197 3}和杉木W=5.261 9D^{2.302 7}。湿地松林的叶生物量(0.822 kg·m^-2)最大,其次为针叶混交林(0.679 kg·m^-2),马尾松林和杉木林相差不大(分别为林0.528和0.572 kg·m^-2)。不同树种、不同年龄、不同类型叶片的比叶面积比较发现,新叶的比叶面积大于老叶,三针一束叶的比叶面积略大于两针一束叶,马尾松的平均半比表面积(8.62 m²·kg^-1)大于湿地松(6.04 m²·kg^-1)和杉木(7.91 m²·kg^-1)。胸径与单木叶片半表面积之间的经验方程为:湿地松LA=0.073D^{2.151 5}、马尾松LA=0.060D^{2.197 3}和杉木LA=0.042D^{2.302 7}。据此计算湿地松林的叶面积指数为5.03,马尾松林和杉木林为4.31,针叶混交林为4.77,该结果比利用CI-110植被冠层数字图像仪测得的结果偏大。     

西双版纳热带季节雨林的生物量及其分配特征

 根据3块1 hm² 样地的调查资料,利用123株样木数据建立以胸径(D)为单变量的生物量预测方程。采用样木回归分析法(乔木层、木质藤本)和样 方收获法(灌木层、草本层), 获取西双版纳热带季节雨林的生物量,并分析了其组成和分配特征。结果表明,西双版纳热带季节雨林的总生物 量为423.908±109.702 Mg•hm^－2(平均值±标准差,n=3) ,其中活体植物生物量占95.28%,粗死木质残体占4.07%,地上凋落物占 0.64%。在 其层次分配方面：乔木层优势明显,占98.09%±0.60%;其次为木质藤本,占0.83%±0.31%;灌木层和草本层生物量均小于木质藤本的生物量; 附生植物最低,仅为0.06%±0.03%。总生物量的器官分配以茎所占比例最高,达68.33%;根、枝、叶的比例分别为18.91%、11.07%和1.65 %。 乔木层生物量的径级分配主要集中于中等径级和最大径级。大树(D＞70 cm)具有较高的生物量,占整个乔木层的43.67%±12.67%。树种分配方 面,生物量排序前10位的树种占乔木层总生物量的63.43%±4.09%,生物量集中分配于少量优势树种。西双版纳热带季节雨林乔木层叶面积指数 为6.39±0.85。西双版纳热带季节雨林乔木层的地上生物量位于世界热带湿润森林的中下范围。     

Size-fractionated Primary Production in the South Atlantic and Atlantic Sectors of the Southern Ocean

Results are presented from size fractionated chlorophyll a (Chla) and primary production studies along a transect between Antarcticaand southern Africa during the second South African AntarcticMarine Ecosystem Study (SAAMES II), conducted in late australsummer (January to February) 1993. Total integrated Chl a alongthe transect was highest in the vicinity of the Marginal IceZone (MIZ) and Antarctic Polar Front (APF). At these stations,integrated Chl a biomass was always >25 mg Chl a m^–2and was dominated by microphytoplankton. Although nominal increasesinChl a biomass were also associated with the Subantarctic Front(SAF) and Subtropical Convergence (STC), total Chl a biomassin these regions was dominated by nanophytoplankton. Withinthe inter-frontal regions, total integrated Chl a biomass waslower, generally <25 mg Chl a m^–2, and was always dominatedby nanophytoplankton. An exception was found in the AgulhasReturn Current (ARC) where picophytoplankton dominated. Totaldaily integrated production along the transect ranged between60 and 436 mg C m^–2 day^–1. Elevated production rateswere recorded at stations occupied in the vicinity of the MIZand at all the major oceanic frontal systems. The contributionsof the various size fractions to total daily production displayedthe same spatial pattern as integrated biomass, with microphytoplanktonbeing the most important contributor in areas characterizedby elevated phytoplankton biomass. Outside these regions, nanophytoplanktondominated the total phytoplankton production. Again, an exceptionwas found in the ARC north of the STC where picophytoplanktondominated total production. There, the lowest production alongthe entire transect was recorded, with total daily integratedproduction always <90 mg C m^–2 day^–1. The increasedproduction rates recorded in the MIZ appeared to result fromincreased water column stability as indicated by a shallow mixed-layerdepth. Within the inter-frontal regions, the existence of adeep mixed layer appeared to limit phytoplankton production.Low silicate concentrations in the waters north of the APF mayalso have limited the growth of large microphytoplankton.     

模拟氮沉降对湿地植物生物量与土壤活性碳库的影响

在两种水分条件下(W₁:非淹水,W₂:淹水)分4个氮处理(分别相当于氮沉降率0、1、3、5 g N·m^-2·a^-1)模拟了三江平原典型湿地植物湿草甸小叶章(Deyeuxia angustifolia)植株及土壤活性碳库对氮沉降的响应.结果表明：模拟氮沉降下小叶章的生物量(总生物量、地上生物量、根生物量)均高于对照,其中根生物量的增长程度最大;根中碳含量及分配比例均显著提高,而地上部位的碳含量则显著降低(P<0.05).氮沉降对土壤活性碳库具有显著影响,各活性碳库含量均以5 g N·m^-2·a^-1处理最高,氮沉降对各活性碳库的影响程度依次为CHC(碳水化合物碳)＞LBC(易氧化有机碳)＞DOC(水溶性有机碳)＞MBC(微生物量碳),氮沉降与淹水条件的耦合作用有利于活性碳的释放;回归分析表明,土壤活性碳库与小叶章相关参数间存在显著相关性.氮沉降显著提高了小叶章植株生物量及土壤的活性碳含量.     

高寒草甸土地退化及其恢复重建对植被碳、氮含量的影响

以青海省达日县高寒草甸原生高寒嵩草(Kobresia)草甸封育系统为对照,研究了土地退化对植被生产力的影响,检验了不同人工重建措施(两个人工种植处理:混播(HB)、翻耕单播(DBF)和1个退化草地封育自然恢复处理(NR)及1个退化草地自然状态(SDL))对植被生产力的相对影响程度。结果表明,原生植被封育处理(YF)地上总生物量为265.1 g·m^-2,混播(HB)和翻耕单播(DBF)处理中地上总生物量分别为原生植被封育处理的116%和68%。退化草地封育自然恢复处理(NR)和重度退化自然状态下地上总生物量分别为原生植被封育的76%和53%。YF处理根系生物量远大于其它处理。原生植被封育系统中植被地上部分碳储量为 110.14 g·m^-2,地下根系(0~30 cm)碳储量为2 957 g·m^-2,植被总碳储量为 3 067.14 g·m^-2;重度退化草地系统中植被地上部分碳储量为 57.07 g·m^-2,地下根系(0~30 cm)碳储量为 357 g·m^-2,植被总碳储量为 414.07 g·m^-2。由此可见,高寒草甸严重退化后,通过植物组织流失的碳达到2 653.35 g·m^-2,即86.5%的碳损失;原生植被封育系统植被总氮储量为 56.85 g·m^-2,而重度退化草地植被总氮储量为 18.02 g·m^-2,高寒草甸严重退化使植物组织68.30%氮损失。与重度退化地相比,由于恢复重建措施增加了植物的生物量输入和群落组成,除翻耕单播处理外,其它恢复重建措施均能恢复系统植被的碳氮储量。这些恢复重建措施将会逐步改善土壤的物理和化学特性,最终使这些生态系统逐步由碳源向碳汇方向的转变成为可能。     

Determination of a Critical Nitrogen Dilution Curve for Winter Wheat Crops

A set of N-fertilization field experiments was used to determinethe 'critical nitrogen concentration', i.e, the minimal concentrationof total N in shoots that produced the maximum aerial dry matter,at a given time and field situation. A unique 'critical nitrogendilution curve' was obtained by plotting these concentrationsN_ct (% DM) vs. accumulated shoot biomass DM (t ha^-1). It couldbe described by the equation: N_ct = 5·35DM^-0·442 when shoot biomass was between 1·55 and 12 t ha^-1. Anexcellent fit was obtained between model and data (r² = 0·98,15 d.f.). A very close relationship was found using reducedN instead of total N, because the nitrate concentrations inshoots corresponding to critical points were small. The criticalcurve was rather close to those reported by Greenwood et al.(1990) for C₃ plants. However, this equation did not apply whenshoot biomass was less than 1·55 t ha^-1. In this case,the critical N concentration was independent of shoot biomass:the constant critical value N_ct = 4·4% is suggested forreduced-N. The model was validated in all the experimental situations,in spite of large differences in growth rate, cultivar, soiland climatic conditions; shoot biomass varying from 0·2to 14 t ha^-1. Plant N concentration was found to vary by a factor of fourat a given shoot biomass level. In the heavily fertilized treatments,shoot N concentration could be 60% higher than the criticalconcentration. Most (on average 80%) of the extra N accumulatedwas in the form of reduced N. The proportion of nitrate to totalN in shoot mainly depended on the crop stage of development.It was independent of the nitrogen nutrition level.Copyright1994, 1999 Academic Press Winter wheat, Triticum aestivum, arable crops, plant N concentration, aerial biomass, critical nitrogen, dilution curve, fertilization, reduced N, nitrate     

Microplankton and its function in a zone of shallow hydrothermal activity:the Craternaya Bay, Kurile Islands

Biomass and productivity of microplankton were measured in theCraternaya Bay (Kurile Islands), which is influenced by hydrothermalactivity and volcanic heating. The hydrothermal fields are situatedaround its shores and underwater within the 0–20 m depth.A dense ‘bloom’ of photoautotrophic microplanktonwas observed there, dominated by diatoms, phytoflagellates andthe symbiont-containing ciliate Mesodinium rubrum. The biomassof these ciliates attained 3–11 g m^-3 in the upper waterlayer. The total biomass of the phototrophic microplankton reached30–46 g m^-3. The primary production in the water columnwas, correspondingly, enormously high: 6–10 g C m^-2 day^-1.The depth of the euphotic zone was 7 m. Pelagic photosynthesiswas inhibited in the upper 0–1 m by the spreading of alayer of low-salinity hydrothermal water. The numerical densityof bacterioplankton in the upper zone of the water column variedfrom 1 x 10⁶ to 2.9 x 10⁶ cells ml^-1, and its wet biomass from250 to 750 mg m^-3. Its production varied at stations from 70to 390 mg m^-3 day^-1. Chemosynthesis contributed up to 30% ofthis production in the sites neighbouring the hydrothermal vents.Outside their direct impact however, its share was negligible.The biomass of heterotrophic planktonic ciliates varied from30 to 270 mg m^-3. The mechanisms of possible influence of shallowvolcanic activity on development and function of microplanktonin the Craternaya Bay is discussed.     

不同海拔云南黄连生物量和主要有效成分变化

研究了不同海拔(2 100～2 700 m)下,野生和人工栽培云南黄连的生物量、主要有效成分含量及产量.结果表明:野生云南黄连根茎和根生物量沿海拔梯度呈上升趋势,但无显著性差异(P>0.05);人工栽培云南黄连根茎生物量平均值在海拔2 600 m和2 700 m处分别为87.5 kg·hm^-2和97.0 kg·hm^-2,显著高于海拔2 300 m处(34.8 kg·hm^-2,P<0.05),且海拔2 300、2 600和2 700 m的人工栽培云南黄连根茎和根生物量均大于野生云南黄连,但无显著性差异(P>0.05). 野生云南黄连的根茎和根生物量均与全株生物量呈显著正相关. 野生云南黄连根茎和根小檗碱含量在海拔2 700 m处最高,分别为4.60%和1.93%; 根茎巴马汀和药根碱含量、根药根碱含量在海拔2 600～2 700 m处最高;根巴马汀含量在2 300 m处最高.人工云南黄连根茎和根小檗碱含量在海拔2 600 m处最高,分别为4.41%和1.90%; 根茎巴马汀含量,根小檗碱、巴马汀和药根碱含量在海拔2 600～2 700 m处最高;根茎药根碱含量在海拔2 300 m处最高.海拔2 600～2 700 m处野生云南黄连根茎和根中各有效成分产量显著高于海拔2 100和2 300 m处(P<0.05). 野生云南黄连分株的根茎生物量、根生物量、叶生物量、总生物量、高度和冠幅沿海拔梯度呈先升后降趋势.增大种植密度和加强人工管理可以提高云南黄连生物量和主要有效成分产量.     

Phosphorus gain by bacterivory promotes the mixotrophic flagellate Dinobryon spp. during re-oligotrophication

Bacterivory by mixotrophic flagellates may contribute to theirnutrient supply, providing a competitive advantage in oligotrophicwaters. We hypothesized an increase in Dinobryon biomass duringthe re-oligotrophication process in the large and deep LakeConstance. To estimate whether bacterivory contributed substantiallyto the flagellates’ phosphorus supply, we determined ingestionrates. Dinobryon biomass increased with decreasing total phosphorusconcentrations in the lake over a period of 17 years (P = 0.0005).The promotion of Dinobryon biomass during re-oligotrophicationmay be explained by the increasing light availability due tothe decreasing biomass of other phytoplankton yielding a releasefrom competition. The date of the Dinobryon abundance maximumshifted to earlier time points in the year, probably becausea smaller phosphorus pool was depleted more quickly. Ingestionrates of Dinobryon ranged between 0.5 and 13 bacteria cell^–1h^–1 (0.2–5.4 fg C pg C^–1 h^–1), and clearancerates varied between 0.2 and 3.2 nL cell^–1 h^–1 (4–78pL pg C^–1 h^–1), leading to bacterial losses of upto 30% day^–1 of bacterial standing stock. The ingestionof bacteria covered 77% of the phosphorus need of the flagellateduring the period of maximum growth in 1996 (net growth rate0.34 day^–1), and it fully covered the need at all othertimes.     

Response of Sargasso Sea phytoplankton biomass, growth rates and primary production to seasonally varying physical forcing

The response of phytoplankton biomass, growth rates and primaryproduction to seasonally varying physical forcing was studiedat a station southeast of Bermuda over an 18 month period. Phytoplanktongrowth rates and primary production were measured using thepigment-labeling method, and phytoplankton biomass was calculatedfrom these measurements. Phytoplankton carbon biomass variedsystematically over the year. Highest values were observed duringthe winter and spring. Seasonal variations of chlorophyll (Chi)a in the surface layer could primarily be attributed to variationsin phytoplankton biomass and secondarily to photoacclimation.During the summer period, average values of carbon (C)/Chl ratios(g C g^–1 Chi) ranged from 160 at the surface to 33 atthe 1.6% light level, changes attributed to photoacclimationof the phytoplankton, consistent with the observation that phytoplanktonbiomass did not vary as a function of depth. Phytoplankton growthrates in the surface layer did not vary systematically overthe year, ranging from 0.15 to 0.45 day^–1, in spite ofseasonally varying concentrations of nitrate. Growth rates variedas a function of depth from average values of 0.3 day^–1in the surface layer to <0.1 day¹ at the 1.6% light level.Thus, the primary response of the phytoplankton community tonutrient enrichment during the winter period was an increasein phytoplankton biomass rather than an increase in growth rates.A simple nutrient-phyto-plankton-zooplankton model was usedto explore this phenomenon. The model demonstrated that theobserved response of the phytoplankton to nutrient enrichmentis only possible when phytoplankton growth is not severely limitedby nutrients.     

Structure and Function of Oak Forests in Central Himalaya. I. Dry Matter Dynamics

The present study deals with structure and functioning of threeareas of Himalayan oak forest. Low- and mid-altitude oaks, namelyQuercus leucotrichophora, and Quercus floribunda, form predominantevergreen forests in Central and Western Himalaya. The totaltree basal cover ranged between 33·89 m² ha^–1 (Q.floribunda site) to 36·83 m² ha^–1 (Q. leucotrichophorasite). The density ranged between 570 and 760 individuals ha^–1.Allometric equations relating biomass of different tree componentsto GBH (girth at breast height) were significant with the exceptionof leaf biomass in Q. leucotrichophora and Rhododendron arboreum.Total vegetation biomass (29·40–467·0 tha^–1) was distributed as 377·1 t ha^–1 intrees, 5·40 t ha^–1 in shrubs and 1·23 tha^–1 in herbs. Total forest floor biomass ranged between4·6 and 6·2 t ha^–1. Of the total annuallitter fall (4·7–4·8 t ha^–1), 77·5% was contributed by leaf litter, 17·8 % by wood litterand 4·7 % by miscellaneous litter. Turnover rate of treelitter varied from 0·66 to 0·70. Net primary productionof total vegetation ranged between 15·9 and 20·6t ha^–1 yr^–1, of which the contribution of trees,shrubs and herbs was 81·2 %, 8·6 % and 10·2%, respectively. A compartment model of dry matter on the basisof mean data across sites was developed to show dry matter storageand flow of dry matter within the system. Quercus leucotrichophora forest, Q. floribunda forest, Q. lanuginosa forest, biomass, litter fall, net primary production, compartmental transfer