Spatial changes of soil fungal and bacterial biomass from a sub-alpine coniferous forest to grassland in a humid, sub-tropical region

 Fungal and bacterial biomass were determined across a gradient from a forest to grassland in a sub-alpine region in central Taiwan. The respiration-inhibition and ergosterol methods for the evaluation of the microbial biomass were compared. Soil fungal and bacterial biomass both significantly decreased (P<0.05) with the shift of vegetation from forest to grassland. Fungal and bacterial respiration rates (evolved CO₂) were, respectively, 89.1 μl CO₂ g^–1 soil h^–1 and 55.1 μl CO₂ g^–1 soil h^–1 in the forest and 36.7 μl CO₂ g^–1 soil h^–1 and 35.7 μl CO₂ g^–1 soil h^–1 in the grassland surface soils (0–10 cm). The fungal ergosterol content in the surface soil decreased from the forest zone (108 μg g^–1) to the grassland zone (15.9 μg g^–1). A good correlation (R ²=0.90) was exhibited between the soil fungal ergosterol content and soil fungal CO₂ production (respiration) for all sampling sites. For the forest and grassland soil profiles, microbial biomass (respiration and ergosterol) declined dramatically with depth, ten- to 100-fold from the surface organic horizon to the deepest mineral horizon. With respect to fungal to bacterial ratios for the surface soil (0–10 cm), the forest zone had a significantly (P<0.05) higher ratio (1.65) than the grassland zone (1.05). However, there was no fungal to bacterial ratio trend from the surface horizon to the deeper mineral horizons of the soil profiles. Received: 30 March 2000     

Biomass production and related characters in the core collection of Pisum germplasm

Retention of residue on the soil surface following harvest is an effective method of reducing soil erosion from both wind and water. The pea crop produces small amounts of residue to effectively reduce soil erosion. Severe erosion occurs in pea production areas such as the Palouse Region of the US Pacific Northwest (PNW) when low residue crops such as spring pea or lentil are followed by fall-sown wheat. The current study was conducted to determine the range of total aboveground biomass (TAB), seed yield, and straw (residue) production from the plant identification (PI) accessions that comprise the core collection of Pisum germplasm. In addition, the potential for increasing seed yield and straw production simultaneously was evaluated. Three hundred and ninety PI accessions were screened in the field in 1996 and 1997. The variation for TAB, seed yield and straw production among the PI accessions exceeded that of the controls both years. Seed yield was positively correlated with straw production (r = 0.81, p< 0.01) indicating that seed and straw production can be increased simultaneously through positive selection for both traits. Significant favorable variation is present among accessions in the USDA core collection of Pisum germplasm which could be used to increase both seed yield and total biomass production of adapted breeding lines.     

Methods for the investigation of metabolic activities and shifts in the microbial community in a soil treated with a fungicide

Samples from a sandy agricultural soil were treated with increasing amounts of a fungicide (Sportak). The effects on the soil microflora were investigated over several weeks by monitoring basal and substrate-induced respiration and basal and substrate-induced heat output. The microbial biomass, metabolic quotient (qCO₂), relative heat output (rqheat), lag phase of substrate use, and calorimetric: respirometric ratio were used as ecophysiological parametèrs. As structural and community-specific parameters, we recorded tryptophan contents and auxin metabolism, and calculated the ratios of fungal to bacterial respiration by antibiotic inhibition of substrate-induced respiration. Sportak either inhibited or stimulated the microbiota, depending on the length of exposure to the fungicide and the amount applied. Mineralization of dead biomass was reflected in increased soil tryptophan contents after the Sportak application. A shortened lag phase demonstrated inhibition and a prolonged lag phase stimulation of substrate use. This changed with the experimental phase. The rqheat and the calorimetric: respirometric ratio proved to be suitable parameters for the detection of stress metabolism (repair processes) in soil microbiota, because thermodynamic processes and catabolic and anabolic metabolism are taken into account at the same time. Following the application of Sportak, indole 3-acetic acid biosynthesis decreased while indole-3-ethanol biosynthesis increased, probably as a result of a transitional community shift from K-strategists towards r-strategists. It was not the fungicide but the formulation (mainly xylol) that damaged the organisms. A shift in the ratio of fungi to bacteria was also observed, suggesting that the bacteria were probably more sensitive to xylol than the fungi.     

超高产栽培杂交中籼稻的生长发育特性

以5个杂交中籼稻品种(含品系)扬两优6号、P88S/747、珞优8号、珞优234和天两优2号为材料,研究大田条件下超高产水平(产量≥12.0 t hm^-2)的物质生产、产量构成及养分吸收特性。试验结果表明,与高产水稻(产量≥9.0 t hm^-2)相比,超高产水稻具有以下特征,幼穗分化期、齐穗期和灌浆结实期(齐穗后10 d) LAI大,分别为6.5~7.2、8.5~8.9和6.5~7.0;齐穗期的高效叶面积比率高,为60.0%~66.5%;齐穗期、灌浆期和成熟期积累较多的干物质,分别为13.5~15.0、15.0~16.0和25.0~28.0 t hm^-2;分蘖盛期对氮(N)、磷(P)、钾(K)吸收利用优势不明显,而幼穗分化期、齐穗期和成熟期对N、P、K 吸收利用高而且积累速度快。此外,具有穗数多(有效穗数介于250×10⁴ ~290×10⁴ 穗 hm^-2)、结实率高(88.2%~92.3%)、千粒重大(29.0~31.0 g)的特点。     

沙质海岸火炬松幼树生物量的研究

为了对沙质海岸火炬松人工林的合理经营提供基础资料和科学依据,我们于2003年对胶南沙质海岸海防林9年生火炬松幼树的生物量进行研究,结果表明:随年龄的增长,火炬松累积生物量在各器官的分配比例有所差异,树干在生物量中所占的比重逐渐增大,树枝和树叶在生物量中所占的比重则随年龄的增长基本呈下降趋势;火炬松生物量的空间分布不均匀,81.6%的生物量分布在树干3.5m以下,3.5m以上部分仅分布着大约18.4%的生物量,枝叶在树干上的分布不成比例;用W=aDb能很好地估计火炬松人工幼林生物量,且精确度高,R2值达0.9以上。     

集约与粗放经营杨树人工林生物量的研究

文中对集约经营与粗放经营杨树人工林的生物量及其在各器官中的分布进行了研究，结果表明．经营方式对林分生物量生长影响显著．集约经营林木的生物量总值及其在各器官中的分布值明显高于粗放经营林。在生物量分布中．干重与根重所占的比重较大。应用幂函数方程．建立了各器官生物量与树高，胸径因于之间的关系方程，由于生物量生长与材积生长关系密切．结合材积生长数据．耐两林分干生物量、总生物量的生长进行了预测．为合理培育橱树人工林提供了科学的依据。     

中国寒温带,温带落叶松林群落生物量的研究概述

文章系统地分析了中国寒温带、温带落叶松林主要群落类型的群落学特征，以及兴安落叶松林，长白落叶松林，华北落叶松林，阿尔泰落叶松林四种森林群落的生物量，年净生产量及其在不同层次上的分配，并探讨了四种森林群落及不同落叶松种群间的干物质累积速率（ＮＰ／Ｂ）。结果表明：１１６～１３０年生的已郁闭的落叶松林群落生物量和乔木层落叶松生物量：华北落叶松混交林为２７４．８９和２１４．３１ｔ／ｈｍ＾２，长白落叶松林２     

金顶侧耳液体培养基的优化筛选

采用正交设计的方法,以金顶侧耳菌丝体的生物量及其多糖含量为测量指标,对金顶侧耳液体发酵培养基进行了优化研究。结果表明：当发酵培养基的配方为：马铃薯20％,蛋白胨0．3％,葡萄糖2．5％,KH_2PO_4和MgSO_4·7H_2O各为0．15％时,其菌丝体的生物量最高：而当培养基的配方为：马铃薯20％,蛋白胨0．1％,葡萄糖3．0％,H_2PO_4和MgSO_4·7H_2O各为0．15％时,其菌丝体胞内多糖含量最高。结果表明生物量最高的培养基中其菌丝体的胞内多糖的产量并非最高。     

基于管道模型理论的树形结构分析

依据长白落叶松生物量标准地的调查数据,研究发现,在树冠以下,不同部位树干的断面积生长量基本相同;心材的形成(按颜色的不同区分)在同一年轮内是由上向下的渐变过程。在树冠内,树干边材断面积生长量与其上部的枝条边材断面积生长量大致相等。但这一关系受到树木直立及叶片空间伸展的静力学需求的制约,即树形结构是树木生理需求和力学需求的统一。     

饲用玉米生物产量和籽粒产量与相关因素的灰色关联分析

运用灰色关联分析方法对13个饲用玉米品种生物学产量和籽粒产量与相关因素关系的研究分析,结果表明,饲用玉米生物学产量与主要性状间的关联度顺序为:株高>穗位高>成熟期保绿度>穗行数>行粒数>结实长>吐丝期>穗长>穗粗>籽粒产量>千粒重;籽粒产量与主要性状间的关联度顺序为:千粒重>穗长>结实长>行粒数>穗粗>行数>生物产量>株高>穗位高>成熟期保绿度>吐丝期。