短期寒潮天气对福州市绿地土壤呼吸及组分的影响

城市生态系统土壤呼吸在区域乃至国家尺度上的碳预算与碳循环中都具有重要地位,研究突发天气下城市生态系统土壤呼吸及其组分的变化对准确估算城市土壤碳排放具有重要意义。以亚热带城市草坪(沟叶结缕草,Zoysia matrell)和片林(南洋杉,Araucaria heterophylla)为研究对象,于2011年2月10日至19日通过监测一次突发短期降温天气前后土壤呼吸及其组分(微生物呼吸和根系呼吸)的动态变化,探讨了短期低温天气对城市生态系统土壤呼吸的影响。结果表明:在突发寒潮天气发生后,片林和草坪的土壤温度均显著降低,降温幅度最大分别达7.4℃和5.5℃,二者的土壤呼吸均因降温而骤降,降低比例分别高达79.4%和71.2%。但土壤呼吸及组分也随期间的降水事件而呈现出明显波动。整个观测期间片林土壤呼吸、微生物呼吸与根系呼吸的日均值分别2.54 μmol · m^-2 · s^-1、0.76 μmol · m^-2 · s^-1和1.78 μmol · m^-2 · s^-1,而在草坪中三者分别为1.07 μmol · m^-2 ·s^-1、0.83 μmol · m^-2 · s^-1和0.24 μmol · m^-2 · s^-1。土壤温度是控制降温过程中城市绿地土壤呼吸及其组分的关键限制因子并与之呈指数正相关关系,但由于冠层结构简单、耐寒性较低,草坪对温度变化的响应更加敏感。在短期降温中草坪土壤呼吸、微生物呼吸与根系呼吸的Q₁₀值明显提高,分别高达4.18、8.17和18.17。受降水与降温的共同影响,草坪与片林各土壤呼吸类型同时受土壤温度、土壤含水量与降水量的控制,由这3个因子构成的多元回归模型可以较好地拟合各呼吸类型的日均值变化(R²>0.55)。     

上海典型城市草坪土壤呼吸特征

采用CFX-2开放式呼吸测定系统测定了上海城区百慕大、黑麦草-百慕大混播、结缕草和狗牙根4种典型草坪的土壤呼吸速率。结果表明：4种草坪的土壤呼吸速率均呈明显季节变化,最大值出现在7—8月,最小值出现在12月—翌年1月;4种草坪土壤呼吸平均速率依次为百慕大草坪<黑麦草-百慕大混播草坪<结缕草草坪<狗牙根草坪,其中百慕大草坪的土壤呼吸速率变化范围为0.13～2.25 μmol·m^-2·s^-1,黑麦草-百慕大混播草坪为1.16～5.95 μmol·m^-2·s^-1,结缕草草坪为0.93～8.27 μmol·m^-2·s^-1,狗牙根草坪为1.21～9.27 μmol·m^-2·s^-1;4种草坪的土壤呼吸速率与气温、5 cm地温和10 cm地温均呈极显著指数相关;百慕大草坪和黑麦草-百慕大混播草坪的日变化均呈单峰曲线,与气温、5 cm地温和10 cm地温的日变化趋势一致;4种草坪土壤呼吸对温度的敏感性指数即Q₁₀值为1.60～2.66;除结缕草外,其他草坪的土壤呼吸速率与土壤含水率相关性不显著;草坪的呼吸特征与其生长习性直接相关,而冷暖季混播草坪Q₁₀值小,对提高城市生态景观和环境质量有积极作用。     

黄土高原刺槐人工林地表凋落物对土壤呼吸的贡献

于黄土高原沟壑区王东沟小流域26年刺槐人工林(Robinia pseudoacacia)中,设置对照(CK)、去除凋落物(no litter, NL)和倍增凋落物(double litter, DL)3个处理,利用Li-8100系统测定各处理的土壤呼吸速率。结果表明,添加或去除凋落物显著影响土壤呼吸(P = 0.091-0.099),与对照(CK)的土壤呼吸速率(3.23 μmol m^-2 s^-1)相比,添加凋落物(DL)使土壤呼吸速率增加26%,去除凋落物(NL)使土壤呼吸速率减少22%。NL、CK和DL的累积土壤呼吸分别为631、787和973 g C m^-2a^-1。各处理土壤呼吸速率与土壤温度呈显著的指数关系(R²=0.81-0.90,P < 0.0001),但与土壤水分的关系不明显。NL、CK和DL的Q₁₀依次为1.92、2.29和2.31。地表凋落物对土壤呼吸年平均贡献量为20%。相关性分析表明,各测定日地表凋落物贡献与土壤温度(r=0.54,P < 0.05)或土壤水分关系显著(r=0.68, P < 0.05)。刺槐人工林地表凋落物的输入量为213 g C m^-2a^-1,大于凋落物引起的呼吸量156 g C m^-2a^-1。在黄土区通过植被恢复治理水土流失过程中,随着地表凋落物的积累,林地生态系统的碳汇功能将逐步得到加强。     

模拟氮沉降对石栎和苦槠幼苗土壤呼吸的影响

用LI-8100开路式土壤碳通量测量系统测定模拟氮沉降4种不同处理水平(0、60、120\,240 kg · hm^-2 · a^-1)下石栎(Lithocarpus glabra)和苦槠(Castanopsis sclerophylla)幼苗的土壤呼吸速率及土壤温度、含水量对其土壤呼吸的影响。结果表明,氮沉降对土壤呼吸的影响根据施氮水平和幼苗的种类不同而异。低氮(60 kg · hm^-2 · a^-1)处理下石栎和苦槠的土壤呼吸速率平均值分别为(4.014±0.812)μmol · m^-2 · s^-1和(5.170±0.689)μmol · m^-2 · s^-1,比对照组(0 kg · hm^-2 · a^-1)土壤呼吸速率平均值(3.802±0.948)μmol · m^-2 · s^-1和(3.557±0.906)μmol · m^-2 · s^-1分别高5%和45%;两树种在中、高氮处理下均出现对土壤呼吸明显的抑制。其中石栎中、高氮实验组的土壤呼吸速率分别为(2.653±0.681)μmol · m^-2 · s^-1、(2.592±0.736)μmol · m^-2 · s^-1, 比对照组低27%和29%。苦槠中、高氮实验组的土壤呼吸速率为(3.563±0.402)μmol · m^-2 · s^-1、(3.466±0.994)μmol · m^-2 · s^-1, 比对照组低7%和8%;石栎在高氮(240 kg · hm^-2 · a^-1)处理水平下,其土壤呼吸速率同10cm土壤温度之间呈现显著的指数关系(R²=0.811,P=0.001),而在低、中氮实验均未发现有明显指数关系。苦槠各处理水平下其土壤呼吸与土壤温度之间均未发现有明显的指数关系;在土壤呼吸与5cm土壤含水量的相关性方面,仅有苦槠高氮实验组表现出明显的二次方程关系(R²=0.722),而其低、中氮实验组及石栎各实验组均未有明显的相关性;与单因素(温度、含水量)拟合它们与土壤呼吸速率的方程相比,多元回归分析得到的土壤呼吸速率同土壤温度和含水量之间的拟合方程在P=0.05水平上能更好地解释土壤呼吸的变化情况。石栎和苦槠在氮沉降处理下的土壤呼吸温度系数Q₁₀值分别为2.29、1.95、1.59和1.46、1.41、1.76,同对照组2.64和1.78相比,均有明显降低,且两者Q₁₀值的变化分别呈递减和先减小后增大的趋势,表明氮沉降是影响石栎和苦槠土壤CO₂通量的一个重要因素。     

Photoinhibition during acclimatization of micropropagatedSpathiphyllum “Petite” plantlets

Summary MicropropagatedSpathiphyllum “Petite” plantlets were acclimatized at low- or high-light intensities [photosynthetic photon flux density (PPFD) 100 or 300 μmol·m⁻²·s⁻¹]. During the first days chlorophyll fluorescence measurements show a partial photoinhibition of the photosynthetic apparatus, expressed by a decrease of the variable over maximal fluorescence ratio (F_v/F_m). This inhibition of F_v/F_m was significantly higher for plants grown at high-light intensity, leading to a photooxidation of chlorophyll. Newly formed leaves were better adapted to the ex vitro climatic condition (as shown by the increase of the F_v/F_m ratio) and had a higher net photosynthesis compared with in vitro formed leaves. Nevertheless, plants grown at 300 μmol·m⁻²·s⁻¹ were photoinhibited, compared with those at 100 μmol·m⁻²·s⁻¹. A sudden exposure to high-light intensity of 1-, 10- or 25-d-old transplanted plants (shift in PPFD from 100 to 300 μmol·m⁻²·s⁻¹) gave a linear decrease of F_v/F_m over a 12-h period, which was reflected in a 50% reduction of net photosynthesis. No significant interaction between day and hour was found, indicating high-light exposure causes the same photoinhibitory effect on in vitro and ex vitro formed leaves.     

西南高山地区土壤异养呼吸时空动态

土壤异养呼吸是陆地和大气之间的重要通量,是决定陆地生态系统碳源汇的关键因素之一,与气候变化紧密相关。西南高山地区是响应气候变化的重点区域,研究西南高山地区土壤异养呼吸动态及其对气候变化的响应,对于评估区域碳循环对全球气候变化的贡献具有重要意义。应用生态系统模型(CEVSA)模型估算了1954-2010年西南高山地区土壤异养呼吸(HR)的时空变化,分析了其对气候变化的响应。结果表明:(1)西南高山地区1954-2010年平均异养呼吸量为422 g C·m^-2·a^-1,在空间分布上,HR自东南向西北递减,与年平均温度(r=0.721,P<0.01)、年降水量(r=0.564,P<0.01)均显著正相关;(2)在时间尺度上,西南高山地区1954-2010年 HR总量增加趋势显著(P<0.05),变化范围为197-251 Tg C/a,平均每年增加0.710 Tg C,其中主要植被类型草地、常绿针叶林和常绿阔叶林均增加趋势显著(P<0.01),增加速度分别为1.621、1.496和1.055 g C·m^-2·a^-2。(3)土壤HR的年际变化主要受温度影响,且西北部高海拔地区较东南部低海拔对温度变化更为敏感,主要植被类型温度敏感系数Q₁₀从大到小依次为草地(2.35)、常绿针叶林(2.34)、常绿阔叶林(1.93)。     

黄土旱塬裸地土壤呼吸特征及其影响因子

于中国科学院长武生态试验站(始于1984年),采用动态密闭气室法(Li-8100,USA)于2008年3月至2009年3月监测了裸地土壤呼吸日变化、季节变化以及0-60cm土层的温度和含水量,研究了裸地土壤呼吸的日变化、季节变化特征及其与土壤温度和含水量之间的关系。结果表明:裸地土壤呼吸四季的日变化和季节变化均呈单峰型曲线,与气温变化趋势一致;日变化峰值出现在14:00左右或16:00左右,最低值出现在0:00左右或者6:00左右;季节变化表现为夏季最高,冬季最低,春秋季无明显差异,年平均呼吸速率为0.94μmolCO₂·m^-2·s^-1。土壤呼吸与温度具有极显著(P<0.01)的正相关关系,且可以用R_s=ae^bx形式的指数函数很好地拟合,其中与5cm深度的土壤温度相关性最好。水分对土壤呼吸的影响复杂。裸地土壤呼吸的双变量模型关系显著(P<0.01),比相应的单变量模型更好地解释了土壤呼吸变异。     

Enhancement of phenylpropanoid enzymes and lignin in Phalaenopsis orchid and their influence on plant acclimatisation at different levels of photosynthetic photon flux

Effects of three levels of photosynthetic photon flux (PPF: 60, 160 and 300 μmol m⁻²s⁻¹) were investigated in one-month-old Phalaenopsis plantlets acclimatised ex vitro. Optimal growth, chlorophyll and carotenoid concentations, and a high carotenoid:chlorophyll a ratio were obtained at 160 μmol m⁻²s⁻¹, while net CO₂ assimilation (A), stomatal conductance (g), transpiration rate (E) and leaf temperature peaked at 300 μmol m⁻²s⁻¹, indicating the ability of the plants to grow ex vitro. Adverse effects of the highest PPF were reflected in loss of chlorophyll, biomass, non-protein thiol and cysteine, but increased proline. After acclimatisation, glucose-6-phosphate dehydrogenase, shikimate dehydrogenase, phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) increased, as did lignin. Peroxidases (POD), which play an important role in lignin synthesis, were induced in acclimatised plants. Polyphenol oxidase (PPO) and β-glucosidase (β-GS) activities increased to a maximum in acclimatised plants at 300 μmol m⁻²s⁻¹. A positive correlation between PAL, CAD activity and lignin concentration was observed, especially at 160 and 300 μmol m⁻²s⁻¹. The study concludes that enhancement of lignin biosynthesis probably not only adds rigidity to plant cell walls but also induces defence against radiation stress. A PPF of 160 μmol m⁻²s⁻¹was suitable for acclimatisation when plants were transferred from in vitro conditions.     

通量的初步研究

该文利用涡度协方差法和生理生态学方法（不同分量的累积和）获得的通量观测数据,对老山落叶松(Larix gmelinii)林(45°20′N, 127°34 ′E)的碳收支进行了分析。通过对每0.5 h所测数据进行的分析表明,能量平衡达到75％,说明涡度协方差法适应于本站的研究。较阴天气情况 下,林分光照利用效率显著高于晴朗天气,可能归因于阴天较多的散射光。以单位土地面积计算发现,通过涡度协方差法计算的落叶松林生态 系统的总初级生产力在20～50 μmol•m^-2•s^-1之间,远高于冠层叶片的总光合速率9.8～23.4μmol•m^-2•s^-1 (平均值16.2μmol•m^-2•s^-1 ),而 当综合考虑冠层光合和林下植物光合作用时,两种方法测定结果吻合性较好,说明林下植物对落叶松林碳平衡有重要影响。在估计森林生态系 统呼吸方面,以有风夜晚净生态系统交换量（NEE）来代表生态系统呼吸总量（3～9μmol•m^-2•s^-1）低估了生态系统呼吸总量,粗略估计较生 理生态学方法（不同呼吸分量的累积和）低估了50%左右（14.2μmol•m^-2•s^-1）。结果发现两种方法在估计森林碳平衡方面存在一定的差异, 呼吸量的估计差异应是今后研究的重点。     

苹果三维树冠的净光合速率分布模拟

构建三维树冠光合模型可模拟出叶片净光合速率(P_n)、气孔导度(G_s)和光能利用效率(LUE)在树冠内的三维分布。以17年生纺锤形"富士"苹果树(Malus domestica Borkh. cv. ‘Fuji’)为试材,通过实测确定三维树冠内叶片和辐射分布,根据不同部位叶片最大光合速率经验公式模拟叶片P_n 在三维树冠空间内分布,并据2007-2009年测定数据拟合相关模型参数。模拟表明,苹果树冠叶片P_n 和辐射的三维分布相似,在树冠上部P_n 三维分布比较平缓,然后随辐射的减少而迅速降低。高辐射条件下(PAR=1500 μmol·m^-2·s^-1),从树冠上部3 m处降到到1 m,平均相对辐射从71.18%降到8.05%,减少了89%,叶片平均P_n从15.05 μmol·m^-2·s^-1降到1.92 μmol·m^-2·s^-1,减少了87%。单位体积小室内的总净光合速率大小主要取决于叶面积密度,部分取决于P_n。G_s三维分布与P_n相似,而LUE分布与辐射相反,中下部高,上部低。根据光合机理模型、树冠内辐射和叶面积三维分布可模拟出苹果三维树冠内叶片的P_n、G_s和LUE分布,该模型参数少,可方便用于其它果树三维光合模型构建和果树整形修剪研究。     

A parametric distribution for the fraction of outdoor soil in indoor dust

For a chemical that does not have a source inside a house, the ratio of its dust concentration indoors to its soil concentration outdoors is equal to the fraction of house dust that is composed of soil. To estimate the fraction of soil in house dust, we compiled ratios of the concentrations of a chemical in dust and soil from the scientific literature. We find that a lognormal distribution fits the data extremely well. This distribution is suitable for use in public health risk assessments for single‐family homes in temperate climates.     

渭北旱塬苹果园土壤紧实化现状及成因

本研究通过分析渭北旱塬苹果园土壤的紧实化现状及其诱导因素,找出影响当地苹果园健康发展的土壤退化隐性因素,为果园科学管理提供理论依据。分别选取种植年限＜10年(4～6年)、10～20年(14～16年)和＞20年(24～26年)的苹果园各4个,分析0～60 cm土层土壤容重和紧实度随土层深度的变化规律,探明果园土壤内部紧实化发生的部位和退化程度,同时,通过分析土壤团聚体数量及其稳定性、土壤黏粒和有机质含量,揭示引起渭北果园土壤内部紧实化的原因。结果表明: 渭北果园0～60 cm土层土壤容重和紧实度均随植果年限和土层深度的增加而显著增大。以20 cm土层为界,渭北各园龄段苹果园土壤具有明显的“上松下实”变异特征,20 cm以上土层上述各指标基本满足苹果树的正常生长需求,20 cm以下土层土壤则已超出了苹果树健康生长的阈值。造成渭北苹果园亚表层以下土壤紧实化的原因主要是土壤团聚作用差、有机质含量低,加之植果期间人为扰动少,土壤中分散的黏粒会向下层移动。此外,随着植果年限的增加,土壤紧实化过程更加明显。     

黄土和风沙土藓结皮土壤呼吸对模拟降雨的响应

生物结皮土壤呼吸是干旱和半干旱生态系统碳循环的重要组成部分,但目前其对降雨的响应规律尚不明确。针对黄土高原黄土和风沙土上发育的藓结皮,分别进行2、4、6、10、20、30、40 mm的模拟降雨,并使用便携式土壤碳通量分析仪测定雨前和雨后藓结皮的呼吸速率,对比分析降雨量对藓结皮呼吸速率的影响;同时,在40 mm降雨后的0—24 h连续测定藓结皮的呼吸速率变化,分析藓结皮呼吸速率随雨后历时的变化规律。结果显示,7种降雨量后两种土壤上藓结皮的呼吸速率均显著升高,黄土上藓结皮呼吸速度的增幅为2.89—6.38倍,风沙土上藓结皮呼吸速率的增幅为0.73—4.38倍。0—6 mm降雨中,两种土壤上藓结皮的呼吸速率均随降雨量增加而迅速升高,二者成显著线性正相关关系;6—40 mm降雨中,黄土上藓结皮的呼吸速率随降雨量增加而缓慢升高,但风沙土上藓结皮的呼吸速率随降雨量增加而快速降低。两种土壤上藓结皮的呼吸速率随雨后历时表现出相似的变化规律,即雨后迅速升高、之后逐渐降低,并在24 h左右回归到雨前水平;但黄土上藓结皮的呼吸速率在雨后即刻达到峰值,而风沙土上藓结皮的呼吸速率在雨后30 min左右方达到峰值。黄土上藓结皮的呼吸速率一致高于风沙土上的藓结皮,前者在不同降雨量和雨后历时中平均比后者高150.0%和59.6%。此外,藓结皮呼吸速率与表层土壤含水量存有显著相关关系,在含水量较低(小于约4%)时二者显著正相关,在含水量较高(大于约4%)时二者对于黄土上藓结皮为正相关、对于风沙土上藓结皮为负相关。研究表明,黄土高原藓结皮土壤呼吸对降雨响应快速而直接,但其响应规律对于黄土和风沙土上的藓结皮是不同的,总体而言黄土上藓结皮对降雨的响应更为持久有效。     

恩诺沙星残留对土壤微生物功能的影响

研究了恩诺沙星残留对土壤呼吸作用、纤维分解作用、氨化作用、硝化作用的影响 ,结果表明 ,相对较低浓度恩诺沙星残留(0 .0 1μg/ g土 ,0 .1μg/ g土 )刺激土壤呼吸作用 ,相对较高浓度恩诺沙星残留 (1μg/ g土 )对土壤呼吸作用产生抑制 ,药物作用活性维持期为 6 d;恩诺沙星残留对土壤纤维分解作用影响较不明显 ;较低浓度恩诺沙星残留 (0 .0 1μg/ g土 ,0 .1μg/ g土 )对土壤氨化作用有刺激作用 ,而较高浓度恩诺沙星残留 (1μg/ g土 ,10μg/ g土 )则会对其起抑制作用 ,药物作用活性期为 9d;不同浓度恩诺沙星对土壤硝化作用影响极其显著 ,当恩诺沙星浓度达到 1μg/ ml时 ,在 3～ 9d内 ,对土壤硝化作用有一定抑制作用。当恩诺沙星浓度达到 10μg/ ml时 ,强烈抑制了土壤硝化作用 ,直到本试验结束时 ,其抑制作用未见减弱。结果表明恩诺沙星残留影响了土壤微生物这些功能 ,因而可能影响到土壤特性和土壤中一些生态过程     

Concept,Components, and Strategies of Soil Health in Agroecosystems

The terms ''''soil health'''' or ''''soil quality'''' as applied to agroecosystems refer to the ability of soil to support and sustain crop growth while maintaining environmental quality. High-quality soils have the following characteristics: (i) a sufficient, but not excess, supply of nutrients; (ii) good structure (tilth); (iii) sufficient depth for rooting and drainage; (iv) good internal drainage; (v) low populations of plant disease and parasitic organisms; (vi) high populations of organisms that promote plant growth; (vii) low weed pressure; (viii) no chemicals that might harm the plant; (ix) resistance to being degraded; and (x) resilience following an episode of degradation. Management intended to improve soil health involves creatively combining a number of practices that enhance the soil''s biological, chemical, and physical suitability for crop production. The most important general strategy is to add plentiful quantities of organic matter—including crop and cover crop residues, manures, and composts. Other important strategies include better crop rotations, reducing tillage and keeping the soil surface covered with living and dead residue, reducing compaction by decreasing heavy equipment traffic, and using best nutrient management practices. Practices that enhance soil quality frequently reduce plant pest pressures.     

Various Applications of Soil Contaminant Database Developed for the Central Artery/Tunnel Project

One of the largest environmental assessment programs in the United States was initiated in the early 1990s to determine the chemical characteristics of soil located within the planned alignment for the Central Artery (I-93) / Tunnel (I-90) (CA/T) Project in Boston, Massachusetts. The primary purpose of the program was to support management of the handling and disposal of over 17 million cubic yards of soil to be excavated during construction of the CA/T Project. As part of this work, more than 8,000 soil samples were collected from more than 2,600 soil borings and analyzed for a range of chemical contaminants, including volatile organic compounds, acid/base neutral compounds, total petroleum hydrocarbons, polychlorinated biphenyls, and heavy metals. The soils encountered during the investigations exhibited properties influenced by numerous anthropogenic activities. These activities, such as vehicular emissions, historic industrial/manufacturing operations, and waterfront filling with both building rubble and dredge spoils from Boston Harbor, resulted in soils primarily contaminated with petroleum hydrocarbons and metals. As a result of this program, an extensive database of the chemical constituents present in urban soils in downtown Boston was developed. These results were primarily used to delineate the limits of contaminated areas affecting the planned construction. In addition, the database has been used by the Project to support various soil management activities, as well as by the regulatory community in developing guidelines and criteria governing the management of contaminated soils in Massachusetts. This paper focuses on the various applications of this database throughout the course of the Project, and with the additional aim of stimulating potential future applications by both the regulatory and scientific communities.     

不同地表覆盖方式对苹果园土壤性状及果树生长和产量的影响

以黄土高原9年生红富士果园生态系统为对象,研究不同地表覆盖模式（清耕、生草覆盖、地膜覆盖、秸秆覆盖和砂石覆盖）对果园土壤性状及果树生长和产量的影响.结果表明：生草覆盖土壤水分剖面分异最低,砂石覆盖土壤水分剖面分异最高;砂石覆盖提高了根层水分含量,有利于果树对水分的利用.不同地表覆盖模式土壤热量状况变化显著,处理间差异明显,极端最高温度下降,但地膜覆盖处理夏季地温超过果树根系生长的上限温度,对果树根系生长和生理功能发挥不利.除地膜覆盖外,其他地表覆盖模式均能提高土壤CO₂释放速率,其中生草覆盖的效果最为显著.不同地表覆盖模式对果树枝条类型比例及产量影响较大,砂石覆盖处理的中短枝比例和果实产量最高;生草覆盖处理的果实产量最低.因子分析结果表明,对于黄土高原沟壑区盛果期果园,砂石覆盖处理是较为适宜的地表覆盖模式.     

A rapid,cost-effective procedure for the extraction of microbial DNA from soil

Here we describe a DNA extraction method that is based on a simple, rapid polyvinylpolypyrrolidone–calcium chloride precipitation to release microorganisms from the soil combined with lysozyme–proteinase–SDS lysis of the microbial community. The extracted DNA is of high quality and allows direct detection of specific genes by the polymerase chain reaction (PCR) as well as cloning of indigenous microbial DNA. This method facilitates the extraction of 36 500-mg soil samples simultaneously in a 2-h period by one person. The procedure is safe, inexpensive, and does not require specialized equipment or generate hazardous wastes.     

Trajectories of change: riparian vegetation and soil conditions following livestock removal and replanting

Riparian zones provide critically important ecological functions, including the interception of nutrients and sediments before they enter waterways. Consequently, riparian zones, and the vegetation they support, are often considered as an important ‘final buffer’ between waterways and adjacent land. In agricultural ecosystems, riparian zones are therefore increasingly recognized as an important component of strategies aimed at minimizing the flow of nutrients and sediments into waterways. Accordingly, riparian zones are increasingly afforded protection and are targeted for restoration. Here we present results of a study in which we aimed to identify patterns of change in soil and vegetation properties in riparian zones, under different management regimes, adjacent to tributary streams in one of south‐eastern Australia's main agricultural regions. We compared riparia that were heavily impacted by agricultural activities, were in remnant condition or had undergone some restoration activities and were thus in a transitional state. There was an increase in plant cover and soil C concentration between impacted through to remnant sites, with transitional sites intermediate, suggesting that improvements in soil conditions were becoming evident following restoration activities. In our assessment of soil physicochemical properties we investigated the relationships between riparian condition and soil properties, taking into account the influence of adjacent land use on these relationships. Importantly, the concentrations of NO₃^‐ and plant available P in riparian surface soils were more or less influenced by concentrations in the adjacent land depending upon riparian condition. This will, in turn, have consequences for nutrient inputs into streams. This study emphasizes that riparian zones need to be managed within their wider landscape context. Furthermore, the results of this study will inform efforts seeking to minimize impacts of agricultural activities on waterways, through the conservation and/or restoration of riparian ecosystems.     

土壤微生物资源管理、应用技术与学科展望

土壤中蕴藏着高度的微生物多样性,在陆地生态系统中发挥着非常重要的功能,加强对土壤微生物资源的综合管理与开发应用是提升生态系统稳定性与生产力及农产品质量的重要途径。首先,土壤微生物多样性具有全球性的重大意义,有待完善对土壤微生物的检测与监测技术研究,进而实现土壤微生物多样性与土壤功能的耦合以及对土壤质量的评定;其次,土壤微生物作为一种宝贵的生产资料和可持续资源,要加强其在土壤肥力强化与保育、土壤障碍消减与调节、土壤污染控制与修复等3个领域的应用研究。最后,未来土壤微生物学发展将会形成土壤微生物系统学、土壤微生物过程学与土壤微生物功能学3个子学科,要建立土壤微生物种质资源库与遗传信息库,推进土壤微生物生理代谢过程、生物化学过程及生态行为过程的研究,联结土壤微生物与土壤功能的关系,并从土壤中的功能微生物出发对环境变化作出积极响应和主动调控。此外,原创性方法的建立与应用是限制土壤微生物学发展的技术瓶颈,联合生物地理学与生物信息学破译重要基因的特定生态功能,并将其应用到生态模型以及生态系统未知领域的研究中去,是土壤微生物学面临的挑战。