Response of microbial community composition and activity in agricultural and grassland soils after a simulated rainfall

Rainfall in Mediterranean climates may affect soil microbial processes and communities differently in agricultural vs. grassland soils. We explored the hypothesis that land use intensification decreases the resistance of microbial community composition and activity to perturbation. Soil carbon (C) and nitrogen (N) dynamics and microbial responses to a simulated Spring rainfall were measured in grassland and agricultural ecosystems. The California ecosystems consisted of two paired sets: annual vegetable crops and annual grassland in Salinas Valley, and perennial grass agriculture and native perennial grassland in Carmel Valley. Soil types of the respective ecosystem pairs were derived from granitic parent material and had sandy loam textures. Intact cores (30 cm deep) were collected in March 1999. After equilibration, dry soil cores (approx. −1 to −2 MPa) were exposed to a simulated Spring rainfall of 2.4 cm, and then were measured at 0, 6, 24, and 120 h after rewetting. Microbial biomass C (MBC) and inorganic N did not respond to rewetting. N₂O and CO₂ efflux and respiration increased after rewetting in all soils, with larger responses in the grassland than in the agricultural soils. Phospholipid fatty acid (PLFA) profiles indicated that changes in microbial community composition after rewetting were most pronounced in intensive vegetable production, followed by the relict perennial grassland. Changes in specific PLFA markers were not consistent across all sites. There were more similarities among microbial groups associated with PLFA markers in agricultural ecosystems than grassland ecosystems. Differences in responses of microbial communities may be related to the different plant species composition of the grasslands. Agricultural intensification appeared to decrease microbial diversity, as estimated from numbers of individual PLFA identified for each ecosystem, and reduce resistance to change in microbial community composition after rewetting. In the agricultural systems, reductions in both the measures of microbial diversity and the resistance of the microbial community composition to change after a perturbation were associated with lower ecosystem function, i.e. lower microbial responses to increased moisture availability.     

豫西北地区暖性灌草丛类草地生态系统固碳特征

草地中灌木数量动态变化是影响草地生态系统碳收支的重要因素,灌木层的碳储量是草地生态系统碳库中最不确定的组分之一。暖性灌草丛在豫西北丘陵山地广泛分布,属区域典型植被类型。为揭示暖性灌草丛类草地生态系统固碳特征,对豫西北地区7个样地的灌木层、草本层与土壤碳密度进行了调查,并对生态系统碳密度进行了计算。结果表明,植被与土壤平均有机碳密度分别为2360.07和4610.47 g C·m^-2,其中灌木层植被碳密度(981.63 g C·m^-2)低于草本层(1387.44 g C·m^-2),但差异不显著(P>0.05)。植被碳密度主要由根系所贡献,占整个植被碳密度的93.04%,其中灌木层根系所占比例为41.51%,略小于草本层。生态系统中土壤碳密度占有较大比例,约占整个生态系统碳密度的62.80%。对不同样地而言,由于各自所处生境不同,其生态系统固碳特征存在一定区域差异。各样地的植被碳密度大小顺序依次为P₁>P₅>P₂>P₄>P₆>P₇>P₃,但差异并不显著(P>0.05);土壤碳密度大小顺序依次为P₁>P₂>P₆>P₅>P₄>P₃>P₇,其中P₁与P₄、P₃、P₇存在显著差异(P<0.05);生态系统碳密度大小顺序依次为:P₁>P₂>P₆>P₅>P₄>P₇>P₃,其中P₁与P₄、P₃、P₇差异显著(P<0.05)。     

山西4类主要天然草地的生物量空间分布特征

通过对山西省暖性草丛类、暖性灌草丛类、温性草原类、温性山地草甸类4类主要天然草地的70个大样地进行调查,测定草地地上、地下生物量,分析4个海拔梯度,6个纬度梯度和5个经度梯度的生物量变化规律,旨在掌握山西天然草地生物量的空间分布特征,为充分了解山西草地生态系统及合理利用奠定基础。结果表明,山西省主要类型天然草地生物量随海拔的升高呈现出先升高后降低的趋势,海拔1 200-1 600 m的地下生物量和总生物量最高,分别为1 412.86和2 037.87g·m~(-2);而地上活体生物量和凋落物生物量则是在800m的海拔处最高,分别为301.5和105.97g·m~(-2)。随纬度从南向北地下生物量和总生物量呈先增加后降低的趋势,且南边略高于北边(P0.05)。随经度从西向东地下生物量和总生物量呈先增加后降低再增加的趋势。不同草地类型地上生物量存在较大差异,暖性草丛类草地的地上活体生物量显著高于其余3类草地类型(P0.05)。暖性草丛类和温性山地草甸类草地的凋落物生物量显著高于暖性灌草丛类和温性草原类草地(P0.05)。     

Microbial communities of a native perennial bunchgrass do not respond consistently across a gradient of land-use intensification

To test if native perennial bunchgrasses cultivate the same microbial community composition across a gradient in land-use intensification, soils were sampled in fall, winter and spring in areas under bunchgrasses (‘plant’) and in bare soils (‘removal’) in which plots were cleared of living plants adjacent to native perennial bunchgrasses (Nassella pulchra). The gradient in land-use intensification was represented by a relict perennial grassland, a restored perennial grassland, and a perennial grass agriculture site on the same soil type. An exotic annual grassland site was also included because perennial bunchgrasses often exist within a matrix of annual grasses in California. Differences in soil resource pools between ‘plant’ and ‘removal’ soils were observed mainly in the relict perennial grassland and perennial grass agriculture site. Seasonal responses occurred in all sites. Microbial biomass carbon (C) and dissolved organic C were greater under perennial bunchgrasses in the relict perennial grassland and perennial grass agriculture site when comparing treatment means of ‘plant’ vs. ‘removal’ soil. In general, soil moisture, microbial respiration, and nitrate decreased from fall to spring in ‘plant’ and ‘removal’ soils, while soil ammonium and net mineralizable nitrogen (N) increased only in ‘plant’ soils. A canonical correspondence analysis (CCA) of phospholipid fatty acid (PLFA) profiles from all sites showed that land-use history limits the similarity of microbial community composition as do soil C and N dynamics among sites. When PLFA profiles from individual sites were analyzed by CCA, different microbial PLFA markers were associated with N. pulchra in each site, indicating that the same plant species does not retain a unique microbial fingerprint across the gradient of land-use intensification.     

茶树食叶害虫——茶黑毒蛾

茶黑毒蛾(Dasychira baibarana Matsumura)是茶树上一种重要的食叶类害虫,常在茶园暴发成灾,严重影响茶树的树势和茶叶的产量。本文介绍了茶黑毒蛾的主要形态特征、发生特点和防治方法,为生产上正确识别和防治提供参考。     

茶毛虫性信息素对茶毛虫防治效果研究

在贵州湄潭茶场和平坝茶场研究了茶毛虫性信息素引诱剂大面积诱杀茶毛虫的效果,结果表明,茶毛虫性信息素引诱剂以B型效果最好,42天内两地每盆每晚平均可诱到3.41头和7.51头,最高可诱到198头,大面积使用区内茶毛虫雌蛾怀卵量比对照区减少93.50%,卵块减少85.21% ,幼虫数量减少81.15%,说明茶毛虫性信息素引诱剂诱蛾效果非常明显。     

环茸毒蛾生物学特性初报

油茶(Camellia oleifera Abel.)为我国特有的重要油料树种。茶油不饱和脂肪酸含量达90%以上,还含有丰富的维生素E、维生素D、维生素K和β-胡萝卜素,具有极高的营养价值和保健功能[1-2]。随着油茶经济地位的提升,种植面积及开发力度的日     

昆虫性信息素在信阳茶园中的应用效果初报

为了探索昆虫性信息素在茶园中的应用效果,利用茶毛虫和茶尺蠖性信息素在信阳震雷山茶园进行了引诱试验.结果发现,当虫口密度较低时,性诱剂诱虫量与害虫的种群数量呈正相关,能准确反映害虫种群数量的变化动态.如茶尺蠖第1代成虫,性诱剂每日诱虫量高于黑光灯诱虫量,其中性诱剂日诱虫量最多为35头,而同日黑光灯的诱虫量仅为3头;茶毛虫...     

云南茶叶茸毒蛾的生物学特性与综合防治

 对云南茶叶上发生危害的茸毒蛾主要种类的生物学特性及综合防治研究进行了报道.云南茶园内常见的6个茸毒蛾种类,以茶茸毒蛾、皱茸毒蛾和蔚茸毒蛾危害为主.茶茸毒蛾在茶园中1年发生4～5个世代;生长时期完成1个世代需要61.2～71.5d;越冬代长达146.8d.茸毒蛾的综合防治,充分利用茶叶——害虫——天敌相互作用的生态调控作用,发展生物制剂、农业防治、生态防治等结合的综合治理方法,尽力减少化学农药使用量或者不用化学农药,建立可持继发展的害虫综合防治体系.     

外源激素对杂种酸模叶组培效果的影响

对不同外源激素配比影响杂种酸模叶组培效果进行了试验,结果表明,诱导形成愈伤组织和分化形成芽的最佳激素配比为ＭＳ＋１ｍｇ／Ｌ ＩＢＡ＋１ｍｇ／Ｌ ６－ＢＡ;促进芽丛分化的激素配比为１／２ ＭＳ附加０．５ｍｇ／Ｌ ６－ＢＡ＋０．８ｍｇ／Ｌ ＩＢＡ。还对试管内和试管外生根的激素选择及其成活率进行了比较,试管外生根明显优于试管内生根。