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Johnson Chris J. Boyce Mark S. Mulders Robert Gunn Anne Gau Rob J. Cluff H. Dean Case Ray L. 《Landscape Ecology》2004,19(8):869-882
Multiscale analyses are widely employed for wildlife-habitat studies. In most cases, however, each scale is considered discrete and little emphasis is placed on incorporating or measuring the responses of wildlife to resources across multiple scales. We modeled the responses of three Arctic wildlife species to vegetative resources distributed at two spatial scales: patches and collections of patches aggregated across a regional area. We defined a patch as a single or homogeneous collection of pixels representing 1 of 10 unique vegetation types. We employed a spatial pattern technique, three-term local quadrat variance, to quantify the distribution of patches at a larger regional scale. We used the distance at which the variance for each of 10 vegetation types peaked to define a moving window for calculating the density of patches. When measures of vegetation patch and density were applied to resource selection functions, the most parsimonious models for wolves and grizzly bears included covariates recorded at both scales. Seasonal resource selection by caribou was best described using a model consisting of only regional scale covariates. Our results suggest that for some species and environments simple patch-scale models may not capture the full range of spatial variation in resources to which wildlife may respond. For mobile animals that range across heterogeneous areas we recommend selection models that integrate resources occurring at a number of spatial scales. Patch density is a simple technique for representing such higher-order spatial patterns. 相似文献
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养殖废弃物堆肥中抗生素和抗性基因的降解研究 总被引:2,自引:1,他引:1
抗生素的滥用及排放会造成细菌产生耐药性以及抗生素抗性基因(Antibiotic resistance genes, ARGs)的传播和扩散。畜禽粪便是导致环境中抗生素污染的主要来源之一。本文综述了四环素类、大环内酯类、喹诺酮类、β-内酰胺类、磺胺类和氨基糖苷类等在水土环境中广泛存在的抗生素及其环境残留水平和对动植物、微生物的影响,分析了当前利用堆肥技术降解畜禽粪便中抗生素和ARGs效果及机制的研究情况。总结得出,猪粪中抗生素残留量最高,其中四环素类残留量为1390~354 000 mg·kg^-1,磺胺类170.6~89 000 mg·kg^-1,氟喹诺酮类411.3~1 516.2 mg·kg^-1,硝基呋喃类85.1~158.1 mg·kg^-1,大环内酯类1.4~4.8 mg·kg^-1。堆肥对大部分抗生素具有好的降解效果,其中四环素类抗生素降解率为62.7%~99%,磺胺类为0~99.99%,对大环内酯类几乎可以完全降解,但是,堆肥无法降解喹诺酮类抗生素。养殖废弃物堆肥过程中,ARGs的降解情况同样因抗生素种类和堆肥方式而不同。已有的研究表明,除大环内酯类ARGs外,堆肥对其他ARGs均具有有效的降解效果,降解率为50.03%~100%。堆肥初期的优势菌门是厚壁菌门、放线菌门、变形菌门和拟杆菌门;堆肥结束后放线菌门成为最优势菌门。初始抗生素的浓度不影响堆肥结束时微生物的群落组成。温度和pH是影响抗生素降解的最主要因素,而ARGs的降解效果主要受温度影响。 相似文献
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以‘长富2号’苹果为试验材料,采用RT-PCR的方法,从其芽中克隆得到INDETERMINATE DOMAIN(IDD)转录因子基因MdIDD7,其开放阅读框长度为1 626 bp,编码541个氨基酸。序列比对和结构域分析表明,该转录因子含有1个核定位信号和4个高度保守的锌指蛋白结构域。系统进化树分析表明,MdIDD7与白梨(Pyrus×bretschneideri,XP_009364602.1)、桃(Prunus persica,XP_007225628.1)和梅(Prunus mume,XP_008220893.1)聚在一起。实时荧光定量PCR表明,MdIDD7在‘长富2号’不同组织(茎、叶、花、果和芽)中均有表达,其中芽的表达量最高。花后40~60 d,MdIDD7在易成花品种‘烟富6号’芽中表达量显著高于难成花品种‘长富2号’。"小年"树顶芽组织中MdIDD7的表达量显著高于"大年"树。在花芽诱导前期,外源GA处理诱导MdIDD7下调表达,而蔗糖处理诱导其上调表达,说明MdIDD7响应激素和糖信号,促进苹果成花。 相似文献
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Excessive application of N fertilizer in pursuit of higher yields is common due to poor soil fertility and low crop productivity. However, this practice causes serious soil depletion and N loss in the traditional wheat cropping system in the Loess Plateau of China. Growing summer legumes as the green manure (GM) crop is a viable solution because of its unique ability to fix atmospheric N2. Actually, little is known about the contribution of GM N to grain and N utilization in the subsequent crop. Therefore, we conducted a four-year field experiment with four winter wheat-based rotations (summer fallow-wheat, Huai bean–wheat, soybean–wheat, and mung bean–wheat) and four nitrogen fertilizer rates applied to wheat (0, 108, 135, and 162 kg N/ha) to investigate the fate of GM nitrogen via decomposition, utilization by wheat, and contribution to grain production and nitrogen economy through GM legumes. Here we showed that GM legumes accumulated 53–76 kg N/ha per year. After decomposing for approximately one year, more than 32 kg N/ha was released from GM legumes. The amount of nitrogen released via GM decomposition that was subsequently utilized by wheat was 7–27 kg N/ha. Incorporation of GM legumes effectively replaced 13–48% (average 31%) of the applied mineral nitrogen fertilizer. Additionally, the GM approach during the fallow period reduced the risk of nitrate-N leaching to depths of 0–100 cm and 100–200 cm by 4.8 and 19.6 kg N/ha, respectively. The soil nitrogen pool was effectively improved by incorporation of GM legumes at the times of wheat sowing. Cultivation of leguminous GM during summer is a better option than bare fallow to maintain the soil nitrogen pool, and decrease the rates required for N fertilization not only in the Loess Plateau of China but also in other similar dryland regions worldwide. 相似文献