分类： 生物学 >> 生物化学 分类： 生物学 >> 生态学 提交时间： 2018-11-22
摘要： Atmospherically-deposited nitrogen (N) can stimulate complex soil N metabolisms and accumulations over time. Whether long-term (decadal) N deposition effects on soil N transformations and functional microbes differ from the short-term (annual) effects have rarely been assessed. Here we conducted a laboratory 15N tracing study with soil samples from a short-term (one year) N addition site and a long-term (12 years) site in a subtropical forest. The effects of simulated N deposition on soil N2O emissions, N transformation rates and microbial nitrifying and denitrifying genes were determined. Our results showed that: (1) long-term N addition did not change soil N2O fluxes significantly in comparison to the short-term N addition. Denitrification, heterotrophic nitrification and autotrophic nitrification contributed 53%, 23% and 18% to total N2O emissions, respectively. (2) Autotrophic nitrification was the dominant N transformation process, except for the high-N treatment at the long-term site. The magnitude of soil N transformation rates was significantly different among N addition treatments but not between short- and long-term N addition sites. However, long-term N addition changed the responses of specific N transformation rates to N addition markedly, especially for the rates of nitrification, organic N mineralization to NH4+, NO3- immobilization and dissimilatory NO3- reduction to NH4+ (DNRA). (3) Responses of ammonia oxidizing archaea and bacteria (AOA and AOB) were stronger than denitrifying N2O-producers (nirK) and denitrifying N2O-reducers (nosZ) at the long-term site compared to the short-term site. (4) The close correlations among N2O flux, functional genes and soil properties observed at the short-term site was weakened at the long-term site, posing a decreased risk for N losses in the acid subtropical forest soils. There is evidence for an adaptation of functional microbial communities to the prevailing soil conditions and in response to long-term natural and anthropogenic N depositions.
分类： 心理学 >> 认知心理学 提交时间： 2018-11-22
摘要： 睾酮是一种类固醇激素，主要的雄性激素之一，在神经科学与神经内分泌学领域中，早期研究发现睾酮会对人类的攻击性、社会交往、冲动性等方面产生一定的影响；因此心理学研究者开始关注睾酮与决策之间的关系，包括社会性决策的信任、合作、利他与竞争方面以及经济性决策的风险决策。多项研究显示，睾酮的水平与经济性决策中的风险寻求行为呈正相关关系；在社会性决策领域中，高水平睾酮的个体会趋向于更高的攻击性、支配性和公平性行为，同时表现出更低的人际信任。然而这些研究结果间也存在难以重复验证的现象，需要更多的研究探寻可能影响睾酮与决策的其他因素。未来对睾酮与决策的研究可以关注睾酮与消费决策领域、探寻青少年睾酮水平与社会行为的关系以及临床应用等。
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