東アジア乾燥地の外来種ニセアカシア植林地および在来種ナラ林における土壌微生物が駆動する窒素循環

京都大学0048新制・課程博士博士(農学)甲第22477号農博第2381号新制||農||1074(附属図書館)学位論文||R2||N5257(農学部図書室)京都大学大学院農学研究科森林科学専攻(主査)准教授 舘野 隆之輔, 教授 北島 薫, 教授 德地 直子学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDGA

The effect of the direction of intergroup comparison, sharing another category, and trait self-esteem on the rejective attitude toward a superior in-group member

In a real society, individuals who do well on a task are sometimes exclusively treated from in-group members. It is because they may threaten the other in-group members' personal identity. This study examined whether such rejective attitude is constrained in the condition where the direction of intergroup comparison and sharing another category were manipulated. Seventy-six participants who are undergraduate students were asked to take a test of social intelligence and them received information about social intelligence. Using sex category as in-group, the direction of inergroup comparison was manipulated. After that, participants were received the feedback of their own point and an in-group member's point which are higher than their own point, that is, all participants were in the interpersonal upward comparison condition. At the same time, whether another category is shared with each other or not was manipulated, using arts-science category. Finally participants were asked the tendency of rejective attitude toward the comparison taget, and debriefed. Results showed that in the condition of intergroup upward comparison and unsharing another category, individuals with low trait self-esteem constrain rejective attitude, although they are less skilled at avoiding the threat to their identity. This study illustrated that the motive to maintain and/or enhance their personal and social identity affect the tendency of rejective attitude toward a superior in-group member

Temperature effects on the first three years of soil ecosystem development on volcanic ash

Little is known of the earliest stages of soil ecosystem development on volcanic ash, and how this process is affected by temperature. We studied the first three years of soil development in a field-based mesocosm experiment, situated in different climates across Japan. Newly fallen, sterilized volcanic ash from the Sakurajima volcano (Kyushu, Japan) was placed into pots and positioned at six locations with mean annual temperatures ranging from - 1.6 °C to 18.6 °C. At 24 months into the experiment, C and N accumulation showed only a weak linear correlation with temperature, but by 36 months there was a clear exponential relationship. This applied only to the top 2 cm of the developing soil, and was not apparent in the lower part of the ash. We suggest that this acceleration in warmer climates relates to a positive feedback involving bryophyte cover, which had become much denser by the third year in the warmer sites. Surprisingly, the abundance of 16S rRNA gene copies of bacteria, fungi, archaea - as well as ammonia oxidizers – did not increase from 12 months to 36 months, and did not show any relationship to temperature, suggesting that input from plants is the major factor in increasing C and N buildup in the soil. Overall it appears that temperature effects on bryophyte cover buildup may be important in controlling the temperature relationship in soil development on volcanic ash

Stability of ammonia oxidizer communities upon nitrogen fertilizer pulse disturbances is dependent on diversity

Diversity of the soil microbial community is an important factor affecting its stability against disturbance. However, the impact of the decline in soil microbial diversity on the stability of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) is not known, particularly considering the repeated soil nutrient disturbances occurring in modern agricultural systems. Here, we conducted a microcosm experiment and modified the soil microbial diversity using the dilution-to-extinction approach to determine the stability and population dynamics of AOB and AOA communities with repeated nitrogen (N) fertilizer application. Our results demonstrated that the AOB community became more abundant and stable against repeated disturbances by N in the treatments with the highest microbial diversity. In contrast, the abundance of AOA decreased following repeated N fertilizer application, regardless of the microbial diversity. Notably, during the initial application phase, AOA displayed a potential for increased abundance in treatments with high soil microbial diversity. These findings highlight that the soil microbial diversity controls the stability of ammonia oxidizers during short- interval repeated N disturbances

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