探討暖化下地上部與地下部的生物交互作用-路徑分析與直接、間接交互作用之量化

Identify the Path Structure and Quantify Direct and Indirect Effects in an Above-below-ground System under Warming

曾子榮(Tzu-Jung Tseng)

指導教授 ： 何傳愷

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.02675

摘要

暖化可能會影響地上部地下部的生物交互作用，改變直接或間接的交互作用的強度，但是相關的研究卻相當缺乏。為幫助了解暖化對生物交互作用的影響，並量化其中的直接和間接的生物交互作用，本研究在生長箱中建立地上部地下部生物交互作用的系統，藉由調控溫度來模擬正常(日均溫22.5℃，夜均溫18.5℃)及暖化(日夜均溫各加 4℃)的兩個情景。本研究在各溫度下設立了四種處理:控制組(只有植物竹仔菜Commelina diffusa)、蚯蚓組(植物加皮質遠環蚓Amynthas corticis)、蚜蟲組(植物加棉蚜Aphis gossypii)，及蚯蚓蚜蟲組(加入植物、蚯蚓、蚜蟲)。記錄植物的形態變化、土壤的物化性質、落葉分解速度、蚯蚓的重量、及蚜蟲的族群增長，以便探討及量化各因素間的直接或間接關係。資料分析以冗餘分析來探討植物受蚜蟲蚯蚓及暖化的影響，以貝氏階層模式來量化直接效應，以導向分離法及中介分析來判別並量化可能存在的間接效應。研究結果顯示，蚯蚓及蚜蟲對植物的影響強度類似，但是方向相反；而暖化雖然對植物有很強的影響，但此效應隨著時間而呈線性地下降，且不會影響蚯蚓及蚜蟲對植物的效應。蚯蚓、蚜蟲及暖化處理的交互作用並不影響系統中的任何特質，代表這三個因子的影響是加成性的。中介分析顯示出植物氮含量及土壤物理性質是這系統中的中介因子，分別是蚯蚓能藉由增加植物氮含量而間接增加蚜蟲的族群量，以及暖化和蚯蚓處理能改善土壤的物理性質，進而間接促進植物的生長（節數的增加）。整體而言，這試驗顯示出暖化可以透過直接及間接的路徑，進而影響地上部與地下部的系統。

關鍵字

地上部地下部交互作用 ； 暖化 ； 蚯蚓 ； 蚜蟲 ； 中介分析

並列摘要

Climate warming could affect the interactions between above- and below- ground biota and change the strength of direct or indirect effects, but relevant studies are sparse. To better understand above-below-ground interactions under warming, this study examined a system including the plant Commelina diffusa, the aphid Aphis gossypii, and the earthworm Amynthas corticis under 2 scenarios: (1) normal (day and night temperature at 22.5 and 18.5oC, respectively) and (2) warming (a 4 oC increase in day and night temperature). Each scenario included four treatments: a) control treatment (plants only), b) earthworm treatment (plants, earthworms), c) aphid treatment (plants, aphids), and d) earthworm–aphid treatment (plants, aphids, earthworms). To qualify and quantify the direct and indirect effects in this system, I measured the traits of plants, earthworms, aphids, litter, and soil. Data analyses were conducted by (1) redundancy analysis for exploring the general patterns of plant traits in response to the treatment factors (earthworm, aphid, and warming); (2) Bayesian hierarchical modelling to quantify the direct effects in the system; (3) d-sep test and mediation analysis for identifying and quantifying the indirect effects. The results showed that (1) the effect sizes of earthworm and aphid treatments on plants were similar but different in direction, and showed a non-contingent response to warming; (2) the effect of warming treatment on plants was strong but decreased linearly with time; (3) there were no interactions among aphid, earthworm, and warming treatments in this system; thus, the effects of these 3 factors were additive. In addition, I found 2 indirect effects in this system, suggesting plant nitrogen content and soil physical property as mediators in above-below-ground interactions: (1) earthworm treatment increased aphid population by increasing plant nitrogen content, and (2) warming and earthworm treatments increased plant growth (i.e. plant node number) by modifying soil physical property. Overall, this study reveals that warming can affect an above-below-ground system via direct and indirect pathways.

並列關鍵字

above-below-ground interaction ； climate warming ； aphid ； earthworm ； mediation analysis

參考文獻

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