科研動態

科研動態

《Nature Climate Change》雜志發表生態與環境學院盧蒙博士及合作者的最新研究成果

發布時間:2019-10-23 瀏覽次數:

濱海濕地為包括人類在內的眾多生物提供了寶貴的生態系統服務功能,然而這一重要的生態系統正日益受到人為活動的威脅。自工業革命以來,大氣中的二氧化碳(CO2)濃度從280 ppm增加到410 ppm,預計到2100年將超過900 ppm。在陸地生態系統中,CO2濃度的上升通常會促進C3植物的光合作用和初級生產力,從而導致植物形態的變化。但是,與木本植物或農作物相比,非木本克隆植物對CO2升高的形態響應模式卻鮮有研究。考慮到絕大多數鹽沼植被都是克隆植物,且其形態變化將直接決定濱海濕地生態系統的結構和功能,盧蒙博士及合作者在位于美國東海岸Chesapeake Bay的鹽沼濕地開展了30余年的CO2倍增實驗并測量了超過20萬株的植物形態數據,以探討全球變化背景下鹽沼濕地植物形態變化對生態系統結構和功能的影響。

項目組研究表明,30年的倍增CO2控制實驗提高了鹽沼濕地生態系統初級生產力和植被的密度,但降低了優勢克隆物種Schoenoplectus americanus的莖稈直徑和高度(Fig. 1)。較小,較密的莖稈與根和根狀莖的擴張有關,以減輕CO2倍增條件下導致的氮(N)限制,這一點可由莖稈、細根、根狀莖和凋落物中升高的N含量,增加的植物組織碳氮比(CN ratio),和降低的土壤孔隙水無機氮含量所證明(Fig. 2a)。在另一組倍增CO2和氮添加(CO2 + N)控制實驗中,Schoenoplectus americanus的形態變化得到反轉,即莖稈直徑和高度同時增加(Fig. 2b)。因此我們得出,土壤有效氮是控制植物形態對CO2濃度變化響應的關鍵因子(Fig. 3)。

同時,項目組根據鹽沼植被形態學和生物量的變化,模型模擬了未來氣候變化和海平面上升情景下濱海濕地生態系統土壤沉積物的積聚響應模式,結果表明CO2N的交互作用能促進鹽沼濕地的抬升(Table 1),從而為濱海濕地生態系統應對海平面上升提供有力的保障。

該研究成果發表在最新一期的《Nature Climate Change》雜志。

全文鏈接:

https://www.nature.com/articles/s41558-019-0582-x

DOIhttps://doi.org/10.1038/s41558-019-0582-x

Fig. 1 Elevated CO2 responses of individual stem of S. americanus in the C3 community of Experiment 1 from 1987 to 2016. The mean ± s.e.m. (n=5 replicate plots) of stem density (a), stem biomass (b), stem height (c), and stem diameter (d) are shown separately for ambient CO2 (open circles) and elevated CO2 chambers (filled circles).

Fig. 2 The response ratios of key parameters from the two experiments. Elevated CO2 caused symptoms of N limitation such as increased root:shoot ratio and lower available soil N, effects that were mitigated by N addition. Each bar (elevated CO2: open bars, elevated CO2 plus N addition: filled bars) is the mean (± s.e.m.) response ratio (Elevated/Ambient) in Experiment 1 (a) and Experiment 2 (b) across all years in the record.

 

Fig. 3 A conceptual framework for the responses of clonal plant aboveground growth pattern to CO2 enrichment and nitrogen availability.


Table 1. Impacts of elevated CO2 and N on plant growth and accretion. Mean values for frontal area per unit volume (m-1), belowground organic accretion (mm yr-1, from Pastore et al. 2017), total belowground productivity (g m-2 yr-1), stem density (shoot m-2), aboveground biomass (g m-2), and modeled aboveground mineral accretion (mm yr-1) for Experiments 1 and 2. Means ± s.e.m. with the same letter in the same column and experiment are not significantly different from one another (A, B for Experiments 1 and a, b, c for Experiments 2).

 

Frontal   Area

Measured   Belowground Organic Accretion*

Belowground   productivity

Stem   density

Aboveground   Biomass

Modeled   Aboveground Mineral Accretion

Experiment   1

Ambient

2.2 (0.2)A

N/A

269 (21)

538 (25)

497 (33)

4.5 (0.1)A

CO2

2.4 (0.2)B

N/A

349 (28)

784 (30)

564 (33)

5.7 (0.1)B

Experiment   2

Ambient

2.4 (0.2)a

0.46 (0.3)

143 (23)

527 (23)

587 (52)

4.2 (0.1)a

CO2

2.6 (0.2)a,b

1.84 (0.4)

228 (25)

598 (30)

645 (66)

4.9 (0.1)b

CO2+N

3.2 (0.3)b

1.70 (0.6)

187 (35)

633 (31)

803 (83)

5.7 (0.1)c

N

2.3 (0.2)a

1.81 (0.5)

110 (15)

503 (28)

555 (60)

4.4 (0.1)a

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