台灣山蘇花基質氮源與無脊椎動物群聚之研究

Study on the Nitrogen Source and Invertebrate Community in the Substrate of Bird's Nest Fern (Asplenium nidus L.)

顏睦歆(Mu-Hsin Yen)

指導教授 ： 吳文哲

共同指導教授 ： 王巧萍(Chiao-Ping Wang)

國立臺灣大學/生物資源暨農學院/昆蟲學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01255

摘要

本研究於福山試驗林，採集共13株台灣山蘇花 (Asplenium nidus L.)，分離出基質動物相，以探討台灣山蘇花大小對其基質無脊椎動物數量之影響，其後測量植體及動物體樣品之乾重與穩定同位素天然含量 (δ13C ‰、δ15N ‰)，來探討山蘇利用動物性氮源之可能，並藉以分析基質動物相之食性層級。平均葉長大於60 cm 以上的台灣山蘇花因基質乾重及植體總乾重呈現指數成長而大量累積，生長於其中的無脊椎動物生物量總乾重則隨之呈對數型成長，對數轉換之動物體總生物量與山蘇總乾重呈良好之線性廻歸 (R2 = 0.7，P < 0.01)，由此可知植體生物量的累積與動物體之增長形式 (速率) 不同，因而造成單位基質重之動物體乾重百分比在平均葉長40~60 cm 的山蘇 (中型山蘇) 較高 (0.3~2.2%)，而小型山蘇 (平均葉長 < 30 cm) 及大型山蘇 (平均葉長 > 60 cm) 則較低 (0~0.6%)。由新鮮山蘇葉片與其腐植質δ15N的分析發現 (新鮮山蘇葉 -6.5~-3.5‰，腐植質 -7~-3‰)，然其中有4株山蘇之葉片異常呈現比腐植質為高的15N含量，其可能原因為，除山蘇在基質含有使「葉片15N變重」的動物性氮源外，同時亦受到可使「腐植質15N變輕」的外來枯落物之稀釋作用；而其中中型山蘇可能受動物性氮源之影響較大，而大型山蘇則由於較容易承接到大量外來枯落物。由∆δ15N可看出捕食者 (蜘蛛目及唇足綱，5.5~10‰) 較高於初級消費者 (植食者、碎食者以及食真菌者，1~7‰)，∆δ13C測值則明顯可區分出植食者 (鱗翅目幼蟲，1~3.5‰)、食真菌者 (纓毛蕈蟲，3.52 ± 0.19‰) 及碎食者 (等腳目、寡毛綱及倍足綱，4.25~7.5‰)，說明初級消費者間可能有不同之食源，尤其碎食者可能取食到C4、Crassulacean acid metabolism (CAM) 植物使其13C含量較高。由∆δ15N 分析家蟻亞科、山蟻亞科及蟋蟀科Duolandrevus sp. 等雜食者的食性層級，山蟻亞科應為初級消費者 (∆δ15N 3.73 ± 1.32‰)，而家蟻亞科則介於捕食者與初級消費者間 (∆δ15N 5.76 ± 1.28‰)，然家蟻亞科中捕食性的細毛瘤顎蟻∆δ15N較低 (4.94‰)，蟋蟀科Duolandrevus sp.則屬於初級消費者 (∆δ15N 3.00 ± 1.03‰)，顯示穩定同位素15N天然含量的分析可作為雜食性昆蟲食性分析之方法。

關鍵字

台灣山蘇花 ； Asplenium nidus ； 穩定同位素分析 ； 天然含量 ； 食性功能群

並列摘要

Thirteen bird's nest ferns (Asplenium nidus L.) were collected from Fushan experimental forest. First, we separated the invertebrates from substrate, then measured the dry weight of the bird’s nest ferns and invertebrates to investigate the relationship between invertebrates and nest fern sizes. This investigation employed δ13C and δ15N analysis of sampled bird's nest ferns and invertebrate, to determine whether epiphytes derived nitrogen from animal sources with increased plant size. Trophic level was also analysied from stable isotope data of invertebrates. The nest fern total biomass and substrate biomass exponentially increased with mean leaf length and the biomass (or substrate) largely accumulated in "large ferns" (mean leaf length > 60 cm). Invertebrates total biomass logarithmically increased with nest fern total biomass and linearly increased with nest fern total biomass using logarithmic transformation (R2 = 0.7, P < 0.01). It is concluded that the biomass accumulation of nest fern was different from invertebrates increasing with increased plant size. In "medium ferns" (mean leaf length 40-60 cm) had higher invertebrate biomass (substrate-1) (0.3-2.2%), while both in "small" (< 30 cm) and "large" (> 60 cm) ferns had lower invertebrate biomass (substrate-1). Contrary to soil-plant systems, we found 4 nest ferns' δ15Nfern leaf higher than δ15Nhumus (fern leaf -6.5--3.5‰, humus -7--3‰), potentially besides the available N from animals sources (enriched-15N) absorbed by plants, the influence of a large amount of decomposed imported litter (depleted-15N) diluted the δ15N of humus also existed. Though the "enriched" sources may be the main effect in "medium ferns" and in the "large ferns", the "depleted" litter input may be the main factor because of the dilution of large amount imported litter received. ∆δ13C and ∆δ15N revealed trophic levels of invertebrates in 13 nest ferns. ∆δ15N of invertebrates distinguished into predators (Araneae and Chilopoda; 5.5-10‰) and primary consumers (herbivores, detritivores and fungivores; 1-7‰). ∆δ13C could further distinguish primary consumers into herbivores (Lepidoptera larvae; 1-3.5‰), fungivores (Ptiliidae; 3.52 ± 0.19‰) and detritivores (Isopoda, Oligochaeta and Diplopoda; 4.25-7.5‰) whereas the high value of detritivores’ ∆δ13C indicate they may have food sources from C4 and Crassulacean acid metabolism (CAM) plants in canopy. The trophic level analysis of omnivores (Myrmicinae, Formicinae and Gryllidae (Duolandrevus sp.)) by ∆δ15N revealed that Formicinae significantly aligned with primary consumers (unpaired t-test P > 0.01 with primary consumers; δ15N -2.355 ± 1.58‰，∆δ15N 3.725 ± 1.32‰), Myrmicinae aligned between predators and primary consumers (unpaired t-test P > 0.01 with 4 functional groups; δ15N -0.099 ± 1.36‰，∆δ15N 5.757 ± 1.28‰) and ∆δ15N of Strumigenys formosensis, one of the predators in Myrmicinae, was low (4.94‰), and Gryllidae (Duolandrevus sp.) also significantly aligned with primary consumers (unpaired t-test P > 0.01 with primary consumers; δ15N -2.414 ± 1.07‰，∆δ15N 3.000 ± 1.03‰). Our results confirm the use of 15N natural abundance in animal-diet studies of omnivorous species and exemplify the importance of trophic level study in epiphytes by stable isotope analysis.

並列關鍵字

Asplenium nidus ； stable isotope analysis ； natural abundance ； trophic functional groups

參考文獻

Lin, K. C., N. H. Chang, C. P. Wang, and C. P. Liu. 2002. Green foliage decomposition and its nitrogen dynamics of 4 tree species of the Fushan Forest. Taiwan J. For. Sci. 17: 75-85.

Wang, C. P., and K. C. Lin. 2003. Variation of 15N natural abundance in leaves and soils of two natural Lauro-Fagaceae forest in Taiwan. Taiwan J. For. Sci. 18: 153-157.

Yang, J. T., M. Y. Chen, and Y. Y. Jiang. 2001a. Biodiversity of the invertebrate community in epiphytic substrates of Guandaushi forest ecosystem, central Taiwan. Formosan Entomol. 21: 99-117. (in Chinese)

Yang, J. T., M. Y. Chen, and Y. Y. Jiang. 2001b. Biodiversity of ant-guest community in the epiphytic substrates of Guandaushi forest ecosystem, central Taiwan. Quart. J. For. Res. Taiwan 23: 31-44. (in Chinese)

Amundson, R., A. T. Austin, E. A. G. Schuur, K. Yoo, V. Matzek, C. Kendall, A. Uebersax, D. Brenner, and W. T. Baisden. 2003. Global patterns of the isotopic composition of soil and plant nitrogen. Glob. Biogeochem. Cycles 17: 31-1-31-5.