在鳥類行為的干擾逆境下，雨林地被層蕨類可以幫助小樹苗存活

文獻出處

Song, GZM, et al. (2012) Rain forest understorey ferns facilitate tree seedling survival under animal non-trophic stress. J. Veget. Sci., 23(5): 847-857.

摘要

• Questions： 動物物種多樣性豐富的森林中，動物的非營養階層行為對植物的影響就跟直接的營養階層行為一樣普遍。但，大多數的研究並未檢驗動物的非營養影響對於植物間交互作用有無關聯。動物的這些行為可能改變植物間交互作用的淨效果嗎？特別是對於動物較易接觸到的地被植物與小樹苗？生物的組成與動物行為之間的關聯性又是如何呢？
• Location： The Main Range National Park, southeast Queensland, Australia.
• Methods：沿著 0.5m X 200m 的樣帶，研究人員監測了地被中(主要為 Lastreopsis decomposita 這種蕨類)小苗的存活率長達兩年。將面積 10% 的樣帶以籠子隔絕，避免鳥類進入以評估動物行為對植物間交互作用的影響，持續一年。放置200個 5X5 cm^2 的塑膠標籤以估計鳥類活動的頻度與枯落物累積量。
• Results：地被蕨類對於小苗的影響可以分為正面與負面。正面效果如降低小苗被鳥類拔起的比率、降低小苗被枯落物掩埋率，這些正面效果主要受到鳥類活動與其他非生物因子所驅動；負面小果如使小苗的受光量不足、吸引更多植食者或分解者，使小苗容易凋萎或分解。實驗結果隔絕了鳥類活動，造成地被蕨類對小苗的影響由正轉為中性；小苗存活率與地被蕨類覆蓋率有正相關性。
• Conclusion：除了生物間食物鏈(營養階層的關係)，動物行為造成植物間交互作用改變的效果是明顯的，此研究證實植物間交互作用會受到系統中的動物物種影響，並提供一概念性模型用以解釋此現象。

Abstract

• Questions: Although forest ecosystems harbour many animal species and animalnon-trophic effects are as ubiquitous as trophic effects, few studies have examined animal non-trophic effects on plant–plant interactions. Can animal non-trophic behaviour influence plant–plant interactions and thus, change the net effect of interactions, especially those between understorey vegetation and tree seedlings? How do the species traits of understorey vegetation and animals  contribute to their interactionswith seedlings?
• Location: TheMain Range National Park, southeast Queensland, Australia.
• Methods: Seedling survival related to the cover of understorey vegetation (mainly the fern Lastreopsis decomposita) was monitored in a 0.5-m wide and 200-m long transect for 2 yrs. Ten per cent of the transect was caged to estimate the effects of non-trophic disturbances fromtwo pheasant-size, ground-dwelling birds (Menura alberti and Alectura lathami) for 1 yr. Two hundred plastic tags (5 9 5 cm) were placed in the transect to quantify bird disturbance and litter input.
• Results: The negative effects of the fern understorey on seedlings were increased light deficits, greater risk of herbivory and wilting or rotting; the positive effects were reduced uprooting and litter smothering due to abiotic and bird disturbances. Notably, the exclusion of bird activity changed the net effect of the fern understorey from positive to neutral, and seedling survival was positively correlated with fern cover.
• Conclusions: The net effect of plant-plant interactions is subject to change when additional species are involved. In addition to trophic effects, non-trophic effects are such that they can change interactions between plants. A conceptualmodel of species traits contributing to interactions is presented.