Assessing the Effect of Eastern Hemlock (Tsuga canadensis) Decline from Hemlock Woolly Adelgid (Adelges tsugae) Infestation on Ectomycorrhizal Colonization and Growth of Red Oak (Quercus rubra) Seedlings

IF 0.6 4区 环境科学与生态学 Q4 Agricultural and Biological Sciences
Kathryn E. Caruso, J. Horton, A. Hove
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引用次数: 0

Abstract

Abstract. Eastern hemlock (Tsuga canadensis (L.) Carrière) is a foundation species in eastern North American forests, providing critical habitats for a number of species. These trees are experiencing widespread decline due to the spread of hemlock woolly adelgid (HWA: Adelges tsugae Annand Order Hemiptera) into their range, potentially resulting in the disappearance of hemlocks from eastern forests. Hemlock dieback can lead to cascading effects on associated ecosystems, including belowground, mycorrhizal fungal communities. Ectomycorrhizal fungi (EM), which are mutualistic with many tree species and provide nutrients to plant hosts, are known to colonize hemlock as well as neighboring tree species at lower levels following HWA infection. This study investigated the effect of hemlock decline from HWA infestation on mycorrhizal communities, as inferred from colonization on northern red oak (Quercus rubra L.) “bait” seedlings grown near “host” hemlock trees. Hemlock health surveys were conducted in healthy (Carl Sandburg Home National Historic Site – CARL) and declining (Warren Wilson College – WWC) stands in western North Carolina, and host trees were paired between stands based on diameter. In each stand, northern red oak seedlings were planted within a meter of host hemlocks in early summer and allowed to grow for 8 w, when they were harvested. Seedling growth and dry biomass were recorded at harvest and roots were sampled for mycorrhizal colonization frequencies. Different mycorrhizal morphotypes were collected from seedling roots for subsequent DNA barcoding analyses to characterize EM taxonomic richness to compare mycorrhizal community assemblages between the two stands. Mycorrhizal colonization frequencies (percentage of the total number of EM-colonized root tips per seedling) and growth in seedling height were significantly greater at CARL than WWC, suggesting healthy hemlock stands are more favorable for oak seedling growth than declining stands. Moreover, a greater proportion of seedlings grown in the healthy stand were colonized by EM, indicating EM assemblages differ between a healthy and a declining hemlock stand. Differences between EM communities corresponded with altered seedling growth allocation, as seedlings in the declining stand had higher root to shoot ratios with reduced stem height, but showed greater investment in root biomass and stem diameter growth. We conclude EM communities differ between a healthy and declining hemlock stands, and changes in EM communities following hemlock dieback may affect the growth of replacement species.
红橡树(Quercus rubra)幼苗外生菌根定植及生长对东铁杉(Tsuga canadensis)和铁杉(Adelges tsugae)侵染的影响
摘要东铁杉(Tsuga canadensis, L.)carririre)是北美东部森林的基础物种,为许多物种提供了重要的栖息地。这些树木正经历着广泛的衰退,因为铁杉毛杉(HWA: Adelges tsugae Annand目半翅目)进入了它们的活动范围,可能导致铁杉从东部森林中消失。铁杉枯死会导致相关生态系统的级联效应,包括地下菌根真菌群落。外生菌根真菌(EM)与许多树种共生,并为植物宿主提供营养,已知在HWA感染后,其在铁杉和邻近树种中的定殖水平较低。本研究通过北红橡树(Quercus rubra L.)“诱饵”幼苗在“寄主”铁杉附近的定殖,研究了HWA侵染铁杉对菌根群落的影响。在北卡罗来纳州西部的健康(Carl Sandburg Home National Historic Site - Carl)和衰退(Warren Wilson College - WWC)林分中进行了铁杉健康调查,并根据林分直径对宿主树进行配对。在每个林分中,在初夏将北红橡树幼苗种植在距离宿主铁杉1米的地方,并在收获时让它们生长8周。在收获时记录幼苗生长和干生物量,并对根系进行菌根定植频率取样。从幼苗根系中收集不同的菌根形态,随后进行DNA条形码分析,表征EM分类丰富度,比较两种林分之间的菌根群落组合。菌根定植频率(占每株幼苗根尖总数量的百分比)和幼苗高的生长均显著高于WWC,说明健康的铁杉林分比衰败的铁杉林分更有利于橡树幼苗生长。此外,在健康林分生长的幼苗中,EM定域的比例更大,这表明健康和衰退铁杉林分的EM组合存在差异。EM群落间的差异与幼苗生长分配的变化相对应,衰败林分的幼苗根冠比较高,茎高降低,但根系生物量和茎粗的生长投入较大。我们得出结论,在健康和衰退的铁杉林分中,EM群落存在差异,铁杉枯死后EM群落的变化可能会影响替代物种的生长。
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来源期刊
American Midland Naturalist
American Midland Naturalist 环境科学-生态学
CiteScore
1.20
自引率
0.00%
发文量
38
审稿时长
18-36 weeks
期刊介绍: The American Midland Naturalist has been published for 90 years by the University of Notre Dame. The connotations of Midland and Naturalist have broadened and its geographic coverage now includes North America with occasional articles from other continents. The old image of naturalist has changed and the journal publishes what Charles Elton aptly termed "scientific natural history" including field and experimental biology. Its significance and breadth of coverage are evident in that the American Midland Naturalist is among the most frequently cited journals in publications on ecology, mammalogy, herpetology, ornithology, ichthyology, parasitology, aquatic and invertebrate biology and other biological disciplines.
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