MacDonald Aaron A, Dowling Quincy S, Cardon Zoe G
University of Toronto, Toronto, ON, M5S 1A1, Canada.
Marine Biological Laboratory, Woods Hole, MA, 02543, USA.
Oecologia. 2025 Sep 9;207(10):153. doi: 10.1007/s00442-025-05790-5.
Beech leaf disease (BLD) poses a serious threat to the health of beech forests throughout the northeastern USA and Canada. Caused by invasive nematodes, BLD first appeared in 2012 in Ohio and has rapidly spread eastward. We investigated the effects of BLD on leaf and litter chemistry and leaf litter decomposition rate from four infected beech stands in Falmouth, Massachusetts. Attached leaves exhibiting differential infection intensity were collected from trees in October 2023 and analyzed for metrics of carbon (C) and nitrogen (N) content including %C, δC, %N, and δN. Severely infected and asymptomatic newly fallen leaf litter was gathered in November 2023 and analyzed for %C and %N only. We tested the effect of BLD-altered litter chemistry (separate from BLD-altered leaf structure) on litter decomposition rates by incubating ground litter in soil. Despite notably lower C:N in severely infected (C:N ~ 25) vs. asymptomatic (C:N ~ 43) litter, the difference in CO evolution was negligible in short-term incubations. Percent N was significantly higher in severely infected (cupped) vs. asymptomatic litter (P = 0.00076), but significantly lower in severely infected leaves compared to asymptomatic green leaves (P = 0.021). δC tended to increase with infection intensity, possibly reflecting increased water use efficiency with infection stress; δN showed no clear pattern. The severely symptomatic cupped leaves (gathered in October) and litter (gathered in November) had indistinguishable %N, suggesting trees retranslocated far less N out of infected leaves than out of asymptomatic leaves prior to leaf fall.
山毛榉叶病（BLD）对美国东北部和加拿大的山毛榉林健康构成严重威胁。由入侵线虫引起的BLD于2012年首次出现在俄亥俄州，并迅速向东蔓延。我们调查了BLD对马萨诸塞州法尔茅斯四个受感染山毛榉林分的叶片和凋落物化学性质以及落叶分解速率的影响。2023年10月从树木上收集了表现出不同感染强度的附着叶片，并分析了碳（C）和氮（N）含量指标，包括%C、δC、%N和δN。2023年11月收集了严重感染和无症状的新落叶，并仅分析了%C和%N。我们通过在土壤中培养地面凋落物来测试BLD改变的凋落物化学性质（与BLD改变的叶片结构分开）对凋落物分解速率的影响。尽管严重感染的凋落物（C:N约为25）与无症状的凋落物（C:N约为43）相比C:N明显更低，但在短期培养中，CO释放的差异可以忽略不计。严重感染（卷曲）的凋落物中%N显著高于无症状凋落物（P = 0.00076），但与无症状绿叶相比，严重感染叶片中的%N显著更低（P = 0.021）。δC倾向于随着感染强度增加，这可能反映了感染胁迫下水分利用效率的提高；δN没有明显模式。严重症状的卷曲叶片（10月收集）和凋落物（11月收集）的%N无法区分，这表明在落叶前，树木从感染叶片中重新转运出的N远少于从无症状叶片中转运出的N。
