Canopy cover data from the Ice Storm Experiment (ISE) plots

Large-scale disturbances such as ice storms may increase in frequency
and intensity as climate changes. While disturbances are a natural
component of forest ecosystems, climatically driven alteration to
historical patterns may impart fundamental change to ecosystem
function. At Hubbard Brook Experimental Forest, NH, experimental ice
storms of varying severity were applied to replicate plots of mature
northern hardwoods to quantify their effects on forested ecosystems.
We assessed ice storm treatment effects on insectivorous
foliage-gleaning birds and their interactions with larval Lepidoptera.
These birds are charismatic, of conservation concern, and are a major
predator of caterpillars. In turn, lepidopterans are the dominant
herbivores in temperate forests and are integral to ecosystem
function. We predicted that avian abundance would increase due to
additional structural heterogeneity caused by ice treatments, with a
concomitant increase in caterpillar predation. Point counts were used to measure insectivorous bird activity in the
ice storm experiment plots and additional control plots before and
after treatments. Point counts were conducted in June 2015 and June
2016. Icing occurred in January-February 2016. We deployed and
retrieved plasticine model caterpillars and estimated predation from
characteristic marks to these surrogates. Abundance of
foliage-gleaning birds was higher in the ice storm plots and birds
responded to treatments as a single diffuse disturbance rather than on
an individual plot level. All species except one were observed both
before and after the ice treatments. Surprisingly, predation on
caterpillar models was unaffected by ice storm treatments but rather
was a function of caterpillar density. The increase in avian abundance
in the ice storm treatment plots corroborates other studies of bird
responses to relatively small-scale disturbances in forests and the
limited change in species composition was expected given the plot
size. We conclude that ice storms may provide beneficial changes for
foliage-gleaning birds in the growing season following the
disturbance. These data were gathered as part of the Hubbard Brook Ecosystem Study
(HBES). The HBES is a collaborative effort at the Hubbard Brook
Experimental Forest, which is operated and maintained by the USDA
Forest Service, Northern Research Station. A complete analysis of these data can be found in: Leuenberger, W. M.
(2017). Response of larval lepidoptera and their avian
predators to experimental ice storms in a northeastern
forest (Order No. 10282770). Available from ProQuest
Dissertations & Theses A&I. (1950488566).

随着气候变化，冰风暴等大规模扰动事件的发生频率与强度或呈上升趋势。扰动本是森林生态系统的天然组成部分，但由气候驱动的历史扰动格局改变，可能会对生态系统功能造成根本性改变。

在美国新罕布什尔州哈伯布鲁克实验林（Hubbard Brook Experimental Forest），研究人员对成熟北方硬阔林的重复样地施加了不同强度的人工冰风暴，以量化其对森林生态系统的影响。本研究评估了冰风暴处理对叶面觅食食虫鸟类（insectivorous foliage-gleaning birds）及其与鳞翅目（Lepidoptera）幼虫的相互作用效应。

这类鸟类兼具公众关注度与保护价值，是毛虫的主要捕食者；而鳞翅目幼虫是温带森林中的优势植食类群，对生态系统功能至关重要。

我们预测，冰风暴处理所带来的额外结构异质性将提升食虫鸟类的丰度，并同步加剧对毛虫的捕食压力。

研究分别于2015年6月与2016年6月开展样点计数法（point counts），以测定冰风暴实验样地及额外对照样地内食虫鸟类的活动情况；人工冰风暴施加于2016年1-2月。

我们部署并回收了橡皮泥毛虫模型（plasticine model caterpillars），通过该替代物上的特征性咬痕来估算捕食强度。

结果显示，冰风暴样地内的叶面觅食食虫鸟类丰度更高，且鸟类对扰动的响应呈现为单一弥散性扰动效应，而非针对单个样地的特异性响应。除一个物种外，其余所有物种在冰风暴处理前后均被观测到。出乎意料的是，毛虫模型所受的捕食强度并未受冰风暴处理的影响，反而与毛虫密度呈显著相关。冰风暴样地内鸟类丰度的提升，与此前针对森林小规模扰动的鸟类响应研究结果一致；而考虑到样地规模，物种组成的有限变化也符合预期。

我们得出结论：冰风暴或可在扰动发生后的生长季为叶面觅食食虫鸟类带来利好变化。

本数据集作为哈伯布鲁克生态系统研究（Hubbard Brook Ecosystem Study, HBES）的一部分收集而成。该研究项目由美国农业部林务局（USDA Forest Service）北方研究站运营维护的哈伯布鲁克实验林开展协作研究。

对本数据集的完整分析可参见：Leuenberger, W. M. (2017). 《东北森林中鳞翅目幼虫及其鸟类捕食者对人工冰风暴的响应》（学位论文编号：10282770）。可通过ProQuest博硕士论文文摘与全文数据库（ProQuest Dissertations & Theses A&I）获取（检索号：1950488566）。