Vertical stratification of leaf physical traits exerts bottom-up pressures on insect herbivory in a sugar maple temperate forest

Do vertical gradients in temperate forest structure insect herbivore communities?  We tested the hypothesis that the increase in light intensity from understory to forest canopy level drives differences in leaf physical traits and budburst phenology that impact insect herbivores and thus play a role in structuring both herbivore communities and the leaf damages they cause. Twelve sugar maple (Acer saccharum) sites were monitored in southern Quebec, examining insect herbivore patterns from understory to the shaded and sun canopy over the summers of 2020, 2021, and 2022. Additionally, we recorded leaf physical traits, temperature, humidity, and sun exposure. Our findings revealed that leaf thickness increased along the vertical gradient in 2021, making leaves less favorable to herbivores in the canopy level. Accordingly, we recorded a consistent decrease in insect herbivory damage rates from the understory to the shaded canopy and sun canopy in 2020 and 2021, driven by leaf cutters, skele..., Study site and plant species
We conducted our sampling at the Kenauk Nature property, located in southwestern Quebec, Canada (45°42'N; 74°53'W). The property spans two regions from the Outaouais river valley to the Laurentian Mountains. Based on the provided domains map by the Quebec Ministry of Forests it is in a maple/bitternut hickory domain of temperate deciduous forest (Quebec Ministry of Forests 2023). To consider the variation in insect herbivory throughout the growing season, three sampling sessions were conducted at the end of June, end of July, and middle of August in 2020, 2021, and 2022. During each session, we sampled the same 12 sites, each spaced more than 15 meters apart and tree species composition was relatively uniform in all sites. These sites were selected based on the similarity in tree size and safety considerations for climbing. Each site comprised one mature sugar maple tree and one sapling. We collected samples from both the sunlit and shaded canopy levels of t..., , We have submitted our raw data including Insect herbivory damages on leaves, recorded environmental factors, and measured leaf traits in 2020 and 2021(**Leaf damage.trait.2020.2021.csv**), insect herbivore specimen information collected in 2022 (**herbivore.guilds.22.csv**), recorded budburst phenology raw data for all sampled trees in 2022 (**sugar.maple.budburst.22.csv**), data needed for leaf trait correlation with leaf herbivory damages in RDA analysis (**rda.dam.trait.21.csv**), four data sets created out of *Leaf damage.trait.2020.2021.csv* for illustrating line graphs for insect herbivory damages variation thorough time and between tree strata for 2020 and 2021 (**Av.dam.sampling.20.csv, Av.dam.sampling.21.csv, Av.dam.20.strata.csv, Av.dam.21.strata.csv**) and R script (**Damage.trait.20.21.R**).

### Descriptions

#### **Leaf damage.trait.2020.2021.csv**

* *Month*: Sampling performed in 1 = June, 2= July and 3=August
* *Site*: each selected 12 sites includes one mature sug...

温带森林的垂直梯度是否塑造昆虫植食者群落？我们验证了如下假说：从林下层到林冠层的光照强度升高，会驱动叶片物理性状与芽物候的差异，进而影响昆虫植食者，从而在塑造植食者群落及其造成的叶片损伤中发挥作用。2020、2021、2022年夏季，我们在魁北克南部对12个糖枫（Acer saccharum）样地开展监测，探究从林下层、遮阴林冠到向阳林冠的昆虫植食者分布格局。此外，我们还记录了叶片物理性状、温度、湿度与日照暴露情况。

研究结果显示，2021年叶片厚度沿垂直梯度递增，使得林冠层叶片对植食者的适宜性下降。据此，2020和2021年我们观测到昆虫植食损伤率从林下层到遮阴林冠、再到向阳林冠持续降低，该现象由切叶类、食骨类（skele...）昆虫驱动。

### 研究地点与植物种类
我们的采样工作在加拿大魁北克西南部的Kenauk Nature保护区开展（北纬45°42′，西经74°53′）。该保护区涵盖从奥特莱河谷到劳伦琴山脉的两个区域，根据魁北克林业部提供的区域分布图，其属于温带落叶林的枫/山核桃域（魁北克林业部，2023）。

为考量昆虫植食作用在整个生长季的动态变化，我们分别于2020、2021、2022年的6月末、7月末与8月中旬开展三次采样。每次采样均覆盖全部12个样地，各采样点间距均超过15米，且各样地的树种组成相对均一。样地选取基于树木大小的一致性与攀爬安全性考量，每个样地包含1棵成熟糖枫与1棵糖枫幼树。我们从向阳林冠与遮阴林冠层分别采集样品……

### 已提交数据集
我们已提交的原始数据包括：2020与2021年的叶片植食损伤、记录的环境因子与测得的叶片性状数据（**Leaf damage.trait.2020.2021.csv**）、2022年采集的昆虫植食者标本信息（**herbivore.guilds.22.csv**）、2022年所有采样树木的芽物候原始记录数据（**sugar.maple.budburst.22.csv**）、用于冗余分析（Redundancy Analysis, RDA）的叶片性状与植食损伤相关性分析数据（**rda.dam.trait.21.csv**）、从*Leaf damage.trait.2020.2021.csv*中导出的4份数据集，用于绘制2020和2021年昆虫植食损伤随时间及树木层位变化的折线图（**Av.dam.sampling.20.csv, Av.dam.sampling.21.csv, Av.dam.20.strata.csv, Av.dam.21.strata.csv**），以及配套的R脚本（**Damage.trait.20.21.R**）。

#### 数据集描述
##### **Leaf damage.trait.2020.2021.csv**
* *Month*：采样月份编码，1代表6月，2代表7月，3代表8月
* *Site*：共选取12个样地，每个样地包含1棵成熟糖……