The Impacts of Canopy Cover on Species Abundance in a Woodlot Habitat

<b>Methods</b> This experiment was conducted by Setareh Rezvani, Khondoker Sadid, Arian Nouraee and Ellora Arockiadoss on a windy day with a climate of 7° C in the woodlot (43.768756, -79.5079) at York University on Monday October 24, 2016 at approximately 3:00 PM. Survey method, quadrats: The quadrats, each sized to 1 meter by 1 meter, were placed every 2 meters along a 50 meter transect placed at random throughout the forest. For each replicate, the quadrat was placed either on the left side of the transect for odd quadrat replicate numbers, or right side for even quadrat replicate number. First, the number of individuals belonging to species native to the site was counted (native abundance), followed by a count of the number of species that are exotic to the site (exotic abundance), and lastly the number of flower heads present in each quadrat. Native and exotic species were identified and differentiated with help from the experiment supervisor (TA). This was repeated for a total of 25 times replicates up to the entire length of the transect. Survey method, transect: A 50 meter transect was obtained and placed from one end of the woodlot to the other. At every two meters, the abundance of woody plants that was within 0.5 meters on either side of the transect was recorded. Additionally, the canopy coverage, vegetative ground coverage, and total number of flowers were also recorded at 2 m intervals on the transect. A total of 25 replicates were obtained in this data set. Survey method, point survey: Using the 50 meter transect, the abundance and species of vertebrates, as well as the number of humans that did not belong to the lab was collected within a 50 meter radius of the woodlot over a span of 15 minutes. Additionally, the abundance of invertebrates was collected within a 5 metre radius in the woodlot area over a span of 15 minutes. Survey method, pan trap: Using the 50 meter transect, six solo bowls were set 3 meters apart at distances of 0 meters, 3 meters, 6 meters, 9 meters, 12 meters, and 15 meters parallel to the transect. The six yellow, blue and white bowls in alternating colours were then filled with soap water to about ¾ full and were left undisturbed for 45 minutes. At the end, the number of insects present within the bowls were accounted for within the woodlot. Survey method, sweep net: A 50 meter transect was placed. Using a sweep net, the number of invertebrates captured along the 50 meters was measured and recorded. After the first measurement, the remainder of the calculations were walked in distances of 1 or 2 meters away from the transect but continued 50 meters parallel to the transect. This procedure was conducted in the woodlot for a total of 10 replicates at each area. <b>Metadata:</b> Native abundance is a discrete variable that provides the total number of individuals observed within the area of the quadrat belonging to species that have been identified as native to the site being studied. Exotic abundance is a discrete variable that provides the total number of individuals observed within the area of the quadrat belonging to species that have been identified as exotic to the site being studied Abundance of woody plants is a discrete variable that provides the number of woody plants found in each sample replicate. A woody plant is defined as a tree greater than 1.5 meters in height. Canopy cover is a continuous variable that provides the percentage of canopy coverage that was observed when looking towards the sky in each sample replicate. Ground cover is a discrete variable that provides the percentage of vegetative ground cover in each sample replicate. Vegetative ground cover was visually identified as grass. Number of flowers is a discrete variable that provides the total number of flowers in each sample replicate. Flowers were identified as any plant with a blooming bud. Abundance of vertebrates (eg. birds, squirrels, rabbits) is a discrete variable that measures the number of individual vertebrates in a 50 metre radius over a period of 15 minutes. Vertebrate species is a discrete variable that shows the number of different species that were observed in a 50 metre radius over a period of 15 minutes. Abundance of humans is a discrete variable that provides the number of human beings which were visualized within a 50 metre radius over 15 minutes. Abundance of invertebrates is a discrete variable which accounted for the total number of insects such as ants, flies, bees and dragonflies that were found in each sample within a 5 metre radius over a 15 minute period. Abundance invertebrates pan traps is a discrete variable that represents the number of invertebrates captured in the solo bowls filled with soap after 45 minutes. Abundance invertebrates sweeps is a discrete variables is a discrete variable that represents the number of invertebrates captured in the sweep net along a 50 m transect. <b>Hypothesis:</b>There will be higher abundance and diversity of wooded plants than herbaceous plants in the woodlot area due to the lack of sunlight filtering through the dense canopy cover (less light for herbaceous plants). This leads to amensalism between herbaceous and wooded plants, as herbaceous species are negatively affected by the presence of wooded plants, while wooded plants are unaffected by herbaceous plants.<br><b>Predictions</b>1. Abundance of herbaceous plant species will be lower than wooded plants in the woodlot2. As canopy cover in the woodlot increases, abundance of herbaceous plant species will decrease 3. Abundance of invertebrates and vertebrates will increase as canopy cover increases due to the shade (protection from sunlight) provided by the presence of wooded plants.

<b>研究方法</b> 本实验由Setareh Rezvani、Khondoker Sadid、Arian Nouraee与Ellora Arockiadoss完成，于2016年10月24日周一下午约3点，在约克大学（York University）的林地（坐标43.768756, -79.5079）内开展，当日有风，气温7℃。
<b>样方调查法：</b> 每个样方（quadrat）尺寸为1米×1米，沿随机布设于林地内的50米样线（transect）每隔2米放置1个。对于每一次重复，当样方重复编号为奇数时，将样方置于样线左侧；编号为偶数时则置于样线右侧。首先统计样方内本地物种的个体总数（本地多度，native abundance），随后统计外来物种的个体总数（外来多度，exotic abundance），最后统计每个样方内的头状花序数量。本地与外来物种的鉴定与区分由实验助教（TA）协助完成。该流程沿样线全程共重复25次。
<b>样线调查法：</b> 布设一条从林地一端延伸至另一端的50米样线。在样线每间隔2米处，记录样线两侧0.5米范围内的木本植物多度。此外，在样线每2米间隔处，同步记录冠层盖度、植被地表盖度以及总花数。本数据集共获取25组样线调查重复样本。
<b>点位调查法：</b> 依托前述50米样线，在林地周边50米半径范围内开展为期15分钟的调查，记录脊椎动物的多度与物种种类，以及非本实验室人员的数量。此外，在林地内5米半径范围内开展为期15分钟的调查，记录无脊椎动物的多度。
<b>盘诱法调查：</b> 依托50米样线，沿样线平行方向，分别在0米、3米、6米、9米、12米、15米处设置6个独立诱集碗，各碗间距3米。将黄、蓝、白三色交替排列的6个诱集碗装入约3/4容量的肥皂水，静置45分钟。实验结束后，统计林地内诱集碗中捕获的昆虫数量。
<b>扫网法调查：</b> 布设50米样线，使用扫网（sweep net）统计并记录沿样线50米范围内捕获的无脊椎动物数量。首次测量完成后，后续测量沿偏离样线1或2米、且与原样线平行的路径开展，同样覆盖50米长度。该流程在林地内每个区域共重复开展10次。
<b>元数据：</b> 本地多度：离散变量，记录样方范围内被鉴定为研究区域本地物种的个体总数。
外来多度：离散变量，记录样方范围内被鉴定为研究区域外来物种的个体总数。
木本植物多度：离散变量，记录每组样本重复中发现的木本植物数量。木本植物定义为高度大于1.5米的树木。
冠层盖度：连续变量，记录每组样本重复中，仰视天空时观测到的冠层覆盖百分比。
地表植被盖度：离散变量，记录每组样本重复中的植被地表覆盖百分比。经目视判定，植被地表覆盖物为草本植物。
花数：离散变量，记录每组样本重复中的总花数。花被定义为带有开放花苞的植物。
脊椎动物多度：离散变量，记录15分钟内、50米半径范围内观测到的脊椎动物个体总数（例如鸟类、松鼠、野兔）。
脊椎物种类数：离散变量，记录15分钟内、50米半径范围内观测到的不同脊椎动物物种数量。
人员多度：离散变量，记录15分钟内、50米半径范围内目视到的人员数量。
无脊椎动物多度：离散变量，记录15分钟内、林地内5米半径范围内每组样本中发现的昆虫（例如蚂蚁、苍蝇、蜜蜂、蜻蜓）总数。
盘诱法无脊椎动物多度：离散变量，记录经45分钟肥皂水诱集后，独立诱集碗中捕获的无脊椎动物数量。
扫网法无脊椎动物多度：离散变量，记录沿50米样线使用扫网捕获的无脊椎动物数量。
<b>研究假设：</b> 由于浓密的冠层遮挡了阳光，导致草本植物可获取的光照不足，因此林地内木本植物的多度与多样性将高于草本植物。这会造成草本植物与木本植物之间的偏害共生（amensalism）关系：木本植物的存在会对草本物种产生负面影响，而木本植物不受草本植物的影响。
<b>预测结果：</b> 1. 林地内草本植物物种的多度将低于木本植物。
2. 随着林地冠层盖度升高，草本植物物种的多度将下降。
3. 由于木本植物提供的树荫可规避直射阳光，随着冠层盖度升高，无脊椎动物与脊椎动物的多度将上升。