Trade-off between reproduction and growth in American Buckthorn species in woodlots on York University campus

The study site chosen for this experiment was the woodlots on the eastern end of York University campus near Chimneystack Road. Data was collected from 3:00-4:45p.m on Friday, October 17, 2014 (mild wind, cloudy and at about 15˚C) and Friday, October 24, 2014 (sunny, not windy and at about 15˚C). The sampling method used was block sampling – measured the distance between the base of one sample to the base of the other sample using a transect tape. To maintain consistency only trees with diameter at breast height of 13cm and greater (to avoid measuring saplings) were measured and recorded. The dbh was measured using a transect tape. To further maintain consistency all branches that were sampled on each tree were approximately 50cm in length (measured using a measuring tape). The purpose of this investigation was to see if there is a trade-off between reproduction and growth in the American Buckthorn plant species. In order to observe any correlations we sampled 50 trees, and on each tree three branches were sampled. The total amount of fruits on each branch were counted and recorded. The average number of fruits per branch was then calculated ((branch1 + branch2 + branch3) /3). On each branch three leaves near the terminal end were picked and the diagonal dimensions were measured and recorded using a measuring tape. These dimensions were used to calculate the approximate surface area of the rhombus shaped leaves (SA= ((diagonal x diagonal)/2). The average surface area was then calculated and recorded ((SA1 + SA2…+SA9)/9). A fruit was picked near each leaf on each branch and the diameter was measured and recorded using a measuring tape. The average fruit diameter was then calculated and recorded ((d1+ d2…+ d9)/9). In order to observe growth in the species the height of each tree was approximated into one of three categories: less than 10ft, 10-20ft, or greater than 20ft. The results from this dataset generally showed: taller trees had larger leaves and had less and smaller fruits whereas, smaller trees had smaller leaves but bared more and larger fruits. This study also provided as a way to gain experience in field sampling techniques with plants and experimental design. Study members were Lilach Dahoah-Halevi, Cait Carew, and Sija Srikanthan.本实验选取的研究样地为约克大学（York University）校区东端毗邻烟囱路（Chimneystack Road）的林地。数据采集于2014年10月17日周五（风力温和、多云，气温约15℃）以及2014年10月24日周五（晴朗无风，气温约15℃）的15:00至16:45。本次采用样块采样法（block sampling），通过样带卷尺（transect tape）测量两个采样样本基部之间的间距。为保证采样一致性，仅测量并记录胸径（diameter at breast height, DBH）13cm及以上的树木，以排除幼树样本。胸径的测量同样使用样带卷尺完成。为进一步维持采样一致性，每棵树选取的采样枝条长度均约为50cm，测量工具为卷尺。本研究的核心目的为探究美国鼠李（American Buckthorn）物种的繁殖与生长之间是否存在权衡关系。为观测二者的相关性，本次共采样50棵树木，每棵树采集3根枝条。统计并记录每根枝条上的总果实数，随后计算单枝平均果实数：(枝条1果实数+枝条2果实数+枝条3果实数)/3。每根枝条选取靠近顶端的3片叶片，使用卷尺测量其对角线尺寸并记录。基于该尺寸计算菱形叶片的近似表面积，计算公式为：SA=(对角线长度×对角线长度)/2。随后计算并记录单株树的平均叶片表面积：(SA1 + SA2 + … + SA9)/9。在每根枝条的对应叶片附近各采摘一枚果实，使用卷尺测量其直径并记录，随后计算并记录单株树的平均果实直径：(d1 + d2 + … + d9)/9。为观测该物种的生长状况，将每棵树的高度划分为三个类别：低于10英尺(ft)、10-20英尺，以及高于20英尺。本数据集的整体结果显示：较高大的树木叶片更大，结出的果实更少且尺寸更小；而低矮树木的叶片更小，但结出的果实更多且尺寸更大。本研究同时为参与者积累了植物野外采样技术与实验设计方面的实践经验。参与本次研究的人员包括Lilach Dahoah-Halevi、Cait Carew与Sija Srikanthan。