Lab 2- Danby Woodlot Dataset

Site Description: The sampling was taken on Wednesday, September 21st, 2016 in the Danby Woodlot on York University Keele Campus. The observations were made between 2:30-5:30pm on a clear, sunny, summer afternoon with no wind and in 23°C weather. The woodlot ground was covered in lots of tree sticks, dirt, fallen leaves and was mostly shaded due to the canopy of many trees. The data was collected with my lab partner Carrie Ewins, while the rest of the class and the teaching assistant participated in their own lab roles in proximity. Metadata: Distance to Next Tree: The first factor is distance to next tree. To collect this data we used a transect measuring tape to measure the distance between two adult trees along a straight path starting from the middle back of one tree, to the middle front of the next tree. Diameter at Breast Height: The second factor is diameter at breast height. To collect this data we used a measuring tape and held it up close to the selected tree’s trunk to estimate the diameter of each tree trunk at the level of my lab partner's breast. Condition: The response variable is condition. This was determined by rating the tree on a scale ranging from 0= dead, 1= living, and 2= huge green canopy. Methods: A 25m transect measuring tape was used to measure the distance in cm between two trees and recorded on a datasheet. We selected adult trees that appeared to fall along a straight path. An adult tree had to meet the criteria of being equal to or more than 10cm in diameter. We measured trees at my lab partner's breast height of 153cm, which was a recorded measurement from the ground up to the middle of her chest. We measured the diameter at breast height of each tree by using a measuring tape. The distance from an adult tree to the next closest adult tree along the straight path was measured from the middle of the back of the first tree to the middle of the front of the next tree. We started by choosing a random adult tree in the woodlot. The condition of the tree was observed with our eyes, and was determined on a scale of 0-2, with 0 meaning that the tree was dead, 1 meaning that the tree was living, and 2 meaning that the tree looked like it was thriving with a full green canopy. This procedure was repeated 9 more times to get a total of 10 replicates. We used a sample size of 11 adult trees in total and recorded the distance from the 10th tree to the 11th tree but didn’t record the condition or diameter at breast height of the last tree, since the data for only 10 trees was needed. Hypothesis: I hypothesize that both the distance between trees and the diameter at breast height will have an effect on the tree's condition. This is because with increasing distance between trees there are more nutrients available for each and there is less of a need to compete for resources required for growth. Each tree gets a chance to grow and spread out using as much of the nutrients available around it without interference. A tree in good health is due to the fact that it has the chance to use all the resources around it to grow big, tall, and with a rich green canopy. These trees have easy access to capture sunlight, while the trees below a full canopy are shaded and robbed from the sun. Each tree requires enough space to thrive. Predictions: As the distance between two trees increases, the condition of each tree increases. The greater the diameter at breast height, the worse the condition of the next tree.采样地点与环境说明：本次采样于2016年9月21日星期三，在约克大学基尔校区的丹比林地（Danby Woodlot）内开展。观测时段为当日下午2:30至5:30，天气晴朗无风，为夏季午后，气温23℃。林地地表覆盖大量树枝、泥土与落叶，因成片林木的冠层遮蔽，整体光照偏弱。本数据由笔者与实验搭档Carrie Ewins共同采集，其余同班同学与教学助理在附近区域各司其职完成实验任务。 元数据： 1. 相邻树距：本实验的首个测量因子为相邻树木间距。数据采集时，我们使用样带卷尺（transect measuring tape）沿直线测量两棵成年树木的间距，测量起点为第一棵树树干后侧中点，终点为下一棵树树干前侧中点。 2. 胸径（Diameter at Breast Height）：第二个测量因子为胸径。采集数据时，我们使用卷尺紧贴待测树干，在实验搭档的胸部高度处测量树干直径。 3. 健康状况：本实验的响应变量为树木健康状况。我们通过0-2级评分标准判定：0代表树木死亡，1代表树木存活，2代表树木长势旺盛、冠层茂密翠绿。 实验方法：本次实验使用25米样带卷尺测量两棵树的间距（单位：厘米），并将数据记录至数据表中。我们选取沿直线分布的成年树木作为观测对象，成年树木的判定标准为胸径不小于10厘米。本次测量选取的胸高位置为实验搭档的胸部高度（153厘米，即从地面至其胸部中点的垂直距离）。我们通过卷尺测量每棵树的胸径；沿直线测量成年树木与下一棵最近成年树的间距时，仍以第一棵树树干后侧中点为起点，下一棵树树干前侧中点为终点。实验初始阶段，我们在林地中随机选取一棵成年树木，通过目视评估其健康状况，并按照0-2级评分标准判定：0为死亡，1为存活，2为冠层茂密翠绿、长势旺盛。上述实验流程重复9次，最终获得10组重复样本。本次实验共选取11棵成年树木作为样本，仅记录第10棵至第11棵树的间距，但未采集最后一棵树的健康状况与胸径数据，因实验仅需10棵树的完整数据。 研究假设：本实验假设树木间距与胸径均会对树木健康状况产生影响。究其原因，树木间距越大，单棵树可获取的养分越多，对生长所需资源的竞争压力越小，单棵树木可充分利用周边养分自由生长扩张，不受其他植株干扰。健康状况良好的树木可充分利用周边资源，生长为高大挺拔、冠层翠绿茂密的植株。这类树木可高效获取光照，而冠层下方的树木则会被遮蔽，无法获得充足阳光。可见每棵树木均需足够生长空间以维持旺盛长势。 研究预测：随着两棵树木间距的增大，单棵树木的健康状况将随之提升；而胸径越大的树木，其相邻树木的健康状况则越差。