Soil moisture and plant abundance in a woodlot and grassland on York University campus

Data was collected on York University campus in the grassland adjacent to Stong Pond and in the Saywell Woodlot between 2:40pm and 5:30pm over two days: October 19, 2015 and October 26, 2015. On October 19, the temperature was approximately 15 degrees Celsius and it was partially cloudy. On October 26, the temperature was approximately 10 degrees Celsius and it was partially cloudy. 70 replicates in the grassland adjacent to Stong Pond and 70 replicates in the Saywell Woodlot were examined. To determine the placement of the first quadrat, a ball was thrown from the edge of the habitat by an experimenter with her eyes closed. The quadrat was placed where the ball landed. Subsequent quadrat placements were determined by an experimenter throwing the ball with her eyes closed from the location of the completed quadrat. In each quadrat, experimenters visually estimated the total percentage of the quadrat that was covered by vegetation, the percentage of the quadrat that was covered by grass, and the percentage of the quadrat that was covered by ground cover plants. Ground cover plants were defined as plants that did not have a stem or trunk with a diameter over 2cm. Experimenters obtained a soil sample from the centre of each quadrat. One handful of soil was taken in each quadrat. The sample consisted of soil from the surface to approximately 3cm deep. Soil moisture was estimated in each quadrat using the United States Department of Agriculture’s guide, “Estimating Soil Moisture by Feel and Appearance”[1]. Each soil sample was squeezed in a fist, bounced gently from hand-to-hand, and pinched between the thumb and forefinger. Based on these observations, the available soil moisture was estimated as 0-25%, 25-50%, 50-75%, or 75-100% using the USDA guidelines. [1] [USDA] United States Department of Agriculture. 1998. Estimating Soil Moisture by Feel and Appearance. Program Aid Number 1619.

本数据集采集于约克大学（York University）校园内毗邻斯汤塘（Stong Pond）的草地，以及塞韦尔林地（Saywell Woodlot），采集时段为2015年10月19日与26日每日的14:40至17:30，共计两天。2015年10月19日的气温约为15摄氏度，天气为局部多云；10月26日气温约为10摄氏度，同样为局部多云。本次研究共布设70组重复样方（quadrat）于毗邻斯汤塘的草地，另70组重复样方设于塞韦尔林地。

首个样方的位置由实验者闭眼从生境边缘掷出的小球落点确定；后续样方的布设位置，则以已完成布设的样方位置为起点，由实验者闭眼掷球确定落点后放置。在每个样方中，实验者通过目视估算三项覆盖度指标：样方总植被覆盖率、草本植被覆盖率以及地被植物覆盖率。其中地被植物被定义为无直径超过2厘米的茎或主干的植物。

实验者从每个样方的中心采集土壤样本，每个样方采集1捧土壤，样本采集深度为地表至约3厘米处。土壤湿度估算采用美国农业部（United States Department of Agriculture，USDA）发布的《通过触感与外观估算土壤湿度》指南[1]：实验者手握土壤样本，在双手间轻轻弹动后，用拇指与食指捏取样本，基于上述操作的观察结果，按照USDA的标准将有效土壤湿度划分为0-25%、25-50%、50-75%及75-100%四个区间。

[1] [USDA] 美国农业部. 1998. 《通过触感与外观估算土壤湿度》. 项目援助编号1619.