Relationship between Grass Coverage on Plant Diversity, Total Vegetation Cover and Plant Abundance

Meta-data: Travelled to a grassland at York University Keele campus to collect data (43.776131, -79.496162). This data was collected within a 1m x 1m quadrat. Data pertaining to total number of plant species was collected with cluster sampling low, medium(rep1-12) and high plants(13-25) by counting them individually and then adding the number of grass plants within ¼ of the quadrat times 4. The number of different species was counted and distinguished by comparing plants side by side. The most common grass species was considered a reference to distinguish species from the sedge and reed family. The total vegetation cover was visually approximated by percent; percentage of all plants covering the ground within the quadrat. The total grass cover was visually approximated by percent; percentage of only the grass species covering the ground within the quadrat. In considering total vegetation and grass coverage, we were considering both live and dead plant matter. In total an area of 25m² was sampled starting from quadrats with high plants the same species from rep1-rep12 going to medium to low plants from rep13-rep25. The only selection factor was height but the species was variable. High plants are considered to be over 100cm and medium between 100- 20cm and low plants below 20cm. Attributes 1) Total number of Plants (within a quadrat): Numerical 2) Total Number of Different Plant Species (within a quadrat): Numerical 3) Total Vegetation cover by % (within a quadrat): Numerical 4) Total Grass cover by % (within a quadrat): Numerical Location: Data was collected at York University Keele campus at a grassland with few deciduous trees dotting the grassland. This grassland, on one side was bordering a dense forest with many deciduous and coniferous trees. Location with GPS coordinates was 43.776131, -79.496162. Outside this area were well-circulated roads. There were no sources of water nearby, neither waterfowl. Entire grassland was densely covered with grass both dead and alive. The weather was mostly cloudy with temperatures reaching 30C and humidity reaching 40%. Although the humidity was high and dark clouds were forming; it did not rain much (max 2mm) in the area. This is reflective of the entire summer in Toronto (2016); intense heat and very little precipitation. (1) 1: http://www.citynews.ca/2016/08/10/heat-wave-set-to-blanket-the-gta/. Method: Data was collected within a 1m x 1m quadrat by visual observation and cluster sampling. This quadrat was moved from area to area 25 times; moving from grassy areas with tall plants (rep1-12) to grassy areas low and medium height plants (rep13-25). High plants are considered to be over 100cm and medium between 100- 20cm and low plants below 20cm. We counted the number of non-grass plants first individually then split the quadrat into 4 and counted the number of grass plants in the ¼ section. We multiplied it by 4 and added it to the number of non-grass plants. The number of species was counted by visual discrimination and comparison to other plants species within the quadrat. Vegetation coverage was roughly determined by eying the percent of the quadrat’s ground was covered by the total vegetation. Grass coverage was roughly determined by eying the percent of the quadrat’s ground was covered by the only the grass species. All data was recorded first on to a notebook. Key to variables: Total number of plants observed within the quadrat was measured by first counting the non-grass species and then counting the number of grass plants within ¼ of a quadrat and then multiplying it by 4. The total number of different species was counted and species were distinguished by side by side comparison. The total vegetation cover was roughly measured by eye; how much of the vegetation covers the ground within the quadrat by percent. The total grass cover was roughly measured by eye; how much of only the grass covers the ground within the quadrat by percent. Hypothesis: The higher the coverage of grass can lead to lower diversity due to other plants being crowded out in nutrients, water and other resources. Since grass’ roots are so strongly attached to the soil, even after death, it gives little room for larger or different species of plants to push their roots. This is why there are very few large trees/plants in a grassland. Predictions: 1) In areas with a lower grass coverage but higher total vegetation coverage, we can expect a higher number of different species and lower number of total plants because of more soil room and nutrients to sustain larger and different plants. There are fewer plants because of the inter-species competition for soil room and the number of grass plants were the bulk of the total plants. 2) In areas with higher grass coverage and lower vegetation coverage, we can expect a lower number of different species and higher number of total plants because the grass species is able to spread very densely, dominating the area by outcompeting and out crowding neighboring plants. 3) In areas with a large number of individuals and a couple of different species, we can expect there to be a grass coverage of roughly half of the total vegetation coverage. In this case, the non-grass plants have been long established and not strongly affected by the roots of the grass plants.

元数据：本次数据采集于约克大学基尔校区的一片草原（GPS坐标：43.776131, -79.496162），所有数据采集于1米×1米的样方（quadrat）内。
针对植物物种总数的采集采用整群抽样（cluster sampling）法，按植株高度将采样分为低、中（样本组1-12）、高（样本组13-25）三类：先逐个计数非禾本科植物，再统计样方四分之一区域内的禾本科植物数量并乘以4，将两部分相加得到总植株数。不同物种的数量通过植株间的并排对比进行计数与区分，以区域内最常见的禾本科物种为参照，用以区分莎草科与芦苇科植物物种。
植被盖度与禾本科盖度均通过目视估算，以百分比表示：总植被盖度指样方内所有植株（含活体与枯亡植株）覆盖地面的比例；禾本科盖度仅指样方内禾本科物种覆盖地面的比例。本次采样总面积达25m²，采样顺序为：先采集样本组1-12的高植株样方（对应物种一致），再依次采集样本组13-25的中等植株与低植株样方。本次采样仅以植株高度为筛选标准，物种组成则存在差异：高植株定义为株高超过100cm，中等植株株高介于20-100cm之间，低植株株高低于20cm。
采集的属性指标如下：
1. 样方内总植株数：数值型
2. 样方内不同植物物种总数：数值型
3. 样方内总植被盖度（百分比）：数值型
4. 样方内禾本科盖度（百分比）：数值型

采样地点：数据采集于约克大学基尔校区的一片草原，区域内点缀少量落叶乔木。该草原一侧毗邻一片茂密的森林，林中包含多种落叶与针叶树种。采样点GPS坐标为43.776131, -79.496162，区域外围为车流量较大的道路，周边无水源及水禽活动迹象。整片草原覆盖茂密的禾本科植物，包含活体与枯亡植株。当日天气以多云为主，气温达30℃，相对湿度为40%；尽管湿度较高且云层密布，但区域内降雨量极少（最大降雨量仅2mm）。该采样情况反映了2016年多伦多夏季的整体气候特征：极端高温且降水稀少。相关参考链接：1) http://www.citynews.ca/2016/08/10/heat-wave-set-to-blanket-the-gta/

数据采集方法：本次数据采集于1米×1米的样方内，采用目视观测与整群抽样法。共移动样方25次，采样顺序为先采集高植株草原区域（样本组1-12），再采集中、低植株草原区域（样本组13-25）。植株高度分类标准同前：高植株株高超过100cm，中等植株株高介于20-100cm之间，低植株株高低于20cm。
计数流程为：先逐个计数非禾本科植物，再将样方划分为4个相等区域，统计其中1/4区域内的禾本科植物数量，将该数值乘以4后与非禾本科植物计数结果相加，得到总植株数。物种数量通过目视判别，并通过与样方内其他植物物种对比进行区分。总植被盖度通过目视估算，以百分比表示样方内地面被所有植被覆盖的比例；禾本科盖度通过目视估算，以百分比表示样方内地面仅被禾本科植物覆盖的比例。所有数据首先记录于纸质笔记本中。

变量说明：
1. 样方内观测到的总植株数：先计数非禾本科物种数量，再统计样方1/4区域内的禾本科植物数量并乘以4，将两部分结果相加得到总植株数。
2. 样方内不同植物物种总数：通过植株间并排对比进行计数与物种区分。
3. 总植被盖度：通过目视估算样方内地面被所有植被覆盖的百分比。
4. 禾本科盖度：通过目视估算样方内地面仅被禾本科植物覆盖的百分比。

研究假设：禾本科盖度越高，植物多样性越低。原因在于禾本科植物会通过竞争养分、水分与其他资源，排挤其他植物的生存空间。此外，禾本科植物的根系与土壤结合紧密，即使植株枯亡后，仍会限制其他较大或不同物种的植物扎根生长，这也是草原区域大型乔木/植株较为稀少的原因。

研究预测：
1. 在禾本科盖度较低但总植被盖度较高的区域，预计存在更多的不同物种，但总植株数较少。这是因为该区域拥有充足的土壤空间与养分，可支撑体型更大或种类更多的植物生长；而由于种间竞争土壤空间，且禾本科植物通常构成总植株数的主体，因此总植株数相对较少。
2. 在禾本科盖度较高但总植被盖度较低的区域，预计不同物种数量较少，但总植株数较多。这是因为禾本科植物可通过高密度扩散，通过竞争与排挤周边植物占据主导地位。
3. 在植株个体数量较多但仅存在少数物种的区域，预计禾本科盖度约占总植被盖度的一半。此种情况下，非禾本科植物已长期定殖，受禾本科植物根系的影响较弱。