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.

Meta-data（元数据）：
本数据集采集于约克大学（York University）基尔校区的一片草原，采样坐标为(43.776131, -79.496162)，所有数据均采集于1m×1m的样方（quadrat）内。
针对总植株数的数据采用分层集群采样法：将植株按低、中（样本1-12）、高（样本13-25）进行分组，先逐个计数非禾本科植物，再计数样方1/4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。
通过逐株比对植株形态的方式计数并区分不同植物物种，以样方内最常见的禾本科物种作为参照，区分莎草科与芦苇类物种。
总植被盖度通过目视估算，以百分比表示样方内所有植物（包括活体与枯体）覆盖地面的比例；禾本科植被盖度同样通过目视估算，以百分比表示样方内仅禾本科植物覆盖地面的比例。
本次采样共覆盖25㎡的区域，采样顺序为从高植株样方（样本1-12）开始，依次过渡到中、低植株样方（样本13-25）。本次采样仅以植株高度作为筛选依据，物种组成存在差异：高植株定义为株高超过100cm，中植株株高为20-100cm，低植株株高低于20cm。

Attributes（属性）：
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) 样方内禾本科植被盖度（百分比）：数值型

Location（采样地点）：
本数据集采集于约克大学基尔校区的一片草原，草原上点缀着少量落叶乔木，一侧毗邻一片生长着众多落叶与针叶乔木的茂密森林。采样点GPS坐标为(43.776131, -79.496162)，区域外围分布着通行繁忙的道路，附近无水源与水禽活动。整片草原的地面均被活体与枯败的草本植物密集覆盖。
采样期间天气以多云为主，最高气温达30℃，相对湿度达40%；尽管湿度较高且乌云密布，但区域内降雨量极少（最大降雨量仅2mm），这与2016年多伦多整个夏季的气候特征相符：酷热少雨。
(1) 来源链接：http://www.citynews.ca/2016/08/10/heat-wave-set-to-blanket-the-gta/

Method（采样方法）：
本数据集通过目视观测与集群采样法，在1m×1m的样方内完成采集。共移动样方25次，采样区域从高植株草本区域（样本1-12）过渡到中、低植株草本区域（样本13-25）。高植株定义为株高超过100cm，中植株株高为20-100cm，低植株株高低于20cm。
首先逐个计数非禾本科植物，再将样方均分为4份，计数1/4样方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。物种数量通过目视判别，并与样方内其他植物物种进行比对完成计数。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；禾本科植被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。所有数据首先记录于纸质笔记本中。

Key to variables（变量说明）：
样方内观测到的总植株数通过以下方式计算：先计数非禾本科物种数量，再计数1/4样方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。不同植物物种的数量通过逐株比对完成计数与区分。总植被盖度通过目视估算，以百分比表示样方内地面被植被覆盖的比例；禾本科植被盖度通过目视估算，以百分比表示样方内地面仅被禾本科植物覆盖的比例。

Hypothesis（研究假设）：
禾本科植被盖度越高，植物多样性越低。这是因为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。由于禾本科植物的根系与土壤结合紧密，即使植株枯死后，仍会限制其他大型或不同物种的植物扎根生长，这也是草原区域内大型乔木/植物稀少的原因。

Predictions（预测结果）：
1) 在禾本科盖度较低但总植被盖度较高的区域，预计样方内的不同植物物种数量更多，但总植株数更少。这是因为该区域拥有更多的土壤空间与养分，可供不同体型与种类的植物生存；由于物种间对土壤空间与养分的竞争，总植株数相对更少，且禾本科植物仅占总植株数的一部分。
2) 在禾本科盖度较高但总植被盖度较低的区域，预计样方内的不同植物物种数量更少，但总植株数更多。这是因为禾本科植物能够密集扩散，通过竞争与排挤周边植物占据区域主导地位。
3) 在个体数量较多但物种种类较少的区域，预计禾本科盖度约为总植被盖度的一半。此时非禾本科植物已长期定植，受禾本科植物根系的影响较弱。