Ecology lab on tree litter

Introduction

The critical processes that create nutrient supply and site fertility from litter are mineralization and decomposition. Generally, decomposition encompasses many processes that break down organic matter to smaller particles for the soil to absorb nutrients. Decomposition in forest ecosystems many different soil-dwelling animals play an important role, but the fungi and bacteria complete the majority of the chemical transformation. The control of the growth and success of these fungi and bacteria is temperature, so a change in climate can change the results of litterfall. Looking at other biomes, there has been climate change that affects litterfall, “Arctic climate change is expected to lead to a greater frequency of extreme winter warming events. During these events, temperatures rapidly increase to well above 0 degrees C for a number of days, which can lead to snow melt at the landscape scale, loss of insulating snow cover and warming of soils. ((Bokhorst, Bjerke, J. W, et all)”1 For the purpose of this experiment, we took samples from the University of Denver’s campus because it is also an arboretum. The five trees that were used from the University of Denver’s arboretum were; Acer, Cronus, Fagus, Fraxinus, and the Quercus. Each year, the loss of fruits, flowers, twigs, leaves, and bark are what makes up the litterfall represented by the energy flow. In most forests, 70% of the above ground litter input is leaves; This percentage is determined by the chemical make-up of the litter. There are many things that determine litterfall, but temperature significantly influences the amount of litter fall produced. When examining the five trees around the arboretum on campus, each tree should have a significant amount of litterfall because it reflects that the process of decomposition is creating nutrient supply and site fertility.

MATERIALS

Fresh litter

Mesh screen

Hand held torch

soil

Soil trays

trowels

Open-top balances

Weight boats

Drying oven

Lab markers

Drying oven aper bags for drying samples

Flagging tape

Stapler

Methods:

Decomposition Initial Set Up

In Groups, we collected the separated leaf samples in paper bags, from trees on campus, and

brought them back to lab. A weigh boat was placed on the open-

top balance and tared or zeroed the balance. Weights were recorded (Fresh WtLB, where “LB” stands for litterbag) Approximately 5 grams of litter was weighed out. Screening was measured and cut out to construct a suitable sized litterbag. The screening was measured and given up to build a litter bag to fit the proper size. Three of the open ends of the shroud fabric were sealed with a handheld torch. The litter was poured into the open of the screen, and then the litter bag was sealed. A piece of flagging tape was stapled around one end and marked with initials and the letters corresponding to the genus and species (Fs, Fa, As, Qr, or Cs) and Mon, Tues, Weds, or Thurs (day/time of day).

Next, an extra 5-gram sample of each species was weighed out. These samples were placed in paper bags with initials and lab section on the paper bag, along with the letters fitting with genus and species, and stapled close. These labeled bags were placed into the drying oven, which will be warm to 60°C. The oven-dry weights were acquired one week afterward. The ratios of dry weight to the wet weight of these samples will be utilized to estimate the initial dry. The litterbag samples were collected from the second floor of Olin and placed into a soil bin. The bin was covered with 1 cm of soil and labeled with tape. The bin was kept moist by the greenhouse mist scheme on an even day -15min. cycle, and it will be incubated below a 24° / 18° C day/night heat regiment.

Following week:

The samples were removed from the oven and the new weights were taken for the dry samples.

Four weeks after the original set up, After removing the samples from the litter bags, the soil was lightly brushed off from the leaf surface. This preserved the soil sample and eliminated the need to collect excess soil. Samples were put into labeled paper bags and placed into the drying oven. During the fifth week, After the samples were removed from the oven, excess soil was brushed off and the samples were weighed. The dry weights for each species were recorded on the information sheet. The data for the lab section were pooled for statistical analysis.

RESULTS:

These results were pooled to include the summer class of 2011 data collection and are grouped by lab section.

Figure 1: This table shows the pooled data; the dry weights, measured in grams, of the liter from each genius of tree collected. The data was collected and 2011 and had four separate groups that collected from the five sampling trees. This data collection was repeated through eight other sections of the lab to create the full data set.

Figure 2: These were the results of the two sample t-tests to determine the p-value of the data collected. The purpose of the p-value is to determine if the data collected is significant. This also shows if the data presented is significant or not.

DISCUSSION:

After the data was pooled in the table it was determined through a t-test that the p-value was 0.0022, so this proves that there was a significant amount of liter fall from these samples over the years. On top of that, this shows that over the past ten years, there have been significant amounts of litterfall from all the trees sampled.

REFERENCES:

S. Bokhorst, J.W. Bjerke, J. Melillo, T.V. Callaghan, G.K. Phoenix,

Impacts of extreme winter warming events on litter decomposition in a sub-Arctic heathland,

Soil Biology and Biochemistry,

Volume 42, Issue 4,

2010, Pages 611-617,

ISSN 0038-0717,

https://doi.org/10.1016/j.soilbio.2009.12.011.

(https://www.sciencedirect.com/science/article/pii/S003807170900474X)

Ecology paper

The grass lands are a flatter biome than the nearby mountain biome. There is more consistency with the temperature and rail fall in the grass steppe when compared to the mountain biome. This can be observed because the grass steppe has a direct relationship between temperature and rainfall. On top of that, there is less variation in the temperature in the mountains.

During my walk in the woods, I found a dead stump of a tree. It had many different types of mosses and lichen growing all over the stump and the detached limb. By looking at other fallen trees in the forest, I learned that wildlife use these dead organisms as shelter from their predators, it provides a good place to hide food too.

I learned that in the forest biome that we explored , there were many ponderosa pines all over the place, this is because the mountain campus is centered at the perfect climate and altitude for these trees to thrive. I think fires in the front range play the role of regrowth when there is an overabundance of current growth. In other words, the fires serve as a way for there to be a clearing of species that are struggling to survive in the environment and from the regrowth comes species that can survive the change in climate or any other natural environmental change.