Kreider Leaf litterWrite-Up

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Leaf Litter Decomposition Rates in Liriodendron Tulipera and Quercus Paultruis By: Madison Kreider Background and Research Prediction Support Plant litter decomposition is a crucial component of ecosystems everywhere. Litter decomposition is the essential pathway for nutrient cycling and transfers to above-ground nutrients. At global levels, leaf traits in different species of leaves are very important in discovering decomposition rates. In this study, two leaf species were chosen, Liriodendron Tulipera and Quercus Paultruis, while both leaves differ in traits in many ways. Leaf decomposition rates in different leaf species vary greatly. One will decompose faster in two leaf species, Tulip poplar, and Pin Oak. In a study Tulip poplar (Liriodendron Tulipifera), has a decomposition coefficient of >0.010/day, which is a quick decay rate (Herbert et al.,2001). Pin Oak Leaves (Quercus palustris), tend to have high levels of lignin ranging from 20% to 30% (Herbert & Meyer 2001). It can be expected that tulip poplar (Liriodendron Tulipifera) will have decomposed faster than Pin Oak (Quercus palustris). Methods A lab was performed to understand decomposition rates in different leaf species better. The procedures of this lab were as follows. Bags made of mesh were filled with different leave species, On August 25, 2023, leaf litter bags (mesh bags were sealed with two types of leaves, tulip poplar, and pin oak), were buried in a small clearing in Hort Woods in State College, Pennsylvania. The surroundings of this area consisted of many large trees, weeds, and other plants. These bags with mixed leaf species were placed in a small cluster, orderly, so that no

bags were touching other bags to dispel the decomposition results. These bags were buried under more leaves that were already in the forest. On October 29, 2023, these leaf litter bags were recovered from Hort Woods. When the bags were brought back to the lab, the bags were weighed and observed, and calculations were made to see the leaf litter decomposition rates. Procedure: Procedures outlined in BIOL220W Lab Manual 2023 were followed. Results 0 5 10 15 20 25 30 35 Tree Spec. 1 (Pin Oak) Tree Spec. 2(Tulip Poplar) Percent Mass Loss Figure 1. In the bar chart above, Pin Oak and Tulip Poplar’s percentages of mass loss are being compared. The gray bars represent the averages of the percentage mass loss of each species (N=5), with the error bars extending above and below the averages ( ± 1 SE). These two tree species have significantly different percentages of mass loss (p= 0.048). b a

Interpretation: In this bar chart it is visible that there is statistically different data, due to the p- value obtained from the t-test. The p-value is less than 0.05, so that means the percent mass losses are enough to state significance between each other. Table 1. In this table each tree was evaluated for its Carbon Nitrogen Ratios were evaluated. This table shows the lignin percentage of each tree species' leaves. The numbers were averages based on Lignin slows the rate of decomposition, so the higher the lignin percentage the longer it will take for the leaves to decompose. In this table are also the standard errors listed next to the averages of the Carbon Nitrogen Ratio, and the Lignin Percentage. Common Name C:N Ratio % Lignin Sugar Maple 59.80 ± 1.8 8.6 ± 0.07 Pin Oak 43.76 ± 0.56 16.7 ± 0.52 White Oak 46.21 ± 1.86 13.1 ± 0.52 Tulip Poplar 60.01 ± 0.83 7.6 ± 0.56 Loblolly Pine 102.63 ± 2.00 13.4 ± 0.47

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6.0 8.0 10.0 12.0 14.0 16.0 18.0 0 5 10 15 20 25 30 35 40 f(x) = − 2.88 x + 54.07 R² = 0.67 Percent Lignin Percent Mass Loss Figure 3. This scatterplot shows a comparison in the percentage mass loss, compared to the percentage of lignin in the leaves. This correlation has a negative slope, with the equation of the line being y=-2.8825x +54.07, with an R-squared value of 0.6743. Interpretation: The scatter graph showing the relationship between the percentage of lignin and the percent mass loss of leaf litter, have a strong negative correlation. This correlation shows that as the percentage of lignin increases, the percentage of mass loss decreases.

0 5 10 15 20 25 30 35 40 0 20 40 60 80 100 120 f(x) = − 0.73 x + 76.38 R² = 0.19 Carbon to Nitogen Ratios Percent Mass Loss Figure 4. This scatterplot shows a relationship between the variable percentage of mass loss and the carbon-to-nitrogen ratios in the leaves. The equation of the linear line is y=0.271x+56.373, and the R squared value found was 0.0319. Interpretation: In this scatterplot, shows the relationship between the carbon-to-nitrogen relating to the percent mass loss of leaf litters. The relationship of these two variables has a very weak negative slope, which means there isn’t a strong relationship between these variables. The carbon-to-nitrogen ratios do not have a direct relationship to the percent mass loss. Conclusions Before conducting this lab, and calculating the results, predictions were made about whether the leaf species Tulip Poplar or Pin Oak, would have a faster decomposition rate. The prediction was that the species, Tulip Poplar, would have a faster decomposition rate than the species, Pin Oak. In agreement with the prediction, it was found that Tulip Poplar would

decompose at a higher rate compared to the Pin Oak species. In the calculations, it was found that the percent mass loss of the Tulip Poplar species was 37.9 percent, compared to the Pin Oak species which had a percent mass loss of 14.3 percent. The species Liriodendron Tulipifera was found to decompose twice as fast as the species Quercus Paultruis. The results obtained important significant evidence that backed the prediction of Tulip Poplar having a higher decomposition rate compared to Pin Oak. In a study done on Tulip Poplar species of leaves, the decay rate was observed at four different streams, and they all found the tulip poplar decay rate to be equal to less than 0.010 per day, which is a fast decay rate for a species of leaves (Herbert & Meyer 2001). Discussion The first data compared in Figure 1 is the percent mass lost, comparing the two tree species Tulip Poplar, and Pin Oak. The percent mass loss of both species was found to be statistically different from each other. The percent mass loss of the Pin Oak species was 14.3 percent, and the percent mass loss of the Tulip Poplar tree species was 37.95 percent. After calculating the t-test, the p-value was found to be equal to 0.048. Since the p-value is less than 0.05, we can assume that there is a statistical difference between the two tree species. As the results are examined in closer detail, it is visible that certain molecules are present in leaf litter that can prevent leaf litter from decaying at the same rates as other leaf litter. Out of all five leaf species tested, the species that decayed the fastest was Liriodendron Tulipera (tulip poplar), with a percent mass loss measuring 31.7 percent, and the lignin percentage of the leaf litter measured in at 7.6 percent. In contrast, the leaf litter that had the lowest percentage of decomposition was Lolbolly Pine, with a decomposition rate of 1.7 percent, and a lignin

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percentage of 13.4 percent. Looking at the relationships between the percent mass loss and the percentage of lignin, it is evident that there is a negative correlation between these two variables. In Figure 3, you can see that as the lignin percentage increases, the percent mass loss decreases. This correlation has an explanation, lignin inhibits decomposition due to the complex bonding, cross-linking, and low nitrogen rate in the molecules. Another factor that affects decomposition rates in leaf litter is carbon and nitrogen. The carbon-to-nitrogen ratio is a further way to determine how the leaf litter will decompose and to see if there is an equal balance between carbon and nitrogen. In the carbon to nitrogen ratio, lower ratios tend to decompose more rapidly, due to the higher nitrogen content compared to carbon. If a carbon-nitrogen rate is higher, that suggests that decomposition will occur at a lower rate, because nitrogen becomes limiting. After the calculations were performed for the carbon and nitrogen rates, it was evident that Lolbolly pine had the highest carbon-to-nitrogen ratio at 102.63, and it had a percent mass loss of 1.65. This supports the idea of higher carbon to nitrogen levels, resulting in a low percentage mass loss. It was also found that the lowest carbon to nitrogen ratio was the species pin oak, with a ratio of 43.76, with a percent mass loss of 14.3. In the scatterplot made with the relationship between the carbon-to-nitrogen ratio and the percentage mass loss, there was a very weak positive correlation, showing there is almost no relationship between the two variables. With these results, the carbon-nitrogen ratio can have an impact on the decomposition rates, but not as much of an impact as lignin has on decomposition rates. When all these aspects are evaluated together, comparing the percent mass loss of different leaf species, there are certain components of leaf litter that slow decomposition or speed it up. As determined in the figures, it is evident that lignin slows down decomposition in leaf

litter. This means the lower the lignin levels, the faster the leaf litter will decompose. On the opposite, the higher the lignin levels, the slower the leaf litter will decompose. Another factor that plays into the decomposition levels in leaf litter is the carbon-nitrogen ratio in leaf litter. If the carbon-to-nitrogen rate is high, the decomposition levels tend to be lower. When carbon-to- nitrogen levels are lower, the liters tend to decompose faster. In a separate study done across a tropical rainforest, evaluating leaf litter decomposition, it was found that low lignin, and a low carbon-to-nitrogen ratio increase decomposition rates. In this study decomposition rates declined as along with the changes in climate conditions, including temperature and precipitation (Paudel et. al, 2015).

References Cited Herbert, S., Meyer, J., Armbrust, K., & Shuman, L. (2001). Breakdown Rates of Tulip-Poplar leaves in Streams SuburbanWatersheds. https://repository.gatech.edu/server/api/core/ bitstreams/1016cb4d-f69a-4789-b76b-3724af673332/content Links to an external site. Rowell, R. M., Pettersen, R., & Tshabalala, M. A. (2021). Handbook of Wood Chemistry and wood composites . ROUTLEDGE. Yuan-Yuan Zhao, Zhuo-Ting Li, Ting Xu, An-ru Lou, Leaf litter decomposition characteristics and controlling factors across two contrasting forest types, Journal of Plant Ecology , Volume 15, Issue 6, December 2022, Pages 1285–1301, https://doi.org/10.1093/jpe/rtac073 Paudel, E., Dossa, G. G., de Blécourt, M., Beckschäfer, P., Xu, J., & Harrison, R. D. (2015). Quantifying the factors affecting leaf litter decomposition across a tropical forest disturbance gradient. Ecosphere , 6 (12), 1-20. Brunner, G. (2014). Lignin decomposition . Lignin Decomposition - an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/chemistry/lignin-decomposition

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