Investigating the Presence of Pebbly Loess in Nassau County, Long Island and its Impact on Plant Life

Joseph DeMarco JosephDeMarco90@gmail.com

Abstract This research is to examine the presence of pebbly loess in Nassau County of Long Island and study if its existence influences the plant life in a region. Pebbly loess is present in Suffolk County, Westchester, and other regions throughout North America. The researcher collected fifty soil samples from seven locations in Nassau County and each sample underwent a grain size analysis. The soil was located just below the Organic Layer and had no presence of till or outwash. Research found that the soil samples have a high concentration of sandy loam and pebbles are present. Pebbles are present in 96% of the soil samples. The pebbles are mostly made of quartz and range in size and shape from angular to round. This indicates the existence of pebbly loess in this region. The locations in southern Nassau County had a higher frequency of large pebbles than locations in northern Nassau County. The findings also indicate that the pebbly loess impacts the type of plant life in a region and is impacted by the ratio of sand, silt, and clay. Introduction The researcher is investigating the presence of pebbly loess in Nassau County of Long Island by categorizing the sediment found at seven locations in this region. Further, the researcher is seeking to investigate if the presence of pebbly loess controls the amount of progression in plant succession. Loess is wind-deposited sediment that is mostly composed of silt-sized particles (Kundic, Zhong, Hemming, & Hanson, 2010). Loess is present on Long Island and is the basis of local agriculture as it creates very fertile soil (deLaguna, 1963; Kundic et al., 2010; Newman, 1967; Nieter, Newman, & Krinsley, 1975; Sirkin, 1967). Loess on Long Island is typically about one meter in thickness. According to Long Island Soil Survey, loess is mostly characterized as “silt loam” (Soil-Conservation-Service, 1975, as cited in Kundic et al., 2010). Long Island loess is usually located on the surface. North American loess are believed to have originated when glaciers grinded with bedrock, producing large quantities of silt. Heavy winds relocated the silt from outwash plains and braided stream flood plains (Kundic et al., 2010). Optically Stimulated Luminescence (OSL) and 14C on charcoal grains were used to find that loess formed between 12,900 and 11,500 years ago, coinciding with the Younger Dryas event (Kundic, 2005). Loess has no presence of outwash or till, providing additional evidence that the loess was formed after the last glacier departed from Long Island. In addition to the origin of loess on Long Island, researchers have also studied the categorization of the loess’ sediment and the presence or lack of pebbles in loess (Dominguez, 2015; Kundic et al., 2010; Zhong, 2002). Dominguez (2015) characterizes soil samples from various locations in Suffolk County as having sandy loam, loamy sand, and silt loam texture. These three textures were also found to be the most common in Westchester, New York (Danz, 2016). Pebbles were also found in soil samples at these locations, indicating the presence of pebbly loess (Danz, 2016; Dominguez, 2015). Pebbly loess is wind-deposited sediment with imbedded pebbles. Pebbly loess has a distinct tan color. The pebbles are believed to come from underlying sediments such as till. As well as pebbly loess being present on Long Island and in Westchester, pebbly loess exists in Alaska, Minnesota, and Ohio (Kay, 1931; Leverett & Sanderson, 1932, as cited in Danz, 2016). Prior research suggests that the type of sediment in the loess may control the foliage in the location. Dominguez (2015) found that Suffolk County Farms, an agricultural area, has a high

concentration of silt. The Dwarf Pine Plains have a high concentration of sand (Dominguez, 2015). This research suggests that the deciduous plant life of Suffolk County Farms is promoted by silt-enriched sediment. The high concentration of sand in Dwarf Pine Plains may restrict the environment, characterizing it as scrubland. The procedure used in this study was to collect fifty soil samples at seven locations throughout Nassau County to determine if pebbly loess is present in this region and if it controls plant life. The soil samples underwent a grain size analysis and settling procedure to find the ratio of sand, silt, and clay. There is a lack of research on the presence of pebbly loess in Nassau County. The researcher is conducting the investigation of pebbly loess in Nassau County in order to add to the body of knowledge about pebbly loess throughout Long Island. Methods The researcher collected soil samples at seven locations across Nassau County of Long Island. The researcher collected soil at locations that were undisturbed so as not to put the research at risk. The researcher retrieved the soil at each location by digging a circular hole that was approximately one foot in diameter and six inches to one foot deep. Precise depths were measured and recorded. The researcher collected soil from the base and the walls of the hole. Samples from each location were stored in a Ziploc bag and the latitude, longitude, sample number, date, depth, and site were noted on the Ziploc bag. After the samples were collected, they were brought indoors and placed on clean sheets of white paper and were left to dry for twenty-four hours.

The researcher then began the procedure to analyze the grain size of the soil. The researcher removed pebbles and any organic matter from each sample. The researcher used a two-millimeter sieve to separate the sample. Each sample was placed in the sieve and the researcher sieved the sample. The soil fell onto a large plate that was placed under the sieve while pebbles and organic material remained in the sieve. The researcher measured the smallest and largest pebbles from each sample using a ruler that measures millimeters and the range of pebble size in millimeters was recorded. The researcher placed all pebbles and organic material in a separate Ziploc bag and noted the sample number and range of pebble size on each Ziploc bag.

The researcher used a grain size analysis procedure that is adapted from Soil Texture of Fracture protocol and was modified based on the suggestions of Dr. Gilbert Hanson (ecoplexity.org; Hanson, G., Oral Presentation, 2016). The researcher placed fifteen milliliters of the sediment sample that was obtained into a 50-milliliter centrifuge tube in order to find the grain size of the sample. One milliliter of dispersant was placed in the centrifuge tube. The researcher added tap water to each centrifuge tube to reach a volume of 45 milliliters. Samples were then placed in an ultrasonic jewelry cleaner for five minutes in order to separate the sediment. The researcher filled the ultrasonic jewelry cleaner with water. The researcher then shook each test tube for two minutes and recorded settling rates in addition to classifying the sediment. In order to be classified as sand, sediment had to have fallen within thirty seconds. Sediment was classified as silt if it settled within the first thirty minutes. Any additional sediment that was found after twenty-four hours was classified as clay. The researcher placed a bright light against each centrifuge tube in order to gather measurements of sand and silt. This aided in determining the volume of the unsettled samples. The researcher recorded all measurements. It should be noted that the measurement markings on the centrifuge tubes began at 5 milliliters. The accuracy of measurements was not put at risk as all of the samples that were collected had more than 5 milliliters of sand. The researcher totaled and graphed the relative percent values of silt, sand, and clay on the United States Department of Agriculture soil texture calculator.

Results

Maps of Long Island and an over view of all seven sample collection sites are shown below.

Figure 1: Map of Long Island with the seven different sites marked

Figure 2: Map of Long Island with the Pine Barrens and Prairie Communities. Source: Hanson, 2016.

Figure 3: Long Island Water Table. Source: U.S. Geological Survey, 2010.

Figure 4: Map of South Eastern Nassau County of Long Island and the seven different field sites the researcher visited.

Shown below are maps of the locations and the sites of soil collection, a table with the locations’ grain size and pebble size data, and the soil texture diagrams for each location.

Figure 5a: Map of Mill Pond, Wantagh, NY. The five sites where soil was collected are marked. This area is classified as Wetland Forest. Table 1: Grain-Size Data: Mill Pond. The researcher started collecting soil samples on the west side of the location and traveled east.

Sample Number

Latitude

Longitude

% of Pebbles

% of Sand

% of Silt

% of Clay

Pebble Size

Range

Sample Depth

1 40.39.976 73.31.184 51 47 52 1 2-18 mm 17.6 cm 2 40.40.030 73.31.169 25 67 31 2 2-20 mm 20.2 cm 3 40.40.089 73.31.193 31 67 32 1 2-13 mm 24.0 cm 4 40.40.158 73.30.758 55 67 32 1 2-23 mm 28.4 cm 5 40.39.898 73.31.020 57 50 49 1 2-28 mm 27.3 cm

Figure 5b: Soil Texture Diagram: Mill Pond. The samples at this location are predominately sandy loam, 80% sandy loam, and 20% silt loam.

Figure 6a: Map of Brookside, Merrick, NY. The three sites where soil was collected are marked. This area is classified as forest.

Table 2: Grain-Size Data: Brookside. The researcher traveled from south to north while collecting the soil samples.

Sample Number

Latitude Longitude % of

Pebbles % of Sand

% of Silt

% of Clay

Pebble Size

Range

Sample Depth

6 40.41.231 73.34.331 56 48 49 3 2-22 mm

24.4 cm

7 40.41.175 73.34.361 5 50 46 4 2-7 mm 26.7 cm

8 40.41.239 73.34.376 65 50 46 4 2- 14 mm

23.8 cm

Figure 6b: Soil Texture Diagram: Brookside. The soil is predominately sandy loam, 100% sandy loam.

Figure 7a: Map of Nassau Community College Nature Preserve, Garden City, NY. The four sites where soil was collected are marked. This area is classified as a grassy plane. Table 3: Grain-Size Data: Nassau Community College Nature Preserve. The researcher traveled from southwest to northeast while collecting the soil samples.

Sample Number

Latitude Longitude % of

Pebbles % of Sand

% of Silt

% of Clay

Pebble Size

Range

Sample Depth

9 40.43.661 73.35.240 24 54 44 2 2-5 mm 29.5 cm

10 40.43.714 73.35.185 39 50 47 3 2-13 mm

28.0 cm

11 40.43.757 73.35.110 37 50 49 1 2-35 mm

30.7 cm

12 40.43.793 73.35.092 38 60 40 0 2-13 mm

28.9 cm

Figure 7b: Soil Texture Diagram: Nassau Community College. The soil is predominately sandy loam, 100% sandy loam.

Figure 8a: Map of the north side of Bethpage State Park, Bethpage, NY. The eleven sites where soil was collected are marked. This area is classified as forest.

Table 4: Grain-Size Data: North side Bethpage State Park. The researcher traveled from the parking lot shown in Figure 8a, moving northeast along the trail until reaching the road while collecting the soil samples.

Sample Number

Latitude Longitude % of

Pebbles % of Sand

% of Silt

% of Clay

Pebble Size

Range

Sample Depth

13 40.45.248 73.27.848 12 50 49 1 2-3 mm

27.6 cm

14 40.45.216 73.27.698 13 67 31 2 2-4 mm

28.4 cm

15 40.45.380 73.27.663 25 54 44 2 2-25 mm

29.1 cm

16 40.45.526 73.27.761 29 67 32 1 2-27 mm

30.2 cm

17 40.45.485 73.27.916 18 50 48 2 2-15 mm

28.7 cm

18 40.45.406 73.28.147 0 67 31 2 n/a 26.9 cm

19 40.45.297 73.28.199 21 50 48 2 2-10 mm

27.4 cm

20 40.45.151 73.28.111 15 48 51 1 2-6 mm

31.2 cm

35 40.45.089 73.28.242 7 60 29 1 2-4 mm

29.8 cm

36 40.45.051 73.28.14 43 80 20 0 2-31 mm

27.3 cm

37 40.44.937 73.28.338 56 37 63 0 2-6 mm

28.2 cm

Figure 8b: Soil Texture Diagram: The north side of Bethpage State Park. The soil is predominately sandy loam, 73% sandy loam, 18% silt sand, 9% loamy sand.

Figure 9a: Map of Twin Lakes Nature Preserve, Wantagh, NY. The thirteen sites where soil was collected are marked. This area is classified as wetland forest.

Table 5: Grain-Size Data: Twin Lakes Nature Preserve. The researcher traveled from the parking lot shown in Figure 9a, moving east then south along the Westside trail until reaching the southern most part. The researcher then traveled on the east side of the ponds while collecting the soil samples.

Sample Number

Latitude Longitude % of Pebbles

% of Sand

% of Silt

% of Clay

Pebble Size

Range

Sample Depth

21 40.40.906 73.31.017 47 87 13 0 2-15 mm

20.4 cm

22 40.40.922 73.30.925 63 88 12 0 2-22 mm

18.6 cm

23 40.40.889 73.30.923 40 73 27 0 2-32 mm

19.4 cm

24 40.40.821 73.30.931 45 69 31 0 2-17 mm

16.7 cm

25 40.40.727 73.30.934 0 50 50 0 n/a 19.7 cm

26 40.40.601 73.30.960 36 80 20 0 2-14 mm

20.1 cm

27 40.40.660 73.30.926 64 50 50 0 2-25 mm

19.6 cm

28 40.40.481 73.30.982 60 67 32 1 2-30 mm

19.3 cm

29 40.40.525 73.30.949 22 33 66 1 2-15 mm

18.7 cm

30 40.40.404 73.30.974 30 50 50 0 2-20 mm

17.5 cm

31 40.40.312 73.31.015 62 41 59 0 2-32 mm

18.0 cm

32 40.40.534 73.30.914 56 50 49 1 56 19.2 cm 33 40.40.614 73.30.821 52 57 43 0 52 22.4 cm

Figure 9b: Soil Texture Diagram: Twin Lakes Nature Preserve. The soil is predominately sandy loam, 45% sandy loam, 27% silt sand, 13% loamy sand, and 13% sand.

Figure 10a: Map of Undeveloped land behind Jerusalem BOCES School, Bellmore, NY. The one site where soil was collected is marked. This area is classified as forest.

Table 6: Grain-Size Data: Undeveloped Land behind Jerusalem BOCES School. The researcher traveled from the parking lot shown in Figure 10a, moving north while collecting the soil sample. Trails were unkempt and the researcher was unable to collect more data from this location.

Sample Number

Latitude Longitude % of Pebbles

% of Sand

% of Silt

% of Clay

Pebble Size

Range

Sample Depth

34 40.41.582 73.32.862 52 93 7 0

2-21 mm

32.6 cm

Figure 10b: Soil Texture Diagram: Undeveloped land behind Jerusalem BOCES School. The soil is predominately sand, 100% sand.

Figure 11a: Map of Massapequa Nature Preserve, Massapequa, NY. The Thirteen sites where soil was collected are marked. This area is classified as wetland forest.

Table 7: Grain-Size Data: Massapequa Nature Preserve. The researcher traveled north while collecting the soil samples.

Sample Number

Latitude Longitude % of Pebbles

% of Sand

% of Silt

% of Clay

Pebble Size

Range

Sample Depth

38 40.40.656 73.27.944 62 80 19 1 2-30 mm

22.5 cm

39 40.40.783 73.27.902 40 83 17 0 2-22 mm

23.2 cm

40 40.40.796 73.27.763 71 67 33 0 2-20 mm

19.8 cm

41 40.40.793 73.27.671 77 35 65 0 2-25 mm

21.6 cm

42 40.40.723 73.27.836 64 64 34 2 2-20 mm

27.1 cm

43 40.40.795 73.27.778 55 72 27 1 2-23 mm

24.9 cm

44 40.40.973 73.27.580 61 88 12 0 2-25 mm

24.2 cm

45 40.41.082 73.27.638 54 78 22 0 2-30 mm

23.7 cm

46 40.41.198 73.27.572 42 72 27 1 2-27 mm

22.8 cm

47 40.41.336 73.27.448 32 64 35 1 2-21 mm

24.0 cm

48 40.41.578 73.27.371 38 68 31 1 2-18 mm

24.7 cm

49 40.41.822 73.27.280 28 57 43 0 2-20 mm

25.2 cm

50 40.42.012 73.27.235 24 54 46 0 2-17 mm

23.8 cm

Figure 11b: Soil Texture Diagram: Massapequa Nature Preserve. The soil is predominately sandy loam, 63% sandy loam, 7% silt sand, 23% loamy sand, 7% sand.

Discussion

The researcher collected soil samples at seven locations in Nassau County (Figure 1 & 4). Pebbly loess is present in Nassau County, Long Island. The sediment that was collected and studied was small, wind-blown sediment, tan in color, and had pebbles present in the wind-blow sediment. Figure 12 indicates that the majority of the samples that were collected are sandy loam, which shares the same characteristics in pebbly loess found in Suffolk County of Long Island and Westchester, New York (Danz, 2016; Dominguez, 2015). Pebbles are present in all but two samples and are predominately made of quartz and vary from angular to round in shape. This aligns with the pebble composition and shape of the pebbly loess in Westchester, NY (Danz, 2016).

The locations that are in southern Nassau County have larger pebbles and a higher frequency of pebbles than the locations that are more towards the north (Tables 1-7). The southern locations saw a gradual progression of grain size. The northern sites have a large gap between grain sizes of the pebbles. In the north, pebble sizes jump from two millimeters to fifteen millimeters or higher, while the southern sites have a more uniform increase in grain size.

Soil was collected in the Hempstead Plains region of Long Island, with some areas bordering on the Oak Brush Plains region (Figure 1 and 2). All of the sample collection locations are located in very close proximity to the water table, expect for Nassau Community College Preserve and Bethpage State Park (Figure 3). Sediment is better able to retain water when there is more silt composing that sediment. Locations with sandy sediment do not retain water as well and this prevents deciduous plant life from growing. Twin Lakes and Massapequa Preserve both have a high sand concentration in their sediment (Figure 9b & 11b). The soil at Twin Lakes and Massapequa Preserve also has a large quantity of pebbles, 44% and 50% of the soil composition respectively (Table 5 & 7). The soil samples that were collected at these two locations share characteristics of the soil at Dwarf Pine Plains (Dominguez, 2015). This region promotes the growth of Dwarf Pines, which do not require a steady, large amount of water. Despite the sandy concentration of the soil at Twin Lakes and Massapequa Preserve, the plant life in the locations is rather deciduous, including Red Maple and Post Oak (Appendix A: Figure 2, 3, & 4). This is interesting as the plant life at these two locations widely differs from the plant life at Dwarf Pine Plains. The variations in plant life between the two regions may be due to the Nassau County locations’ proximity to the water table, and not the presence of pebbly loess as hypothesized.

The soil collected at the North Side of Bethpage State Park has a higher silt concentration than the soil at Twin Lakes and Massapequa Preserve (Figure 10). There is also a lower average pebble percentage by weight at Bethpage State Park (21%) (Table 4). This combination of sediment characteristics promotes deciduous plant life more than the soil conditions at Twin Lakes and Massapequa Preserve. The foliage at Bethpage State Park is similar to that of Twin Lakes and Massapequa Preserve (Appendix A: Figure 2, 3, 4, & 5). However, the Red Maple at Bethpage State

Figure 12: Soil texture diagrams of sites as follows: Mill Pond, Brookside, Jerusalem BOCES School, Twin Lakes, Massapequa Preserve, Nassau Community College, Bethpage State Park.

Park provides a much taller canopy and appears healthier. This is most likely due to the fertile soil conditions of Bethpage State Park.

Nassau Community College Nature Preserve has a high silt percentage (Figure 7b). This type of soil promotes deciduous forest. This location, however, is a grassy plain. The majority of the plant life at Nassau Community College was grass and Wolf’s Claw Club Moss (Appendix A: Figure 1). The soil samples show a high concentration of silt, similar to the soil at Bethpage State Park. This location is equidistant from the water table as Bethpage State Park (Figure 3). It is thought that the similarities between the soil compositions at these two locations as well as their similar proximity to the water table would promote analogous plant life. It may be that the content of the soil (i.e., magnesium concentration), and not the grain size of the soil, is a large contributing factor to the type of plant life that a region has.

Conclusion

Pebbly loess is present in Nassau County of Long Island. The soil at the seven locations is mostly sandy loam with the presence of pebbles and is tan in color. The findings may hint at a correlation between plant life and the soil composition of the pebbly loess.

In southern Nassau County, the availability of land to conduct this type of research is not high. The undisturbed areas are few and far between. The Brookside and Jerusalem BOCES School sites are not heavily discussed because of their proximity to developed land and the uncertainty of the area being undisturbed. Further research should be conducted in order to investigate the extent of pebbly loess in Nassau County. A study could utilize a mastersizer to perform a more accurate grain size analysis. Future studies should include the collections of soil samples from locations that are further east and north than those in the present study in order to identify if there is a presence of pebbly loess in other parts of Nassau County. Future studies should also consider the composition of the soil and not solely the grain size.

References

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Appendix A

Figure 1: Wolf’s Claw Club Moss at Nassau Community College Preserve, Garden City

Figure 2: Post Oak at Twin Lakes, Wantagh.

Figure 3: Red Maple at Twin Lakes, Wantagh.

Figure 4: Red Maple at Massapequa Preserve, Massapequa.

Figure 5: Red Maple at the North Side of Bethpage State Park, Bethpage.