Growth of Bald Cypress Boles and Knees As Influenced by Precipitation and Inundation at Sardis Lake, Mississippi

University of Mississippi eGrove

Electronic Theses and Dissertations Graduate School

2014

Growth Of Bald Cypress Boles And Knees As Influenced By Precipitation And Inundation At Sardis Lake, Mississippi

Emily M. Stauss University of Mississippi

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Recommended Citation Stauss, Emily M., "Growth Of Bald Cypress Boles And Knees As Influenced By Precipitation And Inundation At Sardis Lake, Mississippi" (2014). Electronic Theses and Dissertations. 373. https://egrove.olemiss.edu/etd/373

This Thesis is brought to you for free and open access by the Graduate School at eGrove. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of eGrove. For more information, please contact [email protected]. GROWTH OF BALD CYPRESS BOLES AND KNEES AS INFLUENCED BY

PRECIPITATION AND INUNDATION AT SARDIS LAKE, MISSISSIPPI

A Thesis

presented in partial fulfillment of requirements

for the degree of Master of Science in the Department of Biology

The University of Mississippi

EMILY M. STAUSS

May 2014

ABSTRACT

The growth of bald cypress (Taxodium distichum) boles and knees in response to inundation and precipitation over small (< 4 m) elevation gradients was examined by measuring interannual growth increments of boles and knees at five sites at Sardis Lake, Mississippi. There was a significant (p=0.019) growth response to precipitation during November to April (the wet season), but there was not a significant growth response to inundation during the growing season

(May to October). Because lake level at Sardis is controlled by the Army Corps of Engineers for flood control, the Sardis Lake shoreline area may be a habitat where growth response to precipitation and inundation differs from systems where precipitation and inundation are linked.

The growth of knees from bald cypress roots was compared to growth of the boles in order to determine if knees and boles respond to the same environmental factors. It was found that the knees have high positive correlation coefficients when compared to the tree’s bole if we assume that knee growth is initiated in response to a major flood event. If we assume knees grow in response to stress that limits bole growth, we would expect but do not find any discernable relationship between the initiation of knee growth and the timing of flood events.

DEDICATION

I would like to dedicate this work first to my parents, Brian and Cathy Stauss, who sent me away to Girl Scout camp when I was six years old, where I fell in love with nature and my life was changed forever. I would like to dedicate this work secondly to Ms. Ann Stevens, my middle school science teacher, who took that love of nature, streamlined it into a distinct interest in biology, and opened my eyes to the fascinating world of science. She is easily one of the most creative, gifted, and inspiring teachers I have ever known, and she sparked my desire to pursue biology. Lastly, I would like to recognize my family and cousins, without whose love and support I would never have gotten this far.

iii

ACKNOWLEDGMENTS

I would like to thank Dr. Stephen Threlkeld for taking me on as his graduate student.

Without him, earning this degree would not have been possible, and I am immensely grateful for his patience and guidance. I would also like to thank Dr. Marjorie Holland and Dr. Gregg

Davidson for their support and direction. My gratitude is also extended to the University of

Mississippi and the Biology Department and its staff, for their assistance and encouragement, and for employing me and giving me invaluable experience researching and teaching. A special thanks is extended to Dr. Jason Hoeksema and Dr. Megan Rúa for their generous help with R.

Thank you to the University of Mississippi Geology and Engineering Department, especially Hal

Robinson, for allowing me to use your surveying equipment. I also thank the Army Corps of

Engineers, especially Chris Gurner, for allowing me to work on their property and study the habitat and trees at Sardis Lake. Lastly, I am indebted to the graduate students at the University of Mississippi, whose advice, friendship, help, and support has made this thesis possible.

TABLE OF CONTENTS

Page

1. Abstract……………………………………………………………………………………ii

2. Dedication……………………………………………………………………………...... iii

3. Acknowledgments…………………………………………………………………….….iv

4. List of Tables…………………………………………………………………………...... vi

5. List of Figures……………………………………………………………………………vii

6. Introduction………………………………………………………………………………..1

7. Methods………………………………………………………………………………...... 4

8. Results…………………………………………………………………………………....17

9. Discussion………………………………………………………………………………..23

10. List of References……………………………………………………………………28-30

11. Appendix……………………………………………………………………………..31-34

12. Vita……………………………………………………………………………………….35

LIST OF TABLES

Page

1. Correlation Results Between Knee and Bole Growth Records……………………..…21

LIST OF FIGURES

Page

1. Locations of Trees at Pat’s Bluff 1 at Sardis Lake, MS………………………………………...5

2. Locations of Trees at Pat’s Bluff 2 at Sardis Lake, MS………………………………………...6

3. Locations of Trees at Blackjack Point at Sardis Lake, MS……………………...……………...8

4. Locations of Trees at Thompson Creek at Sardis Lake, MS………………………...…………9

5. Locations of Trees at Moccasin Point at Sardis Lake, MS……………………………………10

6. Image of Part of a Cross-Section of a Bald Cypress Knee………...... 13

7. A Comparison of the Growth of the Bole of Tree 67 with the Growth of One of Its Knees.....15

8. Total Precipitation Per Year…………………………………………………………………...16

9. Response of Trees to Precipitation at Increasing Elevation during November-April………...19

10. Response of Trees to Inundation at Increasing Elevation during April-October…………….20

11. Growth of Knees Compared to Daily Lake Level at Sardis Lake, MS…...………………….22

12. Response of Trees to Precipitation at Increasing Elevation during November-April, Polynomial Comparison………………………………………………………………………….27

vii

I. INTRODUCTION

Bald cypress [Taxodium distichum (L.) Rich.] often grows in standing water or saturated soils for a substantial part of the year, yet a positive relationship between precipitation and interannual variation in radial growth of bald cypress boles has been documented (Stahle et al.

1985b). Stahle and his colleagues have used this relationship to reconstruct southeastern United

States climate (Stahle et al. 1985a; Stahle and Cleaveland 1992) and reasons for the failure of a

southeastern colonial settlement (Stahle et al. 1998). The relationship of growth to precipitation 5 is sometimes altered when trees experience major changes in their hydrology, as occurs from subsidence following an earthquake (Stahle et al. 1992, Van Arsdale et al. 1988), or changes in drainage caused by road construction (Young et al. 1995) or from channel incision (Valentine et al. 1997). Such changes can affect the growth-precipitation relationship for extended periods of time (3-17 years).

Weber (2010) examined interannual growth in groups of trees along a 1 m elevation gradient at Sky Lake, MS, an oxbow of the Yazoo River near Belzoni, MS, and found that there were differences in growth response to inundation and precipitation between groups of trees even though the elevation difference was a meter or less between them. Interannual growth of trees at the lowest elevation was directly related to inundation, while growth of trees at higher elevations was more influenced by precipitation. Growth of trees at intermediate elevations was not significantly related to either inundation or precipitation.

Keeland and Sharitz (1995) examined within-season variations in bole growth using dendrometer bands and found that bald cypress growth was greatest under shallow permanent

flooding (water level at 39 + 8 cm to -5 + 13 cm over the course of one year; p. 1086), less under periodic flooding (“frequent, short-term flood events throughout the year”; p. 1088), and most limited in deep, permanently flooded sites (water level 86 + 8cm to 50 + 12cm over the course of one year). Their evidence suggested that magnitude and variation in water depth influenced growth in bald cypress. It is not known, however, when bole growth is responding to inundation and when it is responding to precipitation, and if one of these events is more influential on growth during different parts of the year.

Interannual and seasonal variation in growth of bald cypress knees is unstudied, although

it is widely accepted that knees grow in response to inundation (Kramer et al., 1956; Whitford

5 1956; Kernall and Levy 1990); the claim that they facilitate gas exchange in the roots is not supported by experimental evidence (Mitsch and Gosselink 2007; Nabors 2004). It is unknown if certain environmental factors trigger knee growth and during what part of the year they are growing. Knees have been observed to show signs of new tissue growth (“blistering”) during the late winter and early spring months, right before the new leaf season in March. Although thought to be a response to inundation (Kernell and Levy 1990; but see Penfound 1952), it is not known if knees grow when the bole is growing or if knees grow in response to stress at times when bole growth is limited.

The impoundment of the Little Tallahatchie River in northern Mississippi in 1939-1941 formed Sardis Lake and flooded upland habitat near the Little Tallahatchie River. Bald cypress were present along the tributaries to the Little Tallahatchie, but once flooded, trees could then colonize the newly formed shoreline areas. Since complete records of precipitation and water level exist for the entire history of Sardis Lake, relating records of bole and knee growth to precipitation and inundation becomes possible for trees along the shoreline. This study

investigates the relationship of bald cypress growth (knees and boles) to variation in inundation and precipitation using trees at Sardis Lake in northern Mississippi. The effects of slight differences in water elevation (sensu Weber 2010) on the growth of bald cypress boles will be examined using the longer elevation and precipitation records available for Sardis. It was expected that boles would respond directly to variation in precipitation, while inundation of lower elevation trees would also have positive effects on bole growth (as had been seen at Sky

Lake). It was also expected that initiation of the growth of knees would be associated with significant flood events in the trees’ lifespan.

II. METHODS

Sardis Lake is a flood control reservoir built on the Little Tallahatchie River near Sardis,

MS, in 1939-1941 by the Army Corps of Engineers. Bald cypress trees are common along the shoreline of Sardis Lake and easily accessed by roadways to shoreline recreation areas. Daily water level records of Sardis Lake are available for the lifespan of almost all of the trees along

the shoreline.

Eighty-one cores were collected from forty-one bald cypress trees at five locations at 5

Sardis Lake (located in Pat’s Bluff 1: 34° 25’ 14.29” N, 89° 44’ 09.39” W; Pat’s Bluff 2: 34° 25’

21.48” N, 89° 43’ 56.77” W); Blackjack Point (34° 23’ 36.38” N, 89° 45’ 35.74” W); Thompson

Creek Landing (34° 24’ 19.71” N, 89° 45’ 32.88” W); and Moccasin Point (34° 26’ 26.31” N,

89° 46’ 41.81” W). These locations on both sides of the lake provided locations containing 7-17 trees along each elevation gradient.

Two sites were established at Pat’s Bluff (see Figures 1 and 2). The first site contained 9 trees, the lowest at 79.27 m ASL and the highest at 81.77 m ASL. Two knees were taken from two trees at this site by cutting them at the base with a hacksaw as close to the soil surface as possible. The second site at Pat’s Bluff contains 8 trees located near a streambed in a forested area and above a sand berm. The trees furthest from the lake are in a shallow depression behind the sand berm and may be inundated for short periods of time throughout the year independently of lake level. The elevations ranged from 78.39 to 81.77 m ASL. Three knees were cut from two trees at the second Pat’s Bluff site. Pat’s Bluff was subdivided into two sites because the differing topography and streambeds provided an opportunity to study the trees’ growth patterns

and relationship to precipitation and inundation in the presence of a stream or pooling because of a sand berm. Blackjack Point has 7 trees (see Figure 3). Tree 70 is located on lakebottom free of other vegetation, 300 m from trees 68 and 69, which are on a bluff, and these two trees are 175 m from trees 64-67, which are located in a transect along a stream in a wooded area. Six knees were taken from two trees within the forest. The trees ranged from 78.19-83.00 m ASL.

Thompson Creek has 9 trees (see Figure 4), which are on a transect beginning on the lake bottomland and ending within the forest, ranging from 80.72 to 83.72 m ASL. More than half of

the trees sampled at this site were above a high water debris line, and surrounded by other

vegetation (pine trees, buttonbush, etc.) One knee was taken from one tree at Thompson Creek. 8

Moccasin Point has 8 trees (see Figure 5), all of which are situated on the sandy lake bottomland and ranging from 78.25 to 80.29 m ASL. Three knees from two trees were taken at

Moccasin Point. No trees at any site occurred at an elevation higher than the spillway (85.76 m

ASL). Knees were chosen based on their size, accessibility, and with a high amount of certainty that they belonged to a certain tree. More growth rings in the knee produces more definitive results when correlating the knee with the bole growth, so knees that were very small were not sampled.

At least two cores were taken from each tree above the buttress using an increment borer

(Haglöf 16”, 2 thread, 4.3 mm), and some trees were cored three times to increase confidence that the bole growth was consistent on all sides of the tree. In five cases, only one core from a tree was usable. All trees were marked with numbered metal tags. Fourteen knees from nine trees were also collected. Elevation records of each tree were also taken using a transect and a level, along with a Trimble GeoXH handheld GPS unit in conjunction with a TruPulse 360R

Laser Range Finder, and they were processed using Trimble’s Terrasync software.

In the lab, cores were placed on labeled wooden mounts and allowed to dry for two weeks in a hood. When the cores were dry, they were attached to the mounts with wood glue.

After drying, each core was sanded so that its cells could be seen using a standard light microscope. The cores and the knee cross-sections were sanded four times - first with 150-grit sandpaper, then following with 220-grit, 320-grit, and 400-grit sandpapers, respectively. They were polished with #000 and #0000 steel wools.

The widths of the rings for each year in the duplicate or triplicate cores were measured using the ocular micrometer within the microscope eyepiece, and false and any possible missing

rings were noted. Cypress knees have asymmetrical cross sections, and their growth rings are 10 not circular. To reliably measure the growth rings in the knees, four perpendicular radii were drawn on each slice and the spacing of growth rings were measured at these four locations. Each growth ring had to be present on all four radii to confirm that there were no missing or false rings. A picture of growth rings in bald cypress knees can be found in the Appendix.

Because there has been no published work (but see Harris et al. 2007) on microscopic examination of knees and measurements of their growth, cross sections and sagittal sections of cypress knees were examined. Knees were taken either from roots that were exposed around a tree (to be sure that the knee came from that tree), or they were taken from trees that were not close to any other specimens of T. distichum. The knees were cut as close to the ground as possible, so that as many growth rings as possible would be collected. Using a tablesaw, the base of the knee was cut off, producing a cross-sectional slice of about 1cm in thickness. A knee was also cut sagittally, and the rings within it are arced, an observation also made by Kramer,

Riley and Bannister (1952). The ring closest to the center has the smallest arc, and each

subsequent arc reaches above the one before it, with the outermost arc forming the top of the knee.

A Wild Heerbrug light dissecting microscope was used to examine the cores and the knees at 12x magnification and 20x ocular. After cutting and polishing, growth rings are often visible within the cypress knees (see Figure 6). Smaller knees sometimes lack visible rings and are instead entirely comprised of a glossy pith. The cell structure of the larger knees is similar to the cell structure of cores from the bole of the tree. The growth rings in the knees look similar to the growth rings in the bole cores. In the knees, the compressed dark cells [that form in the boles

during the winter months (i.e., the “ring”)] are always small – often only two or three cells in 10 width – whereas there are frequently rings in the boles that are several times that size in width. I assume that because the cell structure within the knee is similar to that found in the bole, the rings within the knee are annual growth rings.

The radial growth of knees and boles was compared using a variation of the cross dating technique (Stokes and Smiley 1968) that is used to assemble a chronology based on several wood samples of unknown ages. In this technique, growth records are compared and the best fit

(highest correlation) of growth-record sequences in two samples is used to determine when overlap in the growth of the two wood samples occurred. If the growth of boles and the knee are responding to the same environmental variables, they should have a positive correlation. If the production of knees is a response to stress that otherwise is limiting to the boles, they would be expected to have a negative correlation. Bole and knee growth measurements were normalized and the standard normal residuals were used in the correlation analysis to determine when the knee’s growth was initiated. The bole growth records range from 21 - 57 years, and the collected knees have 3- 14 growth rings. Because only the visible part of the knees above the ground were

collected, the growth records for the knees will be shorter than the knee’s entire lifespan, but the correlation model can still be used to determine when the knee was growing. The most positive correlation occurs when knee and bole growth records are most coherent, and the most negative correlation occurs when knee and bole growth records are least coherent (see Figure 7). The time periods determined to be the most or least coherent were compared to the appropriate water level and elevation data to determine if initiation of knees was associated with particular flood events.

Analysis of the relationship between the bole growth (Annual Growth Increment,

“AGI”), and precipitation and inundation (determined by elevation at each tree) was determined 13 using regression analysis. Variation in the slope of the AGI-precipitation and AGI-inundation relationships was then regressed against elevation and study site. Because the majority of rainfall in northern Mississippi occurs during November-April, but the growing season includes

May-October (see Figure 8), the effects of precipitation were based on November-April records, while inundation effects were based on May-October records. All data analysis was completed using R (R Core Team 2012, 2013).

Start of knee growth? 13

Start of knee growth?

Figure 7: A comparison of the growth of the bole of Tree 67 with the growth of one of its knees. The top graph depicts the knee’s first collected growth year placed at the year with which it is most coherent, and the bottom graph depicts the knee’s first collected growth year placed at the year with which it is least coherent.. Because the knee was cut at the ground and not at the root, its entire lifespan is not represented by the growth records. A black arrow estimates the year of knee initiation, approximately 5 years prior.

III. RESULTS

The 42 trees used in this study produced cores ranging from 12 to 57 years at 5 sites above the dam. Each site included trees along a slight (< 4 m) increase in elevation. Two of the five sites (Pat’s Bluff 1 and Moccasin Point) show a negative response to growth-precipitation

regression slopes as elevation increases, while trees at two other sites (Pat’s Bluff 2 and

Blackjack Point) show a positive response as elevation increases. Thompson Creek shows no 16 response to elevation, but the relationship would be strongly positive without the outlier at 80.72 m ASL (Tree 78) (see Figure 9). The slopes of growth vs. inundation regressions against elevation from April-October show substantial variation in responses across the 5 sites (see

Figure 10). With all sites combined, there was a significant (p=0.019) growth response to

November-April precipitation across elevation.

Comparing variation in knee growth and bole growth records provided some evidence that knees were associated with flood events. Based on most-correlated series, it was found that the knees were most likely to occur several years after a major flooding event, with many knees having apparent start dates in the years 1988-1989 and between the years 1994-1999, both periods being associated with extreme, prolonged flooding. The start dates from least-correlated years of knee growth did not have any discernible pattern. Table 1 shows the year with which each knee growth record was most or least correlated. These time periods for most-correlated growth each occur approximately 3-7 years after a major flooding event – one in 1983 and one in

1991 – both years when the water flowed over the spillway at Sardis Dam. Figure 11 shows the

daily lake level at Sardis, with black bars representing each knee’s growing period. The hollow

circles represent the least-correlated starting year associated with each knee.

Correlation Results Between Knee and Bole Growth Records

Tree Site Knee MC Year Coefficient LC Year Coefficient 51 Pat's Bluff 1 1 1999 0.90 1995 -0.66 53 Pat's Bluff 1 2 2003 0.99 2004 -0.99 55 Pat's Bluff 2 3 2007 0.99 1995 -0.99 56 Pat's Bluff 2 4 1988 0.99 1987 -0.99

56 Pat's Bluff 2 5 1998 0.96 1991 -0.96

66 Blackjack Point 6 1996 0.46 1992 -0.75 19 66 Blackjack Point 7 1994 0.84 1996 -0.32 66 Blackjack Point 8 1996 0.70 2002 -0.58 66 Blackjack Point 9 1995 0.37 1991 -0.51 67 Blackjack Point 10 1986 0.79 1994 -0.54 67 Blackjack Point 11 1987 0.71 1993 -0.57 79 Thompson Creek 12 2001 0.53 1999 -0.63 87 Moccasin Point 13 1979 0.93 1999 -0.76 87 Moccasin Point 14 1970 0.99 1997 -0.93 108 Moccasin Point 15 1988 0.99 1996 -0.99

Table 1: The year that is most correlated (MC) and least correlated (LC) with each knee is shown. The “Tree” column shows the tree that the knee was taken from. The first number is the tree tag, and the second number is which core was most correlated with the knee. “Coefficient” shows how correlated each knee is with each year. “1” is a perfect positive correlation, “-1”, is a perfect negative correlation, and “0” is no correlation.

IV. DISCUSSION

Bald cypress knees appear to be a response to a flooding event, and once they begin to form, their growth is coherent with bole growth. If knees were a response to stress that had a measurable effect on tree growth, then we might expect knee and bole growth to be incoherent.

The growth of boles at Sardis Lake does not vary with inundation as was expected based on the

Sky Lake work done by Weber (2010). An earlier study by Chambers (2002) also showed no 22 relationship between growth and inundation, although there were no measurements of tree elevation made.

By comparing the groundwater system of Sky Lake and Sardis Lake there may be an answer to these disparate views. Sky Lake currently experiences downwelling of water through its sediments possibly brought about by groundwater withdrawals near the lake (Davidson et al.

2006; Coupe et al. 2012). Precipitation flowing into Sky Lake, even if it accumulates to substantial depths, is eventually flushed downward through the root zone and into a groundwater cone of depression in the area (Coupe et al. 2012), creating more favorable conditions for bald cypress growth (Davidson et al. 2006; Weber 2010). At Sardis, which is designed to hold water for scheduled releases to prevent downstream flooding, trees at lower elevations suffer possible root zone stagnation from inundation associated with high amounts of precipitation (which is detrimental to bald cypress growth: Pezeshki and Santos. 1998). Although growth is directly related to precipitation for trees at mid-elevations at Sardis, at lower elevations, the positive effect of precipitation appears to be offset by adverse effects of inundation. In Figure 9, the trees

at the highest elevation (82-83 m ASL) experience less growth than the trees at mid-elevations

(79-82 m ASL), and about the same growth as experienced by frequently flooded trees. Most of the trees at the highest elevation are at Thompson Creek, and all of these trees are located in the woods above the high-water debris line that separates open stands of bald cypress from those surrounded by other woody species (see Figure 4). The negative response of growth to precipitation at the highest elevations might be associated with the effects of competition from other plants surrounding the trees. When these different ideas are merged into one hypothesis, the data in Figure 9 is seen to better fit with a curvilinear model (see Figure 12), where negative

growth-precipitation relationships are seen when inundation of trees at lower elevations negates 22 the positive effects of precipitation. At the highest elevations infrequent flooding allows the development of a plant community where the usually positive response of bald cypress to precipitation is possibly negated by competition with other plants. Across a broad elevation gradient without competition or inundation effects, the growth vs precipitation relationship is independent of elevation.

The timing of initiation of knees appears to be associated with a significant inundation event in the trees’ lifespan. The correlation results show that with the exception of knee 4 (from

Tree 56), initiation of most knees is positively associated with a major flooding event 3-7 years earlier. This conclusion was made because the positive correlations of the knees to the boles show a cluster of years several years after each major flood (1972, 1983, 1991) or after the tree was inundated for a long period of time (see Tables 1-3). There are no discernable patterns or environmental events associated with the least-correlated years, and the least-correlated years also have poorer correlation coefficients overall than the most-correlated years. Because the knees were cut from the base of the tree above ground and not from where they began forming

on the root underground, it is highly plausible that these flooding events initiated knee growth and the knee did not emerge above ground for 3-7 years after the flood event. Examination of a sagittal section of a knee also indicates that knees grow approximately 1.7 cm per year. The roots from which the sampled knees were taken were about 7-8 cm underground, and at a rate of

1.7 cm per year, would take around 4-5 years to emerge from the ground, which corresponds to the flood response results. Because the knees have differing ages, but all have similar periods in which they started growing, it appears that knee growth is initiated by a strong flooding event and the knees continue to grow continuously afterwards, coherent with bole growth. Knee 4

from Tree 56 is correlated with 1988, which is part of a timespan that is affiliated with the flood 22 year of 1983. Four of the 15 knees are correlated with this flood year; however, the elevation records show that Tree 56 did not experience any inundation associated with the 1983 flood.

This exception may be tied to Tree 56 being located in the Pat’s Bluff 2 site, which is surrounded by sand berms and which experiences seasonal flooding from the stream instead of from rising lake level. While the lake level records do not document an inundation event from the 1983 flood near Tree 56, it may have been exposed to stream water inflow and flooding related to the high lake level that year or related to precipitation. If the roots of Tree 56 were inundated by stream flow for a significant period of time, it may have started producing knees even though it did not experience inundation from the 1983 flood.

A similar flood control structure in the same climatic region as Sardis Lake that has older bald cypress trees could facilitate a similar study in order to increase confidence that bald cypress knee growth is responding to the previous years’ hydrologic events. The sample of knees used in this study was also small, and more, and larger, knees from similar areas will be

needed to confirm that knees are a response to significant inundation events, or if they are also

associated with precipitation or groundwater activities below the surface of the soil.

LIST OF REFERENCES

Chambers, Julieann Morris. 2002. Bald Cypress (Taxodium distichum) Growth in the Little Tallahatchie River Basin: Effects of a Flood Control Dam. Master’s Thesis. University of Mississippi. pp. 1-50.

Coupe, Richard H., Jeannie R. B. Barlow, and Paul D. Capel. 2012. Complexity of human and ecosystem interactions in an agricultural landscape. Environmental Development 4: 88-104.

Davidson, G.R., Brian C. Laine, Stanley J. Galicki, and Stephen T. Threlkeld. 2006. Root-zone hydrology: Why bald cypress in flooded wetlands grow more when it rains. Tree-Ring Research 62:3-12.

Harris, M.D., Rock, B. N., Hale, S. R., Hayden, L. B., Porter, W. 2007. Assessing the Function of Cypress Knees – A Watershed Watch Student Project. American Geophysical Union, Fall Meeting 2007, abstract #ED11C-0630. .

Keeland, Bobby and Rebecca Sharitz. 1995. Seasonal growth patterns of Nyssa sylvatica var. biflora, Nyssa aquatica and Taxodium distichum as affected by hydrologic regime. Canadian

Journal of Forest Research 25: 1084-1096. 27

Kernell, Judith Leeds and Gerald F. Levy 1990. The Relationship of Bald Cypress (Taxodium distichum (L.) Richard) Knee Height to Water Depth. Castanea 55(4): 217-222.

Kramer, Paul J., Walter S. Riley, and Thomas T. Bannister. 1952. Gas Exchange of Cypress Knees. Ecology 33(1): 117-121.

Mitsch, William J. and James G. Gosselink. 2007. Wetlands. 4th ed. Hoboken, NJ: John Wiley and Sons, Inc. p 214.

Nabors, Murray W. 2004. Introduction to Botany. San Francisco: Pearson. p 77.

Penfound, William T. 1952. Southern Swamps and Marshes. The Botanical Review 18: 413- 446.

Pezeshki, S.R., and M.I. Santos. 1998. Relationships among rhizosphere oxygen deficiency, root restriction, photosynthesis, and growth in bald cypress (Taxodium distichum L.) seedlings. Photosynthetica 35:381-390.

R Core Team. 2012. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing. Vienna, Austria. .

Stahle, David W. and Malcolm K. Cleaveland. 1992. Reconstruction and Analysis of Spring Rainfall over the Southeastern U.S. for the Past 1000 Years. Bull. Amer. Meteorological Soc. 73: 1947–1961.

Stahle, David W., Malcolm K. Cleaveland, Dennis B. Blanton, Matthew D. Therrell, and David A. Gay. 1998. The Lost Colony and Jamestown Droughts. Science, 280: 564-566.

Stahle, David W., M. K. Cleaveland, and J. G. Hehr. 1985a. A 450-year drought reconstruction for Arkansas, United States. Nature 316: 530-532.

Stahle, David W., Edward R. Cook, and James W. C. White. 1985b. Tree-Ring Dating of Baldcypress and the Potential for Millennia-Long Chronologies in the Southeast. American Antiquity, 50(4): 796-802.

Stahle, David W., Roy B. Van Arsdale, and Malcolm K. Cleaveland. 1992. Tectonic Signal in Baldcypress Trees at Reelfoot Lake, Tennessee. Seismol. Res. Lett. 63: 439-447.

Stokes, Marvin A. and Terah L. Smiley. 1968. An Introduction to Tree-Ring Dating. Chicago: University of Chicago Press.

Valentine, K. A., B. Libman, and S. Threlkeld. 1997. Interannual Variation in radial growth of bald cypress along an incised stream channel. P.1047-1052, in S. Wong, E. J. Langendoen and F.

D. Shields, Jr. (eds.), Proc. Conf. Management of Landscapes Disturbed by Channel Incision.

University of Mississippi. 27

Van Arsdale, R. B., David W. Stahle, Malcolm K. Cleaveland, and Margaret J. Guccione. 1998. Earthquake signals in tree-ring data from the New Madrid seismic zone and implications for paleoseismicity. Geology 26(6):515-518.

Whitford, L. A. 1956. A Theory on the Formation of Cypress Knees. Journal of the Mitchell Society. 80-83.

Weber, Katherine. 2010. Statistical Analysis of Precipitation and Inundation Effects of Trees in Different Flooding Regimes. Sally McDonnell Barksdale Honors College. University of Mississippi, Thesis. pp. 1-29.

Young, P. J., B. D. Keeland, and R. R. Sharitz. 1995. Growth Response of baldcypress [Taxodium distichum] to an altered hydrologic regime. The American Midland Naturalist 133:206-212.

APPENDIX

Depiction of Methods

Step 1: A core is taken from a tree and the distance between each year (AGI) is

measured in ocular micrometers.

Step 2: The AGI is standardized across the years of the tree’s lifespan.

Step 3: The AGI is regressed against precipitation and also against inundation records that correlate to the tree’s lifespan, and the slope of the line is taken from the results in R.

Step 4: The slopes for precipitation and inundation of each tree are regressed against the elevations of each tree. The trend at each site is compared to determine if a relationship exists between precipitation, inundation, and elevation.

R Code for Cross-Dating Knee and Bole Records example<-read.csv(file.choose()) attach(example) knees<-subset(example, knee_width!='NA') numknees<-length(knees$knee_width) numtrees<-length(tree_width) numcorrs<-numtrees-numknees coefficients <- rep(NA,numcorrs) firstvalues<- rep(NA,numcorrs) treetest<-rep(NA,numknees) end<-0 for(i in 1:numcorrs) { end<-i+numknees-1

treetest[1:x]<-example$tree_width[i:end]

testcorr<-cor(knee_width[1:numknees],treetest) 27 coefficients[i] <-testcorr firstvalues[i]<-i } results<-data.frame(coefficients,firstvalues) results<-results[order(coefficients) , ] results

VITA

Emily Marie Stauss was born in Louisville, Kentucky, on October 24, 1988. She attended elementary school at Our Lady of the Valley Catholic School in Indian Springs,

Alabama, and graduated high school at John Carroll Catholic High School in Birmingham,

Alabama, in May 2007. The following August she enrolled in Spring Hill College in Mobile,

Alabama, and earned a Bachelor of Science degree in May 2011, with minors in Chemistry and

Spanish. In June 2011 she entered the University of Mississippi to pursue her Master of Science 27 degree, and she defended her thesis on April 23, 2014.