Cedar Creek LTER

Our long-term studies at Cedar Creek, which were begun in 1982 with the funding of our LTER proposal by the National Science Foundation, are focused on six major issues and questions. These six foci explore topics of fundamental scientific interest and of relevance to human-driven global environmental change, especially the impacts of elevated nitrogen deposition, of increased concentrations of atmospheric carbon dioxide, and of the loss of biodiversity on ecosystem functioning. In addition, we have performed other shorter-term related studies. These studies are supported by grants from the National Science Foundation, Department of Energy, the Andrew Mellon Foundation, and other sources.

The Cedar Creek LTER combines long-term experimentation and observation to examine the controls of successional dynamics and spatial patterning in ecosystems at the prairie-forest boundary. The LTER project has established more than 1100 permanent, long-term experimental plots as well as 2300 permanent observational plots distributed across a chronosequence of 22 old fields. Our studies focus on hypotheses concerning the direct, indirect and feedback effects of various species and ecosystem elements on each other. Although we study whole ecosystem processes, a major goal of our project is to understand the underlying mechanisms that control these processes. Work focuses on:

1. Mechanisms of plant competition for nutrients and light;
2. Dynamics of carbon and nitrogen in the soil;
3. Controls of the primary productivity, species competition and species diversity of grasslands;
4. Herbivory, including feedback effect of herbivores on soils and plants;
5. Disturbance;
6. Modeling and ecological theory.

Our studies of the mechanisms of plant competition, done by David Tilman and David Wedin, use results from over 900 plots in a long-term experimental garden in which we are growing many major grassland species in monocultures and in various pairwise combinations. These plots were established on an experimental soil nitrogen gradient. We routinely monitor soil nitrate and ammonium concentrations, as well as plant biomass and allocation patterns, in these plots. Our studies of soil carbon and nitrogen dynamics, which involve David Grigal, John Pastor, Don Zak, Peter Homann, David Tilman, David Wedin and Jean-Alex Molina, include work on litter decomposition, species-specific litter feedback effects, N mineralization, nitrification and leaching, N fixation, microbial and mycorrhizal biomass, and dissolved organic carbon dynamics. Studies of primary productivity and the controls of plant community involve Scott Wilson, Martha Phillips, Richard Inouye, Mark Davis, Nancy Huntly, Tania Vincent and Mark McGinley.

This research includes nutrient addition experiments in uplands and wetlands, water table manipulations in wetlands, detailed studies of the nutrient and light dependence of growth of major plant species, studies of the role of soil heterogeneity and of plant colonization, growth and competition in patchy habitat. Herbivory research, led by Nancy Huntly, Richard Inouye, Mark Ritchie, John Pastor, and David Tilman, includes long-term observations on the population dynamics of the major herbivores (small mammals, deer, and grasshoppers), selective removal of herbivore guilds, deer exclosure experiments, gopher exclosure experiments, comparisons of fenced and unfenced nitrogen gradients, studies of the impact of herbivores on carbon and nitrogen dynamics and cycling, and studies of replicated monoculture and competition plots in our experimental garden that either do or do not have one or more grasshopper species.

Our studies of disturbance, coordinated by Scott Wilson, David Tilman, Eville Gorham, John Tester, and Richard Inouye, consist of comparisons of disturbed and undisturbed plots that receive different rates of nitrogen addition, our 29-year running set of prescribed burns in oak savanna, a 6-year running set of prescribed burns in an old field, manipulations of depth to water table (as a mimic of effects of climatic change), and observations on the pattern and frequency of disturbances in old fields, savanna, forest, and wetlands. We are also working on analytical and simulation models of various ecosystem attributes. These models, which address processes occurring on a range of spatial and temporal scales, are being developed and tested under the direction of David Tilman, John Pastor, and others.

The first 500 acres of CCESR were acquired in the early 1940s with the understanding that they would be kept in their natural condition and used for scientific and educational purposes. Funds for acquisition of additional land, development of permanent buildings and preparation of accurate maps became available from a variety of sources including personal contributions, the National Science Foundation, the Max Fleischmann Foundation, the Minnesota Natural Resources Commission and the US Land and Water Conservation Program. Cedar Creek lies at the boundary between prairie and forest. It is a mosaic of uplands dominated by oak savanna, prairie, hardwood forest, pine forests, and abandoned agricultural fields and of lowlands comprised of ash and cedar swamps, acid bogs, marshes, and sedge meadows. Large tracts of the pre-agricultural ecosystems of the region are preserved within its boundaries as is a successional chronosequence of more than 80 old fields of known history.

A program of prescribed burns, begun in 1964 in a large tract of native oak savanna, has 12 blocks with fire frequencies ranging from one per year, to one per 7 years, to unburned controls. These have diverged dramatically in their vegetation and soils in response to fire frequency and some areas are now exhibiting characteristics not seen in this region since settlement in the 1800s. The soils of Cedar Creek, derived from a glacial outwash sandplain, span five of the ten soil orders. Upland soils are nitrogen poor: numerous nutrient addition experiments performed in both old fields and native savanna have shown that nitrogen is the major soil resource that limits plant growth. Cedar Creek has a continental climate with cold winters, hot summers, and precipitation (66 cm/yr) spread fairly evenly throughout the year. The mean July temperature is 22.2OC while the mean January temperature is -lOoC.

The discovery of the Cedar Creek Forest, as it had been called, was in itself quite remarkable. Grace Nute, while on a weekend trip to the north shore of Lake Superior, had questioned her friend, Cora Corniea, about the origin of the interest in the acquisition and preservation of the Cedar Bog. Consequently, in June of 1958 Dr. Lawrence wrote to Dr. William S. Cooper with the request that he inform Mrs. Corniea about how he had discovered the area and when he and Dr Otto Rosendahl had first tramped around in the swamp. Dr. Cooper's letter to Cora Corniea, dated June 19, 1958, included the following account:

"The airplane trip on which I first saw the bog took place on April 6, 1930 My pilot was Mark Hurd and the plane was a very small one intended for one person; two of us crowded into it. There was a terrific north wind blowing, and I remember noticing that the north-bound cars were moving faster than we were. It was quiet when we turned around and headed for home Our route that day was straight north over New Brighton, Ham Lake, Fish Lake, then circling around to cover the northeast corner of Anoka County Incidentally, the door on my side of the plane was removed, to give me a little more extra room and to make vertical shots possible. I don't mind looking down...As to the date of Dr. Rosendahl's visit with me, I cannot give an exact date. I made a very complete set of field notes on July 11, 1931, but I cannot believe that I waited more than a year to investigate the place that had interested me so much from the air. I can say with some assurance that this visit was sometime during the summer of 1930, probably early in the season. I took along the picture that I had made from the air, and we struck in from about where the Crone property now is. On our first attempt we missed the lake entirely, coming out on the upland east of it. Our second try brought us to the south end of the lake."

According to Dr. John W. Moore (1952) the Cedar Creek Forest first received serious attention in 1929 when N. C. Huff visited the Isanti County portion of the bog. On the 24th of June in 1929 he obtained pictures of Pyrola asarifolia. In a letter that Dr. Lawrence received from Helen Buell, the wife of Dr. Murray Buell, she raised an interesting question: "Does anyone around Minnesota know that Cedar Bog Lake used to be called Decodon Pond? (and the bog Decodon Bog?)--because Rosendahl and Butters were so impressed with the Decodon. I didn't know it by any other name when we were students." [1930-1933] (The University Herbarium's earliest collection of Decodon from the Area is by Dr. Rosendahl on Aug. 13, 1931; the next is by Murray and Helen Buell on Aug. 3, 1933, the place designated "Decodon Pond".)

As will become very evident the Minnesota Academy of Science became much involved in the early development of the Cedar Creek Natural History Area. In 1937 the Academy established a Committee on the Preservation of Natural Conditions. According to an account written by Dr. Arthur N. Wilcox, "Soon after the appointment of the Committee its attention was called to the desirability of a portion of this area by Dr. William S. Cooper, who had become acquainted with the area after discovering it from the air. The preservation of this portion, known as Cedar Creek Bog, included a small lake, bog and wooded swamp, was recommended in the committee's first report published in the 1938 Proceedings."

Within the next few years the Academy, with the aid especially of Drs. Cooper, J. W. Buchta, and L. M. Gould, was able to obtain the donation of sufficient funds from about 25 members so that by 1940 the Academy had purchased or had made arrangements to purchase important parts of the Cedar Creek area. In the following year the Committee for Preservation of Natural Conditions raised a large sum of money for the acquisition of more parcels of land. Dean Buchta and Dr. Cooper were very much involved in the fund raising. According to Dr. Cooper, "At the beginning of things Dr. Buchta, who was President of the Academy, proposed to me that we hold up Campus Club members as they came from lunch, and make them promise to contribute $25.00 each. We even landed Middlebrook!"

Mr. Middlebrook was both Secretary of the Board of Regents and Comptroller of the University at that time. Before proceeding further with an account of additional land acquisition and program development it is fitting that we pause to pay tribute to a truly extraordinary and memorable person, Cora Alta Corniea (Mrs. Albert Corniea). What will be said about her outstanding and unselfish contributions is taken, often verbatim, from the writings of Meribeth J. Mitchell (1960) and Grace Lee Nute (1961). According to Grace Nute if only one person could be held responsible for beginning the crusade to save Cedar Bog that individual would be Cora Corniea. She says that from the 1930s through the 1940s and for most of the 1950s Mrs. Corniea was either buying land herself, paying taxes on it, or holding it until a permanent organization for preserving it in the public interest could be formed. She also visited farmers and their wives who owned the boglands, telling them of her plans and sometimes inducing them to give their land.

She also tried to interest scientists, scientific organizations, professors and deans of the University of Minnesota and others to move in the direction of public or semi-public ownership. Cora Corniea first learned of the Cedar Creek Natural History Area in 1937 about the same time that Dr. Cooper had called the attention of the Academy Committee on the Preservation of Natural Conditions to the desirability of acquiring a portion of the area. She purchased an 80 acre tract on March 25, 1937 from the Louis Peterson estate. According to Meribeth Mitchell's account Mrs. Corniea learned that certain members of the Minnesota Academy of Science were also interested in such a project. So, during the summer of 1937, she invited the membership out to her cabin in order that they might see the area personally and then be persuaded to support the Academy's desire to save the region. This was one of many groups and individuals she entertained to interest them in the project. In 1939 she made the first of many subsequent additional purchases of land. She studied tax delinquent lists and prevailed upon County Auditors of both Isanti and Anoka Counties to notify her when land in which she might be interested became available. A search through the records reveals that she personally bought parcels of land totaling about 600 acres. In 1940 she was made a member of the Academy Committee for the Preservation of Natural Conditions chaired by Arthur N. Wilcox.