Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 5-1972 Canopy Structure and Phenology of Alpine Tundra Vegetation Marcee Fareed Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Plant Sciences Commons Recommended Citation Fareed, Marcee, "Canopy Structure and Phenology of Alpine Tundra Vegetation" (1972). All Graduate Theses and Dissertations. 6314. https://digitalcommons.usu.edu/etd/6314 This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. ,, rn.ea . ,1 ,.I,. "'' CANOPYSTRUCTURE AND PHENOLOGY OF ALPINE TUNDRA VEGETATION by Marcee Fareed A thesis submitted in partial fulfillment · of the requirements for the degree of MASTEROF SCIENCE in Plant Ecology Approved: MaJor Professor Committeeman ·committeeman Dean of Graduate Studies UTAHSTATE UNIVERSITY Logan, Utah 1972 ii ACKNOWLEDGEMENTS Grateful acknowledgement is made to Dr. Martyn Caldwell for his suggestions on the fieldwork and the preparatton of the thesis. Appreciation is also extended to Thomas Shoemaker and Diane and Roger Hanson for their assistance in gathering the data, and to Professor Arthur Holmgren for helping in the identification of plant species in the voucher collection. Dr. Larry Tieszen is responsible for developing the computer programs used in the analysis of the data. This study was supported by the Tundra Biome of the International Biological Program. ~~ Marcee Fareed iii TABLE OF CONTENTS Page Acknowledgements ii List of Tables .. iv Li st of Figures v Abstract vi Introduction . 1 Description of Study Area . 3 Physical Features 3 Climate . 3 Vegetation . 4 Methods . 8 Results . 9 Live LAI . 9 Senesced LAI . 16 Phenology 18 r· Discussion . 24 Canopy Structure 24 Phenology . 26 Productivity 31 Summary . 35 Literature Cited . 34 iv List of Tables Table Page l. Live leaf area index values for the Kobresia stand site on successive sampling dates in 1971 . 10 2. Live leaf area index values for the Deschamosia meadow site on successive sampling dates in' 1971 12 3. Leaf area index values and standard deviations of selected species and the total foliage in the Kobresia and Deschampsia sites during 1971 . 13 4. Species with incomplete phenological development 29 v LIST OF FIGURES Figure Page l. Climatic diagram of Niwot Ridge, Colorado . 5 2. Mean monthly solar radiation on Niwot Ridge 6 3. Distribution of leaf area at various heights in the Kobresia stand site . 14 4. Distribution of leaf area at various heights in the Deschampsia meadowsite. 15 5. Distribution of senesced leaf area indices at various heights in the Kobresia and Deschampsia site canopies during 1971 .......... 17 6. Phenological strips for Geumrossii, Polygonum bistortoides, Kobresia myosuroides, and the total foliage in the Kobresia stand site on Niwot Ridge during the summer of 1971 ... 20 7. Phenological strips for Artemisia scopulorum, Geum rossii, Deschampsia caespitosa, and the total foliage in the Deschampsia site on Niwot Ridge during the summer of 1971 ............ 22 8. Soil temperature curves at 2.5 and 7.5 cm and average soil moisture in the Kobresia and Des- champsia sites during 1971 . 27 9. Total foliage leaf area indices at various heights in the canopy throughout the 1971 growing season at Barrow, Alaska . 33 vi ABSTRACT An inclined point frame was used to measure leaf area indices in an alpine tundra Kobresia stand and Deschampsia meadowon Niwot Ridge, Colorado. Measurements were made throughout the summerof 1971 at various heights in the canopy and for each species in the two communities. Maximumleaf area indices of 2.2 and 2.0 occurred in the Kobresia and Deschampsia sites, respectively. The Kobresia site was characterized by a single dominant species, Kobresia myosuroides, and a predominance of vegetation within 2.5 cm of mean ground level. The Deschampsia site had no single dominant species. The region of maximumfoliage shifted from the 2.5 to 5 cm height zone in June to the 5 to 10 cm zone in early August. Phenological observations revealed a greater number of vegetative contacts in the Deschampsia site on all sampling dates. Certain shared species varied in their phenological patterns. It is suggested that differences in the duration of ~now cover and surface melt-water may be related to the variation in phenological patterns in the two sites. In both communities, maximumLAI occurred when flower and fruit production overlapped. Arctic tundra LAI values, measured using similar methods, were less than half the maximumLAI values reached in the alpine communities examined here. INTRODUCTION A number of studies have examined the productivity of alpine tundra plants. Bliss (1962a) and Billings & Mooney(1968) have reviewed the methods and results of earlier alpine productivity studies. The chief method used in tundra productivity studies has been the harvest method. The annual above-ground productivity in most tundra ecosystems ranges from 40 to I 128 gm-2 (Bliss, 1962a). Scott and Billings (1964), working with alpine tundra communities in the Medicine BowMountains of Wyoming,found that above-ground standing crops were in the range of l 00 to 200 gm-.2. Considering that productivity rates for temperate region herbaceous communities vary from l to 10 gm~2day-l, the annual alpine rates, when calculated on a daily basis, appear low (Bliss, 1966). If roots are included, the total net productivity may be as high as 11.l gm-2day-l on mesic sites (Scott and Billings, 1964). These rates are, however, com- parable to those for many temperate region communities, if daily pro­ ductivity rates are calculated using the length of the growing season as a basis (Bliss, 1962a). Another technique for tundra analysis utilizes the inclined point frame method to estimate leaf area indices for each species as a function of position in the canopy (Warren Wilson, l960a, 1963). Leaf area index, LAL, is the ratio of the surface area of one side of a leaf to the ground area. This method has been used extensively in pasture research (Booysen, 1966; Warren Wilson, l960b; Brown, Blaser, and Dunton, 1966; Goodall, 1953c; Watson, 1958; Winkworth, 1955; Loomis and Williams, 1969; Hoyt and Bradfield, 1962; Mccree and Troughton, 1966) and, recently, in the arctic tundra research of the IBP Tundra Biome Program (Tieszen, unpublished data). In contrast to the harvest method, the point frame 2 method is non-destructive. The course of development and progression of senescence of the same vegetation can be followed through time. The data acquired provide knowledge of the number of layers and orientation of photosynthetic elements in the canopy. Leaf area index, in a strict sense, is an indicator of productivity. Successive determinations reveal leaf growth rates of individual species as well as changes in the total canopy morphology. Canopy structure affects light penetration into the canopy, amount of chlorophyll exposed to incoming radiation, aerodynamic roughness of the canopy and transfer of co2~ water vapor, and heat (Loomis and Williams, 1969). The present study utilizes an inclined point frame to describe the canopy structure of two alpine tundra communities on Niwot Ridge, Colorado. The phenologic response of species in these two communities was also examined during the summerof 1971. Holwayand Ward (1965) reviewed the literature on alpine plant phenology. 3 DESCRIPTIONOF STUDYAREA Physical features A Kobresia community and a Deschampsia meadowwere selected for study on Niwot Ridge (40° 04 1 N, 105° 361 W) at an elevation of approximately 3476 min the Front Range, the easternmost range of the Rocky Mountain System in Colorado. The Kobresia site had a southwest asoect and 5° slope, as compared to the 4° slope and southeast aspect of the Deschampsia site. Bedrock of the alpine zone is composed of Precambrian granites to granodiorites and metamorphics in large batholithic masses. Tertiary quartz monzonites to diorites occur as stocks, dikes, and sills injected into the Precambrian rocks. Schists and phyllites are also present (Marr, 1967}. The soils on Niwot Ridge h~ve undergone one or more of the geomorphic processes associated with freeze-thaw cycles: heaving, thrusting, sorting, and down-slope movement. Kobresia meadowsoils are primarily silty-loams (Marr, 1967). Where soils have been stable for a considerable time, soil profiles are well developed with upper horizons rich in humus· and up to 30 cm thick. During the winter months, soil ice is present and in some areas it persists throughout the year. Retzer (1956) has described alpine turf, meadow, and bog soils in the Rocky Mountains of Colorado. An intensive soil survey has also been made on the Fraser alpine area (Retzer, 1962). Climate Climatic data has been collected at tundra and subalpine stations on Niwot Ridge by Marr (1967) and summarized by Barry (1972). During the 4 short summer growing season, minimumtemperatures above 3050 m range from Oto 5 C and maximumtemperatures range from 12 to 18 C (Figure 1). Highest temperatures have been recorded during July and August, when plant growth is most active. During the winter, temperatures may be as low as -12 C and during the months of October to Maydaily temperatures may never be above freezing. Wind speeds are generally reduced during the summerseason. Mean minimummonthly values are between 3 and 4 ms-1 during July and August. In January, average wind speeds may be 13 ms-1. The prevailing wind direction is from the West, but significant amounts of precipitation come with both easterly and westerly winds. Summerconvectional thunderstorms are frequent in the alpine tundra and monthly precipita- tion, often in the form of hail or sleet, can be as high as 102 mm. Most of the annual precipitation occurs in the spring. Mean monthly solar radiation during the period of most active plant growth ranges from 610 lyday-1 in May to 290 lyday-l in October (Figure 2).