Mapped permanent quadrats: A window through time into herbaceous plant demography

Long-term spatially explicit mapped datasets of herbaceous plant population dynamics are rare and intrinsically valuable beyond measure. These types of data can provide vital information to address key ecological questions related to plant demography, population and community responses to climate and anthropogenic modifications across the landscape. The long-term historical dataset, which is the focus of this thesis, provides examples of the ecological value of data derived from long-term permanent chart quadrats. In Chapter 2, I provide metadata from a long-term dataset that consists of 98 permanent 1-m2 quadrats located in the ponderosa pine-bunchgrass ecosystem surrounding Flagstaff, Arizona, USA. Individual plants in these quadrats were identified and mapped annually from 2002-2014. Original quadrats were established in 1912-1927 and were mapped sporadically until 1940. Quadrats were located in ungrazed exclosures and in pastures grazed at various intensities by livestock. I provide the following data and data formats: (1) high-resolution image files (*.tiff); (2) the digitized maps in shapefile format; (3) a tabular representation of centroid or point location (x, y coordinates), and basal cover for plants mapped as polygons; (4) a species list including the total records for each species; (5) quadrat inventory of the years each quadrat was sampled; (6) quadrat information including GPS coordinates and elevation; and (7) monthly precipitation and temperature records. The metadata results (data products) will be published in research archives. In addition, data from these permanent chart quadrats will be used to determine species-specific vital rates in Chapter 4. In Chapter 3, I developed an electronic field data collection method to remap the herbaceous vegetation on the chart quadrats described above. The method uses ESRI ArcMap to collect plant data on field computers, which: (1) creates a digital data capture system; (2) allows the ability to search and manipulate the data from directly in the field; (3) allows for a visual display of the previous year’s data map for reference in the field; (4) reduces the likelihood of data transposition errors; and (5) removes the need to digitize maps from paper copies. I tested the electronic field data collection method against the traditional paper mapping method to assess the efficiency of each method. The electronic data collection method increased the amount of time necessary to map the vegetation on each quadrat, however, the electronic method significantly diminished the amount of time needed to process each quadrat in the office. Implementing the electronic method can reduce the amount of time and resources needed to annually re-map permanent chart quadrats. In Chapter 4, I used detailed local climate variables and data from the annually remapped data set (2002-2014) described above to examine the effects of climate on the demographic rates of a dominant graminoid, Arizona fescue (Festuca arizonica Vasey). I constructed life tables to examine vital rates (e.g., survival probabilities, growth, and life expectancies) for this focal species. I made population projections using the species’ state (size) and precipitation variables using Integral Projection Models (IPMs) to quantify the direct influence of seasonal precipitation on the vital rates of this dominant perennial bunchgrass. We found that altering the size structure of the population of Arizona fescue can increase life span by increasing the number of individuals belonging to the larger size classes with higher probabilities of survival. Furthermore, we found that the survival and growth of Arizona fescue was strongly linked with winter and spring precipitation, respectively. In summary, in this thesis I compiled metadata from a historical dataset, developed an electronic field capture method, and used these data to examine the demographic rates of a dominant bunchgrass species in northern Arizona. Gaining a better understanding of the climatic factors that drive plant populations will allow land managers to make informed decisions regarding land-use practices and the implementation of restoration treatments in the Southwest. In an era characterized by anthropogenic climate and land-use change, understanding the impacts these changes may have on forest ecosystems is crucial in our effort to anticipate how plant communities may respond over time