ESPM 129, Biometeorology, Dennis Baldocchi Instructor Lecture 1, Introduction 1Lecture 1. Introduction and Overview August 25, 2010 ESPM/EPS 129, Biometeorology MWF 11-12 306 Wellman Hall University of California, Berkeley Instructor: Dennis Baldocchi Professor of Biometeorology Ecosystem Science Division Department of Environmental Science, Policy and Management 345 Hilgard Hall University of California, Berkeley Berkeley, CA 94720 Email: [email protected] Phone: 510-642-2874 Fax: 510-643-5098 Web Site: http://nature.berkeley.edu/biometlab Lecture 1 Outline 1. Introduction: What is Biometeorology? 2. Goals of the Course, Philosophy and Expectations 3. Course Outline L1.1 Introduction Biometeorology involves the study of interactions between the physical environment and all of Life's forms, including terrestrial and marine vertebrates, invertebrates, plants, funghi and bacteria. In ESPM/EPS 129, we will focus on a narrower aspect of biometeorology: ‘how the terrestrial biosphere breathes?’ Principles taught in this course will serve students interested in quantitative and qualitative aspects of environmental sciences. Lectures draw on principles derived from a diverse but interconnected set of fields like atmospheric science, ecosystem ecology, plant physiology, biogeochemistry, hydrology, soil physics, agriculture and forestry. Agricultural and Forest Management problems that require biometeorological information include integrated management of pests, frost and spray drift, irrigation scheduling, crop modeling, vineyard, orchard and plantation site selection, optimal crop design, wind breaks, and cultural practices (e.g. tillage practice, row orientation and soil mulching). Science problems using biometeorological principles and data involve the predicting and diagnosing weather and climate, biogeochemical cycles of carbon, waterESPM 129, Biometeorology, Dennis Baldocchi Instructor Lecture 1, Introduction 2and nutrients, water balance of watersheds and the growth and dynamics of forests and ecosystems. L1.2 Topic Overview A link between climate and vegetation have long been recognized by farmers, foresters and playwrights for hundreds, if not thousands, of years. The word climate is coined from the Greek word for slope, ‘klima’. The Greeks understood that different types of vegetation and weather occurred on different hill slopes. Citations to plant-atmosphere interactions can also be drawn from more contemporary literature. In the play, Uncle Vanya by Anton Checkov (1899), the Doctor refers to plants and climate, with a modern sense: "... forests tremble under the axe, millions of trees are lost, animals and birds have to flee, rivers dry out, beautiful landscapes are lost forever.....waters are polluted, wildlife disappears, the climate is harsher...". In a latter passage he says: "...the forest teaches us to appreciate beauty, it softens the harshness of the climate", The physical status of the atmosphere is defined by its temperature, humidity, wind speed, and pressure. But how does the atmosphere maintain its physical state? To answer this question we must assess the fluxes of heat, energy and momentum into and out of the atmosphere, which is analogous to studying the flows of water into and out of a bathtub to determine the level of water inside. For an illustrative example, let’s consider the factors that control atmospheric humidity (Figure 1). Its content in the atmosphere depends on gains by surface evaporation and losses by precipitation (rain, snow) and dew formation. The pertinent question asked by the biometeorologist is: what controls evaporation? To answer this question we must start invoking explanations that involve plants. Plants intercept sunlight and the intercepted sunlight heats the soil and leaves and drives transpiration and evaporation. Plants also exert drag on the wind. This alters turbulent mixing and the transfer of moisture from the surface to the atmosphere.ESPM 129, Biometeorology, Dennis Baldocchi Instructor Lecture 1, Introduction 3 Figure 1 Links between plants and the flow of heat, water, CO2 and sunlight. The ability of plants to exert an influence on the humidity budget of the atmosphere also depends upon how plants respond to their environment. The humidity of the air alters the opening of stomata on leaves and rates of transpiration. The heat budget and the consequential temperature of the leaves controls respiration (leaves, roots, microbes), photosynthesis, trace gas volatilization, saturation vapor pressure, plant growth, kinetic rates of biochemical reactions. Sunlight drives photosynthesis, which is linked to stomatal conductance and growth. Photosynthesis and photorespiration depend upon CO2 levels. Finally, if moisture in the atmosphere condenses, it forms clouds and these clouds can precipitate. On climatic time scales, the water balance of the soil affects transpiration, stomatal conductance, photosynthesis, soil respiration, plant growth, plant competition, species and leaf area. The rates at which trace gases and energy are transferred between the biosphere and atmosphere depend upon a complex and non-linear interplay among physiological, ecological, biochemical, chemical and edaphic factors and meteorological conditions. Contemporary theories consider the exchanges of energy and mass in concert. Flows of energy need to be calculated because the biosphere requires energy to perform work. Gas exchange activities requiring energy and work include biosynthesis, evaporation, transport of nutrients and carbon dioxide fixation. Concurrently, these activities require flows of substrate material. Water and carbon and nitrogen based compounds are the most important forms of matter for the sustenance of life.ESPM 129, Biometeorology, Dennis Baldocchi Instructor Lecture 1, Introduction 4Scale is an important concept we must concern ourselves with when studying biometeorology. To understand why, let’s consider the functioning of a plant canopy, 1 m tall. It consists of leaves, an order of magnitude smaller, and it is the functioning of the leaves, a smaller scale phenomenon, that helps us understand the functioning of the canopy. Now the environment imposed on the canopy comes from a much larger scale, that of the planetary boundary layer and regional weather, with scales of kilometers. Another concept to consider is emergent processes. As we