 Any questions on course logistics that I can help with? You've seen that maybe from there. You've seen that the practice questions are up on B-space and that I won't put answers up anytime soon. So the intention is that you will try the questions and talk about them with your colleagues as a means of learning about them. Any questions on course logistics that I can help with now? Yes? No. The midterm is 33 questions. She asked if that's how long the midterm is. No, that is not meant to reflect the midterm in any way. And this is the danger of giving you guys practice questions. I don't think all the instructors will do that because students tend to think that this is what the midterm is like. Can't promise that. Haven't written the midterm yet. I don't know what the midterm is going to be like. Might be a lot harder. Don't know. But it is important for you guys to understand what a multiple choice question is like that I write. I didn't write all of the ones I just gave you, but I wrote some of them. And they are much like the types that I will ask you. But they could be harder on the test. So don't slack off, please. What else? Anything else? OK. Feel free to email me if anything comes up that you need answers to. We are continuing today with ecosystem ecology. And we will first cover some geology, really, as a means of understanding the physical basis for observed patterns on a global scale in the biota in biological communities and ecosystems. We will review the terrestrial biomes of the world very briefly. Your book covers it well. In the context of global precipitation and temperature patterns, climographs, we will look at aquatic biomes focusing on the physical structure of lakes and oceans and consider nutrient limitation and productivity of such systems. And then consider productivity of ecosystems on a global scale comparing biomes to one another. I put something in here on diversity gradients. And the causes behind high tropical diversity hopefully will get to something I haven't put in before and I want to get to during the lecture cycle. So I put it in, but I didn't bullet it here. And I'm not sure if we'll get to hydrological and biogeochemical cycles. If we don't, I may just give you the slides and ask you to review it in the book because I don't want to go into much more detail than the book already provides. So for some of you, this will be review for others, perhaps not for everyone. This is of interest and importance because you are earthlings and you are subject to these forces of global climate. And more and more pressing are these forces with the changes that we're seeing in recent decades, recent centuries, as a result of human activities. The first thing to consider, and I won't review much here, is the fact that the earth as a result of being spherical receives solar energy with greater intensity in the equatorial regions as a result of the more direct strike of photons in those regions. The sun's rays strike more obliquely toward the poles and this means less solar input. The earth is also tilted on its axis and it orbits the sun. And as a result, we have our seasonal cycles. The details of that physical process isn't of importance, but you can read about it in the book if you want to. It's not of importance for our purposes. Note that because of the intensity of solar energy at the equator that water evaporates in this area and as the air is heated it rises. Upon rising, this now moist air releases that moisture. It condenses out and rains and generates the phenomenon of the hot wet tropics, hot wet tropical regions. As the air continues its ascent, losing moisture, it cools and becomes denser and it's dry and it descends. Note where we are on the earth, where some 23 to 30 degrees north latitude here, but the same phenomenon is happening in the south of the equator, to the south of the equator. And this dry descending air absorbs moisture, actually pulls moisture from the land and out of the air. And as a result, these tend to be very arid regions. And your great deserts of the world are indeed situated at these latitudes north and south, your Atacama Desert, one of the driest places on earth, your North American great southwestern deserts. That dry air, some of it, will then travel northward. It's warm, it's going to rise, it's picking up moisture, and it drops it again in this part of the world. Not as much as it dropped in the tropics, but still a lot. And this generates the phenomenon of our temperate rainforests, like we have on the Olympic Peninsula, say, in Washington, or even in some areas of California, where you get the very big trees and very dense forests with lush vegetation growth as a result of this very phenomenon. Something similar is happening in Patagonia, in southern Chile, Argentina, with these temperate rainforests as opposed to tropical rainforests. And then you can follow it further as that air, some of that rising air now dry descends over the poles, dry air absorbing even more moisture, and the poles are quite desiccated and cold, of course. So you can see from a solar driver at the equator how much can be explained about not only global air circulation patterns and precipitation, but vegetation. Also very cool. The details are not critical. I'll just highlight a few things here, though. The fact that the warming of the ocean surfaces at the equator as a result of intense solar energy produces a north circulating current on the surface waters, the hot air, the hot water being at the surface. It cools as it trends north, and that cool denser water dives deep. This is the Gulf Stream, dives deep and circulates in deep channels all around the world. And this deep water may remain in these currents for as long as 1,000 years or more before it makes its way back to the surface in the warmer water conditions. This interaction between warm and cold currents in this area produces a lot of fog. And something related is happening in our area with the fog that we see here. This is in our area related primarily to the temperature differential between our cold currents. They're shown as getting warmer here. They are getting warmer, but they're still very cold currents that we experience off our coast. And the interaction of those cold currents with warm air masses is in part responsible for the generation of fog over our waters offshore here. Now with the generation of this fog over the oceans here, some of it's pulled onto land. Some of it's pushed onto land by winds behind it. But some of it is pulled onto land as a result of the action of warm air over the land rising. Think of how hot it gets in the interior of California or in the hills or just over the hills here in summertime. This warm air is rising and the cool air from the oceans is being drawn in to replace that warm rising air. And there's often fog in the summertime in that air being pulled onto land. Sometimes works in cycles where that air conditioning fog cools the air over the land and interrupts this kind of cycle. So I'm highlighting that in relation to the fog here, but this has a moderating effect on climate in coastal areas in general because the warm land air is going to be replaced by cool marine air. And that's what makes the coasts more moderate in their climates than areas inland. And something similar is happening over the oceans themselves where the warmer air from the land is warming up the cool oceanic air. But let's look at this fog phenomenon because it's one of the really interesting characteristics of our position right here on Earth and has a great effect on local ecosystems as evidenced by research conducted in this department in relation to the vegetation and in relation to redwood communities. Look at the levels of fog across the year. It's really foggy in the summer, right? That's why San Francisco is so darn cold in the summer because of this fog. We've had a very foggy summer. At least the early part of the summer here was extremely foggy, not much sunshine. And when these fog levels are so high, look at rainfall. Rainfall is at its lowest points around the same time that fog peaks. Think of this in terms of the plants and organisms needed for water. How do we possibly get such massive forests growing in this area when rainfall is so low during the hottest times of the year? As you might suspect, it's related to this fog phenomenon. And some of the research on this is just fabulous done by various teams of researchers, including the Dawson lab, Todd Dawson's lab here. These are the study I'm going to show you. It's a study in eco-physiology. And the data that they rely on for untangling this phenomenon is the science of biogeochemistry. Those are things you'll hopefully investigate further in your educations here. I'll talk a little more about biogeochemistry next week. Here's just showing the fog offshore. I mean, burr, right? Someone I heard once say, well, it's kind of like a cozy blanket. And if you think of it that way, it's a little more acceptable. But it can really make things frigid throughout much of the summer here. So you don't need to understand isotope chemistry to understand this study in biogeochemistry. Biogeochemistry. Let me just skip back to that real quick. Look at that word, bio, life, right? Geo, earth, chemistry, chemistry. So biogeochemistry is the study of this kind of interactive system. It's the use of chemistry to study the interaction between life and earth. It's chemistry to study living ecosystems. Eco-physiology. Physiology related to the ecology of individual organisms in the context of local ecosystems. These are great integrative fields. And no surprise that there are those in this department in integrative biology who are superb in this work. As I said, you don't need to understand isotopes in a chemical sense to understand this work. Just to say that atomic elements exist in different isotopic forms as a result of differences in neutrons in their nucleus. So an isotope ratio is the ratio of a heavy isotope to a light isotope. In this case, heavy hydrogen to light hydrogen, deuterium to hydrogen. But just recognize that this is a quantification of atomic nuclei in relation to the water in fog and the water in rainfall. So rainwater here and fog water here, quantified by their hydrogen isotope ratio. Fog water is very heavy in hydrogen isotopes. It has a lot of the heavy isotope, deuterium in it. Much different from rainfall. No overlap. They're completely distinct. When you look at various plants that grow in the rainforest community, including, I'm sorry, in the redwood community, including redwoods themselves, Sequoia, Semperberans, you see that the water inside these plants is of an isotopic ratio between the fog and the rainfall and that it cycles in relation to both over the course of each year, these being the 12 months and three different years. You can do the math and determine that almost a third of the water used by the plants in these systems is coming from the fog itself. The leaves are not drinking the fog, but the fog is collecting on the plants and dripping into the soils and being consumed by the plants. And that's fantastic. That's really cool. That's why you can get such magnificent forests of such complexity, probably, in these regions as a result of fog input during the driest and hottest times of the year. Thus, and you might also think about what changes in fog levels, what kind of impact that would have on local communities in the context of global climate change, fog is one phenomenon that's likely to change quite a lot. You may have heard of this phenomenon of air when ascending against a landmass drops its moisture during the ascent, such that when it finds the leeward side of the mountain, it's lost all its moisture and has nothing to rain out. So on the leeward side of a mountain, you often get areas of great aridity. Think of much of Nevada or the Mojave Desert in the South as a result of the rain shadow created by the Sierra Nevada, the Great Basin. It's a picture of the Mojave Desert, which many of you have probably been to in some of your great cloud forests and alpine wet forests may occur in these conditions. So that's some of the global background to the distribution of vegetation on a very broad brushstroke, but it's helpful. And this is a science of macro climate and macro scale community structure. A biome is a community at a very large scale. It's a community that shares, it's actually many communities, that share certain characteristics such that they are distinguishable from collections of communities in neighboring areas. These are biomes and they're distinct in terms of the organisms that live there, in terms of the climates that they're exposed to and partly driven by those climates. They're distinct in many ways. And so you need to take your macroscope to study these things. Some of the semi-cologists speak of leaving the microscope in the lab and taking out the macroscope and going to the field and seeing whole systems through that. It's a metaphor, obviously. How do you distinguish these biomes? You can do it yourself based on what you already know as a result of what a helpful term sometimes is physiognomy, the physiognomy of these systems. It's really just their general gestalt appearance, how they look to you. This one has a bunch of waving grasses, some trees on the edges. That's a pretty heavy forest and a grassy patch in the middle. You may not know specifically what kind of ecosystem it is, but it looks like a dry forest. It looks like a seasonal dry forest or something like that. That might look like near a natural area and near where you grew up, many of you from California. That's Chaparral, this near area, with these no trees of, the trees are just very small, much smaller in here, mostly shrubby, low-lying growth that we call Chaparral. In the distance, you see more conifer forest. It's just how it looks. These are big trees. These are small spindly trees and these are shrubby, lower-lying bits of vegetation. This is the physiognomy of these systems. That's a very lush system with lots of epiphytic growth, plants growing on other plants. These trunks are caked with green leaves. You have vines hanging down from the canopy. You have mosses growing on the rock. What kind of system do you think this is? Someone said a cloud forest. Yeah, it could very well be a cloud forest or a rain forest. A tropical forest environment, probably. Some lush forest. This one looks more to me, very lush also. It looks more to me like a temperate rain forest. The ferns and, I don't know, maybe sorrel down there, I don't know. You'll know better after the botany module what these things are. Or this, very characteristic. Open grassland tends to be dry, occasional spotty trees. It's a savanna, right? It's a great savanna. You can tell by the stripey horses here that you're in Africa that could be very nearby here. These low, gradually sloping hills, eroded. These eroded hilltops, grasslands, modified for agriculture or grazing, probably. Scattered trees, oaks, something like that. Could be a park in the East Bay. So I'm just giving you a hint of how you can just look at these systems and you recognize their differences. You already do. It's because you have these sensory systems you use to distinguish among them. It's just a natural thing to do. So now let's put some technical names on them. So you know what to call them in the scientific sense. That will be the process of naming our terrestrial biomes. This is a climograph. We call this a climograph where on your axes of precipitation and temperature, you can analyze the distribution of terrestrial vegetation more or less accurately. This is something of a cartoon, but it's based on real data. You can see how nicely these biomes, these vegetation types, can be modeled on just those two axes of temperature and precipitation. So if it's real hot but really dry, you get a desert, a subtropical desert. A bit more water, you might have a tropical dry forest like you saw in that one image or a savanna. And if it's really hot but really wet, talking about a rainforest. Does anyone know anything about savannas? What else? Helps to drive and structure them? We can talk about that in a minute. I just like savannas. Or if it's really cold and really dry, the tundra, somewhat more moisture, the high latitude forests, boreal forests. I'll show you pictures of all these. Okay, you get the idea. And then our temperate rainforests where still there's a lot of moisture. Not as much as in a tropical rainforest probably. And not as hot. But that's our temperate rainforest that you would get north of here. You drove up the coast. Cool. And just another view, focused more on North America. Axis switched just for you to look at on your own time. So these are the biome types that your book provides and we'll just stick with those. And please look at the book for the details on the structure of these systems, what distinguishes them. I won't spend too much time on that. And I've already mentioned most of these. Your tropical forests distributed around the world, this one from Borneo, but Central Africa, the Amazon of course, some fabulous ones in Central America, Southeast Asia. These are the tropical rainforests. These are intensely modified ecosystems for living space and for agriculture, for harvesting of timber. And these are the so-called lungs of the earth because of just how much the major importance of these systems in processing carbon dioxide, for example. So the loss of these systems is of great importance to all of us as a result of its influence on the global atmosphere and much as being done to try to curtail the destruction of these systems. Contrast that with the desert. With your plants heavily modified for retaining moisture, sometimes the leaves are just reduced to spines that serve a protective function but also help to avoid water loss, spacing in between the individual plants. You wouldn't see this kind of thing in a rainforest where the canopy, the canopy just being the layer of leafy growth of photosynthetic capture would be closed. You would speak of a closed canopy. There's a lot of gaps in the canopy here. And savannas. So what is it about savannas? One thing that why I don't really appreciate putting them just onto a climograph. So simply, what's one factor in savannas that's so important to their maintenance? Somebody must have an idea. Sorry? Heard savannas. Yeah, grazing is a big importance in a savanna. And of very great importance. So yeah, that's one factor. Yes, they often do have very drastic wet and dry seasons. So does a dry seasonal forest. So why a dry seasonal forest with thick forest patches that still can survive an intensive dry season but in the savanna, just these scattered trees? Yes. Fires. Fires play a major role in these systems and help to structure what you see of its physiognomy here. Just individual trees often growing, your beautiful spreading acacia that the giraffe might be nibbling on as opposed to more extensive patches of forest that may not survive regular burns or something like that. So savannas are, at least the African savannas are probably in many ways evolved to deal with regular fire input. And it's certainly interesting to think about that in relation to human evolution that's been occurring there for millions of years and the domestication and use of fire by humans or human ancestors. California chaparral. Note that what we call chaparral occurs here in this Mediterranean climate where we have the hot dry summer and a cool moist winter. Forget fog in the equation for the moment because you get the chaparral occurring without major fog input, for example, in Southern California. So a hot dry summer and a cool fairly wet winter, that occurs not only here in California but around the Mediterranean. So you sometimes hear of this as a Mediterranean climate, our climate as a Mediterranean climate and this type of vegetation as a Mediterranean vegetation. It's nice. I think your book is the one that uses chaparral. That's great because that's really a term from California. Let's export that to Europe. Why not? You also have something similar going on at the tip of Africa, maybe a bit in Australia, certainly a bit in Chile. But only in those spots. Do you get this kind of structured vegetation as a result of this unique combination of climatic factors? It's pretty cool. These are also fire prone systems too, as we know all too well here. Temperate grasslands. Some of your great agricultural growing regions, right? From these what once were vast temperate grasslands. The northern coniferous forests or boreal forests are marked primarily by the conifer trees, softwood trees, the pines and spruces and hemlocks and things like that in the boreal forest zone. It's a huge region. So if only for that reason, it's of great great importance. Also intensely harvested for timber and things but we speak of the lungs of the earth down here but this region is also incredibly important for gas capture on a global scale. Temperate broadleaf forests. These are the types of system I grew up in and I just love them. You get your fall foliage colors as a result of dropping the leaves off the trees in the fall and winter. It snows a lot in some of these areas but it's really dry because snow is not available for uptake by plants. So that's a time of aridity for many plants. It is a period of winter when it's maybe a lot of precipitation but it's not available for use and it's also just cold and many plants can't function in low temperatures. So one of the solutions plants use is to drop their leaves. They are deciduous. They drop the leaves during that season. The tundra, treeless. This is latitudinally above tree line. You can get something similar if you ascend a mountain. You can ascend a mountain through the forests and get above tree line and get a type of alpine tundra. You can do that in the Sierras or in the Rocky Mountains. And that highlights the fact that mountains, as you move up a mountain, it's analogous to moving up in latitude. So you can see as you ascend a mountain in some cases, a marching through of these physiognomy, these biomes that you see at higher and higher latitudes. So you would want to distinguish the true tundra of north and of the high latitudes against an alpine tundra that you would see up in a mountainous area. Lots of herbaceous growth. No tree growth at all. Okay, let's switch to the aquatic realm. And most broadly, we want to distinguish fresh water from marine water based on its concentration of salts. And within fresh water systems, it's helpful to distinguish still water systems from flowing water systems. Fancy terms there if you want to use them, lentic and lotic. Not sure if the book uses them. I find them helpful for flowing water systems, the lotic systems. So in a still water system like a lake, we divide it up in a simple way. And these terms, if you're talking about aquatic communities, you'll be using these terms just all the time. We distinguish these systems in terms of the light penetration. So the photix zone where light does penetrate and photosynthesis occurs with the maybe rooted plants in the shallows or algae and bacteria in these open areas. And then an aphotic zone where there's less light penetration or none at all at the depths. Also in terms of the distance from the shoreline and the depth, so the literal zone is this near shore zone where you might get these rooted plants and a lymnetic zone further from shore and usually deeper. And let's talk about the pelagic. You'll often hear that term, the pelagic zone, just this open water zone as against the benthic zone, the zone on the substrate itself, marked by the community of organisms called the benthos, B-E-N-T-H-O-S, the benthos, the unique organisms that live in the muck and mire and on the surfaces of this zone. Fantastic creatures there. So here are two lentic systems, one high elevation system with very clear waters, not much vegetation growth, and another system where the waters are very dark, can't see the bottom here at all, and with abundant vegetation growing in it. Besides an elevational difference here perhaps, let's assume that they're at the same latitude as they could be. What's one difference in these systems in the aquatic environment here? Substrate, well, maybe this is a rocky substrate here. You just can't see it because it's so dark. The water's so dark. Yeah. The water source probably differs, but let's just say that this is from streams coming down out of these hills and that this one there's hills in the foreground with streams entering it too. Temperature, it certainly looks warmer here than it does there, so this is a somewhat higher, but let's focus on differences that might exist within the water itself. The temperature could exist within the water itself. This is probably a warmer body of water, I guess from appearances, but let's assume not. Oxygen? Oxygen is likely to differ partly as a consequence of the things I'm thinking of. Yes. Light penetration will differ, partly because of the vegetation at the surfaces, but also as a result of the lack of clarity signaling more sediment and more stuff in the water. Yes? Nutrients is the one I was thinking about firstly, but as a consequence of differences in nutrients, a lot of the other things you guys mentioned would be true also. Nutrients are typically the major limiting factor in the productivity of aquatic systems. Which nutrient it is may differ system to system, but it's usually nutrients, and this system is poor in nutrients, and as a result has little vegetative growth, little less biological activity in general. As a result of less biological activity, there's going to be a greater amount of oxygen available, less used by the respiration of the organisms. This system with much more biological activity, less oxygen in the depths, has more nutrients, and our terms we need are oligotrophic and eutrophic. Oligotrophic and eutrophic, I think. At least eutrophic is here. A great experiment, a classic experiment in ecology showed the importance of nutrient inputs to lakes by dividing this sort of dumbbell shaped lake at the middle and putting nutrients into both sides of the lake. Nitrogen, carbon and phosphorus into this side, sorry, nitrogen, carbon and phosphorus into this side, and only nitrogen and carbon into this side. This is up in Northern Canada, and this was at a time when lakes were seen to be showing these kinds of effects, where you had these blooms of algae, or blooms of bacteria in particular, cyanobacteria in particular, particularly in polluted waters. It was a big concern to people when your waters go from being clear and swimmable to choked with undesirable growth. What these investigators showed so starkly was the role of phosphorus and phosphates as a limiting nutrient, phosphorus as a limiting nutrient that when input could cause these types of blooms that would absolutely choke other organisms out as a result of depletion of oxygen and alteration in the photic zone. Phosphorus was entering waterways as a result of sewage input and runoff from farms and detergents that were heavy in phosphates, making their way into water supplies and into local waters. When these images were showed in Congress, they had a big rippling effect on our laws about detergents and pollution. There's a lovely utrophic system somewhere in the world. I don't know where, I just like the picture. I like these systems also. Savannah's I like, but particularly I like these wetland systems. At the ecotone, at the ecotone between water and land. Often your Savannah is back behind here in Africa. You have a rim of trees, vegetation, a riparian zone you would call it if this were a flowing body. And then this ecotone, this interface between water and land. That's the system I study in Africa. Okay, so a couple of examples of flowing systems. Of course, a big river like this starts as a bunch of little creeks and streams and smaller rivers that gather together to form a big river. And you might imagine the organisms that occupy a system like this and a system like this differ a lot from ones in lakes. They have many different physical forces to deal with. Flowing water is very different from still water. Ultimately, the river is going to flow into the sea typically. There are counter examples, but most rivers flow ultimately to the sea. At the coasts, they may form deltas like this where they back up and form all these channels. It's a delta system, deltaic system. And an estuary. This area influenced by the tides of the ocean where you get some salt water input, some marine input. But with continuous freshwater output is a mixed water system, a brackish system if you want, that we call an estuary. And they're very productive systems, these estuaries. High nutrient input from the continental surface and organisms and salts from the ocean mingling together and especially in a tropical environment. This is a recipe for a lot of biological activity. Marine zones, we divide up much like we do the freshwater zones in terms of light penetration, photic and aphotic, distance from shore. Just swap terms a little bit. The neuritic zone, the oceanic zone. And again, open water and bottom, pelagic and benthic. So those are the same. Those terms are the same. The continental shelf and the intertidal zone. The intertidal, remember, is just that zone between the uppermost high tide and the lowermost low tide with its characteristic organisms. And in some ways, you can consider this an ecotonal system, an ecological system between two other major systems, an oceanic one and a terrestrial one. It's an intertidal system. That term ecotone, I won't formally define, but hopefully you're getting the idea of what I mean by it. An intertidal system. Pies after perhaps. There are your muscles, your barnacles, your algae. A nice system with your keystone predator present. Beautiful anemones. You can see this right down coast here. You can see tide pools like this on our coast. And I urge you to go check them out. And coral reefs, of course. Just offshore, these shallow water reefs that receive so much solar input, as well as nutrients coming off of the oceans. Occurring in waters that are very nutrient poor, typically. Tropical waters. You go to your beautiful tropical beach with your palm tree behind you and you're sipping on your drink and gazing on the lovely blue-green sea that you can snorkel in and see 25 feet down to the bottom. It's so clear and beautiful, that water, partly because it's so nutrient poor and there's very little growth. But then you cross the lagoon and you're on a reef like this. It's just a riot of biological activity. How can you grow a reef like this in nutrient poor waters? I put an article related to that on B-Space in that news folder. So please read about it there. It's a required reading. Just a short National Geographic article can help you understand that or at least a hypothesis for how that works. Photosynchlorophyll, plants rely on chlorophyll for photosynthesis, absorbs visible light and reflects, tends to reflect other wavelengths of light, like infrared light. Whereas physical surfaces, non-growing surfaces, reflect light differently. So you can take satellite images of the Earth and map and translate reflectance of light, of wavelengths of light into different substrate types, like sand versus stone versus sand. It reflects not only the vegetation but productivity. So on a satellite image like this, I don't have what the scale bar is here, but this is measured in something like kilograms of carbon per unit space. You can get a sense for how productive these surfaces of the world are. The gray here is no net primary productivity, less than zero net primary productivity in this great desert or in these polar conditions. And your reds and yellows are your more productive areas in your rainforests and so forth. The ocean tends to be very low in productivity with some huge dead zones in terms of productivity. But because of its enormous size, the ocean has almost as much primary productivity as the land surface, just because it's so big. But note carefully how low in primary productivity it is, and this is primarily a consequence of nutrient limitations. It's most productive on coastal shelves where you either have upwelling of deep water oceanic nutrients or the flowing off of nutrients from the continents themselves. And this I'll let you read carefully. It breaks down various ecosystem types and biomes in relation to the percentage of the Earth's surface area they occupy and their average net primary productivity. And you can see that some systems like swamps and marshes or algal beds and reefs are very productive, but they just don't occupy much of the Earth's surface. So in terms of the Earth's total primary productivity, they're fairly low. And that the tropical rainforests, because they're both so productive and so numerous in terms of space on Earth, they account for so much of Earth's primary productivity. I'm losing you guys, so you can study these things on your own time and read about them in the book. All right, see you next time.