hello everybody welcome to the forest ecology lecture so what is a forest forest is the trees and everything below them when we're talking about the trees and everything below them shrubs while our grasses wildlife soil water insects fungi bacteria microorganisms and then even nonliving things rocks climate any sort of other factors you want to throw in there all the living and nonliving components within that canopy of trees well that really seems very similar to the definition of an ecosystem which is a specific area of the earth that includes all the living organisms and nonliving components of the environment well then a forest is an ecosystem by the way that we define it and it really it becomes really important to look at it that way because you have to really understand that everything that happens in the forest is all interconnected and it all ties together and it's all one big beautiful things that needs all these different necessary components to function correctly so here's just a little graphic trying to paint that picture bottom left we've got our stream with with fish and some aquatic plant life we've got large mammals we've got small mammals we've got birds we've got insects we've got fungi we've got soil and we've got our trees of course we've got grass we've got all these different things that are interconnected and working together they all will be filling some sort of a niche that gives them purpose within this ecosystem and they're all working together because they're all they all have a function to play a role to play within this ecosystem why do we need to learn about forest ecology and the simple ideas that ecology leads to proper management's and so if we can understand these basic ecological concepts we can better manage these forested areas because you know ultimately we have decided to inject ourselves into these ecosystems we are a part of these ecosystems and in order to do proper ecosystem management we have to think about all pieces of the ecosystem and how it all works together now it all comes together in all all plays out because without having that understanding of ecology without having that understanding of how all these different all these different organisms and nonliving components all merge together and interact if you don't understand how that works you can't properly manage that area you can't properly fit into the ecosystem without causing problems and the big thing that we're trying to get to now with our understanding of the environment is that we want to be in the environment but we don't want to be a detriment to the environment and ecology gives us that basic understanding of how this ecosystem works and how it functions properly and how it functions at a at a wonderful level whereas if we're gonna insert ourselves in there we don't want that level to drop off we want to have that level be just as successful and so in order to be able to manage it so that we feel comfortable getting what we can from the environment but also making sure that we are not a detriment to the environment we really need to have a good understanding of these ecological concepts so how do we then define forest ecology well I think we just kind of merge merge it together the study of forest ecosystems focusing on the interactions among living organisms and nonliving factors so we're just gonna put the ideas the ideas of an ecosystem and the idea of a forest together and really if is it the idea of the tree and everything below them and everything below them being all the living organisms and nonliving components absolutely and then when we're talking about the ecology of it just studying the interactions how do all those things come together and work in form this one working ecosystem so let's figure it out so let's start with the physical factors that can influence the force so we're talking about topography climate physicochemical of nature the soil and water the geological material and then of course the anthropogenic influence so the human-caused influences that will influence your forests I'm gonna kind of focus on certain ones of these because I think that they're a little more important or the ecology side of things that we're talking about so let's kind of look at some of these ones in particular so the first one that I want to focus on is forest soils because I think when you're talking about the trees and everything below them well everything comes from the soil so we want to basically start at the bottom and work our way up and really kind of really understand what's going on in the forest so in terms of soil soil is the substrate upon which plants grow and where they get their nutrients in water that's that's our basic definition of soils the substrate on which plants grow and where they get their nutrients and water what type of soil you have will determine what plants can and cannot grow there how fast they can grow and how much biomass those plants can produce there different soils will have different amounts of organic matter and that becomes important because organic matter is where everywhere soil gets its nutrients from but it depends on the age of the soil and the location or this area here the majority if you go far enough down you're gonna get to granite and basically it and all these areas around the Sierra Nevada mountains its granite and if you don't know what granite looks like you've ever been to Yosemite National Park or seen pictures of it and you seen El Capitan and Half Dome and you see these big huge rocks sticking out of the ground those are just big huge slabs of granite and that's what is underneath us if you go down far enough now what's interesting to understand about soil is to really understand this idea of weathered parent rock so through millions of years and through wind and water erosion all all that soil is is just rocks broken down and broken down and broken down and broken down and broken down it's you start with you start with bedrock and then with wind and water you start getting cracks here and there and those you get big pieces of rock that become smaller pieces of rock and then those pieces of rock just eventually ground up into particles and that's how we end up with soil now you start getting other organic matter in there like like plants dying out leaves fall into the ground branches fall into the ground animals pooping animals dying and decomposing and all of that combines together to give us soil it's something that's interesting because I don't think people really understand it or really think about it in a simplistic way that that's all soil is and that's and that's how it's made up but that's really all it comes down to you when we're talking about soil now with soil though there's a lot that goes into it so we're we're gonna talk about these different chemical and physical properties so the texture the structure the organic matter content the nutrients and the acidity and all those things together they determine the capacity for the soil to grow plants the susceptibility of the soil to erosion and water transmission and the suitability for roads and buildings so it's soil all these different properties that soil have are extremely important to understand to be able to understand how how to use soil how it can benefit us but also how we can take care of it so let's start with texture so there's three basic textures for soil so there's three basic particles sand silt and clay sand is the biggest one clay is the smallest one sand just think of the beach or were a playground sandbox that we can see those particles we can feel how rough those are silt is much harder for us to see and clay we can't even see clays is tiny and they have very different shapes so if we look at these this close-up of them sand are these bigger aggregate particles silt smaller aggregate particles but then clay is actually these flat long blocks that are bound together so they end up giving this different texture when you get more of one or less of the other and so every soil every soil is just some combination of sand silt and clay and so if we look here on the soil texture triangle on the right hand side can you get a soil that is just all clay yep can you get one that's all sand yes you get one that's all silt absolutely you can't but all sails no matter where you are are gonna find themselves to be somewhere on this chart because there there's some sort of combination of sand silt and clay and when you flips we go when you get a when you get a combination we're kind of in middle of all of them where you get a good mixture of all of them that's called a loamy soil so that's right here in the middle of our of our textural chart and so a lot of agricultural soils are loam soils because you kind of want a mixture of these three things because clay is really good at holding water but not get it transmitting water whereas and is really good at transmitting water through the particles but it doesn't hold water well in so alone when you get a loam soil you get these combinations of these particles and it really makes for a great soil that you can use really well so how do you get texture well textures the result of weathering so the result of that physical and chemical breakdown of the rocks and the minerals so you get materials weathering at different rates so you end up with these different levels of sand silt and clay in these soils and it kind of depends on where you are and how weathered your soils get so for instance if you're in the desert where it's you know during the summer there's not a lot of water and it's a hundred degrees every day your soils gonna get a lot more weathered because you don't have as much organic matter because not as many plants and animals live there because of the climate and so you're gonna end up with a much different soil than if you were on the coast of Alaska or you know next to a river or something where there's always water president there's always animals so you're always going to have plant life in animal life and so it's these different all the different ways that these that these ecosystems work together soil becomes just another one of those things that is both a component of how how that happens but also is a result of that interact of those interactions within the ecosystem so our soil structure so another way to think about that is our soil profile so we have horizons or layers within the soil so we're gonna have a or an organic layer or a litter layer at the top we're gonna have a top soil layer we're gonna have our our subsoil or on this chart here it's also called the zone of accumulation but it's a subsoil layer we're gonna have our parent material layer and then we're gonna have a bedrock and so our structure is just the arrangement and binding together of the soil particles into large clusters called aggregates or peds and so the idea that that the soil kind of just has these different layers now why is that important because the layers all influence each other and it's really just an understanding of how soil gets built so looking at this graphic here on the right here is our bedrock and so at one point in time that is what the soil look like but then eventually that got broken down into these bigger rocks than these smaller rocks then eventually with weathering with wind and with water we and with organic material we then got down to where we started to get this much more of what we would think of as soil but then you can see now up here we get this darker color to our soil because we've got roots in it we've got microorganisms we got water we've got all these other things and on the top layer we've got this really dark layer of soil and that's because we've got a lot of organic matter in it so the darker the soil the more organic matter that you have in it the lighter the soil the less amount of organic matter that you have in it so soils typically will go from darker to lighter as you go farther down into the ground now what's also interesting is that not every soil is going to have these same layers this is your typical structure this Oh a B C R so organic layer topsoil subsoil Tyrael bedrock that is your typical structure for a soil profile however sometimes you might not have an old layer sometimes you might not have an a layer sometimes you might go straight from an a layer to a C layer it doesn't have to be the same every single time and that just depends on your climate of your area where you're at and the other factors that might be influencing it like topography so for instance in the desert more than likely no old layer and maybe either a small a layer or not even than a layer and if you think about what you think about when you picture the desert in your head you picture this kind of lighter tannish colored sand colored soil right light colored doesn't have a lot of organic matter in it whereas if you think about the soil in the forest so you're thinking about grass growing on top of it and trees going over it thinking probably that soils gonna look a lot darker than that soil in the desert and that's and that's the right way to think about it and that's because you're gonna end up with this old layer and this a layer the organic layer and then the topsoil within a forested area so just kind of give you trying to give you a look at it so if you look on the very right of your screen you'll see what we're actually talking about in terms of these layers being able to see an old layer and then a topsoil layer and here this is actually an e layer in this one so we've got a light-colored one that comes in there so like I said before there is a typical structure the OAB see our organic layer topsoil subsoil parent material bedrock that's our typical profile but it can change depending on where you are so here's an eel a ur a layer of alluvium that's worked its way in there then we've got our B layer and then down to the C layer and below so we can see that there's these different layers to the soil and they all kind of have their different jobs there we're gonna see a lot more roots up in the up in the a layer the old layers providing a lot of that organic material that we need and then eventually you're going to get down to the C layer the weathered parrot material where you got more more rocks than you do soil and that becomes important because that's actually where we're gonna find our groundwater to be held so that's gonna be important when we start talking about watershed management and so all these different layers all are important all have a role to play when it comes to the forests so soil is made up of four things most people probably don't think about it this way but soil is a quarter air a quarter water 45% minerals and then five percent organic matter and within that five percent of organic matter 80 percent of its what we call human or basically once organic matters broken down and we can't really identify what it is that's houmous and then ten percent of it is organisms and ten percent of it is roots so half of half of all soils so when you're holding soil in your hands half of that is just air and water the other half most of it is the mineral manners that make up soil and then about five percent of that other half is organic matter but that organic matter is super important because it provides it provides nutrients to the soil organic matter is made up mostly of decomposed remains of plants and animals when we're talking about our getting matter that's what we're talking about it holds soil particles together and precise and provides the phosphorus sulfur and nitrogen essential for plant growth so those two of those are what will called macronutrients so extremely important nitrogen phosphorus and then sulfur is a secondary nutrient that's also very important for plant growth so it's really important to understand organic matter in the role organic matter plays because it's only 5% of soil even I'm holding a cup of soil in my hands only 5% of that is organic matter but that 5% is holding those soil particles together in providing essential nutrients for plant growth and darker colored soil means higher organic matter concept so just right away if you look at soil and you see once oil is lighter colored and when it's darker colored darker colored one is going to have more organic matter in it so then how does it work how how does how does having the soil or good soil why is that important well because it's all part of nutrient cycling and providing nutrients to the trees so soil supplies all the necessary nutrients for plant growth except for carbon and that is what they pull out of the atmosphere so we've talked about that before the idea of trees being able to do gaseous exchange where they take in co2 and they give off OH - well if we look at that simple calculation co2 in BO - out that means the sea stayed and if the sea stayed that C stands for carbon so the soil is given the trees all the nutrients that they need to survive except for carbon so where are they getting the carbon out of the air out of the atmosphere and so that's how trees are able to function and that's why trees are really important to how this planet functions overall because it they feed off the soil and they feed off the atmosphere and they use all these things this none of the things that happen on this planet happened by accident it all comes together in this beautiful kind of in these beautiful interactions the three most important macronutrients are nitrogen phosphorus and potassium or NPK you're gonna see that while most fertilizer so if you go to Home Depot or Lowe's or any of those places and you get a fertilizer mix for your garden or for your plants or any of that you're gonna probably see some sort of combination of NPK or you're gonna see it say something on the fertilizer bag like 10 10 10 well what that 10 10 10 means is 10 percent nitrogen 10 percent phosphorous 10 percent potassium and so forth usually you're most limiting factor enforces nitrogen so if if you're forced is having issues or having trouble more than likely fertilizer becomes an option because you one of your first thought should be that for soils themselves are low in nitrogen so it's gonna be something that they have a hard time providing to the trees so that might be something to think about so when we're talking about nutrient cycling we want to kind of paint the picture that it's it's all of these things working together so the trees gets nutrients from the soil it grows healthy the trees also pulling in that carbon from the atmosphere we get water precipitation coming in that helps feed the soil and the trees the trees are doing photosynthesis so the trees are also providing energy they're providing sugar and energy down to the soil they're taking water up in the soil you got dead leaves falling down animals pooping animals decomposing and from our parent material we're getting that weathered bedrock and then we're getting that eventually work its way in the soil so all of this all comes together it all works together in this nutrient cycling to make sure that there are these constant nutrients available because when the trees grow bigger in the grass grows than that the wildlife have something to eat therefore the wildlife then can poop and then the other wildlife can then eat that wildlife and then we get our decomposed remains all of it all works together in harmony we talked about this before but just to try and emphasize this again because yes trees pull carbon out of the atmosphere but there's also a lot of other places where carbon can get stored and this just kind of paints the picture of that idea of carbon but what I also like about this infographic it's just really getting people that understand what else is going on in the soil because it's not just kind of the graphics that I showed before it's not just that simple like you can see all the different insects and fungi and animals burrowing and all of the roots and even what's happening with the water going in all sorts of different things happening within the soil the soil is extremely important in terms of the health of the ecosystem acidity so this is usually a pretty complicated idea but I like to keep it simple so acidity bees measured in pH and so one of the things to understand at first is that for soils overall usually are in this range for pH so they're in the 3 to 5 range roughly for pH the idea with pH is that you want to be as close to neutral as possible on the scale the scale goes from 0 to 14 so 7 is neutral water is a 7 and so the closer you are to neutral the better it's going to be for plant growth in fact if you're anywhere between five point five and eight you're gonna be really ideal for plant growth but we know forest soils overall start off more than likely they're gonna be somewhere more like three two maybe almost six or really like three to five and a half so they're already more on this acidic side so we know there's going to be some nutrient deficiencies but we really want it to be more at this five and a half to eight some of them are going to be just fine some of them we know we might have to do a little more work to get them to go from being acidic to more neutral so all of this all of these different chemical and physical properties really tie into the soil productivity and the soil productivity can increase over time as organic matter increases and more walks whether in the soil which is important to understand just the idea that your soil can get better if you get more organic matter into the system or you get more soil into the system that's those are the type of things that allow your soil to be more productive it can also be improved through management if you're adding organic matter you know through fertilization you can tail up the land kind of open it up that way you can allow more air and more water to get in and that thus kind of kick-starting that weathering process so there's ways to make yourself more productive the hard part is if we're managing large forest areas if I'm managing two million acres of a National Forest it's gonna be really hard to just say well let's go fertilize two million acres or let's go till up two million acres it doesn't really work that way so we kind of have to just really think about overall forest health and the different things that we can do so you know how can I increase organic matter in in my over a large forest tract wealth I know that organic matter comes from animals animals pooping and animals dying and it also comes from from the trees decomposing leaves dropping branches those sorts of things so if I have more trees and more shrubs and more of these things on my land then I know I can get more exact but matter that way if I've got more animals on my land I can get more again it matter that way so I start thinking about all right well how do i improve the wildlife habitat and how many trees can this land hold where I'm adding to the ecosystem but not taking away from it and that's how you start kind of this idea of taking your basic knowledge of ecology and then turning it into how you're gonna figure out your management principles so what else in terms of ecology plays a role so let's go away from the soil now and let's start thinking about other things so one of the things that influences the soil but will also influence it the trees is the amount of light coming from the from the Sun and when we're talking about the light work we're talking about the idea of energy and so with trees you're gonna have shade tolerant trees and you're gonna have shade intolerant trees and so you're gonna have trees that are really aggressive in terms of wanting to get sunlight and get and outgrow other trees because they can't handle the idea of being in another trees shade whereas there are other trees that know that they cannot grow really fast and they can't handle that so they're going to focus on the idea of just waiting and biding their time and kind of growing slower and so let's go over the idea of shade intolerant trees so these grow best at high light levels so when we're seeing high light levels full sunlight they don't like competition they want to get to the Sun first it's a race to to the Sun so often these trees are going to be trees that grow tall and straight so some a lot of conifer trees really end up being these shade intolerant trees there you can tell that is because they're triangular nature to them they're trying to win that race to the Sun first so they're not going to spend a lot of time growing out they want to spend their time growing up so they want to outgrow and out-compete so ponderosa pine is a good example of a shade intolerant tree whereas shade tolerant trees trees that can grow at lower light levels or at high light levels these trees cannot regenerate easily or grow quickly they usually establish themselves in the shade of the other tree so as this tree grows up there's another tree here that's growing much slower and basically their idea is to outlast their gonna wait till this tree grows and grows and grows and eventually that tree dries and then this tree this big wide tree grows up in its place and it's not gonna let anything else grow underneath its shade and so what that means and we're gonna talk about it later once we get to the idea of succession is that these trees usually end up being the climax tree species or in our pattern or for succession these are going to be the trees that are at the very end of the successional pattern because once they get there they're not going to let any of these other trees these shading tolerant trees grow in their in their area because they want to stay around so and they've spent all this time growing in the shadow of the of the other trees so once they get there they're there to last so what does that look like so I put this picture on the left to get the idea of white and the different amounts of light that you're gonna get in the forest and so you can see the taller trees they're gonna they're up there because they want to get full sunlight but there's still things growing underneath the taller trees and because they're growing underneath the taller trees they're gonna have a different strategy so they're gonna grow bigger leaves so that they can have more surface area and they're gonna have more branches and they're gonna stick out in all these different directions because they want to try and catches much light as possible where as though the trees towards the top of the canopy are gonna just grow up because they want to get to the Sun as quick as possible and we look let me look on the right here at this graphic the big thing to understand is if you have this dense stand of trees here on the left notice there's nothing growing beneath them not only is there nothing right underneath them but even on them themselves they start to self prune and they start to get rid of these lower branches because they really just want to get to the top and they want to keep growing they want to get it's a race to the Sun first and because of that there's nothing here in terms of of trees growing underneath it there's nothing here because these are shades aren't use these trees took their time once they got up here now they're not letting anything grow underneath them we're out here in the full sunlight now all these different trees and things we got little shrubs here we got little trees we got bigger trees all these things can grow out here because there's full sunlight and there's nothing in their way blocking them from coming up slope and aspect also play a part in how trees grow and where trees grow and so it's really important to understand the idea of north south east and west and so when you have when we're talking about aspect you're talking about the direction the slope is facing so notice here on the graphic on the right notice here's our direction so the North is this way south is this way east and west ok so because this is north the north is going to have a south-facing slope over here so it's the direction this slope is facing so even though this is north because the hill faces this way south-facing slope whereas this one is going this way so it's a north-facing slope so that becomes important in the idea of understanding the Sun and how and how our light levels change during the day so in the northern hemisphere which is where we are here the Sun appears in the east it moves on a southerly access to the west and so what's going to happen is throughout the day the sun's gonna appear in the east it's gonna move on a southerly axis and rotate above us all the way till it gets to the west and so what happens when that when that occurs is that during the beginning of the day our East facing things are going to get heated up quickly but not too much because it's not very hot in the mornings for most most days then though what else is getting Sun during that time anything that is south-facing because the the Sun is then gonna rotate on that side early access things that face to the north are not gonna get all that much Sun throughout the day at all and then when it's hottest is when the Sun is actually over towards the west and so that becomes extremely important to understand because think that's gonna affect how things grow so when you see places with topography and trees you're gonna see more dense stands of trees on north and eastern slopes and on on things that are south-facing or west facing you're gonna see more grass and more shrubs and so what does that look like it looks something like this so you can see areas like this where you're if you get much more Sun it's gonna look different than if you don't get that Sun and that's the difference between an aspect and this is can either be a south and a south-facing aspect in the north-facing aspect or this could be a west-facing aspect and then east facing aspect but I I know this is either going to be south or west because of the vegetation here versus the vegetation on this side same with this picture down here we get our shaded slopes so this is probably north facing on the side north or east facing because it's cool and damp where is this it's gonna be south facing and it's gonna be hot and dry so what's if you're looking for a good example of this drive on the grapevine I five either doesn't matter which way you're coming from either from LA up here or from here down to LA and your if you just understand your directions you're north south east and west and you start looking at all the different slopes and the directions they're facing you'll see that that the vegetation grows differently depending on which way the slope is facing and so that that takes us to the idea of topography because it's extremely important because California has some crazy differences in topography so you can get elevation ranging from 282 feet below sea level in Death Valley all the way up to fourteen thousand four hundred ninety-six feet above sea level and Mount Whitney and those two places one that's almost 300 feet below sea level and the other one that's almost fifteen thousand feet above sea level are only 15 miles apart so with less than an hour you can go from the highest place in the state all the way to the lowest place and we've got four different large mountain ranges we've got the Coast Range the Sierra Nevadas the Klamath and the transverse mountains down here in Southern California and so just trying to kind of put topography into perspective in terms of California and the differences that it provides it really can change the look and really change the way the amount of light levels that we get in the different amounts of weathering that the soils going to get in the different amounts of precipitation that an area might get and just to kind of go back to the soil so the idea of what does granite look like and what's kind of below if you go deep enough into the soil it's going to look a lot like this down here in the bottom right so another way to look at it and really try and paint the picture of how important topography and these different elevations can be is this idea here it's a it's a drawing of what trees are in the Sierra Nevada mountains but you can see at different elevations you're going to get different trees and they're not going to get all the same trees at all these different elevations so down here below 2,000 feet we get a lot of hardwoods we get our oak trees of our oak trees going in the foothills but as we go up in elevation we're getting much different now we're getting into some pine trees and we get higher up in elevation and we get to curve trees in giant sequoias and then we get way high up and we start getting into hemlocks and pop and specific types of pine and when you get all the way up here at 12,000 feet you're only getting certain types of pine trees that can grow up there so your topography can even influence what types of trees grow there and then you start throwing in slope and aspect and soils and the climate and all of a sudden now you start saying well I get cottonwoods over here and I get Torreya over here and I get dogwood over here a giant sequoia over here and it really starts to really paint this picture that I get these ones on the western slope I get these ones on the eastern slope and it depends on what's happening at what elevation as to as the different community I might have you