BIOEB303 - Terrestrial Ecology PDF

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BIOEB303 - Terrestrial EcologyLecture 1 - Intro to terrestrial ecologyTerrestrial ecology = “The study of interactions of organisms with each other (biotic) and the environment abiotic) on land”Life on land imposes unique constraints, such a desiccation bringing about adaptations for maintaining wat...

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BIOEB303 - Terrestrial Ecology Lecture 1 - Intro to terrestrial ecology Terrestrial ecology = “The study of interactions of organisms with each other ( biotic) and the environment abiotic) on land” Life on land imposes unique constraints, such a desiccation bringing about adaptations for maintaining water balance, and gravity meaning organisms have to work harder to remain upright. Soil is the foundation of most biomes, holding the majority of biodiversity and heavily influences the diversity of life above ground. Life is dependant on the physical properties of soil, texture, moisture, depth, and also on the chemical properties such as nutrients. A multi-scale perspective is required to understand ecological patterns, from species to landscapes. Mechanisms driving the ecosystem: - Human impact - Predator/prey interactions - Energy flow - Biodiversity - Species interactions

Lecture 2 - Terrestrial Ecosystems Biogeographic regions are areas containing organisms that have evolved in relative isolation from common ancestors, and hence are genetically similar. Biomes are distinct biological communities where organisms share common characteristics due to adaptations to specific climatic conditions, and are morphologically similar. Terrestrial biomes can be plotted onto a gradient of precipitation and temperature. There’s not clear boundaries, but boundaries are there due to dominant plant type distributions. They are also influenced by biogeographic features such as topography and soil, and also disturbances such as fire or glaciation. Dominant plant types determine the biome, and these can be grasses (grasslands), shrubs (shrublands) or trees (forest/woodland). These three differ with climatic and physical gradients due to different allocations of carbon into their tissues. Grasses allocate most of their carbon into their photosynthetic tissues, resulting in good photosynthetic conditions, but this also means less carbon is allocated to supportive tissue, hence why grasses are not well supported. Shrubs allocate a little more to supportive tissue, providing advantages of height and light access with a cost of maintenance and respiration Trees allocate the most to supportive tissue, but this results in a bad photosynthetic conditions, hence why woodlands are more common in conditions adverse for ps (dry, low nutrients, low temp).

Evergreens determined by harsh or stable conditions, needle-leaf (low production) and broadleaf (high production). Tropical Forests Constant high temps and rainfall leads to constant leached soils and chemical weathering. There’s a high rate of leaf litter onto the floor and rates of pp, but minimal accumulation due to very high decomposition rates. These high rates are because nutrients is badly needed and are very quickly taken up by the vegetation, hence very nutrient poor soils. Tropical Savannahs Ground covered with grass and scattered shrubs and trees. Climate is similar to that of the rainforest, but with limited rainfall with seasonal patterns. Typically have nutrient poor soils, and seasonal highs of productivity with rainfall. Temperate Grasslands 25-80cm of annual rainfall, maintained by natural disturbances such as fire, drought or overgrazing, many now a result of human activity - agriculture. High diversity of herbivorous animals both above and below ground, hence some plants have evolved to withstand herbivory. Deserts Defined by arid conditions, cold can have several shrubs but hold deserts are usually void of any vegetation. Main limiting factor is water, driving very specific adaptations. Mediterranean Dominated by evergreen shrubs and hard leaves trees adapted to hot summers and cool winters, well adapted to drought, fire and low nutrient soils. Temperate forests Dominated by broadleaf deciduous forests in north hemisphere, and temperate evergreen in the southern hemisphere, Characterised by distinct seasonality in temp and high rainfall within growing season Boreal forests Coniferous trees dominate. Have low temps and a short growing season. Has a unique animal community

Lecture 3 - The metabolic theory of ecology Metabolism = “The process by which organisms take up, transform, and allocate energy via photosynthesis or respiration.” Measured as the rate of carbon dioxide uptake in plants, or oxygen consumption in heterotrophs. Three main factors influence metabolic rates, 1. Body mass Whole organisms metabolic rate scales approx at I=aM^0.75. Due to constant scaling rules of body mass with branching structures (circulatory and respiratory systems), large organisms must metabolise at a slower PER MASS rate due to inefficiency of fuel transport. Overall, they metabolise FASTER with increased body mass. 2. Temperature Biochemical reactions increase exponentially with temperature, this is the same with metabolism. This is explained by the Arrhenius relation e^-E/kT. Reaction rate (e) increases exponentially to the power of -E (activation energy), divided by k (Boltzmann constant) time T (Temp (K)). Exponential increase only holds over the range of normal activity (0-40 degrees C) If we put these two together, we get; I = aM^0.75 * E^-e/kT 3. Stoichiometry This is the proportion of elements in chemical reactions or organisms. Fundamental relationships dictate quantities of elements transformed into metabolic reactions. Energetic demand is directly linked to elemental materials being metabolised. Due to metabolism scaling with body size and temperature, this means we can explain and predict many ecological patterns and processes using body mass and temperature. Organisms divide metabolism into activities for maintenance and for growth/reproduction. Biomass production scales positively with metabolic rates, and hence, body size and temperature. Not too hard to imagine survival and mortality rates also scale with these, so we can use metabolism to estimate survival/mortality of the population, the larger they are the longer they live. Population density is limited by carrying capacity of the environment, so density will be dependant on body size and temperature (due to these determining metabolic demands). Energy equivalence is total resource availability will limit the total population metabolism, so for a given population there can be a few large individuals, or many small. This is demonstrated by the thinning law in plants, larger plants have more surrounding room to grow

Lecture 4 - Defining the structure of Ecological Communities Auto-ecology = “How organisms of a single species interact with their environment, explaining variation among individuals of a population. Population ecology = “How populations of a given species varies over space and time, variation among populations of species. Community Ecology = “How groups of populations interact with each other and the environment Rank abundance gives us an insight to the composition of species in a community, composed of two pieces of information: - Species evenness - Species richness Shannon's index is a measure of diversity, including abundance and evenness H = -∑(pi)(lnpi) Pi = proportion of individuals represented in a community Species evenness quantifies equality of distribution of individuals across species, 1 represents complete evenness EvH = H/Hmax H = species richness Β diversity is the difference in composition between communities, Bray-Curtis equation calculates dissimilarity between communities. Biomass gives us an indication of productivity of a community, but biomass and abundance do not scale 1:1, so this must act independently of richness and abundance.

Lecture 5 - Structure of interaction networks Interaction networks are a representation of all biotic interactions in an ecosystem. Can represent social, competitive, mutualistic, parasitic or trophic relationships. There are two main types: - Bipartite networks describe interactions between two assemblages of species, e.g. pollination, host-parasitic - Unipartide networks describe all trophic interactions with species assemblages spanning multiple trophic levels. A food web. A fundamental need is energy intake, and energy flow is represented in food webs. A binary information matrix is a visual representation table of food webs with consumers and resources. 0 = no interaction and 1 = interaction. A weighted matrix uses the likelihood of interactions as a value of preference for different resources. Basal species feed on nothing in the matrix, all consumer values are 0 Top predators are fed on by nothing within the matrix, all resource values are 0. The topology of food webs influences dynamics of populations and processes, and can tell us how they differ from each other. Four indicators of complexity: - Total number of interactions - Links per species (link density) - Connectance (probability a pair will be linked) - Mean chain length Food webs often also composed of modules, groups of species in networks that interact frequently among themselves, but less with other modules. Associates with body size, prey size and habitat use. Functional groups are groups of species that exploit their resource in a similar fashion, they can be used to simplify food webs, e.g. decomposers, herbivores etc Trophic interactions follow scaling rules, predators must be able to overcome their prey, so they’re usually larger

Lecture 6 - Soil Ecosystems Soil provides a large range of ecosystem services, directly linked to biodiversity below ground. Intensive agriculture has large negative impacts on this diversity, increasing risks of health impacts on humans. Soil development 1. Parent layer (inorganic) 2. A horizon develops above with accumulation and decomposition of organic matter 3. B horizon develops with accumulation of organic material derived from A horizon beneath parent and A horizon 4. E horizon develops above B horizon and below A in humid climates due to leaching. ‘Hot spots’ in soil occur with lots of biological activity. Aboveground communities are affected by direct and indirect consequences of belowground activity Indirect could be feeding activity stimulates nutrient turnover and this affects plant nutrient acquisition Direct effects are mutualistic relationships with soil biota, or antagonistic relations Interactions may be due to species traversing the boundary at some point in their life cycle: - Transient species are predominantly aboveground, sometimes feeding in soil - Temporary species may have one or two life cycles in the soil - Periodic species spend their life in the soil but may forage aboveground - Permanent species are always below ground Classifying soil biota: - Microflora/fauna = up to ~100 micrometres - Mesofauna = between 100 micrometres and 2mm - Macrofauna = between 2 and 20mm - Megafauna = 20mm+ and usually vertebrates. Soil bacteria are essential for decomposition and nutrient cycling, only microbes capable of N fixation. Soil fungi, saprotrophic species are important for decomposition and mycorrhizal fungi are important plant symbionts, known to colonise roots of >80% known plant species.

Lecture 7 - Pollination ecology This is “The study of pollination within its broader ecosystem ecology”. Successful pollination relies on… - Timing: Availability of flowers and pollinators must line up, phenology is the timing of important life history events, and refers to synchronicity of flower and pollinator availability. Flowers must be receptive at the right time, and have strategies to ensure this and increase cross pollination. - Rewards & costs: Plants provide pollen, nectar and oils to the pollinator, and they provide a pollination service and increased genetic diversity. On the other hand, plant costs include the energetic cost of the rewards, growth trade off and risk of disease/robbing, and pollinator costs include foraging costs and risk of predation. - Environmental processes: Phenological cues, flower damage and disease. Generally, pollination is a mutualistic interaction, but can be deceptive with nectar robbing. Plant-pollinator maps are used to map interactions. How an invader affects a plant-pollination network: First the invader has to successfully establish in their habitat, generalists have more luck, highly abundant and have a lack of regulatory processes. Invasion leads to native dependence, measured by linkage levels. Connectance is barely affected by invaders, as it’s just one additional species. Nestedness is unique to mutualistic networks and increases robustness to extinction. Invasion increases nestedness. Conservation of threatened species is affected, and preventing species loss due to the specificity of pollinators. Restoration cannot be successful in the long term if pollinators of restored plants aren’t present.

Lecture 8 - Food webs across environmental gradients Gradients occur naturally and due to anthropogenic sources, this alters food webs. It alters the occurrence and strength of the interactions across the gradients due to: - Direct alterations of interactions, i.e. direct physiological change - Change in species abundances, higher resource pressures with increased populations - Change to species composition, i.e. niche specialisation Trophic interactions impose direct and indirect effects on food webs. Direct effects include; - Top-down effects, where predators control abundance of prey - Bottom-up effects, where prey controls the abundance of predators. Indirect effects include apparent competition, when two species that don’t directly compete affect each other indirectly by both being prey for the same predator. A trophic cascade can occur is a predator suppresses its prey, which increases abundance of the next trophic level down, or the top down effect cascades to the next trophic level.

Lecture 9 - Invasive species “Widespread, non-native species that establish and have adverse effects on the invaded habitat” Usually have large economic impacts, E.g. $5million spent to repair damage to crops by fruit flies and $19billion in the USA for damage done by rats to crops, electric equipment and wildlife, Characteristics of invasive species: - Rapid dispersal - Fast and rapid reproduction - Exploit natural community - Phenotypic plasticity - R-species Example of a NZ invasive species in the NZ mud snail in yellowstone, consuming ~50% of the available food and outcompeted the other species providing food to fish. Vectors of introduction: - Intentional by humans, e.g. bush-tail possum in NZ for fur hunting - Accidental by humans, e.g. in seeds, ships, planes etc - Natural vectors, e.g. wind/water currents. Lots of factors make environments susceptible to invasion, including those unbalanced by human disturbances, and those whose native species evolved in the absence of predators and are therefore unequipped to handle them, such as ariel invaders in NZ. Similar habitats to their native habitat increases likelihood of establishment. Impacts of invasions: - Biodiversity effects: increased competition and predation pressures - Ecosystem properties, habitat characteristics - Evolutionary impact, changing the morphology and behaviour of native species - Genetic effects, fragmented metapopulations - Risk of disease A direct effect is a primary interaction between two organisms A cascading effect is indirect effects of primary interactions onto a third species Management of pests includes removal, control or eradication.

Lecture 10 - Decomposition and Nutrient Cycling Essential nutrients are recycled within an ecosystem into their organic and inorganic forms. Decomposition is the breakdown of chemical bonds formed during construction. Also achieved by leaching, fragmentation and changes in structure Mineralization is the breakdown of plant tissues for other plants to take up Calculating rates of decomposition: Y = e^-kT Which is then rearranged for k. Influences on the rate of decomposition: - Quality of plant litter as a food source, simple or complex compounds present. More lignen = faster breakdown - Features of the surrounding environment such as temperature and climate. Daily temperature oscillations create a diurnal activity in microbes. N is mineralized by being turned from its organic form to its inorganic form within the soil. It is then incorporated into the decomposers own mass, due to it being a limiting factor. This is immobilization. Decomposed litter forms a thin layer of nutrient rich humus, easily eroded. Rhizosphere is where plant roots function, rapid decomposition The microbial loop is an interplay between decomposers and their predators, influencing plant growth. Roots will secrete carbs which feed bacteria, which are then eaten by nematodes. These nematodes release N which is uptaken by the roots.

Lecture 11 - Ecosystem Energetics 2 main laws of thermodynamics: - Energy can’t be created or destroyed - Energy will always be lost as heat - entropy Primary production is plants fixing energy from the sun. Gross primary production is ALL energy formed from photosynthesis Net primary productivity is the rate of energy storage after respiration, so NPP = GPP - Respiration. This can be measured by the change in standing crop biomass, and death and consumption are also taken into account. NPP can vary due to the climate (Precipitation, temp and seasonal changes) and nutrient availability (carbon and nitrogen). Different plants allocate carbon to different tissues. Grasses allocate more carbon into photosynthetic tissue, resulting in rapid growth (and a higher SCB), essential for grasses in poor photosynthetic conditions (grasslands) in order to grow quickly, and to recover from grazing/droughts/fires rapidly. Trees allocate more carbon into supportive tissue, and hence are more woody, resulting in a lower SCB. They can afford to do this due to good photosynthetic conditions, such as in a tropical rainforest. Primary production limits secondary production. Energy is lost as it ascends trophic levels through respiration and waste (heat and excretions), the remaining energy is invested by organisms into production. Consumption efficiency = The total proportion of a resource that is consumable, e.g. leaves are but wood is not Assimilation efficiency = The proportion of ingested energy that is not excreted as waste Production efficiency = The proportion of ingested energy used for production Assimilation efficiency increases with trophic levels, as lower levels process lower quality resources, e.g. herbivores have to digest plant tissue with lots of cellulose, whereas carnivores eat protein-rich sources which is easy to digest All around efficiency increases with temperature Ecological efficiency = Proportion of energy transferred across trophic levels The food web energetics approach assumes that what comes in MUST go out, through metabolism, predation and assimilation efficiency Energy flux = 1/e (X+L) e = Assimilation efficiency X = Metabolic rate L = loss to predation Quantifying this in ecosystems can tell us valuable information such as rate of processes (pest control, decomposition, carbon storage). It quantifies top-down and bottom-up effects in ecosystems and provides an insight into how different ecosystems are linked through trophic interactions (terrestrial, freshwater, marine)

Lecture 12 - Biodiversity and Ecosystem performance The convention on biological diversity in 1992 established three main goals: 1. Conservation of biological diversity 2. Sustainable use of its components 3. Equitable sharing of the provided benefits Ecosystem functions are ecological processes that control the fluxes of energy, nutrients and organic matter through the environment, e.g. PP, nutrient cycling & decomposition Ecosystem services are the suite of benefits received by humans from ecosystems, e.g. provisioning services such as food and wood, or regulating services such as climate regulation and pest control. Stability within an ecosystem is an ecosystems ability to resist a disturbance and it’s resilience to recover from a disturbance. BEF experiments have taught us: - Selection identity effects: The chance of including a highly productive organism increases with diversity, and species identification is very important - Niche complimentarity: Different species utilise different resources, more species more completely utilises the ...