6.4 Climate controls on ecosystem structure and function

Climate shapes ecosystems by controlling productivity, biomass, and nutrient cycling. Temperature and precipitation affect plant growth, while extreme events can disrupt ecosystems. Climate influences species distributions and interactions, shaping community structure.

Climate change alters ecosystems by shifting species ranges and phenology. It impacts biogeochemical cycles, disturbance regimes, and species interactions. These changes can lead to ecosystem state shifts and affect vital services like carbon sequestration and water purification.

Climate's Influence on Ecosystems

Climate Factors and Ecosystem Productivity

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• Temperature, precipitation, and solar radiation directly affect photosynthesis rates and plant growth determining ecosystem productivity
• Net Primary Productivity (NPP) varies across biomes due to climatic constraints
  • Tropical rainforests have the highest NPP
  • Deserts have the lowest NPP
• Climate-driven seasonality influences timing and duration of growing seasons affecting annual productivity patterns and biomass distribution
• Extreme climate events cause significant short-term reductions in productivity and biomass
  • Droughts decrease water availability for plants
  • Heat waves increase plant stress and reduce photosynthetic efficiency
• Climate controls on soil moisture availability and evapotranspiration rates determine plant water use efficiency and overall ecosystem productivity
  • Higher temperatures increase evapotranspiration rates
  • Precipitation patterns affect soil moisture retention

Biomass Accumulation and Climate Relationships

• Relationship between climate and biomass accumulation often non-linear with thresholds and tipping points
  • Gradual changes in temperature or precipitation can lead to sudden shifts in ecosystem structure
  • Example: Transition from grassland to shrubland with increased aridity
• Climate factors influence plant allocation strategies affecting biomass distribution
  • Plants in water-limited environments allocate more resources to root biomass
  • Plants in light-limited environments allocate more resources to aboveground biomass
• Long-term climate trends shape ecosystem carbon storage capacity
  • Warmer temperatures can increase decomposition rates reducing soil carbon storage
  • Changes in precipitation patterns affect plant productivity and litter inputs

Climate Impact on Nutrient Cycling

Temperature and Moisture Effects on Decomposition

• Temperature and moisture regimes strongly influence microbial activity driving decomposition and nutrient mineralization processes
  • Warmer temperatures generally accelerate microbial metabolism
  • Optimal moisture conditions promote microbial growth and activity
• Freeze-thaw cycles in colder climates accelerate physical breakdown of organic matter influencing nutrient release patterns
  • Repeated freezing and thawing causes cell lysis and tissue fragmentation
  • Leads to pulses of nutrient availability during spring thaw
• Climate-induced changes in soil pH and redox conditions alter nutrient bioavailability and microbial community composition
  • Increased precipitation can lead to more reducing conditions affecting iron and manganese availability
  • Drought can increase soil alkalinity affecting phosphorus solubility

Precipitation and Vegetation Impacts on Nutrient Dynamics

• Precipitation patterns affect leaching rates of nutrients impacting ecosystem nutrient retention and loss
  • Higher rainfall increases nutrient leaching especially in sandy soils
  • Drought conditions can lead to nutrient accumulation in topsoil
• Climate-driven changes in vegetation composition affect litter quality and quantity altering nutrient inputs to soil and cycling rates
  • Shift from deciduous to coniferous trees can increase soil acidity and slow decomposition
  • Changes in plant community composition affect C:N ratios of litter inputs
• Extreme climate events lead to pulses of nutrient availability or losses disrupting typical nutrient cycling patterns
  • Forest fires release large amounts of nutrients stored in biomass
  • Heavy rainfall events can cause significant nutrient runoff

Climate Change and Ecosystem Function

Shifts in Species Distribution and Phenology

• Temperature and precipitation regime shifts alter species distributions leading to changes in community composition and ecosystem structure
  • Poleward and upslope migrations of plant and animal species
  • Local extinctions of species unable to adapt or migrate
• Climate change-induced phenological mismatches disrupt species interactions and ecosystem processes
  • Earlier spring bloom times may not align with pollinator emergence
  • Shifts in bird migration timing can affect seed dispersal patterns
• Increased frequency and intensity of extreme weather events lead to greater ecosystem disturbance and potential state shifts
  • More frequent hurricanes can alter coastal forest structure
  • Prolonged droughts can trigger transitions from forest to savanna ecosystems

Atmospheric and Biogeochemical Changes

• Increased atmospheric CO2 concentrations affect plant physiology and water use efficiency altering competitive dynamics and ecosystem productivity
  • Enhanced water use efficiency in some plant species under elevated CO2
  • Potential for increased growth rates in CO2-limited environments
• Climate change modifies disturbance regimes leading to cascading effects on ecosystem structure and function
  • Increased fire frequency in boreal forests due to warmer drier conditions
  • More frequent pest outbreaks due to milder winters and extended growing seasons
• Alterations in biogeochemical cycles affect ecosystem services such as carbon sequestration water purification and soil fertility
  • Changes in soil carbon storage capacity with warming temperatures
  • Altered nitrogen cycling rates affecting plant productivity and water quality
• Climate-driven changes in hydrological cycles impact aquatic and riparian ecosystems altering habitat availability and biogeochemical processing
  • Reduced streamflow affecting aquatic organism habitat and nutrient transport
  • Changes in groundwater recharge rates influencing wetland ecosystems

Climate's Role in Species Interactions

Climate as an Environmental Filter

• Climate acts as an environmental filter determining which species can persist in a given area influencing potential for species interactions
  • Temperature and precipitation thresholds limit species distributions
  • Climatic extremes (heat waves, cold snaps) can cause local extinctions
• Climatic conditions affect strength and nature of competitive interactions between species potentially leading to shifts in community dominance and diversity
  • Changes in water availability can alter competitive outcomes between plant species
  • Temperature shifts can affect metabolic rates and competitive abilities of ectotherms
• Climate-driven changes in resource availability alter outcomes of facilitative and competitive interactions among species
  • Increased drought stress can enhance facilitative interactions in plant communities
  • Changes in nutrient availability due to altered decomposition rates affect competitive hierarchies

Climate Influence on Ecological Relationships

• Temporal and spatial variations in climate influence dynamics of host-parasite and predator-prey relationships affecting population cycles and community stability
  • Warmer winters can increase parasite survival and transmission rates
  • Changes in snowpack depth affect predator-prey interactions (lynx and snowshoe hare)
• Climate extremes act as disturbance events creating opportunities for colonization and succession shaping community assembly processes
  • Post-hurricane succession in tropical forests
  • Primary succession following glacier retreat due to warming temperatures
• Interplay between climate and species' physiological tolerances determines potential for range expansions and contractions influencing community composition at broader scales
  • Thermophilic species expanding ranges poleward
  • Cold-adapted species experiencing range contractions
• Climate-mediated changes in phenology lead to temporal mismatches between interacting species potentially disrupting mutualistic relationships and trophic interactions
  • Asynchrony between flowering times and pollinator activity
  • Mismatch between peak food availability and offspring demands in migratory birds