BIOL10130 Biology in Action: Climate-Vegetation Feedback

A set of 30 vocabulary flashcards reviewing key biological and ecological terms, water cycle dynamics, plant adaptations, and climate feedback concepts from the lecture notes.

What process describes the movement and evaporation of water through plants from their roots to the atmosphere via leaf stomata?

Transpiration

The physiological process where roots absorb water from the soil, transport it through vascular xylem tissues, and release it into the atmosphere as water vapor through open stomatal pores during carbon dioxide uptake.

What specific type of drought is caused exclusively by a decrease in atmospheric precipitation?

Climate drought

A meteorological drought condition defined solely by a reduction in precipitation relative to historical regional averages.

What type of drought occurs when less precipitation becomes available in the soil and root zone, often intensified by canopy interception or vegetation biomass changes?

Ecological drought

A deficit in soil water availability, affecting natural ecosystems, driven by a combination of lower effective rainfall, plant canopy interception, and evapotranspiration demands.

Which photosynthetic pathway fixes atmospheric carbon dioxide directly using the enzyme Rubisco, operating most efficiently at moderate temperatures?

*C3 photosynthesis

A photosynthetic metabolic pathway where carbon dioxide($\text{CO}_2$) is directly fixed by Rubisco into a 3-carbon compound. It has an optimal temperature range of 15-25 degrees celsius and requires high water consumption per unit of biomass formed.

Which photosynthetic pathway fixes carbon dioxide into an intermediate organic compound (malate) before delivering it to Rubisco, increasing water efficiency in warmer climates?

C4 photosynthesis

An adapted photosynthetic pathway where carbon dioxide

($\text{CO}_2$) is initially fixed in mesophyll cells into malate before being transferred to bundle-sheath cells for Rubisco. It operates optimally at higher temperatures 30-47 degrees celsius and conserves water effectively.

Which ecohydrological theory states that deep-rooted woody plants draw water from deeper soil layers during long wet periods, while shallow-rooted grasses draw water from upper soil layers during short wet periods?

Walter's two-layer hypothesis

A classic ecohydrological concept explaining ecological niche partitioning in drylands, where grasses exploit shallow soil moisture from brief rain events and shrubs/trees access deeper subsoil water reserves.

What climate modeling scenario framework projects specific greenhouse gas atmospheric concentrations and radiative forcing levels by the year 2100?

Representative Concentration Pathway

(RCP): Standardized greenhouse gas concentration trajectories used by climate scientists and the IPCC to model potential future climate change outcomes based on radiative forcing targets by 2100.

In the SOILWAT ecosystem water model, what flux represents rainfall caught by the plant canopy before reaching the soil?

Interception(Int):

The portion of total precipitation intercepted and held by foliage and plant canopies, which subsequently evaporates back into the atmosphere without infiltrating the soil.

In the SOILWAT water model, what parameter measures the downward movement of water through different soil layers?

Percolation(P):

The vertical downward movement and drainage of water through the soil profile driven by gravity.

In the SOILWAT water model, what mechanism describes the redistribution of water upwards through plant root systems within the soil profile?

Hydraulic redistribution(HR):

The passive transport of water through plant root networks from wetter soil regions (often deeper) to drier soil regions (often shallower) along water potential gradients.

In the SOILWAT water model, what term refers to the water loss that drains beyond the active plant rooting zone?

Deep drainage(D):

The portion of soil water that percolates beneath the maximum rooting depth of vegetation, making it unavailable for plant uptake and contributing to groundwater recharge.

In the SOILWAT water model, what process describes the entry of surface water into the top layer of soil?

Infiltration(Inf):

The entry and downward entry rate of surface water from rainfall or snowmelt into the upper soil layer.

What type of system feedback loop amplifies or reinforces an initial environmental change, creating a destabilizing impact on the system?

Positive feedback loop:

A self-reinforcing system mechanism where an initial perturbation causes effects that further magnify the original perturbation (e.g., warming causing vegetation loss, leading to further local drying).

What type of system feedback loop counteracts or dampens an initial change, promoting stability and balance within an ecosystem?

Negative feedback loop:

A self-regulating system process where an initial change produces responses that oppose or reduce the original change, restoring equilibrium.

Which $C_4$ perennial grass species is a defining component of shortgrass prairie ecosystems, utilizing dense shallow roots for rapid water uptake?

Blue grama (Bouteloua gracilis): A characteristic $C_4$ grass species adapted to temperate dryland prairies, featuring a shallow, expansive root system optimized for absorbing water from short, infrequent rainfall events.

What is the specific water requirement range for $C_3$ plants to produce one kilogram of dry matter during photosynthesis?

$450\text{ to }950\,\text{kg H}_2\text{O}$ per $\text{kg}$ of dry matter produced: This high water requirement reflects lower water-use efficiency due to stomatal opening and photorespiration risks at warm temperatures.

What is the specific water requirement range for $C_4$ plants to produce one kilogram of dry matter during photosynthesis?

$250\text{ to }350\,\text{kg H}_2\text{O}$ per $\text{kg}$ of dry matter produced: This lower water requirement demonstrates high water-use efficiency achieved through specialized carbon-concentrating mechanisms.

What term collectively describes structural plant adaptations—such as thick cuticles, rolled leaves, hairs, succulence, and reduced leaf area—that limit water loss?

Xeromorphic leaf adaptations: Anatomical and morphological modifications evolved by dryland plants to reduce transpiration rates, resist desiccation, and maintain water balance in arid environments.

Which low greenhouse gas emission scenario models an atmospheric $\text{CO}_2$ concentration of $421\,\text{ppm}$ by 2100?

RCP2.6: A stringent mitigation scenario representing strong global emissions reductions, projecting an atmospheric $\text{CO}_2$ level of $421\,\text{ppm}$ and minimal global temperature increase by 2100.

Which high greenhouse gas emission scenario models an atmospheric $\text{CO}_2$ concentration of $936\,\text{ppm}$ by 2100?

RCP8.5: An unmitigated high-emissions scenario ('business-as-usual') projecting radiative forcing leading to $\text{CO}_2$ concentrations reaching $936\,\text{ppm}$ by 2100.

What parameter quantifies the combined loss of water from an ecosystem through surface evaporation and plant transpiration?

Actual Evapo-transpiration (AET): The real, measured total flux of water returning to the atmosphere from soil/surface evaporation and vegetation transpiration, recorded as $272 \pm 54\,\text{mm/year}$ in sagebrush steppe ecosystems.

What term describes climate change impacts on soil water availability that occur directly from changing meteorological conditions without accounting for plant responses?

Direct effects of climate change: Environmental changes resulting straight from abiotic factors like shifted precipitation patterns or rising atmospheric temperatures, excluding ecological and plant biomass feedbacks.

What term describes climate change impacts on ecosystem water availability caused by shifts in plant biomass, vegetation structure, and species composition?

Indirect effects of climate change: Hydrological changes driven by altered vegetation dynamics—such as increased canopy interception or altered transpirational demand resulting from altered plant growth.

What climatic and aridity threshold criteria defined the global temperate dryland study areas in Tietjen et al. (2017)?

Group D in Trewartha's climatic classification (temperate climate zone) paired with a United Nations Aridity Index of less than $0.5$.

How do plants under chronic water stress modify their xylem vessel structure to maintain sap transport?

They produce thinner, narrower xylem vessels: Narrower vessel diameters increase capillary cohesion and adhesion of the water column, preventing air cavitation and embolism under severe negative water potential.

Why do dry climate conditions produce narrow annual tree rings in woody plant species?

During water-stressed dry periods, plants produce smaller, narrower xylem vessels to prevent cavitation. This reduced growth rate and smaller cell size result in narrow annual growth rings visible in cross-sections.

What temperature range provides the optimal rate of photosynthesis for $C_3$ plants?

$15^\circ\text{C}\text{ to }25^\circ\text{C}$: At higher temperatures, Rubisco oxygenase activity increases, leading to photorespiration and decreased photosynthetic efficiency.

What temperature range provides the optimal rate of photosynthesis for $C_4$ plants?

$30^\circ\text{C}\text{ to }47^\circ\text{C}$: The $C_4$ pathway concentrates $\text{CO}_2$ around Rubisco, suppressing photorespiration and allowing efficient carbon fixation under hot conditions.

In the SOILWAT water model, what flux accounts for the direct phase transition of solid snowpack into water vapor?

Sublimation (SL): The physical phase change where solid snow or ice evaporates directly into atmospheric water vapor without converting to liquid water first.