Question sets!

Define specific root length (SRL) and root tissue density (RTD)

Specific root length is root length per unit dry mass while root tissue density is root dry mass per unit volume — higher SRL = thinner, more acquisitive roots, higher RTD = denser, more conservative roots

What does the Root economics spectrum describe? How does it differ from the Root economics space?

RESpectrum = the one dimensional axis of acquisitive to conservative; RESpace = additional axes to include the collaboration-DIY axes

How would increased lignin and suberin affect SRL, RTD, and microbial colonization?

— lignin and suberin are C expensive and their deposition increases plant defense and lifespan but decreases absorptive efficiency 

increased lignin/suberin would increase tissue density (higher RTD), reduce permeability (lower SRL), and possibly reduce microbial colonization

If nutrient availability suddenly increases, how would you expect SRL, BI, and RTD to respond?

—when resources are abundant, plants favor rapid exploration and lower structural investment to capture nutrients quickly

—abundant nutrients favor rapid exploration and turnover; plants invest less in structural protection and more in quick nutrient capture. Thin highly branched roots maximize contact area for uptake and microbial exchange

SRL and BI would likely increase and match/capture localized nutrients; RTD would likely decrease as carbon shifts from structural support to foraging

Why are fine roots the primary sites of microbial activity in long-lived trees?

—they form the main interface for nutrient and carbon exchange where mcrobes can access root resources

—microbes depend on C exudates and root permeability; fine roots supply both and act as metabolic interface for mutualists and pathogens

they have high surface area, metabolic activity, and labile exudation; creates nutrient rich microhabitats for nutrient exchange and microbial colonization

Suppose trees face alternating wet-dry seasons. Predict how their root trait expression and microbial associations might shift annually

—moist, nutrient-rich conditions favor fast foraging roots and microbes that exploit labile C; drought favors dense, persistent roots and microbes tolerant of low C and moisture

WET SEASON
—water and nutrients are more accessible, reducing C constraints. Plants form fast, fine, highly branched roots; labile C exudates stimulate copiotrophs that thrive on abundant C and O
—higher SRL and BI, lower RTD

DRY SEASON
—drought and nutrient scarcity increase stress; roots shift toward thicker, lignified tissues that conserve water and C. Microbes tolerant of low C and moisture persist, and long-distance EMF maintain resource access through stable hyphal networks
—lower SRL, BI; higher RTD

How could phenotypic plasticity in root architecture buffer a tree against tradeoffs between growth and defense?

—allows for modulating traits based on environmental cues. Temporal flexibility minimizes fitness loss across variable environment by shifting along the RES continuum as needed

plasticity allows dynamic reallocation of resources among root traits without permanent shifts in strategy, maintaining performance under changing environments

Summarize the main roles of auxin (IAA) and jasmonic acid (JA) in roots?

auxin promotes elongation, lateral growth, foraging efficiency; JA triggers defense pathways, lignin synthesis, secondary metabolite production, can reduce growth

—auxin drives growth and foraging while JA shifts resources to defense; together they govern allocation balances

What is meant by growth-allocation state vs defense-allocation state?

growth-allocation = resources devoted towards primary metabolism and cell expansion; defense-allocation = resources redirected to secondary metabolism and protective structures

Define defense priming and distinguish it from inducible defense

inducible defense activates after attack; priming is a “ready” state induced by microbes or hormones, allows faster defense activation later at a reduced activation cost
—priming saves energy by keeping defense genes poised rather than constantly on

Describe how auxin and JA signaling can interact or antagonize each other belowground?

How might cross-talk between hormone pathways affect root exudate chemistry?

growth state may lead to sugar/amino acid exudation
defense state may lead to phenolics and terpenoids

—hormonal balance redirects carbon either to rhizpsphere feeding or antimicrobial protection

Why did you choose auxin (growth) and JA (defense) over other hormones (like SA or GA?) to represent the allocation modes?

Predict outcomes if auxin and JA treatments were applied simultaneously instead of sequentially

How might environmental stress alter hormone sensitivity and shift growth-defense balance?

Define copiotrophs and oligotrophs. Describe them with respect to microbes.

—copiotroph =fast growing microbes using labile C
—oligotrophs = slow, stress tolerant microbes using recalcitrant C

What are ectomycorrhizal exploration types, and how might they differ in carbon cost?

contact < short < medium < long

—from less to greater C costs — foraging range also increases with cost
—longer hyphal networks require more maintenance C but reach distant nutrient patches

Explain the difference between mutualists, commensals, and pathogens in the rhizosphere.

—mutualists benefit the host for carbon
—commensals are more neutral-or one partner benefits
—pathogens = detrimental for the host

How would you expect alpha and beta diversity to change between high vs low nutrients?

high nutrients likely = high alpha and low beta diversity
low nutrients likely = low alpha and high beta diversity

—resource homogenecity promotes similar communities but stress filters them

Why might conservative or defense-oriented roots host more oligotrophic microbes?

—low labile C and high phenolics exclude fast taxa
—dense, chemically tough roots favor microbes that tolerate scarcity and toxicity

How might EMF interact with pathogens?

—compete for space/nutrients and induce host ISR
—-EMF occupy infection sites and prime host defenses, limiting pathogen success

If long-distance EMF become carbon-limited, how could that alter host resource allocation or shift the symbiosis?

—reduced nutrient return, possible parasitism
—mutualism shifts negative when C provision to microbe exceeds nutrient gain

Distinguish between primary and secondary metabolites as root exudates

—primary = sugars, amino acids, organic acids
—secondary = phenolics, terpenoids, alkaloids
—primary fuels microbes for growth;

—secondary mediates defense and signaling

Name key classes of defensive secondary compounds and their functions?

—phenolics and tannins —> bind proteins, inhibit enzymes, strengthen walls
—terpenoids and resins
—lignin and suberin
—alkaloids

—each targets different “enemies”

What roles to tannins and phenolics play in root growth/defense?

How do changes in root exudate composition influence microbial recruitment or suppression?

—labile C recruits copiotrophs—phenolics favor resistant guilds
—exudate chemistry is a filter for microbes

What ecological tradeoffs exist between releasing labile carbon vs antimicrobial compounds?

labile C enhances nutrient cycling but raises pathogen risk and antimicrobials suppress pathogens but reduce C availibility—its a direct manifestation of the growth-defense balance

Predict how exudation patterns might shift through tree ontogeny or under nutrient limitation

—young/high nutrients likely labile C exudates
—old/low nutrients likely phenolics and lignin
—maturity and stress shift allocation from acquisition to protection

propose a way to quantify chemical changes in exudates following hormone treatment

—potentially use a hydroponics system — analyze via LC-MS/GC-MS—normalize to root area
—direct chemical profiling links hormone state to metabolite output

define alpha diversity and beta diversity - how do they differ?

alpha = within sample diversity, richness and evenness
beta = between sample dissimilarity

—capture different scales of community organization

How would you interpret a significant PERMANOVA result but overlapping NMDS clusters?

—centroids differ statistically, dispersion overlaps visually
— groups are distinct on average but not fully separable in ordination space— not well represented in the 2D space likely due to high within-group variability

If RDA shows GTI explaining 20% of community variation, what does this mean biologically?

—root growth traits account for that portion of microbial composition
—traits help filter and structure microbial communities

Suppose SEM shows an indirect positive path from JA to microbial diversity to plant biomass. How would you interpret this mechanistically?

—JA raises microbial diversity that enhances nutrient supply
—indirect positive effect or microbial mediation of defense costs

If beta diversity differs by nutrient level but not hormone treatment, what might that indicate about microbial filtering?

—nutrient regime will likely dominate filtering
—abiotic context may outweigh the hormonal effects structuring communities

Summarize growth-defense tradeoff theory

growth and defense compete for limited carbon and nutrients; increasing investment in one function reduces availability for the other — both require shared metabolic substrates (like C, N, ATP), so allocation is inherently zero-sum under finite resources

explain the relevance of the resource availability hypothesis

Explain the relevance of CSR

—stress tolerance typically adopts conservative, defense related traits similar to high RTD and low SRL

CSR classification system, classifying plants according to 3 principal strategies (Competitors [C], Stress tolerators [S], Ruderal [R]), which represent a spectrum of plant forms and functions arising under conditions of competition, abiotic restriction to growth, or periodic disturbance, respectively.

Why are belowground tradeoffs in long-lived trees harder to measure than aboveground ones?

—roots are hidden, heterogeneous, constantly interacting belowground so allocation shifts are hard to isolate/track
—trait expression

How does the root economics spectrum integrate both structural and microbial dimensions?

—it links the acquisitive to conservative root traits with a myco axis
—root structure determines physical foraging, while EMF reflects a strategic C investment into microbe partners

Propose how microbial mediation couple reshape the classic growth-defense tradeoff framework

—microbes can reduce/buffer defense costs (priming, pathogen suppression) or increase growth benefits (via nutrient uptake), shifting the tradeoff curve
—when microbial partners provide outsources defense or nutrient access, plants may have better growth and defense results/or simultaneous functions 

How might incorporating microbial costs and benefits redefine “optimal allocation” for long-lived tree roots?

—optimal allocation becomes where microbial benefits outweigh the C cost of maintaining roots and symbionts
—allocation is no longer tissue vs defense alone but is instead tissue + microbes vs C limitations

Growth-differentiation balance hypothesis (GDBH) predictions

—Growth needs N and C
—defense only needs C
—when growth slows —> C surplus may fuel defense

when nutrients constrain growth but carbon continues to accumulate (light > N), plants will divert carbon to secondary metabolism; defense peaks under intermediate resource availability; resource limitation or stress = slower growth but higher defense

How does GDBH explain the occurrence of high secondary metabolite concentrations in slow-growing plant on nutrient-poor soils?

—-Growth-differentiation balance hypothesis—
because growth is nutrient-limited (not C limited), carbon accumulates and is redirected toward secondary metabolite synthesis

Resource Availability hypothesis (RAH) predictions

—in resource poor environments more may be invested into constitutive defense because replacing damaged tissues is costly—when replacement is expensive, prevention is cheaper than repair

high-defense strategies in slow-growing species; low-defense, fast growing strategies in ruderal/herbaceous species

why might a pine maintain high lignin and resin investment in a low-nutrient sire, according to RAH?

because tissue replacement cost is high; defense investment preserves limited tissue resources
—high value tissues require higher protection when regeneration is slow
—damage is costly to replace so defense may pay off more

Carbon-Nutrient Balance Hypothesis (CNBH) predictions

—relative resource availability controls which metabolites are feasible
—c based defenses dominate under N limitation
—n based defenses dominate under N enrichment
—plants use whichever resource is more abundant as the precursor for secondary metabolism according to CNBH

How might CNBH explain the shift from phenolics to alkaloids across a fertilization gradient?

As N increases, relative C:N decreased, making N-based defense more efficient/feasible

—defense composition follows resource stoichometry

Growth-rate hypothesis (GRH) predictions

tissue stoichiometry (high N:P) correlates with rapid growth; nutrient enrichment can reduce allocation by relaxing stoichiometric constraints

According to the GRH, how would you expect high-nutrient soils to alter growth-defense balance?

I would expect an increase in N/P availability, supporting higher growth rate and reduced defense investment
—can free up resources for rapid tissue production

Optimal defense theory (ODT) predictions

high-value tissues (meristems, seeds, fine roots) receive strongest defense investment; defense allocation is spatially and temporally variable

Which root zones would ODT predict to have the highest defensive investment?

—root meristems, pericycle initiation zones, and new root tips
—they are metabolically active and determine future growth and are vulnerable to pathogens

How does microbial mediation challenge the classical assumption of a fixed growth-defense tradeoff?

microbes may lower the costs of either function, provide defense, recude the reverse or reallocation of resources

What factors influence the successful establishment of a species?

Abiotic: climate, soil fertility, moisture, disturbances
Biotic: mutualists (EMF), pathogens, competitors, herbivores
Intrinsic: dispersal ability, stress tolerance, life history traits, phenotypic plasticity, reproductive strategy

How do external (environmental) factors play a role in species establishment?

they may set the realized niche (temperature, moisture, nutrient gradients); limit or enable establishment through stress tolerance thresholds 

To what degree do internal (trait) factors play a role in species establishment?

they determine how individuals respond to environmental filters; root architecture, defense chemistry,, symbiotic compatibility dictate persistence and resource capture

When would you expect an external factor to be more important than an internal (species trait) one?

Under extreme or novel stress where plasticity cannot compensate (extreme drought, etc)

What factors may prevent range shifts that are predicted under climate change?

Dispersal limitation (seed dispersal, propagule availability)
soil-microbe mismatch (failure of symbiotic recruitment)
biotic resistance (competition, pathogens)
abiotic lag (soil formation, microclimate buffering)

What role does recruitment of new generations play?

recruitment determines whether a population tracks climate change through regeneration; seedling establishment integrates soil, microbe, and stress filters; failure at this point halts range advancement

What indicators show a tipping point beyond recovery?

no juvenile recruitment despite viable seed input; increasing adult mortality, declining EMF colonization, soil pathogen buildup

Do biotic and abiotic stressors operate on different timescales?

yes - abiotic (drought, etc) often occurs seasonally to decadal; biotic (pathogen adaptation) evolves or accumulates more slowly;
Abiotic stress often triggers immediate mortality while biotic stress may erodes resilience over generations

How can you account for the interactive effects of biotic and abiotic factors on trait-tradeoffs?

use factorial experimental designs (nutrient x hormone x microbial inoculation; include interaction terms in models (nutrient x microbial diversity); mechanistically, abiotic stress modifies microbial community composition, which alters trait expression feedbacks

Can you determine if/when interactive effects cancel each other out?

yes when opposite effects (nutrient enrichment and growth increase but pathogen pressure and defense increase yields no net trait change; statistically, indicated by non-significant interaction terms or opposite directional coefficients in SEM paths

What role does evolution play in the development of trait tradeoffs?

long-term genetic differences in allocation strategies (constitutive defenses in low-resource lineages); balancing selection maintains variation along the growth-defense continuum—when plasticity enhances fitness and selection reinforces plastic responses
—adaptive plasticity accelerates evolutionary trajectory

Why does plasticity matter?

short-term adjustment mechanism allowing individuals to shift allocation without genetic change; enables dynamic optimization of tradeoffs under fluctuating environments

When do evolution and plasticity interact positively? negatively?

—positively: when plasticity enhances fitness and selection reinforces that capacity (inducible defenses)
—negatively: when plasticity masks genetic variation, slowing adaptive evolution; hides heritable variation

Describe the auxin biosynthesis pathway

— this cascade will convert a metabolic signal into targeted gene expression for cell expansion and branching

Auxin or indole-3-acetic acid (IAA), is synthesized mainly from tryptophan (Trp) in a two-step process
Step 1) Tryptophan to indole-3-acetic acid (IPA)
—conversion of Trp to indole-3-acetic acid (IPA) by enzymes (like TAA1)
—this reaction can involve another amino acid like pyruvate as a co-substrate, producing another amino acid as a byproduct
Step 2) IPA to IAA
— the conversion of IPA to IAA by YUCCA enzymes

Describe the auxin signaling pathway

—repressor based system the pathway relies on a system of transcripitonal repressors (Aux/IAA) that are targeted for degradation
—auxin binding in the presence of auxin, the hormone binds to the TIR1/AFB F-box protein family
—ubiquitination and degradation the auxin-TIR1/AFB complex acts as an E3 ubiquitin ligasee, tagging the Aux/IAA repressor proteins for degradation by the proteasome
—gene activation the removal of Aux/IAA repressors allows auxin response factors (ARFs)t to function as transcription activators, binding to DNA and initiating the transcription of auxin-responsive genes

how does auxin influence microbial interactions?

promotes root branching and exudation, increasing microbial access and nutrient cycling near root tips

—stimulates root branching and exudation that feed rhizosphere microbes

Describe the jasmonic acid biosynthesis pathway

—the pathway transduces stress signals into transcriptional activation of defense metabolism

step 1) stress or wounding triggers the release of a-linolenic acid from chloroplast membrane lipids by phospholipases

step 2) 13-Lipoxygenase oxygenates a-linolenic acid to form 13-HPOT

step3) allene oxide synthase (AOS) to 12,13-epoxy-octadecatrienoic acid

step 4) allene oxide cyclase (AOC) to OPDA

step 5) OPDA is transported from the chloroplast to the peroxisome

step 6) in perixomes, OPDA reductase (OPR3) reduces OPDA to 3-oxo-2-(2’-pentenyl)-cyclopentane-1-octanoic acid (OPC-8:0)

step 7) B-oxidation shortens OPC-8:0 to produce jasmonic acid (JA)

Describe the jasmonic acid signaling pathway

—> JA is converted to JA-lle
—JA and its derivatives can also be methylated to MeJA for systemic or airborne signaling

Signaling
step 1) JA-lle binds to the COl1 receptor

step 2) this interaction targets JAZ repressors for degradation by the 26S proteasome

step 3) removel of JAZ receptore releases MYC and ERF transcription factors and activates expression for defense related secondary metabolite genes

Define carbon-based defenses and provide examples

—-plant growth is nutrient limited: when plants cannot maintain a high growth rate due to lack of N, they accumulate excess C compounds which may be used towards C-based defenses
—carbon is abundant relative to nitrogen

derived from photosynthetic carbon, lignin, tannins, terpenoids, and suberin; functions include physical barriers, antimicrobial activity, deterrence

Define nitrogen-based defenses and provide examples

—plant growth is carbon-limites: plants are under low light conditions and assimilate less C which makes C compounds a limiting resource.
—Nitrogen is abundant relative to carbon =

synthesized from amino acids; alkaloids, cyanogenic glycosides, glucosinolates; functions include toxicity to pathogens/herbivores and nitrogen storage

under what conditions do carbon- vs nitrogen-based defenses dominate?

—-plant growth is nitrogen limited: when plants cannot maintain a high growth rate due to lack of N, they accumulate excess C compounds which may be used towards C-based defenses
—carbon is abundant relative to nitrogen = carbon-based defenses (phenolics, lignin); nutrient-rich = nitrogen-based defenses (alkaloids, cyanogenic glycosides)

—plant growth is carbon-limited: plants are under low light conditions and assimilate less C which makes C compounds a limiting resource.
—Nitrogen is abundant relative to carbon

how can microbes expand a plant’s realized niche?

symbionts enhance stress tolerance and nutrient access, allowing persistence beyond physiological limits

what factors influence successful establishment?

—abiotic: climate, moisture, nutrients
—biotic: mutualists, pathogens, competitors
—intrinsic: dispersal ability, plasticity, life history

what limits predicted range shifts under climate change?

dispersal limitation, soil-microbe mismatch, biotic resistance, and abiotic lags

how do VOCs link growth-defense tradeoffs?

—metabolic cost = VOC synthesis draws on primary metabolic precursors
—allocation shift = under stress or herbivory, plants divery C from growth to VOC production representing a defense reallocation
—indirect defense =VOCs often act through third-party recruitment and attract natural enemies of herbs or beneficial microbes which reduces the need for expensive defences
—environmental feedback = VOC emission strength and composition vary with resource status, developmental stage, and microbial associations

how do biotic and abiotic factors jointly structure trait tradeoffs?

—they create conflicting environmental pressures that select for a balance of traits like growth vs defense (sets the resource ceiling) while biotic partners and antagonists modify the relative payoff of investing into growth or defense

—abiotic factors like nutrient availability, water stress, and temp set physiological limits under which growth and defense compete

—biotic factors microbes, plants, herbivores, alter the costs and benefits of allocation choices by influencing nutrient access and defense demands

—might compete for the same resource
—abiotic stress modifies microbial composition, altering nutrient availability

—hormonal and genetic regulation
—modifying susceptibility

explain the difference between Jasmonic acid, methyl jasmonate, and jasmonates

—Jasmonic acid = core signaling molecule within cells

—methyl jasmonate = volatile derivative that mediates systemic and airborne communication

—jasmonates = collective term for JA, MeJA, JA-lle and related oxylipin derivatives involved in JA signaling

How do JA and auxin interact belowground?

—their antagonism coordinates resource allocation; JA prioritizes defense when stress signals override growth cues

—both regulate development and stress responses through overlapping transcriptional networks
—JA signaling suppresses PIN-mediated auxin transport and reduces ARF activation, restraining growth during defense induction
—under low stress, auxin signaling can repress JA- responsive genes, favoring elongation and branching
—crosstalk is mediated via shared regulators (like GH3 conjugating enzymes, AUX/IAA proteins, and reactive oxygen intermediates)
—the resulting hormone balance determines whether resources are allocated to growth (auxin dominant) or defense (JA dominant) processes

How might VOC-mediated signaling alter microbial colonization patterns in your proposed experiment?

applications of MeJA could upregulate root-emitted VOCs that attract defensive or stress tolerant microbes while repelling pathogens — would represent an indirect microbial-mediated defense response

what biochemical evidence would indicate a growth-to-defense shift involving VOCs?

upregulation of terpene synthase genes, increased MeJA or isprene emissions, and concurrent decline in growth markers (like cell expansion or SRL)

Why might belowground VOCs be more stable or localized than aboveground ones?

soil structure and moisture slow diffussion, causing VOCs to persist longer and act in short-range conditions, microbi-targeted signaling rather than long-distance atmospheric cues

what processes drive microbial community assembly in your system?

—community assembly is shaped by environmental filtering (nutrients/temp/moisture/etc), plant filters (roots, exudates, etc), and biotic factors (competition, facilitation, priority effects, etc)
—stochastic forces like dispersal and drift also contribute
—root microbial communities are governed by both deterministic filters and random colonization events, especially in soil where microsite heterogenecity is high

how might priority effects alter how microbes respond to hormone treatments?

early arriving microbes can occupy space and use resources, altering how later microbes respond to auxin or JA induced exudate shifts
—they may suppress or enhance colonization by hormone responsive data
—priority effects give first colonizers a competitive advantage, altering the success of later arriving microbes independent of plant signaling

why do ECM exploration types vary among species and environments?

exploration types differ in C cost and foraging
—species in nutrient poor or patchy soils select for longer-distance types, while species in nutrient rich soils favor contact or short distance types
—the optimal fungal foraging strategy depends on environmental nutrient spatial distribution and host C availability

how would you separate deterministic vs stochastic drivers in your experiment?

use null-model approaches (NST, BNTI), compare observed beta diversity to randomized expectations and incorporate environmental predictors in RDA or SEM
—deterministic assembly shows predictable responses to traits or environmental, stochastic assembly resembles random drift or dispersal patterns

how might EMF facilitate nutrient acquisition during stress?

EMF maintain external mycelial networks that continue accessing water and nutrients when roots are impaired
—they also mobilize nutrients like organic N and P and improve host drought tolerance
—mycorrhizal hyphae penetrate soil micropores inaccessible to roots, buffering host nutrient supply during stress

how does root age influence microbial colonization potential?

—younger absorptive roots with thin tissues and active exudation host diverse microbes
—older roots lignify and suberize, limiting colonization
—root age alters permeability, exudation, and defense, directly shaping microbial accessibility

how do radial gradients in lignification affect microbial access?

increasing lignin from epidermis to cortex to endodermis forms sequential barriers that restrict microbial penetration
—lignificattion reduces tissue permeability and ophysically blocks microbial access/entry

what determines root lifespan in long-lived trees?

—several factors like RTD, degree of suberization/lignification, C cost, environmental stress, microbes
—dense, well defenses tissues persist longer while thin absorptive roots are short lived and expendable

why is absorptive function concentrated in the distal few millimeters?

these root tips have high SRL, low lignin, abundant labile C exudation, and max surface area
—they prioritize rapid nutrient uptake and microbial symbiosis before aging reduces permeability

how does water stress alter root hydraulic behavior and microbial associations?

—drought reduces hydraulic conductivity, increases suberization, and shifts microbes toward stress tolerant oligotrophs or EMF
—water stress triggers anatomical and chemical changes that reduce root vulnerability but also constrain microbial access

how does nutrient heterogegecity influence root growth-defense strategies?

—patchy nutrietns induce localized auxin-driven branching and reduced defense investment in nutrient rich patches
—plants allocate growth where the yield is highest and can relax defenses when nutrients are abundant

how do microbes alter nutrient mineralization rates that feedback into the roots or root traits?

—microbes accelerate or slow decomp and nutrient cycling, influencing the nutrient environment that shapes SRL, RTD, and exudate profiles
—microbial activity modifies nutrient availability, shaping traits

how does C/N stoichiometry influence microbial guild structure?

high C:N favors oligotrophs and fungi
—low C:N favors copiotrophs and fast growing bacteria
—microbial metabolism is constrained by elemental ratios, selecting guilds adapted to the available resources

how do eco-evo dynamic shape growth-defense tradeoffs?

—long term biotic and abiotic pressures select for stable allocation strategies, while short-term plasticity modulates trait expression

how do trait tradeoffs constrain range expansion under climate change?

—conservative traits improve survival but slow microbial colonization
—acquisitive traits aid spread and establishment but reduce tolerance
—can limit how fast populations can shift with changing climates

why are seedlings more sensitive to soil microbes than adults?

—they have limited C reserves and underdeveloped root systems, making them more vulnerable to pathogens and reliant on beneficial microbes
—early stages face stronger biotic filtering and lack the ability to compensate for imbalances, etc