urban-to-rural gradients

Urban-to-rural gradientsUrban-to-rural gradients

100 80 60 40 20 0

overlap.traffic3500

-100

-50

0

50

100

150pe

rcen

t.di

ff%

cha

nge

from

noi

sy t

o qu

iet

site

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% song overlap with traffic noise

R2 = 0.4p = 0.0002

More abundantin quiet sites

More abundant in noisy sites

White-breasted Nuthatch

Red-bellied Woodpecker

Effects on bird composition

Fragmentation in the Fragmentation in the “Triangle”“Triangle”

38% population 38% population growth:1990-2000growth:1990-2000

About 20.5% of About 20.5% of forest cover lostforest cover lost

Triangle Research Triangle Research Initiative: Initiative: economics, forest economics, forest ecology, bird ecology, bird behavior…behavior…

Land-use change until Land-use change until 19201920

Mostly Mostly hardwood foresthardwood forest

Much of Much of landscape landscape clearedcleared Not too wet or Not too wet or

too drytoo dry Not too hillyNot too hilly

Farm abandonment and Farm abandonment and successionsuccession

Many farms Many farms abandonedabandoned ““Worst of the best”Worst of the best” Now dominated by Now dominated by

pinespines Pinus taedaPinus taeda Pinus echinataPinus echinata

Hardwood forests Hardwood forests changingchanging More red mapleMore red maple Less oakLess oak

Fragmentation in Fragmentation in “Triangle”-“Triangle”-

central questionscentral questions What is the effect of forest What is the effect of forest

fragmentation on NC Piedmont forests?fragmentation on NC Piedmont forests? Where is deforestation occurring?Where is deforestation occurring? How do edges affect abiotic and biotic How do edges affect abiotic and biotic

processes in forests?processes in forests? Do patterns of fragmentation affect patterns Do patterns of fragmentation affect patterns

of forest dynamics at a large scale?of forest dynamics at a large scale?

What are the effects of What are the effects of edges?edges?

Change in abiotic conditionsChange in abiotic conditions For plants, big things are light, For plants, big things are light,

temperaturetemperature Change in biotic conditionsChange in biotic conditions

Increased flux of exotic speciesIncreased flux of exotic species

Experimental design-Experimental design-forest dynamicsforest dynamics

66 edges selected66 edges selected 30m transect30m transect All trees greater than All trees greater than

breast height sampled breast height sampled within 5mwithin 5m

All stems sampled All stems sampled within 1mwithin 1m

Tree cores taken from Tree cores taken from trees > 10cm DBHtrees > 10cm DBH

Forest

Non-Forest

Light sensor

Schematic of edge transects.

Temp. sensor and moisture sensor

Experimental design-Experimental design-microclimatemicroclimate

8 intensive 8 intensive transectstransects 50% south-facing50% south-facing 50% deciduous50% deciduous

2 light sensors at 2 light sensors at 0m and 30m0m and 30m

3 temp/humidity 3 temp/humidity sensors are 0m,5m, sensors are 0m,5m, and 30mand 30m

Forest

Non-Forest

Light sensor

Schematic of edge transects.

Temp. sensor and moisture sensor

What’s the climate like What’s the climate like near edges?near edges?

Sensor data Sensor data recorded every 10 recorded every 10 minutesminutes

Aggregated to daily Aggregated to daily PPFD, max. and PPFD, max. and min. temp., and RHmin. temp., and RH

3-factor crossed 3-factor crossed ANOVA design: ANOVA design: south, deciduous, south, deciduous, monthmonth

More light…More light…

Canopy closure is less Canopy closure is less near edgenear edge

Light is more: Light is more: +3.9molPPFD/day+3.9molPPFD/day

The magnitude of the The magnitude of the effect varies monthly:effect varies monthly: Jan.: +6.0 mol PPFD/dayJan.: +6.0 mol PPFD/day Aug.: +3.5 mol PPFD/dayAug.: +3.5 mol PPFD/day

Seasonality varies with Seasonality varies with aspectaspect0

2040

6080

100

Perce

nt ca

nopy

clos

ure

0 0-5 5-10 10-15 15-20 20-25 25-30

Distance from edge (m)

Higher maximum Higher maximum temperatures…temperatures…

South-facing edges, max. temp. South-facing edges, max. temp. +3.0+3.0°C°C

North-facing edges, max. temp. North-facing edges, max. temp. +0.2°C+0.2°C

Magnitude of edge effect on max. Magnitude of edge effect on max. temp. does not vary by monthtemp. does not vary by month

No effect on minimum temperatureNo effect on minimum temperature

Greater swings in RHGreater swings in RH

Similar RH at night near edgesSimilar RH at night near edges Much lower RH during the Much lower RH during the

afternoonafternoon Complicated three-way interaction: Complicated three-way interaction:

Month, South, EdgeMonth, South, Edge Low RLow R22

Do trees grow faster?Do trees grow faster?

Over 1200 cores Over 1200 cores collectedcollected

Average 5-year Average 5-year growth rate growth rate calculatedcalculated

Log(Growth) = Log(Growth) = f(dist. to edge, f(dist. to edge, species, soil species, soil nutrients, soil nutrients, soil moisture proxies, moisture proxies, competition) competition)

Some do…Some do…

DBH in cm

ave

rag

e g

row

th r

ate

in m

m

0 10 20 30 40 50

05

10

15

0-5mgreater than 5m

Pinus taeda

DBH in cm

ave

rag

e g

row

th r

ate

in m

m

0 10 20 30 40 50

05

10

15

0-5mgreater than 5m

Liriodendron tulipifera

Some don’tSome don’t

No growth response from red maple and No growth response from red maple and sweet gumsweet gum

Environmental variables measured explain Environmental variables measured explain about 65% of plot-level variance, and are about 65% of plot-level variance, and are more important than edge effectsmore important than edge effects

Soil variables are very important, Soil variables are very important, especially Percent Base Saturationespecially Percent Base Saturation

Greater TCI means a greater growth ratesGreater TCI means a greater growth rates Only significant interaction term: for Only significant interaction term: for P. P.

taeda taeda there is a greater increase in growth there is a greater increase in growth rates on dry edges than on wet edgesrates on dry edges than on wet edges

But lot’s of exoticsBut lot’s of exotics

Increased Tree-of-Increased Tree-of-Heaven, Princess Heaven, Princess Tree…Tree…

Also increased oak Also increased oak abundanceabundance

Reduced Reduced abundance of red abundance of red maplemaple