Plant Growth

Christian Giardina & Lisa MasonInstitute of Pacific Islands Forestry

USDA Forest Service

Hilo, Hawaii

Summer 2017

Learning Objectives

What is plant growth?

How does plant growth vary

across ecosystems and why?

How does this information bind us

to our environment?

Rainfall Temperature

Seasonality

Soils

Species

Site History

Hydrology

Photo by Dan Binkley

Variables that regulate plant growth

Soil Carbon

Rhizosphere

Roots

Belowground

Carbon Flux

Mineral soil surface

Gross Primary Production

Photosynthesis: conversion of light into chemical energy:

CO2 + H2O O2 + CH2O

Light

Chlorophylls/photopigments, enzyme content

Temperature – enzyme activity

CO2 and water and nutrients

Soil Carbon

Rhizosphere

Roots

Belowground

Carbon Flux

Mineral soil surface

Aboveground Net Primary Production

Respiration: conversion of chemical energy into potential

energy and heat:

O2 + CH2O CO2 + H2O

Sugar supply

Light

Enzyme content

Temperature – enzyme activity

CO2

Soil Carbon

Rhizosphere

Roots

Belowground

Carbon Flux

Mineral soil surface

Coarse wood and litter

CO2Aboveground Net Primary Production

With senescence of plant parts (leaves, branches, trees),

carbon is returned to soil as litter and coarse woody debris.

These processes occur at different time scales – from

seconds to months to years.

CO2

Soil Carbon

Roots and

mycorrhizzae

Belowground

production

CO2Aboveground Net Primary Production

Coarse wood and litter

Temperature

Warmer

temperatures

will increase

plant growth

The Orographic Cloud

Hahai nō ka ua i ka ululāʻauThe rain follows the forest..

H2O

Temperature

Species

Nutrients

Important concept!

Factors interact to control productivity.

Energy flows, matter cycles!

Temperature affects the water cycle

• Evaporation & Transpiration

– Amount of sun / cloud cover

– Humidity

– Wind

– Temperature

• Water for Growth

Hahai nō ka ua i ka ululāʻau.

Hahai nō ka ua i ka ululāʻau.

From Hawaii Heritage

Program

Intact native

wet forest

Laupahoehoe

Natural

Area

Reserve

Heavily invaded

forest

Laupahoehoe

Natural

Area

Reserve

Hakalau Forest National Wildlife RefugeUS Fish & Wildlife Service

Photosynthesis

& Respiration

are also very

variable across

Planet Earth

www.grin.hq.nasa.gov

Ise et al. 2010. Journal of Geophysical Research.

Aboveground

productivity

(g C/m2/yr)

Photo by Dan Binkley

Northern Hardwood

Forests

Because of a cool, seasonal climate, these forests are not

very productive. Lots of land-use and poor soils means

they now store low amounts of dead wood

and organic matter in soil.

Tropical Plantation

Forests

These forests are among the fastest growing in the world!

Because they are often planted on degraded or poor sites,

they don’t store a lot of dead wood or organic matter in

soil, but they accumulate live biomass quickly.

Photo by Dan Binkley

Photo by Christian Giardina

Subalpine Conifer

Forests

Because of a cold climate and dry summers, these

are among the Earth’s least productive forests, but they

store lots of dead wood and organic matter in soil.

Hawaiian

Montane Rainforest

These forests are really productive, and they store lots of

dead wood. Because of a wet climate and volcanic soils,

they store a lot of organic matter in soil.

Photo of the USDA FS

Brazil1990 – 2007

SOYBEAN agriculture in the Amazon Basin

LandSat remote sensing satellite imagery

WorldwidePalm Oil

Production1960 - 2010

SE Asia

MalaysiaIndonesia

PALM OIL production

in southeast Asia

Energy flows, matter cycles!

Understanding the sources of emissions

is a good place to start

Transportation

and electric

power account

for more than

85% of total

emissions in

Hawaii

ICF 2008 Emissions Report

January 15th Legislative Hearing

IPCC 2007

Atmospheric CO2 concentrations are increasing

Photo of the USFS

Free Air CO2 Exposure study in Wisconsin:

exposes forests to both elevated CO2 and Ozone

Elevated ozone reduces

stand productivity

Elevated CO2 increases

stand productivity

2001 2002 2003 2004

100

150

200

250

300

350

400

Lit

terf

all

(g

/ m

2)

150

200

250

300

350

400

Control

CO2

O3

CO2+O

3

Birch-Aspen

Pure Aspen

Year

Liu et al., 2005. Tree Physiology

Photo of the USFS

• Controls on plant productivity vary across

time and space, and so productivity also vary

across time and space.

• Key controls are temperature, rainfall,

seasonality, soils, hydrology, nutrients, and

site history.

• Humans are adding new gases, species and

management into the mix!

• If we want to understand PLACE…………

we need to understand CHANGE.

System health requires holistic thinking

about managing change

Energy flows, matter cycles!

This is especially critical in Hawai`i where

culture is linked to natural resources

voyaging

hula, oli, and mo‘olelo

unique biota

I ola 'oe, i ola makou nei

“My life is dependent on your life,

your life is dependent on mine“

Photo by Ashley Shaw