Plant Growth, Biomass and Productivity

1
Lecture 4

• Plant Growth, Biomass and Productivity

2
Lecture 4 topics

• How plants grow
• Carbon allocation
• 3. Forest Biomass and Forest Productivity

3
Week 2 Learning Objectives

• You should be able to
• Recognize characteristics and general
  distribution of biomes and what factors influence
  their spatial coverage
• Describe difference between biome based on actual
  cover and potentialcover (spatially and
  temporally)
• Describe various biome/life zone types (globally
  and locally) and their productivity
• Understand spatial variation (gradients) in
  forest types (e.g., elevation, latitude,
  disturbance, temperature, precipitation)
• Describe basic photosynthesis and plant
  productivity (gross primary productivity, net
  primary productivity, differences in plant
  requirements)
• Understand the role of vegetation in carbon
  storage (sequestration)
• Think about spatial and temporal differences in
  ecosystems

4
1. How plants grow .
5

a. MERISTEMS In humans and other animals growth
can occur in most parts of the body.  Trees do
not grow like this and only produce new cells in
a very limited number of places called meristems
(zones of intense activity).  Trees grow in
height as a result of apical meristems that are
located at their branch tips.  All buds that
you see on a tree contain apical meristems Roots
also expand through the soil as a result of
root-tip apical meristems.  Trunk diameter
growth occurs as a result of another meristem
called vascular cambium.  Apical meristems
(primary) cambium (secondary)
6

• Unlike animals, plants continue to grow
  throughout their life span (cant move)
• They have meristems which correspond to stem
  cells in animals (can differentiate into any
  organ)
• Apical meristems on roots and shoots
• Respond to light, searching for soil resources,
  responding to herbivory

7
Buds
Roots
Primary meristems
Secondary meristems cause it to grow laterally
(i.e., larger in diameter). Vascular cambium,
produces secondary xylem and secondary phloem
8
Where plants grow and what they need

• Species have different needs for many abiotic
  factors including
• Light
• Water (precipitation)
• Nutrients
• Soil types
• Temperature

9
(No Transcript)
10
(No Transcript)
11
Ages and dimensions of forest trees on better
sites in the PNW and shade tolerance
Species (conifers) Age Diam Ht Tol (yrs) (
cm) (m) Thuja plicata (western red
cedar) 1000 150-300 60 TOL Chamaecyparis
nootkatensis 1000 100-150 30-40 TOL (Alaska
yellow cedar) Picea sitchensis (Sitka
spruce) 800 180-230 70-75 TOL Pseudotsuga
menziesii Doug fir) 750 150-220 70-80 INTOL Lari
x occidentalis (W. larch) 700 140 50 INTOL Pinu
s ponderosa (ponderosa pine) 600 75-125 30-50 IN
TOL Picea engelmannii 500 100 45-50 TOL
(Engelmann spruce) Abies amabilis (Pacific silver
fir) 400 90-100 45-50 VTOL Abies procera (Noble
fir) 400 100-150 45-70 INTOL Pinus monticola
W. white pine) 400 110 60 INTER Tsuga
heterophylla (W. hemlock) 400 90-120 50-65 VTOL
Tsuga mertensiana (Mt. hemlock) 400 75-100 25-35
TOL Abies grandis (grand fir) 300 75-125 40-60
TOL Abies lasiocarpa (subalpine
fir) 250 50-60 25-35 TOL Pinus contorta
(lodgepole pine) 250 50 25-35 INTOL
12
Hardwoods
Species Age Diam Ht Tol (yrs) (cm) (m) Q
uercus garryana (Garry oak) 500 60-90 15-25 INTOL
Acer macropyhyllum (Big leaf
maple) 300 50 15 TOL Populus trichocarpa
(Cottonwood) 200 75-90 25-35 INTOL Alnus
rubra (red alder) 100 55-75 30-40 INTOL
13

• 2. Carbon allocation

14
So where does the Carbon come from?
Carbon dioxide via photosynthesis
15
PRODUCTIVITY Photosynthesis CO2 H2O light
C6H12O6 O2 H20 Respiration C6H12
O6 O2 CO2 H2O
energy Production increase in biomass or
volume on a given area over a given time period
(usually a year). Gross Primary Production
(GPP) Photosynthesis Net Primary Production
(NPP) Photosynthesis Respiration
16
homestead-farm.net
17
Measures of Productivity

• Ecological production and production for energy
  biomass production - (kg per ha per year or g C
  /sq m/year or Kcal/sq m/year)
• Timber production (board feet per acre per year,
  cubic feet per acre per year or cubic meters per
  hectare per year)
• Energy kcal per square meter per year
• Tree height at a given age for given species.
  e.g., Douglas-fir

1 g Carbon 2.2 g organic matter 8420 Kcal
18
microbewiki.kenyon.edu
19
How do plants partition biomass (carbon,
carbohydrates)?Goal is to minimize resource
limitation and maximize resource capture and NPP

• If water or nutrients are limiting grow roots
• If light is limiting grow shoots

utsa.edu
article.wn.com
20
3. Biomass and Productivity
21
Biomass

• Biomass (the quantity of living plant material)
  is most abundant in forests.
• Tropical forests account for 50 of Earths total
  plant biomass, although they occur on only 13 of
  the ice-free land area
• Other forests contribute an additional 30 of
  global biomass (Chapin et al. 2002)
• Measured in various ways
• in-situ measurements,
• national forest inventories,
• administrative-level statistics,
• model outputs and
• regional satellite products.

22
Hoh Rainforest
23
Biomass (Old-growth forest Hoh River Valley,WA)
Mg/ha (western hemlock, Douglas-fir, western
redcedar, Pacific silver fir, Sitka
spruce) Total live tree 1044.1 Shrubs and
herbs 0.7 Standing dead trees
171.0 Logs 92.3 Dead shrubs and herbs
0.5 Forest floor
89.8 Soil 360.3 Roots
------ TOTAL
1758.6
24
Terrestrial Production

• Carbon balance of vegetation governs productivity
  of the biosphere
• Enters the system as gross primary productivity
  (GPP) and
• accumulates as biomass
• Returns to atmosphere via respiration or
  disturbance
• NPP (Net primary production) GPP respiration
• Plants lose carbon through other avenues besides
  respiration, e.g.,
• Litterfall
• Root exudations (secretions of soluble organic
  compounds)
• Carbon transfers to microbes
• To herbivores (being eaten)

25
Net Primary Production (NPP) kg (g C, Kcal)
per hectare per year NPP Growth Detritus
(Litterfall, etc.) Loss to Grazing
26
Average Net Primary Productivty (kcal/m2/year
Estuaries Swamps/Marshes Tropical rain
forest Temperate forest Northern conifer
Savanna Ag land Woodland/shrubland Temperate
grassland Lakes and streams Continental
shelf Tundra Open ocean Desert scrub Extreme
desert
27
Total global net productivity (billion kcal/year
Open ocean Tropical rain forest Temperate
forest Savanna Northern conifer Continental
shelf Ag land Temperate grassland Woodland/shrubla
nd Estuaries Swamps and marshes Desert
scrub Lakes and streams Tundra Extreme desert
28
(No Transcript)
29
(No Transcript)
30
Site Index

• Site index measure of the productivity of a
  site based on how tall trees will grow over a
  specified period of time.
• Indexes to a base age, usually 50 or 100.
• For example, a 50-year site index of 120 means
  that at age 50, the dominant trees (of the given
  species) would be expected to be 120 feet tall. T
• Higher the site index, signifies more productive
  a sites for a given species
• Can get site class information from USDA
• http//websoilsurvey.nrcs.usda.gov/app/HomePage.ht
  m.

31
Total height (ft)
Age at Breast Height - Years
32
theglobaleducationproject.org
33
Carbon sequestration

• the process through which carbon dioxide (CO2)
  from the atmosphere is absorbed by trees, plants
  and crops through photosynthesis, and stored as
  carbon in biomass (tree trunks, branches, foliage
  and roots) and soils.
• Forests and soils have a large influence on
  atmospheric levels of carbon dioxide (CO2)
• Tropical deforestation is responsible for about
  20 of the world's annual CO2 emissions, these
  emissions are more than offset by the uptake of
  atmospheric CO2 by forests and agriculture.

34
Carbon sequestration

• Carbon sequestration rates vary by tree species,
  soil type, regional climate, topography and
  management practice.
• Carbon accumulation in forests and soils
  eventually reaches a saturation point
• Economic considerations and end use of wood
  product is important

35
Methods of sequestration in land management
Management Afforestation Tonnes C/acre/year 0.6- 2.6 Time to saturation (yrs) 90- 120
Reforestation 0.3- 2.1 90-120
Lengthening rotations 0.2-0.8 15-20
Switch to reduced tillage 0.2-0.3 15-50
Grazing changes 0.02- 0.5 25-50

36
Tonnes of carbon (C) per hectare(total carbon
Gt)
162
35
85
Central Am
175
75
105
37
(No Transcript)
38
How Can Forest Management Help with Carbon
Storage? Best case scenario On a global basis,
forests could store up to one-third of total
carbon emissions. Longer rotations bigger
effect on westside than eastside Retain woody
debris on site or utilize it for products Extend
the life cycle of wood products encourage
recycling, re-use Protect forests from crown
fire (suppression, fuel management)
39
Summary

• Photosynthesis drives the carbon cycle
• Plants allocate carbon to maximize resource use
• Productivity is affected by a suite of ecological
  conditions
• Management can play a role in carbon sequestration