Ecosystem Services of Florida Grasslands
Lynn E. Sollenberger Agronomy Department University of Florida/IFAS
Outline • Definition of grassland ecosystem services • Brief description of the range of ecosystem services provided by grasslands • Focus on carbon sequestration of Florida grasslands
Ecosystem Services • Definition –Services from grasslands beyond providing a source of livestock feed, –particularly those that enhance environmental quality and ecosystem sustainability
Grassland Ecosystem Services • Include: – Wildlife habitat – Species conservation – Preservation/enhancement of water quality – Preservation/enhancement of soil quality including soil carbon sequestration
Grassland Ecosystem Services • Wildlife habitat – In an increasingly urban state like Florida, grasslands provide habitat for 2/3s of our wildlife
Florida Native Grassland Sites
Fresh Water Marsh and Pond
Florida Native Grassland Sites
South Florida Flatwoods Range Fresh Water Marsh and Pond
Florida Native Grassland Sites
North Florida Flatwoods
Grassland Ecosystem Services • Species conservation – Native grasslands are one of Florida’s natural ecosystems, preserving many plants and animals (332 native grasses in FL)
Grassland Ecosystem Services • Species conservation – More than 100 different plant species can be found on a single range unit of longleaf-slash pine-wiregrass range type (biodiversity)
Grassland Ecosystem Services • Water quality • Water capture, minimizing particulate flow to surface water • Filtration, removing potential pollutants from shallow ground water • Reduce likelihood of ground water contamination from agricultural, industrial, or municipal effluent irrigation
Secondary Services • Soil quality – Grasses reduce erosion, preserving topsoil needed to produce food for current and future generations – Adding bahiagrass in rotation with a peanut-cotton system (Katsvairo et al., 2007): • Increased earthworm populations • Resulted in greater water infiltration • Increased plant residues and soil moisture
Grasses & Soil C Sequestration • 90-95% of the C in grassland systems is below ground, most occurring as soil organic C (SOC; Wedin, 2004) • 22% of total global SOC resides under grasslands (Jobbagy and Jackson, 2000)
Grasses & Soil C Sequestration
Grasses & Soil C Sequestration • Jobbagy and Jackson (2000) state: – SOC increases with precipitation for both grasslands and woodlands, but the rate of increase is 2.6 times greater for grasslands – Based on a worldwide survey of soil profiles, woodlands predicted to have 43% less SOC than grasslands when annual precipitation is > 1000 mm
Grasses & Soil C Sequestration • Three primary ways in which C sequestration can occur (assumes SOC has reached equilibrium in natural ecosystems) – Changes in land cover or land use (most common and best understood) – Altered management within an ecosystem type – Altered ecosystem function
Grasses & Soil C Sequestration • Changes in land cover or land use – Bermudagrass establishment on previously continuously cropped land increased SOC (top 6 cm) by 1.4 tons C/ ha/yr when grazed (Franzluebbers, 2007).
Grassland Use & Soil C Sequestration Grassland use
Increase in SOC in 0-6 cm soil layer (ton/ha/yr)
Hayed
0.3
Unharvested
0.6
Grazed – low intensity
1.4
Grazed – high intensity
1.4
Soil C Sequestration • Changes in land cover or land use – Increase in soil C sequestration under grassland of 1.86 tons/ha/yr over 23 years (Trumbore et al., 1995) – 90% of depleted soil C due to continuous cropping was restored after 9 yr of pasture (Romkens et al., 1999)
Characteristics of Florida Grasses • Grasses of warm-climate origin (C4) – Photosynthetic pathway has 2X the nitrogen efficiency compared to temperate grasses – Results in large C:N ratios in plant litter and especially in roots and rhizomes, thus degradation is slow.
Example of Bahiagrass • Bahiagrass – approximately 1 million ha (2.5 million acres) in Florida • The most widely planted grass in the state
Bahiagrass Fraction Mass N rate (kg/ha)
Herbage (Mg/ha)
40 120 360 Interrante et al. (in review)
Litter (Mg/ha)
Roots + Rhizomes (Mg/ha)
Bahiagrass Fraction Mass N rate (kg/ha)
Herbage (Mg/ha)
Litter (Mg/ha)
Roots + Rhizomes (Mg/ha)
40
2.9
2.0
19.0
120
3.0
2.0
15.6
360
3.8
2.1
16.8
Interrante et al. (in review)
Bahiagrass Fraction Mass N rate (kg/ha)
Herbage (Mg/ha)
Litter (Mg/ha)
Roots + Rhizomes (Mg/ha)
% of mass below ground
40
2.9
2.0
19.0
79
120
3.0
2.0
15.6
76
360
3.8
2.1
16.8
74
Interrante et al. (in review)
Bahiagrass Fraction [N] N rate (kg/ha)
Herbage (g/kg)
Litter (g/kg)
Roots + rhizomes (g/kg)
40
11
12
9
120
12
13
8
360
17
18
13
Interrante et al. (in review)
Bahiagrass Fraction C:N Ratio N rate (kg/ha)
Herbage
Litter
Roots + rhizomes
40
38
33
44
120
33
29
51
360
24
21
30
Interrante et al. (in review)
Example of Bahiagrass
Carbon Distribution in Various Pools (Point in time) in a Florida Bahiagrass Pasture (Dubeux, 2004) Carbon Pool
kg/ha (% of total C pool)
Leaves
2,100 (3)
Stems
420 (1)
Roots + rhizomes
22,600 (32)
Litter
2,030 (3)
Manure
1,620 (2)
Soil A layer (0-15 cm) Soil E layer (15-33 cm)
15,500 (22)
Soil Bt layer (33-90 cm)
16,960 (24)
Belowground
9,460 (13) 91%
100 90 80 70 60 50 40 30 20 10 0
Leaves Stem Root + rhizomes Cow manure
Days after incubation
315 336 357
273 294
210 231 252
168 189
105 126 147
63 84
Litter
0 21 42
% DM remaining
Predicted Degradation of Pool DM
Predicted Degradation of SOM 100 99.8 99.6 99.4 99.2 99 98.8 98.6 98.4 98.2
A layer E layer
Days
364
336
308
280
252
224
196
168
140
112
84
56
28
Bt layer
0
% SOM remaining
SOM mineralization per layer
Over Time • SOC accumulates under bahiagrass because of: – The slow mineralization of existing SOM – The high proportion of plant biomass that is belowground – The slow rate of degradation of this high C:N material
Conclusions • Grassland ecosystems provide vital services to the Florida environment • Grasslands play a critical role in long-term C storage • Grasslands sequester large amounts of new C, particularly following land-use changes • Sequestration occurs regardless of grassland use, but is greatest when grazed
Questions
