P. K. Ramachandran NAIR

Distinguished ProfessorUniversity of Florida, Gainesville, FL, USA

May 2011

AGROFORESTRY SYSTEMS AND ENVIRONMENTAL QUALITY

1980 1990

2000 2010

ICRAF

1977

• MPTs • Soil related• Alley cropping• Germplasm• D & D • Gender

• Improved Fallow• Biodiversity• AF Tree Product• Econ. Benefit• Impact

Assessment• Scaling up

• Poverty alleviation• MDGs• Environment:

• GHGs, C seq • Ecosyt.

services • Value chains• Multifunctionality

• Low-hanging fruits

AF: Programs, Paradigms, Sound-bytes

Poverty Alleviation

Food Security

Deforestation

Fodder- and Fuelwood Supply

Environmental Protection

Land Degradation

Income Generation

Biodiversity Conservation

Water Quality

Social Quality of Life

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Agroforestry and the Top Ten Land-Use Challenges

Nair, 2007

Row trees around farms and fields, managed as part of crop or livestock operation to protect crops, animals, and soil from wind hazardsWindbreaks

Combining trees with forage (pasture or hay) and livestock production

Silvopasture

Strips of perennial vegetation (tree/shrub/grass) planted between croplands/pastures and streams, lakes, wetlands, ponds, etc.

Riparian buffer strips

Producing specialty crops for medicinal, ornamental, or culinary

uses in forested areas Forest farming

Trees planted in single or grouped rows with crops in the wide alleys between the tree rows

Alley cropping

Agroforestry Practices in North America

Journal of Environmental Quality Volume 40 (3), May – June 2011,

pages 784–866.

SPECIAL SUBMISSIONS:

AGROFORESTRY SYSTEMS

AND ENVIRONMENTAL

QUALITY

Environmental Quality is becoming a serious issue…

EDITORIAL : Published: May 4, 2011 (in print on May 5, 2011)

Washing Away the Fields of IowaTo an untrained eye, the fields of Iowa have a reassuring solidity. You cannot tell that the state has lost half its topsoil in the past century. According to a new report from the Environmental Working Group, Iowa’s soil is washing away at rates far higher than anyone realized. … This pace of erosion … has been exacerbated by a fundamental bias in federal farm policy and supports. In the dozen years before 2009, Iowa received nearly $17 billion in subsidies that fostered high-intensity farming and less than $3 billion to support conservation. … there is an intense push to create greater yield on more acreage and less incentive than ever to practice sound soil conservation.

This is all the more tragic because the techniques for conserving soil are well understood. It requires planting buffer zones between fields and rivers and contour strips on sloping fields and planting regimes that keep crop cover on the soil by rotating between 3 and 4 crops, not just soybeans and corn. It also requires comprehensive conservation regulations and enforcement and, above all, facing the fact that erosion is not nature or bad farmers at work. It is the legacy of bad agricultural policy.

Ecosystem Services of Agroforestry

• Soil Productivity

• Carbon Sequestration

• Biodiversity Conservation

• Water-Quality Enhancement

Major tree-mediated processes that determine the extent and rate of soil improvement in AFS:

1. Nutrient cycling related to tree biomass 2. Biological N2 fixation by (NFTs)3. Nutrient uptake from deeper soil layers.

Other tree-mediated benefits:• Improved soil physical conditions and higher

soil microbiological activities• Soil erosion control and soil conservation.

Mechanisms of Soil Productivity Improvement in Agroforestry

Maintaining variation in genetic composition and a variety of species.

For the purposes of conserving diversity through agroforestry systems, both genetic diversity and species diversity are important

Biodiversity

Agroforestry and Biodiversity

Compared to agri. systems, AF systems have:

• Higher number of various life forms (birds, mammals, anthropods, insects, …)

• Improved plant species richness and diversity including endangered plant species (IUCN Red List)

• Enhanced land connectivity (animal and insect corridors)

• Better aquatic diversity in streams and waterways following better water-quality

1.27Mean Shannon-Wiener Index

(Evenness and abundance)

5.92Mean Margalef Index

(Species richness)

3.0Mean species density (no. of species /100m2)

35Mean # of plant species/garden (less than 1.0 ha in size)

Ecological Diversity of Tropical Homegardens

Mohan et al., 2007.

BIODIVERSITY

Taxon Location Systems Compared Species Richness(AF=Agroforestry, F=Forest,

M= Monoculture)

Reference

Birds Bocas del Toro, Panama

Shaded cacao vs. forest fragments

188 spp. in AF 148 spp. In F

Van Bael et al., 2007.

Birds Talamanca , Costa Rica

Shaded cacao and shaded banana vs. forest and banana monoculture

160 spp. in AF ( cocoa) 134 spp. in AF (banana) 132 spp. in F 34 spp. In M

Harvey and Villalobos, 2007.

Bats Talamanca , Costa Rica

Shaded cacao and shaded banana vs. forest and banana monoculture

37 spp. in AF (cocoa)28 spp. in AF (banana)16 spp. in F19 spp. in M

Harvey and Villalobos, 2007.

Terrestrial Mammals

Talamanca, Costa Rica

Shaded cacao and shaded banana vs. forest and banana monoculture

25 spp. in AF 19 spp. in F 6 spp. in M

Harvey et al., 2006.

Habitat Protection for Vertebrates under Agroforestry Systems

Mixed-species AF can help maintain a higher level of biodiversity in various ways:

1. Intensification of AFS leading to reduced exploitation of protected areas,

2. Increasing biodiversity in working landscapes through the expansion of AFS into traditional farmlands, and

3. Increasing the species diversity of trees in farming systems.

4. Better aquatic diversity in streams and waterways following better water-quality

Agroforestry and Biodiversity

• Nutrient-leaching rates from soils under AFS can be lower than those from treeless systems.

• The “safety-net” effect: The deeper and more extensive tree roots will take up more nutrients from the soil compared to crops with shallower root systems.

• The reduction of nutrient loading leads to water-quality enhancement in heavily fertilized agricultural landscapes.

Water Quality Enhancement

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WSP concentration (mg kg-1)

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(cm

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Silvopasture (Alachua)

Treeless (Alachua)

Silvopasture (Suwannee)

Treeless pasture (Suwannee)

Water soluble P (WSP) concentrations by depth in silvopasture and treeless pasture sites on Spodosols in two counties (Alachua and Suwannee) in Florida, USA.

Michel et al., 2007.

Riparian buffers for reclamation

of degraded croplands

Degraded cropland

… the same site, 15 years later

Source: A. M. Gordon and N. Thevathasan, Univ of Guelph, ON, Canada.

Multiple Species Riparian Vegetative Buffer Strips (VBS)

• An effective approach to reducing NPSP (non-point source pollution).

• Possible mechanisms: enhanced infiltration of runoff and sediment trapping.

• Tall fescue (Festuca arundinacea), the most effective species in the claypan region near Columbia, MO.

• VBS reduced sediment, total N, and total P losses by 32, 42, and 46%, resp., compared to control during 2004 to2008 (Udawatta et al., 2011).

Riparian Buffer: Bear Creek National Restoration Watershed (ISU)

Carbon Sequestration

The process of capture and secure storage of C from the atmosphere

It entails the transfer of atmospheric C, especially CO2, and its secure storage in long-lived pools.

(UNFCCC = UN Framework Convention on Climate Change)

Average Global Temperature and Atmospheric Carbon Dioxide Concentrations, 1880-2007

Mitigation (of) & Adaptation (to) Climate Change

Mitigation

Avoiding emissions and sequestering GHGs: [Technological change and substitution that reduce emissions]

Adaptation

Reducing the vulnerability of natural systems against actual or expected climate change effects.

Climate Change MitigationGoal: Reduce net emissions and enhance sink capacity1. Avoiding or Reducing the Emissions

• Increasing input-use efficiency (Management interventions)

• Decreasing losses (Soil and water conservation)

2. Sequestering CO2 in Terrestrial Biosphere• Forest/woody biomass

(Aboveground, belowground)• Soil C sequestration (Aggregation, physical protection, recalcitrant C)

Climate Change Adaptation

Goal: Develop strategies to reduce the negative impacts

1. Enhancing Soil Resilience• Increasing SOC pool • Restoring degraded lands

2. Adopting efficient land-use systems/practices • Conservation agriculture • Agroforestry• INM, IPM, …

3. Improving NPP• New and improved germplasm • GM crops, etc.

C Sequestration in Land-Use Systems

• Aboveground (Vegetation)• Belowground (Soils) AFS are believed to have a higher potential to sequester

C because of their perceived ability for greater capture and utilization of growth resources (light, nutrients, and water) than in single-species crop- or pasture systems.

Estimates of C stored in AFS (Mg C ha-1):• Aboveground: 0.29 to 15.21 yr-1

• Belowground: 30 to 300, up to 1-m depth.

Carbon sequestration in soils as a climate-change-mitigation strategy is based on the assumption that the movement (flux) of C from air to soil can be increased while the release of C from the soil back to the atmosphere is decreased.

Carbon Sequestration in Soils

The soil C pool, to 1 m depth, consists of:• Soil organic C (SOC) estimated at 1550 Pg

(1 petagram = 1015 g = 1 billion ton), and

• Soil inorganic C about 750 Pg.

• The total soil C pool (2300 Pg) is 3X the atmos. pool

Schematic presentation of the general land-use continuum in most forested tropical countries, with changes in both types and amount of tree cover in landscapes. Schematic presentation of the general land-use continuum in most forested tropical countries, with changes in both types and amount of tree cover in landscapes.

General land-use continuum in forested tropical countries with changes in types and extent of tree cover. (Source: Consortium Research Program, 2011.)

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SilvopastureFlorida, USA

Dehesa, Northern Spain

3

Homegardens Kerala, India

4

ParklandsSégou, Mali

Shaded cacaoBahia, Brazil

6

Silvopasture MG, Brazil

Univ. Florida, Cent for Subtropical Agroforestry: Carbon Sequestration Studies, 2005 -

Sites

Agroforestry Systems Location Coordinates

Climate (m.a.p; mean temp. range)

Soil

Florida, USA

28°to 29° N; 81° to 83° W

Humid subtropical; 1330 mm; -3 to 28o C

Ultisols Silvopasture: slash pine (Pinus elliottii) + bahiagrass (Paspalum notatum); 5–20 yr

Northern/ Central Spain 40 to 43o N; 6 to 7o W

Humid Atlantic/ subhumid Mediterranean; 1200/ 600 mm; 6-18°C/ 8-26°C

Alfisols Dehesa oak silvopasture (Quercus suber); >50 yr

Kerala, India

10o32’ N; 76o14’E

Humid tropical;

2700 mm; 27 to 32oC

Inceptisols Homegardens: Intensive multispecies mixtures of trees, shrubs, and herbs in small (< 0.5 ha) holdings; > 35 yr

Ségou, Mali

13o 20’ N; 6o 10’ W

Semiarid tropical; 500 to 700 mm; 29 to 36oC

Alfisols Parklands: Intercropping under scattered trees, > 30 yr old; and live fences and fodder banks, ~ 9 yr.

Bahia, Brazil

14o 0’ S; 39o 2’ W

Humid tropical;

1500 mm; 25 to 32oC

Reddish-yellow Oxisols

Cacao (Theobroma cacao) under thinned natural forest (cabruca) or planted shade trees; 30-yr old.

Minas Gerais, Brazil

17o 36’ S; 46o 42’ W

Cerrado: Subhumid tropical; 1350 mm; 22oC

Oxisols Silvopasture: Eucalyptus spp. with understory of Brachiaria spp (fodder grass) or rice (Oryza sativa).

Locations of CSTAF (Univ of FL) Soil Carbon Sequestration Studies

General Objectives

• Quantify SOC accumulation and sequestration in different types of agroforestry systems in a variety of ecological and geographical conditions.

• Determine C storage in different soil fractions up to at least 1 m depth

• Quantify, wherever possible, C contribution by C3 and C4 plants (~ trees and herbaceous plants) using natural C isotopic differences between the two groups.

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∆A

F (

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Agroforestry vs. Agricultural System

Agroforestry vs. ForestNear Tree vs.Far from Tree

262.5

∆AF (%) = [(AF-Non AF) / Non AF] *100

# Systems; age (# years since AF system installation) Location Soil Order

1 Pine + pasture vs. treeless pasture; 30 yr Florida, USA Ultisols

2 Pasture under birch trees vs. treeless pasture; Northern Spain Inceptisols

3 Home garden vs. rice paddy; >50 y Kerala, India Inceptisols

4 Under tree vs. away from trees ( Dehesa); 80 y Northern SpainAlfisols

5 Under trees vs. away from trees; Parkland system; >50 y Ségou, Mali Alfisols

6 Homegardesn vs. forest: >50 y Kerala, India Inceptisols

7 Cacao under shade vs. forest; > 30 y Bahia, Brazil Oxisols

8 Brachiaria + Eucalyptus vs. Treeless forage stand; 30 y Minas Gerais, Brazil Oxisols

Changes in soil C stock under different AF vs. non-AF systems (Nair et al., 2010).

Summary of Results• Tree-based systems, compared to treeless under

similar conditions, store more C in deeper soil.• High tree density → high SOC content, esp. in the

upper 50 cm soil and <53 µm soil fraction. • SOC stock under longer term AF systems with high

tree-density (e.g., homegardens, shaded perennials) comparable to that of natural forests.

• In sparse tree-density AFS, soil stores more C near than away from the tree.

• C3 plants (trees) contribute to more C in the silt- + clay-sized (<53 µm) fractions than C4 plants in deeper soil profile.

• Traditional systems with large C stock seem to have limited potential for sequestering additional C.

Some Recent PublicationsBook: Kumar BM, and Nair PKR 2011 C Seq in AF Systems. Springer, Netherlands

Journal Articles:

Nair PKR. 2011. J Env Qual 40: 784–790.

Howlett D, Mosquera-Losada M-R, Nair P KR, Nair, VD. 2011. J Env Qual 40:825-832.

Tonucci RG, Nair PKR, Nair VD, Garcia R 2011. J Env Qual 40: 833–841.

Nair PKR, Nair VD, Kumar BM, Showalter JM 2010. Adv Agron 108: 237–307.

Haile SG, Nair VD, Nair PKR. 2010. Global Change Biology 16: 427–438.

Gama-Rodrigues EF, Nair PKR, Nair VD, et al. 2010. Environ Manage 45: 274–283.

Saha SK, Nair PKR, Nair VD, Kumar BM. 2010. Plant and Soil 328: 433–446.

Nair PKR, Kumar BM, Nair VD. 2009. J Soil Sci. Pl Nutrition 172: 10–23.

Nair PKR, Nair VD, Kumar BM, Haile SG. 2009. Environ Sci Policy 12: 1099–1111.

Saha SK, Nair PKR, Nair VD, Kumar, B. M. 2009. Agrofor Syst 76: 53–65.

Haile SG, Nair PKR, Nair VD. 2008. J Env Qual 37: 1789–1797.

Takimoto A, Nair PKR, Nair VD. 2008. Agri Ecosyst Env 125:159–166.

Takimoto A, Nair PKR, Alavalapati JRR. 2008. Mitig Adapt Strat 13: 745–761.

Takimoto A, Nair VD, Nair PKR. 2008. Agrofor Syst 76: 11–25.

Methodological Challenges• Ambiguous Concepts• Allometric Equations• Soil Sampling: Depth, Sampling Plan• Soil Analytical Issues• Fixed Effect Models:

Pseudo-replicationRepeated measures

• Inadequate/Inaccurate Reporting: Soil BD, extrapolation of site specific values

Bulk Density of Soils Bulk Density is the mass of a unit volume of soil;

i.e., weight of the solid particles in a standard volume of field soil

Weight of soilBD = Volume of soil

If weight is 1.33 Mg and volume is 1 m3,

“Average” BD = 1.33 Mg m-3

Consider two soils, BD 1.0 and 1.2; same C content (%): The latter will store 20% more C than the

former per unit volume.

AF: The Way Forward • The debate on the role of AF is focused on econ. and

accounting, not enough on science.• A practice cannot bypass the principles. • Available sci. data on AF are not rigorous.• Precise measurements are difficult: expenses, sampling

problems, dynamic nature of systems.• Powerful analytical/predictive tools not applied.• The “why”s and “how”s of observed behavior…• Chronosequence studies, rate processes, …• Meeting the criteria of research quality:

Peer-reviewed publications in high-impact journals.Publications that stand the test of time.