Improving fine root sampling methods for landscape-level ecosystem studies using root anatomy and morphology

Kirsten Lloyd

M.S. Candidate

Complex Systems Research Center

University of New Hampshire, USA

In the White Mountain National Forest, we know:

1) Foliar chemistry (e.g., nitrogen content) is related to forest productivity.

2) Hyperspectral methods allow remote-sensing of canopy chemistry.

HoweverHowever, theoretical links from aboveground to belowground , theoretical links from aboveground to belowground processes have not been established due to methodological difficulties.processes have not been established due to methodological difficulties.

My research is an initial step to My research is an initial step to include include belowground processesbelowground processes into an on-going campaign of into an on-going campaign of

landscape-level ecosystem studies. landscape-level ecosystem studies.

Location of Bartlett Experimental Forest (BEF) in the White Mountain National Forest, New Hampshire, USA

10 km

Bartlett Experimental Forest

AVIRIS remote sensing scenes

Northeastern U.S.

White Mountain National

Forest, NH

360,000 ha

A Landscape-Level Field Study in the A Landscape-Level Field Study in the White Mountain National ForestWhite Mountain National Forest

MMapping andapping and AAnalysis of nalysis of PProductivity androductivity and

BBioioggeochemicaleochemical CCyclingycling

Canopy Chemistry

Remote Sensing Field Work Modeling &Data Synthesis

ProductivityProductivity N Cycling,Nitrification

SoilMineralogy

Stream Chemistry

MAPBGCMAPBGC

LeafLeaf

ChemistryChemistry

VEGETATION

400 800 1200 1600 2000 2400Wavelength (nm)

Refl

ecta

nce

0 0

.2 .4

. 6

.8

1.0

REMOTE SENSING OF FOLIAR N MAPBGCMAPBGC

W h i t e M o u n t a i n N a t i o n a l F o r e s t

AVIRIS EO-1Hyperi

on

0.50

1.00

1.50

2.00

2.50

3.00

0.50 1.00 1.50 2.00 2.50 3.00Field Measured %N

AV

IRIS

Pre

dic

ted

%N

R2 = 0.84

AVIRIS Foliar NPredicted (PLS) vs. Observed

Hardwood

Conifer

Forest Productivity and Nitrogen StatusForest Productivity and Nitrogen Status

0

200

400

600

800

1000

0.5 1.0 1.5 2.0 2.5 3.0

AN

PP

(g

m-2

yr-1

)

Foliar N Concentration (%)

Aboveground NPP

Belowground Belowground Production not yet Production not yet known.known.

Smith et al. 2002 Ecol. App.

Using Canopy N to Drive Ecosystem Models

Predicted NPP Using AVIRISBartlett Experimental Forest, NH

< 700< 700

600600

700700

800800

900900

10001000

>1300>1300

(g m(g m-2-2 yr yr-1-1))

Kilometers0 1

Old Sugar Maple on deep till soils

(540 m)

Upper elevation Spruce on shallow bedrock (800 m)

Eastern Hemlock(300 m)

Mixed White Pine on sandy outwash

(220 m)

Cut + NPK Fertilizer,

1963

N

Root Root ChemistryChemistry

? ?

QUESTION:QUESTION:Are foliar and root

chemistry related?

Canopy Chemistry

Productivity Cycling,Nitrification

Mineralogy Chemistry

LeafLeaf

ChemistryChemistry

PROBLEM:PROBLEM:In order to directly compare foliar and root chemistry, we must In order to directly compare foliar and root chemistry, we must be able to sample roots similarly to foliage (be able to sample roots similarly to foliage (by speciesby species).).

HOW CAN WE IMPROVE ROOT SAMPLING?HOW CAN WE IMPROVE ROOT SAMPLING?

Use secondary xylem anatomy to identify Use secondary xylem anatomy to identify woody rootswoody roots

Develop morphological parameters by Develop morphological parameters by species (or genus) for fine rootsspecies (or genus) for fine roots

MethodsSampling: Roots were collected from soil pits dug at 9 plots within BEF. The plots represent a gradient of site fertility/productivity and species compositions. The roots of six angiosperm species (Acer rubrum L., Acer saccharum Marsh., Betula alleghaniensis Britt., Betula papyrifera Marsh. Fagus grandifolia Ehrh., and Fraxinus americana L.) and three gymnosperm species (Picea rubens Sarg., Pinus stobus L., and Tsuga canadensis (L.)Carr.) were sampled.

Anatomy: Secondary roots approximately 2 to10 mm in diameter were hand-sectioned on transverse and longitudinal planes. Unstained, fresh sections were examined using light microscopy. Roots were identified based on diagnostic traits of secondary xylem. Images were acquired using an Olympus Vanox microscope (Model BHT), Olympus U-PMTVC camera and ImagePro 4.0 image processing software.

Morphology: Ephemeral segments of identified roots were photographed on a 1-mm grid.

Results: Gymnosperms

Species Resin ducts

Cross-field pitting Morphology

Picea rubens

present piceoid Cenococcum;

very fine

Pinus strobus

present fenestriform root hairs; dichotomousbranching

Tsuga canadensis

absent1 cupressoid perpendicularbranching

1 may have central axial resin canal in primary xylem

Results: Angiosperms

Species Perforation plates

Vessel pitting

Vessel thickenings

Morphology

Acer sp. simple alternate spiral “beaded” short roots

Betula sp. scalariform alternate, minute

absent fine, smooth periderm

Fagus grandifolia

simple opposite or scalariform

absent wide rays (cross-section)

Fraxinus americana

simple alternate absent light-colored periderm

Conclusions

Woody roots can be identified using Woody roots can be identified using secondary xylem anatomy.secondary xylem anatomy.

Ephemeral root morphology can be used Ephemeral root morphology can be used to identify fine roots for sampling. to identify fine roots for sampling.

Project direction

Status Task

Complete Characterize morphological traits of fine roots to allow genus- or species-level identification.

Complete Sample foliage and ephemeral roots from tree species at the Bartlett Experimental Forest.

In progressAnalyze chemistry (e.g., carbon and nitrogen) to determine trends among foliage and roots.

Future Evaluate the potential for relationships among foliar and fine root tissue chemistry to be extended spatially using hyperspectral remote-sensing estimates of forest canopy chemistry.

References

Smith, M.L., et al. 2002. Ecological Applications 12, 1286 – 1302.

Ollinger, S.V., et al. 2002. Ecology 83, 339-355.

Research support provided by the New Hampshire Space Grant

Consortium graduate fellowship program.