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Accomplishments, failures and challenges in tropical forest

ecology: a personal perspective on 40 years'

research

David B. ClarkUniversity of Missouri- St. Louis

St. Louis, MO USA

Forest ecology: Processes and structure related to

capturing energy and producing and retaining

biomass, e.g. productivity, disturbance, turnover,

nutrient cycling, physical and biological structure of

tropical forests.

Accomplishments in tropical forest

ecology over the last 40 years

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Parque Nacional

Braulio Carrillo

La SelvaParcelas de vegetación

Parcelas de Muestreo(AMI) = 100ha

TransectoAltitudinalLa Selva – PNBC,100 – 2800 msnm

Area de Monitoreo Integrado

Volcán Barva

Steady progress in increasing the size and number for forest inventory plots, cf. CTFS, RainFor, CI TEAM Project, ABERG.

Reviewer #2 “This paper is utterly lacking in scholarship”

Modified from Wright et al. Cons. Biol. 2009

Global climate change is

universal – all forests in the

world have been impacted

from rising temperature

and CO2 levels.

Drake, J.B.,et al. 2002. Estimation of tropical forest

structural characteristics using large-footprint lidar. Remote

Sensing of Environment 79:305-319.

Development,

maturation, and wide-

spread application of

powerful remote sensing

technologies including

radar, lidar and high-

spatial resolution optical

sensors. Multiple

collaborations between

forest ecologists and

remote sensing scientists.

Spatial scale from

individual trees to the

entire world.

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J.M. Read et al. 2003. Application of 1-m and 4-m resolution satellite data to research and management in tropical forests.

Journal of Applied Ecology 40: 592-600.

High-spatial-resolution satellite data make possible canopy tree demography from space.

Clark, D.B. et al. 2004. Quantifying

mortality of tropical rain forest trees using

high-spatial-resolution satellite data.

Ecology Letters 7:52-59.

Single-pass lidar can produce landscape-scale estimates of forest structure

including basal area, biomass, canopy gap frequency and Leaf Area Index.

Drake, J.B. et al. 2002. Estimation of tropical forest structural characteristics using large-footprint lidar.

Remote Sensing of Environment 79:305-319.

Repeat lidar overflights can establish carbon source/sink status of

entire landscapes

Dubayah, R.O. et al. 2010. Estimation of

tropical forest height and biomass dynamics

using lidar remote sensing at La Selva, Costa

Rica. Journal of Geophysical Research –

Biogeosciences doi:10.1029/2009JG000933.

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Radar remote sensing, which penetrates clouds, can be

combined with optical, lidar, and ground data, to

estimate biomass at global scales

Saatchi et al. PNAS 2011Site history and sampling design have emerged as important

factors for interpreting results from forest inventory plots

Körner 2003 Science 300:1242-1243

Fisher et al. (2008) Ecology Letters 11:554-563.

GPS: a massive step forward for spatially-referenced field studies in tropical ecology

Where are my

#@!&+^$ satellites? Yep,

we’re

lost

Thomas, R.Q. et al. 2013. Low mortality in

tall tropical trees. Ecology 94:920-929

The combination of GPS

capability and GIS

analysis tools make

possible landscape-

scale studies even in

roadless areas of

continuous forest.

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Dramatic increase in the number of forest ecologists in tropical

countries, many trained in OTS and OTS-like courses around the world

Internet connectivity has revolutionized the flow of information

between rural and urban areas and among countries.

936,000 hits on “tropical secondary forest”

Exponential increase in research in tropical secondary and managed forests

Hurtado, J. and D.B. Clark. 2011. Local technicians in long-term research projects: evaluation of 25 years

experience in an active tropical research station. Revista de Biología Tropical 59:1455-1462.

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Areas where progress has been slow, negligible, or negative

Clark, D.A., D.B. Clark and S.F. Oberbauer.

2013. Field-quantified responses of tropical

rainforest aboveground productivity to

increasing CO2 and climatic stress, 1997-

2009. Journal of Biogeosciences 118:1–12.

Few studies use measured forest response to measured climate variables to

test current hypotheses linking forest productivity to changing climate.

There is an pronounced overabundance of modeling and hypothesis

generation in relation to field tests of models and hypotheses with long-term

forest performance data.

Clark, D.A et al. 2013. Journal of Biogeosciences 118:1–12.

Failure to adequately

sample tropical forest

landscapes in space………

…and time

Tropical forest ecologists and remote sensing scientists have

repeatedly committed the “fallacy of misplaced

concreteness”, confounding the abstract (estimates) with the

concrete things.

Well-defined and useful concepts such as biomass, Leaf Area

Index and Net Primary Productivity are being replaced with

terms with the same name but different meanings.

Estimates are not the same thing as direct measurements,

and failure to distinguish the two impedes theoretical and

practical progress.

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As a profession we have failed to create a culture of free

access to the data and metadata behind published papers.

As a result, our science depends virtually entirely on results

which cannot be independently replicated or verified.

Tropical forest ecology moving forward

How to we maintain existing magnet research sites and establish

new ones to increase the diversity of sampling of tropical old-

growth, secondary and managed forests?

One example: the CARBONO Project

1997-present

Focus is on sub-annual to annual sampling

of major components of above-ground NPP

and the impacts of climate on ANPP*

Longest data set in the tropics on annually-

measured ANPP* (wood growth + complete

litterfall by components)

18 0.5 ha plots in random design stratified

by soil nutrient status and topography

100+ publications and many dozen scientists

and students

Annual operating budget $90,000 including

two full-time local technicians

Clark et al. 2010. Global Change Biology 16:747-759.

Forest performance-climate interactions are most evident at time scales from

minutes to one year, but most TRF forest ecology studies use multi-annual census

intervals or very short time scales. We need more studies on time-scales that can be

used to quantify and predict the effects of climate change on forest productivity and

dynamics.

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Tang, H.et al. 2012. Remote Sensing of Environment 124:242–250.

Forest ecologists and

remote sensing

scientists must work to

carry out ground

measurements at the

same spatial scale as

remotely-sensed

observations.

This is not easy, but it

is possible for high-

spatial resolution

sensors.

Free and open data

access

Complete metadata

No sign-in requirement

No usage restrictions

We need to develop a new professional culture of open access to data

and metadata

Thank you for:

Financial support: U.S. National Science Foundation,

U.S. NASA, U.S. Department of Energy, TEAM Project-

Conservation International, Andrew W. Mellon

Foundation, Organization for Tropical Studies.

Logistic and administrative support: staff of the La

Selva Biological Station and the Costa Rican and North

American offices of the Organization for Tropical

Studies.

Permission to carry out field research for 30+ years

in Costa Rica: Ministerio del Ambiente y Energía.

And most especially my deep gratitude to the Costa

Rican field technicians over the decades, particularly Leonel Campos, William Miranda,

Marcos Molina and Gilbert Hurtado.

D.B. Clark publications: www.umsl.edu/~biology/faculty/davidclark.html