signal in a transient absorption experiment. Efforts are
currently under way to circumvent these difficulties for future
studies of this and related systems.
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40. L. Flamigni, A. Barbieri, C. Sabatini, B. Ventura, F. Barigelletti,
Top. Curr. Chem. 281, 143–203 (2007).
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Organometallics 33, 2012–2018 (2014).
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equally well in the coupling reaction as dtbbpy, and it was used
here for ease of synthesis of 9.
43. D. Rehm, A. Weller, Isr. J. Chem. 8, 259–271 (1970).
44. It is highly unlikely that a SET reduction would lead to
reductive elimination; however, this assumption cannot be
guaranteed a priori.
45. J. R. Lakowicz, Principles of Fluorescence Spectroscopy
(Springer Science+Business Media, New York, ed. 3, 2006).
46. We thank a reviewer for an interesting discussion on the
possibility of a disproportionation reaction subsequent to energy
transfer that would lead to an active Ni(III) species responsible
for reductive elimination. We can imagine two scenarios for
this process, the first being bimolecular association of two
photoexcited Ni(II)* species. The low light flux used in the reaction
makes this scenario untenable. In addition, disproportionation
between one photoexcited Ni(II)* and one ground-state Ni(II)
species is possible; however, the low concentration of the Ni(II)
species coupled with what is likely to be a sub-nanosecond
lifetime of the Ni(II) excited state makes it unlikely that an
excited Ni(II) complex can form an adduct with another Ni(II)
complex before ground-state recovery of Ni(II)*.
Research reported in this publication was supported by the
National Institute of General Medical Sciences (NIGMS), NIH, under
award number R01 GM078201-05 (D. W.C.M., E.R. W., and C.C.L.)
and the NSF under the award number CHE-1300096 (J.K.M. and
D.A.R.). The content is solely the responsibility of the authors and
does not necessarily represent the official views of the NIGMS or
NSF. Additional data supporting the conclusions are available in
Materials and Methods
Figs. S1 to S20
Tables S1 to S6
19 October 2016; accepted 29 December 2016
Airborne laser-guided imaging
spectroscopy to map forest trait
diversity and guide conservation
G. P. Asner,1 R. E. Martin,1 D. E. Knapp,1 R. Tupayachi,1 C. B. Anderson,1 F. Sinca,1
N. R. Vaughn,1 W. Llactayo2
Functional biogeography may bridge a gap between field-based biodiversity information and
satellite-based Earth system studies, thereby supporting conservation plans to protect more
species and their contributions to ecosystem functioning. We used airborne laser-guided
imaging spectroscopy with environmental modeling to derive large-scale, multivariate forest
canopy functional trait maps of the Peruvian Andes-to-Amazon biodiversity hotspot. Seven
mapped canopy traits revealed functional variation in a geospatial pattern explained by geology,
topography, hydrology, and climate. Clustering of canopy traits yielded a map of forest beta
functional diversity for land-use analysis. Up to 53% of each mapped, functionally distinct
forest presents an opportunity for new conservation action. Mapping functional diversity
advances our understanding of the biosphere to conserve more biodiversity in the face of land
use and climate change.
Global ecology and conservation are chal- lenged by a disconnection between two scale-dependent views of Earth’s biota. One view, based on spatially discontinuous field inventories of species composition, has generated local- to global-scale estimates of biological
diversity (1). The other view, from spatially continuous satellite observations, partitions the world
into vegetation classes, such as forests and grasslands (2), with further analysis of vegetation properties, such as leaf cover and biomass (3, 4). An
example of the disconnection between these two
views is that forest cover and biomass are weak
indicators of biological diversity (5).
The concept of functional diversity can bridge
the disconnection between biological diversity
and ecosystem processes (6). Functional diversity
is the value and distribution of traits among orga-
nisms that simultaneously influence their indi-
vidual fitness and ecosystem functioning. Studies
of traits among communities of coexisting plant
species have shown that plant floristic and func-
tional composition can track one another in space
and time (7). In turn, the functional diversity of
plant communities affects ecosystem functioning,
and vice versa (8). Despite growing understanding
of this interaction, spatially continuous, multi-
variate plant trait data are lacking for large por-
tions of the biosphere. As a result, little is known
about ongoing changes in the functional bio-
geography of the Earth system, which hampers
spatially explicit strategies to conserve functional
diversity in the face of land use and climate change.
Tropical forests, such as in the Andes-to-Amazon
region in Peru, are a critical case in point. Be-
ginning with von Humboldt (9), numerous field
surveys have generated an enormous bank of
plant and animal specimen data for this region,
revealing that it harbors the highest biological
diversity in the terrestrial biosphere (10, 11). Yet
compilations of field taxonomic data do not pro-
vide the information needed to construct a geog-
raphy of forest functional composition or its
underlying human and environmental controls.
Consequently, there has been no way to assess
the portfolio of current protections or the rise of
new threats with respect to the functioning of
this or other high-diversity regions.
To map tropical forest functional diversity as
an indicator of biological diversity and ecosystem
processes, the target traits must be (i) functionally relevant, (ii) linked to spatial variation in
species and communities, and (iii) accessible
using remote sensing approaches. A candidate
suite of plant canopy traits may meet these
criteria. Foliar nitrogen (N) and water and leaf
mass per unit area (LMA) underpin photosynthesis, primary production, and plant responses
to climate change (12, 13); are organized by canopy
species in tropical forests (14); and have proven
to be remotely measureable (15). Foliar defense
compounds, such as polyphenols and lignin, are
tied to both phylogeny and forest compositional
patterns (16) and can be remotely sensed (17).
Last, foliar phosphorus (P) and calcium (Ca),
which can also be mapped (18), are related to
species community turnover in tropical forests
(19) and are mediated by topo-edaphic patterns
and biogeochemical processes (20). Mapping
these seven canopy traits may offer a new window into the functional diversity of forests, with
linkages to biological diversity and ecosystem
Recent methodological advances in airborne
laser-guided imaging spectroscopy have made it
possible to map these seven canopy foliar traits
(21). We used this technique, combined with computational machine learning, to generate multivariate forest functional composition and diversity
maps for a large portion of the tropical biosphere
(22) (figs. S1 to S8 and table S1). Peruvian tropical
forests cover 76 million ha, from hot Amazonian
lowlands to cool Andean treelines, and harbor
thousands of canopy species. This biodiversity
hotspot provides a model system to explore forest
functional biogeography across a global range
of tropical conditions, and it is under both increasing land-use pressure and conservation focus.
With this mapping of forest canopy functional
diversity, combined with government land-use
data, we assess conservation threats, protections,
and opportunities to sustain functional diversity
throughout this region.
1Department of Global Ecology, Carnegie Institution for
Science, 260 Panama Street, Stanford, CA 94305, USA.
2Dirección General de Ordenamiento Territorial, Ministerio
del Ambiente, San Isidro, Lima, Perú.
*Corresponding author. Email: email@example.com