Content uploaded by Zhao Xudong
Author content
All content in this area was uploaded by Zhao Xudong on Aug 30, 2015
Content may be subject to copyright.
22 FEBRUARY 2013 VOL 339 SCIENCE www.sciencemag.org
904
LETTERS
edited by Jennifer Sills
LETTERS I BOOKS I POLICY FORUM I EDUCATION FORUM I PERSPECTIVES
907
Old ways
worth following
To haze and
haze not
911
COMMENTARY
CREDIT: GRZEGORZ MIKUSINSKI
Old Trees: Cultural Value
AS D. B. LINDENMAYER ET AL. POINT OUT
(“Global decline in large old trees,”
Perspectives, 7 December 2012, p. 1305),
large old trees play a key ecological role
in many different environments, and their
observed decline may have disastrous con-
sequences for biodiversity and ecosystem
integrity. However, the value of large trees as
part of our cultural heritage, often neglected
in conservation, may be essential for address-
ing the problem of their global decline.
Old trees span several human generations
and thereby constitute a living link between
them. Cultural, religious, spiritual, and sym-
bolic values of the large trees, as well as indig-
enous communities’ reliance on services pro-
vided by them, provide a firm foundation
for practical conservation. In many cases,
the general society’s preferences concerning
large trees may coincide with the broad con-
servation interest (1).
Moreover, large trees wake emotions,
appeal to our aesthetic sentiments, and are
often perceived as important landmarks. In
this sense, they may be perfect fl agship ele-
ments of the conservation strategies. For
example, a concern for big trees in the begin-
ning of the 20th century led to action that
Old Trees: Extraction, Conservation Can Coexist
BECAUSE LARGE OLD TREES ARE ESSENTIAL FOR FOREST ECOSYSTEM INTEGRITY AND BIODIVER-
sity, timber extraction in managed forests should preferentially be concentrated where large old
trees are least likely to develop (“Global decline in large old trees,” D. B. Lindenmayer et al.,
Perspectives, 7 December 2012, p. 1305). However, timber extraction and the conservation of
large old trees are not necessarily mutually exclusive.
Current forest policy and management practices in Flanders, Belgium, aim to convert
even-aged stands (areas in which trees are all the same age) to stands with trees of varying
ages in an effort to increase forest ecosystem stability and resilience and to allow trees to
grow old. As part of their ecologically sustainable forest management, public forest man-
agers have adopted a large-tree retention approach [see also (1, 2)]. Tree islands within
stands managed for production of high-quality timber are reserved for conservation, and
trees within these islands will never be extracted. Large old trees of commercially valuable
species that have grown beyond the commercially optimal dimensions will
not be logged either. And no tree beyond a threshold diameter [currently set at
dbh (diameter at breast height) of more than 102 cm] will ever be logged. The
strip-shelterwood system (in which trees are cut in linear strips and surround-
ing trees are given time to grow old) and the coppice-with-standards system
(in which some trees are left to grow while others around them are cut) are
two examples of forest management that allows the combination of sustain-
able forest exploitation and conservation of large old trees.
RAF AERTS
Division Forest, Nature and Landscape, University of Leuven, Celestijnenlaan 200E-2411, BE-3001
Leuven, Belgium. E-mail: raf.aerts@biw.kuleuven.be
References
1. D. B. Lindenmayer, W. F. Laurance, Biol. Conserv. 151, 11 (2012).
2. D. B. Lindenmayer et al., Conserv. Lett. 5, 421 (2012).
safeguarded the future of giant sequoias, per-
ceived as “natural temples” (2). When con-
sidering a multitude of large trees’ virtues, it
seems that the value of these iconic organ-
isms should be more broadly recognized by
the conservation community, as it may sup-
port their conservation goals.
MALGORZATA BLICHARSKA1* AND
GRZEGORZ MIKUSINSKI2
1Department of Aquatic Sciences and Assessment, Swedish
University of Agricultural Sciences, 750 07 Uppsala, Swe-
den. 2School for Forest Management, Swedish University
of Agricultural Sciences, 739 21 Skinnskatteberg, Sweden.
*To whom correspondence should be addressed. E-mail:
Malgorzata.Blicharska@slu.se
References
1. A. M. Lykke, J. Environ. Manage. 59,
107 (2000).
2. Science 54, 43 (1921).
Old Trees:
Large and Small
D. B. LINDENMAYER ET AL.
(“Global decline in large
old trees,” Perspectives, 7
December 2012, p. 1305),
report a global decline in
large old trees and show that
climate change and human
disturbance are reducing the abundance of
these ecologically important organisms.
Such framing of the problem leads to confl a-
tion of two issues: Old trees and large trees
are not synonymous.
While the term “old growth” brings to
mind the iconic sequoias described by the
authors, stunted and slow-growing forests
in extreme environments also play impor-
tant ecological roles, and declines in small
old trees are of increasing concern. Land-
scapes with small old trees (often surviving at
the edge of their ranges) function as genetic
repositories and population refugia, which
play a critical role in the long-term persis-
tence of forest ecosystems (1, 2).
Published by AAAS
on February 21, 2013www.sciencemag.orgDownloaded from
www.sciencemag.org SCIENCE VOL 339 22 FEBRUARY 2013 905
915 920
Cryopreservation
of plant diversity
IBI Prize Essay
In southern Brazilian Atlantic forests,
where highly diverse isolated populations can
persist over several millennia, small old trees
have shown recent growth decline (3). Here,
at the southernmost limit of tropical forest dis-
tribution, trees more than 40 cm in diameter
are rare, and landscapes dominated by small
trees provide essential services, but very lit-
tle of the original forest cover is protected by
nature reserves. A hemisphere away, in north-
ern Ontario, Canada, live some of the largest
undisturbed old-growth pine forests in North
America (4). Recent work suggests that here,
too, the growth of small old trees (typically
less than 50 cm in diameter, from 150 to more
than 300 years) has been declining (5). As cli-
matic changes and human demands increase,
widespread growth declines and increased
mortality threaten global forests (6–8). The
struggles of large old trees are important, but
they are by no means unique.
JACOB CECILE,1 LUCAS R. SILVA,2
MADHUR ANAND1*
1Global Ecological Change and Sustainability Laboratory,
School of Environmental Sciences, University of Guelph,
Guelph, ON, N1G 2W1, Canada. 2Department of Land, Air,
and Water Resources, University of California Davis, Davis,
CA 95616, USA.
*To whom correspondence should be addressed. E-mail:
manand@uoguelph.ca
References
1. J. S. McLachlan, J. S. Clark, P. S. Manos, Ecology 86,
2088 (2005).
2. L. C. R. Silva, M. Anand, Ecosystems 14, 1354 (2011).
3. L. C. R. Silva, M. Anand, J. M. Oliveira, V. D. Pillar, Glob.
Change Biol. 15, 2387 (2009).
4. M. D. Leithead, M. Anand, L. C. R. Silva, Oecologia 164,
1095 (2010).
5. L. C. R. Silva, M. Anand, M. D. Leithead, PLoS ONE 5, 7
(2010).
6. L. Andreu-Hayles et al., Global Change Biol. 17, 2095
(2011).
7. P. J. van Mantgem et al., Science 323, 521 (2009).
8. B. Choat et al., Nature 491, 752 (2012).
Response
CECILE ET AL. TAKE ISSUE WITH OUR RECENT
Perspective on the rapid global decline of large
old trees by asserting that “large” and “old”
are not synonymous. Of course, some ancient
trees are indeed short in stature [e.g., (1)].
Nonetheless, many of the world’s largest trees
are also old (more than 500 to 1000 years) (2,
3), so it is correct to highlight this reality.
Cecile et al. further argue that small old
trees are declining in some ecosystems, and
we agree that this is a matter of concern.
However, large old trees are particularly vul-
nerable to disturbances such as insect attack,
pathogens, drought, and fi re in some environ-
ments (4–6). Large old trees also play a range
of key roles (e.g., as wildlife habitat and for
carbon storage) that are not played by small
old trees. Unlike large old trees, small old
trees are rarely deliberately removed during
agricultural intensifi cation (7) or because of
safety concerns in urban environments (4).
In addition, small old trees are less likely to
be targeted for logging [although they may be
specifi cally targeted in some restoration proj-
ects in western North America because of
prohibitions on removal of larger trees (8)].
The particular risks faced by large old trees,
combined with their unique ecological roles,
mean that their management and conserva-
tion warrant special mention.
DAVID B. LINDENMAYER,1* WILLIAM F. LAURANCE,2
JERRY F. FRANKLIN3
1Fenner School of Environment and Society, The Australian
National University, Canberra, ACT 0200, Australia. 2Cen-
tre for Tropical Environmental and Sustainability Science
(TESS), and School of Marine and Tropical Biology, James
Cook University, Cairns, QLD 4878, Australia. 3School of
Environmental and Forest Science, University of Washing-
ton, Seattle, WA 98195, USA.
*To whom correspondence should be addressed. E-mail:
david.lindenmayer@anu.edu.au
References
1. Umeå University, Press Release, “World’s oldest living tree
discovered in Sweden” (16 April 2008); http://info.adm.
umu.se/NYHETER/PressmeddelandeEng.aspx?id=3061.
2. J. Chambers, N. Higuchi, J. P. Schimel, Nature 391, 135
(1998).
3. W. F. Laurance et al., Forest Ecol. Manage. 190, 131
(2004).
4. B. J. Palik, M. E. Ostry, R. C. Venette, E. Abdela, Forest
Ecol. Manage. 261, 128 (2011).
5. M. Simard, E. N. Powell, K. F. Raffa, M. G. Turner,
Glob. Ecol. Biogeogr. 21, 556 (2012).
6. D. C. Nepstad, I. M. Tohver, D. Ray, P. Moutinho,
G. Cardinot, Ecology 88, 2259 (2007).
7. M. Maron, J. A. Fitzsimons, Biol. Conserv. 135, 587 (2007).
8. J. F. Franklin, K. N. Johnson, J. Forestry 110, 429 (2012).
China’s Little Emperors
Show Signs of Success
IN THE REPORT “LITTLE EMPERORS: BEHAVIOR
impacts of China’s one-child policy”
(22 February, p. 953; published online 10
January), L. Cameron et al. suggest that
being an only child as a result of China’s
one-child policy (OCP) might carry negative
implications for success and well-being. We
caution against overgeneralization from the
economic experiments and personality sur-
veys conducted in this study.
In longitudinal studies among the first
post-OCP cohort—the same cohort as that
studied by Cameron et al.—some single-
tons showed more behavioral problems and
less independence in childhood. Yet, by ado-
lescence, differences in behavioral prob-
lems disappeared and independence levels
reversed (1, 2). In contrast to the experimen-
tal context, more pro-social behaviors among
singletons than non-singletons were found in
community samples (2). In education, single-
tons performed as well as or better than their
peers in verbal and math skills and showed
better school adjustment and lower levels of
anxiety, but they demonstrated inferior test-
ing and study methods (3, 4). Once they
became parents, this cohort of singletons
showed no difference in marriage adjustment
compared with their counterparts, and in fact
demonstrated higher levels of life satisfaction
and higher intergenerational family fusion
(5). Contrary to the hypothesis that malad-
justment might be magnifi ed in later post-
OCP cohorts, singletons born in the 1990s
have shown equal or superior interpersonal
relationships with peers, teachers, and family
members compared with non-singletons (6).
All this is not to deny legitimate concern
over the OCP, only-child status, or the com-
bination of both. Yet, against expectation and
stereotype, research has shown that as “little
emperors” transition into adulthood, their well-
being and performance are comparable with, if
not superior to, those with one or more siblings.
In such complex systems as that of human psy-
chology and behavior, one must move beyond
linear notions of causality. Circular processes
of self-correction at the individual, family, and
social levels often provide surprising compen-
satory responses to initial conditions.
XUDONG ZHAO,1 XIQUAN MA,1 YUHONG YAO,2
CHONGHUA WAN,3 EMI LY NG4*
Letters to the Editor
Letters (~300 words) discuss material published in
Science in the past 3 months or matters of gen-
eral interest. Letters are not acknowledged upon
receipt. Whether published in full or in part, Let-
ters are subject to editing for clarity and space.
Letters submitted, published, or posted elsewhere,
in print or online, will be disqualifi ed. To submit a
Letter, go to www.submit2science.org.
Published by AAAS
on February 21, 2013www.sciencemag.orgDownloaded from
22 FEBRUARY 2013 VOL 339 SCIENCE www.sciencemag.org
906
LETTERS
17050 Montebello Rd, Cupertino, CA 95014
Email: AAASInfo@betchartexpeditions.com
www.betchartexpeditions.com
For a detailed brochure,
please call (800) 252-4910
All prices are per person twin share + air
Grab your binoculars and cameras
and discover Iceland—the world’s
oldest democracy. Its wildlife and
natural wonders are truly magical!
Join naturalist Siggi Tomasson for
a tremendous introduction to the
heritage of Iceland, from geology to
history and wildlife! $3,995 + air
BETCHART EXPEDITIONS Inc.
Land of Fire & Ice
& Nature’s Paradise!
Wild Iceland
June 13-22, 2013
Produced bythe
Scienc
e
/AAAS Custom Publishing Ofˇce India
Innovations&Opportunities
Advancing Science
in India
InThisIssue
Science in Indiaison the move in abig way.The governmenthasinitiated
multibillion dollarinvestments to kickstart research, education, and innovation
overthe next fiveyears.Though severalchallenging issuesremain forthe country,
Indiaís best and brightest expats living in the United Statesand Europe are
being enticed backtoëMotherIndiaíwiththe promise of world-class research
infrastructureand solid funding.
See the full story on page 981.
Upcoming Features
Postdocs:Identifying OpportunitiesóMarch8
RegionalFocus:GermanyóMarch22
CancerResearchCareersóMarch29
1Shanghai East Hospital; Department of Psychosomatic
Medicine, School of Medicine at Tongji University, Shang-
hai, China. 2Psychological Counseling and Education Cen-
ter, Tongji University, Shanghai, China. 3School of Humani-
ties and Management, Guangdong Medical College, Dong-
guan, China. 4Department of Anthropology, University of
California, Berkeley, Berkeley, CA 94720, USA.
*To whom correspondence should be addressed. E-mail:
emily.ng@berkeley.edu
References
1. M. Wang et al., World Cultural Psychiatry Res. Rev. 2,
118 (2007).
2. X. Feng, Zhongguo Shehui Kexue (Social Sciences in
China) 13, 118 (2000).
3. T. Falbo, D. L. Poston, Child Dev. 64, 18 (1993).
4. Z. Li, S. Wu, X. Zhang, Qingnian Yanjiu (Youth Research)
4, 31 (1998).
5. X. Ma, F. Yin, Y. Yao, X. Zhao, Zhongguo Xinli Weisheng
Zazhi (Chinese Mental Health Journal) 2, 118 (2012).
6. Y. Yao, doctoral dissertation, School of Medicine at Tongji
University (2011).
CORRECTIONS AND CLARIFICATIONS
This Week in Science: “Proton still too small” (25 January,
p. 371). The study examined muonic hydrogen, not muon-
ium. Muonic hydrogen is the name given to a system made
from a proton and a negative muon. Muonium is the exotic
atom made from a positive muon and a (negative) electron.
The HTML and PDF versions online have been corrected.
News Focus: “The children’s study: Unmet promises” by
J. Kaiser (11 January, p. 133). The January 2013 workshop
to review the study plan described in the text and time-
line was sponsored by the National Academy of Sciences,
not the Institute of Medicine. The HTML and PDF versions
online have been corrected.
Letters: “NextGen speaks” (4 January, p. 30). Ali Jawaid’s
essay referred to Pakistan, not Switzerland. Jiang Zhao is
at Beihang University, not Beijing University. Guilherme
Martins Santos’s address should be Laboratory of Molecu-
lar Pharmacology, Department of Pharmaceutical Sciences,
Faculty of Health Sciences, University of Brasília, Brazil, CEP
70910-900, Brazil. In the online-only essays, Homare Yama-
hachi’s essay referred to Greece, not Norway. These changes
have been made in the HTML and PDF versions online.
Reviews: “Conversion of wastes into bioelectricity and chem-
icals by using microbial electrochemical technologies,” by B.
E. Logan and K. Rabaey (10 August 2012, p. 686). In the Fig.
2 legend, the symbols should have been identifi ed as fol-
lows: “There is roughly an inverse relationship between the
value of these products (circles) and the current densities (tri-
angles)....” On p. 689, “4.5 a.m.–2” should have been written
as “4.5 A m–2.” The authors also wish to thank T. Lacoere and
J. Desloover for assistance in preparing the draft fi gures and
funding from the Commonwealth Scientifi c and Industrial
Research Organization Flagship cluster “Biotechnological
solutions to Australia’s transport energy and greenhouse gas
challenges.” The HTML version online has been corrected.
TECHNICAL COMMENT ABSTRACTS
Comment on “Bilaterian Burrows
and Grazing Behavior at >585 Million
Years Ago”
Claudio Gaucher, Daniel G. Poiré, Jorge Bossi,
Leda Sánchez Bettucci, Ángeles Beri
Pecoits et al. (Reports, 29 June 2012, p. 1693) describe
bilaterian trace fossils and assign them an Ediacaran age
based on the age of a granite interpreted as intrusive. We
argue that the granite is not intrusive but in fact repre-
sents the basement of the sedimentary succession. More-
over, we show that identical trace fossils occur in nearby
Carboniferous-Permian glacigenic rocks.
Full text at http://dx.doi.org/10.1126/science.1230339
Response to Comment on
“Bilaterian Burrows and Grazing
Behavior at >585 Million Years Ago”
Ernesto Pecoits, Kurt O. Konhauser,
Natalie R. Aubet, Larry M. Heaman,
Gerardo Veroslavsky, Richard Stern,
Murray K. Gingras
Gaucher et al. suggest that their fi eld observations and
petrographic analysis of one thin section do not support
an Ediacaran age for the trace fossils–bearing strata of the
Tacuarí Formation. We have strengthened our conclusion
of an Ediacaran age for the Tacuarí Formation based on
reassessment of new and previously presented fi eld and
petrographic evidence.
Full text at http://dx.doi.org/10.1126/science.1230677
CREDIT: WILLIAM LEAMAN/ALAMY
Published by AAAS
on February 21, 2013www.sciencemag.orgDownloaded from