This study examines the relationship between woody plant species richness and the impact of drought events on forest canopy cover, as measured by NDVI anomalies, across different forest types in Catalonia, Spain. Forest plot data on species richness were compared to satellite imagery showing NDVI responses during a major drought in 2003. The relationship between richness and NDVI response differed among forest types and interacted with climate, as summarized by the Thorntwaite index. In some drier forest types, lower richness was linked to greater NDVI decreases during drought, while the opposite pattern emerged in some moister forest types. The results suggest the diversity-stability relationship shifts across the regional climatic gradient.
Assessing the Impact of Blister Rust Infected Whitebark Pine in the Alpine Treelines of Glacier National Park and the Beartooth Plateau, U.S.A. Presented by Emily Smith-Mckenna at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.
Assessing the Impact of Blister Rust Infected Whitebark Pine in the Alpine Treelines of Glacier National Park and the Beartooth Plateau, U.S.A. Presented by Emily Smith-Mckenna at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.
The rural-urban socioecological transformation of Mediterranean mountain areas under global change. Local studies in Olzinelles and Matadepera (Barcelona Metropolitan Region)
Impact of past and future climate change on diversity in tropical rainforestsUniversity of Adelaide
Craig’s research centers on the use of molecular approaches to study ecology and evolution and addresses questions including;
(1) the use of molecular markers to infer current and historical population processes at various spatial and temporal scales;
(2) the effects of historical changes in habitat on current distributions and diversity of faunas, with particular reference to rainforest biotas;
(3) improving the use of molecular information in conservation biology and the development of strategies that recognize evolutionary processes.
The geographic focus of this research program spans the tropical forests of Australasia, especially the wet tropics of northeastern Australia and western North America
DE presentation to IISD on May 7, 2008. Title: Amazon Resilience and Busines...DE Design and Environment
Presentation given to the Natural Resources Management Group of the International Institute for Sustainable Development on May 7, 2008. The topics were: Estimating Resilience of Amazonian Ecosystems and Design and Business Evolution
The rural-urban socioecological transformation of Mediterranean mountain areas under global change. Local studies in Olzinelles and Matadepera (Barcelona Metropolitan Region)
Impact of past and future climate change on diversity in tropical rainforestsUniversity of Adelaide
Craig’s research centers on the use of molecular approaches to study ecology and evolution and addresses questions including;
(1) the use of molecular markers to infer current and historical population processes at various spatial and temporal scales;
(2) the effects of historical changes in habitat on current distributions and diversity of faunas, with particular reference to rainforest biotas;
(3) improving the use of molecular information in conservation biology and the development of strategies that recognize evolutionary processes.
The geographic focus of this research program spans the tropical forests of Australasia, especially the wet tropics of northeastern Australia and western North America
DE presentation to IISD on May 7, 2008. Title: Amazon Resilience and Busines...DE Design and Environment
Presentation given to the Natural Resources Management Group of the International Institute for Sustainable Development on May 7, 2008. The topics were: Estimating Resilience of Amazonian Ecosystems and Design and Business Evolution
why are the tropics so diverseplease expaint this queation in det.pdfarihantmobilepoint15
why are the tropics so diverse?
please expaint this queation in details.
Solution
Answer:
Added biodiversity in the tropics as compared to the higher latitudes probably stems from the
flux of photons in the tropics, but our earth is a dynamic system and thus its far more
complicated than that.
Mutations can occur randomly, evolutionarily the strongest contributor is error during DNA
replication. This can be argued to be a function of temperature and if so, then temperature plays a
small role in DNA copying.
Another contributor would be that of the flux of photons. Photons have the ability to cause
mutations and there is a noticeable difference in photon flux between the higher latitudes and the
tropics.
The tropics are enormous, spreading across the waistline of the globe. Increasing size provides
ample opportunity for geographic separation for groups within a species. In conjunction with this
is the fact that this broad band girdling the planet has, overall, fairly constant temperature and
humidity.
The tropics also exhibit relatively stable climatic conditions which will result in steady food
supplies for animals as animals could specialize on 1 to 5 food sources and they would be
available more or less year round.
The richness of tropical rainforests in plant life is perhaps due to high levels of solar energy. The
sun lies overhead during the entire year, there is a great deal of light available to support the
plants in the lower strata, more than twice as much as is available to a temperate forest. And
since plants in the tropics don’t suffer from (low) temperature stress, they can devote their
energies to growth and reproduction at even very low light intensities. Light intensities in
tropical forests are also very patchy and heterogeneous. Thus, plants living under the tall canopy
can specialize in exploiting particular light regimes, many of which are not available in
temperate forests. And with plant diversity comes animal diversity, since all of these plants
provide food and shelter for animals.
High mean annual temperature, primary productivity, and evapotranspiration rates are probably
all involved also, but we do not know whether or not the higher energy levels found in
rainforests are causal factors in the generation of biodiversity
The presence of pathogens is a contributing factor but it complex because their related to higher
temperatures but they will cause speciations as organism will need to develop the ability to
defend against them
Storms and high winds are common in tropical areas, and frequently lead to considerable damage
and the formation of fairly large gaps in forests. When the gap in the forest is small (as when one
or a few trees fall), pioneer species will normally enter the gap and flourish, eventually being
replaced by climax tree species.
Tropical regions are large, as well as topographically complex. As mentioned above, the
complexity of the rainforest environment allows for considerable specialization of org.
Vegetation dynamics in the western himalayas, diversity indices and climate c...Shujaul Mulk Khan
Vegetation provides the first tropic trophic level in mountain ecosystems and hence requires proper documentation and quantification in relation to abiotic environmental variables both at individual and aggregate levels. The complex and dynamic Himalayas with their varying climate and topography exhibit diverse vegetation that provides a range of ecosystem services. The biodiversity of these mountains is also under the influence of diverse human cultures and land uses. The present paper is not only first of its kind but also quite unique because of the use of modern statistical techniques for the quantification of Diversity Indices of plant species and communities. The vegetation was sampled in three categories, i.e., trees, shrubs and herbs, as follows: a height of ≥ 5m were classified in the tree layer, shrubs were all woody species of height 1m and 5m and, finally, the herb layer comprised all herbaceous species less than 1m in height. The presence/absence of all vascular plants was recorded on pre-prepared data sheets (1, 0 data). For the tree layer, the diameter of trees at breast height was measured using diameter tape. Coverage of herbaceous vegetation was visually estimated according to Daubenmire and Braun Blanquet methods. It gives overall abundance of vascular plants on one hand and composition of these species on the other. Data was analysed in Canonical Community Coordination Package (CANOCO) to measure diversity indices of plant communities and habitat types. Results for five plant communities/habitat types indicated that plant biodiversity decreased along the altitude. Shannon Diversity Index values range between 3.3 and 4. N2 index and Index of Sample Variance were also designed. All of these Diversity Indices showed the highest values for the communities/habitats of north facing slopes at middle altitudes. Higher plant diversity at these slopes and altitudes can be associated to the period of snow cover which is longer and a relatively denser tree cover as compared to the southern slopes and hence the soil has high moisture which supports high biodiversity in return. Global warming causes desertification in number of fragile mountain ecosystem around the globe. These findings suggest that species diversity decreases along the measured ecological gradient under the influence of deforestation coupled with global climatic change.
As climate changes, the effects of forest diseases on forestecosystems will change. We review knowledge of relationshipsbetween climate variables and several forest diseases, as well as current evidence of how climate, host and pathogen interactions are responding or might respond to climate change. Many forests can be managed to both adapt to climate change and minimize the undesirable effects of expected increases in tree mortality. We discuss four types of forest and disease manage-ment tactics – monitoring, forecasting, planning and mitigation – and provide case studies of yellow-cedar decline and sudden aspen decline to illustrate how forest diseases might be managed in the face of climate change. The uncertainties inherent to climate change effects can be diminished by conducting research, assessing risks, and linking results to forest policy, planning and decision making.
Regional and global elevational patterns of microbial species richness and ev...sediman
Although elevational gradients in microbial biodiversity have attracted increasing attention recently, the generality in the patterns and underlying mechanisms are still poorly resolved. Further, previous studies focused mostly on species richness, while left understudied evenness, another important aspect of biodiversity. Here, we studied the elevational patterns in species richness and evenness of stream bio lm bacteria and diatoms in six mountains in Asia and Europe. We also reviewed published results for elevational richness patterns for soil and stream microbes in a literature analysis. Our results revealed that even within the same ecosystem type (that is, stream) or geographical region, bacteria and diatoms showed contrasting patterns in diversity. Stream microbes, including present stream data, tend to show signi cantly increasing or decreasing elevational patterns in richness, contrasting the ndings for soil microbes that typically showed nonsigni cant or signi cantly decreasing patterns. In all six mountains for bacteria and in four mountains for diatoms, species richness and evenness were positively correlated. e variation in bacteria and diatom richness and evenness were substantially explained by anthropogenic driven factors, such as total phosphorus (TP). However, diatom richness and evenness were also related to di erent main drivers as richness was mostly related to pH, while evenness was most explained by TP. Our results highlight the lack of consistent elevational biodiversity patterns of microbes and further indicate that the two facets of biodiversity may respond di erently to environmental gradients.
ECOLOGY, BEHAVIOR AND BIONOMICSEucalyptus Edge Effect on QEvonCanales257
ECOLOGY, BEHAVIOR AND BIONOMICS
Eucalyptus Edge Effect on Quercus-Herbivore Interactions
in a Neotropical Temperate Forest
C HERNÁNDEZ-SANTIN1, M CUAUTLE1 , M DE LAS N BARRANCO-LEÓN2, J GARCÍA-GUZMÁN1, El BADANO2,
F LUNA-CASTELLANOS1
1Depto de Ciencias Químico Biológicas, Univ de las Américas Puebla, Cholula, Puebla, Mexico
2División de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica, San Luis Potosí, Mexico
AbstractKeywords
Quercus , herbivory, edge effect,
Lepidoptera caterpillars
Correspondence
M Cuautle, Depto de Ciencias Químico
Biológicas, Univ de las Américas Puebla,
Cholula, Puebla, Mexico; [email protected]
hotmail.com
Edited by Martin F Pareja – UNICAMP
Received 18 June 2018 and accepted 26
April 2019
* Sociedade Entomológica do Brasil 2019
Fragmentation leads to the formation of edges between habitats, which in
turn changes biotic and abiotic factors that might influence herbivory or
plant-herbivory interactions. The aims of this study were to describe the
herbivory community associated with oak (Quercus) and to determine the
effects of proximity to a Eucalyptus edge and season on insect herbivory.
We selected three forest sites that were subsequently divided into three
quadrants located at different distances from the Eucalyptus edge: edge
(0 m), intermediate (30 m), and oak forest interior (60 m). We randomly
selected 10 oak trees per quadrant and conducted monthly surveys, during
the dry and rainy season (from February to October 2010), where we
quantified leaf area and the percentage of herbivory. These were analyzed
using linear mixed models, with distance and season as fixed factors and
individual and site as random factors. The primary oak herbivores were
Lepidoptera caterpillars. We found that herbivory increased away from
the edge but just during the rainy season, although higher herbivory levels
were found during the dry season. These results seem to be related to a
specialist community of herbivorous associated to the Quercus. This study
emphasizes the importance of considering border effect, especially within
Natural Protected Areas to establish strategies to improve and maintain
native oak forest and the biodiversity of its Lepidoptera herbivorous
community.
Introduction
Landscape modification due to anthropogenic activities (e.g.,
land conversion to agricultural or livestock) has resulted in
habitat fragmentation, one of the major threats for forest
conservation (Buckley 2000, Franklin et al 2002).
Fragmentation is defined as the disruption or breakdown of
large vegetation patches into smaller ones resulting in a dis-
continuity of resource distribution that affects species occu-
pancy, reproduction, and/or survival (Franklin et al 2002).
One of the important features of this phenomenon is an
increase in edge length relative to the forest area, particular-
ly in small habitat fragments (Laurance 1991, Laurance &
Yensen 1991, Murcia 1995, Laurance et al 2007, De
Carvalho ...
Biological screening of herbal drugs: Introduction and Need for
Phyto-Pharmacological Screening, New Strategies for evaluating
Natural Products, In vitro evaluation techniques for Antioxidants, Antimicrobial and Anticancer drugs. In vivo evaluation techniques
for Anti-inflammatory, Antiulcer, Anticancer, Wound healing, Antidiabetic, Hepatoprotective, Cardio protective, Diuretics and
Antifertility, Toxicity studies as per OECD guidelines
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
How to Build a Module in Odoo 17 Using the Scaffold MethodCeline George
Odoo provides an option for creating a module by using a single line command. By using this command the user can make a whole structure of a module. It is very easy for a beginner to make a module. There is no need to make each file manually. This slide will show how to create a module using the scaffold method.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
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আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
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Advantages and Disadvantages of CMS from an SEO Perspective
WOODY PLANT RICHNESS AND NDVI RESPONSE TO DROUGHT EVENTS IN CATALONIAN (NORTHEASTERN SPAIN) FORESTS - Francisco Lloret
1. Ecology, 88(9), 2007, pp. 2270–2279
Ó 2007 by the Ecological Society of America
WOODY PLANT RICHNESS AND NDVI RESPONSE TO DROUGHT EVENTS
IN CATALONIAN (NORTHEASTERN SPAIN) FORESTS
F. LLORET,1,5 A. LOBO,2 H. ESTEVAN,3 P. MAISONGRANDE,4 J. VAYREDA,3 AND J. TERRADAS1
1
CREAF (Center for Ecological Research and Forestry Applications) - Departament de Biologia Animal, Biologia Vegetal i Ecologia,
Universitat Auto `noma de Barcelona, 08193 Bellaterra, Barcelona, Spain
2
Institut de Cie`ncies de la Terra ‘‘Jaume Almera’’ (CSIC), Lluis Sole´ Sabarı´s s/n, 08028 Barcelona, Spain
3
CREAF (Center for Ecological Research and Forestry Applications), Universitat Auto `noma de Barcelona, 08193 Bellaterra,
Barcelona, Spain
4 ´
Centre d’Etudes Spatiales de la Biosphe`re (CESBIO), bpi 2801, 18, avenue Edouard Belin, 31401 Toulouse Cedex 9, France
Abstract. The role of species diversity on ecosystem resistance in the face of strong
environmental fluctuations has been addressed from both theoretical and experimental
viewpoints to reveal a variety of positive and negative relationships. Here we explore
empirically the relationship between the richness of forest woody species and canopy
resistance to extreme drought episodes. We compare richness data from an extensive forest
inventory to a temporal series of satellite imagery that estimated drought impact on forest
canopy as NDVI (normalized difference vegetation index) anomalies of the dry summer in
2003 in relation to records of previous years. We considered five different types of forests that
are representative of the main climatic and altitudinal gradients of the region, ranging from
lowland Mediterranean to mountain boreal-temperate climates.
The observed relationship differed among forest types and interacted with the climate,
summarised by the Thorntwaite index. In Mediterranean Pinus halepensis forests, NDVI
decreased during the drought. This decrease was stronger in forests with lower richness. In
Mediterranean evergreen forests of Quercus ilex, drought did not result in an overall NDVI
loss, but lower NDVI values were observed in drier localities with lower richness, and in more
moist localities with higher number of species. In mountain Pinus sylvestris forests NDVI
decreased, mostly due to the drought impact on drier localities, while no relation to species
richness was observed. In moist Fagus sylvatica forests, NDVI only decreased in plots with
high richness. No effect of drought was observed in the high mountain Pinus uncinata forests.
Our results show that a shift on the diversity–stability relationship appears across the
regional, climatic gradient. A positive relationship appears in drier localities, supporting a null
model where the probability of finding a species able to cope with drier conditions increases
with the number of species. However, in more moist localities we hypothesize that the
proportion of drought-sensitive species would increase in richer localities, due to a higher
likelihood of co-occurrence of species that share moist climatic requirements. The study points
to the convenience of considering the causes of disturbance in relation to current
environmental gradients and historical environmental constraints on the community.
Key words: climate change; ecosystem resistance; forest dieback; Mediterranean forests; NDVI; species
diversity.
INTRODUCTION between diversity and the resistance of the ecosystem
The role of species diversity in the functioning of (Tilman and Downing 1994, McGrady-Steed et al. 1997,
ecosystems has become one of the most challenging Naem and Li 1997). However, Loreau (2000) used a
topics in recent ecological research. Evidence of great model approach to conclude that resistance may decrease
human-induced transformations ranging from the local or increase with increasing diversity. A selection mech-
to the global scale has highlighted the importance of this anism (Huston 1997) (equivalent to the sampling effect
question. One particular issue concerns the role of species described by Tilman et al. 1997), by which ‘‘diversity
diversity on ecosystems’ ability to face strong environ- increases the range of trait variation and a selective
mental fluctuations, such as extreme climate events, process promotes dominance by species with extreme
which in some cases can be considered as disturbances. trait values’’ (Loreau 2000), would explain these different
Experimental results point to a positive relationship relationships. A positive relationship would be found if
the disturbance has a negative effect on most species and
diversity enhances the probability of finding the species
Manuscript received 13 July 2006; revised 7 February 2007;
best adapted to afford the new conditions (Loreau 2000).
accepted 12 February 2007. Corresponding Editor: T. J.
Stohlgren. This response would be enhanced by historically-
5 E-mail: francisco.lloret@uab.es fluctuating selective pressures that remain promoting
2270
2. September 2007 DROUGHT RESISTANCE AND PLANT RICHNESS 2271
the occurrence of traits fitting the new conditions. In addition, extensive forest inventories provide
Alternatively, a greater number of species may imply reliable information about the forest composition of
greater changes in ecosystem properties under the new woody species across large territories, and both types of
disturbance conditions when competitive pressures information may be integrated into geographical infor-
under non-disturbance conditions tended to eliminate mation systems (GIS).
disturbance-tolerant species from the community. During the summer of 2003 an intense drought
Climate models and current empirical trends point to an episode occurred in southwestern Europe, which was
increase of climatic variability in some regions, resulting in well documented by remote sensing imagery (Gobron et
a greater number and intensity of extreme events (Voss et al. 2005, Lobo and Maisongrande 2005). In the present
al. 2002). In the particular case of the Mediterranean study, we analyze the relationship between woody
Basin, where water availability is the major environmental species richness obtained from extensive forest invento-
constraint to plant growth, and where episodes of drought ries in Catalonia (northeastern Spain) and drought
resulting in forest dieback have been recorded in the last impact on the canopy of forests, estimated as NDVI
decades (Penuelas et al. 2001, Lloret et al. 2004), current
˜ anomalies of the year 2003 in relation to median NDVI
models predict warmer and drier conditions (Houghon et records of previous years. We assume that the canopy
al. 2001, Gibelin and Deque 2003), with increased NDVI values in the dense forests under study were
seasonal and inter-annual variability resulting in more mostly determined by woody species. We consider five
common and intense drought events (Houghton et al. different types of forests, defined by their dominant tree
2001, Sanchez et al. 2004). species, which are representative of the main climatic
As experimental manipulation of climate and richness and altitudinal gradients of the region. Our main
in forest ecosystems is unlikely to be performed, direct hypothesis is that species richness correlates positively
with canopy resistance to drought, this pattern being
observations of the effect of extreme climate events are
more evident in those communities where drought
currently the most reliable approach for investigating
intensity was higher, and where drought-driven selection
the relationship between forest species richness and the
has been historically prevalent.
effects of extreme drought on forest properties. In
addition, extensive sampling is recommended to inves- METHODS
tigate regional patterns, on a similar scale to that at
Study area
which drought occurs. The scaling-up of the level of
observation requires integrative variables related to Catalonia (0815 E, 40830 0 N to 3815 0 E, 42840 0 N,
0
ecosystem functioning, although accurate details of ;31 900 km2) is located in the northeast of the Iberian
functioning at stand level may be missed. Remote Peninsula, including the Pyrenean range to the north
sensing imagery has been revealed as a useful tool to and bounded to the east by the Mediterranean Sea.
describe structural patterns of vegetation determining Most of the area falls under different degrees of
primary productivity in relation to between-year climat- Mediterranean climate, with a main climatic-topograph-
ic variability at local and regional scales (Tucker and ic gradient from a temperate-boreal climate (mean
Sellers 1986, Paruelo et al. 2001). NDVI (normalized annual precipitation of up to 1500 mm) in the Pyrenees,
difference vegetation index) is a normalized contrast to a Mediterranean climate of mild winters and dry
between near infrared and red reflectance, thus empha- summers (mean annual precipitation from 530 mm) in
sizing the presence of green vegetation in the area the southern extreme. There is also a continental,
corresponding to the pixel. Since NDVI integrates both semiarid gradient inland towards the west, with colder
the abundance of green vegetation and its greenness, it winters, very hot summers, and low rainfall (mean
has a certain consubstantial ambiguity. Also, as NDVI annual precipitation around 400 mm). Vegetation types
is a two-dimensional approximation to a three-dimen- across the climatic-topographic gradients include scle-
rophyllous, evergreen shrublands and forests, deciduous
sional reality in which leaves tend to be arranged in
forests, and coniferous forests (Folch 1981), all with a
different layers, the relationship between NDVI and
long history of human management.
PAR tends to saturate in the case of highly multilayered
canopies. Notwithstanding, if time series are available Climatic data and remote sensing estimation
for post-processing and certain observations (i.e., of forest drought
extreme angles) are disregarded, NDVI is a linear
`
From the Atlas Climatic Digital de Catalunya, we
estimate of the fraction of photosynthetically active
obtained for each plot locality the Thorntwaite index as
radiation (PAR) that is intercepted by the photosynthe-
a standard index that effectively describes the aridity–
sizing tissue of vegetation present in the pixel. Because
moisture climatic gradient, from the Mediterranean
of the aforementioned multilayering, NDVI correlations
coast to the mountains inland (Lloret et al. 2005; atlas
between NDVI and LAI (leaf area index; i.e., Chen and
available online). 6 The Thorntwaite index was
Cihlar 1996, Cohen et al. 2003) are more variable, with a
calculated as follows:
less close fit and quicker saturation than in the case of
APAR. NDVI has also been found to correlate to
ecosystem CO2 flux (Wylie et al. 2003, Li et al. 2005). 6 hhttp://magno.uab.es/atles-climatic/i
3. 2272 F. LLORET ET AL. Ecology, Vol. 88, No. 9
Thorntwaite index ¼ ðP À ETP Þ 3 100=ETP average annual series of monthly mean NDVI images
for the period 1999–2002, which we used as the
where P is annual precipitation (mm), and ETP is annual
‘‘normal’’ reference, and an annual series of monthly
potential evapotranspiration (mm), which is the sum of
mean NDVI images for 2003. We calculated the
monthly evapotranspiration values calculated following
difference between the respective 2003 and 1999–2002
the Thorntwaite formula (Thorntwaite 1948). This
mean NDVI values, and we finally estimated NDVI
calculation considers for each plot locality the mean
anomalies as the difference between the respective 2003
monthly average values of temperature, that were
and 1999–2002 mean NDVI values (Fig. 1). Considering
`
obtained from the Atlas Climatic Digital de Catalunya,
that the period of drought concluded by the end of
and a coefficient estimated by the numbers of days in a
August in southwestern Europe, we use in this study the
month and the daily hours of sun as a function of
anomaly of NDVI in August 2003 as an estimate of the
latitude.
impact of the drought in the canopy. Also, this month is
The difference between precipitation and evapotrans-
at the peak of the dry season, when a large part of the
piration can be considered as an estimation of the
herbaceous vegetation has probably burned off, causing
balance between atmospheric water supply and demand
the minimal interference to the NDVI scores.
(Lobo and Maisongrande 2005). During the drought
episode of the summer of 2003, in most of our region of Species richness data
study, the difference between total precipitation and
evapotranspiration showed a negative anomaly of more Richness data are based on circular field plots
than 100 mm (Lobo and Maisongrande 2005). This established in the Third National Forest Inventory of
information was obtained by comparing climate and ´
Spain (IFN3; Direccion General de Conservacion de la´
meteorological data of June, July, and August 2003 to Naturaleza 2006). Sampling was conducted from 2000 to
data of the same months for the period 1961–2000, 2001 at a density of 1 plot/km2, following a regular
provided as grids of 5 3 5 km resolution by the Spanish design within the forested surface of the whole territory
Instituto Nacional de Metereologia (INM) (Lobo and (Fig. 1). Each plot was located in the field by a global
Maisongrande 2005). positioning system (GPS), allowing for cross-references
The vegetation response to water deficit was assessed with climatic databases (see footnote 6).
from the normalized difference vegetation index (NDVI; The IFN3 survey includes exhaustive information on
Tarpley et al. 1984) included in the S10 products that are the composition of canopy and understory woody
derived from images acquired by the VEGETATION species, as well as on production and structure. We
instrument onboard satellite SPOT. VEGETATION is restricted our analysis to this group as no consistent
an optical multi-spectral instrument that acquires a daily information is available for non-woody species. Shrub
and almost complete cover of the Earth’s surface at 1- and regenerative trees (defined as those with a normal
km2 resolution in four spectral bands (Hagolle et al. diameter, measured 50 cm above the ground surface,
2004). S10 products are calibrated, atmospherically and below 75 mm) were sampled within circular plots with a
geometrically corrected images. radius of 10 and 5 m, respectively). Extensive stands of
The VEGETATION S10 collection is produced from regenerative trees after clearing are not common in the
temporal compositing of calibrated, atmospherically region and are not included in the study. Plot size for
and geometrically corrected images, by the combination sampling the rest of the trees varied in order to sample
of daily images in periods of 10 days. The aim is to enough individuals belonging to the largest size classes
create a synthetic reconstruction from cloud-free images present in the plot. In order to minimize species richness
that is assumed to be representative of each 10-day bias due to plot size, we compared the richness shown by
period. The maximum value composite (MVC; Holben plots of different size in each forest type. In the cases
1986) procedure is used for compositing in VEGETA- where differences arose (Fagus sylvatica and Pinus
TION S10 products. MVC selects, for each pixel, the sylvestris forests), we only selected the most common
maximum NDVI value among 10 daily images. Al- size (15 m radius), which was considered to be the most
though alternative compositing methods have been representative for that type of forest. When there were
developed (Hagolle et al. 2005), MVC is the only no significant differences in species richness between
method currently implemented in the processing chain plots of different size (Quercus ilex, Pinus halepensis, and
of the S10 collection. Time series of NDVI composites Pinus uncinata forests), we pooled these plots in the
produced by this method have been used successfully to analysis. This process reduced the original 9126 IFN3
monitor surface dynamics at global and regional scales plots for Catalonia to 7567, most of them with a radius
(Zhou et al. 2001, Lucht et al. 2002, Nemani et al. 2003). of 15 m. Finally, since large variation in richness among
We used a data set of S10 products of the region of plots may produce no significant differences between
study from 1999 to 2003, with a resolution of 3200 plot size classes, we minimized the effect of plot size on
(seconds). NDVI values in S10 products are linearly the relationship between NDVI anomaly and species
scaled from the observed jÀ0.1, 0.9j range to the integer richness by including it as an explicative variable in the
range j0, 250j, and we kept this scale. We computed an statistical analysis, as detailed below.
4. September 2007 DROUGHT RESISTANCE AND PLANT RICHNESS 2273
FIG. 1. Map of the studied region (Catalonia, Spain) showing the pattern of the woody species richness obtained from field
plots (left) and the 2003 summer NDVI (normalized difference vegetation index) anomaly (right). The darker the gray, the greater is
the species richness and drought impact, respectively. Negative values of the NDVI anomaly correspond to lower values of NDVI
in August 2003 than in the reference August. Values of NDVI are linearly scaled to the range j0, 250j.
Data analysis from plots should show some degree of autocorrelation
In order to ensure a reliable correspondence between in short distances (1 km). Alternatively, a random
IFN3 information and pixel information, we applied an spatial distribution of richness values from sites 1 km
additional filter to avoid plots located in heterogeneous apart would indicate that the richness estimated in small
areas, so that reflectance from the forest canopy does sampling units is not representative of spatial patterns
not dominate the corresponding pixel values. Thus, we on a larger scale. This assumption was supported by a
defined a 1-km2 grid coincident with the pixels of the spatial autocorrelation analysis of the selected plots,
imagery and selected those cells including inventory which indicated that the pattern of species richness does
plots and satisfying two criteria: (1) land cover category not change across the neighbouring areas (Mantel test in
having dense forest in more than 50% of the cell, and (2) which the main factors were the absolute differences
tree canopy cover being more than 50% in the respective between species richness for each pair of inventory plots
inventory plots. This second filter reduced the number of and the geographical Euclidean distance between them, r
plots (and pixels) to 3504. After applying the filters, we ¼ 0.125, P , 0.001; for distances up to 15 km, r ¼ 0.075,
crossed the selected inventory data and the NDVI values P , 0.001; for distances up to 60 km, r ¼ 0.036, P ,
obtained in the respective 1-km2 pixel surrounding the 0.001).
plot location, following the nearest neighbor procedure We also tested this assumption by comparing plot
of the Miramon GIS (Pons 2000). Since 1-km2 NDVI richness values to records of species richness on larger
anomalies are obtained from averaged continuous forest spatial scales obtained from the BIOCAT data bank
canopies, we assumed that they can be applied to smaller (available online).7 BIOCAT provides the list of plant
pieces of forest, such as those sampled at the plot scale. species recorded by botanists at 10 3 10 km UTM grids
We also assumed that the number of woody species at covering the whole Catalonia territory. We selected 33 10
plot level is a reliable estimate of woody species richness 3 10 km grids where forest cover was largely dominant
in the surrounding forest areas. More specifically, we (more than 75% of the territory) and included at least 10
assumed that the spatial pattern of richness in small plots, from which we calculated the mean species
sampling units 1 km apart follows the same pattern as
adjacent 1-km2 units. If this assumption is true, richness 7 http://biodiver.bio.ub.es/biocat/homepage.htmli
5. 2274 F. LLORET ET AL. Ecology, Vol. 88, No. 9
TABLE 1. GLM results for the different forest types considering NDVI anomaly (August 2003) as the dependent variable and
woody species richness, Thorntwaite index, UTM x and y coordinates, and plot size as explicative variables.
Pinus halepensis Quercus ilex
Parameter Parameter
Parameter F1, 457 P estimate F1, 556 P estimate
Richness (R) 7.02 0.008 0.238 (0.009) 10.33 ,0.001 0.402 (0.105)
Thorntwaite index (T ) 1.82 0.178 À0.118 (0.009) 14.61 ,0.001 0.115 (0.036)
R3T 3.16 0.076 0.076 (0.011) 6.74 0.010 À0.007 (0.003)
Coordinate x 0.08 0.776 0.79 0.374
Coordinate y 58.97 ,0.001 1.76 0.185
Plot size 0.01 0.909 0.27 0.603
Notes: Values in parentheses are SE.
richness. We obtained a significant positive correlation (r may determine richness values and consequently may
¼ 0.765, F1,32 ¼ 43.74, P , 0.0001, slope ¼ 4.39) between indirectly influence the relationship between NDVI
woody species richness at the plot scale and at the 10 3 10 anomaly and species richness we also included plot size
km scale, supporting our assumption that richness values in the model as an additional explicative variable.
obtained at plot level may be correlated to NDVI 1-km2 We also built similar GLMs for each type of forest,
estimates at intermediate scales. including woody species richness, Thorntwaite index,
We selected five types of forests that were represen- UTM x and y coordinates and plot size as explicative
tative of the climatic conditions of the area of study. variables. Since all the plots in F. sylvatica and P.
These forest types were defined by its respective sylvestris were of the same size (15 m radius), this
dominant species (accounting for .50% of the plot variable was not included in the analysis of these two
basal area): Pinus halepensis (Mediterranean, coniferous types of forests.
forests), Quercus ilex (broadleaf, evergreen, Mediterra-
nean), Pinus sylvestris (mesic and mountain coniferous RESULTS
forests), Fagus sylvatica (moist, broadleaf, deciduous The relationships between NDVI anomaly and woody
forests), and Pinus uncinata (high-mountain, coniferous species richness and between NDVI anomaly and
forests) (Folch 1981, Gracia et al. 2004). As we Thorntwaite index were not the same in the different
disregarded those plots located in other types of forests, types of forests, as shown by the significant interactions
the total number of plots (and pixels) was 2087: 464 P.
forest type 3 richness and forest type 3 Thorntwaite
halepensis plots, 565 Q. ilex plots, 749 P. sylvestris plots,
(F4,2063 ¼ 3.37, P , 0.005 and F4,2063 ¼ 2.56, P ¼ 0.037,
91 F. sylvatica plots, and 218 P. uncinata plots.
respectively). NDVI anomaly was also significantly
We built a general linear model (GLM), including the
influenced by the UTM y coordinate (F4,2063 ¼ 74.42,
NDVI anomaly (difference between August 2003 and
P , 0.001). Therefore, we analyzed these relationships
mean values for the same month of the period 1999–
for each forest type separately. The effect of plot size
2002) as the dependent variable, and forest type, woody
was not significant in the analysis of the model
species richness, and Thorntwaite index as independent
considering the five types of forests (F2,2065 ¼ 0.63, P ¼
factors. We included the interactions between these
independent variables in the model. Since some sam- 0.533), nor was it in the analysis of each forest separately
pling points may experience some degree of spatial (Table 1).
autocorrelation, we included in the model two spatial NDVI values in P. halepensis forests significantly
terms corresponding to UTM x and y coordinates. decreased in the 2003 summer (anomaly mean: À2.14,
Including the x and y coordinates may not compensate SD ¼ 7.98, Student’s t test of significant differences from
for small scale spatial biases. Given the large number of zero, t ¼ 5.77, P , 0.001). NDVI loss was lower in P.
sampling points, small scale heterogeneity is unlikely to halepensis plots with higher woody species richness
bias strongly our main results, but we tested the (Table 1, Fig. 2). Although NDVI loss was not
autocorrelation pattern of NDVI anomalies by correlo- significantly influenced by the Thorntwaite index, a
gram based on Mantel tests and we found that when marginally significant interaction between woody species
considering larger distances, NDVI anomaly tends to richness and Thorntwaite index points to more vulner-
diverge gradually without relevant leveling that could ability to the 2003 drought episode in moist localities
indicate small scale heterogeneity at range lower than (within the distribution range of these forests) with less
about 40 km. We also checked GLM analysis including species (Table 1, Fig. 1). NDVI anomaly was signifi-
higher order spatial coordinate parameters, but they did cantly influenced by the UTM y coordinate, with less
not improve the model, instead in several cases they drought impact in northern localities occupied by this
resulted in collinearity problems. Finally, since plot size type of forest.
6. September 2007 DROUGHT RESISTANCE AND PLANT RICHNESS 2275
TABLE 1. Extended.
Pinus sylvestris Fagus sylvatica Pinus uncinata
Parameter Parameter Parameter
F1, 743 P estimate F1,85 P estimate F1, 210 P estimate
0.17 0.680 À0.015 (0.073) 5.96 0.017 À0.187 (0.114) 0.28 0.595 0.502 (0.943)
11.15 ,0.001 0.119 (0.031) 2.71 0.104 À2.194 (0.899) 0.84 0.361 0.038 (0.042)
0.17 0.678 À0.0004 (0.0003) 1.38 0.243 0.014 (0.012) 0.06 0.813 À0.002 (0.007)
9.48 0.002 6.54 0.012 46.80 ,0.001
22.15 ,0.001 14.08 ,0.001 1.68 0.197
0.35 0.704
FIG. 2. Contour graphs of the 2003 summer NDVI (normalized difference vegetation index) anomaly (linearly standardized) in
relation to woody species richness and Thorntwaite index (lower values are found under drier conditions) for the five types of
forests. Darker surfaces indicate more negative anomalies, i.e., lower NDVI than in previous years, as shown by anomaly values
drawn over the contour lines. Arrows show the direction of the drought impact, estimated by NDVI decrease in relation to the
species richness and the climatic gradient. Dots indicate the situation of field-sampled plots in the richness–Thorntwaite index
space. The graphs were obtained after fitting a second-order polynomical surface, following the GLM module of the Statistica 5.1.
package (StatSoft, Tulsa, Oklahoma, USA).
7. 2276 F. LLORET ET AL. Ecology, Vol. 88, No. 9
In Q. ilex forests, NDVI in August 2003 was among coniferous forests, NDVI decreased in Mediter-
significantly higher than in previous years (anomaly ranean (P. halepensis) and mesic (P. sylvestris) forests,
mean ¼ 0.98, SD ¼ 6.61, t ¼ 3.53, P , 0.001). Although while it did not change significantly in mountain (P.
both richness and the Thorntwaite index were positively uncinata) pine forests. The lack of drought effect on P.
correlated to this increase (Table 1), a significant uncinata forests also concurs with the patches of positive
interaction between them indicates that lower NDVI NDVI anomaly found by Lobo and Maisongrande
values were observed in drier localities with lower (2005) in high-mountain areas, where water availability
species richness and they also appear to be in moister was sufficient to compensate for the 2003 drought event.
localities with a higher number of species, although This general concordance with studies based on land
relatively few plots shared this profile (Table 1, Fig. 2). cover maps supports our approach based on scaling-
Pinus sylvestris forests showed a significant decrease down parameters obtained for large spatial units, in
in NDVI values (mean ¼ À3.80, SD ¼ 7.02, t ¼ 14.81, P which remote-sensing information is available, to stand
, 0.001). This decrease was not related to woody species level information taken from field surveys. In fact,
richness, but was lower in moister localities (Table 1, special care was taken to select representative forest
Fig. 2). The NDVI anomaly was significantly influenced stands that were located in the middle of forested
by the UTM x and y coordinates, indicating less drought patches of land. This is relevant because an important
impact in southern and western inland localities. source of variability in NDVI signal comes from
NDVI values of Fagus sylvatica forests were not herbaceous vegetation, which experiences important
significantly lower in August 2003 (mean ¼ À0.44, SD ¼ phenological changes over the course of a summer
8.03, t ¼ À0.52, P ¼ 0.606), and consequently there was (Lobo and Maisongrande 2005). Furthermore, upscal-
no significant correlation with the Thorntwaite index ing approaches have been used when field measures of a
(Table 1). However, NDVI values decreased significant- given variable are unlikely to be obtained for the whole
ly in plots with higher woody species richness (Table 1, territory (Williams and Rastetter 1999, Hernandez-
Fig. 2). NDVI anomaly was significantly determined by Stefanoni and Ponce-Hernandez 2004). In our case, the
the UTM x and y coordinates, with less drought impact assumption that species richness recorded at plot level is
in northern and eastern localities. a reliable estimate of woody plant diversity on a larger
Pinus uncinata forests did not show significantly scale is supported by correlation to records for larger
different values of NDVI in August 2003 when pieces of land (10 3 10 km) obtained from plant
compared to previous years (mean ¼ À0.22, SD ¼ 7.10, distribution data banks. Also, the observed autocorre-
t ¼ À0.46, P ¼ 0.643) (Table 1), and this pattern lation in Mantel tests ensures that local heterogeneity
remained present in the plots with higher species does not result in random patterns on a scale of 1 km.
richness (Fig. 2). NDVI anomaly was significantly Finally, extensive forestry inventories are the most
influenced by the UTM x coordinate, with less drought reliable source of information at a regional level on
impact in eastern localities. species coexisting in the field. This empirical information
avoids the problems of other estimates of regional
DISCUSSION patterns of species richness based on merging individual
The regional decrease in vegetation green cover species distribution maps, which do not take into
(NDVI) in southern Europe (Gobron et al. 2005, Lobo account species interactions or local habitat variability
and Maisongrande 2005) during the 2003 drought (Terradas et al. 2004). However, our study does not
episode exhibited important differences between forest consider habitat heterogeneity within 1-km2 pixels. This
types, although water deficit occurred across the whole may result in a source of error when estimates of species
territory under study. Lobo and Maisongrande (2005), richness are scaled-up.
after crossing the 2003 remote-sensing anomaly with The relationship between species richness and drought
CORINE Land Cover 2000 cartography, reported resistance showed an important variability between the
higher anomalies in herbaceous than in woody vegeta- different types of forests. Forest type is a complex
tion, and in deciduous than in evergreen broadleaf category involving species composition and forest
forests, but no analysis of coniferous forests was structure resulting from community assembly under
undertaken. Our study excludes herbaceous communi- different climatic constrictions and human management.
ties but also found more NDVI loss in F. sylvatica In fact, the five selected forests correspond to categories
forests than in Q. ilex ones. Evergreen canopies are distributed in a complex gradient from drier, warmer
expected to be more resistant to NDVI changes than conditions for open P. halepensis and close Q. ilex
deciduous canopies, which should be able to respond forests to moister conditions for P. sylvestris and F.
faster to changes in water availability by shedding leaves sylvatica ones, and to cold, mountain conditions for P.
or losing other photosynthetic tissues. Unexpectedly, Q. uncinata ones. However the climatic gradient, synthe-
ilex forest even showed higher NDVI values in the 2003 sized by the Thorntwaite index, failed in itself to explain
summer than in previous years, perhaps due to the loss the pattern of NDVI anomaly variation, as reflected by
of old leaves that are more likely to fall under drought the significant interaction between forest type and the
conditions (Ogaya and Penuelas 2003). As expected,
˜ climatic index. The Thorntwaite index is a complex
8. September 2007 DROUGHT RESISTANCE AND PLANT RICHNESS 2277
environmental variable correlated with altitude, temper- mountain P. uncinata forests where the drought effect
ature, and precipitation that did not account for the was not significant, species richness was not related to
complete set of factors contributing to forest canopy NDVI variability.
response to drought. Structural differences among Therefore, the proportion of drought-tolerant species
forests types also emerge (Gracia et al. 2004), associated within the community would play an important role in
with different management including selection logging in explaining NDVI anomaly. In drier P. halepensis forests,
Q. ilex and F. sylvatica forests, shelterwood systems in higher diversity would involve the recruitment of species
P. sylvestris forests and seed tree systems in P. uncinata that are drought tolerant. In contrast, in F. sylvatica
forest, while logging is relatively rare in unproductive P. forests, occurring in moister zones, higher diversity
halepensis forests. Overall, these types of forest can be would be caused by the recruitment of drought-
considered as distinct systems where the relationship intolerant species, and the more diverse canopy would
between species diversity and ecosystem function may lead to higher evapotranspiration rates. Quercus ilex
perform differently. forests, intermediate between dry and somewhat moister
Within each type of forest, patterns of drought impact zones, seem to display a more complex response,
in relation to species richness may result from the somewhere between that of the P. halepensis and F.
interaction with other variables, such as those related to syvatica forests.
climate. As previously reported in herbaceous commu- The recovery of forest canopy after the drought
nities (Tilman and Downing 1994), the hypothesis of episode is not considered in this study, but canopy
species richness enhancing drought resistance was greenness is expected to have achieved average values
supported in forests growing under Mediterranean after rainfall, as reported by field observations in
conditions, such as P. halepensis forests. According to previous drought episodes (Penuelas et al. 2001, Lloret
˜
the selection mechanism, the greater the number of et al. 2004). Since an increase of extreme climate
species, the greater the probability of finding species able episodes is expected in some regions, further exploration
to cope with drying conditions. In this case, the negative of the role of diversity in forest resistance in the face of
effect of the drought episode on species performance frequent droughts may be achieved by increasing the
coincides with the historical selective pressures that have effort put into long-term monitoring and the surveying
promoted the acquisition of drought tolerance or ´
of climate forest diebacks (Suarez et al. 2004).
avoidance traits in Mediterranean species (Mooney Our exploration of the relationship between species
1989, Martı´ nez-Ferri et al. 2000). This hypothesis is richness and ecosystem resistance may have also been
also supported by the trend of drier localities of P. influenced by the parameter used to estimate ecosystem
halepensis forests with more species to exhibit lower drought-resistance. NDVI is a rough estimate of some
NDVI anomalies than moister ones. In the more mesic global ecosystem properties, such as productivity, that is
Q. ilex forest, a more complex pattern of interaction affected by multiple factors, including canopy structure
between species richness and climate appears. As in P. and moisture state. To minimize these limitations, we
halepensis forests, NDVI values were higher in richer used forest homogeneous pixels, and the NDVI value
forests growing in drier conditions, but the opposite obtained in the drought period was compared to average
trend was observed in moister localities, where more values of normal years. Therefore, NDVI loss also
NDVI was observed in forests with low richness. Sala illustrates the relevant ecological consequences of
and Tenhunen (1994) also found that water deficits drought on the physiological (i.e., loss of photosynthetic
during dry summers were more severe in valley bottom activity), structural (i.e., crown partial dieback), func-
localities of Q. ilex forests than in ridge top ones, where tional (i.e., complete or partial foliage drop and
trees may have developed more conservative strategies reduction leaf longevity with consequences on nutrient
of water use. cycling), and demographic (i.e., tree mortality) proper-
Significant relationships between species richness and ties of the forest ecosystem, although it reflects poorly
drought resistance tended to disappear in more humid the details of these responses in the understory
P. sylvestris forests, where NDVI decrease became vegetation.
significant in drier localities. In these types of forests, Species homogeneity may be partly responsible for the
historical selective pressures may have not favoured unexplained effect of richness on drought impact: plots
those species able to face drought, making the whole with a high number of species may be dominated by just
community more sensitive to drier conditions. Within a few of them, while a few species on poor plots may be
the moister F. sylvatica forests, the climatic gradient evenly represented in the canopy, greatly influencing
would not be sufficiently contrasted to produce such a NDVI. Unfortunately, our forestry inventories did not
pattern. The distribution of these forests is restricted in provide enough reliable information to calculate this
the moister temperate localities of the region and they parameter because the estimates of the abundance of
are a refuge for many Euro-Siberian species (Folch rare species within plots were not accurate enough.
1981). In these cases, species-rich communities made up Nevertheless, we managed to detect that the number of
of many drought-sensitive species exhibited high nega- species significantly explained the variability of NDVI
tive NDVI anomalies. Finally, as expected, in high anomalies, probably because plot richness acts as a
9. 2278 F. LLORET ET AL. Ecology, Vol. 88, No. 9
robust indicator of diversity patterns in this group of biophysical variables and Landsat ETMþdata. Remote
plants on a larger scale, as supported by correlations Sensing of Environment 84:561–571.
´ ´
Direccion General de Conservacion de la Naturaleza. 2006.
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10 3 10 km in the BIOCAT data bank (see footnote 6). Ministerio de Medio Ambiente, Madrid, Spain.
In spite of the difficulties of scaling up the species ´
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Mongolia. Journal of Geophysical Research: Atmospheres
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