Coupling ordination techniques and GAM to spatially predict vegetation assemblages along a climatic gradient in an ENSO‐affected region of extremely high climate variability

Questions El Nino Southern Oscillation (ENSO) is a strong driver of climatic and ecosystem variability in coastal NW Peru. La Nina amplifies the already dry local conditions, and led to depleted ecosystems in 2011. However, the 2012 La Nina event triggered rainfall far above the average. (1) Did plant species diversity, primary productivity and vegetation assemblages change along a climatic gradient between two climatologically different La Nina years; (2) Is there a difference in explanatory power of environmental predictors between the 2 yr; and (iii) is it possible to predict the observed vegetation patterns spatially? Location Transect along a climatic gradient in the Sechura Desert of Piura, NW Peru (corresponds to the terrestrial part of the El Nino region 1 + 2) – a region of extremely high climatic variability. Methods We visited 50 30 m × 30 m randomly sampled plots in 2011 and 2012. A Procrustes analysis of two non-metric multidimensional scaling (NMDS) ordinations provided information on the temporal change of species assemblages. Variation partitioning revealed the differences in explanatory power of the predictors. We employed a generalized additive model (GAM) to fit the scores of the first ordination axis with a floristic gradient map as a result. Results Generally, higher rainfall resulted in a positive feedback when considering biodiversity, productivity and vegetation assemblages. The floristic gradient map resulting from the GAM displayed the spatial distribution of the three main assemblages along the climatic gradient. Edaphic variables added no independent portion to the explanation of the vegetation assemblages, but explained in conjunction with topography and NDVI a considerable amount of the variance. Conclusions Strong Atlantic easterly winds crossing the Andes can boost plant growth even during a La Nina situation. This underscores the need for a deeper understanding of ENSO-related climate variability of ENSO. Combining vegetation maps with accurate predictions of such climatic anomalies would aid the effective execution of conservation and recovery strategies. Additionally, coupling an unconstrained ordination with a GAM appears to be a promising tool for vegetation mapping, especially in the presence of a non-linear gradient.

[1]  Niall P. Hanan,et al.  Assessment of Desertification Around Deep Wells in the Sahel Using Satellite Imagery , 1991 .

[2]  J. Bendix,et al.  El Niño meets La Niña – anomalous rainfall patterns in the “traditional” El Niño region of southern Ecuador , 2011 .

[3]  Jean-Jacques Bedet,et al.  Distributed Active Archive Center , 1993 .

[4]  J. Gower.  Generalized procrustes analysis , 1975 .

[5]  H. Wehrden,et al.  Inter-annual rainfall variability in Central Asia – A contribution to the discussion on the importance of environmental stochasticity in drylands , 2010 .

[6]  Peter R. Minchin,et al.  An evaluation of the relative robustness of techniques for ecological ordination , 1987 .

[7]  A. Lundberg,et al.  Land-cover changes during the past 50 years in the semi-arid tropical forest region of northern Peru , 2012 .

[8]  K. Wesche,et al.  Relationships between climate, productivity and vegetation in southern Mongolian drylands. , 2007, Basic and applied dryland research.

[9]  Fabian M Jaksic,et al.  A synthesis of ENSO effects on drylands in Australia, North America and South America , 2006 .

[10]  F. Putz,et al.  Soil Effects on Forest Structure and Diversity in a Moist and a Dry Tropical Forest , 2012 .

[11]  M. Gregory,et al.  Mapping gradients of community composition with nearest-neighbour imputation: extending plot data for landscape analysis , 2011 .

[12]  Joern Fischer,et al.  Global assessment of the non-equilibrium concept in rangelands. , 2012, Ecological applications : a publication of the Ecological Society of America.

[13]  K. Wesche,et al.  Effects of fertilization and irrigation on productivity, plant nutrient contents and soil nutrients in southern Mongolia , 2011, Plant and Soil.

[14]  Alexander Brenning,et al.  Data Mining in Precision Agriculture: Management of Spatial Information , 2010, IPMU.

[15]  J. Ellis,et al.  Stability of African pastoral ecosystems: alternate paradigms and implications for development , 1988 .

[16]  L. Gillson,et al.  Rangeland Ecology in a Changing World , 2007, Science.

[17]  I. Noy-Meir,et al.  Desert Ecosystems: Environment and Producers , 1973 .

[18]  Fabian M Jaksic.  Ecological effects of El Niño in terrestrial ecosystems of western South America , 2001 .

[19]  M. Bertness,et al.  Positive interactions in communities. , 1994, Trends in ecology & evolution.

[20]  S. Bridgewater,et al.  The phytogeography of the seasonally dry tropical forests in Equatorial Pacific South America , 2003 .

[21]  D. A. White,et al.  Vegetation patterns and environmental gradients in tropical dry forests of the northern Yucatan Peninsula , 2004 .

[22]  P. Beier,et al.  Do Habitat Corridors Provide Connectivity? , 1998 .

[23]  H. Das,et al.  Impacts of Present and Future Climate Variability and Change on Agriculture and Forestry in the Arid and Semi-Arid Tropics , 2005 .

[24]  R. A. Scofield,et al.  Characteristics of extreme rainfall events in northwestern Peru during the 1982–1983 El Niño period , 1987 .

[25]  Jörg Bendix,et al.  Precipitation dynamics in Ecuador and northern Peru during the 1991/92 El Nino: A remote sensing perspective , 2000 .

[26]  Henrik von Wehrden,et al.  Pluralism and diversity: trends in the use and application of ordination methods 1990-2007. , 2009 .

[27]  S. Sullivan.  The impacts of people and livestock on topographically diverse open wood-and shrub-lands in arid north-west Namibia , 1999 .

[28]  J. Powers,et al.  Aboveground biomass in mature and secondary seasonally dry tropical forests: A literature review and global synthesis , 2012 .

[29]  Thomas W. Gillespie,et al.  Dissecting NDVI–species richness relationships in Hawaiian dry forests , 2012 .

[30]  J. L. Parra,et al.  Very high resolution interpolated climate surfaces for global land areas , 2005 .

[31]  C. Ginzler,et al.  Mapping alpine vegetation based on image analysis, topographic variables and Canonical Correspondence Analysis , 2003 .

[32]  R. Lal.  Carbon Sequestration in Dryland Ecosystems , 2004, Environmental management.

[33]  M. Walter,et al.  Impacts of disturbance on soil properties in a dry tropical forest in Southern India , 2008 .

[34]  R. Whittaker.  Evolution and measurement of species diversity , 1972 .

[35]  Nick M. Haddad,et al.  CORRIDOR USE BY DIVERSE TAXA , 2003 .

[36]  Alexander Brenning,et al.  Spatial cross-validation and bootstrap for the assessment of prediction rules in remote sensing: The R package sperrorest , 2012, 2012 IEEE International Geoscience and Remote Sensing Symposium.

[37]  Campbell O. Webb,et al.  Regional and phylogenetic variation of wood density across 2456 Neotropical tree species. , 2006, Ecological applications : a publication of the Ecological Society of America.

[38]  Hannes Feilhauer,et al.  Combining Isomap ordination and imaging spectroscopy to map continuous floristic gradients in a heterogeneous landscape , 2011 .

[39]  R. DeFries,et al.  A global overview of the conservation status of tropical dry forests , 2006 .

[40]  Milena Holmgren,et al.  Rainfall‐Tuned Management Facilitates Dry Forest Recovery , 2012 .

[41]  M. Hill,et al.  Detrended correspondence analysis: an improved ordination technique , 1980 .

[42]  M. Holmgren,et al.  Tree establishment along an ENSO experimental gradient in the Atacama desert , 2007 .

[43]  P. Legendre,et al.  Partialling out the spatial component of ecological variation , 1992 .

[44]  S. Wood.  Stable and Efficient Multiple Smoothing Parameter Estimation for Generalized Additive Models , 2004 .

[45]  Omar Cabrera,et al.  What Factors Affect Diversity and Species Composition of Endangered Tumbesian Dry Forests in Southern Ecuador? , 2011 .

[46]  Xuewen Huang,et al.  Plant Species Richness and Ecosystem Multifunctionality in Global Drylands , 2012, Science.

[47]  S. Sabaté,et al.  Climatic signals in growth and its relation to ENSO events of two Prosopis species following a latitudinal gradient in South America , 2006 .

[48]  T. Ricketts,et al.  Confronting a biome crisis: global disparities of habitat loss and protection , 2004 .

[49]  Kalle Ruokolainen,et al.  Mapping gradual landscape-scale floristic changes in Amazonian primary rain forests by combining ordination and remote sensing , 2005 .

[50]  Thomas W. Gillespie,et al.  The Utility of Spectral Indices from Landsat ETM+ for Measuring the Structure and Composition of Tropical Dry Forests 1 , 2005 .

[51]  C. Tucker.  Red and photographic infrared linear combinations for monitoring vegetation , 1979 .

[52]  Hannes Feilhauer,et al.  Mapping continuous fields of forest alpha and beta diversity , 2009 .

[53]  Steven R. Archer,et al.  Rainfall, land use and woody vegetation cover change in semi‐arid Australian savanna , 2005 .

[54]  R. Navarro-Cerrillo,et al.  Aboveground biomass in Prosopis pallida (Humb. and Bonpl. ex Willd.) H. B. K. ecosystems using Landsat 7 ETM+ images , 2007 .

[55]  Arko Lucieer,et al.  Combining vegetation indices, constrained ordination and fuzzy classification for mapping semi-natural vegetation units from hyperspectral imagery , 2010 .

[56]  A. Gentry.  Seasonally Dry Tropical Forests: Diversity and floristic composition of neotropical dry forests , 1995 .

[57]  Ken Takahashi,et al.  The atmospheric circulation associated with extreme rainfall events in Piura, Peru, during the 1997--1998 and 2002 El Niño events , 2004 .

[58]  Y. Nunes,et al.  Changes in tree and liana communities along a successional gradient in a tropical dry forest in south-eastern Brazil , 2009, Plant Ecology.

[59]  H. Tuomisto,et al.  Distribution and Diversity of Pteridophytes and Melastomataceae along Edaphic Gradients in Yasuní National Park, Ecuadorian Amazonia1 , 2002 .

[60]  Stéphane Dray,et al.  Spatial modelling: a comprehensive framework for principal coordinate analysis of neighbour matrices (PCNM) , 2006 .

[61]  Michael H. Glantz,et al.  ENSO as an Integrating Concept in Earth Science , 2006, Science.

[62]  Henrik von Wehrden,et al.  Predictive Mapping of Plant Species and Communities Using GIS and Landsat Data in a Southern Mongolian Mountain Range , 2009, Folia Geobotanica.

[63]  M. Richter,et al.  MONITORING PLANT DEVELOPMENT AFTER EL NIÑO 1997/98 IN NOR T HWESTERN PERÚ , 2005 .

[64]  David D. Breshears,et al.  The grassland–forest continuum: trends in ecosystem properties for woody plant mosaics? , 2006 .

[65]  Chris R. Dickman,et al.  Extreme climatic events shape arid and semiarid ecosystems , 2006 .

[66]  Alexander Brenning,et al.  Geomorphic process rates of landslides along a humidity gradient in the tropical Andes , 2012 .

[67]  J. Rodríguez,et al.  Tropical Dry Forests of Venezuela: Characterization and Current Conservation Status 1 , 2005 .

[68]  Jian Yang,et al.  Landsat remote sensing approaches for monitoring long-term tree cover dynamics in semi-arid woodlands: Comparison of vegetation indices and spectral mixture analysis , 2012 .

[69]  R. Ejrnæs,et al.  Can we trust gradients extracted by Detrended Correspondence Analysis , 2000 .

[70]  H. Wehrden,et al.  Similar performance in central and range‐edge populations of a Eurasian steppe grass under different climate and soil pH regimes , 2011 .

[71]  P. G. Murphy,et al.  Ecology of Tropical Dry Forest , 1986 .

[72]  S. Wold,et al.  PLS-regression: a basic tool of chemometrics , 2001 .

[73]  Reynaldo Linares‐Palomino,et al.  Diversity and endemism of woody plant species in the Equatorial Pacific seasonally dry forests , 2009, Biodiversity and Conservation.

[74]  P. Balvanera,et al.  Distribution Patterns of Tropical Dry Forest Trees Along a Mesoscale Water Availability Gradient , 2011 .