Blanca L. Figueroa-Rangel

4200 YEARS OF PINE-DOMINATED UPLAND FOREST DYNAMICS IN WEST-CENTRAL MEXICO: HUMAN OR NATURAL LEGACY?

The pine-dominated forests of west-central Mexico are internationally recognized for their high biodiversity, and some areas are protected through various conservation measures including prohibition of human activity. In this region, however, there is evidence for human settlement dating back to ca. AD 1200. It is therefore unclear whether the present forest composition and structure are part of a successional stage following use by indigenous human populations during the past, or due to natural processes, such as climate. We present a study reconstructing the vegetation dynamics of pine-dominated forest over the past 4200 years using paleoecological techniques. Results from fossil pollen and charcoal indicate that, in this region, pine-dominated forests are the native vegetation type and not anthropogenically derived secondary succession. The predominant driving mechanism for the expansion of pine-dominated forest appears to be intervals of aridity and naturally induced burning. A close association is noted between pine abundance and longer-term climatic trends, including intervals of aridity between ca. 4200 and 2500, 1200 and 850, and 500 and 200 cal yr BP and shorter-term trends. Evident periodicity occurs in pine and Poaceae abundance every 80 years. These short-term quasi-periodic oscillations have been recorded in a number of lake and ocean sediments in Mexico and are thought to be linked to solar forcing resulting in drought cycles that occur at approximately the same time intervals.

Regeneration patterns in relation to canopy species composition and site variables in mixed oak forests in the Sierra de Manantlán Biosphere Reserve, Mexico

Regeneration patterns in relation to canopy species composition and site variables were analyzed in mixed oak forests of the Sierra de Manantlán in western Mexico with the aim of establishing an ecological basis for the design of management alternatives. Using ordination (canonical correspondence analysis) and classification (two-way indicator species analysis) methods, five different canopy types and three different seedling associations were revealed according to species composition, all of them dominated by one or more oak species. Red–far red ratio, slope, altitude, topography, canopy type and grazing intensity were the main variables that explained differences in species composition among the seedling associations. Oak seedlings were relatively scarce in the sampling plots, with the lowest frequency values of all species recorded except for those of Quercus crassipes Humb. & Bonpl., and also the lowest density values. The presence of a particular oak seedling species was strongly associated with a particular percentage of canopy openness; Quercus candicans Née, Quercus laurina Humb. & Bonpl. and Quercus rugosa Née were present in the plots with the least-open canopy (6.4%, 2.9 and 6.2%, respectively), while Quercus castanea Née and Quercus crassipes Humb. & Bonpl. were present in the plots with the most-open canopy (13 and 8.1%, respectively). Every oak seedling species was more frequent, although not dependent, on the canopy type where the same oak species dominated. Because of the great heterogeneity in species composition and the physiographical factors of mixed oak forests in the Sierra de Manantlán, we concluded that management alternatives must be prescribed for each ecological situation where the different oak species are growing.

Late-Holocene successional dynamics in a transitional forest of west-central Mexico

The determination of past successional stages, as well as the factors triggering succession, is crucial for the understanding of forest dynamics and the design of current and future management and conservation strategies. Shifts between successional stages can take decades or even centuries to occur because of tree longevity; therefore palaeoecological studies are important tools for their study. The present research involved the palaeoreconstruction of a transitional forest dominated by Pinus-Carpinus-Quercus in west-central Mexico over the last ~1230 years. The proxies employed include fossil pollen, microscopic fossil charcoal, magnetic susceptibility and organic matter content evaluated by multivariate techniques. The findings reveal that an initial cloud forest stage developed from 1230 to 1050 cal. yr BP. This stage was then interrupted for ~400 years (1050–690 cal. yr BP) when a regional climate change event decreased the number of cloud forest taxa and increased herbaceous taxa including Asteraceae, Poaceae, Plantago and Zea. The cloud forest stage recovered at 690 cal. yr BP and the community has persisted to the present time, yet this stage is dominated by human-induced taxa such as Pinus and Acacia. Whilst the dynamics of individual taxa were related to forest fires and soil erosion, changes between community types were related to an interval of regional climate change (greater aridity) that occurred between 1050 and 690 cal. yr BP. Results from this study indicate that, in order to preserve the cloud forest stage, human disturbances such as logging and agriculture should be excluded; a conservation strategy established in the transitional forest in recent years.

Correction for Willis et al., How can a knowledge of the past help to conserve the future? Biodiversity conservation and the relevance of long-term ecological studies

Correction for ‘How can a knowledge of the past help to conserve the future? Biodiversity conservation and the relevance of long-term ecological studies’ by Katherine J. Willis, Miguel B. Araújo, Keith D. Bennett, Blanca Figueroa-Rangel, Cynthia A. Froyd and Norman Myers (Phil. Trans. R. Soc. B 362, 175–186. (doi: 10.1098/rstb.2006.1977)). The dates of the textual citations and the entries in the reference list for the following references should have been 2007 but were incorrectly given as 2006. The correct forms of these references are given below.

Acer binzayedii (Sapindaceae), a new maple species from Mexico

Acer binzayedii, a new species of Sapindaceae from cloud and high elevation forests in Jalisco State, Mexico, is described and illustrated. Acer binzayedii is characterized by deeply sagittate anther bases bearing scattered trichomes, the wing sulcus covering more than half of the nutlet, sparsely distributed coalescent and anastomose veins of the wings with reticulate veinlets sometimes present, trichomes on the abaxial leaf surfaces with short nodulations of reduced prominence, conical buds, and grey bark with long vertical ridges. The new species is compared to putative relatives A. skutchii, A. floridanum, A. saccharum, A. grandidentatum, and A. nigrum.ResumenAcer binzayedii, especie nueva de Sapindaceae de los bosques nubosos en elevaciones altas en el estado de Jalisco, México, se describe e ilustra. Acer binzayedii se caracteriza por la antera pronunciadamente sagitada en la base con tricomas esparcidos, el surco del ala cubre más de la mitad del fruto, las venas coalescentes y anastomosas del ala están espaciadamente distribuídas con venas secundarias reticuladas algunas veces presentes, los tricomas en el lado abaxial de la hoja con nódulos cortos de prominencia reducida, yemas cónicas, corteza gris con costillas largas verticales. La especie nueva se compara con los parientes más cercanos A. skutchii, A. floridanum, A. saccharum, A. grandidentatum, y A. nigrum.

Environmental History of Mangrove Vegetation in Pacific West-Central Mexico during the Last 1300 Years

Abstract Mangroves are a highly threatened ecosystem due to climate change and human activity, which increases coastal vulnerability. Knowledge about the ecological dynamics of mangroves on a centennial timescale can reveal the different responses in vegetation, which is useful for implementing basic actions for mangrove restoration, conservation and management. A mangrove ecosystem in the Cuyutlan Lagoon area along the Pacific coast of west-central Mexico is significantly altered as a result of industrialization, salt extraction, and road construction. The long-term dynamics of the mangrove ecosystem has also been controlled by Holocene climatic variability. This study reconstructs the environmental history of mangrove vegetation around the Cuyutlan Lagoon during the last ~1300 years in response to periods of human activity and climate change. The reconstruction was performed using paleoecological techniques in sediment cores that include the use of fossil pollen as a proxy for vegetation and magnetic susceptibility and geochemical data (determined by loss-on-ignition and X-ray fluorescence) as a proxy for past environmental changes. The chronology was determined using 14C dating and the age-depth model was constructed by linear interpolation. Redundancy analysis and non-metric multidimensional scaling (NMDS) were used to discern patterns of distribution of the different proxies. Results revealed that the mangrove pollen assemblage of the Cuyutlan Lagoon was dominated by the arboreal taxa Rhizophora mangle, Euphorbiaceae, Moraceae and Pinaceae, herbaceous taxa like Poaceae, Chenopodiaceae/Amaranthaceae, and aquatics such as Typhaceae and Cyperaceae. NMDS showed a clear separation between two events of human activity—the Spanish Occupation of Colima (~AD 1523-1524) and the opening of the Manzanillo port (~AD 1824-1825). Climate change events such as the Medieval Climate Anomaly (MCA) (~AD 800-1200) and the Little Ice Age (LIA) (~AD 1350-1850) were also successfully identified. The main responses were mangrove expansion (driven by R. mangle) during the LIA and the Manzanillo Port Opening, while the MCA was a highly perturbed period marked by multiple hurricane events and low or no pollen deposition in the sediment. During the Spanish Occupation, the aquatic taxa Typhaceae expanded together with an increase in Ca, Sr and carbonate contents.