Encarnación Montoya

Modern non-pollen palynomorphs sedimentation along an elevational gradient in the south-central Pyrenees (southwestern Europe) as a tool for Holocene paleoecological reconstruction

Non-pollen palynomorphs (NPPs) are microfossils other than pollen and spores from plants found within samples prepared for pollen analyses. Their utility as paleoecological indicators is rapidly growing because of their potential to complement palynological reconstructions of past communities and environments. The study of modern NPP sedimentation patterns using surface samples from different substrates, vegetation types, and environmental conditions is needed to characterize the main environmental and anthropogenic factors involved in establishing ecological gradients. Here, we analyze modern NPP distribution along an elevational transect from the south-central Pyrenees. We use these data to test the potential influence of elevation, vegetation type, sampling sites, and human disturbance on modern NPP distribution and to obtain a NPP modern-analog model, which will enhance further paleoecological interpretations. Our study used the same surface samples obtained in a previous modern-analog palynological study, along an elevational transect from 870 to 2600 m a.s.l. We identified 55 NPPs, including 13 unidentified morphotypes that were described and depicted. Individual NPP analysis and multivariate statistical methods showed that altitude plays a significant role in the NPP distribution along the transect, but other factors such as soil moisture, landscape openness, and grazing intensity also influenced the composition of NPP assemblages. Our results also recognized some characteristic NPP assemblages linked to elevational vegetation belts and individual NPP morphotypes related with specific microhabitats, both with potential paleoecological indicator capacity. This work is a first step to improve the knowledge of the NPP’s indicator value in the study area.

Bureaucratic obstruction of conservation science in the Guayana Highlands.

Unfortunately, field research in the area [northern South America Guayana Highlands (GH)] has been stopped for nearly 20 years. Official permits to visit the tepui summits were suspended in 1989, until a detailed management plan could be made (Huber 1995a). Today most of the tepuis are in national parks and other protection areas, and there is also a special policy for their summits (Huber 1995a). There is an administrative process through which fieldwork permits can be obtained, but the process is so difficult that no scientific expedition has been carried out since closure of the area. Studies involving genetic analysis are not allowed. Thus, officials will not consider permit requests that do not explicitly state that no samples will be used for any type of genetic study. This prohibition makes it impossible to develop phylogenetic and phylogeographic surveys, which are crucial to understanding the origin and maintenance of GH biodiversity (Rull 2007).

An 8700-year record of the interplay of environmental and human drivers in the development of the southern Gran Sabana landscape, SE Venezuela

The vegetation of the southern Gran Sabana (SE Venezuela) consists primarily of a treeless savanna with morichales (Mauritia flexuosa palm stands), despite the prevailing climate being more favorable for the development of extensive rainforests. Here, we discuss the results of our 8700-year paleoecological reconstruction from Lake Encantada based on the analysis of pollen, algal remains, charcoal, and geochemical proxies. We use the findings to assess a number of hypotheses that seek to explain the dominance of savanna vegetation and consider the relative importance of factors such as climate, fire, and erosion on the landscape. The reconstruction of vegetation changes suggests the following trends: open savanna with scattered forest patches (8700–6700 yr BP), forest-savanna mosaic (6700–5400 yr BP), open savanna with forest patches (5400–1700 yr BP), and treeless savanna with morichales (1700 yr BP–the present). We conclude that the interplay between climate and fire and the positive feedback between the presence of grasses and increased fire frequency played a major role in the vegetation dynamics from the early to middle Holocene (8700–6700 yr BP). The synergistic action between reduced fires and wetter conditions appears to be a determinant in the development of rainforest around 6700 yr BP. Despite higher available moisture at ~5400 yr BP, the savanna expanded with the increased frequency of fire, potentially driven by human land-use practices. We also propose that the interplay between fire and erosion created forest instability during the middle and late Holocene. The current southern Gran Sabana landscape is the result of the complex interplay between climate, fire, erosion, and vegetation.

CLAFS, a Holistic Climatic-Ecological-Anthropogenic Hypothesis on Easter Island's Deforestation and Cultural Change: Proposals and Testing Prospects

This paper reviews the existing hypotheses concerning the cultural shift from the Ancient Cult (AC) to the Birdman Cult (BC) that occurred on Easter Island (Rapa Nui) during the last millennium and introduces a holistic new hypothesis called CLAFS (Climate-Landscape-Anthropogenic Feedbacks and Synergies), which considers a variety of potential drivers of cultural change and their interactions. The CLAFS hypothesis can be tested with future paleoecological studies on new sedimentary sequences such as the new continuous and coherent record encompassing the last millennium from Rano Kao (KAO08-03) using a combination of pollen, non-pollen palynomorphs (NPP), charcoal, and fecal lipid analyses, at decadal to multidecadal resolution. The Kao record should be be compared with other continuous records of the last millennium available for the two other freshwater bodies of the island, Rano Aroi and Rano Raraku, to obtain an island-wide perspective of spatio-temporal deforestation patterns in relation to climatic shifts and human activities. The CLAFS hypothesis predicts that the shift from the AC to the BC was associated with the drying out and deforestation of Rano Raraku (the center of the AC) by ~1570 CE, followed by human migration to Rano Kao (the social center of the BC), where freshwater and forests were still available. Under the CLAFS scenario, this migration would have occurred by ~1600 CE. Findings to the contrary would require modification and refinement, or outright rejection, of the CLAFS hypothesis and the consideration of alternate hypotheses compatible with new paleoecological evidence. Regardless the final results, archaeological evidence will be required to link climatic and ecological events with cultural developments.

The neotropical Gran Sabana region: Palaeoecology and conservation

The Gran Sabana (GS) is a key region for understanding the origin of neotropical savannas and is an ideal location to test ecological hypotheses on long-term vegetation dynamics under the action of natural and anthropogenic drivers. The conservation of the GS is a controversial issue because of the confluence of disparate cultural and socio-economic interests, with a strong debate surrounding fire practices by indigenous people. Late glacial to Holocene pollen and charcoal records obtained thus far in this region have documented the main palaeoecological trends along with the climatic and anthropogenic (mostly fire) drivers involved. Here, we discuss how these records can be used to inform conservation and restoration practices in the GS. The main points of the discussion are the local versus regional character of palaeoecological evidence, the support provided by this evidence for the existing fire management proposals and the role of spatiotemporal environmental and ecological heterogeneity in the definition and evaluation of realistic restoration targets. A general conclusion is that past ecological reconstructions do not fully support either of the current options for fire management, that is, either total fire suppression or the continuity of indigenous fire practices. It is recommended to replace this dual and rigid conservation framework with a more diverse and flexible approach that considers the complex spatiotemporal heterogeneity documented in palaeoecological records.

Historia de la Amazonía: contribución de la paleoecología al debate de ocupación precolombina y sus efectos en el ecosistema

Delgado L.A. 2018. Landscape Heterogeneity and tree species diversity in a tropical forest. Development and validation of a methodological proposal. Ecosistemas 27(1): 105-115. Doi.: 10.7818/ECOS.1475 Many landscapes exist as unstable spatial-temporal mosaics where changes in patterns of biodiversity are affected by nature processes and the dynamic interaction between social and ecological factors. It is a consequence of the natural dynamics of socio-economic systems that regulate man-made tropical forests. However, a significant proportion of studies have made generalizations about the relative values of biodiversity, without taking into account the high levels of internal heterogeneity in the biophysical properties and land uses of each site. The purpose of this study is to propose and validate a methodology to delimit the heterogeneity of the landscape based on criteria that integrate the coupling of human-ecological systems such as: space-time dynamics of deforestation and fragmentation; complexity of the landscape structure; current and historical land use and biophysical variability. For this, the use of satellite images, landscape metrics, field work, documentary review and multivariate analysis were combined. The proposed methodology is intended to help guide the empirical delimitation of landscape heterogeneity as a prerequisite for the selection of similar landscapes and forest patches in studies of the diversity of tree species, in order to provide an opportunity to control the possible difficulties caused by variability in the proportion of forests, landscape configuration and successional states, in estimating its effects on forest richness and floristic composition.