Deforestation in the Dominican Republic: a village-level view, 1997, Brothers Ts,

Deforestation is still rapid in some parts of the Caribbean, though it has attracted much less attention than deforestation in mainland Latin America. This paper examines the history and causes of the recent rapid deforestation of a lowland karst region of the Dominican Republic in the light of models derived from studies in Central America and the Amazon. Investigation was limited to the vicinity of a single village (Los Limones). Information was drawn from interviews, questionnaires and ground reconnaissance, in addition to archival information and aerial photographs. Deforestation at Los Limones involved many of the same elements seen in mainland deforestation, including construction of access roads, spontaneous agricultural colonization, and pasture conversion, but it followed no single mainland model. Logging, not normally emphasized as a cause of Latin American deforestation, played an important role in opening up the forest to agricultural settlement. Pasture conversion was not a matter of aggregation of large ranches by wealthy absentee landowners, as in the Amazon, but apparently a local response to the economic and ecological advantages of cattle raising. Government actions strongly influenced deforestation, but not via colonization schemes or economic subsidies for cattle ranching; the rhythm of deforestation at Los Limones was tied to the monopolistic practices of the dictatorship of Rafael Trujillo and the social disorganization following his assassination. The national government in fact bears the primary responsibility for deforestation of Los Haitises, a conclusion that contradicts the government's own suggestion that the destruction was largely carried out by poor farmers. Prospects for rehabilitation of the deforested area are gloomy because of the extent of ecological damage and the continued adversarial relationship between the government and the rural population

Palaeoenvironments in semi-arid northeastern Brazil inferred from high precision mass spectrometric speleothem and travertine ages and the dynamics of South American rainforests, 2004, Auler A. S. , Wang X. , Edwards R. L. , Cheng H. , Cristalli P. S. , Smart P. L. , Richards D. A.

Understanding past environmental changes in tropical rainforests is extremely important in order to assess the response of such environments to present and future climatic changes and understand causes and the present patterns of biodiversity.
Earlier hypothesis on the origin of biodiversity have stressed the role of past climatic changes in promoting speciation. According to the “refuge hypothesis” (Haffer, 1982), dry periods could have led to forest fragmentation, isolating more humid forested zones (called refuges) within an environment largely dominated by savannas. The refuge hypothesis does not assign timescales for rainforest fragmentation, although recent studies have suggested that speciation could have occurred over timescales of millions of years (Knapp and Mallet, 2003). Although the focus of heavy criticism (Colinvaux, et a., 2000), the refuge hypothesis has generated a large amount of research. In general, pollen studies (Colinvaux, et a., 1996, Haberle and Maslin, 1999) tend to support a continuous forest cover throughout late Quaternary climatic shifts, although large variations in rainfall have also been demonstrated by other pollen and isotopic studies (van der Hammen and Absy, 1994; Maslin and Burns, 2000).
Amazon and Atlantic rainforests are the two major forested zones in South America. Amazon rainforest, the largest rainforest in the world, comprise a total original area of 4.1 million km2 and is renowned for hosting the large biodiversity in the world (30% of all the world’s known plant and animal species). Atlantic rainforest, also a biodiversity hotspot, occurs along the coast and has been subjected to heavy deforestation since European arrival. Nowadays only c. 7% of its original forested area of 1.3 million km2 remains. These two rainforests are separated by drought-prone semi-arid northeastern (NE) Brazil. Our study does not address the refuge hypothesis directly although it sheds new light on the dynamics of forest expansion in the past as well as indicates alternative ways of promoting speciation. It has long been hypothesized, due to botanical (Mori, 1989; Andrade-Lima, 1982) and faunistic (Costa, 2003) similarities, that the Amazon and Atlantic rainforests were once linked in the past. Although numerous connecting routes have been postulated (Bigarella, et al, 1975; Por, 1992; De Oliveira, et al, 1999), the timing of forest expansion and their possible recurrence have remained elusive.
The study area lies in the driest portion of NE Brazil “dry corridor”, close to the village of Laje dos Negros, northern state of Bahia. Mean annual precipitation is around 480 mm and potential evapotranspiration is in excess of 1,400 mm/year (Fig.1). Present vegetation comprises a low arbustive scrubland known locally as caatinga. The area contains a well-developed underground karst (Auler and Smart, 2003) with abundant secondary calcite precipitates, both underground (speleothems) and on the surface (travertines).

Land use change and soil nutrient transformations in the Los Haitises region of the Dominican Republic, 2005, Templer P. H. , Groffman P. M. , Flecker A. S. , Power A. G. ,

We characterized soil cation, carbon (C) and nitrogen (N) transformations within a variety of land use types in the karst region of the northeastern Dominican Republic. We examined a range of soil pools and fluxes during the wet and dry seasons in undisturbed forest, regenerating forest and active agricultural sites within and directly adjacent to Los Haitises National Park. Soil moisture, soil organic matter (SOM), soil cations, leaf litter C and pH were significantly greater in regenerating forest sites than agricultural sites, while bulk density was greater in active agricultural sites. Potential denitrification, microbial biomass C and N, and microbial respiration g(-1) dry soil were significantly greater in the regenerating forest sites than in the active agricultural sites. However, net mineralization, net nitrification, microbial biomass C, and microbial respiration were all significantly greater in the agricultural sites on g(-1) SOM basis. These results suggest that land use is indirectly affecting microbial activity and C storage through its effect on SOM quality and quantity. While agriculture can significantly decrease soil fertility, it appears that the trend can begin to rapidly reverse with the abandonment of agriculture and the subsequent regeneration of forest. The regenerating forest soils were taken out of agricultural use only 5-7 years before our study and already have soil properties and processes similar to an undisturbed old forest site. Compared to undisturbed mogote forest sites, regenerating sites had smaller amounts of SOM and microbial biomass N, as well as lower rates of microbial respiration, mineralization and nitrification g(-1) SOM. Initial recovery of soil pools and processes appeared to be rapid, but additional research must be done to address the long-term rate of recovery in these forest stands. (C) 2004, Elsevier Ltd. All rights reserved

Hypogene Speleogenesis: Hydrogeological and Morphogenetic Perspective., 2007, Klimchouk A. B.

This book provides an overview of the principal environments, main processes and manifestations of hypogenic speleogenesis, and refines the relevant conceptual framework. It consolidates the notion of hypogenic karst as one of the two major types of karst systems (the other being epigenetic karst). Karst is viewed in the context of regional groundwater flow systems, which provide the systematic transport and distribution mechanisms needed to produce and maintain the disequilibrium conditions necessary for speleogenesis. Hypogenic and epigenic karst systems are regularly associated with different types, patterns and segments of flow systems, characterized by distinct hydrokinetic, chemical and thermal conditions. Epigenic karst systems are predominantly local systems, and/or parts of recharge segments of intermediate and regional systems. Hypogenic karst is associated with discharge regimes of regional or intermediate flow systems.

Various styles of hypogenic caves that were previously considered unrelated, specific either to certain lithologies or chemical mechanisms are shown to share common hydrogeologic genetic backgrounds. In contrast to the currently predominant view of hypogenic speleogenesis as a specific geochemical phenomenon, the broad hydrogeological approach is adopted in this book. Hypogenic speleogenesis is defined with reference to the source of fluid recharge to the cave-forming zone, and type of flow system. It is shown that confined settings are the principal hydrogeologic environment for hypogenic speleogenesis. However, there is a general evolutionary trend for hypogenic karst systems to lose their confinement due to uplift and denudation and due to their own expansion. Confined hypogenic caves may experience substantial modification or be partially or largely overprinted under subsequent unconfined (vadose) stages, either by epigenic processes or continuing unconfined hypogenic processes, especially when H2S dissolution mechanisms are involved.

Hypogenic confined systems evolve to facilitate cross-formational hydraulic communication between common aquifers, or between laterally transmissive beds in heterogeneous soluble formations, across cave-forming zones. The latter originally represented low-permeability, separating units supporting vertical rather than lateral flow. Layered heterogeneity in permeability and breaches in connectivity between different fracture porosity structures across soluble formations are important controls over the spatial organization of evolving ascending hypogenic cave systems. Transverse hydraulic communication across lithological and porosity system boundaries, which commonly coincide with major contrasts in water chemistry, gas composition and temperature, is potent enough to drive various disequilibrium and reaction dissolution mechanisms. Hypogenic speleogenesis may operate in both carbonates and evaporites, but also in some clastic rocks with soluble cement. Its main characteristic is the lack of genetic relationship with groundwater recharge from the overlying or immediately adjacent surface. It may not be manifest at the surface at all, receiving some expression only during later stages of uplift and denudation. In many instances, hypogenic speleogenesis is largely climate- independent.

There is a specific hydrogeologic mechanism inherent in hypogenic transverse speleogenesis (restricted input/output) that suppresses the positive flow-dissolution feedback and speleogenetic competition in an initial flowpath network. This accounts for the development of more pervasive channeling and maze patterns in confined settings where appropriate structural prerequisites exist. As forced-flow regimes in confined settings are commonly sluggish, buoyancy dissolution driven by either solute or thermal density differences is important in hypogenic speleogenesis.

In identifying hypogenic caves, the primary criteria are morphological (patterns and meso-morphology) and hydrogeological (hydrostratigraphic position and recharge/flow pattern viewed from the perspective of the evolution of a regional groundwater flow system). Elementary patterns typical for hypogenic caves are network mazes, spongework mazes, irregular chambers and isolated passages or crude passage clusters. They often combine to form composite patterns and complex 3- D structures. Hypogenic caves are identified in various geological and tectonic settings, and in various lithologies. Despite these variations, resultant caves demonstrate a remarkable similarity in cave patterns and meso-morphology, which strongly suggests that the hydrogeologic settings were broadly identical in their formation. Presence of the characteristic morphologic suites of rising flow with buoyancy components is one of the most decisive criteria for identifying hypogenic speleogenesis, which is much more widespread than was previously presumed. Hypogenic caves include many of the largest, by integrated length and by volume, documented caves in the world.

The refined conceptual framework of hypogenic speleogenesis has broad implications in applied fields and promises to create a greater demand for karst and cave expertise by practicing hydrogeology, geological engineering, economic geology, and mineral resource industries. Any generalization of the hydrogeology of karst aquifers, as well as approaches to practical issues and resource prospecting in karst regions, should take into account the different nature and characteristics of hypogenic and epigenic karst systems. Hydraulic properties of karst aquifers, evolved in response to hypogenic speleogenesis, are characteristically different from epigenic karst aquifers. In hypogenic systems, cave porosity is roughly an order of magnitude greater, and areal coverage of caves is five times greater than in epigenic karst systems. Hypogenic speleogenesis commonly results in more isotropic conduit permeability pervasively distributed within highly karstified areas measuring up to several square kilometers. Although being vertically and laterally integrated throughout conduit clusters, hypogenic systems, however, do not transmit flow laterally for considerable distances. Hypogenic speleogenesis can affect regional subsurface fluid flow by greatly enhancing initially available cross- formational permeability structures, providing higher local vertical hydraulic connections between lateral stratiform pathways for groundwater flow, and creating discharge segments of flow systems, the areas of low- fluid potential recognizable at the regional scale. Discharge of artesian karst springs, which are modern outlets of hypogenic karst systems, is often very large and steady, being moderated by the high karstic storage developed in the karstified zones and by the hydraulic capacity of an entire artesian system. Hypogenic speleogenesis plays an important role in conditioning related processes such as hydrothermal mineralization, diagenesis, and hydrocarbon transport and entrapment.

An appreciation of the wide occurrence of hypogenic karst systems, marked specifics in their origin, development and characteristics, and their scientific and practical importance, calls for revisiting and expanding the current predominantly epigenic paradigm of karst and cave science.

Dokumentation von zwei Quarzithöhlen am Roraima Tepui (Brasilien, Guyana) , 2011, Plan L. , Hölzel M. , Auler A.

The Gran Sabana extends over the area between the Amazonas and Orinoco River in the northern part of South America. There about hundred table mountains (locally named Tepuis) are rising above the wet savannah plain. One of these, the Roraima Tepui, is situated at the triple border junction of the states of Brazil, Guyana and Venezuela. The plateau is built up of sandstones and quartzites of palaeoproterozoic age (c. 1.9 Billion years). Several caves which have mainly developed due to mechanical erosion of not or just partly lithified sandstone layers have been explored. The aim of a Brazilian Austrian expedition in November 2010 was to visit caves in the southern part of the Roraima Tepui and search for new caves in the less accessible northern part. The Cueva Ojos de Cristal (or Sistema Roraima Sur) was visited. With a mapped length of 16.1 km it is the biggest quartzite cave known in the world. Two caves were mapped, the Hotel Coati and the Lake Gladys Cave, which are the highest lying documented caves of Guyana and Brazil respectively. The Hotel Coati is situated in the north of the Tepui and is a cave often used as a bivouac. It is a shaft, acting as ponor, which is accessible through galleries aligned at rectangularly arranged fissures. North of that cave, in the Guyanese part, the single lake on the plateau, the Lake Gladys is situated at 2665 m a.s.l. There, the Lake Gladys Cave with a total length of 68 m is draining the lake. The entrance lies behind a boulder fall and water disappears into a sump. At the Roraima Tepui there are other not docu - mented objects so far, as the shaft ponor El Fosso (The Pit). Even though no major systems were found during this short expe - dition, the potential of finding further caves in the northern part seems still good.

Evaporite karst in three interior layered deposits in Iani Chaos, Mars, 2015,

This paper describe the karst landforms observed in three interior layered deposits located in Iani Chaos, a large depression located in the equatorial region of Mars, characterised by spectral signatures of monohydrated and polyhydrated sulfate such as kieserite and gypsum. A morphological and morphometric survey of the ILD surface morphologies through an integrated analysis of the available Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) highlighted the presence of depressions of various shapes and sizes. These Martian landforms interpreted as doline of polygenetic origin resemble similarly karst landforms that can be observed both in different karst terrains on Earth and in other regions of Mars. The karst landforms observed suggest a climatic change and the presence of liquid water, probably due to ice melting, in the late Amazonian age.