DDD 2020
Environmental problems of drylands such as desertification processes, land degradation and rehabilitation, land cover and land use change, climatic change, droughts, early warning, and more, are characterized by both spatial and temporal dimensions. Therefore, remote sensing techniques, based on long-term monitoring and repetitive data, over vast expanses of unsettled regions, are applicative and powerful tools for research and implementation in these areas.
Special sessions on REMOTE SENSING - TOOLS AND IMPLICATIONS IN DRYLAND will take place as part of the conference to promote scientific exchange between experts who work on remote sensing and geoinformation issues of the above drylands-related aspects with special intention to restoration actions and processes.
Ecosystems are highly nonlinear systems that often admit multiple alternative stable states. Multiplicity of stable states in variable and disturbed environments is of high concern because of the possible occurrence of regime shifts, i.e. transitions to alternative stable states that involve loss of ecosystem function. One class of regime shifts are tipping-point phenomena, generally conceived as abrupt responses encompassing the whole ecosystem. Several ways of tipping have been studied, including a passage through a bifurcation point (B-tipping), a result of environmental fluctuations (N-tipping), or a result of fastly varying environmental conditions (R-tipping). Another class of regime shifts is gradual, domino-like processes. Such shifts are initiated by local disturbances that form spatially confined domains of an alternative state, which subsequently expand by front propagation. The purpose of this session is to present the state of art in regime-shift studies, highlighting mechanisms of regime shifts, possible early-warning signals for abrupt shifts, and means of reversing gradual shifts.
Drought-induced tree mortality has been increasing in recent decades and is expected to increase further due to global warming and desertification, especially in already dry ecosystems. In deserts, trees such as Acacia Tamarix, Populus, and Prosopis are often the only woody species, and as such, they are considered keystone species. Successful desert trees are essential locally for their associated ecosystems and functions. Globally desert trees are also important for their unique eco-and molecular physiology. Tree species that already survive under arid conditions could provide vital information on successful drought resistance. Resolving tree drought resistance strategies, specifically in semi-arid and soon to be arid environments, is a major interest of scientists and stakeholders alike, with many social, ecological and economic implications.
Bringing together scientist working on trees that grow in dry environments, this session will include talks on physiology, phenology, strategies of water use and the increasing use of eco genomics in understanding how trees might cope in a drying world, while emphasising what more needs to be studied in this field for securing the future of trees in a changing world.
Biogeochemical cycles in drylands are regulated by the interplay between biological activity during short pulses of water availability and abiotic reactions. The rewetting of dry soils represents abrupt step change in soil biophysical conditions, causing rehydration of microbes, induces changes in plant activity, and increases local nutrient availability. Emissions of trace gases (nitric and nitrous oxides, methane, and carbon dioxide; NO, N2O, CH4 , and CO2 ) from soils during wetting events are products and by-products of microbial activity. While during long dry conditions most likely produced by abiotic reactions Understanding the controls on trace gases emissions are needed since those gases play an important role in atmospheric chemistry and are pathway of nutrient losses from dryland ecosystems.
During our session we are interested in expanding our knowledge on the trace gases emissions from drylands.
Overview: The study of the subsurface is increasingly making use of electrical methods to characterize the subsurface, primarily relying on the electrical conductance of water. While this relatively simple approach is already being downscaled from geological structure to environmental and agricultural scales, there are still many knowledge gaps and opportunities to be explored. In the following we will explore these opportunities to identify current and future knowledge needs, with respect to soil water, soil-water-plant interaction, and applied use of these methods.
Session 1: Electrical properties and signals of soil systems
The study of bulk properties of soils dates to the 1940’s and even before, initially with respect to geological structure and mineral exploration, and more recently to environmental and agricultural reasons. In this session we will explore the current trends in the use of geo-electrical methods in soil and agricultural exploration, starting from electrical resistivity tomography (ERT) of agricultural fields, through induced polarization (IP) methods to explore soil chemical composition, ending with passive electrical signatures such as self-potential (SP) associated with redox reactions in the subsurface. In parallel we will also look at environmental applications of geo-electrical methods.
Session 2: Electrical signatures from the soil-plant environment
In recent years the idea of using the more advanced geo-electrical methods to understand phenomenon such as root uptake or tree trunk structure gaining momentum. But in parallel, more basic methods such as ERT is increasingly being used in smaller scales to understand the spatial patterns of water and nutrients in the soil-plant environment. This session will try to look at these processes from both the applied and the theoretical points of view.
Non-rainfall water inputs (NRWIs), i.e., a gain of water to the surface soil layer that is not caused by rainfall, comprise fog deposition, dew formation, and water vapor adsorption. In drylands, the annual amount of NRWIs sometimes exceeds that of rainfall and, in many areas, NRWIs are the sole source of liquid water during the long dry summer. NRWIs in drylands are known to significantly contribute to the water cycle. It has been suggested that they also contribute to biogeochemical dynamics through promoting microbial activity and nutrient recycling in the upper few centimeters of the soil profile. Their ecological and environmental role in dryland ecosystems is thus important, but far from being fully understood. We invite contributions on the quantification of NRWIs by measurements and modeling, and on their effect on ecosystems, both natural and agricultural.
Our current understanding of dryland forests and their contribution to the climate system is very much shaped by the groundbreaking research coming out of the Yatir research station, in central Israel. The first flux tower in a dryland forest was established in 2000 by Prof. Dan Yakir of the Weizmann Institute of Science. Dan realized the large knowledge gaps existing in biogeochemistry and ecology in arid and semi-arid regions, and the research bias towards temperate ecosystems, in Europe and North America. In 20 years of laborious research, studies at the Yatir pine forest revolutionized almost everything we know about dryland ecosystems. For example, we learnt about the large potential in carbon sequestration in the semi-arid zone; about the albedo-related warming effect and the tradeoff with the long-term cooling potential; and the role of soil in buffering periods of drought that put the trees at risk. The session will highlight some of these discoveries, while bringing topics of current discussions and open questions.
Arid and semi-arid regions globe wide are currently under an aggressive soil erosion phase, causing escalating rates of agricultural soils degradation. This process is rapidly developed into a world-wide disaster undermining food security, promoting social instability among rural communities. These destructive processes are often attributed to land mismanagement, overgrazing and recent climate change, leading to desertification of vast areas in almost all continents. However, increasing volume of field observations in desert ecosystems globe wide indicate that most of the present arable soils developed some 70,000-24,000 years BP, mainly during the Late Pleistocene glacial period (OIS 4 and 3). These soils developed in agreement with past environments and climates. As the climate shifted to form the present day Holocene climate, these soils became unstable. Therefore, the current phase of massive soil erosion is promoted by geological-scale environmental shift, initiated long before human intervention became significant in the environment. As this process was already fully active during historical times, ancient desert societies took actions to combat soil erosion and to conserve the agricultural potential of their arable lands. In light of their huge efforts for land conservation aimed to achieve food security, as documented in the archeological record, we call for better evaluation of past environments and human activities. This will allowed the improvement of modern strategies for combating desertification, based on better understanding of the deep roots of desertification processes.
This session is dedicated to papers focused on various aspects of long-term records of environmental degradation in drylands. We invite contributions from different disciplines: geology, geomorphology, soil sciences, ecology, archeology, agriculture and more which (i) introduce new data and techniques to quantify and compare components of natural aspects of desertification in various datasets; (ii) identify patterns (in time/ space) of these aspects between different dryland environments; (iii) test key assumptions and predictions of long-term desertification process aiming to improve strategists to combat present desertification processes.
Human-Induced Rapid Environmental Changes (HIREC) such as climate change and desertification, are expected to elicit a strong behavioral response in animals experiencing this change. For example, some animals may choose to move away from the disturbed area into a more suitable environment, others may choose to alter their activity times, or change their behavior (assuming they have the capacity to do so) in a way that will maximize fitness under the new conditions. Such large-scale responses can cascade through the entire food- web and alter the dynamics of an entire community or ecosystem. Moreover, because in many cases the changes caused by climate change and desertification at the habitat scale are novel and rapid in evolutionary terms and were not previously experienced by the animal, animals may either: fail to recognize the change, fail to respond, respond inappropriately, or respond in a manner that initially or seemingly is beneficial but might have long-term negative consequences. In this session we will explore behavioral and physiological responses of wildlife to climate change and desertification, discuss the consequences of these responses on the community and ecosystem scales, and discuss possible solutions.
Desert animal communities in Israel have been shaped by complex interaction between shifting climate at the edge of the Mediterranean region, overlap between different biogeographical zones, and human impact on a fragile environment. All these factors possess an appreciable historical depth that can be studied using paleozoological methods, revealing hitherto hidden dimensions of the current desert landscape and its formation. The papers in this session will focus on recent paleozoological and archaeological research in the Judean desert that relate to paleoenvironmental reconstruction, hunting, changes in settlement intensity, and shifts in mammal community composition. By bringing together the different strands of evidence, we hope to take a step towards understanding how the desert has assumed its present faunistic makeup.
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