Ilan Stavi

Agroforestry and biochar to offset climate change: a review

Expansion of agricultural land use has increased emission of greenhouse gases, exacerbating climatic changes. Most agricultural soils have lost a large portion of their antecedent soil organic carbon storage, becoming a source of atmospheric carbon-dioxide. In addition, agricultural soils can also be a major source of nitrous oxide and methane. Adoption of conservation agricultural practices may mitigate some of the adverse impacts of landuse intensification. However, optimal implementation of these practices is not feasible under all physical and biotic conditions. Of a wide range of conservation practices, the most promising options include agroforestry systems and soil application of biochar, which can efficiently sequester large amounts of carbon over the long-run. In addition, these practices also increase agronomic productivity and support a range of ecosystem services. Payments to farmers and land managers for sequestrating carbon and improving ecosystem services is an important strategy for promoting the adoption of such practices, aimed at mitigating climate change while decreasing environmental footprint of agriculture and sustaining food security.

Livestock grazing impact on soil wettability and erosion risk in post-fire agricultural lands

Fires in agricultural areas are common, modifying the functioning of agro-ecosystems. Such fires have been extensively studied, and reported to considerably affect soil properties. Yet, understanding of the impact of livestock grazing, or more precisely, trampling, in fire-affected lands is limited. The objective of this study was to assess the impact of low- to moderate-fire severity and livestock trampling (hoof action) on the solid soils wettability and related properties, and on soil detachment, in burnt vs. non-burnt croplands. The study was implemented by allowing livestock to access plots under high, medium, and low stocking rates in (unintentionally) burnt and non-burnt lands. Also, livestock exclusion plots were assigned as a control treatment. Results showed that fire slightly decreased the soil wettability. At the same time, water drop penetration time (WDPT) was negatively related to the stocking rate, and critical surface tension (CST) was ~13% smaller in the control plots than in the livestock-presence treatments. Also, the results showed that following burning, the resistance of soil to shear decreased by ~70%. Mass of detached material was similar in the control plots of the burnt and non-burnt plots. At the same time, it was three-, eight-, and nine-fold greater in the plots of the burnt×low, burnt×medium, and burnt×high stocking rates, respectively, than in the corresponding non-burnt ones. This study shows that livestock trampling in low- to moderate-intensity fire-affected lands increased the shearing of the ground surface layer. On the one hand, this slightly increased soil wettability. On the other hand, this impact considerably increased risks of soil erosion and land degradation.

Geodiversity decreases shrub mortality and increases ecosystem tolerance to droughts and climate change: Geodiversity increases shrub tolerance to droughts

Mass mortality of shrubs, especially the Noaea mucronata species, has been observed in the semi-arid Negev of Israel since the early twenty-first century. This has followed a long-term drought episode, and suggests a hysteresis-like effect. However, recent studies have revealed that the mortality has been varied across the region. Therefore, we assessed the depth and stoniness of the soil profile, in homogeneous and heterogeneous hillslopes. Then, we studied the volumetric moisture content during two consecutive growing seasons, in the topsoil of shrubby patches and of inter-shrub spaces in these hillslopes. The study shows that geodiversity – characterized by shallow soil, a high content of stones in the soil, and a high cover of rock fragment on the surface – reduced shrub mortality. This was attributed to the soil moisture content, which was considerably greater in the heterogeneous hillslopes, than that in the homogeneous hillslopes. It is proposed that the shallow soil halted the growth of herbaceous vegetation in the inter-shrub spaces of the heterogeneous hillslopes. Therefore, under rainstorms, this hillslope configuration results in considerable generation of overland water flow in the inter-shrub spaces. The water accumulates in the shrubby patches, allowing them to thrive, even during long-term dry episodes. In hillslopes with a deep soil layer, no stoniness in the soil profile, and no cover of rock fragments, the herbaceous vegetation is well developed, covering a considerable share of the inter-shrub spaces. This negates runoff formation and source–sink relations, limiting water availability for the shrubs, and resulting in their mass mortality. Despite no direct pastoral value for livestock, the shrubs play an important role in overall ecosystem functioning. This is due to their capacity to transect hydraulic connectivity, and negate ecosystem collapse. We propose a conceptual model for demonstrating the role played by geodiversity in alleviating drought stress in drylands. Copyright

Intentional, dual purpose of ancient wine presses as cisterns for runoff water harvesting in drylands

Rock-quarried wine presses were prevalent across the Mediterranean Basin throughout ancient times and particularly during the Late Roman and Byzantine ages. Archeological surveys have uncovered many presses across Israel. Overall, a ratio of ~5 m−1 has been recorded between treading floor area (in m2) and volume of collecting vat (in m3). A recent survey of two presses located at the transition zone between the semi-arid northern Negev, Judean Lowlands, and Southern Hebron Hills of Israel revealed a considerably smaller ratio between the treading floor and collecting vat. In addition, extensive rock exposures were located around the treading floors of the two presses. A 3D laser scanning revealed that the surrounding rock exposure formed a drainage network which flows to the treading floor. Moreover, indications for light modifications of the surrounding rock exposure were recorded for the two presses. In one of the presses, this modification was indicated by remnants of ancient plaster, which were found filling several gaps in the surrounding rock exposure. It is suggested that the purpose of the plaster was for allowing hydrological connectivity between the upslope and downslope edges of these gaps. In the second press, this modification included the chiseling of adjacent bedrock, for the purpose of, it is suggested, channeling runoff water to the treading floor. The findings suggest the intentional collection of raindrops falling on the surrounding rock exposure, together with those falling on the treading floor, which were drained as runoff into the collecting vat. The collected runoff could be used for domestic consumption in this dryland region, augmenting the provision of water for the local populations during the agricultural off-season.