Hydrologic History Research Articles

Human impact on African forests

Paleoecology About 2600 years ago, continuous forest in western central Africa was replaced by a mosaic of forest and savanna. It has been unclear, however, whether this was caused by climate change or expansion of the contemporary human population. Using a sedimentary record of vegetation and hydrological history from Cameroon, Garcin et al. confirm the key role of humans in this transition. Although the pollen record indicates an abrupt fragmentation of the forest, there is no signature of an accompanying hydrological change. Nor did the hydrology alter 500 years later when the landscape reverted once more to forest, indicating a negligible role for climate. Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1715336115 (2018).

Naturally occurring 32Si and low-background silicon dark matter detectors

The naturally occurring radioisotope 32Si represents a potentially limiting background in future dark matter direct-detection experiments. We investigate sources of 32Si and the vectors by which it comes to reside in silicon crystals used for fabrication of radiation detectors. We infer that the 32Si concentration in commercial single-crystal silicon is likely variable, dependent upon the specific geologic and hydrologic history of the source (or sources) of silicon “ore” and the details of the silicon-refinement process. The silicon production industry is large, highly segmented by refining step, and multifaceted in terms of final product type, from which we conclude that production of 32Si-mitigated crystals requires both targeted silicon material selection and a dedicated refinement-through-crystal-production process. We review options for source material selection, including quartz from an underground source and silicon isotopically reduced in 32Si. To quantitatively evaluate the 32Si content in silicon metal and precursor materials, we propose analytic methods employing chemical processing and radiometric measurements. Ultimately, it appears feasible to produce silicon detectors with low levels of 32Si, though significant assay method development is required to validate this claim and thereby enable a quality assurance program during an actual controlled silicon-detector production cycle.

Dry-wet cycles of kettle hole sediments leave a microbial and biogeochemical legacy

Understanding interrelations between an environment's hydrological past and its current biogeochemistry is necessary for the assessment of biogeochemical and microbial responses to changing hydrological conditions. The question how previous dry-wet events determine the contemporary microbial and biogeochemical state is addressed in this study. Therefore, sediments exposed to the atmosphere of areas with a different hydrological past within one kettle hole, i.e. (1) the predominantly inundated pond center, (2) the pond margin frequently desiccated for longer periods and (3) an intermediate zone, were incubated with the same rewetting treatment. Physicochemical and textural characteristics were related to structural microbial parameters regarding carbon and nitrogen turnover, i.e. abundance of bacteria and fungi, denitrifiers (targeted by the nirK und nirS functional genes) and nitrate ammonifiers (targeted by the nrfA functional gene). Our study reveals that, in combination with varying sediment texture, the hydrological history creates distinct microbial habitats with defined boundary conditions within the kettle hole, mainly driven by redox conditions, pH and organic matter (OM) composition. OM mineralization, as indicated by CO2-outgassing, was most efficient in exposed sediments with a less stable hydrological past. The potential for nitrogen retention via nitrate ammonification was highest in the hydrologically rather stable pond center, counteracting nitrogen loss due to denitrification. Therefore, the degree of hydrological stability is an important factor leaving a microbial and biogeochemical legacy, which determines carbon and nitrogen losses from small lentic freshwater systems in the long term run.

A novel flood defense decision support system for smart urban management based on classification and regression tree

With the development of the internet of things technology and awareness technology, all kinds of big data in the city have started to emerge. Under the background in internet plus era, using big data to effectively forecast urban flood disaster, formulating the flood control and disaster mitigation countermeasures in time, is an important subject of urban flood control and research. In this paper, a novel flood defense decision support system (NFDDSS) is proposed. Using historical hydrology data in Hangzhou, this paper proposed a comprehensive consideration of time correlation and spatial correlation of water level prediction model based on classification and regression tree. This model can predict the water level in one to six hours effectively. With this system, supervisors can get timely and effective guidance of flood control and disaster mitigation when the flood season comes.

The potential of historical hydrology in Switzerland

Abstract. Historical hydrology is based on data derived from historical written, pictorial and epigraphic documentary sources. It lies at the interface between hydrology and environmental history, using methodologies from both disciplines basically with the goal of significantly extending the instrumental measurement period with experience from the pre-instrumental past. Recently this field of research has gained increased recognition as a tool to improve current flood risk estimations when EU guidelines regulated by law the quantitative consideration of previous floods.1 Awareness to consider pre-instrumental experience in flood risk analysis seems to have risen at the level of local and federal authorities in Switzerland as well. The 2011 Fukushima catastrophe probably fostered this rethinking process, when pressure from the media, society and politics as well as the regulations of the International Atomic Energy Agency (IAEA) forced the authorities to reassess the current flood risk analysis for Swiss nuclear power plants. In 2015 a historical hydrological study was commissioned by the Federal Office for the Environment (FOEN) to assess the magnitudes of pre-instrumental Aare River flood discharges, including the most important tributaries (the Saane, Emme, Reuss and Limmat rivers). The results of the historical hydrological study serve now as the basis for the main study, EXAR (commissioned under the lead of FOEN in cooperation with the Swiss Nuclear Safety Inspectorate (ENSI), the Swiss Federal Office of Energy (SFOE), the Federal Office for Civil Protection (FOCP), and the Federal Office of Meteorology and Climatology (MeteoSwiss)), which combines historical and climatological analysis with statistical approaches and mathematical models with the goal of better understanding the hazards and possible interactions that can be caused by extreme flood events. In a second phase the catchment of the River Rhine will be targeted as well. More recently several local historical hydrological studies of smaller catchments have been requested by the responsible local authorities. The course for further publicly requested historical hydrological analysis seems thus to have been set. This paper therefore intends to discuss the potential of historical hydrological analysis, with a focus on the specific situation in Switzerland. 1Guideline 2007/60/EG of the European Parliament and Council from 23 October 2007 on assessment and management of flood risks, Official Journal of the European Union, L 288, 27–34, Brussels, 2007.

Errors in Martian paleodischarges skew interpretations of hydrologic history: Case study of the Aeolis Dorsa, Mars, with insights from the Quinn River, NV

Changes in Martian fluvial geomorphology with time-stratigraphic age, including decreases in paleochannel widths, suggest waning paleodischarges through time. Where fluvial landforms do not preserve paleochannel widths (e.g., meander deposits), other landform dimensions (i.e., radius of curvature) may be used to estimate paleodischarges. In the Aeolis Dorsa region, topographically inverted and stacked fluvial deposits – wide meander point bars overlain by thin channel fills – preserve ostensible evidence of decreasing paleodischarges through time. However, a robust paleohydraulic analysis of these distinct deposits requires knowledge of the accuracy of a terrestrial-based empirical relationship that estimates channel width from point-bar radius of curvature. We assess the accuracy of this radius-width relationship by applying it to a well-studied terrestrial analog, the Quinn River, Nevada. We find that radii of curvature from the Quinn River exceed the values predicted from the empirical relationship. These anomalously high radii are associated with greater resistance in the channel cut banks, indicating that bank strength is a confounding factor in the radius-width relationship. Some deposits in the Aeolis Dorsa include irregular meander morphologies, suggesting variably resistant channel banks and overestimates of both paleochannel widths and paleodischarges. Furthermore, the morphometry of the overlying thin channel fills suggests their widths have been eroded, such that their paleodischarges are underestimates. These overestimates and underestimates, when considered together, suggest little change in paleodischarge during the stratigraphic transition from meander deposits to channel fills. This work demonstrates the importance of terrestrial analog studies for revealing confounding factors in Martian fluvial systems and cautions against simplistic interpretations of Martian fluvial history. The discovered inaccuracies of paleodischarge estimates expose sources of uncertainty in the extant paleodischarge data that bias inferences toward waning hydrologic activity through time.

Hydrologic and geologic history of the Ozark Plateau drive phylogenomic patterns in a cave‐obligate salamander

AbstractAimHabitat specialization can constrain patterns of dispersal and drive allopatric speciation in organisms with limited dispersal ability. Herein, we tested biogeographic patterns and dispersal in a salamander with surface‐dwelling larvae and obligate cave‐dwelling adults.LocationOzark Plateau, eastern North America.MethodsA population‐level phylogeny of grotto salamanders (Eurycea spelaea complex) was reconstructed using mitochondrial (mtDNA) and multi‐locus nuclear DNA (nucDNA), primarily derived from anchored hybrid enrichment (AHE). We tested patterns of molecular variance among populations and associations between genetic distance and geographic features.ResultsDivergence time estimates suggest rapid formation of three major lineages in the Middle Miocene. Contemporary gene flow among divergent lineages appears negligible, and mtDNA suggests that most populations are isolated. There is a significant association between phylogenetic distance and palaeodrainages, contemporary drainages and sub‐plateaus of the Ozarks, as all features explain a proportion of genetic variation. However, the greatest proportion of genetic variation is explained by the combined effects of palaeodrainages and sub‐plateaus.Main conclusionsThe geologic and hydrologic history of the Ozark Plateau has influenced lineage diversification in the grotto salamander, leading to genetic isolation among populations. Limited gene flow and strong phylogeographic structure in this complex may result from the restriction of highly specialized adults to caves.

Reconstruction of the hydrologic history of a shallow Patagonian steppe lake during the past 700 yr, using chemical, geologic, and biological proxies

AbstractThe limnological conditions during the past 700 yr were reconstructed based on multiproxy analysis of a short sedimentary sequence from El Toro Lake (~40°S, 70°W). Mineralogical and geochemical features, as well as ostracods and chironomids, record hydrologic changes in the El Toro Lake basin. The ostracodLimnocythere rionegroensisvar. 1, a reliable indicator of high salinity, andEucypris fontana, a euryhaline species with preferences for moderate-salinity waters, are studied as paleolimnological proxies. The chironomid fauna indicates less saline conditions in the mid-twentieth century. These salinity changes are interpreted in terms of negative–positive hydrologic balance. High lake level and low salinity between AD 1500 and 1700 match with the wetter and colder climate during the second pulse of the Little Ice Age in northern Patagonia. High-salinity conditions occurred during the late nineteenth century, corresponding to the driest period during the past 400 yr in northeastern Patagonia. An increase in the precipitation around the middle of the twentieth century, in contrast to the records from the Chilean side of the mountains, correlates with a positive phase of the Southern Annular Mode. This is associated, in turn, with a strengthening, poleward shift of the midlatitude westerlies, possibly enhancing easterly moist air flows into central-north Patagonia.

Shallow Subsurface Evidence for Postglacial Holocene Lakes at Ivanpah Dry Lake: An Alternative Energy Development Site in the Central Mojave Desert, California, USA

Dry lakes, or playas, in the American Southwest have become important locations for alternative energy solar electric generation systems. Many of these playas have not been investigated for past environmental conditions prior to their development, causing alterations to the shallow sediment profile and altering subsurface chemical and physical data important to recent geologic and hydrologic histories of these areas. Recent studies of these features commonly have focused on surficial data with little or no subsurface geologic data to delineate wet and dry cycles of playa lakes. Many of the playa margins are covered with a surficial layer of alluvial and/or aeolian sands varying in thickness, which could interfere with correct interpretations of data gathered only on the surface material on these lands. Over the past 13,000 years Ivanpah Dry Lake has had at least three episodes of lake highstands up to ~10m in response to climate changes, based on data in this study with the oldest episode dates to ~13,000 cal yrs BP. This study has a link to other sites as many other playas are slated for energy development and could endure subsurface data alteration during site reworking and occupation, resulting in a loss in their collective historical geologic and hydrologic records if more complete studies of important sites are not carried out before developments begin.

PALEOLIMNOLOGY OF LAKE HAMOUN (E IRAN): IMPLICATION FOR PAST CLIMATE CHANGES AND POSSIBLE IMPACTS ON HUMAN SETTLEMENTS

Abstract: Environmental changes since the late deglaciation are reconstructed from the sediment of Lake Hamoun. Lake Hamoun is located at the border of Iran and Afghanistan where inflowing rivers originate from the drainage basins of SW Hindu Kush Mountains and westernmost Himalaya. The lake has experienced a complex hydrological history during the late Quaternary due to climatic changes. Geochemical, sedimentological, and paleontological proxies as well as geomorphological data were used to investigate environmental changes of the lake. The results demonstrate that since the late glacial, the basin has directly and/or indirectly received its moisture from various climatic systems. During the early Holocene, both the Indian summer monsoon (ISM) and the mid-latitude westerlies (MLW) intensified and consequently the basin received higher precipitation. This interpretation is supported by higher content of total organic matter (mean: 8.2%), finer-grained sediments with low δ18O values (mean: -3.5‰), as well ...

Has Technology Trumped Adaptive Management? A Review of Israel’s Idiosyncratic Hydrological History

Abstract Adaptive management has been championed as an effective strategy for designing water policy and its implementation. An effective water management strategy, it is argued, must be adaptive and build in an ability to change management practices based on new experiences and insights. While such an approach was not part of official nomenclature, over the years, Israel’s water managers developed a nimble orientation, responding to available data, hydrological exigencies and emerging technological opportunities. This retroactive look at Israel’s water management history through this adaptive paradigm, identifies five distinct stages: Hydro-Socialism, Wastewater Reuse, Water Storage, Conservation and Demand Reduction . Although threats to a reliable supply remain, Israel’s water managers’ ability to adapt to numerous changes enabled a dryland country to flourish, with a highly productive agricultural sector and a plentiful and clean water supply for a rapidly growing population. Israel’s desalination plants are less subject to the stochastic variability of the climate. But Israel will still have to maintain an ‘adaptive management strategy’, albeit with less reason to monitor rainfall and more to monitor geopolitical and environmental threats to a sustainable water supply.

Greater contrast in Martian hydrological history from more accurate estimates of paleodischarge

AbstractCorrelative width‐discharge relationships from the Missouri River Basin are commonly used to estimate fluvial paleodischarge on Mars. However, hydraulic geometry provides alternative, and causal, width‐discharge relationships derived from broader samples of channels, including those in reduced‐gravity (submarine) environments. Comparison of these relationships implies that causal relationships from hydraulic geometry should yield more accurate and more precise discharge estimates. Our remote analysis of a Martian‐terrestrial analog channel, combined with in situ discharge data, substantiates this implication. Applied to Martian features, these results imply that paleodischarges of interior channels of Noachian‐Hesperian (~3.7 Ga) valley networks have been underestimated by a factor of several, whereas paleodischarges for smaller fluvial deposits of the Late Hesperian‐Early Amazonian (~3.0 Ga) have been overestimated. Thus, these new paleodischarges significantly magnify the contrast between early and late Martian hydrologic activity. Width‐discharge relationships from hydraulic geometry represent validated tools for quantifying fluvial input near candidate landing sites of upcoming missions.

Amphibian dynamics in constructed ponds on a wildlife refuge: developing expected responses to hydrological restoration

Management actions are based upon predictable responses. To form expected responses to restoration actions, I estimated habitat relationships and trends (2002–2015) for four pond-breeding amphibians on a wildlife refuge (Montana, USA) where changes to restore historical hydrology to the system greatly expanded (≥8 times) the flooded area of the primary breeding site for western toads (Anaxyrus boreas). Additional restoration actions are planned for the near future, including removing ponds that provide amphibian habitat. Multi-season occupancy models based on data from 15 ponds sampled during 7 years revealed that the number of breeding subpopulations increased modestly for Columbia spotted frogs (Rana luteiventris) and was stationary for long-toed salamanders (Ambystoma macrodactylum) and Pacific treefrogs (Pseudacris regilla). For these three species, pond depth was the characteristic that was associated most frequently with occupancy or changes in colonization and extinction. In contrast, a large decrease in colonization by western toads explained the decline from eight occupied ponds in 2002 to two ponds in 2015. This decline occurred despite an increase in wetland area and the colonization of a newly created pond. These changes highlight the challenges of managing for multiple species and how management responses can be unpredictable, possibly reducing the efficacy of targeted actions.

From overexploitation to sustainable use, an overview of 160 years of water extraction in the Amsterdam dunes, the Netherlands

Dune slacks are low-lying, nutrient-poor, species-rich, inter-dunal, seasonally flooded wetlands, are amongst the most threatened habitats in the Dutch coastal dunes. Since 1853 Waternet has been extracting groundwater from the coastal dunes southwest of Haarlem to produce its drinking water. Dune slacks largely disappeared due to the desiccation caused by this water abstraction, over more than a century biodiversity declined as a consequence. Increased societal concern pushed habitat restoration high on the political agenda by the end of the 1980s. It was agreed to do what is possible to restore original dune slacks without endangering the water supply. Far reaching interventions in the dune water system were foreseen to achieve this mutual goal. To allow reliable decision making, the entire hydrological history of the drinking water production in the Amsterdam Dunes since 1853 and its ecological consequences were evaluated over a 10-year study period. The main tool was a 3D groundwater model constructed using all information gathered to date and calibrated using the long-term monitoring data available and widely extended for the purpose, to which ecological modeling was added and calibrated with the available long-term and extended vegetational inventories. These scientific tools were used to assess proposed interventions to be decided upon, which aimed at finding a new balance between groundwater extraction and nature restoration. In 1996 and 2007 large-scale measures were taken, which include filling in of recovery canals, mowing, grazing and sod-cutting to support the native plant communities of wet dune slack habitats. Results of these measures in terms of the restoration of natural hydrological conditions are shown together with the first results for the recovery of wet slacks vegetation that resulted from the combined hydrological and ecological restoration measures that were taken since 1995.

The Holocene history of Lop Nur and its palaeoclimate implications

Abstract The Holocene hydrological history of Lop Nur in northwestern China's Tarim Basin and its response to climate conditions are inferred from a relatively well-dated multi-proxy record including grain-size, pollen and spores, and soluble salt data. A dated pit section (YKD0301) with a depth of 570 cm in the center of the dry Lop Nur Basin was investigated. The sediments contain a total of twenty fining-upward cycles as a result of strong discharge from the catchment to the lake during relatively wet conditions. The fluvial sediments were probably widely dispersed by wind-driven waves and currents in the large and shallow basin of Lop Nur. Higher runoff and dilution of lake waters are also indicated by lower contents of soluble salt in the sediments and recorded ostracod shells of brackish and oligohaline to freshwater species. In contrast, sediment sections with smaller mean grain size and fewer flood layers are dominated by aeolian sediments which were accumulated during drier periods. Ostracod shells are mostly lacking from these sections, suggesting a higher salinity in the lake. Lop Nur experienced six stages during the last 9 ka. Relatively wet conditions existed between 9.0–8.9, 8.7–5.1 and 2.4–1.8 ka, with periods of increased aridity in between and after 1.8 ka. The lowest salinity was recorded between 8.7 and 5.1 ka which represents the wettest phase during the last 9 ka and probably the regional Holocene Optimum. Relatively wet climate conditions between 2.4 and 1.8 ka and dry conditions afterwards possibly first fostered and later on caused the devastation of the ancient Loulan Kingdom in the region. The uppermost sediments of the section represent a massive salt crust formed during the final desiccation of the lake in the last century. The effective moisture change pattern of the Lop Nur region is roughly consistent with synthesized Holocene moisture records for western China dominated by the westerlies.

A century-scale, human-induced ecohydrological evolution of wetlands of two large river basins in Australia (Murray) and China (Yangtze)

Abstract. Recently, the provision of food and water resources of two of the world's largest river basins, the Murray and the Yangtze, has been significantly altered through widespread landscape modification. Long-term sedimentary archives, dating back for some centuries from wetlands of these river basins, reveal that rapid, basin-wide development has reduced the resilience of biological communities, resulting in considerable decline in ecosystem services, including water quality. Large-scale human disturbance to river systems, due to river regulation during the mid-20th century, has transformed the hydrology of rivers and wetlands, causing widespread modification of aquatic biological communities. Changes to cladoceran zooplankton (water fleas) were used to assess the historical hydrology and ecology of three Murray and Yangtze river wetlands over the past century. Subfossil assemblages of cladocerans retrieved from sediment cores (94, 45, and 65 cm) of three wetlands: Kings Billabong (Murray), Zhangdu, and Liangzi lakes (Yangtze), showed strong responses to hydrological changes in the river after the mid-20th century. In particular, river regulation caused by construction of dams and weirs together with river channel modifications, has led to significant hydrological alterations. These hydrological disturbances were either (1) a prolonged inundation of wetlands or (2) reduced river flow, both of which caused variability in wetland depth. Inevitably, these phenomena have subsequently transformed the natural wetland habitats, leading to a switch in cladoceran assemblages to species preferring poor water quality, and in some cases to eutrophication. The quantitative and qualitative decline of wetland water conditions is indicative of reduced ecosystem services, and requires effective restoration measures for both river basins which have been impacted by recent socioeconomic development and climate change.

Common Denominators of Swainson's Warbler Breeding Habitat in Bottomland Hardwood Forest in the White River Watershed in Southeastern Arkansas

Abstract The most intensively studied breeding population of Limnothlypis swainsonii (Swainson's Warbler) is in the White River watershed of southeastern Arkansas. However, because vegetation sampling protocols employed at this site have been significantly different from those used elsewhere, it has been difficult for land managers to reconcile datasets across the species' range in order to construct consensus quantitative benchmarks for optimal breeding habitat in bottomland hardwoods. We used a standardized sampling protocol to compare the physiognomic and floristic characteristics of breeding territories at 2 sites in the White River watershed with comparable data from other populations in Arkansas, Mississippi, Louisiana, Florida, and Virginia. Breeding territories in the combined dataset for this rare migratory species varied substantially in successional stage, floristic diversity, hydrology, and management history. Visual screening provided by understory thickets of saplings, vine tangles, and shru...

High-end climate change impact on European runoff and low flows – exploring the effects of forcing biases

Abstract. Climate models project a much more substantial warming than the 2 °C target under the more probable emission scenarios, making higher-end scenarios increasingly plausible. Freshwater availability under such conditions is a key issue of concern. In this study, an ensemble of Euro-CORDEX projections under RCP8.5 is used to assess the mean and low hydrological states under +4 °C of global warming for the European region. Five major European catchments were analysed in terms of future drought climatology and the impact of +2 °C versus +4 °C global warming was investigated. The effect of bias correction of the climate model outputs and the observations used for this adjustment was also quantified. Projections indicate an intensification of the water cycle at higher levels of warming. Even for areas where the average state may not considerably be affected, low flows are expected to reduce, leading to changes in the number of dry days and thus drought climatology. The identified increasing or decreasing runoff trends are substantially intensified when moving from the +2 to the +4° of global warming. Bias correction resulted in an improved representation of the historical hydrology. It is also found that the selection of the observational data set for the application of the bias correction has an impact on the projected signal that could be of the same order of magnitude to the selection of the Global Climate Model (GCM).

Comparison of speleothem fabrics and microstratigraphic stacking patterns in calcite stalagmites as indicators of paleoenvironmental change

In the necessary task of obtaining high-resolution paleoclimate series from speleothems, the characterization of their internal microstratigraphy is a useful tool for: a) improving geochronology, and b) reaching a more complete knowledge of the speleothem formation and evolution through time and thus obtaining additional paleoenvironmental information. However, the development of standardized methodologies for microstratigraphic characterization is a pending task. In this paper, two different approaches allow construction of microstratigraphic logs for three stalagmites retrieved from two different caves. The logs correspond to vertical variations in speleothem fabrics and in microstratigraphic stacking patterns. The “fabrics logs” essentially provide information about the drip rate (sometimes used as a precipitation proxy) and the regularity or irregularity of each drip in the short-term. The “microstratigraphic stacking patterns logs” can be interpreted to obtain information about the changes in drip rates in the mid- and long-term. The results show a broad correlation between both kinds of logs that supports their validity as paleoenvironmental proxies. Fabrics formed under relatively constant and regular drips (columnar compact, open and elongated) usually constitute aggradational or progradational microstratigraphic stacking patterns. On the other hand, retractional stacking patterns are usually related with fabrics precipitated under more irregular drips (dendritic and columnar microcrystalline). However, this relation is not rigid and the information obtained from the logs is not equivalent, but complementary. The combination of both logs allows reconstruction of the hydrological history for each drip site. As all the obtained information derives directly from the drip conditions, drip effects result to be very important and can, in some cases, overwhelm the paleoclimate information recorded in each stalagmite.

Carbon and nutrient cycling in kettle hole sediments depending on hydrological dynamics: a review

Kettle holes as a specific group of isolated, small lentic freshwater systems (LFS) often are (i) hot spots of biogeochemical cycling and (ii) exposed to frequent sediment desiccation and rewetting. Their ecological functioning is greatly determined by immanent carbon and nutrient transformations. The objective of this review is to elucidate effects of a changing hydrological regime (i.e., dry–wet cycles) on carbon and nutrient cycling in kettle hole sediments. Generally, dry–wet cycles have the potential to increase C and N losses as well as P availability. However, their duration and frequency are important controlling factors regarding direction and intensity of biogeochemical and microbiological responses. To evaluate drought impacts on sediment carbon and nutrient cycling in detail requires the context of the LFS hydrological history. For example, frequent drought events induce physiological adaptation of exposed microbial communities and thus flatten metabolic responses, whereas rare events provoke unbalanced, strong microbial responses. Different potential of microbial resilience to drought stress can irretrievably change microbial communities and functional guilds, gearing cascades of functional responses. Hence, dry–wet events can shift the biogeochemical cycling of organic matter and nutrients to a new equilibrium, thus affecting the dynamic balance between carbon burial and mineralization in kettle holes.