Precipitous Fall Research Articles

Elevation‐dependent precipitation response to El Niño‐Southern oscillation revealed in headwater basins of the US central Rocky Mountains

AbstractWe used nonparametric analyses of gridded precipitation data from the Parameter‐Elevation Relationships on Independent Slopes Model (PRISM) to examine teleconnections between the El Niño‐Southern Oscillation (ENSO) and elevation‐related precipitation variability from 1950 to 2016 over the Snake‐Salt, Wind‐Bighorn, Green, and Platte basins, which span the North American continental divide. Our analyses parse data into three‐month‐long meteorological seasons and use the Japan Meteorological Agency (JMA) index to examine seasonal precipitation during El Niño and La Niña years. The results reveal statistically significant elevation‐related variability in seasonal precipitation response: ENSO‐related differences in precipitation were most widespread during winter, with below‐normal precipitation during El Niño and above‐normal precipitation during La Niña. These connections were particularly clear, with p‐values <.01, in analyses focused on high elevations, where most precipitation falls. Hence, the most apparent ENSO‐related impacts on precipitation were observed during months and at elevations that are crucial to snowpack growth. In addition, our analyses of low elevations of the Platte Basin reveal above‐normal spring and fall precipitation during El Niño and below‐normal fall precipitation during La Niña. Comparison of PRISM and North American Regional Reanalysis (NARR) datasets for the period of overlap (1979–2016) suggest that the elevational response is robust. Together, our findings expand the scope of documented ENSO teleconnections in western North America and underscore the importance of parsing precipitation response over temporal and spatial scales that are relevant to the timing and location of dominant precipitation inputs in the topographically diverse western United States.

Step Increase in Eastern U.S. Precipitation Linked to Indian Ocean Warming

AbstractA step increase in annual precipitation over the eastern United States in the early 1970s commenced five decades of invigorated hydroclimate, with ongoing impacts on streamflow and water resources. Despite its far‐reaching impacts, the dynamical origin of this change is unknown. Here analyses of a century of atmospheric and oceanic data trace the dynamics to changes in the Indian Ocean. Increases in fall precipitation contribute most strongly to the step increase, and the associated mechanism is emergence of a pan‐Pacific atmospheric wave emanating from deep convection over the warming Indian Ocean. Documentation of this fall teleconnection draws attention to projected anthropogenic increases in tropical oceanic heat content and their potential impacts on hydroclimate of the midlatitudes.

United States

Much of the Financial Sector Assessment Program (FSAP) work was conducted prior to the COVID-19 pandemic. The lockdown of the economy has led to a massive growth shock. Following the precipitous fall, risk asset prices have rebounded, and financial conditions eased. The vulnerability analysis has been updated and largely captures this shock. Recommendations on strengthening policy and institutional frameworks remain pertinent. The approach to financial regulation and supervision was risk-focused given the high degree of compliance against international standards assessed during the 2015 FSAP. 

Climatic Fluctuations in Dry Steppes and Their Role in the Demutation Process

The water availability in dry steppes during various active growing seasons is analyzed for the first time. Climatic fluctuations are examined, and their specific features are determined. Contrary to the popular opinion that the maximum precipitation in the steppe zone occurs during the summer period and that this is a distinctive feature of the steppe zone that is applicable to all its subzones, analysis of dry steppes in the Lower Volga Region over a period of 64 years shows that the maximum precipitation is attributed to summer only in 39% of the studied years, to spring in 27% of the years, and to fall in the remaining 34% of the years. Analysis of the water availability time series produced for various seasons covering more than a semicentennial period shows a general trend: the summer precipitation is decreasing, while the precipitation in spring and fall is increasing. The application of the exponential smoothing method to the time series and regression analysis indicate a growth dynamics of water availability in the spring period after the watershed years of 1989 and 1990 (the data validity is confirmed by the Student’s t-test; the probability value is 0.0005) amid a decrease in the fall precipitation (the probability value is 0.01). These trends characterize the demutation processes ongoing in the secondary fallow phytocoenoses, which are manifested by the predomination of loose- and firm-bunch grasses: water availability in late spring (May) and early summer (June) plays a critical role in the generative process of these plants. In total, 28 species belonging to the Poaceae family have been identified in the studied phytocoenoses; their share in the total species richness is 24.5%. The water availability patterns indicate aridization of the climate in dry steppes. The presence of ephemeral and ephemeroid plants in the communities additionally confirms this: the spring precipitation is their key life support factor. The ephemeral and ephemeroid species constitute 8% of the total species richness.

Formation of Soil Chemical Environment in Coastal Pinus thunbergii Parlatore Forest in Southwestern Japan

We investigated the chemical properties of precipitation and litter fall, and their effects on soil chemistry, in a coastal forest consisting of pure Pinus thunbergii stands, Pinus-dominated stands with broadleaf trees in the understory, mixed stands of Pinus and evergreen broadleaf trees, and evergreen broadleaf stands. Throughfall pH in the pure Pinus stand was significantly lower than those in the other three stands, and the soil in the pure Pinus stand was determined to be acidic (pH = ca. 5.0). In Pinus-dominated stands with broadleaf species in the understory, precipitation had a neutralizing effect in the foliage of broadleaf species in the understory of the Pinus stand and the pH levels of their surface mineral soil were significantly higher than those in the pure Pinus stand. The soil pH level was low in the pure Pinus stand, and then increased with an increasing dominance of broadleaf species in the understory. The soil pH was lowered with an increasing dominance of broadleaf species in the canopy layer. A litter layer consisting of decomposable litter of broadleaf species with low C/N ratio acidified precipitation that was deposited as throughfall on the litter surface. Nitrates in the soil-extracted water from the mixed stand and from the evergreen broadleaf stand were significantly higher than the nitrates of stands with high dominance of Pinus. Higher nitrogen flux in the mixed stand and in the evergreen broadleaf stand, as well as a lower C/N ratio of the litter of broadleaf species, accelerated nitrogen accumulation in the soil in stands with high broadleaf species dominance in the canopy compared to the Pinus-dominated stand. Thus, the accumulation of nitrogen in the soil through litter fall is a possible factor that promotes succession from Pinus stands to evergreen broadleaf stands.

Samoa

This paper discusses Samoa’s Request for Disbursement Under the Rapid Credit Facility. Samoa has shown resilience to multiple past economic shocks, underpinned by the authorities’ strong commitment to support the economy, and financial assistance provided by the international community. The global coronavirus disease 2019 pandemic has exacerbated the impact of the measles outbreak of late-2019 on Samoa’s economy. The border closure, combined with a sudden stop of tourist arrivals and decline in remittances, has led to a precipitous fall in two vital sources of foreign earnings and resulted in an urgent balance of payments need. Beyond the immediate response, the authorities will continue to implement structural reforms, with policies appropriately balanced between safeguarding debt sustainability and promoting economic growth. They also need to continue their efforts to enhance spending efficiency, strengthen social protection programs and safety nets, further improve tax administration, strengthen public financial management, and safeguard financial stability. Addressing vulnerability to climate change remains a key medium-term challenge to create a fiscal buffer.

The American Mind Is Dead, Long Live the American Mind

The story of American intellectual history has a mythic quality: a slow beginning, a rise to great heights, and a precipitous fall. Early in the twentieth century, the study of American history and literature grew in American colleges and universities, after many years of teaching European ideas in lieu of an American canon. Then, from a literature department arose Vernon Louis Parrington and from an American studies department Perry Miller—their writing compelling, learned, and suggestive. Their books and their students established the new field of American intellectual history, drawing readers far and wide into their interpretations of how not just individuals but entire peoples had “minds” that hovered above society, transmitting ideas from the past and changing with the times. Miller pioneered this approach with The New England Mind: The Seventeenth Century, which became required reading for historians for decades—and ever since, for Puritan specialists. Miller used the published sermons of the most prominent theologians—and their European sources—to describe a crisis in Puritan thought over the character of their faith and therefore purpose. The concept of the regional or national mind became so popular that when Parrington's student Henry Steele Commager published The American Mind at mid-century, the book met a hungry public and went into eight printings in seven years.

The ethics of United Nations sanctions on North Korea: effectiveness, necessity and proportionality

ABSTRACTIf the legal foundation and political consensus underpinning United Nations resolutions suggests that North Korea's denuclearization can be understood as a just cause, were the means used by the United Nations also just? This essay draws on jus in bello analogies to analyze UN sanctions via standard ethical criteria of effectiveness, necessity and proportionality. It shows that UN sanctions did not fulfill the effectiveness criterion as they were never likely to result in the denuclearization of North Korea. The necessity condition was strained as the alternative instrument of diplomacy was not utilized in a sustained manner. Expanded sanctions from 2016 did not distinguish between the military and civilian economies. Stringent energy sanctions introduced in 2017 contributed significantly to a precipitous fall in agricultural production in 2018 such that the country could no longer feed about a third of the 25 million population. Post-2016 UN sanctions did not meet the proportionality criterion as they jeopardized the food security of millions of innocents. The DPRK government has primary responsibility for the welfare of its citizens but this assumption does not abrogate the responsibilities of others. Broad UN sanctions on the DPRK are neither effective nor proportionate and are, therefore, unethical.

Oxygen availability and mitochondrial respiration: Impact on permeabilized and isolated in vitro preparations

Skeletal muscle mitochondrial respiration assessed in vitro is typically performed in hyperoxia utilizing either permeabilized fibers or isolated mitochondria preparations. However, although it remains to be comprehensively assessed, growing evidence supports that mitochondrial respiration is likely influenced by oxygen availability and this may have a different impact in these two preparations. Therefore, we tested the hypotheses that hyperoxia would 1) increase peak mitochondrial respiration (Vmax) in permeabilized fibers, but not in isolated mitochondria, without altering submaximal respiration in either preparation, and 2) not alter the mitochondrial critical partial pressure of O2 (PO2) in either preparation.MethodsFiber permeablization and mitochondrial isolation techniques were performed on muscle samples, and mitochondrial respiration was measured by high‐resolution respirometery (O2k) in both moderate (MOD, 100–125 mmHg) and high (HIGH, 250–300 mmHg) initial PO2 conditions, for both preparations. Respiration and chamber PO2 were continuously measured until the cessation of respiration, allowing for the assessment of Vmax, submaximal respiration, and critical PO2.ResultsVmax was significantly greater in HIGH than MOD with permeabilized fibers (~57%, p<0.05, effect size (d) =2.8), but was not significantly different between conditions with isolated mitochondria (~1%, p>0.05, d=0.07). Submaximal respiration was not significantly different between HIGH and MOD conditions with permeabilized fibers (~4%, p>0.05, d=0.1), but was significantly lower in HIGH with isolated mitochondria (~33%, p<0.05, d=2.4). The critical PO2 with isolated mitochondria was lower in HIGH (0.48±0.25 mmHg) compared to MOD (0.97±0.08 mmHg, p=0.1, d=1.5). In contrast, in the permeabilized fibers, in both MOD and HIGH, there was no precipitous fall in respiration with falling oxygen availability, and respiration ceased despite 3–10 mmHg PO2 remaining in the chamber.ConclusionThese findings reveal differing effects of oxygen availability on mitochondrial respiration, dependent upon the mitochondrial preparation, which need to be considered when making such measurements.Support or Funding InformationNational Heart, Lung, and Blood Institute at the National Institute of Health (PO1 HL1091830) and Veterans Administration Rehabilitation Research and Development Service (E6910‐R, E1697‐R, E1433‐P, E9275‐L and E1572‐P)

SUN-174 EFFICACY AND SAFETY OF INTRAVENOUS LABETALOL FOR HYPERTENSIVE CRISIS IN CHILDREN

Hypertensive crisis is uncommon in children. American Association of Pediatrics acknowledges the lack of robust evidence-based management guidelines for the same. Most data on the choice of drugs is extrapolated from adults and small case series in children. The objectives of this study were to determine the efficacy and safety of IV labetalol as a first-line agent or an add on drug compared to IV nitroprusside/nitroglycerine in the management of hypertensive crisis in children. A retrospective chart review of 56 consecutive children (age 1 month to ≤ 12 years) with hypertensive crisis admitted to pediatric intensive care unit (PICU) during a 10-year period (July 2009- 2019) was done. Data with respect to baseline demographics, clinical presentation, etiological workup, treatment details, and blood pressure (BP) trends were recorded. The choice of antihypertensive agents was left to the clinician's discretion. The proportion of patients, attaining target BP (95th percentile) in >12 to ≤ 48 hours after admission was taken as primary endpoint. The secondary endpoints were PICU needs, morbidity, and mortality. The median age of the children was 7 years (range 1-12). Hypertensive crisis comprised < 1 % of PICU admissions. Most crisis presented as hypertensive emergency (89%) and had renal etiology as the leading cause (61%). The proportion of children attaining the primary endpoint was significantly more in the group receiving labetalol (n=23) as compared to those not receiving labetalol (n=33) (62% vs. 29%, p < 0.0001). The proportion of children having precipitous fall in BP before 12 hours, leading to hypotension was similar in both treatment groups (13% vs 15%). The PICU needs for ventilation (0% vs 27%, p < 0.0001), renal replacement therapy (0% vs 9%, p = 0.003) and raised intracranial pressure (ICP) (0% vs 9%, p = 0.003) were significantly less in the labetalol group. The central nervous system (CNS) morbidity was also significantly reduced in the labetalol group (41% vs. 9%, p < 0.0001). One child compared to three died in the labetalol and non-labetalol group respectively (4.3% vs. 9%, p = 0.2). The data were also analyzed for practice variations between two periods of five years each (2009-2013 and 2014-2019). There latter cohort showed significantly more use of labetalol (74% for 2014-2019 vs. 26% for 2009-2013, p < 0.0001). Labetalol, when used alone or as an add on drug was more efficacious than IV nitroprusside/nitroglycerine in attaining the primary endpoint. There was a lesser need for ventilation and renal replacement therapy with labetalol. The CNS morbidity at discharge was also lesser. The propensity to hypotension was however similar in both groups. There is only one study looking at the safety and efficacy of labetalol in children with hypertensive crisis up to ≤ 24 months of age. Ours is the only study to the best of our knowledge in children up to 12 years of age. However, our study suffers from the inherent problems of a retrospective analysis. In conclusion, our study shows that labetalol is safe and efficacious in hypertensive crisis in children up to ≤ 12 years of age.

Potential impacts of land use/cover and climate changes on ecologically relevant flows

This study explored the sensitivity of ecologically relevant flows to individual and combined impacts of climate and land use/cover (LULC) change as well as to their synergistic impacts (combined effect minus sum of individual effects) in a rapidly urbanizing watershed in Alabama, USA. The Soil and Water Assessment Tool (SWAT) was first calibrated (1988–1993) and validated (2008–2013) at daily time scale for streamflow. Then, bias-corrected and downscaled Coupled Model Intercomparison Project Phase 5 (CMIP5) climate data from 2035 to 2060 with eleven climate models under two different representative concentration pathways (RCP 2.6 and RCP 8.5) were fed into SWAT to quantify the effects of future climate. Watershed LULC change was represented in SWAT via a future projected dataset developed by the United States Geological Survey (USGS). Past, present, and future potential streamflow responses to LULC and climate changes were analyzed for various ecologically relevant flow parameters. A total of 38 key flow parameters known to have significant impacts on aquatic flora and fauna were examined including high, low, and median flows, as well as flashiness. Increased summer temperature and decreased fall precipitation are expected in the study region accompanied by rapid urbanization. Climate change is expected to increase maximum monthly streamflows, especially in June-September potentially altering habitat availability for aquatic organisms. When climate change was combined with LULC change, more frequent drought and flood events are expected, which may negatively affect many fish species. Significant shifts in the timing of annual extreme streamflow conditions were also predicted in the future, which may adversely impact the life cycle of various aquatic species.

Earlier fall precipitation and low severity fire impacts on cheatgrass and sagebrush establishment

AbstractIn arid and semiarid ecosystems, invasion by exotic grasses may be driving state changes in vegetation defined by losses of native shrub communities. Changes in wildfire regimes and fall precipitation timing related to climate change may promote fluctuations in resource availability that reinforces invasion and state changes in vegetation. The objective of this study was to investigate how earlier fall precipitation timing and fire affected the germination, establishment, and growth of the dominant native shrub Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis), and one of the most problematic invaders, cheatgrass (Bromus tectorum L.) in the Great Basin. We extracted soil cores from Rush Valley, Utah (UT), USA, on the eastern side of the Great Basin ecoregion and placed them in a common garden in Provo, UT, and planted seeds of sagebrush and cheatgrass in individual cores. We measured the response of sagebrush and cheatgrass to experimental fire and two fall precipitation timing pulses in a full factorial design. Water was added for two weeks in early September (early fall treatment) and mid‐October (late fall treatment). We measured seedling emergence, plant height, biomass, density, seed production, and survival. Early fall precipitation did not significantly affect the amount of cheatgrass or sagebrush seedling emergence. Early fall precipitation significantly increased cheatgrass density, height, biomass, and seed production, and sagebrush height and biomass, but not density. Surprisingly, cheatgrass did not respond positively to fire. In contrast, fire increased sagebrush density (twofold) and survival. These findings indicate that fire can have positive impacts on sagebrush establishment. The data suggest that projected increases in fall moisture in the Great Basin due to climate change are likely to have positive impacts on both cheatgrass and sagebrush. However, additional studies are needed to identify how fall precipitation timing and fire might impact competitive interactions between sagebrush and cheatgrass and the bearing on invasion success at influencing state changes in the Great Basin.

Precession‐ and Obliquity‐Induced Changes in Moisture Sources for Enhanced Precipitation Over the Mediterranean Sea

AbstractEnhanced winter precipitation over the Mediterranean Sea at times of minimum precession and maximum obliquity, that is, times of enhanced insolation seasonality, could provide freshwater required to form orbitally paced sedimentary cycles across the Mediterranean, offering a possible alternative to monsoonal runoff. We investigate the sources of the enhanced winter precipitation, by applying a moisture tracking model on the results of idealized orbital extreme experiments with a state‐of‐the‐art climate model. Precession and obliquity enhance precipitation in fall and winter. Our study shows that the source of enhanced precipitation over the Mediterranean Sea differs during the winter half‐year. In fall, the majority of the precession‐induced precipitation increase originates from the Mediterranean itself. However, in late winter, the increase can be attributed to enhanced moisture advection from the Atlantic. This agrees with changes in evaporation and air‐sea temperature differences over the Mediterranean. The obliquity‐induced precipitation increase shows much less differences, with an equal contribution of local and Atlantic sources. The mechanism behind the Atlantic source of moisture, particularly important in late winter for precession‐induced precipitation changes, is related to a weakened Azores High and slightly higher surface pressure over North Africa. The resulting anomalous circulation patterns generate enhanced Atlantic moisture transport toward the Mediterranean. These mechanisms coincide with weaker storm track activity over the North Atlantic, opposite to previous studies that often attribute enhanced Mediterranean winter precipitation to a southward shift and intensification of the Atlantic storm track. We thus provide an alternative mechanism for Atlantic sources of orbitally paced Mediterranean precipitation changes.

Causal factors for pesticide trends in streams of the United States: Atrazine and deethylatrazine.

Pesticides are important for agriculture in the United States, and atrazine is one of the most widely used and widely detected pesticides in surface water. A better understanding of the mechanisms by which atrazine and its degradation product, deethylatrazine, increase and decrease in surface waters can help inform future decisions for water quality improvement. This study considers causal factors for trends in pesticide concentration in U.S. streams and models the causal factors, other than use, in structural equation models. The structural equation models use a concomitant trend in corn (Zea mays L.) and a latent variable model, indicating moisture supply and management. The moisture supply and management latent variable model incorporates long-term moisture conditions in the individual watersheds by using the Palmer hydrologic drought index, human influence on the hydrologic cycle through the percentage of the watershed drained by tile drains in 2012, and the base-flow contribution to streamflow, using the base-flow index. The structural equation models explain 77 and 38% of the variability in atrazine and deethylatrazine trends, respectively, across the conterminous United States. The models highlight future water quality challenges, particularly in tile-drained settings where fall precipitation and heavy precipitation are increasing.

Prediction of Early Season Beet Leafhopper Populations in Southern New Mexico

Curly top is an important widespread disease in semiarid regions that can be caused by several Curtovirus and Becurtovirus species. The strains of beet curly top virus (BCTV) have been some of the most widely reported to be associated with curly top. The viruses causing curly top are phloem limited and transmitted by the beet leafhopper (BLH), Circulifer tenellus Baker (Hemiptera: Cicadellidae). The BLH can also transmit other important pathogens such as phytoplasmas. Both the virus and insect vector have a broad host range of crops and weeds, including the winter annual weed London rocket (Sisymbrium irio L.). Prior prediction of disease would allow growers a window of opportunity to make informed management choices. A prediction model of BLH abundance was developed for southern New Mexico based on fall precipitation, which corresponds with London rocket emergence, and BLH sticky trap catch data for 2001 to 2018. Regression analyses showed positive associations between BLH numbers and October + November rainfall (P &lt; 0.001) for two areas within southern New Mexico. A third area, where good weed management was used, had lower BLH numbers, and the relationship with precipitation was not significant (P = 0.190). Cumulative-season BLH abundance was correlated with BLH abundance in late April (r = 0.43) and late May (r = 0.56), indicating that early season knowledge of BLH abundance is useful for planning later season management. Although models based on October + November precipitation are good predictors of BLH abundance through June, they may not predict year-long BLH abundance because other environmental and biological factors contribute to subsequent BLH success and movement.

Глаголы с семантикой падения в современном персидском языке

The article provides a classification of approximately 30 verbs used to describe situations associated with the falling of animate and inanimate objects. The authors conclude that in the modern Persian language, the choice of the exact verb to denote falling depends on the degree of integrity of the falling object in question. Only situations in which verbs are used in their direct meaning are considered; where necessary, stylistic differences in the use of verbs are discussed separately. Examples are taken from both literary and colloquial Persian (all examples have been assembled from Internet resources). The authors conclude that in modern Persian language, when choosing a verb to describe a fall, the integrity of the falling object matters. Analysis of the cited material shows that the most frequent verb is oftādan. It is used regardless of which surface and along which path the object falls (solid or liquid), as well as the fact that the object remains on the surface or falls under a layer, into a liquid or granular substance, or into a vessel. However, the scope of the verb oftādan is limited. It does not serve situations of falling populations associated with the disintegration of an integral object into parts, and only in very rare cases is it used to describe the fall of liquid masses, loose bodies and precipitation. In situations describing the fall of parts of an object or the destruction of a structure, the verbs rixtan, rizeš kardan, foru rixtan are used. Also, to describe various situations related to the semantics of the fall, in modern Persian there are a number of verbs with a limited scope. All examples are taken from Internet resources and provided with links.

Seasonal contributions of water and pollutants to Lake St. Charles, a drinking water reservoir

Surface waters are widely used as sources of drinking water in Canada. The identification of the main sources of pollutants to surface waters, often associated with increasing urbanization, is needed to improve management strategies. We used stable water isotopes (δ18O and δD), and nutrient and fecal coliform mass fluxes to estimate the seasonal contributions of water and pollutants of different inflows to Lake St. Charles (LSC). Our results indicate that out of six identified LSC water sources, groundwater (GW), Hurons River (HR) and small stream tributaries (SSTs) represent the major contributors (in terms of water volume). The three other water sources, including two wastewater treatment plants (WWTPs), Delage Lake (DL) and precipitation (rain and snow), represent smaller seasonal contributions. During the high-flow seasons (spring and fall), LSC receives water mainly from SSTs and HR, while during the low-flow season (summer), the lake relies mainly on GW inflows. Estimates of point source (WWTPs) versus non-point source (primarily septic installations) concentrations of nutrients and fecal coliforms show that the latter represents a seasonally variable and greater source of pollutants (5% WWTPs vs. 95% septic installations). HR and SSTs, draining densely occupied areas of single housing units with individual septic installations, are categorized as non-point sources, and as such are considered major nutrient and fecal coliform contributors. The higher precipitation in spring and fall caused increased fluxes of nutrients and fecal coliforms through higher stream discharge. Due to the seasonally variable and difficult to predict discharge dynamics of SSTs and HR, these two sources represent a potentially larger threat to LSC water quality. We advocate that improved management requires reducing the number of individual septic installations in the LSC watershed.

Fall Water Effects on Growing Season Soil Water Content and Plant Productivity

Understanding fall precipitation effects on rangelands could improve forage production forecasting and inform predictions of potential climate change effects. We used a rainout shelter and water addition to test effects of seasonal precipitation on soil water and annual net primary production of C3 perennial grass, C4 perennial grass, annual grasses, forbs, and all plants combined. Treatments were 1) drought during September−October and April−May (DD); 2) drought plus irrigation during September−October and drought during April−May (WD); 3) year-long ambient conditions (WW); and 4) ambient plus irrigation during September−October (W + W). Treatments created conditions ranking among the driest and wettest September−October periods since 1937. Fall water effects on soil water were not detectable by May at 15 cm and 30 cm. Effects persisted into July at 60 cm and 90 cm, depths below the primary root zone. With spring drought, annual net primary production was 344 kg ha−1 greater when the previous fall was wet rather than dry. No differences were detected between fall water treatments when spring was wet and fall was about 184% (1 938 ± 117 kg ha−1) or 391% of the median (1 903 ± 117 kg ha−1). Fall water increased C3 perennial grass when spring was also wet and had no effect under spring drought, when forage production concerns are greatest. Fall water did not affect C4 perennial grass, and extremely wet fall conditions reduced forb production about 50%. The greatest effect of fall water was increased annual grass production. Even record high levels of fall water had minor effects on biomass, functional group composition, and soil water that were short-lived and overwhelmed by the influence of spring precipitation. Movement of fall water to deep soil by the growing season suggests plants that would most benefit from fall precipitation are those that could use it during fall (winter annuals), or deep-rooted species (shrubs).

Historical Trends in Air Temperature, Precipitation, and Runoff of a Plateau Inland River Watershed in North China

Understanding historical trends in temperature, precipitation, and runoff is important but incomplete for developing adaptive measures to climate change to sustain fragile ecosystems in cold and arid regions, including the Balagaer River watershed on the Mongolian Plateau of northeast China. The objective of this study was to detect such trends in this watershed from 1959 to 2017. The detection was accomplished using a Mann-Kendall sudden change approach at annual and seasonal time scales. The results indicated that the abrupt changes in temperature preceded that in either runoff or precipitation; these abrupt changes occurred between 1970 and 2004. Significant (α = 0.05) warming trends were found at the minimum temperatures in spring (0.041 °C a−1), summer (0.037 °C a−1), fall (0.027 °C a−1), and winter (0.031 °C a−1). In contrast, significant decreasing trends were found in the precipitation (−1.27 mm a−1) and runoff (−0.069 mm a−1) in the summer. Marginally increasing trends were found in the precipitation in spring (0.18 mm a−1) and fall (0.032 mm a−1), whereas an insignificant decreasing trend was found in the runoffs in these two seasons. Both precipitation and runoff in the wet season exhibited a significant decreasing trend, whereas in the dry season, they exhibited a marginally increasing trend. Sudden changes in spring runoff and sudden rises in temperature are the main causes of sudden changes in basin rainfall.

Seasonal patterns of growth phenology and nutrient dynamics in four matorral shrubs in Central Chile

Chile is one of five global regions exhibiting a mediterranean-type climate regime characterized by evergreen sclerophyll shrublands. These matorral shrublands which dominate the foothills and slopes of the Coastal Mountains and foothills of the Andes in central Chile have received much less study than evergreen shrublands in other mediterranean-type climate regions of the world. Phenological development, growth, and nutrient dynamics of the four widespread matorral shrub species, Lithrea caustica (Anacardiaceae), Colliguaja odorifera (Euphorbiaceae), Kageneckia oblonga (Rosaceae), and Retanilla trinervia (Rhamnaceae), were monitored in central Chile from 1971 to 1975. The four study species all demonstrated growth dynamics and nutrient relations similar to chaparral shrub species of southern California. The species exhibited a sequential development of phenological stages in leaf components following fall precipitation. Colliguaja with relatively shallow root systems showed a sharp peak of new leaf production at the beginning of summer, dropping quickly as summer drought occurred. Another shallow- rooted species while Retanilla initiated leaf production in the late winter, earlier than the other two species, and presented a growth pattern dependent on soil moisture availability. Lithrea and Kageneckia, a more deep-rooted species, initiated leaf production in late spring and continued through the summer. Overall, Chilean shrubs exhibited higher nutrient contents than those of chaparral shrubs in California, suggesting a difference in soil nutrient availability. Reproductive tissues represent a significant portion of the new biomass and nutrient allocation in all four matorral shrubs. Biomass allocation of new tissues (i.e. new leaves, new stems and reproductive tissues) ranged from 8.2% in Retanilla to 16.7% in Colliguaja. Overall, the phenology and nutrient relations of matorral shrubs were similar to those found in chaparral, shrubs indicating that the similar climate regimes can lead to convergence in leaf traits, phenology, and nutrient relationships.