Poorly drained depressions can be hotspots of nutrient leaching from agricultural soils.

Much of the US Corn Belt has been drained with subsurface tile to improve crop production, yet poorly drained depressions often still flood intermittently, suppressing crop growth. Impacts of depressions on field-scale nutrient leaching are unclear. Poor drainage might promote denitrification and physicochemical retention of phosphorus (P), but ample availability of water and nutrients might exacerbate nutrient leaching from cropped depressions. We monitored nitrate, ammonium, and reactive P leaching across multiple depression-to-upland transects in north-central Iowa, using resin lysimeters buried and retrieved on an annual basis. Crops included conventional corn/soybean (Zea mays/Glycine max) rotations measured at fields with and without a winter rye (Secale cereale) cover crop, as well as juvenile miscanthus (Miscanthus × giganteus), a perennial grass. Leaching of nitrogen (N) and P was greater in depressions than in uplands for most transects and years. The median difference in nutrient leaching between paired depressions and uplands was 56 kg N ha-1 year-1 for nitrate (p = 0.0008), 0.6 kg N ha-1 year-1 for ammonium (p = 0.03), and 2.4 kg P ha-1 year-1 for reactive P (p = 0.006). Transects managed with a cover crop or miscanthus tended to have a smaller median difference in nitrate (but not ammonium or P) leaching between depressions and uplands. Cropped depressions may be disproportionate sources of N and P to downstream waters despite their generally poor drainage characteristics, and targeted management with cover crops or perennials might partially mitigate these impacts for N, but not necessarily for P.

Water quality performance of wetlands receiving nonpoint-source nitrogen loads: Nitrate and total nitrogen removal efficiency and controlling factors.

Nonpoint-source nitrogen (N) loads in the U.S. Corn Belt are a major concern both for local impacts on receiving waters and for contributing to hypoxia in the Gulf of Mexico. Nonpoint-source nutrient loads can be ameliorated by a combination of in-field and offsite practices, and wetland restoration is a particularly promising approach for reducing N loads from agricultural drainage. However, there is considerable variability among wetlands, and adequate performance data are available for relatively few systems receiving unregulated nonpoint-source loads. We measured N mass balances of 26 restored wetlands receiving a wide range of unregulated, naturally varying hydraulic and nutrient loads to evaluate the N removal performance of these systems and the effects of major factors controlling their performance. Nitrogen loads were primarily in the form of nitrate, and all of the wetlands were effective in reducing both nitrate and total N loads. Nitrate N and total N removal rates averaged 1,500 and 1,440 kg N ha-1  yr-1 , respectively, with the slightly lower total N removal rates reflecting a small net export of reduced N (averaging 66 kg N ha-1  yr-1 ). Average nitrate and total N removal rates were substantially higher than typically reported for Corn Belt wetlands but comparable with highly loaded systems elsewhere. Nitrate removal efficiency ranged from 9 to 92% and was strongly related to hydraulic loading rate and temperature. Results demonstrate the substantial capacity of wetlands to reduce unregulated and highly variable nonpoint-source N loads over a broad range of weather and loading conditions and provide a reasonable basis for predicting average wetland performance based on hydraulic loading rate, temperature, and nitrate concentration.

A new species of Proceroplatus Edwards (Diptera: Keroplatidae) in Miocene amber from the Dominican Republic.

Keroplatid fungus gnats (Diptera: Keroplatidae) were hitherto known from the Caribbean island of Hispaniola from a single named species in Miocene amber from the Dominican Republic. Here we describe the new fossil species Proceroplatus preziosii Evenhuis & Penney based on a mature male specimen, which differs markedly from both fossil and extant taxa in the structure of its gonostyli and U-shaped wing pattern. We also document the first record of extant Keroplatidae, Proceroplatus pictipennis (Williston), from Hispaniola.

A new fossil cricket of the genus Proanaxipha in Miocene amber from the Dominican Republic (Orthoptera, Gryllidae, Pentacentrinae).

A new species of the cricket genus Proanaxipha Vickery & Poinar (Orthoptera: Gryllidae: Pentacentrinae) from Early Miocene Dominican amber is described and illustrated. Proanaxipha madgesuttonaesp. n. is distinguished from congeners by: (1) head capsule bearing a distinctive posteriorly bilobed colour spot on the vertex; (2) presence of crossveins in the proximal part of the mediocubital area; (3) apical field of tegmen entirely dark; and (4) median process of epiphallus short. The poorly known Proanaxipha bicolorata Vickery & Poinar, of questionable affinity and status, is herein regarded as a nomen inquirendum.

Ancient Ephemeroptera-Collembola symbiosis fossilized in amber predicts contemporary phoretic associations.

X-ray computed tomography is used to identify a unique example of fossilized phoresy in 16 million-year-old Miocene Dominican amber involving a springtail being transported by a mayfly. It represents the first evidence (fossil or extant) of phoresy in adult Ephemeroptera and only the second record in Collembola (the first is also preserved in amber). This is the first record of Collembola using winged insects for dispersal. This fossil predicts the occurrence of similar behaviour in living springtails and helps explain the global distribution of Collembola today.