Widespread planting of maize throughout the agricultural Midwest may result in detritus entering adjacent stream ecosystems, and 63% of the 2009 US maize crop was genetically modified to express insecticidal Cry proteins derived from Bacillus thuringiensis. Six months after harvest, we conducted a synoptic survey of 217 stream sites in Indiana to determine the extent of maize detritus and presence of Cry1Ab protein in the stream network. We found that 86% of stream sites contained maize leaves, cobs, husks, and/or stalks in the active stream channel. We also detected Cry1Ab protein in stream-channel maize at 13% of sites and in the water column at 23% of sites. We found that 82% of stream sites were adjacent to maize fields, and Geographical Information Systems analyses indicated that 100% of sites containing Cry1Ab-positive detritus in the active stream channel had maize planted within 500 m during the previous crop year. Maize detritus likely enters streams throughout the Corn Belt; using US Department of Agriculture land cover data, we estimate that 91% of the 256,446 km of streams/rivers in Iowa, Illinois, and Indiana are located within 500 m of a maize field. Maize detritus is common in lowgradient stream channels in northwestern Indiana, and Cry1Ab proteins persist in maize leaves and can be measured in the water column even 6 mo after harvest. Hence, maize detritus, and associated Cry1Ab proteins, are widely distributed and persistent in the headwater streams of a Corn Belt landscape.genetically modified crops | crop detritus | ELISA | rivers

The aggressive cattail species Typha X glauca and Typha angustifolia have established in wetlands across the Great Lakes region, decreasing native plant diversity and altering environmental conditions. We relied on a parallel study in which 80 years of historical aerial photographs from a large Lake Michigan wetland complex were used to map the spread and determine the age of invasive cattail stands. Floristic, edaphic, and environmental data were collected from plots across an invasion-age gradient. Compared with reference uninvaded sites, litter mass more than doubled within 10 years of invasion (P< 0.001), plant diversity declined by more than 50% within 25 years of invasion (P=0.003), and soil organic depth was more than 29-cm deeper in areas invaded for more than 35 years compared with areas invaded for 10 years or less (P=0.006). These time-dependent changes in plant communities, soil, and environmental conditions fundamentally alter the structure of invaded wetlands, likely influencing a range of ecosystem services.

Aim Determining the spatial‐temporal spread of an invasive plant is vital for understanding long‐term impacts. However, invasions have rarely been directly documented given the resources required and the need for substantial foresight. One method widely used is historical photography interpretation, but this can be hard to verify. We attempt to improve this method by linking historical aerial photos to a paleobotanical analysis of pollen cores. Location Laurentian Great Lakes coastal wetlands, United States of America. Methods We chose invasive cattail ( Typha) as our model species because it is identifiable from aerial imagery and has persistent, identifiable pollen, and its ecological impacts appear to be time‐dependent. We used Geographic Information Systems, aerial photo‐interpretation and field verification to post‐dict the invasion history of Typha in several wetland ecosystems. Using 210 Pb and 137 Cs sediment dating and pollen classification, we correlated the temporal dominance of Typha to our estimates of per cent coverage at one site. The pollen record was then used to estimate the Typha invasion dynamics for dates earlier than those for which aerial photos were available. Results Typha spread through time in all study wetlands. Typha pollen dominance increased through time corresponding with increased spatial dominance. Hybrid cattail, T. × glauca increased in pollen abundance relative to T. angustifolia pollen through time. Main conclusions This study illustrates the value of generating historical invasion maps with publically available aerial imagery and linking these maps with paleobotanical data to study recent (< 100 years) invasions. We determined rates of Typha expansion in two coastal wetland types, validated our mapping methods and modelled the relationship between pollen abundance and wetland coverage, enhancing the temporal precision and breadth of analyses. Our methodology should be replicable with similar invasive plant species. The combination of pollen records and historical photography promises to be a valuable additional tool for determining invasion dynamics.

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