02369nas a2200241 4500008004100000245013000041210006900171300001200240490000700252520156900259653001601828653002401844653001901868653002001887653002001907653002801927653002301955653001801978100002401996700001802020700002302038856006602061 2019 eng d00aRemoval of woody riparian vegetation substantially altered a stream ecosystem in an otherwise undisturbed grassland watershed0 aRemoval of woody riparian vegetation substantially altered a str a64 - 760 v223 a

Riparian zones are key interfaces between stream and terrestrial ecosystems. Yet, we know of no whole-watershed experiments that cut only woody vegetation in the riparian zone in an otherwise intact watershed to isolate the role of riparian zones on stream ecology. We removed all of the woody riparian vegetation (from 10- and 30-m-wide buffers in headwaters and main channels, respectively) for 5 km of stream in a single watershed while leaving the remainder of the grassland watershed un-impacted. We assessed water chemistry changes 3 years before and 3 years after riparian wood removal and in two neighboring control watersheds with a before–after, control-impact design and analysis. Riparian woody removal caused 10–100-fold increases in mean stream water nitrate concentrations and pulses of high nitrate for 3 years thereafter. Other nutrients and total suspended solids increased 2–25 times for the 3 years of post-removal. In-stream rates of gross primary production, ecosystem respiration, and net ecosystem production had large treatment effect sizes but also high variance among samples. Past studies of whole-watershed deforestations showed similar water quality responses to our riparian deforestation. Riparian zones of grassland streams are sensitive to disturbance and likely impart relatively greater influence on stream structure and function than the upslope of the watershed. Our results further emphasize the role of riparian zones in biogeochemically linking aquatic and terrestrial habitats.

10adisturbance10aprairie restoration10aPrairie stream10ariparian buffer10awater chemistry10awhole-stream metabolism10awoody encroachment10awoody removal1 aLarson, Danelle, M.1 aDodds, W., K.1 aVeach, Allison, M. uhttps://link.springer.com/article/10.1007%2Fs10021-018-0252-203044nas a2200157 4500008004100000245009000041210006900131300001400200490000700214520252100221100002102742700002402763700001902787700001802806856006202824 2017 eng d00aProbing whole-stream metabolism: influence of spatial heterogeneity on rate estimates0 aProbing wholestream metabolism influence of spatial heterogeneit a711 - 7230 v623 a

1. Whole-stream metabolism has been estimated by measuring in-stream oxygen (O2) concentrations since the method was introduced over 50 years ago. However, the influence of measurement location and estimation method on metabolism rates is understudied. We examined how the placement of O2 probes (i.e. depth, separation from the thalweg), differences in methodology (1-station, 2-station, area-weighted) and reach lengths influenced estimated rates of whole-stream metabolism in a tallgrass prairie watershed.

2. Metabolism estimates made in the thalweg differed from estimates made in backwaters due to disconnection in flow, and estimates made in deep pools differed from surface estimates due to thermal stratification (temporary flow disconnection). The 1-station respiration estimates differed from short 2-station reach-scale estimates (c. 20 m) but were more similar to larger 2-station reach-scale estimates (c. 100 m). In contrast, the 1-station gross primary production was most similar to the short 2-station reaches occurring immediately upstream and became less similar at longer 2-station reach lengths. The different estimation methodologies (1-station, 2-station, area-weighted) accounting for the longest reach scale did not result in different metabolism rates.

3. The temporary phenomena of thermal stratification of stream pools during a warm day, which disconnected pool bottoms from the surface waters, likely affected not only the pool estimates but also estimates made in the downstream thalweg (i.e. an O2 deficit accrued from respiration during the day in the bottom of the pool abruptly moved downstream during mixing).

4. Oxygen probe placement mattered and affected rate estimates according to habitat type and reach length (i.e. scale) due to the influence of small-scale heterogeneity on community respiration. Selection of reach length can be critical for studies depending on whether local heterogeneity is of interest or should be averaged.

5. We conclude that the intuitive use of thalwegs and reaches that are at least 10 times the stream width are likely appropriate for whole-stream metabolism estimates, although the exact reach length necessary and potential stream-specific characteristics, such as stratified pools, need to be carefully considered in probe placement. We encourage other studies to report the placement characteristics of O2 probes in streams as well as consider the potential confounding factor of local habitat heterogeneity.

1 aSiders, Adam, C.1 aLarson, Danelle, M.1 aRüegg, Janine1 aDodds, W., K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.12896