@article {KNZ001323, title = {Centimeter-scale stream substratum heterogeneity and metabolic rates}, journal = {Hydrobiologia}, volume = {623}, year = {2009}, pages = {53 -62}, abstract = {

Spatial heterogeneity of substrata in streams may influence dissolved oxygen (O2) transport and nutrient forms. We studied the relationship between scales of substratum heterogeneity and O2. Heterogeneous systems could have greater respiration rates as a result of increased interfacial surfaces in the biogeochemically active areas between oxic and anoxic zones. We used grids with twelve 7 \× 3.5 cm cells; half the cells were filled with sand and the other half with gravel to quantify the effect of centimeter-scale heterogeneity on respiration. The sand and gravel cells were arranged within the grids to give low, medium, and high heterogeneity. Grids were incubated for 15\–17 days in a prairie stream, and then whole grid respiration was analyzed in closed recirculating chambers. Depth to anoxia and substratum metabolism were calculated from O2 microelectrode profiles measured in each cell of the grid and compared with data from natural stream transects from agricultural, urban, and prairie land use types. Shannon\–Weaver (H\′) diversity and \“probability of change\” indices were also used to compare heterogeneity of the grids to the natural stream transects. No significant differences were found among grid heterogeneity levels for respiration rate, but the anoxic interface was deeper in the gravel of higher heterogeneity grids, probably due to greater transport rates of O2 in the coarse-grained substratum. The H\′ and probability of change indices indicated that the grids had levels of heterogeneity within the range of real streams. Grid depth to anoxia and substratum metabolism rates were similar to those found in streams, though less variable. In streams, H\′ and probability of change values showed a slight difference among land use types, with some urban and agricultural sites displaying very low heterogeneity.

}, keywords = {LTER-KNZ, Dissolved oxygen, nutrients, O2 microelectrodes, stream, Substratum}, doi = {10.1007/s10750-008-9647-y}, url = {https://link.springer.com/article/10.1007\%2Fs10750-008-9647-y}, author = {Wilson, K.C. and W. K. Dodds} } @article {KNZ001322, title = {Spatial heterogeneity of denitrification genes in a highly homogenous urban stream}, journal = {Environmental Science \& Technology}, volume = {43}, year = {2009}, pages = {4273 -4279}, abstract = {

Human modification of natural streams by urbanization has led to more homogeneous channel surfaces; however, the influence of channel simplification on in situ microbial distribution and function is poorly characterized. For example, denitrification, a microbial process that reduces soluble nitrogen (N) levels, requires peripheral anoxic zones that might be lost in artificial channels such as those with a concrete lining. To examine how microbial function might be influenced by channel simplification, we quantified denitrification rates and conditions in microbial mats within an urban concrete channel. We quantified spatial and diurnal patterns of nitrate uptake, diurnal dissolved oxygen (DO) levels, and nutrient conditions, along with the spatial distribution of DO, solids, chlorophyll a, and genes associated with denitrification (nirS and nirK), ammonia-oxidizing bacteria (AOB), cyanobacteria, and algal chloroplasts. Despite the channel being superficially homogeneous, nir genes were distributed in a patchy manner. Two types of gene patches were observed: one associated with nirK, which had diurnally variable DO levels and high nocturnal nitrate uptake rates, and the other associated with nirS, which had elevated AOB genes, thicker layers of mud, and an apparent 24 h nitrate uptake. All active nir patches had elevated microbial photosynthetic genes. Results imply that even artificial channels, with reduced macroscale heterogeneity, can sustain significant rates of denitrification, although the responsible communities vary with space and time. This patchiness has significant implications to extending local data to landscape level predictions and field sampling strategies but also suggests alternate channel designs to increase N retention rates.

}, keywords = {LTER-KNZ}, doi = {10.1021/es9001407}, url = {https://pubs.acs.org/doi/abs/10.1021/es9001407}, author = {Knapp, C.W. and W. K. Dodds and Wilson, K.C. and O{\textquoteright}Brien, J.M. and Graham, D.W.} } @article {KNZ001207, title = {Comparing ecosystem goods and services provided by restored and native lands}, journal = {BioScience}, volume = {58}, year = {2008}, pages = {837 -845}, abstract = {

We determined the relative benefits for eight categories of ecosystem goods and services associated with native and restored lands across the conterminous United States. Less than 10\% of most native US ecosystems remain, and the proportion that is restored varies widely by biome. Restored lands offer 31\% to 93\% of native land benefits within a decade after restoration, with restored wetlands providing the most economic value and deserts providing the least. Restored ecosystems that recover rapidly and produce valuable commodities return a higher proportion of total value. The relative values of the benefits provided by restoration vary both by biome and by the ecosystem goods and services of interest. Our analysis confirms that conservation should be the first priority, but that restoration programs across broad geographic regions can have substantial value. \“No net loss\” policies should recognize that restored lands are not necessarily equivalent to native areas with regard to estimated ecosystem benefits.

}, keywords = {LTER-KNZ, conservation, ecosystem goods, ecosystem services, ecosystem valuation, restoration}, doi = {10.1641/B580909}, url = {https://academic.oup.com/bioscience/article/58/9/837/250939}, author = {W. K. Dodds and Wilson, K.C. and Rehmeier, R.L. and Knight, G.L. and Wiggam, S. and Falke, J.A. and Dalgleish, H.J. and Bertrand, K.N.} } @article {KNZ001116, title = {The saturation of N cycling in Central Plains streams: 15N experiments across a broad gradient of nitrate concentrations}, journal = {Biogeochemistry}, volume = {84}, year = {2007}, pages = {31 -49}, abstract = {We conducted 15NO 3 - stable isotope tracer releases in nine streams with varied intensities and types of human impacts in the upstream watershed to measure nitrate (NO 3 - ) cycling dynamics. Mean ambient NO 3 - concentrations of the streams ranged from 0.9 to 21,000 μg l-1 NO 3 - {\textendash}N. Major N-transforming processes, including uptake, nitrification, and denitrification, all increased approximately two to three orders of magnitude along the same gradient. Despite increases in transformation rates, the efficiency with which stream biota utilized available NO 3 - -decreased along the gradient of increasing NO 3 - . Observed functional relationships of biological N transformations (uptake and nitrification) with NO 3 - concentration did not support a 1st order model and did not show signs of Michaelis{\textendash}Menten type saturation. The empirical relationship was best described by a Efficiency Loss model, in which log-transformed rates (uptake and nitrification) increase with log-transformed nitrate concentration with a slope less than one. Denitrification increased linearly across the gradient of NO 3 - concentrations, but only accounted for \~{}1\% of total NO 3 - uptake. On average, 20\% of stream water NO 3 - was lost to denitrification per km, but the percentage removed in most streams was <5\% km-1. Although the rate of cycling was greater in streams with larger NO 3 - concentrations, the relative proportion of NO 3 - retained per unit length of stream decreased as NO 3 - concentration increased. Due to the rapid rate of NO 3 - turnover, these streams have a great potential for short-term retention of N from the landscape, but the ability to remove N through denitrification is highly variable.}, keywords = {LTER-KNZ, denitrification, Nitrate, nitrification, Saturation, stream, Uptake}, doi = {10.1007/s10533-007-9073-7}, author = {O{\textquoteright}Brien, J.M. and W. K. Dodds and Wilson, K.C. and Murdock, J.N. and Eichmiller, J.} } @mastersthesis {KNZ001012, title = {Hyporheic oxygen flux and substratum spatial heterogeneity: effects on whole-stream dynamics}, volume = {MS Thesis}, year = {2005}, pages = {1 -65}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, author = {Wilson, K.C.} }