@article {KNZ001712, title = {Drivers of variation in aboveground net primary productivity and plant community composition differ across a broad precipitation gradient}, journal = {Ecosystems}, volume = {19}, year = {2016}, pages = {521-533}, abstract = {

Aboveground net primary production (ANPP) is a key integrator of C uptake and energy flow in many terrestrial ecosystems. As such, ecologists have long sought to understand the factors driving variation in this important ecosystem process. Although total annual precipitation has been shown to be a strong predictor of ANPP in grasslands across broad spatial scales, it is often a poor predictor at local scales. Here we examine the amount of variation in ANPP that can be explained by total annual precipitation versus precipitation during specific periods of the year (precipitation periods) and nutrient availability at three sites representing the major grassland types (shortgrass steppe, mixed-grass prairie, and tallgrass prairie) spanning the broad precipitation gradient of the U.S. Central Great Plains. Using observational data, we found that precipitation periods and nutrient availability were much stronger predictors of site-level ANPP than total annual precipitation. However, the specific nutrients and precipitation periods that best predicted ANPP differed among the three sites. These effects were mirrored experimentally at the shortgrass and tallgrass sites, with precipitation and nutrient availability co-limiting ANPP, but not at the mixed-grass site, where nutrient availability determined ANPP exclusive of precipitation effects. Dominant grasses drove the ANPP response to increased nutrient availability at all three sites. However, the relative responses of rare grasses and forbs were greater than those of the dominant grasses to experimental nutrient additions, thus potentially driving species turnover with chronic nutrient additions. This improved understanding of the factors driving variation in ANPP within ecosystems spanning the broad precipitation gradient of the Great Plains will aid predictions of alterations in ANPP under future global change scenarios.

}, keywords = {LTER-KNZ, dominant species, Great Plains, Nutrient Network (NutNet), nutrients, precipitation periods, rare species}, doi = {10.1007/s10021-015-9949-7}, url = {https://link.springer.com/article/10.1007\%2Fs10021-015-9949-7}, author = {Kimberly J. La Pierre and D.M. Blumenthal and C.S. Brown and Klein, J.A. and M.D. Smith} } @article {KNZ001756, title = {Tight coupling of leaf area index to canopy nitrogen and phosphorus across heterogeneous tallgrass prairie communities}, journal = {Oecologia}, volume = {182}, year = {2016}, pages = {889 - 898}, abstract = {

Nitrogen (N) and phosphorus (P) are limiting nutrients for many plant communities worldwide. Foliar N and P along with leaf area are among the most important controls on photosynthesis and hence productivity. However, foliar N and P are typically assessed as species level traits, whereas productivity is often measured at the community scale. Here, we compared the community-level traits of leaf area index (LAI) to total foliar nitrogen (TFN) and total foliar phosphorus (TFP) across nearly three orders of magnitude LAI in grazed and ungrazed tallgrass prairie in north-eastern Kansas, USA. LAI was strongly correlated with both TFN and TFP across communities, and also within plant functional types (grass, forb, woody, and sedge) and grazing treatments (bison or cattle, and ungrazed). Across almost the entire range of LAI values and contrasting communities, TFN:TFP ratios indicated co-limitation by N and P in almost all communities; this may further indicate a community scale trend of an optimal N and P allocation per unit leaf area for growth. Previously, results from the arctic showed similar tight relationships between LAI:TFN, suggesting N is supplied to canopies to maximize photosynthesis per unit leaf area. This tight coupling between LAI, N, and P in tallgrass prairie suggests a process of optimal allocation of N and P, wherein LAI remains similarly constrained by N and P despite differences in species composition, grazing, and canopy density.

}, keywords = {LTER-KNZ, Co-limitation, fire, grassland, grazers, nutrients}, issn = {0029-8549}, doi = {10.1007/s00442-016-3713-3}, url = {https://link.springer.com/article/10.1007\%2Fs00442-016-3713-3}, author = {Klodd, A.E. and Jesse B. Nippert and Z. Ratajczak and Waring, H. and Phoenix, G.K.} } @mastersthesis {KNZ001332, title = {Ecosystem Processes of Prairie Streams and the Impact of Anthropogenic Alteration on Stream Ecological Integrity}, volume = {MS Thesis}, year = {2010}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, abstract = {

orth America has lost more than 95\% of the original tallgrass prairie because of heavy land conversion, making prairie streams some of the most endangered habitats in North America. In order to effectively manage aquatic systems and improve biotic integrity of prairie streams research is needed that assesses the ecosystem characteristics of natural systems and evaluates the influence of anthropogenic alteration. We described the ecosystem characteristics of six ephemeral headwater streams draining tallgrass prairie within the Osage Plains of southwest Missouri. NO-3-N among all sites ranged from 1.56-91.36 μg L-1, NH+4-N ranged from 5.27-228.23 μg L-1, soluble reactive phosphorus ranged from below detection (1.0 μg L-1) to 41.22 μg L-1, TN ranged from 113.82-882.89 μg L-1, and TP ranged from 8.18-158.5 μg L-1during baseflow conditions. TN:TP molar ratios ranged from 22:1 to 53:1 indicating possible P was limiting relative to N in some streams. TSS during baseflow conditions ranged from 0.27-31.80 mg L-1. Autotrophic and heterotrophic comparisons of our study sites and reference sites classified our study streams as oligo-, meso-, and eu-autotrophic (N= 1, 4, and 1, respectively) and oligo-, meso-, and eu-heterotrophic (N= 4, 1, and 1, respectively). This study suggests that good water quality and moderate heterotrophic condition, with greater GPP resulting from an open canopy, are common conditions of tallgrass prairie streams. We also investigated interactions between land use/land cover, discharge rate, hydrologic alteration, and in-stream total suspended solids concentration in 23 Kansas- Missouri streams. Most streams had break points in the TSS loading rates at discharge rates exceeded \<25\% of days. Our estimates showed that 88\% of the total annual TSS load occurred during the 11\% of days with the greatest discharge rates. Buffered streams with greater percentages of grass and/or forest riparian areas had lower breakpoint values (indicating greater discharge rates were required to transport solid particles) and lower regression intercepts, which correlated to lesser TSS concentrations relative to unbuffered streams during high discharge days. In addition, grass buffered streams had smaller flood peaks and slower rise rates and forest buffered streams had less frequent floods, which lead to less total TSS transport.

}, keywords = {LTER-KNZ, ecosystem, metabolism, nutrients, solids, stream}, url = {http://hdl.handle.net/2097/6849}, author = {Winders, K.} } @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 {KNZ00636, title = {Suggested classification for stream trophic state: Distributions of temperate stream types by chlorophyll, total nitrogen and phosphorus}, journal = {Water Research}, volume = {32}, year = {1998}, pages = {1455 -1462}, abstract = {Aquatic scientists and managers have no conventional mechanism with which to characterize and compare nutrients and algal biomass in streams within a broader context analogous to trophic state categorization in lakes by chlorophyll (chl) and nutrients. We analyzed published data for a large number of distinct, temperate, stream sites for mean benthic chl (n=286), maximum benthic chl (n=176), sestonic chl (n=292), total nitrogen (n=1070), and total phosphorus (n=1366) as a first effort to establish criteria for trophic boundaries. Two classification systems are proposed. In the first system, the boundary between oligotrophic and mesotrophic categories is defined by the lower third of the cumulative distribution of the values. The mesotrophic{\textendash}eutrophic boundary is defined by the upper third of the distribution. In the second system, individual streams are placed more precisely in a broad geographic context by assessing the proportion of streams that have greater or lesser nutrient and chl values. The proposed relationships for streams were compared to trophic criteria published for lakes. The proposed trophic boundaries for streams generally include a broader range of values in the mesotrophic range than conventional criteria for lakes. The ratio of maximum to mean benthic chl for streams was significantly higher than that found for planktonic chl in lakes, reflecting the greater variance in streams. This high variance in streams suggests that the proposed stream trophic criteria should be viewed only as a general first approach to categorizing stream ecosystems.}, keywords = {LTER-KNZ, Chlorophyll, eutrophic, mesotrophic, nitrogen, nutrients, oligotrophic, periphyton, Phosphorus, rivers, streams}, doi = {10.1016/S0043-1354(97)00370-9}, author = {W. K. Dodds and Jones, J.R. and Welch, E.B.} }