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Algal growth potential tests using the green algae Raphidocelis subcapitata (=Pseudokirchneriella subcapitata = Selenastrum capricornutum) were performed on ambient waters collected from 6 Idaho streams from September 7 to 21, 2007. Tests were conducted by a contract laboratory, GEI/Chadwick Ecological Division, Littleton, Colorado.
Phosphorus (P) has been proposed to directly limit primary productivity in some temperate grassland ecosystems. Our study of a recovering prairie on Colorado's Front Range suggests that P availability, possibly via regulation of nitrogen (N) fixation, may strongly influence N availability in recovering prairie soils. Consequently, increased P availability could indirectly affect plant growth through the alleviation of N limitation. At our site, concentrations of soil inorganic N were nearly three times higher in plots fertilized with P than in control plots. Subsequent acetylene reduction analyses showed that soil N fixation rates were more than double for P fertilization plots. These results highlight potential...
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We used in situ nutrient diffusing artificial substrates (NDS) to test for nutrient limitation of benthic algae. Concentrated nutrients are enclosed in vials with diffusive fritted glass tops, which allow nutrients contained in an agar gel to slowly leach through the substrates. Periphyton accumulates on diffusive surfaces when NDS are deployed in natural waters, and differences in accumulation rates between nutrient treatments and controls are interpreted as evidence of periphyton nutrient limitation. The NDS data are original, whereas the associated ambient data have been previously released in Brightbill and Frankfurter (2010) and Mebane and others (2014), and are repeated here for convenience References Brightbill,...
Nitrogen (N) and phosphorus (P) availability limit plant growth in most terrestrial ecosystems. This review examines how variation in the relative availability of N and P, as reflected by N : P ratios of plant biomass, influences vegetation composition and functioning. Plastic responses of plants to N and P supply cause up to 50-fold variation in biomass N : P ratios, associated with differences in root allocation, nutrient uptake, biomass turnover and reproductive output. Optimal N : P ratios ? those of plants whose growth is equally limited by N and P ? depend on species, growth rate, plant age and plant parts. At vegetation level, N : P ratios <10 and >20 often (not always) correspond to N- and P-limited biomass...
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Nutrient limitation tests were performed with a laboratory bioassay that uses a macrophyte, Lemna minor L. (duckweed) and attached epiphytes to characterize the status of ambient and nutrient-enriched waters. In summary, we measured morphological (number of fronds, longest surface axis, root length) and population-level (number of plants, dry mass) responses of L. minor, and community-level (ash free dry mass [AFDM] and chlorophyll a [chl a]) responses of epiphytes to nutrient enrichment. About 90L of water were collected on 23April2008 from streams expected to have low with low nitrogen (N) and low phosphorus (P) (Big Cottonwood and Stalker Creeks, respectively) and were transported to the Stream Ecology Center...
1. The effects of phosphorus enrichment and grazing snails on a benthic microbial community that builds stromatolic oncolites were examined in an experiment at Rio Mesquites, Cuatro Ci�negas, Mexico. Chemical analyses of stream water samples indicated that overall atomic ratios of total nitrogen (N) to total phosphorus (P) were approximately 110, indicating a strong potential for P-limitation of microbial growth. 2. Phosphorus enrichment involved addition of 5 ?mol Na2HPO4 L-1 to streamside microcosms receiving intermittent inputs of stream water while grazer manipulation involved removal of the dominant grazer, the snail Mexithauma quadripaludium. After 7 weeks, we examined responses in organic matter content,...
Atmospheric nitrogen (N) deposition to lakes and watersheds has been increasing steadily due to various anthropogenic activities. Because such anthropogenic N is widely distributed, even lakes relatively removed from direct human disturbance are potentially impacted. However, the effects of increased atmospheric N deposition on lakes are not well documented. We examined phytoplankton biomass, the absolute and relative abundance of limiting nutrients (N and phosphorus [P]), and phytoplankton nutrient limitation in alpine lakes of the Rocky Mountains of Colorado (USA) receiving elevated (>6 kg N�ha?1�yr?1) or low (<2 kg N�ha?1�yr?1) levels of atmospheric N deposition. High-deposition lakes had higher NO3-N and total...
Knapweeds (Centaurea spp.) are among the most invasive of non-indigenous plant species that have colonized western North America over the last century. We conducted a 4-year experiment in a reconstructed grassland to test hypotheses related to the ability of grasslands to resist the invasion of diffuse knapweed (C. diffusa). We experimentally invaded C. diffusa and three native species into areas where we manipulated soil nitrogen (N) and phosphorus (P) availability and removed extant grasses to reduce competition. We evaluated the growth response of these species to these resources and competitive manipulations. Of the native species that were experimentally added, only one species, Ratibida pinnata (prairie coneflower),...


    map background search result map search result map 1. Green algae growth stimulation testing 2. Duckweed and epiphyte growth stimulation testing 3. Algal accrual on nutrient diffusing substrates (NDS) 2. Duckweed and epiphyte growth stimulation testing 3. Algal accrual on nutrient diffusing substrates (NDS) 1. Green algae growth stimulation testing