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Soil nitrogen: Traits: Competition and Resource Reduction for Five Grass Species Grown in Monoculture and Competition in Soils with Different Nitrogen Availabilities

This experiment was designed to determine the relationships between plant traits, successional status, and resource reduction for five grass species that were grown for three years in monoculture in replicated field plots on soils prepared to have different availabilities of nitrogen. It also determines the results of competition experiments among various combinations of these species as well as the differing feedback effects of each species on soil nitrogen mineralization rates. All of this work has motivated the desire to more fully understand the mechanisms of interactions among plants and their resources, in the belief that this might eventually allow predictions of the dynamics, diversity, and composition of plant communities.

Percent light penetration and maximum plant height: Traits: Competition and Resource Reduction for Five Grass Species Grown in Monoculture and Competition in Soils with Different Nitrogen Availabilities

Seed weight : Traits: Competition and Resource Reduction for Five Grass Species Grown in Monoculture and Competition in Soils with Different Nitrogen Availabilities

Available light at soil surface: Traits: Competition and Resource Reduction for Five Grass Species Grown in Monoculture and Competition in Soils with Different Nitrogen Availabilities

Plant species percent cover data: Plant Competition Under Different Nitrogen Levels:A Garden Experiment

This garden plot experiment is located next to the E026 gardens in Field E (Old Field 44). This garden contained monocultures of major grass species from across the grassland biome of North America, and also 3 legume species (E070). The design and purpose were similar to E026, except the plots were larger. The basic experimental design consisted of growing plants in monoculture and in various competitive combinations on each of 14 different soil mixtures. In 1988 a bulldozer was used to remove 30 inches of top soil at the site. To each plot a certain amount of black dirt, ranging from 0.3 inches to 10 inches, was added. Total carbon ranged from 0.1928% to 5.63134% and total nitrogen ranged from 0.0158% to 0.4591%. The exact amounts of black soil added to each plot are described in the field operations. Equal amounts of MgSO4, CaCO3, P2O5 \

Plant aboveground biomass carbon and nitrogen: Multiple Traits of Multiple Plant Species Measured in Monoculture Gardens

These gardens were started in order to establish monocultures of several species of native prairie plants common to Cedar Creek.

Plant species inventory: Interactive Effects of Deer, Fire and Nitrogen

In 2000 we began to examine impacts of three anthropogenic effects on successional grasslands in an area with rapid woody encroachment toward white pine forest. We established a factorial experiment that manipulates N (0 or 3 g m-2 yr-1), fire (none or every 2nd year), and deer (fenced or open to deer), with a total of 32 plots, each 20 x 20 m. We hypothesized that the response of this ecosystem to the combined effects of fire, N, and herbivory would depend on the ability of pine and other species to invade and the magnitude of their response to the different disturbance factors: warm-season grasses increase with and encourage fire, resist herbivores, and inhibit woody plant invasion (Davis et al. 1998, Inouye et al. 1994); cool-season plants are favored by N deposition (Tilman 1987) but are fire-intolerant and palatable to herbivores; legumes tolerate fire but decrease with herbivory and N deposition; and finally, woody plants are fire-intolerant and may be more susceptible to herbivory. We are measuring treatment effects on composition and diversity of plants and consumers (insects, small mammals, lizards) as well as plant and soil C and N.

Plant species percent cover data: Interactive Effects of Deer, Fire and Nitrogen

openCC0Oct 2020View details →

TeRaCON eight years data - species composition, productivity (NPP), soil carbon emissions and plant carbon stocks:BioCON: Biodiversity, CO2, and Nitrogen

BioCON (Biodiversity, CO2, and Nitrogen) is an ecological experiment started in 1997 at the University of Minnesota's Cedar Creek Ecosystem Science Reserve. BioCON's goal is to explore the ways in which plant communities will respond to three environmental changes that are known to be occurring on a global scale: increasing nitrogen deposition, increasing atmospheric CO2, and decreasing biodiversity. Why Biodiversity, CO2, and Nitrogen? While there are many uncertainties in global change biology, there are also some well documented facts. Some of these are: 1. The amount of carbon dioxide (CO2) in the atmosphere is rising. Since the industrial revolution, the CO2 concentration in the atmosphere has increased from approximately 275 parts per million (ppm) to about 378 ppm today. This has been largely the result of fossil fuel burning. It is expected that CO2 levels will continue to rise, and that by the year 2050 these levels will be approximately 550 ppm. CO2 is the raw material for photosynthesis and is known to affect plant growth and development. 2. The amount of nitrogen moving through terrestrial ecosystems has increased in the recent past. While natural "background" levels of nitrogen fixation have remained constant, human additions to the system through fertilizer production and fossil fuel use have increased dramatically. Nitrogen is a key nutrient for plant growth and plays a critical role in plant community structure and composition in many environments. 3. Biodiversity levels are falling. While the research and data are not as complete as they are for CO2 and nitrogen, data indicate that the number of species globally, is being reduced. Perhaps more important for ecosystem function, diversity levels on local to regional scales have fallen due to land use change, biotic invasion and many other drivers. While much is known about how each of these factors affects ecosystem functioning, many questions remain. There is also little data on how these issues affe

openOpenJan 2020View details →

SGS-LTER Effects of water and nitrogen additions on plant species density and cover in shortgrass ecosystems on the Central Plains Experimental Range, Nunn, Colorado, USA 1997-2011, ARS Study Number 143

This data package was produced by researchers working on the Shortgrass Steppe Long Term Ecological Research (SGS-LTER) Project, administered at Colorado State University. Long-term datasets and background information (proposals, reports, photographs, etc.) on the SGS-LTER project are contained in a comprehensive project collection within the Digital Collections of Colorado (http://digitool.library.colostate.edu/R/?func=collections&collection_id=3429). The data table and associated metadata document, which is generated in Ecological Metadata Language, may be available through other repositories serving the ecological research community and represent components of the larger SGS-LTER project collection. The objective of this research is to evaluate the long-term response of shortgrass ecosystems to additional water and nitrogen inputs. An experiment was conducted during the IBP project (1970-1975) in which water and nitrogen were applied (Lauenroth et al. 1978, Dodd and Lauenroth 1979, Milchunas and Lauenroth 1995). While we gained an enormous increment in our knowledge about shortgrass ecosystems from this experiment it raised as many questions as it answered. One of the problems was that the treatments were very high levels of nitrogen (100-150kg/ha N) and water (600 mm/growing season) additions. Additional information and referenced materials can be found: http://hdl.handle.net/10217/85629.

opencc-zeroNov 2020View details →

Data from: Drought and soil nutrients effects on symbiotic nitrogen fixation in seedlings from eight Neotropical legume species

Symbiotic nitrogen fixation is a dominant source of nitrogen to many terrestrial ecosystems, and thus may influence their responses to global change. High legume species diversity and abundance are thought to lead to high rates of symbiotic nitrogen fixation in Neotropical forests. However, how changes in water and nutrient availability will affect symbiotic nitrogen fixation have only recently been explored, even as droughts begin to increase in severity and frequency in the Neotropics. To explore these effects, we grew eight species of Neotropical woody legume seedlings in a shadehouse for four months while manipulating soil water, phosphorus and molybdenum availability. Overall, drought reduced nodule biomass, nitrogenase activity (acetylene reduction g-1 nodule), and acetylene reduction per seedling by 33%, 27%, and 41%, respectively, but reduced seedling biomass by only 18%. Species varied in the manifestation of drought effects. For example, drought reduced the probability that nodules formed in some species, but in others reduced the nitrogenase activity or acetylene reduction per seedling. In contrast, the effects of phosphorus and molybdenum availability were more species-specific. However, fertilization did affect (both positively and negatively) one or more symbiotic nitrogen fixation response variables in two of the eight species. Our results indicate drought reduces symbiotic nitrogen fixation in Neotropical legume seedlings, but the mechanism of response may be species-specific. Therefore, predicting the response of symbiotic nitrogen fixation in the Neotropics to a changing climate, with expected increases in drought frequency and severity, may require grappling with the diversity of responses among nitrogen-fixing legumes.

opencc-zeroDec 2020View details →

Divergent responses of forest dominant trees species to the manipulated canopy and understory nitrogen additions in terms of foliage stoichiometric, economic and hydraulic traits

Nitrogen (N) deposition effects on the stoichiometric balance and photosynthetic and hydraulic couplings in subtropical forests has drawn wide attentions. The previously adopted understory application of N fertilization is criticized because it might ignore foliar N retention for different species. This paper reports a fertilizing application from the canopy (CAN) and under the canopy (UAN) in a phosphorus (P) limited ecosystem. Foliage stoichiometric, photosynthetic and hydraulic traits of six dominant species were measured and analyzed. Both treatments equally enhanced foliage N and N/P, but not foliage P, who was highly species-specific depending on tree height, which implied enhanced P limitation. Decreased isotope abundance of 15N (δ15N) that approaching to the level in the urea fertilizer under CAN suggested the existence of canopy retention of N. Besides, N response sensitivity of N, P and δ15N that positively related to tree height (H) under CAN indicated different exposure to the added N, which promoted stoichiometric imbalance among species. The photosynthetic traits represented by net photosynthesis (An) increased under both treatments. A divergent foliar photosynthetic and hydraulic traits varations was identified by signifcant decreased stomatal conductance (gs) and An /gs for CAN treatments, which induced the elevated isotope abundance of 13C (δ13C). Correspondingly, foliage hydraulic traits that shifted to water use efficiency axis were identified only under CAN in principal component analysis. Overall, our results proved that the canopy obsorbtion and species heterogeneity should be considered regarding foliar safety vs efficiency trade-off in response to nitrogen additions in the future.

opencc-zeroDec 2020View details →

Data from: Variations in ratio and loads of soil nitrogen and phosphorus explain the coexistence of dominant tree species in a boreal forest of Xinjiang, northwest China

The resource ratio hypothesis (RRH) and the nutrient-load hypothesis (NLH) state that species coexistence is driven by the ratios and loads (contents) of multiple limiting resources, respectively. However, roles of resource ratios and loads to mature forest ecosystems remains unclear. Data were collected within 300 quadrats (20m×20m) spread across a 12 ha plot of boreal forest in the Kanas of Xinjiang, northwest China. We used torus translation tests to analyze the associations of dominant tree species with specific microhabitats. The linear mixed models were used to assess effects of resource ratios and contents on abundance and basal area of specific species, as well as within different life stages. Two shade-tolerant species, Picea obovata and Pinus sibirica, exhibited opposite relationships to the spatial distribution of soil nitrogen (N) content and phosphorus (P) content. Picea. obovata was associated with microhabitats with high N:P ratio, while P. sibirica preferred microhabitats with low N:P ratio. The light-demanding trees, Betula pendula clustered at both low N and P sites. Another light-demanding trees, Larix sibirica, did not show any significant habitat preferences. Moreover, N:P ratio mainly affected species abundance, while their contents largely impacted basal area of species. And effects of N:P ratio or contents on species distribution showed a decreasing trend from sapling to adults. Overall, our findings indicate that niche partitioning caused by resource variations may alleviate interspecific competition and contribute to the species coexistence, providing convincing proof for the importance of resource ratio and load on maintaining diversity in boreal forests.

opencc-zeroJan 2022View details →

The allometry of plant height explains species loss under nitrogen addition

Light asymmetry, with a higher light acquisition per unit biomass for larger plants, has been proposed as a major mechanism of species loss after nitrogen addition. However, solid evidence for this has been scarce. We measured the allometric size-height relationships of 25 plant species along a nitrogen addition gradient manipulated annually for eight years in a speciose alpine meadow and found that the positive relationship between species relative abundance and the height scaling exponent in natural conditions disappeared after nitrogen addition. Those species with lower height scaling exponents increased in relative abundance after nitrogen addition, thereby decreasing the community weighted mean and dispersion of the height scaling exponent and ultimately the species richness. Our results provided some unique evidence for light asymmetry induced species loss after nitrogen addition and a new insight from the perspective of allometric scaling to explain biodiversity maintenance in the face of global changes.

opencc-zeroDec 2014View details →

Data from: Phosphorus amendment mitigates nitrogen addition-induced phosphorus limitation in two plant species in a desert steppe, China

Background and aims: The increasing deposition of atmospheric nitrogen (N) due to anthropogenic activities has significantly enhanced N inputs to ecosystems, resulting in an imbalance in the N: phosphorus (P) ratios in plants and soils. This study aimed to determine whether, and to what extent, P addition alleviates N-induced P limitation in a desert steppe ecosystem. Methods: We conducted a multi-level N:P supply experiment (i.e., constant N with varied P-addition levels) for a grass species, Pennisetum centrasiaticum, and a N-fixing species, Glycyrrhiza uralensis. Results: With increasing amounts of P addition (thereby decreasing the N:P ratio), green-leaf P concentrations of the two species studied tended to increase, while P-resorption proficiency and efficiency tended to decrease. There were no consistent trends in green-leaf N concentrations in response to P addition. However, both species exhibited high N-resorption proficiency, especially in G. uralensis, with high P addition. Generally, the carbon (C):P and N:P ratios both in soils and in green leaves had positive relationships with green-leaf N concentration and P-resorption proficiency of P. centrasiaticum as well as P-resorption traits of G. uralensis, but negative relationships with green-leaf P concentrations in both species. Conclusions: Our study indicates that P addition can alter P-conservation strategy and thereby releasing plant species from the N-induced imbalance of N:P ratios. However, large amounts of P addition could overcompensate and pose a risk of N limitation in desert steppe ecosystems.

opencc-zeroDec 2013View details →

Data from: Plant species richness promotes soil carbon and nitrogen stocks in grasslands without legumes

1. The storage of carbon (C) and nitrogen (N) in soil are important ecosystem functions. Grassland biodiversity experiments have shown a positive effect of plant diversity on soil C and N storage. However, these experiments all included legumes, which constitute an important N input through N2-fixation. Indeed, the results of these experiments suggest that N2-fixation by legumes is a major driver of soil C and N storage. 2. We studied whether plant diversity affects soil C and N storage in the absence of legumes. In an 11-years grassland biodiversity experiment without legumes, we measured soil C and N stocks. We further determined above-ground biomass productivity, standing root biomass, soil organic matter decomposition and N mineralization rates to understand the mechanisms underlying the change in soil C and N stocks in relation to plant diversity and their feedbacks to plant productivity. 3. We found that soil C and N stocks increased by 18 and 16% in eight-species mixtures compared to the average of monocultures of the same species, respectively. Increased soil C and N stocks were mainly driven by increased C input and N retention, resulting from enhanced plant productivity, which surpassed enhanced C loss from decomposition. Importantly, higher soil C and N stocks were associated with enhanced soil N mineralization rates, which can explain the strengthening of the positive diversity-productivity relationship observed in the last years of the experiment. 4. Synthesis: We demonstrated that also in the absence of legumes plant species richness promotes soil carbon (C) and nitrogen (N) stocks via increased plant productivity. In turn, enhanced soil C and N stocks showed a positive feedback to plant productivity via enhanced N mineralization, which could further accelerate soil C and N storage in the long term.

opencc-zeroDec 2017View details →

Data from: Complementary responses of morphology and physiology enhance the stand-scale production of a model invasive species under elevated CO2 and nitrogen

1. Elevated atmospheric carbon dioxide (eCO2) concentrations and nitrogen (N) enrichment are known to enhance plant productivity and invasion. However, the implications of their interactive effects for plant productivity are not well understood, especially at the stand scale, presumably because morphological and physiological responses to these global change factors are rarely studied together in the field or assessed at the stand-level. 2. We first determined how leaf-level morphological and physiological traits responded to factorial combinations of ambient and elevated CO2 and N. We collected trait data from the model invasive species Phragmites australis (common reed) that were measured over three years in a long-term global change field experiment. We then combined the trait data and additional descriptions of P. australis canopies in a simulation model of carbon assimilation to determine how morphology and physiology contribute to P. australis' stand scale productivity. 3. At the leaf level, we found that light-saturated rates of photosynthesis were strongly stimulated by eCO2 (37%) and that this effect was enhanced by increasing salinity. N had a smaller effect (17% stimulation) on physiological responses than eCO2, but leaf morphological traits responded primarily to N; plant height increased by 27% and leaf area increased by 47%. 4. Stand scale simulations demonstrated that that morphological and physiological adjustments induced approximately additive responses when P. australis experienced both eCO2 and N enrichment. The simulations also indicated that morphological changes (which were primarily associated with canopy size) influenced stand scale carbon assimilation more than physiological changes. Moreover, 97% of the N response was due to changes in morphology, whereas 62% of the eCO2 response was caused by physiological shifts. 5. Our analysis indicates that morphological and physiological trait responses to elevated CO2 and nitrogen are likely to enhance the productivity of P. australis in complementary ways, potentially accelerating its invasion in North America. Furthermore, our data suggest that changes in morphological traits may have a greater influence on carbon gain than leaf-level physiology under near-future environmental conditions. Our study also highlights the importance of accounting for both morphological and physiological responses when attempting to infer global change responses from leaf-level data.