@proceedings {KNZ00436,
	title = {Aboveground biomass in tallgrass prairie: effect of time since last fire},
	year = {1994},
	pages = {165 -170},
	keywords = {LTER-KNZ, tallgrass prairie},
	url = {http://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC13/reference/econatres.napc13.jbriggs.pdf},
	author = {J. M. Briggs and Fahnestock, J.T. and Ward, L. and Alan K. Knapp},
	editor = {Wickett, R.G. and Lewis, P.D. and Woodliffe, A. and Pratt, P.}
}
@article {KNZ00454,
	title = {Elevated CO2 alters dynamic stomatal responses to sunlight in a C4 grass},
	journal = {Plant Cell and Environment},
	volume = {17},
	year = {1994},
	pages = {189 -195},
	abstract = {Native tallgrass prairie in NE Kansas was exposed to elevated (twice ambient) or ambient atmospheric CO2 levels in open-top chambers. Within chambers or in adjacent unchambered plots, the dominant C4 grass, Andropogon gerardii, was subjected to fluctuations in sunlight similar to that produced by clouds or within canopy shading (full sun > 1500 μmol m-2 s-1 versus 350 μmol m-2 s-1 shade) and responses in gas exchange were measured. These field experiments demonstrated that stomatal conductance in A. gerardii achieved new steady state levels more rapidly after abrupt changes in sunlight at elevated CO2 when compared to plants at ambient CO2. This was due primarily to the 50\% reduction in stomatal conductance at elevated CO2, but was also a result of more rapid stomatal responses. Time constants describing stomatal responses were significantly reduced (29{\textendash}33\%) at elevated CO2. As a result, water loss was decreased by as much as 57\% (6.5\% due to more rapid stomatal responses). Concurrent increases in leaf xylem pressure potential during periods of sunlight variability provided additional evidence that more rapid stomatal responses at elevated CO2 enhanced plant water status. CO2-induced alterations in the kinetics of stomatal responses to variable sunlight will likely enhance direct effects of elevated CO2 on plant water relations in all ecosystems.},
	keywords = {LTER-KNZ},
	doi = {10.1111/j.1365-3040.1994.tb00282.x},
	author = {Alan K. Knapp and Fahnestock, J.T. and Owensby, C.E.}
}
@article {KNZ00439,
	title = {Responses of forbs and grasses to selective grazing by bison: interactions between herbivory and water stress},
	journal = {Vegetatio},
	volume = {115},
	year = {1994},
	pages = {123 -131},
	abstract = {Two abundant tallgrass prairie forb species, Ambrosia psilostachya and Vernonia baldwinii, are commonly found intact in patches where the grasses have been selectively grazed by bison. Microclimatic patterns and physiological responses of these forbs were measured in grazed and ungrazed patches. These experiments demonstrated that bison herbivory indirectly enhanced water availability and productivity of forbs growing in grazed patches. This was due primarily to the reduction in transpiring grass leaf area in grazed patches and an increase in light availability. In grazed patches, incident light at forb mid-canopy height was 53\% greater than ungrazed sites at midseason and soil temperatures were always warmer (e.g., 10 ?C at 5 cm), perhaps enabling forbs to initiate growth earlier in the spring. Enhanced leaf xylem pressure potential and stomatal conductance in plants in grazed areas were most evident when water availability was low (i.e., late in the growing season and over short-term dry periods characteristic of the tallgrass prairie environment). Relative to individuals in ungrazed areas, end-of-season biomass of A. psilostachya was 40\% greater and reproductive biomass and head number of V. baldwinii was 45\% and 40\%  greater, respectively, in plants in grazed patches. A favorable growing environment maintained in grazed patches during periods of water limitation enhances carbon gain in forbs leading to increased biomass and potential fitness.},
	keywords = {LTER-KNZ, bison, Light reduction, Selective herbivory, tallgrass prairie, water stress},
	doi = {10.1007/BF00044867},
	url = {http://link.springer.com/article/10.1007/BF00044867},
	author = {Fahnestock, J.T. and Alan K. Knapp}
}
@proceedings {KNZ00456,
	title = {Water relations and biomass responses to irrigation across a topographic gradient in tallgrass prairie},
	year = {1994},
	pages = {215 -220},
	keywords = {LTER-KNZ, Water relations},
	url = {http://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC13/reference/econatres.napc13.aknapp.pdf},
	author = {Alan K. Knapp and Koelliker, J.K. and Fahnestock, J.T. and J. M. Briggs},
	editor = {Wickett, R.G. and Lewis, P.D. and Woodliffe, A. and Pratt, P.}
}
@article {KNZ00413,
	title = {Landscape patterns in soil-water relations and primary production in tallgrass prairie},
	journal = {Ecology},
	volume = {74},
	year = {1993},
	pages = {549 -560},
	abstract = {Landscape variation in soil water relations, leaf xylem pressure potential ({\textdegree}) and leaf{\textemdash}level net photosynthesis (A) in Andropogon gerardii, and net primary production (NPP) were evaluated during the 1989 and 1990 growing seasons in a northeast Kansas (USA) tallgrass prairie. Landscape patterns were assessed along transects that spanned upland and lowland topographic positions in an annually burned and a long{\textemdash}term unburned watershed. Landscape variability in volumetric soil water content ({\textdegree}) was significantly greater in the unburned watershed (coefficient of variation [CV] = 0.425 and 0.479 for 0{\textemdash}15 and 0{\textemdash}30 cm soil depths in unburned prairie vs. 0.285 and 0.330 for similar depths in the burned watershed). In both watersheds, significantly higher {\textdegree} and total soil water content (0{\textemdash}30 cm) were measured in lowlands compared to uplands. Topographic anomalies, such as a lowland ridge, resulted in local, small{\textemdash}scale variation in soil moisture that equaled watershed variation. Variation across landscapes in predawn {\textdegree}, which was expected to reflect soil water content, was similar in both watersheds (CV = 0.312). Variation in midday @j was significantly greater across the burned than the unburned watershed in 1990 (maximum range in @j from uplands to lowlands was 0.708 MPa at predawn and 0.662 MPa at midday in the burned watershed). In both watersheds, variation in midday @j was much lower relative to {\textdegree}. Landscape patterns in leaf{\textemdash}level A in A. gerardii, the dominant species in this tallgrass prairie, were inconsistent when upland and lowland sites were compared. During an extended period of drought, A was significantly higher in plants in the unburned watershed. In both watersheds, NPP was strongly correlated with {\textdegree}. However, variability in NPP across topographic gradients in the unburned watershed was much less pronounced (CV = 0.224{\textemdash}0.245) than in the annually burned watershed (CV = 0.364{\textemdash}0.430). Moreover, the slope of the relationship between NPP and {\textdegree} was significantly greater in the annually burned watershed. We propose that relatively uniform energy limitations across topographic gradients in unburned tallgass prairie, caused by detrital accumulation that absorbs/reflects sunlight, reduced topographic variability in NPP in unburned watersheds. This pattern occurred in unburned watersheds despite greater landscape variation in {\textdegree} relative to burned watersheds. Analysis of long{\textemdash}term records of NPP from several watersheds supported the hypothesis that variability in NPP associated with topographic position is lower in unburned vs. burned watersheds. Variability in @j across watersheds and between years was muted by negative feedback of canopy leaf area (transpiring surface) on plant{\textemdash}soil water relations. We concluded that patterns in landscape variability in A and @j which may vary significantly over short time intervals, were not good predictors of seasonal carbon dioxide exchange or productivity in this tallgrass prairie. Nonetheless, interactions between A and @j, when combined with nitrogen and energy limitations to A. provide the mechanisms for integrated responses measured across these landscapes.},
	keywords = {LTER-KNZ, tallgrass prairie},
	doi = {10.2307/1939315},
	author = {Alan K. Knapp and Fahnestock, J.T. and Hamburg, S.P. and Statland, L.J. and Seastedt, T.R. and Schimel, D.S.}
}
@article {KNZ00396,
	title = {Water relations and growth of tallgrass prairie forbs in response to selective herbivory by bison},
	journal = {International Journal of Plant Science},
	volume = {154},
	year = {1993},
	pages = {432 -440},
	abstract = {The indirect effects of selective grass herbivory by bison (Bison bison) on the xylem pressure potentials (ψ) and primary production of ungrazed tallgrass prairie forbs were assessed during the 1990 growing season on the Konza Prairie Research Natural Area (KPRNA) in northeast Kansas. Responses in three forb species, Vernonia baldwinii, Ambrosia psilostachya, and Aster ericoides, were measured in grazed and adjacent ungrazed patches. Seasonal predawn and midday ψ responses in these forbs were also compared with responses in Andropogon gerardii, the dominant grass in tallgrass prairie. Reductions in grass leaf area by herbivory may result in greater availability of soil water to the remaining forbs, if the forbs and grasses utilize similar soil water resources. Overall, selective herbivory of the grasses had an inconsistent effect on leaf ψ in the remaining forbs. When ψ were relatively high during the growing season, no significant differences in water status were detected between A. gerardii and the forbs. However, when ψ were low, predawn and midday ψ were higher in V. baldwinii (as much as 1.0 MPa), and midday ψ were higher in A. psilostachya (0.5 MPa) compared with A. gerardii. In contrast, ψ were not significantly different between A. ericoides and A. gerardii. Grazing by bison substantially increased light availability to ungrazed forbs (> 40\%) in grazed relative to ungrazed areas. Compared with ungrazed areas, end-of-season aboveground biomass in grazed patches was 40\% greater for individuals of A. psilostachya and 33\% and 26\% greater for reproductive biomass and floret numbers, respectively, in V. baldwinii. We conclude that the potential benefits of selective grass herbivory on forb water relations may be reduced or offset by other factors such as significant alterations in the microclimate of grazed patches. Nonetheless, increased productivity in grazed patches in two of the three forbs studied indicates that selective consumption of grasses by bison may benefit some forb species.},
	keywords = {LTER-KNZ, Water relations},
	url = {http://www.jstor.org/stable/2995662},
	author = {Fahnestock, J.T. and Alan K. Knapp}
}
@mastersthesis {KNZ00355,
	title = {Indirect effects of selective grass herbivory by bison on tallgrass prairie forbs},
	volume = {MS Thesis},
	year = {1992},
	pages = {1 -64},
	school = {Kansas State University},
	type = {M.S. Thesis},
	address = {Manhattan, KS},
	keywords = {LTER-KNZ, tallgrass prairie},
	author = {Fahnestock, J.T.}
}
@article {KNZ00290,
	title = {Influence of plant size on the carbon and water relations of Cucurbita foetidissima HBK},
	journal = {Functional Ecology},
	volume = {4},
	year = {1990},
	pages = {789 -797},
	abstract = {<p>Plant size varies by two orders of maginitude within populations of Cucurbita foetidissima HBK. a perennial, prostrate vine of deserts and grasslands in the western USA. Differences in plant size in in this species growing in Kansas (USA) brome grassland were most evident in leaf size (10 times greater in larger vs 13 g in small plants). and taproot mass (c 7000g in large vs 13g in small plants). This study examined the influence of plant size on net photosynthetic CO2 uptake (A), stomatal conductance to water vapour (g), transpiration rate (E), xylem pressure potential and leaf temperature (Tleaf). During a period of drought in which co-occurring grasses and forbs experienced significant water stress (xylem pressure potential\&lt; -2*5 MPa), xylem pressure potential in large- and intermediate-sized plants of C. foetidissima was always\&gt; -0*6 MPa. In small plants, minimum xylem pressur potential was c-1*3 MPa. No substantial diurnal reductions in A or g were measured in the two groups of larger plants, but CO2 uptake was reduced to zero after midday in small plants, presumably due to water stress. Increased mass of succulent taproots and greater rooting depth may have contributed to greater xylem pressure potential in larger vs small individuals of C. foetidissima. Water use efficiency (WUE) was greater in larger vs small individuals of C. foetidissima. Water use efficiency (WUE) was greater in leaves from large- and intermediate-sized plants relative to small plants under all environmental conditions. During brief periods of low irradiance due to clouds or artificial shading, 5-10oC reduction in Tleaf in plants with large leaves resulted in low E, enhancing WUE. Much smaller reductions in Tleaf and E occurred during shade in the small leaves of small individuals. These results indicate the greater size in C. foetidissima, while not increasing interception of irradiance in this grassland, resulted in greater independence from resource limitations as well as water conservation during periods of variable sunlight. Key words: Cucurbita, photosynthesis, plant size, water stress</p>},
	keywords = {LTER-KNZ, Water relations},
	doi = {~10.2307/2389445},
	author = {Alan K. Knapp and Fahnestock, J.T.}
}
@article {KNZ00274,
	title = {Response of Andropogon gerardii  to simulated acid rain},
	journal = {Transactions of the Kansas Academy of Science},
	volume = {93},
	year = {1990},
	pages = {85 -90},
	abstract = {<p>In this study the authors examined the effects that moderate exposure to acidic precipation had on growth and physiological responses in Andropogon gerardii, the dominant grass in tallgrass prairie. Naturally occurring monocultures of A. gerardii were treated with simulated acid rain (pH 4.0 or 3.0) or precipitation with a pH similar to natural rainfall (pH 5.0) throughout a growth season. No visual effects of the acid rain treatments were observed and there were no statistically significant effects on net photosynthetic CO2 uptake, stomatal conductance to water vapor, or tiller mass in A. gerardii. However, tiller density was significantly reduced as treatment pH decreased. These data suggest that a moderate increase in the number of rainfall events with low pH will have little discernible short-term impact on tallgrass prairie dominated by A. gerardii, but longer-term effects need to be evaluated</p>},
	keywords = {LTER-KNZ, tallgrass prairie},
	doi = {10.2307/3628150},
	author = {Fahnestock, J.T. and Alan K. Knapp}
}
