02594nas a2200169   4500008004100000245012200041210006900163300001500232490000700247520200200254100001402256700001802270700002302288700001902311700001702330856007702347       2008                        eng d00aChanges in grassland  ecosystem function due to extreme rainfall events: implications for responses to climate change0 aChanges in grassland ecosystem function due to extreme rainfall   a1600 -16080 v143 a<p>Climate change is causing measurable changes in rainfall patterns, and will likely cause increases in extreme rainfall events, with uncertain implications for key processes in ecosystem function and carbon cycling. We examined how variation in rainfall total quantity (Q), the interval between rainfall events (I), and individual event size (SE) affected soil water content (SWC) and three aspects of ecosystem function: leaf photosynthetic carbon gain (inline image), aboveground net primary productivity (ANPP), and soil respiration (inline image). We utilized rainout shelter-covered mesocosms (2.6 m3) containing assemblages of tallgrass prairie grasses and forbs. These were hand watered with 16 I&times;Q treatment combinations, using event sizes from 4 to 53 mm. Increasing Q by 250% (400&ndash;1000 mm yr&minus;1) increased mean soil moisture and all three processes as expected, but only by 20&ndash;55% (P&le;0.004), suggesting diminishing returns in ecosystem function as Q increased. Increasing I (from 3 to 15 days between rainfall inputs) caused both positive (inline image) and negative (inline image) changes in ecosystem processes (20&ndash;70%, P&le;0.01), within and across levels of Q, indicating that I strongly influenced the effects of Q, and shifted the system towards increased net carbon uptake. Variation in SE at shorter I produced greater response in soil moisture and ecosystem processes than did variation in SE at longer I, suggesting greater stability in ecosystem function at longer I and a priming effect at shorter I. Significant differences in ANPP and inline image between treatments differing in I and Q but sharing the same SE showed that the prevailing pattern of rainfall influenced the responses to a given event size. Grassland ecosystem responses to extreme rainfall patterns expected with climate change are, therefore, likely to be variable, depending on how I, Q, and SE combine, but will likely result in changes in ecosystem carbon cycling.</p>1 aFay, P.A.1 aKaufman, D.M.1 aNippert, Jesse, B.1 aCarlisle, J.D.1 aHarper, C.W.  uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01605.x03504nas a2200169   4500008004100000245011200041210006900153300001300222490000700235520287400242100001703116700002003133700001403153700002003167700001903187856012803206       2005                        eng d00aIncreased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland ecosystem0 aIncreased rainfall variability and reduced rainfall amount decre  a322 -3440 v113 aPredicted climate changes in the US Central Plains include altered precipitation regimes with increased occurrence of growing season droughts and higher frequencies of extreme rainfall events. Changes in the amounts and timing of rainfall events will likely affect ecosystem processes, including those that control C cycling and storage. Soil carbon dioxide (CO2) flux is an important component of C cycling in terrestrial ecosystems, and is strongly influenced by climate. While many studies have assessed the influence of soil water content on soil CO2 flux, few have included experimental manipulation of rainfall amounts in intact ecosystems, and we know of no studies that have explicitly addressed the influence of the timing of rainfall events. In order to determine the responses of soil CO2 flux to altered rainfall timing and amounts, we manipulated rainfall inputs to plots of native tallgrass prairie (Konza Prairie, Kansas, USA) over four growing seasons (1998–2001). Specifically, we altered the amounts and/or timing of growing season rainfall in a factorial combination that included two levels of rainfall amount (100% or 70% of naturally occurring rainfall quantity) and two temporal patterns of rain events (ambient timing or a 50% increase in length of dry intervals between events). The size of individual rain events in the altered timing treatment was adjusted so that the quantity of total growing season rainfall in the ambient and altered timing treatments was the same (i.e. fewer, but larger rainfall events characterized the altered timing treatment). Seasonal mean soil CO2 flux decreased by 8% under reduced rainfall amounts, by 13% under altered rainfall timing, and by 20% when both were combined (P<0.01). These changes in soil CO2 flux were consistent with observed changes in plant productivity, which was also reduced by both reduced rainfall quantity and altered rainfall timing. Soil CO2 flux was related to both soil temperature and soil water content in regression analyses; together they explained as much as 64% of the variability in CO2 flux across dates under ambient rainfall timing, but only 38–48% of the variability under altered rainfall timing, suggesting that other factors (e.g. substrate availability, plant or microbial stress) may limit CO2 flux under a climate regime that includes fewer, larger rainfall events. An analysis of the temperature sensitivity of soil CO2 flux indicated that temperature had a reduced effect (lower correlation and lower Q10 values) under the reduced quantity and altered timing treatments. Recognition that changes in the timing of rainfall events may be as, or more, important than changes in rainfall amount in affecting soil CO2 flux and other components of the carbon cycle highlights the complex nature of ecosystem responses to climate change in North American grasslands.1 aHarper, C.W.1 aBlair, John, M.1 aFay, P.A.1 aKnapp, Alan, K.1 aCarlisle, J.D.  uhttp://knz.lternet.edu/content/increased-rainfall-variability-and-reduced-rainfall-amount-decreases-soil-co2-flux-grassland00560nas a2200133   4500008004100000245009200041210006900133260004300202300001000245490001400255653002200269100001700291856011800308       2002                        eng d00aAltered rainfall patterns affect belowground ecosystem processes in a tallgrass prairie0 aAltered rainfall patterns affect belowground ecosystem processes  aManhattan, KSbKansas State University  a1 -820 vMS Thesis10atallgrass prairie1 aHarper, C.W.  uhttp://knz.lternet.edu/content/altered-rainfall-patterns-affect-belowground-ecosystem-processes-tallgrass-prairie01540nas a2200229   4500008004100000245009000041210006900131300001500200490000800215520084900223100002001072700001401092700002001106700002401126700001601150700001901166700001701185700001701202700001501219700001901234856005701253       2002                        eng d00aRainfall variability, carbon cycling and plant species diversity in a mesic grassland0 aRainfall variability carbon cycling and plant species diversity   a2202 -22050 v2983 a<p>Ecosystem responses to increased variability in rainfall, a prediction of general circulation models, were assessed in native grassland by reducing storm frequency and increasing rainfall quantity per storm during a 4-year experiment. More extreme rainfall patterns, without concurrent changes in total rainfall quantity, increased temporal variability in soil moisture and plant species diversity. However, carbon cycling processes such as soil CO2 flux, CO2 uptake by the dominant grasses, and aboveground net primary productivity (ANPP) were reduced, and ANPP was more responsive to soil moisture variability than to mean soil water content. Our results show that projected increases in rainfall variability can rapidly alter key carbon cycling processes and plant community composition, independent of changes in total precipitation.</p>1 aKnapp, Alan, K.1 aFay, P.A.1 aBlair, John, M.1 aCollins, Scott., L.1 aSmith, M.D.1 aCarlisle, J.D.1 aHarper, C.W.1 aDanner, B.T.1 aLett, M.S.1 aMcCarron, J.K.  uhttps://science.sciencemag.org/content/298/5601/2202