Altered Rainfall Regimes Research Articles

Separating the role of biotic interactions and climate in determining adaptive response of plants to climate change

Altered rainfall regimes will greatly affect the response of plant species to climate change. However, little is known about how direct effects of changing precipitation on plant performance may depend on other abiotic factors and biotic interactions. We used reciprocal transplants between climatically very different sites with simultaneous manipulation of soil, plant population origin, and neighbor conditions to evaluate local adaptation and possible adaptive response of four Eastern Mediterranean annual plant species to climate change. The effect of site on plant performance was negligible, but soil origin had a strong effect on fecundity, most likely due to differential water retaining ability. Competition by neighbors strongly reduced fitness. We separated the effects of the abiotic and biotic soil properties on plant performance by repeating the field experiment in a greenhouse under homogenous environmental conditions and including a soil biota manipulation treatment. As in the field, plant performance differed among soil origins and neighbor treatments. Moreover, we found plant species-specific responses to soil biota that may be best explained by the differential sensitivity to negative and positive soil biota effects. Overall, under the conditions of our experiment with two contrasting sites, biotic interactions had a strong effect on plant fitness that interacted with and eventually overrode climate. Because climate and biotic interactions covary, reciprocal transplants and climate gradient studies should consider soil biotic interactions and abiotic conditions when evaluating climate change effects on plant performance.

Rain events decrease boreal peatland net CO2 uptake through reduced light availability.

Boreal peatlands store large amounts of carbon, reflecting their important role in the global carbon cycle. The short-term exchange and the long-term storage of atmospheric carbon dioxide (CO2 ) in these ecosystems are closely associated with the permanently wet surface conditions and are susceptible to drought. Especially, the single most important peat forming plant genus, Sphagnum, depends heavily on surface wetness for its primary production. Changes in rainfall patterns are expected to affect surface wetness, but how this transient rewetting affects net ecosystem exchange of CO2 (NEE) remains unknown. This study explores how the timing and characteristics of rain events during photosynthetic active periods, that is daytime, affect peatland NEE and whether rain event associated changes in environmental conditions modify this response (e.g. water table, radiation, vapour pressure deficit, temperature). We analysed an 11-year time series of half-hourly eddy covariance and meteorological measurements from Degerö Stormyr, a boreal peatland in northern Sweden. Our results show that daytime rain events systematically decreased the sink strength of peatlands for atmospheric CO2 . The decrease was best explained by rain associated reduction in light, rather than by rain characteristics or drought length. An average daytime growing season rain event reduced net ecosystem CO2 uptake by 0.23-0.54gCm(-2) . On an annual basis, this reduction of net CO2 uptake corresponds to 24% of the annual net CO2 uptake (NEE) of the study site, equivalent to a 4.4% reduction of gross primary production (GPP) during the growing season. We conclude that reduced light availability associated with rain events is more important in explaining the NEE response to rain events than rain characteristics and changes in water availability. This suggests that peatland CO2 uptake is highly sensitive to changes in cloud cover formation and to altered rainfall regimes, a process hitherto largely ignored.

Does altered rainfall regime change pesticide effects in soil? A terrestrial model ecosystem study from Mediterranean Portugal on the effects of pyrimethanil to soil microbial communities under extremes in rainfall

In this century, agroecosystems are subjected to multiple global change stressors acting in concert such as alterations in rainfall regimes and pesticide use. Alterations in rainfall regimes, characterised by more extreme intra-annual rainfall regimes, have been forecasted for the Mediterranean region. At the same time, the use of pesticides continues to rise. Here, we report the responses of soil microbial community to a model pesticide, i.e., fungicide pyrimethanil (PYR) under altered rainfall regimes (i.e., drought and heavy rainfall) two and eight weeks after PYR application. We measured the functional responses as enzyme activities, potential nitrification and BIOLOG carbon substrate utilisation. We also characterised the soil bacterial communities using polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) method. After two weeks, enzyme activities were mainly responsive to PYR and kinetic parameters, calculated from BIOLOG carbon substrate utilisation, indicated interaction effects from PYR and rain treatments. Bacterial band richness increased with PYR treatment under normal rain and drought regimes, but bacterial band richness was higher at 1X than 5X PYR under heavy rainfall. Bacterial community structure was also different with the PYR and rainfall treatments. By week eight, PYR treated soils remained functionally different from untreated soils. Bacterial band richness was consistent across PYR treatment regardless of rain regime. However, the bacterial community structure remained significantly different among the PYR treatments under different rain regimes. We conclude that rainfall extremes can alter the effect of PYR on the soil microbial community structure without altering PYR effects on soil functions (measured as enzyme activities, potential nitrification and BIOLOG carbon substrate utilisation).

Impact of rainfall gradient on aboveground biomass and soil organic carbon dynamics of forest covers in Gujarat, India

AbstractAlterations in precipitation are affecting forest ecosystems’ soil carbon cycling. To understand how shifts in rainfall may alter these carbon pools, above‐ground biomass (AGB), soil organic carbon (SOC), and microbial biomass carbon (MBC) of tropical forest covers were measured across a rainfall gradient (543–1590 mm) in Gujarat (India), a state falling under semi arid to tropical dry–wet conditions. Species diversity, tree density and soil texture were also measured. Field visits and data collection were carried out for 2 years (2009–2011) in 95 plots of 250 × 250 m in the forest covers across four distinct rainfall zones (RFZs). Data analysis showed that differences seen in the values of the measured parameters across the RFZs are statistically significant (P < 0.05). Positive correlations were observed between mean annual precipitation (MAP) and tree density, species diversity, AGB, SOC, and MBC. Across the RFZs, AGB ranged between 0.09 and 168.28 Mg ha−1; SOC values (up to 25 cm soil depth) varied between 2.94 and 147.84 Mg ha−1. Soil texture and MBC showed a significant impact on the dynamics of SOC in all the RFZs. MBC is more influenced by SOC rather than AGB. Both vegetation type and MAP have an important role in the regulation of SOC in tropical soils. Together, these results reveal complex carbon cycle responses are likely to occur in tropical soils under altered rainfall regimes.

Asplenium bird’s nest ferns in rainforest canopies are climate-contingent refuges for frogs

Epiphytes are important for canopy dwelling organisms because they provide a cool and moist microhabitat in the relatively hot and dry canopy. Here we examine whether epiphytic Asplenium ferns act as important habitats for arboreal frogs. We conducted extensive fern and habitat surveys for frogs in the Philippines, and complimented these surveys with roaming day and night canopy surveys to identify the full extent of habitat use across the vertical strata. We artificially dried ferns of various sizes to identify relationships between water and temperature buffering. Ferns are the preferred diurnal microhabitat and breeding habitat for arboreal frogs. A strong positive relationship exists between fern size and frog usage and abundance. Our drying experiments show that large ferns buffer maximum temperatures and reduce variability in temperatures, and buffering is directly linked to their hydration. Frogs are likely using large ferns for their moist, cool, environments for breeding and daytime retreat, which supports the buffered microhabitat hypothesis—these plants promote species coexistence through habitat creation and amelioration of physical stress. However, drying experiments suggest that this buffering is contingent on regular rainfall. Altered rainfall regimes could lead to the unexpected loss of the functional capacity of these important fern habitats.

Contrasting above‐ and belowground sensitivity of three Great Plains grasslands to altered rainfall regimes

Intensification of the global hydrological cycle with atmospheric warming is expected to increase interannual variation in precipitation amount and the frequency of extreme precipitation events. Although studies in grasslands have shown sensitivity of aboveground net primary productivity (ANPP) to both precipitation amount and event size, we lack equivalent knowledge for responses of belowground net primary productivity (BNPP) and NPP. We conducted a 2-year experiment in three US Great Plains grasslands--the C4-dominated shortgrass prairie (SGP; low ANPP) and tallgrass prairie (TGP; high ANPP), and the C3-dominated northern mixed grass prairie (NMP; intermediate ANPP)--to test three predictions: (i) both ANPP and BNPP responses to increased precipitation amount would vary inversely with mean annual precipitation (MAP) and site productivity; (ii) increased numbers of extreme rainfall events during high-rainfall years would affect high and low MAP sites differently; and (iii) responses belowground would mirror those aboveground. We increased growing season precipitation by as much as 50% by augmenting natural rainfall via (i) many (11-13) small or (ii) fewer (3-5) large watering events, with the latter coinciding with naturally occurring large storms. Both ANPP and BNPP increased with water addition in the two C4 grasslands, with greater ANPP sensitivity in TGP, but greater BNPP and NPP sensitivity in SGP. ANPP and BNPP did not respond to any rainfall manipulations in the C3 -dominated NMP. Consistent with previous studies, fewer larger (extreme) rainfall events increased ANPP relative to many small events in SGP, but event size had no effect in TGP. Neither system responded consistently above- and belowground to event size; consequently, total NPP was insensitive to event size. The diversity of responses observed in these three grassland types underscores the challenge of predicting responses relevant to C cycling to forecast changes in precipitation regimes even within relatively homogeneous biomes such as grasslands.

The Influence of Altered Rainfall Regimes on Early Season N Partitioning Among Early Phenology Annual Plants, a Late Phenology Shrub, and Microbes in a Semi-arid Ecosystem

In Mediterranean-type ecosystems, nitrogen (N) accumulates in soil during dry summer months and rapidly becomes available during early season rain events. The availability of early season N could depend on the size of rainfall events, soil microbial activity, and phenology of the plant community. However, it is poorly understood how precipitation patterns affect the fate of early season N. Microbes and plants with early phenology may compete strongly for early season N but theory suggests that microbial N storage can meet plant N demands later in the season. Using a 15N tracer and rainfall manipulation we investigated the fate of early season N. N allocation patterns differed substantially between microbes, early and late phenology plants. As expected early phenology annuals and microbes took up 15N, within 1 day, whereas a late-phenology shrub allocated 15N to leaves later in the season. We saw no evidence for microbial storage of early season N; the peak of 15N in shrub leaves did not coincide with detectable levels of 15N in the microbial biomass or labile soil pool. This suggests that shrubs were able to access early season N, store and allocate it for growth later in the season. Although we saw no evidence of microbial N storage, N retention in soil organic matter (SOM) was high and microbes may play an important role in sequestering N to SOM. Plant N uptake did not respond significantly to 1 year of rainfall manipulation, but microbes were sensitive to dry conditions. 1 year after 15N addition shrubs had resorbed up to half of the N from leaves whereas N in annuals remained as dead leaf litter. Differences in end-of-season N partitioning between dead and living biomass in the two vegetation types suggest that plant species composition could affect N availability in the following growing season, but it may take several years of altered precipitation patterns to produce rainfall-dependent changes.

Effects of experimental rainfall manipulations on Chihuahuan Desert grassland and shrubland plant communities

Aridland ecosystems are predicted to be responsive to both increases and decreases in precipitation. In addition, chronic droughts may contribute to encroachment of native C3 shrubs into C4-dominated grasslands. We conducted a long-term rainfall manipulation experiment in native grassland, shrubland and the grass-shrub ecotone in the northern Chihuahuan Desert, USA. We evaluated the effects of 5 years of experimental drought and 4 years of water addition on plant community structure and dynamics. We assessed the effects of altered rainfall regimes on the abundance of dominant species as well as on species richness and subdominant grasses, forbs and shrubs. Nonmetric multidimensional scaling and MANOVA were used to quantify changes in species composition in response to chronic addition or reduction of rainfall. We found that drought consistently and strongly decreased cover of Bouteloua eriopoda, the dominant C4 grass in this system, whereas water addition slightly increased cover, with little variation between years. In contrast, neither chronic drought nor increased rainfall had consistent effects on the cover of Larrea tridentata, the dominant C3 shrub. Species richness declined in shrub-dominated vegetation in response to drought whereas richness increased or was unaffected by water addition or drought in mixed- and grass-dominated vegetation. Cover of subdominant shrubs, grasses and forbs changed significantly over time, primarily in response to interannual rainfall variability more so than to our experimental rainfall treatments. Nevertheless, drought and water addition shifted the species composition of plant communities in all three vegetation types. Overall, we found that B. eriopoda responded strongly to drought and less so to irrigation, whereas L. tridentata showed limited response to either treatment. The strong decline in grass cover and the resistance of shrub cover to rainfall reduction suggest that chronic drought may be a key factor promoting shrub dominance during encroachment into desert grassland.

Greenhouse gas fluxes from Atacama Desert soils: a test of biogeochemical potential at the Earth’s arid extreme

Most terrestrial ecosystems support a similar suite of biogeochemical processes largely dependent on the availability of water and labile carbon (C). Here, we explored the biogeochemical potential of soils from Earth’s driest ecosystem, the Atacama Desert, characterized by extremely low moisture and organic C. We sampled surface soil horizons from sites ranging from the Atacama’s hyper-arid core to less-arid locations at higher elevation that supported sparse vegetation. We performed laboratory incubations and measured fluxes of the greenhouse gases carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) as indices of potential biogeochemical activity across this gradient. We were able to stimulate trace gas production at all sites, and treatment responses often suggested the influence of microbial processes. Sites with extant vegetation had higher C concentrations (0.13–0.68%) and produced more CO2 under oxic than sub-oxic conditions, suggesting the presence of aerobic microbial decomposers. In contrast, abiotic CO2 production appeared to predominate in the most arid and C-poor (<0.08% C) sites without plants, with one notable exception. Soils were either a weak source or sink of CH4 under oxic conditions, whereas anoxia stimulated CH4 production across all sites. Several sites were rich in nitrate, and we stimulated N2O fluxes in all soils by headspace manipulation or dissolved organic matter addition. Peak N2O fluxes in the most C-poor soil (0.02% C) were very high, exceeding 3 ng nitrogen g−1 h−1 under anoxic conditions. These results provide evidence of resilience of at least some soil biogeochemical capacity to long-term water and C deprivation in the world’s driest ecosystem. Atacama soils appear capable of responding biogeochemically to moisture inputs, and could conceivably constitute a regionally-important source of N2O under altered rainfall regimes, analogous to other temperate deserts.

Ungulate community richness, grazer extinctions, and human subsistence behavior in southern Africa's Cape Floral Region

Precipitation, primary productivity, and herbivore biomass are linked to ungulate richness (the number of species) in African ecosystems. This study compares the richness of late-middle to late Pleistocene and Holocene ungulate assemblages in southern Africa's Cape Floral Region (CFR). Regression analysis demonstrates that Pleistocene ungulate assemblages are significantly richer than their Holocene counterparts. Elevated Pleistocene ungulate richness is not explained by differential time-averaging, the presence of extinct taxa in Pleistocene assemblages, or by Middle Stone Age (MSA) to Later Stone Age (LSA) technological change, but instead by a greater number of grazing species in Pleistocene faunal communities. Based on modern African analogs, this implies that the Pleistocene assemblages examined here sample time intervals characterized by elevated primary productivity, particularly of grassland habitats, greater ungulate biomass, and altered rainfall regimes. Declining ungulate richness from the Pleistocene to the Holocene supports the hypothesis that the extinction of specialized grazers at the Pleistocene–Holocene transition in the CFR was driven by declining productivity and availability of grassland habitats. The contrast between rich Pleistocene ungulate communities and impoverished Holocene ungulate communities may also explain important differences in MSA and LSA subsistence behavior. It is proposed that intensified exploitation of fish, shellfish, tortoises, and seabirds by LSA foragers during the Holocene reflects an expansion of diet breadth in response to diminished ungulate biomass on the landscape rather than fundamental behavioral/cognitive advances.

Hydrological response and examination of the water resources in an experimental watershed in Greece

The present study examines the impact of an altered rainfall regime on surface and groundwater resources at a gauged mountainous experimental watershed located on the eastern side of Penteli Mountain, in the prefecture of Attica, Greece. The study period concerns the hydrological years from October 2003 to September 2008. A decrease in the annual rainfall depth in the first years and in particular the distinct decrease in winter rainfall has led to a reduction in runoff and groundwater reserves. The authors recommend an infrastructure-based management programme to ensure the sustainable use of the diminishing water resources.

Patterns of ant species diversity and turnover across 2000 km of Amazonian floodplain forest

AbstractAim To determine the effect and relative importance of geographic and local environmental factors on species richness and turnover of ant assemblages in floodplain forests across the Amazon basin.Location Twenty‐six mature forest sites scattered along the entire extension of the Amazon River in Brazil. The study area encompassed nearly 18° of longitude and 3.5° of latitude.Methods Systematic collections of ants were performed at each site during the low‐water season (i.e. when forests are not inundated) using three complementary sampling methods. We used variance partitioning techniques to assess the relative effects of the spatial (latitude and longitude) and environmental (rainfall, length of the dry season and flood height) variables on ant species richness and composition.Results There was a twofold variation in the number of species per site, which was largely explained by inter‐site variations in rainfall seasonality and flooding intensity. In general, there were more species at sites located in the western part of the basin, where the dry season is less severe, or near the river estuary, where precipitation is also high and flooding is less intense. Ant community composition was also affected by environmental heterogeneity. For instance, some species only occurred at those sites less affected by the river’s seasonal flooding, whereas others were mostly associated with the drier or wetter regions of the basin. In addition, the turnover of species increased significantly as geographic distances increased. Nevertheless, the rate of change was small given that many species had a broad distribution across the study area.Main conclusions Ant distribution patterns along the floodplain forests of the Amazon appear to be controlled to a relatively large extent by the current gradient in flooding intensity and – most importantly – in precipitation. Altered rainfall regimes resulting from global warming and land‐use change thus have the potential to influence these patterns.

How will climate change affect plant—herbivore interactions? A tropical waterbird case study

We review interactions between waterfowl and wetlands and outline the shifts that are likely to occur within these relationships through global climate change. We highlight the relative paucity of research on populations of tropical waterfowl and their food plants, and use an iconic tropical species of waterfowl, the Magpie Goose (Anseranas semipalmata), as a case study. We provide background on the known and hypothesised interactions between Magpie Geese and wetlands and provide a hypothetical framework of the mechanistic changes to these relationships through climatic change, including rises in sea level, temperature increases, elevated CO2 levels and altered rainfall regimes. Intrusion of saline water through sea-level rise and extended periods of inundation following increased annual rainfall are the two plausible drivers of change in the wetland sedge plants that support Magpie Geese populations. We show how the relative importance of these, and other, threatening factors can be challenged with data from the field and laboratory under multiple working hypotheses. Understanding the imminent shifts in the structure of wetland plant communities and the likely response of waterfowl populations will focus management on key threats and critical habitat. This includes identification of important wetlands and the construction of buffers at them to slow salt-water intrusion.

Contrasting relationships between precipitation and species richness in space and time

Future changes in precipitation regimes are likely to impact species richness in water‐limited plant communities. Regional, spatial relationships between precipitation and richness could offer information about how altered rainfall will impact local communities, assuming that processes driving the regional relationship are also dominant at fine spatial and short temporal scales. To test this assumption, we compared spatial and temporal relationships between precipitation and both species richness and species turnover in central North American grasslands. Across a broad geographic gradient, mean plant species richness in 1‐m2 plots increased significantly with mean annual precipitation. In contrast, over a 36‐yr period at one mixed‐grass prairie in the center of the regional gradient, single‐year precipitation and richness were poorly correlated, and consecutive wet years had little effect on richness. Instead, richness increased most in wet years that followed dry years. Geographically dispersed sites receiving different levels of mean annual precipitation displayed strong differences in species composition, whereas temporal variation in precipitation at one site was not related to compositional dissimilarity, indicating that species turnover plays a key role in generating the regional relationship. Analyses of individual species’ presence‐absence suggest that the lagged temporal responses reflect environmental germination cues more than resource competition. These complex cues may dampen the initial impact of altered precipitation on diversity, but over the long term, turnover in species composition should lead to changes in richness, as in the regional, spatial relationship. How quickly this long‐term response develops may depend on the colonization rates of species better adapted to the altered rainfall regime.

Precipitation interception in Australian tropical rainforests: II. Altitudinal gradients of cloud interception, stemflow, throughfall and interception

AbstractThis article presents a comprehensive study of canopy interception in six rainforests in Australia's Wet Tropics for periods ranging between 2 and 3·5 years. Measurements of rainfall, throughfall, stemflow and cloud interception were made at sites characterized by different forest types, canopy structure, altitude, rainfall and exposure to prevailing winds. Throughfall at these sites ranged between 64 and 83% of total precipitation inputs, while stemflow ranged between 2 and 11%. At sites higher than 1000 m, cloud interception was found to contribute up to 66% of the monthly water input to the forest, more than twice the rainfall at these times. Over the entire study period, cloud interception accounted for between 4 and 30% of total precipitation inputs, and was related more to the exposure of sites to prevailing winds than to altitudinal differences alone.Over the duration of the study period, interception losses ranged between 22 and 29% of total water input (rainfall and cloud interception) at all sites except the highest altitude site on Bellenden Ker, where interception was 6% of total water input. This smaller interception loss was the result of extremely high rainfall, prolonged immersion in cloud and a sparser canopy. On a monthly basis, interception losses from the six sites varied between 10 and 88% of rainfall. All sites had much higher interception losses during the dry season than in the wet season because of the differences in storm size and rainfall intensity. The link between rainfall conditions and interception losses has important implications for how evaporative losses from forests may respond to altered rainfall regimes under climate change and/or large‐scale atmospheric circulation variations such as El Niño. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Impacts of Re-greening the Desertified Lands in Northwestern China: Implications from a Regional Climate Model Experiment

This paper describes a study that investigates the local and regional effects of vegetation restoration in northern China via regional climate model simulations, and reports implications for the sustainability of vegetation under the altered rainfall regime. Ensemble simulations with the current vegetation cover and an idealized re-greening scenario for a test area in northwestern China (90 � –110 � E and 36 � –42 � N) were performed using large scale boundary forcing derived from 1998. The results indicate that such re-greening has both significant local and regional effects on the atmospheric circulation and rainfall distribution. Replacing desert and semi-desert areas with grass in the test area increases net radiation at the surface, and hence total heat flux from the surface to the atmosphere. This results in enhanced ascending motions and moisture supply to the atmosphere over the test area. Consequently, rainfall increases in the whole test area. However, the increase in rainfall largely occurs due to an increase in intensity rather than an increase in frequency. Lack of frequent rainfall, especially in the lowlands of the test area, makes it very difficult to maintain a vegetated surface. This implies that the current vegetation restoration activities will be largely limited to areas where water resources are relatively abundant, or they will depend heavily on irrigation. The increased runoff at higher elevations could be important for providing water for irrigation in the lowlands. The increase in rainfall in the highlands and far eastern parts of the test area, which already receive more frequent rainfall, may help support a restored vegetation cover in these regions. The enhanced ascending motions over the test area are compensated by increased subsidence to the east, centered over Yellow River Delta and Shandong Peninsula, resulting in a higher-pressure and anticyclonic circulation anomaly there. Consequently, rainfall decreases at these areas. This anticyclonic anomaly provides significant northeasterly low-level anomalous winds that enhance cyclonic shear vorticity in the Yangtze River Basin and South China when they meet southwesterly monsoonal flow. This causes strong ascending anomalies over southern China and the Sichuan Basin, and increases rainfall in these regions.

Productivity responses to altered rainfall patterns in a C4-dominated grassland.

Rainfall variability is a key driver of ecosystem structure and function in grasslands worldwide. Changes in rainfall patterns predicted by global climate models for the central United States are expected to cause lower and increasingly variable soil water availability, which may impact net primary production and plant species composition in native Great Plains grasslands. We experimentally altered the timing and quantity of growing season rainfall inputs by lengthening inter-rainfall dry intervals by 50%, reducing rainfall quantities by 30%, or both, compared to the ambient rainfall regime in a native tallgrass prairie ecosystem in northeastern Kansas. Over three growing seasons, increased rainfall variability caused by altered rainfall timing with no change in total rainfall quantity led to lower and more variable soil water content (0-30 cm depth), an approximately 10% reduction in aboveground net primary productivity (ANPP), increased root to shoot ratios, and greater canopy photon flux density at 30 cm above the soil surface. Lower total ANPP primarily resulted from reduced growth, biomass and flowering of subdominant warm-season C4 grasses while productivity of the dominant C4 grass Andropogon gerardii was relatively unresponsive. In general, vegetation responses to increased soil water content variability were at least equal to those caused by imposing a 30% reduction in rainfall quantity without altering the timing of rainfall inputs. Reduced ANPP most likely resulted from direct effects of soil moisture deficits on root activity, plant water status, and photosynthesis. Altered rainfall regimes are likely to be an important element of climate change scenarios in this grassland, and the nature of interactions with other climate change elements remains a significant challenge for predicting ecosystem responses to climate change.

Altering Rainfall Timing and Quantity in a Mesic Grassland Ecosystem: Design and Performance of Rainfall Manipulation Shelters

Global climate change is predicted to alter growing season rainfall patterns, potentially reducing total amounts of growing season precipitation and redistributing rainfall into fewer but larger individual events. Such changes may affect numerous soil, plant, and ecosystem properties in grasslands and ultimately impact their productivity and biological diversity. Rainout shelters are useful tools for experimental manipulations of rainfall patterns, and permanent fixed-location shelters were established in 1997 to conduct the Rainfall Manipulation Plot study in a mesic tallgrass prairie ecosystem in northeastern Kansas. Twelv e9x1 4 ‐mfixed-location rainfall manipulation shelters were constructed to impose factorial combinations of 30% reduced rainfall quantity and 50% greater interrainfall dry periods o n6x6 ‐mplots, to examine how altered rainfall regimes may affect plant species composition, nutrient cycling, and above- and belowground plant growth dynamics. The shelters provided complete control of growing season rainfall patterns, whereas effects on photosynthetic photon flux density, nighttime net radiation, and soil temperature generally were comparable to other similar shelter designs. Soil and plant responses to the first growing season of rainfall manipulations (1998) suggested that the interval between rainfall events may be a primary driver in grassland ecosystem responses to altered rainfall patterns. Aboveground net primary productivity, soil CO2 flux, and flowering duration were reduced by the increased interrainfall intervals and were mostly unaffected by reduced rainfall quantity. The timing of rainfall events and resulting temporal patterns of soil moisture relative to critical times for microbial activity, biomass accumulation, plant life histories, and other ecological properties may regulate longerterm responses to altered rainfall patterns.