Frequency Of Rain Events Research Articles

Agronomic and environmental performance of dairy farms in a warmer, wetter climate

The northeast United States has experienced higher temperatures, more annual precipitation, and more frequent heavy rain events in recent decades. These trends appear likely to continue, and they may depress crop yields and exacerbate environmental problems associated with the region’s dairy farms. To investigate these possibilities, we used the Agricultural Policy/Environmental eXtender (APEX) model to simulate runoff, erosion, nutrient losses, and crop yields on two Vermont farms in a small set of possible future climates. Raising temperatures by 2°C, combined with increasing total precipitation or changing the seasonality of precipitation, had relatively modest effects on any outcome (less than 10% change in median values). However, a combination of higher temperatures and more intense precipitation led to increased runoff volumes and larger soil and nutrient losses. Median values of runoff, sediment, and nutrient losses increased by 2% to 15% at one site and by 36% to 58% at the other (although the changes at the latter site were relative to very low baseline values), while the 95th percentile rose by 6% to 19% and 53% to 65%. This suggests that management practices adapted to reducing runoff etc. in extreme precipitation events will be increasingly valuable in the coming years. Corn (<i>Zea mays</i> L.) silage yields changed by less than 10% in all simulations, and in some cases increased slightly. However, modeling that includes many additional factors that can reduce yields (such as new pests, or delays to farm operations in wet conditions) is needed for a more complete understanding of how climate change may affect the viability of forage production on dairy farms in this region.

Potential Release of Zinc and Cadmium From Mine-Affected Soils Under Flooding, a Mesocosm Study

Metal-contaminated mining soils pose serious environmental and health risks if not properly managed, especially in mountainous areas, which are more susceptible to perturbation. Currently, climate change is leading to more frequent and intense rain events, which cause flooding episodes, thereby altering soil redox equilibria and contaminants stability. We evaluated the potential release of Zn and Cd (two of the most common inorganic contaminants) and the factors regulating their solubility and speciation in two heavily contaminated soils representative of a Zn-mining area. The soils were flooded under aerobic (for 24 h) and anaerobic (for 62 days) conditions using mesocosm experiments, sequential extractions, and geochemical modelling. Leaching trials under aerobic conditions showed a high release of Zn and Cd (10 times the legislative limits), with metals possibly migrating via water infiltration or runoff. Under anaerobic conditions Zn and Cd were initially released. Then, solution concentrations decreased gradually (Zn) or sharply (Cd) until the end of the experiment. Sequential extractions and multisurface modelling indicated that both metals precipitated mainly as carbonates. This was confirmed by a geochemical multisurface modelling, which also predicted the formation of sulphides after 60 days in one soil. The model calculated metals to be preferentially complexed by organic matter and well predicted the observed soil solution concentrations. The results showed that during flooding episodes contaminants could be promptly transferred to other environmental compartments. The use of multisurface modelling coupled with laboratory experiments provided useful indications on the potential release and speciation in case of anoxic conditions.

Quantification of spatial and temporal variations in trace element fluxes originating from urban areas at the catchment scale

The release of trace elements (TE) associated with the development of human activities has accelerated since the nineteenth century, leading to the pollution of river systems. Despite a drastic reduction in industrial inputs in northern Europe, diffuse pollution originating from urban areas still prevents achieving the good status required by the European Water Framework Directive. The objectives of the current study, which is a part of a wider project, were to determine the impact of hydrological dynamics on the total exports of TE from an urban catchment and to develop an assessment tool to evaluate the level of contamination of a catchment based on its specific particulate TE fluxes. Accordingly, this research investigated the behavior of TE contamination in a 950 km2 catchment (Orge River, France) showing a strong urbanization gradient in downstream direction. Particulate and dissolved samples were collected in the river during a hydrological year at four stations reflecting the increasing urbanization gradient. Trace element concentrations were measured in the samples using inductively coupled plasma/mass spectrometry (ICP-MS). Daily and annual TE fluxes were calculated at the four stations to evaluate the contribution of urban areas to the total TE exports from the catchment. The quantification of TE fluxes showed that up to 70% of particulate Cu, Zn, Sb, and Pb exported by the Orge River originated from the urban areas located in the lower catchment portions, especially during average water flow periods characterized by frequent rain events. Moreover, the results show that 50% of the dissolved fluxes of Cu, Zn, and Pb are supplied by urban areas during the entire year, regardless of hydrological conditions, and that the specific contribution of floods to these fluxes (i.e., the June 2016 event) is lower than that in other catchments because of the continuous supply of dissolved metal fluxes to the river in this urbanized environment. These results underline the need to integrate all hydrological conditions for the management of TE contamination in urban areas and not to focus on storm events only. Finally, based on a literature survey, the ratios of specific fluxes were homogeneous across different highly urbanized catchments, and they could be used as a tool to compare the levels of anthropogenic pressure in these contrasted study sites. This observation demonstrates the similar impacts of societal development on urban river geochemistry worldwide, although they occurred during different time periods.

A study on variation of atmospheric pollutants over Bhubaneswar during imposition of nationwide lockdown in India for the COVID-19 pandemic.

The nationwide lockdown in India to flatten the pandemic COVID-19 curve has resulted in the reduction of anthropogenic emission sources to a great extent. This study reports change in air quality and its impact on the environment during the unique lockdown scenario at Bhubaneswar, a coastal smart city in east India. The urban air shows a remarkable reduction in the mean pollutant levels influenced by traffic emission viz. NOx (~ 67 %) and BC (~ 47 %) during lockdown over the pre-lockdown. Comparatively, a lower reduction of CO (~ 14 %) is attributed to the dominance of natural atmospheric chemical regulation and biogenic sources in addition to anthropogenic contributions. In addition to the lockdown, frequent rain events due to depression in the Bay of Bengal (BoB) also had a significant role in the reduction of the primary pollutants over the study site. An enhancement of secondary pollutant viz. O3 (~ 3%) with a distinct diurnal pattern was observed during the first phase of lockdown over the pre-lockdown period. An anti-correlation between O3 and NOx during pre-lockdown points to a higher O3 production potential with decreasing NOx. While a reduction in the titration of O3 due to suppression of fresh NO emissions led to accumulation of O3 in the first phase of lockdown, inhibited photochemistry due to cloudy skies as well as reduction in precursors led to lower O3 values during the later phases of lockdown.Electronic supplementary materialThe online version of this article (10.1007/s11869-020-00916-5) contains supplementary material, which is available to authorized users.

Dynamics of fungal and bacterial groups and their carbon sources during the growing season of maize in a long-term experiment

The relative contribution of different microbial groups to soil organic matter (SOM) turnover and utilisation of rhizodeposits during a cropping season has remained largely unknown. We used a long-term field experiment (started in 1956), in which C3 crops were replaced with C4 silage maize in 2000, to investigate dynamics of fungi and bacterial groups and their utilisation of ‘young-C4’ and ‘old-C3’ SOM-derived resource every second week during the cropping season (June–Oct). Treatments include bare fallow, unfertilised, fertilised with mineral N and fertilised with farmyard manure (FYM) addition. Extracted soil phospholipid fatty acids (PLFAs) were pooled into Gram-positive, Gram-negative bacteria and fungi (18:2ω6,9) groups and their δ13C values determined. Total PLFAs amount correlated to the SOM contents (highest in FYM) and increased over the cropping season in N-fertilised and FYM treatments. As a result of a peak in plant growth during a period with frequent rain events in August, δ13C of total PLFAs significantly increased from − 23.8 to − 21.6‰ and − 26.1 to − 24.7‰, in N-fertilised and FYM addition, respectively. This clearly indicated a shift in microbial utilisation from old to young SOM sources, which was linked to increased soil moisture contents and fungal biomass. The abundance of Gram-positive increased and that of Gram-negative bacteria decreased until August and vice versa thereafter. The mean δ13C values of individual microbial groups were highest in fungi (corresponding to their seasonal biomass variation) followed by Gram-positive and Gram-negative bacteria. The results clearly demonstrated that irrespective of fertilisation type, fungi were the main players in seasonal SOM dynamics and were strongly influenced by soil moisture and phenological stage of the maize (i.e. rhizodeposition). Disentangling these microbial controls on C resources utilisation will be crucial for understanding C cycling during a cropping season or on an ecosystem scale.

Sustainable crop production to ensuring food security under climate change: A Mediterranean perspective

The global population is predicted to expand to 9.1 billion by 2050. Countries around the Mediterranean Sea are predicted to achieve a combined population of 529 million by 2025. The current major challenge confronting sustainable agriculture in the Mediterranean region is climate change which has directly affected the extent and frequency of rain events, floods, and droughts, which in turn has influenced land and water productivity and farmers’ livelihoods. The present review highlights the major consequences of climate change for sustainable crop production in the Mediterranean region and evaluates different mitigation strategies for improving agricultural land productivity and water use efficiency along with their impact on farmers’ livelihoods.

Rainfall pulses increased short-term biocrust chlorophyll but not fungal abundance or N availability in a long-term dryland rainfall manipulation experiment

Microbial activity in drylands is mediated by the magnitude and frequency of growing season rain events that will shift as climate change progresses. Nitrogen is often co-limiting with water availability to dryland plants. This study investigated how microbes important to the nitrogen (N) cycle and soil N availability varied temporally and spatially in the context of a long-term rainfall variability experiment in the northern Chihuahuan Desert. Specifically, biological soil crust (biocrust) chlorophyll content, fungal abundance, and inorganic N were measured in soils adjacent to individuals of the grassland foundation species, Bouteloua eriopoda, and in the unvegetated interspace at multiple time points associated with experimental monsoon rainfall treatments. Treatments included 12 small weekly (5 mm) or 3 large monthly (20 mm) rain events, which had been applied during the summer monsoon for nine years prior to this study. Additionally, target plant C:N ratios were measured, and 15N-glutamate was added to biocrusts to determine potential for nutrient transport to B. eriopoda. Biocrust chlorophyll was up to 67% higher in the small weekly and large monthly rainfall treatments compared to ambient controls. Fungal biomass was 57% lower in soil interspaces than adjacent to plants but did not respond to rainfall treatments. Ammonium and nitrate concentrations near plants declined through the sampling period but varied little in soil interspaces. There was limited movement of 15N from interspace biocrusts to leaves but high 15N retention occurred in the soils even after additional ambient and experimental rain events. Plant C:N ratio was unaffected by rainfall treatments. The long-term alteration in rainfall regime in this experiment did not change how short-term microbial abundance or N availability responded to the magnitude or frequency of rain events at the end of the growing season, suggesting a limited response of N availability to future climate change.

The potential of sustainable urban drainage systems (SuDS) as an adaptive strategy to climate change in the Spanish Mediterranean

ABSTRACT Changes in weather pattern caused by climate change generate more frequent extreme rain events as well as droughts. Sustainable urban drainage systems (SuDS) are useful adaptations to this new reality. The paper surveys the use of these systems in other countries in relation to their use in Spain, particularly the Spanish Mediterranean region. There is a future for more detention of floodwaters as well as more use against drought of water which can be treated and reused.

High time-resolved measurements of water-soluble sulfate, nitrate and ammonium in PM2.5 and their precursor gases over the Eastern Mediterranean

High time-resolved measurements of aerosol SO42−, NO3−, NH4+ and their precursor gases HNO3, SO2, NH3 between 27 and 02 January/February and 19–01 August/September 2015 were carried out by applying AIM-IC at a rural site located on the coast of the Eastern Mediterranean, Erdemli, Turkey. The comparison between online and offline techniques revealed better correlation coefficients for SO42− and NH4+ (r > 0.90) than that of NO3− (0.63). Mean concentrations of water-soluble species were found in decreasing order SO42− (2814 ng m−3) > NH4+ (1371 ng m−3) > NO3− (495 ng m−3). NH3 (3390 ng m−3) concentration was more than enough to neutralize SO2 (879 ng m−3) and HNO3 (346 ng m−3). The gas-to-particle conversion ratios (>0.3) implied that SO42−, NO3− and NH4+ were mainly influenced by non-local sources. SO42−, NO3−, NH4+, HNO3, SO2 exhibited remarkable decrease (leastways 40%) in the atmosphere over the Eastern Mediterranean throughout fifteen years. In winter, day time NH3 concentrations illustrated significant relationship with temperature (positive) and humidity (negative), implying evaporation of dew or emission from plant stoma. Whereas, diurnal cycle of SO42− and SO2 was considerably influenced by populated City of Mersin in winter. During summer, HNO3 and SO2 (r = 0.74) demonstrated similar diurnal cycle, suggesting a common source for these precursor gases whilst NH3 was considerably affected by biomass burning emissions. Variability of all species was governed by local or nearly mesoscale transport in winter possibly due to frequent rain events. In summer, air flow from Eastern Mediterranean denoted aged air masses (GPC > 0.65) containing rather uniform concentrations of SO42− (~65 nmol m−3) and NH4+ (~140 nmol m−3). The highest NH3 along with the greatest % KBB contribution to PM2.5 mass was observed under the influence of Northerly airflow, exhibiting significance of biomass burning emissions as a source of NH3 in summer.

Larval exposure to low salinity compromises metamorphosis and growth in the colonial ascidian Botrylloides violaceus

AbstractCoastal and estuarine ecosystems exhibit extreme fluctuations in abiotic factors that influence the success and distribution of many introduced marine invertebrates. The frequency of these fluctuations may worsen under the scenario of climate change due to more intense storm events or greater precipitation. While many studies have focused on the response of adult ascidians to salinity, few have examined the response of larvae to low salinity events or post‐metamorphic asexual reproduction after larval exposure to low salinity. Here we tested the effect of low salinity on larval metamorphosis and post‐metamorphic growth of the introduced ascidian Botrylloides violaceus. We exposed tadpole larvae to salinities ranging 0–30 ppt. Tadpoles metamorphosed in salinities as low as 16 ppt and percent metamorphosis of larvae was not significantly different at salinities &gt;20 ppt. A few tadpoles metamorphosed within 2–4 hr after release, and larval metamorphosis continued for 3–4 days, suggesting that larvae could disperse considerable distances. We then tested post‐metamorphic survival, growth, and asexual reproduction of larvae exposed (5–7 days) to varying salinities (18, 20, 25, and 30 ppt), and placed the resulting colonies in full‐salinity natural seawater; colony growth was monitored for 9 weeks post‐metamorphosis. Results indicated that colonies whose larvae were exposed to low salinity (&lt;25 ppt) had fewer zooids than colonies from larvae exposed to seawater at 30 ppt, but total area occupied by each colony was similar among salinity treatments. Because each individual zooid within a colony filter‐feeds and reproduces through asexual budding, fewer feeding individuals within a colony will likely reduce future growth and reproduction. Due to the likelihood of more frequent heavy rain events and low‐salinity conditions for the northwest Atlantic Ocean, there is need for continued research to assess the response of ascidians to factors like salinity and to evaluate the spread of ascidians and their adaptation to estuarine and coastal habitats.

Tale of Two Storms: Impact of Extreme Rain Events on the Biogeochemistry of Lake Superior.

Climate change is expected to profoundly affect the Great Lakes region of North America. An increase in intensity and frequency of rain events is anticipated to deliver more runoff and to increase riverine inputs to Lake Superior's ecosystem. The effects of these changes on key biogeochemical parameters were analyzed by coupling satellite data, water column sensor profiles, and discrete surface-water sampling after two "500-year" flood events in the Lake Superior basin. This study provides both a spatial and a temporal sense of how plumes interacted within the ecosystem. We also determined the significant differences in water quality parameters for plume versus non-plume waters. These two plumes were important for delivery of nutrients, with variable transport of sediments and colored dissolved organic matter (CDOM). Data from the 2012 storm event showed a significant input of total nitrogen (TN), total phosphorous (TP) and CDOM to the system. In the 2016 storm event, carbon cycling parameters (acidity, total inorganic carbon (TIC), and dissolved organic carbon (DOC), and ammonia levels were elevated within the plume. In neither storm event was there a significant difference in chlorophyll a between plume and non-plume waters during our sampling cruises. These two plume events were similar in amount of precipitation, but their effect on the biogeochemistry of Lake Superior varied due to differences in the watersheds where the rain fell. The studied plume events were dynamic, changing with currents, winds and the settling of suspended sediments.

Does the severity of non‐flow periods influence ecosystem structure and function of temporary streams? A mesocosm study

Abstract Global change is dramatically altering flow regimes worldwide. Among the most important consequences are the transition of many permanent waterways to temporary waterways, the increase in duration and frequency of non‐flow periods of temporary streams, and the increase in the severity (i.e. irradiance, temperature and humidity) of the non‐flow period. Nowadays, there is a lack of knowledge on how changes in duration, frequency and severity of the non‐flow period will reflect on biodiversity and biogeochemical changes in temporary streams. We designed a manipulative experiment using artificial streams to evaluate the effects of severity of the non‐flow period on stream biofilms. Sixteen artificial streams were assigned to four treatments: continuous flow, continuous intermittency and intermittency with and without rain events. Effects were assessed on selected features of stream biofilm structure (i.e. bacterial density and basal fluorescence) and function (photosynthetic efficiency and enzymatic activities), as well as CO2 emissions and dissolved organic matter quantity and quality from water column and sediments. The occurrence of rain events during the non‐flow period enhanced organic carbon processing and CO2 emissions to the atmosphere, reducing the sediment reservoir of exportable organic carbon and therefore reducing the dissolved organic carbon exports from streambeds at flow resumption. Given the ongoing reducing trends in the frequency of rain events in semi‐arid and arid regions, we expect temporary streams to process and emit less and to export more carbon to downstream systems.

Rainfall Intensification Enhances Deep Percolation and Soil Water Content in Tilled and No‐Till Cropping Systems of the US Midwest

Core Ideas Rainfall intensification increased deep percolation in tilled and no‐till systems. Rainfall intensification increased deep soil water content in both cropping systems. A bromide tracer was detected at 1.2‐m depth sooner in no‐till than tilled systems. The effect of rainfall intensification on surface soil moisture varied seasonally. Globally, the proportion of total rainfall occurring as extreme events is increasing, which may have consequences for agriculture. In the US Midwest, we conducted a 234‐d manipulative experiment in 16 paired plots where we increased the proportion of rain falling in extreme events on tilled and no‐till cropping systems. We compared the effects of larger, less frequent rain events (“intensified” rainfall) vs. smaller, more frequent rain events (“normal” rainfall) on soil water content and deep percolation. The effect of intensified rainfall on the volumetric water content (VWC) of soil at the 10‐cm depth during the experiment varied seasonally: in spring, intensified rainfall decreased the average VWC at the 10‐cm depth by 0.05 ± 0.01 cm3 cm−3 compared with normal rainfall, but in summer and fall, it had no effect. In soil at the 100‐cm depth, VWC declined during the summer in normal but not intensified plots. A surface‐added Br− tracer was detected and peaked earlier in soil water at 120 cm under intensified rainfall vs. normal rainfall (by 6 ± 3 and 74 ± 33 d, respectively) regardless of tillage, although it was detected sooner in no‐till than tilled systems (by 9 ± 3 d). Also, less Br− was recovered in soil under intensified (8 ± 8% of total Br− added) vs. normal rainfall (21 ± 3%). Our results suggest that rainfall intensification will increase deep percolation and deep soil water content in cropping systems regardless of tillage. Such changes to soil water dynamics may alter plant water and nutrient availability.

Response of a fractured bedrock aquifer to recharge from heavy rainfall events

Climate change is predicted to lead to an increased frequency of high intensity rainfall events. The impact on groundwater resources, particularly in areas of fractured bedrock aquifer systems, requires knowledge of how recharge is affected. In this study, the response of a fractured bedrock aquifer to heavy rainfall events is characterized. The study area is the Gulf Islands, a temperate region in British Columbia, Canada. Of the 14 provincial observation wells with hourly groundwater level data, only three showed pronounced responses to heavy rain events and were analyzed in detail. A detailed analysis at one well suggests rises in groundwater level were better correlated to all rain events than exclusively heavy rain during summer. The strength of the correlation decreased as the rainfall intensity increased. Solution of the Green-Ampt equation for rainfall events of varying magnitude indicated that an increase in rainfall intensity leads to more surface ponding and overland flow. Thus, the occurrence of more frequent heavy rain events in the future may result in lower net recharge. Thermal infrared images in seepage areas and the δ18O and δ2H composition for precipitation and seepage suggest rapid seepage responses to heavy rain events and rapid seepage dissipation rates. The overall rapid response of the fractured bedrock was advantageous for studying the response of the system to heavy rain events.

Snow deposition patterns on southern Spitsbergen glaciers, Svalbard, in relation to recent meteorological conditions and local topography

ABSTRACTWe present a detailed study on snow cover on six different glaciers in southern Spitsbergen, Svalbard: Amundsenisen, Flatbreen, Hansbreen, Nannbreen, Storbreen and Werenskioldbreen. Fieldwork was carried out in April–May 2013, at the end of the accumulation season, to determine large-scale spatial distribution patterns of snow cover on glaciers surrounding the Hornsund Fjord. Snow depth was measured using an 800 MHz ground-penetrating radar (GPR). In addition, the structure of the snowpack was determined by digging snow pits and collecting snow cores from different glacier facies. These samples were subsequently analysed against circulation types and meteorological data from selected sites. In particular, snow patterns were compared against rain-on-snow events. The mean snow depth measures ranged from 1.90 m (Werenskioldbreen) to 3.80 m (Amundsenisen), whereas the accumulation gradient ranged from 15 cm 100 m−1 (Storbreen) to 74 cm 100 m−1 (Nannbreen). These results followed previous observations, suggesting a decrease in snow accumulation from coastal areas towards the island’s interior. The estimated snow water equivalent values were lower than those measured in the 1990s and during 2010 (Hansbreen: c. −48%), with the exception of Amundsenisen (c. +17%). The relatively high densities found in the snowpack did not compensate for the shallow snow depths measured, which can be ascribed to low precipitation totals and an increased frequency of rain events during the winter months.

Assessing the environmental controls on Scots pine transpiration and the implications for water partitioning in a boreal headwater catchment

Climate change projections indicate reduced summer precipitation and increased air temperature for the northern high latitudes. These climate changes are likely to alter forest water budgets of which plant transpiration (T) forms a significant component. Plant transpiration is regulated by stomata behavior of particular species, which is constrained by ambient air and soil conditions. Here, we measured sap flow in a Scots pine (Pinus Sylvestris) plantation in a low energy Scottish headwater catchment during the main summer growth period. Effects of rainfall on forest transpiration, as well as the response of T to four environmental variables were investigated at a daily scale. In this boreal environment, transpiration was mainly restricted by radiation and vapor pressure deficit. Air temperature was the least important controlling factor. Soil water became an important factor when rainfall was limited. Frequent but small rain events dictated that precipitation met short-term transpiration demand most of the time. The trees needed supplementary water from antecedent soil water stores when weekly rainfall was below ∼8mm, but such periods were rare. Water exchange mainly occurred in the canopy or upper 10cm of the soil, with 47% of rainfall transpired, 45% intercepted and <8% evaporated from the soil surface. Understanding interactions between forests and their hydroclimate, as well as the role of forests in water partitioning is crucial to assist a sustainable land and water management in a changing climate. Whilst such studies are common in semi-arid regions, they are limited in boreal zones, therefore, our findings are a valuable contribution to understanding plant-water relations in a changing environment.

Frequency of extreme Sahelian storms tripled since 1982 in satellite observations.

The hydrological cycle is expected to intensify under global warming, with studies reporting more frequent extreme rain events in many regions of the world, and predicting increases in future flood frequency. Such early, predominantly mid-latitude observations are essential because of shortcomings within climate models in their depiction of convective rainfall. A globally important group of intense storms-mesoscale convective systems (MCSs)-poses a particular challenge, because they organize dynamically on spatial scales that cannot be resolved by conventional climate models. Here, we use 35 years of satellite observations from the West African Sahel to reveal a persistent increase in the frequency of the most intense MCSs. Sahelian storms are some of the most powerful on the planet, and rain gauges in this region have recorded a rise in 'extreme' daily rainfall totals. We find that intense MCS frequency is only weakly related to the multidecadal recovery of Sahel annual rainfall, but is highly correlated with global land temperatures. Analysis of trends across Africa reveals that MCS intensification is limited to a narrow band south of the Sahara desert. During this period, wet-season Sahelian temperatures have not risen, ruling out the possibility that rainfall has intensified in response to locally warmer conditions. On the other hand, the meridional temperature gradient spanning the Sahel has increased in recent decades, consistent with anthropogenic forcing driving enhanced Saharan warming. We argue that Saharan warming intensifies convection within Sahelian MCSs through increased wind shear and changes to the Saharan air layer. The meridional gradient is projected to strengthen throughout the twenty-first century, suggesting that the Sahel will experience particularly marked increases in extreme rain. The remarkably rapid intensification of Sahelian MCSs since the 1980s sheds new light on the response of organized tropical convection to global warming, and challenges conventional projections made by general circulation models.

Governing green stormwater infrastructure: the Philadelphia experience

ABSTRACTMany cities throughout the world are adopting green infrastructure techniques to reduce stormwater and sewer overflows into waterways, which is particularly problematic for places experiencing more frequent and severe rain events. Governance of green stormwater implementation is proving to be as important as the techniques themselves. Building on the climate and sustainability governance literature, we argue that effective governance requires planning across city departments, experimentation and a strategy for organisational learning. We employ a case study of Philadelphia, the first city in the United States to attempt an entirely green approach to meeting federal regulations to examine issues of governance that emerged and how they were addressed. The case study draws on interviews with fourteen public and private sector actors involved in implementation, a site visit to observe the installations and to discuss the approach with a key planner, and grey literature. We find that silos can be broken down and that if open communications and a willingness to change practices are present, obstacles cited in the literature can be overcome. The key implication is that the three elements of governance need to be built into the green infrastructure planning process. While the analysis focuses on a US city, the departments involved and the governance needs of green stormwater infrastructure are similar in cities in much of the world.

Rainfall effects on the sap flow of Hedysarum scoparium.

In arid and semi-arid areas, plant physiological responses to water availability depend largely on the intensity and frequency of rain events. Knowledge on the responses of xerophytic plants to rain events is important for predicting the structure and functioning of dryland ecosystems under changing climate. The sap flow of Hedysarum scoparium in the Mu Us Sand Land was continuously measured during the growing season of 2012 and 2013. The objectives were to quantify the dynamics of sap flow under different weather conditions, and to examine the responses of sap flow to rain events of different sizes. The results showed that the daily sap flow rates of H. scoparium were lower on rainy days than on clear days. On clear days, the sap flow of H. scoparium showed a midday plateau, and was positively correlated with solar radiation and relative humidity. On rainy days, the sap flow fluctuated at low levels, and was positively correlated with solar radiation and air temperature. Rain events not only affected the sap flow on rainy days through variations in climatic factors (e.g., solar radiation and air temperature), but also affected post-rainfall sap flow velocities though changes in soil moisture. Small rain events (<20 mm) did not change the sap flow, whereas large rain events (>20 mm) significantly increased the sap flow on days following rainfall. Rain-wetted soil conditions not only resulted in higher sap flow velocities, but also enhanced the sensitivity of sap flow to solar radiation, vapor pressure deficit and air temperature.

Climate change induced rainfall patterns affect wheat productivity and agroecosystem functioning dependent on soil types

AbstractWheat is a crop of global importance that supplies carbohydrates to more than half of the worlds’ population. We examined whether climate change‐induced rainfall patterns, which are expected to produce less frequent but heavier rain events, will alter the productivity of wheat and agroecosystem functioning on three different soil types. Therefore, in a full‐factorial experiment, Triticum aestivum L. was cultivated in 3‐m2 lysimeter plots, each of which contained one of the following soil types: sandy calcaric phaeozem, gleyic phaeozem and calcic chernozem. Predicted rainfall patterns based on the calculations of a regionalised climate change model were compared with the current long‐term rainfall patterns, and each treatment combination was replicated three times. Future rainfall patterns significantly reduced wheat yield, leaf area index, and plant height at the earlier growth stages; it equally decreased the arbuscular mycorrhizal fungi colonisation of roots and increased the stable carbon isotope signature (δ13C) of wheat leaves. Sandy soils with inherently lower mineralization potential negatively affected wheat growth, harvest index, and yield but stimulated early season root production. The interaction between rainfall and soil type was significant for the harvest index and early wheat development. Our results suggest that changes in rainfall intensity and frequency can significantly affect the functioning of wheat agroecosystems. Wheat production under future rainfall conditions will likely become more challenging as further concurrent climate change factors become prevalent.