Normal Rainfall Years Research Articles

New spatial and temporal indices of Indian summer monsoon rainfall

The overall yearly seasonal performance of Indian southwest monsoon rainfall (ISMR) for the whole Indian land mass is presently expressed by the India Meteorological Department (IMD) by a single number, the total quantum of rainfall. Any particular year is declared as excess/deficit or normal monsoon rainfall year on the basis of this single number. It is well known that monsoon rainfall also has high interannual variability in spatial and temporal scales. To account for these aspects in ISMR, we propose two new spatial and temporal indices. These indices have been calculated using the 115 years of IMD daily 0.25° × 0.25° gridded rainfall data. Both indices seem to go in tandem with the in vogue seasonal quantum index. The anomaly analysis indicates that the indices during excess monsoon years behave randomly, while for deficit monsoon years the phase of all the three indices is the same. Evaluation of these indices is also studied with respect to the existing dynamical indices based on large-scale circulation. It is found that the new temporal indices have better link with circulation indices as compared to the new spatial indices. El Nino and Southern Oscillation (ENSO) especially over the equatorial Pacific Ocean still have the largest influence in both the new indices. However, temporal indices have much better remote influence as compared to that of spatial indices. Linkages over the Indian Ocean regions are very different in both the spatial and temporal indices. Continuous wavelet transform (CWT) analysis indicates that the complete spectrum of oscillation of the QI is shared in the lower oscillation band by the spatial index and in the higher oscillation band by the temporal index. These new indices may give some extra dimension to study Indian summer monsoon variability.

Trends and variability of meteorological drought over the districts of India using standardized precipitation index

Meteorological drought during the southwest monsoon season and for the northeast monsoon season over five meteorological subdivisions of India for the period 1901–2015 has been examined using district and all India standardized precipitation index (SPI). Whenever all India southwest monsoon rainfall was less than −10% or below normal, for those years all India SPI was found as −1 or less. Composite analysis of SPI for the below normal years, viz., less than −15% and −20% of normal rainfall years indicate that during those years more than 30% of country’s area was under drought condition, whenever all India southwest monsoon rainfall was –15% or less than normal. Trend analysis of monthly SPI for the monsoon months identified the districts experiencing significant increase in drought occurrences. Significant positive correlation has been found with the meteorological drought over most of the districts of central, northern and peninsular India, while negative correlation was seen over the districts of eastern India with NINO 3.4 SST. For the first time, meteorological drought analysis over districts and its association with equatorial pacific SST and probability analysis has been done for the northeast monsoon over the affected regions of south peninsular India. Temporal correlation of all India southwest monsoon SPI and south peninsular India northeast monsoon SPI has been done with the global SST to identify the teleconnection of drought in India with global parameters.

Phenocams Bridge the Gap between Field and Satellite Observations in an Arid Grassland Ecosystem

Near surface (i.e., camera) and satellite remote sensing metrics have become widely used indicators of plant growing seasons. While robust linkages have been established between field metrics and ecosystem exchange in many land cover types, assessment of how well remotely-derived season start and end dates depict field conditions in arid ecosystems remain unknown. We evaluated the correspondence between field measures of start (SOS; leaves unfolded and canopy greenness >0) and end of season (EOS) and canopy greenness for two widespread species in southwestern U.S. ecosystems with those metrics estimated from near-surface cameras and MODIS NDVI for five years (2012–2016). Using Timesat software to estimate SOS and EOS from the phenocam green chromatic coordinate (GCC) greenness index resulted in good agreement with ground observations for honey mesquite but not black grama. Despite differences in the detectability of SOS and EOS for the two species, GCC was significantly correlated with field estimates of canopy greenness for both species throughout the growing season. MODIS NDVI for this arid grassland site was driven by the black grama signal although a mesquite signal was discernable in average rainfall years. Our findings suggest phenocams could help meet myriad needs in natural resource management.

Evaluating the impact of artificial groundwater recharge structures using geo-spatial techniques in the hard-rock terrain of Rajasthan, India

Groundwater levels in hard-rock areas in India have shown very large declines in the recent past. The situation is becoming more critical due to a paucity of rainfall, limited surface water resources and an increasing pattern of groundwater extraction in these areas. Consequently, the Ground Water Department with the aid of World Bank has implemented the water structuring programme to mitigate groundwater scarcity and to develop a viable solution for sustainable development in the region. The present study has been undertaken to assess the impact of artificial groundwater recharge structures in the hard-rock area of Rajasthan, India. In this study groundwater level data (pre-monsoon and post-monsoon) of 85 dug-wells are used, spread over an area of 413.59 km2. The weathered and fractured gneissic basement rocks act as major aquifer in the area. Spatial maps for pre- and post-monsoon groundwater levels were prepared using the kriging interpolation technique with best fitted semi-variogram models (Spherical, Exponential and Gaussian). The groundwater recharge is calculated spatially using the water level fluctuation method. The entire study period (2004–2011) is divided into pre- (2004–2008) and post-intervention (2009–2011) periods. Based on the identical nature of total monsoon rainfall, two combinations of average (2007 and 2009) and more than average (2006 and 2010) rainfall years are selected from the pre- and post-intervention periods for further comparisons. All of the water harvesting structures are grouped into the following categories: as anicuts (masonry overflow structure); percolation tanks; subsurface barriers; and renovation of earthen ponds/nadis. A buffer of 100 m around the intervention site is taken for assessing the influence of these structures on groundwater recharge. The relationship between the monsoon rainfall and groundwater recharge is fitted by power and exponential functions for the periods of 2004–2008 and 2008–2011 with R 2 values of 0.95 and 0.98, respectively. The average groundwater recharge is found to be 18% of total monsoon rainfall prior to intervention and it became 28% during the post-intervention period. About 70.9% (293.43 km2) of the area during average rainfall and more than 95% (396.26 km2) of the area during above-average rainfalls show an increase in groundwater recharge after construction of water harvesting structures. The groundwater recharge pattern indicates a positive impact within the vicinity of intervention sites during both average and above-average rainfall. The anicuts are found to be the most effective recharge structures during periods of above-average rainfall, while subsurface barriers are responded well during average rainfall periods. In the hard-rock terrain, water harvesting structures produce significant increases in groundwater recharge. The geo-spatial techniques that are used are effective for evaluating the response of different artificial groundwater recharge techniques.

Modeling the Effects of Biogenic NOX Emissions on the South African Highveld and Waterberg Regions

The Highveld and Waterberg regions in South Africa contain extensive coal fields and therefore have a high concentration of coal-fired power stations. Previous studies assessed the impact of atmospheric deposition of S- and N-containing species from anthropogenic sources in the region but did not include the effect of biogenic emissions. This study models biogenic NOX soil emissions for the regions and includes them in an atmospheric dispersion model to study the effects of biogenic emission on nitrogen deposition rates. Simulated sulfur deposition rates for the Highveld area are also reported on. Anthropogenic and biogenic sulfur and nitrogen emission sources were inventoried for the Highveld and Waterberg regions. Using previous work by Yienger and Levy, biogenic soil NOX emissions were quantified by constructing models for both areas using land use data, rainfall data, and atmospheric ground level temperatures from CALMET data. A CALPUFF dispersion model was used to predict deposition rates for S- and N-containing species with and without biogenic NOx emissions to determine the impact of biogenic emissions for the Highveld. As rainfall is highly variable in the region, meteorological data representative of high, average, and low rainfall years was used to determine the effect of rainfall on deposition rates for the various species. The biogenic NOx made up 3.96, 4.14, and 3.34% of total released NOx for 2001 (average rainfall), 2003 (low rainfall), and 2010 (high rainfall), respectively. Dry nitrogen deposition rates were affected most by the biogenic component, adding from 1.7 to 6.2% at various receptor locations. Wet deposition rates were affected very little (0.13 to 0.75%). Effect on total nitrogen deposition rates ranged from 0.32 to 1.77%. Biogenic emissions for the Waterberg area, being more arid, were calculated to be only 2.3% of total NOx emissions for the area and accordingly have little effect on deposition rates.

Relationship between aerosol and lightning over Indo-Gangetic Plain (IGP), India

The relationship between aerosol and lightning over the Indo-Gangetic Plain (IGP), India has been evaluated by utilising aerosol optical depth (AOD), cloud droplet effective radius and cloud fraction from Moderate Resolution Imaging Spectroradiometer. Lightning flashes have been observed by the lightning Imaging sensor on the board of Tropical Rainfall and Measuring Mission and humidity from modern-era retrospective-analysis for research and applications for the period of 2001–2012. In this study, the role of aerosol in lightning generation over the north-west sector of IGP has been revealed. It is found that lightning activity increases (decreases) with increasing aerosols during normal (deficient) monsoon rainfall years. However, lightning increases with increasing aerosol during deficient rainfall years when the average value of AOD is less than 0.88. We have found that during deficient rainfall years the moisture content of the atmosphere and cloud fraction is smaller than that during the years with normal or excess monsoon rainfall over the north-west IGP. Over the north-east Bay of Bengal and its adjoining region the variations of moisture and cloud fraction between the deficient and normal rainfall years are minimal. We have found that the occurrence of the lightning over this region is primarily due to its topography and localised circulation. The warm-dry air approaching from north-west converges with moist air emanating from the Bay of Bengal causing instability that creates an environment for deep convective cloud and lightning. The relationship between lightning and aerosol is stronger over the north-west sector of IGP than the north-east, whereas it is moderate over the central IGP. We conclude that aerosol is playing a major role in lightning activity over the north-west sector of IGP, but, local meteorological conditions such as convergences of dry and moist air is the principal cause of lightning over the north-east sector of IGP. In addition, atmospheric humidity also plays an important role in regulating the effect of aerosol on the microphysical properties of clouds over IGP region.

Current and future groundwater withdrawals: Effects, management and energy policy options for a semi-arid Indian watershed

Effects of future expansion/intensification of irrigated agriculture on groundwater and surface water levels and availability in a semi-arid watershed were evaluated using an integrated hydrologic model (MIKE SHE/MIKE 11) in conjunction with biophysical measurements. Improved water use efficiency, water storage, and energy policy options were evaluated for their ability to sustain the future (2035) increased groundwater withdrawals. Three future withdrawal scenarios (low = 20, medium = 30, high = 50 wells/100 km2/year) based on the historical rate of growth of irrigation wells were formulated. While well drying from falling groundwater levels was limited to drought and consecutive below average rainfall years, under the current (2015) withdrawals, significant increases in frequency and duration (17–97 days/year) of well drying along with 13–26% (19–37 mm) reductions in surface flows were predicted under the future withdrawals. Higher (27–108%) energy demands of existing irrigation pumps due to declining groundwater levels and reduced hydroelectric generation due to decreased surface flows would create a vicious water-food-energy nexus in the future. Crop failure, one of the main causes of farmers’ emotional distress and death in the region, is predicted to exacerbate under the future withdrawal scenarios. Shift to negative net recharge (−63 mm) and early and prolonged drying of wells under the high scenario will reduce the groundwater availability and negatively affect crop production in more than 60% and 90% of cropped areas in the Rabi (November–February) and summer (March–May) seasons, respectively during a drought year. Individual and combined demand (drip irrigation and reduced farm electricity subsidy) and supply (water storage) management options improved groundwater levels and reduced well drying by 55–97 days/year compared to business-as-usual management under the high scenario. The combined management (50% drip conversion, 50% reduction in subsidy, and enhanced water storage) mitigated well drying even during drought and consecutive below average rainfall years under the high scenario. A conservative economic evaluation for management options under the high scenario showed increases in crop production and per farmer annual profits by $987–$1397 during a drought year (average household income = $1520/year). A scale-up of results showed that diverting 50% state power subsidy ($6 billion for 3–6 years) can almost entirely fund the conversion to drip irrigation ($4.2 billion) and water storage structures ($2.9 billion) and help meet the water supply demand of a 50% increase in irrigated area under the high scenario. Converting flood to drip irrigation in 50% of irrigated area under the high scenario can reduce the electric energy consumption (7 × 106Mwh/year) and carbon footprint (6000 Mt/year) of groundwater irrigation by 24% in the state. Management options considered can potentially create a sustainable water-food-energy nexus in the larger semi-arid hard rock region. Reducing the power subsidy will require a strong political will since it has been used as a tool to win the elections in India. Considering future agricultural intensification, timely interventions are needed to ensure the livelihood and well-being of millions of small- and medium-scale farmers that rely on low storage, hard rock aquifers in the semi-arid regions of the world.

Differential behaviour of a Lesser Himalayan watershed in extreme rainfall regimes

Climatic extremes including precipitation are bound to intensify in the global warming environment. The present study intends to understand the response of the Tons sub-watershed in Lesser Himalaya, in 3 years with entirely different hydrological conditions (July 2008–June 2011) in terms of discharge, sediment flux and denudation rates. Within an uncertainty limit of ±20%, the mean interannual discharge (5.74 ± 1.44 m 3 s −1) (±SE), was found highly variable (CV: 151%; 0.8–38 m 3 s −1). In a normal rainfall year (2008–2009; ∼1550 mm), the discharge was 5.12 ± 1.75 m 3 s −1, whereas in a drought year (2009–2010), it reduced by 30% with the reduction in ∼23% rainfall (CV: 85%). In an excessive rainfall year (once-in-a-century event) (2010–2011; ∼3050 mm), discharge as well as total solid load was ∼200% higher. Monsoon months (July–September) accounted for more than 90% of the annual solid load transport. The ratio of dissolved to suspended solid (C/P ratio) was consistently low (<1) during monsoon months and higher (1–7) during the rest of the dry period. C/P ratio was inversely (R 2=0.49), but significantly (P <0.001) related to the rainfall. The average mechanical erosion rate in the three different rainfall years was 0.24, 0.19 and 1.03 mmyr −1, whereas the chemical erosion was estimated at 0.12, 0.11 and 0.46 mmyr −1, respectively. Thus, the average denudation rate of the Tons sub-watershed has been estimated at 0.33 mmyr −1 (excluding extreme rainfall year: 1.5 mmyr −1). Our results have implications to understand the hydrological behaviour of the Lesser Himalayan watersheds and will be valuable for the proposed and several upcoming small hydropower plants in the region in the context of regional ecology and natural resource management.

Extreme rainfall and snowfall alter responses of soil respiration to nitrogen fertilization: a 3-year field experiment.

Extreme precipitation is predicted to be more frequent and intense accompanying global warming and may have profound impacts on soil respiration (Rs) and its components, that is, autotrophic (Ra) and heterotrophic (Rh) respiration. However, how natural extreme rainfall or snowfall events affect these fluxes are still lacking, especially under nitrogen (N) fertilization. In this study, extreme rainfall and snowfall events occurred during a 3-year field experiment, allowing us to examine their effects on the response of Rs, Rh, and Ra to N supply. In normal rainfall years of 2011/2012 and 2012/2013, N fertilization significantly stimulated Rs by 23.9% and 10.9%, respectively. This stimulation was mainly due to the increase of Ra because of N-induced increase in plant biomass. In the record wet year of 2013/2014, however, Rs was independent on N supply because of the inhibition effect of the extreme rainfall event. Compared with those in other years, Rh and Ra were reduced by 36.8% and 59.1%, respectively, which were likely related to the anoxic stress on soil microbes and decreased photosynthates supply. Although N supply did not affect annual Rh, the response ratio (RR) of Rh flux to N fertilization decreased firstly during growing season, increased in nongrowing season and peaked during spring thaw in each year. Nongrowing season Rs and Rh contributed 5.5-16.4% to their annual fluxes and were higher in 2012/2013 than other years due to the extreme snowfall inducing higher soil moisture during spring thaw. The RR of nongrowing season Rs and Rh decreased in years with extreme snowfall or rainfall compared to those in normal years. Overall, our results highlight the significant effects of extreme precipitation on responses of Rs and its components to N fertilization, which should be incorporated into models to improve the prediction of carbon-climate feedbacks.

Representação de ciclos harmônicos de séries temporais Modis para análise do cultivo da cana-de-açúcar

Resumo O objetivo deste trabalho foi avaliar o cultivo da cana-de-açúcar, em análise harmônica aplicada a uma série temporal de índices de vegetação Modis, com a representação dos termos harmônicos. Os dados diários de precipitação pluvial para o Estado de São Paulo foram obtidos do Agritempo, acumulados para o período de 16 dias das composições Modis, ao longo das safras de 2004/2005 a 2011/2012. Utilizaram-se o índice de vegetação por diferença normalizada (NDVI) e o índice de realce da vegetação (EVI) em séries temporais decompostas em termos harmônicos pela análise harmônica. Para visualizar a condição de crescimento da vegetação de áreas agrícolas, em especial a informação de fase, aplicou-se a transformação HLS aos termos harmônicos obtidos com o algoritmo Hants, por meio do programa Envi. O cultivo da cana-de-açúcar no Estado de São Paulo apresenta padrões espaciais coerentes com o ciclo de desenvolvimento da cultura e consistentes com a variabilidade das precipitações sazonais que afetam diretamente o momento de máximo dos índices de vegetação. O pico vegetativo da cana-de-açúcar ocorre durante a fase de crescimento, em anos com chuvas normais; porém, em anos de pouca chuva, a fase de maturação da cultura é antecipada e, em anos de muita chuva, a fase de crescimento é antecipada, o que causa o atraso da maturação.

Phenotypic variation and differentiated gene expression of Australian plants in response to declining rainfall.

Declining rainfall is projected to have negative impacts on the demographic performance of plant species. Little is known about the adaptive capacity of species to respond to drying climates, and whether adaptation can keep pace with climate change. In fire-prone ecosystems, episodic recruitment of perennial plant species in the first year post-fire imposes a specific selection environment, offering a unique opportunity to quantify the scope for adaptive response to climate change. We examined the growth of seedlings of four fire-killed species under control and drought conditions for seeds from populations established in years following fire receiving average-to-above-average winter rainfall, or well-below-average winter rainfall. We show that offspring of plants that had established under drought had more efficient water uptake, and/or stored more water per unit biomass, or developed denser leaves, and all maintained higher survival in simulated drought than did offspring of plants established in average annual rainfall years. Adaptive phenotypic responses were not consistent across all traits and species, while plants that had established under severe drought or established in years with average-to-above-average rainfall had an overall different physiological response when growing either with or without water constraints. Seedlings descended from plants established under severe drought also had elevated gene expression in key pathways relating to stress response. Our results demonstrate the capacity for rapid adaptation to climate change through phenotypic variation and regulation of gene expression. However, effective and rapid adaptation to climate change may vary among species depending on their capacity to maintain robust populations under multiple stresses.

Sensitivity analysis of crop yields, soil water contents and nitrogen leaching to precipitation, management practices and soil hydraulic properties in semi-arid and humid regions of Canada using the DSSAT model

Sensitivity analysis of DSSAT outputs to inputs parameters was conducted in two Canadian locations: one for spring wheat (Triticum aestivum L.) in the semi-arid Prairies in Swift Current, Saskatchewan and the second for maize (Zea mays L.) under humid conditions in Woodslee, Ontario. The nominal range sensitivity method, regression, and graphical analysis were used to assess the sensitivity of crop yields, biomass, soil inorganic N, nitrate leaching and soil water contents to soil hydraulic properties, management practices and precipitation. Wheat and maize yields were highly sensitive to soil water drainage upper limit, fertilizer nitrogen rate and precipitation at both locations. At Swift Current, very high soil nitrate leaching (25–140 kg N ha−1) was found in 1994, 1996, 1997 and 2003 as affected by high precipitation in the previous years (i.e., 1993, 1995, 1996 and 2002). Soil N leaching was greater in 2011, a wet year at Woodslee, Ontario, with 20–85 kg N ha−1 than in the normal rainfall years of 2010 and 2012. Based on the fitted N response curves, the maximum yields were obtained at 112 kg N ha−1 for spring wheat at Swift Current and 150–210 kg N ha−1 for maize at Woodslee. The optimum planting date for maize at Woodslee was predicted to be from late May to early June. Sensitivity analysis was found to be useful in assessing the influence of crop management practices, soil parameters and precipitation on crop production and potential environment risks.

VOLATILITY OF SORGHUM PRODUCTION UNDER RAINFALL SYSTEM IN GADARIF STATE, SUDAN

This paper aimed at analyzing the impact of the likely changes in rainfall on sorghum production under rain-fed mechanized farming system in Gadarif State of the Sudan. The study used monthly rainfall data for the period 1941-2014 and sorghum area, production and yield for the period 1970-2014. The data were analyzed by simple statistical and econometric regression methods. Generally, rainfall in Gadarif starts in May and ends by mid-October. The number of rainy days and volume (mm) of rain tended to decrease in June and peak up in July and August. The results indicated an increasing trend of rainfall mostly fallen during July and August during 1941-2014. The results also showed that dry rainfall years affected the productivity of sorghum reducing it by 4.9 kg/feddan/year and that floody rainfall years led to the decrease in the productivity by 11.3 kg/feddan/year, while it was decreasing by 3.39 kg/feddan/year in normal rainfall years. The study found a negative relationship between annual rainfall and crop production. Based on the results obtained, this study recommended concluded that identifying and implementing appropriate adaptation techniques to cope effects with the expected rainfall changes in the future.

Genotypic variation in the accumulation of water-soluble carbohydrate in canola and its potential contribution to seed yield in different environments

Water-soluble carbohydrates (WSC) stored in the stems and pod wall in canola (Brassica napus L.) can be an important source of assimilates contributing to yield. However, genotypic variation in WSC and its contribution to yield have not been investigated. The aims of this work were to quantify genotypic variation of WSC and the extent to which WSC contributes to seed yield. We measured the concentration and content of WSC in a number of hybrid and open pollinated triazine tolerant (TT) and non-TT canola genotypes at flowering, podding and maturity from 2009 to 2011. There were significant repeatable differences in WSC concentration among genotypes (28–108mgg−1 at podding) and WSC content (12–113gm−2 at podding). The major difference in WSC content occurred between the TT and non-TT canola while the difference between hybrid and open-pollinated canola was small. On average, non-TT canola produced higher amount of WSC (68gm−2) than TT canola (47gm−2). Seed yield increased with the increased amount of remobilized WSC in the limited water-stressed conditions (2009 and 2011). Despite the high amount of WSC in drought (2010) year, no significant relationship was found between yield and the remobilized WSC because the higher WSC was offset by yield penalty from delay in flowering in these varieties. The contribution of WSC to yield was higher in drought (10–22%, 2010) year than in the average (3–9%, 2009) and above-average (7–12%, 2011) rainfall year. Genotype and environment interaction was relatively small compared to genotype effect. The difference in the amount of WSC between the herbicide tolerant groups and among genotypes was repeatable and the rankings of genotypes for WSC remained similar across the years. Both the WSC content and the ratio of remobilized WSC to yield had large broad-sense heritability (H=0.68–0.85). The high heritability, the positive relationships between seed yield and WSC under limited water stress conditions, and the high contribution of WSC to yield under drought conditions suggest that WSC could be used as a breeding trait to augment yield in the limited water-stress condition and maintain yield under drought conditions by reducing the effect of water stress on yield.

Multi-year water balance assessment of a newly constructed wetland, Fort McMurray, Alberta

Oil sands mining in Alberta transforms the boreal landscape of forests and wetlands into open pits, tailings ponds and overburden piles. Whereas reclamation efforts have primarily focused on upland forests, rebuilding wetland systems has recently become a motivation for research. Wetland creation and sustainability in this region is complicated by the sub-humid climate and salinity of underlying mining material. In 2012, Syncrude Canada Ltd. completed the construction of the Sandhill Fen Watershed (SFW), a 52-ha upland-wetland system to evaluate wetland reclamation strategies on soft tailings. SFW includes an active pumping system, upland hummocks, a fen wetland and underdrains. To evaluate the influence of management practices on the hydrology of the system, this study reports the water balance from January 2013 to December 2014, the first 2 years after commissioning. A semi-distributed approach was taken to examine the fluxes and stores of water in uplands and lowlands. Natural and artificial inputs and outputs were measured using a series of precipitation gauges and pumps, and evapotranspiration was quantified using three eddy covariance towers. A series of near surface wells recorded water table position. Both 2013 and 2014 were normal rainfall years, with 2013 having more and 2014 less snow than normal. In 2013, inflow/outflow from pumping was the predominant hydrological fluxes, resulting in considerable variability in water table position and storage changes throughout the summer. In 2014, the artificial addition of water was negligible, yet the water table remained near the surface in lowland locations, suggesting that wetland conditions could be maintained under current conditions. Evapotranspiration rates between uplands and lowlands were similar between years and sites, ranging from 2.2 ± 1.8 to 2.5 ± 1.2 mm/day and were largely controlled by climate. These rates were less than nearby older upland systems, suggesting that water balance partitioning will change as vegetation develops. Comparison between years and with natural systems provides insight on how management practices influence hydrologic dynamics and the overall water balance of the SFW. Copyright © 2016 John Wiley & Sons, Ltd.

An assessment of crop water deficits of the plants growing on the Małopolska Upland (Poland)

Abstract The problem of water scarcity is unfavourable for the economy, with the most significant water deficits felt by agriculture. In Poland water deficits in agriculture are occurring more frequently, causing losses in yield, not only in the Lowland areas but also in the Uplands. This paper presents an assessment of the water deficits at various excedance probability levels for four varieties of field crop and for soil types with various water retention capacity, which occur in the Małopolska Upland. Calculations were performed by balancing the amount of available soil water in the root zone. The study was based on the meteorological data from the Institute of Meteorology and Water Management for the years 1971–2010. Daily precipitation data from six rainfall stations: Borusowa, Igołomia, Książ Wielki, Miechów, Olewin and Sielec was utilised as well as average decadal air temperature, water vapour pressure, wind speed and sunshine hours from the meteorological station at Kraków–Balice. The water deficits at an excedance probability level of 20% fluctuated during the growing season from 5 mm (Phaeozems) to 190 mm (Leptosols). In the Małopolska Upland in soils with a medium capacity to retain water (110–160 mm), water deficits have occurred even in years of average rainfall (with probability 50%). This study confirms the considerable impact of the high variability of the soil and pluvial conditions in the region on the water deficits of the field crops.

Carbon Dynamics of Pinus palustris Ecosystems Following Drought

Drought can affect forest structure and function at various spatial and temporal scales. Forest response and recovery from drought may be a result of position within landscape. Longleaf pine forests in the United States have been observed to reduce their carbon sequestration capacity during drought. We collected eddy covariance data at the ends of an edaphic longleaf pine gradient (xeric and mesic sites) over seven years; two years of normal rainfall were followed by 2.5 years of drought, then 2.5 years of normal or slightly above-average rainfall. Drought played a significant role in reducing the physiological capacity of the sites and was compounded when prescribed fire occurred during the same periods. The mesic site has a 40% greater basal area then the xeric site, which accounts for its larger sequestration capacity; however, both sites show the same range of variance in fluxes over the course of the study. Following drought, both sites became carbon sinks. However, the xeric site had a longer carry-over effect and never returned to pre-drought function. Although this study encompassed seven years, we argue that longer studies with greater spatial variance must be undertaken to develop a more comprehensive understanding of forest response to changing climate.

Productivity and evapotranspiration of two contrasting semiarid ecosystems following the 2011 global carbon land sink anomaly

Global carbon balances are increasingly affected by large fluctuations in productivity occurring throughout semiarid regions. Recent analyses found a large C uptake anomaly in 2011 in arid and semiarid regions of the southern hemisphere. Consequently, we compared C and water fluxes of two distinct woody ecosystems (a Mulga (Acacia) woodland and a Corymbia savanna) between August 2012 and August 2014 in semiarid central Australia, demonstrating that the 2011 anomaly was short-lived in both ecosystems. The Mulga woodland was approximately C neutral but with periods of significant uptake within both years. The extreme drought tolerance of Acacia is presumed to have contributed to this. By contrast, the Corymbia savanna was a very large net C source (130 and 200gCm−2yr−1 in average and below average rainfall years, respectively), which is likely to have been a consequence of the degradation of standing, senescent biomass that was a legacy of high productivity during the 2011 anomaly. The magnitude and temporal patterns in ecosystem water-use efficiencies (WUE), derived from eddy covariance data, differed across the two sites, which may reflect differences in the relative contributions of respiration to net C fluxes across the two ecosystems. In contrast, differences in leaf-scale measures of WUE, derived from 13C stable isotope analyses, were apparent at small spatial scales and may reflect the different rooting strategies of Corymbia and Acacia trees within the Corymbia savanna. Restrictions on root growth and infiltration by a siliceous hardpan located below Acacia, whether in the Mulga woodland or in small Mulga patches of the Corymbia savanna, impedes drainage of water to depth, thereby producing a reservoir for soil moisture storage under Acacia while acting as a barrier to access of groundwater by Corymbia trees in Mulga patches, but not in the open Corymbia savanna.

An experimental demonstration that predation influences antelope sex ratios and resource-associated mortality

Smaller, enclosed reserves lacking large mammalian predators are an increasingly popular commercial model in southern Africa and elsewhere. The presence or absence of predation is likely to have major effects on the population dynamics of sexually dimorphic ungulates, with contradictory implications for multiple-use reserves, and to provide fundamental insights into predator–prey relationships.Over a two- and four-year period we determined the adult sex ratios and juvenile mortality of two substantial populations of impala Aepyceros melampus in South Africa – one in predator-free Ithala Game Reserve (IGR), the other in neighbouring predator-laden Hluhluwe-iMfolozi Park (HiP). Data were collected monthly, over a five-day period, by repeated road transects covering a representative sample of the reserves’ habitat types. We assessed differences in adult sex ratios by applying Pearson's chi-square test, whilst to explore the relationship between juvenile mortality, the advance of the breeding year, rainfall and the presence or absence of predators, we used a generalized linear model.We found that the impala adult male to adult female ratio was significantly lower in the presence of predation (HiP=0.43, IGR=0.69). The generalized linear model revealed that the overall proportion of juveniles in breeding herds (defined as herds containing at least one juvenile) declined, over the breeding year, at a faster rate in the presence of predators.Impala juvenile mortality over the breeding year was not significantly affected by lower rainfall in the absence of predators, but under predation juvenile mortality declined at a faster rate over a drier year compared to years of near average rainfall – a novel finding amongst African antelope.Such fundamental insights into predator–prey relationships are especially relevant to predator-free reserves, where management and planners should be aware of these influences and, depending on the business model, consider replicating them artificially.

Landscape fragmentation, severe drought, and the new Amazon forest fire regime.

Changes in weather and land use are transforming the spatial and temporal characteristics of fire regimes in Amazonia, with important effects on the functioning of dense (i.e., closed-canopy), open-canopy, and transitional forests across the Basin. To quantify, document, and describe the characteristics and recent changes in forest fire regimes, we sampled 6 million ha of these three representative forests of the eastern and southern edges of the Amazon using 24 years (1983-2007) of satellite-derived annual forest fire scar maps and 16 years of monthly hot pixel information (1992-2007). Our results reveal that changes in forest fire regime properties differentially affected these three forest types in terms of area burned and fire scar size, frequency, and seasonality. During the study period, forest fires burned 15% (0.3 million ha), 44% (1 million ha), and 46% (0.6 million ha) of dense, open, and transitional forests, respectively. Total forest area burned and fire scar size tended to increase over time (even in years of average rainfall in open canopy and transitional forests). In dense forests, most of the temporal variability in fire regime properties was linked to El Nino Southern Oscillation (ENSO)-related droughts. Compared with dense forests, transitional and open forests experienced fires twice as frequently, with at least 20% of these forests' areas burning two or more times during the 24-year study period. Open and transitional forests also experienced higher deforestation rates than dense forests. During drier years, the end of the dry season was delayed by about a month, which resulted in larger burn scars and increases in overall area burned later in the season. These observations suggest that climate-mediated forest flammability is enhanced by landscape fragmentation caused by deforestation, as observed for open and transitional forests in the Eastern portion of the Amazon Basin.