Farming communities in the United States and around the world lose billions of dollars every year due to drought. Drought Indices such as the Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI) are widely used by the government agencies to assess and respond to drought. These drought indices are currently monitored at a large spatial resolution (several thousand km2). Further, these drought indices are primarily based on precipitation deficits and are thus good indicators for monitoring large scale meteorological drought. However, agricultural drought depends on soil moisture and evapotranspiration deficits. Hence, two drought indices, the Evapotranspiration Deficit Index (ETDI) and Soil Moisture Deficit Index (SMDI), were developed in this study based on evapotranspiration and soil moisture deficits, respectively. A Geographical Information System (GIS) based approach was used to simulate the hydrology using soil and land use properties at a much finer spatial resolution (16km2) than the existing drought indices. The Soil and Water Assessment Tool (SWAT) was used to simulate the long-term hydrology of six watersheds located in various climatic zones of Texas. The simulated soil water was well-correlated with the Normalized Difference Vegetation Index NDVI (r ~ 0.6) for agriculture and pasture land use types, indicating that the model performed well in simulating the soil water. Using historical weather data from 1901-2002, long-term weekly normal soil moisture and evapotranspiration were estimated. This long-term weekly normal soil moisture and evapotranspiration data was used to calculate ETDI and SMDI at a spatial resolution of 4km ?? 4km. Analysis of the data showed that ETDI and SMDI compared well with wheat and sorghum yields (r > 0.75) suggesting that they are good indicators of agricultural drought. Rainfall is a highly variable input both spatially and temporally. Hence, the use of NEXRAD rainfall data was studied for simulating soil moisture and drought. Analysis of the data showed that raingages often miss small rainfall events that introduce considerable spatial variability among soil moisture simulated using raingage and NEXRAD rainfall data, especially during drought conditions. The study showed that the use of NEXRAD data could improve drought monitoring at a much better spatial resolution.

In today's technological environment, there is constant competition for audience readership and viewership between various media outlets. News media provides a great deal of information to the general public through television, print, and web sources, especially in terms of agriculture. This study aimed to discover audience perceptions of two different natural disasters by examining the effects of photographic inclusion in print news articles including agricultural perceptions and content recall. Additionally, differences between self-perceived milk industry advocacy and a milk campaign story are also examined. Newspaper articles about the effects of the 2010-2011 drought in Texas and the aftermath of Tropical Storm Irene were also used. Students in the College of Agriculture and Life Sciences at Texas A&M University were surveyed in online pre and posttests. Student responses displayed a moderate relationship between photos and article content in regards to the Hurricane Irene article. A significant relationship was present between self-perceived non-advocates and their outlook on milk consumption and the dairy industry with the inclusion of photographs. There were differences seen between students who have family who work in agriculture, claim membership in an agriculture association, live on a farm or ranch, and were members of FFA as they viewed the drought article to be more positive than those who did not have these agricultural backgrounds. Furthermore, student responses show a relationship between the milk industry article in the pretest (photos included) and posttest (photos not included) by viewing the photos as positive, humorous, and shocking. This study found student perceptions of the two news articles related to the drought as well as the tropical storm to be the same regardless of photographic presence. This leads the researcher to conclude that photos had no effect on the overall perceptions of the news stories. However, students who received photographs did see a relationship between the photos associated with the flood article and the content presented in the story. This effect was not seen with the photographs of the drought story. Since the photos associated with the flood story were the original photos printed with the news story, it is probable to conclude that students properly associated photographic elements with that of the story's content.

Farming communities in the United States and around the world lose billions of dollars every year due to drought. Drought Indices such as the Palmer Drought Severity Index (PDSI) and Standardized Precipitation Index (SPI) are widely used by the government agencies to assess and respond to drought. These drought indices are currently monitored at a large spatial resolution (several thousand km2). Further, these drought indices are primarily based on precipitation deficits and are thus good indicators for monitoring large scale meteorological drought. However, agricultural drought depends on soil moisture and evapotranspiration deficits. Hence, two drought indices, the Evapotranspiration Deficit Index (ETDI) and Soil Moisture Deficit Index (SMDI), were developed in this study based on evapotranspiration and soil moisture deficits, respectively. A Geographical Information System (GIS) based approach was used to simulate the hydrology using soil and land use properties at a much finer spatial resolution (16km2) than the existing drought indices. The Soil and Water Assessment Tool (SWAT) was used to simulate the long-term hydrology of six watersheds located in various climatic zones of Texas. The simulated soil water was well-correlated with the Normalized Difference Vegetation Index NDVI (r ~ 0.6) for agriculture and pasture land use types, indicating that the model performed well in simulating the soil water. Using historical weather data from 1901-2002, long-term weekly normal soil moisture and evapotranspiration were estimated. This long-term weekly normal soil moisture and evapotranspiration data was used to calculate ETDI and SMDI at a spatial resolution of 4km ?? 4km. Analysis of the data showed that ETDI and SMDI compared well with wheat and sorghum yields (r > 0.75) suggesting that they are good indicators of agricultural drought. Rainfall is a highly variable input both spatially and temporally. Hence, the use of NEXRAD rainfall data was studied for simulating soil moisture and drought. Analysis of the data showed that raingages often miss small rainfall events that introduce considerable spatial variability among soil moisture simulated using raingage and NEXRAD rainfall data, especially during drought conditions. The study showed that the use of NEXRAD data could improve drought monitoring at a much better spatial resolution.

No description available.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In the rainfed areas of the South African sugar industry the unpredictability of rainfall is of major concern for producers. Currently, research into the drought tolerance of South African sugarcane varieties is very limited. Knowledge of varietal drought tolerance potential would allow for more informed decision making when it comes to planting a crop that stays in the ground for between five and fifteen years. The aim of this study was to ascertain the drought tolerance potential of commercial sugarcane varieties using historical field trial data by employing statistical modelling. The first step was to establish a reliable methodology of quantifying the level of drought stress, defined through a drought stress index (DSI), employing the sugarcane growth modelling software Canesim. The second step was to use the selected DSI to evaluate and rate the drought tolerance potential of commercial varieties. Of the six DSI’s calculated, the index comprising a ratio of Canesim simulated rainfed yield (representative of a water stressed environment) to Canesim simulated irrigated yield (representative of a water unstressed environment) was the best at quantifyingthe level of trial drought stress. Using three varieties with previously identified drought potential, two intermediate susceptible (IS) and one intermediate (I) variety, this was the only DSI that was able to quantify all the differences between the varieties. Using the selected DSI, two different methodologies were used to evaluate varietal drought tolerance potential: General linear regression and Residual maximum likelihood meta-analysis. The regression method proved to be a better method of varietal rating when using historical field data. The two rainfed regions, coastal and midlands were analyzed separately due to the difference in climatic conditions. Using the regression analysis, with N12 as the observed intermediate reference variety, coastal varieties were rated as being susceptible (N16, N19, N39 and NCO376) or intermediate (N27, N29, N33, N36, N41, N45, N47). Rating of the midlands varieties, with both statistical methods, were unsuccessful. / AFRIKAANSE OPSOMMING: Binne die droëland produksiegebied van die Suid-Afrikaanse suikerindustrie is die wisselvalligheid van reënval ʼn groot bron van kommer vir produsente. Navorsingsresultate aangaande die droogtetoleransie van Suid-Afrikaanse suikerrietvariëteite is baie beperk. Aangesien suikerriet aanplantings vir vyf tot vyftien jaar in produksie mag bly, is kennis aangaande droogtetoleransie noodsaaklik vir ingeligte besluite rondom variëteit keuse. Die doel van hierdie studie was om die droogtetoleransie van kommersiële variëteite met behulp van historiese veldproef resultate en statistiese modellering te bepaal. Die eerste stap was die ontwikkeling van betroubare metodiek wat die graad van droogtestremming kwantifiseer deur middel van droogtestremmingsindekse (DSI’s) wat met die suikerriet produksiemodel, Canesim, bereken is. Die tweede stap was om die DSI’s te gebruik om geselekteerde kommersiële variëteite vir droogtetoleransie te evalueer en volgens toleransie te rangskik. Van die ses DSI’s wat geëvalueer is, was die indeks wat die verhouding tussen Canesim gesimuleerde droëland opbrengs (verteenwoordigend van ʼn omgewing met droogte) en Canesim gesimuleerde besproeide opbrengs (verteenwoordigend van ʼn omgewing sonder droogte) omskryf het, die mees effektiefste om die graad van droogtestremming te kwantifiseer. Hierdie DSI was vervolgens die enigste wat verskille in droogtetoleransie tussen drie variëteite van bekende droogte toleransie kon kwantifiseer. Deur gebruik van hierdie DSI is twee verskillende metodes aangewend om die droogtetoleransie van variëteite te evalueer naamlik: Algemene Lineêre Regressie en Residuele Maksimum Aanneemlikheid. Die regressiemetode was die mees effektiefste om variëteite volgens droogtetoleransie, op grond van historiese veldproef resultate, te rangskik. Die twee droëland produksiegebiede, naamlik die kusstrook en Natalse Middellande is afsonderlik geanaliseer as gevolg van klimaatsverskille. Met behulp van die regressiemetode is die kus-variëteite as droogtesensitief of -intermediêr geklassifiseer, met N27, N29, N33, N36, N41, N45 en N47 as droogte-intermediêr en N16, N19, N39 en NCO376 as droogtesensitief. Soortgelyke klassifisering van die variëteite wat in die Natalse Middellande verbou word was nie met enige van die statistiese metodes suksesvol gewees nie.

The success of C₄ plants lies in their ability to concentrate CO₂ at the site of Rubisco thereby conferring greater efficiencies of light, water and nitrogen. Such characteristics should advantage C₄ plants in arid, hot environments. However, not all C₄ subtypes are drought tolerant. The relative abundance of NADP-ME species declines with increasing aridity. Furthermore, selected species have been demonstrated as being susceptible to severe drought showing metabolic limitations of photosynthesis. However there is a lack of phylogenetic control with many of these studies. The aims of this study were to determine whether the NADP-ME subtype was inherently susceptible to drought by comparing six closely related C₃ and C₄ (NADP-ME) Panicoid grasses. Gas exchange measurements were made during a natural rainless period and a controlled drought / rewatering event. Prior to water stress, the C₄ species had higher assimilation rates (A), and water use efficiencies (WUE[subscript leaf]) than the C₃ species, while transpiration rates (E) and stomatal conductances (g[subscript s]) were similar. At low soil water content, the C₃ species reduced gs by a greater extent than the C₄ species, which maintained higher E during the driest periods. The C₄ species showed proportionally greater reductions in A than the C₃ species and hence lost their WUE[subscript leaf] and photosynthetic advantage. CO₂ response curves showed that metabolic limitation was responsible for a greater decrease in A in the C₄ type than the C₃ type during progressive drought. Upon re-watering, photosynthetic recovery was quicker in the C species than the C₄ species. Results from whole plant measurements showed that the C₄ type had a significant whole plant water use efficiency advantage over the C₃ type under well-watered conditions that was lost during severe drought due to a greater loss of leaf area through leaf mortality rather than reductions in plant level transpiration rates. The C₃ type had xylem characteristics that enhanced water-conducting efficiency, but made them vulnerable to drought. This is in contrast to the safer xylem qualities of the C₄ type, which permitted the endurance of more negative leaf water potentials than the C₃ type during low soil water content. Thus, the vulnerability of photosynthesis to severe drought in NADP-ME species potentially explains why NADP-ME species abundance around the world decreases with decreasing rainfall.

<p>U ovoj disertaciji je definisan i predstavljen pristup monitoringu poljoprivredne su&scaron;e (SPEI-based approach to agricultural drought monitoring - ADM-SPEI) u Vojvodini koji objedinjuje vi&scaron;e poznatih i priznatih metoda i kritičko mi&scaron;ljenje eksperata zasnovano na njihovom znanju i iskustvu i pri tome uzima u obzir lokalne specifičnosti agroklimatskih uslova. Iako je kreiran za područje Vojvodine, predloženi pristup monitoringu poljoprivredne su&scaron;e baziran na SPEI indeksu opisan je generalno kroz tri faze i pripadajuće korake koji su detaljno opisani i obja&scaron;njeni &scaron;to omogućava da se ADM- SPEI pristup modifikuje i primeni u bilo kojim drugim agroklimatskim uslovima. Predstavljeni pristup baziran je na modifikovanom i &scaron;iroko prihvaćenom i kori&scaron;ćenom Standardizovanom Indeksu Padavina i Evapotranspiracije (SPEI). Ovom modifikacijom SPEI je povezan sa&nbsp; specifičnom kulturom &scaron;to omogućava da se su&scaron;a, odnosno uslovi vlažnosti analiziraju individualno za specifičnu ratarsku ili povrtarsku kulturu u agroklimatskim uslovima Vojvodine. Kreiranju pristupa monitoringu poljoprivredne su&scaron;e prethodilo je istraživanje koje se tiče uticaja referentne evapotranspiracije (ET0) na rezultate SPEI indeksa kako bi se potvrdila polazna pretpostavka da različiti metodi za izračunavanje ET0 u okviru SPEI indeksa daju u nekim slučajevima značajno različite vrednosti indeksa na području Vojvodine. Iz navedenih razloga je važno koristiti metod koji najvi&scaron;e odgovara specifičnom području od interesa. Modifikacija SPEI indeksa, odnosno zamena ET0 sa ETc (potencijalnom evapotranspiracijom kulture) izvr&scaron;ena je uključivanjem ekspertskog mi&scaron;ljenja odnosno intervjuisanjem vi&scaron;e stručnjaka različitih ekspertiza iz domena kori&scaron;ćenja i upravljanja vodama u poljoprivredi &scaron;to je omogućilo da se dođe do grupne odluke koja u najvećoj meri reprezentuje lokalne agroklimatske prilike. U tu svrhu upotrebljen je Analitički Hijerarhijski Proces (AHP metod) kao podr&scaron;ka odlučivanju kako bi se dobile individualne odluke stručnjaka i da bi se u narednom koraku dobila jedna grupna odluka o najpogodnijem metodu za izračunavanje ET0, odnosno ETc. U narednoj fazi predloženog pristupa, prateći dalju proceduru originalnog SPEI indeksa izračunati su klimatski vodni bilansi kultura. Analizom su obuhvaćeni podaci sa devet meteorolo&scaron;kih stanica na području Vojvodine, kao i jedanaest ratarskih i povrtarskih kultura. Zatim je statističkim metodama odabrana odgovarajuća teorijska distribucija za koju je potvrđeno najbolje slaganje sa empirijskim vrednostima klimatskog vodnog bilansa kultura i u narednom koraku dobijen modifikovani SPEI povezan sa specifičnom kulturom (agricultural drought SPEI - AD-SPEIcrop). Pristup omogućava i direktnu transformaciju indeksa u vrednosti klimatskog vodnog bilansa kulture, odražavajući potrebe useva za vodom. Sagledavanjem su&scaron;e i sa tog aspekta omogućava analizu mogućnosti sistema za navodnjavanje u borbi protiv su&scaron;e. U sledećoj fazi izvr&scaron;ena je validacija predloženog pristupa sa vi&scaron;e različitih aspekata koji podrazumevaju: ispitivanje povezanosti indeksa sa prinosima kultura, kako na lokalnom nivou op&scaron;tina tako i na nivou cele teritorije Vojvodine; poređenje stepena slaganja sa prinosima kultura u odnosu na originalni indeks SPEI; komparaciju sa op&scaron;te priznatim i prihvaćenim indeksima su&scaron;e (SPI, SPEI i SC-PDSI); i povratnu informaciju od strane eksperata. Bazirajući se na dobijenim rezultatima u fazi validacije može se zaključiti da predloženi pristup monitoringu poljoprivredne su&scaron;e na području Vojvodine baziran na SPEI indeksu može biti uspe&scaron;no primenjen i sa dobrim performansama, odnosno da indeks AD-SPEIcrop, dobijen kao rezultat ovog pristupa, predstavlja adekvatan pokazatelj poljoprivredne su&scaron;e na području Vojvodine.</p> / <p>In the doctoral dissertation, the SPEI-based approach to agricultural drought monitoring (ADM-SPEI) in Vojvodina has been defined and presented. While integrating several well-known and recognized methods and experts&rsquo; critical opinion based on their knowledge and experience, ADM-SPEI takes into account local specificities of agro-climatic conditions. Although it was created for the Vojvodina region, the proposed approach to agricultural drought monitoring based on the SPEI index has been described in three phases alongside the corresponding steps, for which a detailed description and explanation have also been provided. This allows for the ADM-SPEI approach to be modified and applied in any other agro-climatic conditions. The presented approach is based on the modified and widely accepted and used Standardized Precipitation and Evapotranspiration Index (SPEI). The modification enables relating the SPEI to a specific crop, thereby ensuring the possibility for the analysis of drought or moisture conditions separately for specific field or vegetable crops in the agro-climatic conditions of Vojvodina. The creation of the approach to agricultural drought monitoring was preceded by the research of the impact of reference evapotranspiration (ET0) on the results of the SPEI index. The aim of the research was to confirm the initial assumption that different methods for calculating ET0 within the SPEI index give in some cases significantly different index values in the Vojvodina region. For these reasons, it is important to use the most appropriate method for the specific area of interest. Carrying out the modification of the SPEI index, i.e., the replacement of the ET0 with the ETc (potential crop evapotranspiration) included the involvement of experts&rsquo; opinions by interviewing experts of various expertise in the domain of water use and water management in agriculture. This led to making a group decision representing the local agro-climatic conditions. For this purpose, the Analytical Hierarchy Process (AHP method) was used as a decision-making support in order to get experts&rsquo; individual decisions and, in the next step, to obtain a group decision on the most suitable method for calculating ET0 and ETc. In the next phase of the proposed approach, following the procedure of the original SPEI index, the cropspecific climate water balances were calculated. The analysis includes data from nine meteorological stations in the Vojvodina region, as well as eleven field and vegetable crops. Then, statistical methods were used to select the appropriate theoretical distribution which proved to best fit to the empirical values of the crop-specific climatic water balance. In the next step, the modified SPEI related to specific crops (agricultural drought SPEI - ADSPEIcrop) was obtained. The approach also enables the direct transformation of the index into the values of the climate water balance of crops reflecting the crop water needs. Examining drought from this perspective as well makes it possible to analyze the capabilities of irrigation systems to cope with drought. In the next phase, the validation of the proposed approach was carried out from several different perspectives including examining the correlation of the index with the crop yields, both at the local county level and at the level of the entire territory of Vojvodina; the comparison between the degree of the agreement of the AD-SPEIcrop and the original SPEI index with the crop yields, respectively; the comparison with the generally acknowledged and accepted drought indices (SPI, SPEI and SC-PDSI); and experts&rsquo; feedback. According to the obtained results in the validation phase, it can be concluded that the proposed approach to agricultural drought monitoring in the Vojvodina region based on the SPEI index can be applied successfully and with good performance, and that the ADSPEIcrop index obtained as a result of this approach is an adequate indicator of agricultural drought in the Vojvodina region.</p>

<p>Predmet ovog istraživanja je suša i model osiguranja useva od rizika suše na teritoriji Vojvodine. Na osnovu detaljnog istraživanja vremenskih klimatoloških uslova na ispitivanom području, cilj ove disertacije je da se identifikuju meteorološki parametari i indikatori pogodni za indeksno osiguranje, potom da se identifikovani indeksi (padavine, SPI i SPEI indeksi suše) testiraju i odredi koji od njih najviše pogoduje osiguranju useva od rizika suše u Vojvodini.</p> / <p>The subject of this research is drought phenomena and crop insurance model for managing drought risk, on the territory of Vojvodina Province. After detailed research of weather and climate conditions of research area, themain purpose of this dissertation is to identify meteorological parameters and indicators suitable for index based insurance. Then,to test them (rainfall, SPI and SPEI drought indices) in order to determine index that is most suitable for crop insurance in Vojvodina.</p>

Climate warming in recent decades has resulted in more frequent and severe drought events in the western United States. These changes are projected to continue, making it exceedingly important to understand how forests respond to severe drought stress, and how we can manage these forests to reduce mortality during future events. The 2012-2015 California drought is a recent example of a severe, multi-year drought that was coupled with an epidemic-scale outbreak of western pine beetle, killing nearly 90% of ponderosa pines in the central and southern Sierra Nevadas. In the first portion of this study, we compared pairs of surviving and dead ponderosa pines following this drought event to determine how the surviving trees were able to survive. We were also interested in how closely ponderosa pine tree-rings were recording ecosystem responses to this drought event. In the second portion of this study, we compared tree-ring growth rates and stable isotopes to data from an on-site flux tower to determine whether tree-rings were recording important information regarding ecosystem carbon and water fluxes during this severe drought event. Overall, we sought to better understand how the 2012- 2015 California drought event affected ponderosa pines to inform future management practices in forests of the western United States.

Drought stress was studied in rice (Oryza sativa) and maize (Zea mays) to identify drought-responsive genes and associated biological processes. One experiment with rice examined drought responses in vegetative and reproductive tissues and identified drought-responsive genes in each tissue type. The results showed that brief periods of acute drought stress at or near anthesis reduced photosynthetic efficiency and ultimately lowered grain yield. Yield was reduced as a result both of fewer spikelets developed and of lower spikelet fertility. Affymetrix arrays were used to analyze global gene expression in the transcriptomes of rice vegetative and reproductive tissue. Comparative analysis of the expressed genes indicated that the vegetative and reproductive tissues responded differently to drought stress. An experiment was conducted with maize, using GS-FLX pyrosequencing to identify differentially expressed genes in vegetative and reproductive tissues; and these results were compared with those from the just-described rice transcriptome. Some of the drought-responsive genes in the maize reproductive tissue were validated by quantitative real time polymerase chain reaction (qRT-PCR). The differentially expressed genes common to both maize and rice were further analyzed by gene ontology analysis to reveal core biological processes involved in drought responses. In both species, drought caused a transition from protein synthesis to degradation, and photosynthesis was one of the most severely affected metabolic pathways. In a validating experiment, a drought-responsive transcription factor found in rice and dubbed HIGHER YIELD RICE (HYR) was constitutively expressed in rice, and the transgenic HYR plants were studied. Under well-watered conditions, the HYR plants developed higher rates of photosynthesis, greater levels of soluble sugars (glucose, fructose, and sucrose), more biomass, and higher yield. They also exhibited a drought-resistant phenotype, with higher water use efficiency, photosynthesis, and relative leaf water content under drought stress. Taken together, these studies demonstrate the potential value of newer technologies for identifying genes that might impart drought resistance and for using such genes to make crops more productive either in the presence or in the absence of drought stress. / Ph. D.