Wind Erosion Quantification Process in DeliblatoSands

Erozija predstavlja vrlo složen fizički proces u kome pod dejstvom atmosferskih sila nastaju destruktivne promene na površinskom sloju zemljišta. Kada je osnovni agens pokretanja čestica zemljišta vetar, govori se o eroziji vetrom ili eolskoj eroziji. Eolska erozija je specifičan proces koji se odvija u izrazito složenim okolnostima uzajamnog delovanja brojnih prirodnih i antropogenih faktora uglavnom stohastičkog karaktera, zbog čega je njeno istraživanje kompleksan naučno-istraživački problem. Osnovni cilj sprovedenih istraživanja je bio da se na izabranim lokalitetima Deliblatske peščare, najvećeg i najznačajnijeg područja takve vrste u Evropi, uspostavi praćenje stanja procesa eolske erozije, odnosno neposrednim, sistematskim merenjima u terenskim uslovima ustanove količine eolskog nanosa – pronos nanosa, odrede dominantni pravci njegovog kretanja, definiše njegova unutargodišnja raspodela i utvrdi efekat vegetacije na smanjenje intenziteta eolske erozije. U toku četvorogodišnjeg perioda su po prvi put na ovim prostorima, na istom lokalitetu, sprovedena uporedna istraživanja eolske erozije primenom mehaničkih hvatača nanosa i metoda zasnovanih na praćenju aktivnosti radionuklida veštačkog porekla 137Cs u zemljištu, čije količine služe da se posebnim teorijskim modelima pretvore u gubitke zemljišta. Praćenje procesa eolske erozije je vršeno od 2006. do 2009. godine na lokalitetu Cvjićev vis, koji je izabran kao karakterističan, jer je pored centralne pozicije na Deliblatskoj peščari, obrađivani površinski sloj zemljišta bio bez zaštite od vetra. Paralelno sa ovim merenjima, na lokalitetu Dragićev hat – rasadnik, praćenje procesa eolske erozije vršeno je na dva merna mesta u periodu od maja 2006. godine do aprila 2007. godine u uslovima postojanja zaštitne uloge vegetacionog pokrivača i/ili vegetacionog pojasa. Merenje intenziteta eolske erozije je realizovano statičnim hvatačima nanosa tipa deflametar (dimanzija ulaznog otvora 10 x 10 cm) orijentisanih prema određenim pravacima (N, NE, E, SE, S, SW, W, NW) da bi potpuno definisali procese eolske erozije u vektorskom smislu. Kvantifikacija eolskog nanosa statičnim hvatačima stalno usmerenim prema određenim pravcima duvanja vetrova, omogućila je da se posebno evidentiraju i razlikuju „sumarna” produkcija eolskog nanosa (aritmetički zbir zahvaćenih količina nanosa iz svih hvatača) i „rezultujuća” količina eolskog nanosa (vektorski zbir), jer te veličine određuju pored ukupno pokrenute količine eolskog nanosa (produkcija nanosa) i delove nanosa koji se transportuju van granica erozionog polja (gubitak zemljišta), generalni pravac i smer njegovog kretanja. Merenja eolske erozije na lokalitetu Cvijićev vis za period 2006-2009. godine su ukazala na značajne procese eolske erozije koji su definisani srednjim godišnjim pronosom nanosa od 4,48 kg m-1. Ustanovljeno je da su ukupno zahvaćene količine nanosa na 8 hvatača bile Σ = 25,94, 20,92, 52,98 i 43,47 kg m-1 god-1, a pronosi nanosa Σ' (Σ/8) = 3,24, 2,61, 6,62 i 5,43 kg m-1 god-1 u 2006., 2007., 2008. i 2009. godini respektivno. Pronosi nanosa za period od maja 2006. do aprila 2007. godine su pokazali da je na lokalitetu Cvijićev vis koga karakterišu neobraslost i otvorenost površine zabeležen najveći intenzitet eolske erozije na godišnjem nivou koji je 4 puta veći u odnosu na lokalitet Dragićev hat – rasadnik I koga karakterišu neobraslost i zaštićenost površine i 30,2 puta veći u odnosu na Dragićev hat – rasadnik II koga karakterišu obraslost i zaštićenost zemljišta. Na lokalitetu Dragićev hat – rasadnik I intenzitet eolske erozije na godišnjem nivou je 7,5 puta veći od onog na lokalitetu Dragićev hat – rasadnik II. Gubici zemljišta izraženi preko rezultujućih mesečnih pronosa nanosa (vektorski zbir) iznosili su 5,13, 2,04, 4,31 i 11,94 kg m-1 u 2006., 2007., 2008. i 2009. godini respektivno, a procentualni udeo godišnjih gubitaka zemljišta u odnosu na ukupnu produkciju nanosa (aritmetički zbir) se kretao od 8,1% do 27,5. Rezultujući pravac kretanja eolskog nanosa u toku perioda istraživanja bio je jugoistok - severozapad (SE-NW) pod uticajem dominantnog jugoistočng vetra „Košava”. Iako se najpouzdanije determinisanje eolske erozije i njenih efekata postiže na osnovu neposrednih sistematskih merenja u realnim terenskim uslovima, počev od kraja prošlog veka se sve više primenuju i metode praćenja radionuklida iz radioaktivnih padavina, posebno 137Cs, u cilju procene gubitaka zemljišta i prostornog rasporeda eolskog nanosa. Ukupan broj uzetih uzoraka za metodu praćenja količina 137Cs je iznosio 149, od kojih je bilo 9 inicijalnih uzoraka (3 profila po 3 uzorka), 14 osnovnih uzoraka (2 profila po 7 uzoraka), 32 ostala uzorka (8 profila po 4 uzorka), 36 referentnih uzoraka (9 profila po 4 uzorka) i 58 uzoraka uzetih zrakasto po određenim pravcima (N, NE, E, SE, S, SW, W, NW). Osnovni uzorak na neobrađenom zemljištu sa detektovanom količinom 137Cs od 10.603,57 Bq m-2 predstavlja uporednu vrednost, tj. lokalni padavinski ulaz 137Cs za modele pretvaranja količina 137Cs u količine izgubljenog zemljišta. Ovaj uzorak odslikava sredinu na kojoj su sprovedena istraživanja i predstavlja uporednu vrednost koja može korektno da definiše procese eolske erozije. Za pretvaranje izmerenih količina 137Cs u količine izgubljenog zemljišta po modelima Walling-a korišćen je najjednostavniji proporcionalni model (PM) za obrađena zemljišta, a najprimenjeniji model profilne distribucije (PDM) za neobrađena zemljišta u okviru najnovije verzije PC-kompatibilnog softverskog paketa u Microsoft Excel Add-Ins varijanti. Modelom profilne distribucije (PDM) za sve uzorake uzete na eksperimentalnom području dobijeni su prosečni gubici zemljišta od 207,06 t ha-1 god-1 i 2,10 cm. Model Basher & Webb je dao prosečne gubitke zemljišta od 212,18 t ha-1 god-1 i 2,09 cm. Gubici zemljišta dobijeni modelima pretvaranja količina 137Cs u količine izgubljenog zemljišta ukazuju na značajne procese eolske erozije definisane jakom i ekscesivnom eolskom erozijom. Za 58 uzoraka zemljišta uzetih na tačkama raspoređenih zrakasto po određenim pravcima (N, NE, E, SE, S, SW, W, NW), pored koncentracija i količina 137Cs i 210Pbex, određene su prostorne koordinate X i Y i nadmorske visine uzetih uzoraka. Prostorne distribucije koncentracija 137Cs i 210Pbex izražene su izolinijama, a kreiranani su i 3D prikazi u procentima odstupanja 137Cs i 210Pbex od lokalnog padavinskog ulaza 137Cs i 210Pbex. U oba slučaja je primetan dominantan uticaj pravca jugoistok - severozapad (SE-NW), odnosno jugoistočnog vetra „Košava”. Komparativna analiza ovih metoda je ukazala na validnost u kvantifikaciji procesa eolske erozije i mogućnost njihove primene u budućnosti, a dobijeni rezultati produkcije eolskog nanosa i gubitaka zemljišta su dali doprinos oceni stanja degradacije zemljišta i ugroženosti Deliblatske peščare. Erosion is a very complex physical process which, under the impact of atmospheric forces, creates destructive changes on the soil surface layer. In case the primary agent of particle movement is wind, we talk about wind or aeolian erosion. Aeolian erosion is a specific process which occurs in extremely complex situations of mutual interaction of numerous natural and anthropogenic factors of mainly stochastic properties making its research a complex scientific-research problem. The main goal of conducted research was to monitor the process of aeolian erosion at the chosen localities of Deliblato Sands, the largest and the most important area of the kind in Europe. In other words, the goal is to determine the quantities of aeolian sediment – sediment transport by direct systematic measurements in field conditions, determine dominant direction of sediment transport, define its annual distribution and determine the effect of vegetation on reducing the intensity of aeolian erosion. During a four-year period, for the first time in this area, i.e. at the same locality, a comparative research of aeolian erosion have been conducted using the mechanical sediment trap and activities based on 137Cs radioisotope tracing technique for estimating soil losses using special theoretical models. The monitoring of aeolian erosion processes was conducted during the period 2006 – 2009 at Cvijićev vis which was chosen as a typical locality since it was, apart from the central position on Deliblato Sands, a cultivated surface without any wind protection. Alongside with these measurements, at Dragićev hat – nursery garden, the monitoring of aeolian erosion was conducted on two measurement points during the period May 2006 – April 2007 in areas with the protective vegetative covers and/or vegetative belts. Aeolian erosion intensity measurement was performed by static sediment traps of the type “deflametre” (dimension of entry opening 10 x 10 cm) oriented on certain directions (N, NE, E, SE, S, SW, W, NW) in order to define the aeolian erosion processes in vector terms. The quantification of aeolian sediment using static traps constantly facing certain wind blowing directions enabled to log and differentiate “summary” yield of aeolian sediment (arithmetic sum of all sediment quantities from all traps) and “resulting” quantity of aeolian sediment (vector sum), since those quantities determine not only the entire amount of transported aeolian sediment (sediment yield) but also the sediment transported outside the areas of erosion field (soil loss), bur also the general direction of its transport. Aeolian erosion measurement on Cvijićev vis for the period 2006 – 2009 indicated the significant aeolian erosion processes which were defined by medium annual ediment transport of 4.48 kg m-1. It has been determined that the total quantities of moved sediment were 25.94, 20.92, 52.98 and 43.47 kg m-1 year-1, and sediment transport 3.24, 2.61, 6.62 and 5.43 kg m-1 year-1 in 2006, 2007, 2008 and 2009 respectively. Sediment transport for the period May 2006 – April 2007 showed that on Cvijićev vis which is characterized by bareness and openness there was the biggest aeolian erosion – four times bigger compared to Dragićev hat – nursery garden I characterized by bareness and protectiveness and 30.2 times bigger compared to Dragićev hat – nursery garden II characterized by overgrown condition and protectiveness of erosive field. At the locality Dragićev hat – nursery garden I the aeolian erosion was recorded 7.5 times bigger compared to the one recorded on Dragićev hat – nursery garden II. Soil loses expressed through the resulting monthly sediment transport (vector sum) equalled 5.13, 2.04, 4.31 and 11.94 kg m-1 in 2006, 2007, 2008 and 2009 respectively, and the percentage share of annual soil losses compared to total sediment yield (arithmetical sum) varied between 8.1% and 27.5%. The resulting aeolian sediment movement direction was SE-NW under the influence of the dominant southeast wind “Koshava”. Even though the most reliable determination of aeolian erosion and its effects is based on direct systematic measurements in real time conditions in the field, starting from the end of the last century the methods of tracking radionuclide from radioactive precipitation, especially 137Cs, for the purposes of estimating the soil loss and spatial distribution of aeolian sediment, have been used increasingly. The total number of samples taken for the method of monitoring the quantity of 137Cs was 149, 9 of which were initial samples (3 profiles with 3 samples each), 14 main samples (2 profiles with 7 samples each), 32 remaining samples (8 profiles with 4 samples each), 36 reference samples (9 profiles with 4 samples each) and 58 samples taken radially on certain directions (N, NE, E, SE, S, SW, W, NW). The main sample taken from the uncultivated land with the detected quantity of 137Cs of 10,603.57 Bq m-2 represents the comparative value, i.e. local precipitation input of 137Cs for the models of 137Cs quantities conversion into the quantities of lost soil. This sample depicts the area where the research was conducted and represents the comparative value which can properly define the aeolian erosion processes. For converting the measured quantities of 137Cs into the quantities of lost soil using Walling model the simplest proportional model (PM) for cultivated land was used and the most appropriate profile distribution model (PDM) for uncultivated soil with the newest version of PC compatible software package in Microsoft Excel Add-Ins. Using the profile distribution model (PDM) on all samples taken from the experimental area the quantities of average soil loss obtained were 207.06 t ha-1 year-1 and 2.10 cm. Basher & Webb model gave the average soil loss of 212.18 t ha-1 year-1 and 2.09 cm. Soil loss calculated using the conversion of 137Cs quantities into the soil loss quantities indicate the significant aeolian processes defined by strong and excessive aeolian erosion. For 58 soil samples taken from areas radially distributed on certain directions (N, NE, E, SE, S, SW, W, NW), apart from 137Cs and 210Pbex concentrations and quantities, spatial coordinates X and Y were determined as well as the altitude of taken samples. Spatial distribution of 137Cs and 210Pbex quantities are represented by isolines, and also 3D demonstrations were created showing the percentage of deviation of 137Cs and 210Pbex from the local precipitation input of 137Cs and 210Pbex. In both cases, the dominant direction SENW was noticeable, i.e. the southeast wind “Koshava”. The comparative analysis of these methods indicated the validity in the quantification of aeolian erosion process and the possibility of its application in the future and the obtained results of aeolian sediment yield and soil loss contributed to determining the state of soil degradation and vulnerability of Deliblato Sands