Accessible water volume and distance from surface water are important water sub-factors which influences on eucalyptus farming potential. Though eucalyptus species tolerate drought to different degrees, studies in southern Iran have demonstrated that reduction of water decreases tree diameters and heights . During periods of drought or in arid climates, irrigation is essential to support tree growth . Based on this research, annual volume of water accessible in most of the study area is sufficient for eucalyptus farming . Though water salinity is a limiting factor in eucalyptus growth, some species of eucalyptus are tolerant to salinity . Nearly fifty years ago, E. camaldulensis was recommended for cultivation in Khuzestan Province because of its tolerance to salinity . In most of study area, EC for surface water and groundwater is<4 ds/m and this makes these areas suitable for eucalyptus wood-farming . The climate sub-factors were less important than the other subfactors: annual wind speed mean was the most important sub-factor, and annual minimum temperature mean , annual temperature mean , annual relative humidity mean , and minimum temperature followed in order of importance. Annual wind speed mean is the most important factor limiting eucalyptus farming in Khuzestan Province. Eucalyptus is generally sensitive to higher wind speeds , but some species tolerate wind better than others. For example, the ratio of diameter to height is greater in E. microtheca than in E. camaldulensis,led grow lights making the former more resistant to high speed winds . The negative effect of certain wind characteristics on eucalyptus survival has been documented: warm wind decreased survival of eucalyptus seedlings in Fars Province .
Annual minimum temperature mean was second most important climate sub-factor. Eucalyptus is a tropical species and is vulnerable to cold . However, species of eucalyptuses tolerate temperature differently; as E. microtheca is less affected by minimum temperature than E. camaldulensis . Annual maximum temperature mean, maximum temperature, and annual rainfall mean are weighted equivalently and they were the least important determinants for eucalyptus farming in Khuzestan Province. There are shown to be suitable climatic conditions for eucalyptus wood-farming in Khuzestan province based on the results . And of the land cover sub-factors, non-planted sandy hills had the greatest impact of determining land suitability for eucalyptus wood-farming. Other studies have found that eucalyptus thrives in the sandy hills of the Albaji region near Ahvaz City in Khuzestan Province and similar results were found by others . Non-cultivated lands near the Jihad Nasr channels were the next land cover conditions of importance in eucalyptus wood-farming. Though these lands have not been evaluated before, water channels and drainage are suitable characteristics that enhance potential of these lands for eucalyptus plantations. The Jihad Nasr lands are also suitable for eucalyptus farming. Although, the Jihad Nasr lands are private at present, the wide and flat expanse of these lands, water channels around them and a proper drainage system that can decrease water salinity, makes them very suitable for eucalyptus farming. Eucalyptus plantations could replace other crops in these lands; this would only happen if it was economically justifiable and if eucalyptus seedlings were provided by the Forests, Rangelands, and Watershed Organization of Iran . Although, a large area of lands are recognized as suitable for eucalyptus farming , thepriority for wood-farming should be the large patches , because plantations on larger plots would be more economically viable operations. This research showed that accessible water in sufficient amounts, soil salinity, wind speed, and unplanted sandy hills are the sub-factors that most dictate land suitability for eucalyptus wood-farming in southern Iran.
Analysis of the wood-farming potential map based on FAHP showed that 16.8% of the study area is very suitable and 18% is suitable for eucalyptus wood-farming. Additionally, 16.55% of the study area is neither suitable nor unsuitable, 30.23% is unsuitable, and 18.42% is very unsuitable for eucalyptus wood-farming. More than 34% of the study area would be appropriate for eucalyptus wood-farming. This is confirms the hypothesis that Khuzestan Province has very good potential for eucalyptus wood-farming considering eucalyptus’ ecological, climatic, hydrologic, and edaphic needs. The tropical climate, large water supply, proper edaphic conditions especially in the northern half of the province, and existence of sandy lands makes this province ideal for eucalyptus farming. The results of other studies confirm this potential for the province . In the future studies, economic conditions should be considered for eucalyptus plantation in the province as well. The cost of maintaining eucalyptus seedlings during logging period should be assigned by FRWOI. For example, eucalyptus is sensitive to fire , therefore assigning a cost to monitor and protect eucalyptus plantation against future fires is very important , especially in Khuzestan Province. Validation of the wood-farming potential map showed an OA of 82% and a k of 0.71, based on the empirical data from successful eucalyptus plantations in Khuzestan Province. This demonstrates that the FAHP method has high validity for identifying the suitable lands for eucalyptus wood-farming and the wood-farming potential map is valid as well. Many studies have shown similarly high accuracies of FAHP method for environmental assessments . This study is the first to use the FAHP method to predict lands that would be most suitable for eucalyptus wood-farming; and it did so accurately. There are, however, some limitations regarding this approach. The lack of experts and specialists who answer to surveys may have created inconsistency in the results of this approach . In this case, if CR is more than 0.1, the survey procedures should be redone. Furthermore, a lack of experts on the subject is another limitation of this approach. An insufficient amount of data about successful eucalyptus plantations was an important challenge.
In this study, 80 polygons of successful eucalyptus plantation with a total area of 5002.45 ha provided the empirical data. These data were used to validate the wood-farming potential map. Eucalyptus plantations that were unsuccessful, however, were not included in this analysis and they were also removed from the eucalyptus plantation map. For more complete validation, more data are needed from sites of successful eucalyptus plantations in Khuzestan Province. Groundwater is an important water source for drinking, domestic and agricultural purposes particularly in rural areas. Meanwhile, the rural areas are faced with groundwater contamination due to various contamination sources including agricultural fertilizers, livestock manures, and domestic wastes . Recently, the livestock manures are paid attention to as a critical source of groundwater contamination as livestock farming has been expanded and intensified to meet the increased demand for meat . Livestock manures are spread on agricultural fields as fertilizers without composting or temporarily piled up in livestock farming fields without appropriate management until they are transported for treatment , which creates a livestock manure-derived groundwater plume in aquifers persistently affected by fertilizers. For instance, the amount of livestock manures increased from 71,530 tons a day in 1992 to 177,110 tons a day in 2012 in South Korea, and was estimated to be 185,069 tons a day in 2018 . Improper disposal of livestock manures has become a major cause of groundwater contamination in agro-livestock farming areas.Among the inorganic contaminants, nitrogen compounds are a major contaminant found in the LDGP at three forms , of which nitrate is the final product of nitrification and shows the widespread distribution in groundwater due to high mobility and low absorptivity . High levels of nitrate in groundwater are reported to cause diseases in humans such as methemoglobinemia and gastric and colorectal cancer in addition to ecological risks such as eutrophication and algal blooming in surface water . In addition, livestock manures are a source of pathogens such as bacteria, parasites and viruses ; many of those pathogens have been found to survive in the subsurface environment . Thus, careless management of livestock manures can induce pathogen-induced diseases including waterborne diseases on livestock and humans. In order to protect the rural groundwater quality from the livestock manure, it is essential to characterize the spatial and vertical extent of a LDGP. However, strawberry gutter system the evaluation of impacts by an individual pollution source in groundwater is challenging because various point and/or non-point sources complicatedly coexist .
For instance, major hydrochemical compositions including nitrate and SO4 2- come from both fertilizers and livestock manures and hydrochemically evolve in aquifers depending on redox conditions . Thus, recently the dual isotopes of nitrate are widely used to distinguish contamination sources , while they are expensive and time-consuming, and occasionally not applicable because of the isotopic overlap of nitrate sources . An integrated hydrochemical index can be used as an alternative tool to distinguish contamination sources as the river water quality indices and may reduce the uncertainties caused by the isotopic compositions. For the development of hydrochemical indices, hydrochemical indicators should be selected as in Solovey et al. who used Cl- /Br- to determine peatlands affected by anthropopressure and Ca2+/Mg2+ to determine the dominance of rainwater in a fen. Then the hydrochemical indicators should be coupled to provide a single index. Principal component analysis has been widely applied to assess major geochemical processes in aquifers and to choose hydrochemical indicators to address each geochemical process . When PCA is conducted using the isometric log-ratio transformed hydrochemical parameters, the ilr coordinates of a subcomposition can be recommended as a method to integrate the selected ions . This study was conducted to select hydrochemical indicators through the understanding of the hydrochemistry of a LDGP and geochemical processes occurring within the LDGP, and to suggest a hydrochemical index effectively differentiating the LDGP from the pervasive agricultural contamination in shallow unconsolidated aquifers in agro-livestock farming areas. For this purpose, multilevel monitoring wells were installed at both upgradient and downgradient of feedlots and manure piles, and then the hydrochemistry, dual isotopic composition of nitrate, and fecal microorganisms in groundwater with depth were examined. Based on the study result, hydrochemical parameters that differentiated the LDGP were chosen and combined to suggest an integrated hydrochemical index to trace the LDGP in a shallow unconfined aquifer. The applicability of the index was validated using hydrochemical and isotopic compositions from three other agro-livestock farming areas in South Korea. The methodology to select hydrochemical parameters for distinguishing a LDGP and to combine them to develop a hydrochemical index and the biogeochemical processes within the LDGP found in this study will be useful for managing groundwater pollution by livestock manures in agro-livestock farming areas. This study was conducted in an agro-livestock farming area in the Chungnam Province of South Korea , in which the lowland began to be converted to livestock farms from agricultural fields approximately in 1995, and the areal extent of livestock farming was progressively expanded at the down gradient area .
As of 2010, the main land uses included livestock farming and agricultural fields as in Fig. 1a, and livestock farms were located around agricultural fields. The geology consisted of Jurassic biotite granite, which was locally covered with coarse- to medium-grained sand . Colluvium materials such as rock debris, gravel, silt and sand were also observed when MLWs were installed in 2013 . The land surface had elevations in a range of 30 to 50 m above sea level and tended to slope gradually towards the east . In the agricultural fields, which were developed in an upland at elevations of 44 ~ 50 m asl, crops such as peppers, sweet potatoes and beans were cultivated with the application of fertilizers including silicate fertilizers. It should be noted that the application of fertilizers must have occurred all over the study area before 1995 and probably more intensively given that the overuse of fertilizers resulted in the acidification and nitrate contamination of shallow groundwater in South Korea . The use of chemical fertilizers has been regulated since 2004, decreasing the use of chemical fertilizers down to 46% between 1994 and 2014, whereas the use of livestock manures increased by 30% during the same period in South Korea . In the livestock farming area located in a lowland at elevations of 30 ~ 43 m asl, livestock manures were estimated to be produced at a rate of 5,090 kg day− 1 as of 2010 based on a total of 135 dairy cows and average N produced by a dairy cow .