Ilya Gelfand - Academia.edu (original) (raw)

Papers by Ilya Gelfand

Environmental Science & Technology, 2010

The prospect of biofuel production on a large scale has focused attention on energy efficiencies ... more The prospect of biofuel production on a large scale has focused attention on energy efficiencies associated with different agricultural systems and production goals. We used 17 years of detailed data on agricultural practices and yields to calculate an energy balance for different cropping systems under both food and fuel scenarios. We compared four grain and one forage systems in the U.S. Midwest: corn (Zea mays) -soybean (Glycine max) -wheat (Triticum aestivum) rotations managed with (1) conventional tillage, (2) no till, (3) low chemical input, and (4) biologically based (organic) practices, and (5) continuous alfalfa (Medicago sativa). We compared energy balances under two scenarios: all harvestable biomass used for food versus all harvestable biomass used for biofuel production. Among the annual grain crops, average energy costs of farming for the different systems ranged from 4.8 GJ ha -1 y -1 for the organic system to 7.1 GJ ha -1 y -1 for the conventional; the no-till system was also low at 4.9 GJ ha -1 y -1 and the lowchemical input system intermediate (5.2 GJ ha -1 y -1 ). For each system, the average energy output for food was always greater than that for fuel. Overall energy efficiencies ranged from output:input ratios of 10 to 16 for conventional and no-till food production and from 7 to 11 for conventional and no-till fuel production, respectively. Alfalfa for fuel production had an efficiency similar to that of no-till grain production for fuel. Our analysis points to a more energetically efficient use of cropland for food than for fuel production and large differences in efficiencies attributable to management, which suggests multiple opportunities for improvement.

Environmental Science & Technology, 2005

bacteria and Bacteroidetes species were present in all of the DGGE profiles examined. DGGE analys... more bacteria and Bacteroidetes species were present in all of the DGGE profiles examined. DGGE analyses showed significant shifts in the bacterial community composition between profiles over two years of sampling, indicating the presence of a diverse and dynamic microbial community within the functionally stable FBR. The FBR's combined capacity for both oxic and anoxic sulfide oxidation, as indicated by bulk chemical, microsensor, and molecular microbial analyses, gives it significant functional elasticity, which is crucial for proper performance in the dynamic environment of this mariculture system.

Environmental Microbiology, 2003

Bacterial community structure and physiochemical parameters were examined in a sedimentation basi... more Bacterial community structure and physiochemical parameters were examined in a sedimentation basin of a zero-discharge mariculture system. The system consisted of an intensively stocked fish basin from which water was recirculated through two separate treatment loops. Surface water from the basin was pumped over a trickling filter in one loop while bottom-water was recirculated through a sedimentation basin followed by a fluidized bed reactor in the other. Ammonia oxidation to nitrate in the trickling filter and organic matter digestion together with nitrate reduction in the sedimentation basin and fluidized bed reactor, allowed zero-discharge operation of the system. Relatively high concentrations of oxygen, nitrate, sulphate and organic matter detected simultaneously in the digestion basin suggested the potential for a wide range of microbially-mediated transformation processes. In this study, physiochemical parameters were correlated to bacterial diversity and distribution in horizontal and vertical profiles within this basin in an effort to obtain a basic understanding of the chemical and microbial processes in this system. Chemical activity and microbial diversity, the latter measured by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR) amplified 16S rDNA fragments, were higher in the sludge layer than in the overlying aqueous layer of the basin. Chemical parameters in sludge samples close to the basin inlet suggested enhanced microbial activity relative to other sampling areas with evidence of both nitrate and sulphate reduction. Four of the nine DGGE bands identified in this zone were affiliated with the Bacteroidetes phylum. Detected sequences closely related to sequences of organisms involved in the sulphur cycle included Desulfovibrio , Dethiosulfovibrio and apparent sulphur oxidizers from the gamma-proteobacteria. In addition, a number of sequences from the beta and alpha-proteobacteria were identified.

Journal of The World Aquaculture Society, 2003

Results are presented of a zero-discharge marine recirculating system used for the culture of gil... more Results are presented of a zero-discharge marine recirculating system used for the culture of gilthead seabream Sparus aurata. Operation of the system without any discharge of water and sludge was enabled by recirculation of effluent water through two separate treatment loops, an aerobic trickling filter and a predominantly anoxic sedimentation basin, followed by a fluidized bed reactor. The fish basin was stocked for the first 6 mo with red tilapia Oreochromis niloticus × O. aureus at an initial density of 16 kg/m3. During this period salinity was raised from 0 to 20 parts per thousand. Then, gilthead seabream, stocked at an initial density of 21 kg/m3, replaced tilapia at day 167 and were cultured for an additional 225 d. Non steady-state inorganic nitrogen transformations occurred as a result of these salinity changes. After day 210, the system operated at all times with those water quality parameters considered critical for successful operation of mariculture systems, within acceptable limits. Thus ammonia, nitrite, and nitrate concentrations did not exceed 1.0-mg total ammonia-N/ L, 0.5-mg NO2:-N/L and 50-mg NO3-N/L, respectively. Sulfide levels in the fish basin were below detection limits and oxygen > 6 mg/L after the oxygen generator was added at day 315. Ammonia, produced in the fish basin and to a lesser extent in the sedimentation basin, was converted to nitrate in the aerobic trickling filter. Nitrate removal took place in the sedimentation basin and to a lesser extent in the fluidized bed reactor. Sludge, remaining in the sedimentation basin at the end of the experimental period, accounted for 9.2% of the total feed dry matter addition to the system. The system was disease-free for the entire year and fish at harvest were of good quality. Water consumption for production of 1 kg of tilapia was 93 L and 214 L for production of 1 kg of gilthead seabream. Additional growth performance data of gilthead seabream cultured in a similar but larger system are presented. During 164 d of operation of the latter system, maximum stocking densities reached 50 kgl M3 and fish biomass production was 27.7 kg/m3. Relatively poor fish survival and growth resulted from occasional technical failures of this pilot system.

Biogeosciences Discussions, 2007

Ecosystems in dry regions are generally low in productivity and carbon (C) storage. We report, ho... more Ecosystems in dry regions are generally low in productivity and carbon (C) storage. We report, however, large increases in C sequestration following afforestation of a semi-arid shrubland with Pinus halepensis trees. Using C and nitrogen (N) inventories, based in part on site-specific allometric equations, we measured an increase in the standing ecosystem C stock from 2380 g C m −2 in the shrubland to 5840 g C m −2 in the forest after 35 years, with no significant change in N stocks. Carbon sequestration following afforestation was associated with increased N use efficiency as reflected by an overall increase in C/N ratio from 7.6 in the shrubland to 16.6 in the forest. The C accumulation rate in the forest was particularly high for soil organic C (SOC; increase of 1760 g C m −2 or 50 g C m −2 yr −1 ), which was associated with the following factors: 1) Analysis of a small 13 C signal within this pure C 3 system combined with size fractionation of soil organic matter indicated a significant addition of new SOC derived from forest vegetation (68% of total forest SOC) and a considerable portion of the old original shrubland SOC (53%) still remaining in the forest. 2) A large part of both new and old SOC appeared to be protected from decomposition as about 60% of SOC under both land-use types were in mineral-associated fractions. 3) A short-term decomposition study indicated decreased decomposition of lower-quality litter and SOC in the forest, based on reduced decay rates of up to 90% for forest compared to shrubland litter. 4) Forest soil included a significant component of live and dead roots (12% of total SOC). Our results suggest a role for increased N use efficiency, enhanced SOC protection and reduced decomposition rates in the large C sequestration potential following afforestation in semi-arid regions. These results are particularly relevant in light of persistent predictions of drying trends in the Mediterranean and other regions.

Soil Biology & Biochemistry, 2008

To identify factors that influence the relatively high productivity of a semi-arid pine afforesta... more To identify factors that influence the relatively high productivity of a semi-arid pine afforestation system in southern Israel, we investigated inorganic nitrogen deposition and mineralization for more than 2 years. To this end, we measured bulk and dry deposition, in situ N-mineralization over the seasonal cycle, and the potential activity of nitrifying microorganisms by soil slurry incubations. There was a small increase in bulk N deposition in the forest, compared with shrubland, but no change in dry deposition. An unexpected rapid increase in nitrite concentration in the forest soil was observed after soil rewetting by the first winter rains, which could not be explained by deposition. This was accompanied by a decrease in ammonium and only a slight increase in nitrate concentrations. Only a small increase in nitrite and a rapid increase in nitrate concentration in the mineral soil were observed in the surrounding shrubland. Soil slurry incubations from the forest sites exhibited significant delay in nitrite, compared with nitrate accumulation (up to 50 h under lab conditions) in samples taken in the dry season, but not in the wet season. This indicated different rates of ammonium and nitrite oxidation that are most likely linked to differential activation of different microbial populations after the summer stress. The initial oxidation process of ammonia to nitrate, upon soil rewetting in semi-arid environments, appears to occur as a partially uncoupled two-step process, as opposed to a rapid continuous one in wetter environments. This may have implications for the synchronization of nitrate availability to plants and therefore for high forest productivity and nitrogen use efficiency. Forest productivity in the semi-arid regions, in turn, is becoming increasingly more important with persistent predictions of warming and drying trends over the entire Mediterranean basin and other regions.

Soil Biology & Biochemistry, 2009

Nitric oxide (NO) plays a central role in the formation of tropospheric ozone, hydroxyl radicals,... more Nitric oxide (NO) plays a central role in the formation of tropospheric ozone, hydroxyl radicals, as well as nitrous and nitric acids. There are, however, large uncertainties around estimates of global NO emissions due to the paucity of data. In particular, there is little information on the rate of NO emission and its sensitivity to processes such as land use changes in dry environments. Here we report on a two-year study on the influence of afforestation on soil NO fluxes in the semi-arid afforestation system in Southern Israel (Yatir forest, mean annual precipitation ∼280 mm). Laboratory incubations were carried out under seasonally defined conditions of soil moisture and temperature using soils sampled in different seasons from the native shrubland (taken both under shrub canopy and in the inter-shrub areas), and from the adjacent ∼2800 ha, 40-year-old pine afforestation site. Combining laboratory results with field measurements of soil moisture and temperature, we up-scaled soil–atmosphere NO fluxes to the ecosystem level. The different microsites differed in their annual mean NO release rates (0.04, 0.14 and 0.03 mg m−2 d−1 for the shrubland under and between shrubs and for the forest, respectively), and exhibited high inter-seasonal variability in NO emission rates (ranging from zero up to 0.25 mg m−2 d−1 in the wet and dry-rewetting seasons, respectively), as well as in temperature responses. Up-scaling results to annual and ecosystem scales indicated that afforestation of the semi-arid shrubland could reduce soil NO emission by up to 65%.

Environmental Science & Technology, 2010

The prospect of biofuel production on a large scale has focused attention on energy efficiencies ... more The prospect of biofuel production on a large scale has focused attention on energy efficiencies associated with different agricultural systems and production goals. We used 17 years of detailed data on agricultural practices and yields to calculate an energy balance for different cropping systems under both food and fuel scenarios. We compared four grain and one forage systems in the U.S. Midwest: corn (Zea mays) -soybean (Glycine max) -wheat (Triticum aestivum) rotations managed with (1) conventional tillage, (2) no till, (3) low chemical input, and (4) biologically based (organic) practices, and (5) continuous alfalfa (Medicago sativa). We compared energy balances under two scenarios: all harvestable biomass used for food versus all harvestable biomass used for biofuel production. Among the annual grain crops, average energy costs of farming for the different systems ranged from 4.8 GJ ha -1 y -1 for the organic system to 7.1 GJ ha -1 y -1 for the conventional; the no-till system was also low at 4.9 GJ ha -1 y -1 and the lowchemical input system intermediate (5.2 GJ ha -1 y -1 ). For each system, the average energy output for food was always greater than that for fuel. Overall energy efficiencies ranged from output:input ratios of 10 to 16 for conventional and no-till food production and from 7 to 11 for conventional and no-till fuel production, respectively. Alfalfa for fuel production had an efficiency similar to that of no-till grain production for fuel. Our analysis points to a more energetically efficient use of cropland for food than for fuel production and large differences in efficiencies attributable to management, which suggests multiple opportunities for improvement.

Environmental Science & Technology, 2005

bacteria and Bacteroidetes species were present in all of the DGGE profiles examined. DGGE analys... more bacteria and Bacteroidetes species were present in all of the DGGE profiles examined. DGGE analyses showed significant shifts in the bacterial community composition between profiles over two years of sampling, indicating the presence of a diverse and dynamic microbial community within the functionally stable FBR. The FBR's combined capacity for both oxic and anoxic sulfide oxidation, as indicated by bulk chemical, microsensor, and molecular microbial analyses, gives it significant functional elasticity, which is crucial for proper performance in the dynamic environment of this mariculture system.

Environmental Microbiology, 2003

Bacterial community structure and physiochemical parameters were examined in a sedimentation basi... more Bacterial community structure and physiochemical parameters were examined in a sedimentation basin of a zero-discharge mariculture system. The system consisted of an intensively stocked fish basin from which water was recirculated through two separate treatment loops. Surface water from the basin was pumped over a trickling filter in one loop while bottom-water was recirculated through a sedimentation basin followed by a fluidized bed reactor in the other. Ammonia oxidation to nitrate in the trickling filter and organic matter digestion together with nitrate reduction in the sedimentation basin and fluidized bed reactor, allowed zero-discharge operation of the system. Relatively high concentrations of oxygen, nitrate, sulphate and organic matter detected simultaneously in the digestion basin suggested the potential for a wide range of microbially-mediated transformation processes. In this study, physiochemical parameters were correlated to bacterial diversity and distribution in horizontal and vertical profiles within this basin in an effort to obtain a basic understanding of the chemical and microbial processes in this system. Chemical activity and microbial diversity, the latter measured by denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR) amplified 16S rDNA fragments, were higher in the sludge layer than in the overlying aqueous layer of the basin. Chemical parameters in sludge samples close to the basin inlet suggested enhanced microbial activity relative to other sampling areas with evidence of both nitrate and sulphate reduction. Four of the nine DGGE bands identified in this zone were affiliated with the Bacteroidetes phylum. Detected sequences closely related to sequences of organisms involved in the sulphur cycle included Desulfovibrio , Dethiosulfovibrio and apparent sulphur oxidizers from the gamma-proteobacteria. In addition, a number of sequences from the beta and alpha-proteobacteria were identified.

Journal of The World Aquaculture Society, 2003

Results are presented of a zero-discharge marine recirculating system used for the culture of gil... more Results are presented of a zero-discharge marine recirculating system used for the culture of gilthead seabream Sparus aurata. Operation of the system without any discharge of water and sludge was enabled by recirculation of effluent water through two separate treatment loops, an aerobic trickling filter and a predominantly anoxic sedimentation basin, followed by a fluidized bed reactor. The fish basin was stocked for the first 6 mo with red tilapia Oreochromis niloticus × O. aureus at an initial density of 16 kg/m3. During this period salinity was raised from 0 to 20 parts per thousand. Then, gilthead seabream, stocked at an initial density of 21 kg/m3, replaced tilapia at day 167 and were cultured for an additional 225 d. Non steady-state inorganic nitrogen transformations occurred as a result of these salinity changes. After day 210, the system operated at all times with those water quality parameters considered critical for successful operation of mariculture systems, within acceptable limits. Thus ammonia, nitrite, and nitrate concentrations did not exceed 1.0-mg total ammonia-N/ L, 0.5-mg NO2:-N/L and 50-mg NO3-N/L, respectively. Sulfide levels in the fish basin were below detection limits and oxygen > 6 mg/L after the oxygen generator was added at day 315. Ammonia, produced in the fish basin and to a lesser extent in the sedimentation basin, was converted to nitrate in the aerobic trickling filter. Nitrate removal took place in the sedimentation basin and to a lesser extent in the fluidized bed reactor. Sludge, remaining in the sedimentation basin at the end of the experimental period, accounted for 9.2% of the total feed dry matter addition to the system. The system was disease-free for the entire year and fish at harvest were of good quality. Water consumption for production of 1 kg of tilapia was 93 L and 214 L for production of 1 kg of gilthead seabream. Additional growth performance data of gilthead seabream cultured in a similar but larger system are presented. During 164 d of operation of the latter system, maximum stocking densities reached 50 kgl M3 and fish biomass production was 27.7 kg/m3. Relatively poor fish survival and growth resulted from occasional technical failures of this pilot system.

Biogeosciences Discussions, 2007

Ecosystems in dry regions are generally low in productivity and carbon (C) storage. We report, ho... more Ecosystems in dry regions are generally low in productivity and carbon (C) storage. We report, however, large increases in C sequestration following afforestation of a semi-arid shrubland with Pinus halepensis trees. Using C and nitrogen (N) inventories, based in part on site-specific allometric equations, we measured an increase in the standing ecosystem C stock from 2380 g C m −2 in the shrubland to 5840 g C m −2 in the forest after 35 years, with no significant change in N stocks. Carbon sequestration following afforestation was associated with increased N use efficiency as reflected by an overall increase in C/N ratio from 7.6 in the shrubland to 16.6 in the forest. The C accumulation rate in the forest was particularly high for soil organic C (SOC; increase of 1760 g C m −2 or 50 g C m −2 yr −1 ), which was associated with the following factors: 1) Analysis of a small 13 C signal within this pure C 3 system combined with size fractionation of soil organic matter indicated a significant addition of new SOC derived from forest vegetation (68% of total forest SOC) and a considerable portion of the old original shrubland SOC (53%) still remaining in the forest. 2) A large part of both new and old SOC appeared to be protected from decomposition as about 60% of SOC under both land-use types were in mineral-associated fractions. 3) A short-term decomposition study indicated decreased decomposition of lower-quality litter and SOC in the forest, based on reduced decay rates of up to 90% for forest compared to shrubland litter. 4) Forest soil included a significant component of live and dead roots (12% of total SOC). Our results suggest a role for increased N use efficiency, enhanced SOC protection and reduced decomposition rates in the large C sequestration potential following afforestation in semi-arid regions. These results are particularly relevant in light of persistent predictions of drying trends in the Mediterranean and other regions.

Soil Biology & Biochemistry, 2008

To identify factors that influence the relatively high productivity of a semi-arid pine afforesta... more To identify factors that influence the relatively high productivity of a semi-arid pine afforestation system in southern Israel, we investigated inorganic nitrogen deposition and mineralization for more than 2 years. To this end, we measured bulk and dry deposition, in situ N-mineralization over the seasonal cycle, and the potential activity of nitrifying microorganisms by soil slurry incubations. There was a small increase in bulk N deposition in the forest, compared with shrubland, but no change in dry deposition. An unexpected rapid increase in nitrite concentration in the forest soil was observed after soil rewetting by the first winter rains, which could not be explained by deposition. This was accompanied by a decrease in ammonium and only a slight increase in nitrate concentrations. Only a small increase in nitrite and a rapid increase in nitrate concentration in the mineral soil were observed in the surrounding shrubland. Soil slurry incubations from the forest sites exhibited significant delay in nitrite, compared with nitrate accumulation (up to 50 h under lab conditions) in samples taken in the dry season, but not in the wet season. This indicated different rates of ammonium and nitrite oxidation that are most likely linked to differential activation of different microbial populations after the summer stress. The initial oxidation process of ammonia to nitrate, upon soil rewetting in semi-arid environments, appears to occur as a partially uncoupled two-step process, as opposed to a rapid continuous one in wetter environments. This may have implications for the synchronization of nitrate availability to plants and therefore for high forest productivity and nitrogen use efficiency. Forest productivity in the semi-arid regions, in turn, is becoming increasingly more important with persistent predictions of warming and drying trends over the entire Mediterranean basin and other regions.

Soil Biology & Biochemistry, 2009

Nitric oxide (NO) plays a central role in the formation of tropospheric ozone, hydroxyl radicals,... more Nitric oxide (NO) plays a central role in the formation of tropospheric ozone, hydroxyl radicals, as well as nitrous and nitric acids. There are, however, large uncertainties around estimates of global NO emissions due to the paucity of data. In particular, there is little information on the rate of NO emission and its sensitivity to processes such as land use changes in dry environments. Here we report on a two-year study on the influence of afforestation on soil NO fluxes in the semi-arid afforestation system in Southern Israel (Yatir forest, mean annual precipitation ∼280 mm). Laboratory incubations were carried out under seasonally defined conditions of soil moisture and temperature using soils sampled in different seasons from the native shrubland (taken both under shrub canopy and in the inter-shrub areas), and from the adjacent ∼2800 ha, 40-year-old pine afforestation site. Combining laboratory results with field measurements of soil moisture and temperature, we up-scaled soil–atmosphere NO fluxes to the ecosystem level. The different microsites differed in their annual mean NO release rates (0.04, 0.14 and 0.03 mg m−2 d−1 for the shrubland under and between shrubs and for the forest, respectively), and exhibited high inter-seasonal variability in NO emission rates (ranging from zero up to 0.25 mg m−2 d−1 in the wet and dry-rewetting seasons, respectively), as well as in temperature responses. Up-scaling results to annual and ecosystem scales indicated that afforestation of the semi-arid shrubland could reduce soil NO emission by up to 65%.