The forest soil organic N was investigated using N K-edge X-ray absorption near-edge structure （XANES） to gain an insight into the relationship between N speciation and its transformation in quantity. Soil samples w...The forest soil organic N was investigated using N K-edge X-ray absorption near-edge structure （XANES） to gain an insight into the relationship between N speciation and its transformation in quantity. Soil samples were collected from spruce, hemlock and pine forests in central Taiwan. Results showed that various organic N types could be revealed by XANES spectra. Amide and pyrrolic N are the major parts of the composition in the humic substance, soluble organic nitrogen and original soils. The relative distribution of N speciation differed in treatments and vegetations samples. The spruce had a significant difference from the hemlock in soluble organic nitrogen （SON） spectra at 402.3 eV energy peak. In the A-horizon soils, the relative amount of pyridinic N was much higher than that in the O-horizon soils, indicating N transformation in quantity in the mineral horizon was different from that in the organic horizon, which might play an important role in N cycling of forest ecosystems.展开更多
Indaziflam is a preemergent herbicide widely used for the control of weeds in pecan(Carya illinoinensis)orchards in the southwestern region of the United States.Given the paucity of data regarding the effect of indazi...Indaziflam is a preemergent herbicide widely used for the control of weeds in pecan(Carya illinoinensis)orchards in the southwestern region of the United States.Given the paucity of data regarding the effect of indaziflam on the biochemical properties of soils supporting pecan production,this study was conducted to evaluate the effects of different application rates of indaziflam on soil microbial activity,diversity,and biochemical processes related to nitrogen(N)cycling.During two consecutive growing seasons(2015 and 2016),soil samples were obtained from experimental mesocosms consisting of soil-filled pots where pecan saplings were grown and treated with indaziflam applied at two different rates(25 and 50 g active ingredient(ai)ha^(-1),with the higher rate being slightly lower than the recommended field application rate of 73.1 g ai ha^(-1)).Soil samples were collected approximately one week before and one week after herbicide application for determination of soil microbial biomass and diversity,N mineralization,andβ-glucosaminidase activity.Soil samples collected from the control mesocosms without herbicide application were treated in the laboratory with two rates of indaziflam(75 and 150 g ai ha^(-1))to determine the immediate effect on microbial activity.No significant effect of herbicide treatment on soil respiration and microbial biomass was detected.The results showed a slight to moderate decrease in microbial diversity(7%in 2015 and 44%in 2016).However,decreasedβ-glucosaminidase activity with herbicide treatment was observed in soils from the mesocosms(33%)and soils treated with indaziflam in the laboratory(45%).The mineral N pool was generally dominated by ammonium after indaziflam application,which was consistent with the drastic decrease(75%)in nitrification activity measured in the laboratory experiment.The results of this study indicate that indaziflam,even when applied at higher than recommended rates,has limited effects on soil microbial activity,but may affect N cycling processes.展开更多
基金This paper was supported by Front Project of Knowl-edge Innovation Program, Chinese Academy of Sciences (ISSASIP0205)
文摘The forest soil organic N was investigated using N K-edge X-ray absorption near-edge structure （XANES） to gain an insight into the relationship between N speciation and its transformation in quantity. Soil samples were collected from spruce, hemlock and pine forests in central Taiwan. Results showed that various organic N types could be revealed by XANES spectra. Amide and pyrrolic N are the major parts of the composition in the humic substance, soluble organic nitrogen and original soils. The relative distribution of N speciation differed in treatments and vegetations samples. The spruce had a significant difference from the hemlock in soluble organic nitrogen （SON） spectra at 402.3 eV energy peak. In the A-horizon soils, the relative amount of pyridinic N was much higher than that in the O-horizon soils, indicating N transformation in quantity in the mineral horizon was different from that in the organic horizon, which might play an important role in N cycling of forest ecosystems.
文摘Indaziflam is a preemergent herbicide widely used for the control of weeds in pecan(Carya illinoinensis)orchards in the southwestern region of the United States.Given the paucity of data regarding the effect of indaziflam on the biochemical properties of soils supporting pecan production,this study was conducted to evaluate the effects of different application rates of indaziflam on soil microbial activity,diversity,and biochemical processes related to nitrogen(N)cycling.During two consecutive growing seasons(2015 and 2016),soil samples were obtained from experimental mesocosms consisting of soil-filled pots where pecan saplings were grown and treated with indaziflam applied at two different rates(25 and 50 g active ingredient(ai)ha^(-1),with the higher rate being slightly lower than the recommended field application rate of 73.1 g ai ha^(-1)).Soil samples were collected approximately one week before and one week after herbicide application for determination of soil microbial biomass and diversity,N mineralization,andβ-glucosaminidase activity.Soil samples collected from the control mesocosms without herbicide application were treated in the laboratory with two rates of indaziflam(75 and 150 g ai ha^(-1))to determine the immediate effect on microbial activity.No significant effect of herbicide treatment on soil respiration and microbial biomass was detected.The results showed a slight to moderate decrease in microbial diversity(7%in 2015 and 44%in 2016).However,decreasedβ-glucosaminidase activity with herbicide treatment was observed in soils from the mesocosms(33%)and soils treated with indaziflam in the laboratory(45%).The mineral N pool was generally dominated by ammonium after indaziflam application,which was consistent with the drastic decrease(75%)in nitrification activity measured in the laboratory experiment.The results of this study indicate that indaziflam,even when applied at higher than recommended rates,has limited effects on soil microbial activity,but may affect N cycling processes.
