Measurements of concentrations of easily extractable soil nitrogen(N) were carried out on samples collected at the Heron Wood Reserve,Scotland,concurrently with investigations of N associated with total microbial biom...Measurements of concentrations of easily extractable soil nitrogen(N) were carried out on samples collected at the Heron Wood Reserve,Scotland,concurrently with investigations of N associated with total microbial biomass and the abundances of bacteria,fungi,and invertebrates.Soil biota at the studied site appeared to be limited by N.There was a remarkable difference between the ambient(i.e.,easily extractable N) and biomass nitrogen.The abundance data of bacteria,protozoa and nematodes significantly negatively correlated with ambient N but showed positive correlations with the total microbial N content.There were,however,remarkable differences between the correlation patterns exhibited by the fungal and the bacterial pathways,as fungi did not show any correlations with chemical variables.These differences should be taken into account whilst interpreting biological interactions both at this important site and elsewhere.展开更多
There is a need to simultaneously preserve evidence of interactions between the biological community and soil structural properties of a soil in as near an intact （natural） state as possible. Three dehydration techn...There is a need to simultaneously preserve evidence of interactions between the biological community and soil structural properties of a soil in as near an intact （natural） state as possible. Three dehydration techniques were implemented and assessed for their ability to minimise disruption of both biological and physical properties of the same arable soil sample. Dehydration techniques applied until samples were at constant weight were i） air-drying at 20℃ （AD）; ii） -80 ℃ freeze for 24 h, followed by freeze-drying （-80FD）; and iii） liquid nitrogen snap freeze, followed by freeze-drying （LNPD） and were compared to a moist control. Physical structure was determined and quantified in three dimensions using X-ray computed tomography and microbial phenotypic community composition was assessed using phospholipid fatty acid （PLPA） profiling. This study confirms that any form of dehydration, when preparing soil for simultaneous biological and physical analysis, will alter the soil physical properties, and cause some change in apparent community structure. Freeze-drying （both the LNFD and -80FD treatments） was found to minimise disruption （when compared to the moist control soil） to both the soil physical properties and the community structure and is a preferable technique to air-drying which markedly alters the size and character of the pore network, as well as the phenotypic profile. The LNFD was the preferred treatment over the -80FD treatment as samples show low variability between replicates and a fast turn-around time between samples. Therefore snap freezing in liquid nitrogen, followed by freeze drying is the most appropriate form of dehydration when two sets of data, both physical and biological, need to be preserved simultaneously from a soil core.展开更多
Nutrient limitation in agriculture is a big problem in many tropical areas. Much research has focused on the optimal use of crop residues in agriculture. Recent work indicates that plant residue decomposition rates, i...Nutrient limitation in agriculture is a big problem in many tropical areas. Much research has focused on the optimal use of crop residues in agriculture. Recent work indicates that plant residue decomposition rates, including nutrient release rates can be increased by pre-exposure to sunlight. This has potential as a technology to manipulate nutrient release from residues to match crop demands. The possible development and use of this technology is discussed. There is some evidence that this could increase emissions of trace gases, but the increase is thought to be small. Research needs are discussed.展开更多
基金Supported by the Scottish Higher Education Funding Council (SHEFC),UKthe European Social Fund (ESF),UK.
文摘Measurements of concentrations of easily extractable soil nitrogen(N) were carried out on samples collected at the Heron Wood Reserve,Scotland,concurrently with investigations of N associated with total microbial biomass and the abundances of bacteria,fungi,and invertebrates.Soil biota at the studied site appeared to be limited by N.There was a remarkable difference between the ambient(i.e.,easily extractable N) and biomass nitrogen.The abundance data of bacteria,protozoa and nematodes significantly negatively correlated with ambient N but showed positive correlations with the total microbial N content.There were,however,remarkable differences between the correlation patterns exhibited by the fungal and the bacterial pathways,as fungi did not show any correlations with chemical variables.These differences should be taken into account whilst interpreting biological interactions both at this important site and elsewhere.
文摘There is a need to simultaneously preserve evidence of interactions between the biological community and soil structural properties of a soil in as near an intact （natural） state as possible. Three dehydration techniques were implemented and assessed for their ability to minimise disruption of both biological and physical properties of the same arable soil sample. Dehydration techniques applied until samples were at constant weight were i） air-drying at 20℃ （AD）; ii） -80 ℃ freeze for 24 h, followed by freeze-drying （-80FD）; and iii） liquid nitrogen snap freeze, followed by freeze-drying （LNPD） and were compared to a moist control. Physical structure was determined and quantified in three dimensions using X-ray computed tomography and microbial phenotypic community composition was assessed using phospholipid fatty acid （PLPA） profiling. This study confirms that any form of dehydration, when preparing soil for simultaneous biological and physical analysis, will alter the soil physical properties, and cause some change in apparent community structure. Freeze-drying （both the LNFD and -80FD treatments） was found to minimise disruption （when compared to the moist control soil） to both the soil physical properties and the community structure and is a preferable technique to air-drying which markedly alters the size and character of the pore network, as well as the phenotypic profile. The LNFD was the preferred treatment over the -80FD treatment as samples show low variability between replicates and a fast turn-around time between samples. Therefore snap freezing in liquid nitrogen, followed by freeze drying is the most appropriate form of dehydration when two sets of data, both physical and biological, need to be preserved simultaneously from a soil core.
文摘Nutrient limitation in agriculture is a big problem in many tropical areas. Much research has focused on the optimal use of crop residues in agriculture. Recent work indicates that plant residue decomposition rates, including nutrient release rates can be increased by pre-exposure to sunlight. This has potential as a technology to manipulate nutrient release from residues to match crop demands. The possible development and use of this technology is discussed. There is some evidence that this could increase emissions of trace gases, but the increase is thought to be small. Research needs are discussed.
