Effect Of Management And Environment Factors On Soil Carbon And Nitrogen And Biota Character

Soil carbon is an important part of the terrestrial ecosystem. Soil microbe is the main driving force to carbon dynamic and nutrient turnover in the biogeochemical cycling. The effect of management practice and environmental factors on soil carbon and nitrogen dynamic, biomass and diversity and community structure of microbe and earthworm were tested in typical ecosystems in the eastern US. We tested the effect of management duration and intensity on soil carbon, microbial biomass and activity in turfgrass system, we also determine carbon stability in different density fraction and carbon proportion derived from C3 and C4 plant by test C13; the effect of management duration, management intensity and chemical usage on biomass and community structure of earthworm was tested in golf course and phytotron environment; the effect of field management practice on soil carbon dynamic, microbial biomass, microbial activity, microbial community structure and stability was tested; soil carbon, microbial properties in different agriculture system was tested; the effect of greenhouse gases on microbial was simulate in open top chamber.The objective of this research were to determine if and how management practice and environmental factors influenced carbon dynamic and stability, and the function of microbe in carbon and nitrogen cycling. The results of this research were showed as following:1. The effect of management duration and intensity on soil carbon and microbial properties in turfgrass systemOur result showed that the management duration positively affect the carbon sequestration and nitrogen retention. The carbon and nitrogen accumulate rate was 71.89 g m2 y-1 and 10.63 g m²y^-1 respectively in 1 m depth. The management duration, land-use change and climate change all influenced the soil microbial biomass and activity. Microbial carbon and nitrogen was highest in the native pine tree system in normal climate condition but highest in the longest management system when the dry season occurred. Microbial activity was highest in the longest management system. Management intensity was also affect the soil carbon, soil nitrogen, microbial carbon, microbial nitrogen and microbial activity. All these indicator were highest in the intermediate intensity systems. Our research indicate that long and moderate management turfgrass system can sequestration more carbon than native pine system, which can facilitate to decrease the concentration of carbon dioxide in the atmosphere.2. The effect of management duration, management intensity and chemical usage on earthworm in turfgrass systemPopulation density and biomass of earthworms tended to be higher in the 80-year than in the 10-year areas, which were all lower than the control under pine trees. Greater abundance and biomass were found in the tee than other areas. However, earthworms were more abundant in the rough than in the fairway in the dry and hot year (2007) while the opposite was true for the wet year (2008), indicating that soil moisture and temperature had a dominant effect on earthworm density and activities. Pesticides affected earthworm population dynamics and activities. Single application of insecticides Sevin and Merit at the manufacturers'maximum dosages significantly inhibited burrowing behaviors of earthworms for at least three weeks without leading to any earthworm death. The toxicity to earthworms, however, increased as application frequency increased. Weekly applications of chemicals Sevin, Merit and T-methyl for four weeks led to the mortality at 35, 45 and 80 %, respectively. In field, consecutive weekly applications of T-methyl and Sevin for 5 times reduced the population and biomass of earthworms as compared to the control with suppressive effect lasting for at least 6 weeks after chemical application stopped. Taken together, these findings suggest that earthworm activities in turfgrass systems may be managed through appropriate irrigation and pesticide applications; our result also indicate that the invasive species were favorite with the area with more resource.3. The effect of field management practice on soil carbon and microbial propertiesAfter 15 years of continuous treatments with six different management regimes, soil C and N pools and microbial parameters diverged. Tillage dominated the effect of management practices on soil C and N, although organic practice also exerted significant impacts. Both no tillage and organic inputs significantly promoted soil microbial biomass and activity, and enhanced total soil C and N accumulation. The combination of no tillage and organic management increased soil organic C by 140 % over the conventional tillage control, leading to soil C content comparable to an un-disturbed grassland. No tillage and organic farming also altered the distribution of soil organic C among different density fractions. Under the no tillage plus organic input treatment, the percentage of organic C was reduced in the light fraction but increased in the heavy fraction, suggesting an increased transformation of organic C from the labile into the stabile pool. Organic input dominated the effect of management practices on soil microbial diversity and community structure, although no-tillage practice also exerted significant impacts. Both no-tillage and organic inputs significantly promoted soil microbial diversity and community stability. The combination of no-tillage and organic management slightly increased 6.46 % soil microbial diversity over the conventional tillage control and so similar to undisturbed grassland. No-tillage and organic farming also altered the microbial community structure among different production systems. Under the no-tillage plus organic input treatment, the microbial community structure was more similar to the natural grassland systems. These results indicate that effective management through reducing tillage and increasing organic C inputs can enhance soil C accumulation, improving soil fertility while mitigating the atmospheric CO₂ rise. Effective management through reducing tillage and increasing organic C inputs can enhance soil microbial diversity and the community stability, which improving soil health and quality.4. The influence of agroecosystems on soil carbon and microbial propertiesResult showed that extreme dry climate event can significantly decreased soil moisture condition and available resource, extractable carbon, which many affect microbial living. Soil carbon and nitrogen were highest in moderately disturbance agroecosystems than other intensive and lowly disturbed agroecosystems. Extractable carbon was highest in lowly disturbed system. Carbon dynamic was significantly affected by the management disturb, Light fraction carbon was highest in lowly disturbed system and lowest in intensive agroecosystems, while Very heavy fraction carbon was highest in intermediately disturbed ecosystem, no-tillage system and lowest in lowly disturbance system. Microbial biomass carbon, biomass nitrogen, microbial activity was also affected by the different disturbance gradient. Generally, these microbial properties were highest in the moderately than other two extreme disturbance agroecosystems. Principle component analyses of PLFA data showed microbial diversity and community structure diverged among the soils of the six agroecosystems. High microbial diversity was found in the moderately than intensive and lowly disturbed agroecosystems, and the lower disturbance systems more facilitate the development of microbial communities that favor fungi than other groups. Our research indicate that the agroecosystems, which not only facility microbial diversity, but also enhanced soil carbon pool could be achieved.5. The effect of greenhouse gas on soil microbial propertiesThe result showed that high level CO₂ was favorite soil moisture, soil microbial biomass and activity than ambient CO₂. O₃ was suppressed these tested indicators but high level CO₂ can alleviate the negative effects.