| In recent years,grassland ecosystem degradation and ecological damage is becoming progressively serious, enlarging the frequency of many social problems, such as the ecological security, environmental security, food safety.Hunshandake sandy land, one of four biggest sandy lands in china, located in the arid and semi-arid area of northern.Due to the fragility of ecological environment,over grazing and unsuitable production activity for period of long time, the grassland and soil in Hunshandake has been seriously degraded. Although the restoration of degradable grassland ecosystem has been carried for several years, and some staggered achievements have been made, it is not able to realize the development of ecology and economy simultaneously. Scholars have proposed the “farming chicken in grassland”-a new grassland utilization mode in previous studies, which provides a frontier for solving the problems above.The farming chicken raised at Hunshandake grassland ecological research station of Chinese Academy of Sciences were used as the research objects in this paper. The vegetation and soil samples were collected and analyzed, the four indexes including biomass, coverage, species richness, and vegetation height were tested, the eleven physicochemical properties including the soil bulk density, moisture content, p H value, organic matter, organic carbon, ammonium nitrogen, nitrate nitrogen, total nitrogen, available phosphorus, microbial carbon and nitrogen were measured in sample land. The influence and differences of vegetation and soil physiochemical properties between testing land samples and scatter-feeding land samples were counted and analyzed with single factor analysis of variance of SPSS18.0(One-Way ANOVA) method, comparison of biomass substitution pattern, indexes of time scale and correlation, the ecological environment, economic benefits and food safety between the two kinds of farming chicken in farming chicken biomass replacement mode were analyzed, the main conclusions were given as follows:Farming chicken density had a large impact on vegetation coverage, material abundance, biomass of aboveground and underground. Comparing with no farming chicken grassland, it has a certain of negative impact when chicken farming density was above 400 chickens/hm2. There was a linear relationship between the chicken farming density and the indexes including community coverage, species richness and biomass aboveground, it means when farming density was getting smaller, vegetation coverage, species richness and aboveground biomass were getting higher. Compared with reasonable density of farming shepherd, the indexes increased significantly. With the increase of farming chicken years, density of different treatment of aboveground and underground biomass was increased, the underground biomass increased greatly. Vegetation height and coverage, richness, diversity index and evenness index were increased to a certain extent, but the difference was not significant. Results showed that the 400 chickens / hm2 farming density had no obvious influence on the ecological system of ground sand grassland by comparison with the blank site. When the farming density was 800 chickens/ hm2, all of the ecological indexes were better than these of the farming shepherd land. The grassland grazing chicken had over compensation of grassland productivity and Connell intermediate disturbance hypothesis was verified.The farming chicken density on test samples land and intensive free-range land did not have obvious influence on soil bulk density. The difference of distances from the henhouse and vegetation types had significant influence on soil bulk density(P < 0.05), and the lowest soil bulk density was found in the place from the henhouse 8m.There was not obvious difference comparison of the blank sample. With the increase of farming chicken density, soil bulk density increased slightly, but the increase was lower than the shepherd sample land. With the increase of farming time, the soil bulk density decreased, the greatest drop was 7.2%, however, there is a little change at intensive free-range land.Different density, distance, levels along with the interaction of distance and the level to the moisture content of soil were significant difference at test samples and intensive free-range land(P < 0.05). On the whole, with the increase of soil depth, the soil moisture content decreased significantly, the biggest drop was 65.1%. Compared with the blank sample land, the soil moisture content of different density treatments and levels of soil showed a slight decline; compared reasonable shepherd plots, the soil moisture content of 0-10 cm levels were significantly increased, maximum increase of total mean was up to 34.8%. As a whole soil moisture content showed decreasing trend with the increase of the distance, soil moisture content from the henhouse 8m was the biggest under different density treatments. Difference of the intensive backyard plots was significant, total mean of soil moisture content of different levels of IC1 plot was significantly higher than that of IC2 and IC3 plots. With the increase of grazing chicken years, the soil moisture content of different density and levels increased significantly.The soil level had the significantly influence on p H value, p H value was the highest in the 10-20 cm soil level. The largest increase was 12.9%. It had a slight decrease with the increase of the distance. The biggest drop was 2.9%. Compared with the blank sites, different density treatments did not change significantly; compared with the reasonable farming shepherd sites, surface soil p H value of different density increased slightly, the maximum increase was 5.4%, with the increase of farming chicken time, soil p H value had increased with different density and different levels of soil, the range of p H value was 7.6-9.5. Soil level and vegetation type had significantly influence on soil p H value in intensive free-range sample lands. soil p H value in the 20-50 cm soil level was significantly higher than that of 0-10 cm and 10-20 cm level, compared with average value of sample lands, results showed IC1 > IC2 > IC3. The range of average value of p H was 7.00-8.30, it was weakly alkaline. With the increase of farming time, the soil p H value has a little change in a variety of sample lands.The C nutrient was influenced significantly with different soil level(P < 0.05), farming chicken density and level had significant effect on N and P nutrients(P < 0.05). Overall, the C nutrient decreased significantly with the increase of the soil level depth, soil microbial biomass carbon content was the highest in the 10-20 cm level. Compared with blank sample, there was not significant difference. The total mean of organic matter, organic carbon, microbial biomass carbon content were significantly higher than that of the reasonable farming shepherd sample lands in the 0-10 cm soil level. With the increase of the distance that had decreasing trend, the soil organic matter, organic carbon content was the highest at the distance 8m from chicken house. With the increase of farming chicken time, the C nutrient in the soil surface was slightly increased under different farming chicken density treatments. The experimental results in two years showed that the difference of the distribution and variation of nutrient N was larger, on the whole, along with the decrease of the soil level depth, the change of soil nitrate nitrogen, ammonium nitrogen and available nitrogen was not consistent. With the increase of soil level depth, the soil nitrate nitrogen and ammonium nitrogen content decreased, ammonium nitrogen content increased in 2009, however, the soil nitrate nitrogen and ammonium nitrogen content increased, the content of ammonium nitrogen decreased in 2011. Two years study showed that the soil total nitrogen content increased, microbial biomass nitrogen content decreased when the soil level depth increased. In different farming chicken density treatments of soil, nitrate nitrogen, total nitrogen and available nitrogen were higher than that of the blank sample land, compared with reasonable farming shepherd sample lands, nitrate nitrogen, available nitrogen, total nitrogen content were increased significantly in 10-20 cm, 20-50 cm levels of soil, ammonium nitrogen changes very little in the 0-10 cm levels of soil, ammonium nitrogen content significantly increased in the 10-20 cm, 20-50 cm level of soil compared with the blank sample land, the content of soil microbial biomass nitrogen decreased in the 0-10 cm and 10-20 cm level of soil, but 20-50 cm level increased, but compared reasonable farming shepherd lands, it had no obvious change in all levels of soil. Soil nitrate nitrogen, available nitrogen, total nitrogen decreased with the increase of the distance, ammonium nitrogen increased. With the increase of faming chicken time, the nitrate nitrogen, available nitrogen, total nitrogen content of surface soil decreased significantly, ammonium nitrogen increased significantly; but in 20-50 cm soil level, the content of soil nitrate nitrogen available nitrogen, total nitrogen increased significantly, ammonium nitrogen content decreased significantly, microbial biomass nitrogen content significantly increased in 10-20 cm and 20-50 cm levels of soil. Difference of soil available phosphorus was significant among different density, but the change was not obvious. The content of available phosphorus decreased significantly with the increase of soil depth level; compared with the blank sample lands, it increased in different farming density treatments and soil levels; compared with reasonable farming shepherd sample lands, the total mean of soil available P content in 0-10 cm and 10-20 cm levels decreased, it changed very little in 20-50 cm soil level; the soil available P content of different levels in reasonable farming shepherd were higher than that of blank sample. Difference of the total mean was not significant among different distances. With the increase of farming time, the content of available P increased significantly in soil 10-20 cm levels, but it did not change significantly in the other two levels. On the whole, the Connell intermediate disturbance hypothesis was verified by the analysis of soil physical and chemical indicators.The change of C, N, P nutrient was consistent between the study sites and the Intensive free-range sites. Soil organic matter and organic carbon content showed significant difference among different vegetation types, it was significantly higher in IC1 plots than that of IC2 and IC3 samples, soil microbial biomass carbon did not show significant difference among different vegetation types. Difference of N nutrient content was significant among different vegetation types, compared with the total mean of nitrate nitrogen, ammonium nitrogen and available nitrogen, it showed IC2 > IC3 > IC1; total mean of total nitrogen, microbial biomass nitrogen and available phosphorus, it showed IC3 > IC2 > IC1. With the increase of farming time, soil nitrate nitrogen and available nitrogen content of different levels increased in IC1 samples land, it reduced in IC3 sample land, and decreased significantly in 10-20 cm and 20-50 cm levels of IC2. Soil ammonium nitrogen of 10-20 cm and 20-50 cm levels decreased significantly in IC1; that of 0-10 cm, 10-20 cm levels significantly increased in IC2 and IC3; soil total nitrogen content of different distance and levels increased significantly in IC1, soil total nitrogen content of different distance of 0-10 cm level increased significantly in IC2 and IC3; soil microbial biomass nitrogen content from different distance of 0-10 cm and20-50 cm levels increased significantly in IC1,but it decreased obviously in 10-20 cm level; soil microbial biomass nitrogen content of 0-10 cm and 10-20 cm levels increased significantly in IC2 and IC3, but it decreased significantly in 20-50 cm level of IC2 plots.Comparative analysis of each factor index of surface soil between the test sample plots and intensive free-range sample plots showed that soil bulk density of IC3 increased significantly, in different vegetation plots,soil nitrate nitrogen and available nitrogen content increased significantly, these indexes decreased such as p H value, moisture content,organic matter, organic carbon content; soil ammonium nitrogen content increased significantly in IC2, it decreased significantly in IC1 and IC3 plots,but the content of total nitrogen and microbial biomass nitrogen and available phosphorus significantly increased in different vegetation plots. The change of soil indexes between 10-20 cm and 20-50 cm levels and the surface soil was similar.In general,there were consistent of correlation between the indexes from two modes. There was significant positive correlation between organic carbon and organic matter, and there was a significant positive correlation between other N nutrient and phosphorus nutrient as well, N and C nutrient and available phosphorus were correlated significantly, but ammonium nitrogen and nitrate nitrogen negatively correlated, available phosphorus and C nutrient and N nutrient was significant correlation, it was significant negative correlation with p H value; soil p H value was significant positive correlation with ammonium nitrogen and negative correlation with other nutrients, the soil moisture content was significantly correlated with soil nutrients, bulk density was negative correlation with moisture content.To sum up, the farming density under the 400 chickens /hm2 had no obvious influence on the ecology factor of aboveground sandy grassland ecosystem, the effect of chicken density maximum(800 chickens/hm2) on aboveground ecological system was significantly lower than that of reasonable farming shepherd. The nutrient of soil input at farming chicken grassland was greater than the output, soil nutrients increased with the increase of farming chicken time, and was significantly higher than that of the reasonable farming shepherd sample lands. Comprehensive analysis of the best grazing density was 400 chickens/hm2. The grassland grazing chickens has over compensation to grassland productivity,and connell intermediate disturbance hypothesis was verified. The comparative analysis of two sample plots showed that the law of spatial distribution and transfer of soil nutrients and factor correlation were the same between the test sample lands and intensive free-range sample plots, the total nutrient input was slightly higher than that of the test sample plots. Therefore, the grassland farming chickens can effectively restore the ecosystem of grassland degradation, produce significant environmental and ecological benefits, increase the economic income of herdsmen, and have considerable economic benefit; food and feed were saved,by the grassland farming chickens,which products of meat and egg complyed with the EU standard of organic chicken and egg, grain and food satety were protected in some degree by the grassland farming chickens. The study had strong theoretical and practical significance. |
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