Soil food web structure is fundamental to ecosystem process and function; most studies on soil food web structure have focused on agro-ecosystems under different management practices and natural terrestrial ecosystems...Soil food web structure is fundamental to ecosystem process and function; most studies on soil food web structure have focused on agro-ecosystems under different management practices and natural terrestrial ecosystems,but seldom on greenhouses. This study explored the static and temporal variability of soil food structure in two greenhouses of Shandong Province,North China over a two-year period. The static properties were measured directly by surveying functional group composition and a series of parameters portraying the species properties,link properties,chain properties and omnivory properties of the web,as well as indirectly through calculation of nematode indices,enrichment index(EI),structure index(SI),and channel index(CI). The dynamic variability of greenhouse soil food structure was described by the dynamics of functional groups,Bray-Curtis(BC) similarity and cluster analysis. The results showed that the greenhouse soil food web contained 14 functional groups,with microbes having the highest mean biomass,followed by protozoa. Of the three functional groups of protozoa,flagellates were the dominant group on most sampling dates,amoebae only became the dominant group during the summer,while ciliates were the least prevalent group. All nematodes were assigned into one of the four functional groups,bacterivorous,fungivorous,herbivorous and omnivorous,and the fungivorous nematodes had the lowest mean biomass. Mites were assigned into three functional groups and the omnivorous noncryptostigmatic mites were the dominant group. All the functional groups showed significant seasonal changes. The soil food web connectance was 0.15,the maximum food chain length was 5,and the average food chain length was 3.6. The profiles of the EI and SI showed that the food web was resourcedepleted with minimal structure. The results of CI indicated that the bacterial decomposition pathway was the dominant pathway in the food web of the greenhouse soils studied and the results of BC similarity showed that the soil food web had higher variability and instability over time. The cluster analysis showed that the functional groups located at high trophic levels with low biomass were in a cluster,whereas those at low trophic levels with high biomass were closer. Compared with the food web structure of agroecosystem and natural terrestrial ecosystem soils,the structure of greenhouse soil food web was simple and unstable,which was likely driven by high agricultural intensification,particularly over application of fertilizers.展开更多
A short term field mesocosm experiment was performed in semi-deciduous forest areas of Ivory Coast to assess the impact of a decompacting （Hyperiodrilus africanus, Eudrilidae） and two compacting （Millsonia omodeoi ...A short term field mesocosm experiment was performed in semi-deciduous forest areas of Ivory Coast to assess the impact of a decompacting （Hyperiodrilus africanus, Eudrilidae） and two compacting （Millsonia omodeoi and Dichogaster terrae nigrae, Acanthodrilidae） earthworm species on soil properties. These species have been selected for their predominance in the re- gion and their contrasting impact on soil structure. The experimental design consisted of a treatment without worms （control）, and treatments with one, two or three species of earthworms. Both compacting and decompacting earthworms increased water infil- tration rate in all treatments, with marked impact in H. africanus and M. omodeoi＋D, terraenigrae treatments. Interactions be- tween compacting and decompacting species resulted in more large aggregates in comparison to when the compacting species D. terraenigrae was alone. This may be accounted for by their compacting attribute as compacting earthworms are responsible for producing the highest number of large aggregates. The low values of mean weight diameter in treatments combining decompact-ing and compacting earthworms compared with compacting ＂M. omodeoi＂ one also confirmed the trend of decline in soil com-paction in the presence of the decompacting species. These results showed positive impact of species richness on soil structure regulation, which is crucial in ecosystem productivity and support consequently the insurance hypothesis. In fact, this study showed that the preservation of earthworm species belonging to these two contrasting functional groups is essential for the main-tenance of stable soil structure regulation in agro-tropical ecosystems.展开更多
基金Supported by the National Natural Science Foundation of China(No.40901116)
文摘Soil food web structure is fundamental to ecosystem process and function; most studies on soil food web structure have focused on agro-ecosystems under different management practices and natural terrestrial ecosystems,but seldom on greenhouses. This study explored the static and temporal variability of soil food structure in two greenhouses of Shandong Province,North China over a two-year period. The static properties were measured directly by surveying functional group composition and a series of parameters portraying the species properties,link properties,chain properties and omnivory properties of the web,as well as indirectly through calculation of nematode indices,enrichment index(EI),structure index(SI),and channel index(CI). The dynamic variability of greenhouse soil food structure was described by the dynamics of functional groups,Bray-Curtis(BC) similarity and cluster analysis. The results showed that the greenhouse soil food web contained 14 functional groups,with microbes having the highest mean biomass,followed by protozoa. Of the three functional groups of protozoa,flagellates were the dominant group on most sampling dates,amoebae only became the dominant group during the summer,while ciliates were the least prevalent group. All nematodes were assigned into one of the four functional groups,bacterivorous,fungivorous,herbivorous and omnivorous,and the fungivorous nematodes had the lowest mean biomass. Mites were assigned into three functional groups and the omnivorous noncryptostigmatic mites were the dominant group. All the functional groups showed significant seasonal changes. The soil food web connectance was 0.15,the maximum food chain length was 5,and the average food chain length was 3.6. The profiles of the EI and SI showed that the food web was resourcedepleted with minimal structure. The results of CI indicated that the bacterial decomposition pathway was the dominant pathway in the food web of the greenhouse soils studied and the results of BC similarity showed that the soil food web had higher variability and instability over time. The cluster analysis showed that the functional groups located at high trophic levels with low biomass were in a cluster,whereas those at low trophic levels with high biomass were closer. Compared with the food web structure of agroecosystem and natural terrestrial ecosystem soils,the structure of greenhouse soil food web was simple and unstable,which was likely driven by high agricultural intensification,particularly over application of fertilizers.
文摘A short term field mesocosm experiment was performed in semi-deciduous forest areas of Ivory Coast to assess the impact of a decompacting （Hyperiodrilus africanus, Eudrilidae） and two compacting （Millsonia omodeoi and Dichogaster terrae nigrae, Acanthodrilidae） earthworm species on soil properties. These species have been selected for their predominance in the re- gion and their contrasting impact on soil structure. The experimental design consisted of a treatment without worms （control）, and treatments with one, two or three species of earthworms. Both compacting and decompacting earthworms increased water infil- tration rate in all treatments, with marked impact in H. africanus and M. omodeoi＋D, terraenigrae treatments. Interactions be- tween compacting and decompacting species resulted in more large aggregates in comparison to when the compacting species D. terraenigrae was alone. This may be accounted for by their compacting attribute as compacting earthworms are responsible for producing the highest number of large aggregates. The low values of mean weight diameter in treatments combining decompact-ing and compacting earthworms compared with compacting ＂M. omodeoi＂ one also confirmed the trend of decline in soil com-paction in the presence of the decompacting species. These results showed positive impact of species richness on soil structure regulation, which is crucial in ecosystem productivity and support consequently the insurance hypothesis. In fact, this study showed that the preservation of earthworm species belonging to these two contrasting functional groups is essential for the main-tenance of stable soil structure regulation in agro-tropical ecosystems.
