Evaluation of Species diversity effect on some of agroecosystem services in the intercropping of corn, soybean and marshmallow 2- Yield, Land equivalent ratio, soil microbial respiration and biomass, carbon sequestration potential

abstract
Background and objectives
Many researchers in agricultural ecosystems consider the multiple cropping as the most important factor for increasing the diversity of cultures (31, 21, 1) .Increasing of crops diversity through intercropping can be effective to improve the functions and ecosystem services. Ecosystem services are "the conditions and processes through which natural ecosystems and the species provide continuity of life and needs of human". Ecosystem services are very diverse and have dimensions of ecological and environmental. One of the main functions of multiple cropping systems is the increasing soil biological activities. Increasing crops diversity through multiple cropping causes improving soil microorganisms and therefore soil biological activity as one of the ecosystem services increases (29).
Material and methods
The purposes of the study were evaluating of the intercropping efficacy for corn, soybean and marshmallow in terms of land equivalent ratio, microbial biomass and potential of carbon sequestration as different ecosystem services. For this purpose, an experiment was conducted based on a randomized complete block design with three replications at research farm of Ferdowsi university of Mashhad during growing season 2013- 2014. Experimental treatments included the different patterns of intercropping for corn, soybean and marshmallow based on replacement series at seven levels. Each plot had 6 rows. Soybean and corn in intercropping treatments including 4 rows of soybean and 2 rows of corn, soybean and marshmallow intercropping treatments including 4 rows of soybean and 2 rows of marshmallow, Corn and marshmallow intercropping treatments including 4 rows of Marshmallow and 2 rows of Corn, planting a mixture of three species and the sole cropping of the three species.The studied characterizes included land equivalent ratio (LER), microbial respiration and biomass and carbon sequestration potential. Anderson method (3) was used to measure microbial respiration. Fumigation -incubation method (12) was used for the measurement of soil microbial biomass.
Results
Results showed that LER was larger than one under all treatments of intercropping (withaout any significant differences, in range from 1.01 to 1.08), which indicating the efficacy of the intercropping compared to sole cropping systems. Using of the intercropping systems caused to increase in soil microbial respiration and biomass in comparison with sole cropping systems, so that the highest microbial respiration (94.17 mg CO2 kg-1 day-1( and biomass (820.34 mg kg-1) were obtained by intercropping of corn + soybean + marshmallow. Experimental results showed that carbon sequestration potential affected by different patterns of intercropping and the highest carbon sequestration potential (1487.5, 3210.1, 4502.0 kg C ha-1 in scenarios of 30, 70 and 100% residue, respectively) was observed in corn + marshmallow intercropping. Therefore as comprehensive suggestion, increasing plant diversity through intercropping can be considered as one of the effective approaches to increase services such as improvement of microbial activity and potential of carbon sequestration; and valuation the services in multi-planting systems and comparing them with sole cropping systems were suggested for the next studies.
Conclusion
Using of multiple cropping increased soil microbial biomass and this can increase nutrition circle and productivity of soil. Although increasing microbial biomass may lead to a reduction of carbon sequestration in the soil. Because under increasing microbial biomass conditions, residues decomposition rate and microbial respiration are increased and more carbon dioxide is entered to the atmosphere which results in reduction of carbon sequestration. Another important function of multiple cropping is carbon sequestration potential so that in multiple cropping increased this potential so using of multiple cropping can mitigate negative effects of climate change. Choosing species and keeping plant residues on soil surface have effective role in success of multiple cropping in carbon sequestration potential.