Ectomycorrhizal Colonization Rates Of Root Tips Of Larix Gmelinii,Picea Koraiensis And Pinus Koraiensis In Pure Plantations And In Mixed Plantations With Fraxinus Mandshurica

Ectomycorrhiza (ECM) could remarkably enhance the uptake capacity of soil nutrients and water for roots in coniferous species. Study the factors that affect ectomycorrhiza colonization in coniferous trees is important in understanding the eco-physiological processes and growth of root systems. Recent studies indicated that coniferous-hardwood mixed forests, comparing with coniferous monoculture forests, alter litter qualities, soil fertility conditions and root distribution pattern, as well as their competition ability. However, few studies focus on the effects of coniferous species mixed with hardwood trees on ECM colonization.In this study, three ECM coniferous species, Korean pine (Pinus koraiensis), Korean spruce (Picea koraiensis) and Dahurian larch (Larix gmelinii), and one endomycorrhizal hardwood species Machurian ash (Fraxinus mandshurica), were used in three independent experiments. Experiment1is conducted in26years old mixed plantations of the three coniferous species mixed with Machurian ash. Experiment2is conducted in three coniferous monoculture plantations, but the original coniferous leaf litter was removed from plots, and input ash leaf litter. Experiment3is use one year old seedlings in pots, each of the three coniferous seedling planted with ash seedling in pots. These three experiments were conducted in2011, and the main objectives were to investigate the effects of coniferous species mixed with hardwood, hardwood leaf litter addition and root interactions on ECM infections.ECM colonization of Korean pine, Korean spruce and Dahurian larch in mixtures with Machurian ash were decreased by8.5%,4.8%, and3.4%, respectively. Higher soil pH, microbial biomass nitrogen, microbial biomass carbon, total nitrogen and carbon were observed in mixtures compared with coniferous monocultures. There were significant negative correlations between ECM colonization and soil pH, total nitrogen, total carbon, respectively, in all plots of the three coniferous tree species.Addition ash leaf litter, after removed the original coniferous litter layer, reduced ECM colonization by8.7%(Korean pine),4.3%(Korean spruce) and5.1%(Dahurian larch), respectively. Litter addition has also decreased soil total nitrogen and total carbon, but increased soil pH, soil microbial biomass nitrogen and microbial biomass carbon. The ratio of soil total carbon to nitrogen, together with microbial biomass nitrogen and microbial biomass carbon, can explain61%and47%of the variations in ECM colonization for Korean pine and Dahurian larch, respectively.ECM colonization in pots of Korean spruce and Dahurian larch seedlings were reduced by18.6%and23.2%in mixed Machurian ash seedling, but slightly enhanced in Korean pine seedlings (2%). On the other hand, root-root interactions changed soil properties in pot experiments, such as reducing soil pH, total nitrogen, and total carbon in mixed pots. However, responses of soil microbial biomass nitrogen and microbial biomass carbon to ash seedlings mixed differed among the coniferous species, it was higher in Korean spruce and Dahurian larch seedlings in mixed pots and was lower in Korean pine seedlings.These results suggest that ECM colonization of roots decrease in coniferous species mixed with ash and in coniferous monocultures with ash litter addition. The key reasons perhaps enhance soil pH, soil microbial biomass nitrogen and microbial biomass carbon in both experiments. In addition, roots interaction between conifers and hardwood seedlings may also influence ECM infection in pot experiments, however, such influence depended on species. Our results in this study are important in understanding the interactions between conifer and hardwood, and shed light on the mechanisms of roots in their ECM infections.