Effects Of Eucalyptus Grandis Leaf Litter On Brassica Chinensis L. And Soil Environment During The Early Stage Of Decomposition

A pot-experiment, adding eucalypt leaf litter to simulate the natural gradient of allelopathy impact, was carried out to characterize the effects of allelopathy on the photosynthesis of B.chinensis during the early decomposition stage of eucalypt leaf litter. Five levels of eucalypt leaf litter mass (0 g,20 g,40 g,80 g and 120 g per pot) was used to simulate impacts of natural releasing process of allelopathic substances of eucalypt leaf litter on the photosynthesis of B.chinensis and soil nutrients and microbial biomass, the Morphological and physiological index of B.chinensis were observed under the different eucalypt-gradient at the 40 d,60 d and 80 d after budding in this study. And the five same levels of eucalypt leaf litter digestied was used as black control group without allelochemicals to simulate impacts of the soil property, the Morphological and physiological index of B.chinensis were observed at the 80 d after budding. I found that:1) No statiscal difference were detected across the gradient after digestion. The Fresh weight biomass, plant height, root length and net photosynthetic rate were not statistical differences between the 80g per pot and non-eucalypt pot. This result indicated that adding eucalypt leaf litter could not influence the soil property and the growth of plant.2) Majority of liable organic matter released during the early decomposition of eucalypt litter. No obvious effect of Eucalypt litter application on soil nutrient content occurred. With the treatment proceed, TN, TPP, TPK decrease slightly (non-significant), the soil total carbon (TC) reduction in the early stage but increased later. TC and TN content at each treatment were measured with the increasing amount of leaf litter, and the difference between the levels gradually increased, indicating that the release of substances in leaf litter are mainly C and N; TPP and TPK increased with the increasing amount of leaf litter during the early stage, while decreased gradually later. The impact of the litter decomposition on liable nutrients was significantl. The content of APP and APK were high during the early observation, while decrease gradually later.3) During the observation, the content of soil microbial biomass increased with the incresing amount of leaf litter, but each of the microbial content were all lower than the control (CK), which dicating that the imposition of leaf litter of eucalypt inhibit microbial content, however with the increasing amount of leaf litter, due to the changes in the physical environment and a large number of more liable organic matter benefiting the micro-organisms, which could offset the inhibition of microorganisms.4) During the early stage, the application of eucalypt foliar litter of B. chinensis L. was significantly inhibited fresh weight biomass and leaf area index, two indicators of value with the increase in application rate decreased gradually, allelopathy, inhibition rates were increased (P<0.05). With the treatment proceed, decreased inhibition, the fresh weight of leaf litter biomass increased rapidly, the increase in leaf litter processing compared to the control (0 g/pot) of 3 to 4 times increase. Moreover, the increase in the leaf area index was detected non-significant different from the control.5) The photosynthetic indexes of cabbage was inhabited by the leaf litter with the increase of inhibition increased, however, with treatment proceed, the inhibition fade or even disappeared. Chlorophyll content of each component significant difference in dealing with the early, late period of treatment and then the increased content was lower, and the difference between leaf litter processing becoming obviously, which Chlb content of leaf litter by the most sensitive to allelopathic effects. Gas exchange parameters Pn, Tr, Ci, Gs, WUE and Ls in the early phase of treatment with increasing amounts of leaf litter reduced post was no significant difference among treatments (P> 0.05). CO2 response and light response curves of the fitting parameters. In dealing with pre-treatment was significantly different, the parameter value with the leaf litter increased and decreases with treatment time and decreased post-treatment difference was not significant (P> 0.05). The light adapted fluorescence parameters with the treatment capacity and gradient reduced processing time, only incremental qp content.6) The effects of eucalypt leaf litter on the physiological index of B.chinensis differ from each level. Permeability regulators of soluble sugar and content of nitric acid treatment time with the overall reduction of inconsistencies among the treatments, the few amount of leaf litter (20 g/pot) for the more amount of leaf litter (80 g/pot,120 g/pot) inhibition, to 20 g/ pot most resistant to treatment cabbage, its variety of stress regulatory pathways; soluble protein content altered little in the early stage, later to increase rapidly, but in the entire treatment period, showed an increase with the amount of litter decreasing trend; oxidation resistance enzyme system, SOD, POD and CAT activity inhibited by inconsistency, CAT fastest, SOD and POD followed; with the treatment proceed, SOD activity decreased rapidly decreased in the late, POD and CAT activity increased gradually and then growth accelerated. Protective enzymes to the higher application rate of leaf litter most rapidly, and this sensitivity and the application rate was proportional to the leaf litter.