| Punica granatum is currently the mainstream variety in the Punica granatum market,widely loved by consumers because of its excellent taste,and its planting area has been expanding in recent years,accounting for more than 50% of the country’s output.Compound planting of forest and grass is one of the commonly used land management methods in orchards,which plays an important role in improving the ecological environment of orchards and improving the economic benefits of orchards.In this paper,four mass concentration gradients(0,0.005,0.025,0.05 g·m L-1)were used to study the effects of four mass concentration gradients.Punica granatum leaf water extract on three common forage herbs Trifolium repens,Medicago sativ,and Lolium perenne by setting different incubation temperatures of 15°C,25 °C and variable temperature(15 °C/25 °C)the effects of seed germination and seedling growth;A 360-day outdoor potted semi-natural decomposition experiment was conducted by setting up three grass planting modes,Loliumperenne-Punica granatum,Medicago sativa-Punica granatum and Trifolium repens Punica granatum,and a total of 7 litter combinations(4 litter of a single s-pecies,3 species of mixed litter)as the research object,and the semi-natural decomposition experiment of outdoor potted plants was carried out for 360 days,mainly to study the dry weight loss rate,decomposition rate,biostoichiometric ratio,fine root weight change and morphological characteristics of each litter at different decomposition stages.Relationship between soil biostoichiometry and growth and development characteristics of Punica granatum trees.The effects of Punica granatum leaf litter on seed germination and seedling growth of understory forage under the compound planting mode of forest grass,as well as the decomposition effect of single litter and mixed litter,were preliminarily studied,so as to provide theoretical support for Punica granatum-forage compound planting and orchard management.The main findings are as follows:(1)In the seed germination test,there are differences in the effects of Punica granatum leaf water extract on seed germination and seedling growth allelopathic effects of three forage grasses at different test temperatures.Punica granatum leaf extract with mass concentrations of 0.005,0.025 and 0.05 g·m L-1 had different degrees of inhibitory effect on seed germination of three forage plants,and the inhibition effect of high quality extract is significant,and the inhibitory effect increased with the increase of concentration.Under the conditions of 15 °C and 25 °C,the growth of three forage seedlings is inhibited by different mass concentrations of extract,and the inhibitory effect on the radicle of seedlings is stronger than that on the germ;Under variable temperature conditions,Punica granatum leaf extract with different mass concentrations had different degrees of promotion effect on the growth of three forage seedlings.By analyzing the comprehensive allelopathic effect index of Punica granatum leaf water extract on three kinds of forages,it can be seen that the allelopathic effect of Punica granatum leaf water extract on three forages at 15 °C is Trifolium repens > Lolium perenne > Medicago sativa.At 25 °C,the order of allelopathic effect is Medicago sativa > Lolium perenne > Trifolium repens.Under variable temperature conditions,the order of allelopathic effect is Trifolium repens > Lolium perenne >Medicago sativa,and the water extract of Punica granatum leaves have the weakest allelopathic inhibition effect on the three forages under variable temperature conditions.(2)In the semi-natural experiment of potting plants,the decomposition time and planting mode have a significant effect on the mass loss of fallen leaves.After 360 days of decomposition,the dry weight loss rate of litter of a single species is between72.3267%-90.3383%,which is manifested as Trifolium repens > Medicago sativa >Lolium perenne.The dry weight loss rate of litter in the two species combination is71.2850%-87.8883%,which is manifested as Trifolium repens + Punica granatum leaf >Medicago sativa + Punica granatum leaf > Lolium perenne + Punica granatum leaf.At different decomposition times,litter loss rate is always the largest in the Trifolium repens-Punica granatum group,followed by Medicago sativa-Punica granatum group,and litter decomposition is the slowest in Lolium perenne-Punica granatum group.The modified Olson exponential decay model is used to fit the decomposition process of litter of a single species and mixed litter of two species(R2 ≥ 0.825),and according to the model,the annual decomposition rate K values of single litter Trifolium repens and Medicago sativa are 1.8 times and 1.5 times that of Lolium perenne,respectively,and the annual decomposition rate K values of mixed litter Trifolium repens + Punica granatum leaf and Medicago sativa + Punica granatum leaf were 1.7 times and 1.5times that of Lolium perenne + Punica granatum leaves,respectively.The half-life and turnover periods of single litter Lolium perenne,Medicago sativa and Trifolium repens are 0.53 a,0.35 a,0.29 a,2.3 a,1.52 a,and 1.26 a,respectively.The half-life and turnover periods of mixed litter Lolium perenne + Punica granatum leaves,Medicago sativa + Punica granatum leaves,Trifolium repens + Punica granatum leaves were 0.55 a,0.37 a,0.32 a,2.37 a,1.61 a,and 1.40 a,respectively.(3)The C content,N content and ecological stoichiometry ratio of litter changed during the decomposition of litter.In the decomposition of 360 days,the C and N of each litter are continuously released,and both show a net release mode,and the C and N release rates of Trifolium repens is higher than those of Medicago sativa and Lolium perenne.For Lolium perenne,litter C and N release rates after mixing with Punica granatum leaves is greater than those of single pasture litter,while Medicago sativa and Trifolium repens are the opposite,and the release rates of the same litter C and N is N >C.The stoichiometric ratio of litter differed greatly between several species and different decomposition times,among which the C/N of single litter Lolium perenne and mixed litter Lolium perenne + Punica granatum leaves show a gradual upward trend and is significantly higher than that of Medicago sativa and Trifolium repens,and C/N of Medicago sativa and Trifolium repens show a fluctuating downward trend.(4)The fresh weight,dry weight and morphological characteristics of fine roots and dry weight of each litter layer change differently with the increase of litter decomposition time.In this study,the fresh weight and dry weight of fine roots in single litter Trifolium repens and Medicago sativa are at a high level,and higher than Lolium perenne.After 360 days of decomposition,the mixed litter Lolium perenne + Punica granatum leaves and Trifolium repens + Punica granatum leaf layer had higher fresh weight,dry weight,total root length and total surface area than its single litter,and Medicago sativa + Punica granatum leaves is the opposite.In the single litter Trifolium repens,the total length and total surface area of fine roots show a decreasing trend,while the total length and total surface area of fine roots in the litter layer of Medicago sativa and Lolium perenne show an overall increase trend.The total root length and total surface area of the mixed litter layer of the two species decrease overall,and the total root length and total surface area of the Lolium perenne + Punica granatum leaf litter layer is the largest.(5)With the decomposition of litter,the soil nutrient content and ecological stoichiometry ratio changed significantly under different grass modes,and the planting mode and litter decomposition time are important influencing factors.Compared with CK,after 360 days of decomposition,the addition of different litter increase the soil carbon,nitrogen content and C/N ratio,and the soil carbon and nitrogen contents show Trifolium repens-Punica granatum > Medicago sativa-Punica granatum > Lolium perenne-Punica granatum when litter decomposed to the 360 th day.(6)During the decomposition of litter,the SPAD value and N content of Punica granatum leaves changed significantly.The SPAD values and N contents of Punica granatum leaves in Lolium perenne-Punica granatum,Medicago sativa-Punica granatum and Trifolium repens-Punica granatum gradually increased from June to August,and gradually decreased after reaching a peak in August,and the SPAD values of Punica granatum leaves in the three grass modes in August are 59.5167,61.7278 and 72.3667,respectively,which is significantly higher than those in June,and the SPAD values of Punica granatum leaves in the Trifolium repens-Punica granatum mode is significantly higher than those in the other two grass modes and control group.In summary,the low concentration of Punica granatum leaf extract have a significant promoting effect on Trifolium repens,and the single pasture litter is easier to decompose than the mixed litter of forage + Punica granatum leaf,and the litter of Trifolium repens and Medicago sativa is easier to decompose than Lolium perenne litter,and its nutrient elements are easier to release,and the three grass modes could increase soil carbon and nitrogen content and chlorophyll content and nitrogen content of Punica granatum leaves. |
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