| Alpine grasslands on the Tibetan Plateau are experiencing the combined effects of climate change and human activities,resulting in serious local degradation,which threatens the water resources security and ecological safety of the region.The restoration of alpine degraded grasslands by no-till replanting of native grass species is considered as a climate-and environment-friendly means to restore alpine grassland seed sources.Improving the success rate of no-till replanting of native grass seeds is a technical challenge that needs to be overcome in order to practice this theory.The application of grass seed coating or pelletizing technology is a common way to seek a solution to the low replanting efficiency due to the poor single grain weight of similar grass seeds,but the current coating technology,which usually aims to increase the mechanized replanting capacity of grass seeds,rarely has the application of auxiliary nutrients,growth regulators and microbial fungicides that aim to restore the whole ecosystem.In response to the above problems,this research tried to develop suitable grass seed coating technology for cultivating alpine degraded grassland on the Tibet Plateau by coating the seeds of three grasses,such as Elymus mutans,Festuca sinensis and Poa pratensis,through germination tests and potting tests,selecting six groups of superior coating agent formulations,and conducting field validation using randomized zonal trials in severely degraded grassland in Guoluo,the main results are as follows:(1)Development of layered coating:In order to solve the influence of other coating agents on the activity of microbial fungicides in the coating,this research independently developed a layered coating technology,using carbon powder as a barrier layer,and the results of laboratory confirmed that the technology is effective and significantly increases the survival rate of microbial fungicides in the seed coating.Subsequently,germination rate experiments of coated seeds are conducted to select the most suitable seed coating concentration formulations for grass seed germination:1%concentration(mass ratio of ingredients to seed coating agent,same below)of growth regulator,2.5%concentration of compound fertilizer,and 0.1%concentration of micronutrient fertilizer formulations show optimal laboratory germination results,with germination rates of 95%,84%,and 80%,significantly higher than the control(46%)and other formulations(P<0.05).(2)Selecting the optimal formulations verified in the laboratory:the coating formulation of compound fertilizer and micro fertilizer and growth regulator and compound microbial fungicide is the optimal formulations.Except for the 14-day seedling emergence rate of Festuca sinensis,the seedling emergence effect of each coating formula is close to naked seeds,and the optimal formulation of coating has the highest day 14 seedling emergence rate of 65%,56%and 46%for Elymus mutans,Festuca sinensis and Poa pratensis,respectively.Pot test reveals that the optimum coating formulation of Poa pratensis has the best establishment with 40±15 g/m~2 and41±6 g/m~2 of aboveground and underground biomass,respectively,while the best establishment of Festuca sinensis is 71±9 g/m~2 and 33±10 g/m~2 of aboveground and underground biomass for the compound fertilizer and micro fertilizer and compound microbial fungicides formulations,respectively,and the best establishment of Festuca sinensis with the compound microbial fungicides formulation The best establishment of aboveground biomass is 52±16 g/m~2,while the best establishment of belowground biomass is 21±7 g/m~2 for compound fertilizer and micro fertilizer and compound microbial fungicides formulation.(3)Field validation using six laboratory coating formulations:a)Absolute cover(absolute community cover for photo conversion,as described in Material Methods)is significantly higher in all seed coating formulations(55-64%)than in CK1(43±6%,P<0.05);among all formulations,absolute cover is highest in grasses coated with compound fertilizer and micro fertilizer and growth regulator and compound microbial fungicides,with a 21%increase(absolute value)relative to grasses without reseeding;b)For the replanted species,the relative cover(sum of cover by species)of grasses is highest(75±11%)in the coated formulations of compound fertilizer and micro fertilizer and growth regulator and compound microbial fungicides formulation,and lowest(43±12%)in compound microbial fungicides formulation,but all are significantly higher than the non-replanted(CK1,<1%),naked seed replant(CK2,32±6%)and filler-coated(CK3,34±8%),while the other functional groups were not significantly different.c)Community height(species height according to the weighted mean of cover,9-17 cm)of the seed-coated formulations is significantly higher than CK1(<1.0 cm,P<0.05);The results of biomass and diversity in the restored grassland show that:a)aboveground biomass(138±15 g/m~2)is significantly higher in the replanting of the coated formulation of compound fertilizers and micro fertilizers and growth regulators and microbial fungicides than in CK1(72±10 g/m~2,P<0.05),and underground biomass(714±177 g/m~2)is also significantly higher in the replanting sample plots of this formulation than in the other treatments and the control(Treatment 1:336±82g/m~2,Treatment 2:284±66 g/m~2,Treatment 3:462±107 g/m~2,Treatment 4:459±107 g/m~2,Treatment 5:446±118 g/m~2,CK1:196±34 g/m~2,CK2:279±54 g/m~2,CK3:379±78 g/m~2,P<0.05);b)Simpson’s index(0.86-0.89)is significantly higher in the grasses of all seed coating formulation replanting treatments than in CK1(0.78±0.03,P<0.05).The Whittaker diversity index(3.0-3.8)is significantly lower for all formulations than CK1.The species richness(9.5-10.7)is significantly higher for all formulations than CK1(7.5±0.8).The above findings confirm that the use of layered coating to layer seeds according to the optimal ratio of coating agents(plant growth regulators,micro fertilizers and compound fertilizers)significantly increased the biomass,cover and height of subsequent plantings.In addition,the added coating ingredients not only increased the field establishment of the target species,but also increased the growth(cover,high and biomass)and enrichment of other functional groups of plants with the addition of active ingredients.In particular,the layered coating technology restored the plant community composition,structure and productivity of severely degraded grasslands without destroying the grass mat layer and tillage.The use of native grass species closer to nature,supplemented with active formulations of plant growth regulators,micro fertilizers,nutrients,and microbial fungicides provides scientific and technological support for policy decisions and grassland management in alpine regions with environmentally and climate-friendly restoration initiatives. |
