Lucerne-dominated fields recover native grass diversity without intensive management actions

摘要

1Spontaneous succession is often underappreciated in restoration after the cessation of intensive agricultural management. Spontaneous succession could improve the success of restoration programmes, and offers a cost-effective option with little active intervention. 2We studied the spontaneous recovery of loess grasslands in extensively managed lucerne Medicago sativa fields mown twice a year using space for time substitutions to highlight the importance of spontaneous processes in grassland restoration. 3With increasing field age a gradual replacement of lucerne by perennial native grasses and forbs and increase of mean species richness was detected. As the age of fields increased, lucerne decreased from 75% to 2% of total vegetation cover, whereas perennial graminoids increased from 0.5 to 50% cover. Mean total cover showed no significant differences between the age groups; weed cover was less than 10%. 4The phytomass of lucerne was negatively correlated with graminoid phytomass. As the age of the fields increased, lucerne phytomass decreased and grass phytomass increased. We found a negative correlation between litter and forb phytomass but there was no relationship with the age of the field. There was no litter accumulation and no increase of mean total phytomass as the age of fields increased. 5Synthesis and applications. Native grasses within loess grasslands recovered within 10 years, but characteristic native forbs remained rare. The advantages of spontaneous succession in lucerne fields compared to technical reclamation include: (i) no early stages dominated by weeds, (ii) minimal litter accumulation, (iii) a spontaneous decrease in lucerne over time, and (iv) negligible cost. In addition, the requirement for twice yearly mowing in the early years will guarantee farmer involvement because of the high forage value of lucerne. The complete restoration of species rich grasslands will require more active management such as propagule transfer by hay and/or moderate grazing to encourage the return of native forbs.