Community-scale seedbank response to less intense rotation and reduced herbicide input at three sites.

摘要

Species diversity and abundance in weed seed banks were measured at the beginning, and after 3 and 6 years of the TALISMAN experiment at ADAS Boxworth, Drayton and High Mowthorpe, UK. Fifty species were distinguished in the seed banks of treatmentscomprising winter and spring rotations and full and reduced herbicide input. After 6 years, the number of seed bank species in the main treatments ranged from 11 in the most intense to 26 in the least intense management. Principal co-ordinate analysis showed that the seed bank community diverged over time between sites and additionally between the two rotation treatments at Boxworth. Only four species were common to all sites but community-scale descriptors indicated that the change in seed banks following reduced inputs had common features at the three sites. Firstly, species-area relations showed a greater relative increase in number of taxa at a plot scale than in the site as a whole, indicating lower inputs encouraged the common weeds more than rare species. Secondly, both the mean and the standard deviation of the species-abundance distribution at 6 years increased in response to reduced inputs. As a result, the number of species slightly more than doubled as herbicide units were reduced from four to one while the total number of seeds increased by two orders of magnitude. Some causes of seed bank change were identified: spring germinating species tended to increase when spring cultivation was common in the rotation, while some competitive weedshad a relatively low abundance when they were targeted by herbicide. The results are discussed in relation to optimizing the various functions of the seed bank.