Growth and reproductive strategies of Thalictrum petaloideum under different stocking rates

Abstract

Aims Grazing is one of the major measures for grassland management in Nei Mongol steppe. The growth and reproductive strategies of grassland plants are developed under their long-term co-evolution with ungulates in grassland ecosystems. This study was conducted to understand how Thalictrum petaloideum would change its growth and reproductive strategies with increasing stocking rate. Methods By using a grazing experiment in a typical steppe ecosystem initiated by the Nei Mongol Grassland Ecosystem Research Station in 2006, we examined the responses of T. petaloideum to stocking rates at population, individual and organ levels during the 2012 and 2013 growing seasons. Important findings With increasing stocking rate, the number of reproductive individuals decreased and the reproductive process ceased in T. petaloideum at the population level. The threshold for ceasing the reproductive process was at a stocking rate of 7.5 sheep per hm 2 . The plant height, plant biomass and the numbers of reproduc- tive branches, flowers and seeds all decreased with increasing stocking rate at an individual level. Two shifts were detected for the reproductive allometric relationships with increases in stocking rate. With the increase of stocking rates, T. petaloideum reduced the number of flowers per reproductive branch decreased but the individual seed weight increased with increasing stocking rate at the organ level. A trade-off between the number of seed and the weight of seed was found, which might be an important mechanism in T. petaloideum responding to grazing dis- turbance.