Small-Scale Spatial Pattern of Potentilla acaulis Population Under Different Grazing Intensities

Using Ripley′s K function and Monte-Carlo random simulation methods,the fine-scale spatial patterns of Potentilla acaulis were quantified under four grazing intensities: no grazing,light grazing(1.33 sheep/hm~(2)),medium grazing((4.00) sheep/hm~(2)) and heavy grazing(6.67 sheep/hm~(2)).The effect of grazing on the spatial patterns was studied.Based on life circle characteristics and strategies of ecological adaptation of P.acaulis and interspecific interaction in the community,the mechanisms generating and maintaining these patterns were explored.The results showed that:(1) Grazing would greatly affect the spatial patterns of P.acaulis,which changed with increasing of scales even under the same grazing intensity;(2) Under non-grazing condition,P.acaulis was aggregated at the scale of 0～96 cm,but randomly distributed at 96～100 cm;under light-grazing condition,it was aggregated at 0～92 cm, but randomly distributed at 92～100 cm;under medium-grazing condition,it was aggregated at 0～72 cm,but randomly distributed at 72～100 cm;under heavy-grazing condition,it was aggregated at 20～22 cm,regularly distributed at 15～17 cm,23～28 cm and 46～50 cm,and randomly at 0～15 cm,17～20 cm,22～23 cm,28～46 cm and 50～100 cm;(3) At the same grazing intensity,the spatial pattern of P.acaulis changed from aggregation to random distribution with the scale increasing.The scale,where the spatial pattern of P.acaulis changed,decreased with grazing intensity increasing;(4) At 0～100 cm scales,the aggregation intensity of P.acaulis decreased with the increasing of grazing intensity,that is,no grazinglight grazingmedium grazingheavy grazing;(5) The grazing activity changed relative importance of processes determining the community structure.Fig 2,Ref 24