Alterations in canopy size and reproduction of Caragana stenophylla along a climate gradient on the Inner Mongolian Plateau

In this study, we examined the alterations in canopy size and reproduction of Caragana stenophylla along the climatic drought gradient on the Inner Mongolia Plateau, China. We found that the canopy area and height of C. stenophylla increased gradually with increase of drought stress from the semi-arid zone to the strongly arid zone. The proportions of sexual reproduction decreased and the asexual reproduction increased with increase of the climatic drought stress. The majority of C. stenophylla offspring grew (separately) outside shrubs in the semi-arid (63.9%) and the arid zones (45.8%). But in the strongly arid zone, C. stenophylla offspring only grew inside shrubs. With the increase of climatic drought stress the ramet radius increased, while the spacer length decreased. In both the semi-arid and arid zones, the spacer length was more than 2 times of the ramet radius. Thus, some spaces were kept between the crowns of ramets. On the other hand, the spacer length was less than 2 times of the ramet radius in the strongly arid zone, so that the crowns were closely intertwined. Our results demonstrate that with the increase of climatic drought stress and associated desertification, the reproduction of C. stenophylla changes from more sexual reproduction to more clonal propagation; offspring establishment strategy changes from having more outside-shrub offspring to having only inside-shrub offspring; the clonal architecture changes from guerrilla type to phalanx type. Alterations in the reproduction of C. stenophylla along the climatic drought gradient result due to an increase of its canopy size from the northeast to the southwest on the Inner Mongolia Plateau.