Grazing limits natural biological controls of woody encroachment in Inner Mongolia Steppe

Biology Open

卷:6

Chunguang Liu¹  Chelse M. Prather²  Lina Xie³  Yinhua Wang³  Hongyu Guo³  Linjing Guan³  Chengcang Ma³ 

[1] College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China;

[2] Department of Biology, University of Dayton, Dayton, OH 45419, USA;

[3] Tianjin Key Laboratory of Animal and Plant Resistance, College of Life Sciences, Tianjin Normal University, Tianjin 300387, China;

关键词: Caragana microphylla;    Grazing;    Inner Mongolia Steppe;    Herbivorous insects;    Parasitic plants;    Woody encroachment;   

DOI  :  10.1242/bio.026443

来源: DOAJ

【 摘 要 】

Woody encroachment in grasslands has become increasingly problematic globally. Grazing by domestic animals can facilitate woody encroachment by reducing competition from herbaceous plants and fire frequency. Herbivorous insects and parasitic plants can each exert forces that result in the natural biological control of encroaching woody plants through reducing seeding of their host woody plants. However, the interplay of grazing and dynamics of herbivorous insects or parasitic plants, and its effects on the potential biological control of woody encroachment in grasslands remains unclear. We investigated the flower and pod damage by herbivorous insects, and the infection rates of a parasitic plant on the shrub Caragana microphylla, which is currently encroaching in Inner Mongolia Steppe, under different grazing management treatments (33-year non-grazed, 7-year non-grazed, currently grazed). Our results showed that Caragana biomass was highest at the currently grazed site, and lowest at the 33-year non-grazed site. Herbaceous plant biomass followed the opposite pattern, suggesting that grazing is indeed facilitating the encroachment of Caragana plants in Inner Mongolia Steppe. Grazing also reduced the abundance of herbivorous insects per Caragana flower, numbers of flowers and pods damaged by insect herbivores, and the infection rates of the parasitic plant on Caragana plants. Our results suggest that grazing may facilitate woody encroachment in grasslands not only through canonical mechanisms (e.g. competitive release via feeding on grasses, reductions in fires, etc.), but also by limiting natural biological controls of woody plants (herbivorous insects and parasitic plants). Thus, management efforts must focus on preventing overgrazing to better protect grassland ecosystems from woody encroachment.

【 授权许可】

Unknown