He Feng, Wang Kun, Hannaway David B, Li Xianglin
Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.
Department of Grassland Science, China Agricultural University, Beijing, People's Republic of China.
PLoS One. 2017 Dec 29;12(12):e0190450. doi: 10.1371/journal.pone.0190450. eCollection 2017.
Leymus chinensis (Trin.) is the dominant vegetation type in eastern Eurasian temperate grasslands but is decreasing due to the combined pressure of reduced precipitation and overgrazing. This study evaluated the separate and combined effects of precipitation and defoliation on net primary productivity (NPP) and composition of a L. chinensis steppe to promote the sustainable development of temperate grasslands through improved management practices. The effects of three precipitation gradients (precipitation unchanged, reduced by 50%, and increased by 50%) and two clipping intensities (clipping once or twice per year) were examined on NPP and composition of the L. chinensis community using a 7-year in situ controlled trial at the Guyuan State Key Monitoring and Research Station of Grassland Ecosystem in China. The results showed that: (1) a 50% reduction in natural precipitation significantly decreased NPP; a 50% increase in precipitation did not significantly increase NPP, but it decreased the importance value of L. chinensis because more water promoted the growth of competing species. (2) Clipping twice per year increased NPP, but the increase was from the dry matter of other species (DMO) component, and not from the dry matter of L. chinensis. (3) The standardized coefficients of a regression model (β) for DMO, NPP, and the importance value of L. chinensis were 0.685, 0.532, and -0.608 for precipitation, and 0.369, 0.419, and -0.276 for clipping mode, respectively. This study demonstrated that variation in precipitationis the key driver of NPP and composition of a L. chinensis steppe under the precipitation range and clipping intensities evaluated. This improved understanding of the effects of precipitation and clipping on NPP and composition will allow for improved, sustainable management of L. chinensis temperate grassland steppes.
羊草（Leymus chinensis (Trin.)）是欧亚大陆东部温带草原的优势植被类型，但由于降水减少和过度放牧的综合压力而正在减少。本研究评估了降水和刈割对羊草草原净初级生产力（NPP）和组成的单独及综合影响，以通过改进管理措施促进温带草原的可持续发展。利用中国固原草地生态系统国家重点监测与研究站进行的为期7年的原位对照试验，研究了三个降水梯度（降水不变、减少50%和增加50%）和两种刈割强度（每年刈割一次或两次）对羊草群落NPP和组成的影响。结果表明：（1）自然降水减少50%显著降低了NPP；降水增加50%并未显著增加NPP，但降低了羊草的重要值，因为更多的水分促进了竞争物种的生长。（2）每年刈割两次增加了NPP，但增加的是其他物种干物质（DMO）部分，而非羊草的干物质。（3）降水对DMO、NPP和羊草重要值的回归模型标准化系数（β）分别为0.685、0.532和 -0.608，刈割方式的标准化系数分别为0.369、0.419和 -0.276。本研究表明，在所评估的降水范围和刈割强度下，降水变化是羊草草原NPP和组成的关键驱动因素。对降水和刈割对NPP和组成影响的这种更好理解将有助于改进羊草温带草原的可持续管理。
