Lv Yanyan, Shen Menghong, Meng Baoping, Zhang Huifang, Sun Yi, Zhang Jianguo, Chang Li, Li Jingrong, Yi Shuhua
Institute of Fragile Eco-Environment, Nantong University, Nantong 226007, China.
School of Geographic Science, Nantong University, Nantong 226007, China.
Plants (Basel). 2021 Sep 13;10(9):1890. doi: 10.3390/plants10091890.
The asymmetric response of productivity to precipitation was recently proposed as an early warning signal for the shifts in temperate grassland function in China. It was hypothesized that the asymmetry was influenced by the increased growth of the newly emerged seedlings from the soil seed bank. Therefore, the seed density in the soil seed bank and the similarity between species composition of the vegetation and the soil seed bank should be maximized where asymmetry was maximized. However, this knowledge was still limited and unconfirmed. In this study, the desert steppe, typical steppe and the transition zone between them (with the highest asymmetry) were selected for studying the similarity index in both 2018 (dry year) and 2019 (wet year). Plant species composition was monitored in situ using an unmanned aerial vehicle. Soil seed bank samples were collected, and the seed bank density and species composition were then examined and identified in the laboratory. Results showed that: (1) The variation in vegetation species richness between the two years was the highest (41%) in the transition zone ( < 0.05), while it was only 7% and 13% for the desert steppe and typical steppe, respectively. The presence of herbaceous species mainly caused the differences in variation among three grassland types. (2) Seed density was the highest in the transition zone (114 seeds/m and 68 seeds/m in the transient and persistent soil seed bank, respectively) ( < 0.05). Additionally, herbaceous species were the main components of the soil seed bank. (3) The similarity index was the highest in the transition zone ( < 0.05), with 38%/44% and 33%/44% for the transient/persistent soil seed bank in 2018 and 2019, respectively. Our study demonstrated that variation in vegetation species composition was very similar to the composition of the seeds accumulated in the soil seed bank. These results warrant further investigation for the mechanism of asymmetric response of productivity to precipitation.
生产力对降水的不对称响应最近被提出作为中国温带草原功能转变的一个早期预警信号。据推测，这种不对称性受到土壤种子库中新出现幼苗生长增加的影响。因此，在不对称性最大的地方，土壤种子库中的种子密度以及植被与土壤种子库的物种组成之间的相似性应该最大化。然而，这方面的知识仍然有限且未经证实。在本研究中，选择了荒漠草原、典型草原及其之间的过渡带（不对称性最高），在2018年（干旱年份）和2019年（湿润年份）研究相似性指数。使用无人机对植物物种组成进行原位监测。采集土壤种子库样本，然后在实验室中检查并鉴定种子库密度和物种组成。结果表明：（1）两年间植被物种丰富度的变化在过渡带最高（41%）（<0.05），而荒漠草原和典型草原分别仅为7%和13%。草本物种的存在主要导致了三种草原类型间变化的差异。（2）种子密度在过渡带最高（瞬时和持久土壤种子库中分别为114粒/平方米和68粒/平方米）（<0.05）。此外，草本物种是土壤种子库的主要组成部分。（3）相似性指数在过渡带最高（<0.05），2018年和2019年瞬时/持久土壤种子库的相似性指数分别为38%/44%和33%/44%。我们的研究表明，植被物种组成的变化与土壤种子库中积累的种子组成非常相似。这些结果为进一步研究生产力对降水不对称响应的机制提供了依据。
