Zhang Rui, Hu Xiaowen, Baskin Jerry M, Baskin Carol C, Wang Yanrong
State Key Laboratory of Grassland Agro-Ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University Lanzhou, China.
Department of Biology, University of Kentucky, Lexington KY, USA.
Front Plant Sci. 2017 Jan 31;8:103. doi: 10.3389/fpls.2017.00103. eCollection 2017.
Litter accumulation resulting from land use change (enclosure) is one of the key variables influencing seedling recruitment and consequently the regeneration of plant populations and seed persistence in the soil seed bank. A better understanding of the effects of litter on seed germination and seedling emergence is crucial for developing a new set of indicators for grassland ecosystem health and for grassland management policy. We investigated the effects of seed position in litter and amount of litter covering the seed on seedling emergence and seed persistence of three common species on the Loess Plateau in northwestern China. Seed position beneath the litter layer provided a suitable environment for seedling emergence of the three species. A moderate amount of litter (160 g/m) was beneficial for seedling emergence of the small-seeded species and from seeds from beneath the litter layer. The large-seeded species was more tolerant of a high amount of litter (240 g/m) than the two small-seeded species. Seed persistence in the soil differed among the three species and also was affected by seed position in litter and amount of litter cover. The proportion of viable seeds of and on top of the litter layer increased with an increase in amount of litter. Seedling emergence and seed persistence varied significantly among species, amount of litter and seed position in litter. A moderate amount of litter and seeds positioned beneath the litter layer were better for seedling recruitment than for those on top of the litter layer. A high amount of litter was more favorable for persistence of seeds positioned on top of the litter than for those beneath the litter. Our study showed that maintaining litter amount between 80 and 160 g/m is optimal for dominated grassland on the Loess Plateau. We suggest that litter amount can serve as a guide for monitoring and managing grassland ecosystems, as it is an indicator of ecosystem processes that are essential for biodiversity conservation and restoration.
土地利用变化（围栏）导致的凋落物积累是影响幼苗更新以及植物种群再生和土壤种子库中种子持久性的关键变量之一。更好地了解凋落物对种子萌发和幼苗出土的影响对于制定一套新的草地生态系统健康指标和草地管理政策至关重要。我们研究了中国西北黄土高原三种常见物种的种子在凋落物中的位置以及覆盖种子的凋落物量对幼苗出土和种子持久性的影响。凋落物层下方的种子位置为这三种物种的幼苗出土提供了适宜的环境。适量的凋落物（160 g/m）有利于小种子物种从凋落物层下方的种子中出土。大种子物种比两个小种子物种更能耐受大量的凋落物（240 g/m）。三种物种在土壤中的种子持久性存在差异，并且还受到种子在凋落物中的位置和凋落物覆盖量的影响。凋落物层顶部的 和 的有活力种子比例随着凋落物量的增加而增加。幼苗出土和种子持久性在物种、凋落物量和种子在凋落物中的位置之间存在显著差异。适量的凋落物和位于凋落物层下方的种子比位于凋落物层顶部的种子更有利于幼苗更新。大量的凋落物更有利于位于凋落物层顶部的种子的持久性，而不是位于凋落物下方的种子。我们的研究表明，对于黄土高原以 为主的草地，将凋落物量维持在80至160 g/m之间是最佳的。我们建议凋落物量可以作为监测和管理草地生态系统的指南，因为它是对生物多样性保护和恢复至关重要的生态系统过程的指标。
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