Bush clearing of encroached rangelands is crucial for restoration of herbaceous cover and diversity. Regeneration after bush clearing depends largely on the soil seed bank (SSB) size and composition. To assess the potential of the SSB to facilitate post-clearing herbaceous restoration, we examined the SSB density, composition and diversity and similarity between SSB and aboveground vegetation (AGV). The study was conducted in semi-arid rangelands of Maseding and Kgomokgomo in North-West Province of South Africa. In each rangeland, all woody plants in three 1250 m2 plots were cut using saws and loppers, with the stumps treated with picloram. Paired observations were conducted in cleared and uncleared microsites. Soil samples were collected at three depths (0–10, 10–20 and 20–30 cm) in each microsite in April (pre-treatment), August, October and December 2016 and in April and August 2017. SSB was assessed using seedling emergence method, whereas pre- and post-clearing surveys of AGV were conducted in February 2016 and 2017, respectively. Cleared microsites had significantly (p < 0.01) higher seed bank densities (1872 and 693 seeds m-2 at Maseding and Kgomokgomo, respectively) relative to uncleared microsites in August 2017, with grasses accounting for higher densities than other plant functional groups in the upper 0–10 cm. Pioneer grasses (Aristida congesta subsp. barbicollis, Brachiaria eruciformis and Tragus berteronianus) and invasive forbs (Bidens pilosa and Schkuhria pinnata) dominated the SSB in cleared microsites at Maseding, whereas succulents (Portulaca spp.) and pioneer grasses (T. berteronianus and Urochloa mosambicensis) were abundant at Kgomokgomo in August 2017. SSB and AGV were dissimilar until December 2016; thereafter, similarity increased significantly (p < 0.05) in cleared microsites (Sørensen’s coefficient = 0.60 to 0.66 at Maseding and 0.43 to 0.52 at Kgomokgomo) compared to uncleared microsites. Species diversity was highest in August 2016 and April 2017 at Maseding, but it did not differ between two microsites (p > 0.05). At Kgomokgomo, SSB was more diverse in cleared than uncleared microsites in April and August 2017. High seed bank densities in the upper soil layer in cleared microsites would promote passive restoration, but regeneration is likely to be initiated by early successional species. However, close monitoring and eradication of invasive forbs and succulents is necessary following bush clearing. The tendency of SSB resembling AGV over time in cleared microsites signifies that seed production from AGV is important for passive restoration following bush clearing.

中文翻译：

---

土壤种子库是否是南非灌木丛清除的半干旱牧场被动恢复的可靠来源？

布什清理被侵蚀的牧场对于恢复草皮和多样性至关重要。清除灌木后的再生很大程度上取决于土壤种子库（SSB）的大小和组成。为了评估SSB促进清理后的草体恢复的潜力，我们检查了SSB的密度，组成，多样性和相似性与地上植被（AGV）之间的相似性。这项研究是在南非西北省的Maseding和Kgomokgomo的半干旱牧场进行的。在每个牧场中，使用锯和剪裁机切割三个1250平方米的地块中的所有木本植物，并用苦瓜子处理树桩。在已清除和未清除的微场所中进行了配对观察。在4月（预处理），8月，2016年10月和2016年12月以及2017年4月和2017年8月。使用幼苗出苗方法评估SSB，而AGV的清理前和清理后调查分别在2016年2月和2017年进行。相对于2017年8月未清理的微地点，已清理的微地点的种子库密度（分别在Maseding和Kgomokgomo的种子库密度（分别为1872和693种子m-2））显着更高（p <0.01），其中草类比上层的其他植物功能组更高0-10厘米。在Maseding的空地中，先锋草（Aristida congesta亚种的barbicollis，Brachiaria eruciformis和Tragus berteronianus）和侵入性的Forbs（Bidens pilosa和Schkuhria pinnata）主导着SSB，而肉质植物（Portulaca spp。）和先锋草则占据了主导地位。2017年8月，Kgomokgomo的berteronianus和Urochloa mosambicensis丰富。直到2016年12月，SSB和AGV都不同。此后，与未清除的微网站相比，在清除的微网站上的相似度显着提高（p <0.05）（在Maseding，Sørensen系数= 0.60至0.66；在Kgomokgomo，Sørensen系数= 0.43至0.52）。物种多样性在2016年8月和2017年4月在Maseding最高，但在两个微型站点之间没有差异（p> 0.05）。在Kgomokgomo，2017年4月和2017年8月开垦的SSB比未开垦的微型地点的多样性更高。在开垦的微型地点的上层土壤层中较高的种子库密度将促进被动恢复，但再生可能是由早期演替物种发起的。但是，清理灌木丛后，必须密切监测和根除侵入性的多肉植物和多肉植物。