Exploring the potential of topsoil pellets to improve native seedling establishment on degraded agricultural land

<i>Background and aims</i><i> </i>Agricultural activities can degrade soils and promote weeds, posing challenges to native species restoration. In agricultural restoration, removing contaminated topsoil is a method designed to reduce elevated soil nutrients caused by fertilisation. This strategy targets weed control by eliminating both aboveground weeds and their soil seed bank before direct seeding. However, it also diminishes native soil seed banks and beneficial soil microbes. We investigated the potential of fresh topsoil pellets containing seeds to improve seedling performance in a degraded grassy woodland where topsoil had been removed.<i>Methods</i><i> </i>We tested various pellet recipes, including one using commercial ingredients and three with different topsoil proportions (30%, 50%, and 70%). The study was conducted in a degraded grassy woodland in southeastern Australia, where topsoil was removed for restoration. We explored the effect of these pellet varieties on seedling emergence and growth of six native species common in this community, as well microbial activity in the soil surrounding the seedlings.<i>Results</i><i> </i>Pellets significantly improved the emergence of <i>Chrysocephalum apiculatum</i>, providing evidence of their effectiveness. However, pellets significantly reduced <i>Arthropodium milleflorum </i>and <i>Glycine tabacina </i>emergence. <i>Linum marginale </i>and<i> Rytidosperma caespitosum </i>emergence remained unaffected by pellets<i>.</i> One species, <i>Bothriochloa macra, </i>had insufficient emergence for analysis. The microbial activity of the soil surrounding <i>Rytidosperma caespitosum</i> seedlings was significantly improved by pellets, with no significant effects observed for other species.<i>Conclusion </i>Our results demonstrate that topsoil pellets improved the emergence of one native species, but reduced emergence for two others, indicating species-specific responses to pelleting.

### 背景与目的
农业活动可造成土壤退化并滋生杂草，给本地物种恢复工作带来严峻挑战。在农业生态恢复中，移除受污染表土 (topsoil) 是一种旨在降低施肥导致的土壤养分富集的手段。该策略通过在直接播种前清除地上杂草及其土壤种子库 (soil seed bank) 来实现杂草防控，但同时也会损耗本地土壤种子库与有益土壤微生物。本研究针对一处已移除表土的退化草本林地，探究搭载种子的新鲜表土丸粒 (topsoil pellets) 对幼苗生长表现的改善潜力。

### 方法
本研究测试了多种丸粒配方，其中1种采用商用原料，另外3种分别设置了30%、50%、70%的不同表土占比。试验于澳大利亚东南部一处为恢复目的移除了表土的退化草本林地中开展。本研究探究了上述不同丸粒配方对该群落常见的6个本地物种的幼苗出苗率与生长情况的影响，同时检测了幼苗周边土壤的微生物活性。

### 结果
表土丸粒可显著提升<i>Chrysocephalum apiculatum</i>的出苗率，证实了该手段的有效性。但该丸粒会显著降低<i>Arthropodium milleflorum</i>与<i>Glycine tabacina</i>的出苗率。<i>Linum marginale</i>与<i>Rytidosperma caespitosum</i>的出苗率则不受丸粒处理的影响。另有1个物种<i>Bothriochloa macra</i>的出苗数量不足，无法开展统计分析。对于<i>Rytidosperma caespitosum</i>幼苗周边的土壤，丸粒处理可显著提升其微生物活性，而其余物种的土壤微生物活性未受显著影响。

### 结论
本研究结果表明，表土丸粒可提升1个本地物种的出苗率，但会降低另外2个物种的出苗率，这说明不同物种对丸粒处理的响应存在特异性。