Northeastern U.S. coastal grasslands are biologically, culturally, and historically significant but are being lost through the invasion of woody plants, including native species Gaylussacia baccata Wangenh. and Smilax rotundifolia L. Soil changes induced by these woody plants have important implications for herbaceous species diversity and restoration potential. We determined the effects of young and old G. baccata and S. rotundifolia patches on soil properties and plant diversity and identified relationships among soil properties and plant diversity. On a coastal grassland on Naushon Island (MA, USA) in 2015 and 2016, we used a time sequence of satellite imagery to identify young (< 5 years) and old (> 20 years) patches of G. baccata and S. rotundifolia. In these areas and in remaining grassland patches, we sampled soil properties, leaf ¹⁵N, and herbaceous plant diversity. All soils had low pH and higher extractable NH₄⁺ than NO₃⁻. G. baccata had relatively low extractable soil NO₃⁻, soil potential nitrification, and leaf δ¹⁵N, while S. rotundifolia had relatively high extractable soil NH₄⁺, low soil pH, and high leaf %N. Herbaceous plant diversity was low under S. rotundifolia and nearly absent under G. baccata, and most effects were more pronounced in older woody plant patches. Species diversity correlated with different soil variables between the two woody plants, indicating different mechanisms may drive diversity loss. Especially in older woody plant patches, restoration efforts should take into account soil changes, such as by making use of soil amendments. This could help offset soil effects after woody plant clearance and better enable grassland species recovery.

中文翻译：

---

木本植物侵占沿海草原：对土壤特性和植物多样性的影响

美国东北沿海草原在生物学，文化和历史上具有重要意义，但由于入侵木本植物而丧失，其中包括本土物种盖卢萨西亚baccata Wangenh。和土圆叶由这些木本植物诱导L.土壤变化对草本植物多样性与恢复潜力具有重要意义。我们确定了年轻和旧的G. baccata和S. rotundifolia斑块对土壤特性和植物多样性的影响，并确定了土壤特性和植物多样性之间的关系。在2015年和2016年，在Naushon岛（美国马萨诸塞州）的沿海草地上，我们使用卫星图像的时间序列来识别幼年（<5年）和年老（> 20年）的斑块。G. baccata和S. rotundifolia。在这些地区和剩余的草地上，我们对土壤性质，叶片¹⁵ N和草本植物多样性进行了采样。所有土壤具有低pH值和较高的可提取的NH ₄ ⁺比NO ₃ ^- 。G.山定子具有相对低的可提取土壤NO ₃ ^- ，土壤潜在硝化和叶δ ¹⁵ N，而S.圆叶具有相对高的可提取土壤NH ₄ ⁺，低土壤pH值，和高叶％N。圆叶链球菌下的草本植物多样性较低，而巴卡塔菌下的草本植物多样性几乎不存在，大多数影响在较老的木本植物斑块中更为明显。物种多样性与两种木本植物之间不同的土壤变量相关，表明不同的机制可能驱动多样性丧失。特别是在较早的木本植物斑块中，恢复工作应考虑土壤变化，例如通过使用土壤改良剂。这可能有助于抵消木本植物清除后对土壤的影响，并更好地恢复草地物种。