Combining active restoration and targeted grazing to establish native plants and reduce fuel loads in invaded ecosystems
Combining active restoration and targeted grazing to establish native plants and reduce fuel loads in invaded ecosystems
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结合主动恢复和有针对性的放牧，建立本土植物并减少入侵生态系统的燃料负荷
DOI：
10.1002/ece3.4642
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发表时间：
2018
影响因子：
2.6
通讯作者：
E. Leger
中科院分区：
文献类型：
--
作者：
Lauren M. Porensky;B. Perryman;M. Williamson;M. Madsen;E. Leger
许多旱地已经从多年生为主的生态系统转变为入侵的、一年生为主的火灾易发系统。需要创新的方法来破坏火灾入侵反馈。有针对性的放牧可以减少入侵植物的数量和相关的可燃燃料，并且燃料中断可以限制火灾的蔓延。恢复的原生植物带（原生绿带）可以作为燃料休息，同时也提供饲料和栖息地的好处。然而，在入侵的旱地上建立原生绿带的方法还不发达。此外，如果燃料减少和绿化带的建立是同时进行的，那么了解有针对性的放牧如何与植物的建立相互作用是至关重要的。我们确定了有针对性的放牧处理如何与种子率、空间种植安排（混合与单一种植条带）、种子包衣技术和物种特性（五种本地草）相互作用，以影响实验绿条带的立木生物量和种子植物密度。我们监测了两个生长季节，以记录幼苗建立阶段的影响。在不同的种植处理中，未放牧的围场第二年种子植物密度和林分生物量最高。在第二个生长季节的秋季放牧的围场比五个月后的春季放牧的围场幼苗少。高种子率使放牧对植物生长的负面影响最小化。在种子种中，羊草（Elymus trachycaulus）和羊草（Poa secunda）第二年密度最高，但其实现途径不同。羊草（Elymus trachycaulus）一年生苗最多，但对放牧的反应有所下降，而次生羊草（P. second unda）一年生苗一般，但在不同放牧处理下成活率较高。我们明确了在入侵的山艾草草原上减少燃料负荷和建立本地植物之间的权衡；其他被入侵的旱地可能也存在类似的权衡。在我们的系统中，通过提高种子率、使用耐放牧的物种和延迟放牧来最小化权衡。在被入侵的生态系统中，将有针对性的放牧与高投入的恢复相结合可能创造机会，限制野火风险，同时也将植被转向更理想的物种。
Abstract Many drylands have been converted from perennial‐dominated ecosystems to invaded, annual‐dominated, fire‐prone systems. Innovative approaches are needed to disrupt fire‐invasion feedbacks. Targeted grazing can reduce invasive plant abundance and associated flammable fuels, and fuelbreaks can limit fire spread. Restored strips of native plants (native greenstrips) can function as fuelbreaks while also providing forage and habitat benefits. However, methods for establishing native greenstrips in invaded drylands are poorly developed. Moreover, if fuels reduction and greenstrip establishment are to proceed simultaneously, it is critical to understand how targeted grazing interacts with plant establishment. We determined how targeted grazing treatments interacted with seed rate, spatial planting arrangement (mixtures vs. monoculture strips), seed coating technology, and species identity (five native grasses) to affect standing biomass and seeded plant density in experimental greenstrips. We monitored for two growing seasons to document effects during the seedling establishment phase. Across planting treatments, ungrazed paddocks had the highest second‐year seeded plant densities and the highest standing biomass. Paddocks grazed in fall of the second growing season had fewer seedlings than paddocks grazed in spring, five months later. High seed rates minimized negative effects of grazing on plant establishment. Among seeded species, Elymus trachycaulus and Poa secunda had the highest second‐year densities, but achieved this via different pathways. Elymus trachycaulus produced the most first‐year seedlings, but declined in response to grazing, whereas P. secunda had moderate first‐year establishment but high survival across grazing treatments. We identified clear tradeoffs between reducing fuel loads and establishing native plants in invaded sagebrush steppe; similar tradeoffs may exist in other invaded drylands. In our system, tradeoffs were minimized by boosting seed rates, using grazing‐tolerant species, and delaying grazing. In invaded ecosystems, combining targeted grazing with high‐input restoration may create opportunities to limit wildfire risk while also shifting vegetation toward more desirable species.