Black greasewood ( Hook., Torr) is a native halophytic, resprouting shrub found on saline rangeland soils in the western United States, including the western Great Plains grasslands. Stands can become dense, with limited native herbaceous biomass, and are prone to invasion by exotic species. We tested fall and spring prescribed fire compared with nonburned controls in a degraded rangeland site near Miles City, Montana, and a healthy rangeland site near Laramie, Wyoming to determine effects on greasewood shrub survival, density, and canopy structure. We additionally tested fuel load, time since fire, fire seasonality and prefire measurement effects on postfire greasewood canopy structure. In a second experiment at the Montana site only, nontreated controls, fall fire, 2,4-D, and 2,4-D preceded by fire were tested for effects on herbaceous biomass and greasewood survival, density, and canopy structure. Fire did not affect greasewood survival, but fire in either season reduced canopy volume by 52% across two growing seasons and models projected four or five growing seasons for structural recovery. Fine fuel load was negatively related to greasewood density and canopy structure. Herbicide reduced greasewood survival by 55%, and fire plus herbicide reduced survival by 30%. No treatment effects were detected for herbaceous biomass at the degraded site. Prescribed fire can reduce greasewood canopy structure for multiple years without killing the shrubs. Herbicide is more effective than fire if the objective is to reduce greasewood density, but multiple applications may be required. While 2,4-D herbicide was less effective when applied to resprouts after fire, results may improve with later postfire application. Although 2,4-D provided the greatest reduction of greasewood, skeletons of dead shrubs remained. Following herbicide treatment with fire could be a treatment combination to strategically reduce greasewood influence because fire would remove skeletons and further reduce canopy structure.

中文翻译：

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西部大平原火灾季节和除草剂对螟虫生存和结构的影响

黑油木 (Hook., Torr) 是一种本土盐生、再发芽灌木，发现于美国西部盐碱牧场土壤，包括西部大平原草原。林分可能变得茂密，本土草本生物量有限，并且容易受到外来物种的入侵。我们在蒙大拿州迈尔斯城附近的退化牧场和怀俄明州拉勒米附近的健康牧场测试了秋季和春季规定的火灾与未燃烧的对照，以确定对油木灌木生存、密度和树冠结构的影响。我们还测试了燃料负荷、火灾发生后的时间、火灾季节性和火灾前测量对火灾后油木树冠结构的影响。仅在蒙大拿州进行的第二次实验中，测试了未经处理的对照、秋季火灾、2,4-D 和火灾前的 2,4-D 对草本生物量和油木存活、密度和冠层结构的影响。火灾并未影响油木的生存，但任一季节的火灾都使两个生长季节的树冠体积减少了 52%，模型预测需要四个或五个生长季节才能进行结构恢复。精细燃料负荷与油木密度和树冠结构负相关。除草剂使油枝存活率降低 55%，火加除草剂则使存活率降低 30%。在退化地点没有检测到草本生物量的处理效果。规定的火灾可以在多年内减少油木树冠结构，而不会杀死灌木。如果目标是降低油木密度，除草剂比火更有效，但可能需要多次施用。虽然 2,4-D 除草剂在火灾后施用于新芽时效果较差，但火灾后稍后施用效果可能会有所改善。尽管 2,4-D 最大程度地减少了油木，但枯死的灌木的骨架仍然存在。除草剂处理后用火处理可能是一种策略性减少油木影响的处理组合，因为火会去除骨架并进一步减少树冠结构。