Phenology as a basis for management of exotic annual plants in desert invasions

Abstract

1. Exotic annual plants are an increasingly important ecological issue and new, creative approaches to management are required. In desert ecosystems of the southwestern USA, the forbs Brassica tournefortii, Erodium cicutarium and Schismus spp. dominate and alter native annual communities. Hand weeding B. tournefortii is currently the most common control method employed, but weeding is inadequate and expensive for managing large-scale invasions. New methods must be developed to conserve and restore desert ecosystems. 2. Exotic annuals in desert systems have rapid germination and phenology compared to natives, indicating that a window for selective control of exotic annuals may occur immediately after exotic seedling emergence. We tested the role of timing in control methods by comparing a cotyledon-stage glyphosate application to a bolting-stage application and to hand weeding B. tournefortii, plus an untreated check. Treatments were tested at two sites dominated by either exotic or native annuals and followed for 2 years; early application was repeated the second year. Cover and richness were evaluated during seedling and peak flowering stages underneath and between shrubs. 3. Early glyphosate application did not affect native cover, but did reduce exotic cover. Late herbicide negatively impacted both exotics and natives. Natives had little positive response, and then only through hand weeding under shrubs, but the same treatment caused an increase in the exotic E. cicutarium. 4. Synthesis and applications. The rapid phenology of exotic annuals may be exploited to control exotics while minimizing impacts on native plants in desert communities. This approach may be useful for other invasions in other ecosystems by species with rapid, early germination, or may act as a supplement to improve the efficacy of existing management regimes.

Biodiversity, phenology and temporal niche differences between native- and novel exotic-dominated grasslands

“…However, further work needs to be conducted on natives and exotics in various mixture combinations, and at key life stages (e.g. including seedling establishment, Yurkonis et al, 2005;Wardle et al, 2011) crossed with a variety of other predicted global climate changes (Marushia et al, 2010;Wolkovich and Cleland, 2011).…”

The effect of soil inoculants on seed germination of native and invasive species

“…Information regarding the germination biology of native species used in restoration allows practitioners to refine seeding methods in the field and increases the success of plant propagation in containers or in native seed farms (Broadhurst et al 2016;Limon and Peco 2016). Knowledge regarding the timing of germination for native species compared to invasive species may help clarify the outcome of competitive interactions (Forbis 2010;Wainwright and Cleland 2013) and may help land managers with the timing of herbicide application and weeding in restoration (Marushia et al 2010). For instance, land managers might use specialized herbicides during times when only certain functional groups have emerged or to allow crews to weed early-germinating non-native species prior to native species emergence, both of which would reduce costs associated with educating field crews on native and non-native species identification.…”

Status and management of non-native plant invasion in three of the largest national parks in the United States

“…increased native annuals but also increased the non-native forb Erodium cicutarium. Similarly, hand weeding Brassica tournefortii increased Erodium (Marushia et al 2010). In a post-fire environment dominated by non-native annuals, Steers and Allen (2010) had more encouraging results where herbicide not only reduced the grasses Bromus and Schismus, it also reduced Erodium.…”

“…The treatments exploited the accelerated early season phenology of non-native annuals (compared to native annuals) by applying herbicide early in the growing season. Refining knowledge of the earliest possible time for treating non-natives -which might vary among years -is warranted to manage single-and multi-species infestations while promoting natives (Marushia et al 2010.…”

“…Requiring species inventory data, prioritization systems are under development in many areas and rank species for treatment based on factors such as species traits, impacts, and management difficulty (Andreu andVilà 2010, Randall et al 2008). Identifying sites invaded by multiple species is important, because invaders differing in phenology can necessitate multiple treatments at different times (Marushia et al 2010).…”