Demographic processes limiting seedling recruitment in arid grassland restoration

Abstract

Summary 1.Seeding is an important management tool in aridland restoration, but seeded species often fail to establish. Previous research has largely focused on the technical aspects of seeding with little effort directed at identifying demographic processes driving recruitment failures. 2. In tilled plots, in each of 3 years, we estimated life stage transition probabilities for three species commonly used in sage steppe restoration. We also took similar measurements on seed sown by managers following four major fires. 3. Point estimates and associated Bayesian confidence intervals demonstrated germination probabilities that were consistently high, averaging 0AE72. However, estimates suggest only 17 and 7% of the germinated seeds emerged in the tilled plots and fire sites, respectively. Following emergence, survival across the seedling, juvenile and adult transitions averaged 0AE72. This suggests the transition from a germinated seed to an emerged seedling was the major bottleneck in recruitment. Although most individuals died during emergence, this was not always the principal source of variation in recruitment across sites. 4. Synthesis and applications. Processes occurring after emergence, such as mortality during spring and summer drought, may contribute to site-to-site variation in recruitment but are unlikely to be the main causes of restoration failures. Instead, recruitment may largely be determined by processes occurring during emergence, such as freezing and thawing of the seedbed, development of physical soil crusts and pathogen attack on germinated seeds. Using tools such as seed coatings and soil amendments to manage processes inhibiting emergence and developing seed mixes with higher emergence probabilities are likely to greatly improve restoration outcomes in the sage steppe and similar aridland systems.

Quantifying restoration effectiveness using multi‐scale habitat models: implications for sage‐grouse in the Great Basin

“…Greater heat or water stress on seeded plants during key lifecycle phases (e.g., emergence, germination) likely impedes restoration efforts that could benefit sage-grouse habitat after wildfire. A study of seeded grass recruitment in the Great Basin found that seedling emergence (and likely environmental conditions) in March-May was the main barrier to recruitment, with springsummer drought adding to mortality, but at lower levels (James et al 2011). Sites within the Snake River Plain were an exception to the latitudinal trend we observed, but these locations were also typically low in elevation and total precipitation.…”

Advances in restoration ecology: rising to the challenges of the coming decades

“…However, in other areas and particularly for restoration at scale, the removal of barriers necessitates the efficient collection, handling and use of large volumes of viable seed. The development of the restoration seed bank concept, in conjunction with a systems approach, has highlighted the connected nature of processes ranging from seed procurement at scale, breaking of dormancy and emergence, to early establishment and subsequent maturation of the young plant at restoration sites (James et al 2011, Merritt and Dixon 2011, James et al 2013. Without considering all components of this chain of seed use, there remain impediments to increasing the likelihood of plant establishment in a cost-effective and predictable manner (James et al 2013).…”

The potential of novel native plant materials for the restoration of novel ecosystems

“…The four key life transitions that make up seedling recruitment are germination, seedling emergence, seedling establishment to an autotrophic state, and seedling survival through the end of the first growing season (Fenner and Thompson, 2005). Of these, emergence has been shown to be the most important for rangeland species ( James et al, 2011;Larson et al, 2014). Thus, native plant materials with an improved ability to emerge, particularly in unfavorable soil environments, may increase the probability of successful seedling recruitment.…”