Increased soil temperature and decreased precipitation during early life stages constrain grass seedling recruitment in cold desert restoration

Abstract

1. Seed-based restoration is one of the most difficult challenges for dryland restoration. Identifying environmental conditions that drive variation in seed and seedling mortality across similar restoration efforts could increase understanding of when and where restoration outcomes are likely to be favourable and identify new tools and strategies to improve outcomes.2. We asked how variation in a suite of environmental predictors influenced germination, emergence, seedling establishment and juvenile survival of four commonly sown perennial grass species across 33 seeding experiments distributed over an ~160,000-km 2 area of the Great Basin, a cold desert system in the western United States.3. Across experiments, we observed wide variation in the rates of four demographic transitions and wide variation in environmental conditions experienced by plants at each stage. For all species, higher precipitation during the first 30 days following seeding was associated with an increase in germination. Conversely, higher soil temperature over this same time period was associated with a significant decrease in germination and emergence, and soil temperature was associated with a substantial portion of the variation in germination and emergence probabilities observed across our seeding experiments. 4. Within the range of precipitation variation observed, we were unable to detect a significant relationship between seedling establishment the first growing season and cumulative precipitation the first year, precipitation during the first spring growing season or annual climatic water deficit (CWD) the first year. Higher CWD the second growing season reduced seedling survival over that time period. Synthesis and applications.Our results show higher soil temperature negatively impacts grass seedling establishment. Restoration efforts should be prioritized when seasonal or subseasonal temperature forecasts indicate likely periods of below average temperatures. These results also indicate that climate warming will make 2610 |

Small-scale water deficits after wildfires create long-lasting ecological impacts

“…Although we assessed sagebrush occupancy years later, our data suggest that initial sagebrush germination and emergence success is dictated by daily water availability and temperatures of soil in the first March postfire. Our results are similar to those of James et al (2019), who found increased soil temperatures reduce the establishment of seedlings in the Great Basin ( figure 3). Similarly, James et al (2019) and Young et al (2019) also did not find a correlation between a climatic drought variable, monthly climatic water deficit (CWD = potential evapotranspiration/actual evapotranspiration), and seedling establishment (figure 2).…”

RestoreNet: An emerging restoration network reveals controls on seeding success across dryland ecosystems

“…Together with studies showing monsoonal precipitation largely controls perennial plant recruitment in the southwestern US (e.g. Peters, Herrick, Monger, & Huang, 2010), this suggests outcomes of seeding in drylands will likely be affected by deviations in precipitation in the future (Pascale et al, 2017) and that restoration efforts should be prioritized when seasonal and sub‐seasonal forecasts predict average or above‐average precipitation (James et al, 2019). These deviations likely overwhelmed site‐level differences in mean annual precipitation in the wet year of our study, though mesic sites may prove more successful in dry to average years of precipitation.…”

“…However, since warmer, drier conditions are forecasted for the study region (Seager et al, 2007), species established from warmer‐adapted seed mixes may have longer‐term potential to persist under future climate conditions. These recruitment trends indicate the importance of climate in determining restoration outcomes and suggest aligning restoration plant niche information with forecasted environmental conditions could be an important tool for increasing seeding success in drylands (Butterfield et al, 2016; James et al, 2019). Projections of seasonal and sub‐seasonal conditions are increasingly incorporated into land management and adaptive restoration decision‐making (Bradford, Betancourt, Butterfield, Munson, & Wood, 2018), and can allow managers to adjust the timing and strategies of management actions such as restoration seed mix species selection to optimize the likelihood of success, given projected conditions (Sitters, Holmgren, Stoorvogel, & López, 2012).…”

“…First, we found strong effects of precipitation on seedling recruitment. Since low water availability is often a key limitation to restoration seeding success in drylands (Hardegree, Jones, Roundy, Shaw, & Monaco, 2011;James et al, 2011;Muñoz-Rojas et al, 2016), that seedling recruitment tracked precipitation over time (Figure 4 Peters, Herrick, Monger, & Huang, 2010), this suggests outcomes of seeding in drylands will likely be affected by deviations in precipitation in the future (Pascale et al, 2017) and that restoration efforts should be prioritized when seasonal and sub-seasonal forecasts predict average or above-average precipitation (James et al, 2019). These deviations likely overwhelmed site-level differences in mean annual precipitation in the wet year of our study, though mesic sites may prove more successful in dry to average years of precipitation.…”

Local landscape position impacts demographic rates in a widespread North American steppe bunchgrass

“…Despite generally higher seed production per plant on south‐facing slopes, the lower survival of small plants means that higher recruitment rates are likely needed for the south‐facing populations to remain stable. This may have major implications for population persistence in the face of climate change given that in semi‐arid ecosystems recruitment may be particularly sensitive to increasing temperature and aridity (e.g., James et al 2019). Although we expect temperature and moisture to be important direct drivers of demographic process, other differences between slopes, such as the degree of competition with invasive annuals, may have also contributed to the divergent demographic patterns we observed.…”