Site Conditions Determine a Key Native Plant’s Contribution to Invasion Resistance in Grasslands

Many plant invasion studies in grasslands suggest that resident plants that share functional traits with invaders can reduce invasion by competing for limiting resources. However, since invasion studies often occur in highly controlled plots or microcosms, it is unclear how heterogeneous site conditions alter competitive interactions under realistic scenarios. To explore how landscape heterogeneity affects biotic resistance provided by competitive resident plants, we conducted a field‐based experiment across four sites in California grasslands. Plots contained naturally occurring populations of native Hemizonia congesta, but differed in other characteristics, including litter cover, annual grass cover, soil moisture, and species richness. We invaded plots with the functionally similar nonnative Centaurea solstitalis (yellow starthistle) and, at one site, supplemented one‐half of the established plots with water to test the effects of increasing a limiting resource. As in simplified plots and microcosms, increasing H. congesta abundance reduced starthistle biomass by competing for limited soil moisture, but only in plots with high starthistle germination. We conclude that higher abundances of native H. congesta can reduce starthistle invasion in heterogeneous grasslands, but competition is also affected by both abiotic (soil moisture) and biotic (starthistle germination number) conditions that vary across sites

Global change shifts trade‐offs among ecosystem functions in woodlands restored for multifunctionality

1. Ecological restoration increasingly aims at improving ecosystem multifunctionality and making landscapes resilient to future threats, especially in biodiversity hotspots such as Mediterranean-type ecosystems. Plants and their traits play a major role in the functioning of an ecosystem. Therefore, successful restoration towards long-term multifunctionality requires a fundamental mechanistic understanding of this link under changing climate. An integrated approach of empirical research and simulation modelling with a focus on plant traits can allow this understanding. 2. Based on empirical data from a large-scale restoration project in a Mediterranean-type ecosystem in Western Australia, we developed and validated the spatially explicit simulation model ModEST, which calculates coupled dynamics of nutrients, water and individual plants characterised by functional traits. We then simulated all possible combinations of eight plant species with different levels of diversity to assess the role of plant diversity and traits on multifunctionality, the provision of six ecosystem functions that can be linked to ecosystem services, as well as trade-offs and synergies among the functions under current and future climatic conditions. 3. Our results show that multifunctionality cannot fully be achieved because of trade-offs among functions that are attributable to sets of traits that affect functions differently. Our measure of multifunctionality was increased by higher levels of planted species richness under current, but not future climatic conditions. In contrast, single functions were differently impacted by increased plant diversity and thus the choice and weighting of these functions affected multifunctionality. In addition, we found that trade-offs and synergies among functions shifted with climate change due to different direct and indirect (mediated via community trait changes) effects of climate change on functions. 4. Synthesis and application: With our simulation model ModEST, we show that restoration towards multifunctionality might be challenging not only under current conditions, but also in the long-term. However, once ModEST is parameterized and validated for a specific restoration site, managers can assess which target goals can be achieved given the set of available plant species and site-specific conditions. It can also highlight which species combinations can best achieve long-term improved multifunctionality due to their trait diversity

Emerging approaches to successful ecological restoration: five imperatives to guide innovation

As the science of restoration ecology and the practice of habitat restoration adapt to new sets of goals in a changing climate, we turn our attention to novel techniques and emerging approaches in the field. This special issue brings together eight papers that answer the question, Given that we have defined our goals, can we find better ways to reach them? From them, we derive five directives for ecologists and practitioners seeking to innovate with new methods, analyses, or applications: (1) ground the approach in ecological theory; (2) take advantage of the latest technology and models; (3) reject dogma; (4) subject the analysis to critique; and (5) be aware of time, budget, and expertise constraints faced by stakeholders and practitioners. Our five imperatives are illustrated by examples of papers from the special issue.12 month embargo; published online: 17 December 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Plant cover and abundance data

Excel file including: treatment descriptions, plant cover values, and plant abundance data

Appendix A. Tables presenting repeated-measures ANOVA results.

Tables presenting repeated-measures ANOVA results

Susceptibility of Spring-flowering Garden Plants to Herbivory by Mule Deer

Many people look forward to spring flowers, only to discover that mule deer (Odocoileus hemionus) have eaten the sprouting plants and flower buds. One potential method to prevent this problem is to grow unpalatable flowering plants in gardens where deer herbivory is expected, but this requires knowledge about the relative palatability of plant species. We examined spring‐flowering plants in gardens located in Cache County, Utah, USA (2010 through 2017), and recorded the proportion of leaves and flower buds browsed by mule deer. Mule deer browsing was greatest on tulips (Tulipaspp.), grape hyacinths (Muscari spp.), and crocuses (Crocus spp.) and lowest on iris (Iris spp.) and daffodils (Narcissus spp.) We hypothesized that the first plants to sprout in the spring experienced greater levels of deer herbivory because of the lack of alternate plants that deer can browse during that time of year. To test this hypothesis, we started plants in greenhouses so that they sprouted at the same time. We then placed these plants in locations throughout Cache Valley where there were deer trails and deer feces. Among these plants, tulip, liatris (Liatris spp.), and grape hyacinth were browsed heavily, suggesting that deer found these plants palatable. In contrast, crocus were rarely eaten, suggesting that deer damage on this plant results more from its early sprouting rather than its palatability. Planting unpalatable plants may be a viable approach to reducing homeowners’ angst from finding that their spring‐flowering plants have been browsed. Wildlife biologists and Cooperative Extension agents should find our results useful when guiding homeowners in selecting which spring‐flowering plants to grow in areas where deer herbivory can be expected

The Ridgefield Multiple Ecosystem Services Experiment: can restoration of former agricultural land achieve multiple outcomes?

The ability of restoration approaches to provide valued ecosystem services needs to be assessed. The emerging carbon market provides an incentive to afforest agricultural landscapes and could potentially achieve multiple outcomes. However, planting monocultures for carbon sequestration may preclude effective delivery of other ecosystem services. Here, we describe the rationale behind the Ridgefield Multiple Ecosystem Services Experiment, a long-term investigation into trade-offs that might prevent the simultaneous provision of high levels of multiple services in the agricultural landscape of south-western Australia. We compare a monoculture treatment of a fast growing native species (Eucalyptus loxophleba) with mixtures of 2, 4 or 8 native plant species. We selected species based on different traits that we predict will relate to the provision of different levels of multiple ecosystem services. We ask: Can restoration of multiple ecosystem services be achieved along with carbon sequestration? Nested treatments of nitrogen deposition and weed removal test whether ecosystem service outcomes respond to environmental changes. We show that historical land-use at the site has the potential to affect service delivery via different soil characteristics and survival of planted species. Ridgefield tests the possibility of restoring and managing agricultural landscapes for multiple ecosystem services, providing a much needed experimental investigation of trade-offs among ecosystem functions

Effects of plant diversity on productivity strengthen over time due to trait-dependent shifts in species overyielding.

Plant diversity effects on community productivity often increase over time. Whether the strengthening of diversity effects is caused by temporal shifts in species-level overyielding (i.e., higher species-level productivity in diverse communities compared with monocultures) remains unclear. Here, using data from 65 grassland and forest biodiversity experiments, we show that the temporal strength of diversity effects at the community scale is underpinned by temporal changes in the species that yield. These temporal trends of species-level overyielding are shaped by plant ecological strategies, which can be quantitatively delimited by functional traits. In grasslands, the temporal strengthening of biodiversity effects on community productivity was associated with increasing biomass overyielding of resource-conservative species increasing over time, and with overyielding of species characterized by fast resource acquisition either decreasing or increasing. In forests, temporal trends in species overyielding differ when considering above- versus belowground resource acquisition strategies. Overyielding in stem growth decreased for species with high light capture capacity but increased for those with high soil resource acquisition capacity. Our results imply that a diversity of species with different, and potentially complementary, ecological strategies is beneficial for maintaining community productivity over time in both grassland and forest ecosystems