Launching the Counterattack: Interdisciplinary Deployment of Native-Plant Functional Traits for Repair of Rangelands Dominated by Invasive Annual Grasses

Ecosystem restoration: recent advances in theory and practice

Restoration of damaged ecosystems is receiving increasing attention worldwide as awareness increases that humanity must sustain ecosystem structure, functioning, and diversity for its own wellbeing. Restoration will become increasingly important because our planet will sustain an increasingly heavy human footprint as human populations continue to increase. Restoration efforts can improve desirable ecological functioning, even when restoration to a historic standard is not feasible with current practice. Debate as to whether restoration is feasible is coupled to long-standing disputes regarding the definition of restoration, whether more-damaged lands are worthy of restoration efforts given limited financial resources, and ongoing conflicts as to whether the novel ecosystem concept is a help or a hindrance to restoration efforts. A willingness to consider restoration options that have promise, yet would have previously been regarded as ‘taboo’ based on the precautionary principle, is increasing. Functional restoration is becoming more prominent in the scientific literature, as evidenced by an increased emphasis on functional traits, as opposed to a simple inventory of vascular plant species. Biodiversity continues to be important, but an increasingly expansive array of provenance options that are less stringent than the traditional ‘local is best’ is now being considered. Increased appreciation for soil health, plant–soil feedbacks, biological crusts, and water quality is evident. In the United States, restoration projects are becoming increasingly motivated by or tied to remediation of major environmental problems or recovery of fauna that are either charismatic, for example, the monarch butterfly, or deliver key ecosystem services, for example, hymenopteran pollinators.

When local isn't best

This paper attempts to explain circumstances under which local may be or may not be best. Natural selection may lead to local adaptation (LA), or it may be constrained by gene flow, founder effects, small population size, genetic drift, and archetype. ‘Specialist’ species display greater LA than ‘generalist’ species. Local genotypes are to a certain extent transient, being a consequence of past historical genetic patterns. Two recent meta-analyses found that while local performance exceeded the performance of a randomly chosen nonlocal population in 71% of comparisons, general adaptation across environments was as frequent as LA. Genotypes for restoration are most likely to be effective if they are adapted to current site conditions. As environmental change accelerates, both globally and locally, exceptions to ‘local is best’ may increase. For these reasons, ‘local is best’ may be better thought of as a testable hypothesis rather than as a general assumption. While either local or nonlocal plant material may be most effective for restoration practice depending on individual circumstances, local material will continue to be the first choice for restoration practitioners whenever this option is feasible and effective.

Native perennial grasses show evolutionary response to Bromus tectorum (cheatgrass) invasion

Invasive species can change selective pressures on native plants by altering biotic and abiotic conditions in invaded habitats. Although invasions can lead to native species extirpation, they may also induce rapid evolutionary changes in remnant native plants. We investigated whether adult plants of five native perennial grasses exhibited trait shifts consistent with evolution in response to invasion by the introduced annual grass Bromus tectorum L. (cheatgrass), and asked how much variation there was among species and populations in the ability to grow successfully with the invader. Three hundred and twenty adult plants were collected from invaded and uninvaded communities from four locations near Reno, Nevada, USA. Each plant was divided in two and transplanted into the greenhouse. One clone was grown with B. tectorum while the other was grown alone, and we measured tolerance (ability to maintain size) and the ability to reduce size of B. tectorum for each plant. Plants from invaded populations consistently had earlier phenology than those from uninvaded populations, and in two out of four sites, invaded populations were more tolerant of B. tectorum competition than uninvaded populations. Poa secunda and one population of E. multisetus had the strongest suppressive effect on B. tectorum, and these two species were the only ones that flowered in competition with B. tectorum. Our study indicates that response to B. tectorum is a function of both location and species identity, with some, but not all, populations of native grasses showing trait shifts consistent with evolution in response to B. tectorum invasion within the Great Basin.