Think globally, measure locally: The MIREN standardized protocol for monitoring plant species distributions along elevation gradients

Abstract

Climate change and other global change drivers threaten plant diversity in mountains worldwide. A widely documented response to such environmental modifications is for plant species to change their elevational ranges. Range shifts are often idiosyncratic and difficult to generalize, partly due to variation in sampling methods. There is thus a need for a standardized monitoring strategy that can be applied across mountain regions to assess distribution changes and community turnover of native and non‐native plant species over space and time. Here, we present a conceptually intuitive and standardized protocol developed by the Mountain Invasion Research Network (MIREN) to systematically quantify global patterns of native and non‐native species distributions along elevation gradients and shifts arising from interactive effects of climate change and human disturbance. Usually repeated every five years, surveys consist of 20 sample sites located at equal elevation increments along three replicate roads per sampling region. At each site, three plots extend from the side of a mountain road into surrounding natural vegetation. The protocol has been successfully used in 18 regions worldwide from 2007 to present. Analyses of one point in time already generated some salient results, and revealed region‐specific elevational patterns of native plant species richness, but a globally consistent elevational decline in non‐native species richness. Non‐native plants were also more abundant directly adjacent to road edges, suggesting that disturbed roadsides serve as a vector for invasions into mountains. From the upcoming analyses of time series, even more exciting results can be expected, especially about range shifts. Implementing the protocol in more mountain regions globally would help to generate a more complete picture of how global change alters species distributions. This would inform conservation policy in mountain ecosystems, where some conservation policies remain poorly implemented.

Rapid upwards spread of non-native plants in mountains across continents

“…Non-native plant species spreading away from roads into the surrounding undisturbed vegetation have so far been limited at higher elevation 11,16 but this might change with increasing anthropogenic disturbance and changing climate. Roadside surveys like ours 36 might therefore be valuable for the early detection of possible emerging threats to native species and ecosystems. To support such measures, future work should continue to interrogate which species traits promote fastest rates of spread 15,16,29,41,42 , which species have the potential for greatest impacts and which features of high-elevation ecosystems (for example, native community structure, disturbance regimes, rates of climatic or land use changes) are associated with greater levels of invasion 16,43 .…”

“…Data were collected by MIREN using a standard protocol 36 . Sampling started in 2007/2008, is repeated every 5 years and is still ongoing.…”

“…In each region, three roads were selected (two in Central Chile, four in Hawaii and five in Victoria), all of them open to vehicle traffic for at least part of the year. The bottom of each road was defined as the point below which no major elevational change occurred, while the top was set by the highest point of the road 36 . Each road was evenly stratified by elevation into 20 sampling transects (60 per region, although this varied due to local logistics; Supplementary Table 4), totalling 651 sampling transects.…”

“…Here, we analysed data from a standardized survey of non-native plant distributions (developed by the Mountain Invasion Research Network (MIREN); www.mountaininvasions.org, ref. 36 ) to quantify and compare temporal patterns of invasions in mountains across the globe. We surveyed elevational gradients along mountain roads and adjacent seminatural vegetation in 11 mountain ranges from 5 continents, ranging from 68° N (Norway) to 37° S (Australia).…”

Historic disturbance events may overrule climatic factors as drivers of ruderal species distributions in the Scandinavian mountains

“…Here we combined 1) historical vegetation data (1903, 1913, and 1983) from along the Rallarvägen with 2) a new resurvey of the Rallarvagen in 2021 and 3) an additional survey performed in 2016 by the Mountain Invasion Research Network (MIREN;Haider et al 2022) along two hiking trails leading from the Rallarvagen into the mountains: the Björkliden and Låktatjåkka trail (Wedegärtner et al 2022).…”