Living at the Edge: Increasing Stress for Plants 2–13 Years After the Retreat of a Tropical Glacier

Abstract

Rapid warming is a major threat for the alpine biodiversity but, at the same time, accelerated glacial retreat constitutes an opportunity for taxa and communities to escape range contraction or extinction. We explored the first steps of plant primary succession after accelerated glacial retreat under the assumption that the first few years are critical for the success of plant establishment. To this end, we examined plant succession along a very short post-glacial chronosequence in the tropical Andes of Ecuador (2–13 years after glacial retreat). We recorded the location of all plant individuals within an area of 4,200 m2 divided into plots of 1 m2. This sampling made it possible to measure the responses of the microenvironment, plant diversity and plants traits to time since the glacial retreat. It also made it possible to produce species-area curves and to estimate positive interactions between species. Decreases in soil temperature, soil moisture, and soil macronutrients revealed increasing abiotic stress for plants between two and 13 years after glacial retreat. This increasing stress seemingly explained the lack of positive correlation between plant diversity and time since the glacial retreat. It might explain the decreasing performance of plants at both the population (lower plant height) and the community levels (lower species richness and lower accumulation of species per area). Meanwhile, infrequent spatial associations among plants indicated a facilitation deficit and animal-dispersed plants were almost absent. Although the presence of 21 species on such a small sampled area seven years after glacial retreat could look like a colonization success in the first place, the increasing abiotic stress may partly erase this success, reducing species richness to 13 species after 13 years and increasing the frequency of patches without vegetation. This fine-grain distribution study sheds new light on nature's responses to the effects of climate change in cold biomes, suggesting that faster glacial retreat would not necessarily result in accelerated plant colonization. Results are exploratory and require site replications for generalization.

Microclimatic Warming Leads to a Decrease in Species and Growth Form Diversity: Insights From a Tropical Alpine Grassland

“…On the Antisana volcano, about 63 km southeast of our study site, Moret et Time is an essential variable in warming experiments. OTCs accelerate the rate to visualize change compared to prolonged comparative studies (Porro et al, 2019;Steinbauer et al, 2020;Anthelme et al, 2021), and our study found significant changes after 7 years of sampling. However, studies in non-tropical ecosystems found differences in a much shorter timeframe; for example, studies in tundra found changes in plant communities after two growing seasons (Walker et al, 2006).…”

Multi‐taxa colonisation along the foreland of a vanishing equatorial glacier

“…The rapid shrinkage of tropical glaciers induces an accelerated reduction of glacial influence in adjacent ecosystems, and may have considerable consequences on biodiversity. The decrease in meltwater supply reduces aquatic habitat availability for aquatic species (Milner et al 2017), and increases the risk of desiccation for terrestrial habitats (Breen and Levesque 2006, Anthelme et al 2021). Indeed, as precipitation gradient along elevations is often inverted in the tropics (Leuschner 2000, Anthelme and Dangles 2012), tropical alpine plants rely significantly on ground surface water sourcing from glacier melting.…”

Vegetation Assembly, Adaptive Strategies and Positive Interactions During Primary Succession in the Forefield of the Last Venezuelan Glacier

“…Glacier retreat rates have accelerated in the last five decades (Zemp et al, 2019), while there is increasing evidence that alpine species distributions are shifting upward (Lenoir and Svenning, 2015). This offers a unique opportunity to study climate change impacts in high mountain environments and opens up important questions regarding the development of novel ecosystems and the ability of high elevation specialists to become established and to maintain viable populations in newly exposed areas (Cannone et al, 2008;Zimmer et al, 2018;Cuesta et al, 2019;Anthelme et al, 2021).…”

“…In tropical alpine regions additional limiting factors include reduced plant protection from seasonal snow and particularly fast rates of highelevation warming and glacier retreat (Rabatel et al, 2013;Wang et al, 2016;Vuille et al, 2018). However, studies of the patterns and mechanisms of primary succession in glacier forefields are scarce in the alpine tropics (see Spence, 1989;Mizuno, 2005;Mizuno and Fujita, 2014;Suárez et al, 2015;Zimmer et al, 2018;Anthelme et al, 2021;Rosero et al, 2021), especially under the harsh conditions that occur in mountains where they are about to become extinct.…”

“…The tropical Andes concentrate more than 95% of all tropical glaciers (Veettil et al, 2017). In the few available chronosequence studies of glacier forefields in the region, analyses of spatial association patterns and plant dispersal strategies have suggested that vegetation development could be slowed down by strong limitations in zoochoric seed dispersal and the effectiveness of facilitation mediated by nurse-plants (Zimmer et al, 2018;Anthelme et al, 2021). These studies have focused on the first two to six decades of succession, but how these findings apply for longer successional periods and to areas where remaining glaciers are less extensive or about to go completely extinct, remains largely unexplored.…”