Recruitment Traits Could Influence Species’ Geographical Range: A Case Study in the Genus Saxifraga L.

The reasons why species occur widespread and others have a narrow geographical range may be explained by habitat specialization or ecological niche breadth. For species in the genus Saxifraga, habitat specialization alone cannot explain the distributional differences observed, and neither do dispersal strategies. Thus, geographical range differences may be explained by differences in recruitment responses and levels of intraspecific variability.

We studied recruitment traits (i.e., germination, emergence, survival) in 25 Saxifraga from 79 populations from across the European Alps, using laboratory and common garden experiments. We found differences between the groups (widespread, narrow-ranged) in germination to temperature, with widespread species having a higher tolerance to warm temperatures. Furthermore, we found that cold conditions triggered germination better than warmer conditions, for both groups. This is an exception to the globally stated pattern of warm cues for germination previously found for alpine species. However, in five of six studied traits, widespread and narrow-ranged Saxifraga species behaved similarly. Considering intraspecific variability, widespread species had a broader variation in their emergence timing than narrow-ranged species. This was also reflected by a broader variation in mean annual temperatures of seed collection sites, pointing towards a strong link between climatic conditions and recruitment responses.

This study highlights that the overall contribution of seedling recruitment to distribution ranges is mainly driven by the earliest life-stage, that timing is key for adaptation and, that species of the genus Saxifraga have adapted their whole life cycle to cold conditions, which means a severe challenge for the genus in a warmer world.  

 

Science Flash Margreiter2

(A) Plant life cycle of Saxifraga bryoides, a perennial hemikryptophyte flowering multiple times. The early life stages cover transitions from seed to seedling and seedling to juvenile plant, which are key processes in population dynamics that can influence species abundances. (B) Saxifraga species from top left clockwise: S. bryoides, S. exarata, S. aizoides, S. rudolphiana.

 

Competition-free gaps are essential for the germination and recruitment of alpine species along an elevation gradient in the European Alps

Although the physiology and ecology of Alpine plants in the adult stage is well studied, surprisingly little is known about seedling recruitment, leading to a limited understanding of population dynamics in alpine systems. Here, we present the results of a seed-sowing experiment performed along an elevation gradient (2000-2900 m a.s.l.) in the European eastern Alps. We monitored the germination of seeds and seedling recruitment for two years, investigating effects of sites and home sites (seed origin), effects of gaps, and plant-plant interactions (competition, facilitation) in experimentally manipulated rings.

We found germination decreasing with increasing elevation, independent of the seed home site, but in line with the globally stated pattern for germination by warm cues for alpine species. Recruitment was, however, site-specific and high seedling mortalities were observed, especially at lower elevations. Sowing in above- and belowground competition-free gaps favoured recruitment, pointing out the important role of belowground competition and soil components for recruitment. In gaps with one neighbouring species, neutral plant-plant interactions occurred. However, considering the relative vegetation cover of each experimental site, high vegetation cover resulted in positive effects on recruitment at 2600-2900 m a.s.l., confirming positive interactions in this case.

This study provides important but rare data on alpine seedling recruitment studied in situ from seeds and discusses several key factors of reproduction in alpine systems.

 

Science Flash Margreiter1

(a) Experimental design. Seed collections at 2300 m and 2600 m a.s.l. represent the locations with optimal seed production of the target species, indicated in the theoretical diagram as their home sites. (b) The experiment was performed along an abiotic stress-gradient at four experiment sites. Germination and recruitment were monitored for two years. Seed sowing was done in experimentally created gaps. (c) The effects of experimental gaps on germination and recruitment were studied by including three gap types: ’gap+roots’: aboveground competition-free gap with belowground competition; ‘neighbor+roots’: only-one-central-plant-left aboveground gap; and ‘no-comp’: artificial gap (i.e., no competition and no interaction;). (d) Gap-type manipulations provided zero aboveground cover in ‘gaps+roots’ and ‘no-comp’, and 10.5% top cover in ‘neighbor+roots’ (d, upper panel). Gap-type manipulations were similar at each experiment site (d, lower panel).

 

Margreiter, V., Porro, F., Mondoni, A., and Erschbamer, B. (2022). Recruitment Traits Could Influence Species’ Geographical Range: A Case Study in the Genus Saxifraga (L.). Front. Plant Sci. 13:827330. https://doi.org/10.3389/fpls.2022.827330

 


 

Widespread greening suggests increased dry-season plant water availability in the Rio Santa valley, Peruvian Andes

Changing water availability is making climate change tangible and is often a great concern for affected societies. In rural settings of the global south where the livelihood of many people relies on subsistence-based agriculture, changes in seasonality of climate variables or increasing weather extremes can have far-reaching consequences including rural exodus and increase of poverty and vulnerability. The slopes of the Rio Santa basin, located in the Peruvian Andes, are home to many farmers whose livelihoods have already been increasingly challenged by economical and societal developments in the past decades. The local agriculture is mostly rain-fed and plant-growth is determined by the appearance of seasonal rainfalls which are occurring during an annual cycle of a distinct wet and dry season.

Recently, farmers reported that they are facing changed timing and intensities of seasonal rainfalls with detrimental effects on crop yields. These reports were not supported by analysis of historical meteorological records in previous research, but there remains considerable uncertainty regarding the quality of the data. To overcome this, we exploited 20 years of satellite-derived vegetation greenness data as a proxy for water availability. In comparison to the analysed rainfall products, these data are available in unpreceded spatio-temporal resolution and allowed us to gain new insights into recent trends and changes in the variability of plant available water.

We confirmed that no clear conclusion can be drawn from several rainfall datasets but we find a significant increase of plant greenness in the Rio Santa basin, particularly pronounced during the dry season. This indicates an overall increase of plant available water over the past two decades. In agreement to these greening patterns, we found a delayed end of the growing season which either implies a later retreat of the seasonal rainfalls or larger amounts of rainfall during the wet season feeding storages of the hydrological system. The start of the growing season, however, fluctuates highly from year to year with variation of up to two months, governing the overall growing season length. This variability is likely linked to the perception of local farmers, as it hampers the planning of sowing dates and overall complicates successful farming.

 

Science Flash Hänchen

The ridgelines display the variability in timing of the growing season for each of the 20 growing seasons between 2000 and 2020. A smaller width of the distribution can be interpreted as plant growth in the Rio Santa basin being temporally more uniformly, while a larger width shows larger deviations of the timing. Additionally, the plot displays the large interannual variability of the start of the growing season and the increasingly delayed end of the growing season.

 

Hänchen, L., Klein, C., Maussion, F., Gurgiser, W., Calanca, P., & Wohlfahrt, G. (2022) Widespread greening suggests increased dry-season plant water availability in the Rio Santa valley, Peruvian Andes. Earth System Dynamics 13(1): 595-611. DOI: https://doi.org/10.5194/esd-13-595-2022

 




Previous Science Flash contributions: 

DP ABGC Student Paper Award 2021

DP ABGC Student Paper Award 2020

The multifunctionality of mountain landscapes

Pros and cons of using a standard protocol to test germination of Alpine species

Agent-Based Modelling of a Coupled Water Demand and Supply System

Wolbachia megadiversity: 99% of these microorganismic manipulators unknown

DP ABGC Student Paper Awards 2019

Benthic Diatom Communities in an Alpine River Impacted by Waste Water Treatment Effluents as Revealed Using DNA Metabarcoding

The microbiome of plants: R. glacialis and its rhizobiome along a high-alpine altitudinal gradient

Lots of ‘junk’ in the genome of a small aquatic invertebrate

A dataset for future monitoring of climate change effects in Alpine streams 

Forest fires: How surviving trees can suffer from heat injuries

 


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