Beyond the Tree-Line: The C3-C4 “Grass-Line” Can Track Global Change in the World’s Grassy Mountain Systems

von Humboldt’s tree-line concept has dominated mountain ecology for almost two hundred years, and is considered a key indicator for monitoring change in biome boundaries and biodiversity shifts under climate change. Even though the concept of life zones and elevation gradients are a globally observed phenomenon, they have not been thoroughly explored for many contexts. One such example is the tree-line ecotone, a widely used conceptual tool to track climate change in many regions, which has limited application in the widespread tree-sparse, grassy systems that comprise a third of the world’s mountain systems. Among grasses (Poaceae), temperature is linked to variation in photosynthetic performance and community dominance for C3 and C4 metabolic groups, due to its role in limiting photorespiration in the C3 photosynthesis process. Here, we investigate this community shift in grassland-dominated mountains to demonstrate the role of climate in driving this transition and discuss the potential applications of this tool to mountain ecosystem conservation worldwide. For identifying grass-dominated mountains worldwide, we measured the grass-cover using satellite data. We then compiled Poaceae distribution data for ten grass-dominated mountains spanning from 42°S to 41°N and determined the temperature intervals and elevation ranges at which each genus was found, testing for effects of temperature, precipitation, and latitudinal gradients on the dominance of C3-C4 grasses. Temperature was the main driver of C3 dominance, with the richness of C3 genera tending to surpass the taxonomic dominance of C4 plants along mountain temperature gradients where the annual mean temperature was colder than ca. 14.6°C. Similar patterns were observed in eight out of ten mountains, suggesting that this may constitute an isotherm-driven ecotone. Consequently, this C3-C4 transition offers a promising tool for monitoring climate change impacts in grassy mountains. C3-C4 grass community shifts in response to environmental change will likely have major implications for fire frequency and severity, rangeland productivity and livelihoods, food security, and water budgets in mountain systems. Given the severity of the implications of global change on these social-ecological systems, we propose that a “grass-line” monitoring protocol be developed for global application.

Features of biodiversity of the Uchursky landscape nature reserve (Ayano-Maiskoye district of Khabarovsk Territory)

It was revealed that the botanical and geographical feature of the vegetation cover of the Uchursky complex nature reserve is its position in the zone of convergence of the continental and monsoon climates, claimed by sharply contrasting phlorogenetic elements of the vegetation cover. The gradient of continentality - oceanicity in the vegetation cover is quite clearly traced between the eastern and western macroslopes of the mountain systems of the Uchur River basin. A complex history of the formation of the territory, the height difference from 1,000 to 2,000 meters, the variety of rocks created the conditions for the existence of floristic complexes of different ecology and origin. In this regard, on the territory of the nature reserve, an overlap of the marginal zones of plants ranges of oceanic and continental origin was found, which defines the richness of the region’s biodiversity, but makes both species and communities unstable. The uniqueness of the flora of the Geran Ridge was revealed, with the main core formed by species of non-Angarid origin, concentrated on the weathering crust of the basic rocks. The participation of alpinogenic, arctic and arctic-alpine species is noted. The pine-larch forests, which are unique in their species composition, are found on the outcrops of carbonate rocks on the right bank of the Uchur River, opposite the mouth of the Lyalmi River and in the Uchur-Ulkan interfluve. In this area, there are 79 species of endemic highland species of North Asia. The Red Book of Khabarovsk Territory includes 37 species of vascular plants, 4 species of lichens and 1 representative of the kingdom of mushrooms.

The unevenness of the north Iberian crustal root, a snapshot of an elusive stage in margin reactivation

Crustal roots are identified in collision chains worldwide. Frequently mirroring the summits of mountain systems, they elegantly encapsulate the concept of isostasy. The rugged topography of northern Iberia results from convergence with the European plate during the Alpine orogeny that formed the Pyrenean-Cantabrian mountain range. From east to west, the range comprises three distinct parts: the Pyrenees, the Basque Cantabrian region, and the Cantabrian Mountains. The identification of the Pyrenean root in the 1980s and the observation of a similar geometry beneath the Cantabrian range in the 1990s gave place to the current view of crustal thickening as a continuous feature, resulting from the northward subduction of Iberian crust. Recent developments in rift architecture have delivered a complex rifting template for the area prior to convergence, and contrasting views based on two-dimensional restorations have led to a debate over its evolution. A crucial geophysical constraint is Moho topography. Using two different data sets and techniques, we present the most accurate Moho surface to date, evidencing abrupt changes throughout the orogen. The complexity of hyperextended margins underlies the current Moho topography, and this is ultimately transferred to the nonuniform orogenic pattern found in northern Iberia.

Gradient analysis of soil-plant interactions from the alpine-nival ecotone to the snowline on slopes of the Central Great Caucasus (Kazbegi Region, Georgia)

Alpine ecosystems are especially sensitive to climatic changes which affect the relationships among glaciers, snow, vegetation and soils. Our aim was to examine how the variation in the abiotic environment affected soil properties and plant species distribution at regional and local scales. We sampled soil and vegetation along two transects set on the opposite-facing slopes (North versus South), from the alpine-nival ecotone to the snowline (Central Great Caucasus, Kazbegi, Georgia). We measured also soil temperature and controlled for the slope inclination. Multivariate ordination methods were used to link abiotic factors, soil properties and plant species distribution along the gradients. We found that ordination models were better resolved when soil properties were used as environmental variables instead of abiotic ones such as elevation, inclination and slope aspect. Soil pH and plant available potassium were the best predictors of plant species distribution in these habitats. We conclude that the models that account for the role of soils as a mediator between the abiotic environment and vegetation can more accurately describe plant species distribution at local and regional scales: a potentially important amendment with implications for the monitoring of the effects of climate change on vegetation at least in high mountain systems.

What can we learn from weather apps user complaints?

<p>Meteored’s goal is to provide a weather forecast to an heterogeneous audience around the world through its websites and mobile apps.  Although the meteorological information is available through several products such as radar, satellite or weather field maps, most of the views are focused on checking the forecast for a specific location. Our weather forecast is built on the HRES model from ECWMF, which is post processed, spatially interpolated to the interested coordinates,  and, finally, summarized in several weather symbols. If any user doesn’t agree with the symbol that represents the forecast, she/he can select which symbol better represents its weather perception.</p><p>Using this simplification to validate forecast entails several challenges: 1) Spatial representativeness; there aren’t weather stations at each location where users demand to validate, 2) timing; sometimes there is lack of concurrency between a weather phenomenon and the user weather check,  3) user perception; same symbol can represent different weather for different users, and 4)  population density; most of the user complaints are focused on the most populated regions but this doesn't mean the performance is worse there.</p><p>Last year more than 374000 symbol suggestions were recorded from worldwide users, mainly from Europe and Southamerica. The percentage of complaints were 39% cloudy, 24% rainy, 21% suny, 8% storm, 5% snow and 3 % foggy. 16 % of the complaints happen when a cloudy symbol is shown but the user suggests a rainy symbol. Temporal series show more feedback during summer and slightly lower during March (maybe due to the pandemic). Complaints about snow significantly increased due to the historical event in Spain during January. From weather feedback, the straightforward question is: why most frequent complaining is about cloudiness? We can find several answers: there is an important error in the weather modelling, there is an error in the symbol representation, it is a frequent meteorology event or it is one of the most relevant in users daily life.</p><p>In order to understand how reliable the user’s feedback is, our forecast is compared against almost 10000 SYNOP observations, assessing 2 m temperature, 10 m wind speed, precipitation, fog and also, symbols. Preliminary results show a pronounced dependence of the bias with the orography with larger errors over some islands and over main mountain systems. This spatial variability for bias is smoothed in Meteored forecast due to biquadratic interpolation. However, the Meteored forecast has a diurnal cycle bias error with higher temperatures during the daytime and lower temperature at nighttime due to the temporal interpolation approach.  Regarding to the weather symbols validation is difficult to extract conclusion since failures and hits are hetereogenously distributed. In addition,  most discrepancies are related to fog although it has a low percentage of complaints. </p>

RELATIONSHIP OF THE FORMATION OF OROGENS AND SEDIMENTARY BASINS OF ASIA IN THE MESOZOIC-CENOZOIC

The stages of the formation of mountain systems (orogens) and sedimentary basins of Asia are highlighted and an analogy is given. The stages are manifested in the Jurassic, Cretaceous, and Cenozoic as a result of collisions to the southern active margin of the Asian continent, respectively, of the Quingtang, North China, and Indian continental blocks, which led to the formation of large intracontinental orogenic belts that are the source of sedimentary basin demolition.