Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts

Abstract

Biological soil crusts (BSC) are the dominant functional vegetation unit in some of the harshest habitats in the world. We assessed BSC response to stress through changes in biotic composition, CO 2 gas exchange and carbon allocation in three lichen-dominated BSC from habitats with different stress levels, two more extreme sites in Antarctica and one moderate site in Germany. Maximal net photosynthesis (NP) was identical, whereas the water content to achieve maximal NP was substantially lower in the Antarctic sites, this apparently being achieved by changes in biomass allocation. Optimal NP temperatures reflected local climate. The Antarctic BSC allocated fixed carbon (tracked using 14 CO 2 ) mostly to the alcohol soluble pool (low-molecular weight sugars, sugar alcohols), which has an important role in desiccation and freezing resistance and antioxidant protection. In contrast, BSC at the moderate site showed greater carbon allocation into the polysaccharide pool, indicating a tendency towards growth. The results indicate that the BSC of the more stressed Antarctic sites emphasise survival rather than growth. Changes in BSC are adaptive and at multiple levels and we identify benefits and risks attached to changing life traits, as well as describing the ecophysiological mechanisms that underlie them.

A Case Study on Fog/Low Stratus Occurrence at Las Lomitas, Atacama Desert (Chile) as a Water Source for Biological Soil Crusts

“…However, it has to be stated that further research is required to quantify the contributions of the different water sources to the water budget of the BSCs in the Atacama. Because dominated by green algae or green algal lichens BSC are well adapted to hyper-arid conditions, even such a low input of water is sufficient for biological activity of BSCs also in other areas of the world (Lange and Redon, 1983;Lange et al, 1994;Colesie et al, 2014Colesie et al, , 2016. In the future, to understand the heterogeneous vegetation patterns along the coast and to quantify ecosystem services provided by the local vegetation and particularly the BSCs, comprehensive and spatially explicit information about fog water fluxes in the Atacama will be of great importance.…”

Physiology of Photosynthetic Organisms Within Biological Soil Crusts: Their Adaptation, Flexibility, and Plasticity

“…Optimal temperatures in polar regions are low. Mosses from the Ross Sea region had optima of 6.8 C for Ceratodon purpureus, 9.1 to 15.9 C for Bryum argenteum, and 12.0 C for Bryum pseudotriquetrum (Pannewitz et al 2003), while green algal lichen biocrusts ranged from 5 C at Darwin area (80 S latitude) to 17 C at Homburg (Germany, 50 N;Colesie et al 2014b). Biocrusts in arid areas range from 21 C (Fulgensia fulgens, Diploschistes diacapsis) to 29 to 32 C, Collema tenax, Cladonia convoluta, Squamarina lentigera, and Collema cristatum (Table 18.1).…”

Biological soil crusts of Arctic Svalbard and of Livingston Island, Antarctica

“…Few studies have so far focused on the BSCs of Antarctica, and of those that have, continental Antarctica has been the focus (Green and Broady 2001;Colesie et al 2013Colesie et al , 2014Büdel et al 2014). The climatic and latitudinal gradients from Continental Antarctica to the Antarctic Peninsula and Maritime Antarctic are huge, and therefore, inferring information regarding the composition of BSCs based on these previous studies is of limited value.…”