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PREMISEDesiccation tolerance (DT) is a widespread phenomenon among land plants, and variable ecological strategies for DT are likely to exist. UsingSyntrichia caninervis, a dryland moss and model system used in DT studies, we hypothesized that DT is lowest in juvenile (protonemal) tissues, highest in asexual reproductive propagules (gemmae), and intermediate in adults (shoots). We tested the long‐standing hypothesis of an inherent constitutive strategy of DT in this species. METHODSPlants were rapidly dried to levels of equilibrating relative humidity (RHeq) ranging from 0 to 93%. Postrehydration recovery was assessed using chlorophyll fluorescence, regeneration rates, and visual tissue damage. For each life phase, we estimated the minimum rate of drying (RoD_min) atRHeq= 42% that did not elicit damage 24 h postrehydration. RESULTSDT strategy varied with life phase, with adult shoots having the lowestRoD_min(10‒25 min), followed by gemmae (3‒10 h) and protonema (14‒20 h). Adult shoots exhibited no detectable damage 24 h postrehydration following a rapid‐dry only at the highestRHeqused (93%), but when dried to lower RHs the response declined to <50% of control fluorescence values. Notably, immediately following rehydration (0 h postrehydration), shoots were damaged below control levels of fluorescence regardless of theRHeq, thus implicating damage. CONCLUSIONSLife phases of the mossS. caninervishad a range of strategies from near constitutive (adult shoots) to demonstrably inducible (protonema). A new response variable for assessing degree of DT is introduced as the minimum rate of drying from which full recovery occurs. 

Summary With global climate change, water scarcity threatens whole agro/ecosystems. The desert mossSyntrichia caninervis, an extremophile, offers novel insights into surviving desiccation and heat. The sequencedS. caninervisgenome consists of 13 chromosomes containing 16 545 protein‐coding genes and 2666 unplaced scaffolds. Syntenic relationships within theS.caninervisandPhyscomitrellapatensgenomes indicate theS. caninervisgenome has undergone a single whole genome duplication event (compared to two forP. patens) and evidence suggests chromosomal or segmental losses in the evolutionary history ofS. caninervis. The genome contains a large sex chromosome composed primarily of repetitive sequences with a large number ofCopiaandGypsyelements. Orthogroup analyses revealed an expansion ofELIPgenes encoding proteins important in photoprotection. The transcriptomic response to desiccation identified four structural clusters of novel genes. The genomic resources established for this extremophile offer new perspectives for understanding the evolution of desiccation tolerance in plants. 

Abstract Plant functional trait analyses have focused almost exclusively on vascular plants, but bryophytes comprise ancient and diverse plant lineages that have widespread global distributions and important ecological functions in terrestrial ecosystems. We examined a diverse clade of dryland mosses,Syntrichia, and studied carbon balance during a precipitation event (C‐balance), a functional trait related to physiological functioning, desiccation tolerance, survival, and ecosystem carbon and nitrogen cycling. We examined variability in C‐balance among 14 genotypes ofSyntrichiaand measured an additional 10 physiological and 13 morphological traits at the cell, leaf, shoot, and clump level. C‐balance varied 20‐fold among genotypes, and highest C‐balances were associated with long, narrow leaves with awns, and small cells with thick cell walls, traits that may influence water uptake and retention during a precipitation event. Ordination analyses revealed that the axis most strongly correlated with C‐balance included the maximum chlorophyll fluorescence,F_m, indicating the importance of photosystem II health for C exchange. C‐balance represents a key functional trait in bryophytes, but its measurement is time intensive and not feasible to measure on large scales. We propose two models (using physiological and morphological traits) to predict C‐balance, whereby identifying simpler to measure traits for trait databases. 

Abstract The capture and use of water are critically important in drylands, which collectively constitute Earth's largest biome. Drylands will likely experience lower and more unreliable rainfall as climatic conditions change over the next century. Dryland soils support a rich community of microphytic organisms (biocrusts), which are critically important because they regulate the delivery and retention of water. Yet despite their hydrological significance, a global synthesis of their effects on hydrology is lacking. We synthesized 2,997 observations from 109 publications to explore how biocrusts affected five hydrological processes (times to ponding and runoff, early [sorptivity] and final [infiltration] stages of water flow into soil, and the rate or volume of runoff) and two hydrological outcomes (moisture storage, sediment production). We found that increasing biocrust cover reduced the time for water to pond on the surface (−40%) and commence runoff (−33%), and reduced infiltration (−34%) and sediment production (−68%). Greater biocrust cover had no significant effect on sorptivity or runoff rate/amount, but increased moisture storage (+14%). Infiltration declined most (−56%) at fine scales, and moisture storage was greatest (+36%) at large scales. Effects of biocrust type (cyanobacteria, lichen, moss, mixed), soil texture (sand, loam, clay), and climatic zone (arid, semiarid, dry subhumid) were nuanced. Our synthesis provides novel insights into the magnitude, processes, and contexts of biocrust effects in drylands. This information is critical to improve our capacity to manage dwindling dryland water supplies as Earth becomes hotter and drier. 

Biological soil crusts (biocrusts) are a complex community of algae, cyanobacteria, lichens, bryophytes, and assorted bacteria, fungi, archaea, and bacteriophages that colonize the soil surface. Biocrusts are particularly common in drylands and are found in arid and semiarid ecosystems worldwide. While diminutive in size, biocrusts often cover large terrestrial areas, provide numerous ecosystem benefits, enhance biodiversity, and are found in multiple configurations and assemblages across different climate and disturbance regimes. Biocrusts have been a focus of many ecologists, especially those working in semiarid and arid lands, as biocrusts are foundational community members, play fundamental roles in ecosystem processes, and offer rare opportunities to study biological interactions at small and large spatial scales. Due to these same characteristics, biocrusts have the potential to serve as an excellent teaching tool. The purpose of this paper is to demonstrate the utility of biocrust communities as a model system in science education. Functioning as portable, dynamic mini ecosystems, biocrusts can be used to teach about organisms, biodiversity, biotic interactions, abiotic controls, ecosystem processes, and even global change, and can be easy to use in nearly every classroom setup. For example, education principles, such as evolution and adaptation to stress, or structure and function (patterns and processes) can be applied by bringing biocrusts into the classroom as a teaching tool. In addition, discussing the utility of biocrusts in the classroom – including theory, hypothesis testing, experimentation, and hands-on learning – this document also provides tips and resources for developing education tools and activities geared toward impactful learning.