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Studies on soil organic carbon stocks (SOCS) are increasingly relevant to developing efficient mitigation and adaptation strategies for climate change. Reliable information on soil organic carbon (SOC) content, bulk density (BD), and coarse fragments (CF) are required for precise SOCS calculation. The data quality of SOCS‐related variables is important to represent SOCS realistically across different levels of disturbance in the terrestrial ecosystems of Guatemala. The main objective is to develop Guatemala's first national SOC database to support studies of SOCS magnitudes and spatial trends. We identified and collected national sources of variables related to SOCS (SOC, BD, CF) across the country, mainly distributed in the central zone dominated by disturbed ecosystems and agricultural territories. We integrated 910 observations (soil samples and soil profiles) of SOC content (range 1.45–162 g·kg−1), 704 of BD (range 0.42–1.69 g·cm−3), and 8 of CFs (0%–21% weight). This new database represents the edaphic, climatic, and land use variability of Guatemalan territory. The database contains soil observations collected from 1965 to 2010. The year 2010 has the majority of soil observations (41%). SOCS‐related variables are standardized at 0–30 centimetres of depth using mass conservative splines, which are used to represent SOCS and soil depth relationships. We provide new information on SOCS across various ecological and environmental conditions to enable SOC monitoring systems to report reliable and accurate estimates. The new database is appealing for scientific and commercial purposes, such as representing Guatemalan soils in Earth system models or using soil information in the ecosystem services market (e.g., carbon markets). The new database is accessible to all users through the platform of the Environmental Data Initiative https://doi.org/10.6073/pasta/8dd15238c604c3ac75daf985548bd05c. [ABSTRACT FROM AUTHOR]

The genetic diversity of Agave plants is threatened by clonal commercial reproduction and climatic change. Sexual reproduction is uncommon and research on seed germination is scarce. The present study evaluated the seed germination of Agave lechuguilla, Agave striata, Agave americana var. marginata, Agave asperrima, Agave cupreata, Agave duranguesis, Agave angustifolia ssp. tequilana and Agave salmiana at constant temperatures (10, 15, 20, 25, 30, 35 and 40°C). Initial imbibition (after the first 12 h) was significantly variable among species, positively correlated with seed weight ( r = 0.6560, P < 0.001) and increased with temperature (from 35% at 10°C to 66% at 40°C). Temperature affected maximum imbibition (83-150%) for A. asperrima, A. lechuguilla, A. salmiana and A. striata; other species averaged 110%. Most germination kinetics best fitted a logistic model, whereas only a few treatments fit a Weibull model. The time to germination onset diminished ( P < 0.05) from 125-173 h at 15°C to 68-84 h at 25°C, and then ascended to 84-196 h at 35°C. The mean germination rate and seed germination percentage after 312 h peaked at 25°C (0.50-0.95% seeds/h and 85-99%, respectively) and fell ( P < 0.05) to near zero at 10 and 40°C. Temperatures of 10, 35 and 40°C were partially lethal to A. asperrima, A. duranguensis and A. salmiana seeds. The time to germination onset, seed germination percentage after 312 h and mean germination rate are best described by a Gaussian distribution, with its optimum at approximately 25°C. Thus, optimum temperatures are related to the ecological characteristics of each species area. [ABSTRACT FROM AUTHOR]

Introduction: Some entomopathogenic fungi act as endophytes and promote plant growth. Such benefits can be explained by improvements in physiological processes. In this research, the effect of commercial strains of entomopathogenic endophytic fungi and isolates from agricultural soils of San Luis Potosi on growth, photosynthesis, gas exchange and production in poblano chili plants was evaluated, considering the effect of the inoculation method used. Methodology: Poblano chili plants (Capsicum annuum L.) was used as a model which was sown under controlled conditions and in a greenhouse. Seven HEE strains were evaluated: three native isolates from agricultural soils of San Luis Potosi that by their characteristics belong to the genus Metarhizium (RV01 strain), Paecilomyces (RV05 strain) and Penicillium (SL14 strain); two strains isolated from insects, Beauveria bassiana [(Bals.-Criv.) Vuill. 1992] (BB42 strain) and Metarhizium anisopliae [(Metschn.) Sorokin 1883) (MA25 strain) and two commercial strains of B. bassiana (BB09 strain) and M. anisopliae (MA25 strain). A conidial solution was prepared, and two methods were tested: 1) seed inoculation; and 2) substrate spraying and a second application when the first true leaf emerged. Controls were included in each treatment (water and the surfactant were inoculated). Photosynthetic parameters (maximum and effective efficiency of PSII, photochemical and non-photochemical dissipation, electron transfer rate), gas exchange parameters (net assimilation rate, stomatal conductance, and transpiration) and colonization percentage of steam, leaf and root were evaluated during the experiment. At the end of the experiment total dried biomass, dry weight of the aerial part of the plant and the root, and root length was measured. Results: At 33 days after inoculation it was observed how inoculation with RV01, MA25, BB09 and SL14 increased CO2 assimilation and stomatal conductance, with respect to controls, when inoculated by seed or by spraying. Inoculation directly over the seed significantly improved CO2 assimilation, photochemical quenching, and effective efficiency of PSII comparing to plants inoculated by foliar spraying. The isolate RV05 stood out due to the results observed in the greenhouse, with a higher total biomass production. The plants inoculated by seed showed an increase in the production of total biomass, and in the dry weight of the aerial part and roots with respect to the plants inoculated by aspersion. Greater growth in plants was associated with endophytic colonization. Conclusion: HEE isolated from agricultural soils of San Luis Potosi can compete with commercial strains in promoting growth in poblano chili plants in greenhouse. Direct seed inoculation of endophytic entomopathogenic fungi generated better results, although with variations depending on the strain. [ABSTRACT FROM AUTHOR]

In Mexico, the young cladodes (nopalitos) and floral buds (tunitas) of Nopalea cochenillifera are consumed as vegetables, but there is no information on the content of structural polysaccharides and dietary fiber in floral buds. The objective of this study was to extract, purify and quantify the structural polysaccharides (mucilages, pectins, loosely and tightly hemicelluloses bound to cellulose, and cellulose) and dietary fiber (soluble, insoluble and total) in floral buds of N. cochenillifera in four stages of development. The hypothesis was that soluble structural polysaccharides increase during the development of floral buds. Floral buds were harvested between 06:00 and 09:00 h in the municipality of San Ciro de Acosta, San Luis Potosí, Mexico; they were classified by their length and development in four stages (GS); thorns were eliminated, lyophilized and crushed. The structural polysaccharides were extracted in sequence with aqueous solvents (water, ammonium oxalate and potassium hydroxide). Soluble dietary fiber was determined as the sum of mucilage, pectin and loosely bound hemicelluloses, and insoluble as the sum of tightly bound hemicelluloses and cellulose. Total dietary fiber was the sum of all structural polysaccharides. The experimental design was completely randomized with four replications per treatment. The content of mucilage and loosely bound hemicelluloses varied between GS, from 5.6 to 9.8 % and from 3.1 to 15.0 %. Pectins, tightly bound hemicelluloses and cellulose remained stable during the development of floral buds (6.4, 12.4 and 12.7 %). The GS2 had the highest dietary fiber content (46.3 %). The content of mucilages, loosely bound hemicelluloses and total and soluble dietary fiber increased in floral buds of N. cochenillifera in GS2, followed by their decrease in GS3 and GS4. [ABSTRACT FROM AUTHOR]

We assessed inter-seasonal dynamics of seed banks, dormancy and seed germination in three endemic Chihuahuan Desert succulent species, under simulated soil warming conditions. Hexagonal open top-chambers (OTCs) were used to increase soil temperature. Seeds of Echinocactus platyacanthus (Cactaceae), Yucca filifera and Agave striata (Asparagaceae) were collected and buried within and outside OTCs. During the course of one year, at the end of each season, seed batches were exhumed to test viability and germination. Soil temperature in OTCs was higher than in control plots. Yucca filifera seeds always had high germination independently of warming treatment and season. Agave striata seeds from OTCs had higher germination than those from control plots. Agave striata exhibited low germination in fresh seeds, but high germination in spring. Seeds from this species lost viability throughout the experimental timeframe, and had no viable seeds remaining in the soil. Echinocactus platyacanthus showed high germination in fresh seeds and displayed dormancy cycling, leading to high germination in spring, low germination in summer and autumn, and high germination in winter. Germination of this species was also higher in seeds from OTCs than those from control plots. Echinocactus platyacanthus formed soil seed banks and its cycle of inter-seasonal dormancy/germination could be an efficient physiological mechanism in a climate change scenario. Under global warming projections, our results suggest that future temperatures may still fall within the three studied species' thermal germination range. However, higher germination for A. striata and E. platyacanthus at warmer temperatures may reduce the number of seeds retained in the seed bank, and this could be interpreted as limiting their ability to spread risk over time. This is the first experimental study projecting an increase in soil temperature to assess population traits of succulent plants under a climate change scenario for American deserts. [ABSTRACT FROM AUTHOR]

Leaf color and area are important characteristics in plant physiology and genetic studies, but data collection is laborious and requires optical integrators and colorimeters. Nowadays, data collection could be automated through digital image analysis (DIA). Free software for DIA to measure leaf area or color is available, but user intervention is required to record dimensions or leaf color. This study shows the Macf-IJ routine for DIA to measure leaf area and color. Results from DIA of seven geometric figures were compared to physical measurements with a LI-COR 3000® Leaf Area Integrator. Additionally, leaf area was measured in 13 herbaceous plants, and color and relative chlorophyll content (RCC) was recorded for Rhynchosia minima (L.) DC with a SPAD 502®. DIA was performed with Digitizer 4.3.5® and Black Spot Leaf. Duration of each measurement was recorded for each case. The area measured with the integrator for any figure varied less than 8.96 % with Macf-IJ and less than 1.82 % with photographs. R2 between methods was 0.999 (p⩽0.001). With exception of five grasses, leaf area measured with the integrator correlated well with the Macf-IJ (r>0.989, p⩽0.001); Macf-IJ, Black Spot Leaf and Digimizer® had an R2 greater than 0.99 (p⩽0.001). Duration was not significantly different between methods, but Macf-IJ registered additional data such as length (cm), width (cm), circularity (0-1) and red (R), green (G) and Blue (B) colors. There was correlation between RCC and green (r=-0.946, p⩽0.01), red (r=-0.941) and blue (r=-0.881) colors and between RGB obtained the Digimizer® and CRC (r=-0.939, -0.942 and -0.811 for red, green and blue colors, respectively). [ABSTRACT FROM AUTHOR]

Human-induced warming may increase the risk of local extinction for plant species with low tolerance of elevated temperatures. The Chihuahuan desert harbors the highest diversity of globose cacti in the world and most of them are at risk of extinction. Predictive models of climate change indicate an increase in summer temperature of 1-2°C by 2030 for this desert. Nevertheless, studies on the vulnerability of cacti species in early development phases to future climate change are scarce. We assessed the survival of three threatened cacti species from the Chihuahuan desert under induced warming. Open-top chambers ( OTCs) were used to simulate the effect of global warming on 2-year seedlings of E chinocactus platyacanthus f. visnaga, F erocactus histrix and S tenocactus coptonogonus. OTCs had higher temperature and lower humidity than control plots, and these elevated temperatures reduced seedling survival. Within the OTCs, no living individuals of any species were found after 105 days. Conversely, in the control plots, the three cacti species showed variable numbers of survivors after this period. Therefore the predicted global warming scenarios will greatly limit plant recruitment and the long-term persistence of natural populations of Mexican endemic cacti species. [ABSTRACT FROM AUTHOR]

The responses of desert plants to climate warming have been poorly assessed, perhaps due to the overall expectation that desert vegetation will expand as a consequence of this component of climate change. However, determining what plant species will tolerate the expected increase in temperature is a question that remains unanswered. The Chihuahuan Desert is the largest warm desert of North America, and predictive models of climate change indicate that summer temperatures in this desert will increase by 1–2 °C in the next decade. This study experimentally assessed the performance of an endangered cacti species from the Chihuahuan Desert under simulated warming conditions. Hexagonal open top-chambers (OTCs) were used to simulate the effects of global warming on five-years-old individuals of the specially protected species Echinocactus platyacanthus . Temperature was 1.9 °C higher in open top-chambers than in control plots. In contrast, relative humidity was 3.1% higher in control plots than in open top-chambers. E. platyacanthus showed 100% survival for 14 weeks in both OTC and control plots. However, induced warming negatively affected the photosynthetic performance of this species. Cacti located within OTCs displayed lower maximum quantum efficiency of photosystem II ( F v / F m ), effective quantum yield of photosystem II (Φ PSII ), and electron transport rate (ETR) values, but higher non-photochemical quenching (NPQ) values, than cacti from control plots. This is the first study focused on the potential impact of climate warming on survival and photosynthetic performance of young individuals of a succulent species from American deserts. Induced warming negatively affected the photosynthetic performance of young E. platyacanthus , but it also increased non-photochemical quenching, a mechanism for avoiding photoinhibition. [ABSTRACT FROM AUTHOR]

• We assessed the effect of induced warming on an economically important Agave species. • Both developmental phases showed high tolerance under induced global warming. • The younger plants had higher chlorophyll and carotenoid content than older plants. • Our target species displayed higher photochemical activity than other succulents. Agave species are a key component of the structure vegetation in the American drylands and have various anthropogenic uses. Agave angustifolia subsp. tequilana is an economically and culturally important Mexican species. Negative impacts on biodiversity are expected as a consequence of global warming; however, it has been documented that some Agave species are not affected by projected warming. Previous studies on some succulent species under induced global warming have shown a certain level of tolerance to temperature stress. We evaluated the potential temperature stress tolerance of two early developmental phases of A. angustifolia subsp. tequilana , by means of the following photochemical parameters: maximum quantum efficiency of photosystem II (F v /F m); effective quantum yield of PSII (Φ PSII); electron transport rate (ETR); non-photochemical quenching (NPQ); and pigment content (total chlorophyll, carotenoids and anthocyanins) in two-year-old plants and five-year-old plants under induced warming. Temperature and vapor pressure deficit (VPD) were higher in open-top chamber (OTCs) induced warming treatment than control plots, reproducing current climatic conditions. Both developmental phases showed high F v /F m values in both OTCs and control plots. Two-year-old plants displayed higher NPQ values than five-year-old plants under warming. The Φ PSII and ETR values were low in both warming treatments and developmental phases. Low anthocyanin content was found in both treatments and developmental phases. Independently of warming, the two-year-old plants showed higher total chlorophyll and carotenoid content values than the five-year-old plants. Despite that induced warming affected the photochemical activity of A. angustifolia subsp. tequilana , the high NPQ and pigment values indicate that this species has a high tolerance to future global warming. Our results provide novel evidence of the high physiological tolerance that could act in the early developmental phases of a key Agave species to cope the effects of global warming. [ABSTRACT FROM AUTHOR]