Marisela Pando-Moreno

Specimens of webspinners (order Embioptera) of the family Oligotomidae from two biological collections in Mexico were examined (n = 431), revealing a greater state-level distribution than previously recorded for the three species of the genus Oligotoma . Oligotoma humbertiana is newly recorded for the states of Baja California Sur, Ciudad de México, Colima, Guerrero, Michoacán, Nayarit, Oaxaca, Sinaloa, Sonora, Veracruz, and Yucatán; Oligotoma nigra is newly recorded for Baja California Sur, Chihuahua, and Colima; and Oligotoma saundersii is newly recorded for Coahuila, Colima, Nayarit, Nuevo León, Oaxaca, Sonora, Veracruz, and Yucatán. An illustrated key that includes Haploembia solieri and the three aforementioned species of Oligotoma is proposed.

En Nuevo León, México, se decretaron tres áreas naturales protegidas (ANP) para conservar a Cynomys mexicanus; sin embargo, las actividades agropecuarias continúan dentro de estas áreas, aunado a la carencia de información sobre la condición de su hábitat. En este estudio se evaluó la salud del pastizal y la producción de biomasa de las tres áreas (la Trinidad, la Hediondilla y Llano la Soledad) para determinar su funcionalidad. La salud del ecosistema de La Hediondilla estuvo deteriorad y su zona núcleo presentó el estado funcional más crítico; además, presentó la mayor producción de biomasa (0.53 Mg/ha-1) debido al cambio de uso de suelo y la vegetación invasora. Las actividades productivas en el Llano La Soledad son básicamente ganaderas, aunque la producción de biomasa fue menor (0.14 Mg/ha-1), presentó las mejores condiciones de salud, ya que toda su superficie es de uso restringido. La salud deteriorada del pastizal es una amenaza para Cynomys mexicanus y la biodiversidad de su ecosistema.

Carbon dioxide (CO2) in the soil is produced by mineralization of organic matter and by respiration of soil organisms. Biocrusts contribute to this f lux and is a key factor for the functioning of arid and semi‑arid ecosystems. This research was conducted in an area of microphyllous desert shrubland in northeastern Mexico. Four microenvironments were selected: open area without biocrusts (Aa), open area with biocrusts (AaC), under plant without biocrusts (Bp) and under plant with biocrusts (BpC). The biocrusts were mainly constituted by lichens and cyanobacteria. The following hypotheses were tested: i) biocrusts contribute to soil respiration in these areas to a greater extent than vascular plants; ii) soil respiration is higher in biocrusts microenvironments than in open areas without biocrusts; iii) soil respiration rates increase as soil temperature increases, regardless of the presence/ absence of biocrusts. Soil respiration was measured in situ using an EGM-4 equipment with a closed soil respiration chamber. Data were analyzed by Kruskal Wallis and Mann Whitney U tests. The relationship between temperature and soil respiration rate was evaluated with a Spearman correlation analysis. Statistical analyzes were performed in the SPSS® Statistics version 19 software. The results showed that the average respiration rate was higher in soil with biocrusts than in soils lacking biocrusts, with 3.03 μmol CO2 m-2 s-1. Respiration rates dif fered between microsites. AaC, BpC and Bp microenvironments reached equal respiration rates among them and were overall higher than the soil respiration rates in Aa, except for Bp, which showed similar values. The results also showed a positive relationship between soil respiration and temperature for all microenvironments. We conclude that the respiration rates were higher in areas with biocrust coverage ≥ 40%, compared with soil without biocrusts, both in the presence and absence of vascular plants.

Competition and facilitation are important factors affecting seedling survival. These factors probably affect plant distribution and abundance. Interactions between species relate to phylogeny, in that closely related species are likely to compete more for resources and facilitation is expected between more distantly related species. We tested for Tamaulipan thornscrub plants, grown with close and distant relatives if they differed in survival, length and weight of shoots and roots, assuming that closely related species would compete more than distant ones. We also explored whether seed mass was associated with plant size from 1-24 months after germination. We grew plants from Tamaulipan thornscrub, with a sibling or with one individual from other species from 1-24 months. Seedling survival was similar for all species when their seedlings grew alone or under competition, at 1, 6 and 12 months. At 24 months seedling survival of Vachellia farnesiana was lower when grown with Havardia pallens. There was no evidence of stronger competition or facilitation for phylogenetically closer species. Seedling size correlated with seed mass one month after germination but not after 6 months. Maximum and mean adult plant height did not correlate with seed mass or with plant height in our trials. We found no evidence of phylogeny explaining nearest neighbors in competition during germination for Tamaulipan thornscrub.

Antecedentes: La siembra directa de especies nativas puede ser una buena alternativa en términos de beneficio/costo para la restauración en ecosistemas semiáridos. En esos casos, es indispensable contar con datos sobre la germinabilidad, porcentaje y tiempo medio de germinación para definir estrategias que aseguren la cantidad de planta suficiente y oportuna. Preguntas: ¿Cambia la germinabilidad y tiempo medio de germinación de semillas representativas del Altiplano mexicano, en un lapso de dos años? ¿Qué porcentaje de germinación presenta cada especie? Especies de estudio: Frankenia gypsophila , Machaeranthera pinnatifida , Muhlenbergia villiflora , Scleropogon brevifolius , Dasyochloa pulchella y Zinnia anomala . Sitio y años de estudio: pastizales de la RTP El Tokio y Laboratorios de la Facultad de Ciencias Forestales del 2017 al 2019. Métodos: Se evaluó la germinabilidad de semillas, mediante ensayos de germinación, de seis especies nativas de los pastizales de la RTP El Tokio, después de cero, ocho, 24 y 27 meses de recolectadas en campo. Resultados: Solo una especie ( Frankenia gypsophila ) se mantuvo viable hasta los 27 meses y para esa fecha su porcentaje de germinación fue tres veces menor con respecto a las dos primeras fechas. Todas las especies evaluadas presentaron valores de t50 inferiores a siete días. Conclusiones: El porcentaje y tiempo medio de germinación de las especies estudiadas permitirán estimar la cantidad de semilla para obtener la densidad deseada en una siembra con propósitos de restauración. Los resultados sugieren que no son especies adecuadas para preservarse en un banco de semillas ex-situ almacenadas bajo condiciones ambientales semi-controladas.

This work analyzes whether the soil conservation and reforestation actions carried out three years ago in the study area are reflectedin a better functionality of the landscape. The functionality of the landscape will be evaluated partially using the method known asLandscape Function Analysis (LFA) under the precept that a landscape is functional when it is able to retain its resources (soil,water, nutrients) regardless of internal redistributions. The “Las Barretas” ejido, where this research was carried out, is located 12km east of the city of Linares, Nuevo León. One hundred and thirty transects were established to obtain the percentage of totalcoverage and relative frequency of each type of coverage. Likewise, the attributes that contribute to interrupting, diverting orabsorbing surface runoff and transported materials were evaluated. To achieve this, the length and width of the vegetated patchesand the length of the interpatches without vegetation were measured. More bare soil (61%) and more rock presence (27%) wererecorded in the control area than in the area with soil conservation works. Herbaceous and pasture covers were slightly higher in thearea with conservation actions than in the control. The average length and width of the patches are significantly greater in the controlarea, however the average length of the interpatches is also greater, which means a greater surface of bare soil exposed to risk oferosion. The area with soil conservation actions has smaller but more continuous patches, the foregoing is evidenced by the higherBare Soil Index that resulted in the area without conservation works. The coverage at ground level (herbaceous, litter, pasture)seems to be increasing in the areas where soil conservation actions were carried out.

Antecedentes: La distribución de plantas depende de dispersores que transportan semillas a hábitats adecuados y de plantas que faciliten o inhiban germinación y establecimiento. Es importante conocer cómo estos factores influyen en la distribución de la vegetación y contemplar esta información en planes de manejo. Hipótesis: Las semillas y plántulas de las especies estudiadas diferirán en abundancia bajo diferentes especies de árboles y posición respecto al borde de la vegetación. Se espera una mayor densidad de semillas y plántulas bajo especies de árboles dispersos por animales y en los bordes de los fragmentos. Método. Se realizó conteo directo de semillas y plántulas de Zanthoxylum fagara (L.) Sarg. en México y Zanthoxylum coco Gillies ex Hook.f. & Arn. en Argentina, en fragmentos de vegetación remanente bajo copas de árboles, en borde e interior de vegetación. Resultados: Para ambas especies, la densidad de semillas fue similar en borde y en interior. La densidad de plántulas de Z. fagara fue mayor en el borde que 40 m al interior, así como bajo las copas de árboles dispersados por fauna. Para Z. coco no se encontraron diferencias . Conclusiones: Para ambas especies los dispersores de semillas no parecen importantes, se presenta similar densidad de semillas en borde e interior. Quizá tengan efecto en regeneración de Z. fagara , con mayor densidad de plántulas en borde que al interior. Es probable que mayor disponibilidad de luz en borde promueva regeneración de esta especie. Para Z. coco no parece existir un efecto de los dispersores en la regeneración.

In the State of Nuevo Leon (northeast of Mexico), there are two species of Amoreuxia: A. palmatifida Moc. & Sesse ex DC. and A. wrightii A. Gray both listed as endangered in the Mexican Official Standard NOM 059- SEMARNAT- 2010. Amoreuxia wrightii grows mainly in semiarid regions (^{Cedano, 2000}) or in disturbed sites, it is a rare and scarce plant (^{Rzedowski, 1994}) and it is considered as an element of secondary vegetation, usually growing on stony ground (^{Cedano, 2000}).

Most of carbon in grasslands comes from underground biomass, particularly in arid grassland ecosystems. However, estimation of root biomass in these ecosystems has been poorly studied. In this study was analyzed the correlation between above ground plant variables and root biomass to develop statistical models for reliable root biomass estimations. Twenty-six plant species were collected within grazing-excluded grasslands. Linear, exponential and logarithmic regression models were performed for each species and for the whole data set to determine the variables that best predicted root biomass. Only Frankenia gypsophila and Dalea gypsophila showed root/shoot ratio (RSR) higher than one. Enneapogon desvauxii and Atriplex acantocarpha had a RSR close to one. Eight species showed statistical significance in at least one of the correlation analyses but only Tiquilia canescens, Bouteloua gracilis, Machaerantera pinnatifida, Lesquerella fendleri, and Atriplex acanthocarpa had both statistical significance and acceptable coefficient of determination (r2 ≥0.50). Using the Marquardt exponential method, 14 out of 15 studied species showed a high determination coefficient and statistical significance. This method was adequate (r2=0.853) to estimate root biomass for the whole set of plants from plant height and crown diameter.