Artículo de publicación ISIA high proportion of plant species is predicted to be threatened with extinction in the near future. However, the threat status of only a small number has been evaluated compared with key animal groups, rendering the magnitude and nature of the risks plants face unclear. Here we report the results of a global species assessment for the largest plant taxon evaluated to date under the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, the iconic Cactaceae (cacti). We show that cacti are among the most threatened taxonomic groups assessed to date, with 31% of the 1,478 evaluated species threatened, demonstrating the high anthropogenic pressures on biodiversity in arid lands. The distribution of threatened species and the predominant threatening processes and drivers are different to those described for other taxa. The most significant threat processes comprise land conversion to agriculture and aquaculture, collection as biological resources, and residential and commercial development. The dominant drivers of extinction risk are the unscrupulous collection of live plants and seeds for horticultural trade and private ornamental collections, smallholder livestock ranching and smallholder annual agriculture. Our findings demonstrate that global species assessments are readily achievable for major groups of plants with relatively moderate resources, and highlight different conservation priorities and actions to those derived from species assessments of key animal groupsConsejo Nacional de Ciencia y Tecnologia 000000000011820
Arbuscular-mycorrhizal (AM) fungi stabilize the soil and enhance plant growth by alleviating nutrient and drought stress. Their contributions to agriculture are well known, but their role in desert ecosystems has received less attention. The AM status of perennial plants in disturbed and undisturbed plots were investigated in the Sonoran Desert near La Paz, Baja California Sur, Mexico to determine if AM fungi contribute to resource-island stability and plant establishment. All perennial plants (46 species) in the study plots were AM, but root colonization varied widely ( Ͻ 10 to Ͼ 70%). Roots of plants that established in greatest numbers in plant-free zones (colonizers) of disturbed areas were highly AM. Plants with trace ( Ͻ 10%) root colonization (cacti of the tribe Pachycereae : Pachycereus pringlei , Machaerocereus gummosus , and Lemaireocereus thurberi ; and Agave datilyo ) established preferentially in association with nurse trees. The pachycereid cacti grew under Prosopis articulata and A. datilyo under Olneya tesota canopies. Of the nine species of trees and arborescent shrubs in the area, the mature ( Ͼ 20 yr) nurse-legumes P. articulata and O. tesota supported the largest number of under-story plants. Younger plants had only occasional associates. AM propagule densities in plant-free areas were lower than under plant canopies (40 vs. 280 propagules/kg soil). Occurrence of soil mounds (islands) under plants owing to soil deposition was related to the nature of the canopies and to the AM status of the roots. Island soils were enmeshed with AM-fungal hyphae, especially in the upper layer (approximately 10 cm). Seedlings of P. pringlei , growing in a screenhouse for six months in soil collected under P. articulata , had a biomass ten times greater than plants growing in bare-area soil. The results are consistent with the proposition that AM fungi contributed to the plant-soil system of our study area by: (1) helping to stabilize windborne soil that settles under dense plant canopies; (2) enhancing the establishment of colonizer plants in bare soils of disturbed areas; and (3) influencing plant associations through differences in the mycotrophic status of the associates. . 1996. A framework for tackling drought and land degradation. Journal of Arid Environments 33:309-320.
1Autor para la correspondencia: jlleon04@cibnor.mx Resumen: Los objetivos de este trabajo fueron integrar el listado florístico de la selva baja caducifolia en la península de Baja California y delimitar su presencia. Esta comunidad vegetal ocupa una superficie de 3,325 km 2 en el extremo sur peninsular, que se ha propuesto como la versión más seca de las selvas bajas en México. Después de décadas de esfuerzos, actualmente se considera que su composición florística está adecuadamente representada en el herbario del Centro de Investigaciones Biológicas del Noroeste. El listado cuenta con 645 taxa de plantas superiores y de ellos 37 son endémicos. Con base en muestreos de campo, se discute la composición florística de los dominantes ecológicos de esta comunidad. Sobresale Lysiloma microphyllum como especie indicadora de este tipo de vegetación. En el análisis de las formas de crecimiento, se resalta el de las trepadoras, cuyo número es similar al registrado para el desierto Sonorense y comunidades contiguas, pero notablemente inferior al de otras selvas bajas caducifolias del sur de México. Palabras clave: bosque neotropical, endemismos, Lysiloma microphyllum, trepadoras. Abstract:The objective of this research was to prepare a floristic list of the tropical dry forest in Baja California Peninsula and to delimit its coverage. This forest covers 3,325 km 2 in the mountainous southernmost part of the peninsula; this community is the driest version of its type in Mexico. After decades of fieldwork, the representation of the flora in the herbarium of the Centro de Investigaciones Biologicas is almost complete. There are 645 taxa of vascular plants, of which 37 are endemics to this area. The authors discuss the floristic composition of the ecologically dominant plants based on field surveys. Lysiloma microphyllum is the most important species in this vegetation community. Using growth form analysis, we found that climbers have a proportional frequency similar to that of the Sonoran Desert flora and neighboring communities, but are significantly less than other dry tropical forests in southern Mexico. Key words: climbers, endemicity, Lysiloma microphyllum, neotropical forest.FLORÍSTICA Y TAXONOMÍA D e acuerdo con Miranda y Hernández-X. (1963), la vegetación tropical seca en México se conceptualiza bajo la denominación selva baja caducifolia (SBC), mientras que Rzedowski (1978) la denomina bosque tropical caducifolio. El concepto engloba a la vegetación de franca afinidad tropical cuya principal característica consiste en que la mayor parte de los árboles y arbustos pierden sus hojas al menos durante seis meses debido a la prevalencia de un período sin lluvias.En el contexto mundial la SBC mexicana forma parte del concepto del seasonally tropical dry forest que se extiende discontinuamente a través de la vegetación subtropical en América (Gentry, 1982;Pennington et al., 2009;Dirzo et al., 2011). Según Holdridge et al. (1971 este tipo de vegetación se distribuye en las regiones subtropicales del planeta, en un nivel altit...
Antecedentes y Objetivos: Se presenta el primer listado florístico de las playas y dunas costeras de México, actualizado y respaldado por ejemplares de herbario.Métodos: Se revisaron 14 herbarios nacionales y extranjeros. Se sobrepuso una retícula de 2 × 2 km al mapa de la costa y de las dunas costeras de México para referir todos los registros que corresponden a 2180 sitios con 12,419 ejemplares de plantas. Se calcularon índices de diversidad, similitud, diversidad taxonómica y redundancia.Resultados clave: La flora registrada consta de 153 familias, 897 géneros y 2075 especies de plantas vasculares, las cuales representan 9.5% de la flora vascular de México. Las cinco colecciones con índices de redundancia altos IR≥0.7 son los herbarios de la Universidad Nacional Autónoma de México (MEXU, IR=0.9), del Centro de Investigación Científicas de Yucatán (CICY, IR=0.8), y los del Centro de Investigaciones Biológicas del Noroeste (HCIB), el Instituto de Ecología, A.C. (XAL) y el del Museo de Historia Natural de San Diego (SD), cada uno con un IR de 0.7. Se reconocen cinco regiones florísticas que corresponden a los mares de México. El Pacífico Norte tiene mayor diversidad taxonómica y el Pacífico Sur menor diversidad taxonómica. El Golfo de California, Golfo de México y Mar Caribe tienen diversidades taxonómicas similares. Las especies con más registros son Trianthema portulacastrum (165), Croton punctatus (107), Echites umbelllatus (106) e Ipomoea pes-caprae (90). Por el carácter de ecotono de las dunas costeras, la mayoría de las especies se comparten con los tipos de vegetación vecinos (selvas, matorrales, y humedales como las marismas y manglares).Conclusiones: Esta primera lista de la flora en playas y dunas de México es la base para múltiples estudios florísticos regionales y locales, biogeográficos, y ecológicos; además, que será importante para su uso en temas de impacto ambiental y manejo costero.
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