Floristic and vegetation structure of a grassland plant community on shallow basalt in southern Brazil

Few studies have adequately described the floristic and structural features of natural grasslands associated with shallow basalt soils in southern Brazil. This study was carried out on natural grazing land used for livestock production in the municipality of Santana do Livramento, in the Campanha region of the state of Rio Grande do Sul, Brazil. The aim of the study was to describe the floristic and structural diversity of the area. The floristic list obtained comprises 229 plant taxa from 40 botanical families, with a predominance of the families Poaceae (62), Asteraceae (28), Fabaceae (16) and Cyperaceae (12). The estimated diversity and evenness in the community were 3.00 and 0.874, respectively. Bare soil and rock outcrops accounted for 19.3% of the area, resulting in limited forage availability. Multivariate analysis revealed two well-defined groups among the sampling units. One group showed a high degree of internal aggregation, associated with deep soils, and was characterized by the presence of tussocks, whereas the other was less aggregate and was characterized by prostrate species growing on shallow soil. Ordination analysis indicated a gradient of moisture and of soil depth in the study area, resulting in different vegetation patterns. These patterns were analogous to the vegetation physiognomies described for Uruguayan grasslands. Overall, the grassland community studied is similar to others found throughout southern Brazil, although it harbors more winter forage species. In addition, the rare grass Paspalum indecorum Mez is locally dominant in some patches, behaving similarly to P. notatum Fl., a widespread grass that dominates extensive grassland areas in southern Brazil

Developmental Reaction Norms for Water Stressed Seedlings of Succulent Cacti

Succulent cacti are remarkable plants with capabilities to withstand long periods of drought. However, their adult success is contingent on the early seedling stages, when plants are highly susceptible to the environment. To better understand their early coping strategies in a challenging environment, two developmental aspects (anatomy and morphology) in Polaskia chichipe and Echinocactus platyacanthus were studied in the context of developmental reaction norms under drought conditions. The morphology was evaluated using landmark based morphometrics and Principal Component Analysis, which gave three main trends of the variation in each species. The anatomy was quantified as number and area of xylem vessels. The quantitative relationship between morphology and anatomy in early stages of development, as a response to drought was revealed in these two species. Qualitatively, collapsible cells and collapsible parenchyma tissue were observed in seedlings of both species, more often in those subjected to water stress. These tissues were located inside the epidermis, resembling a web of collapsible-cell groups surrounding turgid cells, vascular bundles, and spanned across the pith. Occasionally the groups formed a continuum stretching from the epidermis towards the vasculature. Integrating the morphology and the anatomy in a developmental context as a response to environmental conditions provides a better understanding of the organism's dynamics, adaptation, and plasticity

More Stable Productivity of Semi Natural Grasslands than Sown Pastures in a Seasonally Dry Climate

In the Neotropics the predominant pathway to intensify productivity is generally thought to be to convert grasslands to sown pastures, mostly in monoculture. This article examines how above-ground net primary productivity (ANPP) in semi-natural grasslands and sown pastures in Central America respond to rainfall by: (i) assessing the relationships between ANPP and accumulated rainfall and indices of rainfall distribution, (ii) evaluating the variability of ANPP between and within seasons, and (iii) estimating the temporal stability of ANPP. We conducted sequential biomass harvests during 12 periods of 22 days and related those to rainfall. There were significant relationships between ANPP and cumulative rainfall in 22-day periods for both vegetation types and a model including a linear and quadratic term explained 74% of the variation in the data. There was also a significant correlation between ANPP and the number of rainfall events for both vegetation types. Sown pastures had higher ANPP increments per unit rainfall and higher ANPP at the peak of the rainy season than semi-natural grasslands. In contrast, semi-natural grasslands showed higher ANPP early in the dry season. The temporal stability of ANPP was higher in semi-natural grasslands than in the sown pastures in the dry season and over a whole annual cycle. Our results reveal that, contrary to conventional thinking amongst pasture scientists, there appears to be no increase in ANPP arising from replacing semi-natural grasslands with sown pastures under prevailing pasture management practices in seasonally dry climates, while the temporal distribution of ANPP is more even in semi-natural grasslands. Neither sown pastures nor semi-natural grasslands are productive towards the end of the dry season, indicating the potential importance of the widespread practice of retaining tree cover in pastures

Tissue culture of ornamental cacti

Cacti species are plants that are well adapted to growing in arid and semiarid regions where the main problem is water availability. Cacti have developed a series of adaptations to cope with water scarcity, such as reduced leaf surface via morphological modifications including spines, cereous cuticles, extended root systems and stem tissue modifications to increase water storage, and crassulacean acid metabolism to reduce transpiration and water loss. Furthermore, seeds of these plants very often exhibit dormancy, a phenomenon that helps to prevent germination when the availability of water is reduced. In general, cactus species exhibit a low growth rate that makes their rapid propagation difficult. Cacti are much appreciated as ornamental plants due to their great variety and diversity of forms and their beautiful short-life flowers; however, due to difficulties in propagating them rapidly to meet market demand, they are very often over-collected in their natural habitats, which leads to numerous species being threatened, endangered or becoming extinct. Therefore, plant tissue culture techniques may facilitate their propagation over a shorter time period than conventional techniques used for commercial purposes; or may help to recover populations of endangered or threatened species for their re-introduction in the wild; or may also be of value to the preservation and conservation of the genetic resources of this important family. Herein we present the state-of-the-art of tissue culture techniques used for ornamental cacti and selected suggestions for solving a number of the problems faced by members of the Cactaceae family

Evaluación de la heterogeneidad estructural y funcional de los pastizales naturales para su manejo. (Capítulo 12).

Los pastizales del Río de la Plata son una de las áreas más extensas de pastizales templados del planeta. ---- 1. Los pastizales naturales como base de la ganadería extensiva: desafíos desde la perspectiva agronómica, ambiental, social y económica. -- 2. La situación actual. -- 3. Conocimiento y herramientas generados. -- 3.1. Descripción de las comunidades y subcomunidades de los pastizales naturales de Uruguay. -- 3.2. Protocolos de evaluación a campo del estado de cada comunidad. -- 3.3. Definición de estados y fases para cada comunidad. -- 3.4. Generación de hipótesis de las transiciones medianteprocesos de coinnovación. -- 4. Impacto sobre transiciones agroecológicas. -

Bases ecológicas y tecnológicas para el manejo de pastizales II.

Este libro ofrece a la comunidad académica, a los técnicos y a los productores una compilación de los resultados de investigaciones sobre los pastizales uruguayosrealizados en el marco de un proyecto financiado por el Fondo de Promoción de Tecnología Agropecuaria ("CARACTERIZACIÓN DE ESTADOS DEL CAMPO NATURALEN SISTEMAS GANADEROS DE URUGUAY: DEFINICIÓN Y USO DE INDICADORES DE CONDICIÓN COMO HERRAMIENTAS DE MANEJO" FPTA-305). Constituyeuna continuación de las investigaciones reportadas en la Serie FPTA 26 "Bases ecológicas y tecnológicas para el manejo de los pastizales"

Where and why to conserve grasslands socio-ecosystems? A spatially explicit participative approach.

ABSTRACT.- Grasslands of southern South America are being replaced by annual crops and forest plantations. The environmental and social consequences of this expansion generate the need for its regulation. If a conservation policy were established, it would be critical to define which areas would have priority for conservation. Multi-criteria analysis techniques are useful tools in territorial planning processes since they allow incorporating diverse and even opposing opinions and objectives. We present a methodological approach to define the Grasslands? Conservation Value (GCV) from a spatially explicit territorial diagnosis, based on multiple criteria and incorporating explicitly and quantitatively the valuations and opinions of stakeholders. The study was developed as part of the strategy of a public inter-institutional entity to contribute in defining grasslands conservation policies. The methodological approach included workshops in which the definitions of the conservation criteria and their weighting were agreed upon. Definitions were based on a multidimensional technical characterization of the territory through indicators, for which the information used was compiled, analyzed, shared, and synthesized. Based on multi-criteria analysis, each of 12 stakeholders? groups representatives established the individual weighting of the criteria for determining the GCV and then, established a consensus weighting. The GCV was mapped by integrating territorial diagnosis of these criteria with the weightings carried out by the stakeholders. The degree of agreement among stakeholders in the differential valuation of the ecological criteria was high for 8 of the 12 stakeholders (Pearson's correlation coefficients >0.92), showing a high agreement between their opinions and those resulting from the group consensus. In all cases, the agreement about the spatial variation of conservation value was higher than on the criteria weights (Pearson's correlation coefficients >0.92 for 10 stakeholders). Furthermore, the sites with lower values in the consensus map corresponded mostly to those sites with lower agreement among stakeholders. The proposed methodology allowed the incorporation of different perceptions not only in the definition of conservation criteria but also in their prioritization, in a transparent and auditable process. This could contribute to the implementation of future regulations that restrict the replacement of grasslands, increasing the legitimacy of territorial planning processes. Copyright © 2022 Staiano, Gallego, Altesor and Paruelo