Cacti are ecologically significant in American fire-prone dry ecosystems but understudied regarding fire effects. We evaluated how fire impacts survival and resprouting of Trichocereus terschekii, a key arborescent cactus in northwestern Argentina. We assessed fire effects in three situations: A) one year post-fire (n = 151); B) five years post-fire (n = 151); and C) unburned control (n = 101), and analyzed their relationship with plant size, fire severity and microenvironment. Survival differed between the control (79 %) and burned sites (20 % in situation A and 23% in situation B; p < 0.001), but not between the latter (p = 0.58), indicating that fire's main impact occurs within the first post-fire year. Plant size positively influenced survival in burned sites (p < 0.0001), while fire severity had a negative influence (p < 0.0001). In situation A, charred vegetation percentage -a measure of fire severity- was negatively correlated with remaining green epidermis (Spearman's rho = -0.62; p < 0.001; N = 151). In turn, resprouting in situation B was positively related to green epidermis (p = 0.0022; N = 34), but not to plant size (p = 0.80), indicating dependence on photosynthetic tissue, rather than underground reserves. Microenvironment influenced survival (p < 0.004), with patterns differing between burned sites. This study contributes to understanding post-fire dynamics of cacti and to designing appropriate conservation and restoration strategies.

Terrestrial ecosystems degraded by overgrazing and plant invasions challenge restoration programmes that must remain compatible with local livelihoods. Invasive shrub control often relies on livestock, which suppresses resprouting but generates woody debris that may function as inadvertent herbivore exclusions, with unclear effects on woody plant recruitment. Understanding these effects is critical for guiding restoration. We conducted a field experiment modifying livestock access using standardized exclosures intentionally assembled from woody debris generated by cutting invasive Pyracantha angustifolia. These debris piles also may provide perching sites for frugivorous birds, offering a unique opportunity to explore assisted natural regeneration pathways following invasive management. By comparing woody plant recruitment inside and outside woody debris patches, we tested their ability to promote native regeneration and potential facilitation of invasives. We selected 28 cuts from 2020 and 28 from 2022, each paired with a control, and measured recruit identity and height in 2024 to evaluate short and medium-term dynamics under contrasting grazing pressure. Woody debris patches reduced livestock browsing and increased woody establishment and growth of invasives, showing rapid growth and higher likelihood of being bird-dispersed, particularly under 4-year exclusions. Community composition shifted among treatments, reflecting species-specific responses and within-site variability. Synthesis and applications. Woody debris patches prevented observable livestock browsing, facilitating invasive species under prolonged exclusion. Grazing thus operates as a strong biotic filter against invasives, highlighting the need to combine exclusion with targeted management of woody debris. Effective strategies include maintaining livestock access through partial or rotational exclusion, strategically redistributing woody debris to avoid persistent refuges for invasives and selectively using thorny debris to protect native saplings. Our results offer practical guidance for invasive control and livestock production, contributing to integrated restoration frameworks that consider ecological and socioeconomic dimensions. Los ecosistemas terrestres degradados por sobrepastoreo y plantas invasoras representan un desaf & iacute;o para los programas de restauraci & oacute;n que deben mantenerse compatibles con los medios de vida locales. El control de arbustos invasores suele favorecerse por la presencia de ganado que reduce el rebrote, pero genera restos le & ntilde;osos que pueden funcionar como exclusiones involuntarias de herb & iacute;voros, con efectos a & uacute;n poco claros sobre el reclutamiento de plantas le & ntilde;osas. Comprender estos efectos es fundamental para orientar las estrategias de restauraci & oacute;n. Realizamos un experimento de campo modificando el acceso del ganado mediante exclusiones estandarizadas construidas intencionalmente a partir de restos le & ntilde;osos generados por el corte del arbusto invasor Pyracantha angustifolia. Estas pilas de restos le & ntilde;osos tambi & eacute;n pueden funcionar como sitios de posado para aves frug & iacute;voras, ofreciendo una oportunidad & uacute;nica para explorar v & iacute;as de regeneraci & oacute;n natural asistida tras el manejo de arbustos invasores. Al comparar el reclutamiento de plantas le & ntilde;osas dentro y fuera de las exclusiones formadas por restos le & ntilde;osos, evaluamos su capacidad para promover la regeneraci & oacute;n nativa y su potencial para facilitar especies invasoras. Seleccionamos 28 individuos cortados en 2020 y 28 en 2022, cada uno pareado con un sitio control, y medimos la identidad y la altura de los renovales en 2024 para evaluar din & aacute;micas de corto y mediano plazo bajo presiones de pastoreo contrastantes. Las pilas de restos le & ntilde;osos redujeron el ramoneo del ganado e incrementaron el establecimiento y el crecimiento de plantas le & ntilde;osas invasoras, mostrando un r & aacute;pido crecimiento y una mayor probabilidad de ser dispersadas por aves, particularmente bajo exclusiones de cuatro a & ntilde;os. La composici & oacute;n de la comunidad vari & oacute; entre tratamientos, reflejando respuestas espec & iacute;ficas de las especies y variabilidad dentro de cada sitio. S & iacute;ntesis y aplicaciones. Las pilas de restos le & ntilde;osos impidieron el ramoneo observable del ganado, facilitando a las especies invasoras bajo exclusiones prolongadas. El pastoreo act & uacute;a como un fuerte filtro bi & oacute;tico frente a las invasoras, lo que pone de manifiesto la necesidad de combinar estrategias de exclusi & oacute;n con un manejo dirigido de los restos le & ntilde;osos. Estrategias efectivas incluyen mantener el acceso del ganado mediante exclusiones parciales o rotativas, redistribuir estrat & eacute;gicamente los residuos le & ntilde;osos para evitar refugios persistentes para las invasoras, y utilizar selectivamente ramas espinosas para proteger renovales nativos. Nuestros resultados ofrecen lineamientos pr & aacute;cticos para el control de invasoras y la producci & oacute;n ganadera, contribuyendo a marcos de restauraci & oacute;n integrados que consideran dimensiones ecol & oacute;gicas y socioecon & oacute;micas.

Studies on plant germination responses to fire have primarily relied on laboratory simulations, typically using oven-based heat shock treatments and liquid smoke applications. However, the extent to which these approaches reproduce real fire conditions remains debated, and an alternative experimental approach involves the use of controlled biomass burning. In this study, we compared germination responses under controlled biomass burns with those under equivalent laboratory treatments, using cacti as a model system. Cacti are conspicuous components of arid and semiarid ecosystems across the Americas and are increasingly threatened by anthropogenic pressures, including changes in fire regimes. Despite much of their distribution occurring in fire-prone environments, few studies have evaluated their germination responses to fire. We assessed germination (percentage and mean germination time) of 16 cactus species using two experimental approaches across seven treatments: a control; four biomass burning treatments with different fuel loads (50 g, 50 g + ash, 100 g, and 100 g + ash); and two equivalent laboratory treatments (100 °C/5 min and 130 °C/5 min), both combined with liquid smoke. We also evaluated the effect of seed mass on germination. Germination responses differed markedly between experimental approaches. Under biomass burning treatments, germination was consistently very low—often null—across all species, whereas laboratory treatments elicited germination responses in most species. Under the moderate-intensity laboratory treatment (100 °C + smoke), responses did not differ significantly from the control. Mean germination time varied among species: in some cases it did not differ from the control, whereas in others it either increased or decreased under laboratory treatments. Seed mass had no significant effect on germination percentage, but significantly influenced mean germination time. Overall, our results indicate that conventional laboratory experiments do not adequately reproduce real fire conditions and may substantially overestimate germination responses in cacti.

Differences in climatic factors associated with elevation can lead to natural selection for local adaptation in species with a wide distribution range, with some regenerative characteristics changing along the gradient. Most Cactaceae species occur in heterogeneous environments, mainly in mountains. The increasing severity of environmental conditions along elevational gradients could affect seed size, influencing seedling growth. The main aims of the study were to analyse whether seed mass, and seedling size and shape are related to elevational gradients in different populations of four species of the genus Gymnocalycium and to evaluate the relationship between seed mass and bioclimatic variables. Populations of four species of Gymnocalycium (G. andreae, G. erinaceum, G. monvillei and G. mostii) were sampled; the populations were located along three different elevation gradients, with each population corresponding to an elevational class (extremes and intermediate sites). At each elevational site, mature fruits were collected and seed mass and seedling traits were measured. A shape index was calculated by dividing height by width. A value of 1 represents 'globose' seedlings, while increasing values indicate that the seedlings become 'columnar'. The Pearson correlation coefficient was calculated to analyse the relationship between seed mass and seedling size variables. Linear models were used to analyse seed size and seedling shape. First, with elevation as a predictor and then for seed mass, the 19 bioclimatic variables were extracted from WorldClim. The results show that seed mass was positively correlated with seedling shape index, and with seedling height and width. Differences in seed mass among populations were explained by the species and the gradient where they lived, as well as by the environmental variables mean temperature of the coldest quarter, precipitation of the wettest month, and precipitation of the driest month. In conclusion, the intraspecific analyses of the four Gymnocalycium species revealed that the seedling shape patterns were similar across all species in relation to elevation. However, seed mass varied with elevation differently for each species. These findings suggest that each species possesses unique characteristics that enable them to thrive in varying climatic conditions along elevational gradients.

Cacti have undergone some of the fastest diversification events in the plant kingdom despite their slow growth rates and extended generation times. This rapid evolution may be driven by intense ecological interactions. Here we tested, for the first time, the evolutionary dynamics of the ecological niches of Gymnocalycium species focusing on two key environmental factors: temperature and precipitation. To explore patterns of niche conservatism and/or evolution and identify major contributing factors, we reconstructed ancestral niches associated with these climatic dimensions using the binned ancestral range coding method. Our findings reveal that (1) the climatic-niches of narrow-ranged Gymnocalycium species are not highly conserved across the phylogeny (i.e., niches are evolving), (2) the evolutionary dynamics of thermal and precipitation niches across the Gymnocalycium phylogeny do not follow similar patterns, (3) a bioregion-specific pattern of niche evolution exists, and (4) the Early-Middle Pleistocene glaciations (i.e., GPG and three Post-GPG phases) potentially drove the patterns of lineage divergence in Gymnocalycium species, triggering the evolution of climatic niches. These results suggest that (i) Gymnocalycium species with fascicular roots may require special attention for conservation, (ii) in a warming climate, the species distributed in the South American transition zone, South Brazilian dominion, and Chacoan dominion may face serious risks, and (iii) the relatively 'more tight-less tight' pattern in conserving the precipitation and temperature niches could be a strategy for conserving the critical variable at the expense of the other. This study has not only provided valid insights into the evolutionary history of Gymnocalycium species but also highlights the importance of conservation efforts, essential to protect these species.

Cactaceae is an important plant family in the semi-arid ecosystems of the Americas. However, few studies have analyzed their responses after wildfires. In this study, we assessed the survival rate and resprouting capacity of cacti from different growth forms one year after a wildfire in the Córdoba Mountains, central Argentina. Eight species are present in the study area, which were classified into four growth forms; then we established 158 plots and recorded the status (dead or alive) of each cactus, and size-related variables. We also documented microenvironmental characteristics (percentage cover of grasses, forbs, shrubs, rock and bare ground) and topographic information (slope and slope orientation) for each plot, estimating the resprouting capacity of each growth form. Survival rates and resprouting capacity varied among growth forms. The survival rate for arborescent growth form was 25%, while for globose, opuntioid and short columnar forms were 84%, 69% and 55%, respectively. Microenvironmental and topographic factors influenced resprouting capacity, though effects varied among growth forms. Globose growth form showed the highest recovery capacity after the wildfire, contrasting with arborescent growth form, of which only 2% of the individuals resprouted, predominantly on south- and north-facing slopes. In contrast, short columnar and opuntioid growth forms showed no significant relationship between survival or resprouting capacity, and the measured variables. These findings provide key insights into the role of fire in shaping cacti populations and highlight the need to consider species-specific and environmental interactions in conservation and management strategies for the Chaco forest.

The main challenges to conserving native Cactaceae in Southern Brazil and Central Argentina (Pampas) are summarized. To date, Rio Grande do Sul (Southern Brazil) holds 65 cactus species, 17 of them (26.15

The Argentine ant is one among the 100 worst invasive animal species of the world. It has invaded six continents, and poses significant threats to the native invertebrate fauna. Prior knowledge on the suitable ecological niches of Argentine ants may help to devise better management plans. This study delineates the niches of Argentine ants using the ecological niche modeling approach by maintaining the temporal match between the distributional information and environmental data. We used an exhaustive methodological framework to understand the niche characteristics of Argentine ants in their native and invaded ranges. The model developed using combined native and invaded range distributional information provided better habitat suitability predictions in the invaded ranges. Efforts were also made to identify the suitable niches of this invasive species globally. The current global model was projected onto two future periods (2041–2070 and 2071–2100) under two different emission scenarios (SSP126 and SSP585). Our study highlights four important features related to the ecological niches of Argentine ants: (1) large habitat preference towards permanent streams in the native ranges, (2) native ecological niche is only partly conserved across invaded ranges, (3) invaded range niches are largely differentiated, and (4) global warming induces an increase in habitat suitability in the northern hemisphere. The results of this study may provide potential insights for the effective implementation of management strategies.

All 32 Brazilian species of Parodia Speg (Cactaceae) occurring in Rio Grande do Sul State are considered threatened, according to the IUCN criteria. Until 2021, Parodia rechensis (CR) was known by only two small populations. However, a new population with over 400 individuals was discovered in 2021, prompting the study of its reproductive biology as a way to promote its conservation. Anthesis, breeding system, and natural pollination were studied in the field. The breeding system was studied by applying controlled pollination treatments to plants excluded from pollinators (bagged). Germination features were studied at the Seed Bank of the Porto Alegre Botanical Garden under controlled temperatures (20, 25, and 30 °C). The anthesis is diurnal and lasts for up to four days. The flowers offer pollen as the sole resource to the pollinators. The study species is unable to set fruit and seed without the agency of pollinators and has self-incompatible (unable to set fruit and seeds when pollinated with pollen of the same individual) characteristics that can considerably restrict its reproduction. Native bees of Halictidae and Apidae (Hymenoptera) are the main pollinators, with a smaller contribution of Melyridae (Coleoptera) and Syrphidae (Diptera). Natural fruit set is moderate (≤64%, per individual), but the species presents vegetative growth, producing several branches from the mother plant. Seeds showed the optimum germination rate at 20 °C and an inhibition of 75% in germinability at 30 °C. Our findings suggest the need to manage the species’ habitat to guarantee the permanency of the plants and healthy populations of pollinators as well. Our findings raise concerns about the germination and establishment of new individuals in the context of rising temperatures caused by climate change. Suggestions for the possible management of the extant populations are made.

Resource allocation in plants is a fundamental aspect of life history theory. In Cactaceae, the specific trade-off between sexual reproduction and vegetative growth has still not been studied. The aim of this work was to assess if there is a trade-off between growth and reproduction, and to analyse whether both growth and allocation to reproduction depend on size of the individual. In this study, we used Gymnocalycium monvillei, a globose cactus endemic to the mountains of central Argentina, as a model species. Specifically, we analysed the relationship of growth (percentage increase in diameter) and size of individuals (diameter) to seed production, seed mass, germination, and mean germination time. To relativize the effect of size on seed production, two variables were calculated: the ratio of seed production to plant size (RSPS), and the ratio of total seed mass to plant size (RSMS). We found that both seed production and total seed mass were significantly related to cactus size. However, growth was not related to seed mass or to seed production, even when they were relativized. Germination and mean germination time were not related to plant size or growth. In the studied species, a slow-growing globose cactus, we did not find a trade-off between growth and reproduction.

Background and aims: Invasive plants succeeding at high-elevation ecosystems threaten biodiversity and ecosystem services conservation in mountain protected areas. In this study we assessed whether an exotic woody species, Cotoneaster franchetii Bois, responds to mountain environmental heterogeneity in a similar way to the dominant coexisting native woody species, Polylepis australis Bitter, or if it instead occupies a greater variety of habitats aided by the wide environmental tolerance expected for mountain invaders. M&M: We recorded C. franchetii and P. australis occurrence and cover in 120 square plots between 1200 and 2200 masl, inside and surrounding "Quebrada del Condorito" National Park and "Pampa de Achala" natural reserve (Cordoba, Argentina). We compared both species' distribution and its relationship with vegetation and topograpy. Results: Each species dominated at different elevations. However, at local scale, both species were more frequent in plots placed at valleys and south-facing steep slopes, with less cover of tussock grassland and more rock cover. Contrary to the native species, C. franchetii cover was unaffected by vegetation and topographic characteristics. Conclusions: High occurrence and no restrictions for increasing cover once established suggest a high spread potential of C. franchetii in these mountains. Polylepis australis is seemingly at risk since both species share habitat preferences. Wide environmental tolerance would not only trigger upward expansion of invasive species in mountains but also towards natural vegetation.

Introducción y objetivos: El aumento de plantas invasoras en ecosistemas de altura amenaza la conservación de la biodiversidad y de los servicios ecosistémicos en áreas protegidas de montaña. En este trabajo evaluamos si una leñosa exótica, Cotoneaster franchetii Bois, responde a la heterogeneidad ambiental de manera similar a la leñosa nativa dominante, Polylepis australis Bitter, o si puede ocupar una mayor variedad de hábitats dado el carácter generalista que se espera de ella. M&M: Registramos la ocurrencia y cobertura de ambas especies en 120 parcelas entre los 1200 y los 2200 msnm, dentro y en inmediaciones del Parque Nacional Quebrada del Condorito y la Reserva Hídrica Pampa de Achala (Córdoba, Argentina). Comparamos su distribución en relación con la vegetación y la topografía. Resultados: Cada especie dominó en altitudes diferentes pero, a escala local, ambas fueron más frecuentes en valles y laderas sur, con menor cobertura de pajonal y mayor cobertura rocosa y pendiente. Al contrario que la nativa, la cobertura de C. franchetii no se vio afectada por las características topográficas ni de la vegetación circundante. Conclusiones: La elevada ocurrencia de C. franchetii y la ausencia de restricciones para aumentar su cobertura una vez establecida sugieren un elevado potencial invasor. Su expansión representa un riesgo directo para P. australis por preferir hábitats similares. Al igual que en la expansión altitudinal, una elevada tolerancia ambiental promovería la invasión por leñosas hacia la vegetación natural en montañas

Altitudinal gradients in mountain environments impose selection pressures that could result in marked heterogeneity in genetic characteristics, population features and reproductive success. Most Cactaceae occur in arid and semi-arid areas of the American continent, from sea level to 4500 m a.s.l., and some species have wide altitudinal ranges. The aim of this work was to analyse how cytogenetic features (mitotic chromosomes analysed using molecular cytogenetic techniques, DNA content estimated by flow cytometry), amplified fragment length polymorphism genetic diversity, population features (population density and individual size) and reproductive success (seeds per plant and fruit production) are related to an altitudinal gradient in five sites of Gymnocalycium monvillei located between 878 and 2230 m a.s.l. Our results showed that the sites at three intermediate altitude have optimal conditions as greatest genetic diversity, highest population density and highest seed production, whereas extreme sites are characterized by greatest reproductive isolation and highest DNA content and seed mass. The results indicate that the species has various mechanisms to survive along altitudinal gradients.

KEY MESSAGE:Through a multidisciplinary study we found that Gymnocalycium bruchii, an endemic cactus from central Argentina, acts as a dioecious species, which is the first record in this genus. Cactaceae species are typically hermaphroditic; however, about 2% have other different reproductive systems. These non-hermaphroditic species may develop sexual dimorphism in flowers or other reproductive, vegetative or ecological traits, besides a specific breeding system and floral ontogeny. Therefore, multidisciplinary research is necessary to fully understand reproduction in those species. For this purpose, we studied Gymnocalicium bruchii, a globose cactus endemic to central Argentina that is presumably dioecious or gynodioecious. We made observations in two natural and two cultivated populations. We made morphological observations of plants and flowers, and performed quantitative analyses to determine the sex ratio, size of plants and flowers, flower production, fruiting, among other variables. We performed hand-pollination, self-fertilization and free-pollination tests to determine the breeding system. Finally, we studied the anatomy and ontogeny of the reproductive organs using permanent histological slides of flower morphs at different stages. Our results confirm that Gymnocalicium bruchii is a dioecious species. Female flowers have atrophied anthers and a functional gynoecium that produces fruits and seeds. Male flowers are bigger and have a functional androecium but a sterile gynoecium. In the cultivated population, the sex ratio was 1/1, whereas the number of male individuals was higher in both natural populations. Pollination tests corroborated dioecy. Ontogenetic studies revealed that in female flowers the anthers collapse before microspore maturation, while in male flowers the gynoecium shows normal development of the ovary, style, stigma, and ovules; however, the latter are never fertilized.

Plant invasion is one of the major global environmental threats with the potential to alter the ecosystem stability and functioning. In water-limited ecosystems, the impacts of non-native invasive trees on the water balance are particularly relevant since they can compromise the use of water by native taxa of the ecosystem and water provision for humans. In this paper, we assessed the hydrological impacts of the Ligustrum lucidum (Chinese glossy privet) invasion on a mountain seasonally dry forest of the Chaco region (Central Argentina). More specifically, we determined volumetric soil water content, runoff, and actual evapotranspiration, and their relations to the size of rainfall events in native forest stands and its adjacent invaded stands. We combined three-years field measurements and remote sensing data. L. lucidum stands showed less water content through the soil profiles than the native forest (0-70 cm depth; 19.6 and 23.1 %, respectively), particularly during the dry conditions. The drier condition in the deeper soil layers compared to the upper ones in the invaded stands indicated less rainwater percolation throughout the soil profile over the year, independently of the magnitude of the rainfall events. Daily variation of deep-water content (60-70 cm depth), only observed in L. lucidum stands, showed nightly increase and day-time decrease in dry conditions. Runoff was similar and almost nil in both native and invaded forests, even after large rainfall events (>30 mm). L. lucidum stands showed similar to 18% higher annual actual evapotranspiration rates than native stands. Based on our results, relatively higher water consumption for mono-specific L. lucidum stands in periods when photosynthetic activity of multi-specific native dry forest is still low may represent a competitive advantage in terms of plant invasion, and at the same time it generates negative impacts on water resources, reducing soil water content and limiting deep-water recharge in a water-limited ecosystem.

There are about 2200 cactus species, and most of them occur in fire-prone ecosystems. Nevertheless, there is scarce information about fire effects on the ecology of cactus species. In this study, we assessed the effects of a wildfire on the survival and growth of coexisting globose cactus species and their relation with microenvironment conditions in rocky outcrops from the Cordoba Mountains, central Argentina. A fire event occurred in spring 2011, and measurements were recorded in the first subsequent growing season, in winter. We selected 26 rocky outcrops and established three 3 x 1 m plots per outcrop. In each plot, we quantified all cactus individuals of the four species present in the area: Echinopsis aurea, Gymnocalycium bruchii, G. mostii and Parodia submammulosa. We also recorded if each individual cactus was dead or alive, and measured its size and post-fire growth. In addition, we measured the relative cover of rocks and bare soil, and the size of the rocks within a radius of 30 cm of each individual. Individual cactus survival (70-80%) did not vary among species. The highest post-fire growth was recorded in G. bruchii. For E. aurea, P. submammulosa and G. mostii, post-fire growth was negatively related to pre-fire size, suggesting that smaller individuals recovered faster than larger ones. Microenvironment characteristics did not affect post-fire growth in any of the species. Our results provide a preliminary insight into possible fire tolerance of globose cacti in the Cordoba Mountains, supported by their relatively high survival and growth after a fire event.

As a group, cacti are regarded as plants that tolerate water scarcity, since they present a number of adaptations. However, little is known about how species of the family varied their morphoanatomical characteristics along environmental gradients. The aim of this study was to analyze how six Gymnocalycium species occurring in three sites along a precipitation gradient (arid site: G. pugionacanthum, G. marianae; semiarid site: G. hybopleurum, G. stellatum; subhumid site: G. oenanthenum, G. baldianum) differ in their biomass partitioning and morphoanatomical characteristics. We collected mature individuals of each species and analyzed their biomass partitioning (to spines, aboveground stem, underground stem, main root, and lateral and thin roots), morphological characteristics (such as size ratios, spine length and width, and areole density) and anatomical characteristics (stoma number, and cuticle, epidermis, and hypodermis width). Species differed, both qualitatively and quantitatively, in most of the analyzed variables. For example, biomass allocated to spines was highest in G. pugionacanthum, lowest in G. baldianum, and intermediate in the remaining species. However, these variations were not clearly associated with aridity, but were related to the subgenus of the species. These patterns were clearly observed in the PCA. Phylogenetic relatedness is the main factor associated with morphoanatomical characteristics.

In iteroparous plants, an increase in allocation to reproduction is expected with increasing plant size. The aim of this study was to analyze how plant diameter is related to total produced seed mass, seed number, mean seed mass, percentage and mean germination time (MGT), and seedling size and shape in Wigginsia sessiliflora (Hook.) D.M. Porter (Cactaceae), a slow-growing globose species from central Argentina. Plant diameter was measured in a population of 185 individuals, and fruits were collected. We counted all seeds to obtain seed number, and weighed them to get seed mass and total seed mass. Seeds were germinated and data of germination percentage and MGT were collected. We also measured the size (height and width) and shape of seedlings (height/width relationship). Fifty-four percent of the plants did not produce fruits. Plant diameter was unimodally related to fruit number, total seed mass, and seed number, i.e., intermediate-sized plants presented the highest values. Height and shape of seedlings were positively related to plant diameter. Surprisingly, plant diameter was related in a unimodal way to reproductive outputs. As plants grow, surface–volume ratio decreases, meaning that respiratory losses would be higher than the increase in photosynthetic capacity; therefore, fewer resources may be available for reproduction.

The transformation of forests to treeless landscapes as a result of disturbances (deforestation transitions) is an ongoing process in many regions of the world. Here we first revise the historical context of these transformations and then, we focus on its consequences for litter decomposition. We also present a case study, based on four ecosystems of central Argentina (Sub-Andean, Mountain Chaco, Espinal and Arid Chaco), evaluating how deforestation transitions can modify ecosystem decomposition by altering its main controls. Although there is evidence of consequences of deforestation transitions on the local environment for decomposition and on leaf litter quality it is not clear how those changes would impact the decomposition of natural mixed litter in the field. In our study case, we show that the deforestation transitions evaluated across four ecosystems resulted in no consistent changes in standard substrate decomposition but a consistent increase in the litter mixtures’ decomposability and quality. Likely as a consequence of this pattern, the loss of trees resulted in a consistent increase in the in situ mixtures decomposition across the ecosystems studied. Beyond our particular findings, our analysis highlights how the accurate prediction of the consequences of deforestation transition on changes in carbon and nutrient cycling needs to understand the behaviour of its controls. Only through this understanding, we will be able to interpret the patterns of in situ mixtures decomposition and predict the consequences of deforestation transitions adequately on carbon (C) and nutrient cycling. Additionally, the recent literature, in coincidence with our results, gives evidence that the presence of non-leafy plant debris and local-scale variation in the local environment may play a stronger role than previously thought in C and nutrient cycling.