Journal of Arid Environments最新文献

Many South American dry woodlands lack good historical or paleoecological baseline data to inform restoration and conservation. However, functionalist approaches such as those popularized by rewilding suggest that functional interactions producing target ecosystem processes are valid even without data confirming compositionalist values such as a long coevolutionary histories or known historical range overlaps of target species. In central Chile, the guanaco (Lama guanicoe) has been extirpated but is known to browse trees in other regions of South America, and the tree Vachellia [Acacia] caven shows adaptations to browsing but has no extant browsers within its Chilean range. Both species are native to Chile but there are no data to assess their historical levels of interaction. Here we test the hypothesis that they can act as mutual “Eltonian proxy” species: interacting species for which we lack sufficient data (the Eltonian shortfall) to prove they are not proxies. Specifically we predict that they have complementary adaptations such that guanacos will browse Vachellia [Acacia] caven and the latter will show adaptive responses to their browsing. We introduced five guanacos into an enclosure of Vachellia [Acacia] caven “espinal” woodland, and over two years measured the growth responses of individual branches, compared to branches of trees in an area without browsing. We predicted that Vachellia [Acacia] caven would show compensatory growth in response to guanaco browsing resulting in an increase in branching. Guanacos browsed throughout the two years. In the presence of guanaco browsing, Vachellia [Acacia] caven branches grew longer, grew more sub-branches, and showed more densely streamlined branch architectures. These results indicate that guanacos could be used to substitute anthropogenic pruning as a restoration and management technique in Vachellia [Acacia] caven “espinal” woodlands. However, other extinct megaherbivores or extirpated deer may also be key components of a past herbivore community to which Vachellia [Acacia] caven was adapted. Further attention to a network of multiple interacting browsers, and their indirect and nontrophic effects, is an area for further research.

Key environmental influences on soil basal respiration (Rs) and nitrogen mineralization (ΔIN) are temperature and soil water content (SWC) and both are being altered by climate change. Yet we cannot expect that variation in temperature and SWC will equally affect all ecosystems. We examine the influences of temperature and SWC on R_s and ΔIN in two grassland plant communities dominated by C3 or C4 species. We collected soil samples from these communities and incubated them at temperatures (5 °C, 10 °C, 15 °C, and 25 °C) and four SWC (10%, 20%, 30% and 40% by weight). After four one-month incubation experiments, we found that (1) plant communities, temperature, and SWC significantly influenced R_s and ΔIN; (2) the highest R_s and ΔIN occurred at 25 °C and 30% SWC in the C4 plant community; (3) in the driest soils, N was immobilized in both communities regardless of temperature. We suggest that there is a greater limitation to C and N mineralization in the C3 plant community than in the C4 plant community making the C3 community less sensitive to variation in temperature and SWC.

The objective of this study was to select progenies of Opuntia undulata Griffiths cv. African Elephant Ear (AEE) through morphological, productive, and nutritional traits, and also evaluate the repeatability and selection gain. The experiment was carried out between 2018 and 2020, in the semiarid region of Brazil. A completely randomized design was used, with ten replications. The treatments consisted of 12 progenies of Opuntia undulata cv. AEE. Morphological, productive, and nutritional characteristics were evaluated, also the selection gain and repeatability were estimated. There was a variation in the productivity of up to 11.2 t DM ha⁻¹. Progenies number 6 and 7 stood out in terms of selection gain. Progenies 6, 7, 9, and 12 were the most productive. Progeny 6 stood out in terms of dry matter production and minor presence of spines; both traits are of great interest in breeding programs of forage cacti. Based on the repeatability analysis, fewer evaluations were enough to predict with confidence morphological traits and dry matter production in different progenies of Opuntia undulata Griffiths.

To understand the various adaptations of endothermic desert adapted species to their hot arid environment it is crucial to understand their drinking habits. Birds of prey, including the species of the genus Falco, are said to be able to survive without drinking even in hot arid environments, and acquire the water they require (for evaporative cooling, for example) through their food. The Grey Falcon (Falco hypoleucos), a rare Australian endemic, stands out among its congeners in that its entire population is absolutely restricted to a hot arid environment. These birds have fewer and less reliable surface water sources than congeners in more mesic environments. Surprisingly, we have only two observations of Grey Falcons drinking in the wild. We describe these here, the first such records, and relate them to the extended periods spent observing these birds. We propose that water intake through food plays a greater role in the biology of the desert adapted Grey Falcon than in any other species of the genus Falco. Further investigations into the dependency of the Grey Falcon on food for its water will help to understand the complex interplay of physical, physiological, behavioural and environmental characteristics that allow these and other animals to persist in extreme desert environments. The issue appears relevant to many desert-living animal species because frequency and severity of weather extremes are predicted to increase under a changing climate.

The co-occurrence of mistletoes and Lantana camara (hereafter, lantana) is common in southern Africa, yet little is known about how they interact. To fill this gap, we investigated whether mistletoe-infected trees facilitate lantana invasion in a semi-arid southern African savanna. We compared invasibility, native woody plant diversity and soil parameters beneath mistletoe-infected and non-infected trees. We trapped bird droppings beneath mistletoe-infected and non-infected trees and conducted germination experiments to check if they contained viable lantana seeds. Regardless of whether trees were legumes or non-legumes, the subcanopy environments of mistletoe-infected trees had significantly higher invasibility than non-infected trees. The probability of lantana invasion beneath trees increased with mistletoe-infection levels. Soil nutrient concentrations were higher beneath mistletoe-infected trees than non-infected trees. Subcanopy invasibility was positively correlated with soil nutrient concentrations and negatively with native woody plant diversity. We found viable lantana seeds in bird droppings beneath mistletoe-infected trees. Put together, our findings indicate that mistletoes indirectly facilitate lantana invasion by enriching soil nutrients and attracting lantana seed dispersers. Our work provides a rationale for the necessity to simultaneously manage mistletoes and lantana where they co-occur to reduce invasion of the latter.

Cacti are threatened mainly by loss of habitat and illegal commerce. Because of this, it is essential to know their demographic characteristics. We systematically reviewed the publications with matrix population models (MPM) and integral projection models (IPM) in indexed journals, databases like the COMPADRE Plant Matrix Database and grey literature. In each publication, we recorded the literature characteristics, the population attributes, and the methods and metrics applied to describe them. We reviewed studies published until April 2022. We found 83 publications applied demographic modeling, 43 of which were of grey literature. Most studies were conducted in North America and on the tribe Cacteae, with a scarce representation of South American cactus. Compared to a previous review from 20 years ago, our study recorded a 488% increase in the number of publications and a 33.3% increase in the COMPADRE demographic database. We found demographic data for 65 taxa and very few studies covered a medium-to long-term period. MPMs were the most used until the 2009 when IPMs began to gain popularity. Population growth rates were commonly close to the unit (λ ≈ 1), but we identified a wide range of λ values. Species position in the demographic triangle showed that the populations in the tribes Echinocereae, Cereeae and Cylindropuntieae were located towards the end of the survival axis, while those in the tribes Cacteae, and Opuntieae had a more variable location. Applications of demographic models have focused on the analysis of life history traits (growth and turnover) and employing numerical simulations to simulate the consequences of variations in vital rates on λ. Interactions with the climate and the nurse-protected system are analyzed frequently. Nonetheless, a limited number of research explores the socioeconomic and political components of management and conservation. Finally, even though Cactaceae is the plant group with the most extensive demographic research, models are available for only 3.5% of the species.

Knowledge pertaining avian reproductive phenology and life history is important to understand population dynamics under current climate change. Understanding about changes that occur in these dynamics and factors influencing nesting success in modified habitats is also necessary. We studied reproductive phenology and nest characteristics of birds that nest in an agricultural area within an arid region of central Mexico, and evaluated changes in survival and nesting initiation throughout three years having variation in weather patterns. We registered more nests and greater avian reproductive success in years having the highest rainfall. Within years, nest survival increased as nest age advanced and with increasing nest height in some species. We observed lower incidence of nest parasitism in the agroecosystem in relation to those reported for less modified habitats in semiarid environments. We also observed cases of ectoparasitism by dipteran larvae in chicks of two bird species.

We evaluated the emergence of three shrub native species from the Monte Desert, the most arid ecoregion of Argentina, in substrates artificially constructed (technosols) with different texture and salinity under nursery garden conditions. Two of the studied species (Strombocarpa strombulifera and Neltuma alpataco) had high emergence percentages (96.00 ± 4.62% and 98.00 ± 2.31) regardless of differences in texture and salinity. On the other hand, Larrea divaricata showed high emergence (72.00 ± 6.68%) in non-saline sandy loam soil with gravel, and minimum values in saline and fine-textured substrate (18.33 ± 6.22%). We conclude that studying seedling emergence performance in substrates under nursery garden conditions constitutes a preliminary step for the pre-selection of species for seed-based restoration in arid lands. We also found that technosols can serve as amendments, promoting the emergence of seedlings from various species depending on their formulation.

We present the first empirical information on floral traits, floral visitors, and breeding system of Anarthrophyllum strigulipetalum, a rare and charismatic plant species that inhabits rocky terrains in the harsh semi-arid landscapes of northwestern Patagonia. Despite being large plants (∼1.7 m² surface area), with a showy floral display (>100,000 flowers/plant), protracted flowering period (∼1 month), high nectar production (16.7 μl per flower), high pollen viability (96%) and pollen receipt (∼200 grains/stigma), species reproductive success was very low, with less than 1% of the flowers developing into fruit. Only birds triggered the flower-opening mechanism and carried pollen, whereas insects behaved as nectar thieves. The addition of nectar seemed to increase fruit formation compared to control flowers, whereas nectar removal tended to decrease fruit set. The natural low fruiting levels could be the result of a combination of factors such as low legitimate pollinator visitation rate, low-diverse and poor-quality pollen receipt due to geitonogamy promoted by the great floral display and the abundant floral reward, intense levels of nectar theft by native insects, and even climatic stress. The reduced size of populations and low fitness settles the grounds for potentially low genetic diversity, inbreeding depression and, ultimately, demographic declines.