Grazing represents the most extensive use of land worldwide. Yet its impacts on ecosystem services remain uncertain because pervasive interactions between grazing pressure, climate, soil properties, and biodiversity may occur but have never been addressed simultaneously. Using a standardized survey at 98 sites across six continents, we show that interactions between grazing pressure, climate, soil, and biodiversity are critical to explain the delivery of fundamental ecosystem services across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. Considering interactions between grazing and local abiotic and biotic factors is key for understanding the fate of dryland ecosystems under climate change and increasing human pressure.

The anatomical structure of the leaves and stems of the 13 species of Isostigma (Asteraceae: Heliantheae) has been examined by using light microscopy. All species of Isostigma have Kranz anatomy in their leaves, containing one or more Kranz units (=KU, the unit constituted by the vascular bundle/s, the parenchyma sheath and the surrounding mesophyll). It is demonstrated that there are the following two different types of Kranz anatomy in leaves of Isostigma: (1) Eryngiophyllum type, with one KU per leaf and with sclerenchyma tissue (I.�brasiliense, I. cordobense, I. crithmifolium, I. dissitifolium, I. peucedanifolium, I. riedelii, I. simplicifolium and I.�speciosum); and (2) Isostigma type, with more than one KU per leaf, without sclerenchyma tissue (I. acaule, I.�herzogii, I. hoffmannii, I. molfinianum and I. scorzoneraefolium). The stems of all 13 species of Isostigma show also Kranz anatomy, without variation among species. Until the present, the Eryngiophyllum and the Atriplicoid types were the only reported for Asteraceae. The Isostigma type is a new type for the family, characteristic of plants growing in humid places. The following evolutionary sequence of Kranz anatomy is hypothesised: Atriplicoid–Isostigma–Eryngiophyllum where numerous KUs become continuous to reach a unique, compound KU.

Biological soil crusts are widely distributed in arid and semiarid regions. They have an important ecological role, especially by modifying physical and chemical properties of soils. Biological crusts may also modify seed germination and seedling establishment. The effects vary widely according to the type of crust and the vascular plant species. The objective of this study was to determine the effect of moss-dominated biological soil crusts on the emergence, biomass and survival of Poa ligularis Nees ex Steud. under different irrigation regimes. We collected seeds of P. ligularis and biological soil crusts composed of two species of mosses: Syntrichia princeps (De Not.) Mitt and Ceratodon purpureus (Hedw.) Brid. from an area in the Monte of Argentina. The result showed that seedling emergence of P. ligularis was higher in treatments with bare soil than in soil covered by crusts, and also in those with watering to field capacity. Mean emergence time was higher in treatments with bare soil and watering to field capacity. Seedling biomass also showed significant differences between treatments. These results suggest that biological soil crusts dominated by mosses do not promote P. ligularis emergence, although they would not affect its survival.

In arid and semiarid lands around the world, vegetation is distributed in patches within a bare soil matrix. Vegetation in the North-east Patagonian Monte, Argentina is a shrubland steppe, and patches are dominated by shrubs, with grasses, forbs and cryptogams under their canopy. It was hypothesised that grazing increases patchiness; and fires and wind erosion homogenise the distribution of vegetation. It was predicted that there would be: (1) greater cover, specific frequency and richness of shrubs in grazed sites; (2) greater cover, specific frequency and richness of herbs and preferred grasses in ungrazed sites; and (3) a random pattern of distribution in burnt areas. Aerial cover of all perennial species was measured at six sites with different land-use histories: heavily grazed, medium grazed, ungrazed, long exclosure from grazing followed by grazing, burnt and then ungrazed, and burnt and then grazed. Species were grouped into five functional types: shrubs, sub-shrubs, preferred grasses, non-preferred grasses and forbs. The results showed significant differences in the cover of preferred and non-preferred grasses, forbs and total cover with previous grazing but there was no evidence of shrub encroachment. Species frequency and richness decreased especially with increased grazing intensity. The pattern of spatial distribution changed from aggregated in grazed sites to random in ungrazed and burnt sites for all plant functional types. At the population level, the cover of the grass, Poa ligularis, was greatest on ungrazed sites whereas the cover of the shrub, Chuquiraga erinacea, was greatest on burnt sites. It is concluded that, after applying a heterogeneous patchwork of disturbance, such as grazing, or with fire, followed by periods of rest, the plant diversity is increased.