Search

The influence of the ancient landscape configuration and the land use legacies on forest cover change has been thoroughly investigated in temperate and tropical forests while it remains barely explored at high-latitudinal regions. This study explores the landscape drivers leading forest cover changes and their influence on current forest attributes in the world’s southernmost forests (Argentina). Nothofagus antarctica forest cover changes were determined by combining multitemporal photo-interpretation of aerial photographs (1961) and satellite images (2016–2019). We analyzed changes in land covers and landscape diversity indexes. We also explored the potential relationships among descriptors of forest structure, soil or understory characteristics, and the magnitude of forest increase. Forest cover increased in 55 sites (72% of study area), and decreased in 21 sites (28% of study area). Cleared forests and forest edges decreased by half from past to the present, while woody encroachment increased. This resulted in a diversification of the current landscape by an increase in the number of land cover categories and Shannon–Wiener index. The increase in forest cover was positively influenced by land cover diversity and latitude, i.e., major increases at southern latitudes. Forests with greater recovery presented more similar understory attributes than those with lower recovery, while in other forest structures and soil properties, different magnitudes of recovery occurred. Sites with a high proportion of forest recovery evidence a reduction of past land use legacies (e.g., forage plant species introduced for livestock) at a local scale. These results expand our knowledge about the current natural dynamic of high-latitude forests, although the precise anthropic pressure changes (e.g., livestock density) leading to this process are still unclear and should be further investigated. Management practices should consider these spatial differences in the response to recovery of sub-Antarctic forests, such as the management of densely regenerated areas by thinning, or the restoration of degraded forests, as well as the monitoring of woody encroachment in natural grasslands and peatlands. Although we document an overall gain in N. antarctica forests, the results could vary when incorporating other forest types (N. pumilio, N. betuloides) and geographic zones (e.g., Andean mountains), due to the complex dynamics of these coupled human-natural systems. [ABSTRACT FROM AUTHOR]

We evaluated the annual litterfall and nutrients return in primary forests of Nothofagus antarctica growing at three different site classes (SC) (III, IV and V) and compared two of these forests with adjacent stands under silvopastoral use (thinned 40 years ago), in Patagonia, Argentina. Traps were installed in each stand and sampled monthly during the litterfall over 10 years. Sample from the five stands was ground for further analyses of nutrients (N, P, K, Ca, Mg and S). The litterfall varied significantly between SC, but not between years, from 1,306 to 1,972 kg ha in the best site. The nutrients return from litterfall did not change neither between site classes and years in most nutrients. Comparing primary forests with silvopastoral stands, in SCIV, significant differences among uses occurred for litterfall production and nutrients return, being higher in primary forest. While, in SCV, the litterfall and nutrients return practically did not change among uses. The results showed the incidence of site quality and forest use on the litterfall and nutrients return in N. antarctica forests. [ABSTRACT FROM AUTHOR]

Key message: This study is the first to quantify tree water use below 50°S. Tree morphology differs markedly among the two investigated species, reflecting adjustment to different environmental cues. Abstract: A pronounced environmental gradient dictates the dominance of Nothofagus in the foothills on the eastern side of the Andes Mountains in Patagonia, Argentina. Below 50° southern latitude, open forests of Nothofagus antarctica (ñire) dominate the landscape towards the Patagonian steppe where annual rainfall is low. With increasing rates of annual rainfall, corresponding with an increase in elevation, closed forests of N. pumilio (lenga) replace those of ñire. During a short-term study we assessed differences in stand structure and examined environmental, structural and functional traits related to tree water use of ñire and lenga. Sap velocity reached similar maximum rates (95-100 L m sapwood h), but whole-tree water use ( Q) was significantly lower in ñire (8-13 L day tree) compared to lenga (20-90 L day tree) resulting in lower stand transpiration (ñire: 0.51 mm day; lenga: 3.42 mm day) despite similar tree densities. Related to this, wind speed had a particularly significant impact on Q of ñire, but not lenga. The ratio of leaf area to sapwood area ( A/ A) clearly identified ñire to be more structurally proficient at conserving water. While stem diameter (DBH) and crown area ( A) were well related in both species, only lenga exhibited relationships between variables related to tree allometry and physiology ( A/ Q, DBH/ Q). Our results provide the first ecophysiological characterization of the two Nothofagus species that define important and widespread ecosystems in southern Patagonia (not only below 50°S), and provide useful data to scale water use of both species from tree to stand. [ABSTRACT FROM AUTHOR]

Conservation strategies of forested landscapes must consider biodiversity of the included site types, i.e. timber-quality forests and associated non-timber-quality stands. The objectives were to characterize forest overstory structure in timber-quality versus associated non-timber-quality stands; and to compare their understory communities. Six forest types were sampled in Nothofagus forests of Tierra del Fuego (Argentina): two timber-quality N. pumilio forests, and four associated non-timber-quality stands (edge, N. antarctica, wetlands and streamside forests). Overstory structure and understory vegetation (species richness, frequencies, cover and biomass) were characterized during spring and summer seasons. Analysis of variance and multivariates were carried out. Overstory structure differed across the site types, with higher tree size, canopy closure and tree volume in timber-quality stands. Fifty-one understory plant species were observed, but understory variables varied with site types, especially wetlands (highest native and exotic richness, cover and biomass, and 25% of exclusive species). Site types were grouped in three: N. antarctica stands, streamside stands and the other N. pumilio forests according to multivariate analysis. Forty three percent of plants were distributed in all site types, and all timber-quality forest understory species were present in some associated non-timber-quality stands. Timber-quality N. pumilio forests have a marginal value for understory conservation compared to associated non-timber-quality stands, because these last include all the plants observed in timber-quality forests and also possess many exclusive species. Therefore, protection of associated non-timber-quality stands during forest management planning could increase understory conservation at landscape level, and these could be better reserves of understory diversity than retentions of timber-quality stands. [ABSTRACT FROM AUTHOR]