Temperate Forest Of Patagonia Research Articles

Effect of Huntiella decorticans and drought on Nothofagus dombeyi seedlings.

In the temperate forests of Patagonia, Argentina, Nothofagus dombeyi, commonly known as Coihue, has shown sensitivity to intense drought events, leading to mortality. Studies have been conducted on Coihue decline and mortality using a variety of approaches, including the role of extreme heat waves and drought, pests and pathogens, particularly the fungus Huntiella decorticans. This work aimed to evaluate survival, vitality, necrosis extension and growth response of inoculated and non-inoculated Coihue seedlings from different provenances exposed to different soil moisture levels. To achieve this goal, 96 Coihue seedlings from 2 different provenances were assigned to 8 different experimental treatments. Treatments were composed of the presence or absence of H. decorticans and different soil moisture content conditions, dry, wet and the exposure to dry condition at different times of the experiment. Both dry conditions and H. decorticans had negative effects on the survival and growth rate of Coihue. The combination of both factors resulted in 100 % mortality, regardless of the plants' geographical provenances. Mortality began to be observed 3 months after pathogen inoculation, during the warmest month. Necrosis extension produced by the pathogen was similar for most of the inoculated treatments. The treatment under wet condition during the experiment but subjected to dry condition in the previous growing season presented lower necrosis extension (8.4 ± 3.2 %), than the other treatments. The radial increase was also affected by the treatments and geographical provenance, being those plants exposed to dry conditions which grew less (0.19 ± 0.21 mm). This study enhances our understanding of the plant-pathogen interaction. According to our results, Coihue may become more susceptible to mortality, when H. decorticans and water deficit conditions act synergistically.

The disruption of a keystone interaction erodes pollination and seed dispersal networks.

Understanding the impacts of global change on ecological communities is a major challenge in modern ecology. The gain or loss of particular species and the disruption of key interactions are both consequences and drivers of global change that can lead to the disassembly of ecological networks. We examined whether the disruption of a hummingbird-mistletoe-marsupial mutualism by the invasion of non-native species can have cascading effects on both pollination and seed dispersal networks in the temperate forest of Patagonia, Argentina. We focused on network motifs, subnetworks composed of a small number of species exhibiting particular patterns of interaction, to examine the structure and diversity of mutualistic networks. We found that the hummingbird-mistletoe-marsupial mutualism plays a critical role in the community by increasing the complexity of pollination and seed dispersal networks through supporting a high diversity of interactions. Moreover, we found that the disruption of this tripartite mutualism by non-native ungulates resulted in diverse indirect effects that led to less complex pollination and seed dispersal networks. Our results demonstrate that the gains and losses of particular species and the alteration of key interactions can lead to cascading effects in the community through the disassembly of mutualistic networks.

Trajectory assessment of the vulnerable marsupial Dromiciops gliroides in the Patagonian temperate forest

We studied the movement of the marsupial Dromiciops gliroides by means of an innovative approach that makes use of two complementary techniques, specifically devised for the monitoring of small animals that live in dense forests. Despite playing a key role in the Southern Temperate Forest of Patagonia, very little is known about the ecology and habitat use of this “almost threatened species” (according to IUCN), the only living representative of an entire order (Microbiotheria). We present here novel results about the movement and explored area of D. gliroides at different spatio-temporal scales using complementary approaches: the spool-and-line and a radiotelemetry techniques. Both are complemented in such a way that, while the first one allows to obtain trajectories at small spatial scale with very precise resolution for relatively short periods, the second one provides longer temporal records at larger spatial scales adding temporal resolution. We show in this work very precise nocturnal trajectories unknown so far of 41 individuals of D. gliroides using spool and line, analyzing several of their statistical properties. For instance, from the turning angle distribution we find that, after release, the animals followed paths that exhibited little angular deviation between steps. In a complementary way, using radiotelemetry, we were able to study the velocity distribution of their movements, assessing a most probable value of $$2.0\pm 0.8$$ m/min and a median value of $$7.2\pm 2.8$$ m/min. The combination of both approaches brings new opportunities for studying other cryptic and poorly known forest dwellers.

Non-native ungulates indirectly impact foliar arthropods but not soil function

One of the greatest challenges in contemporary ecology is to understand how the homogenization of biodiversity at all levels of organization and spatial scales will influence the assembly of communities and the functioning of ecosystems. Such homogenization can occur through the gain of non-native species and the loss of native species. Here, we show that by disrupting a keystone mutualistic interaction, non-native ungulates indirectly impact foliar arthropod abundance and richness, but not soil properties (soil respiration, temperature and humidity), in a temperate forest of Patagonia. The results of this study show that the gain of non-native ungulates and the loss of a key interaction can trigger unnoticed cascading effects. Our findings highlight the importance of assessing biodiversity not only as the sum of different components but also through the direct and indirect interactions among them.

Competition effects of grazing-modified herbaceous vegetation on growth, survival and water relations of lenga (Nothofagus pumilio) seedlings in a temperate forest of Patagonia, Argentina

In this study, we determined the competition effects of herbaceous vegetation on survival, growth, and plant water relations of planted lenga (Nothofagus pumilio) seedlings under field and nursery conditions in western Patagonia, Argentina. In the field, thirty (1.5 × 1.5 m) plots were randomly set in a grazing-free exclosure built in a typical grazing-degraded lenga canopy gap mainly colonized by non-native herbs and grasses (empastado). Herbaceous aerial and root biomass was removed in half of the plots (non-competition treatment, NCT), while the others (competition treatment, CT), remained undisturbed. Four similarly-sized lenga seedlings were planted per plot. In the nursery, 120 lenga seedlings were planted in individual pots containing soil of the field study site, and set to a factorial experiment including two competition levels (CT and NCT) and two watering regimes: normal (simulating average rains during the growing season, 500 mm, NW), and high (equivalent to 1000 mm, HW). During three growing seasons, we determined seedling survival, growth, and plant and soil water status of both experiments. Higher survival and growth, and better plant water status values were obtained in NCT as compared to CT in both experiments. In the nursery, HW did not improve survival and growth as compared to NW. In restoration trials implying grazing-degraded areas, increases in lenga seedling survival and growth could be achieved by reducing nearby competition of grasses and herbs, while extra watering appears unnecessary. However, limitations in the experimental design (pseudo-replication), limits generalization of results to other forest ecosystems with similar structural and functional characteristics.

Spatial patterns of caddisflies from Austral South America

Trichoptera are relevant members of the freshwater benthos that can exploit a broad variety of habitats. We explored their distribution patterns in Austral South America using a network quantitative approach applied on point occurrence data. The primary goal was to recognize groups of species connected by strong links of sympatry and secondarily to evaluate the structure of the sympatry network (patterns of connectivity) at higher taxonomic levels. We compiled 2,522 geographic points associated with 446 species. The strength of sympatry links were inferred directly from dot maps. Using the taxonomic resolution of species, we identified two major groups of co-occurring species that mimic in a geographic context the classic zoogeographic division of the study area: the Andean–Patagonian complex (of “cold-adapted” organisms) versus the Extra-Andean domain (of “warm-adapted” organisms) spanning the subtropical belt of the region. Within these major divisions, groups of highly co-distributed species were also found which in turn show a variety of overlapping spatial configurations. Overlap was centred at the following pivoting areas: Yungas of NW Argentina, Paranaense forest of NE Argentina and Valdivian temperate forest of Patagonia. Three very interesting findings emerged from the analyses: (i) Sierras Centrales of Córdoba correspond to the southern portion of many subtropical elements occurring in NW Argentina, (ii) some elements fit the disjunction between NW and NE Argentina and (iii) Uruguay is more closely related to NE Argentina than to Buenos Aires, suggesting that the Pampas region (Uruguay + Buenos Aires) could be an ill-defined biogeographic entity. Patterns at the species level become progressively blurred in going upward through the hierarchical classification.

Influence of habitat factors on the distribution and abundance of a marsupial seed disperser

Abstract Understanding factors that influence the distribution and abundance of seed dispersers is important because of the role these species play in maintaining plant communities. The temperate forest of Patagonia has an unusually high frequency of mutualisms, including obligate seed dispersal of a keystone mistletoe (Tristerix corymbosus) by the marsupial Dromiciops gliroides. We examined whether the distribution and abundance of D. gliroides was related to the distribution and abundance of this mistletoe, which is a principal food source, or alternatively, whether other habitat features constrain the distribution and abundance of this marsupial. We conducted field surveys for D. gliroides, mistletoe, and other habitat variables and developed a set of habitat models in which model variables were defined a priori. We found that the distribution of D. gliroides was related to bamboo cover. Bamboo is an important source of nest material and nest sites. However, when the minimum requirement for bamboo cove...

Ecological consequences of a massive flowering event of bamboo (Chusquea culeou) in a temperate forest of Patagonia, Argentina

AbstractQuestion: What changes occur as a consequence of the massive flowering and senescence of the dominant understory species of bamboo, Chusquea culeou (E. Desvaux)? In this study, we documented some of the ecological consequences of this rare event that occurred in 2001, the previous flowering having occurred more than 60 years ago.Location: Nothofagus temperate forest, Patagonia, Argentina.Methods: We assessed changes in environmental variables and bamboo biomass post‐flowering in an old‐growth southern beech forest. In addition, we monitored the demography of emergent Ch. culeou seedling and Nothofagus nervosa saplings, comparing non‐flowered (live understory) and flowered (senescent understory) patches within the forest matrix.Results: Bamboo flowering dramatically increased light availability in the forest understory but, surprisingly, other environmental changes were not observed. Bamboo seedlings emerged in both patch types, and experienced gradual but modest mortality through time. Bamboo dieback promoted higher survivorship and an increment in biomass, height, number of leaves and buds in the saplings of Nothofagus nervosa.Conclusion: The high density of bamboo seedlings 5 years after the flowering event and the independence of emergence from environmental variables suggest that understory regeneration is a gradual process that is not strongly regulated by initial seedling density or resource limitation. In contrast, microenvironmental conditions created after the flowering event significantly increased Nothofagus sapling growth and survival. These results suggest that overstory forest regeneration could be enhanced in this temperate forest in the first years after this infrequent bamboo flowering event.

Seed dispersal by a frugivorous marsupial shapes the spatial scale of a mistletoe population

Summary Seed dispersal is considered critical for shaping the spatial structure of plant populations, though little empirical effort has been made to interpret this effect in terms of the scale at which plant species are distributed and cope with environmental heterogeneity. We assessed the spatial role of seed dispersal in Tristerix corymbosus, a mistletoe dispersed exclusively in the temperate forests of Patagonia by the endemic marsupial Dromiciops gliroides. We examined how fruit resource tracking and seed dispersal by the marsupial affects mistletoe recruitment, employing a spatially explicit approach aimed at breaking down the spatial structure of the mistletoe and marsupial populations at different scales. In a single fruiting season, we evaluated the abundance of mistletoe fruits, adult plants, dispersed seeds and recruits (seedlings and saplings), as well as the abundance of marsupials, along a 1500‐m linear transect. Both mistletoe and marsupial abundances were distributed hierarchically in space, with large patches containing smaller ones. Marsupial patchiness matched that of mistletoe fruits, at least at a broad scale within the transect. Marsupial abundance also varied at a large‐scale, being conditioned by habitat features and decreasing progressively along the transect. Mistletoe seed rain accounted for the patchiness of adult plants and fruits, and for the large‐scale pattern of marsupial activity. The spatial pattern of mistletoe recruitment closely matched seed rain. Synthesis. Seed dispersal by marsupials shaped the scale of mistletoe recruitment in two ways. First, marsupials created a spatial match between mistletoe adults and recruits as a result of fruit resource tracking. Second, they generated patchiness in mistletoe offspring at a larger scale than in adults. Dispersal process performed as a strong demographic filter capable of changing the mistletoe spatial structure from adults to recruits, despite a low frequency of far‐from‐adult dispersal events. Similar effects of scale shaping by seed dispersers may be generalized among plants in which there is a sharp spatial match between fruits and frugivores, and whose dispersed seeds have a higher probability of recruiting than undispersed ones.

Gregarious bamboo flowering opens a window of opportunity for regeneration in a temperate forest of Patagonia

Rare gregarious flowering of understorey bamboo species occurs in temperate and subtropical forests around the world, but the ecological consequences of this phenomenon for forest regeneration are not well understood.Field experiments were conducted in an old-growth temperate forest in Patagonia,Argentina after a massive bamboo flowering event, to examine whether light quality and other changes in microhabitats could affect seed germination and growth of overstorey species. Germination of southern beech (Nothofagus obliqua) was positively correlated with red:far red (R:FR) ratios in a range of microhabitats generated by the death of the understorey bamboo (Chusquea culeou). Experimental modification of understorey R:FR ratios to mimic alternative light environments reversed this germination response in plots with senescent understorey, but not in plots with live bamboo. Laboratory incubations demonstrated a significant interaction between R:FR ratios and thermal amplitude in promoting seed germination. Microhabitats also significantly affected the growth of emerged seedlings. Microenvironmental changes generated by this flowering event appear to have opened a window of opportunity for germination and growth of overstorey species.We demonstrate that natural gradients in light quality associated with this ecological phenomenon are a major component affecting forest regeneration in this ecosystem.

El Mantenimiento De La Recolección De Plantas Silvestres Comestibles En Una Comunidad Mapuche De La Patagonia

The Mapuche communities of Argentina and Chile have a vast knowledge of useful plants from temperate forests of Patagonia. However, present processes of transculturation and uprooting seem to have caused a decline in wild plant gathering. This is a case study of a Mapuche community that now lives far away from the forests that their ancestors inhabited. Nineteen families from the Rams Mapuche community (83% of the total population) were interviewed using a semi-structured questionnaire, with the aim of finding out which edible wild species are known and still used, and what factors, according to the people perception, have caused the decline. People mentioned a total of 49 edible wild plants including four types of resources: Araucaria araucana seeds, the fruits and roots of bushes and herbs, and leaves of edible weeds. Factors such as the difficulty access to forests which no longer belong to them, drought and soil deterioration from overgrazing were indicated by people acting negatively on the preservation of the knowledge of plants in the younger generations.