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Vegetationsdynamik verlandeter Biberteiche auf der Insel Navarino (Feuerland-Archipel, Chile)
(2009)
Die vorliegende Fallstudie veranschaulicht die Auswirkungen des invasiven Nordamerikanischen Bibers (Castor canadensis) auf den autochthonen Nothofagus-Wald der ca. 2500 km2 großen Insel Navarino im Feuerland-Archipel (Archipiélago de Tierra del Fuego), Chile. Dazu wurden auf den Sukzessionsflächen verlandeter Biberteiche (1) Diversität (absolute Artenzahl, mittlere Artenzahl, Artendichte, Shannon-Wert und Evenness), (2) Artenzusammensetzung, (3) Anteil gebietsfremder Pflanzenarten. (4) Baumartenzusammensetzung, (5) Dichte, (6) Stammdurchmesser und (7) die Wuchshöhe der Gehölzverjüngung untersucht. Die Ergebnisse zeigen auf den Sukzessionsflächen eine deutliche Zunahme der Diversität mit Ausnahme der mittleren Artenzahl. Die ehemaligen Biberteiche zeichnen sich durch eine charakteristische Artenzusammensetzung aus, die insbesondere durch Weide- und Überschwemmungszeiger bestimmt wird und sich erheblich von biberfreien Waldflächen unterscheidet. Der Anteil gebietsfremder Pflanzenarten variiert stark, wofür noch keine Determinanten festgestellt werden konnten. Im Unterschied zu von Bibern unbeeinflussten Nothofagus-Wäldern wird die Verjüngung auf den Sukzessionflächen von Nothofagus antarctica dominiert. Es wurden folgende fünf Faktoren identifiziert, die als wesentliche Steuergrößen für die Etablierung von Nothofagus in Betracht gezogen werden können: (1) relative Lage des Spenderbiotops, (2) Vorkommen von Totholz, (3) Beweidung, (4) Konkurrenz und (5) Überschwemmung.
Roads contribute to habitat fragmentation and function as dispersal barriers for many organisms. At the same time many nonnative plant species are associated with road systems, a relationship that has been explained by the availability of disturbed habitats along roadsides and traffic-mediated dispersal of species. By studying secondary wind dispersal (SWD) over paved ground in an urban road corridor, we add the perspective of corridor-specific, but traffic-independent dispersal processes to the complex dispersal systems along roads. We analyzed (1) the seed shadow of an invasive tree Ailanthus altissima along a sidewalk subsequent to a strong wind and (2) the movements of painted samaras of this species released at ground level at the same site to identify the functioning of SWD. For the first experiment, we searched for samaras in the vicinity of an isolated tree three days after a strong wind. For the second experiment, we tracked the movement of the released samaras repeatedly over a period of 9–11 days, approximated probability-distance functions to the frequency distribution of samaras along the transect for different times after release, and related nearby measured wind data to changes in dispersal kernels. Single samaras from an isolated tree formed a seed shadow that extended for a distance of up to 456 m, and fragments of fruit clusters traveled up to 240 m. Forty-two percent of the sampled samaras were moved >100 m. The second experiment revealed that painted samaras released on the ground were moved up to 150 m over the pavement. Dispersal distances increased with time after seed release. A wider distribution of diaspores over the transect was significantly related to higher wind sums. Habitat shifts to safe sites for germination occurred during SWD, and different types of pavement influenced these processes. Smooth-surfaced pavement enhanced SWD, while cobbles with irregular surfaces slowed down or terminated SWD. During the observation period, 17% of released samaras accumulated in patches with a planted tree. Some were recaptured within the median strip and thus must have been lifted and moved over four lanes of heavy traffic. Our results suggest that impervious surfaces within road corridors can function as powerful avenues of wind-mediated long-distance dispersal and may counteract fragmentation of urban habitats. This also offers a functional explanation for the invasion success of Ailanthus at isolated urban sites.
Climate change may alter the distribution and activity of native and alien pathogens that infect trees and, in severe cases, cause tree death. In this study, potential future changes in climate suitability are investigated for three forest pathogens that occur in western North America: the native Arceuthobium tsugense subsp tsugense, hemlock dwarf mistletoe, and two alien invasive species, Dothistroma septosporum, the cause of red band needle blight or Dothistroma needle blight, and Phytophthora ramorum, the cause of sudden oak death or ramorum blight. Specifically, the software CLIMEX is used to calculate Cold-Stress, Heat-Stress, and Dry-Stress indices for each pathogen in 98,224 grid cells in North America. Downscaled climate projections from the general circulation models CGCM1, CSIROMk2, and HadCM3 drive forecasts for 2020, 2050 and 2080. These climate projections are then analyzed to forecast shifts in the geographic extent of abiotic stresses that are severe enough to directly kill pathogen propagules and prevent year-round establishment of these pathogens. Cold stress currently has a major impact on climate suitability for all three pathogens; heat stress is likely to become more significant in the future. I forecast that the geographic extent of cold stress will decline from its current levels by a constant 5% (} 1%) of all grid cells in each 30-yr projection horizon for all three pathogens. Forecasts suggest the extent of heat stress will increase concurrently by 4% (+/- 1%) in each 30-yr projection horizon. Drought stress shows no consistent trend over time. No disproportionate effect of climate change on the two alien invasive pathogens over the native is forecasted. These results suggest that forecasts of future climate suitability for pathogens based on historical climate normals are accurate for less than 30 yrs. Adaptive management strategies in forestry will be needed to respond as these changes unfold.
Invasions by non-native species are a threat to biodiversity because invaders can impact native populations, communities and entire ecosystems. To manage this threat, it is necessary to have a strong mechanistic understanding of how non-native species affect local species and communities. We reviewed 259 published papers (1972–2012) that described field experiments quantifying the impact of aquatic nonnative species, to examine whether various types of study biases are limiting this understanding. Our review revealed that invasion impacts had been experimentally quantified for 101 aquatic non-native species, in all major freshwater and marine habitats, on all continents except Antarctica and for most higher taxonomic groupings. Over one-quarter (26%) of studies included tests for impacts on local biodiversity. However, despite this extensive research effort, certain taxa, habitats and regions remain poorly studied. For example, of the over one hundred species examined in previous studies, only one was a marine fish and only six were herbivores. Furthermore, over half (53%) of the studies were from the USA and two-thirds (66%) were from experiments conducted in temperate latitudes. By contrast, only 3% of studies were from Africa and <2% from high latitudes. We also found that one-fifth (20%) of studies were conducted in estuaries, but only 1% from coral reefs. Finally, we note that the standard procedure of pooling or not reporting non-significant treatments and responses is likely to limit future synthetic advancement by biasing meta-analysis and severely limiting our ability to identify non-native species with none or negligible ecological impacts. In conclusion, a future focus on poorly-studied taxa, habitats and regions, and enhanced reporting of results, should improve our understanding and management of impacts associated with aquatic non-native species.
Bostrichidae (Coleoptera) are a family of beetles with specialized xylophagous feeding habits that allow consumption of dry woody plant tissues. Bostrichids are often polyphagous and therefore pose a significant threat to many agricultural and forestry products, particularly in tropical regions. Bostrichids are commonly detected in solid wood packaging material at in ternational ports of entry. Notably, Sinoxylon anale Lesne has been intercepted in wood crates and pallets worldwide and has now become established in Brazil. This paper reports the first documented establishment of S. anale in Brazil, being found both in domestic wood pallets and within native forest and monoculture. The origin of these populations remains uncertain, but introductions through infested wood packaging at ports of entry is a likely scenario. Similarly, the exact time of establishment is unknown. Given that S. anale adults are attracted to light and ethanol, trapping using light or ethanol could be used in monitoring surveys. This species typically infests dead or decaying woody material, and therefore does not pose a direct threat to healthy, live trees. Although more common in tropical regions, S. anale has exhibited some adaptability to temperate climates, which may allow it to spread across the tropical and subtropical regions of Brazil and potentially to other parts of South America.
ZooBank registration. urn:lsid:zoobank.org:pub:9B47075B-AC63-4AA4-AFB6-E2689346CC11
An updated list is given of 25 species of soft scale insects (Hemiptera: Coccidae) which have been intercepted on plants imported into South Korea during the period of 1996 to 2021. Information on the number of interceptions, host plants, distribution and origin of species intercepted at South Korean ports of entry is provided. In addition, data on intercepted species was analyzed to determine potential invasive species of soft scales that could threaten South Korean plants.
ZooBank registration. urn:lsid:zoobank.org:pub:4EB0B411-5611-4F24-B004-922E76F024DD