Misplaced Pages

#75924

35-654: The history of the Dyke Ditch was initially closely related to the history of the Sperberhai Dyke. Not until the completion of the dyke in 1734 could large watercourses east of Clausthal be tapped into: the streams of the Großer and Kleiner Gerlachsbach. In the years that followed, the Dyke Ditch was continually extended eastwards. In 1736 it was extended as far as the Kleiner Oker. In 1742, a neighbouring ditch,

70-399: A locator by insects that are attracted by it, such as flies, which may intend to harm the bark beetle itself. These chemicals interact with pine trees as the bark beetle's host, based on the behavioral, physiological, and biochemical effects of monoterpenes. Monoterpenes are a chemical fragrance that plays a significant role in tree-insect interactions, specifically within pine trees. It

105-553: A new natural forest, rich in its variety of species, is now growing in the heart of the Harz National Park. The Wolfswarte , at 918 m above NN , is generally considered as the summit, even if it is not the highest elevation on the Bruchberg. It is a domed hilltop ( Kuppe ) made of weathered Acker-Bruchberg quartzite. The Wolfswarte rises east of the mountain town of Altenau and, in good visibility,

140-428: A number of insecticidal and fungicidal compounds that can kill, injure, or immobilize attacking insects. Sap is one of the first lines of defense of pines against bark beetles. Released sap or resins can plug bored holes of bark beetles and seal wounds. Resins also trap insect pests making some initial entry by bark beetles unsuccessful. Chemical compounds can also be induced by tree species that bind with amino acids in

175-576: A tree and lay their eggs in the phloem of the tree. This usually occurs in mid to late summer. Once the eggs hatch, the larvae then live in the tree, feeding on the living tissues below the bark, often leading to death of the tree if enough larvae are present. At the end of the larval stage, chambers are usually constructed for the pupae to overwinter until they are ready to emerge as an adult. Bark beetles are distinct in their morphology due to their small size and cylindrical shape. Bark beetles also have small appendages, with antennae that can be folded into

210-594: Is also known as the Upper Bruchberg Way or Oberer Bruchbergweg ) runs past Okerstein in a fairly straight line up to the Wolfswarte . This track is linked by several lateral tracks to the Steile Wand road ( Steile-Wand-Straße ) from Altenau to Torfhaus. The easiest way to get to the Wolfswarte is to take the last lateral track at a height of about 760 m, shortly before the first carpark on

245-494: Is an aggregation pheromone that attracts insects to the plant/ tree host, including the bark beetle. Monoterpenes has also been known to prevent fungal growth and are also toxic to bark beetles at high vapor concentrations. This latter process demonstrates a defense of pines using monoterpenes against the bark beetle. There are around 6,000 described species of bark beetles in 246 genera, placed into 26 distinct tribes . Bark beetles are most commonly recognized by their impact on

280-497: Is not on the summit, but about 200 metres down the hill to the southwest on the Wolfswarte Weg . Bark beetle Cortylini Cryphalini Crypturgini Dryocoetini Hylastini Hylesinini Hylurgini Hypoborini Ipini Phloeosinini Phloeotribini Polygraphini Scolytini Scolytoplatypodini Taphrorychini Thamnurgini Tomicini Xyleborini Xyloterini A bark beetle

315-468: Is the Harzwasserwerke . The Dyke Ditch draws its water from the region of six Harz rivers: The Dyke Ditch system crosses several watersheds as a result. The Dyke Ditch today is 19 km long. 15.4 km of that are open ditches and 3.6 km are underground water tunnels. Depending on how they are counted, its associated ditch system has an overall length of 49 km. On most routes

350-539: Is the common name for the subfamily of beetles Scolytinae . Previously, this was considered a distinct family ( Scolytidae ), but is now understood to be a specialized clade of the "true weevil " family ( Curculionidae ). Although the term "bark beetle" refers to the fact that many species feed in the inner bark (phloem) layer of trees, the subfamily also has many species with other lifestyles, including some that bore into wood, feed in fruit and seeds, or tunnel into herbaceous plants. Well-known species are members of

385-406: Is the spruce ips Ips typographus . A tiny bark beetle, the coffee berry borer , Hypothenemus hampei is a major pest on coffee plantations around the world. Bark beetles go through four stages of life: egg, larvae, pupae, and adult, with the time to develop often relying on the species as well as the current temperature. While there is variation among species, generally adults first bore into

SECTION 10

#1732797901076

420-873: The Brocken can be seen from here. The bald summit of the Wolfswarte is easily visible from other peaks in the area, notably the Glockenberg in Altenau, the Schulenberg and also from the Torfhaus. To the southwest the heights of the Bruchberg are continued by the Acker Ridge with its mountain hut , the Hanskühnenburg . From Altenau the Wolfswarte Way ( Wolfswarter Weg ; its upper section

455-555: The Steile Wand road and then to branch off after a few hundred metres onto the rather rough track, the Butterstieg , which is not suitable for cyclists. From Torfhaus there is a longer, but more direct route to the Wolfswarte which is about 4 km long. This is also not very suitable for bicycles. Since 2007 the Wolfswarte has been a checkpoint on the Harz Walking Route ( Harzer Wandernadel ). The checkpoint

490-778: The Upper Harz is the second highest mountain in Lower Saxony and the third highest in the Harz mountains in North Germany. It lies between Altenau and Torfhaus in the middle of the Harz National Park . The Bruchberg is more like a plateau and has no real summit. This plateau is partly covered with trees, but on the sunny southern slopes the trees have largely died as a result of bark beetle infestation (see photograph below). Following this insect destruction,

525-476: The extant mostly Neotropical genus Microborus is also known from the Cenomanian aged Burmese amber of Myanmar. Bark beetles are preyed upon by birds such as woodpeckers , other beetles such as the black-bellied clerid ( Enoclerus lecontei ) and certain other members of family Cleridae , flies such as the long-legged flies (Dolichopodidae), and certain phoretic mites. Phoretic mites use

560-411: The mountain pine beetle ( Dendroctonus ponderosae ), do attack living trees, many bark beetle species feed on weakened, dying, or dead spruce, fir, and hemlock. Most restrict their breeding area to one part of the tree: twig, branch, stem, or root collar. Some breed in trees of only one species, while others in numerous species of tree. In undisturbed forests, bark beetles serve the purpose of hastening

595-702: The type genus Scolytus , namely the European elm bark beetle S. multistriatus and the large elm bark beetle S. scolytus , which like the American elm bark beetle Hylurgopinus rufipes , transmit Dutch elm disease fungi ( Ophiostoma ). The mountain pine beetle Dendroctonus ponderosae , southern pine beetle Dendroctonus frontalis , and their near relatives are major pests of conifer forests in North America. A similarly aggressive species in Europe

630-753: The Clausthal Flood Ditch, the Flörichshai Ditch and Abbe Ditch enabled water from east of the Bruchberg and the western Brocken to be made available for the Upper Harz mines. Yet another extension would have been possible but was no longer discussed. Now, attempts were made to fundamentally solve the energy problem in the Upper Harz mines by building deeper drainage adits (such as the Ernst August Adit). In addition from

665-729: The Morgenbrodtstal Ditch, was built to carry water from the Große and Kleine Söse rivers to the Dyke Ditch. In 1774, it was lengthened as far as the so-called Wiege ("scales") on the Dyke Ditch and in 1820, after the two Kellwasser tunnels had been driven and the Blochschleife Ditch laid, the Kellwasser and the Blochschleife were connected to the Dyke Ditch system. The last addition was made in 1827, when

700-686: The Sperberhai Dyke to the Clausthal Plateau. That made it one of the most important lifelines in the Upper Harz mining region. Following the closure of the mines the Dyke Ditch supplied water up to about 1978 for the generation of electricity in Kaiser Wilhelm Shaft. Since 1978 the water of the Dyke Ditch has been led to the Mönch valley of the Oker Reservoir at the end of the Dyke Ditch, where it still drives turbines for

735-582: The bark beetle to move from one location to the next, but some of these mite species also prey on the eggs or larvae of the bark beetles or act as parasites. The braconid wasp Spathius canadensis is known to parasitize the native elm bark beetle Hylurgopinus rufipes . Some bark beetles form a symbiotic relationship with certain Ophiostomatales fungi , and are named " ambrosia beetles ". The ambrosia beetles (such as Xyleborus ) feed on fungal "gardens" cultivated on woody tissue within

SECTION 20

#1732797901076

770-455: The body and large mandibles to aid in the excavation of woody tissue. The legs of most bark beetles are very short and can be retracted or folded into the body. The combination of their shape and appendages greatly helps in the excavation of woody tissue. The eyes are also flattened and hypothesized to help see in low-light conditions. Bark beetles feed and breed between the bark and the wood of various tree species. While some species, such as

805-488: The fact that these rising temperatures provide the optimal conditions for larval growth, the development time that the larvae need to become an adult also drops, from 8–9 weeks to 6–7 weeks. As a third the result of global warming, the breeding season of the bark beetle is extended, meaning that number of generations per year will increase. All these factors contribute to an increasing amount of bark beetles and will thus likely result in an increasing frequency of infestations. In

840-480: The generation of electricity and is then made available for the drinking water supplies of the Harzwasserwerke . Until about 2000, the Dyke Ditch also provided drinking water to the mining town of Altenau . This has since been withdrawn because the natural water supply was very unreliable, especially in winter and the quality of the water could also change very quickly. The operator of the Dyke Ditch today

875-475: The gut of bark beetles, reducing their ability to process woody materials. When in large quantities, the sheer number of beetles can overwhelm the tree's defenses with resulting impacts on the lumber industry , water quality, fish and wildlife, and property values. The oldest known member of the group is Cylindrobrotus from the Early Cretaceous ( Barremian ) aged Lebanese amber . A species of

910-411: The lumber industry. Massive outbreaks of mountain pine beetles in western North America after about 2005 have killed millions of acres of forest from New Mexico to British Columbia . Bark beetles enter trees by boring holes in the bark of the tree, sometimes using the lenticels , or the pores plants use for gas exchange, to pass through the bark of the tree. As the larvae consume the inner tissues of

945-460: The maintenance overhead and winter operations, the increase in incline (the same drop being covered in a shorter distance) played an important role in increasing the hydraulic capacity. The water tunnels, built around 1850, were the Rothenberg, Coventhai, Dietrichsberg and Bielenwiese Tunnels. During its middle years the Dyke Ditch could carry up to 13 million cubic metres of water per year over

980-425: The past, fire has been suggested as potential mechanism for controlling bark beetle populations; however, most studies of wildfire after beetle outbreaks have found no effect of beetle-caused tree mortality on wildfire size or severity. Bark beetles can also be transporters of different plant pathogens such as cankers. The transport of the pathogens also result in the increase of fungi, mites and nematodes within

1015-440: The recycling and decomposition of dead and dying wood and renewing the forest. However, a few species are aggressive and can develop large populations that invade and kill healthy trees and are therefore known as pests . Bark beetles often attack trees that are already weakened by disease , overcrowding, conspecific beetles, or physical damage. In defense, healthier trees may produce sap, resin or latex , which often contains

1050-450: The reliance on the fungi for food and the fungi's ability to overcome some of the plant's chemical defenses. While the majority of ambrosia beetles infect dead trees, several species will infect trees considered healthy or under stress. The bark beetle's pheromones , including kairomones , can attract other insects. The pheromones distinguished as kairomones are hormones, pheromones, or allomones of bark beetles, which in turn are used as

1085-427: The second half of the 19th century other forms of energy (steam engines) were brought into operation, initially alongside water power. In the middle of the 19th century work was carried out to optimise water flow in area of the 10 km long section between Sperberhai Dyke and Clausthal. By cutting tunnels, several ditch detours around mountains were able to be shortened considerably. In addition to clear advantages in

Dyke Ditch - Misplaced Pages Continue

1120-478: The tree, they often consume enough of the phloem to girdle the tree, cutting off the spread of water and nutrients. Ambrosia beetles are also known to aid in the spread of pathogens, such as diseases that can cause cankers , further damaging the trees they infect. Like many other insects, Scolytinae emit pheromones to attract conspecifics , which are thus drawn to trees already colonized by bark beetles. This can result in heavy infestations and eventually death of

1155-640: The tree. Many are also attracted to ethanol produced as a byproduct of microbial growth in the dead woody tissues. Increases in international trade, as well as the use of wood containers for storage, has aided numerous species of bark beetle in spreading across the world. They are also extremely adaptable and able to quickly spread through new environments, as seen in France with eleven different species. Bark beetle infestations are also predicted to increase with global warming , meaning infestations will most likely increase in frequency as temperatures rise. Besides

1190-427: The tree. Ambrosia beetles carry the fungal spores in either their gut or special structures, called mycangia , and infect the trees as they attack them. Once a beetle chooses a tree, they release spores of this fungus along tunnels within the tree. These spores grow and eventually produce fruiting structures to be consumed by the beetles. This can allow for ambrosia beetles to indirectly feed from more tree species due to

1225-540: The water descends by around 60 m. Its flow rate reaches a maximum of about 1 m/s. A footpath from Osterode to Thale , the Harzer Hexenstieg ("Harz Witches' Climb"), runs along the Dam Ditch. 51°48′10″N 10°30′12″E  /  51.80278°N 10.50333°E  / 51.80278; 10.50333 Bruchberg At 927 m above  sea level (NN) , the Bruchberg in

#75924