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Helmut Brandl 《Small-Scale Forestry》2006,5(1):145-159
Today the Black Forest is an internationally renowned tourist region in Germany. For centuries the Black Forest remained as
a low mountain range regarded as not suitable for settlement due to its unfavourable climatic conditions and difficult terrain.
Clearing the dense forests and settlement therefore started at a historically late stage compared to other regions of Germany,
about 1000 years ago. Due to the special conditions in this area, the structure of the settlement had to be quite different
to those landscapes with more favourable conditions for agriculture. A single-farm settlement developed, farms situated 200
to 400 m away from each other, surrounded by meadows, agricultural land and forests and owned by the farmer’s family. This
structure has remained in some areas until today; in other areas different types of settlement took place, and great changes
occurred during history. A special type of agroforestry — a slash-and-burn-management of forests — also took place 150 to
200 years ago. 相似文献
4.
Latitudinal shifts in tree species distributions are a potential impact of climate change on forest ecosystems. It has been hypothesized that some tree species may become extirpated as climate change effects may exceed their migration ability. The goal of this study was to compare tree species compositions in northern urban areas to tree compositions in forestland areas in the eastern U.S. as an indicator of the potential for urban trees to facilitate future forest tree species migration. Results indicated that a number of tree species native to eastern U.S. forests of southern latitudes are currently present in northern urban forests. The biomass density (Mg/ha) of urban tree species is typically less than half of forestland densities with the majority of urban tree species found in nearby (<100 km) forestland. Urban tree propagation is often facilitated by humans, whereas the necessary pollinators and agents of tree seed dispersal in forestlands may be lacking regardless of climate change. It is suggested that urban areas may serve divergent, dual roles as both a native tree seed source and refuge for a limited number of forestland tree species, but also a facilitator of non-native tree invasion. 相似文献
5.
Jacqueline W.M. Postma Pål Axel Olsson Ursula Falkengren-Grerup 《Soil biology & biochemistry》2007,39(2):400-408
Colonisation by root endophytes can be beneficial to plants growing on acid, nutrient-poor soils. Arbuscular mycorrhizal (AM) fungi can supply herbs with nutrients and may give protection against aluminium toxicity. Two other root colonising fungi, fine endophytes (FE) and dark septate fungi (DSE), are less well known but are potentially of benefit to their host plant. AM fungi are the most prevalent symbionts in herbs at neutral to acidic soil pH. At extremely low pH, fungal growth can be limited and AM colonisation is usually rare. Fine and dark septate endophytes, on the other hand, have been observed more often under these conditions. In order to relate endophyte colonisation to a gradient in soil pH, we investigated root colonisation by AM, FE and DSE in Maianthemum bifolium, Galium odoratum, Mercurialis perennis and Stellaria nemorum, from a range of acidic beech forests. With decreasing pH, colonisation by AM decreased, whereas the other two endophytes increased. AM and FE colonisation were inversely correlated in Maianthemum bifolium. We compared changes in root colonisation with those in chemical composition of soil and leaf samples and found a positive correlation between leaf magnesium concentrations and the presence of DSE in Galium odoratum. Aluminium concentration in Maianthemum bifolium tended to be lower when FE colonisation was high, suggesting a possible role for the fungi in plant protection against Al. We suggest that FE and DSE may replace AM fungi in herbaceous vegetation at extremely low pH, counteracting some of the negative effects of high soil acidity on plants. 相似文献
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生物炭和堆肥提高西澳大利亚沙质平原土壤上的作物产量但这种效应是短期的 总被引:2,自引:0,他引:2
Sandplain soils on the south coast of Western Australia
have low inherent fertility, which is mainly due to poor
nutrient retention caused by insufficient clay and organic
colloidal material. Previous research has shown the
benefits in nutrient levels and retention from adding clay
to sandplain soils; however, there is almost no information
on the addition of organic amendments. A field experiment
was established at the Esperance Downs Research Station,
Western Australian, in May 2010, to assess the effects of
wheat straw (WS) and chicken manure (CM) biochars and
compost with and without phosphorus (P) addition on soil
properties and crop production over five growing seasons.
The five seasons alternated between winter and summer
crops.~The CM and WS biochar and compost treatments significantly
increased crop yields and P uptake in 3, 2 and 1 of the
five seasons, respectively. The yield increases $(P<0.05)$
were no more than 8\%. By the end of the third season, no
differences in crop yields were found that could be
attributed to the organic amendments. The addition of P
increased crop yields in each winter cropping season.
Phosphorus addition explained more than 30\% of the
variation in crop yields. Despite marginal P levels and
summer drought conditions, arbuscular mycorrhizal root
colonisation was not affected by the organic amendments.
There were no significant interactions between the organic
amendments and P addition in terms of crop yields, P uptake
or P uptake efficiency. We conclude that much of the effect
of the organic amendments was due to direct nutrient
addition which dissipated over time. 相似文献
7.
Evelyn Stokes 《Asia Pacific viewpoint》1999,40(2):137-158
In the mid-1950s Professor R. Gerard Ward carried out his first significant research project as a graduate student in the ‘Taupo country’– a diverse volcanic landscape with a rich Maori history in the central North Island of New Zealand. This paper traces my own ‘journeys’ into the Taupo country and my association with the complexities of both historical and contemporary understandings and realities of Maori land tenure. I use several specific examples, and draw on a variety of experiences to argue that the ‘Taupo country’ cannot be understood without an appreciation of the enduring Maori values which still permeate society and land tenure in New Zealand’s ‘volcanic desert’ landscape. Despite legislative efforts to impose on Maori a title system derived from British property law, and all the subsequent pressures to assimilate, enduring Maori values intertwined with ancestry and identity cannot be ignored either in reconstructions of the history or in current planning for the future of the Taupo region. 相似文献
8.
The Japanese archipelago is a biodiversity hotspot with a unique regional climate influenced by the Asian monsoon circulation, surrounding seas, and complex topography. Japan has numerous mountains and islands, which are potentially vulnerable to climate change. This study evaluated the potential impact of climate change on species diversity in Japan, using 25 conifer tree species as a case study. We applied ensemble models based on generalised additive models, artificial neural networks, generalised boostedmodels, and random forests to species’ locality records at 1 km2 resolution. The results indicated a substantial impact, such that 80% of the species may lose over half of their current climatically suitable areas by 2100. The lower altitudinal range limits were projected to shift upwards by 293 m on average, suggesting that alpine/sub-alpine and sub-boreal species may face widespread local extinctions. The impacts on sub-alpine species may be moderated by assisted migration to the northern island where they currently do not occur. However, climatically suitable areas for these species and sub-boreal species that occur on the island overlapped significantly, indicating that assisted migration may entail the risk of introducing biotic competition or interbreeding. Thus, rugged topography and dispersal barriers between islands are likely to amplify the future impacts of climate change in Japan. Limited areas in the central mountain region were identified as potential bioclimatic refugia, which should be conserved as a priority. 相似文献
9.
Global climate change poses an immense challenge for conservation biologists seeking to mitigate impacts to species and ecosystems. Species persistence will depend on geographic range shifts or adaptation in response to warming patterns as novel climates and community assemblages arise. Assisted colonization has been proposed as a method for addressing these challenges. This technique, which consists of transporting species to a new range that is predicted to be favorable for persistence under future climate scenarios, has become the subject of controversy and discussion in the conservation community due to its highly manipulative nature, questions about widespread feasibility, and uncertainty associated with the likelihood of translocated species becoming invasive. We reviewed the discussion and criticism associated with assisted colonization and sought to identify other conservation techniques that also display potential to promote the colonization and adaptation of species in response to climate change. We propose an integrated conservation strategy that includes management for habitat connectivity, conservation genetics, and when necessary, assisted colonization of species that are still unable to shift their ranges even given implementation of the above standard conservation approaches. We argue that this integrated approach will facilitate persistence for a larger proportion of species than is possible by solely using assisted colonization. Furthermore, a multi-faceted approach will likely reduce the uncertainty of conservation outcomes and will become increasingly necessary for conservation of biodiversity in a changing climate. 相似文献
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