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Lewis Clifford E. Burton Glenn W. Monson Warren G. McCormick W. C. 《Agroforestry Systems》1983,1(4):277-297
Agroforestry Systems - Native forages of southern United States are frequently low in nutrients and poorly digestible, while improved pastures are the opposite. Since this area produces rapid... 相似文献
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为研究茂名小良水保站桉树的化学成分,测定了小良5种桉树的8种营养元素的含量,其中K、Ca、Mg、Cu、Fe、Mn、Zn的含量采用火焰原子吸收光谱法进行测定,P含量采用钼酸铵分光光度法测定。结果表明：同一品种桉树同一器官中各营养元素含量比较,四种大量营养元素含量总体表现为K>Ca>Mg>P,四种微量营养元素含量绝大部分植物以Mn含量最高,Cu含量最低;四种大量元素P、K、Ca、Mg含量都表现为叶最大,枝次之,根和干中的含量较小;而四种微量元素Cu、Fe、Mn、Zn在植物各器官含量的高低排序缺乏一致规律;不同种桉树间的营养元素含量差别总体上缺乏一致规律。 相似文献
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In the United States, diseased oaks (Quercus species) exhibit tip blight, branch and stem cankers, and dieback often attributed to Diplodia species or related fungi. Emergence of Diplodia corticola as a pathogen of European oaks, and reports of this fungus in the eastern and western United States, prompted re‐examination of strains from Wisconsin. These had been obtained in the late 1990s and early 2000s and previously identified only as Diplodia species. Nuclear ribosomal ITS sequences were obtained from the Wisconsin strains and analysed with other sequences from GenBank. Wisconsin strains confirmed as D. corticola were from northern red oak (Q. rubra), black oak (Q. velutina), white oak (Q. alba) and bur oak (Q. macrocarpa). Other strains from oaks in Wisconsin were D. mutila and D. seriata. Wound inoculation of northern red, white and bur oak seedlings with D. corticola in a greenhouse resulted in shoot death and stem lesions, from which the pathogen was reisolated. We conclude that D. corticola has been present in the northcentral United States for at least two decades and report two previously unrecognized hosts of this pathogen: white oak and bur oak. The roles of D. corticola, related fungi and influences of other environmental factors in deterioration of oak health in North America merit additional investigation. 相似文献
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Uluguru forests are globally recognized as important biodiversity hotspots, but anthropogenic pressure threatens their value. This study examined species diver-sity, abundance, and structure of trees i... 相似文献
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We summarized the status of wolves (Canis lupus), elk (Cervis elaphus), and woody browse conditions during the 20th century for the upper Gallatin elk winter range in southwestern Montana, USA. During this period, wolves were present until about the mid-1920s, absent for seven decades, and then returned to the basin in 1996. A chronosequence of photographs, historical reports, and studies indicated willows (Salix spp.) along streams became heavily browsed and eventually suppressed following the removal of wolves, apparently due to unimpeded browsing by elk. However, after wolf establishment in 1996, browsing intensity on willows lessened in some areas and we hypothesized that, at both a landscape and fine scale, browsing pressure reflects terrain configurations influencing predation risk (nonlethal effects), in conjunction with lower elk densities (lethal effects). We measured browsing intensity and heights of Booth willow (S. boothii) along 3000 m reaches of the Gallatin River and a tributary to examine the potential influence of wolf/elk interactions upon willow growth. Where the Gallatin Valley is relatively narrow (high predation risk), willows began releasing in 1999 and by 2002 were relatively tall (150–250 cm). In contrast, willow heights along a wider portion of the Gallatin Valley, along the open landscape of the tributary, and an upland site (all low predation risk) generally remained low (<80 cm). We identified terrain and other features that may contribute to the perceived risk of wolf predation, by elk for a given site. Although alternative mechanisms are discussed, changes in willow communities over time following wolf removal and their subsequent reintroduction were consistent with a top-down trophic cascade model involving nonlethal and possibly lethal effects. If similar top-down effects upon vegetation hold true in other regions of North America and other parts of the world where wolves have been extirpated, wolf recovery may represent a management option for helping to restore riparian plant communities and conserve biodiversity. 相似文献
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广州从化市江埔风水林主要群落类型及其多样性初步研究 总被引：1，自引：1，他引：0
基于广州从化江埔地区的5个群落类型9个400m^2的样地数据,对该地区风水林的植物群落结构及其物种多样性特征进行了初步研究。结果显示：9个风水林群落样方中,共统计有维管植物96种,隶属于48科。群落类型主要有荷木林、藜蒴林、中华锥林、黄桐林和黄樟林,乔木层常见树种为荷木（SchimaSU—perba）、藜蒴（Castanopsisfissa）、中华锥（Castanopsischinensis）、黄桐（Endospermumchinense）、黄樟（Cinnamo—mumparthenoxylon）等;灌草层以罗伞树（Ardisiaquinquegona）、九节（Psychotriaasiatica）、疏花卫矛（Euonymuslaxiflorus）、华山姜（Alpiniachinensis）、半边旗（Pterissemipinnata）等植物为优势种。乔木层多样性指数从大到小依次为荷木林〉中华锥林〉黄桐林〉黄樟林〉藜蒴林,灌草层多样性指数由大到小依次为中华锥林〉黄桐林〉荷木林〉黄樟林〉藜蒴林。藜蒴林群落乔木层和灌草层种类较单一,生物多样性较低。 相似文献
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Seeds of Celtis australis were collected from 13 different sources, ranging from 550 to 1980 masl, in Central Himalaya, India. Significant (p = 0.05) variations were observed for seed traits among provenances. However, among various characters, seed weight exhibited
maximum variation between seed populations compared to other morphological characters. Between provenances, seed weight ranged
from 47.8 to 83.1 g/1000 seed, with mean value of 66.9 ± 10.7 g/1000 seed. Significant (p = 0.01) positive correlation was found between morphological characters of seeds including seed weight and elevational range
of seed source. For one year old seedlings, average shoot and root growth was 61.1 ± 13.3 and 30.5 ± 5.4 cm, respectively,
irrespective of provenance variation. Inter-comparing biomass yield of the seedlings with altitude, average biomass production
was 8.4 ± 2.5, 9.4 ± 3.3 and 12.7 ± 1.7 g/plant, respectively, for low (550–1000 masl), middle (1050–1250 masl) and high (1350–1980 masl)
altitudinal populations. Significant (p = 0.01) positive correlation between growth performance of seedlings and altitude of the seed source was recorded. Across
the provenances, shoots had the highest proportion of total biomass (42.3%), followed by leaves (32.6%) and roots (24.6%).
Among various provenances, Badiyargaon, Agroda, Guptakashi, Jakholi, Gajeli, Srinagar and Palampur populations produced heavier
seedlings and grew faster compared to seedlings of other sources. 相似文献
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A survey was conducted to determine richness of Vascular Endemic Plants of the Uluguru Mountains in Morogoro, Tanzania. Strict and near-endemic species were identified and their habits, habitats and altitudinal ranges were indicated. About 108 strict endemic plant species were identified in the Uluguru Mountains. Most of the endemic species are shrubs followed by herbs, trees and climbers, and are confined to the families Rubiaceae (38 species in 11 general), Orchidaceae (13 species in 7 general) and Balsaminaceae (11 species in 1 genus). The major habitat for endemic species is the montane rain forest on the windward side ranging between 1200 and 2450 m a.s.l. The major areas where the Uluguru endemics are concentrated are the forests of Bondwa/Lupanga followed by Lukwangule/Chenzema and then Bunduki and Mgeta. These areas are therefore the major hotspots for the endemism in the Uluguru Mountains. The information presented in this paper will contribute to the conservation and management of the biodiversity of the Uluguru Mountains. 相似文献
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We quantified species diversity of birds in mangroves at Kundapura from April-2010 to March-2013. We recorded 79 species of 36 families and 14 orders. Of these 71% are resident species, 22% are residential migrants and 8% are migratory. One endangered species, three near threatened species, and a few occasional visitors were re-corded. Species diversity and abundance of birds were greater during from October through May as there was availability of food, increased vegetation and the arrival of migratory birds. Minimum diversity was recorded from June through September owing to heavy rains, increased flow of water, limited availability of food and return of migratory birds. 相似文献
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Field studies of damage and mortality were carried out through 16 years in six young plantations, mostly of Pinus contorta, but also P. sylvestris and P. sibirica. Differences between pine species, P. contorta provenances, sites, and soil treatments are reported and discussed, as are influences of environment, climatic conditions, snow cover, and nutrient deficiency. Gremmeniella abietina was by far the most important cause of mortality; there were great differences between the sites as to development and seriousness. Other important causes of mortality and damage were Phacidium infestans, elk (Alces alces L.), voles, and snow pressure. 相似文献
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Sarah Taylor Lovell V. Ernesto Mendez Daniel L. Erickson Chloe Nathan S’ra DeSantis 《Agroforestry Systems》2010,80(2):153-171
Agroecosystems can serve as multifunctional landscapes when treed habitats such as woodlots, hedgerows, riparian buffers,
windbreaks, and orchards, are conserved on farms. We investigated the extent, pattern, and multifunctionality of on-farm treed
habitats for 16 Vermont farms in the Lamoille watershed of the Lake Champlain Basin. The site was selected because the land
use pattern is representative of the region, containing a mixture of agriculture and forest in different habitat types. We
used a GIS-based approach to delineate treed habitats on farms and conducted semi-structured interviews with farmers to explore
their perception of the functions of treed habitats. Through an evaluation of the relationship between farm characteristics
and spatial attributes of treed habitats, we found farm size to be an important variable. Larger farms had more land in treed
habitats, while the pattern of these habitats was more complex on smaller farms. Average elevation of the farm, an indicator
of biophysical conditions, was a stronger predictor of the extent of treed habitats than farm characteristics. From interviews,
we found that farmers benefited from alternative forest products, both for direct consumption and sale, including firewood,
timber, maple sugar, edible fruits and nuts, and wood crafts. Most farmers also recognized cultural and ecological functions
provided by treed habitats. These results have implications for developing policies to promote the conservation of treed habitats,
considering the preferences of the landowner or farmer. 相似文献
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Setting monitoring transect in the middle and shallow water area(altitude 156-172 m) in Three Gorges reservoir hydro-fluctuation belt to research the changing characteristics of the contents of N, P,K,pH and organic matter of the soil which experienced the influence of fluctuation the first time. The results showed that by the influence of water level fluctuating,contents of soil N,P,K,pH and organic matter had reduced in different soil layers in hydro-fluctuation belt.The available N decreased by 41.53%-59.87%,available P decreased by 5.26%- 36.76%,available K decreased by 3.55%-45.56%, total N decreased by 9.52%-40.00%,total P had no change generally,total K had decreased a little, content of organic material decreased by 7.62%- 37.83%%,pH value turned to neutral,changed by 1.73%-9.58%. 相似文献
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P. Felker C.T. Sorensson D. Ueckert P. Jacoby E. Singer R. Ohm 《Agroforestry Systems》1998,42(2):159-179
Seventy seedlots of Leucaena leucocephala, L. pallida, L. diversifolia, L. retusa, L. esculenta, L. confertifolia, L. greggii
and L. pulverulenta and various hybrid combinations were examined for survival to freezing weather, biomass production, leaf
protein content and in vitro dry matter digestibility in Texas. Three sites along a 600 km north-south transect were chosen
to provide a wide range in exposure to freezing weather. The minimum temperature on the warmer Three Rivers site was −7 °C
while the minimum temperatures on the colder Vernon site was −14 °C. At the Three Rivers site where −7 °C temperatures occurred
and where forage production was a priority and some winter frost damage was not a problem, L. leucocephala K636 and hybrids
containing L. diversifolia and L. pallida have the most promise. If total lack of damage to −7 °C is essential, species such
as L. retusa, L. pulverulenta (seedlot 61, 62) and hybrids such as L. retusa × L. greggii (53) and L. retusa × L. pulverulenta
(55) have the greatest potential. This study examined only one family from each of the cold-hardy species as a parent in the
promising hybrids. As extensive intraspecific genetic variation is present within these leucaena species there is great potential
to find hybrids with much better combinations of cold hardiness, forage production, leaf protein and dry matter digestibility.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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几种城市绿化树种叶片中铅砷铬镉汞元素的含量特征 总被引：10，自引：6，他引：4
2003年对昆明、思茅、丽江3个城市的16个绿化树种叶片中的铅、砷、铬、镉、汞5种重金属元素的含量进行了测定，并结合采集地的空气污染指数进行了相关分析。结果表明：麻栗坡含笑、山玉兰和杜英叶片中Pb的含量与空气污染指数间的相关性显著；石楠、云南拟单性木兰、山玉兰、冬樱花叶片中As的含量与空气污染指数间的相关性达显著或极显著水平；杜英、山玉兰、石楠、天竺桂、云南拟单性木兰叶片中Cr的含量与空气污染指数间的相关性均为显著和极显著；石楠、杜英、冬樱花叶片中Cd的含量与空气污染指数间有显著或极显著的正相关性；8个树种叶片中Hg的含量与污染指数间均没有显著的正相关性。而16个树种中，冬樱花叶片中5种重金属元素的总含量最大，为15．563mg／kg；总含量最低的树种是竹柏（0．692mg／kg）等，两者总含量的差异达14．871mg／kg。不同树种对环境中Pb、As、Cr、Cd、Hg等5种元素的吸收富集能力有较大的差异。16个树种叶片中Cd和Cr含量的相关系数为r0.05=0．582^＊，说明Cr与Cd之间有显著的互相促进作用；Cd与Hg元素含量的相关系数为r0.01=0．807^＊＊，也表明Cd与Hg间有十分显著的互相促进的作用。 相似文献
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