scholarly journals The shape of things to come: woodland herb niche contraction begins during recruitment in mesic forest microhabitat

2010 ◽  
Vol 278 (1710) ◽  
pp. 1390-1398 ◽  
Author(s):  
Robert J. Warren ◽  
Mark A. Bradford
Keyword(s):  
Biotic Interactions ◽  
Natural Abundance ◽  
Early Life Stages ◽  
Plant Populations ◽  
Mesic Forest ◽  
Woodland Herb ◽  
Physiological Tolerances ◽  
Woodland Herbs ◽  
Resource Levels ◽  
To Come

Natural abundance is shaped by the abiotic requirements and biotic interactions that shape a species' niche, yet these influences are rarely decoupled. Moreover, most plant mortality occurs during early life stages, making seed recruitment critical in structuring plant populations. We find that natural abundance of two woodland herbs, Hexastylis arifolia and Hepatica nobilis , peaks at intermediate resource levels, a pattern probably formed by concurrent abiotic and biotic interactions. To determine how this abundance patterning reflects intrinsic physiological optima and extrinsic biotic interactions, we translocate adults and seeds to novel locations across experimentally extended abiotic gradients. These experiments indicate that the plant distributions probably reflect biotic interactions as much as physiological requirements, and that adult abundance provides a poor indication of the underlying niche requirements. The positive response exhibited by adult transplants in the wettest conditions is offset by increased fungal attack on buried seeds consistent with peak natural abundance where soil moisture is intermediate. This contraction of niche space is best described by Connell's model—species are limited by physiological tolerances where resources are low and biotic interactions where resources are high.

scholarly journals Effects of Forest Cover on Fruit Set in the Woodland Herb, Maianthemum canadense (Liliaceae)

2008 ◽  
Vol 122 (3) ◽  
pp. 234 ◽  
Author(s):  
Hisatomo Taki ◽  
Peter G. Kevan ◽  
Yuichi Yamaura
Keyword(s):  
Forest Cover ◽  
Spatial Scales ◽  
Plant Populations ◽  
Multiple Spatial Scales ◽  
Natural Landscapes ◽  
Woodland Herb ◽  
Woodland Herbs ◽  
Maianthemum Canadense ◽  
Local Extirpation ◽  
Animal Pollination

Animal pollination has been recognized as an essential ecosystem function that is potentially under various environmental stresses. We investigated the landscape effects of forest cover at multiple spatial scales on the sexual reproductive success of a common woodland herb in North America, Maianthemum canadense. This species is a self-incompatible species and pollinated by insects requiring natural landscapes. Nine populations were selected in deciduous forests within agricultural fields of southern Ontario, Canada. We investigated whether fruiting success decreases as forest cover surrounding the plant populations increases at the landscape scale. Forest cover was quantified by the proportion of forest within six different radii from 250 to 1500 m. Analyses showed relationships with the proportion of forest at 750- and 1000-m radii and fruiting success in populations of M. canadense. These findings suggest potential local extirpation of M. canadense and indicate that forest loss can negatively impact on even some common woodland herbs.

Multiple feedbacks due to biotic interactions across trophic levels can lead to persistent novel conditions that hinder restoration.

2020 ◽  
pp. 402-420
Author(s):  
Stephanie G. Yelenik ◽  
Carla M. D'Antonio ◽  
Evan M. Rehm ◽  
Iain R. Caldwell
Keyword(s):  
Species Interactions ◽  
Native Species ◽  
Biotic Interactions ◽  
Terrestrial Ecosystems ◽  
Trophic Levels ◽  
Native Grasses ◽  
Positive Feedbacks ◽  
Mesic Forest ◽  
Management Context ◽  
Multiple Challenges

Abstract Unlike traditional successional theory, Alternate Stable Equilibrium (ASE) theory posits that more than one community state is possible in a single environment, depending on the order that species arrive. ASE theory is often invoked in management situations where initial stressors have been removed, but native-dominated communities are not returning to degraded areas. Fundamental to this theory is the assumption that equilibria are maintained by positive feedbacks between colonizers and their environment. While ASE has been relatively well studied in aquatic ecosystems, more complex terrestrial systems offer multiple challenges, including species interactions across trophic levels that can lead to multiple feedbacks. Here, we discuss ASE theory as it applies to terrestrial, invaded ecosystems, and detail a case study from Hawai'i that exemplifies how species interactions can favour the persistence of invaders, and how an understanding of interactions and feedbacks can be used to guide management. Our system includes intact native-dominated mesic forest and areas cleared for pasture, planted with non-native grasses, and later planted with a monoculture of a native nitrogen-fixing tree in an effort to restore forests. We discuss interactions between birds, understorey fruiting native species, understorey non-native grasses, soils and bryophytes in separate feedback mechanisms, and explain our efforts to identify which of these feedbacks is most important to address in a management context. Finally, we suggest that using models can help overcome some of the challenges that terrestrial ecosystems pose when studying ASE.

Multiple feedbacks due to biotic interactions across trophic levels can lead to persistent novel conditions that hinder restoration.

2020 ◽  
pp. 402-420
Author(s):  
Stephanie G. Yelenik ◽  
◽  
Carla M. D’Antonio ◽  
Evan M. Rehm ◽  
Iain R. Caldwell ◽  
...  
Keyword(s):  
Species Interactions ◽  
Native Species ◽  
Biotic Interactions ◽  
Terrestrial Ecosystems ◽  
Trophic Levels ◽  
Native Grasses ◽  
Positive Feedbacks ◽  
Mesic Forest ◽  
Management Context ◽  
Multiple Challenges

Unlike traditional successional theory, Alternate Stable Equilibrium (ASE) theory posits that more than one community state is possible in a single environment, depending on the order that species arrive. ASE theory is often invoked in management situations where initial stressors have been removed, but native-dominated communities are not returning to degraded areas. Fundamental to this theory is the assumption that equilibria are maintained by positive feedbacks between colonizers and their environment. While ASE has been relatively well studied in aquatic ecosystems, more complex terrestrial systems offer multiple challenges, including species interactions across trophic levels that can lead to multiple feedbacks. Here, we discuss ASE theory as it applies to terrestrial, invaded ecosystems, and detail a case study from Hawai'i that exemplifies how species interactions can favour the persistence of invaders, and how an understanding of interactions and feedbacks can be used to guide management. Our system includes intact native-dominated mesic forest and areas cleared for pasture, planted with non-native grasses, and later planted with a monoculture of a native nitrogen-fixing tree in an effort to restore forests. We discuss interactions between birds, understorey fruiting native species, understorey non-native grasses, soils and bryophytes in separate feedback mechanisms, and explain our efforts to identify which of these feedbacks is most important to address in a management context. Finally, we suggest that using models can help overcome some of the challenges that terrestrial ecosystems pose when studying ASE.

Limitations to Lake Trout ( Salvelinus namaycush ) Rehabilitation in the Great Lakes Imposed by Biotic Interactions Occurring at Early Life Stages

1995 ◽  
Vol 21 ◽  
pp. 505-517 ◽  
Author(s):  
Michael L. Jones ◽  
Gary W. Eck ◽  
David O. Evans ◽  
Mary C. Fabrizio ◽  
Michael H. Hoff ◽  
...  
Keyword(s):  
Great Lakes ◽  
Early Life ◽  
Lake Trout ◽  
Biotic Interactions ◽  
Salvelinus Namaycush ◽  
Life Stages ◽  
Early Life Stages

Investor-State Dispute Settlement under NAFTA Chapter 11: The Shape of Things to Come?

1998 ◽  
Vol 35 ◽  
pp. 263-290
Author(s):  
J. Anthony VanDuzer
Keyword(s):  
Free Trade Agreement ◽  
Dispute Settlement ◽  
Trade Agreement ◽  
Minimum Standards ◽  
The North ◽  
State Behaviour ◽  
Nafta Chapter 11 ◽  
To Come ◽  
The Right

SummaryRecently, there has been a proliferation of international agreements imposing minimum standards on states in respect of their treatment of foreign investors and allowing investors to initiate dispute settlement proceedings where a state violates these standards. Of greatest significance to Canada is Chapter 11 of the North American Free Trade Agreement, which provides both standards for state behaviour and the right to initiate binding arbitration. Since 1996, four cases have been brought under Chapter 11. This note describes the Chapter 11 process and suggests some of the issues that may arise as it is increasingly resorted to by investors.

Scanning Electron Microscopy-cuticular Lesions on the Roundworm Ascaris Suum

1970 ◽  
Vol 28 ◽  
pp. 114-115
Author(s):  
P. A. Madden ◽  
W. R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Freeze Drying ◽  
Room Temperature ◽  
Secondary Electron ◽  
Distilled Water ◽  
Freeze Dried ◽  
Silver Paint ◽  
To Come ◽  
Scanning Electron

The intestinal roundworm of swine is pinkish in color and about the diameter of a lead pencil. Adult worms, taken from parasitized swine, frequently were observed with macroscopic lesions on their cuticule. Those possessing such lesions were rinsed in distilled water, and cylindrical segments of the affected areas were removed. Some of the segments were fixed in buffered formalin before freeze-drying; others were freeze-dried immediately. Initially, specimens were quenched in liquid freon followed by immersion in liquid nitrogen. They were then placed in ampuoles in a freezer at −45C and sublimated by vacuum until dry. After the specimens appeared dry, the freezer was allowed to come to room temperature slowly while the vacuum was maintained. The dried specimens were attached to metal pegs with conductive silver paint and placed in a vacuum evaporator on a rotating tilting stage. They were then coated by evaporating an alloy of 20% palladium and 80% gold to a thickness of approximately 300 A°. The specimens were examined by secondary electron emmission in a scanning electron microscope.

The microstructure change of low-carbon electrical steels by residual aluminum

1989 ◽  
Vol 47 ◽  
pp. 286-287
Author(s):  
C.K. Hou ◽  
C.T. Hu ◽  
Sanboh Lee
Keyword(s):  
Annealing Treatment ◽  
Low Carbon ◽  
Electrical Steels ◽  
Vacuum Degassing ◽  
Spherical Inclusions ◽  
Residual Aluminum ◽  
Average Grain Size ◽  
The Matrix ◽  
Fine Size ◽  
To Come

The fully processed low-carbon electrical steels are generally fabricated through vacuum degassing to reduce the carbon level and to avoid the need for any further decarburization annealing treatment. This investigation was conducted on eighteen heats of such steels with aluminum content ranging from 0.001% to 0.011% which was believed to come from the addition of ferroalloys.The sizes of all the observed grains are less than 24 μm, and gradually decrease as the content of aluminum is increased from 0.001% to 0.007%. For steels with residual aluminum greater than 0. 007%, the average grain size becomes constant and is about 8.8 μm as shown in Fig. 1. When the aluminum is increased, the observed grains are changed from the uniformly coarse and equiaxial shape to the fine size in the region near surfaces and the elongated shape in the central region. SEM and EDAX analysis of large spherical inclusions in the matrix indicate that silicate is the majority compound when the aluminum propotion is less than 0.003%, then the content of aluminum in compound inclusion increases with that in steel.

409 The likely numbers to come: trends in hospitalisation for heart failure in the ‘sample’ town of trieste and its region

2003 ◽  
Vol 2 (1) ◽  
pp. 84
Author(s):  
D CHERSEVANI ◽  
A DILENARDA ◽  
P GOLIANI ◽  
M GRELLA ◽  
F BRUN ◽  
...  
Keyword(s):  
Heart Failure ◽  
Its Region ◽  
To Come

Suicidal Behavior in Black South Africans

Crisis ◽  
2003 ◽  
Vol 24 (1) ◽  
pp. 24-28 ◽  
Author(s):  
Lourens Schlebusch ◽  
Naseema B.M. Vawda ◽  
Brenda A. Bosch
Keyword(s):  
South African ◽  
Suicidal Behavior ◽  
Health Care Facilities ◽  
South African Society ◽  
South Africans ◽  
The Past ◽  
The People ◽  
Care Facilities ◽  
Black South Africans ◽  
To Come

Summary: In the past suicidal behavior among Black South Africans has been largely underresearched. Earlier studies among the other main ethnic groups in the country showed suicidal behavior in those groups to be a serious problem. This article briefly reviews some of the more recent research on suicidal behavior in Black South Africans. The results indicate an apparent increase in suicidal behavior in this group. Several explanations are offered for the change in suicidal behavior in the reported clinical populations. This includes past difficulties for all South Africans to access health care facilities in the Apartheid (legal racial separation) era, and present difficulties of post-Apartheid transformation the South African society is undergoing, as the people struggle to come to terms with the deleterious effects of the former South African racial policies, related socio-cultural, socio-economic, and other pressures.

DySlExIa: Good News, More to Come!

1985 ◽  
Vol 30 (4) ◽  
pp. 305-306
Author(s):  
Dennis F. Fisher
Keyword(s):  
Good News ◽  
To Come
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