bluuebunny/crossref_metadata_2025 huggingface dataset:
Depression and Retirement in Late Middle‐Aged U.S. Workers
Authors: Doshi Jalpa A. , Cen Liyi , Polsky Daniel
Published: September 2007

Objective.To determine whether late middle‐aged U.S. workers with depression are at an increased risk for retirement.

Data Source.Six biennial waves (1992–2002) of the Health and Retirement Study, a nationally representative panel survey of noninstitutionalized 51–61‐year‐olds and their spouses started in 1992.

Study Design.Workers aged 53–58 years in 1994 were followed every 2 years thereafter, through 2002. Depression was coded as lagged time‐dependent variables measuring active depression and severity of depression. The main outcome variable was a transition to retirement which was measured using two distinct definitions to capture different stages in the retirement process: (1) Retirement was defined as a transition out of the labor force in the sample of all labor force participants (N=2,853); (2) In addition a transition out of full time work was used as the retirement definition in the subset of labor force participants who were full time workers (N=2,288).

Principal Findings.In the sample of all labor force participants, the presence of active depression significantly increased the hazard of retirement in both late middle‐aged men (adjusted OR: 1.37 [95 percent CI 1.05, 1.80]) and women (adjusted OR: 1.40 [95 percent CI 1.10, 1.78]). For women, subthreshold depression was also a significant predictor of retirement. In the sample of full time workers, the relationship between depression and retirement was considerably weaker for women yet remained strong for men.

Conclusions.Depression and depressive symptoms were significantly associated with retirement in late middle‐aged U.S. workers. Policymakers must consider the potentially adverse impact of these labor market outcomes when estimating the cost of untreated depression and evaluating the value of interventions to improve the diagnosis and treatment of depression.
When thinking hurts: Attachment, rumination, and postrelationship adjustment
Authors: SAFFREY COLLEEN , EHRENBERG MARION
Published: September 2007

The current study used an attachment framework to explore postrelationship rumination and adjustment. Young adults (N= 231) involved in a romantic relationship that (a) was of 3 months duration or longer and (b) ended in the last 12 months participated in the study. The study assessed rumination generally (brooding, regret, and reflection), and specifically concerning the ended relationship (relationship preoccupation and romantic regret). At the general level, brooding and regret were associated with more negative adjustment, whereas reflection was associated with more positive adjustment. At the relationship level, both relationship preoccupation and romantic regret were associated with more negative adjustment. Models tested indicated that rumination largely mediated the association between attachment anxiety and adjustment.
Empathic accuracy of intimate partners in violent versus nonviolent relationships
Authors: CLEMENTS KAHNI , HOLTZWORTH‐MUNROE AMY , SCHWEINLE WILLIAM , ICKES WILLIAM
Published: September 2007

This study compared the empathic accuracy of men and women who had perpetrated physical intimate partner violence with that of partners in nonviolent but distressed and nonviolent and nondistressed relationships. Examined was the empathic accuracy (a) of partners for one another’s thoughts and feelings during a relationship problem discussion in the laboratory, (b) of partners’ empathic accuracy for each other with the empathic accuracy of objective observers who watched the couples’ interactions, and (c) the males’ empathic accuracy for their female partner to their empathic accuracy for female strangers. No significant group differences were found among women’s empathic accuracy, but the data suggest that violent men exhibit poor empathic accuracy when attempting to understand their female partner’s thoughts and feelings.
From bad to worse: Relationship commitment and vulnerability to partner imperfections
Authors: ARRIAGA XIMENA B. , SLAUGHTERBECK ELIZABETH S. , CAPEZZA NICOLE M. , HMUROVIC JILLIAN L.
Published: September 2007

Having a satisfying romantic relationship is not always feasible, particularly as one discovers less‐than‐perfect partner characteristics. It is suggested that less committed couple members are more vulnerable to negative partner characteristics than are highly committed couple members. Forty‐one dating couples individually indicated their commitment level, were randomly assigned to receive positive‐ or negative‐false feedback about the partner’s personality, and indicated their postmanipulation satisfaction and uncertainty levels. Negative partner feedback affected the satisfaction of less committed but not highly committed individuals. Feeling uncertain about the relationship mediated less committed couple members’ increased vulnerability to negative partner information. The association between uncertainty and commitment was curvilinear and stronger under conditions of relationship threat. Self‐esteem did not predict responses to threat.
Misperception of sexual and romantic interests in opposite‐sex friendships: Four hypotheses
Authors: KOENIG BRYAN L. , KIRKPATRICK LEE A. , KETELAAR TIMOTHY
Published: September 2007

Two online studies evaluated the misperception of sexual and romantic interests in established relationships and tested four hypotheses: a simple sex‐difference hypothesis, a projection hypothesis, a mate value hypothesis, and a mediation hypothesis. Two hundred thirty‐eight (Study 1) and 198 (Study 2) members of young adult opposite‐sex friendship dyads indicated their sexual and romantic interests in their friend and their perceptions of their friend’s sexual and romantic interests in them. Participants projected their own levels of sexual and romantic interests onto their opposite‐sex friend, mediating the following effects: males overperceived and females underperceived their friends’ sexual (but not romantic) interest, and participants of both sexes misperceived the sexual (but not romantic) interest of friends depending on the friends’ mate value.
Attachment style and two forms of affect coregulation between romantic partners
Authors: BUTNER JONATHAN , DIAMOND LISA M. , HICKS ANGELA M.
Published: September 2007

This study examined 2 forms of affect coregulation in 48 cohabiting heterosexual couples who provided daily ratings of positive and negative affect for 21 days. Coregulation was operationalized as covariation in partners’ daily levels of affect and coupling of the rates of change of partners’ affective cycles. Both forms of coregulation were detected, and both were moderated by attachment style. These results are interpreted with respect to the timescales and time courses of each form of coregulation, suggesting that covariation may be more sensitive to discrete affective episodes unfolding during couples’ shared time together, whereas coupling may be a longer term process in which partners manifest sensitivity to one another’s overall patterns of affective fluctuation.
Changes in contact and support exchange in personal networks after widowhood
Authors: GUIAUX MAURICE , VAN TILBURG THEO , BROESE VAN GROENOU MARJOLEIN
Published: September 2007

The convoy model conceptualizes older adults’ networks of personal relationships as convoys of social support. This prospective study examined how contact and support in several relationships changed due to widowhood. Using observations between 1992 and 2002 from the Longitudinal Aging Study Amsterdam, multilevel models describe change in contact and support of 227 widowed and 408 married older adults. Contact and support were low before widowhood and increased in all relationships after widowhood, and more so in child and sibling relationships. Around 2.5 years after widowhood, contact and support started to decrease. Our findings increase our understanding of the heterogeneity of network changes in old age and of the instability of the network as a social convoy in late life.
Attachment, sexual experience, and sexual pressure in romantic relationships: A dyadic approach
Authors: BRASSARD AUDREY , SHAVER PHILLIP R. , LUSSIER YVAN
Published: September 2007

The goal of this research was to extend the previously documented associations between attachment style and sexual experiences in samples of adolescents and college students to adult couples in committed romantic relationships. A sample of 273 French‐Canadian heterosexual couples aged 18–35 years completed measures of attachment‐related anxiety and avoidance, sexual coercion, and sexual experiences in their relationships. Avoidant attachment was related to two strategies for limiting intimacy in sexual relationships: avoidance of sexual encounters and avoidance of sexual fantasies about one’s partner (the latter for women only). Anxious attachment appeared to interfere with comfortable intimacy, especially among men, who viewed their partner as avoiding sex and who applied more insistent pressure to have sex.
Missionaries, Colonialism and Language in Nineteenth‐Century South Africa
Authors: Gilmour Rachael
Published: September 2007

Throughout the nineteenth century, driven by the need both to communicate with potential African converts and to produce written Scriptural translations, Christian missionaries set about studying, transliterating and transforming South African languages. Their work served, in various ways, the demands of the developing British colonial order; established new ‘standard forms’ of South African vernaculars; and facilitated the development of literacy among African people in the region. The close relationship between missionaries, colonialism and language study in South Africa has been documented and analysed by scholars from a wide range of disciplines. This article summarizes some of the key issues in the field, as they have defined critical debates since the 1980s, by focusing on models of ‘invention’ on the one hand and ‘reciprocity’ on the other, and exploring continuities and dissonances between these debates and the wider fields of colonial studies and colonial discourse analysis. It concludes by arguing for a balance. On the one hand, it is vital that we acknowledge the significance of missionary language study as a mode of colonial discourse with the power to shape the social, linguistic, and political realities it purported only to describe. On the other, this should not eclipse our understanding of missionary linguistic work in social context, as the product of fraught, complex, and often mutually transformative encounters between European missionaries and African speakers of the languages in question.
Civil Wars in the Sudan
Authors: Collins Robert
Published: September 2007

This article spans the fifty years of the independent Sudan (1956–2006) during which the country was torn by five civil wars made manifest by the historic marginalization of the Sudanese on the periphery by the powerful riverine Sudanese living in the heartland along the Nile, theawlad al‐bahr(people of the river) and the deep cultural, ethnic, linguistic, and religious differences between those of the center and the periphery that have produced four of the five civil wars. The longest, most violent, and destructive were the two civil wars between the northern and southern Sudanese, the Anya‐Nya civil war, 1963–1972 and the second southern civil war, 1983–2006. Moreover, the second southern civil war experienced from 1991 to 1996 its own internal civil war between the Dinka and Nuer that caused enormous casualties and suffering before the Sudan People's Liberation Army could establish its supremacy. After the military coup détat (June 30, 1989) and the subsequent Islamist revolution, insurgencies erupted both in the East led by the Beja Congress in 1994 and in the West in Darfur by the Sudan Liberation Movement and the Justice and Equality Movement in 2003. The Beja insurgency was settled in 2006 but the disaster in Darfur continues after great loss of life. This article summarizes each of these insurgencies, interprets their ideology, and analyzes the deep tensions which produced them.
Women, Gender and Lordship in France, c.1050–1250
Authors: LoPrete Kimberly A.
Published: September 2007

Arguing that scholars should follow methods of analysis developed by historians of women in the early Middle Ages and must confront problems in the so‐called ‘Duby thesis’, this article shows how anachronistic analytical categories and insufficient source criticism have masked our appreciation of the extensive political activities of non‐royal aristocratic women in France during the eleventh to thirteenth centuries. Emphasising the domestic context of lordship and political action in this period, as well as the multivalence of gender as an explanatory category, it reveals strong continuities between women's powers in the early and central Middle Ages and shows that female lords were a routine and acceptable part of the medieval French political scene.
Construction of a composite pressure–temperature path: revealing the synorogenic burial and exhumation history of the Sevier hinterland, USA
Authors: HARRIS C. R. , HOISCH T. D. , WELLS M. L.
Published: September 2007

Metamorphic pressure–temperature (P–T) paths derived from 16 growth‐zoned garnets, nine from this study and seven from a previous study, have been combined to construct a detailed composite path for an area in the hinterland of the Cretaceous to early Tertiary Sevier orogenic belt in southern Idaho and north‐west Utah. Samples are from two Proterozoic units in the footwall of the Basin‐Elba thrust: the schist of Mahogany Peaks in the central Albion Mountains, Idaho, and the schist of Stevens Spring in the Basin Creek area of the Grouse Creek Mountains, Utah, ∼40 km to the south. The simulated portions of the garnets analysed in this study grew from reactions involving the breakdown of chlorite in the upper greenschist to lower amphibolite facies. Multiple garnets were analysed from three samples. Overlapping segments ofP–Tpaths from different garnets in the same sample correlate with respect to slope and garnet Mn concentration. The compositeP–Tpath documents three episodes of sharply increasing pressures separated by two episodes of pressure decrease, all during progressively increasing temperatures. The path is interpreted to represent alternating episodes of synconvergent thrusting and extensional exhumation in the hinterland of the Sevier orogen. Burial was probably caused by the Basin‐Elba fault, the only major thrust exposed in the region. Extensional exhumation may have occurred along the Mahogany Peaks or Emigrant Spring faults, or by extensional reactivation of the Basin‐Elba fault. This method of correlating partialP–Tpaths to reveal a more complete composite path provides a powerful tool in unveiling orogenic histories in metamorphic terranes, where evidence of major structures responsible for burial and exhumation is commonly obscured by later events.
Zircon U–Pb age and Hf isotope evidence for contrasting origin of bimodal protoliths for ultrahigh‐pressure metamorphic rocks from the Chinese Continental Scientific Drilling project
Authors: CHEN R.‐X. , ZHENG Y.‐F. , ZHAO Z.‐F. , TANG J. , WU F.‐Y. , LIU X. M.
Published: September 2007

A combined study of zircon morphology, U–Pb ages and Hf isotopes as well as whole‐rock major and trace elements was carried out for ultrahigh‐pressure (UHP) eclogite and felsic gneiss from the main hole (MH) of the Chinese Continental Scientific Drilling (CCSD) project in the Sulu orogen. The results show contrasting Hf isotope compositions for bimodal UHP metaigneous rocks, pointing to contrasting origins for their protoliths (thus dual‐bimodal compositions). The samples of interest were from two continuous core segments from CCSD MH at depths of 734.21–737.16 m (I) and 929.67–932.86 m (II) respectively. Zircon U–Pb dating for four samples from the two core segments yields two groups of ages at 784 ± 17 and 222 ± 3 Ma, respectively, corresponding to protolith formation during supercontinental rifting and metamorphic growth during continental collision. Although the Triassic UHP metamorphism significantly reset the zircon U–Pb system of UHP rocks, the Hf isotope compositions of igneous zircon can be used to trace their protolith origin. Contrasting types of initial Hf isotope ratios are, respectively, correlated with segments I and II, regardless of their lithochemistry. The first type shows positive ɛHf(t) values of 7.8 ± 3.1 to 6.0 ± 3.0, with young Hf model age of 1.03 and 1.11 Ga. The second type exhibits negative ɛHf(t) values of −6.9 ± 1.6 to −9.1 ± 1.1, with old Hf model ages of 2.11 and 2.25 Ga. It appears that the UHP rocks from the two segments have protoliths of contrasting origin. Consistent results are also obtained from their trace element compositions suggesting that mid‐Neoproterozoic protoliths of bimodal UHP metaigneous rocks formed during supercontinental rifting at the northern margin of the South China Block. Thus, the first type of bimodal magmatism formed by rapid reworking of juvenile crust, whereas the second type of bimodal magmatism was principally generated by rift anatexis of Paleoproterozoic crust. Melting of orogenic lithosphere has potential to bring about bimodal magmatism with contrasting origins. Because arc–continent collision zones are the best place to accumulate both juvenile and ancient crusts, the contrasting types of bimodal magmatism are proposed to occur in an arc–continent collision orogen during the supercontinental rifting, in response to the attempted breakup of the supercontinent Rodinia at c. 780 Ma.
P–T–t evolution and textural evidence for decompression of Pan‐African high‐pressure granulites, Lurio Belt, north‐eastern Mozambique
Authors: ENGVIK A. K. , TVETEN E. , BINGEN B. , VIOLA G. , ERAMBERT M. , FEITO P. , DE AZAVEDO S.
Published: September 2007

Pan‐African high‐pressure granulites occur as boudins and layers in the Lurio Belt in north‐eastern Mozambique, eastern Africa. Mafic granulites contain the mineral assemblage garnet + clinopyroxene + plagioclase + quartz ± magnesiohastingsite. Garnet porphyroblasts are zoned with increasing almandine and spessartine contents and decreasing grossular and pyrope contents from core (Alm46Prp32Grs21Sps2) to rim (Alm52Prp26Grs19Sps3). This pattern is interpreted as a retrograde diffusion zoning with the preserved core chemistry representing the peak metamorphic composition. Mineral reaction textures occur in the form of monomineralic and composite plagioclase ± orthopyroxene ± amphibole ± biotite ± magnetite coronas around garnet porphyroblasts. Thermobarometry indicates peak metamorphic conditions of up to 1.57 ± 0.14 GPa and 949 ± 92 °C (stage I), corresponding to crustal depths of ∼55 km. Zircon yielded an U–Pb age of 557 ± 16 Ma, inferred to date crystallization of zircon during peak or immediately post‐peak metamorphism. Formation of plagioclase + orthopyroxene‐bearing coronas surrounding garnet indicates a near‐isothermal decompression of the high‐pressure granulites to lower pressure granulite facies conditions (stage II). Development of plagioclase + amphibole‐coronas enclosing the same garnet porphyroblasts shows subsequent cooling into amphibolite facies conditions (stage III). Symplectitic textures of the corona assemblages indicate rapid decompression. The high‐pressure granulite facies metamorphism of the Lurio Belt, followed by near‐isothermal decompression and subsequent cooling, is in accordance with a long‐lived tectonic history accompanied by high magmatic activity in the Lurio Belt during the late Neoproterozoic–early Palaeozoic East‐African–Antarctic orogeny.
Zircon U–Pb ages and Hf isotope compositions of migmatite from the North Dabie terrane in China: constraints on partial melting
Authors: WU Y.‐B. , ZHENG Y.‐F. , ZHANG S.‐B. , ZHAO Z.‐F. , WU F.‐Y. , LIU X.‐M.
Published: September 2007

Migmatite gneisses are widespread in the Dabie orogen, but their formation ages are poorly constrained. Eight samples of migmatite, including leucosome, melanosome, and banded gneiss, were selected for U–Pb dating and Hf isotope analysis. Most metamorphic zircon occurs as overgrowths around inherited igneous cores or as newly grown grains. Morphological and internal structure features suggest that their growth is associated with partial melting. According to the Hf isotope ratio relationships between metamorphic zircon and inherited cores, three formation mechanisms for metamorphic zircon can be determined, which are dissolution–reprecipitation of pre‐existing zircon, breakdown of Zr‐bearing phase other than zircon in a closed system and crystallization from externally derived Zr‐bearing melt. Four samples contain magmatic zircon cores, yielding upper intercept U–Pb ages of 807 ± 35–768 ± 12 Ma suggesting that the protoliths of the migmatites are Neoproterozoic in age. The migmatite zircon yields weighted mean two‐stage Hf model ages of 2513 ± 97–894 ± 54 Ma, indicating reworking of both juvenile and ancient crustal materials at the time of their protolith formation. The metamorphic zircons give U–Pb ages of 145 ± 2–120 ± 2 Ma. The oldest age indicates that partial melting commenced prior to 145 Ma, which also constrains the onset of extensional tectonism in this region to pre‐145 Ma. The youngest age of 120 Ma was obtained from an undeformed granitic vein, indicating that deformation in this area was complete at this time. Two major episodes of partial melting were dated at 139 ± 1 and 123 ± 1Ma. The first episode of partial melting is obviously older than the timing of post‐collision magmatism, corresponding to regional extension. The second episode of partial melting is coeval with the widespread post‐collision magmatism, indicating the gravitational collapse and delamination of the orogenic lithospheric keel of the Dabie orogen, which were possibly triggered by the uprising of the Cretaceous mid‐Pacific superplume.
Intra‐ and Interannual Vegetation Change: Implications for Long‐Term Research
Authors: Korb Julie E. , Fulé Peter Z.
Published: September 2007

To draw reliable conclusions from forest restoration experiments, it is important that long‐term measurements be repeatable or year‐to‐year variability may interfere with the correct interpretation of treatment effects. We used permanent plots in a long‐term restoration study in southwestern Colorado to measure herbaceous and shrub vegetation at three dates within a single year (June, July, and August), and between years (2003 and 2005), on untreated control plots in a warm, dry mixed conifer forest. Growing season precipitation patterns were similar between 2003 and 2005, so differences in vegetation should be related primarily to differences in the sampling month. Significant indicator species for each sampling month were present within a single year (2005), primarily reflecting early‐season annuals. We found no significant differences for total species abundance (2005). Species richness, abundance, and indicator species were significantly different between years for different sampling months indicating that sampling should be conducted within a similar time frame to avoid detecting differences that are not due to treatment effects or variations in year‐to‐year climate. These findings have implications for long‐term research studies where the objectives are to detect changes over time in response to treatments, climate variation, and natural processes. Long‐term sampling should occur within a similar phenological time frame each year over a short amount of time and should be based on the following criteria: (1) the sampling period is congruent with research objectives such as detecting rare species or peak understory abundance and (2) the sampling period is feasible in regard to personnel and financial constraints.
Effects of Competition and Life History Stage on the Expression of Local Adaptation in Two Native Bunchgrasses
Authors: Rice Kevin J. , Knapp Eric E.
Published: September 2007

Concerns about the use of genetically appropriate material in restoration often focus on questions of local adaptation. Many reciprocal transplant studies have demonstrated local adaptation in native plant species, but very few have examined how interspecific competition affects the expression of adaptive variation. Our study examined regional scales of adaptation between foothill and coastal populations of two California native bunchgrasses (Elymus glaucus and Nassella pulchra). By combining competitive manipulations with reciprocal transplants, we examined the importance of the vegetation at a site as a selective factor in the process of local adaptation. By monitoring survival and reproduction of reciprocally transplanted populations over the course of 3 years, we also studied the effect of life history stage on the expression of local adaptation. For most of the fitness components we measured, local adaptation was detected and interspecific competition consistently amplified its expression. Expression of local adaptation was especially apparent in the more inbreeding species E. glaucus and suggests that with weaker gene flow, selection may be more effective in creating ecotypes within this species. Local adaptation was detected at all life history stages but was most strongly expressed in traits associated with adult reproduction and the viability of seeds produced by the transplants. Taken together, our results indicate that the importance of local adaptation will become more apparent in the later stages of a restoration project as the plants at a site begin to reproduce and as they experience greater interspecific competition from the maturing vegetation at the site.
Post‐Flood Recovery of a Macroinvertebrate Community in a Regulated River: Resilience of an Anthropogenically Altered Ecosystem
Authors: Rader Russell B. , Voelz Neal J. , Ward James V.
Published: September 2007

Preservation of biodiversity depends on restoring the full range of historic environmental variation to which organisms have evolved, including natural disturbances. Lotic ecosystems have been fragmented by dams causing a reduction in natural levels of environmental variation (flow and temperature) and consequently a reduction of biodiversity in downstream communities. We conducted a long‐term study of the macroinvertebrate communities before and after natural flood disturbances in an unregulated reference site (natural flows and temperatures), a regulated site (regulated flows and temperatures), and a partially regulated reference site (regulated flows and natural temperatures) on the upper Colorado River downstream from a deep‐release storage reservoir. We aimed to test the hypothesis that floods and temperature restoration would cause an increase in macroinvertebrate diversity at the regulated site. Over the short term, macroinvertebrate richness decreased at the regulated site when compared to pre‐flood levels, whereas total macroinvertebrate density remained unchanged. Over the long term (1 and 10 years after the floods), macroinvertebrate diversity and community structure at the regulated site returned to pre‐flood levels without increasing to reference conditions. Occasional floods did not restore biodiversity in this system. As long as the physical state variables remain altered beyond a threshold, the community will return to its altered regulated condition. However, temperature restoration at the partially regulated site resulted in an increase in macroinvertebrate diversity. Our results indicate that restoration of the natural temperature regime will have a stronger effect on restoring biodiversity than occasional channel‐forming floods.
Impact of Regional Species Pool on Grasshopper Restoration in Hay Meadows
Authors: Knop Eva , Schmid Bernhard , Herzog Felix
Published: September 2007

Agri‐environment schemes are the most widely adopted political measure to maintain and restore farmland biodiversity in Europe. However, abiotic and biotic factors often limit the success of ecological restoration. Among the biotic factors, the size of the local and regional species pool is a major constraint. This is only well documented for plants. We therefore wanted to know if a small regional species pool can also limit restoration efforts of invertebrates. Specifically, we tested if by relocating grasshoppers from further away, we could overcome regional species pool limitations on hay meadows under the Swiss agri‐environment scheme, so‐called Ecological Compensation Area meadows (ECA meadows). All meadows had been under restoration for 6 years and were formerly intensively used hay meadows. Two grasshopper species, Euthystira brachyptera and Mecostethus parapleurus, were selected; E. brachyptera was not found in the regional species pool and M. parapleurus had nearly disappeared. In 2004, 1,400 grasshopper individuals of each species were taken from the nearest large source populations and distributed equally on seven ECA meadows and seven control meadows. In 2005, we evaluated whether the species had successfully established. Only one individual of M. parapleurus was found. We conclude that a small regional species pool is not the only constraint for the reestablishment of grasshoppers on restoration meadows. Also, other factors such as habitat quality appear to constrain the reestablishment of grasshoppers on restoration meadows. Additional restoration efforts specifically targeted at grasshopper restoration are needed, and innovative techniques have to be developed to overcome the relocation constraints.
The Effect of Fire Reintroduction on Endemic and Rare Plants of a Southeastern Glade Ecosystem
Authors: Scot Duncan R. , Anderson Corinna B. , Sellers Heather N. , Robbins Erin E.
Published: September 2007

Open habitats dominated by herbaceous plants on thin, rocky soils occur within the forests of eastern North America. Although these habitats vary in origin, structure, geology, and species composition, all contribute greatly to regional biodiversity by harboring endemic and/or rare plants. Little is known about how disturbances affect plant populations in these ecosystems. Fire once was a frequent natural disturbance in the Ketona dolomite glades of Alabama, an ecosystem harboring eight endemic taxa and numerous other species of conservation concern. We designed an experiment to determine how the reintroduction of fire into the glades and surrounding longleaf pine forests affects populations of rare glade plant species. Experimental and control plots were established within the glades. Experimental plots were burned in April 2004, and all plots were surveyed during two subsequent growing seasons (2004 and 2005). Populations of three of 14 species of conservation concern declined significantly after the initial fire but recovered the next year. Among other herbaceous species, only five and two differed in population size in 2004 and 2005, respectively. In 2004, more species were more abundant in control than burned plots, but this difference was not detected in 2005. Multivariate community‐level analyses of species presence–absence suggested that the effects of fire were negligible by the 2005 survey. Populations of young trees that had invaded the glades declined dramatically as a result of treatment fires. These results suggest that the reintroduction of fire will not harm glade species and may help prevent encroachment of the surrounding forest.
Has Botanical Enhancement of Broad‐Leaved Plantations in Milton Keynes, United Kingdom, Resulted in More Woodland‐Like Insect Assemblages?
Authors: Moffatt Colin , Morton Alan J. , McNeill Stuart
Published: September 2007

Two methods of invertebrate sampling were used to determine how the deliberate introduction of field layer vegetation to broad‐leaved plantations influenced the associated insect assemblages. Enclosed pitfall traps and tent‐like emergence traps were employed at (1) 25‐year‐old plantations where botanical enhancement had taken place a decade previously; (2) “nonenhanced” plantations of a similar age; and (3) local ancient woods, all in Milton Keynes, Buckinghamshire, United Kingdom. The aim was to discover whether enhancement had produced a community intermediate to nonenhanced plantations and naturally established woodland. Enhancement had not successfully created plantations botanically more woodland‐like and plantation types were not constant; however, plant species richness had increased. This was also true of the insect assemblages (Coleoptera, Diptera and Hemiptera), which showed more variation in composition, though woodland communities could still be distinguished. However, those insect species present in the naturally established woods did have a significantly greater frequency and abundance in the enhanced plantations compared to the nonenhanced plantations, especially so with “woodland edge” species. Mantel tests showed significant correlations between the plant species present and insect assemblages taken by both sampling types. Although insect species richness was not significantly higher in the enhanced plantations, this correlated strongly with plant species richness and a measure of vegetation volume. The overall findings suggest that the enhancement had created plantations only subtly more like the local woodlands, though the insect assemblages had responded. However, relative to the time scale of woodland development, it is still early days.
Local Adaptation and Effects of Grazing among Seedlings of Two Native California Bunchgrass Species: Implications for Restoration
Authors: Hufford Kristina M. , Mazer Susan J. , Camara Mark D.
Published: September 2007

Adaptation to environmental factors may influence the germination and establishment of focal species in ecological restoration. Reciprocal transplants remain one of the best methods to detect local adaptation, but long‐term studies are often not feasible. We conducted reciprocal transplants of the native California bunchgrasses Elymus glaucus and Bromus carinatus between two central California locations to seek evidence of adaptation to local environmental conditions in a single growing season. Experimental plots at one location included grazed and ungrazed sites. The combination of locations and grazing treatments allowed us to determine whether the ability to detect evidence for adaptation depended on grazing regime. In addition, we measured the direct effects of grazing on seedling growth and survival concurrent with our investigation of local adaptation. We detected a homesite advantage for seedling growth or survival in both species, but the factors contributing to adaptive differentiation were species specific. Evidence of local adaptation was detected for seedling biomass in Bromus and for survivorship in Elymus. The homesite advantage observed in both species was greatly reduced under grazed conditions and in Elymus was significant only in the ungrazed plots. Climate and soil analyses detected significant differences between locations in five soil attributes and two climate variables. In particular, differences in exchangeable magnesium indicated that one of the two transplant locations consisted of serpentine soil, which is widely known to drive adaptation in plant populations. Together, these results suggest that it is possible to investigate the scale and factors involved in local adaptation with short‐term transplant studies.
Soil Nitrogen Conditions Approach Preinvasion Levels following Restoration of Nitrogen‐Fixing Black Locust (Robinia pseudoacacia) Stands in a Pine–Oak Ecosystem
Authors: Malcolm Glenna M. , Bush Douglas S. , Rice Steven K.
Published: September 2007

Restoring native plant communities on sites formerly occupied by invasive nitrogen‐fixing species poses unique problems due to elevated soil nitrogen availability. Mitigation practices that reduce available nitrogen may ameliorate this problem. We evaluated the effects of tree removal followed by soil preparation or mulching on native plant growth and soil nitrogen transformations in a pine–oak system formerly occupied by exotic nitrogen‐fixing Black locust (Robinia pseudoacacia) trees. Greenhouse growth experiments with native grasses,Andropogon gerardiiandSorghastrum nutans, showed elevated relative growth rates in soils from Black locust compared with pine–oak stands. Field soil nutrient concentrations and rates of net nitrification and total net N‐mineralization were compared 2 and 4 years since Black locust removal and in control sites. Although soil nitrogen concentrations and total net N‐mineralization rates in the restored sites were reduced to levels that were similar to paired pine–oak stands after only 2 years, net nitrification rates remained 3–34 times higher in the restored sites. Other nutrient ion concentrations (Ca, Mg) and organic matter content were reduced, whereas phosphorus levels remained elevated in restored sites. Thus, 2–4 years following Black locust tree removal and soil horizon mixing achieved through site preparation, the concentrations of many soil nutrients returned to preinvasion levels. However, net nitrification rates remained elevated; cover cropping or carbon addition during restoration of sites invaded by nitrogen fixers could increase nitrogen immobilization and/or reduce nitrate availability, making sites more amenable to native plant establishment.
Organic Matter Stimulates Bacteria and Arbuscular Mycorrhizal Fungi in Bauhinia purpurea and Leucaena diversifolia Plantations on Eroded Slopes in Nepal
Authors: Shrestha Vaidya Geeta , Shrestha Keshab , Khadge Buddi R. , Johnson Nancy C. , Wallander Håkan
Published: September 2007

Erosion resulting from landslides is a serious problem in mountainous countries such as Nepal. To restore such sites it is essential to establish plant cover that protects the soil and reduces surface erosion. Mycorrhizal fungi growing in symbiosis with plants are essential in this respect because they improve both plant nutrient uptake and soil structure. We investigated the influence of organic matter and P amendment on recently produced biomass of bacteria and arbuscular mycorrhizal (AM) fungi in eroded slopes in Nepal. Eroded soil mixed with different types of organic matter or P was placed in mesh bags, which were buried around trees of Bauhinia purpurea and Leucaena diversifolia between June 2003 and December 2003 (the wet season) or between December 2003 and June 2004 (the dry season). Signature fatty acids were used to determine bacterial and AM fungal biomass after the 6‐month intervals. The amount and composition of AM fungal spores were analyzed in the mesh bags from the dry season. More microbial biomass was produced during the wet season than during the dry season. Furthermore, organic matter addition enhanced the production of AM fungal and bacterial biomass during both periods. The positive influence of organic matter addition on AM fungi could be an important contribution to plant survival in plantations on eroded slopes. Different AM spore communities and bacterial profiles were obtained with different organic amendments and this suggests a possible way of selecting for specific microbial communities in the management of eroded sites.
The Role of Endangered Species Reintroduction in Ecosystem Restoration: Tortoise–Cactus Interactions on Española Island, Galápagos
Authors: Gibbs James P. , Marquez Cruz , Sterling Eleanor J.
Published: September 2007

We evaluated the role that endangered species reintroduction efforts can play in the larger context of ecosystem restoration. To do so, we examined interactions between endangered giant tortoises (Geochelone nigra hoodensis), currently being reintroduced to Isla Española, Galápagos, and an arboreal cactus (Opuntia megasperma var. megasperma), which is itself endangered and a keystone resource for many animals on the island. We collected information on spatial patterns of occurrence of cacti, tortoises, and woody vegetation and compared recruitment of juvenile cacti in areas occupied versus unoccupied by tortoises. Reintroduced tortoises appeared to suppress cactus recruitment near the few remaining adult cacti at the study site, but facilitate it at longer distances, with tortoise–cactus interactions mediated by the presence of woody vegetation, which likely alters tortoise movements and thereby patterns of cactus seed dispersal. The net effect of tortoises on cacti appeared to be positive insofar as tortoise presence was associated with greater recruitment of juveniles into cactus populations. Our study provides support for reintroducing endangered reptiles and other animals to aid ecosystem restoration in areas where they might once have played an important role in grazing upon and dispersing plants.
First‐Generation Forests Are Not Necessarily Worse than Long‐Term Managed Forests for Lichens and Bryophytes
Authors: Lõhmus Asko , Lõhmus Piret
Published: September 2007

For biodiversity, natural afforestation is generally more favorable than plantation‐based afforestation, but the difference may be less important if both methods fail to provide habitats for sensitive old‐forest species. Given that some conditions, such as substrates, can be actively restored in new forests, their effect on biodiversity should be separated from dispersal limitation. We asked whether, and to what extent, lichen and bryophyte vegetation is impoverished on old‐forest substrates in non‐intensively afforested lands of the twentieth century compared with similar substrates in managed long‐term forestlands. We measured the diversity and abundance of all lichens and bryophytes as well as the cover of human‐sensitive (hemerophobic) species on large deciduous trees, logs, snags, and windthrows on 30 random 2‐km transects in a 900‐km2forest landscape in Estonia, hemiboreal Europe. Altogether, 235 species, including 39 hemerophobic species, were detected on 781 structural elements. New forests were not significantly worse than long‐term forests in any of the cryptogam community characteristics, which was explained by the predominance of natural afforestation (many native tree species present), time for substrate development and cryptogam dispersal (most stands >40 years old), few cuttings in the new forests (only about 20% of stands thinned), and short distances to long‐term forests (67% of substrates within 250 m). Under such conditions, afforested areas appeared to be as suitable as traditional managed forests both for developing multifunctional forestry and as starting points for habitat restoration for threatened species.
Decreasing the Abundance of Juncus effusus on Former Agricultural Lands with Noncalcareous Sandy Soils: Possible Effects of Liming and Soil Removal
Authors: Smolders Alfons J. P. , Lucassen Esther C. H. E. T. , Van Der Aalst Martijn , Lamers Leon P. M. , Roelofs Jan G. M.
Published: September 2007

More and more agricultural land in the Netherlands is becoming available for ecological restoration projects. However, nutrient levels in the top layer of the soils are high because the agricultural lands have been heavily fertilized for decades. As drainage ditches are no longer maintained when agricultural use ends, the agricultural lands usually become much wetter. As a result, former agricultural soils tend to develop extensive monotonous stands of Juncus effusus, which have little value from an ecological point of view. In this article, we present the results of field measurements/observations and experiments to examine the relationship between nutrient availability and J. effusus growth. In addition, we present and discuss results of experiments to study the potential beneficial effects of liming. Our findings show that the growth of J. effusus on moist or wet soils seems to be strongly determined by the Olsen‐P concentration in the soil. The restoration of diverse, species‐rich vegetation types on former agricultural lands with a noncalcareous sandy soil will in most cases not be possible within a reasonable time span without topsoil removal. Liming might be a valuable additional measure to enhance the quality of the soil after topsoil removal, and to prevent mobilization of P to groundwater or surface water. If removal of the topsoil is considered to create P limitation, it is important to study P concentrations at various depths to establish the amount of soil that has to be removed.
Declining Diversity in Natural and Restored Salt Marshes: A 30‐Year Study of Tijuana Estuary
Authors: Zedler Joy B. , West Janelle M.
Published: September 2007

Between 1974 and 2004, Tijuana Estuary’s natural salt marsh underwent pulse disturbance (an 8‐month nontidal period in 1984), which caused the sudden loss of two short‐lived halophytes (Salicornia bigelovii[Sb] andSuaeda esteroa[Se]) and rapid dominance of a productive native succulent (Sa. virginica[Sv]), plus ramp disturbance that led to gradual codominance byJaumea carnosa(Jc) (another productive succulent) by 1994. Species richness was high in 1974 (4.2 species/0.25‐m2plot), low in 1984 (1.4 species), and not fully recovered by 1994 (3.7 species) or 2004 (3.9 species). Restoration efforts (reseeding former habitat and excavating and planting new sites) did not recover the populations of Sb or Se. In a 1997 project, plantings of these and six other native halophytes survived initially, but by 2005, short‐lived species were lost and Sv and Jc dominated, as in the natural marsh. In a 2000 restoration site, planting mortality was high for five species, but Sv recruited voluntarily and dominated by 2005. We attribute recent vegetation changes to frequent catastrophic storms, flooding, and sedimentation, which contrasted strongly with the benign conditions of decades prior to 1974. Sediment blocked tidal channels in 1984 and gradually elevated the marsh plain, degrading the diverse salt marsh and hindering efforts to restore it. Future restoration efforts will require even greater control over sediment inflows plus contouring sites to include natural topographic features that appear critical to sustaining high species richness and evenness.
Evaluation of Herbicides for Restoring Native Grasses in Buffelgrass‐Dominated Grasslands
Authors: Tjelmeland Aaron D. , Fulbright Timothy E. , Lloyd‐Reilley John
Published: September 2007

Buffelgrass (Pennisetum ciliare) is an exotic grass that threatens arid and semiarid ecosystems. The objective of this study was to determine effectiveness of several herbicides at reducing competition from buffelgrass to enhance establishment of planted native grasses. In Duval County, Texas, plots were delineated in two experiments in a buffelgrass‐dominated pasture and mowed on 2 September 2002. On 18 September 2002 and 7 October 2002, a 41% glyphosate (N‐(phosphonomethyl) glycine) herbicide was applied to all plots. A mixture of three native grasses—green sprangletop (Leptochloa dubia), plains bristlegrass (Setaria leucopila), and four‐flower trichloris (Chloris pluriflora)—was planted on 8 October 2002. On 9 October 2002, 1.12 and 2.24 kg/ha of a 80% tebuthiuron (N‐[5‐(1,1‐dimethyethyl)‐1,3,4‐thiadiazol‐2‐yl]‐N,N’‐dimethylurea) herbicide was applied preemergence to the first experiment, and all other herbicides were applied postemergence on 27 July 2003 to the second experiment. Percent canopy cover of vegetation was estimated with a 20 × 50–cm sampling frame during April, June, and October 2003 and August 2004. Postemergent herbicides had no significant effect on canopy cover of buffelgrass or planted species (p≥ 0.05). Canopy cover of native grasses did not exceed 8% on any treatment or sampling date, and buffelgrass cover returned to pre‐treatment conditions in less than 1 year; however, the 2.24 kg/ha rate of tebuthiuron suppressed (p < 0.05) canopy cover of buffelgrass compared with controls and increased (p < 0.05) native grasses almost 2 years past application. Tebuthiuron may have potential value in reducing buffelgrass canopy cover and increasing cover of native grasses, particularly Chloris spp.