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41.
The interaction between nitrogen cycling and carbon sequestration is critical in predicting the consequences of anthropogenic increases in atmospheric CO2 (hereafter, Ca). The progressive N limitation (PNL) theory predicts that carbon sequestration in plants and soils with rising Ca may be constrained by the availability of nitrogen in many ecosystems. Here we report on the interaction between C and N dynamics during a four-year field experiment in which an intact C3/C4 grassland was exposed to a gradient in Ca from 200 to 560 micromol/mol. There were strong species effects on decomposition dynamics, with C loss positively correlated and N mineralization negatively correlated with Ca for litter of the C3 forb Solanum dimidiatum, whereas decomposition of litter from the C4 grass Bothriochloa ischaemum was unresponsive to Ca. Both soil microbial biomass and soil respiration rates exhibited a nonlinear response to Ca, reaching a maximum at approximately 440 micromol/mol Ca. We found a general movement of N out of soil organic matter and into aboveground plant biomass with increased Ca. Within soils we found evidence of C loss from recalcitrant soil C fractions with narrow C:N ratios to more labile soil fractions with broader C:N ratios, potentially due to decreases in N availability. The observed reallocation of N from soil to plants over the last three years of the experiment supports the PNL theory that reductions in N availability with rising Ca could initially be overcome by a transfer of N from low C:N ratio fractions to those with higher C:N ratios. Although the transfer of N allowed plant production to increase with increasing Ca, there was no net soil C sequestration at elevated Ca, presumably because relatively stable C is being decomposed to meet microbial and plant N requirements. Ultimately, if the C gained by increased plant production is rapidly lost through decomposition, the shift in N from older soil organic matter to rapidly decomposing plant tissue may limit net C sequestration with increased plant production. 相似文献
42.
PROBLEM: Parents are an important potential influence on the driving safety of their children. This study examined the relationship of parental driving record on male and female offspring's at-fault collision risk. METHOD: Drivers aged 16-21 on the date of full licensure were selected from driver records and a matching process was used to identify putative parents in two-parent households. Poisson regression models were developed to predict at-fault collisions of male and female youth in the three years following full licensure from parents' at-fault collisions, speeding offenses, and other moving offenses in the four years prior to children's licensure. One set of models examined the relative risk associated with increasing numbers of maternal and paternal at-fault collisions and offenses. Other models examined the joint versus separate maternal and parental contributions. RESULTS: Controlling for region of residence, both mothers' and fathers' at-fault collisions were associated with an increased risk in both male and female youth at-fault collisions. Mothers' and fathers' speeding offenses were also associated with increased relative risk of at-fault collisions for both sons and daughters, while fathers' other moving offenses increased collision risk for sons but not daughters. DISCUSSION: Further research is required to identify how parental driving risk is transmitted to children. IMPACT ON INDUSTRY: (a) Parents of young children should be informed of their role in influencing their children's future driving risk; (b) The results identify risk factors that could be of interest to licensing authorities and the insurance industry. 相似文献
43.
44.
Murali-Baskaran Ramasamy Kanagaraj Senthil-Nathan Sengottayan Hunter Wayne Brian 《Environmental science and pollution research international》2021,28(3):2626-2637
Environmental Science and Pollution Research - Silicon (Si) is considered an important component for plant growth, development, and yield in many crop species. Silicon is also known to reduce plant... 相似文献
45.
Arian D. Wallach Erick Lundgren Chelsea Batavia Michael Paul Nelson Esty Yanco Wayne L. Linklater Scott P. Carroll Danielle Celermajer Kate J. Brandis Jamie Steer Daniel Ramp 《Conservation biology》2020,34(4):997-1007
Conservation science involves the collection and analysis of data. These scientific practices emerge from values that shape who and what is counted. Currently, conservation data are filtered through a value system that considers native life the only appropriate subject of conservation concern. We examined how trends in species richness, distribution, and threats change when all wildlife count by adding so-called non-native and feral populations to the International Union for Conservation of Nature Red List and local species richness assessments. We focused on vertebrate populations with founding members taken into and out of Australia by humans (i.e., migrants). We identified 87 immigrant and 47 emigrant vertebrate species. Formal conservation accounts underestimated global ranges by an average of 30% for immigrants and 7% for emigrants; immigrations surpassed extinctions in Australia by 52 species; migrants were disproportionately threatened (33% of immigrants and 29% of emigrants were threatened or decreasing in their native ranges); and incorporating migrant populations into risk assessments reduced global threat statuses for 15 of 18 species. Australian policies defined most immigrants as pests (76%), and conservation was the most commonly stated motivation for targeting these species in killing programs (37% of immigrants). Inclusive biodiversity data open space for dialogue on the ethical and empirical assumptions underlying conservation science. 相似文献
46.
Amphibian Declines: Judging Stability, Persistence, and Susceptibility of Populations to Local and Global Extinctions 总被引:14,自引:0,他引:14
Extinctions are normal biological phenomena. Both mass extinctions in geological time and local extinctions in ecological time are well documented, but rates of extinction have increased in recent years—especially in vertebrates, including amphibians—as illustrated by recent reports of their population declines and range reductions. We suggest that long-term population data are necessary for rigorously evaluating the significance of the amphibian declines. Due to the physiological constraints, relatively low mobility, and site fidelity of amphibians, we suggest that many amphibian populations may be unable to recolonize areas after local extinction. 相似文献
47.
A regulatory agency enforcing compliance in a declining industry might recognize that certain plants would close rather than comply, imposing large costs on the local community. Data on EPA enforcement activity in the U.S. steel industry are examined for evidence of this with a two-equation model linking EPA enforcement decisions and firms' plant-closing decisions. The results indicate that the EPA directed fewer enforcement actions toward plants with a high predicted probability of closing and plants that were major employers in their community; also, plants predicted to face relatively heavy enforcement were more likely to close. 相似文献
48.
A study of the genetic relationships within and among wolf packs using DNA fingerprinting and mitochondrial DNA 总被引:2,自引:0,他引:2
Niles Lehman Peter Clarkson L. David Mech Thomas J. Meier Robert K. Wayne 《Behavioral ecology and sociobiology》1992,30(2):83-94
Summary DNA fingerprinting and mitochondrial DNA analyses have not been used in combination to study relatedness in natural populations. We present an approach that involves defining the mean fingerprint similarities among individuals thought to be unrelated because they have different mtDNA genotypes. Two classes of related individuals are identified by their distance in standard errors above this mean value. The number of standard errors is determined by analysis of the association between fingerprint similarity and relatedness in a population with a known genealogy. We apply this approach to gray wolf packs from Minnesota, Alaska, and the Northwest Territories. Our results show that: (1) wolf packs consist primarily of individuals that are closely related genetically, but some packs contain unrelated, non-reproducing individuals; (2) dispersal among packs within the same area is common; and (3) short-range dispersal appears more common for female than male wolves. The first two of these genetically-based observations are consistent with behavioral data on pack structure and dispersal in wolves, while the apparent sex bias in dispersal was not expected.USA Offprint requests to: N. Lehman at the present address 相似文献
49.
A molecular genetic analysis of social structure, dispersal, and interpack relationships of the African wild dog (Lycaon pictus ) 总被引:7,自引:0,他引:7
Derek J. Girman M. G. L. Mills Eli Geffen Robert K. Wayne 《Behavioral ecology and sociobiology》1997,40(3):187-198
The African wild dog is a highly social, pack-living predator of the African woodland and savannah. The archetypal wild dog
pack consists of a single dominant breeding pair, their offspring, and non-breeding adults who are either offspring or siblings
of one of the breeding pair. Non-breeding adults cooperate in hunting, provisioning and the protection of young. From these
observations follows the prediction that the genetic structure of wild dogs packs should resemble that of a multigenerational
family, with all same-sexed adults and offspring within a pack related as sibs or half-sibs. Additionally, a higher kinship
between females from neighboring packs should be evident if females tend to have small dispersal distances relative to males.
We test these predictions through analysis of mitochondrial DNA control region sequences and 14 microsatellite loci in nine
wild dog packs from Kruger National Park, Republic of South Africa. We show that as predicted, African wild dog packs generally
consist of an unrelated alpha male and female, subdominant close relatives, and offspring of the breeding pair. Sub-dominant
wild dogs occasionally reproduce but their offspring rarely survive to 1 year of age. Relatedness influences the timing and
location of dispersal events as dispersal events frequently coincide with a change in pack dominance hierarchy and dispersers
often move to areas with a high proportion of close relatives.
Received: 22 February 1996 / Accepted after revision: 16 November 1996 相似文献
50.
On the use of Morphologic and Molecular Genetic Characters to Investigate Species Status 总被引:1,自引:0,他引:1
Robert K. Wayne 《Conservation biology》1992,6(4):590-592