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171.
区域农地市场发育对农户水土保持行为的影响及其空间差异——基于生态脆弱区江西省兴国县、上饶县、余江县村域农户调查的分析 总被引:7,自引:0,他引:7
分析农户水土保持决策过程、建立农户水土保持决策的两阶段概念模型,从理论上分析了土地市场对农户水土保持的影响.运用在江西省兴国县、上饶县和余江县的样本村农户调查资料,通过建立土地流转与农户水土保持相互关系模型,运用Heckman的两阶段法对模型参数进行了估计.运用模型估计结果,分析土地流转对农户水土保持决策的影响并且对其区域差异进行了探讨.结果表明:从全部样本来看,农户是否意识到水土流失问题的存在以及家庭土地税费负担量对农户是否采取水土保持决策有显著影响;在兴国县,土地流入面积和费用2个因素对水土保持决策有显著影响;在余江县土地流入面积和费用也有影响显著,并且土地流入面积对农户水土保持投入的影响更强,而且土地流出面积在余江也有显著影响;上饶县,土地流出面积有显著影响.在全部样本、兴国县以及余江县,土地流出收益对农户水土保持决策的影响都不显著.最后,就进一步推进区域水土流失治理促进土地持续利用提出了相关建议. 相似文献
172.
173.
JENNIFER K. SCHULTZ JASON D. BAKER ROBERT J. TOONEN ALBERT L. HARTING BRIAN W. BOWEN 《Conservation biology》2011,25(1):124-132
Abstract: The Hawaiian monk seal (Monachus schauinslandi) is one of the most critically endangered marine mammals. Less than 1200 individuals remain, and the species is declining at a rate of approximately 4% per year as a result of juvenile starvation, shark predation, and entanglement in marine debris. Some of these problems may be alleviated by translocation; however, if island breeding aggregates are effectively isolated subpopulations, moving individuals may disrupt local adaptations. In these circumstances, managers must balance the pragmatic need of increasing survival with theoretical concerns about genetic viability. To assess range‐wide population structure of the Hawaiian monk seal, we examined an unprecedented, near‐complete genetic inventory of the species (n =1897 seals, sampled over 14 years) at 18 microsatellite loci. Genetic variation was not spatially partitioned (w=?0.03, p = 1.0), and a Bayesian clustering method provided evidence of one panmictic population (K =1). Pairwise FST comparisons (among 7 island aggregates over 14 annual cohorts) did not reveal temporally stable, spatial reproductive isolation. Our results coupled with long‐term tag‐resight data confirm seal movement and gene flow throughout the Hawaiian Archipelago. Thus, human‐mediated translocation of seals among locations is not likely to result in genetic incompatibilities. 相似文献
174.
175.
Pentachlorophenol(PCP) is a widespread,persistent environmental contaminant,and it is enzymatically activated to form a reactive metabolite,tetrachloro-l,4-benzoquinone(TCBQ).To our knowledge,there is no information about TCBQ toxicity on embryonic stem cells.Here,we demonstrated that TCBQ induced significantly apoptosis of mouse embryonic stem cells in a concentration-dependent manner.We also showed that TCBQ elevated genomic5-hydroxymethylcytosine(5hmC) by affecting ten-eleven translocation(Tet) dioxygenases in mouse embryonic stem cells.We further investigated whether Tet dioxygenases were implicated in TCBQ-induced apoptosis.By depleting all three dioxygenases(Tet1-3),we found that Tet dioxygenases slightly inhibited both early and late apoptosis induced by TCBQ at a low concentration(30 μmol/L).Meanwhile,treated by TCBQ at higher concentrations(40and 50 μmol/L),the total percentage of apoptotic cells was not affected by Tet dioxygenases.However,Tet dioxygenases tended to arrest mouse ES cells to be at early apoptotic stage and to reduce the cells to enter later apoptotic stage.These results indicate that Tet dioxygenases play a role in shaping TCBQ-induced apoptosis in mouse embryonic stem cells.Our study provides new insights into the toxicology of PCP and its reactive metabolite TCBQ. 相似文献
176.
为了研究陆生植物博落回(Macleaya Cordata)对不同化学形态铀的富集特征,采用Visual MINTEQ地球化学平衡软件设计了五种含不同化学形态铀[UO22+、CaUO2(CO3)32-、UO2Cit-、(UO2)2(EDTA)24-和UO2HPO4]的培养液,开展水培试验.博落回在这五种培养液中分别培养1、5、10、15、20和25 d后,测定其株高、根长和干质量,并用电感耦合等离子体质谱仪(ICP-MS)测定其地上部分和根部的w(铀).结果表明:在不同化学形态铀胁迫下,博落回株高无显著差异,UO2HPO4可促进博落回根的生长,而(UO2)2(EDTA)24-降低了博落回的干质量.并且,博落回根部对不同化学形态铀的富集能力大小顺序为UO22+ > UO2HPO4 > CaUO2(CO3)32- > UO2Cit- >(UO2)2(EDTA)24-,博落回地上部分对不同化学形态铀的富集能力大小顺序为UO2Cit- >(UO2)2(EDTA)24- > UO22+ > CaUO2(CO3)32- > UO2HPO4.此外,博落回根部对UO22+的富集能力很高,但地上部分很低.添加柠檬酸,培养液中铀的主要化学形态为UO2Cit-,并且在100 mg/L铀的胁迫下,博落回对UO2Cit-的生物富集系数和转移系数分别达到0.09和8.53.因此,要提高博落回对铀污染土壤中铀的富集和转移,可添加柠檬酸,促使土壤中铀的形态以UO2Cit-为主,同时要降低土壤中碳酸盐和磷酸盐的含量. 相似文献
177.
两种钝化剂对土壤Pb、Cd、As复合污染的菜地修复效果 总被引:5,自引:4,他引:1
通过辣椒种植田间试验,研究了硫酸铁和碳酸钙对土壤Pb、Cd和As复合污染的生物有效性以及对辣椒中Pb、Cd、As迁移与累积的影响.结果表明:(1)硫酸铁和碳酸钙都能显著降低土壤中Pb、Cd的TCLP提取态含量,使土壤中As的TCLP提取态含量显著升高.(2)硫酸铁使辣椒果实中Pb和Cd含量分别降低7.2%~22.9%和2.3%~2.9%,而对As含量没有影响;碳酸钙使辣椒果实中Pb、Cd、As的含量分别降低15.8%~16.3%、11.8%~15.0%、0.03%~53.2%.(3)硫酸铁使辣椒茎到果实中Pb、Cd、As的转运系数分别最大降低16.7%、68.0%、10.2%;碳酸钙使辣椒茎到果实中Pb、Cd、As的转运系数分别最大降低16.7%、51.5%、45.6%.硫酸铁和碳酸钙都能有效降低旱地中Pb、Cd、As向辣椒中迁移,且碳酸钙效果比硫酸铁好. 相似文献
178.
We report on the prenatal diagnosis and ultrasonographic findings of a second-trimester fetus with jumping translocation involving chromosome 22. A 28-year-old gravida 2, partus 1, Turkish woman was referred for genetic counselling and ultrasonographic examination at 18 weeks' gestation because of a high risk of trisomy 21 in triple test. Prenatal ultrasonography showed tetralogy of Fallot with a diverticular dilatation of the pulmonary artery, flattened brow, complete absence of the right upper limb, hypospadias, oligodactyly (three digits) in left hand and in both feet, and hyperechogenic abdominal foci. Amniocentesis revealed a karyotype of 46,XY[4]/46,XY,−8,+ der(8),t(8;22)(q24.3;q11.21)[2]/45, XY,−22,−8,+ der(8)t(8;22)(q24.3;q11.21)[22]/45,XY,−22,−5,+ der(5)t(5;22)(q35.3;q11.21)[44]. A C-banding and FISH study with a specific centromeric probe (D14Z1/D22Z1) for chromosome 22 was made. In our case, partial monosomy for the regions 22q11.21→22pter, 8q24.3→8qter and 5q35.3→5qter may partially explain the fetal malformations. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
179.
Mate choice games, context-dependent good genes, and genetic cycles in the side-blotched lizard, Uta stansburiana 总被引:4,自引:0,他引:4
According to mate choice models, a female should prefer males with traits that are reliable indicators of genetic quality
which the sire can pass on to their progeny. However, good genes may depend on the social environment, and female choice for
good genes should be context dependent. The side-blotched lizard, Uta stansburiana, exhibits genetically based throat colors (orange, blue, or yellow) that could be used as a sexually selected signal since
they reliably predict the genetic quality of mates. The frequencies of male and female morphs cycle between years, and both
male and female morphs have an advantage when rare; thus genetic quality will depend on morph frequency. A female should choose
a sire that maximizes the reproductive success of both male and female progeny. We examine a game theoretical model that predicts
female mate choice as a function of morph frequency and population density. The model predicts the following flexible mate
choice rule: both female morphs should prefer rare males in ’boom years’ of the female cycle (e.g., ’rarest-of-N rule’), but
prefer orange males in ’crash years’ of the female cycle (’orange-male rule’). Cues from the current social environment should
be used by females to choose a mate that maximizes the future reproductive success of progeny, given the social environment
of the next generation. We predict that the cue is the density of aggressive orange females. In the side-blotched lizard,
cycling mate choice games and context-dependent mate choice are predicted to maintain genetic variation in the presence of
choice for good genes.
Received: 8 March 2000 / Revised: 26 August 2000 / Accepted: 4 September 2000 相似文献
180.
Matthew A. Albrecht Oyomoare L. Osazuwa-Peters Joyce Maschinski Timothy J. Bell Marlin L. Bowles William E. Brumback Janice Duquesnel Michael Kunz Jimmy Lange Kimberlie A. McCue A. Kathryn McEachern Sheila Murray Peggy Olwell Noel B. Pavlovic Cheryl L. Peterson Jennifer Possley John L. Randall Samuel J. Wright 《Conservation biology》2019,33(3):601-611
Reintroductions are important components of conservation and recovery programs for rare plant species, but their long-term success rates are poorly understood. Previous reviews of plant reintroductions focused on short-term (e.g., ≤3 years) survival and flowering of founder individuals rather than on benchmarks of intergenerational persistence, such as seedling recruitment. However, short-term metrics may obscure outcomes because the unique demographic properties of reintroductions, including small size and unstable stage structure, could create lags in population growth. We used time-to-event analysis on a database of unusually well-monitored and long-term (4–28 years) reintroductions of 27 rare plant species to test whether life-history traits and population characteristics of reintroductions create time-lagged responses in seedling recruitment (i.e., recruitment time lags [RTLs]), an important benchmark of success and indicator of persistence in reintroduced populations. Recruitment time lags were highly variable among reintroductions, ranging from <1 to 17 years after installation. Recruitment patterns matched predictions from life-history theory with short-lived species (fast species) exhibiting consistently shorter and less variable RTLs than long-lived species (slow species). Long RTLs occurred in long-lived herbs, especially in grasslands, whereas short RTLs occurred in short-lived subtropical woody plants and annual herbs. Across plant life histories, as reproductive adult abundance increased, RTLs decreased. Highly variable RTLs were observed in species with multiple reintroduction events, suggesting local processes are just as important as life-history strategy in determining reintroduction outcomes. Time lags in restoration outcomes highlight the need to scale success benchmarks in reintroduction monitoring programs with plant life-history strategies and the unique demographic properties of restored populations. Drawing conclusions on the long-term success of plant reintroduction programs is premature given that demographic processes in species with slow life-histories take decades to unfold. 相似文献