长江经济带旅游产业集聚与旅游业碳排放关系研究

基于2001~2015年长江经济带旅游产业集聚水平与旅游业碳排放量的测算结果,科学构建面板数据模型,实证探讨旅游产业集聚与旅游业碳排放之间的内在联系,以揭示旅游产业集聚水平对其碳排放的影响效应。研究表明:(1)长江经济带旅游产业集聚水平在时序上呈波动上升态势,在空间格局上旅游产业集聚程度省际差异显著;其中,下游地区旅游产业集聚水平高于中上游地区;(2)长江经济带旅游业CO_2排放量由2001年的142×104t抬升到2015年的443×104t,下游地区旅游业CO_2排放占据长江经济带CO_2排放量的主导地位;(3)随着旅游产业集聚程度的逐渐增强,长江经济带旅游业CO_2排放总量出现"倒U型"特征。

Missing Data Imputation for Traffic Flow Based on Improved Local Least Squares

Complete and reliable field traffic data is vital for the planning, design, and operation of urban traf- fic management systems. However, traffic data is often very incomplete in many traffic information systems, which hinders effective use of the data. Methods are needed for imputing missing traffic data to minimize the effect of incomplete data on the utilization. This paper presents an improved Local Least Squares （LLS） ap- proach to impute the incomplete data. The LLS is an improved version of the K Nearest Neighbor （KNN） method. First, the missing traffic data is replaced by a row average of the known values. Then, the vector angle and Euclidean distance are used to select the nearest neighbors. Finally, a regression step is used to get weights of the nearest neighbors and the imputation results. Traffic flow volume collected in Beijing was analyzed to compare this approach with the Bayesian Principle Component Analysis （BPCA） imputation ap- proach. Tests show that this approach provides slightly better performance than BPCA imputation to impute missing traffic data.

Seed traits and rodent community interact to determine seed fate:evidence from both enclosure and field experiments

Animal-mediated seed dispersal is an important ecological process in which a strong mutualism between animals and plants can arise.However,few studies have examined how a community of potential seed dispersers interacts with sympatric seed trees.We employed a series of experiments in the Qinling Mountains in both semi-natural enclosure and the field to assess the interactions among 3 sympatric rodent species and 3 Fagaceae tree seeds.Seed traits all showed similar tannin levels but markedly different physical traits and nutritional contents.We found that seeds with heavy weight,thick coat,and high nutritional contents were less likely to be eaten in situ but more often to be eaten after dispersal or hoarded by rodents.These results support both the handling time hypothesis and the high nutrition hypothesis.Surprisingly,we also found that rodents,maybe,preferred to consume seeds with low levels of crude fiber in situ,and to harvest and hoard those with high levels of crude fiber for later consumption.The sympatric rodent species,Cansumys canus,the largest rodent in our study,harvested and hoarded more Quercus variabilis seeds with high physical and nutritional traits,while Apodemus draco,the smallest rodent,harvested more Q.serrata seeds with low physical and nutritional traits,and Niviventer confucianus harvested and hoarded more Q.aliena seeds with medium physical and nutritional traits.Our study demonstrates that different seed traits play different roles in influencing the seed fate and the shaping of mutualism and predation interactions within a community of rodent species.

Effects of insect infestation on rodent-mediated dispersal of Quercus aliena:results from field and enclosure experiments

Rodents influence plant establishment and regeneration by functioning as both seed predators and dispersers.However,these rodent-plant interactions can vary significantly due to various environmental conditions and the activity of other insect seed predators.Here,we use a combination of both field and enclosure(i.e.individual cage and semi-natural enclosure)experiments,to determine whether rodents can distinguish sound seeds from those infested with insects.We also demonstrate how such responses to insects are influenced by food abun-dance and other environmental factors.We presented rodents with 2 kinds of Quercus aliena seeds(sound and insect-infested seeds)in a subtropical forest in the Qinling Mountains,central China,from September to No-vember of 2011 to 2013.The results showed that rodents preferred to hoard and eat sound seeds than infested seeds in the field and semi-natural enclosure,while they preferred to eat infested seeds over sound seeds in the individual cages.In addition,both hoarding and eating decisions were influenced by food abundance.Rodents hoarded more sound seeds in years of high food abundance while they consumed more acorns in years of food shortage.Compared with field results,rodents reduced scatter-hoarding behavior in semi-natural enclosures and ate more insect-infested seeds in smaller individual cages.These results further confirm that rodents distinguish infested seeds from non-infested seeds but demonstrate that this behavior varies with conditions(i.e.environ-ment and food abundance).We suggest that such interactions will influence the dispersal and natural regenera-tion of seeds as well as predation rates on insect larvae.

Anti-fertility effect of levonorgestrel and/or quinestrol on striped field mouse(Apodemus agrarius):evidence from both laboratory and field experiments

The effect of combined levonorgestrel(P)and quinestrol(E)on the fertility of stripedfield mouse(Apodemus agrarius)has not been evaluated.We performed a series of experiments in both the laboratory andfield to assess the effect of P and/or E on the fertility of A.agrarius.In the laboratory,to test the time-dependent anti-fertility ef-fects of P and E,as well as their mixtures,90 male stripedfield mice were randomly assigned to 6 treatment groups(n=60),and a control group(n=30).Mice in 3 treatment groups were administered 1 of the 3 compounds(1 mg�kg–1[body weight]EP-1,0.34 mg�kg–1 E,0.66 mg�kg–1 P)for 3 successive days(another half for 7 suc-cessive days)via oral gavage;mice were then sacrificed 15 and 45 days after initiating the gavage treatment.Ourfindings indicated that E and EP-1 treatment,but not P or control treatment,significantly decreased the sperm count in the caudal epididymis,as well as the weight of the testes,epididymides,and seminal vesicles.Additionally,fer-tile female mice mated with E-and EP-1-treated males produced smaller pups.These data indicate that E and EP-1 can induce infertility in male A.agrarius.In thefield,the population density of A.agrarius was significantly influ-enced by EP-1,and the rodent density in the treatment group was lower than that in the control group.Overall,our results indicate that EP-1 is an effective contraceptive in A.agrarius,a dominant rodent species in the farmland.