塔里木河下游应急输水前后胡杨年轮生长差异

1972年塔里木河下游大西海子水库建成,下游365km河道彻底断流。为拯救沿河植被,2000年5月启动了塔里木河下游应急输水工程,迄今已经完成了7次应急输水。文章通过对塔里木河中游英巴扎和下游输水河畔英苏、喀尔达依、阿拉干断面胡杨(Populus euphratica)一级枝年轮取样调查,运用统计方法比较不同离河距离输水前后胡杨生长量差异的大小,分析了下游应急输水河畔胡杨种群对输水的响应。结果表明:1)英苏断面和喀尔达依断面在离河0~1000m输水前后胡杨生长量差异极显著。阿拉干断面在离河0~300m输水前后胡杨生长量差异极显著,离河300~700m生长量差异显著,700~1000m生长量差异不显著。由输水前后胡杨年轮生长量均值差可得,同一断面不同离河距胡杨年均生长量随离河距增大而降低。2)输水后下游3个调查断面在离河0~300m胡杨生长量增长由大到小顺序为:喀尔达依>英苏>阿拉干;离河300~700m由大到小顺序为:喀尔达依>阿拉干>英苏。3)以中游胡杨同年生长量作为参照对下游胡杨生长量进行相关比较的结果表明:应急输水前输水河畔各离河距离胡杨生长量均小于中游参照河段的生长量。应急输水后,输水河畔离河0~300m生长量已超过中游的生长量;离河300~700m输水河畔的生长量接近中游生长量;离河700~1000m生长量小于中游参照河段生长量,应急输水明显地促进了胡杨生长。     

Are blue eggs a sexually selected signal of female collared flycatchers? A cross-fostering experiment

Impressive variation in egg colouration among birds has puzzled evolutionary biologists for a long time. The most frequently studied selective forces moulding egg colouration—predation and brood parasitism—have either received little empirical support or may play a role in only a minority of species. A novel hypothesis has suggested that egg colour may be significantly influenced by sexual selection. Females may deposit a blue-green pigment biliverdin into eggshells instead of using it for themselves as a powerful antioxidant. By this handicap, females may signal their quality to males, which are then hypothesized to increase their paternal effort. We experimentally tested the hypothesis in the collared flycatcher (Ficedula albicollis), a species laying blue-green eggs. We cross-fostered clutches between nests to disentangle effects of female/territory quality and egg colour on paternal effort and nestling quality. The results supported two assumptions of sexual signalling through egg colour hypothesis: Blue pigment seems to be a limited resource for females, and female quality is positively correlated with the intensity of the blue-green colour. However, we did not find support for the main prediction of the hypothesis, as male parental effort parameters (feeding frequencies to nestlings and intensity of nest defence) were unrelated to egg colour. We discuss possible reasons for the discrepancy between our results and previous correlative analyses that supported the hypothesis that blue egg colour may be a postmating, sexually selected signal in females.     

Past reproductive effort affects parental behaviour in a cichlid fish,Cichlasoma nigrofasciatum: a comparison of inexperienced and experienced breeders with normal and experimentally reduced broods

Defensive and parental care behaviour of convict cichlids that differed in past effort was compared. Before testing, some fish were bred three times while others were not bred. Age was held constant; all individuals in this study were approximately 20 months old (±2 months) at test time. Furthermore, half of the pairs in this study had their broods experimentally reduced by 50%. Results indicated that past effort across breeding attempts affects investment in the current brood. Experienced pairs were more aggressive toward a model predator than inexperienced parents. However, no major differences were observed in depreciable care (i.e. fanning). Contrary to previous studies, brood size had minor effects on parental care. This discrepancy could be due to the age of the parents; individuals in this study were significantly older than fish tested in previous studies. The results support parental investment theory and suggest that past effort is not only important within breeding episodes but also within an animal's lifetime.     

The dynamics of brood desertion among communally breeding females in the treehopper, Publilia concava

In species that exhibit extended parental care, females sometimes lay eggs communally in order to redistribute the costs of offspring care. Communal egg-laying often involves redundancy in female effort, such that the number of females contributing to reproduction is more than is needed to provide adequate parental care. As a result, a subset of females will often abandon the communal brood, with the time of departure ranging from immediate abandonment after egg-laying (brood parasitism) to delayed abandonment with prolonged care (cooperative breeding). In this paper I approach the parental care dynamics of female-female broods as a desertion game similar to that of mate desertion in species with bi-parental care. I describe a field study of the insect Publilia concava (Hemiptera: Membracidae), a species that exhibits communal oviposition and a full range of egg guarding. This species exhibits full redundancy in female care, with no difference in survival between singly and doubly guarded broods. I find that double guarding is extremely rare in the population, with most communal broods having only one female guard. While this guard was usually the female that initiated the brood, these same females were more likely to abandon when secondary females arrived and when secondary females exhibited longer guarding durations. Paradoxically, the secondary females usually abandoned the broods they visited, resulting in up to 50% of broods with double abandonment. These unguarded broods suffered a 50% reduction in hatching success, reflecting an important risk for primary females that abandon egg masses to secondary females. Overall, P. concava exhibits desertion dynamics similar to mate desertion in vertebrates and it is likely that the theoretical work in this area will be useful for future work that addresses the allocation of parental care among communal breeders.     

Asymmetric costs favor female desertion in the facultatively polyandrous northern flicker (Colaptes auratus): a removal experiment

Previous studies of biparental care in birds have focused on the males contribution and experimental removal of males. Woodpeckers, with a high level of paternal care including nocturnal incubation and brooding by males, offer a meaningful system in which to examine the importance of care by females. I studied the reproductive performance of 17 widowed male and 8 widowed female northern flickers (Colaptes auratus) relative to biparental (control) pairs. Of these single parents all widowed shortly after hatching, only one female abandoned its nest. Single parents boosted their provisioning rates to achieve 83% the provisioning rate of control broods, but reared significantly fewer young and young of poorer quality. However, single males, with 85% of the reproductive success of controls, were more successful than females with 43% the success of controls. Among widowed birds, a not significant lower survival was observed, but the chance of re-pairing with the same partner in a subsequent year was only 16% in the natural population, so long-term costs of desertion may be small. Although females seem to have the incentive and ability to desert, a lack of available males may constrain opportunities. This study demonstrates that when parental care roles are reversed in altricial birds, asymmetric benefits can favor female and not male desertion.     

海河流域不同植物砣含量、地域分异及其输入、输出量研究

海河流域是我国农业发展的一个重要基地,由于不合理开发利用,造成某些地区土壤出现贫瘠化、盐渍化和沙漠化,土壤缺磷也很明显.为了寻找植物对磷的需求特点以及海河流域土壤磷分布规律,可以从植物指示的角度研究不同地区不同植物磷含量特征及其差异,研究植物每年从土壤中输出和输入的磷总量,从而寻找农业生态系统磷循环规律并科学指导施肥.     

中国环保投入拉动内需问题初探

本文就加大环保投入对推动内需问题从现状及潜在力进行了分析初探，并就如何加大环保投入提出建议。     

三峡库区人类活动净氮输入量估算及其影响因素

建立包括食品/饲料,氮肥,大气沉降和生物固氮4部分的人类活动净氮输入模型（NANI）,采用单因素方差分析法（one-way ANOVA）和灰色关联度法,研究2006~2016年三峡库区人类活动净氮输入估量的时空分布、组成特征及其贡献率、影响因素.结果表明：（1）三峡库区的NANI估量存在明显的时空差异特征,从2006年的10715.2kg/（km²·a）到2016年的11974.1kg/（km²·a）,整体呈现先线性上升后下降的年际变化趋势,以及库首,库尾高,库区腹地低且南部高,北部低的空间分布特征.（2）三峡库区的NANI的组成中,氮肥施用量所占比重最大为50%~56%,是主要输入源,其次是大气氮沉降量,所占比重为22%~24%;相关性分析中,氮肥施用量与NANI相关性最强,R²达到了0.81（P<0.0001）.（3）人口密度,粮食产量,农业生产总值和地区生产总值等与NANI的关联度均较高,分别为0.901,0.867,0.794,0.689,NANI值随人口密度的增大而增大,但当人口密度到达一定值（500人/km²）时,其值不再变化;NANI值随着耕地面积的增加而增大,随着森林面积的增加而减小.     

氮输入对沼泽湿地小叶章枯落物分解过程中酶活性的影响

以三江平原沼泽湿地典型湿地植物小叶章枯落物(Calamagrostis angustifolia)为研究对象,采用分解袋法研究了不同外源氮输入(N1、N2分别为6、12g·m-·2a-1)对小叶章枯落物分解过程酶活性的影响,并设置对照区(N0,0g·m-·2a-1)进行比较.研究结果表明,在枯落物最初分解的2个月里,氮输入会抑制蔗糖酶活性,尤其是低氮输入(N1)抑制作用显著(p<0.05),2个月后,氮输入显著促进了该酶活性(p<0.05);;氮输入除在160d时抑制了淀粉酶活性,其它时期均促进了该酶活性,且高氮输入(N2)促进作用显著;;氮输入提高了枯落物分解前2个月的脲酶活性,而在分解后期,低氮输入抑制脲酶活性,高氮输入则主要表现为促进脲酶活性;;低氮输入提高了小叶章枯落物分解前2个月的酸性磷酸酶活性,随后表现为抑制,高氮输入则只在分解后期(160d)抑制酸性磷酸酶活性,其它时期均表现为促进.总体而言,氮输入促进了蔗糖酶、淀粉酶活性,而对于脲酶及酸性磷酸酶活性来说,低氮输入抑制了酶活性,而高氮输入则表现为促进酶活性.     

绍兴平原二种典型农田系统中重金属流及其平衡分析

以浙江省绍兴平原为例,选择水稻（Orgza sativa L.）和蔬菜[大白菜（Brassica campestris L.ssp.pekinensis）]等2种典型农田系统,进行为期1年的观察分析,研究了农田系统中主要重金属元素流及平衡状况。结果表明,研究区农田系统中重金属来源物和农产品及排水中重金属含量有较大的空间变异性。有机肥和生活垃圾中重金属含量明显高于化肥,不同化肥品种中重金属含量：磷肥、复合肥钾肥氮肥。农田系统中重金属的输入量：有机肥施用（60.40%～99.36%）大气沉降（0.46%～39.26%）化肥施用（0.17%～1.45%）灌溉水（0.0016%～1.62%）。农田系统中Pb、Cd、Zn和Hg的输出量：农产品地表排水;重金属总积累量和输入强度：ZnCuPbCdHg。总体上,蔬菜生产系统中重金属的输入和累积量水稻生产系统。