拔节期水稻光合碳输入的动态变化及其对施氮的响应:13C-CO2脉冲标记

水稻光合碳是稻田土壤有机碳的重要来源之一,其在土壤中输入与分配特征受水稻生长状况和土壤肥力的影响.施肥是影响水稻生长的关键因素,为了探讨施氮对水稻拔节期光合碳的传输动态的影响,应用稳定同位素13C-CO2脉冲标记技术,通过盆栽试验,研究光合碳在水稻-(根际/非根际)土壤系统中输入与分配的动态变化及其对施氮的响应.结果表明,施氮显著增加了水稻地上部和根系生物量,降低了水稻根冠比.随着水稻的生长,水稻植株的13C丰度逐渐下降,根际土和非根际土中13C丰度先减少再增加;施氮显著增加了根际土壤中13C丰度,较不施氮相比增加了9.5%~32.6%.施氮使水稻地上部和根系中光合13C含量显著增加,较不施氮处理分别增加了24.5%~134.7%和9.1%~106%.脉冲标记一次性输入的光合13C主要分配在水稻植株体内,不施氮和施氮条件下的分配率分别为85.5%~93.2%和91.3%~95.7%;施氮显著影响光合碳在水稻地上部、根际土和非根际土中的分配特征(P0.01),标记后26 d,与不施氮处理相比,施氮使光合碳在水稻地上部的分配增加了13.4%,在根际土和非根际土中的分配分别减少了21.9%和52.2%.因此,施氮增加了光合碳在土壤-水稻系统中的分配,但降低了光合碳在土壤中的累积.本研究进一步探讨了施氮条件下水稻拔节期光合碳的分配,为明确氮素对光合碳在水稻拔节期的动态变化以及对土壤有机碳库的影响,和深入了解农田土壤有机质累积提供理论依据和数据支持.     

Host pollination mode and mutualist pollinator presence: net effect of internally ovipositing parasite in the fig–wasp mutualism

The Ficus–their specific pollinating fig wasps (Chalcidoidea, Agaonidae) interaction presents a striking example of mutualism. Figs also shelter numerous non-pollinating fig wasps (NPFW) that exploit the fig–pollinator mutualism. Only a few NPFW species can enter figs to oviposit, they do not belong to the pollinating lineage Agaonidae. The internally ovipositing non-agaonid fig wasps can efficiently pollinate the Ficus species that were passively pollinated. However, there is no study to focus on the net effect of these internally ovipositing non-agaonid wasps in actively pollinated Ficus species. By collecting the data of fig wasp community and conducting controlled experiments, our results showed that internally ovipositing Diaziella bizarrea cannot effectively pollinate Ficus glaberrima, an actively pollinated monoecious fig tree. Furthermore, D. bizarrea failed to reproduce if they were introduced into figs without Eupristina sp., the regular pollinator, as all the figs aborted. Furthermore, although D. bizarrea had no effect on seed production in shared figs, it significantly reduced the number of Eupristina sp. progeny emerging from them. Thus, our experimental evidence shows that reproduction in Diaziella depends on the presence of agaonid pollinators, and whether internally ovipositing parasites can act as pollinators depends on the host fig’s pollination mode (active or passive). Overall, this study and others suggest a relatively limited mutualistic role for internally ovipositing fig wasps from non-pollinator (non-Agaonidae) lineages.     

Different patterns of oviposition learning in two closely related ectoparasitoid wasps with contrasting reproductive strategies

Many parasitoid wasps learn host-associated cues and use them in subsequent host-searching behavior. This associative learning, namely “oviposition learning,” has been investigated in many studies. However, few studies have compared multiple species, and no comparative study has previously been conducted on ectoparasitoid species. We compared the effects of oviposition learning on host preference and offspring sex ratio in two closely related ectoparasitoid wasps with contrasting reproductive strategies, Anisopteromalus calandrae (r-strategist) and its sibling species (K-strategist). Using two bruchine hosts, Callosobruchus chinensis and Callosobruchus maculatus larvae infesting the cowpea Vigna unguiculata, oviposition choice experiments were performed at high and low host densities. In both species, no conspicuous effect on the offspring sex ratio was detected, but effects on host preference were found to differ between the species. In A. calandrae, the effects were detected only at high host density, suggesting that oviposition learning plays a role in host discrimination from a short distance but not from a long distance. In the sibling species, those effects were not detected in any of the cases, suggesting the absence of oviposition learning. These results are compatible with those of previous comparative studies of endoparasitoid wasps in that few lifetime oviposition experiences and/or low reward per foraging decision result in low or absent oviposition learning ability. This finding may indicate that ecological traits contributing to learning ability are similar between endoparasitoid and ectoparasitoid wasps. Thus, our species comparison of ectoparasitoids provides another model system for investigating learning and memory dynamics in parasitoid wasps.     

咸水滴灌对棉田土壤N2O排放和反硝化细菌群落结构的影响

淡水资源短缺是干旱区农业可持续发展所面临的严峻问题,合理利用咸水灌溉是缓解淡水资源不足的重要手段.长期咸水灌溉会导致土壤盐分积累,进而影响氮素的转化和N_2O的排放.本研究通过10 a咸水灌溉试验,探究咸水灌溉对棉田土壤N_2O排放、反硝化细菌丰度和群落结构组成的影响.试验采用灌溉水盐度和施氮量两因子2×2随机区组设计,其中灌溉水盐度(以电导率表示)设置2个水平:0.35 dS·m~(-1)和8.04 dS·m~(-1),施氮量设2个水平:0 kg·hm~(-2)和360 kg·hm~(-2)(分别用SFN0、SHN0、SFN360和SHN360表示).结果表明,长期咸水滴灌棉田土壤盐分、含水量和NH~+_4-N含量显著增加,pH值、NO~-_3-N、有机质和全氮含量显著降低.咸水灌溉处理显著抑制N_2O排放,不施氮肥和施氮肥处理下分别较淡水灌溉降低45.19%和43.50%.氮肥施用显著增加N_2O排放,施肥处理N_2O排放较不施肥处理增加161%.不施肥条件下,咸水灌溉显著降低反硝化酶活性、nirK、nirS和nosZ基因丰度,α多样性.施肥条件下,咸水灌溉对nosZ型反硝化细菌的丰度无显著影响,但显著降低反硝化酶活性和nirK、nirS基因丰度.咸水灌溉和氮肥施用共同改变nirK、nirS和nosZ型反硝化细菌群落结构,灌溉水盐度对于反硝化细菌群落结构的影响要大于施肥.Lefse分析显示nirK、nirS和nsoZ型反硝化细菌差异物种随着灌溉水盐度的增加而增加,咸水灌溉显著改变反硝化细菌群落结构,导致优势种群数量增加.上述结果表明,长期咸水灌溉降低土壤N_2O排放,但会导致土壤盐分的持续上升,nosZ、nirK和nirS丰度的增加会促进N_2O排放.     

Diploid males, diploid sperm production, and triploid females in the ant Tapinoma erraticum

Under complementary sex determination (CSD), females of Hymenoptera arise from diploid, fertilized eggs and males from haploid, unfertilized eggs. Incidentally, fertilized eggs that inherit two identical alleles at the CSD locus will develop into diploid males. Diploid males are usually unviable or sterile. In a few species, however, they produce diploid sperm and father a triploid female progeny. Diploid males have been reported in a number of social Hymenoptera, but the occurrence of triploid females has hardly ever been documented. Here, we report the presence of triploid females, diploid males, and diploid sperm (produced by diploid males and stored in queen spermathecae) in the ant Tapinoma erraticum. Moreover, we show variations in the frequency of triploids among female castes: Triploid females are more frequent among workers than virgin queens; they are absent among mated, reproductive queens. The frequency of triploid workers also varies between populations and between nests within populations.     

长期定位有机物料还田对关中平原夏玉米-冬小麦轮作土壤NO排放的影响

农田土壤是大气光化学活性气体一氧化氮(NO)的主要人为源之一.为定量研究有机物料还田对NO排放的影响,利用静态暗箱法对关中平原26 a长期定位施肥夏玉米-冬小麦轮作农田NO排放通量进行周年(2016年6月至2017年6月)观测.除对照(CK)处理全年不施肥外,田间设3个施肥处理,冬小麦季分别为全化肥(NPK,165 kg·hm~(-2))、化肥加秸秆[NPKS,(165+40)kg·hm~(-2)]和化肥加牛粪[NPKM,(50+115)kg·hm~(-2)];夏玉米季均施等量化肥(188 kg·hm~(-2)).观测期内,CK处理NO排放通量较小[12.2 g·(hm~2·d)~(-1)];各施肥处理均在夏玉米播种、施肥和冬小麦施肥后出现排放峰,其中NPK处理峰值最高[112.0 g·(hm~2·d)~(-1)].各处理NO年排放总量和排放系数分别为0.13~0.57 kg·hm~(-2)和0.04%~0.12%.NPKS和NPKM处理年排放总量较NPK分别减少17.6%和增加68.0%(P0.05).与NPK处理相比,NPKS和NPKM冬小麦季排放总量降低41.1%~60.0%(P0.05);但夏玉米季增加25.2%~292.1%(P0.05).冬小麦季添加有机物料有效降低NO排放,而夏玉米季NO排放增加则与土壤有机质含量有关.     

Reproductive disturbance of Japanese bumblebees by the introduced European bumblebee Bombus terrestris

The European bumblebee, Bombus terrestris, is an invasive eusocial species whose distribution is expanding greatly beyond its native range because numerous colonies are imported to or locally produced in non-native countries for pollination of agricultural crops. Closely related species exist in Japan where the unrestricted import and use of B. terrestris has resulted in the establishment of wild colonies. Laboratory studies previously showed that B. terrestris and Japanese native species can copulate and produce fertilized eggs. Although these eggs do not hatch, the interspecific mating can cause a serious reproductive disturbance to native bumblebees. In this study, we determined the frequencies of interspecies mating between B. terrestris males and native bumblebee queens in the wild on the islands of Hokkaido and Honshu by analyzing the DNA sequences of spermatozoa stored in spermathecae of native queens. We found that 20.2% of B. hypocrita hypocrita queens and 30.2% of B. hypocrita sapporoensis queens had spermatozoa of B. terrestris males in their spermathecae. Given that a Bombus queen generally mates only once in her life, such high frequencies of interspecific mating with B. terrestris pose serious threats to the populations of native bumblebees in Japan.     

Effects of two sterol-inhibiting fungicides on populations of pest and beneficial arthropods on apple

This research demonstrated that sterol-inhibiting fungicides alter the population structure of some pest and beneficial arthropods in apple orchards. Orchard populations of European red mite, Panonychus ulmi (Koch) (Acarina: Tetranychidae); the predacious mite, Typhlodromus caudiglans Schuster (Acarina: Phytoseiidae); the spotted tentiform leafminer, Phyllonorycter blancardella Fabr. (Lepidoptera: Gracillariidae); the leafminer parasite Pholetesor ornigis Weed (Hymenoptera: Braconidae); the green apple aphid, Aphis pomi DeGeer (Homoptera: Aphididae); white apple leafhopper, Typhlocyba pomaria McAtee (Homoptera: Cicadellidae); Campylomma verbasci Meyer (Hemiptera: Miridae); chalcids, primarily Sympiesis sericeicornis Nees (Hymenoptera: Chalcididae), were monitored for two growing seasons in a McIntosh apple orchard that had received applications, at 2-week intervals, of two sterol-inhibiting fungicides, bitertanol and flusilazole. High rates of flusilazole were associated with increased numbers of European red mite and decreased numbers of predacious mite species, particularly T. caudiglans. Trees receiving a high rate of bitertanol had fewer European red mites and predacious mite species. Fungicides did not influence spotted tentiform leafminer oviposition or the number of leafminer larvae in May and June 1985. However, in September 1985 there were fewer leafminer pupae in plots treated with the two lower rates of flusilazole and more larvae in plots treated with the high rate of bitertanol, relative to trees sprayed with captan. In 1986, there were more leafminer eggs in plots treated with the low rate of bitertanol compared with captan and non-sprayed trees. However, by 24 June, all treatments showed similar levels of leafminer larvae and pupae. Populations of P. ornigis were generally higher in trees treated with flusilazole in both years. Numbers of aphids and mullein bug were higher in trees treated with flusilazole relative to non-sprayed and captan-treated trees. Chalcid populations were higher in bitertanol-treated trees. Fungicides had no apparent effect on populations of white apple leafhopper.     

Indirect interactions between invasive and native plants via pollinators

In generalised pollination systems, the presence of alien plant species may change the foraging behaviour of pollinators on native plant species, which could result in reduced reproductive success of native plant species. We tested this idea of indirect interactions on a small spatial and temporal scale in a field study in Mauritius, where the invasive strawberry guava, Psidium cattleianum, provides additional floral resources for insect pollinators. We predicted that the presence of flowering guava would indirectly and negatively affect the reproductive success of the endemic plant Bertiera zaluzania, which has similar flowers, by diverting shared pollinators. We removed P. cattleianum flowers within a 5-m radius from around half the B. zaluzania target plants (treatment) and left P. cattleianum flowers intact around the other half (control). By far, the most abundant and shared pollinator was the introduced honey bee, Apis mellifera, but its visitation rates to treatment and control plants were similar. Likewise, fruit and seed set and fruit size and weight of B. zaluzania were not influenced by the presence of P. cattleianum flowers. Although other studies have shown small-scale effects of alien plant species on neighbouring natives, we found no evidence for such negative indirect interactions in our system. The dominance of introduced, established A. mellifera indicates their replacement of native insect flower visitors and their function as pollinators of native plant species. However, the pollination effectiveness of A. mellifera in comparison to native pollinators is unknown. Christine B. Müller, deceased 7 March 2008.     

Biomolecules preserved in ca. 168 million year old fossil conifer wood

Biomarkers are widely known to occur in the fossil record, but the unaltered biomolecules are rarely reported from sediments older than Paleogene. Polar terpenoids, the natural products most resistant to degradation processes, were reported mainly from the Tertiary conifers, and the oldest known are Cretaceous in age. In this paper, we report the occurrence of relatively high concentrations of ferruginol derivatives and other polar diterpenoids, as well as their diagenetic products, in a conifer wood Protopodocarpoxylon from the Middle Jurassic of Poland. Thus, the natural product terpenoids reported in this paper are definitely the oldest polar biomolecules detected in geological samples. The extracted phenolic abietanes like ferruginol and its derivatives (6,7-dehydroferruginol, sugiol, 11,14-dioxopisiferic acid) are produced only by distinct conifer families (Cupressaceae s. l., Podocarpaceae and Araucariaceae), to which Protopodocarpoxylon could belong based on anatomical characteristics. Therefore, the natural product terpenoids are of great advantage in systematics of fossil plant remains older than Paleogene and lacking suitable anatomical preservation.     

The role of plant leaf attributes in linking land use to ecosystem function in temperate grassy vegetation

We tested predictions of the relative changes in plant leaf traits in response to land uses in Australian eucalypt grassy ecosystems. Predictions were determined from responses observed in European landscapes in relation to disturbances associated with agricultural land uses. We measured specific leaf area (SLA) and leaf dry matter content (LDMC) across five land uses: reference sites (closest to pre-European state), native pastures (unfertilized), fertilized pastures, sown pastures (cultivated and fertilized) and enriched grassland (previously fertilized, no longer grazed). Leaves were expected to have higher SLA and lower LMDC at sites with increasing fertility and/or disturbance.The predictions were confirmed, with SLA increasing progressively in land uses associated with (1) grazing; (2) grazing and fertilization; (3) grazing, fertilization and cultivation. Values for LDMC were closely (but inversely) correlated with those of SLA. For both traits, there were relationships with available soil phosphorus but not with soil total nitrogen. The positive correlation of SLA with phosphorus was not evident above 30 mg kg⁻¹, the recommended level of phosphorus for improved pastures.Results confirm patterns of leaf-trait response to disturbance that reflect fundamental constraints to plant survival in habitats with different levels of resources and disturbances. A conservative strategy for low productivity undisturbed habitats is associated with low SLA and high dry matter content in contrast to fertile disturbed habitats which select for high SLA and low dry matter content. The changes in leaf traits across land uses resulted from species substitution rather than variation within species across sites, and most notably the replacement of native by annual exotic species as land use intensifies.Recommended fertilization rates for pasture production convert the ground layer to plants with soft, digestible leaves, that are responsive to fertilizer and desirable for livestock production. However, fertilization also drastically reduces the diversity of native plants and annual plants tend to dominate. The trade-off associated with high production includes increased vulnerability to soil erosion, due to reduced plant cover and low persistence of cover. If alternative ecosystem values such as erosion control, water quality, salinity control and biodiversity persistence are required, incentives may be needed to offset the loss of production that can be gained from fertilizer application.     

Sex-specific effects of parasites on telomere dynamics in a short-lived passerine—the blue tit

The pollination syndrome concept implies that flowers evolved with particular sets of characteristics, such as colors, shapes, orientations, and rewards, as a means of attracting pollinators. However, these traits may have also evolved to deter unwanted visitors. The North American genus Penstemon exhibits a great floral diversity that is mainly associated with bumblebee and hummingbird pollination. Evolutionary shifts from insect pollination to hummingbird pollination have occurred in Penstemon repeatedly, but some species maintain mixed-pollination systems and intermediate floral traits between bee- and hummingbird-pollination modes. The apparently intermediate floral traits of species with mixed-pollination systems might be potentially acting to deter bumblebee foragers. Then, bird-flower traits might be selected with increased hummingbird visitation over evolutionary time might, resulting in specialization to and the evolution of floral traits present in hummingbird-pollinated species. Here, we modified bee-pollination floral traits in Penstemon gentianoides with a mixed pollination system, to resemble hummingbird-pollination traits, and measured the effects of trait modification on bumblebee foraging behavior and plant female reproductive fitness. Our results showed that reduction in the width of the corolla tube and the absence of the corolla lip negatively affects bumblebee visitation and their efficiency as pollinators, and that the synergistic interaction of both traits enhanced the “anti-bee” effect. We conclude that acquisition of floral traits that resemble those of hummingbird-pollination enables Penstemon plant species to deter bumblebee visits.

     

Oviposition by small hive beetles elicits hygienic responses from Cape honeybees

Two novel behaviours, both adaptations of small hive beetles (Aethina tumida Murray) and Cape honeybees (Apis mellifera capensis Esch.), are described. Beetles puncture the sides of empty cells and oviposit under the pupae in adjoining cells. However, bees detect this ruse and remove infested brood (hygienic behaviour), even under such well-disguised conditions. Indeed, bees removed 91% of treatment brood (brood cells with punctured walls caused by beetles) but only 2% of control brood (brood not exposed to beetles). Only 91% of treatment brood actually contained beetle eggs; the data therefore suggest that bees remove only that brood containing beetle eggs and leave uninfected brood alone, even if beetles have accessed (but not oviposited on) the brood. Although this unique oviposition strategy by beetles appears both elusive and adaptive, Cape honeybees are able to detect and remove virtually all of the infested brood.     

Cosmosperma polyloba gen. et sp. nov., a seed plant from the Upper Devonian of South China

Seed plants with ovules were abundant in the Late Devonian of Euramerica and they contribute significantly to our understanding of their early history. However, coeval ovules have been scarce in other regions of the world. Specimens of the seed plant Cosmosperma polyloba gen. et sp. nov. Wang et al. were recently obtained from the Upper Devonian (Famennian) Wutong Formation, at Fanwan Village, Changxing County, Zhejiang Province, China. This new seed plant has cupulate ovules, the uniovulate cupules with up to 16 distal segments and with minute spines on the outer surface, synangiate pollen organs bearing six to eight microsporangia fused only at the base, and planate and highly dissected pinnules in alternate arrangement. It differs from other Devonian seed plants mainly in the organization and position of the uniovulate and ornamented cupule, and in the highly dissected pinnules. Cosmosperma Wang et al. represents the first Devonian ovules recovered from China or eastern Asia and further illustrates the diversity of early spermatophytes. As for the Late Devonian seed plants, it is suggested that the pollen organs are synangiate and simple in organization, and the branches and leaves are generally planate.     

天津市常用绿化树种挥发性有机物排放潜力估算

BVOCs（植被释放的挥发性有机物）对PM_2.5等大气颗粒物的形成有重要贡献,树种BVOCs排放潜力的研究有助于城市绿化树种的科学选择.对天津市城市绿地常见绿化树种BVOCs样品进行采集与鉴定,基于Guenther提出的模型估算了天津市32种常见绿化树种BVOCs的排放量,并对估算过程中的不确定性因素进行分析.结果表明:构树、毛白杨、旱柳和绦柳的BVOCs排放量（以C计）最高,分别为2 179.438、2 147.394、2 116.537、2 045.722 g/（株·a）.从科属的角度来看,杨柳科植物BVOCs排放量最高,豆科、桑科和松科BVOCs排放量位居其次.采用聚类分析方法将32种绿化树种的异戊二烯、单萜烯排放潜力进行分类,其中毛白杨、构树、旱柳和绦柳属于高排放异戊二烯的树种;油松和苹果属于高排放单萜烯的树种.从科属水平而言,豆科和杨柳科植物具有较强的异戊二烯排放潜力.松科和部分蔷薇科的乔木具有较强的单萜烯排放潜力.从叶片类型的角度上,阔叶树主要以排放异戊二烯为主,针叶树主要以排放单萜烯为主,且异戊二烯的排放潜力要大于单萜烯的排放潜力.植物OVOCs（其他VOCs）排放潜力与异戊二烯和单萜烯的排放潜力相比显著较弱.天津市外来树种与本地树种BVOCs排放潜力无显著性差异（P＞0.05）.研究显示,天津市常用绿化树种的单株排放潜力差异明显,因此可优选臭椿、洋白蜡和紫叶李等排放潜力相对较低的树种用作城市绿化.      

Bird pollination of Canary Island endemic plants

The Canary Islands are home to a guild of endemic, threatened bird-pollinated plants. Previous work has suggested that these plants evolved floral traits as adaptations to pollination by flower specialist sunbirds, but subsequently, they appear to have co-opted generalist passerine birds as sub-optimal pollinators. To test this idea, we carried out a quantitative study of the pollination biology of three of the bird-pollinated plants, Canarina canariensis (Campanulaceae), Isoplexis canariensis (Veronicaceae) and Lotus berthelotii (Fabaceae), on the island of Tenerife. Using colour vision models, we predicted the detectability of flowers to bird and bee pollinators. We measured pollinator visitation rates, nectar standing crops as well as seed-set and pollen removal and deposition. These data showed that the plants are effectively pollinated by non-flower specialist passerine birds that only occasionally visit flowers. The large nectar standing crops and extended flower longevities (>10 days) of Canarina and Isoplexis suggests that they have evolved a bird pollination system that effectively exploits these low frequency non-specialist pollen vectors and is in no way sub-optimal. Seed set in two of the three species was high and was significantly reduced or zero in flowers where pollinator access was restricted. In L. berthelotii, however, no fruit set was observed, probably because the plants were self-incompatible horticultural clones of a single genet. We also show that, while all three species are easily detectable for birds, the orange Canarina and the red Lotus (but less so the yellow-orange Isoplexis) should be difficult to detect for insect pollinators without specialised red receptors, such as bumblebees. Contrary to expectations if we accept that the flowers are primarily adapted to sunbird pollination, the chiffchaff (Phylloscopus canariensis) was an effective pollinator of these species.     

The larval parasitoid <Emphasis Type="Italic">Microplitis croceipes</Emphasis> oviposits in conspecific adults

Microplitis croceipes (Hymenoptera: Braconidae) is a larval parasitoid of Helicoverpa/Heliothis spp. In the course of mass rearing of M. croceipes, we found that females oviposited in the conspecific adults in rearing cages. When 20 pairs of inexperienced females and males or of experienced females and males were reared in a cage, the males lived for 14–15 days and the females for 18–20 days on average. At their death, 37–42% of the males and 50–57% of the females contained conspecific eggs or first instar larvae in their abdominal cavity. When two of inexperienced females met on a host-infested leaf of soybean, they attempted to sting each other. Of the attacked females, 30% contained a conspecific egg laid in their abdomen. In abdominal cavity of the adults parasitized by a conspecific female, the majority of the parasitoid eggs laid disappeared within 1 day after oviposition. Only 10–30% of the parasitoid eggs laid in conspecific adults hatched 3–4 days after oviposition, but those larvae never molted to second instar. When the adults were stung by one or two conspecific females, their subsequent longevity was significantly shorter than that for the control adults. Oviposition in conspecific adults may be prevalent in other parasitic wasps that quickly oviposit without intensive host examination, and have cuticle and size of abdomen to be stung by conspeicifcs.     

Mating behavior of a flower-visiting longhorn beetle Zorion guttigerum (Westwood) (Coleoptera: Cerambycidae: Cerambycinae)

Long-range sex pheromones have been demonstrated for several cerambycid beetle species. Our field study on the mating behavior of Zorion guttigerum, on the basis of its temporal and spatial distributions on mating and feeding sites (flowers), and longevity, however, suggests that such pheromones are not used by this species. Plant characteristics rather than long-range sex pheromones may play an important role in bringing both sexes together. Adult activities on flowers occur exclusively during the day with two peaks, one around midday and the other in the late afternoon. Overall operational sex ratio is male-biased (1 :1.5 ) but it becomes very highly male-biased (1 :9 ) when mating and feeding activities decrease to the minimum in mid-afternoon, suggesting that females leave flowers to oviposit during that period of time. For cerambycid species whose females oviposit alone, and in which mating and oviposition occur on different plants or different plant parts, the operational sex ratio appears to vary significantly over time on the mating sites. The number and duration of pair-bondings also vary over time for Z. guttigerum. Fewer and shorter pair-bondings in the morning may suggest a strong sexual selection process. After 2 h of selection, both sexes tend to engage in longer pair-bondings and mate more times before females leave the mating sites in mid-afternoon. Details of the mating behavior are described here.     

长期定位有机物料还田对关中平原冬小麦-玉米轮作土壤N2O排放的影响

为定量研究有机物料还田对农田土壤N2O排放的影响,采用静态暗箱-气相色谱法对关中平原冬小麦-玉米轮作24 a长期定位施肥试验地土壤N2O排放速率和相关环境因子进行了周年观测,试验处理为对照(CK,0 kg·hm~(-2))、氮磷钾(NPK,353kg·hm~(-2))、氮磷钾加秸秆还田[NPKS,(353+40)kg·hm~(-2)]和氮磷钾加牛粪[NPKM,(238+115)kg·hm~(-2)]4个处理.结果表明观测期内,CK处理N2O排放速率较小[2.9 g·(hm~2·d)~(-1)];施肥处理在冬小麦季施肥和玉米季灌溉后均出现排放峰,最高值分别为NPKS[113.4 g·(hm~2·d)~(-1)]和NPKM[495.0 g·(hm~2·d)~(-1)]处理.各处理N2O排放通量与土壤湿度均呈显著正相关关系(r0.28,P0.05).CK、NPK、NPKS和NPKM处理N2O年排放总量分别为(0.1±0.0)、(2.6±0.1)、(3.4±0.7)和(2.9±0.3)kg·hm~(-2),施肥处理排放总量显著高于CK处理(P0.05),但施肥处理之间差异不显著(P=0.06),说明施肥促进了N2O排放,但有机物料还田未能显著增加N2O排放.各施肥处理N2O直接排放系数分别为0.72%、0.83%和0.80%,均低于IPCC缺省值1%.施肥处理中,NPKM处理的单位产量N2O排放量最低.     

秸秆还田配施氮肥对喀斯特农田微生物群落及有机碳矿化的影响

秸秆还田配施氮肥是调控农田土壤有机碳转化的重要措施,为认知秸秆配施氮肥对秸秆和长期施肥土壤有机碳矿化的作用机制,选取喀斯特长期施肥定位试验3种土壤(不施肥、无机肥、秸秆与无机肥配施),采用室内培养结合~(13)C示踪技术,设置不添加秸秆(对照组)及添加秸秆配施3种氮素水平处理(0、214. 0和571. 0 mg·kg~(-1),以干基土计),研究~(13)C标记的秸秆和土壤有机碳的矿化及其机制.结果表明,长期施肥土壤的秸秆CO_2排放量均显著高于不施肥土壤,且氮素水平显著影响不施肥土壤的秸秆有机碳矿化;长期施肥土壤激发效应均显著低于不施肥土壤,且低水平氮素配施降低秸秆添加引起的正激发效应,高水平氮素反而增大. PCA分析表明长期施肥、秸秆还田配施氮肥均显著改变土壤微生物群落,其中秸秆与氮素配施显著增加土壤总PLFAs、细菌和真菌PLFA摩尔质量浓度(与对照相比,增幅分别为40. 3%～53. 0%、41. 1%～62. 6%和60. 5%～148. 6%),但氮素水平影响不显著,土壤G~+/G~-降低并稳定在0. 8左右.结构方程模型结果表明,秸秆还田配施氮肥增加土壤DOC含量、影响土壤革兰氏菌群落结构,从而影响秸秆和土壤有机碳矿化.上述结果表明秸秆还田配施低水平氮肥有利于提升喀斯特农田土壤固碳能力.