两种种植密度下施肥对冬小麦生物学性状及产量的影响

以土垫旱耕人为土为供试土壤,采用大田试验,研究半湿润农田生态系统两种种植密度下不同施肥处理对冬小麦生物学性状及子粒产量的影响。试验设两种种植密度:常规密度(播种量为150.0kg/hm~2)和低密度(播种量为90.0kg/hm~2)。常规密度设7个施肥处理,即不施肥(CK),单施磷肥(PN0),单施氮肥(P0N135)和在施P的基础上每公顷施N45、90、135和180kg(即PN45、PN90、PN135、PN180);低密度施肥处理设不施肥(CK)、单施磷(PN0)、单施氮(P0N135)和氮磷配施(PN135)。结果表明,低密度时,CK处理分蘖数最低(每株平均3.2个),PN135分蘖数最高(每株平均6.9个);常规密度时,仍以CK分蘖数最低(每株平均3.2个),PN180分蘖数最大(每株平均6.8个)。低密度下,PN0和CK与P0N135和PN135间植株绿叶面积差异达显著水平(P<0.05),以PN135绿叶面积最大,PN0绿叶面积最小;常规密度下,PN180绿叶面积最大,为80.7cm~2/单茎,PN0绿叶面积最小,为44.4cm~2/单茎。低密度时,CK旗叶面积最小,PN135旗叶面积最大;常规...

Game Vertebrate Densities in Hunted and Nonhunted Forest Sites in Manu National Park, Peru

Manu National Park of southern Peru is one of the most renowned protected areas in the world, yet large-bodied vertebrate surveys conducted to date have been restricted to Cocha Cashu Biological Station, a research station covering <0.06 percent of the 1.7Mha park. Manu Park is occupied by >460 settled Matsigenka Amerindians, 300-400 isolated Matsigenka, and several, little-known groups of isolated hunter-gatherers, yet the impact of these native Amazonians on game vertebrate populations within the park remains poorly understood. On the basis of 1495 km of standardized line-transect censuses, we present density and biomass estimates for 23 mammal, bird, and reptile species for seven lowland and upland forest sites in Manu Park, including Cocha Cashu. We compare these estimates between hunted and nonhunted sites within Manu Park, and with other Neotropical forest sites. Manu Park safeguards some of the most species-rich and highest biomass assemblages of arboreal and terrestrial mammals ever recorded in Neotropical forests, most likely because of its direct Andean influence and high levels of soil fertility. Relative to Barro Colorado Island, seed predators and arboreal folivores in Manu are rare, and generalist frugivores specializing on mature fruit pulp are abundant. The impact of such a qualitative shift in the vertebrate community on the dynamics of plant regeneration, and therefore, on our understanding of tropical plant ecology, must be profound. Despite a number of external threats, Manu Park continues to serve as a baseline against which other Neotropical forests can be gauged.

Interactions between a cyanobacterial bloom (Microcystis) and the submerged aquatic plant Ceratophyllum oryzetorum Kom.

In aquatic ecosystems, macrophytes and phytoplankton are main primary producers, in which macrophyte plays an important role in maintaining clear water state, while phytoplankton often dominates in turbid waterbodies. In the present study, the growth and photosynthetic activity of the submerged aquatic plant Ceratophyllum oryzetorum Kom. in different cell densities of cyanobacterial bloom are studied. The results show that the plant length and fresh mass of C. oryzetorum are promoted by low cyanobacterial cell densities. Medium and high cyanobacterial cell densities, on the contrary, act as inhibitory. Furthermore, the photosynthetic activity of C. oryzetorum is strongly inhibited by high cyanobacterial cell densities. To a certain extent, the growth of cyanobacteria is inhibited by C. oryzetorum, but no significant effect is found in this study.

Effects of the stocking density and body size of the mitten crab (Eriocheir sinensis) on aquatic plant biomass

Experiments in tanks and cages were conducted to examine the effects of stocking density and body size of the Mitten crab (Eriocheir sinensis) on transplanted submersed macrophyte biomass. The early juvenile crab with 7.0 +/-0.6 mm. carapace width (CW) had little effect on plant biomass, regardless of the stocking densities. However, larger crabs (CW: 18.0 +/-2.2,35.0 +/-3.6, and 60.0 +/-5.7 mm) significantly influenced plant biomass, especially at large stocking densities. Predictive models, using crab body size and stocking density, were generated to demonstrate effect of the mitten crab on the changes Of plant biomass. The results indicate that dense mitten crab populations may adversely affect aquatic plant communities, particularly when its animal food resources are scarce.

Influence of atomic densities on propagation property for ultrashort pulses in a two-level medium

The influence of atomic densities on the propagation property for ultrashort pulses in a two-level atom (TLA) medium is investigated. With higher atomic densities, the self-induced transparency (SIT) cannot be recovered even for 2π ultrashort pulses. New features such as pulse splitting, red-shift and blue-shift of the corresponding spectra arise, and the component of central frequency gradually disappears.