Is deer herbivory directly proportional to deer population density? Comparison of deer feeding frequencies among six forests with different deer density

The intensity of deer herbivory, rather than simply the deer population density, directly affects the forest ecosystem, but a linear relationship between these two factors has generally been assumed. To assess their relationship, we investigated deer population density and tree sapling vegetation in six forests with different deer density on Yakushima Island, Japan. The feeding frequency was used as an index of deer herbivory. Palatable saplings showed high feeding frequency and became rare in deer-abundant areas, while unpalatable saplings showed low feeding frequency and increased with increasing deer density. In addition, feeding frequency on sapling vegetation did not continue to increase with increasing deer population and was limited to only 0.24-0.32 in deer-abundant areas (more than 20 deer/km²). These data suggest that deer shift their main food items from living palatable saplings to other alternatives such as litter fall rather than living unpalatable saplings. Clearly, the nonlinear relationship between deer density and deer herbivory on forest vegetation could result from a change in the food eaten by deer, and it is therefore necessary to assess the impacts of deer based on not only the size of the deer population but also the intensity of direct herbivory.     

雌雄异体生物种群的性比失调及其调控研究现状

雌雄异体生物性比失调现象报道很多,本文总结了该类生物种群性比失调现象及其调控研究现状.Fisher 法则认为雌雄异体生物理论性比为1∶1,但大量案例却表明,自然界雌雄异体生物性比偏离1∶1,而呈现偏雌或偏雄的现象,即性比失调.从遗传决定、环境决定的观点,以及大小依赖性上阐明了种群性比失调的问题.单二倍体机制、染色体重组...     

若尔盖高寒沙化地中伴生草种对杯腺柳凋落叶初期分解的影响

凋落物分解是陆地生态系统中物质循环的关键环节。在青藏高原高寒沙化地生态恢复初期,分别以垂穗披碱草(Elymus nutans)、中华羊茅(Festuca sinensis)和老芒麦(Elymus sibiricus)为杯腺柳(Salix cupularis)的伴生草种,探究三种高原牧草在杯腺柳不同微位置(冠幅中心、冠幅半径中点和冠幅外缘)下对其凋落叶早期分解动态的影响。结果表明：垂穗披碱草伴生下,各微位置的杯腺柳凋落叶质量损失率均最高(P<0.05),且50%和95%分解时间均最短;垂穗披碱草伴生下,凋落叶纤维素和木质素含量变化更剧烈,且在分解第19个月时,木质素含量显著高于对照和其它两种草本伴生(P<0.05);微位置对凋落叶总氮、木质素含量、C/N和木质素/N影响显著(P<0.05)。综上所述,在以杯腺柳为先锋种的高寒沙化地中,垂穗披碱草种植在杯腺柳冠幅下可使杯腺柳凋落叶分解更快,更有利于区域沙化地的生态恢复。     

分子排阻色谱法测定马罗匹坦注射液中磺丁倍他环糊精钠的含量

[目的]建立马罗匹坦注射液中磺丁倍他环糊精钠的含量测定方法.[方法]采用分子排阻色谱法,以0.1 mol/L硝酸钾溶液-甲醇(65∶35)为流动相,采用分子排阻色谱法检测马罗匹注射液中磺丁倍他环糊精钠的含量.[结果]磺丁倍他环糊精钠与相邻峰的分离度均大于3.0;在6～ 180 μg范围内峰面积与浓度呈良好的线性关系(r=0.999 9,n=8);在80％、100％、120％3种添加水平下的平均回收率分别为95.96％ (RSD =0.5％,n=3)、98.41％(RSD =0.4％,n=3)、97.77％(RSD =0.5％,n=3).[结论]该方法专属性强、准确度好、适应范围宽,可作为马罗匹坦注射液中磺丁倍他环糊精钠的含量测定方法.     

山丘区钉螺大小特征与水分依赖性

本文研究了山丘区钉螺壳体长宽鲜重体积,以及疫区壳体长宽与区域降水温度的关系。仁寿县钉螺鲜重0.0162 g(浮动在0.0065 g～0.0219 g之间),体积4.5894 mm3(3.12 mm3～5.6 mm3),长度5.156 mm(3.6 mm～6mm),宽度为2.668 mm(2.2 mm～3 mm)。分析表明,长度5 mm～6 mm为主体,宽度2.5 mm～3 mm为主体,钉螺宽度随着长度作缓慢而显著的增加;鲜重与群体的长度、宽度、体积无关。潮湿稻田生境钉螺长度明显最大,而干燥与湿润生境中次之,但宽度、体积、鲜重差异不明。疫区不同区域钉螺长度、宽度与降水量显著相关,而与温度无关,温度降水量比值与钉螺长度、宽度关系密切,表明钉螺大小有水分依赖性。在疫区内,可能水温匹配性共同塑造了钉螺的大小。     

Nutrient dynamics in decaying leaves of Fagus sylvatica L. and needles of Abies alba Mill.

 The dynamics of nutrients (N, P, K, Ca, Mg) in decomposing beech and fir litters was studied. N, P, Mg and Ca content increased in all litters, whereas K content decreased. Nutrient content correlated to mass loss with a few exceptions for K and P. Final N, K, Mg and Ca content was higher the lower the initial content and the higher the initial C/nutrient ratio was. Final P content correlated neither with initial P content nor with initial C/P ratio. All litters lost K very quickly, mainly by leaching. P was lost initially by leaching, although at a lower rate than K, and later by mineralization. Mg, Ca and N showed alternate phases of accumulation and release. Mg losses by leaching occurred only in litters with high initial Mg content; in litters with low initial Mg content, Mg losses occurred by mineralization. Ca and N were lost only by mineralization. A mobility series K>P>Mg>Ca=N is suggested. Received: 8 May 1997     

Cultivation of the erizo: an evaluation of eggs and postmetamorphic juveniles size selection

Evidence in the course of experiments under controlled conditions proved that the egg and juvenile characteristics of the edible Chilean sea urchin, erizo (Loxechinus albus) influence the cultivation efficiency. Mortalities among larvae originating from eggs with a diameter <110 m were higher than among those originating from eggs with a diameter >100 m. On the other hand, the initial size of the egg did not produce any variation in the percentage of larvae which metamorphosed. The initial size of the late metamorphosing juveniles modified early growth. A direct relationship was established between the size of the juveniles and the growth rate. In conclusion, biological aspects are determinant factors in any consideration of options available for the mass production of larvae and juveniles of this sea urchin.     

滇西北高原纳帕海湿地湖滨带优势植物生物量及其凋落物分解

选取滇西北高原湿地纳帕海湖滨带优势植物茭草(Zizania caducifolia)、水葱(Scirpus tabernaemontani)和刘氏荸荠(Heleocharis liouana),研究其生物量及其凋落物分解特征,结果表明:水葱、茭草、刘氏荸荠为纳帕海湿地湖滨带单优植物群落,均具有较高的地上生物量,不同植物群落地上生物量不同,其中,茭草地上生物量(853.6±58.2)g·m-2·a-1显著高于水葱(730.7±7.8)g·m-2·a-1与刘氏荸荠(338.9±32.6) g·m-2·a-1的地上生物量.3种植物群落凋落物分解速率不同、并随月平均气温升高均呈增加的趋势,其中,刘氏荸荠分解速率k值最大(0.067±0.0026)、茭草(0.062±0.0072)其次、水葱最小(0.039±0.0062).凋落物经过1年的分解,水葱、茭草和刘氏荸荠凋落物存留率分别为(62.0±8.8)％、(47.5±9.0)％和(44.5±7.9)％.综合3种湖滨带植物地上生物量与凋落物年分解,水葱地上生物量年存留量(453.1±4.9)g·m-2·a-1显著高于茭草(405.4±27.7)g·m-2·a-1和刘氏荸荠(150.9±14.5) g·m-2·a-1.研究进一步表明滇西北高原湿地湖滨带植物具有极高的生物量存留率,成为该类型湿地生态系统碳汇功能的基础,其碳汇过程及其贡献率需要进一步深入研究.     

杉木观光木混交林凋落物热值及灰分含量的季节动态分析

通过对福建三明 2 7年生杉木观光木混交林和杉木纯林凋落物的热值、灰分含量及其季节动态的分析表明 ,混交林中杉木凋落物各组分的干重热值介于 2 0 6 37～ 2 1 96 0kJ·g-1之间 ,观光木凋落物各组分干重热值介于 19 6 35～ 2 0 0 5 8kJ·g-1之间 ,杉木纯林凋落物各组分的干重热值介于 2 0 70 5～ 2 1 90 8kJ·g-1之间 ,各树种凋落物均以叶、花的热值较高 ,而果、枝的热值较低。观光木凋落物各组分的灰分含量高于杉木。杉木落叶灰分含量季节间变化均较小 ;而观光木落叶灰分含量的变化模式为 :夏季 >秋季 >春季 >冬季。杉木落叶干重热值和去灰分热值季节变化模式均为 :冬季 >秋季 >春季 >夏季 ,而观光木落叶则均为 :冬季 >夏季 >秋季 >春季     

猪白细胞抗原和生殖激素水平对产仔性能的影响

对２３２头经产母猪进行了ＳＬＡ分型、生殖激素水平和产仔性状测定,其中,Ｄ型母猪的产仔性能显著高于其他类型,表明ＳＬＡ分型可以成为猪繁殖性能的辅助选择遗传标记;在母猪泌乳阶段,促黄体素（ＬＨ）、雌激素（Ｅ２）和孕酮（Ｐ４）的水平都较低,在配种阶段,雌激素分泌达到峰值,在怀孕１５ｄ时,促黄体素和孕酮的分泌达到峰值。高产、中产和低产母猪在各生理阶段的激素水平差异不显著,难以预测产仔数的多少。