退化的半干旱农业生态系统土壤碳的积累--危险和潜力

<京都议定书>意味着新的可能性:人类将把生物圈作为碳库进行管理.无论从环境还是社会经济的观点来看,把农业生态系统作为碳库是最合适可行的.非洲地区退化的生态系统显著受益于土地管理的改善(碳积累计划的一部分).在非洲有大面积的这样的农业生态系统,对它们的恢复是一个亟待解决的问题.我们同意UNEP的观点:<气候变化公约>、<联合国防治沙漠化公约>以及<联合国生物多样性公约>相互之间将会产生潜在而重要的促进作用.我们调查了苏丹半干旱农业生态系统土壤碳含量增加的潜力,发现延长休耕期将使土壤碳增加,而农业边缘区转变成牧场后碳储量将在100年内恢复到天然萨王纳的80%.碳增汇带来的经济收益将会对这些农业生态系统的家庭经济产生显著的贡献.     

北方高纬度地区生态系统动态、生物多样性管理及社会政策

由于受到众多因素大规模作用的影响,高纬度地区生态系统的变化异常活跃.这些地区的生态系统非常脆弱,各种全球变化过程都在影响着可更新林木资源持续生产和当地社会赖以生存的动植物资源丰度.本文对于北半球高纬度地区生态系统的一些新认识及其(所包含的)意义进行了讨论,并对提高生态系统的恢复力所采取的必要管理措施进行了探讨.认为在生态系统面临各种变化和干扰时系统管理的焦点应该从系统的恢复转移到系统功能的维系上来.生物多样性的作用是确保生态系统在经历干扰和重组时能够进行重组和发展,这一作用应该在系统管理与相关的方针政策中得到重视.强调应重新考虑现在的生态保护区的概念以发展一些动态的管理方法,使生态系统在面临环境变化时能够进行可持续的管理.而高纬度地区一些土著人习惯性的生态保护区的特点与那些对保护区进行动态保护的观点往往是一致的.针对高纬度地区动态景观中的生物多样性管理我们提出了新的发展方向,并从非传统的观点方面为其提供了经验例证.这些非传统的观点与看法可能会有助于提高生物多样性可持续管理和生态系统功能发挥的潜力.     

Mating System and Sexual Selection in the Scorpionfly Panorpa vulgaris (Mecoptera: Panorpidae)

Panorpa vulgaris   has become a model insect for testing theories of sexual selection. This contribution summarizes that which has been learned in recent years and presents new data that clearly show that the mating system of P. vulgaris is not simply a resource-defense polygyny, as has previously been thought. In P. vulgaris neither the pattern in food exploitation nor the ratio of variance in the lifetime reproductive success of the two sexes is in accordance with that expected in resource defense polygynous mating systems. Lifetime mating duration is the most important proximate determinant of male fitness. Males employing alternative mating tactics obtain copulations of varying duration in relation to the following sequence: saliva secretion  1  food offering  1  no gift. The number of salivary masses which males provide to females during their lifetime is significantly correlated with the lifetime condition index. The condition index depends on the fighting prowess of males and their ability to find food items. Thus saliva secretion of Panorpa is considered a Zahavian handicap, which can serve as an honest quality indicator used by mating females. Our results confirm four main predictions of the indicator model of the theory of sexual selection: (a) the indicator signals high ecological quality of its bearer, (b) the indicator value increases with phenotypic quality, (c) the indicator value is positively correlated with the genetic quality affecting offspring fitness in a natural selection context, and (d) the quality indicator is more costly for low- than for high-quality individuals. The evolutionary consequences of the mating pattern and the sperm competition mechanism in P. vulgaris are discussed in the context the way in which sexual selection creates and maintains sperm mixing and the evolution of a promiscuous mating system.