物候研究的论文

气候变暖对陆地生态系统的影响*吴循1,2周青1,2**(1.江南大学工业生物技术教育部重点实验室无锡214122;2.江南大学生物科学系无锡214122)摘要人类活动引起的温室效应导致全球气候变暖,气候变暖对全球生态环境的影响越来越受到人们的关注。作为人类赖以生存的环境主体,陆地生态系统对气候变暖将做出何种响应,更是人们关注的重点。植物物候的变化可以直观地反映某些气候变化,尤其是气候变暖。气候变暖影响植物的生长节律,进而引起植物与环境关系的改变及生态系统物质循环(如水和碳的循环)的改变。不同种类植物对气候变化的差异响应,会使植物间和动植物间的竞争与依赖关系发生深刻的变化,如北半球中高纬度地区植被生长季延长、植物提早开花、昆虫提早出现、鸟类提早产蛋以及冰川退缩、永冻土带融化、江河湖泊结冰推迟而融化提早等。本文主要从陆地生态系统的分布和演替两方面着眼,以植物和动物作为考察对象,系统论述了森林、草原、荒漠、湿地及农田等陆地生态系统在气候变暖背景下产生的变化,并从微观和宏观尺度上提出陆地生态系统变化的生态学机制,最后在技术和政策层面给出若干对策。关键词气候变暖陆地生态系统分布演替机制对策

所谓的物候观测，说白了就是对一些自然现象的观测，比如候鸟南飞，就要表示天气快变冷了，候鸟南飞过冬；“冬天麦盖三层被，来年枕着馒头睡”；蜻蜓飞得低，预示天气可能要变阴；“一九二九不出手， 三九四九冰上走”“春雨贵如油”等等很多。这些就是古人根据多年对物候的观测而得到的经验，有些动植物比人“聪明”，还有，一般一个地方的气候具有一定的稳定性，所以物候的观测可以指导农业生产，既可以做长时间的“天气预报”，还可以做短时间的“天气预报”。

题目The role of tree size in the leafing phenology of a seasonally dry tropical forest in Belize, Central America摘要Abstract. Leafing phenology of two dry-forest sites on soils of different depth (S = shallow, D = deep) at Shipstern Reserve, Belize, were compared at the start of the rainy season (April–June 2000). Trees _ cm dbh were recorded weekly for 8 wk in three plots per site. Ten species were analysed individually for their phenological patterns, of which the three most common were Bursera simaruba, Metopium brownei and Jatropha gaumeri. Trees were divided into those in the canopy (> 10 cm dbh) and the subcanopy (_ 10 cm dbh). Site S had larger trees on average than site D. The proportion of trees flushing leaves at any one time was generally higher in site S than in site D, for both canopy and subcanopy trees. Leaf flush started 2 wk earlier in site S than site Dfor subcanopy trees, but only wk earlier for the canopy trees. Leaf flush duration was wk longer in site S than site D. Large trees in the subcanopy flushed leaves earlier than small ones at both sites but in the canopy just at site D. Large trees flushed leaves earlier than small ones in three species and small trees flushed leaves more rapidly in two species. Bursera and Jatropha followed the general trends but Metopium, with larger trees in site Dthan site S, showed the converse with onset of flushing 1 wk earlier in site Dthan site S. Differences in response of the canopy and subcanopy trees on each site can be accounted for by the predominance of spring-flushing or stem-succulent species in site S and a tendency for evergreen species to occur in site D. Early flushing of relatively larger trees in site D most likely requires access to deeper soil water reserves but small and large trees utilize stored tree water in site S.关键词Key Words: hardwood trees, leaf flush, onset, sampling interval, soil depth, spring-flushing trees, tree size简介INTRODUCTIONAlthough water is the limiting factor for part of the year in seasonally dry tropical forests, many tree species flush their leaves during the dry season, before the onset of the rains (Bullock & Solis-Magallanes 1990, Mooney et al. 1995). Two principal reasons for this have been suggested: (1) new leaves may be able to make maximumuse of the higher radiation during the dry season (Wright & van Schaik 1994); and (2) new leaves avoid predation when herbivores are at their least abundant inthe dry season (Murali & Sukumar 1993). Selection would be expected to operate in favour of early leaf flushing, . before the start of the rainy factors alone are often not sufficient to explain phenological variation in tropical dry forests (Borchert 1994a). Water stored in the tree stem, or remaining in the subsoil, buffers the impact of low water availability and allows the production of new leaves during the dry season (Borchert 1980, 1983, 1994a, b; Reich & Borchert 1984). This indicates that tree water status, rather than climatic factors directly, is probably the principal determinant of tree phenology in the seasonally dry & Rivera (2001) have shown that leaf buds remain dormant during the dry season in many tree species of semi-deciduous tropical forests, and bud-break is induced by an increasing photoperiod after the spring equinox. Bud-break is highly synchronous in conspecifics of these ‘spring-flushing’ trees, although some withinspecies differences occurred. One likely explanation for the latter is the amount of stem-, soil- or rain-water available to the tree. Whether leaf flush is triggered by photoperiod or other factors, sufficient water supply is a prerequisite. Bud-break and leaf expansion during the dry season occur only when the trees are fully rehydrated(Borchert 1994a, b; Borchert et al. 2002). The rate of shoot development and the duration of leaf expansion varies strongly with water availability (Borchert 1994b,Borchert & Rivera 2001).