forests论文格式

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).

例如，土壤的针叶 森林西北美国可能 载有50多年的积累凋落， 因为低pH值的垃圾和 缺乏夏季降水抑制微生物 活动。在成熟的森林这种类型， 木质材料，如死亡的树干和 分支机构可以构成50-60 ％的 垃圾。相比之下，土壤阔叶 森林在美国东部 积累仅仅几年'价值 乱抛垃圾，和土壤中某些热带雨林 积累几乎没有，因为条件 更有利于分解 （斯珀和Barnes ， 1980 ） 。暖和的 温度，水分含量高，高 氧可用性，高适口性的 垃圾对微生物所有赞成 分解。更高度木质化 垃圾，不易消化，这是与 更其分解取决于 独特的生物，可降解真菌木质纤维素 退化 生物体主要负责 纤维素退化好氧丝状 真菌类，以及最迅速 degraders这一组中有担子 （柯克和法雷尔， 1987年） 。