云南元江干热河谷木本植物的物候

在中国西南干热河谷的典型地段——元江干热河谷，连续3年观测了32种木本植物的枝条生长、叶片动态、花期、果期和果实类型。这些植物的枝条生长方式可以分为连续生长、枝条枯死、陡长和间歇生长4个类型。其中连续生长型占优势，包括13种植物，它们的枝条在雨季连续不断伸长。9种植物雨季的枝条伸长与连续生长型的相似，但它们顶部的枝条在旱季末期出现枯死现象。6种植物属于陡长型，在2周内完成抽枝，且一年只抽一次枝。4种植物属于间歇生长型，枝条在雨季来临后伸长一段时间，然后生长停滞，过一段时间后再接着伸长。从叶片物候类型看，元江干热河谷植被以落叶植物占优势。落叶植物中冷凉旱季（11月～2月）落叶植物占优势（19种），而干热旱季（3—4月）落叶植物很少（4种）。除红花柴（Indigofera pulchella）和狭叶山黄麻（Trema angustifolia）从雨季中期开始脱落叶片外，其它30种植物从雨季末期开始脱落叶片，落叶期至少延续3个月以上。常绿植物脱落近1／3～1／2的当年生叶片。共有6种植物能在旱季末期长出新叶。常绿植物的叶面积、单个枝条上的总叶面积和枝条承载（总叶面积／枝条长度）比落叶植物小。虽然一年四季都有不同植物开花和结果，但多数植物（29种，占观测树种的91％）的花期集中在旱季和雨季初期，而果实（种子）成熟期从雨季末期延续到旱季末期和下个雨季初期。果实多为核果。

Phenology of Woody Species in Yuanjiang Dry-Hot Valley in Yunnan Province

Shoot elongation, leaf dynamics, flowering and fruiting events, as well as fruit types of 32 woody species were investigated over three successive years in a valley of Yuanjiang,which is one of the typical dry-hot valleys in southwestern China. Shoot elongation of the species studied can be classified into four types：the succeeding type,the flush type,the intermediate type, and the shoot-dieback types. Succeeding type （including thirteen species） was dominant, successively extending their shoots in the rainy season. The shoot elongation in nine species was similar to that of succeeding type in the rainy season, but with upper shoot dieback in the late dry season. Six species belonged to flush type which elongates their shoots once a year with shoots reaching the maximum intermediate type, which extends their shoots length within two weeks. Other four species belonged to after budbreak, stops growing for some time, and then elongates their shoots again. According to the leaf phenology, deciduous species dominated the Yuanjiang valley. The majority of the deciduous species were winter-deciduous （19 species）, with leaf falling during the cool dry season （November to February）, while the other four species were drought-deciduous, with leaf dropping during the hot dry season （ March to April）. Except for Indigofera pulcheUa and Trema angustifolia that started to fall leaves in the middle of the rainy season, other 30 species started to drop their leaves from the late rainy season, and leaf dropping lasted for at least three months. The evergreen species fell 1/3 to 1/2 of their current-year leaves. Among the species studied, six species showed leaf flush in the late dry season. Evergreen species had smaller leaf area and total leaf area per shoot, lower ratio of total leaf area to shoot length （ an index of shoot support） than deciduous species. Although flowering and fruiting events occurred throughout the year, the flowering of the most plants （29 species,91% of the total species investigated