金沙江干热河谷区8个造林树种的生态适应性变化

对金沙江干热河谷区8个造林树种的有关生理生态特性进行了研究。结果表明:相思类树种在旱季水分自然饱和亏缺较大,乡土树种坡柳和3种桉树则是雨季水分亏缺较大,具有WSD高而RWC低的植物同样具有很强的抗旱能力;比叶面积增大是植物提高抗旱能力的一个表现方面,但增加干物质积累、提高细胞质浓度也是途径之一;干热逆境可造成叶绿素含量降低,雨季叶绿素含量有较大提高,叶绿素a/b值也随之得到提高;参试树种的糖分含量旱季比雨季高,除马占相思外,其它树种淀粉与糖的比率则旱季比雨季低;在干热逆境胁迫下,7个树种(除尾叶桉)的游离脯氨酸含量有不同程度增加,旱季植株易出现萎蔫现象,有部分或较多叶片脱落的树种积累的游离脯氨酸较多。除造林效果较差的马占相思与其它7个树种有较多差异外,造林效果较好的7个树种在生理生态变化方面有较多相似性;同时,同类树种间有明显的一致性;乡土树种坡柳则在某些方面更近似于相思类树种,在某些方面又近似于桉树类树种;除马占相思外,3个相思类、3个桉树类树种与乡土树种坡柳同样在金沙江干热河谷区表现出较强的生态适应性。

Ecological Adaptability of Eight Tree Species in Dry and Hot Valley of Jinsha River

The water ecophysiology of eight tree species growing in dry and hot valley of Jinsha River was studied. The result showed that in rain season the index of water saturation deficit (WSD) of indigenous tree species Dodonaea viscosa Jacg, and three eucalyptus species were higher than that of the other tree species. The plant with high WSD index and low relative water content (RWC) has strong drought tolerance. Enlargement of the rate of leaf area and fresh leaf weight is beneficial to enhance the drought tolerance of a plant, while increasing the accumulation of dry materials and the density of cytoplasm is also an effective way. Dry and hot stress may induce chlorophyll content reduced, while the chlorophyll content may increase in rainy seasons with increasing the rate of chlorophyll a and chlorophyll b. In dry seasons, the sugar content of test trees is higher than that in rainy seasons and the starch and sugar contents are lower in dry reasons than in rainy reasons except Acacia manguim De Willd. Under the arid condition, the free proline content of 7 tree species increased with different degrees except Eucalyptus urophylla S. T. Blake. The tree species which are prone to wither and defoliation in dry seasons can accumulate more free proline. There are more ecophysiological similarities among the seven tree species which are suitable for afforestation except Acacia manguim De Willd.; and there exists obvious consistency in ecophysiological characteristics among same genus. Some ecophysiological characteristics of D. viscosa Jacg., the indigenous tree species, are similar to that of Acacia and some others are similar to that of Eucalyptus. Three Eucalyptus species, three Acacia species and D. viscosa Jacg. showed stronger ecological adaptability and grow well in dry and hot valley of Jinsha River.