Reverse phenology and dry‐season water uptake by Faidherbia albida (Del.) A. Chev. in an agroforestry parkland of Sudanese west Africa
Reverse phenology and dry‐season water uptake by Faidherbia albida (Del.) A. Chev. in an agroforestry parkland of Sudanese west Africa
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Faidherbia albida (Del.) A. Chev 在苏丹西非农林公园的逆物候和旱季吸水量
DOI：
10.1046/j.1365-2435.1999.00345.x
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发表时间：
1999
影响因子：
5.2
通讯作者：
E. Dreyer
中科院分区：
文献类型：
--
作者：
O. Roupsard;A. Ferhi;A. Granier;F. Pallo;D. Depommier;B. Mallet;H. Joly;E. Dreyer
1. Faidherbia（Acacia）albida是一种多用途树木，广泛分布于半干旱的非洲，特别是在农林公园。它在旱季长叶，在雨季落叶，因此表现出一种特殊的反向物候。相关的用水策略，包括叶水势，液流，水力传导和吸收的深度，在苏丹西部非洲帕克兰的成年树木进行了监测。
2.尽管表层土壤干旱严重，但F. albida在旱季末期仅下降至约-0.5MPa，表明仅为中度水分胁迫。
3.树干径向生长停止前的旱季结束，可能受到中度干旱胁迫的影响。然而，在干旱季节，绿叶保持不变。落叶发生后的第一场雨，可能是独立的干旱。
4. Faidherbia albida表现出较大的蒸腾速率在有利的条件下，但树干液流的比例Penman蒸散量和土壤叶比水力传导度下降严重接近旱季结束。
5.根的F. albida分布在风化岩石中，深达7米，在永久地下水位附近消失。木质部汁液中氧的同位素组成（δ 18 O）与全年地下水位记录的值非常接近。因此，潜水植物学解释了在旱季维持生长和蒸腾作用的原因。然而，在早期降雨，汁液的δ 18 O转向表层土壤的组成，表明兼性潜水植物。
6.物候期相反，密度低，吸水深度小。Albida表明与一年生作物对水的竞争较低;树木使用的年降雨量的比例估计保持在5%以下。
1.Faidherbia (Acacia) albida is a multipurpose tree widely distributed in semiarid Africa, notably in agroforestry parklands. It is in leaf during the dry season and defoliated during the rainy season, displaying therefore a peculiar reverse phenology. The related water-use strategy, including leaf water potential, sapflow, hydraulic conductance and depth of uptake, were monitored on adult trees in a Sudanese west-African parkland.
2. Despite a severe drought in the superficial soil layers, the predawn leaf water potential of F. albida dropped only to ca.– 0·5 MPa during the end of the dry season, indicating only a moderate water stress.
3. Radial trunk growth ceased before the end of the dry season and could have been affected by the moderate drought stress. However, leafiness remained constant during the dry season. Leaf shedding occurred after the first rains and was probably independent of drought.
4.Faidherbia albida displayed large transpiration rates under favourable conditions but the ratio of sapflow to Penman evapotranspiration and the soil-to-leaf specific hydraulic conductance decreased severely towards the end of the dry season.
5. Roots of F. albida were distributed through the weathered rock, down to a depth of 7 m, and vanished in the vicinity of a permanent water-table. The isotopic composition of oxygen in the xylem sap (δ18O) remained very close to the values recorded in the water-table during the course of the year. Phreatophytism thus explained the maintenance of growth and transpiration during the dry season. Nevertheless, during early rains, δ18O of sap switched towards the composition of the superficial soil layers, indicating facultative phreatophytism.
6. Reverse phenology, low density and depth of water uptake of F. albida indicated a low competition with annual crops for water; the fraction of annual rainfall used by the trees was estimated to remain below 5%.