Camargo-Ricalde Sara Lucía, Esperón-Rodríguez Manuel
Universidad Autónoma Metropolitana-lztapalapa, División de Ciencias Biológicas y de la Salud, Departamento de Biologia, Apdo. Postal 55-535. 09340 México. D. F.
Rev Biol Trop. 2005 Sep-Dec;53(3-4):339-52.
Recent studies have shown that some species of Mimosa (Leguminosae-Mimosoideae) create resource islands (RI), rich in soil organic matter and nutrients, as well as in arbuscular mycorrhyzal fungal (AMF) spores, in the semi-arid Valley of Tehuacán-Cuicatlán. The relevance of this fact is that arid and semi-arid regions are characterized by low fertility soils and scarce precipitation, limiting plant species growth and development; this explains why the presence of AM fungi may be advantageous for mycorrhizal desert plants. Fluctuations in AMF spore numbers could be related to environmental, seasonal and soil factors which affect AMF sporulation, in addition to the life history of the host plant. The aim of this study was to asses the impact of spatial (resource islands vs open areas, OA) and seasonal (wet season vs start of dry season vs dry season) soil heterogeneity in the distribution and abundance of AMF spores in four different study sites within the Valley. We registered AMF spores in the 120 soil samples examined. Significant differences in the number of AMF spores were reported in the soil below the canopy of Mimosa species (RI) comparing with OA (RI > OA), and between Mimosa RI themselves when comparing along a soil gradient within the RI (soil near the trunk > soil below the middle of the canopy > soil in the margin of the canopy > OA); however, there were no significant differences between the soil closest to the trunk vs middle, and margin 's OA. Finally, more spores were reported in the soil collected during the wet season than during the dry season (wet > start of dry > dry). Therefore, the distribution of AMF spores is affected by spatial and seasonal soil heterogeneity. This study points out the relevance of Mimosa RI as AMF spore reservoirs and the potential importance of AM fungi for plant species survivorship and establishment in semi-arid regions. AM fungi have recently been recognized as an important factor determining plant species diversity in arid and temperate ecosystems.
最近的研究表明，在特瓦坎 - 库伊卡特兰半干旱山谷中，一些含羞草属（豆科 - 含羞草亚科）物种形成了资源岛（RI），这些资源岛富含土壤有机质、养分以及丛枝菌根真菌（AMF）孢子。这一事实的相关性在于，干旱和半干旱地区的土壤肥力低且降水稀少，限制了植物物种的生长和发育；这就解释了为什么AM真菌的存在可能对菌根沙漠植物有利。除了宿主植物的生活史外，AMF孢子数量的波动可能与影响AMF孢子形成的环境、季节和土壤因素有关。本研究的目的是评估空间（资源岛与开阔区域，OA）和季节（湿季与旱季开始时与旱季）土壤异质性对该山谷内四个不同研究地点AMF孢子分布和丰度的影响。我们在检测的120个土壤样本中记录了AMF孢子。与OA相比（RI > OA），在含羞草属物种树冠下的土壤（RI）中，AMF孢子数量存在显著差异；并且当沿着RI内的土壤梯度进行比较时（树干附近的土壤 > 树冠中部下方的土壤 > 树冠边缘的土壤 > OA），不同含羞草RI之间也存在显著差异；然而，最靠近树干的土壤与中部和边缘的OA之间没有显著差异。最后，湿季采集的土壤中报告的孢子比旱季更多（湿季 > 旱季开始时 > 旱季）。因此，AMF孢子的分布受空间和季节土壤异质性的影响。本研究指出了含羞草RI作为AMF孢子库的相关性，以及AM真菌对半干旱地区植物物种生存和定植的潜在重要性。AM真菌最近被认为是决定干旱和温带生态系统中植物物种多样性的一个重要因素。
