Winners and losers: tropical forest tree seedling survival across a West African forest-savanna transition.
Winners and losers: tropical forest tree seedling survival across a West African forest-savanna transition.
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DOI：
10.1002/ece3.2133
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发表时间：
2016-05
影响因子：
2.6
通讯作者：
Oliveras I
中科院分区：
文献类型：
--
作者：
Cardoso AW;Medina-Vega JA;Malhi Y;Adu-Bredu S;Ametsitsi GK;Djagbletey G;van Langevelde F;Veenendaal E;Oliveras I
热带非洲的森林正以前所未有的速度侵入稀树草原，导致宝贵的稀树草原栖息地丧失。森林侵蚀的第一阶段之一是在森林-稀树草原过渡处建立树苗。本研究探讨了在西非森林稀树草原过渡带的五种热带森林先锋树幼苗的人口瓶颈。5种热带先锋林树苗种植在稀树草原，混合/过渡，森林植被类型和生长12个月，在此期间，火灾发生在该地区。我们研究了幼苗存活率，高度和茎直径火灾前后，和幼苗生物量和淀粉分配模式火灾后。幼苗成活率显着影响火灾，干旱，植被类型。优先分配更多资源以增加根和叶淀粉（淀粉储存有助于从火灾中恢复）的幼苗在稀树草原环境中存活得更好（经常被烧毁），而将更多资源分配给生长和资源捕获性状（高度，叶片数量，茎直径，比叶面积，比根长，根冠比）的幼苗在混合/过渡和森林环境中存活得更好。较大的（更高的茎直径更大）幼苗比较小的幼苗更好地存活燃烧。然而，即使在没有火灾的情况下，较大的幼苗也比较小的幼苗存活得更好。木棉buonopozense是在热带稀树草原环境中生存最好的森林物种，这可能是由于增加了获得光照的机会，从而允许对地下淀粉储存能力进行更大的投资，因此具有更大的科普火灾的能力。综合：与其他两种植被类型相比，森林先锋树种在热带稀树草原的火灾和干旱中存活得最好。这可能是由于开放式的热带稀树草原提供了更多的光线，从而使幼苗摆脱了光限制，使它们能够制造和储存更多的淀粉。火可以作为一种管理工具，控制森林侵入稀树草原，因为它显着影响幼苗的生存。然而，如果降雨量因全球变化因素而增加，则侵蚀可能更难控制，因为当干旱压力解除时，幼苗存活率表面上会增加。我们建议B. buonopozense作为一个指示物种的森林入侵到稀树草原在西非森林稀树草原过渡。
Forest encroachment into savanna is occurring at an unprecedented rate across tropical Africa, leading to a loss of valuable savanna habitat. One of the first stages of forest encroachment is the establishment of tree seedlings at the forest–savanna transition. This study examines the demographic bottleneck in the seedlings of five species of tropical forest pioneer trees in a forest–savanna transition zone in West Africa. Five species of tropical pioneer forest tree seedlings were planted in savanna, mixed/transition, and forest vegetation types and grown for 12 months, during which time fire occurred in the area. We examined seedling survival rates, height, and stem diameter before and after fire; and seedling biomass and starch allocation patterns after fire. Seedling survival rates were significantly affected by fire, drought, and vegetation type. Seedlings that preferentially allocated more resources to increasing root and leaf starch (starch storage helps recovery from fire) survived better in savanna environments (frequently burnt), while seedlings that allocated more resources to growth and resource‐capture traits (height, the number of leaves, stem diameter, specific leaf area, specific root length, root‐to‐shoot ratio) survived better in mixed/transition and forest environments. Larger (taller with a greater stem diameter) seedlings survived burning better than smaller seedlings. However, larger seedlings survived better than smaller ones even in the absence of fire. Bombax buonopozense was the forest species that survived best in the savanna environment, likely as a result of increased access to light allowing greater investment in belowground starch storage capacity and therefore a greater ability to cope with fire. Synthesis: Forest pioneer tree species survived best through fire and drought in the savanna compared to the other two vegetation types. This was likely a result of the open‐canopied savanna providing greater access to light, thereby releasing seedlings from light limitation and enabling them to make and store more starch. Fire can be used as a management tool for controlling forest encroachment into savanna as it significantly affects seedling survival. However, if rainfall increases as a result of global change factors, encroachment may be more difficult to control as seedling survival ostensibly increases when the pressure of drought is lifted. We propose B. buonopozense as an indicator species for forest encroachment into savanna in West African forest–savanna transitions.