Figueroa-Rangel Blanca L, Willis Katherine J, Olvera-Vargas Miguel
Oxford Long-term Ecology Laboratory, Oxford University Centre for the Environment, School of Geography, South Parks Road, Oxford, OX1 3QY, United Kingdom.
Ecology. 2008 Jul;89(7):1893-907. doi: 10.1890/07-0830.1.
The pine-dominated forests of west-central Mexico are internationally recognized for their high biodiversity, and some areas are protected through various conservation measures including prohibition of human activity. In this region, however, there is evidence for human settlement dating back to ca. AD 1200. It is therefore unclear whether the present forest composition and structure are part of a successional stage following use by indigenous human populations during the past, or due to natural processes, such as climate. We present a study reconstructing the vegetation dynamics of pine-dominated forest over the past 4200 years using paleoecological techniques. Results from fossil pollen and charcoal indicate that, in this region, pine-dominated forests are the native vegetation type and not anthropogenically derived secondary succession. The predominant driving mechanism for the expansion of pine-dominated forest appears to be intervals of aridity and naturally induced burning. A close association is noted between pine abundance and longer-term climatic trends, including intervals of aridity between ca. 4200 and 2500, 1200 and 850, and 500 and 200 cal yr BP and shorter-term trends. Evident periodicity occurs in pine and Poaceae abundance every 80 years. These short-term quasi-periodic oscillations have been recorded in a number of lake and ocean sediments in Mexico and are thought to be linked to solar forcing resulting in drought cycles that occur at approximately the same time intervals.
墨西哥中西部以松树为主的森林因其高度的生物多样性而在国际上得到认可，一些地区通过包括禁止人类活动在内的各种保护措施得以保护。然而，在该地区，有证据表明人类定居点可追溯到公元1200年左右。因此，目前尚不清楚当前的森林组成和结构是过去土著人口利用后演替阶段的一部分，还是由于气候等自然过程所致。我们开展了一项研究，利用古生态技术重建了过去4200年以松树为主的森林的植被动态。化石花粉和木炭的结果表明，在该地区，以松树为主的森林是原生植被类型，而非人为衍生的次生演替。以松树为主的森林扩张的主要驱动机制似乎是干旱期和自然引发的火灾。注意到松树丰度与长期气候趋势之间存在密切关联，包括约4200至2500、1200至850以及500至200 cal yr BP之间的干旱期和短期趋势。松树和禾本科植物的丰度每80年出现明显的周期性。这些短期准周期性振荡已在墨西哥的许多湖泊和海洋沉积物中记录到，被认为与太阳强迫有关，导致干旱周期以大致相同的时间间隔发生。
