非洲湿润期结束时东非赤道地区的高地森林动态

IF 1.9 3区地球科学 Q3 GEOGRAPHY, PHYSICAL

Quaternary International Pub Date : 2024-10-21 DOI:10.1016/j.quaint.2024.10.007

Sarah J. Ivory , Elizabeth MacDougal , Andrea Mason , Eleanor Pereboom , Sloane Garelick , Katherine Ficken , Matthew J. Wooller , Bob R. Nakileza , James Russell

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引用次数: 0

摘要

热带山地生态系统具有巨大的生态和经济重要性，但它们面临着热带气候变化带来的不成比例的风险。例如，东非现今的山地植被以不同的植物种类为特征，由于环境的耐受性，这些植物种类生长在某些海拔高度，并受其限制。随着气候变化和温度/降雨带在山上移动，这些物种必须迅速调整它们的活动范围，否则就有灭绝的危险。古环境记录提供了对过去气候和生态系统动态的宝贵见解，有助于预测持续的气候变化影响。特别是，全新世中期热带东非的变暖和湿润导致了低地和高地森林的扩张。然而，降雨和温度变化对山地生态系统的相对影响以及低地森林扩张对山地群落的影响尚不完全清楚。利用化石花粉研究了乌干达鲁文佐里山区两个不同海拔湖泊的植被变化：Mahoma湖（山地森林带）和Upper Kachope湖（非洲高山带）。此外，利用最近重新启动的非洲花粉数据库和最近的温度重建，我们提供了鲁文佐里植被变化的区域综合，然后将其与赤道东非其他山区（特别是肯尼亚山）观测到的变化进行比较。在鲁文佐里山脉全新世早期到中期，主要受气温升高的影响，低地森林中常见的树木占主导地位。4000年前（4ka）以后，非洲山地的森林树木和草地逐渐取代了低地的树木。并非所有网站都经历了相同的转变。例如，在与Mahoma湖海拔相同的肯尼亚山上的Rutundu湖，竹子的扩张先于非洲山地森林的生长，可能受到火灾变化的影响。方差划分表明，不同立地对温度和降雨的响应不同。因此，这些特定地点的生态反应强调了在制定管理策略时考虑生物地理遗产的重要性，尽管现代生态学有相似之处。

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Highland forest dynamics across equatorial East Africa during the end of the African humid period

Tropical mountain ecosystems hold immense ecological and economic importance, yet they face disproportionate risks from shifting tropical climates. For example, present-day montane vegetation of East Africa is characterized by different plant species that grow in and are restricted to certain elevations due to environmental tolerances. As climate changes and temperature/rainfall zones move on mountains, these species must rapidly adjust their ranges or risk extinction.

Paleoenvironmental records offer valuable insights into past climate and ecosystem dynamics, aiding predictions for ongoing climate change impacts. In particular, warming and wetting in tropical East Africa during the mid-Holocene resulted in both lowland and highland forest expansion. However, the relative impacts of rainfall and temperature change on montane ecosystems along with the influence of lowland forest expansion on montane communities is not completely understood. We use fossil pollen to study the vegetation changes in two lakes at different altitudes in the Rwenzori Mountains, Uganda: Lake Mahoma (Montane Forest belt) and Upper Kachope Lake (Afroalpine belt). Further, using the newly relaunched African Pollen Database and recent temperature reconstructions, we provide a regional synthesis of vegetation changes in the Rwenzori and then compare this with changes observed from other equatorial East African montane sites (particularly Mt Kenya).

In the early to mid-Holocene in the Rwenzori Mountains, trees common today in lowland forests dominated, driven largely by warmer temperatures. After 4000 years ago (4ka), Afromontane forest trees along with grasses progressively replaced lowland trees. Not all sites experienced identical transitions. For instance, at Lake Rutundu on Mt Kenya at the same elevation as Lake Mahoma, bamboo expansion preceded Afromontane forest growth, likely influenced by variations in fire. Variance partitioning indicates that each site responded differently to changes in temperature and rainfall. Therefore, these site-specific ecological responses underscore the importance of considering biogeographic legacies as management strategies are developed, despite similarities in modern ecology.

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来源期刊

Quaternary International 地学-地球科学综合

CiteScore

5.60

自引率

4.50%

发文量

336

审稿时长

3 months

期刊介绍： Quaternary International is the official journal of the International Union for Quaternary Research. The objectives are to publish a high quality scientific journal under the auspices of the premier Quaternary association that reflects the interdisciplinary nature of INQUA and records recent advances in Quaternary science that appeal to a wide audience. This series will encompass all the full spectrum of the physical and natural sciences that are commonly employed in solving Quaternary problems. The policy is to publish peer refereed collected research papers from symposia, workshops and meetings sponsored by INQUA. In addition, other organizations may request publication of their collected works pertaining to the Quaternary.