Drought in tropical forests: the role of tree height and wood density for hydraulic efficiency, productivity and vulnerability to cavitation of trees along a lowland precipitation gradient (tropical moist to seasonally-dry)

热带森林的干旱：树高和木材密度对水力效率、生产力和低地降水梯度（热带湿润到季节性干燥）树木空化脆弱性的作用

• 批准号: 253019017
• 负责人: Professor Dr. Bernhard Schuldt
• 金额: --
• 依托单位: Julius Kühn-Institut (JKI) - Bundesforschungsinstitut für Kulturpflanzen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/253019017?language=en
• 关键词: Drought; tropical; forests; role; tree

Several studies have reported accelerated tree mortality in tropical moist as well as dry forests in response to severe drought periods in the past. Although it still remains unclear how tropical trees will respond to increased drought frequency as predicted by several climate change scenarios, it is safe to conclude that drought will cause major shifts in community composition and ecosystem functioning in tropical forests in the future. The mechanisms leading to drought-induced mortality in trees are far from being understood, but it appears that large and tall tropical trees are carrying a disproportionally higher risk for drought-induced tree mortality than smaller and understory trees, both in seasonally-dry and in perhumid tropical environments. Tropical trees with light wood seem also to be at greater risk of drought-induced die-back, but the related findings are less consistent. Both tree height and wood density are thus thought to be key functional traits influencing growth and survival, but they have rarely been studied in adult trees along environmental gradients in combination with hydraulic measurements with the aim to predict the trees susceptibility to drought. In the light of climate change, there is an urgent need to identify easily measurable functional traits that determine the drought sensitivity of tropical trees of contrasting tree functional types and communities in order to assess the vulnerability of tropical forests.The proposed project aims at examining the interrelationship between hydraulic architecture, water consumption, productivity, carbon investment in storage pools and vulnerability to cavitation and their assumed control by wood density and tree height in a large sample of tropical trees across a precipitation gradient in Costa Rica. In close collaboration with Costa Rican scientists, 40 tree species (200 mature trees) will be studied comparatively in five perhumid to seasonally-dry lowland forests. By measuring a set of productivity-related (wood production, non-structural carbohydrates, tree height), hydraulic (hydraulic conductivity, P50, sapflux density) and anatomical parameters (vessel dimensions, wood density) from the stem and sun-canopy branches, 12 hypotheses on the interrelationship between anatomy, carbon relations and water relations in the trees with different phenology (evergreen vs. deciduous), physiological constitution (isohydric vs. anisohydric) and drought exposure will be tested. These findings will help to clarify whether hydraulic failure and/or carbon starvation are the primary causes of drought-induced die-back, and to identify easily accessible key functional traits that determine the drought-sensitivity of tropical trees in perhumid to semi-arid climates.

一些研究报告说，在过去的严重干旱时期，热带潮湿和干燥森林的树木死亡率加快。虽然目前还不清楚热带树木将如何应对几种气候变化情景预测的干旱频率增加，但可以肯定地得出结论，干旱将导致未来热带森林群落组成和生态系统功能的重大变化。导致干旱引起的树木死亡的机制还远未被理解，但似乎高大的热带树木比较小的林下树木具有更高的干旱引起的树木死亡风险，无论是在季节性干旱还是在过湿的热带环境中。木质较轻的热带树木似乎也有更大的干旱导致枯死的风险，但相关的研究结果不太一致。因此，树高和木材密度被认为是影响生长和存活的关键功能性状，但它们很少被研究成树沿着环境梯度结合水力测量，目的是预测树木对干旱的敏感性。鉴于气候变化，迫切需要确定容易测量的功能特征，这些特征决定了不同功能类型和群落的热带树木对干旱的敏感性，以便评估热带森林的脆弱性。碳投资在存储池和脆弱性空化和他们的假设控制木材密度和树高在一个大样本的热带树木跨越降水梯度在哥斯达黎加。在与哥斯达黎加科学家的密切合作下，将对五个过湿到季节性干旱的低地森林中的40个树种（200棵成熟树木）进行比较研究。通过测量一组与生产力相关的（木材生产，非结构性碳水化合物，树高），水力（导水率、P50、液流密度）和解剖参数（导管尺寸，木材密度）从干和阳光冠层分支，12个假设之间的相互关系解剖，碳关系和水分关系的树木与不同的物候（万年青对落叶）、生理结构（等水对异水）和干旱暴露将被测试。这些研究结果将有助于澄清是否液压故障和/或碳饥饿是干旱引起的枯死的主要原因，并确定容易获得的关键功能性状，确定干旱敏感性的热带树木在过湿半干旱气候。