Effects of nutrient manipulation (NUMEX) on the performance of tropical montane trees and interactions with climate variation and ENSO-related weather extremes

热带山区生态系统及其植被被认为对全球环境变化特别敏感。由于这些生态系统的复杂性和不同驱动因素(土地利用变化、气候变化和不断增加的养分沉积)的相互作用，了解当前的响应和预测未来的变化是困难的，但也是迫切需要的。更高的大气氮磷沉降速率对热带生态系统生物多样性和生态系统功能的影响仍然知之甚少，我们对热带森林生态系统中氮磷限制的了解仍然有限，但了解养分有效性增加对保护这些生态系统的影响将是至关重要的。在正在进行的厄瓜多尔养分操纵实验(NUMEX)中，沿着厄瓜多尔南部安第斯森林的海拔样带调查了持续添加养分的影响。Numex于2008年1月开始在1000米、2000米和3000米的代表性林分中添加适量的N(50 kg ha-1 yr-1)、P(10 kg ha-1 yr-1)以及N和P。该项目为期12个月，将综合在Numex样地上检索的9年数据，包括收集关于地上生产力和树木招募的最终数据集。此外，当前的厄尔尼诺事件(2015-2016年)和预期的拉尼娜事件(2016-2017年)为研究极端天气事件对养分操纵林地的影响提供了独特的机会。通过拟议的项目，将分析气候变化和天气季节性对树木生长的影响，以及气候和增加的N、P有效性之间的潜在相互作用或反馈。为了更好地了解生态系统对环境变化的反应以及树种组成对这种反应的贡献，有必要弄清与气候有关的驱动因素和养分供应的影响。结果将能够预测由于养分沉积增加而导致的树种组成和森林结构的未来变化，并应纳入安第斯森林监测计划和这些森林提供的生态系统服务。该项目将继续负责Numex的协调和维护。延长阶段的另一个目标是总结Numex 9年来地上和地下植被对林分和物种水平的影响，并领导对参与项目的汇总数据进行最后的联合综合。

Tropical mountain ecosystems and their vegetation are considered to be especially sensitive to global environmental change. Due to the complexity of these ecosystems and the interaction of different drivers (land use change, climate change, and increasing nutrient deposition), understanding current responses and predicting future changes in mountain ecosystems is difficult but urgently needed. The effects of higher rates of atmospheric N and P deposition on the biological diversity and ecosystem functioning of tropical ecosystems are still poorly understood and our knowledge of N and P limitation in tropical forest ecosystems is still limited, but it will be of critical importance to know the effects of increased nutrient availability to conserve these ecosystems. The effects of continued nutrient addition are investigated along an elevational transect of Andean forests in southern Ecuador within the ongoing Ecuadorian NUtrient Manipulation EXperiment (NUMEX). NUMEX started in January 2008 adding moderate amounts of N (50 kg ha-1 yr-1), P (10 kg ha-1 yr-1), and N and P to representative stands at 1000, 2000 and 3000 m. The project of 12 months duration will synthesize 9 years of data retrieved on the NUMEX plots and includes the collection of a final data set on aboveground productivity and tree recruitment. In addition, the current El Niño event (2015-2016) and the expected La Niña event (2016-2017) offer the unique opportunity to study the effects of extreme weather events on nutrient-manipulated forest plots. With the proposed project, the influences of climate variation and weather seasonality on tree growth and the potential interactions or feedbacks between climate and increasing N and P availability will be analysed. For a better understanding of the ecosystem response to a changing environment and the contribution of tree species composition to this response, it is essential to disentangle the effects of climate-related drivers and nutrient availability. The results will allow predicting future changes in tree species composition and forest structure as a consequence of increasing nutrient deposition and should be incorporated in monitoring schemes for Andean forests and the ecosystem services provided by these forests. The project will continue to be responsible for the coordination and maintenance of NUMEX. Further objectives of the prolongation phase are to summarize above- and belowground vegetation effects on stand and species level for the 9 years of NUMEX and to lead the final joint synthesis of the aggregated data of the participating projects.