IPY: Collaborative Research: Study of arctic ecosystem changes in the IPY using the International Tundra Experiment

该项目将利用国际冻土带实验网络（ITEX）的采样能力，量化过去10-15年来冻土带因气候变化和实验变暖而发生的物候、植被和生态系统特性的变化，并将该网络作为监测和预测未来变化的基础。北极气候变暖的最早信号之一是生命周期事件（物候学）的季节时序变化。植物长叶、开花和结果的时间比以往任何记录都要早。由于物候和生理是紧密耦合的，生态系统的功能，如初级生产，以及竞争的结果取决于物候反应。不同物种对变暖的物候和生理反应不同，导致群落组成、生物多样性和生态系统功能的变化。然而，与物候学相反，群落组成的变化很难被发现并归因于特定的现象。据报道，整个北极地区物候学和物种丰富度的变化与ITEX网络长期实验变暖的结果一致。ITEX网络是一个从1990年开始在冻土带生物群系进行的图尺度、非破坏性变暖实验。遥感分析也发现了极地地区更早的绿化和生物量的增加，但不能很容易地确定群落组成变化的基础，只能推断功能，对群落轨迹一无所知。ITEX网络专门用于研究物候和群落组成，也被有效地用于研究生态系统过程。它非常适合深入、全面地研究物候、群落组成和生态系统功能对背景气候变化的响应的年代际变化，并具有长期实验变暖的附加价值。ITEX网络的基线数据和采样能力及其实验方法是无与伦比的。这项工作将比较国际年期间在温暖样地和对照样地重新开展的物候和植物群落组成野外测量活动的结果与10-15年前的历史数据。pi将举办两次研讨会，综合整个网络中观察到的长期物候和群落变化。此外，一套新的微创测量方法将交叉比较生态系统功能指数，包括：叶片、凋落物和土壤养分；同位素组成;还有二次化学反应——在整个网络的控制区和暖化区。这些实验的长期性和协调网络的全球覆盖将使人们对冻土带对过去、正在进行和未来气候变化的反应产生独特的见解。

This project will use the sampling power of the International Tundra Experiment (ITEX) Network to quantify changes in phenology, vegetation, and ecosystem properties that have occurred in tundra over the past 10-15 years in response to climate change and experimental warming, and to use the Network as the foundation for monitoring and prediction of future changes. Among the earliest signals of climate warming in the Arctic have been changes in the seasonal timing of life cycle events (phenology). Plants are leafing, flowering, and fruiting earlier than ever recorded. Because phenology and physiology are tightly coupled, ecosystem functions such as primary production, as well as the outcome of competition depend on phenological responses. Species phenological and physiological responses to warming differ, causing changes in community composition, biodiversity, and ecosystem function. However, in contrast to phenology, change in community composition is difficult to detect and ascribe to a particular phenomenon. Changes in phenology and species abundance being reported across the Arctic are consistent with the findings of the long-term experimental warming of the ITEX network, a plot-scale, nondestructive, warming experiment conducted across the tundra biome beginning in 1990. Remote sensing analyses have also detected earlier greening and increased biomass across polar regions, but cannot readily identify the basis for changes in community composition, can only infer function, and can say nothing about community trajectories.The ITEX network was specifically designed to study phenology and community composition, and has also been used effectively to study ecosystem processes. It is perfectly positioned for an intensive, comprehensive study of decadal-scale changes in phenology, community composition, and ecosystem function in response to background climate change, and has the added value of long-term experimental warming. The baseline data and sampling power of the ITEX network and its experimental approach are unparalleled. This effort will compare the results of a renewed field campaign of phenology and plant community composition measurements on warmed and control plots during the IPY with historical data from 10-15 years ago. The PIs will hold two workshops to synthesize the long-term phenological and community changes observed across the network. Furthermore, a new suite of minimally invasive measurements will cross compare indices of ecosystem function - including: leaf, litter, and soil nutrients; isotopic composition; and secondary chemistry - in the control and warmed plots across the network. The long-term nature of these experiments and the global coverage of the coordinated network will lead to unique insights regarding the tundra response to past, ongoing, and future climate changes.