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(ITEX)网络的采样能力，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，并将该网络用作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)季节性时间的变化。植物开叶、开花和结果的时间比以往任何时候都要早。因为物候学和生理学是紧密耦合的，所以生态系统的功能，如初级生产，以及竞争的结果，取决于物候反应。不同物种对气候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，与物候相反，群落组成的变化很难发现并归因于某一特定现象。北极各地报告的物候和物种丰度的变化与ITEX网络长期实验变暖的结果一致，ITEX网络是从1990年开始在冻土带生物群中进行的一项地块规模的非破坏性变暖实验。遥感分析也检测到极地地区更早的绿化和生物量增加，但不能很容易地确定群落组成变化的基础，只能推断功能，无法说明群落轨迹。ITEX网络是专门为研究物候和群落组成而设计的，也被有效地用于研究生态系统过程。它非常适合于深入、全面地研究物候、群落组成和生态系统功能在十年尺度上的变化，以应对背景气候变化，并具有长期实验变暖的附加值。ITEX网络及其实验方法的基线数据和采样能力是无与伦比的。这项工作将把在IPY期间对变暖和对照地块进行的新一轮物候和植物群落组成的实地测量的结果与10-15年前的历史数据进行比较。PIS将举办两次研讨会，综合整个网络观察到的长期物候和群落变化。此外，一套新的微创测量将在整个网络的对照和升温地块中交叉比较生态系统功能的指标-包括：树叶、凋落物和土壤养分；同位素组成；次生化学。这些实验的长期性质和协调网络的全球覆盖将导致对冻土带对过去、正在进行和未来气候变化的反应的独特见解。

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.