Time-series maps reveal widespread change in plant functional type cover across Arctic and boreal Alaska and Yukon
Time-series maps reveal widespread change in plant functional type cover across Arctic and boreal Alaska and Yukon
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DOI：
10.1088/1748-9326/ac6965
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发表时间：
2022-05-01
影响因子：
6.7
通讯作者：
Goetz, Scott J.
中科院分区：
文献类型：
--
作者：
Macander, Matthew J.;Nelson, Peter R.;Goetz, Scott J.
由于火灾等干扰的加剧以及苔原灌木扩张等气候驱动的植被动态，北极和北方生态系统中植物功能类型（PFT）的分布和丰度正在发生广泛变化。为了了解这些变化如何影响北方和苔原生态系统，我们需要首先量化近年来多个 PFT 的变化。虽然景观斑块通常由 PFT 的混合组成，但大多数先前的中等分辨率 (30 m) 遥感分析都基于主要 PFT 绘制了植被分布和土地覆盖类别内的变化；或者一个或几个 PFT 的连续分布，但针对单个时间点。在这里，我们绘制了阿拉斯加北部和中部以及加拿大西北部 1.77 x 10(6) km(2) 研究区域内七个 PFT 的 35 年时间序列（1985-2020）顶盖 (TC)。我们通过对 TC（植物丰度的连续测量）进行建模来改进以前检测植被变化的方法。 PFT 共同包括研究区域内的所有维管植物以及轻型大型地衣，这是一种对驯鹿管理非常重要的非维管植物。我们确定了落叶灌木 (66 x 10(3) km(2))、常绿灌木 (20 x 10(3) km(2))、阔叶树 (17 x 10(3) km(2)) 和针叶树 (16 x 10(3) km(2)) 的净增加，以及禾本科植物 (-40 x 10(3) km(2)) 和光的净减少整个地图区域上都有大型地衣 (-13 x 10(3) km(2))，北极、口北极和北方生物气候区也有类似的模式。使用空间阻塞、嵌套五重交叉验证来评估模型性能，总体均方根误差范围为 8.3% 至 19.0%。尽管 PFT TC 变化也明显是由火灾干扰造成的，但大多数净变化是由于未受近期火灾影响的地区内的演替或工厂扩张而发生的。这些地图对于评估地表能量预算、永久冻土变化、养分循环以及野生动物管理和运动分析具有重要应用。
Widespread changes in the distribution and abundance of plant functional types (PFTs) are occurring in Arctic and boreal ecosystems due to the intensification of disturbances, such as fire, and climate-driven vegetation dynamics, such as tundra shrub expansion. To understand how these changes affect boreal and tundra ecosystems, we need to first quantify change for multiple PFTs across recent years. While landscape patches are generally composed of a mixture of PFTs, most previous moderate resolution (30 m) remote sensing analyses have mapped vegetation distribution and change within land cover categories that are based on the dominant PFT; or else the continuous distribution of one or a few PFTs, but for a single point in time. Here we map a 35 year time-series (1985-2020) of top cover (TC) for seven PFTs across a 1.77 x 10(6) km(2) study area in northern and central Alaska and northwestern Canada. We improve on previous methods of detecting vegetation change by modeling TC, a continuous measure of plant abundance. The PFTs collectively include all vascular plants within the study area as well as light macrolichens, a nonvascular class of high importance to caribou management. We identified net increases in deciduous shrubs (66 x 10(3) km(2)), evergreen shrubs (20 x 10(3) km(2)), broadleaf trees (17 x 10(3) km(2)), and conifer trees (16 x 10(3) km(2)), and net decreases in graminoids (-40 x 10(3) km(2)) and light macrolichens (-13 x 10(3) km(2)) over the full map area, with similar patterns across Arctic, oroarctic, and boreal bioclimatic zones. Model performance was assessed using spatially blocked, nested five-fold cross-validation with overall root mean square errors ranging from 8.3% to 19.0%. Most net change occurred as succession or plant expansion within areas undisturbed by recent fire, though PFT TC change also clearly resulted from fire disturbance. These maps have important applications for assessment of surface energy budgets, permafrost changes, nutrient cycling, and wildlife management and movement analysis.