Spatial dynamics of alpine treelines under global warming: what explains the mismatch between tree densification and elevational upward shifts at the treeline ecotone?

Aim

Most studies focusing on the alpine treeline responses to climate warming have used either the tree densification within the ecotone or its elevational upshift as indicators. However, it is acknowledged that the relation between densification and upshift is spatially heterogeneous, making inferences and comparability among studies tricky. The lack of consistent empirical evidence on this potential mismatch and its drivers leads us to focus on this issue in this study. The aim was twofold: (i) to quantify the mismatch between the two processes at a regional scale, and (ii) to identify its site-specific determinants.

Location

French eastern Pyrenees

Time period

1953-2015

Major taxa studied

Pinus uncinata (Ramond ex DC)

Methods

An object-oriented supervised classification procedure was performed on historical (1953) and current (2015) air-photos. Based on the resulting rasters, densification of the treeline ecotone and upward shift of the treeline were estim...

研究目标
现有针对高山林线（alpine treeline）响应气候变暖的相关研究，多以生态交错带（ecotone）内的林木致密化或林线的海拔上移作为指示指标。但已有研究证实，林木致密化与林线上移之间的关系存在空间异质性（spatially heterogeneous），这使得不同研究间的推论与对比颇具难度。目前学界尚未就该潜在不匹配现象及其驱动因子形成一致的实证证据，因此本研究聚焦于此问题。本研究的目标分为两点：（i）在区域尺度上量化这两类过程间的不匹配程度；（ii）明确其样地特异性决定因素。

研究区域
法国东比利牛斯山脉

研究时段
1953-2015

研究类群
瑞士山松（Pinus uncinata Ramond ex DC）

研究方法
对1953年的历史航空影像与2015年的现今航空影像开展面向对象监督分类。基于生成的栅格数据，本研究对林线生态交错带的致密化程度以及林线的海拔上移幅度进行估算……