College of Urban and Environmental Sciences, Sino-French Institute of Earth System Science, PKU Saihanba Station and MOE Laboratory for Earth Surface Processes, Peking University, Beijing, China.
Institute of General and Experimental Biology, Siberian Branch, Russian Academy of Sciences, Ulan-Ude, Russia.
Glob Chang Biol. 2022 Sep;28(17):5243-5253. doi: 10.1111/gcb.16284. Epub 2022 Jun 19.
Hemiboreal and boreal forests growing at the southern margin of the permafrost distribution are vulnerable to climate warming. However, how climate warming threatens the growth of dominant tree species that are distributed on permafrost remains to be determined, particularly in synchrony with warming-induced permafrost degradation. Tree growth in the permafrost region of southern Siberia was hypothesized to be highly sensitive to temperature increasing and warming-induced permafrost degradation. To test this hypothesis, we sampled the tree ring width of 535 trees of dominant species, larch (including Larix gmelinii and L. sibirica) and white birch (Betula platyphylla), in ten hemiboreal to boreal forest plots within different permafrost zones. The relationships between the tree ring basal area index (BAI) and temperature, precipitation, and the Palmer drought severity index (PDSI) were compared among plots located in two permafrost zones. In the isolated permafrost zone, white birch grows better than larch and is not drought-stressed (p < .05). We suggest that the deep-rooted white birch benefits from the water from thawing permafrost, while the growth of the shallow-rooted larch is stressed by drought. In the sporadic discontinuous permafrost zone, both white birch and larch benefited from permafrost melting, but the sensitivity of larch growth to PDSI is still significant (p < .05), indicating drought is still an important climatic factor limiting the growth of larch. Our results imply that the permafrost degradation caused by climate warming affects tree growth by creating the root layer additional water source. In the future, it is necessary to focus on monitoring permafrost degradation to better predict forest dynamics at the southern margin of the permafrost distribution.
生长在多年冻土分布南缘的半湿润和湿润森林容易受到气候变暖的影响。然而，气候变暖如何威胁到分布在多年冻土上的优势树种的生长，特别是与变暖引起的多年冻土退化同步，仍有待确定。西伯利亚南部多年冻土区的树木生长被假设对温度升高和变暖引起的多年冻土退化高度敏感。为了验证这一假设，我们在不同多年冻土带的 10 个半湿润到湿润森林样地中，对 535 棵优势树种（落叶松包括欧洲落叶松和西伯利亚落叶松）和白桦（白桦）的树木年轮宽度进行了采样。我们比较了位于两个多年冻土带的样地之间树木年轮基面积指数（BAI）与温度、降水和帕尔默干旱严重指数（PDSI）之间的关系。在孤立的多年冻土带，白桦的生长优于落叶松，且不受干旱胁迫（p < .05）。我们认为，深根的白桦受益于融化的多年冻土中的水分，而浅根的落叶松的生长则受到干旱的压力。在零星不连续多年冻土带，白桦和落叶松都受益于多年冻土融化，但落叶松生长对 PDSI 的敏感性仍然显著（p < .05），表明干旱仍然是限制落叶松生长的重要气候因素。我们的结果表明，气候变暖引起的多年冻土退化通过创造根层额外的水源来影响树木生长。未来，有必要重点监测多年冻土退化，以更好地预测多年冻土分布南缘的森林动态。
