Guest essay by Eric Worrall
h/t Dr. Willie Soon – a study into why alpine tree lines haven’t kept pace with adjusted global warming measurements has concluded that the trees are being prevented from colonising higher slopes by unspecified soil chemistry issues.
Climate change-induced march of treelines halted by unsuitable soils
New University of Guelph research dispells the myth that climate change is enabling treelines to move farther uphill and northward
Date:July 12, 2018
Source: University of Guelph
Researchers have discovered unsuitable soil at higher altitudes may be halting the advancement of treelines. This finding dispels the commonly held assumption that climate change is enabling trees to move farther uphill and northward. The researchers looked at plant growth at higher altitudes in the Canadian Rockies, grew spruce and fir seedlings at varying elevations and collected soil samples from the same areas to grow spruce seeds in growth chambers.
New research from the University of Guelph is dispelling a commonly held assumption about climate change and its impact on forests in Canada and abroad.
It’s long been thought that climate change is enabling treelines to march farther uphill and northward. But it turns out that climate warming-induced advances may be halted by unsuitable soils.
It is an important finding for resource managers looking to preserve individual species or entire ecosystems.
“There’s a common belief about the impacts of climate change,” said U of G researcher Emma Davis. “It’s actually a more complicated story than people believe.”
The abstract of the study;
Limited prospects for future alpine treeline advance in the Canadian Rocky Mountains
Emma L. Davis Ze’ev Gedalof
First published: 01 June 2018
Treeline advance has occurred throughout the twentieth century in mountainous regions around the world; however, local variation and temporal lags in responses to climate warming indicate that the upper limits of some treelines are not necessarily in climatic equilibrium. These observations suggest that factors other than climate are constraining tree establishment beyond existing treelines. Using a seed addition experiment, we tested the effects of seed availability, predation and microsite limitation on the establishment of two subalpine tree species (Picea engelmannii and Abies lasiocarpa) across four treelines in the Canadian Rocky Mountains. The effect of vegetation removal on seedling growth was also determined, and microclimate conditions were monitored. Establishment limitations observed in the field were placed in context with the effects of soil properties observed in a parallel experiment. The seed addition experiment revealed reduced establishment with increasing elevation, suggesting that although establishment within the treeline ecotone is at least partially seed limited, other constraints are more important beyond the current treeline. The effects of herbivory and microsite availability significantly reduced seedling establishment but were less influential beyond the treeline. Microclimate monitoring revealed that establishment was negatively related to growing season temperatures and positively related to the duration of winter snow cover, counter to the conventional expectation that establishment is limited by low temperatures. Overall, it appears that seedling establishment beyond treeline is predominantly constrained by a combination of high soil surface temperatures during the growing season, reduced winter snowpack and unfavourable soil properties. Our study supports the assertion that seedling establishment in alpine treeline ecotones is simultaneously limited by various climatic and nonclimatic drivers. Together, these factors may limit future treeline advance in the Canadian Rocky Mountains and should be considered when assessing the potential for treeline advance in alpine systems elsewhere
The tree line issue has been a thorn in the side of the climate alarmists since Russian Scientist Rashit Hantemirov tried to explain Arctic Dendrochronology to the Climategate scientists.
According to reconsructions most favorable conditions for tree growth have been marked during 5000-1700 BC. At that time position of tree line was far northward of recent one.
[Unfortunately, region of our research don’t include the whole area where trees grew during the Holocene. We can maintain that before 1700 BC tree line was northward of our research area. We have only 3 dated remnants of trees from Yuribey River sampled by our colleagues (70 km to the north from recent polar tree line) that grew during 4200-4016 and 3330-2986 BC.]
This period is pointed out by low interannual variability of tree growth and high trees abundance discontinued, however, by several short (50-100 years) unfavorable periods, most significant of them dated about 4060-3990 BC. Since about 2800 BC gradual worsening of tree growth condition has begun. Significant shift of the polar tree line to the south have been fixed between 1700 and 1600 BC. At the same time interannual tree growth variability increased appreciably.
During last 3600 years most of reconstructed indices have been varying not so very significant. Tree line has been shifting within 3-5 km
near recent one. Low abundance of trees has been fixed during 1410-1250 BC and 500-350 BC. Relatively high number of trees has been
noted during 750-1450 AD.
There are no evidences of moving polar timberline to the north during last century.
Climategate Email 09079795032.txt (Source Wikileaks)
I can understand dumping a tree straight into poor quality soil is bad for the tree. But history suggests colonisation occurs rapidly in a natural setting when local temperature changes make a location more suitable for plant growth. Excusing the lack of colonisation of higher slopes on a large scale as being due to “unsuitable soil chemistry” seems pretty flimsy.