A tree-ring-based drought index reconstruction for far-western Mongolia: 1565-2004

N. K. Davi; G. C. Jacoby; R. D. D'Arrigo; N. Baatarbileg; Li Jinbao; A. E. Curtis

doi:10.1002/joc.1798

Linking Increasing Drought Stress to Scots Pine Mortality and Bark Beetle Infestations

The Scientific World JOURNAL ◽

10.1100/tsw.2007.58 ◽

2007 ◽

Vol 7 ◽

pp. 231-239 ◽

Cited By ~ 60

Author(s):

Matthias Dobbertin ◽

Beat Wermelinger ◽

Christof Bigler ◽

Matthias Bürgi ◽

Mathias Carron ◽

...

Keyword(s):

Drought Stress ◽

Tree Ring ◽

Scots Pine ◽

Bark Beetle ◽

Drought Index ◽

Summer Drought ◽

Forest Protection ◽

Mortality Index ◽

Rhone Valley

In the dry Swiss Rhone Valley, Scots pine forests have experienced increased mortality in recent years. It has commonly been assumed that drought events and bark beetles fostered the decline, however, whether bark beetle outbreaks increased in recent years and whether they can be linked to drought stress or increasing temperature has never been studied.In our study, we correlated time series of drought indices from long-term climate stations, 11-year mortality trends from a long-term research plot, and mortality probabilities modeled from tree rings (as an indicator of tree vitality) with documented occurrences of various bark beetle species and a buprestid beetle, using regional Forest Service reports from 1902 to 2003 and advisory cases of the Swiss Forest Protection Service (SFPS) from 1984 to 2005. We compared the historical findings with measured beetle emergence from a 4-year tree felling and breeding chamber experiment.The documented beetle-related pine mortality cases increased dramatically in the 1990s, both in the forest reports and the advisory cases. The incidents of beetle-related pine mortality correlated positively with spring and summer temperature, and with the tree-ring-based mortality index, but not with the drought index. The number of advisory cases, on the other hand, correlated slightly with summer drought index and temperature, but very highly with tree-ringbased mortality index. The tree-ring-based mortality index and observed tree mortality increased in years following drought. This was confirmed by the beetle emergences from felled trees. Following dry summers, more than twice as many trees were colonized by beetles than following wet summers.We conclude that increased temperatures in the Swiss Rhone Valley have likely weakened Scots pines and favored phloeophagous beetle population growth. Beetles contributed to the increased pine mortality following summer drought. Among the factors not addressed in this study, changed forest use may have also contributed to increased beetle populations and Scots pine mortality, whereas air pollution seems to be of lesser importance.

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Drought Sensitiveness on Forest Growth in Peninsular Spain and the Balearic Islands

Forests ◽

10.3390/f9090524 ◽

2018 ◽

Vol 9 (9) ◽

pp. 524 ◽

Cited By ~ 16

Author(s):

Marina Peña-Gallardo ◽

Sergio Vicente-Serrano ◽

J. Camarero ◽

Antonio Gazol ◽

Raúl Sánchez-Salguero ◽

...

Keyword(s):

Tree Ring ◽

Drought Index ◽

Net Primary Production ◽

Ring Width ◽

Forest Growth ◽

Balearic Islands ◽

Drought Indices ◽

Tree Ring Width ◽

Drought Impacts ◽

Peninsular Spain

Drought is one of the key natural hazards impacting net primary production and tree growth in forest ecosystems. Nonetheless, tree species show different responses to drought events, which make it difficult to adopt fixed tools for monitoring drought impacts under contrasting environmental and climatic conditions. In this study, we assess the response of forest growth and a satellite proxy of the net primary production (NPP) to drought in peninsular Spain and the Balearic Islands, a region characterized by complex climatological, topographical, and environmental characteristics. Herein, we employed three different indicators based on in situ measurements and satellite image-derived vegetation information (i.e., tree-ring width, maximum annual greenness, and an indicator of NPP). We used seven different climate drought indices to assess drought impacts on the tree variables analyzed. The selected drought indices include four versions of the Palmer Drought Severity Index (PDSI, Palmer Hydrological Drought Index (PHDI), Z-index, and Palmer Modified Drought Index (PMDI)) and three multi-scalar indices (Standardized Precipitation Evapotranspiration Index (SPEI), Standardized Precipitation Index (SPI), and Standardized Precipitation Drought Index (SPDI)). Our results suggest that—irrespective of drought index and tree species—tree-ring width shows a stronger response to interannual variability of drought, compared to the greenness and the NPP. In comparison to other drought indices (e.g., PDSI), and our results demonstrate that multi-scalar drought indices (e.g., SPI, SPEI) are more advantageous in monitoring drought impacts on tree-ring growth, maximum greenness, and NPP. This finding suggests that multi-scalar indices are more appropriate for monitoring and modelling forest drought in peninsular Spain and the Balearic Islands.

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