The Climate-Growth Relationship between Picea smithiana (Wall.) Boiss. and Abies pindrow (Royle ex D.Don) Royle along the Latitudinal Gradient in Northern Pakistan

Abstract

A changing climate and global warming have adversely affected Pakistan’s moist and dry temperate vegetation. Abies pindrow (fir) (Royle ex D.Don) Royle and Picea smithiana (spruce) Wall.) Boiss are the two major representative species of the moist and dry temperate forests in Northern Pakistan. The dendroclimatic study of both species is crucial for the assessment of climate variability at various spatial and temporal scales. This study examined the dendroclimatology of fir and spruce, and analyzed the growth–climate relationship along the latitudinal gradient. Two hundred and nineteen samples (ring cores) of the two species were collected from five different sites (Shogran (SHG), Upper Dir (UDS), Bahrain Swat (BSG), Astore Gilgit (NPKA), and Sharan Kaghan (SHA)) in Northern Pakistan. The cores were cross-dated, and chronologies were generated for the species and climatic data (precipitation, temperature, and Palmer Drought Severity Index (PDSI)) correlated with radial growth. The interspecies correlations for fir were calculated as 0.54, 0.49, 0.52, 0.60, and 0.48 for SHG, UDS, BSG, NPKA, and SHA, respectively, whereas in the case of spruce, the interspecies correlations were 0.44 for SHG, 0.55 for UDS, and 0.49 for BSG. Climate variability was observed in the samples of both species, which showed significant drought and humid years at specific intervals. With respect to the correlation between tree-ring width and climatic factors, a positive correlation was observed between fir growth and summer season precipitation, mean temperature, and PDSI in the spring, summer, and autumn seasons. Similarly, the growth of spruce was positively correlated with precipitation (in February, September, and May) and PDSI (in the summer and autumn seasons); however, no correlation was observed between monthly temperature and spruce growth. The relationship of fir and spruce growth with seasonal precipitation and PDSI showed a change from a negative to a positive correlation after 1980, following rapid warming. During the winter and spring, the correlation coefficient between fir radial growth and seasonal temperature showed an initial upward trend followed by a progressive decrease along with increasing latitude. Seasonal variations were observed regarding the correlation coefficient between spruce radial growth and increasing latitude (increasing in winter; a decreasing trend in spring and summer; an initial increase and then a decrease in autumn). In the same way, the correlation of seasonal temperature and PDSI with the radial growth of both species showed increasing trends with increasing latitude, except in the autumn season.

Multi-century (635-year) spring season precipitation reconstruction from northern Pakistan revealed increasing extremes

“…Therefore, response of tree-growth to temperature is not uniform across the whole of Pakistan because some trees from high elevation regions are showing positive responses to temperature, while those from dry sites are showing negative responses to temperature. Similar to the present study, a negative response of Picea smithiana with the spring season temperature has been reported in the Karakoram region of northern Pakistan 60 , with the same for the C. deodara from the Hindu Kush range of Pakistan 61 . Similarly, Zafar et al 62 found a negative relationship between temperatures and the P. smithiana and P. gerardiana chronologies from the Gilgit and Hunza valleys of northern Karakorum during most of the months of recent years.…”

Climatically induced anomalies in tree-ring structure of Abies pindrow (Royal ex D. Don) and Taxus baccata (L.) growing in Hindu-Kush mountainous region of Pakistan

“…The climate growth response of both species against climatic parameters was similar. The growth of both species was positively correlated with precipitation and negatively correlated with temperature, similar to the findings of Ullah et al (2022) and Ahmed et al (2010). In dry temperate regions, precipitation becomes the limiting factor for growth of conifer species, and lack of rainfall with increasing temperature results in drought conditions, leading to decreased growth rate of trees (Thapa et al 2013).…”

“…Pindrow and T. baccata are more vulnerable to climate changes (Thapa et al 2013, Yousaf et al 2022. These two species in this temperate forest are dominant (Muhammad et al 2021), having rapid growth and according to recent studies these species have potential sensitivity for dendroclimatological studies (Thapa et al 2013, Shaheen et al 2015, Koc et al 2018, Ullah et al 2022. However, little is known on the relationship between climate and growth for these two species in the study site, we explored this correlation with regional temperature and precipitation variability to assess their potential for climate reconstruction.…”