Masoud Irannezhad

Water‐table‐dependent hydrological changes following peatland forestry drainage and restoration: Analysis of restoration success

A before-after-control approach was used to analyze the impact of peatland restoration on hydrology, based on high temporal resolution water-table (WT) data from 43 boreal peatlands representative of a south-boreal to north-boreal climate gradient. During the study, 24 forestry drained sites were restored and 19 pristine peatlands used as control sites. Different approaches were developed and used to analyze WT changes (mean WT position, WT fluctuation, WT hydrograph, recession, and storage characteristics). Restoration increased WT in most cases but particularly in spruce mires, followed by pine mires and fens. Before restoration, the WT fluctuation (WTF) was large, indicating peat temporary storage gain (SG). After restoration, the WT hydrograph recession limb slopes and SG coefficients (Rc) declined significantly. Drainage or restoration did not significantly affect mean diurnal WT fluctuations, used here as a proxy for evapotranspiration. Overall, the changes in WT characteristics following restoration indicated creation of favorable hydrological conditions for recovery of functional peatland ecosystems in previously degraded peatland sites. This was supported by calculation of bryophyte species abundance thresholds for WT. These results can be used to optimize restoration efforts in different peatland systems and as a qualitative conceptual basis for future restoration operations.

THE ROLE OF ATMOSPHERIC CIRCULATION PATTERNS IN AGROCLIMATE VARIABILITY IN FINLAND, 1961–2011

Abstract This study evaluates interannual variations and trends in growing season daily temperature sum and daily precipitation sum in Finland during 1961–2011, and their connections to well known atmospheric circulation patterns. Changes in summer (June–August) climate partially explain changes in growing season daily temperature sum and daily precipitation sum over Finland, which naturally decreased from south to north. On a national scale, growing season warmed and became wetter during 1961–2011, as growing season daily temperature sum and daily precipitation sum significantly (p < 0.05) increased by 5.01 ± 3.17°C year–1 and 1.39 ± 0.91 mm year–1, respectively. The East Atlantic pattern was the most influential atmospheric circulation pattern for variations in growing season daily temperature sum (rho = 0.40) across Finland and the East Atlantic/West Russia pattern was most influential for growing season daily precipitation sum variability (rho = –0.54). There were significant (p < 0.05) increasing trends in growing season daily temperature sum and daily precipitation sum throughout Finland during 1961–2011. Increased growing season daily temperature sum was mainly observed in northern, central, western, eastern and coastal areas of south‐western Finland. This warming was positively associated with the East Atlantic pattern in the north, centre and south, but negatively associated with the East Atlantic/West Russia pattern in eastern Finland. Increased GSP mostly occurred in southern, eastern, western, central, northern and north‐western Finland. These wetting trends were positively correlated with the East Atlantic pattern in the north and negatively correlated with the Polar pattern in the south and the East Atlantic/West Russia pattern in the east, west, centre and north‐east of Finland. The overall agroclimatic year‐to‐year variability in Finland between 1961 and 2011 was mostly linked to variations in the East Atlantic and East Atlantic/West Russia patterns.

Spatiotemporal Variability and Trends in Extreme Temperature Events in Finland over the Recent Decades: Influence of Northern Hemisphere Teleconnection Patterns

Fifteen temperature indices recommended by the ETCCDI (Expert Team on Climate Change Detection and Indices) were applied to evaluate spatiotemporal variability and trends in annual intensity, frequency, and duration of extreme temperature statistics in Finland during 1961–2011. Statistically significant relationships between these high-resolution (10 km) temperature indices and seven influential Northern Hemisphere teleconnection patterns (NHTPs) for the interannual climate variability were also identified. During the study period (1961–2011), warming trends in extreme temperatures were generally manifested by statistically significant increases in cold temperature extremes rather than in the warm temperature extremes. As expected, warm days and nights became more frequent, while fewer cold days and nights occurred. The frequency of frost and icing days also decreased. Finland experienced more (less) frequent warm (cold) temperature extremes over the past few decades. Interestingly, significant lengthening in cold spells was observed over the upper part of northern Finland, while no clear changes are found in warm spells. Interannual variations in the temperature indices were significantly associated with a number of NHTPs. In general, warm temperature extremes show significant correlations with the East Atlantic and the Scandinavia patterns and cold temperature extremes with the Arctic Oscillation and the North Atlantic Oscillation patterns.

Impacts of changes in climate and land cover-land use on flood characteristics in Gorganrood Watershed (Northeastern Iran) during recent decades

ABSTRACT This study evaluated the effects of changes in climate and land cover-land use (LCLU) on flood intensity and frequency in the Gorganrood Watershed (GW) located in the northeast of Iran during recent decades. For this purpose, hydroclimatic (precipitation, temperature, and river discharge) time series recorded at nine stations placed in the GW during 1973–2014 were used. Flood characteristics in terms of mean, maximum and number of peaks at five discharge stations (Galikash, Gonbad, Huji Ghushan, Tamar, and Tangrah) sited in the outlet of GW sub-basins were determined applying the Peak-Over-Threshold (POT) method to daily specific discharges. This is designed to remove the effect of the different size of sub-basins. The whole study period was divided into three 14-years segments (1973–1986, 1987–2000 and 2001–2014) based on satellite LCLU maps produced for 1973, 1986, 2000 and 2014. In the GW and its sub-basins during recent decades, both flood intensity and frequency increased, the climate became wetter and warmer, and LCLU mostly converted from rangeland to farmland. The partial correlation analyses identified that flood frequency in GW was primarily connected to the LCLU conversions, but moderately to observed wetter and warmer climate. Similarly, the Tamar sub-basin experienced effects of LCLU and climate on the maximum and the number of peaks. In Haji Ghushan, wetter and warmer climate resulted in more intense and frequent floods. Increases in precipitation appear to have played the most important role in the higher flood frequency in Galikash.