Tommervik H.,Norwegian Institute for Nature Research |
Bjerke J.W.,Norwegian Institute for Nature Research |
Gaare E.,Norwegian Institute for Nature Research |
Johansen B.,Northern Research Institute Norut |
Thannheiser D.,University of Hamburg
Fungal Ecology | Year: 2012
During the last 25. yr, Sami reindeer husbandry in parts of Finnmarksvidda in the Norwegian Arctic has been in a critical state because of overexploitation of lichen-dominated tundra, which serves as winter forage. To better understand the ecosystem's capabilities for recovery we investigated vegetation cover changes over a 7-yr period, starting in 1998, at 52 sites dispersed over a large area at Finnmarksvidda. Two types of plots were established: one fenced from reindeer grazing and trampling and one open for reindeer. The investigations in 2005 showed that lichen cover had had a significant and rapid increase (up to 8.6-fold per year). The cover of vascular plants, mainly dwarf shrubs, also increased significantly, while barren areas and the cover of litter decreased significantly during the period. Mean relative growth rate of lichen biomass was 0.083 ± 0.011 per year in open plots, which is considered very rapid recovery compared to previous studies. Lichen recovery was significantly faster on leeward ridges than on exposed ridges, and fencing alone did not have any significant effects on lichen recovery, but in interaction with time, fencing contributed to increasing recovery rates. The lichen heath recovery was reciprocally correlated with reindeer density. In addition, lichen recovery was probably facilitated by recent climate changes, viz. shallower snow depths which made leeward tundra and forest floor vegetation accessible for reindeer, and increased summer precipitation rates which improved growth rates. The results from this study show that in a very short time there was a transition from an overexploited depauperate vegetation and barren ground state to a flourishing lichen-dominated vegetation state, suggesting that the injuries were repairable. The vegetation transitions which have taken place in the study area are considered to be reversible with fewer persistent effects. © 2011 Elsevier Ltd and The British Mycological Society.
Reeves J.A.,Stanford University |
Knight R.,Stanford University |
Zebker H.A.,Stanford University |
Schreuder W.A.,Principia Mathematica |
And 2 more authors.
Water Resources Research | Year: 2011
In the San Luis Valley (SLV), Colorado legislation passed in 2004 requires that hydraulic head levels in the confined aquifer system stay within the range experienced in the years 1978-2000. While some measurements of hydraulic head exist, greater spatial and temporal sampling would be very valuable in understanding the behavior of the system. Interferometric synthetic aperture radar (InSAR) data provide fine spatial resolution measurements of Earth surface deformation, which can be related to hydraulic head change in the confined aquifer system. However, change in cm-scale crop structure with time leads to signal decorrelation, resulting in low quality data. Here we apply small baseline subset (SBAS) analysis to InSAR data collected from 1992 to 2001. We are able to show high levels of correlation, denoting high quality data, in areas between the center pivot irrigation circles, where the lack of water results in little surface vegetation. At three well locations we see a seasonal variation in the InSAR data that mimics the hydraulic head data. We use measured values of the elastic skeletal storage coefficient to estimate hydraulic head from the InSAR data. In general the magnitude of estimated and measured head agree to within the calculated error. However, the errors are unacceptably large due to both errors in the InSAR data and uncertainty in the measured value of the elastic skeletal storage coefficient. We conclude that InSAR is capturing the seasonal head variation, but that further research is required to obtain accurate hydraulic head estimates from the InSAR deformation measurements. Copyright 2011 by the American Geophysical Union.
Pedersen P.,Northern Research Institute Norut |
Pedersen P.,University of Tromso
Norsk Geografisk Tidsskrift | Year: 2013
The coupling of different databases unlocks numerous possibilities for research on people's movements over time. The article shows how time series data can be converted to longitudinal statistics and how longitudinal data enable migration careers to be traced over several years. This is demonstrated by an analysis of the mobility patterns of persons in the age group 20-25 years in Northern Norway over a five-year period, with regard to the frequency and different types of migration, and the selection processes manifested in long-distance migration. Northern Norway is a peripheral region characterised by large distances between population centres, low population density, and an economy dependent upon raw materials. There are long distances to large labour market clusters both within the region and elsewhere in Norway. The analysis of the settlement patterns and migration careers indicates that the majority of the young adults, both male and female, did not migrate. Rather, the flow of migrants was created by a minority within the studied population. Further, female long-distance migrants to Southern Norway moved back to Northern Norway to a greater extent than men. The study nuances understanding of the migration patterns and demonstrates the value of applying longitudinal statistic in migration analysis. © 2013 © 2013 Norwegian Geographical Society.
Aure M.,Northern Research Institute Norut
Norsk Geografisk Tidsskrift | Year: 2013
The relationship between migration, labour market access, and emotions has not been widely analysed despite ample evidence suggesting that difficulties with labour market entry evoke diverse feelings among migrants. The article analyses migrants' narratives of their feelings toward mobility and subsequent labour market participation based on research material relating to skilled migrants entering Norway. The author examines how understanding migrants' emotions associated with place-specific labour market entry, namely low self-esteem, shame, loss of individuality, and infantilisation, but also pleasure and content, can contribute to studies of the relationship between emotion and migration. Work-related and family-related mobility are often considered the least controversial forms of mobility. However, the article shows how they may have gendered emotional costs for the individuals involved. The author concludes that studies of migration and emotion should include these issues in order to tie migration, place, labour market participation, and gender together. © 2013 © 2013 Norwegian Geographical Society.
Kumar V.,Indian Institute of Technology Bombay |
Venkataramana G.,Indian Institute of Technology Bombay |
Hogda K.A.,Northern Research Institute Norut
International Journal of Applied Earth Observation and Geoinformation | Year: 2011
In this study ascending and descending passes interferometric synthetic aperture radar (InSAR) techniques are used for glacier surface velocity estimation in the Himalaya. Single-track interferometric measurements are sensitive to only a single component of the three dimensional (3-D) velocity vectors. European Remote Sensing satellites (ERS-1/2) tandem mission data in ascending and descending tracks provide an opportunity to resolve the three velocity components under the assumption that glacier flow is parallel to its surface. Using the surface slope as an essential input in this technique the velocity pattern of Siachen glacier in Himalaya has been modelled. Glaciers in the Himalayan region maintain excellent coherence of SAR return signals in one-day temporal difference. As a result we could obtain spatially continuous surface velocity field with a precision of fraction of radar wavelength. The results covering the main course of glacier are analysed in terms of spatial and temporal variations. A maximum velocity of 43 cm/day has been observed in the upper middle portion of the glacier. This technique has been found accurate for monitoring the flow rates in this region, suggesting that routine monitoring of diurnal movement Himalayan glaciers would be immensely useful in the present day context of climate change. © 2011 Elsevier B.V.