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Nilsson, Christer
Publications (10 of 30) Show all publications
Jonsson, K. & Nilsson, C. (2009). Scots Pine (pinus sylvestris L.) on Shingle Fields: A Dendrochronologic Reconstruction of Early Summer Precipitation in Mideast Sweden. Journal of Climate, 22(17), 4710-4722
Open this publication in new window or tab >>Scots Pine (pinus sylvestris L.) on Shingle Fields: A Dendrochronologic Reconstruction of Early Summer Precipitation in Mideast Sweden
2009 (English)In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 22, no 17, p. 4710-4722Article in journal (Refereed) Published
Abstract [en]

Scots pine (Pinus sylvestris L.) trees growing on shingle fields offer a unique possibility to reconstruct precipitation and study climate variability in the fairly humid eastern part of central Sweden. Tree-ring characteristics were compared with monthly (1890-2001) and daily (1961-2001) climate data from an adjacent meteorological station. Chronologies for latewood (LW), earlywood (EW), and tree-ring widths (RW) were constructed from 73 living and dead trees. Correlation analyses show that tree growth is most sensitive to early summer precipitation. EW shows the strongest correlation with precipitation in May and June while LW is best correlated with June and July precipitation. A reconstruction model for May-June precipitation was calculated using principal component analysis (PCA) regression (regular regression) including EW, LW, and RW for present and previous years. The model explained 46% of the variation in May-June precipitation and allowed a reconstruction back to 1560. Information about wet and dry years was collected from historical documents and was used to validate the result. Periods with precipitation above and below the mean show agreement with previous reconstructions of spring precipitation from tree rings in Finland and of spring floods from estuary sediments in the region. Analyses of correlations between meteorological stations and reconstructed precipitation show that the model is valid for the coastal part of central Sweden. The authors conclude that Scots pine trees on shingle fields are well suited for precipitation reconstruction, and the separate analyses of LW and EW improve the reconstruction.

Keywords
NORTH-ATLANTIC OSCILLATION; EAST CENTRAL SWEDEN; MAUNDER MINIMUM; WINTER PRECIPITATION; RING-WIDTHS; TREE-RINGS; ATMOSPHERIC CIRCULATION; CLIMATIC INFLUENCE; WESTERN NORWAY; TEMPERATURE
National Category
Physical Geography
Identifiers
urn:nbn:se:miun:diva-9631 (URN)10.1175/2009JCLI2401.1 (DOI)000269375600017 ()2-s2.0-70350091594 (Scopus ID)
Available from: 2009-09-15 Created: 2009-09-15 Last updated: 2018-01-13Bibliographically approved
Bång, Å., Nilsson, C. & Holm, S. (2007). The potential role of tributaries as seed sources to an impoundment in northern Sweden: a field experiment with seed mimics. Rivers Research and Applications: an international journal devoted to river research and management, 23(10), 1049-1057
Open this publication in new window or tab >>The potential role of tributaries as seed sources to an impoundment in northern Sweden: a field experiment with seed mimics
2007 (English)In: Rivers Research and Applications: an international journal devoted to river research and management, ISSN 1535-1459, E-ISSN 1535-1467, Vol. 23, no 10, p. 1049-1057Article in journal (Refereed) Published
Abstract [en]

Fragmentation and flow regulation of rivers by large dams are known to obstruct the longitudinal dispersal of waterborne plant propagules between impoundments, and to affect plant community composition. However, even several decades after a dam has been built, impoundments may still have a relatively species-rich riparian flora. We hypothesized that free-flowing tributaries act as the major gene pools for such impoundments, thus alleviating the fragmenting effect large dams have on the main channel. The importance of tributaries as seed sources was tested by releasing wooden seed mimics in three different-sized (0.22-6.93 m3 s-1) tributaries of an impoundment in the Ume River in northern Sweden. In each tributary seed mimics were released, during the spring flood peak, from three points approximately 1, 2 and 3 km upstream the outlet in the impoundment. The importance of a tributary as a seed source increased with tributary size. Of the 9000 released seed mimics 1.5 % reached the impoundment; 1.2 % of the 9000 originated from the largest tributary and 0.3 % from the middle-sized one. The smallest tributary retained all its mimics.

Keywords
fragmentation, hydrochory, plant dispersal, impoundment, seed mimics, Ume River, Sweden
National Category
Ecology
Identifiers
urn:nbn:se:miun:diva-1252 (URN)10.1002/rra.1014 (DOI)000252530100001 ()2-s2.0-38349172407 (Scopus ID)4995 (Local ID)4995 (Archive number)4995 (OAI)
Available from: 2008-12-09 Created: 2008-12-09 Last updated: 2017-12-13Bibliographically approved
Dahlström, N. & Nilsson, C. (2006). The dynamics of coarse woody debris in boreal Swedish forests are similar between stream channels and adjacent riparian forests. Canadian Journal of Forest Research, 36(5), 1139-1148
Open this publication in new window or tab >>The dynamics of coarse woody debris in boreal Swedish forests are similar between stream channels and adjacent riparian forests
2006 (English)In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 36, no 5, p. 1139-1148Article in journal (Refereed) Published
Abstract [en]

Although numerous studies have focused on the dynamics of coarse woody debris (CWD) in boreal Fennoscandian forests, information on CWD in streams remains limited. To achieve a better understanding of CWD dynamics in streams we compared amounts and characteristics of CWD between streams and adjacent riparian forests in old-growth and managed forest sites, respectively. We also identified distances to the sources of CWD and evaluated these in relation to the lateral zonation of riparian trees. CWD volumes found in the stream channels were related to, but exceeded, the volumes found in the adjacent forest. In-channel volumes separated by species were better correlated with terrestrial volumes of CWD than with volumes of living trees. Tree species appeared to be zoned across the riparian zone, with slightly higher abundances of deciduous trees and lower abundances of Scots pine trees close to the stream. Similar to upland forests, riparian forests were dominated by coniferous tree species, mainly Norway spruce (Picea abies (L.) Karst.). These findings suggest large similarities in CWD input between streams and riparian forests and substantially slower decomposition rates in stream channels compared with those in riparian forest. The results provide an improved basis for creating reliable models of CWD supply and maintenance in streams based on knowledge of forest development and CWD dynamics in the terrestrial environment. Site productivity could potentially be used to predict CWD volumes in stream channels under pristine conditions.

National Category
Ecology
Identifiers
urn:nbn:se:miun:diva-8689 (URN)10.1139/X06-015 (DOI)000238286000009 ()2-s2.0-33746488836 (Scopus ID)
Note

VR-Biology

Available from: 2009-02-26 Created: 2009-02-26 Last updated: 2017-12-13Bibliographically approved
Hylander, K., Nilsson, C., Jonsson, B.-G. & Göthner, T. (2005). Differences in habitat quality explain nestedness in a land snail meta-community. Oikos, 108(2), 351-361
Open this publication in new window or tab >>Differences in habitat quality explain nestedness in a land snail meta-community
2005 (English)In: Oikos, ISSN 0030-1299, Vol. 108, no 2, p. 351-361Article in journal (Refereed) Published
Abstract [en]

We set up two alternative hypotheses on how environmental variables could foster nestedness; one of "nested habitats" and another of "nested habitat quality". The former hypothesis refers to situations where the nestedness of species depends on a nestedness of discrete habitats. The latter considers situations where all species in an assemblage increase in abundance along the same environmental gradient, but differ in specialisation or tolerance. We tested whether litter-dwelling land snails (terrestrial gastropods) in boreal riparian forest exhibited a nested community structure, whether such a pattern was related to differences in environmental variables among sites, and which of the two hypotheses that best could account for the found pattern. We sampled litter from 100 m(2) plots in 29 mature riparian forest sites along small streams in the boreal zone of Sweden. The number of snail species varied between 3 and 14 per site. Ranking the species-by-site matrix by PCA scores of the first ordination axis revealed a similarly significant nested pattern as when the matrix was sorted by number of species, showing that the species composition in this meta-community can be properly described as nested. Several environmental variables, most notably pH index, were correlated with the first PCA axis. All but two species had positive eigenvectors in the PCA ordination and the abundance increased considerably along the gradient for most of the species implying that the hypothesis of "nested habitats" was rejected in favour of the "nested habitat quality" hypothesis. Analyses of nestedness have seldom been performed on equal sized plots, and our study shows the importance of understanding that variation in environmental variables among sites can result in nested communities. The conservation implications are different depending on which of our two hypotheses is supported; a conservation focus on species "hotspots" is more appropriate if the communities are nested because of "nested habitat quality".

Keywords
skogs, biologisk mångfald, ekologi
National Category
Ecology Biological Sciences
Identifiers
urn:nbn:se:miun:diva-3362 (URN)10.1111/j.0030-1299.2005.13400.x (DOI)000225792700014 ()2-s2.0-13444263736 (Scopus ID)3326 (Local ID)3326 (Archive number)3326 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-08-30Bibliographically approved
Dahlström, N., Jönsson, K. & Nilsson, C. (2005). Long-term dynamics of large woody debris in a managed boreal forest stream.. Forest Ecology and Management, 210(1-3), 363-373
Open this publication in new window or tab >>Long-term dynamics of large woody debris in a managed boreal forest stream.
2005 (English)In: Forest Ecology and Management, ISSN 0378-1127, E-ISSN 1872-7042, Vol. 210, no 1-3, p. 363-373Article in journal (Refereed) Published
Abstract [en]

Little is known about how past forest management in Sweden influenced the quantity and quality of large woody debris (LWD) in streams. The present study provides information of the long-term dynamics of LWD in a reach of a boreal stream intersecting a managed forest. Dendrochronological methods were used to reconstruct mortality years of the pieces of LWD and the general history of fire and cuttings of the surrounding riparian forest. Today, spruce dominates among the living trees, whereas the LWD is dominated by birch in the forest and by pine in the stream. Fire frequency prior to active fire suppression was similar to values reported from boreal forests. Pine trees were more abundant in the riparian forest before selective logging operations and active fire suppression began in the 1800s. Many of the pieces of LWD found in the stream today died more than 200 years ago and derived from a cohort of pines that generated in the early 1600s. Pine LWD in stream channels is highly resistant to decomposition and can reside for more than 300 years. A substantial amount of the LWD found today in managed forest streams in boreal Sweden most likely derives from the time before extensive human influence and is likely to decrease further in the future. Management of riparian forests to ascertain future supply of long-lived LWD in streams should target to increase the proportion of pine trees.

Keywords
Boreal forest, Dendrochronology, Forest management, Large woody debris, Stream, Sweden
National Category
Physical Geography
Identifiers
urn:nbn:se:miun:diva-3661 (URN)10.1016/j.foreco.2005.02.022 (DOI)000229165500027 ()3743 (Local ID)3743 (Archive number)3743 (OAI)
Note
VR-BiologyAvailable from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-01-12Bibliographically approved
Malm Renöfält, B., Jansson, R. & Nilsson, C. (2005). Spatial patterns of plant invasiveness in a riparian corridor. Landscape Ecology, 20(2), 165-176
Open this publication in new window or tab >>Spatial patterns of plant invasiveness in a riparian corridor
2005 (English)In: Landscape Ecology, ISSN 0921-2973, E-ISSN 1572-9761, Vol. 20, no 2, p. 165-176Article in journal (Refereed) Published
Abstract [en]

Analysis of landscape-scale patterns of plant invasiveness can assist in interpreting spatial patterns of plant species richness. We investigated downstream variation in plant invasiveness in the riparian corridor of the free-flowing Vindel River in northern Sweden by introducing seeds of an alien species, Helianthus annuus, in 0.25 m(2) plots of natural vegetation from mountain headwaters to the coast and found a significant downstream pattern with middle reaches having the highest invasiveness. We related invasiveness to species richness, both on a reach scale (200-m long stretches of riverbank encompassing the experimental plots) and on the scale of experimental plots. We found no significant correlation between plant invasiveness and species richness, neither at the reach nor at the plot scale. The number of available soil substrates shows a significant positive quadratic relationship with location along the river and substrate fineness shows a near significant negative quadratic relationship with location along the river, with middle reaches having coarser substrates. Several studies have shown that plant species richness in riparian corridors often exhibits a quadratic pattern with highest species richness in the middle reaches of a river, similar to the pattern we found for invasiveness. Although species richness per se might not be a primary factor for invasibility, the same habitat conditions as those supporting plant species richness, can help in explaining large-scale patterns of plant invasion in riparian zones.

Keywords
SPECIES RICHNESS; UNITED-STATES; BOREAL RIVERS; HOT-SPOTS; DIVERSITY; INVASIBILITY; INVASION; DISPERSAL; SCALE; COMMUNITIES
National Category
Biological Sciences
Identifiers
urn:nbn:se:miun:diva-9812 (URN)10.1007/s10980-004-2262-z (DOI)000230299600004 ()
Available from: 2009-09-22 Created: 2009-09-22 Last updated: 2017-12-13Bibliographically approved
Hylander, K., Nilsson, C., Dynesius, M. & Jonsson, B.-G. (2005). Substrate form determines the fate of bryophytes in clear-cuts and buffer strips along small boreal streams. Ecological Applications, 15(2), 674-688
Open this publication in new window or tab >>Substrate form determines the fate of bryophytes in clear-cuts and buffer strips along small boreal streams
2005 (English)In: Ecological Applications, ISSN 1051-0761, Vol. 15, no 2, p. 674-688Article in journal (Refereed) Published
Abstract [en]

Studies on the effectiveness of forest buffer strips left along streams after logging have long overlooked the biota of the buffers themselves, despite their high species richness. We investigated mosses and liverworts (bryophytes), abundant and species-rich groups in boreal forests, before and 2.5 years after logging along 15 small streams. In each Site, two 1000-m(2) (20 X 50 m) plots along the stream were inventoried; one plot in an area subjected to clear-cutting, and another in a buffer strip (10 m wide on each side of the stream). Ten plots along small streams in forest reserves in the same region were used as references. We found that less than half as many bryophyte species per plot disappeared after logging in the buffer strips compared to the clearcuts. The changes in bryophyte cover and in species composition were smaller in the buffer strips, and the species that were negatively affected in the clearcuts were less affected in the buffer strips. However, there was a significant change in species composition in the buffer strips compared to the references. Substrate form. and taxonomic group were important factors in understanding this turnover. Many species growing on substrates with a convex form (e.g., logs, tree bases, and mesic ground) decreased or disappeared, while species on concave substrates were rather unaffected. This held for both mosses and liverworts, although liverworts were generally more sensitive than mosses. The difference in response of assemblages on convex vs. concave substrates makes changes in microclimate due to logging a likely explanation. The species in most need of protection (i.e., the red-listed species) were among the ones with strongest declines in the 20 m wide buffer strips. In order to function optimally for bryophyte conservation, forests along small streams need to be protected from high wind-throw frequency and strong edge effects. Increasing the width of buffer strips at sites with known or potential values (e.g., large amounts of woody debris or boulders) should be considered a better strategy than using narrow buffer strips with a fixed width.

Keywords
skogs, biologisk mångfald, ekologi
National Category
Ecology Biological Sciences
Identifiers
urn:nbn:se:miun:diva-3361 (URN)10.1890/04-0570 (DOI)000228059000023 ()3325 (Local ID)3325 (Archive number)3325 (OAI)
Note
VR-BiologyAvailable from: 2008-09-30 Created: 2008-09-30 Last updated: 2011-04-08Bibliographically approved
Hylander, K., Nilsson, C. & Gothner, T. (2004). Effects of buffer-strip retention and clearcutting on land snails in boreal riparian forests. Conservation Biology, 18(4), 1052-1062
Open this publication in new window or tab >>Effects of buffer-strip retention and clearcutting on land snails in boreal riparian forests
2004 (English)In: Conservation Biology, ISSN 0888-8892, E-ISSN 1523-1739, Vol. 18, no 4, p. 1052-1062Article in journal (Refereed) Published
Abstract [en]

We investigated the short-term effects of forest clearcutting on land snails (terrestrial gastropods) in 15 forest stands along small streams in Sweden. Two different silvicultural treatments were applied at each site: clearcutting across the stream channel and buffer strips 10 m wide on each side of the stream. Additionally, we studied 10 reference sites in unlogged riparian forests along similar-sized streams. All sites were studied before logging and then 2.5 years after logging. After clearcutting the number of individuals in a 0.5-m(2) sample from each site decreased on average from 107 to 87, and the mean number of species per sample decreased from 9.9 to 7.7. Most species were negatively affected, but there were also clear differences in sensitivity. There were correlations between species survival and ground moisture. At the wettest clearcut sites with an almost intact bryophyte cover, the land snails were unaffected by clearcutting. This result suggests that wet or moist forest floors can serve as refugia even at very small spatial scales (e.g., shallow hollows, crevices). If this is an important mechanism, the spatial distribution of small habitats could be important for the long-term survival of the snail fauna or other small, dispersal-limited organisms at clearcut sites. In the buffer strips, the number of individuals decreased but not the number of species, indicating that buffer-strip retention is a good practice for protecting land snails in riparian forests. The varying effectiveness of the buffer strip could partly be explained by the proportion of the remaining basal area, emphasizing that buffer strips could be even more effective if efforts are made to avoid heavy damage by windthrows.

Keywords
buffer strip, clearcutling, green tree retention, land snails, riparian reserves, terrestrial gastropods
National Category
Ecology
Identifiers
urn:nbn:se:miun:diva-13499 (URN)10.1111/j.1523-1739.2004.00199.x (DOI)000222979400026 ()2-s2.0-4043061535 (Scopus ID)
Available from: 2011-04-08 Created: 2011-04-08 Last updated: 2017-12-11Bibliographically approved
Dahlström, N. & Nilsson, C. (2004). Influence of Woody Debris on Channel Structure in Old Growth and Managed Forest Streams in Central Sweden. Environmental Management, 33(3), 376-384
Open this publication in new window or tab >>Influence of Woody Debris on Channel Structure in Old Growth and Managed Forest Streams in Central Sweden
2004 (English)In: Environmental Management, ISSN 0364-152X, E-ISSN 1432-1009, Vol. 33, no 3, p. 376-384Article in journal (Refereed) Published
Abstract [en]

Anecdotal information suggests that woody debris have had an important channel-forming role in Swedish streams and rivers, but there are few data to support this view. We identified 10 streams within near-natural and 10 streams within managed forest landscapes in central Sweden, and quantified their channel characteristics and content of woody debris. All pieces of woody debris greater than 0.5 m in length and greater than 0.05 m in base diameter were included. The near-natural forests were situated in reserves protected from forest cutting, whereas the managed forests had previously faced intensive logging in the area adjacent to the stream, The two sets of streams did not differ in general abiotic characteristics such as width, slope, or boulder cover, but the number of wood pieces was twice as high and the wood volume almost four times as high in the near-natural streams. This difference resulted in a higher frequency of debris dams in the near-natural streams. Although the total pool area did not differ between the two sets of streams, the wood-formed pools were larger and deeper, and potentially ecologically more important than other pools. In contrast to what has been believed so far, woody debris can be a channel-forming agent also in steeper streams with boulder beds. In a step-wise multiple regression analysis, pool area was positively and most strongly related to the quantity of woody debris, whereas channel gradient and wood volume were negatively related. The frequency of debris dams increased with the number of pieces of woody debris, but was not affected by other variables. The management implications of this study are that the wood quantity in streams in managed forests would need to be increased if management of streams will target more pristine conditions.

Keywords
Debris dams, Streams, Logging, Sweden, Woody debris
National Category
Ecology
Identifiers
urn:nbn:se:miun:diva-3119 (URN)10.1007/s00267-003-3042-2 (DOI)000221646400009 ()3005 (Local ID)3005 (Archive number)3005 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2017-12-12Bibliographically approved
Dynesius, M., Jansson, R., Johansson, M. E. & Nilsson, C. (2004). Intercontinental similarities in riparian-plant diversity and sensitivity to river regulation.. Ecological Applications, 14(1), 173-191
Open this publication in new window or tab >>Intercontinental similarities in riparian-plant diversity and sensitivity to river regulation.
2004 (English)In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 14, no 1, p. 173-191Article in journal (Refereed) Published
Abstract [en]

We asked whether assemblages of species with separate evolutionary histories differed in their response to similar human interventions. We assessed this by comparing the response of riparian plant communities to river regulation on two different continents. We compared free-flowing and regulated rivers between boreal parts of North America (Alberta and British Columbia) and Europe (Sweden), using a standardized Sampling protocol and the same field staff on both continents. Although the two regions shared few species, both riparian plant-species diversity along free-flowing rivers and the response to different kinds of flow regulation were similar between the continents. The number of riparian-plant species and their amount of cover differed among types of water-level regime, but the continental affiliation of a river-margin site did not statistically explain any of the variation. Within continents, the local flora of the regulated river-margin sites was largely similar in species composition to the free-flowing ones, but the sites along storage reservoirs were more species-poor. The similarity in the response to regulation between the continents suggests that general guidelines for rehabilitation of degraded boreal rivers are. a realistic goal.The number of species and genera, plant cover, and species numbers in most trait groups (classified according to growth form and life span) were similar between free-flowing river margins in Europe and North America. Moreover, the regional native species pools of northern Sweden and Alberta were similar in size and composition of species groups, despite the fact that only 27% of the species in Alberta were found in northern Sweden. This is presumably because the floras share a common Tertiary origin and because the regions have had largely similar late-Tertiary and Quaternary histories. The most pronounced difference between the continents was that we found no exotic species on the 183 Swedish river margin sites, whereas 9% of the species found in all 24 North American plots taken together were exotics. All North American exotics found have occurred in Europe since prehistoric times, and the difference in exotic richness most likely reflects a difference in the number of species humans have transferred from one continent to another, rather than a difference in invasibility between the regions.

Keywords
Alberta, British Columbia, community convergence, exotic plant species, hydroelectric development, river regulation, species-area relationship, species diversity, local and regional, species pool, Sweden, vascular plants
National Category
Ecology
Identifiers
urn:nbn:se:miun:diva-2567 (URN)10.1890/02-5127 (DOI)000189130000017 ()1884 (Local ID)1884 (Archive number)1884 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2017-12-12Bibliographically approved
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