Physical disturbance determines effects from nitrogen addition on ground vegetation in boreal coniferous forests

Strengbom, Joachim; Nordin, Annika

doi:10.1111/j.1654-1103.2011.01359.x

Cited by 28 publications

(15 citation statements)

References 49 publications

(82 reference statements)

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“…Previously added N retained in the soil layer may thus be accessible to above ground vegetation as N mineralization rates increases after clear-felling and soil scarification. Previous studies of the same sites as used in the present study revealed fertilizer induced shifts in species composition of the forest floor vegetation [20,23]. In combination with the results from the present study this clearly demonstrates that carry-over effects from previous fertilization events influence several components of the ecosystem, resulting in a long-lasting effect on site productivity.…”

Section: Discussionsupporting

confidence: 86%

“…When fertilizing forests, a large part of the N added is retained in the soil layer [21,22]. Strengbom and Nordin [23] suggested that the disturbance from harvest and site scarification leads to increased mineralization rates of immobilized soil N, explaining why effects of previous (more than 25 years ago) N fertilization was more evident in the early phase of the subsequent stand rotation than within the same stand rotation that were fertilized.…”

Section: Introductionmentioning

confidence: 99%

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Residual Long-Term Effects of Forest Fertilization on Tree Growth and Nitrogen Turnover in Boreal Forest

From

Strengbom

Nordin

2015

Forests

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Abstract:The growth enhancing effects of forest fertilizer is considered to level off within 10 years of the application, and be restricted to one forest stand rotation. However, fertilizer induced changes in plant community composition has been shown to occur in the following stand rotation. To clarify whether effects of forest fertilization have residual long-term effects, extending into the next rotation, we compared tree growth, needle N concentrations and the availability of mobile soil N in young (10 years) Pinus sylvestris L. and Picea abies (L.) H. Karst. stands. The sites were fertilized with 150 kg·N·ha −1 once or twice during the previous stand rotation, or unfertilized. Two fertilization events increased tree height by 24% compared to the controls. Needle N concentrations of the trees on previously fertilized sites were 15% higher than those of the controls. Soil N mineralization rates and the amounts of mobile soil NH4-N and NO3-N were higher on sites that were fertilized twice than on control sites. Our study demonstrates that operational forest fertilization can cause residual long-term effects on stand N dynamics, with subsequent effects on tree growth that may be more long-lasting than previously believed, i.e., extending beyond one stand rotation.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Residual Long-Term Effects of Forest Fertilization on Tree Growth and Nitrogen Turnover in Boreal Forest

From

Strengbom

Nordin

2015

Forests

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“…) and amensalism from the tree layer (Thomas et al. ; Strengbom and Nordin ). Additionally, when the warming experiment was commenced, the optimized fertilization experiment had been ongoing for several years, and the trees and understorey were already significantly affected (Bergh et al.…”

Section: Discussionmentioning

confidence: 99%

“…There are at least three possible reasons for why the effects of warming in most cases were smaller in fertilized than in unfertilized stands: (1) the potential effect of increased nutrient mineralization may be smaller in fertilized stands; (2) the abundance of the forest floor vegetation was strongly reduced by fertilization, implying smaller possible effect sizes; and (3) the reduction in light on the forest floor as an effect of increased canopy cover strongly reduced the possibilities of understorey plants to utilize an increased nutrient supply for growth. None of these reasons exclude each other, but it has been suggested that the effects of increased nutrient availability on boreal forest floor vegetation are strongly mediated by both competition within strata (Strengbom et al 2004) and amensalism from the tree layer (Thomas et al 1999;Strengbom and Nordin 2012). Additionally, when the warming experiment was commenced, the optimized fertilization experiment had been ongoing for several years, and the trees and understorey were already significantly affected , which most likely contributed to this difference in effect of warming.…”

Section: Discussionmentioning

confidence: 99%

Interactions with successional stage and nutrient status determines the life‐form‐specific effects of increased soil temperature on boreal forest floor vegetation

Hedwall

Skoglund²,

Linder

2015

Ecology and Evolution

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The boreal forest is one of the largest terrestrial biomes and plays a key role for the global carbon balance and climate. The forest floor vegetation has a strong influence on the carbon and nitrogen cycles of the forests and is sensitive to changes in temperature conditions and nutrient availability. Additionally, the effects of climate warming on forest floor vegetation have been suggested to be moderated by the tree layer. Data on the effects of soil warming on forest floor vegetation from the boreal forest are, however, very scarce. We studied the effects on the forest floor vegetation in a long-term (18 years) soil warming and fertilization experiment in a Norway spruce stand in northern Sweden. During the first 9 years, warming favored early successional species such as grasses and forbs at the expense of dwarf shrubs and bryophytes in unfertilized stands, while the effects were smaller after fertilization. Hence, warming led to significant changes in species composition and an increase in species richness in the open canopy nutrient limited forest. After another 9 years of warming and increasing tree canopy closure, most of the initial effects had ceased, indicating an interaction between forest succession and warming. The only remaining effect of warming was on the abundance of bryophytes, which contrary to the initial phase was strongly favored by warming. We propose that the suggested moderating effects of the tree layer are specific to plant life-form and conclude that the successional phase of the forest may have a considerable impact on the effects of climate change on forest floor vegetation and its feedback effects on the carbon and nitrogen cycles, and thus on the climate.

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“…This is surprising, since this species has often been considered an indicator of increased nitrogen availability in boreal forest (e.g., Strengbom and Nordin 2012). This is surprising, since this species has often been considered an indicator of increased nitrogen availability in boreal forest (e.g., Strengbom and Nordin 2012).…”

Section: Changes In Species Compositionmentioning

confidence: 99%

Peatland plant communities under global change: negative feedback loops counteract shifts in species composition

Hedwall

Brunet

Rydin

2017

Ecology

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Mires (bogs and fens) are nutrient-limited peatland ecosystems, the vegetation of which is especially sensitive to nitrogen deposition and climate change. The role of mires in the global carbon cycle, and the delivery of different ecosystem services can be considerably altered by changes in the vegetation, which has a strong impact on peat-formation and hydrology. Mire ecosystems are commonly open with limited canopy cover but both nitrogen deposition and increased temperatures may increase the woody vegetation component. It has been predicted that such an increase in tree cover and the associated effects on light and water regimes would cause a positive feed-back loop with respect to the ground vegetation. None of these effects, however, have so far been confirmed in large-scale spatiotemporal studies. Here we analyzed data pertaining to mire vegetation from the Swedish National Forest Inventory collected from permanent sample plots over a period of 20 yr along a latitudinal gradient covering 14°. We hypothesized that the changes would be larger in the southern parts as a result of higher nitrogen deposition and warmer climate. Our results showed an increase in woody vegetation with increases in most ericaceous dwarf-shrubs and in the basal area of trees. These changes were, in contrast to our expectations, evenly distributed over most of the latitudinal gradient. While nitrogen deposition is elevated in the south, the increase in temperatures during recent decades has been larger in the north. Hence, we suggest that different processes in the north and south have produced similar vegetation changes along the latitudinal gradient. There was, however, a sharp increase in compositional change at high deposition, indicating a threshold effect in the response. Instead of a positive feed-back loop caused by the tree layer, an increase in canopy cover reduced the changes in composition of the ground vegetation, whereas a decrease in canopy cover lead to larger changes. Increased natural disturbances of the tree layer due to, for example, pathogens or climate is a predicted outcome of climate change. Hence, these results may have important implications for predictions of long-term effects of increased temperature on peatland vegetation.

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Physical disturbance determines effects from nitrogen addition on ground vegetation in boreal coniferous forests

Cited by 28 publications

References 49 publications

Residual Long-Term Effects of Forest Fertilization on Tree Growth and Nitrogen Turnover in Boreal Forest

Residual Long-Term Effects of Forest Fertilization on Tree Growth and Nitrogen Turnover in Boreal Forest

Interactions with successional stage and nutrient status determines the life‐form‐specific effects of increased soil temperature on boreal forest floor vegetation

Peatland plant communities under global change: negative feedback loops counteract shifts in species composition

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