94 research outputs found
Reconstructing terrestrial nutrient cycling using stable nitrogen isotopes in wood
Although recent anthropogenic effects on the global nitrogen (N) cycle have been significant, the consequences of increased anthropogenic N on terrestrial ecosystems are unclear. Studies of the impact of increased reactive N on forest ecosystemsâimpacts on hydrologic and gaseous loss pathways, retention capacity, and even net primary productivityâ have been particularly limited by a lack of long-term baseline biogeochemical data. Stable nitrogen isotope analysis (ratio of Âčâ”N to ÂčâŽN, termed ÎŽÂčâ”N) of wood chronologies offers the potential to address changes in ecosystem N cycling on millennial timescales and across broad geographic regions. Currently, nearly 50 studies have been published utilizing wood ÎŽÂčâ”N records; however, there are significant differences in study design and data interpretation. Here, we identify four categories of wood ÎŽÂčâ”N studies, summarize the common themes and primary findings of each category, identify gaps in the spatial and temporal scope of current wood ÎŽÂčâ”N chronologies, and synthesize methodological frameworks for future research by presenting eight suggestions for common methodological approaches and enhanced integration across studies. Wood ÎŽÂčâ”N records have the potential to provide valuable information for interpreting modern biogeochemical cycling. This review serves to advance the utility of this technique for long-term biogeochemical reconstructions
Effects of soil warming and nitrogen foliar applications on bud burst of black spruce
Key message: In mature black spruce, bud burst process is anticipated by soil warming, while delayed by foliar applications of nitrogen; however, the effects depend on growth conditions at the site.
Abstract: The observation of phenological events can be used as biological indicator of environmental changes, especially from the perspective of climate change. In boreal forests, the onset of the bud burst is a key factor in the length of the growing season. With current climate change, the major factors limiting the growth of boreal trees (i.e., temperature and nitrogen availability) are changing and studies on mature trees are limited. The aim of this study was to investigate the effects of soil warming and increased nitrogen (N) deposition on bud burst of mature black spruce [Picea mariana (Mill.) BSP]. From 2008 onwards, an experimental manipulation of these environmental growth conditions was conducted in two stands (BER and SIM) at different altitudes in the boreal forest of Quebec, Canada. An increase in soil temperature (H treatment) and a canopy application of artificial rain enriched with nitrogen (N treatment) were performed. Observations of bud phenology were made during MayâJuly 2012 and 2013. In BER, H treatment caused an anticipation (estimated as 1â3 days); while N treatment, a delay (estimated as 1â2 days but only in 2012) in bud burst. No treatments effect was significant in SIM. It has been demonstrated that soil temperature and N availability can play an important role in affecting bud burst in black spruce but the effects of these environmental factors on growth are closely linked with site conditions
Diversity buffers winegrowing regions from climate change losses
Agrobiodiversityâthe variation within agricultural plants, animals, and practicesâis often suggested as a way to mitigate the negative impacts of climate change on crops [S. A. Wood et al., Trends Ecol. Evol. 30, 531â539 (2015)]. Recently, increasing research and attention has focused on exploiting the intraspecific genetic variation within a crop [Hajjar et al., Agric. Ecosyst. Environ. 123, 261â270 (2008)], despite few relevant tests of how this diversity modifies agricultural forecasts. Here, we quantify how intraspecific diversity, via cultivars, changes global projections of growing areas. We focus on a crop that spans diverse climates, has the necessary records, and is clearly impacted by climate change: winegrapes (predominantly Vitis vinifera subspecies vinifera). We draw on long-term French records to extrapolate globally for 11 cultivars (varieties) with high diversity in a key trait for climate change adaptationâphenology. We compared scenarios where growers shift to more climatically suitable cultivars as the climate warms or do not change cultivars. We find that cultivar diversity more than halved projected losses of current winegrowing areas under a 2 âŠC warming scenario, decreasing areas lost from 56 to 24%. These benefits are more muted at higher warming scenarios, reducing areas lost by a third at 4 âŠC (85% versus 58%). Our results support the potential of in situ shifting of cultivars to adapt agriculture to climate changeâincluding in major winegrowing regionsâas long as efforts to avoid higher warming scenarios are successful
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