Multi-model comparison on the effects of climate change on tree species in the eastern U.S.: results from an enhanced niche model and process-based ecosystem and landscape models

Context

Species distribution models (SDM) establish statistical relationships between the current distribution of species and key attributes whereas process-based models simulate ecosystem and tree species dynamics based on representations of physical and biological processes. TreeAtlas, which uses DISTRIB SDM, and Linkages and LANDIS PRO, process-based ecosystem and landscape models, respectively, were used concurrently on four regional climate change assessments in the eastern Unites States.

Objectives

We compared predictions for 30 species from TreeAtlas, Linkages, and LANDIS PRO, using two climate change scenarios on four regions, to derive a more robust assessment of species change in response to climate change.

Methods

We calculated the ratio of future importance or biomass to current for each species, then compared agreement among models by species, region, and climate scenario using change classes, an ordinal agreement score, spearman rank correlations, and model averaged change ratios.

Results

Comparisons indicated high agreement for many species, especially northern species modeled to lose habitat. TreeAtlas and Linkages agreed the most but each also agreed with many species outputs from LANDIS PRO, particularly when succession within LANDIS PRO was simulated to 2300. A geographic analysis showed that a simple difference (in latitude degrees) of the weighted mean center of a species distribution versus the geographic center of the region of interest provides an initial estimate for the species’ potential to gain, lose, or remain stable under climate change.

Conclusions

This analysis of multiple models provides a useful approach to compare among disparate models and a more consistent interpretation of the future for use in vulnerability assessments and adaptation planning.

     

Organic C and N stabilization in a forest soil: Evidence from sequential density fractionation

In mineral soil, organic matter (OM) accumulates mainly on and around surfaces of silt- and clay-size particles. When fractionated according to particle density, C and N concentration (per g fraction) and C/N of these soil organo-mineral particles decrease with increasing particle density across soils of widely divergent texture, mineralogy, location, and management. The variation in particle density is explained potentially by two factors: (1) a decrease in the mass ratio of organic to mineral phase of these particles, and (2) variations in density of the mineral phase. The first explanation implies that the thickness of the organic accumulations decreases with increasing particle density. The decrease in C/N can be explained at least partially by especially stable sorption of nitrogenous N-containing compounds (amine, amide, and pyrrole) directly to mineral surfaces, a phenomenon well documented both empirically and theoretically. These peptidic compounds, along with ligand-exchanged carboxylic compounds, could then form a stable inner organic layer onto which other organics could sorb more readily than onto the unconditioned mineral surfaces (“onion” layering model).To explore mechanisms underlying this trend in C concentration and C/N with particle density, we sequentially density fractionated an Oregon andic soil at 1.65, 1.85, 2.00, 2.28, and 2.55 g cm⁻³ and analyzed the six fractions for measures of organic matter and mineral phase properties.All measures of OM composition showed either: (1) a monotonic change with density, or (2) a monotonic change across the lightest fractions, then little change over the heaviest fractions. Total C, N, and lignin phenol concentration all decreased monotonically with increasing density, and ¹⁴C mean residence time (MRT) increased with particle density from ca. 150 years to >980 years in the four organo-mineral fractions. In contrast, C/N, ¹³C and ¹⁵N concentration all showed the second pattern. All these data are consistent with a general pattern of an increase in extent of microbial processing with increasing organo-mineral particle density, and also with an “onion” layering model.X-ray diffraction before and after separation of magnetic materials showed that the sequential density fractionation (SDF) isolated pools of differing mineralogy, with layer-silicate clays dominating in two of the intermediate fractions and primary minerals in the heaviest two fractions. There was no indication that these differences in mineralogy controlled the differences in density of the organo-mineral particles in this soil. Thus, our data are consistent with the hypothesis that variation in particle density reflects variation in thickness of the organic accumulations and with an “onion” layering model for organic matter accumulation on mineral surfaces. However, the mineralogy differences among fractions made it difficult to test either the layer-thickness or “onion” layering models with this soil. Although SDF isolated pools of distinct mineralogy and organic-matter composition, more work will be needed to understand mechanisms relating the two factors.     

The role of reforestation in carbon sequestration

New Forests - In the United States (U.S.), the maintenance of forest cover is a legal mandate for federally managed forest lands. More broadly, reforestation following harvesting, recent or...     

Two-year dynamics of foliage labelling in 8-year-old <Emphasis Type="Italic">Pinus pinaster</Emphasis> trees with <Superscript>15</Superscript>N, <Superscript>26</Superscript>Mg and <Superscript>42</Superscript>Ca—simulation of Ca transport in xylem using an upscaling approach

• Introduction   

Atmospheric deposition is an important input of major nutrients into forest ecosystems. The long-term goal of this work was to apply stable isotope methodology to assess atmospheric nutrient deposition in forest systems.     

Relationships Between Barley Hordeins and Malting Quality in a Mutant of cv. Triumph I. Genotype by Environment Interaction of Hordein Content

The genetic (G), environmental (E) and G×E effects on total grain protein and hordein fractions, have been studied in a mutant (TL43) and its parent cultivar, the malting barley Triumph, in various seasons at Dundee (E Scotland) and Lleida (NE Spain). The grain protein content of TL43 was consistently about 2% higher than that of Triumph across environments. Differences in hordein composition were shown by SDS-PAGE electrophoresis. TL-43 had three B-hordein bands not present in Triumph which had a further three bands of the same hordein group not present in TL43. TL43 showed higher B-hordein content than Triumph in Scotland but lower in Spain, whereas the mutant showed consistently higher C- and D-hordein content than Triumph across environments, i.e. there was crossover G×E interaction for B-hordein and non-crossover for C- and D-hordein content. There were also differences in grain ultra-structure between the two lines, as TL43 showed a more dense protein matrix than Triumph, together with thinner pericarp, testa and aleurone layers. It was concluded that the mutation in TL43 had a significant effect on storage protein composition.     

Effects on Grain and Malting Quality of Genes Altering Barley Starch Composition

In this study inbred barley lines carrying waxy and/or high amylose genes were obtained from a cross between Waxy Hector and a breeders» line BE285 (high amylose Glacier×Midas) and assessed for malting quality. Inbred lines were assayed and classified as having none, one or both genes. After malting, waxy lines had a slightly lower hot water extract than normal starch lines. Large effects were demonstrated for both grain nitrogen content and hot water extract in high amylose lines and, particularly, in lines with both genes. Endosperm modification during malting was reduced by both starch mutations. Electron microscopy showed that the phenotype with both genes was characterised by a highly compacted endosperm. During malting, this structure was extremely resistant to modification.     

Effects of variety and fertiliser nitrogen on alcohol yield, grain yield, starch and protein content, and protein composition of winter wheat

The effects of nitrogen (N) fertiliser on grain size and shape, starch and protein concentration, vitreosity, storage protein composition, and alcohol yield of two winter wheat varieties contrasting in endosperm texture were studied in a field trial in Herefordshire, UK in 2004. Averaged across varieties, the alcohol yield was 439 L/tonne for grain with a protein concentration of 11.5 g/100 g. The soft endosperm wheat variety Riband produced on average 7.7 L more alcohol per tonne of grain at a given protein concentration than the hard endosperm variety, Option. At the same time, N fertiliser was shown to have significant effects on alcohol production through its major influence on grain protein concentration. Averaged over both varieties, there was a reduction in alcohol yield of 5.7 L for each 10 kg increase in protein content per tonne of grain. The starch concentration of Riband was 2.9 g/100 g higher than Option at a given grain protein concentration, supporting its higher observed alcohol yields. A low conversion of starch to alcohol in this study (6.30 L/10 kg starch) compared to the theoretical value (6.61 L/10 kg starch) indicated that there is potential for improvement of this character. The traits relating to grain size and shape were principally influenced by genotype, and were not influenced by N fertiliser. Conversely, there were only minor genotypic effects on grain protein concentration and vitreosity. An important finding was that there were no interactions between variety and N treatment for any of the variables considered, indicating that the response of the two varieties to changes in applied N was the same, resulting in consistent differences in starch concentration and alcohol yield between genotypes at different levels of grain protein. An analysis of the composition of the wheat storage proteins by size-exclusion chromatography showed that the gliadins increased on average by 0.56 g per g increase in total grain protein and were quantitatively the major protein fraction, suggesting that selection for low gliadin content may be a desirable means by which to reduce grain protein, and thereby increase alcohol yield in wheat. The relationship between alcohol yield per unit area and applied N rate was described by a quadratic function and the maximum alcohol yield per unit area was ca. 3630 L/ha. Statistical analysis suggested that the economic optimum rate of N applied for grain yield was close to the optimum N rate for maximum alcohol productivity.     

Limit dextrinase in barley cultivars of differing malting quality: activity, inhibitors and limit dextrin profiles

Free and total limit dextrinase (LD) activity was measured in four barley varieties of differing malting quality. LD activity was not detected until 2 days after completion of steeping, at which point, total LD activity was 4–5 fold higher in Static and Chariot than in Optic or Hart. Free LD rose to higher levels in Static and Chariot than in Optic and Hart during malting. In addition, the proportion of free to total LD approached 35% in Static and Chariot whereas it did not reach 15% for Optic and Hart. Lower free LD activity was not reflected in a higher total content of branched dextrins in hot water extracts of the different varieties, but may have contributed to the persistence of branched dextrins of higher degree of polymerisation persisting in the hot water extracts of Hart and Optic.The variation in the proportion of free to total LD activity between varieties was not explained by differences in total LD activity and may be related to the presence of inhibitors of LD. Protein extracts made from the malts following steeping inhibited exogenous partially purified LD activity by >80%. After 3 days germination, Chariot, Optic and Static lost much of their inhibitory activity whereas it was retained in Hart. The increase in free LD activities during malting appeared to mirror the disappearance in inhibitory activity.Inhibitors of LD activity were also present in hot water extracts of Chariot and Hart malts. Chariot lost inhibitory activity after 3 days malting and hot water extracts from Chariot after 4 days malting caused apparent activation of LD. By contrast, hot water extracts from Hart retained inhibitory activity up to 5 days malting. These findings are discussed with reference to the availability and effectiveness of LD during malting.     

Harvest impacts on soil carbon storage in temperate forests

Forest soil carbon (C) storage is a significant component of the global C cycle, and is important for sustaining forest productivity. Although forest management may have substantial impacts on soil C storage, experimental data from forest harvesting studies have not been synthesized recently. To quantify the effects of harvesting on soil C, and to identify sources of variation in soil C responses to harvest, we used meta-analysis to test a database of 432 soil C response ratios drawn from temperate forest harvest studies around the world. Harvesting reduced soil C by an average of 8 ± 3% (95% CI), although numerous sources of variation mediated this significant, overall effect. In particular, we found that C concentrations and C pool sizes responded differently to harvesting, and forest floors were more likely to lose C than mineral soils. Harvesting caused forest floor C storage to decline by a remarkably consistent 30 ± 6%, but losses were significantly smaller in coniferous/mixed stands (−20%) than hardwoods (−36%). Mineral soils showed no significant, overall change in C storage due to harvest, and variation among mineral soils was best explained by soil taxonomy. Alfisols and Spodosols exhibited no significant changes, and Inceptisols and Ultisols lost mineral soil C (−13% and −7%, respectively). However, these C losses were neither permanent nor unavoidable. Controls on variation within orders were not consistent, but included species composition, time, and sampling depth. Temporal patterns and soil C budgets suggest that forest floor C losses probably have a lesser impact on total soil C storage on Alfisols, Inceptisols, and Ultisols than on Spodosols, which store proportionately large amounts of C in forest floors with long C recovery times (50–70 years). Mineral soil C losses on Inceptisols and Ultisols indicate that these orders are vulnerable to significant harvest-induced changes in total soil C storage, but alternative residue management and site preparation techniques, and the passage of time, may mitigate or negate these losses. Key findings of this analysis, including the dependence of forest floor and mineral soil C storage changes on species composition and soil taxonomic order, suggest that further primary research may make it possible to create predictive maps of forest harvesting effects on soil C storage.