Twentieth-century land management has altered the structure and composition of mixed-conifer forests and decreased their resilience to fire, drought, and insects in many parts of the Interior West. ...These forests occur across a wide range of environmental settings and historical disturbance regimes, so their response to land management is likely to vary across landscapes and among ecoregions. However, this variation has not been well characterized and hampers the development of appropriate management and restoration plans. We identified mixed-conifer types in central Oregon based on historical structure and composition, and successional trajectories following recent changes in land use, and evaluated how these types were distributed across environmental gradients. We used field data from 171 sites sampled across a range of environmental settings in two subregions: the eastern Cascades and the Ochoco Mountains.
We identified four forest types in the eastern Cascades and four analogous types with lower densities in the Ochoco Mountains. All types historically contained ponderosa pine, but differed in the historical and modern proportions of shade-tolerant vs. shade-intolerant tree species. The Persistent Ponderosa Pine and Recent Douglas-fir types occupied relatively hot-dry environments compared to Recent Grand Fir and Persistent Shade Tolerant sites, which occupied warm-moist and cold-wet environments, respectively. Twentieth-century selective harvesting halved the density of large trees, with some variation among forest types. In contrast, the density of small trees doubled or tripled early in the 20th century, probably due to land-use change and a relatively cool, wet climate. Contrary to the common perception that dry ponderosa pine forests are the most highly departed from historical conditions, we found a greater departure in the modern composition of small trees in warm-moist environments than in either hot-dry or cold-wet environments. Furthermore, shade-tolerant trees began infilling earlier in cold-wet than in hot-dry environments and also in topographically shaded sites in the Ochoco Mountains. Our new classification could be used to prioritize management that seeks to restore structure and composition or create resilience in mixed-conifer forests of the region.
The invasive shrub Scotch broom (Cytisus scoparius (L.) Link) is a pervasive threat to regenerating Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) stands in the Pacific Northwest, ...USA. Field observations indicate that the susceptibility of areas to Scotch broom invasion and dominance can vary by site. We selected 10 sites throughout the western Pacific Northwest that spanned a gradient of soil textures and other factors to test the site-specific susceptibility of Douglas-fir to overtopping by Scotch broom. We expected to find that the ability of Scotch broom to dominate a site was mediated by site-level factors, particularly those influencing soil water--the most limiting factor to growth in the region. We found Scotch broom and Douglas-fir were inversely affected by site-level factors. In general, Douglas-fir absolute height growth rates were more competitive with those of Scotch broom on fine-textured soils than on more coarsely textured soils. We also found Douglas-fir to have a more dramatic response to increasing down woody material than Scotch broom. Scotch broom height growth approached an asymptote at 3 m. Sites with fast-growing Douglas-fir were able to surpass this height 6-7 years after planting and appear likely to avoid suppression by Scotch broom.
Eukaryotic algae have recently emerged as hosts for metabolic engineering efforts to generate heterologous isoprenoids. Isoprenoid metabolic architectures, flux, subcellular localization, and ...transport dynamics have not yet been fully elucidated in algal hosts. In this study, we investigated the accessibility of different isoprenoid precursor pools for C.sub.15 sesquiterpenoid generation in the cytoplasm and chloroplast of Chlamydomonas reinhardtii using the Abies grandis bisabolene synthase (AgBS) as a reporter. The abundance of the C.sub.15 sesquiterpene precursor farnesyl pyrophosphate (FPP) was not increased in the cytosol by co-expression and fusion of AgBS with different FPP synthases (FPPSs), indicating limited C.sub.5 precursor availability in the cytoplasm. However, FPP was shown to be available in the plastid stroma, where bisabolene titers could be improved several-fold by FPPSs. Sesquiterpene production was greatest when AgBS-FPPS fusions were directed to the plastid and could further be improved by increasing the gene dosage. During scale-up cultivation with different carbon sources and light regimes, specific sesquiterpene productivities from the plastid were highest with CO.sub.2 as the only carbon source and light:dark illumination cycles. Potential prenyl unit transporters are proposed based on bioinformatic analyses, which may be in part responsible for our observations. Our findings indicate that the algal chloroplast can be harnessed in addition to the cytosol to exploit the full potential of algae as green cell factories for non-native sesquiterpenoid generation. Identification of a prenyl transporter may be leveraged for further extending this capacity.
European forests are becoming increasingly threatened by climate change and more frequent droughts. The likely responses of species to climate change will vary, affecting their competitiveness, their ...existence, and consequently, forest management decisions and measures. We determined the influence of climate on the radial growth of European beech and silver fir along the Carpathians to find similarities between the two species and the main differences. Along the Carpathian Mountains, seven sites with mature fir–beech stands above 800 m above sea level were selected and analyzed. Our study confirmed different responses depending on species and location. A more pronounced response of tree growth to climate was observed on the eastern side of the Carpathians, while it was less expressed or even absent on the southern sites. Both beech and fir show better radial growth with higher precipitation in July and slower growth with higher average and maximum temperatures in June of the current year. Fir demonstrates a positive correlation between radial growth and temperature in winter, while beech demonstrates a negative correlation between radial growth and temperature in summer. In the 1951–1960 decade, the average tree ring widths in fir and beech were largest at the southern sites compared to the other sites, but since 2011, the southern sites have had the lowest increase while northern sites have had the largest. Both species respond differently to climate and are likely to follow different competitive paths in the future.
•Post-fire regeneration abundance and diversity increased with pre-fire stand age.•Regeneration rates decreased with farther distances to a live seed source.•Post-fire regeneration was abundant up to ...400 m from a live seed source.•Establishment rates were bolstered by cooler/wetter macro- and micro-site conditions.•Structural complexity in late-seral forests promote forest resilience to severe fire.
Tree regeneration is a critical mechanism of forest resilience to stand-replacing wildfire (i.e., where fire results in >90 % tree mortality), and post-fire regeneration is a concern worldwide as the climate becomes warmer. Although post-fire tree regeneration has been relatively well-studied in fire-prone forests across western North America, it is less understood in fire regimes characterized by large patches of stand-replacing fire at long intervals, such as the nominally infrequent, high-severity fire regimes of the western Cascades of Washington and northern Oregon, USA (northwestern Cascadia) where some of world’s highest-biomass forests reside. Recent wildfire activity (2015–2020) in northwestern Cascadia provides a unique opportunity to build understanding of the mechanisms underpinning forest resilience to fire, with implications for forest management and the myriad socio-ecological values associated with these landscapes. Here, we asked: how is post-fire conifer regeneration across northwestern Cascadia affected by pre-fire stand age, burn-patch size, and topo-climatic conditions? We established 39 1-ha long-term monitoring plots across four recent wildfires in northwestern Cascadia to measure post-fire conifer abundance and species composition. We used generalized linear models to test how rates of conifer regeneration (seedlings ha−1 yr−1 of all heights) and establishment (seedlings ha−1 yr−1 with heights >10 cm) respond to differences in pre-fire stand age/seral stage (young, mid-seral, late-seral), distance to the nearest live seed source, and post-fire topo-climate setting. In general, initial post-fire seedling densities suggest tree regeneration is abundant following stand-replacing fire in most areas across the region. For example, at 3–5 years post-fire, established seedlings were present in 100 % of plots, and regeneration and establishment levels exceeded state forest practices minimum density thresholds (470 seedlings ha−1) in 82.1 % and 64.1 % of plots, respectively. Post-fire conifer regeneration and tree species richness were greater when pre-fire stand age was older, and was more dominated by shade tolerant species than when pre-fire stand age was younger. Regeneration decreased with farther distances to the nearest live seed source, though seedlings were still moderately abundant at distances as far as 400 m from edges of high-severity patches. Conifer establishment was greater in areas characterized by cooler and wetter macrosite (e.g., greater post-fire precipitation) and microsite (e.g., greater bryophyte ground cover) conditions. By providing information on the drivers and conditions in which land managers can expect natural regeneration to occur or not, our findings are directly relevant to pre- and post-fire forest management objectives under future climate and increased fire activity in systems structured in part by infrequent and severe wildfires.
•High surface area, magnetized Douglas fir biochar removed aqueous Pb2+ and Cd2+.•Capacities for lead with raw biochar were ∼40 and for magnetized were ∼16mg/g.•Lead and cadmium are widely ...distributed over the biochar surfaces.•Douglas fir biochars had far faster uptake kinetics (2min) than other biochars.
Magnetic biochar (MBC) was produced by magnetite (Fe3O4) precipitation onto Douglas fir biochar (NBC) that had been generated by wet fast pyrolysis. Treating an aqueous Fe3+/Fe2+ solution with NaOH induced Fe3O4 to nucleate and deposit on NBC. The NBC and the resulting MBC were used to remove Pb2+ and Cd2+ from water. Both biochars were characterized by SEM, EDX, TEM, PZC, XRD, elemental analysis, and surface area measurements. Batch sorption studies were carried out from pH 2–7 with adsorbate concentrations from 10 to 250mg/L at 25, 35 and 45°C. MBC and NBC suspensions in the contaminated solutions were vortexed for two min. Then MBC was magnetically removed, while NBC required filtration. Remediated solutions were then analyzed using AAS. The amounts of lead and cadmium adsorbed onto both NBC and MBC were lower at low pH values and increased with increasing pH. The Langmuir and Freundlich adsorption isotherm models were applied to describe equilibrium data. The maximum Langmuir adsorption capacities at pH 5 and 45°C for Pb2+ and Cd2+ uptake were ∼40 and ∼16mg/g for NBC and ∼27 and ∼11mg/g for MBC, respectively. NBC and MBC recycling was carried out after metal ion extraction with 0.1M HCl and water. Adsorption kinetics of NBC and MBC were compared with four other biochars (mixed feed, magnetized mixed feed, pinewood and magnetized switchgrass). Adsorption equilibria of Pb2+ and Cd2+ onto both NBC and MBC were reached within 2min while the other biochars required from 2 to 20h. NBC and MBC have potential as low cost, green adsorbents for rapid lead and cadmium remediation as replacements for more expensive commercial activated carbon.
Abies nephrolepis is a climate-vulnerable species that inhabits high mountains in the Baekdu–Daegan range and is distributed along the southern limit line in South Korea, making it suitable for ...climate change research. This study aimed to observe spatial distribution changes according to scenarios using species distribution models for Abies nephrolepis, analyze the relationship between various environmental factors and Abies nephrolepis density, and contribute to the future conservation and management of subalpine coniferous forests. We conducted a field survey to identify the growth environment of Abies nephrolepis and observed potentially suitable habitats for Abies nephrolepis based on location information obtained through the survey. We also analyzed the relationship between the density of Abies nephrolepis and various environmental factors using multiple linear regression models. Based on the field survey results, most Abies nephrolepis natural habitats in South Korea showed an unstable form. Vulnerability analysis examining the influence of climate change showed that most of these habitats would be affected. We found that various biological factors were significantly related to the density of Abies nephrolepis (diameter at breast height, DBH ≥ 6 cm) and young tree density (stems/ha). We confirmed that species diversity and rock exposure variables had a relatively high impact. Clarifying the relationship between the density of Abies nephrolepis and various environmental factors can provide new insights for setting future restoration directions.
Background and aims Competitive vegetation in forest stands influence seedling growth by changing soil nutrient availability. However, studies on the effects of different weed control methods on ...seedling growth of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) are rare. Methods We applied three weed control methods, comprising artificial sickle weeding (ASW), woody disc weeding (WDW), and nonwoven cloth weeding (nWCW), to explore their effect on growth of Chinese fir seedlings in a plantation in Jiangxi Province, China. Results The weed control methods affected the shoot height and root-collar diameter of the seedlings. The contents of sugar, glucose, triglycerides, total cholesterol, and free fatty acids in newly developed leaves were increased after ASW and nWCW treatment, and were consistent with the expression of genes associated with glucokinase, sucrose phosphate synthase, and sucrose synthase. Weeding method influenced soil properties, including pH, moisture, total nitrogen (TN), ammonium-N, nitrate-N, total phosphorus, available phosphorus, and dissolved organic carbon contents. Moisture content was the main factor that influenced the soil bacterial community and leaf nutrition. High-throughput sequencing of the bacterial 16 S rRNA gene revealed that the weeding methods affected bacterial community structure. Specifically, compared with ASW and nWCW, WDW contributed to lower soil bacterial diversity, simpler bacterial interaction, and increase in pathogenic bacteria potential. Conclusions The weeding methods differ in influence on soil bacterial community structure, soil properties, and plant growth, which are potentially useful to improve the growth of Chinese fir seedlings. ASW and nWCW strategies were recommended to be applied in the practice of weed control on seedling growth of Chinese fir.
Aims
The aim of this study was to investigate the mechanisms by which nitrogen (N) and phosphorous (P) additions affect plant C:N:P stoichiometry via changes in AMF communities in a Chinese fir ...plantation.
Methods
Experimental plots in a 10-year-old Chinese fir plantation were treated with N addition (LN, 30 kg•ha
−1
•yr
−1
, and HN, 60 kg•ha
−1
•yr
−1
) and P addition (LP, 20 mg•kg
−1
, and HP, 40 mg•kg
−1
) for 2 years starting from 2017. Soil properties, leaf C:N:P stoichiometry, and changes in AMF community composition and diversity were measured.
Results
N or P addition increased soil N availability, decreased P availability, and increased N:P in the leaves and soil. Changes in soil pH induced by N and P additions affected the colonization rate and spore density of AMF. AMF colonization rate was increased by N or P addition, and AMF diversity was increased by LN addition. N and P additions altered AMF species composition, and the dominant genus of the AMF in the soil was
Glomus
in all treatments
.
The interaction of N and P treatments had no significant effect on AMF diversity. AMF colonization rate and diversity, rather than its composition, affected leaf C:N:P stoichiometry.
Conclusion
N and P additions affected colonization rate and diversity of AMF though changes in soil pH, which drove leaf C:N:P stoichiometry, and potentially affected forest productivity via the fungi-soil-plant system.
PDF
