The most recent climate change scenarios show that Southern and Eastern Europe will be affected by a significant increase in temperature and drought frequency by the end of the 21st century. Romania ...has already recorded very high temperatures and long periods of drought over recent decades, the most affected regions being the south, west and east of the country. Considering that successful forest management requires suitable species and high-quality reproductive material for reforestation, the aim of this study was to evaluate and compare the growth and drought response of Douglas fir (Pseudotsuga menziessi var. menziesii) and Norway spruce (Picea abies) in two stands installed at the end of the 19th century in western Romania. The growth traits, wood characteristics and drought parameters (resistance, recovery, resilience and relative resilience) of Douglas fir and Norway spruce trees have been analyzed and compared. The climate–growth relationship was determined using growth response functions over the period 1938–2017. Additionally, to simulate the potential impact of climate change on Douglas fir in this region, the RCP4.5 scenario was used over two periods: 2041–2070 and 2071–2100. The results reveal that Douglas fir has an exceptional growth capacity, overcoming the Norway spruce since the early ages in both site conditions. The highest growth performances were seen in the low-productivity site. From analyzing the responses to drought events, considerable differences were found between species. The results highlight the high resistance and relative resilience to extreme droughts of Douglas fir compared to Norway spruce. However, autumn–winter temperatures play an important role in the adaptation of Douglas fir to site conditions in Romania. The use of appropriate provenances of Douglas fir in mixed stands with native broadleaved species may be an option for climatically exposed sites, thus increasing the value of these stands.
The aim of this study was to test the inactivation of viruses on germ carriers of different types of wood using a disinfectant in order to assess the biosafety of wood as a building material in ...animal husbandry. The laboratory disinfectant efficacy tests were based on German testing guidelines and current European standards. Five different types of wood germ carriers, i.e., spruce (
), pine (
), poplar (
sp.), beech (
) and Douglas fir (
), were inoculated with enveloped or non-enveloped viruses and then treated with one of three different disinfectants. The results revealed that intact, fine-sawn timber with a low roughness depth can be effectively inactivated. Peracetic acid proved to be the most effective disinfectant across all tests. Regardless of the pathogen and the type of wood, a concentration of 0.1% of the pure substance at a temperature of 10 °C and an exposure time of one hour can be recommended. At a temperature of -10 °C, a concentration of 0.75% is recommended. The basic chemicals formic acid and glutaraldehyde demonstrated only limited effectiveness overall. The synergistic effects of various wood components on the inactivation of viruses offer potential for further investigation. Disinfectant tests should also be conclusively verified in field trials to ensure that the results from standardised laboratory tests can be transferred to real stable conditions.
For long-lived forest tree species, the understanding of intraspecific variation among populations and their response to water availability can reveal their ability to cope with and adapt to climate ...change. Dissipation of excess excitation energy, mediated by photoprotective isoprenoids, is an important defense mechanism against drought and high light when photosynthesis is hampered. We used 50-year-old Douglas-fir trees of four provenances at two common garden experiments to characterize provenance-specific variation in photosynthesis and photoprotective mechanisms mediated by essential and non-essential isoprenoids in response to soil water availability and solar radiation. All provenances revealed uniform photoprotective responses to high solar radiation, including increased de-epoxidation of photoprotective xanthophyll cycle pigments and enhanced emission of volatile monoterpenes. In contrast, we observed differences between provenances in response to drought, where provenances sustaining higher CO
assimilation rates also revealed increased water-use efficiency, carotenoid-chlorophyll ratios, pools of xanthophyll cycle pigments, β-carotene and stored monoterpenes. Our results demonstrate that local adaptation to contrasting habitats affected chlorophyll-carotenoid ratios, pool sizes of photoprotective xanthophylls, β-carotene, and stored volatile isoprenoids. We conclude that intraspecific variation in isoprenoid-mediated photoprotective mechanisms contributes to the adaptive potential of Douglas-fir provenances to climate change.
► Decreased soil OC stocks after replacement of spruce or pine by Douglas fir or beech. ► Increased soil N stocks after replacement of spruce by Douglas fir/spruce mixture. ► Douglas fir/spruce ...mixtures: particularly effective to sequestrate C and N in soil.
At 18 sites in Bavaria (Germany) with substantial difference in elevation, parent material, climate, and stand age, which encompass most variance of site properties to be found in Central Europe, the effects of a replacement of Norway spruce (Picea abies L. Karst.; 16 sites) or Scots pine (Pinus sylvestris L.; two sites) by Douglas fir (Pseudotsuga menziesii, spp. menziesii) and European beech (Fagus sylvatica) stands on humus form as well as soil organic carbon (OC) and nitrogen (N) concentrations and stocks were investigated by single-site analysis and meta-analysis. At each study site, which comprised adjacent stands of the investigated tree species with similar age, soil samples were taken down to the solid bedrock or 80cm depth at six representative locations of each stand. Replacement of spruce or pine by Douglas fir or beech resulted in a considerable, in most cases significant decrease of the forest floor C/N ratio in the order spruce, pine>mixture of spruce or pine with Douglas fir>Douglas fir>beech. Additionally we noticed a significant decrease of forest floor OC (on average: −38% to −45%) and N stocks (on average: −24% to −29%) in the same order. After replacement of spruce or pine by Douglas fir or beech, we observed insignificant changes of mineral soil OC stocks, but significantly increased (on average: +5% to +8%) mineral soil N stocks. For the total soil, including the forest floor and the mineral soil down to 50cm depth, replacement of spruce with Douglas fir or beech resulted in significantly decreased soil OC stocks (average of all sites: −7% and −11%, respectively). Only two sites with original Scots pine stands located at poorer sites were included in the study: here, the changes of soil C and N stocks as induced by transformation into Douglas fir stands were in the same direction and order of magnitude as for the spruce stands. Replacement of pure spruce by 50%/50%-mixtures of spruce with Douglas fir resulted in statistically insignificant, slight increases of the soil OC stock (average +4%), and significantly increased soil N stocks (average: +7%). The magnitude of replacement effects was dependent on stand age and site properties, such as site N or moisture status. The circumstance that mixtures of Douglas fir with Norway spruce seem to be particularly effective in sequestrating C and N in the soil emphasizes the benefit of mixed stands not only with regard to ecosystem stability, but also with regard to mitigation of atmospheric CO2 enrichment, and minimization of N exports into groundwater aquifers. Our study demonstrates the potential of meta-analysis to (i) identify and quantify small, but significant changes of soil variables with considerable spatial variation, and (ii) reveal site factors which affect these changes.
The importance of structural complexity in forest ecosystems for ecosystem diversity has been widely acknowledged. Tree microhabitat structures as indicators of biodiversity, however, have only ...seldom been the focus of diversity research although their occurrence is highly correlated with the abundance of forest species and ecosystem functions. In this study, microhabitat structures in Douglas-fir (
Pseudotsuga menziesii) forests were defined and their frequency and abundance in natural stands and stands of varying active management histories and stand ages was compared. Indicator microhabitat structures for natural forests were determined and the relationship of the abundance of microhabitat structures with tree diameter of Douglas-fir trees was analysed.
Most of the investigated microhabitats are indeed indicators of natural mature and natural old-growth stands, e.g., broken tree top, bayonet top, crack or scar, bark loss, hollow chamber, stem cavity with decay, bark pocket with and without decay, bark bowl, burl, heavy resinosis, and bark burst. In Douglas-fir trees, resin drops and heavy resinosis were the dominant microhabitats in trees with >20.0–40.0
cm diameter at breast height (dbh), whereas bark structures such as bowls in the bark, bark pockets, and bark pockets with decay were the most abundant microhabitats in Douglas-fir trees >80.0
cm. Both management history (including no treatment in natural stands) and stand age determined the abundance of microhabitats and microhabitat composition of stands in our study. The observed microhabitat variability was highest in stands that had not been harvested or otherwise treated silviculturally in many years (low treatment history) and the natural stands and lowest in the recently managed stands. Recently managed stands had, on average, 115 microhabitats/ha, stands with a low treatment history had 520 microhabitats/ha, and natural mature and natural old-growth stands had 745 microhabitats/ha.
Active management for microhabitats in silviculturally-treated stands is important if the aim is to create structural complexity for a variety of organisms and ecosystem functions in even-aged Douglas-fir stands. Although the management of microhabitats with respect to biodiversity and economic objectives often seem to be in conflict, we suggest silvicultural measures to reduce the current homogenization of forest stands with relatively minor losses of wood production especially if the reduced timber output is compared with the expected longterm social, economic, and ecological benefits. It may, however, take many decades to obtain stands that approximate the criteria for old-growth according to the interim minimum standards for old-growth Douglas-fir forests in their native western Washington and Oregon.
We used the eddy-covariance technique to measure evapotranspiration (
E) and gross primary production (GPP) in a chronosequence of three coastal Douglas-fir (
Pseudotsuga menziesii) stands (7, 19 and ...58 years old in 2007, hereafter referred to as HDF00, HDF88 and DF49, respectively) since 1998. Here, we focus on the controls on canopy conductance (
g
c),
E, GPP and water use efficiency (WUE) and the effect of interannual climate variability at the intermediate-aged stand (DF49) and then analyze the effects of stand age following clearcut harvesting on these characteristics. Daytime dry-foliage Priestley–Taylor
α and
g
c at DF49 were 0.4–0.8 and 2–6
mm
s
−1, respectively, and were linearly correlated (
R
2
=
0.65). Low values of
α and
g
c at DF49 as well at the other two stands suggested stomatal limitation to transpiration. Monthly
E, however, showed strong positive linear correlations to monthly net radiation (
R
2
=
0.94), air temperature (
R
2
=
0.77), and daytime vapour pressure deficit (
R
2
=
0.76). During July–September, monthly
E (mm) was linearly correlated to monthly mean soil water content (
θ, m
3
m
−3) in the 0–60
cm layer (
E
=
453
θ
−
21,
R
2
=
0.69), and GPP was similarly affected. Annual
E and GPP of DF49 for the period 1998–2007 varied from 370 to 430
mm and from 1950 to 2390
g
C
m
−2, respectively. After clearcut harvesting,
E dropped to about 70% of that for DF49 while ecosystem evapotranspiration was fully recovered when stand age was ∼12 years. This contrasted to GPP, which varied hyperbolically with stand age. Monthly GPP showed a strong positive linear relationship with
E irrespective of the stand age. While annual WUE of HDF00 and HDF88 varied with age from 0.5 to 4.1
g
C
m
−2
kg
−1 and from 2.8 to 4.4
g
C
m
−2
kg
−1, respectively, it was quite conservative at ∼5.3
g
C
m
−2
kg
−1 for DF49. N-fertilization had little first-year response on
E and WUE. This study not only provides important results for a more detailed validation of process-based models but also helps in predicting the influences of climate change and forest management on water vapour and CO
2 fluxes in Douglas-fir forests.
Forests play a significant role in the global carbon (C) cycle. Variability in weather, species, stand age, and current and past disturbances are some of the factors that control stand-level C ...dynamics. This study examines the relative roles of stand age and associated structural characteristics and weather variability on the exchange of carbon dioxide between the atmosphere and three different coastal Douglas-fir stands at different stages of development after clearcut harvesting. The eddy covariance technique was used to measure carbon dioxide fluxes and a portable soil chamber system was used to measure soil respiration in the three stands located within 50
km of each other on the east coast of Vancouver Island, British Columbia, Canada. In 2002, the recently clearcut harvested stand (HDF00) was a large C source, the pole/sapling aged stand (HDF88) was a moderate C source, and the rotation-aged stand (DF49) was a moderate C sink (net ecosystem production of −606, −133, and 254
g
C
m
−2
year
−1, respectively). Annual gross ecosystem production and ecosystem respiration also increased with increasing stand age. Differences in stand structural characteristics such as species composition and phenology were important in determining the timing and magnitude of maximum gross ecosystem production and net ecosystem production through the year. Both soil and ecosystem respiration were exponentially related to soil temperature in each stand with total ecosystem respiration differing more among stands than soil respiration. Between 1998 and 2003, annual net ecosystem production ranged from 254 to 424
g
C
m
−2
year
−1 over 6 years for DF49, from −623 to −564
g
C
m
−2
year
−1 over 3 years for HDF00, and from −154 to −133
g
C
m
−2
year
−1 over 2 years for HDF88. Interannual variations in C exchange of the oldest, most structurally stable stand (DF49) were related to variations in spring weather while the rapid growth of understory and pioneer species influenced variations in HDF00. The differences in net ecosystem production among stands (maximum of 1000
g
C
m
−2
year
−1 between the oldest and youngest stands) were an order of magnitude greater than the differences among years within a stand and emphasized the importance of age-related differences in stand structure on C exchange processes.
A study was conducted at two experimental tree plantations in the Pacific Northwest to assess the roles of bacteria and fungi in nitrogen (N) cycling. Soils from red alder (
Alnus rubra) and ...Douglas-fir (
Pseudotsuga menziesii) plots in low- (H.J. Andrews) and high- (Cascade Head) productivity stands were sampled in 2005 and 2006. Fungal:bacterial ratios were determined using phospholipid fatty acid (PLFA) profiles and quantitative (Q)-PCR. Ratios from these two molecular methods were highly correlated and showed that microbial biomass varied significantly between the two experimental sites and to a lesser extent between tree types with fungal:bacterial biomass ratios lower in more N-rich plots.
15N isotope dilution experiments, with ammonium (NH
4
+) and nitrate (NO
3
−), were paired with antibiotics that blocked bacterial (bronopol) and fungal (cycloheximide) protein synthesis. This modified isotope dilution technique was used to determine the relative contribution of bacteria and fungi to net N mineralization and gross rates of ammonification and nitrification. When bacterial protein synthesis was blocked NH
4
+ consumption and nitrification rates decreased in all treatments except for NH
4
+ consumption in the Douglas-fir plots at H.J. Andrews, suggesting that prokaryotic nitrifiers are a major sink for mineral NH
4
+ in forest soils with higher N availability. Cycloheximide consistently increased NH
4
+ consumption, however the trend was not statistically significant. Both antibiotics additions also significantly increased gross ammonification, which may have been due to continued activity of extra- and intracellular enzymes involved in producing NH
4
+ combined with the inhibition of NH
4
+ assimilation into proteins. The implication of this result is that microorganisms are likely a major sink for soil dissolved organic N (DON) in soils.
PDF
