Olive tree pruning, as one of the most abundant lignocellulosic residues in Mediterranean countries, has been evaluated as a source of sugars for fuel and chemicals production. A mild acid ...pretreatment has been combined with a fungal pretreatment using either two endophytes (Ulocladium sp. and Hormonema sp.) or a saprophyte (Trametes sp. I-62). The use of endophytes is based on the important role that some of them play during the initial stages of wood decomposition. Without acid treatment, fungal pretreatment with Ulocladium sp. provided a nonsignificant enhancement of 4.6% in glucose digestibility, compared to control. When a mild acid hydrolysis was carried out after fungal pretreatments, significant increases in glucose digestibility from 4.9% to 12.0% (compared to control without fungi) were observed for all fungal pretreatments, with maximum values yielded by Hormonema sp. However, despite the observed digestibility boost, the total sugar yields (taking into account solid yield) were not significantly increased by the pretreatments. Nevertheless, based on these preliminary improvements in digestibility, this work proves the potential of endophytic fungi to boost the production of sugar from olive tree pruning, which would add an extra value to the bioeconomy of olive crops.
•Historical shifts in forest dominance between temperate and sub-Mediterranean species.•Recent Fagus sylvatica growth decline unprecedented in the last two hundred years.•Higher climate sensitivity ...of temperate F. sylvatica than oak species.•Oak species better suited to current environmental conditions.
Old-growth forests, particularly those located at the interface between different bioregions, are unevaluable sources of long-term vegetation dynamics and historical stand response to natural and anthropogenic disturbances. Although old-growth forests are scarce, the information gathered studying them may assist forest ecosystem restoration and management under forthcoming climate and land-use changes.
We analysed how complementary dynamics of a mixed old-growth forest composed by temperate (Fagus sylvatica, Quercus petraea) and submediterranean (Quercus pyrenaica) tree species were driven in response to global changes in the last two centuries. The old-growth forest, named El Hayedo de Montejo, is located at the interface between the Mediterranean and temperate bioregions in the centre of the Iberian Peninsula. The populations of temperate species growing in El Hayedo de Montejo (F. sylvatica and Q. petraea) are at the dry and warm edges of their natural distribution area in Europe, whereas the submediterranean species Q. pyrenaica is at the core of the distribution range. In order to analyse the long-term dynamics, we developed basal area increment and disturbance chronologies for each of the tree species under study. Furthermore, we assessed the climate influence on tree growth during the most recent decades.
Our results reveal historical shifts in forest dominance (as reflected by growth) induced by changes in climate and forest management between temperate and sub-Mediterranean species. This was particularly noticeable for F. sylvatica and Q. pyrenaica the least and most drought-tolerant species, respectively. A reduction in growth of F. sylvatica unprecedented in the context of the last two hundred years was observed during the last decades concurrent with forest densification and marked changes in climate. Conversely, both oak species seem to be better suited to current environmental conditions as expressed by increasing growth rates.
Question: Is native species occurrence related to soil nutrients in highly invaded Californian annual grasslands? What is the best method to analyze this relationship, given that native species occur ...in very low numbers and are absent from many locations? Location: California, USA. Methods: We investigated the effects of soil characteristics and livestock grazing on native plant occurrence at 40 plots from six sites during the period 2003-2005. Low absolute cover (< 5.8%) of native species resulted in strongly skewed, zero-inflated data sets. To overcome problems in the analysis created by non-normality and correlations within plots, we used GLMs and GLMMs, either with a Poisson or a negative binomial distribution, to analyse native species richness and Nassella pulchra cover. Results: N. pulchra cover was strongly associated with low phosphorus in sandy soils, whereas native species richness was highest in soils with low available nitrogen (high C:N). Conclusion: Under current conditions, phosphorus seems to be a critical factor influencing abundance of N. pulchra. Low fertility soils may provide refugia for native species in highly invaded California grasslands as they may be below a threshold required for non-native annuals to completely dominate. By using non-normal distributions in linear models with random components, we report well fitted models with more accurately tested significant covariates.
Ecosystem productivity estimated with a model calibrated with eddy-covariance data was related to tree-ring growth of two different boreal conifers along a latitudinal gradient. The relationship ...between ecosystem productivity and growth changed with species and site. Greater photosynthesis in spring and summer increased annual anomalies of radial growth in both species, and the response of growth to productivity was earlier in warmer southern stands particularly for pine. Radial growth of jack pine increased in the long-term with higher productivity, whereas this relationship was more reduced in black spruce. This could express species-specific differences in carbon allocation strategies but likely it is a consequence of the limiting marginal soils where spruce is found in the south. Only tree-rings of jack pine at some sites showed certain potential as direct proxies for ecosystem productivity at the low and high-frequency responses.
Black pine (
Pinus nigra Arn.) is a pan-Mediterranean species of high ecological importance and one of the most important timber species in the area. We compare several site dependent height–age ...models for the species in three regions along its natural distribution area in Spain. The best model was a generalized algebraic difference approach (GADA) polymorphic model with variable asymptotes (Cieszewski, C.J., Bailey, R.L., 2000. Generalized algebraic difference approach: theory based derivation of dynamic site equations with polymorphism and variable asymptotes. For. Sci. 46, 116–126). There was no significant increase in error when a reduced model common to the three regions was tested instead of a full model with region-specific parameters. To study possible biases of the proposed model along the trees’ lifespan we carried out a LOWESS analysis of residuals in time. We detected deviations in the model residuals, and a patent growth reduction in the 1960s and 1970s, which might be related to climate and/or changing stand characteristics. Departures from estimated mean past growth should be monitored in the future to adapt models to a changing environment.
To achieve sustainability of a forest system it is necessary to apply appropriate silvicultural management, including preservation measures. The characterization of the status and development of the ...harvested stands, as well as the timber potential of the unmanaged ones, is necessary to achieve a sustainable forest management. In southern Patagonia,
Nothofagus forests are the basis for the sawmill industry. Since European colonization, different silvicultural management regimes have been applied in primary forests. Forestry policies and available sawmill technologies have also been involved. There is little knowledge about the consequences of the different silvicultural systems implemented, as well as about the regeneration status of the harvested stands and future possibilities of the managed forests. The objective of this work is to analyse the logged, affected from harvesting and current forest structures, as well as the regeneration development during the last 40 years and the consequences derived to forests of southern Patagonia.
The harvesting was applied irregularly between the studied decades (30 ± 15% of the original basal area was removed) creating an irregular forest structure. Large quantities of sawn logs were abandoned in the forest floor and a high percentage of the remaining forest structure was damaged during the harvesting. Negligent management and wind throw produced a huge amount of wasted timber, resulting in a scarce standing log volume of very low quality. Nevertheless, regeneration was successfully installed (222 ± 185
thousands/ha) within the harvested stands. No differences in the harvesting intensity were found with the different theoretical silvicultural methods applied through the years (selective cuts, clear-cuts or shelterwood cuts). As a result, the forests present a low current and future economical potential. Hence, the status of the secondary forest must be improved and regulated in order to achieve sustainability. Otherwise, the local forest industry will suffer from negative consequences, and this valuable resource will not be profitable in the future.
Plant-plant interactions influence how forests cope with climate and contribute to modulate species response to future climate scenarios. We analysed the functional relationships between growth, ...climate and competition for Pinus sylvestris, Quercus pyrenaica and Quercus faginea to investigate how stand competition modifies forest sensitivity to climate and simulated how annual growth rates of these species with different drought tolerance would change throughout the 21st century. Dendroecological data from stands subjected to thinning were modelled using a novel multiplicative nonlinear approach to overcome biases related to the general assumption of a linear relationship between covariates and to better mimic the biological relationships involved. Growth always decreased exponentially with increasing competition, which explained more growth variability than climate in Q. faginea and P. sylvestris. The effect of precipitation was asymptotic in all cases, while the relationship between growth and temperature reached an optimum after which growth declined with warmer temperatures. Our growth projections indicate that the less drought-tolerant P. sylvestris would be more negatively affected by climate change than the studied sub-Mediterranean oaks. Q. faginea and P. sylvestris mean growth would decrease under all the climate change scenarios assessed. However, P. sylvestris growth would decline regardless of the competition level, whereas this decrease would be offset by reduced competition in Q. faginea. Conversely, Q. pyrenaica growth would remain similar to current rates, except for the warmest scenario. Our models shed light on the nature of the species-specific interaction between climate and competition and yield important implications for management. Assuming that individual growth is directly related to tree performance, trees under low competition would better withstand the warmer conditions predicted under climate change scenarios but in a variable manner depending on the species. Thinning following an exponential rule may be desirable to ensure long-term conservation of high-density Mediterranean woodlands, particularly in drought-limited sites.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
• In this study we analyzed heterogeneity in nutrient cycling induced by trees in Mediterranean annual grasslands, comparing years of higher and lower than average precipitation and analyzing the ...effects of two different solar radiation scenarios.
• Organic matter and consequently upper soil N, K, Ca and Mg were significantly greater in those locations receiving the highest levels of solar radiation, and as expected from many other studies in the literature, there was an increase in all macronutrients (except P) as well as pH below the canopy.
• Contrary to what was expected, plant nutrient concentrations did not directly reflect those found in the soil, with the exception of K. The studied grassland responded to increased nutrient availability by enhancing growth and changing botanical composition rather than by increasing plant nutrient concentrations. Hence, the total amount of accumulated nutrients in the ecosystem was larger below the tree than outside it, although this is mainly a consequence of plant growth enhancement. The levels of Ca, Mg, and Na in plants decreased during the driest year, and the N content was mostly determined by the composition of the grass.
• Temporal nutrient variability, particularly within-years, explained most of the variability in plant nutrient concentration, while spatial variability induced by trees was determined to be of secondary importance. These results are significant for ecosystem nutrient modelling.
Pruning allows knot-free timber to be obtained, thereby increasing the value of the highest-value wood products. However, the effect of pruning on growth is under discussion, and knowledge about the ...tree response to the simultaneous development of thinning and pruning is scarce. The objective of this study was to analyze the effect of the interaction of thinning and pruning on tree and stand level and the annual radial growth of two pine species native to Mediterranean mountains. We used long-term data of three trials installed in pine stands where several combinations of pruning and thinning were developed. Five inventories were carried out for each trial, and the mean dasometric features of the different treatments were compared using linear mixed models including a competition index. In addition, we collected cores from ten trees per plot in order to evaluate the annual response of trees to the thinning and pruning. We analyzed the annual radial growth using a semiparametric approach through a smooth penalized spline including rainfall and temperature covariates. Pruning did not show any effect on growth. However, larger diameter and increased annual radial growth were found in thinned plots, both with and without pruning, as compared to unthinned plots. Also, we found significant effects of climate on annual radial growth. We recommend the application of thinning and pruning in stands of Mediterranean mountains in order to get knot-free timber since growth reduction was not found in thinned stands.
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