Vulnerability to drought-induced cavitation of riparian cottonwoods in Alberta: a possible factor in the decline of the ecosystem?

Vulnerability of xylem to loss of hydraulic conductivity caused by drought-induced cavitation was determined for three riparian cottonwood species in Lethbridge, Alberta: Populus deltoides Bartr., P. balsamifera L., and P. angustifolia James. These species suffered 50% loss of hydraulic conductivity in one-year-old stem segments when xylem pressure potential fell to -0.7 MPa for P. deltoides and -1.7 MPa for P. balsamifera and P. angustifolia, making them the three most vulnerable tree species reported so far in North America. The possible contribution of drought-induced xylem dysfunction to the decline of riparian ecosystems in dammed rivers is discussed.     

What does it take to get family forest owners to enroll in a forest stewardship-type program?

We estimated the probability of enrollment and factors influencing participation in a forest stewardship-type program, Minnesota's Sustainable Forest Incentives Act, using data from a mail survey of over 1000 randomly-selected Minnesota family forest owners. Of the 15 variables tested, only five were significant predictors of a landowner's interest in enrolling in the program: compensation amount, intention to obtain a forest management plan, opposition to the program's land covenant, prior awareness of the program, and total acres of forest land owned. The estimated median minimum compensation required was approximately $24 per acre per year. One-fourth of the survey respondents were undecided about whether they would participate in the stewardship program, suggesting there may be potential to capture additional interest and participation. Marketing efforts to raise program awareness, increasing annual stewardship payments, and eliminating the land covenant are likely to be effective strategies for increasing program participation.     

Root trenching: a useful tool to estimate autotrophic soil respiration? A case study in an Austrian mountain forest

We conducted a trenching experiment in a mountain forest in order to assess the contribution of the autotrophic respiration to total soil respiration and evaluate trenching as a technique to achieve it. We hypothesised that the trenching experiment would alter both microbial biomass and microbial community structure and that fine roots (less than 2 mm diameter) would be decomposed within one growing season. Soil CO₂ efflux was measured roughly biweekly over two growing seasons. Root presence and morphology parameters, as well as the soil microbial community were measured prior to trenching, 5 and 15 months after trenching. The trenched plots emitted about 20 and 30% less CO₂ than the control plots in the first and second growing season, respectively. Roots died in trenched plots, but root decay was slow. After 5 and 15 months, fine root biomass was decreased by 9% (not statistically different) and 30%, (statistically different) respectively. When we corrected for the additional trenched-plot CO₂ efflux due to fine root decomposition, the autotrophic soil respiration rose to ~26% of the total soil respiration for the first growing season, and to ~44% for the second growing season. Soil microbial biomass and community structure was not altered by the end of the second growing season. We conclude that trenching can give accurate estimates of the autotrophic and heterotrophic components of soil respiration, if methodological side effects are accounted for, only.     

Correction to: RNAi,what is its position in crop protection?

Journal of Pest Science - A correction to this paper has been published: https://doi.org/10.1007/s10340-021-01393-0     

Which factors most influence heartwood distribution and radial growth in plantation teak?

? To investigate the effect of climate on radial growth in young plantation grown teak (Tectona grandis L.), growth ring width was measured in 105 trees and correlated to precipitation and temperature data.

? The social status of trees within the stand was also determined and cross-sectional area (CSA) for the trunk correlated to the proportion of heartwood (HW) within the tree. HW develops asymmetrically in leaning stems of some conifer species, but it is not known if this phenomenon also occurs in broadleaf species. Therefore, we measured HW proportion in leaning and straight stems, along with the number of growth rings in the HW.

? Annual ring width depended strongly on mean monthly temperature during the rainy season and the most significant relationships were found corresponding to the months of June and July. With regard to the weaker relationship between precipitation and radial growth, correlations were highest during the period of bud-break at the beginning of the rainy season.

? The very high stand density affected radial growth, particularly in suppressed trees, which responded little to thinning operations. HW formation was greatest in dominant trees, and was highly regressed with stem CSA.

? Therefore, rapid growth of young stands should be encouraged by reducing stand density. Asymmetric HW formation occurred in both leaning and straight trees, and was significantly greater along the upper sides of leaning stems. It is probable that this eccentric HW formation is linked to mechanical loading on the tree.

     

Leaf angle responds to nitrogen supply in eucalypt seedlings. Is it a photoprotective mechanism?

We examined the adjustment of leaf angle (L theta) and foliar chlorophyll and xanthophyll chemistry in Eucalyptus nitens (Deane and Maiden) Maiden seedlings maintained in various nitrogen (N)-supply treatments over a 6-month period. Adjustment of L theta toward the vertical was greatest under conditions of foliar N deficiency and became incrementally more horizontal with increasing foliar N concentration. Photochemical efficiency (Fv/Fm) and quantum yield were lower in seedlings with low foliar N (low-N seedlings) in winter, but not in autumn. Low-N seedlings generally had low area-based chlorophyll concentrations and high xanthophyll-cycle conversion ratios, particularly during months of low temperature. Under mild temperature conditions, high concentrations of zeaxanthin and antheraxanthin were associated with lower electron transport rates (ETR). Incident light, Fv/Fm, ETR and total chlorophyll concentration were negatively correlated with L theta, with horizontal leaf orientation measured as 0 degrees and vertical leaf orientation as 90 degrees . Xanthophyll conversion ratio was positively correlated with L theta. Adjustments in L theta may play a role in photoprotection of E. nitens seedlings by assisting the leaf to balance its utilization and dissipation of energy.     

Open woodland in Europe in the Mesolithic and in the Middle Ages: Can there be a connection?

In Grazing Ecology and Forest History F.W.M. Vera published his hypothesis that Europe's primeval vegetation was not closed forest but a more open, park-like landscape maintained by the grazing of large herbivores. The palaeoecological evidence has been re-examined a number of times, however, Vera's research and conclusions about more recent periods (ca. 500–1900 a.d.) have so far been neglected. These, nonetheless, are equally significant elements in the testing of the hypothesis, and deserve to be evaluated. It is argued in this paper that historical sources could be used in testing the hypothesis; however, analysis should concentrate on particular areas and periods and derive a synthesis from these. Vera mixes sources from many regions and periods in the same analysis, which therefore does not provide useful information about the hypothesis. Furthermore, Vera's analysis is based on the assumption that early medieval written sources depict a landscape that is in direct connection with the pre-Neolithic open vegetation, although in some early medieval landscapes domestic animals replaced the original large herbivores. He also claims that medieval coppices were formed straight out of this primeval vegetation. However, current landscape archaeological research shows that areas unaffected by human activity were virtually non-existent in the European lowlands by the Early Middle Ages, therefore early medieval Royal Forests and high medieval coppices were not formed out of primeval ‘wilderness.’ Because there is no direct connection between pre-Neolithic and medieval landscapes – although they can be analogous – the historical ecological evidence in Grazing Ecology and Forest History is irrelevant to the hypothesis. The hypothesis could only be tested if it were first proved that at a particular place the pre-Neolithic vegetation survived until the Early Middle Ages.     

Is forest insurance a relevant vector to induce adaptation efforts to climate change?

? Key message

Insurance might be an efficient tool to strengthen adaptation of forest management to climate change. A theoretical model under uncertainty is proposed to highlight the effect, on adaptation decisions, of considering adaptation efforts in forest insurance contracts. Results show that insurance is relevant to increase adaptation efforts under some realistic conditions on forest owner’s uncertainty and risk preferences, and on the observability or not of adaptation efforts.

? Context

One of the challenges of forest adaptation to climate change is to encourage private forest owners to implement adaptation strategies.

? Aims

We suggest the analysis of forest insurance contracts against natural hazards as a vector to promote the implementation of adaptation efforts by private forest owners.

? Methods

We propose a theoretical model of insurance economics under risk and under uncertainty.

? Results

Our results indicate that when climate change makes the probability of the occurrence of the natural event uncertain, then it may be relevant to include adaptation efforts in the insurance contract, leading to an increase in the adaptation efforts of risk-averse and uncertainty-averse forest owners. In addition, we show that the relevance of insurance as a vector to promote adaptation efforts is greater when the forest owner’s effort is unobservable by the insurer as compared to a situation of perfectly observable effort.

? Conclusion

Under some realistic assumptions, the forest insurance contract seems to be a relevant tool to encourage forest owners to adapt to climate change.

     

Production losses due to a summer frost in a Salix viminalis short‐rotation forest in southern Sweden

The effect of a single night frost during late spring on the current year production of two clones of Salix viminalis was determined in two monoclonal stands that displayed a gradient from virtually undamaged plants, shielded from outgoing radiation by a neighbouring spruce forest, to heavily damaged plants in the unshielded parts. Compared with the undamaged stand parts, frost caused production losses of 47% and 60% in the two clones during the first year of the second cutting cycle. The clone‐specific allometric relationship between shoot dry weight and diameter was changed by the frost in one clone, showing lower shoot weights in damaged shoots compared with undamaged shoots of the same diameter. In the other clone, allometric relations were not affected by the frost. The relative variation in weight between the stools did not differ systematically with frost damage intensity, and therefore it could not be concluded that frost in monoclonal stands would enforce a competitive hierarchy. It was inferred that the single night frost indirectly can have a negative effect on the production of the stands during the years to come.     

Commercial income and capital of hunting: an application to forest estates in Andalucía

This paper presents and applies an experimental agroforestry accounting system (AAS) to measure the commercial income and capital of hunting activities in a large territorial area. This application goes beyond the conventional system of national agriculture and forestry accounts. The methodology developed allows the independent valuation of both environmental and manufactured capital which in turn allows the disaggregation of hunting income and other economic indicators by type of capital. The spatial distribution of these economic indicators can also be provided. Results show positive current total capital income but residual manufactured capital income current losses. An underlying economic rationale explaining this phenomenon is offered.     

Timber Harvesting Behaviour in Massachusetts,USA: Does Price Matter to Private Landowners?

Non-industrial private forest is the dominant ownership type in the eastern USA. Most of the private owners have non-consumptive, appreciative values and through surveys report little interest in the generation of timber revenue. Timber harvesting in Massachusetts was investigated for a 25-year period to compare the frequency and volume of harvests for five commercial species on private land, to species-specific stumpage prices reported on a quarterly basis. For four of the five species, there was no relationship; however, for one species a consistent effect was identified, whereby the volume harvested and number of harvest events were found to be significantly related to stumpage price, west of the Connecticut River. This effect is absent for eastern Massachusetts, and also not apparent consistently for other species. It is concluded that under some circumstances, private landowner harvest decisions are influenced by stumpage price.     

Species distribution models applied to plant species selection in forest restoration: are model predictions comparable to expert opinion?

An expert on local flora usually is the best option for plant species selection in most ecological restoration projects; although species selection often needs to be dealt with swiftly as well as on a limited budget, and obtaining the opinion of a local expert may not always be an economically viable alternative. In such cases, species distribution models (SDM) may offer a faster and more cost effective alternative. We asked six experts to rank native tree species according to their suitability at 24 forest sites. The predictive performance of the suitability rankings was evaluated by assessing their ability to discriminate present from absent species in the observed tree assemblages at each evaluation site. We used the area under the receiver operating characteristic curve to calculate the probability that the estimated suitability for a species present at a particular evaluation site is greater than the estimate for an absent species (both picked at random). Suitability rankings were also obtained from the predictions of SDM and the same procedure was used to estimate the predictive performance of the set of models at each site. The experts offered concordant suitability rankings at almost every evaluation site. There were no significant differences in the predictive performance of the SDM and four of the experts, although the SDM performed slightly better than the other two experts. Our results point to the suitability of the proposed species distribution modeling approach to obtain fast and cost effective recommendations for species selection in forest restoration projects.