Muma, RobertWebb, Lynn A.Zald, Harold S. J.Boston, Kevin...
10页
查看更多>>摘要：There is considerable interest in multiaged management as a silvicultural and restoration tool in redwood forests of California. For multiaged silviculture to be successful, a new cohort of trees must first be able to regenerate underneath the residual overstory. We used annual re-measurement data from a replicated manipulative experiment in coastal northern California to determine how understory light, stand density, and spatial arrangement of residual trees affected coast redwood (Sequoia sempervirens) and tanoak (Notholithocarpus densiflorus) stump sprouts regenerating after partial harvest of conifers and felling-to-waste of tanoak. Four treatments (group selection, aggregated retention, low-density dispersed retention, and high-density dispersed retention) were applied at each replicate on redwood-dominated sites. Height growth of redwood sprouts was 49% greater than tanoak sprouts across all treatments. Redwood and tanoak sprouts were sensitive to overstory density. Redwood sprouts were marginally taller under high-density aggregated versus dispersed overstory trees at the same residual stand density (39.5 m2/ha BA). Sprout growth correlated with understory light; redwood sprouts exhibited a significant increase in sensitivity to light availability from year 2 to year 6. No differences in redwood sprout growth were detected when retaining a residual tree on the same root system versus sprouts growing on a root system where all redwood stems were cut. Our finding that cutting unwanted hardwoods in tandem with partial harvesting of merchantable conifers can maintain a competitive advantage for redwood sprouts versus tanoaks is an important consideration for maintaining redwood dominance when transitioning to multiaged management.
查看更多>>摘要：Fire disturbance has been one of the main reasons for the alteration of forest succession trajectory and forest composition in the Daxing'anling Mountain of Inner Mongolia. Therefore, predicting the dynamic process of post-fire regrowth is critical for understanding the specific forest succession trajectory of this region. The 3-PGmix model (i.e., Physiological Principles in Predicting Growth for mixed stands) has been reported as a powerful tool for predicting the growth of mixed forest species. However, simulating post-fire regrowth of mixed forest with 3-PGmix remains challenging due to the uncertainty of species-specific as well as site-specific model parameters. Based on the field measurements from a wide range of environmental conditions, the 3-PGmix model was calibrated by conducting the sensitivity analysis and optimization of species-specific parameters for mixed forest stands of larch (Larix gmelinii) and birch (Betula platyphylla) with the PEST model (Model-Independent Parameter Estimation), and by using our newly developed methods to accurately estimating site-specific parameters (e.g., fertility rating, stand density, climate factors). The calibrated 3-PGmix model was tested against the independent sites and predicted the characteristic of post-fire forest regrowth. The sensitivity analysis shows that the parameters describing the forest canopy are more sensitive to the objective function of the PEST model. The calibrated 3-PGmix model performed well on independent sites, resulting in agreement with the field measured diameter at breast height (DBH), the biomass of components, and stand density with a bias of less than 15% on most sites. The 3-PGmix model prediction of post-fire forest recovery characteristics found that the highest recovery rate of 5.5% per year was predicted from the moderate burn severity scenarios. A higher fertility rating was predicted to accelerate the process of post-fire forest successional and shorten the duration time when the species proportion achieves balance. The mixed-forest specific calibration of the 3-PGmix model in this study enables the explicit prediction of post-fire forest succession, and more simulations over different spatial scales with a wide range of environmental conditions by coupling with remote sensing observations can be expected.
Springer, Judith D.Stoddard, Michael T.Huffman, David W.Laughlin, Daniel C....
13页
查看更多>>摘要：Interest in use of naturally ignited wildland fires managed to meet multiple resource objectives (resource objective wildfire) is increasing among U.S. public forest managers; however, only a limited number of studies have examined this approach for conserving or restoring understory plant diversity, productivity, and community structure. We analyzed understory community changes two and twelve years after resource objective fire, using permanent sample plots in three montane contrasting forest types in Grand Canyon National Park, AZ. Our findings indicated that species composition in the pine-oak forest rebounded to be similar to that observed before the fire, but plant cover did not recover to pre-fire levels by the twelfth year post-fire. Plant cover showed mixed results post-fire in mixed-conifer and spruce-fir forests, and species composition was still characterized by ruderal species twelve years later. Patterns observed in this study likely reflect interacting factors of burn severity, periodic drought, large ungulate herbivory, and inherent site variability. Other than cheatgrass (Bromus tectorum), we found no non-native species occurring with high frequency. Continued monitoring with increased frequency and intensity could lead to better understanding of long-term changes in these forests after resource objective fire, and enhance our understanding of important drivers of variation including interactions of climate, burn severity and herbivory by large ungulates.
查看更多>>摘要：Habitat shift caused by human impact on vegetation structure poses a great threat to species which are specialized on unique habitats. Single layered beech forests, the main foraging habitat of Greater Mouse-eared Bats (Myotis myotis), are threatened by recent changes in forest structure. After this species suffered considerable population losses until the 1970s, their roosts in buildings are strictly protected. However, some populations are still declining. Thus, the spatial identification of suitable foraging habitat would be essential to ensure conservation policy. The aim of this study was (a) to verify the relevance of forest structural variables for the activity of M. myotis and (b) to evaluate the potential of LiDAR (Light Detection and Ranging) in predicting suitable foraging habitat of the species. We systematically sampled bat activity in forests close to 18 maternity roosts in Switzerland and applied a generalized linear mixed model (GLMM) to fit the activity data to forest structure variables recorded in the field and derived from LiDAR. We found that suitable forest foraging habitat is defined by single layered forest, dense canopy, no shrub layer and a free flight space. Most importantly, this key foraging habitat can be well predicted by airborne LiDAR data. This allows for the first time to create nationwide prediction maps of potential foraging habitats of this species to inform conservation management. This method has a special significance for endangered species with large spatial use, whose key resources are hard to identify and widely distributed across the landscape.
Thomas, Sean C.Vantellingen, JulianaGorgolewski, Adam S.
12页
查看更多>>摘要：Skid trails and landings are features within managed forest landscapes where soils are moderately to extremely disturbed by forestry vehicles. They have been found to exhibit reduced methane (CH4) oxidation or CH4 emissions six months to a year after a harvest has ended, but little is known about when these changes begin to occur (either during or after harvests) or how they recover over a longer timeframe. We took periodic measurements of soil CH4 flux from skid trails and landings during a harvest, and also quantified CH4 flux rates from sites that had been harvested up to 15 years prior to form a replicated chronosequence of soil recovery. In the thirteen-week period of active harvesting soil CH4 oxidation steadily declined, with small emissions occurring by the end of the measurement period. The chronosequence measurements revealed high rates of CH4 emissions the first year after harvest followed by a decrease in the following years. Emissions were particularly strong from landings and skid trails that had experienced high amounts of traffic and were located on lower slopes. By the end of the 15-year chronosequence landing and skid trail soils had returned to acting as CH4 sinks; however, the rates of oxidation remained lower than undisturbed forest soils. Further, integration of models created to predict CH4 flux over time indicates that CH4 flux from these soils are unlikely to reach a full recovery within a 20-year period - the average length of time of a harvest cycle in this region. On landings the change from emissions back to oxidation was correlated with soil temperatures, which decreased over time. On some skid trails CH4 flux was correlated with soil moisture content, which initially increased from buried wood's increased water holding capacity and then decreased over time. The results suggest that remediation measures ought to be implemented immediately after harvest to avoid the high emissions that occur in the following few years and should prioritize the removal or prevention of incorporation of wood fragments.
Jagodzinski, Andrzej M.Wozniak, GabrielaChmura, DamianDyderski, Marcin K....
10页
查看更多>>摘要：Forests are the dominant terrestrial ecosystems on the Earth. During natural succession, a quite known pattern of changes occur (i.e., the process of a gradual assemblage of plant species and associated organisms best adapted to the current habitat conditions). Much less is known about novel ecosystem establishment's primary spontaneous successional mechanisms due to human agency such as post-coal mine heaps habitats. The post-coal mine heaps are sites of pure mineral substrates and constrain (e.g., temperature, acidity, drought, salinity) habitat conditions. These conditions are variable both in time and space. Regardless of all these constraints, diverse vegetation is soon spontaneously developing on these sites. A characteristic feature of the vegetation successional development on post-coal mine heaps is the emergence of non-analogous species assemblages when comparing to the natural and seminatural vegetation communities and ecosystems. This study aimed to compare the forest spontaneously developed on the mineral novel material habitat of the post-coal mining heap, with forests in the surrounding, on non-industrial habitats (located in Silesian Upland (South Poland)) in taxonomic, phylogenetic, and functional diversity at alpha (within-site) and beta (among sites) levels. The functional traits values of the recorded species composition were calculated to assess, e.g., the taxonomic alpha diversity Shannon's diversity and evenness index, Simpson index, functional richness (FRic), functional dispersion (FDis), functional divergence (FDA), and functional evenness (FEve). Rao's entropy has standardized the Biotic Novelty Index (BNI) to reflect the proportion of functional diversity contributed by novel species composition. The results revealed higher functional richness and dispersion in coniferous forests than in forests on heaps. The plots from coniferous forests and heaps were distinctly differentiated in terms of species composition. No difference occurred in functional evenness and divergence. Vegetation patches of coniferous forests had 19% higher species richness and twice higher Faith's phylogenetic diversity, while no differences in species diversity described by Shannon's diversity index have been recorded. An almost thirty times higher biological novelty index in forests on heaps than in coniferous forests patches has been recorded. The RLQ - analysis of relationships between plant traits, species composition and environmental variables revealed significant associations between EIVs and type of habitat and plant traits. The plant traits such as SLA and SM seem indifferent and do not differentiate the two studied habitats. The results showed that both understanding mechanisms by which these habitats are shaped and recognizing their biological potential and values are essential for nature conservation and management and challenge future studies.
查看更多>>摘要：We investigated growth and a suite of physiological and structural traits of ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. scopulorum Engelm.) seedlings from different provenances using a field common garden study. Twenty-one provenances from a range of elevations across Arizona and New Mexico were planted in 2018 at a field site in the core of the species range in northern Arizona. We measured stem growth rate for three years (2019-2021), leaf carbon isotope discrimination (delta C-13), and leaf nitrogen concentration in 2020 on all provenances, and leaf-level gas exchange, instantaneous water use efficiency, predawn and midday water potentials, soil-to-leaf hydraulic conductance and specific leaf area on nine provenances in 2020. Provenances differed significantly in stem growth rate, delta C-13, and specific leaf area, and several traits were correlated with provenance environmental and climatic characteristics. Seedlings with higher growth rate had greater delta C-13 suggesting a trade-off between growth rate and water use efficiency. Provenances from warmer sites had lower growth rate and delta C-13 (higher water use efficiency) than provenances from cooler sites during the driest year. Growth rate of provenances in the driest year was positively associated with stomatal conductance, net photosynthetic rate, and soil-to-leaf hydraulic conductance and negatively associated with instantaneous water use efficiency indicating the importance of maintaining water uptake and gas exchange to growth during drought under dry conditions. Our results enhance understanding of physiological mechanisms of establishment for planted ponderosa pine seedlings and show a trade-off between growth rate and water use efficiency of provenances from different thermal environments that should be useful in selection of seed sources for reforestation.
查看更多>>摘要：The objective of our study was to determine the effect of mineral dusts alone or in combination with the entomopathogenic fungus Beauveria bassiana to control the spruce bark beetle Ips typographus. In laboratory experiments with silicon dioxide (SiO2), diatomaceous earth (DE), Otavi-Perlit (R) (OP) and SilicoSec (R) (Ssec), 100% of all beetles died within 7 days on spruce bark at a temperature of 25 degrees C and a relative humidity (RH) of 40%, while the control mortality was 21%. The median survival time (MST) was between 2.0 and 4.1 days compared to the control with 9.8 days. After treatment on artificial diet, only in the SIO2 and DE treatment the mortality and MST were significantly different from the control. At 40% RH all beetles treated with siloxide (SiO) were dead after 3 days, while at 70% and 100% RH no effect of SiO on the beetles was observed, which shows that the effect of SiO on I. typographus is dependent on RH. An aqueous solution of SiO2 (1% and 10%) was as effective against I. typographus as the powder formulation, when the bark was dipped into the solution and dried afterwards. In the combination test, conidia of B. bassiana (1x107 spores/ml) were mixed with a solution of SiO2 at a final concentration of 0.5% and 5%. The highest mortality and lowest MST at 40%, 70% and 100% RH and 25 degrees C were observed in the 5% SiO2/B. bassiana mixture and in the powder formulation of both. In the field, I. typographus beetles were treated in bore holes or nuptial chambers with the B. bassiana product Boverol (R) or SiO2 alone and in combination on spruce logs. After 5 days, the highest number of galleries and pupal chambers was recorded in the untreated control. The mortality in all treatments was between 83 and 93% (control 54%). The rate of mycosis was 75-93% in all Boverol (R) treatments. In a final field experiment, beetles were trapped with pheromones, treated with B. bassiana or Ssec alone and in combination, and then were released on spruce bark in cages. After 7 days, the mortality and MST were significantly higher in all treatments compared to the control. In the B. bassiana treatments the mycosis rate was more than 90%. We suggest testing further mineral dusts alone or in combination with an entomopathogenic fungus (e. g. B. bassiana) against I. typographus in the field and to study the practicability of treatments within forest management strategies.
查看更多>>摘要：Tree-related microhabitats (TreMs) have been identified as key features for forest-dwelling taxa and are often employed as measures for biodiversity conservation in integrative forest management. However, managing forests to ensure an uninterrupted resource supply for TreM-dwelling taxa is challenging since TreMs are structures with a limited availability, some of which are triggered by stochastic events or require a long time to develop. At the tree scale, the role of tree species, diameter at breast height (dbh) and status (i.e. living vs standing dead) for favouring TreM occurrence has been quantified and modelled in several studies, since these tree features are routinely recorded in the field. However, TreM occurrence remains difficult to predict, hampering the elaboration of applicable management strategies that consider TreMs. Using an international database encompassing 110,000 trees, we quantified the explanatory power of tree species, dbh, status, time since last harvest and plot context for predicting TreM occurrence at the tree level. Plot context is so far a "black box" that combines local environmental conditions, past and current management legacies, with local biotic features that have high explanatory power for predicting TreM occurrence. Then, based on the literature, we established a set of 21 factors related to site, stand and tree features for which there is a strong assumption that they play a key role in TreM formation. Finally, we identified a sub-set of nine features that should be recorded in the future to provide additional information to enable better prediction of the occurrence of particular TreMs: (i) at plot level: slope, exposure, altitude and presence of cliffs; and (ii) at tree level: bark features, phyllotaxis and compartmentalization capacity of the tree species, plus ontogenic stage and physiological state of the individual tree sampled.
Lindbladh, MattsElmberg, JohanHedwall, Per -OlaHolmstrom, Emma...
10页
查看更多>>摘要：Retention forestry involves saving important forest structures for flora and fauna during the final felling of a stand, including dead wood and variable amounts of living trees, i.e. green tree retention (GTR). Here we evaluate the long-term effects on avian diversity from GTR by surveying forest birds in 32 mid-rotation stands in southern Sweden, in which broadleaf GTR was present or absent. Complementing the many studies that have assessed GTR in clear-cuts, our results indicated that bird assemblages can also benefit from broadleaf GTR several decades after final felling in conifer dominated production stands. The GTR stands harboured a higher bird abundance and species richness than the control stands without GTR, and also appears to have benefited several important guilds, such as broadleaf-associated birds and cavity nesters. However, variation in the number trees retained, the species composition of retained trees, and their environmental context within the stand (e.g. density and proximity of surrounding production trees), limited our capacity to detect threshold requirements for GTR. In summary, our study provides a "glimpse into the future" as mid-rotation production stands with such old and large retained trees are unusual in today's landscape, but are expected to become more common in the decades to come, in Sweden and many other nations. Our study thereby provides provisional support for the continued and future use of this practice, and indicates that the biodiversity contribution of retention trees continues to occur several decades into the stand's rotation.
NSTL
Elsevier