EISSN : 19994907
Current Publisher: MDPI (10.3390)
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Forests, Volume 11; doi:10.3390/f11040404
Understanding the spatial variation of forest productivity and its driving factors on a large regional scale can help reveal the response mechanism of tree growth to climate change, and is an important prerequisite for efficient forest management and studying regional and global carbon cycles. Pinus massoniana Lamb. is a major planted tree species in southern China, playing an important role in the development of forestry due to its high economic and ecological benefits. Here, we establish a biomass database for P. massoniana, including stems, branches, leaves, roots, aboveground organs and total tree, by collecting the published literature, to increase our understanding of net primary productivity (NPP) geographical trends for each tree component and their influencing factors across the entire geographical distribution of the species in southern China. P. massoniana NPP ranges from 1.04 to 13.13 Mg·ha−1·year−1, with a mean value of 5.65 Mg·ha−1·year−1. The NPP of both tree components (i.e., stem, branch, leaf, root, aboveground organs, and total tree) show no clear relationships with longitude and elevation, but an inverse relationship with latitude (p < 0.01). Linear mixed-effects models (LMMs) are employed to analyze the effect of environmental factors and stand characteristics on P. massoniana NPP. LMM results reveal that the NPP of different tree components have different sensitivities to environmental and stand variables. Appropriate temperature and soil nutrients (particularly soil available phosphorus) are beneficial to biomass accumulation of this species. It is worth noting that the high temperature in July and August (HTWM) is a significant climate stressor across the species geographical distribution and is not restricted to marginal populations in the low latitude area. Temperature was a key environmental factor behind the inverse latitudinal trends of P. massoniana NPP, because it showed a higher sensitivity than other factors. In the context of climate warming and nitrogen (N) deposition, the inhibition effect caused by high temperatures and the lack or imbalance of soil nutrients, particularly soil phosphorus, should be paid more attention in the future. These findings advance our understanding about the factors influencing the productivity of each P. massoniana tree component across the full geographical distribution of the species, and are therefore valuable for forecasting climate-induced variation in forest productivity.
Forests, Volume 11; doi:10.3390/f11040400
Magnitude–frequency (M–F) relationships represent important information on slope deformation and are used in hazard assessment or as supporting data for urban planning. Various approaches have been used to extract such relationships in the past, but most of these methods drove at the problem of exact events´ frequency determination. Dendrogeomorphic (tree ring-based) approaches are actually thought to be the most precise method of dating past mass movement events that occurred within the last several centuries. Together with information on the spatial positions of the analysed trees, they represent a potentially very valuable tool for reconstructing M–F relationships, although their use for this purpose has been very rare in the past. In this study, M–F relationships are reconstructed using dendrogeomorphic methods for three landslides of different types (a translational slide, a flow-like slide, and a rotational slide) occurring in different geological materials (thick-bedded flysch, limestone marls, and volcanic breccia). In total, 572 disturbed trees were analysed, and chronologies of mass movement events were built. Landslide magnitudes were expressed in three ways: (i) the value of the standard It index; (ii) the area, as determined using homogenous morphological units; and (iii) the area, as determined using tree buffers. The power-law nature of M–F relationships was confirmed for all the landslides that were studied and using all the approaches that were applied. All of the combinations of results yielded high correlation values; nevertheless, differences were noted. The advantages and limitations of each approach used to reconstruct M–F relationships are also discussed.
Forests, Volume 11; doi:10.3390/f11040401
Raulí (Nothofagus alpina (Poepp. & Endl.)) and Ulmo (Eucryphia cordifolia Cav.) are mid-tolerant tree species in the Coihue-Raulí-Tepa (ca. 0.55 mill ha) and Evergreen (ca. 4.1 mill ha) forest types in south-central Chile, respectively. These species have been selectively logged in old-growth forests especially during the 20th century, Raulí mostly for its highly valuable timber, and Ulmo for its highly demanded firewood and bark for the tannery industry. Natural regeneration of these species occurs mostly through canopy gaps, but it can be retarded, or even inhibited, when the cover of the understory vegetation becomes unusually dense, such as in high-graded forests. Although underplanting is possible for these species, the knowledge about their growth in forest understories is scarce, and necessary to inform restoration programs. Therefore, we evaluated short-term responses (two years) of underplanted containerized seedlings in root-collar diameter, height, stem volume, and in the slenderness index, as a function of canopy openness (%, continuous variable) and three restoration treatments (categorical variables, plus one control treatment) at two different sites with high-graded old-growth forests for each forest type. By using generalized linear mixed-effects models (GLMMs) we determined that Raulí was more sensitive to the influence of both canopy openness and restoration treatments, while Ulmo was mostly influenced by canopy openness. Specifically, Raulí was positively influenced by canopy openness and restoration treatments in all response variables except for the slenderness index. Conversely, Ulmo was influenced by canopy openness in all response variables except the slenderness index, which was influenced by both predictor variables (canopy openness and restoration treatments). Thus, prospects for restoration with these species are discussed, including possible ontogenetic changes in their responses to light that may demand continuous silvicultural operations to recover the productive and functional roles of these species in these forest ecosystems.
Forests, Volume 11; doi:10.3390/f11040402
Carbon starvation and hydraulic failure are considered important factors in determining the mechanisms associated with tree mortality. In this study, iso/anisohydric classification was used to assess drought resistance and mortality mechanisms in two contrasting poplar species, as it is generally believed that isohydric species are more susceptible to carbon starvation, while anisohydric species are more susceptible to hydraulic failure. However, these assumptions are rarely tested in poplar genotypes with contrasting growth strategies. Thus, we subjected potted poplar genotypes (I-101 (Populus alba L.) × 84K (Populus alba L. × Populus glandulosa Uyeki)) with fast and slow growth rates to drought–rehydration treatments. The slow-growing genotype maintained higher stomatal conductance and lower predawn leaf water potential than the fast-growing genotype, thus exhibiting a near-anisohydric stomatal behavior throughout the treatment period. The nonstructural carbohydrate (NSC) content indicated that the two genotypes had the same trend of carbon change (e.g., the NSC content in the leaves increased with drought and then decreased). However, when NSC content data were combined with the growth and photosynthetic data, it was observed that the slow-growing genotype mobilized carbon to maintain hydraulic safety, while the NSC content of the fast-growing genotype among tissues was static. The percent loss of hydraulic conductivity in the branches during treatments indicated that the fast-growing genotype could recover more quickly from xylem embolism than the slow-growing genotype. The slow-growing genotype with a slow growth recovery after rehydration showed a significant increase in carbon consumption, combined with a significant increase in the hydraulic safety threshold value, indicating that there may be drought tolerance. In comparison, the fast-growing genotype showed a faster hydraulic recovery ability that had no effect on the NSC content in the leaves and roots. Our findings demonstrate intraspecific isohydric behavior in poplar; however, the trade-off between carbon distribution and stomatal regulation should be considered separately within genotypes of the same species. In addition, NSC plays an important role in water–carbon balance in the drought–rehydration cycle.
Forests, Volume 11; doi:10.3390/f11040403
Community forest management (CFM) is often a field of encounter between knowledge systems, where a conventional forestry blueprint is frequently applied in contexts rich in traditional ecological knowledge (TEK). This is the case in Mexico, a bioculturally diverse country and a reference of community forestry. Based on a review of laws, policies, literature, and empirical examples, we explore technical, epistemological, political, and contextual dimensions associated with the inclusion and exclusion of TEK in CFM in Mexico. Our analysis is composed of three steps: (1) A diachronic analysis of how TEK and associated practices have been considered by federal forest laws and codes (1960–2018), (2) a diachronic analysis of the scope of conventional forestry and its evolution in time and space, and (3) situated examples illustrating the inclusion and exclusion of TEK in CFM. We argue that: (1) Legal recognition of TEK as a concept does not necessarily entail the legal recognition of all traditional management practices; (2) the inclusion of TEK in CFM is heterogeneous across communities, ecosystems, regions, products and historical trajectories; and (3) different traditional practices are not equally integrated in CFM: traditional practices that contradict the spatial segregation of activities (i.e., land sparing) favored by conventional forestry tend to be less easily accepted or ignored by government institutions.
Forests, Volume 11; doi:10.3390/f11040393
The scientific debate over how to make visible the connections between the standard System of National Accounts (SNA) and its ongoing satellite Environmental Economic Ecosystem Accounting–Experimental Ecosystem Accounting (SEEA–EEA) is a challenge that is still pending. The literature on environmental accounting of agroforestry and silvopastoral landscapes rarely values the multiple ecosystem services of an area, an economic unit (e.g., farm), or a vegetation type (e.g., holm oak—Quercus ilex L.—open woodland). Generally, the literature presents the market value of the products consumed directly or a correction of the latter that reduces their exchange values in order to approximate them to their resource rents. In our previous publications, we have applied and compared our Agroforestry Accounting System (AAS) with the System of National Accounts (SNA), and we refined the latter to avoid the lag between income generation and its accounting in the period in which the product is extracted. These previous publications did not develop experimental applications of the SEEA–EEA with comparisons to the SNA and it being integrated into the AAS. The main novelty of this article is that, for the first time, we present detailed applications and comparisons of our developments of the refined SEEA–EEA and refined SNA with a simplified version of the AAS. The accounting frameworks applied take the production and capital accounts in the process of being updated by the United Nations Statistics Division (UNSD) at the scale of the holm oak open woodlands of Andalusia into account. In this study, we compare three environmental accounting approaches for ecosystem services and environmental income measurements at basic and social prices: our slightly refined standard System of National Accounts (rSNA); our refined, updated and ongoing satellite System of Environmental Economic Accounting–Experimental Ecosystem Accounting (rSEEA–EEA); and our simplified Agroforestry Accounting System (sAAS). We tested them for 15 economic activities in 1408 thousand hectares of the predominantly mixed holm oak open woodland (HOW) land use tiles in the region of Andalusia, Spain. We considered the government institutional sector to be the collective owner of public economic activities, which we incorporated in the rSNA and the sAAS approaches. We discuss consistencies in environmental incomes identified from the results of the three ecosystem accounting frameworks applied to the HOW. The discrepancies in the measurement of ecosystem services of the government institutional sector between the rSEEA–EEA and the sAAS were due to the omission in the former of the government manufactured costs incurred in the supply of freely consumed public final products. The most notable finding of our comparison is that the ecosystem services and the environmental income results for individual market products offered the same values, whichever the ecosystem accounting framework applied. This was not the case with the ecosystem services of public products without market prices, due to the fact that the rSNA estimates these products at production cost and the rSEEA–EEA did not consider the government manufactured production costs and ordinary manufactured net operating margin of government final public product consumption. We also found that, according to modeling of the scheduled management of future biological resources of the HOW, the environmental income shows biological sustainability of the individual nature-based total product consumption.
Forests, Volume 11; doi:10.3390/f11040394
Forests are a large carbon sink with an additional substitution effect in the merchantable timber compartment of harvested trees, where carbon stored within the same volume of wood varies depending on wood density. Here, we investigated mean annual air-dry wood density variations depending on cambial age, annual radial increment, and two different stem heights of Larix gmelinii (Rupr.), Quercus mongolica Fisch. ex. Ledeb., and Pinus tabulaeformis Carr. from a first climatic region (Mulan Forest) and exclusively of P. tabulaeformis from a second climatic region (Zhongtiaoshan Forest) in the temperate zone of China. We applied linear mixed-effects models with partly transformed variables and estimated marginal means for pairwise comparisons. Results showed that mean wood density was not significantly different between L. gmelinii (0.626 g cm−3) and Q. mongolica (0.596 g cm−3), but significantly different between P. tabulaeformis from the two different climatic regions (0.445 g cm−3 in Mulan Forest and 0.521 g cm−3 in Zhongtiaoshan Forest). Mean annual wood density within trees except for P. tabulaeformis from Mulan Forest was initially increasing until an intermediate cambial age, after which it decreased again to lower values. These findings showed that tree age had to be considered in assessing carbon sequestration in wood. It also could play an important role in decision making for forest management in Mulan Forest and show the benefit of the wood properties and carbon storage potential of the faster growing L. gmelinii compared to Q. mongolica. Furthermore, these findings gave an indication that intermediate old forest stands for some tree species accumulated more carbon per year within their woody biomass than young stands or old growth forests. Our results may have an impact on the planning of rotation lengths and of tree species composition for forest stands in Mulan Forest and Zhongtiaoshan Forest.
Forests, Volume 11; doi:10.3390/f11040395
Forest ecosystems are frequently exposed to abiotic stress, which adversely affects their growth, resistance and survival. For silver fir (Abies alba), the physiological and biochemical responses to water and salt stress have not been extensively studied. Responses of one-year-old seedlings to a 30-day water stress (withholding irrigation) or salt stress (100, 200 and 300 mM NaCl) treatments were analysed by determining stress-induced changes in growth parameters and different biochemical markers: accumulation of ions, different osmolytes and malondialdehyde (MDA, an oxidative stress biomarker), in the seedlings, and activation of enzymatic and non-enzymatic antioxidant systems. Both salt and water stress caused growth inhibition. The results obtained indicated that the most relevant responses to drought are based on the accumulation of soluble carbohydrates as osmolytes/osmoprotectants. Responses to high salinity, on the other hand, include the active transport of Na+, Cl− and Ca2+ to the needles, the maintenance of relatively high K+/Na+ ratios and the accumulation of proline and soluble sugars for osmotic balance. Interestingly, relatively high Na+ concentrations were measured in the needles of A. alba seedlings at low external salinity, suggesting that Na+ can contribute to osmotic adjustment as a ‘cheap’ osmoticum, and its accumulation may represent a constitutive mechanism of defence against stress. These responses appear to be efficient enough to avoid the generation of high levels of oxidative stress, in agreement with the small increase in MDA contents and the relatively weak activation of the tested antioxidant systems.
Forests, Volume 11; doi:10.3390/f11040397
Three systems of additive biomass models were developed and the effects of tree components, tree sizes, and tree growing regions on the carbon concentration were analyzed for Mongolian oak (Quercus mongolica Fisch. ex Ledeb.) in the natural forests of Northeastern China. The nonlinear seemingly unrelated regression (NSUR) method was used to fit each of the three systems simultaneously; namely, aggregated model systems with no parameter restriction (AMS0), aggregated model systems with one parameter restriction (AMS1), and aggregated model systems with three parameter restrictions (AMS3). A unique weighting function for each biomass model was applied to address the heteroscedasticity issue. The systems assertively guarantee the additivity property, in which, the summation of the respective predicted tree components (i.e., root, stem, branch, and foliage) will match the prediction of subtotals (i.e., crown and aboveground) and total biomass. Using one-, two-, and three-predictor combinations (i.e., D (diameter at breast height), D and H (total height), and D, H, and CL (crown length)) as the general model underlying formats, three systems of additive biomass model were developed. Our results indicate that (1) all of the aggregated model systems performed well and the differences between the systems were relatively small; (2) the rank order of the three systems based on an array of statistics are as follows: AMS0 > AMS1 > AMS3; (3) the carbon concentration significantly varied depending on the types of tree tissues and growing regions; (4) the regional respective component carbon concentration and regional weighted mean carbon concentration multiplied by observed biomass value appeared to be the best approach to calculate carbon stock.
Forests, Volume 11; doi:10.3390/f11040396
Wood supply chain performance suffers from risks intensified by more frequent and extreme natural calamities such as windstorms, bark beetle infestations, and ice-break treetops. In order to limit further damage and wood value loss after natural calamities, high volumes of salvage wood have to be rapidly transported out of the forest. In these cases, robust decision support and coordinated management strategies based on advanced contingency planning are needed. Consequently, this study introduces a contingency planning toolbox consisting of a discrete event simulation model setup for analyses on an operational level, strategies to cope with challenging business cases, as well as transport templates to analyze outcomes of decisions before real, costly, and long-lasting changes are made. The toolbox enables wood supply managers to develop contingency plans to prepare for increasing risk events and more frequent natural disturbances due to climate change. Crucial key performance indicators including truck to wagon ratios, truck and wagon utilization, worktime coordination, truck queuing times, terminal transhipment volume, and required stockyard are presented for varying delivery time, transport tonnage, and train pick-up scenarios. The strategy BEST FIT was proven to provide robust solutions which saves truck and train resources, as well as keeps transhipment volume on a high level and stockyard and queuing time on a low level. Permission granted for increased truck transport tonnages was evaluated as a potential means to reduce truck trips, if working times and train pick-ups are coordinated. Furthermore, the practical applicability for contingency planning is demonstrated by highly relevant business cases such as limited wagon or truck availability, defined delivery quota, terminal selection, queuing time reduction, or scheduled stock accumulation. Further research should focus on the modeling and management of log quality deterioration and the resulting wood value loss caused by challenging transport and storage conditions.