Forest Monocultures Research Articles

Diversity of Brachyuran crabs after 12 years natural reforestation at destroyed areas by typhoon Durian in Can Gio mangrove

The regeneration of mangroves in Can Gio following typhoon Durian has been the subject of interesting research, with the hope of developing plans to deal with similar consequences in the future. In this study, we recorded 26 species of crabs belonging to 16 genera and 10 families, of which the Sesarmidae and Ocypodidae families accounted for the highest proportion. The natural reforestation in the destroyed area by the previous Durian typhoon in 2006 has recorded the appearance of 6 new recorded species such as Paracleistostoma depressum, Pilumnopeus sp., Macrophthamus japonicus, Myomenippe hardwickii, Nanosesarma pontianacense and Uca annulipes. Particularly, Perisesarma eumolpe was the dominant species in all areas, indicating their ability to adapt to many habitats. Several new recorded species, especially Uca crabs, were recorded in naturally regenerated areas. The densities and biomass of crabs in regenerated areas were higher than those in intact forests. Shannon Weiner index indicated that the crab community had higher diversity in the regenerated areas. On the contrary, in the intact forest, the Simpson dominance index is higher than in the regenerated areas. The results of this study indicated that natural regeneration has created conditions for the crab community to recover opportunities for many new species to appear. The open canopy of monoculture forests would contribute to increasing the number of crabs,in particular and biodiversity, in general. Retaining the natural conditions after the typhoon had shown effectiveness in helping the ecosystem recover.

Mixed-Species Acacia Plantation Decreases Soil Organic Carbon and Total Nitrogen Concentrations but Favors Species Regeneration and Tree Growth over Monoculture: A Thirty-Three-Year Field Experiment in Southern China

Mixed-species plantations of trees with N-fixing species have the potential of promoting forest productivity and soil fertility. However, few studies in the literature have addressed the advantages of mixed-species plantations of leguminous trees over monocultures of leguminous trees based on in situ inventories over a long time period. Here, we monitored the dynamics of tree community composition, vegetation biomass, soil nutrients, and soil microbial phospholipid fatty acids (PLFAs), in an Acacia mangium monoculture plantation during 33 years of development and compared it with a mixed-species plantation of A. mangium associated with 56 native species which were underplanted 14 years after the initial establishment. Leaf N and phosphorus (P) concentrations of three main species in the overstory and understory of the A. mangium monoculture were measured. Our results showed that the soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP) concentrations significantly increased over time during the approximately thirty years of A. mangium monoculture plantation, while the disadvantages were associated with new species regeneration and the increment of vegetation biomass. In the A. mangium monoculture plantation, leaf N concentration of A. mangium,Rhodomyrtus tomentosa, and Dicranopteris dichotoma continuously increased from 21 to 31 years, while the leaf P concentration of A. mangium and R. tomentosa decreased. The mixed-species plantations of A. mangium with native tree species had lower SOC and soil TN concentrations, more new tree species recruitment in the understory, and faster vegetation biomass increment than the A. mangium monoculture. However, the PLFAs of soil microbial groups were slightly different between the two types of plantations. We conclude that improved soil N nutrient condition by A. mangium monoculture benefits N absorption by A. mangium, R. tomentosa, and D. tomentosa, while low soil AP limits P absorption by A. mangium and R. tomentosa. Meanwhile, transforming the A. mangium monoculture into a mixed-species plantation via the introduction of multiple native species into the A. mangium monoculture decreases SOC and TN concentrations but the advantages include improving forest regeneration and maintaining forest growth in a long-term sequence. These findings provide useful and practical suggestions for managing forest monocultures of A. mangium in subtropical regions.

Legume-bacteria-soil interaction networks linked to improved plant productivity and soil fertility in intercropping systems

Intercropping with legumes is an effective strategy to increase plant productivity, reduce nitrogen (N) inputs, and maintain soil fertility in an industrial monoculture forest. However, the facilitation/complementarity mechanism of the interactions between legumes (keystone species in intercropping), bacteria and soil are still unknown, and the contribution of this triple interaction to plant growth and ecosystem function is still difficult to predict. Taking the introduction of Dalbergia odorifera (D. odorifera), into eucalyptus plantations as an example, we evaluated the changes in nutrient uptake, phytohormone contents, N metabolism-related enzyme activities, and root-associated bacteria of D. odorifera under different N applications (0, 3, 6 and 12 g pot−1) and different planting patterns (monoculture and intercropping), and investigated the regulatory mechanism of these cascaded changes on productivity and soil fertility in response to intercropping. The results showed that intercropping increased the total biomass by 5.90–56.29% compared to monoculture; in particular, intercropping in combination with 6 g N pot−1 had superiority in promoting the gibberellin content, glutamine synthetase activity, nitrogenase activity, soil fertility, and bacterial diversity, as well as the relative abundance of bacteria with the potential to undergo aerobic chemoheterotrophy, N fixation and N respiration. The differentially expressed genes identified via transcriptome analysis were mainly involved in metabolic pathways, signal transduction, and the tricarboxylic acid cycle. To integrate the associations between plant traits, bacterial communities, and soil properties, we built a multivariable network based on multiple plant traits, soil properties, differentially accumulated genera, and differentially expressed genes in monoculture and intercropping. These results led to the identification of candidates related to intercropping advantages, including two genes (acidic endo chitinase, Na+/K+ transporter) and four bacterial genera (Bacteroides, Coxiella, Pseudomonas, SJA-15). More specifically, moderate fertilization of eucalyptus/D. odorifera intercropping systems create a more stable interaction network with additional module hubs. These results highlight the importance of bacterial diversity and the plant-bacteria-soil interaction network in maintaining soil fertility and plant productivity, which may help fertilization practices in eucalyptus plantations and provide guidance for the ecological sustainability of introducing D. odorifera into industrial forests.

What Are the Effects of Moso Bamboo Expansion into Japanese Cedar on Arbuscular Mycorrhizal Fungi: Altering the Community Composition Rather than the Diversity.

The unbridled expansion of moso bamboo (Phyllostachys edulis) occurs throughout the world and has a series of consequences. However, the effect of bamboo expansion on arbuscular mycorrhizal fungi (AMF) is still poorly understood. We assessed the changes in the AMF community during bamboo expansion into Japanese cedar (Cryptomeria japonica) forests by analyzing AMF in three forest types-Japanese cedar (JC), bamboo-cedar mixed (BC) and moso bamboo (MB)-using 454 pyrosequencing technology. We found that the AMF community composition differed significantly among forest types. The relative abundance of Glomerales decreased from 74.0% in JC to 61.8% in BC and 42.5% in MB, whereas the relative abundance of Rhizophagus increased from 24.9% in JC to 35.9% in BC and 56.7% in MB. Further analysis showed that soil characteristics explained only 19.2% of the AMF community variation among forest types. Hence, vegetation is presumably the main driver of the alteration of the AMF community. The α diversity of AMF was similar between JC and MB, although it was higher in BC. Overall, this research sheds more light on AMF community dynamics during moso bamboo expansion. Our results highlight that the consequences of bamboo expansion in monoculture forests differ from those in mixed forests.

Impacts of the world’s largest afforestation program (Three-North Afforestation Program) on desertification control in sandy land of China

ABSTRACT In order to control the desertification, large-scale afforestation programs have been attempted worldwide. Among them, China initiated the world’s largest afforestation program, Three-North Afforestation Program (TNAP, 1978–2050), in which the afforestation in sandy land has been questioned during the first 40 years. In fact, the contribution of the TNAP to vegetation establishment and its effectiveness in desertification control still remain unclear, which limited the further construction of the program. To answer the questions, we detected the dynamics of vegetation distribution (forest, shrubland, and grassland) and desertification status (slight, moderate, severe, and extremely severe) during 1978–2017 in the sandy land (45.5 million ha), by visual interpretation of 5-period remote sensing images with validation based on 3,100 sample plots from field surveys and 15,175 sample plots from the National Forest Resource Inventory. Vegetation degradation was identified by analysis combining the trends of net primary productivity and precipitation use efficiency. By Geographical Detector model, the driving forces of vegetation degradation (climate change, human activities, vegetation type, and sandy land type) were ranked and the contributions of the influential factors (climate change, human activities, and vegetation dynamics) to desertification changes were estimated. The results showed that for the 40 years, vegetation coverage increased by 0.5%, with increasing 113.8% and 338.8% of forest and shrubland, but decreasing 9.0% of grassland. Desertification area had little change while the overall intensity decreased. The TNAP contributed to desertification dynamics by 10.3%, which is lower than expected. Vegetation type was the dominant factor of vegetation degradation in general. Forest is less suitable for afforestation in sandy land than shrubland and grassland because of its lower stand establishment rate, higher degradation rate, and less contribution to desertification control. Thus, adjusting vegetation type to match local conditions (e.g., use shrub-land, grassland, and native species) and improving the vegetation resistance (e.g., transform monoculture forests into mixed forests, and make proper proportion for forest, shrubland, and grassland) was suggested. Our study provided specific and feasible strategies for further planning and implementation of TNAP, and references for vegetation restoration of sandy lands worldwide.

Comparison of Rainfall Partitioning and Estimation of the Utilisation of Available Water in a Monoculture Beech Forest and a Mixed Beech-Oak-Linden Forest

Monoculture forests formed by Fagus sylvatica L. belong to one of the most sensitive forest ecosystems, mainly at low altitudes. Cultivation of this species in mixed stands should reduce its sensitivity to drought in the vegetation period, which is why we researched the water balance in one pure-beech (i.e., monoculture) and one beech–oak–linden (i.e., mixed) forest. This research was carried out in Drahanská vrchovina in the Czech Republic in the period 2019–2021. The total precipitation was measured, together with its partitions (i.e., throughfall and stemflow), and the crown interception was also calculated. The total forest transpiration was calculated from the values measured on the sample trees. The values of each rainfall partition and transpiration (and their percentages) were compared. The rainfall partitions in the monoculture forest differed from those in the mixed forest. While, on average, the annual percentages of the throughfall, stemflow and crown interception in the monoculture forest were 63%, 6% and 31%, respectively, these partitions in the mixed forest were 76%, 2% and 22%, respectively. The crown interception was greater in the monoculture (31% of precipitation) and the effective precipitation (i.e., the sum of throughfall and stemflow) was greater in the mixed forest (78% of precipitation). The greatest differences (in each rainfall partition) between the monoculture and mixed forest were in the summer and winter. The throughfall was greater in the mixed forest (ca. 22% in the summer and ca. 12% in the winter), and the stemflow was greater in the monoculture forest (ca. 66% in the summer and ca. 51% in the winter). The mean annual transpiration was 318 (±52) mm in the monoculture and 451 (±58) mm in the mixed forest, i.e., about 99 (±65) mm more in the mixed forest than in the monoculture forest. The transpiration, in comparison with the effective precipitation, made up, on average, 70% of the effective precipitation in the monoculture forest. On the other hand, the transpiration reached 71% (in 2019), 74% (in 2020) and even 100% (in 2021) of the effective precipitation in the mixed forest. Our results show that an oak–beech–linden mixed forest can manage water better than a beech monoculture because more precipitation leaked through the mixed forest onto the soil than through the monoculture, especially via the throughfall in the summer. On the other hand, the amount of water that transpired was greater in the mixed forest than in the monoculture. However, the utilisation of the effective precipitation by trees was very similar in the monoculture in all three years, while, in the mixed forest, the utilisation of the effective water by trees increased, which may have been caused by the saturation of the deeper soil layers with water in the first two years of measurement. We can, Therefore, say that, at lower altitudes, it will be more suitable in the future to cultivate beech in mixed forests because of the assumed lack of water (mainly in early spring and summer).

Callampas of disaster: negotiations and struggles for the commons under forestry hegemony in Chile

Abstract The massive planting of exotic species under the so-called forestry model has dramatically transformed the landscapes of south-central Chile, replacing diverse agricultural, livestock and forest landscapes with forest monocultures, which are highly water-consuming and prone to massive fires. This has meant a productive simplification, and peasant communities have been displaced and stripped of their traditional ways of life. However, in this landscape of disaster, biotic communities of fungi have flourished, and with them human communities of collectors have learned to sustain themselves in a monocultural and privatized scenario. This paper is based on a multi-local ethnographic approach, built upon 26 semi-structured interviews, participant observation, social mapping, creating a calendar and a trend line. The text documents the processes of two communities affected by massive fires which have developed organization, agencies and practices. Mushrooms (callampas in Chilean Spanish) are claimed as a common good derived from the forestry model, claiming access to their use and usufruct of land belonging to forestry companies. They have also developed local governance systems for the care and better use of this new resource for common use. Forestry companies, for their part, try to subsume these practices in their territorial governance processes, disputing these commons’ meaning and purpose. Both cases contribute to empirically address the central thesis of this article, according to which communalization exercises within contexts of capitalist expansion constitute responses of survival, resistance and adaptation in landscapes transformed and devastated by extractivist industries.

Effects of climatic and edaphic conditions on structuring patterns of soil nematode communities in Japanese cedar (Cryptomeria japonica) plantations

Strong associations exist between organism and soil functions in forest ecosystems at large spatial scales; however, it is unclear the community patterns of soil nematodes. Artificial monoculture forests with poor understory vegetation would provide an ideal model system to characterize the relationship between nematode community structures and local habitat conditions. This study aimed to understand how climate and soil properties influence the community structure of soil nematodes in artificial Japanese cedar (Cryptomeria japonica) plantations. The richness, abundance, and community structure of the nematodes were assessed using soils (20 cm in depth) collected from eight 1 ha C. japonica plantations (40–60 years), which were distributed between 24°N and 42°N, with cool temperate, temperate, and subtropical zones in summer. The soil nematode aggregates were identified using a high throughput sequencing of the MiSeq system. The richness of amplicon sequence variances of nematodes revealed a significant unimodal pattern with latitude, with the greatest richness observed at 33°N. In contrast, nematode abundance showed a significant U-shaped pattern with latitude and was lower at mid-latitudes. Nematode community structures in subtropical zones clearly differed from those in the temperate and cool temperate zones. Among the environmental factors measured, mean annual temperature, soil pH, and C content accounted for the greatest variations in nematode communities. These results indicate that nematode richness and abundance displayed opposite patterns along latitudinal gradients. Moreover, the interrelationship between climate and soil conditions was identified as the best predictor of the community structure of soil nematodes in the monocultural C. japonica forest ecosystems. This study provided a useful view of belowground biodiversity for evaluating forest health in Asian coniferous plantations.

Influence of landscape composition on wild bee communities: Effects of functional landscape heterogeneity

Landscapes dominated by conventional agriculture reduce and simplify natural habitats, with negative consequences for ecosystem regulating services. We examined differences in structure and composition of bee communities across biotic and abiotic gradients to investigate how these communities respond to land-use changes associated with agriculture. Studies like ours which evaluates the relative effect of different components of spatial heterogeneity remain uncommon and are important to conserve pollinator fauna. The diversity of floral resources and habitat richness including the configuration and composition of landscape heterogeneity have been shown to influence the diversity of wild bees on a landscape scale. In this study, we examined how wild bee communities respond to landscape heterogeneity in a semi-arid productive region of Entre Ríos Argentina. We modeled the effect of landscape heterogeneity on wild bee community abundance, species richness, and Chao-1 diversity. We sampled bees using pan traps in four common land-uses in the region (forest plantations, pasture/croplands, mixed use areas and native espinal savanna) for five months in the spring-summer of 2014–2015. We identified 96 bee species among 3407 bees collected in the four habitat types. Pasture/croplands along with native espinal savanna supported the highest abundance, richness, and diversity of bees. Species composition of wild bee communities differed between land uses, with numerous species unique to each land use. Across all land use types, diversity of flower resources consistently supported more abundant and diverse wild bee communities. The richness of habitats along with the diversity of floral resources acted synergistically over wild bee communities. Our findings further clarify the relationship between land-use and wild bee communities, which provide valuable pollination services to crops and native plants. Continued expansion of large-scale monoculture forest plantations will likely come at the expense of the native floral resources, which are a key component to support regional bee species richness. Promoting landscapes with a diversity of crops and flower resources are important for the conservation of pollinators that are key for the functioning of ecosystems.

The effect of tree species on soil organic carbon recovery in a restoration project is associated with vegetation biomass: Evidence from the Pingshuo Mine reclaimed ecosystem, North China

AbstractVegetation and soil surveys were made within three mixed forests and four monoculture forests on opencast coal mine spoils in the Loess Plateau (China) to reveal the tree species effect on reclaimed mine soil (RMS) and carbon (C) sequestration. Results showed that tree biomass, annual litter biomass, and reserved litter biomass varied among forests, with Robinia pseudoacacia L.‐Pinus tabuliformis Carr. recording the highest tree biomass, leaf C, and leaf nitrogen (N) values. The greatest C and N contents in RMS were recorded in the R. pseudoacacia ‐ P. tabuliformis forest in both small macroaggregate (250–2000 μm) and large macroaggregate (>2000 μm) fractions. However, no significant differences among forests were observed in microaggregate (53–250 μm) and silt+clay (<53 μm) associate C and N. Significant positive correlations were observed among soil C and vegetation biomass and vegetation biomass associated C. It was in line with the C isotope analysis, which indicated that C flowed in the order: leaf→litter/root→soil macroaggregate→soil microaggregate/silt+clay. Moreover, negative correlations between soil C and soil δ15N in large and small macroaggregate fraction were recorded, indicating C sequestration in macroaggregate was potentially associated with soil N cycling. Overall, Tree species effect on soil C sequestration was derived from the amount and quality of the vegetation biomass and it was mediated by soil N cycling to some extent. R. pseudoacacia ‐ and P. tabuliformis mixed forest could be proposed as a favourable reclamation choice, due to these species prominent C sequestration ability.

Quantifying effects on tree growth rates of symmetric and asymmetric inter-tree competition in even-aged, monoculture Eucalyptus pilularis forests

Key messageIn even-aged, monoculture eucalypt forest, symmetric inter-tree competition was far more important in determining tree growth rates than asymmetric competition. Tree size principally determined competitive ability at any time.In even-aged, monoculture forests, individual tree growth rates are much affected by the amount of the resources required for growth (particularly light, water and nutrients) that are available to them from the site on which they are growing. In turn, those amounts are much affected by competition for them between neighbouring trees. Competition may be ‘symmetric’, when tree growth rates are directly proportional to tree sizes, or ‘asymmetric’ when growth rates vary disproportionately with tree sizes. Using a large data set from blackbutt (Eucalyptus pilularis Smith) forests of sub-tropical eastern Australia, methods were devised to quantify the effects of symmetric and asymmetric competition; they were determined as the change each causes in individual tree growth rates over growth periods of a few years. It was found that symmetric competition was by far the principal determinant of tree growth rates. Asymmetric competition had much lesser effects, but was sufficient to alter substantially the development with age of the frequency distribution of tree sizes. It is concluded that the size of a tree at any time is the principal determinant of both its metabolic capabilities for growth and its competitive status and, hence, its growth rate.

Home is where the heat is: Thermoregulation of European bats inhabiting artificial roosts and the threat of heat waves

Abstract Anthropogenic land use changes, such as deforestation and commercial forestry, have substantially reduced natural roost sites for European bats. A common conservation solution is to provide artificial roosts (i.e. bat boxes), but there are concerns that these can become hotter than natural roosts in summer and could be death traps during heat waves. Nevertheless, females of several bat species form maternity colonies in these boxes, thus occupying hotter and more humid microclimates than solitarily roosting males. We tested if cooling efficiency and heat tolerance differ between sexes in European bats, and estimated the evaporative water requirements for bats living in bat boxes during hot summer days. We used indirect calorimetry and thermometry to quantify thermoregulation at high air temperatures (Ta) in four species of verspitilionid bats that regularly occupy artificial roosts. We measured resting metabolic heat production, evaporative water loss rates (EWL) and body temperature (Tb) at Ta between 28°C and 48°C during summer. We predicted that females have higher evaporative cooling efficiency (evaporative heat loss/metabolic heat production) than males, allowing them to reach their heat tolerance limit at higher Ta. We found no sex differences in maximum evaporative cooling efficiency, maximum Tb, and maximum Ta tolerated. However, the patterns of increasing EWL with Ta differed between sexes. Females tolerated higher Ta before increasing EWL than males and then rapidly increased EWL to higher values than males at the maximum Ta tolerated. These sex differences in heat dissipation strategies may reflect varying ecological and physiological constraints associated with different summer roosting habits. Synthesis and applications. Our study revealed that some small European bat species are already at risk of succumbing to lethal dehydration during present‐day heat waves, with daytime evaporative water requirements equivalent to ~30% of body mass in sun‐exposed boxes. For conservation managers working with common European bat species, particularly those in monoculture forests with woodcrete bat‐boxes, our physiologically informed recommendations include positioning boxes in diverse locations varying in aspect and sun exposure. This will ensure thermal heterogeneity of roost sites and provide a wide gradient of microclimate conditions, allowing for roost switching when necessary.

Models Relating Individual Tree Basal Area Growth Rates to Tree Basal Areas in Even-Aged, Monoculture Forest Stands

As trees grow larger in even-aged, monoculture forests, stand density increases, taller trees shade smaller trees and a group of smaller, suppressed trees develops that may show little or no growth. Subsequent mortality is most common from this group. This work compares three models that may describe well the relationship between individual tree basal area growth rates and tree basal areas in a forest stand when a suppressed group of trees is present or not. The models are tested using a large collection of data from permanent sample plots in blackbutt (Eucalyptus pilularis Smith) forests in subtropical eastern Australia. An example is given for one stand showing how model parameter values may change as the stand ages; this illustrates how these models have potential for use in the first stage of model development to relate individual tree growth rates to tree sizes and stand characteristics. Such models may then be used widely across the forest population under consideration.

Effects of Pine Forest Management Practices on Bat Functional Traits in a Subtropical Region

Changes in landscape environmental characteristics may influence habitat use by bat species as well as species composition and community functional structure. Landscape features may drive the functional role variability of bat species on the ecosystems. Consequently, landscapes may change the degree of functional differentiation between species. We have evaluated the effect of pine forest monoculture and their environmental characteristics on the distribution and functional attributes of bat species. We sampled bat communities in areas with high (three sites) and low (three sites) forest land use management practices including six mist-netting locations in order to sample for bats at each site. In addition, we have also measured temperature, humidity, percentage of land use coverage (managed forest, agriculture, and native forest), and percentage of canopy openness at each site. We captured 87 bats belonging to eight species representing two families: Phyllostomidae and Vespertilionidae. For the functional analysis, we used three functional attributes to describe wing morphology: wing loading, aspect ratio, and forearm length. No significant effect of any environmental variable was observed on bat species composition. However, bat species distribution was driven by the ability associated with their functional attributes to occupy the space. Moreover, forearm length was positively correlated with forest cover, canopy openness, and humidity. Species with similar wing morphology have responded in a similar way to environmental variables in the studied areas. Functional dispersion was high in the native forest. The monoculture of exotic species may increase the functional attributes related with vulnerability as described by bat wing morphology. Therefore, the native forest conversion to pine forest monoculture may increase the loss of functional attributes in the bat community.

Mixed plantations enhance more soil organic carbon stocks than monocultures across China: Implication for optimizing afforestation/reforestation strategies

Forests play an essential role in mitigating climate change by sequestering carbon dioxide from the atmosphere. The establishment of mixed plantations is a promising way to store carbon (C) in soil compared with monocultures. However, monoculture forests largely dominate the rapid increase in forest areas in China. To optimize afforestation strategies and maximize the subsequent potential of C sequestration, we conducted a meta-analysis with 427 observations across 176 study sites in China. The goal was to quantify changes in the stocks of soil organic carbon (SOC) in mixed plantations compared with monocultures and to identify the predominant drivers for the stocks of SOC, including geological location, climatic factors, land use history, edaphic properties, plantation age, the inclusion of nitrogen-fixing trees, mixing proportion, and mixed plant types. The results showed that mixed plantations significantly increased the SOC stocks by 12% compared with monocultures, and the mixing proportion should not exceed 55% to produce higher SOC stocks in mixed plantations compared with monoculture. Additionally, mixed plantations in barren land are the most likely to increase the SOC stocks with limited water or low temperatures for growth. Additional measures instead of mixed plantations should be explored to increase SOC stocks in north, central, and northwest China. The data from this study demonstrated the spatiotemporal variability on the storage of SOC driven by mixed trees and has valuable implications for the establishment and management of afforestation.

Reclaimed Mine Sites: Forests and Plant Diversity

The relationship between vegetation and selected soil characteristics in different monoculture forest types was investigated as part of a landscape restoration project after brown coal mining. Six forest types were selected: alder (Alnus sp.), spruce (Picea sp.), pine (Pinus sp.), larch (Larix sp.), long-term deciduous forest (Quercus robur, Tilia sp.), and forest created by spontaneous succession. These stands were classified into two age categories (younger and older). The soil attributes, C/N, TC, TN, pH, and A horizon depth were assessed. The observed species were categorized into functional groups by life history, life forms according to Raunkiær, and affinity to the forest environment. C/N ratio, humus thickness, and canopy cover were the main soil parameters affecting plant communities. The highest C/N values were recorded in Pinus and Larix stands, which were significantly different from deciduous and succession stands. The highest diversity index was noted in younger stands of Alnus and the lowest in younger stands of Picea. Intermediate values of the diversity index were achieved in successional stands at both age levels and in Larix and Alnus stands. The species belonging to a functional group was not an important factor in these habitat types. The species composition and vegetation change over time in the Alnus, long-life deciduous, and Larix stands show that these species are more suitable for forestry reclamation than spruce or pine. The study also emphasizes the great value of spontaneous succession areas as full-fledged alternatives to forestry reclamation.

Intensive plantations decouple fine root C:N:P in subtropical forests

Fine roots play key roles in carbon and nutrient cycling in terrestrial ecosystems. Despite the global conversion of natural forests to tree plantations, a quantitative evaluation of the dynamics of fine root nutrients and C:N:P stoichiometry in plantations and natural forests is lacking. This study examined the fine root elemental concentrations and C:N:P stoichiometry of Chinese fir plantations and natural secondary forests (5–41 years old), employing primary forests as a reference. Live fine root C, N, P and K concentrations did not differ with forest types, but live fine roots had lower Ca and Mg concentrations in plantations than natural secondary and primary forests. Dead roots contained higher N, P, and Mg in plantations than in natural forests. Live and dead fine root elemental concentrations and C:N:P stoichiometry did not change with stand age, except for a decrease in dead root Ca and Mg concentrations in 19–31-year-old stands. Live root C:N, C:P, and N:P ratios did not differ between forest types; however, dead root C:N, C:P, and N:P ratios were higher in natural forests than in plantations. Our findings suggest that intensively managed forest monoculture plantations have a negative impact on the resorption proficiency of fine root nutrients and decouple the C:N:P of fine roots in subtropical forests. We recommend reducing fertilization and increasing plant diversity in plantations to optimize the C:N:P of plants.

Chemodiversity of Soil Dissolved Organic Matter and Its Association With Soil Microbial Communities Along a Chronosequence of Chinese Fir Monoculture Plantations.

The total dissolved organic matter (DOM) content of soil changes after vegetation transformation, but the diversity of the underlying chemical composition has not been explored in detail. Characterizing the molecular diversity of DOM and its fate enables a better understanding of the soil quality of monoculture forest plantations. This study characterized the chemodiversity of soil DOM, assessed the variation of the soil microbial community composition, and identified specific linkages between DOM molecules and microbial community composition in soil samples from a 100-year chronosequence of Chinese fir monoculture plantations. With increasing plantation age, soil total carbon and dissolved organic carbon first decreased and then increased, while soil nutrients, such as available potassium and phosphorus and total nitrogen, potassium, and phosphorus, increased significantly. Lignin/carboxylic-rich alicyclic molecule (CRAM)-like structures accounted for the largest proportion of DOM, while aliphatic/proteins and carbohydrates showed a decreasing trend along the chronosequence. DOM high in H/C (such as lipids and aliphatic/proteins) degraded preferentially, while low-H/C DOM (such as lignin/CRAM-like structures and tannins) showed recalcitrance during stand development. Soil bacterial richness and diversity increased significantly as stand age increased, while soil fungal diversity tended to increase during early stand development and then decrease. The soil microbial community had a complex connectivity and strong interaction with DOM during stand development. Most bacterial phyla, such as Acidobacteria, Chloroflexi, and Firmicutes, were very significantly and positively correlated with DOM molecules. However, Verrucomicrobia and almost all fungi, such as Basidiomycota and Ascomycota, were significantly negatively correlated with DOM molecules. Overall, the community of soil microorganisms interacted closely with the compositional variability of DOM in the monoculture plantations investigated, both by producing and consuming DOM. This suggests that DOM is not intrinsically recalcitrant but instead persists in soils as a result of simultaneous consumption, transformation, and formation by soil microorganisms with extended stand ages of Chinese fir plantations.

Problems with models assessing influences of tree size and inter-tree competitive processes on individual tree growth: a cautionary tale

In forest growing at any one site, the growth rate of an individual tree is determined principally by its size, which reflects its metabolic capacity, and by competition from neighboring trees. Competitive effects of a tree may be proportional to its size; such competition is termed ‘symmetric’ and generally involves competition below ground for nutrients and water from the soil. Competition may also be ‘asymmetric’, where its effects are disproportionate to the size of the tree; this generally involves competition above ground for sunlight, when larger trees shade smaller, but the reverse cannot occur. This work examines three model systems often seen as exemplars relating individual tree growth rates to tree size and both competitive processes. Data of tree stem basal area growth rates in plots of even-aged, monoculture forest of blackbutt (Eucalyptus pilularis Smith) growing in sub-tropical eastern Australia were used to test these systems. It was found that none could distinguish between size and competitive effects at any time in any one stand and, thus, allow quantification of the contribution of each to explaining tree growth rates. They were prevented from doing so both by collinearity between the terms used to describe each of the effects and technical problems involved in the use of nonlinear least-squares regression to fit the models to any one data set. It is concluded that quite new approaches need to be devised if the effects on tree growth of tree size and competitive processes are to be quantified and modelled successfully.

Early detection of bark beetle infestation in Norway spruce forests of Central Europe using Sentinel-2

In the past decade, massive outbreaks of bark beetles (Ips spp.) have caused large-scale decline of coniferous-dominated, prevailingly managed forests of Central Europe. Timely detection of newly infested trees is important for minimizing economic losses and effectively planning forest management activities to stop or at least slow outbreaks. With the advancement of Copernicus services, a pair of Sentinel-2 satellites provides a unique remote sensing data source of multi-temporal observations in high spatial resolution on the scale of individual forest stands (although not allowing for individual tree detection). This study investigates the potential for using seasonal trajectories of Sentinel-2 bands and selected vegetation indices in early detection of bark beetle infestation (so–called green-attack stage detection) in Norway spruce monoculture forests in the Czech Republic. Spectral trajectories of nine bands and six vegetation indices were constructed for the 2018 vegetation season using 14 satellite observations from April to November to distinguish four infestation classes. We used a random forest algorithm to classify healthy (i.e., stands not infested) and infested trees with various trajectories of decay. The seasonal trajectories of vegetation indices separated the infestation classes better than did the individual bands. Among the most promising vegetation indices we identified the tasselled cap wetness (TCW) component and normalized difference index constructed from near and shortwave infrared bands. Analysing the inter-annual change of the indices was more promising for early detection than is single-date classification. It achieved 96% classification accuracy on day of year 291 for the tested data set.The algorithm for early detection of tree infestation based on the assessment of seasonal changes in TCW was applied on the time series of Sentinel-2 observations from 2019 and its outputs were verified using field observations of forest conditions conducted on 80 spruce forest plots (located in spruce monoculture stands). The overall accuracy of 78% was achieved for the separation of healthy and green-attack classes. Our study highlights the great potential of multi-temporal remote sensing and the use of shortwave infrared wavelengths for early detection of spruce forest decline caused by bark beetle infestation.