Successful Sequencing Research Articles

Effects of plant nutrient acquisition strategies on biomass allocation patterns in wetlands along successional sequences in the semi-arid upper Yellow River basin.

The ecological environment of wetlands in semi-arid regions has deteriorated, and vegetation succession has accelerated due to climate warming-induced aridification and human interference. The nutrient acquisition strategies and biomass allocation patterns reflect plant growth strategies in response to environmental changes. However, the impact of nutrient acquisition strategies on biomass allocation in successional vegetation remains unclear. We investigated 87 plant communities from 13 wetland sites in the semi-arid upper Yellow River basin. These communities were divided into three successional sequences: the herbaceous community (HC), the herbaceous-shrub mixed community (HSC), and the shrub community (SC). The nutrient composition of stems and leaves, as well as the biomass distribution above and belowground, were investigated. Results revealed that aboveground biomass increased with succession while belowground biomass decreased. Specifically, SC exhibited the highest stem biomass of 1,194.53 g m-2, while HC had the highest belowground biomass of 2,054.37 g m-2. Additionally, significant positive correlations were observed between leaf and stem biomasses in both HC and SC. The nitrogen (N) and phosphorus (P) contents within aboveground parts displayed an evident upward trend along the succession sequence. The highest N and P contents were found in SC, followed by HSC, and the lowest in HC. Stem N was negatively correlated with stem, leaf, and belowground biomass but positively correlated with root-shoot ratio. Leaf P displayed positive correlations with aboveground biomass while showing negative correlations with belowground biomass and root-shoot ratio. The ratios of C:N, C:P, and N:P in stem and leaf exhibited positive correlations with belowground biomass. The random forest model further demonstrated that stem N and leaf P exerted significant effects on aboveground biomass, while leaf P, stem N and P, and leaf C:P ratio had significant effects on belowground components. Additionally, the root-shoot ratio was significantly influenced by leaf P, leaf C:P ratio, and stem N, P, and C:P ratio. Therefore, the aboveground and belowground biomasses exhibited asynchronism across successional sequences, while plant nutrient acquisition strategies, involving nutrient levels and stoichiometric ratios, determined the biomass allocation pattern. This study offers valuable insights for assessing vegetation adaptability and formulating restoration plans in the semi-arid upper Yellow River basin.

Rate of permafrost thaw and associated plant community dynamics in peatlands of northwestern Canada

Abstract The most rapid climate warming is occurring in northern, permafrost environments. Peatlands of these regions are particularly sensitive to climate warming, with the high ground ice content of peat plateaux resulting in the formation of collapse scars as ground temperatures warm. To quantify the rates of permafrost thaw and associated vegetation changes, we sampled the plant and lichen communities in transects spanning actively thawing collapse scar margins at sites from mid‐Boreal to Low Subarctic conditions, within Canada's Northwest Territories. Seventeen transects were sampled in 2007/08 and 14 of these were resampled 10 years later. The rate of lateral permafrost thaw of collapse scar margins ranged from −6 to 63 cm year−1 (mean: 22.0 cm ± 4.7 cm year−1 (SE)); variability was high and no trends with respect to latitude or temperature gradients were detected. Plant communities displayed a clear gradient from lichen‐ and ericaceous shrub‐dominated peat plateaux, to collapse scars primarily characterized by Sphagnum mosses and graminoids. Both space‐for‐time (distance from collapsing margin) and direct measurement of 10‐year changes showed a successional sequence following permafrost thaw; floating mat communities characterized by Sphagnum riparium or S. balticum proceeded to lawn communities of S. angustifolium and, finally, to hummock communities with Mylia anomala or S. fuscum. This successional sequence was associated with increased water table depth and lower soil water content in plant communities farther from the actively collapsing front, illustrating that peat growth above the water table was driving plant community successional changes. The most rapid plant community succession occurred in recently thawed environments as peat growth propelled the ground surface above the water table while the slowest succession occurred in the collapse scar hummock communities located farthest from the actively collapsing peat plateau margin. Synthesis. In just 10 years, significant vegetation change was detected, in association with both permafrost thaw and subsequent plant community succession. These changes occurred across a broad climatic and latitudinal gradient, from mid‐Boreal to Low Subarctic and have implications for wildlife, global C cycle and indigenous communities who depend on this landscape for harvesting, spiritual and cultural practices.

The Impact of Long-Term Mulched Drip Irrigation on Soil Particle Composition and Salinity in Arid Northwest China

The evaluation of soil particle composition and salt dynamics is essential for promoting the sustainable development of oasis agriculture in arid regions under long-term mulched drip irrigation (MDI). In this study, we employed the space-for-time substitution method to investigate the long-term effects of MDI on soil particle composition and salinity. Additionally, seven fields, with MDI durations ranging from 0 to 16 years, were selected to represent the primary successional sequence though time in Northwest China. Soil samples were collected from three soil depths (0–30 cm, 30–60 cm, and 60–100 cm) and then analyzed in the laboratory for soil particle composition and salt content. Our findings demonstrated that influenced by the depth of mechanical cultivation and the maximum wetting front depth, the long-term application of MDI significantly altered both the structure of soil layers and the composition of soil particles after 8 years. Soil sand content and soil salinity gradually decreased, whereas the content of soil silt and clay increased with increasing MDI duration throughout 0–100 cm soil depth. Furthermore, the rates of soil desalination stabilized after 10 years of MDI application, with desalination levels exceeding 90% in the 0–100 cm soil layer. Additionally, the soil mass fractal dimension (Dm) exhibited an upward trend across 0–100 cm soil depth. The changes in soil particle composition indirectly influenced the variations in Dm and salt content. Our study demonstrated that long-term application of MDI effectively mitigated soil salinity, changed soil structure, and ultimately enhanced soil quality and cotton yield.

Clonal propagation, scale dependent assembly, and nucleation drives natural regeneration in a restinga sandy coastal plain

AbstractOn the sandy coastal plains, environmental filters that limit seedling establishment and survival create a naturally heterogeneous landscape, formed by vegetation patches inserted in a matrix of bare sandy soil. The succession processes in these ecosystems depend on some pioneer species that facilitate the recruitment and survival of other species. Here, we evaluated the spatial pattern and changes of vegetation patches of restinga (i.e., coastal sandy plain vegetation) over one decade (2011–2021). The research was carried out in Alagoas State, Northeast of Brazil. We considered as patches the vegetation islands inserted in a matrix of bare sandy soil and applied methodologies of photointerpretation. Landscape metrics included patch area, edge, shape, and core area. To test the effect of landscape metrics on species occurrence and species richness per patch, we applied generalized linear models (GLM) with binomial and quasi‐Poisson distributions, respectively. We used the “betapart” package to evaluate the importance of turnover and nestedness as drivers of beta diversity among patches. Our data indicate that a key plant (Myrciaria floribunda), which can propagate by root suckers, initiates a succession process, creating regeneration nuclei, which seem to follow a deterministic succession pattern until the patch reaches 10 m2 in area. In the successional sequence, the patches grow and coalesce with neighboring patches. Species richness of patches presented an unimodal response to patch size. Overall, there is a greater contribution of species turnover to among‐patch beta diversity. However, for patches smaller than 10 m2, beta diversity was mostly driven by nestedness, reflecting a process of species addition to the growing patches. The succession pattern found in the study area should be considered for the formulation of nature‐based restoration models, expected to be more efficient and effective for ecosystems with similar environmental filters.

Differences in soil chemistry between early and late succession of oak-hornbeam forest after grassland abandonment

Changes in C and nutrient cycling during succession are well studied, however, results can be contrasting for different nutrients and successional sequences. We analyzed soil chemical differences between early and late succession of oak-hornbeam forest. Late forest succession efficiently retained plant-available P, and total Mn, Zn, Fe, Cu, and Ni pools in the soil, as their concentrations were similar to those of early-successional grasslands. Available K, soil organic C, and organic matter content, as well as C:N and C:S ratios were higher in late than in early succession. Soil organic N and S concentrations did not differ between the stages.

Dynamics in eukaryotic algal communities regulate bacterial and fungal communities as biocrusts develop in a temperate desert in Central Asia

Abstract Eukaryotic algae, as the primary group of photosynthetic autotrophs, exert a significant influence on the development and functions of biological crusts in dryland ecosystems. Despite their importance, there are substantial knowledge gaps on the composition of eukaryotic algal communities and their effects on the distributions of bacteria and fungi in dryland soils. This study examined the eukaryotic algal community along a successional sequence of biocrusts in the Gurbantunggut desert, while also investigating their patterns of co‐occurrence with bacteria and fungi through high‐throughput sequencing and bioinformatic analyses. The results showed that nitrogen and phosphorus levels played a crucial role in the regulation of changes in the abundance and composition of the algal community. In particular, changes in the structure of the algal community arise primarily from fluctuations in the main species, rather than from loss and appearance of species during the biocrust succession. The accumulation of nitrogen and phosphorus in the biocrust was associated with the decrease in the relative abundance of Chlorophyta. The results also indicated that eukaryotic algae played an important role in the affecting bacterial and fungal communities and significantly improved the stability of the microbial community, reflected by the robustness of co‐occurrence networks. The network analysis further indicated that eukaryotic algae affected the stability of microbial co‐occurrence networks either by acting as keystone taxa or associating with the keystone bacterial and fungal taxa. These findings reveal a clear mechanism by which soil nitrogen and phosphorus levels affected the composition of eukaryotic algae communities and further regulated bacterial and fungal communities during biocrust development, providing valuable information on the development and functional execution of biocrusts in dryland ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

Quantitative Characteristics and Environmental Interpretation of Vegetation Restoration in Burned Areas of the Dry Valleys of Southwest China

Fire is a common natural disturbance in forest ecosystems and plays an important role in subsequent vegetation patterns. Based on the spatial sequence method, adopted as an alternative to the time successional sequence method, we selected burned areas in different locations in the Anning River Basin, which encompasses typical dry valleys. Quadrat surveys and quantitative classification were used to identify and classify the vegetation and distribution pattern and to carry out environmental interpretation during the natural restoration process after a forest fire. The results showed the following: (1) in the early stage of natural recovery after a forest fire disturbance, the vegetation community could be divided into seven community types, and Quercus guyavaefolia H. Leveille (Qg) was the dominant species in the community; (2) the vegetation samples could be divided into five ecological types, and the classification and distribution pattern of community types in this region changed most notably with altitude; and (3) a detrended correspondence analysis could be used to accurately classify vegetation community types, while a detrended canonical correspondence analysis could reveal the relationships between species and environmental factors. This study provides a scientific basis for guiding the restoration of ecosystem structural stability and biodiversity in burned areas.

An Epifaunal Community Succession Sequence Driven by the Biogeochemical Footprint With Different Methane Seepage Intensity of the Deep Seafloor

AbstractMethane seepage, generated from natural processes or gas hydrate dissociation, drives the development of cold seep ecosystems and leads to atmosphere methane emission, thereby influencing climate change. Uncovering the intrinsic interactions among methane seepage intensities, biogeochemical processes in the sediment, and benthic community characteristics at the seafloor is essential to clarify and predict the ultimate fate of methane leakage from the deep sea. Here, we conducted a systematic investigation of methane intensity, pore fluid migration characteristics, sediment mineral fraction features, and the evolution of biological communities in areas with different methane intensities. Furthermore, analyses of high‐resolution images, pore fluid geochemical feature, and lithologic characteristics of the sediment in the Haima cold seep were also carried out in this study. The results showed that, in areas with different methane intensities, organic matter sulfate reduction and anaerobic oxidation of methane were heterogeneous. The heterogeneity led to the methane transformation zones at different depths, which changed the mineral composition of the sediment and biological communities in the seabed. In addition, a hypothesis of successional sequence of biomes in cold seep was established. This study revealed that the methane seepage intensity was a key factor in determining the biogeochemical process in the sediment of cold seep. The coupling effects of biogeochemical processes and methane seepage intensities dominated the community succession of cold seep. These findings could provide important implications for understanding the dynamic deep marine methane cycle mechanism and the contribution of deep‐sea methane released to climate change.

Echoes of the past: Agricultural legacies shape the successional dynamics of protected semi-natural dry grasslands

European semi-natural dry grasslands are among the most endangered terrestrial ecosystems, being recognised as habitats of community interest by the EU Habitats Directive. The occurrence and preservation of these habitats depend on a combination of anthropogenic and natural factors, although little is known regarding the role of past land-use changes. Here, we investigated the role of time since cultivation abandonment as a major driver of grassland successional dynamics in the Mediterranean agro-pastoral system of Alta Murgia, southern Italy. By integrating cartographic information on the past agricultural land-use with the main abiotic constraints (patch area, slope and aspect), we used generalised additive mixed models to test for the probability of occurrence of current grassland habitat types along time since cultivation abandonment (10 to 200 years). Our results disclosed the successional sequence of grassland plant communities since crop abandonment in the study area, highlighting that the distribution of semi-natural grassland communities largely depends on land use history besides current environmental patterns. Among the habitat types protected under the EU Habitats Directive, we highlighted that xero-thermic communities may represent an intermediate step of grassland succession after cultivation abandonment, while more mesic perennial communities indicate a late successional stage. These successional dynamics are further modulated by mesoclimatic conditions associated with slope and aspect, especially in case of long-standing pastures that were not historically affected by agricultural transformations. Our findings can contribute to a deeper understanding of dynamics relevant to spontaneous vegetation recovery in open environments, which is a prerequisite for setting up effective grassland conservation and restoration actions. Furthermore, our results underline the value of integrating historical maps and current information for the assessment of habitat conservation status.

Trait driven or neutral: understanding the change in functional trait diversity during early plant succession using Price partitions

Habitat filtering, species interactions and neutral colonization as well as extinction dynamics govern the sequence of community assembly and functional diversity (FD) during primary plant succession. To study the factors that influence changes in FD we here use data on plant seed size, seed numbers and specific leaf area from 107 study plots along a 7 year sequence of primary succession (2005–2011) in a 6 ha German artificial catchment. We show that the temporal variability in functional diversity can be partitioned into the effects of trait expression, species richness and plant cover. We observed a dominant role of species richness and community composition on FD. Trade-offs in the influence of species richness and plant cover tended to decrease the change in FD. Average FD steadily increased during the first 4 years of succession (2005–2008). The degree of annual changes in FD were highly plot specific. Average change in FD was comparatively low during the first 4 years and later high. Soil characteristics and light conditions did not significantly influence the detectable change in functional diversity. We conclude that the high plot-specific spatial variability of the annual changes in FD transformed the initially catchment-wide homogeneous distribution of plant species into a mosaic of very different local plant communities. Our partitioning results also indicate that the successional sequences in FD are in accordance with a hidden Markov series.

Soil enzyme activities and microbial nutrient limitation during the secondary succession of boreal forests

Extracellular enzymes are the proximate agents of organic matter decomposition, and its activity can be used as an indicator of microbial nutrient demand. The secondary succession of ecosystem will change the soil properties and microbial community structure, which will affect the nutrient cycle and stability of the ecosystem. However, the research on the changes of soil enzymes during the succession in the boreal forest ecosystems is still lack of insight. Using the method of ‘space-for-time substitution’, we selected four habitats (including grassland, Betula platyphylla forest, Larix gmelinii and Betula platyphylla mixed forest and Larix gmelinii forest) in Greater Khingan Mountains northeastern China to represent the secondary successional sequence of boreal forests, and studied the response mechanism of soil enzyme activities and microbial nutrient limitation to secondary succession of ecosystem after burning. The results showed that during the succession, phosphorus (P) limitation gradually weakened, nitrogen (N) limitation gradually strengthened, and the ratio of carbon (C): N: P of soil enzymes gradually tended to 1: 1: 1. With the progress of succession, C (BG, β-1,4-glucosidase; CBH, β-D-cellobiosidase), N (NAG, β-1,4-N-acetylglucosaminidase; LAP, L-leucine aminopeptidase) related enzyme activity increased and P (AP, acid phosphatase) related enzyme activity did not change significantly. During the secondary succession of ecosystem after burning, the soil microbial community maintains homeostasis, and the nutrient limitation of microorganisms largely depends on the content and stoichiometry of soil nutrients.

Local-scale changes in plant community composition following succession of oak- hornbeam forest after grassland abandonment

In this local-scale synecological study, we investigated the changes in plant community composition throughout secondary succession occurring after cessation of agricultural land use (i.e. grassland abandonment). The successional sequence studied had the following pathway: Avenula pubescens (Huds.) Dumort. haypastures → Brachypodium pinnatum (L.) P.Beauv. successional grassland → Cornus sanguinea L. scrubs → late-successional Populus tremula L. forest → late-successional oak-hornbeam (Quercus-Carpinus) forest. The last forest stage was represented by the association Epimedio-Carpinetum betuli (Horvat 1938) Borhidi 1963. Occurrence of plant species throughout secondary succession was mostly stage-specific; only Fragaria vesca L., Ajuga reptans L., Cornus sanguinea, Prunus spinosa L., and Viola hirta L. showed survival ability throughout almost all stages.

Variations in the soil micro-food web structure and its relationship with soil C and N mineralization during secondary succession of subalpine forests

The soil micro-food web is an important network of belowground trophic relationships and it participates directly and indirectly in soil ecological processes. In recent decades, the roles of the soil micro-food web in regulating ecosystem functions in grasslands and agroecosystems have received much attention. However, the variations in the soil micro-food web structure and its relationship with ecosystem functions during forest secondary succession remain unclear. In this study, we investigated how forest secondary succession affected the soil micro-food web (including soil microbes and nematodes) and soil carbon and nitrogen mineralization across a successional sequence of “grasslands – shrublands – broadleaf forests – coniferous forests” in a subalpine region of southwestern China. With forest successional development, the total soil microbial biomass and the biomass of each microbial group generally increased. The significant influences of forest succession on soil nematodes were mainly reflected in several trophic groups with high colonizer-persister values (particularly bacterivore3, herbivore5 and omnivore-predator5) that are sensitive to environmental disturbance. The increases in the connectance and nematode genus richness, diversity, and maturity index indicated an increasingly stable and complex soil micro-food web with forest succession, which was closely related to soil nutrients, particularly the soil carbon contents. Additionally, we found that the soil carbon and nitrogen mineralization rates also exhibited generally increasing trends during forest succession, which had significant positive correlations with the soil micro-food web composition and structure. The path analysis results indicated that the variances in ecosystem functions induced by forest succession were significantly determined by soil nutrients and soil microbial and nematode communities. Overall, these results suggested that forest succession enriched and stabilized the soil micro-food web and promoted ecosystem functions via the increase in soil nutrients, and the soil micro-food web played an important role in regulating ecosystem functions during forest succession.

Effects of practicing long-term mulched drip irrigation on soil quality in Northwest China

Assessing soil quality variation during the prolonged application of mulched drip irrigation (MDI) is critical to comprehend the sustainability of arid agriculture. To investigate the dynamics of crucial soil-quality indicators caused by the long-term application of MDI, the “space instead of time” methodology was adopted, and six fields were selected to represent the primary successional sequence in Northwest China. A total of 21 vital soil attributes from 18 samples were used as soil quality indicators. Based on the soil quality index calculated from the entire datasets, it was observed that long-term MDI practice enhanced soil quality by 28.21 %–74.36 % due to improvements in soil structure (e.g., soil bulk density, three-phase ratio, and aggregates stability) and nutrients (including total carbon, organic carbon, total nitrogen, and available phosphorus). Compared to natural unirrigated soil, soil salinity in 0–200 cm depth significantly decreased by 51.34 %–92.39 % in cotton fields with increasing years of practicing MDI. In addition, long-term MDI practice restructured soil microbial communities and augmented microbial activity by 259.48 %–502.90 % relative to the natural salt-affected soil. However, soil quality stabilized after 12–14 years of MDI application due to accumulated residual plastic fragments, increased bulk density, and reduced microbial diversity. Overall, practicing long-term MDI promotes soil quality and crop yield by promoting soil microbiome structure and function and soil structure. However, long-term mono-cropping with MDI would result in soil compaction and impair microbial activity.

Phyllosphere antibiotic resistome in a natural primary vegetation across a successional sequence after glacier retreat

The spread of antibiotic-resistance genes (ARGs) has posed a significant threat to human health over the past decades. Despite the fact that the phyllosphere represents a crucial pool of microorganisms, little is known about the profile and drivers of ARGs in less human interference natural habitats. In order to minimize the influence of environmental factors, here we collected leaf samples from the early-, middle- and late-successional stages across a primary vegetation successional sequence within 2 km, to investigate how the phyllosphere ARGs develop in natural habitats. Phyllosphere ARGs were determined using high-throughput quantitative PCR. Bacterial community and leaf nutrient content were also measured to assess their contribution to the phyllosphere ARGs. A total of 151 unique ARGs were identified, covering almost all recognized major antibiotic classes. We further found that there was some stochastic and a core set of the phyllosphere ARGs during the plant community succession process, due to the fluctuant phyllosphere habitat and specific selection effect of plant individuals. The ARG abundance significantly decreased due to the reduction of the phyllosphere bacterial diversity, community complexity, and leaf nutrient content during the plant community succession process. While the closer links between soil and fallen leaf resulted in a higher ARG abundance in leaf litter than in fresh leaf. In summary, our study reveals that the phyllosphere harbors a broad spectrum of ARGs in the natural environment. These phyllosphere ARGs are driven by various environmental factors, including the plant community composition, host leaf properties, and the phyllosphere microbiome.

Зміна біотичних властивостей ґрунтів унаслідок сильватизації колишніх сільськогосподарських угідь (Сколівські Бескиди, Українські Карпати)

The article deals with an impact of the former agriculture land abandonment on biotic properties of soils. In order to better comprehend the processes of spontaneous reforestation (sylvatisation) in a mountain region (the Pohartsi boundary, Koziova village, Stryi district, Lviv regionthe (Skolivski Beskydy physiographic region, the Ukrainian Carpathians) four study plots were selected representing the successional sequence: forest → pasture → hay meadow → arable lands. The study revealed that indicators of microbiological activity is positively affected by the forest floor presence. A zone of the highest soil biotic activity coincides with the limits of the humus horizon Н. Getting deeper into soil profile microbiological activity falls manifold due to changes in physical, hydrophysical and physical-chemical soil properties. In the pasture lands that were least affected by the past agricultural activities, we found both increase and decrease in soil biotic properties. This is foremost caused by the environmental changes. Absence of the forest floor, as a major nutrient source, leads to the 30% decrease in the biomass microorganisms while soil pH shift from a largely to moderately acidic reaction causes 1,5-times higher catalase activity. The latter was the highest in the former pasture lands among all study plots and was assessed as “moderate”. Increase in the urease activity was documented, as well. However its highest values were measured in upper soil horizons of both past and present arable lands. Such an increase of the urease activity is caused by application of organic fertilizers. Despite slightly acidic reaction of the soil water extract from upper horizons of ploughed-up soils the catalase activity here decreases up to 2–2.5 times. This is caused by deterioration of hydric and aeration properties of soils due to their compaction. We noted manifold decrease in the С-СО2 production, as well. The most optimal soil parameters were characteristic for the hay meadow plot despite being significantly affected by anthropogenic activities while the succession of ‘arable lands → pasture → hay meadow’ took a path. Similar moderate soil biotic activity was distinguished for the former pasture land plots. This indicates on the self-restoration and self-regulation capacities of natural ecosystems in the region. We concluded that major indicators of soil biotic activity in the past arable lands are the urease activity, microbial biomass, and soil respiration. The catalase activity makes an additional value for soil degradation assessment of the post-agricultural land uses.

Remote Sensing for Analyzing Forested Landscape Structure and Land-Use Histories in Guyana’s Bauxite Mining Landscapes

Monitoring secondary forest regrowth is a priority in forest restoration strategies. A site history helps in understanding the present status of natural regeneration in the three landscapes impacted by bauxite mining. Nonetheless, high rainfall in bauxite residue storage areas can facilitate natural regeneration of forest. This research analyzed the natural regeneration of forest after thirty years of different land use histories at three bauxite mining areas of the Upper Demerara—Berbice region of Guyana. There are no man made forest plantations in the three landscapes being reviewed. The methodology included: 1) the selection of three sampling landscapes with different land use histories 2) the generation Land Use/Land Cover maps using KMeans unsupervised classification of satellite images in each landscape and 3) the assessment of landscape structure of the land cover classes for year 2020 at class and landscape level using landscape metrics. The assessment of landscape structure of the land cover classes was carried-out with landscape metrics for the comparisons at class and landscape level. Principal component analysis enables the identification of main patterns among landscape-level metrics and land cover classes. Discriminant classification of the landscape classes was analyzed with the different metrics. The results suggest that Normalized Difference Vegetation Index and KMeans unsupervised classification can be used to evaluate the difference in natural forest regeneration among landscapes with differing land use histories. The landscape metrics revealed secondary stages of forest succession. The Landscape Shape Index and Edge Density were the most significant for landscape differentiation. The result of the various land uses reveals a mosaic of early, intermediate, and late successional sequences.

LANDUSE FEATURES IN A MOUNTAIN AREA AND THEIR EFFECTS ON THE PROCESS OF SYLVATISATION (STRYY DISTRICT LVIV REGION)

The Skole District that is nowadays a part of newly established Stryy District (Lviv Region) is entirely situated within the range of the Ukrainian Carpathians. Its area encompasses the Skolivsli Beskydy and the Stryy-San Highland physiographic regions featuring a dominance of considerably high altitudes above sea level, terrain disarticulation, and afforestation. Establishing new villages alongside rural population’s natural increase and land reforms (the capitalist stage of land use (after the abolition of serfdom in 1848) and Soviet stage of land use) called for respective increase in agricultural lands. Forested lands in the Ukrainian Carpathians were the source for such an increase therefore cropland and pasture lands were emerging from deforestation. Harsh weather conditions and low soil fertility significantly impacted the further agricultural land uses in the mountainous region. However, wide-scale decline of agricultural lands occurred in the period of the collapse of the former USSR due to decline of collective and state farms. As a result of denationalization with subsequent privatization of agricultural lands there are nowadays 31 303 land owners and land users in the study area, 97,54 % of which are physical persons. At the same time, despite such remarkable figures citizens share less than a half of total lands for agriculture, residential and construction purposes, whilst the state forestry enterprises are using 51,11 % (75 173,50 ha) in total. In contrast to lowlands, animal farming and husbandry in the Skole District is held exclusively by households. In recent years local animal husbandry is experiencing the livestock decline that leads to certain reduction in the share of both hay meadows and pasturelands. Thus, from 2009 to 2016 the total area of fodder lands in the district decreased by 65 ha (ca. 0,2 % of total privately owned agricultural lands). I assume that ongoing land reform will cause further increase in fallows in the Skole District. In order to better comprehend the processes of spontaneous reforestation (sylvatisation) in a mountain region (the Pohartsi boundary, Koziova village, Stryi district, Lviv regionthe ) four study plots were selected representing the successional sequence: forest → pasture → hay meadow → arable lands. The study showed that areas that were previously used for pasture and were not plowed, are restored to their natural state much faster. These areas are characterized by satisfactory physical, physico-chemical and biotic properties. The decrease in acidity towards the neutral side is explained by an increase in the activity of catalase and urease by approximately 1.5 times. In connection with the developed grass cover, slightly higher nitrogen values were recorded in the upper soil horizon. Due to the absence of a regular annual supply to the base and replenishment of its nutrient reserves due to precipitation and waste of dead phytomass, the content of humus in the upper horizon of the base is half as much as under forest biogeocenoses. Plowing (overturning the lower horizons to the mountain, and vice versa) is a very strong anthropogenic factor, which leads to the almost complete destruction of natural vegetation on the cultivated area and a radical change in the main properties of the soil cover. According to some indicators: physical (total sparability), physico-chemical (nitrogen nitrate and ammonia), biotic (urease, catalase, biomass of microorganisms) in the upper humus horizons were even somewhat close to anthropogenically unaltered ecosystems. However, the changes in the indicators of the density of the soil structure and its solid phase corresponded to the depth of plowing. And the humus content was several times lower than under forest biogeocenoses. Areas that were not plowed in the past are restored due to the main rock of the region Picea abies (L.) Karst.. Areas that were devastated in the past are recovering much more slowly. Such areas begin to overgrow with Alnus incana (L.) Moench., Rosa canina L., Bеtula and others Key words: land use; land owners and land users; fallows; agricultural lands; mountainous region; Skolivski Beskydy.

THE IMPACT OF REFORESTATION ON PHYSICAL AND HYDROPHYSICAL PROPERTIES OF SOILS OF THE FALLOW LANDS (SKOLIVSKI BESKYDY, THE UKRAINIAN CARPATHIANS)

The article tackles the impacts of anthropogenic load on the physical and hydrophysical soil properties. In order to better comprehend the processes of spontaneous sylvatisation in a mountain region (the Pohartsi boundary, Koziova village, the Skolivski Beskydy physiographic region) four study plots were selected representing the successional sequence: forest → pasture → hay meadow → arable lands. Land patches that were affected the least by anthropogenic load restored faster to their natural baseline conditions. Tilling appeared to retardate restoration processes, however those anyway took place. Proper functioning of arable land patches may be facilitated by continuous land care actions (i.e. ploughing or mowing).We found that soil bulking density in arable lands increased in upper soil horizons compared to forest ecosystems. Such an increase is caused by mechanical turning upper soil horizons up down and vice versa, for lower horizons. In pasture lands, upper soil horizons are trampled down by livestock. This leads to lower water permeability of soils: increase in soil bulk density from 0.79 to 1.15 g•cm-3 resulted in a decrease of water permeability by 75 %. In forested lands, values of water permeability similar to those in arable lands (0.55 mm•min⁻¹) are usually observed along the walking trails and in wood trilling plots. On the land patches with scarce herbaceous cover erosion processes are emerging. The latter is especially dangerous for arable land patches causing extra leak of soil nutrients and thus soil depletion. In order to further exploitation soils in such patches need additional fertilizing. As agricultural load diminishes soil upper horizons restore. Restoration occurs through prolonged freezing and thawing cycles during the cold (autumn-winter-spring) season. Another path for soil physical properties restoration is associated with penetration of plant fine roots that loosen the soil. Increase of total sparing indices is observed, as well. For upper horizons of restored soil it is assessed as “intermediate” (62,00 ‒ 65,35 %) whilst for arable land patches it is significantly lower (54,90 %). Soil bulk density gradually decreased along soil profiles and study plots. In forested patches it reached minimum (2,28 g•cm⁻³) and in arable land patches – maximum (2.55 g•cm⁻³) values, which did not change upon termination of anthropogenic load. Significant changes were observed for the field humidity indices. These varied both spatially, along soil profiles, and temporarily, by seasons. Lack of herbaceous vegetation caused over-drying in upper soil horizons. At the same time in lower horizons field humidity increased. Upper soil horizons in forested patches undergo the least changes due to the presence of thick forest floor. We conclude that major indicators of agricultural load within a soil profile are soil bulk density, water permeability and total sparing. Such indicators as the solid phase density and field humidity are of additional value. Key words: reforestation; soil bulk density; water permeability; soil profile; arable lands; pastures; Skolivski Beskydy.

Encroachment order and spatial patterns of broad-leaf tree species in the naturalization of a Cunninghamia lanceolata plantation

The aim of this study was to understand the encroachment order, spatial patterns, interspecific associations, and species diversity of a Cunninghamia lanceolata plantation and to provide context for how to improve the spatial structure of C. lanceolata plantations. We investigated a Guanshan (C. lanceolata) Plantation in the Jiangxi Province. The C. lanceolata plantation was divided into three developmental stages (early, middle and late), with a space-for-time substitution method, according to their diameter at breast height (DBH) measurements. Across these plots, we analyzed encroachment patterns of the species and their interspecific associations with C. lanceolata according to the coordinates of trees in the plot, as well as the variation of species diversity after the encroachment of broad-leaf tree species. Our results show that the encroachment of broad-leaf trees into the C. lanceolata plantation followed a clear successional sequence of tree community assembly: intolerant tree species encroachment first, such as Alniphyllum fortunei and Liquidambar formosana, encroached; neutral tree species then encroachment, such as Daphniphyllum oldhamii and Schima superba, and shade-tolerant tree species encroachment last, such as Castanopsis eyrei and Castanopsis tibetana. Further, the spatial pattern of species establishment differed based upon when they encroached on the plantation. Intolerant and neutral tree species of early and middle developmental stages were distributed randomly. However, intolerant and some shade-tolerant tree species of the late developmental stage were aggregated on a scale of about 0–3 m. In addition, the interspecific associations between broad-leaf species encroachment into the C. lanceolata plantation were mainly negative, among which the most competitive ones were A. fortunei, D. oldhamii and Machilus thunbergii. However, with the development of the community, some species with negative correlations changed to having no correlation with C. lanceolata. We found that species diversity in the plantation gradually increased by nearly-five times from the early to the late developmental stage. Based on our collective results, we conclude that the encroachment and assembly of tree species show obvious order and pattern, which has a strong competitive effect with C. lanceolata in the naturalized plantation. Additionally, the community biodiversity has been significantly improved. Therefore, this successional process is important in the transformation of the C lanceolata plantation and different tree species should be replanted according to C. lanceolata plantation developmental stages with priority given to competitive species, such as A. fortunei, D. oldhamii, and M. thunbergii, so as to promote the C. lanceolata plantation change to C. lanceolata and broadleaf mixed forest.