Cunninghamia Lanceolata Plantation Research Articles

Characteristics of soil viral communities in Cunninghamia lanceolata plantations with different stand ages.

We investigated the dynamics of soil viral community in Cunninghamia lanceolata plantations with different stand ages (8, 21, 27, and 40 years old) in a subtropical region. The viral metagenomics and bioinformatics analysis were used to analyze the compositional and functional differences of soil viral communities across different stand ages, and to explore the environmental driving factors. The results showed that tailed phages dominated soil viral community in subtropical C. lanceolata plantations, with the highest proportion of Siphoviridae (19.6%-39.5%). There was significant difference in soil viral community structure among different stand ages, with the main driving factors being electrical conductance and available phosphorus. The metabolic functional genes encoded by viruses exhibited higher relative abundance. The α-diversity of soil viral function in mature C. lanceolata plantations was higher than other stands. There were significant differences in soil viral functional structure among different stand ages, which were mainly driven by ammonium nitrogen. During the development of C. lanceolata plantations, auxiliary metabolic genes encoded by virus related to nitrogen and phosphorus may regulate the metabolism of host microorganisms, thereby potentially impacting biogeochemical cycling of these elements.

Cylindrocladiella species from Cunninghamia lanceolata plantation soils in southwestern China.

Species of Cylindrocladiella are saprobic or plant pathogenic, and widely distributed in soil in tropical and sub-tropical regions of the world. Limited information is available about the species diversity and distribution of Cylindrocladiella in China. The aim of this study was to identify the Cylindrocladiella isolates from soils collected in a Cunninghamia lanceolata plantation in the Yunnan Province of southwestern China. Species identification was based on DNA phylogeny of his3, ITS, tef1 and tub2 regions, combined with morphological characteristics. Isolates obtained were identified as Cylindrocladiella longistipitata and a novel species, described here as C. yunnanensis sp. nov. Further studies are required, however, to elucidate the lifestyles of these taxa. Citation: Liu Y, Chen SF (2024). Cylindrocladiella species from Cunninghamia lanceolata plantation soils in southwestern China. Fungal Systematics and Evolution 13: 143-152. doi: 10.3114/fuse.2024.13.08.

Effects of short-term simulated acid rain and nitrogen deposition on soil nutrients and enzyme activities in Cunninghamia lanceolata plantation

Acid rain and nitrogen deposition are emerging as global scale environmental issues due to increasing industrial emissions and agricultural pollutants, which seriously impac t the sustainable development of global ecosystems. However, the specific effects both acid rain and nitrogen deposition interactions on forest soil ecosystems, particularly as relates to the soil nutrient content and enzyme activities, remain unclear. Therefore, we established a simulated sample plot of acid rain (SR, NR) and nitrogen deposition (N) and their interactions (SRN, NRN) in a subtropical Cunninghamia lanceolata (C. lanceolata) plantation in the Yangtze River Delta region of China to investigate the impacts of these factors via correlation analysis and structural equation model (SEM). The results showed that acid rain had a stronger effect on soil pH than nitrogen deposition in C. lanceolata plantation, while the simultaneous addition of acid rain and nitrogen deposition exacerbated soil acidification. Soil available potassium, ammonium nitrogen and nitrate nitrogen in C. lanceolata plantation responded more obviously to acid rain and nitrogen deposition, in which acid rain, nitrogen deposition and their interactions significantly reduced soil available potassium content, while acid rain and nitrogen deposition interactions significantly increased soil ammonium nitrogen and nitrate nitrogen content. Nitric acid rain, nitrogen deposition and their interactions significantly increased soil NAGase activity, but significantly decreased soil urease activity; the single-factor treatment of acid rain and nitrogen deposition significantly increased soil arylsulfatase activity, while the interaction of acid rain and nitrogen deposition significantly decreased soil arylsulfatase activity; in general, the interaction of acid rain and nitrogen deposition had a stronger effect on the soil ecosystem of the C. lanceolata plantation than that of single acid rain or nitrogen deposition, of which nitrogen deposition exacerbated the effects of acid rain on the soil ecosystem of C. lanceolata plantation mainly by changing the soil pH and the content of effective nutrients.

Linkages among leaf nutrient concentration, resorption efficiency, litter decomposition and their stoichiometry to canopy nitrogen addition and understory removal in subtropical plantation

BackgroundThe prevalence of understory removal and anthropogenic nitrogen (N) deposition has significantly altered the ecological processes of forest ecosystems at both regional and global scales. However, it remains a pressing challenge to understand how N deposition and understory removal affect leaf nutrient dynamics, nutrient resorption, litter decomposition, and their linkages for better managing forest ecosystems under nutrient imbalances induced by N enrichment. To address this research gap, a field manipulation experiment was carried out in a subtropical Cunninghamia lanceolata plantation with four treatments including: control (CK), canopy N addition (CN), understory removal (UR), and canopy N addition plus understory removal (CN × UR). Green and senesced leaf N and phosphorus (P) concentrations, N and P resorption efficiencies, litter decomposition, and their correlations were measured.ResultsThe results revealed that the average N concentrations of green early and late leaves in UR were increased by 6.61 and 18.89% compared to CK. UR had the highest whereas CN had the lowest P concentrations in green leaves across the two sampling seasons. Following this, UR, leaf type, season, and their interactions significantly affected leaf N, P, and N:P (P < 0.05). The highest leaf N resorption (32.68%) and P resorption efficiencies (63.96%) were recorded in UR. Litter decomposition was significantly retarded in UR (P < 0.01) relative to CN. The regression analysis demonstrated that leaf nutrient status was significantly interconnected with leaf nutrient resorption efficiencies. In addition, leaf nutrient dynamics were strongly correlated with litter nutrients, indicating that both were coupled.ConclusionThese findings can deepen our knowledge of biogeochemical cycling and reveal contrasting nutrient-acquisition strategies on N and P limitation in response to UR and CN. Considering the P limitation, it is important to note that P was resorbed more efficiently, illustrating a remarkable nutrient preservation approach for nutrient-limitations. Resorption may be a crucial mechanism for keeping nutrients in these forests, so better understory management practices are required to prevent reliance on external nutrient pools. Overall, this study sheds meaningful insights into the ability of forest adaptation in response to global climatic change.

Short-term responses of soil enzyme activities and stoichiometry to litter input in Castanopsis carlesii and Cunninghamia lanceolata plantations.

Litter input triggers the secretion of soil extracellular enzymes and facilitates the release of carbon (C), nitrogen (N), and phosphorus (P) from decomposing litter. However, how soil extracellular enzyme activities were controlled by litter input with various substrates is not fully understood. We examined the activities and stoichiometry of five enzymes including β-1,4-glucosidase, β-D-cellobiosidase, β-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase and acidic phosphatase (AP) with and without litter input in 10-year-old Castanopsis carlesii and Cunninghamia lanceolata plantations monthly during April to August, in October, and in December 2021 by using an in situ microcosm experiment. The results showed that: 1) There was no significant effect of short-term litter input on soil enzyme activity, stoichiometry, and vector properties in C. carlesii plantation. In contrast, short-term litter input significantly increased the AP activity by 1.7% in May and decreased the enzymatic C/N ratio by 3.8% in August, and decreased enzymatic C/P and N/P ratios by 11.7% and 10.3%, respectively, in October in C. lanceolata plantation. Meanwhile, litter input increased the soil enzymatic vector angle to 53.8° in October in C. lanceolata plantations, suggesting a significant P limitation for soil microorganisms. 2) Results from partial least squares regression analyses showed that soil dissolved organic matter and microbial biomass C and N were the primary factors in explaining the responses of soil enzymatic activity to short-term litter input in both plantations. Overall, input of low-quality (high C/N) litter stimulates the secretion of soil extracellular enzymes and accelerates litter decomposition. There is a P limitation for soil microorganisms in the study area.

Effects of forest regeneration types on phosphorus fractions of soil aggregates in subtropical forest.

Soil aggregates are important for the storage and availability of phosphorus in the soil. However, how forest regeneration types affect phosphorus fractions of soil aggregates remains unclear. In this study, we examined the composition of aggregate particle size, phosphorus fractions, phosphorus sorption capacity index (PSOR), legacy phosphorus index (PLGC) and degree of phosphorus saturation by Mehlich 3 (DPSM3) in bulk soils and soil aggregates of Castanopsis carlesii secondary forest (slight disturbance), C. carlesii human-assisted regeneration forest (moderate disturbance), and Cunninghamia lanceolata plantation (severe disturbance), aiming to explore the impact of forest regeneration types on phosphorus availability and supply potential of bulk soils and soil aggregates. The results showed that forest regeneration types significantly influenced the composition of soil aggregates. The proportion of coarse macroaggregates (>2 mm) in the soil of C. carlesii secondary forest and human-assisted regeneration forest was significantly higher than that in the C. lanceolata plantation, while the proportion of silt and clay fraction (<0.053 mm) showed an opposite trend. The composition of soil aggregates significantly affected the contents of different phosphorus fractions. The contents of soil labile phosphorus fractions (PSOL and PM3) decreased as aggregate particle size decreased. The contents of soil total phosphorus (TP), total organic phosphorus (Po), mode-rately labile phosphorus fractions (PiOH and PoOH), and occluded phosphorus (POCL), as well as PSOR and PLGC, exhibited a trend of decreasing at the beginning and then increasing as particle size decreased. The contents of TP, Po, and PiOH in coarse and silt macroaggregates was significantly higher than that in fine macroaggregates (0.25-2 mm) and microaggregates (0.053-0.25 mm). Forest regeneration types significantly influenced the contents of phosphorus fractions of bulk soils and soil aggregates. The contents of TP, Po, PSOL, and PM3 in the soil of C. carlesii secondary forests was significantly higher than that in C. carlesii human-assisted regeneration forest and C. lanceolata plantation. The contents of PSOL and PM3 in different-sized aggregates of C. carlesii secondary forests were significantly higher than that in the C. lanceolata plantation. Forest regeneration types significantly influenced the composition and supply potential of phosphorus fractions in soil aggregates. The proportions of PSOL, and PM3 to TP in different-sized soil aggregates were significantly lower in C. carlesii human-assisted regeneration forest compared with C. carlesii secondary forest. PSOR and DPSM3 in different-sized soil aggregates were significantly lower in C. lanceolata plantation than that in C. carlesii secondary forest. Overall, our results indicated that natural regeneration is more favorable for maintaining soil phosphorus availability, and that forest regeneration affects soil phosphorus availa-bility and its supply potential by altering the composition of soil aggregates.

Effects of stand ages on soil enzyme activities in Chinese fir plantations and natural secondary forests.

Forest type and stand age are important biological factors affecting soil enzyme activities. However, the changes in soil enzyme activities across stand ages and underlying mechanisms under the two forest restoration strate-gies of plantations and natural secondary forests remain elusive. In this study, we investigated the variations of four soil enzyme activities including cello-biohydrolase (CBH), β-1,4-glucosidase (βG), acid phosphatase (AP) and β-1,4-N-acetylglucosaminidase (NAG), which were closely associated with soil carbon, nitrogen, and phosphorus cycling, across Cunninghamia lanceolata plantations and natural secondary forests (5, 8, 21, 27 and 40 years old). The results showed that soil enzyme activities showed different patterns across different forest types. The acti-vities of AP, βG and CBH in the C. lanceolata plantations were significantly higher than those in the natural secon-dary forests, and there was no significant difference in the NAG activity. In the plantations, AP activity showed a decreasing tendency with the increasing stand ages, with the AP activity in the 5-year-old plantations significantly higher than other stand ages by more than 62.3%. The activities of NAG and CBH decreased first and then increased, and βG enzyme activity fluctuated with the increasing stand age. In the natural secondary forests, NAG enzyme activity fluctuated with the increasing stand age, with that in the 8-year-old and 27-year-old stand ages being significantly higher than the other stand ages by more than 14.9%. βG and CBH enzyme activities increased first and then decreased, and no significant difference was observed in the AP activity. Results of the stepwise regression analyses showed that soil predictors explained more than 34% of the variation in the best-fitting models predicting soil enzyme activities in the C. lanceolata plantations and natural secondary forests. In conclusion, there would be a risk of soil fertility degradation C. lanceolata plantations with the increasing stand age, while natural secondary forests were more conducive to maintaining soil fertility.

Different Responses of Arbuscular Mycorrhizal Fungal Community Compositions in the Soil and Roots to Nitrogen Deposition in a Subtropical Cunninghamia lanceolata Plantation in China

Elevated nitrogen (N) deposition may stimulate a plant’s dependency on arbuscular mycorrhizal (AM) fungi in phosphorus (P)-deficient subtropical forests. However, the ecological assembly processes and the responses of AM fungal diversity and community structure to N deposition in both the roots and rhizosphere are still unclear. We collected root and soil samples from a Cunninghamia lanceolata plantation forest after four years of N addition and examined the community structure and assembly of AM fungi. Elevated N deposition decreased the AM fungal community diversity in both rhizosphere soil and roots. Glomeraceae was the dominant family of the AM fungal community in both soil and roots across all N addition treatments, followed by Gigasporaceae and Ambisporaceae. However, N addition induced differential variation in the community composition of AM fungi between soil and roots. For soil AM fungi, N addition decreased the Glomeraceae abundance and increased the Gigasporaceae and Ambisporaceae abundance. In contrast, the root AM fungal community was dominated by Glomeraceae under N addition treatments. Furthermore, N addition increased the deterministic community assembly that acted as an environmental filter for soil AM fungi. In contrast, N addition decreased the importance of determinism, implying that the selection of plants on root AM fungi decreased with increasing N addition. Altogether, our findings suggest that the community structure of AM fungi responds differently to N deposition in the soil and roots in subtropical forests and highlight the important role of soil AM fungi in helping host plants respond to N deposition.

Response of erosion-induced carbon loss to rainfall characteristics is forest type dependent

The paucity of studies on the response of erosion-induced carbon (C) loss to rainfall characteristics hinders our ability to estimate how changes in rainfall regime may affect C budget of forests, particularly in regions prone to water erosion. In the current study, we monitored the losses of dissolved organic carbon (DOC) and particulate organic carbon (POC) in relation to rainfall depth, average intensity, maximum 5 min intensity (I5), erosivity (EI30), and vegetation cover in three young forests during the first three years of reforestation. The three forest types include an assisted naturally regenerated (ANR) forest, a young Castanopsis carlessi plantation (YCP), and a young Cunninghamia lanceolata (Chinese fir) plantation (YCF). Our results indicate that POC was the dominant form of C loss, and erosion-induced C loss was lower in the ANR than the two plantations, likely due to its high vegetation cover. Erosion-induced C loss decreased through time across forest types as vegetation cover increased, highlighting the role of vegetation cover in mitigating C loss. The response of C loss to rainfall characteristics varied among different forest types. Vegetation cover and rainfall depth had similar contributions in predicting DOC flux in the ANR, while rainfall depth was more important in the YCP and vegetation cover was more important in the YCF. The most important factor predicting POC loss was vegetation cover in the ANR, I5 in the YCP, while in the YCF vegetation cover and I5 were of similar importance. Overall, DOC loss was mainly driven by rainfall depth, while POC loss was more related to I5. Our results suggest that projected increases in storm intensity associated with climate change are likely to increase erosion-induced C loss. And ANR should be widely promoted as an effective management practice of C conservation.

Responses of arbuscular mycorrhizal fungal morphological traits and the diversity of spore-associated bacteria to simulated nitrogen deposition and drought in a Cunninghamia lanceolata plantation soil

Arbuscular mycorrhizal (AM) fungi play an important role in plant nutrient absorption and stress resistance. AM fungal spore-associated bacteria are essential for mycorrhizal colonization, but their responses to environmental changes remain largely unknown. We collected surface soil samples from a Chinese fir plantation in both summer and winter to investigate the responses of AM fungal morphological traits and spore-associated bacterial communities to simulated nitrogen deposition (40 kg N·hm-2·a-1 addition) and drought (-50% precipitation exclusion). Our results showed that nitrogen addition and precipitation exclusion significantly affected AM fungal spore density and extraradical hyphal length, respectively. AM fungal intraradical colonization rate, extraradical hyphal length and spore density were significantly differed between the two seasons. Compared to control (no nitrogen addition and no precipitation exclusion treatment), both nitrogen addition and precipitation exclusion significantly reduced spore density in winter, while precipitation exclusion alone and the combined nitrogen addition and precipitation exclusion significantly increased extraradical hyphal length in summer. The dominant spore-associated bacterial phyla were Proteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, and Planctomycetes. Nitrogen addition and precipitation exclusion did not affect the diversity of spore-associated bacteria. However, the combined nitrogen addition and precipitation exclusion treatment altered the composition of the bacterial community, with significant variations between the two seasons. The spore-associated bacterial diversity was significantly higher and community variability (or turnover) was lower during summer than winter. Soil total nitrogen, nitrate nitrogen and dissolved organic carbon were important factors influencing the bacterial community composition. In all, the effects of nitrogen addition and precipitation exclusion on the morphological traits of AM fungi are seasonally dependent. The combination of nitrogen addition and precipitation exclusion has a significant impact on AM fungal spore-associated bacterial community structure.

Initial effects of crop tree release and traditional thinning on productivity and carbon storage of Cunninghamia lanceolata plantation

IntroductionThinning has a crucial impact on the carbon dynamics of forest ecosystems. The inconsistencies about the effects of thinning on carbon stocks in previous studies may be attributed to different thinning plans that designed to achieve different management goals.MethodsThis study focuses on Cunninghamia lanceolata as the research object and investigates three treatments: crop tree release (CTR), traditional thinning (TM), and no thinning (CK). The different thinning methods (CTR and TM) had different management objectives and selection of crop trees principle, although with the same thinning density. The short-term effects of CTR and TM treatments on tree growth and carbon storage in Cunninghamia lanceolata plantations were analyzed and compared.ResultsBoth CTR and TM were beneficial to the growth of individual trees when compared to CK, with CTR being more beneficial. The average annual increments in DBH, TH, and volume of a single tree in CTR increased by 62.50%, 61.29%, and 74.07% higher than CK, respectively. So CTR was the best for large-diameter timber yield, which was 77.40% higher than CK, whereas CK had a higher proportion of medium- and small-diameter timber yield. However, CTR had an insignificant short-term boosting effect on stand volume, and its timber volume was considerably higher than that in TM treatment, but not as high as in CK. Therefore, the carbon storage in the tree layer, litter, and different soil layers under different treatments showed that CTR and TM were significantly lower than CK. And the total carbon storage in the three treatments showed that CK &amp;gt; CTR &amp;gt; TM, with CTR showing a 13.07% higher than TM. On the contrary, thinning could effectively improve understory vegetation carbon storage. The carbon storage in the herb and shrub layers under CTR increased by 47.77% and 183.44%, respectively, compared to CK.DiscussionAlthough thinning could significantly promote the growth of individual trees and understory vegetation, their total carbon storage in the short term was lower than that in CK. CTR showed a higher carbon sequestration and sink capacity than TM. It suggests that CTR, as a special type of thinning method, should be encouraged to selected because it has the chance to achieve a faster carbon sequestration rate than traditional thinning and it also can produce higher-quality timber.

Temporal changes in size inequality and stand growth partitioning between tree sizes under various thinning intensities in subtropical Cunninghamia lanceolata plantations

Stand structural complexity and growth partitioning between different tree sizes influence trees competition and resource use efficiency, and thus are closely linked to stand productivity. The main aim of this study was to examine how the stand structure complexity (Gini coefficient Gini) and size-related partitioning of stand growth (growth dominance coefficient GDC and size-growth relationship SGR) temporally changed after different thinning intensities in Chinese fir (Cunninghamia lanceolata) forests, Southeastern China. We analyzed the data of 6 repeated measurements over a nearly 10-year period from a forest thinning experiment with progressively increasing intensity (0, 20%, 25%, 33% and 50% reduction of stand density by selection logging of releasing target trees) and assessed the effects of different thinning intensities using generalized mixed effect model. The thinning intensity of 0 was taken as a control group to identify the stand changes in unthinned stands over time. Size heterogeneity and the relative contribution of larger trees to total stand growth tended to increase as forest grew without thinning management. While the increases in Gini and SGR (excluding between 0 and 0.5) overall negatively influenced the average annual basal area increment of the remaining trees (BAI). Gini in thinned stands decreased during the short term (two years or more) after thinning and the heavy thinning had lower Gini than other treatments several years (eight years or less) after thinning. GDC reduced greater with increasing thinning intensity, and thinning had a significant negative effect on Gini and SGR and a positive effect on BAI. The thinning impacts on BAI increased with the thinning intensity, while the effect magnitudes of different thinning intensities on Gini and SGR were: T50 < T20 < T25 < T33. Overall, thinning increased the stand growth partitioning of small trees, contributing to a uniform stand structure. However, the changes in stand structural complexity and the partitioning of stand growth were related to both thinning intensity and post-thinning time, particularly to thinning intensity. The results provided some implications for designing the intensity and timing of thinning, as well as for determining the size classes of removed trees for different management goals.

Understory vegetation restoration improves soil physicochemical properties, enzymatic activity, and changes diazotrophic communities in Cunninghamia lanceolata plantations but depends on site history

Understory vegetation restoration improves soil physicochemical properties, enzymatic activity, and changes diazotrophic communities in Cunninghamia lanceolata plantations but depends on site history

Spatial distribution of soil organic carbon and its response to forest growth and soil layer in Cunninghamia lanceolata plantations in mid-subtropical China

To investigate the effects of stand age and soil layer on the temporal and spatial distribution of soil organic carbon (SOC) in Cunninghamia lanceolata plantations, five experimental plots and 15 soil sampling sites were established in five stands of different ages (3, 6, 9, 15, and 25 years) in Huitong, Hunan Province. Tree diameter at breast height, tree height, canopy density and elevation in sample plots, and soil organic carbon concentrations (SOCC), soil enzyme activity, soil pH, and soil bulk density at 0–15, 15–30, 30–45 cm soil layers were measured during stand development. The change in SOC distribution with stand age and soil layer, and soil enzyme activity were investigated using ANOVA, LSD test, and inter-subject effect test and simulation analysis. The results showed that the SOC distribution in Cunninghamia lanceolata plantations had spatiotemporal heterogeneity and surface aggregation. The SOC increased with increasing stand age and decreased with increasing soil depth. Furthermore, SOCC and SOC density (SOCD) were strongly correlated with environmental factors; however, the interaction between forest growth and soil layer reduced the variation of SOC distribution. Forest growth and soil enzyme activity were important factors that affect the temporal and spatial distribution of SOC. Therefore, the management measures to promote the growth of the plantation and improve soil enzyme activity can enhance the SOC storage capacity from the angle of balancing ecological and economic benefits, and contribute to the achievement of the goal of “carbon neutrality”.

Stand characteristics and ecological benefits of Chinese Fir, Chinese Cedar, and mixed plantations in the mountainous areas of the Sichuan Basin

Many studies of biodiversity-ecosystem functioning (BEF) relationships indicate that mixed plantations can enhance ecological benefits by enabling ecological niche differentiation between species. However, few studies explore multi-dimensional evidence to fully evaluate the integrated ecological benefits of mixed plantations. This paper aims to assess the stand characteristics and ecological benefits of different forest types, drawing on multiple lines of evidence (trees, shrubs, herbs, soil fauna, and soils) to understand the effects of mixed plantations on integrated ecological benefits. Our study focused on pure Cunninghamia lanceolata (Chinese Fir) plantations (PCL), pure Cryptomeria fortunei (Chinese Cedar) plantations (PCF), and mixed C. lanceolata-C. fortunei plantations (MCC), which are common in the mountainous areas of the Sichuan Basin in southwestern China. We analysed the growth status, spatial structure, understory vegetation diversity, soil fauna characteristics, and physical and chemical soil properties found in plots representing these three forest types. The results showed that productivity was significantly higher in the MCC than in PCL or PCF, by 39.5% and 18%, respectively. Mixed plantations showed higher stand growth rates, but this effect was limited by interspecific competition. The results further showed that mixed plantations promote forest growth by allocating spatial locations between different tree species. In addition, the spatial stand structure in the mixed plantations was more stable than that in the two pure plantations, and the management potential of the mixed plantations was greater. Understory vegetation in MCC was significantly more diverse than in PCL and PCF, by 15.8–20% and 13.2–35.7%, respectively. Moreover, mixed plantations performed better in terms of soil water and soil fertility. Interestingly, we found no difference in soil fauna diversity between mixed and pure plantations. We conclude that, overall, planting mixed plantations can enhance the integrated ecological benefits of afforestation and may be an essential strategy for ensuring that plantations can cope with climate extremes.

Effects of liming on soil respiration and its sensitivity to temperature in Cunninghamia lanceolata plantations.

The primary distribution area of acid deposition coincides with areas of Chinese fir (Cunninghamia lanceolata) plantations. Liming is an effective method of restoring acidified soil. To understand the effects of liming on soil respiration and temperature sensitivity within the context of acid deposition, we measured soil respiration and its components in Chinese fir plantations for one year beginning in June 2020, with 0, 1 and 5 t·hm-2 calcium oxide being added in 2018. The results showed that liming considerably increased soil pH and exchangeable Ca2+ concentration, and that there was no significant difference among different levels of lime application. Soil respiration rate and components in the Chinese fir plantations exhibited seasonal variations, with the highest values during the summer and the lowest values during the winter. Although liming did not alter seasonal dynamics, it strongly inhibited heterotrophic respiration rate and increased autotrophic respiration rate of soil, with minor effect on total soil respiration. The monthly dynamics of soil respiration and temperature were largely consistent. There was a clear exponential relationship between soil respiration and soil temperature. Liming increased temperature sensitivity Q10 of soil respiration and autotrophic respiration but reduced that of soil heterotrophic respiration. In conclusion, liming promoted soil autotrophic respiration and strongly inhibited soil heterotrophic respiration in Chinese fir plantations, which would facilitate soil carbon sequestration.

Forest conversion from pure to mixed Cunninghamia lanceolata plantations enhances soil multifunctionality, stochastic processes, and stability of bacterial networks in subtropical southern China

Forest conversion from pure to mixed Cunninghamia lanceolata plantations enhances soil multifunctionality, stochastic processes, and stability of bacterial networks in subtropical southern China

Effects of thinning on tree growth and soil physiochemical properties in Cunninghamia lanceolata plantation

ABSTRACT Tree growth, along with soil properties, is greatly affected by forest management. We used a typical sampling to study the impact of four thinning intensities (T1: 0%, 2500 stems ha−1; T2: 20%, 2010 stems ha−1; T3: 30%, 1750 stems ha−1; T4: 40%, 1500 stems ha−1) on the tree growth and soil physicochemical properties and their correlation in Cunninghamia lanceolata plantations. The average annual increments in tree height, diameter at breast height (DBH), and volume increased with thinning intensity, and those of T4 differed significantly (P < 0.05) from those of T1. The average annual stand volume increments of T4 were significantly (P < 0.05) lower than that of T1, while the maximum value presented at T3. However, the effect of thinning in promoting the growth of Chinese fir diminished with time. As the thinning intensity increased, the diameter class distribution of the sample stands moved rightwards. Moreover, thinning improved soil physiochemical properties. The effects of thinning on soil properties in 0–20 cm soil layer were greater than those in 20–40 cm soil layer. There was a positive correlation between available nitrogen, available potassium and tree growth. The results of this study showed that thinning had a potential effect on tree growth and soil properties. The heavy thinning intensity (approximately 1500 stems ha−1) was the optimum for maintaining economic and ecological benefits. However, heavy thinning significantly reduced stand volume. From the perspective of improving stand volume and biomass, a moderate thinning intensity (approximately 1750 stems ha−1) could be considered for adoption.

Extraction of tree crown parameters of high-density pure Cunninghamia lanceolata plantations by combining the U-Net model and watershed algorithm.

As one of the important timber species in China, Cunninghamia lanceolata is widely distributed in southern China. The information of tree individuals and crown plays an important role in accurately monitoring forest resources. Therefore, it is particularly significant to accurately grasp such information of individual C. lanceolata tree. For high-canopy closed forest stands, the key to correctly extract such information is whether the crowns of mutual occlusion and adhesion can be accurately segmented. Taking the Fujian Jiangle State-owned Forest Farm as the research area and using the UAV image as the data source, we developed a method to extract crown information of individual tree based on deep learning method and watershed algorithm. Firstly, the deep learning neural network model U-Net was used to segment the coverage area of the canopy of C. lanceolata, and then the traditional image segmentation algorithm was used to segment the individual tree to obtain the number and crown information of individual tree. Under the condition of maintaining the same training set, validation set and test set, the extraction results of the canopy coverage area by the U-Net model and traditional machine learning methods [random forest (RF) and support vector machine (SVM)] were compared. Then, two individual tree segmentation results were compared, one using the marker-controlled watershed algorithm, and the other using the combination of the U-Net model and marker-controlled watershed algorithm. The results showed that the segmentation accuracy (SA), precision, IoU (intersection over union) and F1-score (harmonic mean of precision and recall) of the U-Net model were higher than those of RF and SVM. Compared with RF, the value of those four indicators increased by 4.6%, 14.9%, 7.6% and 0.05, respectively. Compared with SVM, the four indicators increased by 3.3%, 8.5%, 8.1% and 0.05, respectively. In terms of extracting the number of trees, the overall accuracy (OA) of the U-Net model combined with the marker-controlled watershed algorithm was 3.7% higher than that of the marker-controlled watershed algorithm, with the mean absolute error (MAE) being decreased by 3.1%. In terms of extracting crown area and crown width of individual tree, R2 increased by 0.11 and 0.09, mean squared error decreased by 8.49 m2 and 4.27 m, and MAE decreased by 2.93 m2 and 1.72 m, respectively. The combination of deep learning U-Net model and watershed algorithm could overcome the challenges in accurately extracting the number of trees and the crown information of individual tree of high-density pure C. lanceolata plantations. It was an efficient and low-cost method of extracting tree crown parameters, which could provide a basis for developing intelligent forest resource monitoring.

不同林分土壤磷形态与磷酸酶特征

PDF HTML阅读 XML下载 导出引用 引用提醒 不同林分土壤磷形态与磷酸酶特征 DOI: 10.5846/stxb202102130434 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（32171761，U21A20187）；中南林业科技大学研究生科技创新基金项目（CX20191006，CX202102023） Characteristics of soil phosphorus fractions and phosphatases activity in different plantations Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以湖南省平江县国有芦头林场的次生林以及经人工翻垦种植的油茶（Camellia oleifera）、黄桃（Amygdalus persica）、杨梅（Myrica rubra）和杉木（Cunninghamia lanceolata）四种人工林为研究对象，比较了不同林分土壤理化性质、磷酸酶活性与磷形态特征，分析了三者之间的相关性，探讨了次生林转变为人工林后，土壤磷形态和磷酸酶的变化特征以及驱动土壤磷素形态变化的关键因子。结果表明：（1）次生林土壤有机碳（SOC），全氮（TN）、铵态氮（NH4+-N）含量与磷酸酶活性显著高于其他四种林分。（2）五种林分中土壤残余磷（Residual-P）含量最高，是林地土壤主要的磷素存在形态。林分转变后，黄桃林与杉木林树脂提取态无机磷（Resin-Pi）显著增加，黄桃林与油茶林NaHCO3提取态磷（NaHCO3-Pi、NaHCO3-Po）含量显著增加，而四种人工林的NaOH提取态有机磷（NaOH-Po）含量均显著降低。可利用磷、中等可利用磷与稳定态磷含量及其占全磷的比例在五种林分中差异显著，其中黄桃林与油茶林可利用磷占全磷比例较高；杨梅林和杉木林中等可利用磷占总磷比例较高；油茶林与次生林中稳定态磷所占全磷比例较高。（3）相关分析表明土壤中可利用磷与全钾（TK）呈显著正相关，中等可利用磷与硝态氮（NH3--N）呈显著正相关，稳定态磷与SOC、TN、NH4+-N均呈显著正相关，磷酸酶活性与SOC、TN、NH4+-N显著正相关。综上所述，次生林转变为人工林不仅改变了土壤中总磷的含量，而且影响了不同磷形态之间的转化，导致土壤中磷的赋存状况发生改变。 Abstract:In order to clarify the differences in soil phosphorus forms and phosphatase activities in different forest types, we investigated the characteristics of soil properties, phosphorus (P) fractions, and phosphatase activities in a secondary forest and four artificial plantations (Camellia oleifera, Amygdalus persica, Myrica rubra and Cunninghamia lanceolata) in Lutou National Station for Scientific Observation and Research of Forest Ecosystems, Hunan Province. Correlations among soil properties, phosphorus fractions and phosphatase activities were analyzed, and the influencing factors driving the differences in soil phosphorus forms and phosphatase activities were identified. The results showed that:(1) the contents of soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (NH4+-N) and the activities of phosphatase in the secondary forest were higher than in the four plantations. (2) the content of residual-P was the highest in the five forest types, and residual-P was the dominant phosphorus form in forest soils. After forest conversion, resin extractable inorganic P (Resin-Pi) increased significantly in Amygdalus persica and Cunninghamia lanceolata plantations. The contents of NaHCO3 extractable P (NaHCO3-Pi, NaHCO3-Po) increased significantly in Amygdalus persica and Camellia oleifera plantations, whereas the content of NaOH extracted organic P (NaOH-Po) decreased significantly in all plantations. The contents and proportions of easily-available P, moderately-available P and non-available P in soils differed significantly among the five forest types. The proportion of easily-available P in total P was higher in Amygdalus persica and Camellia oleifera plantations than in other forests, while a higher proportion of moderately-available P in total P was found in Myrica rubra plantations and Cunninghamia lanceolata plantations. The proportion of non-available P in total P was higher in Camellia oleifera and the secondary forest compared with other forests. (3) correlation analysis demonstrated that easily-available P was positively correlated with total potassium (TK), moderately-available P was positively correlated with nitrate nitrogen (NH3--N), non-available P was positively correlated with SOC, TN, NH4+-N, and phosphatase activity was positively correlated with SOC, TN, NH4+-N. In conclusion, the conversion of secondary forest to plantations not only changed the soil total P contents, but also affected the transformation of phosphorus forms, resulted in the differences of the occurrence of P in soil. 参考文献 相似文献 引证文献