Search Results (135)

In tropical regions, the establishment of large-scale exotic plantations has addressed the demand for timber resources but has also disrupted the structural stability of native vegetation and altered soil nutrient cycling, thereby impairing ecosystem functions. Identifying effective restoration strategies for these plantations is crucial for sustainable forest management and ecological security. This study examined Acacia mangium Willd., Cunninghamia lanceolata (Lamb.) Hook., and Pinus caribaea Morelet. plantations in Hainan Tropical Rainforest National Park under three treatments: plantation control, girdling, and natural secondary forest. Vegetation surveys and soil analyses were conducted to explore the relationships between community structure, soil physicochemical properties, and enzyme activities. Diversity indices, Pearson correlations, and redundancy analysis were used to assess plant–soil relationships. The results showed that girdling significantly accelerated succession in C. lanceolata and P. caribaea plantations, increased species diversity, and enhanced the dominance of native species. Shrub-layer diversity indices (H_shrub, D_shrub, E_shrub) were the main drivers of soil properties and enzyme activities, while tree-layer effects were weaker. Girdling regulated soil nutrients and biological activity primarily via changes in community structure. These findings highlight the importance of optimizing shrub-layer structure and enhancing diversity for tropical plantation restoration. Combining forest type conversion with moderate interventions can promote coordinated plant–soil development over time. Full article

There is an urgent and constant need for land reclamation and to restore self-sustaining, stable, and resilient ecosystems. It is necessary to enhance the frequency, consistency, and success rates of applying native plant seed for ecological restoration. Smoke-water can affect seed germination of plants, regardless of whether they occur in fire-prone ecosystems. Germination trials of 18 native species of Indigenous value in the southern interior grasslands of British Columbia, Canada were conducted using a smoke aqueous solution. Locally sourced parent plant material was burned to produce smoke-water. Seeds were collected from multiple populations of the species across a wide geographic range within the B.C. southern interior to increase the genetic diversity of the seed stock. Seeds were soaked in smoke aqueous solution in various concentrates, including 0% (control), 1% (1:100), 10% (1:10), 20% (1:5), and 100%. The results indicate that germination rates in the presence of smoke-water are species-specific. Five species showed an increase in germination with smoke-water (Erythronium grandiflorum, Calochortus macrocarpus, Arnica latifolia, Lomatium nudicaule, and Shepherdia canadensis); four species showed no change (Rosa woodsii, Crataegus douglasii, Lewisia rediviva, and Prunus virginiana); and nine species showed some level of decrease (Fritillaria affinis, Fritillaria pudica, Berberis aquifolium, Claytonia lanceolata, Gaillardia aristate, Balsamorhiza sagittata, Allium cernuum, Amelanchier alnifolia, and Lomatium macrocarpum). Smoke-water also affected germination rate by plant form (herbs > shrubs), plant phenology (spring ephemeral and protracted > summer quiescent and summer mature) and plant dispersal mechanism (wind > animal). The treatments applied to encourage the germination of seeds from interior grassland forbs and shrubs have demonstrated that smoke-water can effectively break dormancy and enhance the germination rate from certain native plant species. Full article

Intra-specific variation in functional traits and their inter-relationships reflect how plants allocate resources, adapt, and evolve in response to environmental changes. This study investigated eight functional traits—leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), chlorophyll content (CHL), leaf nitrogen content (LNC), leaf phosphorus content (LPC), twig tissue density (TTD), and wood density (WD)—in Cunninghamia lanceolata plantations of three stand ages (15, 30, and 50 years), using a space-for-time substitution approach. We examined differences in trait values, intra-specific variation, and trait correlations across forest ages and diameter classes. The results showed that (1) Functional traits exhibited varying degrees of intra-specific variation, with LA having the highest coefficient of variation (21.66%) and LPC is lowest (9.31%). (2) Forest age had a stronger influence on trait variation than diameter class, with all traits differing significantly across ages, while only WD varied significantly among diameter classes. (3) PC1 (25.5%) and PC2 (19.4%) together explained approximately 44.9% of the total variation, with PC1 primarily reflecting functional trait changes driven by forest age. PCA results showed that LA and CHL tended to exhibit higher values in young forests, whereas SLA, LDMC, LPC, and LNC had relatively higher values in mature forests. This pattern suggests a shift in functional trait expression from resource acquisition to resource conservation strategies with increasing forest age. (4) Significant positive correlations between LNC and LPC, and negative correlations between SLA and LDMC, were observed in most groups, except in large-diameter trees at the over-mature stage. C. lanceolata adjusts trait combinations to enhance fitness across developmental stages. Juvenile trees adopt traits favoring efficient light and nutrient use to support rapid growth and competition. Middle-aged trees prioritize balanced water and nutrient use to maintain productivity and resist disturbances. Mature trees focus on sustained resource use and offspring protection to support ecosystem stability and regeneration. These findings reveal age-specific adaptive strategies and provide insights into the coordination and trade-offs among traits in response to environmental conditions. Full article

The Mass Ratio Hypothesis states that the growth dynamics of dominant species influence forest species diversity by regulating the niches of subordinate and transient species. However, this prediction has not yet been empirical confirmed in subtropical forests over long term. Using data from 1995 to 2017, we examined how dominant tree species regulate species evenness and richness by analyzing their height and diameter growth in three clear-cut forests (Castanopsis carlesii (Hemsl.) Hayata, Castanopsis fissa (Champ. ex Benth.) Rehder & E. H. Wilson, and Cunninghamia lanceolata (Lamb.) Hook. stands), combined with the mean value of species niche breadth (measures the diversity of resources a species utilizes) across the community, including separate analyzes for subordinate (persistently coexisting with dominants species) and transient species (temporarily occurring species). Our results showed that an increase in height and diameter growth of dominant species had a negative effect on niche breadth of subordinate species, which in turn reduced species evenness (p < 0.01) but showed no significant relationship with species richness (p ≥ 0.05). Growth dynamics of dominants had no significant influence on the niche breadth of transient species. The early-fast growing dominant C. lanceolata significantly restricted the niche breadth of subordinate species (1.16 ± 0.23), resulting in relatively low evenness (0.49 ± 0.11). Conversely, the late-fast growing dominant C. carlesii promoted niche expansion (6.62 ± 1.20), resulting in higher evenness (0.81 ± 0.02). C. fissa -dominated strands with intermediate growth increments, exhibited moderate species evenness. These findings provide long-term empirical support for the Mass Ratio Hypothesis by demonstrating that growths of dominant species modulate niche partitioning in subordinates and thereby shape species diversity in subtropical forest communities. Full article

Forest spatial structure is of significant importance for studying forest biomass accumulation and management. However, above-ground biomass (AGB) estimation based on satellite remote sensing struggles to capture forest spatial structure information, which to some extent affects the accuracy of AGB estimation. To address this issue, this study focused on Chinese fir (Cunninghamia lanceolata) plantations in Zhejiang Province. Using UAV-LiDAR (unmanned aerial vehicle light detection and ranging) data and a seed-point-based individual tree segmentation algorithm, information on individual fir trees was obtained. Building on this foundation, structural parameters such as neighborhood comparison (U), crowding degree (C), uniform angle index (W), competition index (CI), and canopy openness (K) were calculated, and their distribution characteristics analyzed. Finally, these parameters were integrated with UAV-LiDAR point cloud features to build machine learning models, and a geographical detector was used to quantify their contribution to AGB estimation. The research findings indicate the following: (1) The studied stands exhibited a random spatial pattern, moderate competition, and sufficient growing space. (2) A significant correlation existed between the U and AGB (r > 0.6), followed by CI. The optimal stand structure for AGB accumulation was C = 0.25, U < 0.5, CI in (0, 0.8], and K > 0.3. (3) The four machine learning models constructed by coupling spatial structure with point cloud features all improved the accuracy of AGB estimation for the fir forest to some extent. Among them, the XGBoost model performed best, achieving a model accuracy (R²) of 0.92 and a relatively low error (RMSE = 14.02 kg). (4) Geographical detector analysis indicated that U and CI contributed most to AGB estimation, with q-values of 0.44 and 0.37, respectively. Full article

The composition and structure of understory plants are crucial for forest ecosystem succession and stability. This study examined the impact of various Cunninghamia lanceolata mixed plantation patterns on understory biodiversity, aiming to provide a theoretical foundation for sustainable management. Six patterns were evaluated using sample plots at Guanshan Forest Farm in Jiangxi Province, China. Understory vegetation diversity, biomass, and soil properties—including total nitrogen, available nitrogen, total phosphorus, available phosphorus, total potassium, available potassium, soil organic matter, and pH—were quantitatively analyzed. Significant differences in diversity among the patterns were revealed. The ‘Cunninghamia lanceolata + Phoebe bournei (Hemsl.) Yen C. Yang + Schima superba Gardner & Champ’ mixed plantation exhibited the most pronounced enhancement of understory plant diversity, whereas the ‘C. lanceolata + Liquidambar formosana Hance’ pattern demonstrated the least significant effects among all treatments. Significant correlations were detected between soil nutrients and diversity indices. Mixed patterns enhance diversity through expanded ecological niches and optimized microenvironments, thereby strengthening ecological functions and management efficiency. Full article

Global climate change has intensified the heterogeneity of precipitation regimes in subtropical regions, and the increasing frequency of extreme drought events poses a significant threat to biogeochemical cycling in forest ecosystems. Yet, the pathways by which reduced precipitation regulates deadwood decomposition and thereby influences soil nutrient pools remain poorly resolved. Here, we investigated a Cunninghamia lanceolata (Lamb.) Hook. plantation in subtropical China under ambient precipitation (CK) and precipitation reduction treatments of 30%, 50%, and 80%, systematically examining how reduced precipitation alters the chemical properties of deadwood substrates and, in turn, soil nutrient status. Our findings reveal that (1) as precipitation declined, soil water content decreased significantly (p < 0.01), while deadwood pH declined and total organic carbon (TOC), nonstructural carbohydrates (NSCs), and lignin content markedly accumulated (p < 0.01); (2) these shifts in deadwood chemistry affected feedback mechanisms, leading to the suppression of soil nutrient pools: extreme drought (80% reduction) significantly reduced soil TOC, dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP) (p < 0.01) and inhibited N and P mineralization, whereas the 30% reduction treatment elicited a transient increase in soil microbial biomass carbon (MBC), indicative of microbial acclimation to mild water stress; and (3) principal component analysis (PCA) showed that the 80% reduction treatment drove lignin accumulation in deadwood, while the 30% reduction treatment exerted the greatest influence on soil DOC, TOC, and MBC; partial least squares path modeling (PLS-PM) further demonstrated that soil water content and deadwood substrate properties (pH, lignin, soluble sugars, TOC, C/N, and lignin/N) were strongly negatively correlated (r = −0.9051, p < 0.01), and that deadwood chemistry was, in turn, negatively correlated with soil nutrient variables (pH, TOC, DOC, MBC, TP, TN, and dissolved organic nitrogen [DON]; r = −0.8056, p < 0.01). Together, these results indicate that precipitation reduction—by drying soils—profoundly modifies deadwood chemical composition (lignin accumulation and NSC retention) and thereby, via slowed organic-matter mineralization, constrains soil nutrient release and accumulation. This work provides a mechanistic framework for understanding forest carbon–nitrogen cycling under climate change. Full article

Climate change is reshaping the distribution of forest species globally, yet its effects on the temperate tree genus Carpinus in China remain understudied. This study used an ensemble species distribution modeling framework to predict current and future suitable habitats for 32 Carpinus taxa under three shared socioeconomic pathway (SSP) climate scenarios for the 2090s. Five algorithms were integrated, and models with high predictive performance (AUC > 0.9) were used to generate ensemble forecasts. The ensemble models achieved AUC values no lower than 0.987 and TSS values no lower than 0.904. The results showed a clear trend of northwestward and upslope range shifts, with substantial habitat contractions under high-emission scenarios. Temperature seasonality and annual precipitation were identified as key environmental drivers. Two narrowly distributed species, C. omeiensis and C. londoniana var. lanceolata, are projected to lose all suitable habitats under SSP585, indicating a high extinction risk. These findings emphasize the importance of integrating climate-based risk assessments into conservation strategies and highlight the need to prioritize vulnerable species and high-elevation refugia to safeguard the long-term persistence of Carpinus diversity in China. Full article

Cunninghamia lanceolata, contributing 25% to China’s commercial timber production, faces severe drought threats. However, provenance-specific photosynthetic adaptations remain poorly understood. Here, we compared gas exchange, prompt/delayed fluorescence (PF/DF), and modulated 820-nm reflection (MR) responses of two provenances (JXJJ and FJSM) under different drought treatment times. JXJJ maintained a higher net photosynthetic rate (Pn) and stomatal conductance (Gs) than FJSM under drought stress. The declining rates of F_V/F_M, φE_O, Ψ_O, δR_O, PI_ABS, TR_O/CS_M, and ET_O/CS_M were much more rapid in the FJSM than in the JXJJ. An MR kinetics analysis revealed significantly greater PSI impairment in FJSM, evidenced by a 60.2% reduction in P700⁺ re-reduction rate (V_red) compared to only 44.4% in JXJJ (p < 0.05) at 20 d drought treatment. Similarly, DF measurements demonstrated more pronounced PSII energy transfer disruption in FJSM, with the I₂/I₁ ratio increasing by 51.3% vs. 43.0% in JXJJ at 20 d drought treatment. These results demonstrate JXJJ’s superior drought resilience through coordinated stomatal and non-stomatal regulation. Our findings provide actionable criteria for selecting drought-tolerant C. lanceolata provenances, which is essential for sustainable forestry as the climate changes. This study underscores the significance of photosynthetic activity in how C. lanceolata responds to drought and gives insights into boosting drought tolerance in forest species through genetic improvements. Full article

Nitrogen (N) deposition and carbon (C) addition significantly influence the dynamics of plant–microbe interactions, particularly altering the symbiotic relationship between plants and arbuscular mycorrhizal fungi (AMF). However, the effects and underlying mechanisms of labile C input on the relationship between AMF and various plant species in a nitrogen-enriched environment remain a knowledge gap. A seven-year field experiment was conducted to examine how six levels of N and three levels of labile C addition impact AMF colonization in four key plant species: Leymus chinensis (Trin. ex Bunge) Tzvelev, Stipa baicalensis Roshev., Thermopsis lanceolata R. Br. and Potentilla bifurca Linn. Our results showed that N and C additions exert significantly different effects on the relationship between AMF and various plant species. Labile C addition mitigated historical N negative effects, particularly for S. baicalensis, enhancing AMF infection and promoting nutrient exchange under high-N and low-C conditions. The relationship between AMF and both L. chinensis and T. lanceolata changed to weak mutualism under low-N and high-C conditions, with significant decreases in vesicular and arbuscular abundance. Plant root stoichiometry plays a critical role in modulating AMF symbiosis, particularly under high-N and -C conditions, as reflected in the increased AMF infection observed in T. lanceolata and P. bifurca. Our findings emphasize the species-specific and nutrient-dependent AMF symbiosis, revealing that targeted C input can mitigate the legacy effects of N enrichment. Effective nutrient management is of crucial importance for ecological restoration efforts in temperate grasslands affected by long-term N enrichment. Full article

The roots of Codonopsis lanceolata (Siebold & Zucc.) Benth. & Hook.f. ex Trautv. have been traditionally used for medicinal purposes across East Asia. However, their chemical constituents in Japanese-grown varieties remain uninvestigated. This study employed ultra-high-performance liquid chromatography–quadrupole–orbitrap mass spectrometry to perform a comprehensive chemical analysis of the roots of C. lanceolata cultivated in Nagano Prefecture, Japan, leveraging fragment pattern analysis of both isolated and commercially available compounds as references compounds. As a result, 27 compounds, including triterpenoid saponins (19–22), polyacetylenes (6, 15, 18), flavonoids (16, 17), phenylpropanoids (3–5, 7, 9), a lignan (10), glycolipids (8, 11–14), phospholipids (23–27), and amino acids (1, 2), were identified. Notably, a triterpenoid saponin (19) was identified as a previously unreported compound, and ten compounds (3, 6, 8, 10, 13, 17, and 23–27) were identified from C. lanceolata roots for the first time. The ex vivo study revealed that lancemaside A (22) exhibited a time-dependent vasodilatory effect on rat aortic ring specimens. These findings not only advanced the understanding of the chemical constituents and biological activity of C. lanceolata roots but also provided valuable insights for their future applications and quality control. Full article

Girdling is a crucial technique for promoting the close-to-nature transformation of plantation forests in Hainan Tropical Rainforest National Park (HNNP). It has shown effectiveness in aspects such as community structure and biodiversity restoration. However, its impacts on ecological functions like eco-hydrology still require further in-depth investigation. This study analyzes the impact of girdling on the eco-hydrological indices of three plantations—Acacia mangium, Pinus caribaea, and Cunninghamia lanceolata—through field investigations and laboratory tests. The data was evaluated using a game theory combination weighting-cloud model. The results show that the eco-hydrological indicators of leaf litter in A. mangium increased by 5.77% while those of P. caribaea and C. lanceolata decreased by 11.86% and 5.29%, respectively. Soil bulk density decreased slightly across all plantations while total porosity increased, with A. mangium showing the highest increase of 20.31%. Organic carbon content increased by 76.81% in A. mangium and 7.24% in C. lanceolata, whereas it decreased in P. caribaea. Saturated hydraulic conductivity increased by 33.32% in P. caribaea and 20.91% in A. mangium but decreased in C. lanceolata. Based on the cloud model, the eco-hydrological function of A. mangium improved from ‘medium’ to ‘good’, while that of P. caribaea and C. lanceolata declined towards the ‘poor’ level. In summary, during the process of close-to-nature transformation of tropical rainforests, girdling is an effective method to enhance the ecohydrological functions of broadleaf planted forests. However, for coniferous species, the ecohydrological functions of the planted forests weaken in the short term following the transformation. Full article

Ammonium nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃⁻-N) that can be absorbed and utilized by plants are heterogeneously distributed in soil, which affects plant growth and bacterial communities in the roots. To investigate the effects of single and mixed nitrogen (N) on bacterial communities in the rhizospheres and root surfaces of Cunninghamia lanceolata (CR, CRS) and Schima superba (SR, SRS), we subjected three different ratios of NH₄⁺-N to NO₃⁻-N 2:0, 1:1 (control, CK), 0:2 to cultivate the seedlings. Compared with the CK, the ratio of 0:2 increased the number, diversity, and composition of bacteria in CR, whereas the ratios of 2:0 and 0:2 both decreased in CRS, SR, and SRS. The bacterial diversities were both R > RS in two tree species, but there was no discernible trend between the two tree species in the rhizosphere and root surface. Proteobacteria and Bacteroidota were the dominant bacterial phyla in CR and CRS, whereas Proteobacteria and Acidobacteriota dominated in SR and SRS. Patescibacteria and Planctomycetota promoted the aboveground growth of C. lanceolata but negatively drove root growth. Patescibacteria and Cyanobacteria in SR were related to its root growth, whereas the Actinobacteriota in SR and SRS, and the Patescibacteria and Cyanobacteria in SRS, promoted its aboveground growth. Overall, the mixed N addition was more conducive to bacterial community proliferation than single N on rhizospheres compared to root surfaces. The opposite reactions were observed from the aboveground and underground growth, which were driven by a few dominant bacterial phyla. Full article

Forest soils play a key role in the global carbon (C) pool and in mitigating climate change. The mechanisms by which understory and litter management affect soil organic C (SOC) concentrations are unclear in subtropical forests. We collected soils along a 60 cm profile in a Chinese fir (Cunninghamia lanceolata) plantation treated by only aboveground litter removal and understory vegetation preservation (Only-ALR), both aboveground litter and understory vegetation removal (ALR+UVR), and both aboveground litter and understory vegetation preservation (control) for 7 consecutive years. Five SOC fractions, physico-chemical properties, the biomass of microbial communities and the activities of C-acquiring enzymes were measured, and their correlations were analyzed for each of four soil layers (0–10, 10–20, 20–40 and 40–60 cm). Compared with control, Only-ALR decreased labile C pool I (LP-C I), labile C pool II (LP-C II) and dissolved organic C (DOC) in topsoil (0–20 cm) but had no effect on soil C fractions in subsoil (20–60 cm). A higher fungi and bacteria biomass in LP-C II and microbial biomass C (MBC) stock was observed in Only-ALR compared to ALR+UVR treatment. Soil pH and Gram-positive bacteria generally had impact on the variation of soil C fractions in topsoil and subsoil, respectively. Understory vegetation preservation offsets the declines of SOC and recalcitrant C but not the decreases in labile C caused by aboveground litter removal. Understory vegetation helps sustain SOC stock mainly via decreased C input and elevated soil pH which would change microbial biomass and activities when litter is removed. Our findings highlight the potential influence of long-term understory manipulation practices on C pool within a soil profile in subtropical plantation forests. Full article

Enzymes capable of processing a variety of compounds enable plants to adapt to diverse environmental conditions. PRISEs (progesterone-5β-reductase/iridoid synthase-like enzymes), examples of such substrate-promiscuous enzymes, are involved in iridoid and cardenolide pathways and demonstrate notable substrate promiscuity by reducing the activated C=C double bonds of plant-borne and exogenous 1,4-enones. In this study, we identified PRISE genes in Plantago media (PmdP5βR1) and Plantago lanceolata (PlP5βR1), and the corresponding enzymes were determined to share a sequence identity of 95%. Despite the high sequence identity, recombinant expressed PmdP5βR1 was 70 times more efficient than PlP5βR1 for converting progesterone. In order to investigate the underlying reasons for this significant discrepancy, we focused on specific residues located near the substrate-binding pocket and adjacent to the conserved phenylalanine “clamp”. This clamp describes two phenylalanines influencing substrate preferences by facilitating the binding of smaller substrates, such as 2-cyclohexen-1-one, while hindering larger ones, such as progesterone. Using structural analysis based on templates PDB ID: 5MLH and 6GSD from PRISE of Plantago major, along with in silico docking, we identified positions 156 and 346 as hot spots. In PlP5βR1 amino acid residues, A156 and F346 seem to be responsible for the diminished ability to reduce progesterone. Moreover, the double mutant PlP5βR_F156L_A346L, which contains the corresponding amino acids from PmdP5βR1, showed a 15-fold increase in progesterone 5β-reduction. Notably, this modification did not significantly alter the enzyme’s ability to convert other substrates, such as 8-oxogeranial, 2-cyclohexen-1-one, and methyl vinyl ketone. Hence, a rational enzyme design by reducing the number of hotspots selectively, specifically improved the substrate preference of PlP5βR1 for progesterone. Full article