Responses of leaf morphology, NSCs contents and C:N:P stoichiometry of Cunninghamia lanceolata and Schima superba to shading.

BACKGROUND: The non-structural carbohydrates (NSCs), carbon (C), nitrogen (N), and phosphorus (P) are important energy source or nutrients for all plant growth and metabolism. To persist in shaded understory, saplings have to maintain the dynamic balance of carbon and nutrients, such as leaf NSCs, C, N and P. To improve understanding of the nutrient utilization strategies between shade-tolerant and shade-intolerant species, we therefore compared the leaf NSCs, C, N, P in response to shade between seedlings of shade-tolerant Schima superba and shade-intolerant Cunninghamia lanceolate. Shading treatments were created with five levels (0, 40, 60, 85, 95% shading degree) to determine the effect of shade on leaf NSCs contents and C:N:P stoichiometry characteristics. RESULTS: Mean leaf area was significantly larger under 60% shading degree for C. lanceolata while maximum mean leaf area was observed under 85% shading degree for S. superba seedlings, whereas leaf mass per area decreased consistently with increasing shading degree in both species. In general, both species showed decreasing NSC, soluble sugar and starch contents with increasing shading degree. However shade-tolerant S. superba seedlings exhibited higher NSC, soluble sugar and starch content than shade-intolerant C. lanceolate. The soluble sugar/starch ratio of C. lanceolate decreased with increasing shading degree, whereas that of S. superb remained stable. Leaf C:N ratio decreased while N:P ratio increased with increasing shading degree; leaf C:P ratio was highest in 60% shading degree for C. lanceolata and in 40% shading degree for S. superba. CONCLUSION: S. superba is better adapted to low light condition than C. lanceolata through enlarged leaf area and increased carbohydrate reserves that allow the plant to cope with low light stress. From mixed plantation viewpoint, it would be advisable to plant S. superba later once the canopy of C. lanceolata is well developed but allowing enough sunlight.

Asymmetric pruning reveals how organ connectivity alters the functional balance between leaves and roots of Chinese fir.

The functional balance between leaves and roots is believed to be mediated by the specific location of shoots and roots, i.e. differences in transport distances and degrees of organ connectivity. However, it remains unknown whether the adaptive responses of trees to biomass removal depend on the relative orientation of leaf and root pruning. Here, we applied five pruning treatments to saplings of Cunninghamia lanceolata (Chinese fir) under field and glasshouse conditions, namely no pruning (control), half of lateral branches pruned, half of lateral roots pruned, half of the branches and roots pruned on the same side of the plant, and half of the branches and roots pruned on opposite sides of the plant. The effects of pruning on the growth, carbon storage and allocation, and physiology of leaves and fine roots on the same and opposite sides of the plant were investigated. Compared with the effect of root-pruning on leaves, fine roots were more limited by carbon availability and their physiological activity was more strongly reduced by shoot pruning, especially when branches on the same side of the plant were removed. Pruning of branches and roots on the opposite side of the plant resulted in the lowest carbon assimilation rates and growth among all treatments. The results of a stable-isotope labeling indicated that less C was distributed to fine roots from the leaves on the opposite side of the plant compared to those on the same side, but N allocation from roots to leaves depended less on the relative root and leaf orientation. The results collectively indicate that the functional responses of C. lanceolata to pruning are not only determined by the source-sink balance model but are also related to interactions between leaves and fine roots. We argue that the connectivity among lateral branches and roots depends on their relative orientation, which is therefore critical for the functional balance between leaves and fine roots.

Development of the photosynthetic apparatus of Cunninghamia lanceolata in light and darkness.

Here, we compared the development of dark- and light-grown Chinese fir (Cunninghamia lanceolata) cotyledons, which synthesize chlorophyll in the dark, representing a different phenomenon from angiosperm model plants. We determined that the grana lamellar membranes were well developed in both chloroplasts and etiochloroplasts. The accumulation of thylakoid membrane protein complexes was similar between chloroplasts and etiochloroplasts. Measurement of chlorophyll fluorescence parameters indicated that photosystem II (PSII) had low photosynthetic activities, whereas the photosystem I (PSI)-driven cyclic electron flow (CEF) rate exceeded the rate of PSII-mediated photon harvesting in etiochloroplasts. Analysis of the protein contents in etiochloroplasts indicated that the light-harvesting complex II remained mostly in its monomeric conformation. The ferredoxin NADP+ oxidoreductase and NADH dehydrogenase-like complexes were relatively abundantly expressed in etiochloroplasts for Chinese fir. Our transcriptome analysis contributes a global expression database for Chinese fir cotyledons, providing background information on the regulatory mechanisms of different genes involved in the development of dark- and light-grown cotyledons. In conclusion, we provide a novel description of the early developmental status of the light-dependent and light-independent photosynthetic apparatuses in gymnosperms.

A broadleaf species enhances an autotoxic conifers growth through belowground chemical interactions.

Plants may affect the performance of neighboring plants either positively or negatively through interspecific and intraspecific interactions. Productivity of mixed-species systems is ultimately the net result of positive and negative interactions among the component species. Despite increasing knowledge of positive interactions occurring in mixed-species tree systems, relatively little is known about the mechanisms underlying such interactions. Based on data from 25-year-old experimental stands in situ and a series of controlled experiments, we test the hypothesis that a broadleaf, non-N fixing species, Michelia macclurei, facilitates the performance of an autotoxic conifer Chinese fir (Cunninghamia lanceolata) through belowground chemical interactions. Chinese fir roots released the allelochemical cyclic dipeptide (6-hydroxy-1,3-dimethyl-8-nonadecyl-[1,4]-diazocane- 2,5-diketone) into the soil environment, resulting in self-growth inhibition, and deterioration of soil microorganisms that improve P availability. However, when grown with M. macclurei the growth of Chinese fir was consistently enhanced. In particular, Chinese fir enhanced root growth and distribution in deep soil layers. When compared with monocultures of Chinese fir, the presence of M. macclurei reduced release and increased degradation of cyclic dipeptide in the soil, resulting in a shift from self-inhibition to chemical facilitation. This association also improved the soil microbial community by increasing arbuscular mycorrhizal fungi, and induced the production of Chinese fir roots. We conclude that interspecific interactions are less negative than intraspecific ones between non-N fixing broadleaf and autotoxic conifer species. The impacts are generated by reducing allelochemical levels, enhancing belowground mutualisms, improving soil properties, and changing root distributions as well as the net effects of all the processes within the soil. In particular, allelochemical context alters the consequences of the belowground ecological interactions with a novel mechanism: reduction of self-inhibition through reduced release and increased degradation of an autotoxic compound in the mixed-species plantations. Such a mechanism would be useful in reforestation programs undertaken to rehabilitate forest plantations that suffer from problems associated with autotoxicity.

Global Reprogramming of Transcription in Chinese Fir (Cunninghamia lanceolata) during Progressive Drought Stress and after Rewatering.

Chinese fir (Cunninghamia lanceolata), an evergreen conifer, is the most commonly grown afforestation species in southeast China due to its rapid growth and good wood qualities. To gain a better understanding of the drought-signalling pathway and the molecular metabolic reactions involved in the drought response, we performed a genome-wide transcription analysis using RNA sequence data. In this study, Chinese fir plantlets were subjected to progressively prolonged drought stress, up to 15 d, followed by rewatering under controlled environmental conditions. Based on observed morphological changes, plantlets experienced mild, moderate, or severe water stress before rehydration. Transcriptome analysis of plantlets, representing control and mild, moderate, and severe drought-stress treatments, and the rewatered plantlets, identified several thousand genes whose expression was altered in response to drought stress. Many genes whose expression was tightly coupled to the levels of drought stress were identified, suggesting involvement in Chinese fir drought adaptation responses. These genes were associated with transcription factors, signal transport, stress kinases, phytohormone signalling, and defence/stress response. The present study provides the most comprehensive transcriptome resource and the first dynamic transcriptome profiles of Chinese fir under drought stress. The drought-responsive genes identified in this study could provide further information for understanding the mechanisms of drought tolerance in Chinese fir.

[Responses of seed germination and seedling growth of Cunninghamia lanceolata and Schima superba to different light intensities.] / æ‰æœ¨å’Œæœ¨è·ç§å­èŒå‘åŠå¹¼è‹—ç”Ÿé•¿å¯¹å ‰æ¢¯åº¦çš„å“åº”.

Light is a key factor affecting seed germination and seedling growth. In this study, seed germination and seedling growth of Cunninghamia lanceolata and Schima superba were compared under controlled conditions with five light treatments (100%, 60%, 40%, 15% and 5% of full sunlight). The results showed that light intensity significantly impacted seed germination and seedling growth of both species. With decreasing light intensity, the germination rate and germination index of C. lanceolata increased, while those of S. superba showed a trend which increased first and then decreased, with the maximum at 40% light intensity. The seedling survival rate of both species was 0 under full sunlight, while significantly decreased with decreasing light intensity from 60% to 5%. Root length, basal stem diameter and height showed a consistent trend with the change of light availability in both species. Root length significantly decreased, basal stem diameter and height increased first and then decreased with decreasing light intensity, with the minimum at 5% light intensity. With decreasing light intensity, root biomass, stem biomass, leaf biomass and total biomass of C. lanceolata seedlings declined, while high biomass accumulation of S. superba seedlings were observed in 15%-60% light intensities, and lowest at 5% light intensity. Biomass accumulation in each organ of S. superba seedlings was greater than that of C. lanceolata seedlings under the same light intensity. High stem biomass and leaf biomass, low root biomass and root to shoot ratio were a phenotypic response to low light intensity in C. lanceolata and S. superba seedlings grown under poor light condition. The growth of C. lanceolata is better under relatively high light intensity than S. superba. Whereas S. superba is moderately shade-tolerant at the seedling stage, thus is more suitable for planting under closed canopy.

Succession in arbuscular mycorrhizal fungi can be attributed to a chronosequence of Cunninghamia lanceolata.

Arbuscular mycorrhizal (AM) fungi play an important role in plant-fungi communities. It remains a central question of how the AM fungal community changes as plants grow. To establish an understanding of AM fungal community dynamics associated with Chinese fir, Chinese fir with five different growth stages were studied and 60 root samples were collected at the Jiangle National Forestry Farm, Fujian Province. A total of 76 AM fungal operational taxonomic units (OTUs) were identified by high-throughput sequencing on an Illumina Miseq platform. The genera covered by OTUs were Glomus, Archaeospora, Acaulospora, Gigaspora and Diversispora. Glomus dominated the community in the whole stage. The number and composition of OTUs varied along with the host plant growth. The number of OTUs showed an inverted V-shaped change with the host plant age, and the maximum occurred in 23-year. Overall, the basic species diversity and richness in this study were stable. Non-metric multi-dimensional scaling (NMDS) analysis based on bray-curtis distance revealed that there were remarkable differentiations between the 9-year and other stages. Besides, AM fungal community in 32-year had a significant difference with that of 23-year, while no significant difference with that of 45-year, suggesting that 32-year may be a steady stage for AM fungi associated with Chinese fir. The cutting age in 32-year may be the most favorable for microbial community. The pH, total N, total P, total K, available N, available P, available K, organic matter and Mg varied as the Chinese fir grows. According to Mantel test and redundancy analysis, available N, available P, K and Mg could exert significant influence on AM fungal communities, and these variables explained 31% of variance in the composition of AM fungal communities.

Effects of Composite LED Light on Root Growth and Antioxidant Capacity of Cunninghamia lanceolata Tissue Culture Seedlings.

We used the 12th generation of the Cunninghamia (C.) lanceolata tissue culture seedlings, and white light emitting diode (LED) light as control (CK). We applied five composite LED light treatments, red-blue 4:1, 8:1 (4R1B and 8R1B), red-blue-purple 8:1:1 (8R1B1P), and red-blue-purple-green 6:1:1:1, 8:1:1:1 (6R1B1P1G and 8R1B1P1G), to study the effects of light quality on root growth characteristics and antioxidant capacity of C. lanceolata tissue culture seedlings. The results showed that: (1) rooting rate, average root number, root length, root surface area, and root activity were higher with 6R1B1P1G and 8R1B1P1G treatments compared to 4R1B, 8R1B, 8R1B1P and CK treatments; and the root growth parameters under the 8R1B1P1G treatment were as high as 95.50% for rooting rate, 4.63 per plant of the average number of root, 5.95 cm root length, 1.92 cm2 surface area, and 145.56 ng/(g·h) root activity, respectively. (2) The composite lights of 4R1B, 8R1B, 8R1B1P, 6R1B1P1G, and 8R1B1P1G are beneficial for the accumulation of soluble sugar content (SSC) and soluble protein content (SPC), but not conducive for the increase of free proline content (FPC); the plants under 6R1B1P1G and 8R1B1P1G treatments had higher superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) activity and lower malondialdehyde (MDA), polyphenol oxidase (PPO) activity. (3) Redundancy analysis showed that POD activity positively correlated with root activity; SPC, SOD and CAT activities positively correlated with root growth parameters; while SSC, MDA content, APX and PPO activities negatively correlated with root growth parameters. These results suggest that the responses of root growth and antioxidant capacity of the C. lanceolata tissue culture seedlings to different light qualities vary. The relationship between root growth parameters and antioxidant capacity was closely related. Red-blue-purple-green was the most suitable composite light quality for root growth of C. lanceolata tissue culture seedlings, and 8:1:1:1 was the optimal ratio, under which the rooting rate, root activity and root growth of tissue culture seedlings peaked.

[Identification and analysis of differentially expressed genes during wood formation in Chinese fir by SSH].

Wood is an important raw material for the global industry with rapidly increasing demand. To isolate the differentially expressed genes in xylogenesis of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook], a forward subtractive cDNA library was constructed using suppression subtractive hybridization (SSH) method, which was performed using the cDNA from the mutant Dugansha clone as the tester and the cDNA from the normal Jurong 0 clone as the driver. Six hundred and eighteen clones were obtained. Recombinants were identified using PCR with universal T7 and SP6 primers and using EcoR digestion. To further eliminate false positive, dot hybridization was used with four DIG-labeled probes (FSP, RSP, UTP, and UDP). Real-time PCR was performed to confirm the results. A total of 260 unique ESTs were obtained, 60% of the ESTs exhibiting homologies with proteins of known function fell into 4 major classes: metabolism, cell wall biogenesis and remodeling, signal transduction and stress. The systematic analysis of genes involved in wood formation in Chinese fir provides valuable insights into the molecular mechanisms involved in xylem differentiation, is important resources for forest research directed toward understanding the genetic control of wood formation and future endeavors to modify wood and fiber properties for industrial use.

Thinning effect on photosynthesis depends on needle ages in a Chinese fir (Cunninghamia lanceolata) plantation.

Canopies in evergreen coniferous plantations often consist of various-aged needles. However, the effect of needle age on the photosynthetic responses to thinning remains ambiguous. Photosynthetic responses of different-aged needles to thinning were investigated in a Chinese fir (Cunninghamia lanceolata) plantation. A dual isotope approach [simultaneous measurements of stable carbon (δ13C) and oxygen (δ18O) isotopes] was employed to distinguish between biochemical and stomatal limitations to photosynthesis. Our results showed that increases in net photosynthesis rates upon thinning only occurred in the current-year and one-year-old needles, and not in the two- to four-year-old needles. The increased δ13C and declined δ18O in current year needles of trees from thinned stands indicated that both the photosynthetic capacity and stomatal conductance resulted in increasing photosynthesis. In one-year-old needles of trees from thinned stands, an increased needle δ13C and a constant needle δ18O were observed, indicating the photosynthetic capacity rather than stomatal conductance contributed to the increasing photosynthesis. The higher water-soluble nitrogen content in current-year and one-year-old needles in thinned trees also supported that the photosynthetic capacity plays an important role in the enhancement of photosynthesis. In contrast, the δ13C, δ18O and water-soluble nitrogen in the two- to four-year-old needles were not significantly different between the control and thinned trees. Thus, the thinning effect on photosynthesis depends on needle age in a Chinese fir plantation. Our results highlight that the different responses of different-aged needles to thinning have to be taken into account for understanding and modelling ecosystem responses to management, especially under the expected environmental changes in future.

Thinning increases understory diversity and biomass, and improves soil properties without decreasing growth of Chinese fir in southern China.

Sustainable forestry requires adopting more ecosystem-informed perspectives. Tree thinning improves forest productivity by encouraging the development of the understory, which in turn improves species diversity and nutrient cycling, thereby altering the ecophysiological environment of the stand. This study aimed to quantify tree growth, understory vegetation, and soil quality of 9- and 16-year-old Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations in South China, 1-7 years after pre-commercial thinning. The quadratic mean diameter (QMD) and individual tree volume were greatly increased and compensated for the reduced stand yield in thinned stands. In 2011, the stand volume in unthinned and thinned stands were 276.33 and 226.46 and 251.30 and 243.64 m3 ha-1, respectively, for young and middle stage. Therefore, we predicted that over time, the stand volume in thinned stands should exceed that in unthinned stands. The composition, diversity, and biomass of understory vegetation of the plantation monocultures significantly increased after thinning. The effects of thinning management on understory development were dynamic and apparent within 1-2 years post-thinning. Some light-demanding plant species such as Styrax faberi, Callicarpa formosana, Lophatherum gracile, and Gahnia tristis emerged in the shrub and herb layer and became dominant with the larger gaps in the canopy in thinned stands. The trigger effects of thinning management on understory and tree growth were more pronounced in the young stage. The beneficial effects on soil physical and chemical properties were measurable at later stages (7 years after thinning). The strong positive relationship between understory biomass and volume increment (at the tree and stand levels) indicated that understory improvement after thinning did not restrict productivity within Chinese fir stands but rather, benefited soil water content and nutrient status and promoted tree growth.

Growth, biomass allocation and photosynthetic responses are related to intensity of root severance and soil moisture conditions in the plantation tree Cunninghamia lanceolata.

We employed the warm temperate conifer Cunninghamia lanceolata (Lamb.) Hook. as a model of plantation forest species to investigate ecophysiological responses to root treatments (control (0%), and ∼25, 50 or 75% of the initial root mass) under well-watered and water-limited conditions. Our results indicated that total root dry mass accumulation was negatively associated with the severity of root pruning, but there was evidence of multiple compensatory responses. The plants exhibited higher instantaneous and long-term (assessed by carbon isotope composition, δ(13)C) water-use efficiency in pruning treatments, especially under low water availability. Root pruning also increased the fine root/total root mass ratio, specific root length and fine root vitality in both water availability treatments. As a result of the compensatory responses, under well-watered conditions, height, stem dry mass accumulation, leaf/fine root biomass ratio (L/FR), transpiration rate, photosynthetic capacity and photosynthetic nitrogen-use efficiency (EN) were the highest under 25% pruning. Yet, all these traits except L/FR and foliage nitrogen content were severely reduced under 75% pruning. Drought negatively affected growth and leaf gas exchange rates, and there was a greater negative effect on growth, water potential, gas exchange and EN when >25% of total root biomass was removed. The stem/aboveground mass ratio was the highest under 25% pruning in both watering conditions. These results indicate that the responses to root severance are related to the excision intensity and soil moisture content. A moderate root pruning proved to be an effective means to improve stem dry mass accumulation.

Partial shading of lateral branches affects growth, and foliage nitrogen- and water-use efficiencies in the conifer Cunninghamia lanceolata growing in a warm monsoon climate.

The degree to which branches are autonomous in their acclimation responses to alteration in light environment is still poorly understood. We investigated the effects of shading of the sapling crown of Cunninghamia lanceolata (Lamb.) Hook on the whole-tree and mid-crown branch growth and current-year foliage structure and physiology. Four treatments providing 0, 50, 75 and 90% shading compared with full daylight (denoted as Treatment(0), Treatment(50%), Treatment(75%) and Treatment(90%), and Shaded(0), Shaded(50%), Shaded(75%) and Shaded(90%) for the shaded branches and Sunlit(0), Sunlit(50%), Sunlit(75%) and Sunlit(90%) for the opposite sunlit branches under natural light conditions, respectively), were applied over two consecutive growing seasons. Shading treatments decreased the growth of basal stem diameter, leaf dry mass per unit leaf area, stomatal conductance, transpiration rate, the ratio of water-soluble to structural leaf nitrogen content, photosynthetic nitrogen-use efficiency and instantaneous and long-term (estimated from carbon isotope composition) water-use efficiency in shaded branches. Differences between shaded and sunlit branches increased with increasing severity and duration of shading. A non-autonomous, partly compensatory behavior of non-shaded branches was observed for most traits, thus reflecting the dependence between the traits of sunlit branches and the severity of shading of the opposite crown half. The results collectively indicated that tree growth and branch and leaf acclimation responses of C. lanceolata are not only affected by the local light environment, but also by relative within-crown light conditions. We argue that such a non-autonomous branch response to changes in light conditions can improve whole-tree resource optimization. These results contribute to better understanding of tree growth and utilization of water and nitrogen under heterogeneous light conditions within tree canopies.

Stand diameter distribution modelling and prediction based on Richards function.

The objective of this study was to introduce application of the Richards equation on modelling and prediction of stand diameter distribution. The long-term repeated measurement data sets, consisted of 309 diameter frequency distributions from Chinese fir (Cunninghamia lanceolata) plantations in the southern China, were used. Also, 150 stands were used as fitting data, the other 159 stands were used for testing. Nonlinear regression method (NRM) or maximum likelihood estimates method (MLEM) were applied to estimate the parameters of models, and the parameter prediction method (PPM) and parameter recovery method (PRM) were used to predict the diameter distributions of unknown stands. Four main conclusions were obtained: (1) R distribution presented a more accurate simulation than three-parametric Weibull function; (2) the parameters p, q and r of R distribution proved to be its scale, location and shape parameters, and have a deep relationship with stand characteristics, which means the parameters of R distribution have good theoretical interpretation; (3) the ordinate of inflection point of R distribution has significant relativity with its skewness and kurtosis, and the fitted main distribution range for the cumulative diameter distribution of Chinese fir plantations was 0.4∼0.6; (4) the goodness-of-fit test showed diameter distributions of unknown stands can be well estimated by applying R distribution based on PRM or the combination of PPM and PRM under the condition that only quadratic mean DBH or plus stand age are known, and the non-rejection rates were near 80%, which are higher than the 72.33% non-rejection rate of three-parametric Weibull function based on the combination of PPM and PRM.

Significance of exine shedding in Cupressaceae-type pollen.

In conifers, which have non-saccate Cupressaceae-type pollen, the pollen must land on a pollination drop or be picked up by the pollination drop from the surface of the cone near the ovule before it can be taken into the ovule. After contact with the drop, the pollen intine absorbs moisture from the drop, expands and the exine is shed. In this study the significance of the shedding of the exine is interpreted from experiments in which simulated pollination drops and micropyles were used to determine the movement of pollen and other particles in suspension. The non-expanded pollen, which can be observed upon contact with the pollination drop, sheds the exine, which then functions as a non-elastic particle, while the pollen from which the exine was shed swells and functions as an elastic particle because it is enclosed by the flexible intine. Non-elastic particles are not easily transferred through narrow passages (the micropyle and micropylar canal) and tend to plug these passages. However, elastic particles, such as the swollen pollen, are easily transferred along narrow passages even when non-elastic particles are present. The simulated experiments demonstrate that exine shedding is an important feature in getting pollen through the narrow micropyle and micropylar canal to the nucellus of the ovule.

[Comparative study on regeneration systems of Cunninghamia lanceolata hook].

Four regeneration systems derived from cotyledon, hypocotyls, stem and needle explants have been established in the comparative researches of regeneration systems in Cunninghamia lanceolata Hook. A high frequency (93.7% +/- 0.45%) of adventitious buds were induced from cotyledons on DCR medium supplemented with 1 mg/L BA and 0.1 mg/L NAA, with a maximum mean number buds of 3.76 +/- 0.25. A higher frequency (96.2% +/- 0.35%) of adventitious buds were induced from hypocotyls on DCR medium supplemented with 2 mg/L BA and 0.2 mg/L NAA, with a maximum mean number buds of 17.4 +/- 0.18. A highest frequency (100%) of adventitious buds were induced from stem segments on DCR medium supplemented with 1 mg/L BA and 0.1 mg/L NAA, with a maximum mean number buds of 3.28 +/- 0.11. A low frequency (84.5% +/- 0.45%) of adventitious buds were induced from needles on DCR medium supplemented with 1.5 mg/L BA and 0.1 mg/L NAA, with a maximum mean number buds of 1.42 +/- 0.08. Buds were elongated on DCR medium supplemented with 0.2 mg/L BA and 0.02 mg/L NAA. After pre-treating shoots, best rooting result was produced on 1/2 DCR medium supplemented with 0.3 mg/L IBA.

[Effects of plant foliar litter diversity on the growth of Chinese fir seedling and the absorption of (15NH4)2SO4].

Effects of plant foliar litter species composition on the growth of the potted Chinese fir seedling and the absorption of (15NH4)2SO4 was studied. The result showed that there were significant growth responses to foliar litter treatments. A very noticeable trend was that as the tree species of foliar litter placed on pots increases, the growth of Chinese fir seedlings increases steadily. Seedling growth in four-species mixed foliar litter were the largest and that in Cunninghamia lanceolata + Michelia macclurei + Kalooanax septemlobus foliar litter mixture were the second. The others were in order of seedlings in C. lanceolata + M. macclurei + Castanopsis carlesii foliar litter mixture > C. lanceolata + K. septemlobus foliar litter mixture > C. lanceolata + C. carlesii > control (no foliar litter) > C. lanceolata + M. macclurei foliar litter mixture > Chinese fir foliar litter treatment. The recovery of (15NH4)2SO4 by Chinese fir seedlings in no foliar litter treatment was maximum, and seedlings grown in four foliar litter mixture was the second, then it was in order of C. lanceolata + C. carlesii + K. septemlobus = C. lanceolata + C. carlesii + M. macclurei > C. lanceolata + K. septemlobus > C. lanceolata + C. carlesii > C. lanceolata + M. macclurei > C. lanceolata foliar litter treatment. In addition, the residue of (15NH4)2SO4 was greater in soil with foliar litter treatment than in no foliar litter soil. Both of the residual amount of (15NH4)2SO4 in soil and the total recovery of (15NH4)2SO4 increased with the increasing tree species of applied foliar litter.

[Effect of vanillin and P-hydroxybenzoic acid on physiological characteristics of Chinese fir seedlings].

Effects of vanillin and P-hydroxybenzoic acid at different concentrations on physiological characteristic of Chinese fir seedlings were studied by potted experiment. The results showed that 10 mmol.L-1 and 1 mmol.L-1 of two kinds of phenolics significantly reduced the content of chlorophyll, rate of photosynthesis and root activity, and that the higher the concentration of vanillin and P-hydroxybenzoic acid, the more the physiological activities was inhibited. By treatment with 1 and 10 mmol.L-1 vanillin, Chinese fir seedlings reduced its photosynthesis rate 25.1% and 37.0%, transpiration rate 20.3% and 37.0%, stomata conductance 33.7% and 46.8% and root activity 51.6% and 78.8%, respectively. The results suggested that vanillin and P-hydroxybenzoic acid accumulated in the soil by continuous cropping of Chinese fir may have some allelopathic effect on the seedlings of Chinese fir and the effect is one of the factors leading to the low productivity of continuously cropped Chinese fir forest.