[Effects of nitrogen addition on acidolyzable organic nitrogen components and nitrogen mineralization in aggregates of plantations in the Three Gorges Reservoir area, China].

We sieved soils from a plantation in the Three Gorges Reservoir area into four aggregate sizes, including aggregates of 2000-8000 μm (large macroaggregates), 1000-2000 μm (coarse aggregates), 250-1000 μm (small macroaggregates), and <250 μm (microaggregates). We analyzed the differences in the acidolyzable organic N components and net N mineralization of the aggregates under different N addition levels (30, 60, and 90 kg N·hm·a, representing by N, N and N, respectively). The results showed that net nitrification rate of the aggregates ranged from 0.

Soil microbial residue characteristics in Pinus massoniana lamb. Plantations.

A large amount of stable soil organic matter (SOM) is derived from microbial necromass, which can be assessed by quantifying amino sugar biomarkers. Pinus massoniana Lamb. Plantations are widely distributed in China and play a vital role in forest carbon sequestration.

The Relationship between Ectomycorrhizal Fungi, Nitrogen Deposition, and Pinus massoniana Seedling Nitrogen Transporter Gene Expression and Nitrogen Uptake Kinetics.

Analyzing the molecular and physiological processes that govern the uptake and transport of nitrogen (N) in plants is central to efforts to fully understand the optimization of plant N use and the changes in the N-use efficiency in relation to changes in atmospheric N deposition changes. Here, a field experiment was conducted using the ectomycorrhizal fungi (EMF), (Pt) and (Sg). The effects of N deposition were investigated using concentrations of 0 kg·N·hma (N0), a normal N deposition of 30 kg·N·hma (N30), a moderate N deposition of 60 kg·N·hma (N60), and a severe N deposition of 90 kg·N·hma (N90), with the goal of examining how these factors impacted root activity, root absorbing area, NH and NO uptake kinetics, and the expression of ammonium and nitrate transporter genes in seedlings under different levels of N deposition.

Correlations between forest soil quality and aboveground vegetation characteristics in Hunan Province, China.

As a key component of terrestrial ecosystems, soil interacts directly with aboveground vegetation. Evaluating soil quality is therefore of great significance to comprehensively explore the interaction mechanism of this association. The purpose of this study was to fully understand the characteristics of aboveground vegetation, soil quality, and their potential coupling relationship among different forest types in Hunan Province, and to provide a theoretical basis for further exploring the mechanisms underlying soil-vegetation interactions in central China.

Nitrogen addition promotes early-stage and inhibits late-stage decomposition of fine roots in plantation.

Increasing atmospheric nitrogen (N) deposition has a profound impact on the ecosystem functions and processes. Fine root decomposition is an important pathway for the reentry of nutrients into the soil. However, the effect of N addition on root decomposition and its potential mechanism is not well understood with respect to root branch orders.

Photosynthetic product allocations of seedlings inoculated with ectomycorrhizal fungi along a nitrogen addition gradient.

Quantifying the allocation of photosynthetic products among different carbon (C) pools is critical for understanding and predicting plant C turnover response to climate change. A field experiment with ectomycorrhizal fungi (EMF) and nitrogen (N) was established to investigate the effects on allocation of photosynthetic products in (Lamb.) seedlings given increased N deposition.

[Effects of nitrogen addition on soil microbial biomass and enzyme activities of - mixed plantations in the Three Gorges Reservoir Area].

We examined the effects of nitrogen addition (0, 30, 60, and 90 kg N·hm·a) to soil microbial biomass, enzyme activities, and nutrient contents of the mixed plantations in the Three Gorges Reservoir Area, with the aim to provide a theoretical basis for predicting soil carbon dynamics under the background of continuously increasing atmospheric nitrogen deposition in this area. The results showed that nitrogen addition at all levels led to a significant increase of the contents of organic carbon, total nitrogen, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) in the forest soil, while a decrease of soil pH-value, and no significant effect on the total phosphorus content. Nitrogen addition increased the activities of β-1-4 glucosidase (BG), cellobiose hydrolase (CB), acid phosphatase (AP), N-acetylglucosaminosidase (NAG) and peroxidase (POD), while inhibited that of polyphenol oxidase (PPO).

The Effect of Low Irradiance on Leaf Nitrogen Allocation and Mesophyll Conductance to CO in Seedlings of Four Tree Species in Subtropical China.

Low light intensity can lead to a decrease in photosynthetic capacity. However, could N-fixing species with higher leaf N contents mitigate the effects of low light? Here, we exposed seedlings of and (N-fixing trees), and and (non-N-fixing trees) to three irradiance treatments (100%, 40%, and 10% sunlight) to investigate the effects of low irradiance on leaf structure, leaf N allocation strategy, and photosynthetic physiological parameters in the seedlings. Low irradiance decreased the leaf mass per unit area, leaf N content per unit area (), maximum carboxylation rate (), maximum electron transport rate (), light compensation point, and light saturation point, and increased the N allocation proportion of light-harvesting components in all species.

Effects of repetitive submergence on the accumulation and release of nutrient elements in Pinus elliottii seedlings.

Pinus elliottii is an evergreen coniferous tree. It is considered a potential species for ecological restoration in the Three Gorges Reservoir Area (TGRA). To classify the effects of different degrees of flooding stress in winter on nutrient accumulation in Pinus elliottii after experiencing early drought stress in summer, simulated water treatments of deep submergence (DS) and moderate submergence (MS) were imposed after the summer drought period.

Effects of soil nitrogen (N) deficiency on photosynthetic N-use efficiency in N-fixing and non-N-fixing tree seedlings in subtropical China.

Soil nitrogen (N) deficiencies can affect the photosynthetic N-use efficiency (PNUE), mesophyll conductance (g), and leaf N allocation. However, lack of information about how these physiological characteristics in N-fixing trees could be affected by soil N deficiency and the difference between N-fixing and non-N-fixing trees. In this study, we chose seedlings of two N-fixing (Dalbergia odorifera and Erythrophleum fordii) and two non-N-fixing trees (Castanopsis hystrix and Betula alnoides) as study objects, and we conducted a pot experiment with three levels of soil N treatments (high nitrogen, set as Control; medium nitrogen, MN; and low nitrogen, LN).

Seedling leaves allocate lower fractions of nitrogen to photosynthetic apparatus in nitrogen fixing trees than in non-nitrogen fixing trees in subtropical China.

Photosynthetic-nitrogen use efficiency (PNUE) is a useful trait to characterize leaf physiology and survival strategy. PNUE can also be considered as part of 'leaf economics spectrum' interrelated with leaf nutrient concentrations, photosynthesis and respiration, leaf life-span and dry-mass investment. However, few studies have paid attention to PNUE of N-fixing tree seedlings in subtropical China.

Author Correction: Labile organic carbon pools and enzyme activities of Pinus massoniana plantation soil as affected by understory vegetation removal and thinning.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

[Fine root production and turnover of Pinus massoniana and their influencing factors in the Three Gorges Reservoir Area, China].

In this study, the annual production and turnover rate of fine root of Pinus massoniana in Three Gorges Reservoir Area were calculated using sequential soil core,litterbag and compartment flux model methods, and the relationship between fine root production, turnover rate and factors was analyzed. The results showed that the annual mean biomass of <0.5, 0.

Fagaceae tree species allocate higher fraction of nitrogen to photosynthetic apparatus than Leguminosae in Jianfengling tropical montane rain forest, China.

Variation in photosynthetic-nitrogen use efficiency (PNUE) is generally affected by several factors such as leaf nitrogen allocation and leaf diffusional conductances to CO2, although it is still unclear which factors significantly affect PNUE in tropical montane rain forest trees. In this study, comparison of PNUE, photosynthetic capacity, leaf nitrogen allocation, and diffusional conductances to CO2 between five Fagaceae tree species and five Leguminosae tree species were analyzed in Jianfengling tropical montane rain forest, Hainan Island, China. The result showed that PNUE of Fagaceae was significantly higher than that of Leguminosae (+35.

Labile organic carbon pools and enzyme activities of Pinus massoniana plantation soil as affected by understory vegetation removal and thinning.

The effects of forest management on carbon (C) sequestration are poorly understood, particularly in the Three Gorges Reservoir area. We aimed to identify the effects of forest management on C sequestration in Pinus massoniana plantations. An intact control forest (CK), a site undergoing regular shrub cutting with the simultaneous removal of residues (SC), a site under low-intensity thinning (LIT), and a site under high-intensity thinning (HIT) were compared for soil labile organic carbon (LOC), related enzyme activities, and soil characteristics.

Thinning but not understory removal increased heterotrophic respiration and total soil respiration in Pinus massoniana stands.

Quantifying soil respiration (R) and its components [autotrophic respiration (R) and heterotrophic respiration (R)] in relation to forest management is vital to accurately evaluate forest carbon balance. Thus, R, R, and R were continuously monitored from November 2013 to November 2016 in Pinus massoniana forests subjected to four different management practices in China. We hypothesized that understory removal and thinning decrease R and R and thus R, and these decreases will change with time following UR and thinning.

Growth habit and leaf economics determine gas exchange responses to high elevation in an evergreen tree, a deciduous shrub and a herbaceous annual.

Plant growth at high elevations necessitates physiological and morphological plasticity to enable photosynthesis (A) under conditions of reduced temperature, increased radiation and the lower partial pressure of atmospheric gases, in particular carbon dioxide (pCO2). Previous studies have observed a wide range of responses to elevation in plant species depending on their adaptation to temperature, elevational range and growth habit. Here, we investigated the effect of an increase in elevation from 2500 to 3500 m above sea level (a.

[Light response characteristics of photosynthesis and model comparison of Distylium chinense in different flooding durations].

The light responses of photosynthesis of two-year-old Distytum chinense seedlings subjected to a simulated reservoir flooding environment in autumn and winter seasons were measured by using a Li-6400 XT portable photosynthesis system, and the light response curves were fitted and analyzed by three models of the rectangular hyperbola, non-rectangular hyperbola and modified rectangular hyperbola to investigate the applicability of different light response models for the D. chinense in different flooding durations and the adaption regulation of light response parameters to flooding stress. The results showed that the fitting effect of the non-rectangular hyperbola model for light response process of D.

Effect of off-season flooding on growth, photosynthesis, carbohydrate partitioning, and nutrient uptake in Distylium chinense.

Distylium chinense is an evergreen shrub used for the vegetation recovery of floodplain and riparian areas in Three Gorges Reservoir Region. To clarify the morphological and physiological responses and tolerance of Distylium chinense to off-season flooding, a simulation flooding experiment was conducted during autumn and winter. Results indicated that the survival rate of seedlings was 100%, and that plant height and stem diameter were not significantly affected by flooding.

[Effects of litterfall and root input on soil physical and chemical properties in Pinus massoniana plantations in Three Gorges Reservoir Area, China].

An investigation was made on the soil physical and chemical properties in different-aged Pinus massoniana plantations in Three Gorges Reservoir Area under effects of litterfall and roots. The annual litter production in mature stand was 19.4% and 65.

[Fine root production and turnover in Pinus massoniana plantation in Three Gorges Reservoir area of China].

By the methods of sequential soil cores and buried bags, an investigation was conducted to study the seasonal dynamics of fine roots in a 20-year-old Pinus massoniana plantation in Three Gorges Reservoir Area from March to December 2011, with the annual production and turnover rate of the fine roots calculated. In the plantation, the annual mean biomass of <2 mm fine roots was 146.98 g x m(-2) x a(-1), in which, the living root biomass (102.

[Effects of altitudinal gradient on Salix atopantha foliar delta13C].

In 2010, measurements were conducted on the foliar delta13C, photosynthesis, CO2 diffusive conductivity, nitrogen content, photosynthetic nitrogen use efficiency (PNUE), and special leaf area (SLA) of Salix atopantha at different altitudes (2350 m, 2700 m, 3150 m, and 3530 m) in Wolong Natural Reserve. With the increase of altitude, the foliar nitrogen content (especially the nitrogen content per unit leaf area, N(area)) and the PNUE increased, and the foliar delta13C had a significant increase, with an increment of 1.4 per thousand per 1000 m altitude.

[Characteristics of soil seed banks in backwater area of Three Gorges Reservoir water-level-fluctuating zone at initial stage of river-flooding].

A germination test was made to study the characteristics of soil seed banks in the backwater area (including the flooded, non-flooded, and control areas of secondary bush and abandoned farmland) of Three Gorges Reservoir water-level-fluctuating zone. There existed significant differences in the soil seed banks between secondary bush and abandoned farmland, with an average seed density being 6991 +/- 954 seed per m2 and 26193 +/- 6928 seed per m2, respectively. Flooded area had the lowest seed density, while non-flooded area had the highest one.

[Biodiversity of main coniferous forests at low elevation of Three Gorges Reservoir area].

The study showed that at low elevation of Three Gorges Reservoir area, Pinus massoniana, Cupressus funebris and Cunninghamia lanceolata were the main coniferous forests, which were respectively divided into 14, 9 and 5 community types based on field investigation. The whole trend of their species richness index, species diversity index and species evenness index was that shrub layer and herb layer were larger than tree layer. The diversity indices had no obvious trend along the low elevation gradients, which was probably relevant to the high intensity of human activities in the area.

[Analysis on forest plant diversity in the Three Gorges Reservoir Area].

The forest resource is rich in the Three Gorges Reservoir Area, according to the investigation data in the area, there are 41 kinds of forest communities, and the trend of the richness index, species diversity index and evenness index is not regular. In the coniferous forest, the trend of the richness index in different layer along the community is shrub > herb > tree. In the evergreen broadleaf forest, the trend is shrub > tree > herb.