C, N, and P stoichiometry for leaf litter of 62 woody species in a subtropical evergreen broadleaved forest.

To understand leaf litter stoichiometry in a subtropical evergreen broadleaved forest, we measured the contents of carbon (C), nitrogen (N) and phosphorus (P) in leaf litters of 62 main woody species in a natural forest of C. kawakamii Nature Reserve in Sanming, Fujian Province. Differences in leaf litter stoichiometry were analyzed across leaf forms (evergreen, deciduous), life forms (tree, semi-tree or shrub), and main families. Additionally, the phylogenetic signal was measured by Blomberg's K to explore the correlation between family level differentiation time and litter stoichiometry. Our results showed that the contents of C, N and P in the litter of 62 woody species were 405.97-512.16, 4.45-27.11, and 0.21-2.53 g·kg-1, respectively. C/N, C/P and N/P were 18.6-106.2, 195.9-2146.8, and 3.5-68.9, respectively. Leaf litter P content of evergreen tree species was significantly lower than that of deciduous tree species, and C/P and N/P of evergreen tree species were significantly higher than those of deciduous tree species. There was no significant difference in C, N content and C/N between the two leaf forms. There was no significant difference in litter stoichiometry among trees, semi-trees and shrubs. Effects of phylogeny on C, N content and C/N in leaf litter was significant, but not on P content, C/P and N/P. Family differentiation time was negatively correlated with leaf litter N content, and positively correlated with C/N. Leaf litter of Fagaceae had high C and N contents, C/P and N/P, and low P content and C/N, with an opposite trend for Sapidaceae. Our findings indicated that litter in subtropical forest had high C, N content and N/P, but low P content, C/N, and C/P, compared with the global scale average value. Litter of tree species in older sequence of evolutionary development had lower N content but higher C/N. There was no difference of leaf litter stoichiometry among life forms. There were significant differences in P content, C/P, and N/P between different leaf forms, with a characteristic of convergence.

Plastic responses of fine root morphology and architecture traits to nitrogen addition in ectomycorrhizal and arbuscular mycorrhizal tree species in an evergreen broadleaved forest.

We measured the morphology traits (specific root length, specific root surface area, root tissue density, average root diameter) and architecture traits (root fork, root fork ratio, increase rate of root length, root tip density, root fork density) of fine roots in two mycorrhiza tree species, Castanopsis faberi (ectomycorrhizal) and Schima superba (arbuscular mycorrhizal), in an evergreen broadleaved forest in the middle subtropical zone. Root bags method was used in an in situ nitrogen deposition experiment. The aim of this study was to reveal the differences in the plastic responses of fine root morphology and architecture traits to nitrogen deposition between the different mycorrhizal trees. The plastic responses of specific root length, specific root surface area and root fork to nitrogen addition decreased from the first-order root to the fourth-order root, while root tissue density showed an opposite pattern. Such a result indicated a trade-off between nutrient acquisition and resource maintenance of different fine root orders. Different mycorrhizal tree species adopted diffe-rent adaptation strategies to the variations of soil nitrogen availability. C. faberi adopted an opportuni-stic strategy, which relied on fine root to improve nutrient absorption efficiency, enhanced the capacity of space expansion and in-situ nutrient absorption to focus on rapid nutrient absorption strategy. S. superba did not change fine root morphological traits through the trade-off between nutrient absorption efficiency and root construction cost, but relied more on the complementarity between mycorrhizal fungi and fine root architecture traits for nutrient acquisition. The differences in the cost of maintaining and constructing fine root C between different mycorrhizal trees led to fine root adopting the most suitable nutrient capture strategy.

[Plastic responses of fine root morphological traits of Castanopsis fabri and Castanopsis carlesii to short-term nitrogen addition]. / ç½—æµ®æ ²å’Œç±³æ§ ç»†æ ¹å½¢æ€åŠŸèƒ½æ€§çŠ¶å¯¹çŸ­æœŸæ°®æ·»åŠ çš„å¯å¡‘æ€§å“åº”.

Nitrogen deposition will affect the morphology of fine roots and its absorption of nutrien-ts, resulting in changes nutrient cycling in terrestrial ecosystems. In order to understand the effects of nitrogen deposition on fine root morphological traits of Castanopsis fabri and C. carlesii, two ectomycorrhizas tree species, we carried out in situ experiment using the root bags method in an evergreen broadleaved forest in the subtropical zone. The results showed that the plastic responses of specific root length and specific root surface area of low-order roots (first to third order) to nitrogen addition was higher than that of high-order roots (fourth order). The plastic responses of root tissue density to nitrogen addition increased from the first-order to the fourth-order, while the average root diameter of each order had no significant plastic responses to nitrogen addition. There was a certain synergistic change between the plastic response of specific root length and specific surface area in the low order fine root and the plastic response of tissue density in the high order fine root. The specific root length, specific root surface area and root tissue density of the two species showed opposite plastic responses to nitrogen addition, indicating that different ectomycorrhizal tree species had different nutrient foraging strategies. C. fabri adopted rapid absorption strategy by increasing specific root length, specific root surface area, and proliferation rate of fine root length, while C. carlesii adopted a relatively conservative resource absorption strategy by increasing tissue density of fine roots.

[Effects of heterogeneous distribution of soil resources on the growth of Chinese fir seedlings under warming]. / 增温下土壤资源异质分布对杉木幼苗生长的影响.

A three-factor experiment with air temperature manipulation, soil temperature manipulation and nutrients distribution pattern was conducted in Forest Ecosystem and Global Change Research Station of Fujian Normal University in Chenda, Sanming, Fujian Province. We examined the effects of heterogeneous distribution of soil resources and warming on underground and aboveground growth of Chinese fir (Cunninghamia lanceolata) seedlings, and whether warming could change the recognition of fine roots to the heterogeneous distribution of soil resources, to understand the response of Chinese fir seedlings to heterogeneous distribution of soil resources under the background of global warming. The results showed that the recognition degree of Chinese fir to the nutrients distribution pattern was mainly reflected by the absorbing root (0-1 mm diameter class) rather than by the 1-2 mm diameter class fine roots. There were no significant effects of warming on the ratio of fine root biomass between nutrient-poor and nutrient-rich patches, the coefficient of nutrients-avoidance and the coefficient of nutrients-preference of fine roots of young Chinese fir except for the single air warming. Chinese fir had higher fine root biomass (0-1 mm diameter class) and lower height in the heterogeneous soil resource environment. Air warming decreased the biomass of fine roots (both 0-1 and 0-2 mm diameter classes) and increased the height of trees. Soil warming decreased the fine root biomass of 1-2 mm diameter class and increased the height of trees and the length of lateral branches. There was no significant interactive effect of air warming, soil warming and heterogeneity of soil resource on aboveground and belowground growth of Chinese fir. The results demonstrated that the absorbing roots of Chinese fir seedlings could recognize the heterogeneous distribution of soil resources,which was not altered by warming.

[Effects of soil warming on specific respiration rate and non-structural carbohydrate concentration in fine roots of Chinese fir seedlings]. / åœŸå£¤å¢žæ¸©å¯¹æ‰æœ¨å¹¼è‹—ç»†æ ¹å‘¼å¸å’Œéžç»“æž„æ€§ç¢³çš„å½±å“.

A field mesocosm experiment with Chinese fir (Cunninghamia lanceolata) seedlings was conducted in Chenda State-Owned Forest Farm, Sanming, Fujian Province. The effects of soil warming (ambient +5 ℃) on specific respiration rates and nonstructural carbohydrate (NSC) concentrations in fine roots were measured by the ingrowth core method, to reveal the belowground responses and the adaptability of Chinese fir to global warming. The results showed that soil warming caused significant changes of fine root NSC in the second year. The NSC and starch concentrations in 0-1 mm fine roots, and the NSC and sugar concentrations in 1-2 mm fine roots decreased signifi-cantly in January. The NSC, sugar and starch concentrations in 0-1 mm roots and the starch concentration in 1-2 mm roots increased in July. Soil warming had no significant effect on fine root NSC in the third year. The specific root respiration rate of the 0-1 mm roots significantly increased in July of the second year but significantly decreased in July of the third year in the warmed plots. Compared with the 0-1 mm roots, soil warming had no significant effect on the specific root respiration rate of the 1-2 mm roots. In conclusion, the responses of fine root respiration to soil warming depended on the duration of warming. Fine root respiration partly acclimated to soil warming with increasing duration of soil warming, which kept fine root NSC being relatively stable.

[Effects of soil warming and nitrogen addition on the length distributions of different diameter class fine roots of Chinese fir seedlings.] / åœŸå£¤å¢žæ¸©ä¸Žæ°®æ·»åŠ å¯¹æ‰æœ¨å¹¼è‹—ç»†æ ¹å¾„çº§æ ¹é•¿åˆ†å¸ƒçš„å½±å“.

In order to determine how the diameter class length distribution (DCLD) of fine roots of Chinese fir (Cunninghamia lanceolata) would be affected by soil warming, nitrogen addition and their interaction, a factorial experiment of soil warming (ambient, +5 ℃) and nitrogen addition (ambient, +4 and +8 g N·m-2·a-1) was carried out in the Chenda State-owned Forest Farm in Sanming, Fujian Province. An expanded extreme value model fitted the DCLD of roots of all the six treatments very well (R2=0.97). The model parameters showed that soil warming reduced the total root length, but its effect on root diameter was not significant. Nitrogen addition decreased both total root length and root diameter. The interaction of soil warming and nitrogen addition had significant effects on total root length, but had no significant effects on root diameter. DCLD of fine roots under the six treatments could be fitted well by the extreme value function (R2>0.98). The correlation analysis showed that specific root length for roots of 0-1 mm diameter was significantly negatively correlated with the parameter c, and the actual total root length was significantly positively correlated with the parameter b. It was concluded that the root morphology of Chinese fir seedlings would respond to both soil warming, nitrogen addition and their interaction, and these responses could be reflected by the changes in parameters of the extreme value model.

[Effects of precipitation exclusion on fine-root biomass and functional traits of Cunninghamia lanceolata seedlings.] / éš”ç¦»é™æ°´å¯¹æ‰æœ¨å¹¼è‹—ç»†æ ¹ç”Ÿç‰©é‡å’ŒåŠŸèƒ½ç‰¹å¾çš„å½±å“.

A precipitation exclusion experiment was set up in Cunninghamia lanceolata seedling plots in Chenda State-Owned Forest Farm, Sanming, Fujian Province, which included 50% precipi-tation reduction and ambient precipitation (control). Using soil coring and in-growth core me-thods, changes in fine-root functional traits of C. lanceolata seedlings, including fine-root biomass, morphology, stoichiometry, specific root respiration, and nonstructural carbohydrates, were exa-mined after 1 year's precipitation exclusion. The results showed that precipitation exclusion significantly decreased biomass of 0-1 mm diameter roots but had no effect on 1-2 mm diameter roots. However, adaptive morphological changes occurred in the precipitation exclusion treatment. The specific root length (SRL) of the 0-1 and 1-2 mm diameter roots increased by 21.1% and 30.5%, respectively, and root tissue density (RTD) significantly decreased and specific root surface area (SRA) significantly increased in the 0-1 mm diameter roots. Precipitation exclusion led to increase in nitrogen concentration in fine roots, but the absorption capacity for phosphorus was impeded, resulting in increased root N:P, which implied a nutritional imbalance in fine roots. Precipitation exclusion did not significantly change fine root specific respiration rate and nonstructural carbohydrate (NSC) content. However, the soluble sugar content and the ratio of soluble sugar to starch were significantly decreased, and the starch content was increased by 33.3% in the 1-2 mm diameter roots, indicating an adaptation response of C. lanceolata seedlings to reduced precipitation by increasing the storage of nonstructural carbohydrate in fine roots.

[Fine root production in initial stage of Castanopsis carlesii under different regeneration modes in Sanming, Fujian Province, China].

Fine root biomass and production in initial stage of three different regeneration approaches, i.e., natural regeneration with anthropogenic promotion (AR) , the Castanopsis carlesii plantation ( CC) and the Cunninghamia lanceolata plantation ( CL) on the clear-cutting sites of the secondary forest of C. carlesii (CK), in Sanming, Fujian Province, were investigated by using both minrhizotrons and the soil coring methods. The results of a year observation showed that the average fine root biomass was 422.5, 253.1, 197.2 and 162.8 g · m(-2), and the fine root production was 284.0, 182.6, 136.7 and 15.4 g · m(-2) · a(-1) for AR, CC, CL and CK, respectively. The maximum value of production was found in spring for AR and CC, in autumn for CL, and in winter for CK. Fine root production of other plants was higher than that of target tree species in CC, and vice verse in CL. There was a significant positive correlation between monthly fine root production and monthly precipitation in AR and CC. Significant positive correlation was found between monthly fine root production of other plants and monthly temperature in CL. The fine root under annual production and annual average biomass of these three young forests mainly distributed in the soil layer of 20- 40 cm, and mainly in the diameter class of 0-1 mm. The study demonstrated that the biomass and production of fine root under anthropogenic promotion were greater than that of the plantation, and the method of anthropogenic promotion were more conducive to increase the returning of organic matter, improve soil fertility, and maintain a high productivity in initial stage of forest regeneration.

[Effects of tree species diversity on fine-root biomass and morphological characteristics in subtropical Castanopsis carlesii forests].

Fine roots in the Castanopsis carlesii plantation forest (MZ), the secondary forest of C. carlesii through natural regeneration with anthropogenic promotion (AR), and the secondary forest of C. carlesii through natural regeneration (NR) in Sanming City, Fujian Province, were estimated by soil core method to determine the influence of tree species diversity on biomass, vertical distribution and morphological characteristics of fine roots. The results showed that fine root biomass for the 0-80 cm soil layer in the MZ, AR and NR were (182.46 +/- 10.81), (242.73 +/- 17.85) and (353.11 +/- 16.46) g x m(-2), respectively, showing an increased tendency with increasing tree species diversity. In the three forests, fine root biomass was significantly influenced by soil depth, and fine roots at the 0-10 cm soil layer accounted for more than 35% of the total fine root biomass. However, the interaction of stand type and soil depth on fine-root distribution was not significant, indicating no influence of tree species diversity on spatial niche segregation in fine roots. Root surface area density and root length density were the highest in NR and lowest in the MZ. Specific root length was in the order of AR > MZ > NR, while specific root surface area was in the order of NR > MZ > AR. There was no significant interaction of stand type and soil depth on specific root length and specific root surface area. Fine root morphological plasticity at the stand level had no significant response to tree species diversity.

[Spatiotemporal distribution of negative air ion concentration in urban area and related affecting factors: a review].

Negative air ion (NAI) concentration is an important indicator comprehensively reflecting air quality, and has significance to human beings living environment. This paper summarized the spatiotemporal distribution features of urban NAI concentration, and discussed the causes of these features based on the characteristics of the environmental factors in urban area and their effects on the physical and chemical processes of NAI. The temporal distribution of NAI concentration is mainly controlled by the periodic variation of solar radiation, while the spatial distribution of NAI concentration along the urban-rural gradient is mainly affected by the urban aerosol distribution, underlying surface characters, and urban heat island effect. The high NAI concentration in urban green area is related to the vegetation life activities and soil radiation, while the higher NAI concentration near the water environment is attributed to the water molecules that participate in the generation of NAI through a variety of ways. The other environmental factors can also affect the generation, life span, component, translocation, and distribution of NAI to some extent. To increase the urban green space and atmospheric humidity and to maintain the soil natural attributes of underlying surface could be the effective ways to increase the urban NAI concentration and improve the urban air quality.

[Dynamic changes of soil respiration in Citrus reticulata and Castanea henryi orchards in Wanmulin Nature Reserve, Fujian Province of East China].

From January 2009 to December 2009, the soil respiration in the Citrus reticulata and Castanea henryi orchards in Wanmulin Nature Reserve was measured with Li-8100, aimed to characterize the dynamic changes of the soil respiration and its relationships with soil temperature and moisture in the two orchards. The monthly variation of the soil respiration in the orchards was single-peaked, with the peak appeared in July (3.76 micromol x m(-2) x s(-1)) ) and August (2.69 micromol x m(-2) x s(-1)). Soil temperature was the main factor affecting the soil respiration, and explained 73%-86% of the monthly variation of soil respiration. The average annual soil respiration rate was significantly higher in Citrus reticulata orchard than in Castanea henryi orchard, with the mean value being 2.68 and 1.55 micromol x m(-2) x s(-1), respectively. There was a significant positive correlation between the soil respiration rate and soil moisture content in Castanea henryi orchard, but less correlation in Citrus reticulata orchard. The Q10 value of the soil respiration in Citrus reticulata and Castanea henryi orchards was 1.58 and 1.75, and the annual CO2 flux was 10.01 and 5.77 t C x hm(-2) x a(-1), respectively.

[Characteristics of soil respiration in Phyllostachys edulis forest in Wanmulin Natural Reserve and related affecting factors].

By using Li-Cor 8100 open soil carbon flux system, the dynamic changes of soil respiration rate in Phyllostachys edulis forest in Wanmulin Natural Reserve in Fujian Province of China were measured from January 2009 to December 2009, with the relationships between the dynamic changes and related affecting factors analyzed. The monthly variation of soil respiration rate in the forest presented a double peak curve, with the peaks appeared in June 2009 (6. 83 micromol x m(-2) x s(-1)) and September 2009 (5.59 micromol x m(-2) x s(-1)), and the seasonal variation of the soil respiration rate was significant, with the maximum in summer and the minimum in winter. The soil respiration rate had significant correlation with the soil temperature at depth 5 cm (P < 0.05), but no significant correlation with soil moisture (P > 0.05). The monthly variation of litter fall mass in the forest was in single peak shape, and there was a significantly positive correlation between the monthly litter fall mass and soil respiration rate (P < 0.05). Two-factor model of soil temperature and litter fall mass could explain 93.2% variation of the soil respiration rate.

[Soil soluble organic nitrogen content in different forest stands in Wanmulin Nature Reserve].

An investigation was made on the soil soluble organic nitrogen (SON) in two natural forests Altingia gracilies (ALG) and Castanopsis carlesii (CAC) and an adjacent 35-year-old Cunninghamia lanceolata (CUL) plantation in Wanmulin Nature Reserve in Jianou, Fujian Province. Among the three forest stands, ALG had a significantly higher content of soil SON, being 95.3, 78.3, and 72.5 mg x kg(-1) in 0-5 cm, 5-10 cm, and 10-20 cm soil layers, respectively (P<0.05), while CAC and CUL had lesser differences in their soil SON content, which was 74.5, 70.1, and 65.6 mg x kg(-1) in the three soil layers for CAC, and 78.6, 68.9, and 69.1 mg x kg(-1) in the three soil layers for CUL, respectively. The proportion of SON to total soluble nitrogen (TSN) in 0-20 cm soil layer was 79.17-80.78% for CAC, 68.64%-74.51% for CUL, and 59.97%-69.66% for ALG. With increasing soil depth, the proportion of soil SON to soil TSN and total nitrogen (TN) for the three forest stands all increased. Soil SON content had a significant positive correlation with soil organic carbon (r=0.982, P<0.01), and also, had definite correlations with soil TSN, TN, NH4(+)-N, and NO3(-)-N. It also correlated with the factors such as forest type, topography, altitude, and tree age.

[Litter fall production and carbon return in Cunninghamia lanceolata, Schima superba, and their mixed plantations].

From March 2005 to April 2007, an investigation was made on the litter fall production and carbon return of Cunninghamia lanceolata, Schima superba, and their mixed plantations in the Jian' ou Science and Education Park of Soil and Water Conservation, Fujian. In these three plantations, the mean annual litter fall production was from 2470.85 kg x hm(-2) x a(-1) to 4285.99 kg x hm(-2) x a(-1), and dominated by leaf litter, accounting for 68.62%-87.26% of the total production. In C. lanceolata plantation, the litter fall production peaked in April-May, July, and December; while in S. superba and mixed plantations, this production only peaked in March. Comparing with pure plantations, mixed plantation had a higher litter fall production per tree of broadleaved S. superba while a lower litter fall production per tree of coniferous C. lanceolata. Leaf litter in the three plantations was the main body of the litter falls carbon return, and the total amount of the carbon return was the largest (2.12 t C x hm(-2) x a(-1)) in mixed plantation and the smallest (1.19 t C x hm(-2) x a(-1)) in C. lanceolata plantation, which was in accordance with the annual litter fall production of the plantations. This study demonstrated that comparing with pure coniferous or broadleaved plantation, coniferous-broadleaved mixed plantation had higher annual litter fall production and carbon return, and thus, higher potential of C sequestration.

[Root decomposition characteristics of Castanopsis carlesii stand in Wanmulin Natural Reserve of Fujian Province].

By using litter-bag method, the root decomposition characteristics of Castanopsis carlesii stand in Jian'ou Wanmulin Natural Reserve of Fujian Province were studied over two years. Three classes of roots, i.e., 0-1 mm, 1-2 mm, and 2-4 mm in diameter, were tested. During the 2-year period of decomposition, all classes roots showed a bi-phase pattern, being decomposed faster in prophase and slower in anaphase. The leaching loss of extractable substances in roots made root decomposition faster in prophase, while the increase of the acid-insoluble substances concentration in roots restrained the decomposition in anaphase. In the first year, the decomposition rate of all classes roots was controlled by the initial concentrations of their extractive substances and N; while in the second year, the decomposition rate was controlled by the initial C/N and the initial concentrations of acid-insoluble substances, N and P of the roots. During decomposition, all classes roots showed an increasing N concentration and a decreasing P concentration, and the N showed an enrichment-release pattern, while the P showed a direct release pattern.

[Seasonal variation of light fraction organic matter in degraded red soil after vegetation restoration].

This paper studied the seasonal variation of light fraction organic matter (LFOM) in the red soils of severely eroded bare land, and of the bare lands restored to Pinus massoniana forest land, Castanea mollissima plantation, and Paspalum notatum grassland in the Hetian Town of Changting County, Fujian Province, with secondary forest soil as the control. The results showed that in the surface soil of the bare land, LFOM content was between 0.05-0.14 g x kg(-1) and with no significant seasonal variation, while in that of P. massoniana forest land, C. mollissima plantation and P. notatum grassland, LFOM content had a distinct seasonal variation, and was 58%-122% higher in spring, autumn, and winter than in summer. The C content and C/N ratio of the LFOM in the three restored lands were lower in summer than in other seasons, while the nitrogen content of the LFOM was in adverse, indicating that the high temperature and humidity in summer induced a rapid decomposition of soil LFOM. The LFOM in secondary forest soil had the similar variation trend to that in the three restored lands, but the variation range was significantly narrower. The seasonal dynamics of surface soil LFOM was affected not only by micro-climate but also by vegetation types, and the variation range was greater in P. notatum grassland than in forest lands. It was suggested that to enhance the observation precision of soil LFOM, repeated sampling or integrating the factors such as climate, vegetation type, and management measures should be taken to determine the appropriate sampling time.