Temporal dynamics of fine root production, mortality and turnover deviate across branch orders in a larch stand.

Fine roots play a key role in carbon, nutrient, and water biogeochemical cycles in forest ecosystems. However, inter-annual dynamics of fine root production, mortality, and turnover on the basis of long-term measurement have been less studied. Here, field scanning rhizotrons were employed for tracking fine root by branch order over a 6 years period in a larch plantation. For total fine roots, from the first- to the fifth-order roots, annual root length production, length mortality, standing crops, and turnover rate varied up to 3.4, 2.3, 1.5, and 2.3-folds during the study period, respectively. The inter-annual variability of those roots indices in the first-order and the second-order roots were greater than that of the higher order (third- to fifth-order) roots. The turnover rate was markedly larger for the first-order roots than for the higher order roots, showing the greatest variability up to 20 times. Seasonal dynamics of root length production followed a general concentrated pattern with peak typically occurring in June or July, whereas root length mortality followed a general bimodal mortality pattern with the dominant peak in May and the secondary peak in August or October. Furthermore, the seasonal patterns of root length production and mortality were similar across years, especially for the first-order and the second-order roots. These results from long-term observation were beneficial for reducing uncertainty of characterizing fine root demography in consideration of large variation among years. Our findings highlight it is important for better understanding of fine root dynamics and determining root demography through distinguishing observation years and root branch orders.

[Population structure and dynamics of Pinus koraiensis seedlings regenerated from seeds in a montane region of eastern Liaoning Province, China.] / 辽东山区天然更新红松幼苗种群结构与动态.

Based on the static life table and survival curve, we explored the population structure and dynamics of Korean pine (Pinus koraiensis) seedlings regenerated from seeds in three different forest belts of Korean pine plantation in a montane region of eastern Liaoning Province. The results showed that the age structure of Korean pine seedlings in three different forest belts (i.e., larch forest belt, mixed coniferous forest belt, and mixed broadleaved forest belt) showed a "∩" type of left skewed distribution. The abundance of seedlings was rich but the mortality rate was high in the early phase, and the abundance of seedlings decreased in the later phase, which indicated that the population was depressing. The survival curve of the population conformed to the Deevey-Ⅱ type. The life expectancy of Korean pine seedlings at each age class in larch forest belt was higher than that in mixed coniferous forest belt and mixed broadleaved forest belt. The survival analysis showed that the survival rate of Korean pine seedlings in three different forest belts decreased but the cumulative mortality rate increased with increasing age. The death density function tended to be flat after the age class of Ⅱ-Ⅲ, while the risk function value showed a decreasing trend with the increases of age. The time series predictive analysis showed that the population showed a certain growth trend with increasing age class, indicating that the population could achieve natural regeneration and have a certain growth potential, but with regeneration obstacles.

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The relationship between the structure and function of forest ecosystems is the main intere-sts in the research area of forest ecology and management. However, over complex terrains in particular, these studies had been challenged as uneasy tasks due to the limitations in the forest survey and measurement techniques and other supporting technologies. Chinese Academy of Sciences (CAS) funded "Multi-Tower LiDAR/ECFlux Platform for Monitoring the Structure and Function of Secondary Forest Ecosystems" (Multi-Tower Platform, MTP) as a field station network corner-stone research infrastructure project, which was completed by Qingyuan Forest CERN (Chinese Ecosystem Research Network). In a distinctively-bounded and monitored-outlet watershed, the MTP was integrated by light detection and ranging (LiDAR) scanners, eddy covariance (EC) flux instrument systems, whole- and sub-watershed hydrology station network, long-term forest plot arrays, and live data center. Using LiDAR scanning, the MTP can get cloud data for holographic information on canopy structure. The EC-flux instrument system and hydrology station network along with forest plot arrays could ensure the reliability of water and carbon observations over this complex terrain, which allows to verify the studies on flux measurement technologies and methods, as well as to understand the processes of ecohydrology and CO2 exchange between forest ecosystem and the atmosphere. Further, we can also assess the primary ecosystem services, including water conservation and carbon sequestration. All the data from "tower-station" were streamed through wireless network, which would facilitate data monitoring, management, and sharing. There are three tasks of MTP team: 1) defining innovative methods and descriptors to quantify three-dimensional forest structure; 2) developing theories and techniques to measure CO2/H2O fluxes and other trace gases over complex terrains; 3) understanding the relationship between structure and function of forest ecosystems, providing information and rationales for forest management practices to assure broad and sustainable benefits from forests.

Assessment of heavy metal pollution in Red River surface sediments, Vietnam.

Surface sediment samples were collected from upstream down to the subaqueous delta of the Red River in Vietnam to assess heavy metal pollution. Sediment Cr and V concentrations are strongly correlated with Al, Fe, Mn and total organic carbon concentrations, as well as particle size, suggesting that these two metals are derived primarily from natural sources and enriched in the fine fraction of sediments. In contrast, Cu, Cd, Pb, Ni and Zn concentrations show weaker correlations with particle size, with very high concentrations observed at several sites in the upper reach of the river, pointing to anthropogenic input as a possible source of these heavy metals. Enrichment factors (EF) of Cu, Cd, Pb, Ni and Zn suggest that heavy metal pollution is present in sediments with significantly high values in the upstream. The data analysis indicates that Cd, Cu and Pb are the dominant pollutants in the Red River, with their concentrations reaching moderate to serious pollution levels.

Synchrotron X-ray microfluorescence measurement of metal distributions in Phragmites australis root system in the Yangtze River intertidal zone.

This study investigates the distributions of Br, Ca, Cl, Cr, Cu, K, Fe, Mn, Pb, Ti, V and Zn in Phragmites australis root system and the function of Fe nanoparticles in scavenging metals in the root epidermis using synchrotron X-ray microfluorescence, synchrotron transmission X-ray microscope measurement and synchrotron X-ray absorption near-edge structure techniques. The purpose of this study is to understand the mobility of metals in wetland plant root systems after their uptake from rhizosphere soils. Phragmites australis samples were collected in the Yangtze River intertidal zone in July 2013. The results indicate that Fe nanoparticles are present in the root epidermis and that other metals correlate significantly with Fe, suggesting that Fe nanoparticles play an important role in metal scavenging in the epidermis.

Synchrotron micro-scale measurement of metal distributions in Phragmites australis and Typha latifolia root tissue from an urban brownfield site.

Liberty State Park in New Jersey, USA, is a "brownfield" site containing various levels of contaminants. To investigate metal uptake and distributions in plants on the brownfield site, Phragmites australis and Typha latifolia were collected in Liberty State Park during the growing season (May-September) in 2011 at two sites with the high and low metal loads, respectively. The objective of this study was to understand the metal (Fe, Mn, Cu, Pb and Zn) concentration and spatial distributions in P. australis and T. latifolia root systems with micro-meter scale resolution using synchrotron X-ray microfluorescence (µXRF) and synchrotron X-ray computed microtomography (µCMT) techniques. The root structure measurement by synchrotron µCMT showed that high X-ray attenuation substance appeared in the epidermis. Synchrotron µXRF measurement showed that metal concentrations and distributions in the root cross-section between epidermis and vascular tissue were statistically different. Significant correlations were found between metals (Cu, Mn, Pb and Zn) and Fe in the epidermis, implying that metals were scavenged by Fe oxides. The results from this study suggest that the expression of metal transport and accumulation within the root systems may be element specific. The information derived from this study can improve our current knowledge of the wetland plant ecological function in brownfield remediation.

The long-term effects of planting and harvesting on secondary forest dynamics under climate change in northeastern China.

Unlike the virgin forest in the Changbaishan Nature Reserve in northeastern China, little research on a landscape scale has been conducted on secondary forests in the region under conditions of a warming climate. This research was undertaken in the upper Hun River region where the vegetation is representative of the typical secondary forest of northeastern China. The spatially explicit forest landscape model LANDIS was utilized to simulate the responses of forest restoration dynamics to anthropogenic disturbance (planting and harvesting) and evaluate the difference of the restoration process under continuation of current climatic conditions and climate warming. The results showed that: (1) The interaction of planting and harvesting has organizational scale effects on the forest. The combination of planting and harvesting policies has significant effects on the overall forest but not on individual species. (2) The area expansion of the historically dominant species Pinus koraiensis is less under climate warming than under continuation of current climatic conditions. These suggests that we should carefully take historically dominant species as the main focus for forest restoration, especially when they are near their natural distribution boundary, because they are probably less capable of successfully adapting to climate change.

Synchrotron micro-scale study of trace metal transport and distribution in Spartina alterniflora root system in Yangtze River intertidal zone.

This study is focused on micro-scale measurement of metal (Ca, Cl, Fe, K, Mn, Cu, Pb, and Zn) distributions in Spartina alterniflora root system. The root samples were collected in the Yangtze River intertidal zone in July 2013. Synchrotron X-ray fluorescence (XRF), computed microtomography (CMT), and X-ray absorption near-edge structure (XANES) techniques, which provide micro-meter scale analytical resolution, were applied to this study. Although it was found that the metals of interest were distributed in both epidermis and vascular tissue with the varying concentrations, the results showed that Fe plaque was mainly distributed in the root epidermis. Other metals (e.g., Cu, Mn, Pb, and Zn) were correlated with Fe in the epidermis possibly due to scavenge by Fe plaque. Relatively high metal concentrations were observed in the root hair tip. This micro-scale investigation provides insights of understanding the metal uptake and spatial distribution as well as the function of Fe plaque governing metal transport in the root system.

A magnetic record of heavy metal pollution in the Yangtze River subaqueous delta.

The rapid industrial development in the Yangtze River watershed over the last several decades has drawn great attention with respect to heavy metal pollution to the Yangtze River estuary and nearby coastal areas. In this study, a 236 cm long sediment core was retrieved from the Yangtze River subaqueous delta (122°36' E, 31°00' N) in 2008 and analyzed for magnetic properties and geochemical compositions to investigate heavy metal pollution history. The activity of (137)Cs peaked at depth 140 cm, with a broad plateau between 120 cm and 140 cm, suggesting an average sedimentation rate of 3.11 cm yr(-1) for the upper 140 cm layer. Magnetic susceptibility (χ), saturation isothermal remanent magnetization (SIRM), anhysteretic remanent magnetization (χARM) and heavy metal enrichment factors (EF) all showed an upward increase trend above depth 140 cm, suggesting that increased ferrimagnetic mineral concentration was accompanied by heavy metal enrichment in the sediment. Geochemical and granolumetric analyses showed that sediment sources and particle sizes played minor roles in the variations of magnetic properties. The effect of diagenesis, which can lead to the selective removal of magnetic minerals, was noticeable in the lower part of the core (140-236 cm). Co-variation between magnetic properties (χ, SIRM and χARM) and EF of Cu and Pb suggests that the elevated ferrimagnetic mineral concentration can be used as an indicator of heavy metal pollution in the reconstruction of environmental changes in estuarine and coastal settings.

[Aboveground biomass and nutrient distribution patterns of larch plantation in a montane region of eastern Liaoning Province, China].

Larch is the main timber species of forest plantations in North China. Imbalance in nutrient cycling in soil emerged due to single species composition and mono system structure of plantation. Thus it is necessary to grasp its biomass and nutrients allocation for scientific management and nutrient cycling studies of larch plantation. We measured aboveground biomass (stem, branch, bark and leaf) and nutrient concentrations (C, N, P, K, Ca, Mg, Fe, Mn, Cu and Zn), and analyzed the patterns of accumulation and distribution of 19-year-old larch plantation with diameter at breast height of 12. 8 cm, tree height of 15. 3 m, and density of 2308 trees · hm(-2), in a montane region of eastern Liaoning Province, China. The results showed that aboveground biomass values were 70.26 kg and 162.16 t · hm(-2) for the individual tree of larch and the stand, respectively. There was a significant difference between biomass of the organs, and decreased in the order of stem > branch > bark > leaf. Nutrient accumulation was 749.94 g and 1730.86 kg · hm(-2) for the individual tree of larch and the stand, respectively. Nutrient accumulation of stem was significantly higher than that of branch, bark and leaf, whether it was macro-nutrient or micro-nutrient. Averagely, 749.94 g nutrient elements would be removed from the system when a 19-year-old larch tree was harvested. If only the stem part was removed from the system, the removal of nutrient elements could be reduced by 40.7%.

[Forest resources in Qungyuan County of Liaoning, Northeast China: the structure and optimal spatial allocation].

By using RS/GIS techniques and the method of multiple objective grey situation decision, and in considering the forest economic benefits (biomass and stand productivity) and ecological benefits (water and soil conservation) , an optimal spatial allocation of the present forest types in Qingyuan County of Liaoning, Northeast China was approached in this study. After the optimization of spatial allocation, the structural proportions of different forest types in Qingyuan County changed obviously, with the area of coniferous forests reduced from 43% to 23% , the area of broadleaved forests reduced from 51% to 31% , the area of mixed coniferous-broadleaf forests increased from 3% to 43% , and the area of shrubs remained unchanged. As compared with the results before optimization, the biomass, stand productivity, and water conservation function of the forest ecosystem in Qingyuan County after optimization increased by 0.6%, 2.1% , and 31.7%, respectively, and the soil conservation function remained unchanged. It could be concluded that after the optimization of spatial allocation, the forest ecosystem of Qingyuan County could maintain its soil conservation function, and, at the time of keeping higher timber production, fully exert waler conservation function, realizing the maximization of the economic and ecological benefits of the forest ecosystem.

Effects of land use types on surface water quality across an anthropogenic disturbance gradient in the upper reach of the Hun River, Northeast China.

Surface water quality is vulnerable to pollution due to human activities. The upper reach of the Hun River is an important water source that supplies 52 % of the storage capacity of the Dahuofang Reservoir, the largest reservoir for drinking water in Northeast China, which is suffering from various human-induced changes in land use, including deforestation, reclamation/farming, urbanization and mine exploitation. To investigate the impacts of land use types on surface water quality across an anthropogenic disturbance gradient at a local scale, 11 physicochemical parameters (pH, dissolved oxygen [DO], turbidity, oxygen redox potential, conductivity, biochemical oxygen demand [BOD5], chemical oxygen demand [COD], total nitrogen [TN], total phosphorus [TP], NO(3)(-)N, and NH(4)(+)-N) of water from 12 sampling sites along the upper reach of the Hun River were monitored monthly during 2009-2010. The sampling sites were classified into four groups (natural, near-natural, more disturbed, and seriously disturbed). The water quality exhibited distinct spatial and temporal characteristics; conductivity, TN, and NO(3)(-)-N were identified as key parameters indicating the water quality variance. The forest and farmland cover types played significant roles in determining the surface water quality during the low-flow, high-flow, and mean-flow periods based on the results of a stepwise linear regression. These results may provide incentive for the local government to consider sustainable land use practices for water conservation.

Lead accumulation and association with Fe on Typha latifolia root from an urban brownfield site.

Synchrotron X-ray microfluorescence and X-ray absorption near-edge microstructure spectroscopy techniques were applied to Typha latifolia (cattail) root sections and rhizosphere soils collected from a brownfield site in New Jersey to investigate lead (Pb) accumulation in T. latifolia roots and the role of iron (Fe) plaque in controlling Pb uptake. We found that Pb and Fe spatial distribution patterns in the root tissues are similar with both metals present at high concentrations mainly in the epidermis and at low concentrations in the vascular tissue (xylem and phloem), and the major Pb and Fe species in T. latifolia root are Pb(II) and Fe(III) regardless of concentration levels. The sequestration of Pb by T. latifolia roots suggests a potential low-cost remediation method (phytostabilization) to manage Pb-contaminated sediments for brownfield remediation while performing wetland rehabilitation.

Regeneration of a coastal pine (Pinus thunbergii Parl.) forest 11 years after thinning, Niigata, Japan.

To examine the effects of thinning intensity on wind vulnerability and regeneration in a coastal pine (Pinus thunbergii) forest, thinning with intensities of 20%, 30% and 50% was conducted in December 1997; there was an unthinned treatment as the control (total 8 stands). We re-measured the permanent sites to assess the regeneration characteristics 11 years after thinning. In the 50% thinned stand, seedlings aged from 2 to 10 years exhibited the highest pine seedling density and growth. The age composition ranged from 1-3 years with densities of 9.9 and 5.1 seedlings m(-2) in 30% and 20% thinned stands; only 1-year-old seedlings with a density of 6.1 seedlings m(-2) in the unthinned stand. Similar trends were found for the regeneration of broadleaved species such as Robinia pseudoacacia and Prunus serrulata. We speculate that the canopy openness and moss coverage contributed to the regeneration success in the 50% thinned stand, while the higher litter depth and lack of soil moisture induced the regeneration failure in the unthinned stand. The stands thinned at 20% or 30% were less favourable for pine regeneration than the stands thinned at 50%. Therefore, thinning with less than 30% canopy openness (20% and 30% thinned stands) should be avoided, and thinning at higher than 30% canopy openness (50% thinned stand, approximately 1500 stems ha(-1) at ages 40-50 years) is suggested for increasing regeneration in the coastal pine forest. The implications of thinning-based silviculture in the coastal pine forest management are also discussed. The ongoing development of the broadleaved seedlings calls for further observations.

Seed regeneration potential of canopy gaps at early formation stage in temperate secondary forests, Northeast China.

Promoting the seed regeneration potential of secondary forests undergoing gap disturbances is an important approach for achieving forest restoration and sustainable management. Seedling recruitment from seed banks strongly determines the seed regeneration potential, but the process is poorly understood in the gaps of secondary forests. The objectives of the present study were to evaluate the effects of gap size, seed availability, and environmental conditions on the seed regeneration potential in temperate secondary forests. It was found that gap formation could favor the invasion of more varieties of species in seed banks, but it also could speed up the turnover rate of seed banks leading to lower seed densities. Seeds of the dominant species, Fraxinus rhynchophylla, were transient in soil and there was a minor and discontinuous contribution of the seed bank to its seedling emergence. For Quercus mongolica, emerging seedling number was positively correlated with seed density in gaps (R = 0.32, P<0.01), especially in medium and small gaps (<500 m(2)). Furthermore, under canopies, there was a positive correlation between seedling number and seed density of Acer mono (R = 0.43, P<0.01). Gap formation could promote seedling emergence of two gap-dependent species (i.e., Q. mongolica and A. mono), but the contribution of seed banks to seedlings was below 10% after gap creation. Soil moisture and temperature were the restrictive factors controlling the seedling emergence from seeds in gaps and under canopies, respectively. Thus, the regeneration potential from seed banks is limited after gap formation.

[Lead isotope signatures and source identification in urban soil of Baoshan district, Shanghai].

Two soil cores were collected from the Yuepu Park and a vegetable field near the Yunchuan Road in Baoshan district, Shanghai. Particle size, Pb content and Pb stable isotopic ratios were measured to examine Pb contamination status and its source. The results indicate that Pb concentration in the vegetable field soil and Yuepu park soil varies from 17.2 mg x kg(-1) to 34.8 mg x kg(-1) and 17.5 mg x kg(-1) to 36. 5 mg x kg(-1), respectively. The observed Pb isotopic ratios of vegetable field samples vary from 0.827 to 0.849 for 207Pb/206Pb, and 2.082 to 2.101 for 208Pb/206Pb, while those of Yuepu Park samples range from 0.839 to 0.848 and 2.089 to 2.097, respectively. Pb content, its enrichment factor (EF) and Pb stable isotopic ratios increase upward in both soil cores. EF values of surfacial (top 10 cm) vegetable field samples and park samples are mostly greater than 1.5, suggesting that higher Pb contents in topsoils are caused by anthropogenic activities. Compared with previous reports on Pb isotope signatures of different environmental materials in Shanghai, Pb isotopic ratios in the two soil cores are between those of Yangtze River intertidal sediments and the dust of coal combustion, and those of soil samples with EF > 1.5 are closer to the isotopic ratios of coal combustion dust. It indicates that topsoil in the Baoshan district is contaminated by dust derived from coal combustion.

Metal contamination in sediments of the western Bohai Bay and adjacent estuaries, China.

Twelve sediment cores were collected in July 2007 in open waters of western Bohai Bay, the Port of Tianjin, and the adjacent estuaries of the Haihe and Yongding Rivers. While overall concentrations of trace metals at incremental depths in these cores met the Marine Sediment Quality (GB18668-2002) criteria of China, the magnitude of both metal enrichment factors (EF) and geoaccumulation indices (I(geo)) suggested that pollution with Ag, Cd, Cr, Cu and Zn was occurring in the estuaries and Port. Risk analysis also suggested that Ag and Ni concentrations were sufficiently elevated as to cause adverse biological effects in the study area. Although metal concentrations in western Bohai Bay were of less concern, a positive relationship between EF values and excess (210)Pb activity for several metals suggested that their concentrations were increasing over time.

[Characteristics of soil organic carbon and total nitrogen under different land use types in Shanghai].

By the methods of field sampling and laboratory analysis, this paper studied the variations of soil organic carbon (SOC) and total nitrogen (TN) contents and SOC density under different land use types in Shanghai. Significant differences were observed in the test parameters among different land use types. The SOC density was the highest in paddy field (3.86 kg x m(-2)), followed by in upland (3.17 kg x m(-2)), forestland (3.15 kg x m(-2)), abandoned land (2.73 kg x m(-2)), urban lawn (2.65 kg x m(-2)), garden land (2.13 kg x m(-2)), and tidal flat (1.38 kg x m(-2)). The assessment on the effects of three types of land use change on the test parameters showed that the conversion of paddy field into upland resulted in a significant decrease of SOC and TN contents and SOC density; the abandonment of farmland was not an effective way in improving SOC storage in the Yangtze Delta region with abundant water and heat resources, high soil fertility, and high level of field management; while the 4-5 years conversion of paddy field into artificial forestland decreased the SOC and TN contents and SOC density, suggesting that in a short term, the soil carbon sequestration effect of the conversion from paddy field to forestland was at a low level, due to the limitation of vegetation productivity.

[Physical and chemical properties of throughfall in main forest types of secondary forest ecosystem in montane regions of eastern Liaoning Province, China].

From July to September 2008, a measurement was made on the physical and chemical properties of bulk precipitation and throughfall in five main forest types, i.e., larch plantation (LP), Fraxinus rhynchophylla stand (FR), mixed forest stand (MF), Korean pine plantation (KP), and Mongolian oak stand (MO), of secondary forest ecosystem in montane regions of eastern Liaoning Province, China. Comparing with bulk precipitation, the throughfall in the five forest types was significantly acidified (P < 0.05), and the acidification degree was in the order of KP > LP > MF > MO > FR. The conductivity and total dissolved solids of the throughfall increased significantly (P < 0.05), and were in the sequence of MO > FR > LP > MF > KP. The dissolved oxygen concentration of the throughfall lowered significantly (P < 0.05), with the rank of KP > MF > FR > MO > LP, while the Cl- concentration increased significantly, ranked as LP > MO > MF > FR > KP. The NO3-concentrations of the throughfall in FR, MO and MF were higher, while those in LP and KP were lower than that of the bulk precipitation.

[Effects of fertilization on nutrient concentrations of different root orders' fine roots in Larix kaempferi plantation].

With the 16 years old Larix kaempferi plantation in eastern mountain area of Liaoning Province, China as test object, this paper studied the effects of fertilization on the nutrient concentrations of five root orders' fine roots. Under fertilization, less difference was observed in the total C concentration of the fine roots. Among the five orders' fine roots, the first order's had the lowest concentration of non-structural carbohydrate (TNC) and the highest ones of N and P, while the fifth order's was in adverse. The TNC concentration increased with increasing root order, while the N and P concentrations decreased correspondingly. Fertilization only had significant effects on the N and P concentrations of the first order's fine roots. The C/N/P ratio in different orders' fine roots had significant differences, being 423 : 16 : 1 and 726 : 16 : 1 in the first and the fifth order's fine roots, respectively. With the increase of root order, the proportion of C increased significantly, while that of N varied little. N fertilization didn't change the proportion of C, while P or P + N fertilization decreased the proportions of C and N in the first three orders' fine roots at 0-10 cm soil depth or in the first two orders' fine roots at 10-20 cm soil depth.