人为干扰活动对黄河三角洲滨海湿地典型植被生长的影响

为明确人为干扰活动对黄河三角洲滨海湿地植被生长的影响,在黄河三角洲选择受到不同人为干扰程度影响的 4 个研究区(一千二管理站、东营港、五号桩和现黄河入海口),对各研究区内主要植被的株高、密度、盖度、地上生物量、碳氮含量和碳密度等进行测定,并利用主成分分析方法对影响植被生长的关键环境因子进行了分析,以期为黄河三角洲湿地的保护、管理和修复提供有利参考。结果表明,人为活动对黄河三角洲植被生长具有较大影响,表现为人为干扰轻微的黄河入海口地区植被生长状况良好,其中芦苇(Phragmites australis)群落的株高、密度、地上生物量及盖度分别高达(103.0±7.81) cm、(584.11±12.3) plant m 2、(891.32±65.92) g m 2和 98%。与之相反,人为干扰严重的东营港地区,芦苇群落消失,碱蓬(Suaedasalsa)和柽柳(Tamarix chinensis)群落也呈现出零星分布的状态,密度分别为(2.5±0.71) plant m 2和(1.0±0.0) plant m 2。主成分分析结果表明,影响现黄河入海口地区植被生长的关键环境因子是水盐梯度,而在一千二管理站、东营港和五号桩地区影响植被生长的关键环境因子发生了变化,且不同研究区影响植被生长的关键环境因子不同;在人为干扰活动轻微的黄河口研究区,植被化学计量比(碳氮比)相对稳定,而在干扰严重的区域,植被化学计量比变异性较大,这可能是植被对环境的一种适应机制。

地震1年后北川羌族乡镇级干部职业生活质量与心理健康调查

目的了解北川地震1年后北川县羌族与汉族乡镇级干部的心理健康状况以及职业生活质量状况。方法在北川县采用方便抽样法抽取67名乡镇级干部(羌族34名,汉族33名),并进行心理健康自评问卷(SRQ-20)、创伤后应激障碍筛查表(PTSD-7)和职业生活质量量表(Pro QOL)评定。结果 23名(67.6%)羌族乡镇级干部和13名(39.4%)汉族乡镇级干部存在心理问题,但二组差异无统计学意义(t=-1.98,P>0.05);羌族组同情满意(CS)和同情疲乏即次级创伤(CF)评分均高于汉族组(t=-2.01、-2.33,P均<0.05)。结论北川地震1年后北川乡镇级干部仍有不同程度的心理反应,与汉族干部相比,羌族干部职业生活质量如工作同情满意与次级创伤更严重。

Responses of CH_4 Emissions to Nitrogen Addition and Spartina alterniflora Invasion in Minjiang River Estuary, Southeast of China

The nitrogen （N） input and Spartina alterniflora invasion in the tidal marsh of the southeast of China are increasingly serious. To evaluate CH4 emissions in the tidal marsh as affected by the N inputs and S. alterniflora invasion, we measured CH4 emissions from plots with vegetated S. alterniflora and native Cyperus malaccensis, and fertilized with exogenous N at the rate of 0 （NO）, 21 （N1） and 42 （N2） g N/（m2.yr）, respectively, in the Shanyutan marsh in the Minjiang River estuary, the southeast of China. The average CH4 fluxes during the experiment in the C. malaccensis and S. alterniflora plots without N addition were 3.67 mg CHa/（m2.h） and 7.79 mg CH4/（m2-h）, respectively, suggesting that the invasion of S. alterniflora into the Minjiang River estuary stimulated CH4 emission. Exogenous N had positive effects on CH4 fluxes both in native and in invaded tidal marsh. The mean CH4 fluxes of NI and N2 treat- ments increased by 31.05% and 123.50% in the C. malaccensis marsh, and 63.88% and 7.55% in the S. alterniflora marsh, respectively, compared to that of NO treatment. The CH4 fluxes in the two marshes were positively correlated with temperature and pH, and nega- tively correlated with electrical conductivity and redox potential （Eh） at different N addition treatments. While the relationships between CH4 fluxes and environmental variables （especially soil temperature, pH and Eh at different depths） tended to decrease with N additions. Significant temporal variability in CH4 fluxes were observed as the N was gradually added to the native and invaded marshes. In order to better assess the global climatic role of tidal marshes as affected by N addition, much more attention should be paid to the short-term temporal variability in CH4 emission.

Nitrogen Biological Cycle Characteristics of Seepweed(Suaeda salsa) Wetland in Intertidal Zone of Huanghe(Yellow) River Estuary

From April 2008 to November 2009, the nitrogen （N） cycle of plant-soil system in seepweed （Suaeda salsa） wetland in the intertidal zone of the Huanghe （Yellow） River estuary was studied. Results showed that soil N had sig- nificant seasonal fluctuations and vertical distribution, and the net N mineralization rates in topsoil were significantly different in growing season （p 〈 0.01）. The N/P ratio （9.87 ±1.23） of S. salsa was less than 14, indicating that plant growth was limited by N. The N accumulated in S. salsa litter at all times during decomposition, which was ascribed to the N immobilization by microbes from the environment. Soil organic N was the main N stock of plant-soil system, accounting for 97.35% of the total N stock. The N absorption and utilization coefficients of S. salsa were very low （0.0145 and 0.3844, respectively）, while the N cycle coefficient was high （0.7108）. The results of the N turnovers among compartments of S. salsa wetland showed that the N uptake amount of aboveground part and root were 7.764 g/m2and 4.332 g/m2, respectively. The N translocation amounts from aboveground part to root and from root to soil were 3.881 g/m2 and 0.626 g/m2, respectively. The N translocation amount from aboveground living body to litter was 3.883 g/m2, the annual N return amount from litter to soil was more than 0.125（-） g/m2 （minus represented immobili- zation）, and the net N mineralization amount in topsoil （0-15 cm） in growing season was 1.190 g/m2. The assessment of N biological cycle status orS. salsa wetland indicated that N was a very important limiting factor and the ecosystem was situated in unstable and vulnerable status. The S. salsa was seemingly well adapted to the low-nutrient status and vulnerable habitat, and the N quantitative relationships determined in the compartment model might provide scientific base for us to reveal the special adaptive strategy orS. salsa to the vulnerable habitat in the following studies.

Application of Stable Isotope Techniques in Studies of Carbon and Nitrogen Biogeochemical Cycles of Ecosystem

Stable isotope techniques have been proved useful as tools for studying the carbon (C) and nitrogen (N) biogeochemical cycles of ecosystem. This paper firstly introduced the basic principles and the distribution characteristics of stable isotope, then reviewed the recent advances and applications of stable isotope in the C and N biogeochemical cycles of ecosystem. By applying the 13 C natural abundance technique, ecologists are able to understand the photosynthetic path and CO 2 fixation of plants, the CO 2 exchange and C balance status of ecosystem, the composition, distribution and turnover of soil organic C and the sources of organic matter in food webs, while by using the 13 C labeled technique, the effects of elevated CO 2 on the C processes of ecosystem and the sources and fate of organic matter in ecosystem can be revealed in detail. Differently, by applying the 15 N natural abundance technique, ecologists are able to analyze the biological N 2 -fixation, the N sources of ecosystem, the N transformation processes of ecosystem and the N trophic status in food webs, while by using the 15 N labeled technique, the sources, transformation and fate of N in ecosystem and the effects of N input on the ecosystem can be investigated in depth. The applications of both C and N isotope natural abundance and labeled techniques, combined with the elemental, other isotope ( 34 S) and molecular biomarker information, will be more propitious to the investigation of C and N cycle mechanisms. Finally, this paper concluded the problems existed in current researches, and put forward the perspective of stable isotope techniques in the studies on C and N biogeochemical cycles of ecosystem in the future.

Comparison of Carbon, Nitrogen, and Sulfur in Coastal Wetlands Dominated by Native and Invasive Plants in the Yancheng National Nature Reserve, China

The rapid invasion of the plant Spartina alterniflora in coastal wetland areas can threaten the capacity of their soils to store carbon(C),nitrogen(N),and sulfur(S).In this study,we investigated the spatial and temporal distribution patterns of C,N and S of both soil and(native and invasive)plants in four typical coastal wetlands in the core area of the Yancheng National Nature Reserve,China.The results show that the invasive S.alterniflora greatly influenced soil properties and increased soil C,N and S storage capacity:the stock(mean±standard error)of soil organic carbon(SOC,(3.56±0.36)kg/m^3),total nitrogen(TN,(0.43±0.02)kg/m^3),and total sulfur(TS,(0.69±0.11)kg/m^3)in the S.alterniflora marsh exceeded those in the adjacent bare mudflat,Suaeda salsa marsh,and Phragmites australis marsh.Because of its greater biomass,plant C((1193.7±133.6)g/m^2),N((18.8±2.4)g/m^2),and S((9.4±1.5)g/m^2)storage of S.alterniflora was also larger than those of co-occurring native plants.More biogenic elements circulated in the soil-plant system of the S.alterniflora marsh,and their spatial and temporal distribution patterns were also changed by the S.alterniflora invasion.Soil properties changed by S.alterniflora’s invasion thereby indirectly affected the accumulation of soil C,N and S in this wetland ecosystem.The SOC,TN,and TS contents were positively correlated with soil electrical conductivity and moisture,but negatively correlated with the pH and bulk density of soil.Together,these results indicate that S.alterniflora invasion altered ecosystem processes,resulted in changes in net primary production and litter decomposition,and increased the soil C,N and S storage capacity in the invaded ecosystems in comparison to those with native tallgrass communities in the coastal wetlands of East China.

Soil Carbon, Nitrogen and Phosphorus Concentrations and Stoichiometries Across a Chronosequence of Restored Inland Soda Saline-Alkali Wetlands, Western Songnen Plain, Northeast China

Soil carbon(C), nitrogen(N) and phosphorus(P) concentrations and stoichiometries can be used to evaluate the success indicators to the effects of wetland restoration and reflect ecosystem function. Restoration of inland soda saline-alkali wetlands is widespread, however, the soil nutrition changes that follow restoration are unclear. We quantified the recovery trajectories of soil physicochemical properties, including soil organic carbon(SOC), total nitrogen(TN), and total phosphorus(TP) pools, for a chronosequence of three restored wetlands(7 yr, 12 yr and 21 yr) and compared these properties to those of degraded and natural wetlands in the western Songnen Plain, Northeast China. Wetland degradation lead to the loss of soil nutrients. Relative to natural wetlands, the mean reductions of in SOC, TN, and TP concentrations were 89.6%, 65.5% and 52.5%, respectively. Nutrients recovered as years passed after restoration. The SOC, TN, and TP concentrations increased by 2.36 times, 1.15 times, and 0.83 times, respectively in degraded wetlands that had been restored for 21 yr, but remained 29.2%, 17.3%, and 12.8% lower, respectively, than those in natural wetlands. The soil C∶N(RC N), C∶P(R CP), and N∶P(R NP) ratios increased from 5.92 to 8.81, 45.36 to 79.19, and 7.67 to 8.71, respectively in the wetland that had been restored for 12 yr. These results were similar to those from the natural wetland and the wetland that had been restored for 21 yr(P > 0.05). Soil nutrients changes occurred mainly in the upper layers(≤ 30 cm), and no significant differences were found in deeper soils(> 30 cm). Based on this, we inferred that it would take at least 34 yr for SOC, TN, and TP concentrations and 12 yr for RC N, R CP, and RN P in the top soils of degraded wetlands to recover to levels of natural wetlands. Soil salinity negatively influenced SOC(r =-0.704, P < 0.01), TN(r =-0.722, P < 0.01), and TP(r =-0.882, P < 0.01) concentrations during wetland restoration, which indicates that reducing salinity is beneficial to SOC, TN, and TP recovery. Moreover, plants were an important source of soil nutrients and vegetation restoration was conducive to soil nutrient accumulation. In brief, wetland restoration increased the accumulation of soil biogenic elements, which indicated that positive ecosystem functions changes had occurred.

Effects of Reclamation on Soil Carbon and Nitrogen in Coastal Wetlands of Liaohe River Delta,China

To evaluate the influence of wetland reclamation on vertical distribution of carbon and nitrogen in coastal wetland soils, we measured the soil organic carbon(SOC), soil total nitrogen(STN) and selected soil properties at five sampling plots(reed marsh, paddy field, corn field, forest land and oil-polluted wetland) in the Liaohe River estuary in September 2013. The results showed that reclamation significantly changed the contents of SOC and STN in the Liaohe River estuary(P < 0.001). The SOC concentrations were in the order: oil-polluted wetland > corn field > paddy field > forest land > reed marsh, with mean values of 52.17, 13.14, 11.46, 6.44 and 6.16 g/kg, respectively. STN followed a similar order as SOC, with mean values of 1351.14, 741.04, 632.32, 496.17 and 390.90 mg/kg, respectively. Interaction of reclamation types and soil depth had significant effects on SOC and STN, while soil depth had significant effects on SOC, but not on STN. The contents of SOC and STN were negatively correlated with pH and redox potential(Eh) in reed marsh and corn field, while the SOC and STN in paddy field had positive correlations with electrical conductivity(EC). Dissolved organic carbon(DOC), ammonium nitrogen(NH_4^+-N) and nitrate nitrogen(NO_3~–-N) were also significantly changed by human activities. NH_4^+-N and NO_3~–-N increased to different degrees, and forest land had the highest NO_3~–-N concentration and lowest DOC concentration, which could have been caused by differences in soil aeration and fertilization. Overall, the results indicate that reed harvest increased soil carbon and nitrogen release in the Liaohe River Estuary, while oil pollution significantly increased the SOC and STN; however, these cannot be used as indicators of soil fertility and quality because of the serious oil pollution.

Effects of Anthropogenic Disturbance on Sediment Organic Carbon Mineralization Under Different Water Conditions in Coastal Wetland of a Subtropical Estuary

The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P < 0.001), and the interaction between human disturbance activities and water conditions was also significant(P < 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil > aquaculture pond sediment > soil near the discharge outlet > rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R^2 > 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.

测定泥炭中有机质含量的两种方法之比较

准确测定泥炭中的有机质含量对于研究泥炭的特性和泥炭地的碳储存功能及其变化至关重要。测定土壤中有机质含量的方法很多。由于泥炭的有机质含量大,因此,在选择其测定方法时,必须考虑其有机质含量大的特点。利用20世纪80年代全国泥炭资源调查数据,对比采用灼烧法与重铬酸钾氧化-外加热法测定出的泥炭有机质含量的异同,探讨采用两种方法测定出的泥炭有机质含量之间的关系。研究结果表明,采用灼烧法测定的云贵高原区、西藏自治区、若尔盖高原区、长白山区、小兴安岭区、三江平原区的泥炭有机质含量的平均值都大于采用重铬酸钾氧化-外加热法的测定结果;采用两种方法测定的泥炭有机质含量显著正相关;分别建立了6个区采用两种方法测定的泥炭有机质含量之间的一元线性回归方程,使6个区采用两种方法测定的泥炭有机质含量之间可以相互换算。

水盐梯度对闽江河口湿地土壤水稳性团聚体分布及稳定性的影响

为了揭示水盐梯度对河口湿地土壤水稳性团聚体分布及稳定性的影响,对闽江河口不同淹水环境和盐度下短叶茳芏(Cyperus malaccensis)湿地土壤水稳性团聚体进行了测定与分析.结果表明:①闽江河口半咸水湿地和淡水湿地0~30 cm土壤粉+黏团聚体、微团聚体和大团聚体的含量分别为63.12%~77.49%、6.82%~31.64%、4.38%~22.63%.除20~30 cm土层外,高潮滩0~20 cm土壤粉+黏团聚体和大团聚体含量均随盐度的增加而增加,增幅分别为8.74%~9.85%和105.54%~144.40%;0~20 cm土壤微团聚体含量均随盐度的增加而降低,高潮滩降幅为59.56%~65.20%,低潮滩降幅为55.65%~60.92%.②高潮滩土壤团聚体稳定性随盐度的增加而增加,盐度对微团聚体、大团聚体含量(DR0.25)和平均重量直径(MWD)的作用力在不同土层均影响显著,盐度和淹水的交互作用对各级土壤水稳性团聚体分布及稳定性的影响均不显著.③土壤团聚体稳定性与土壤TC含量呈倒"U"型关系.综上,淹水环境变化对土壤水稳性团聚体分布及稳定性的影响较小,盐度和有机碳含量是影响闽江河口湿地土壤水稳性团聚体分布及稳定性的重要限制性参数.