Allometry, biomass, and productivity of mangrove forests: A review

We review 72 published articles to elucidate characteristics of biomass allocation and productivity of mangrove forests and also introduce recent progress on the study of mangrove allometry to solve the site- and species-specific problems. This includes the testing of a common allometric equation, which may be applicable to mangroves worldwide. The biomass of mangrove forests varies with age, dominant species, and locality. In primary mangrove forests, the above-ground biomass tends to be relatively low near the sea and increases inland. On a global scale, mangrove forests in the tropics have much higher above-ground biomass than those in temperate areas. Mangroves often accumulate large amounts of biomass in their roots, and the above-ground biomass to below-ground biomass ratio of mangrove forests is significantly low compared to that of upland forests (ANCOVA, P < 0.01). Several studies have reported on the growth increment of biomass and litter production in mangrove forests. We introduce some recent studies using the so-called “summation method” and investigate the trends in net primary production (NPP). For crown heights below 10 m, the above-ground NPP of mangrove forests is significantly higher (ANOVA, P < 0.01) than in those of tropical upland forests. The above-ground litter production is generally high in mangrove forests. Moreover, in many mangrove forests, the rate of soil respiration is low, possibly because of anaerobic soil conditions. These trends in biomass allocation, NPP, and soil respiration will result in high net ecosystem production, making mangrove forests highly efficient carbon sinks in the tropics.     

Soil Respiration and Belowground Carbon Allocation in Mangrove Forests

Mangrove forests cover large areas of tropical and subtropical coastlines. They provide a wide range of ecosystem services that includes carbon storage in above- and below ground biomass and in soils. Carbon dioxide (CO₂) emissions from soil, or soil respiration is important in the global carbon budget and is sensitive to increasing global temperature. To understand the magnitude of mangrove soil respiration and the influence of forest structure and temperature on the variation in mangrove soil respiration I assessed soil respiration at eleven mangrove sites, ranging from latitude 27°N to 37°S. Mangrove soil respiration was similar to those observed for terrestrial forest soils. Soil respiration was correlated with leaf area index (LAI) and aboveground net primary production (litterfall), which should aid scaling up to regional and global estimates of soil respiration. Using a carbon balance model, total belowground carbon allocation (TBCA) per unit litterfall was similar in tall mangrove forests as observed in terrestrial forests, but in scrub mangrove forests TBCA per unit litter fall was greater than in terrestrial forests, suggesting mangroves allocate a large proportion of their fixed carbon below ground under unfavorable environmental conditions. The response of soil respiration to soil temperature was not a linear function of temperature. At temperatures below 26°C Q10 of mangrove soil respiration was 2.6, similar to that reported for terrestrial forest soils. However in scrub forests soil respiration declined with increasing soil temperature, largely because of reduced canopy cover and enhanced activity of photosynthetic benthic microbial communities.     

Variable effects of nutrient enrichment on soil respiration in mangrove forests

Background and Aims

Mangrove forests are globally important sites of carbon burial that are increasingly exposed to nutrient pollution. Here we assessed the response of soil respiration, an important component of forest carbon budgets, to nutrient enrichment over a wide range of mangrove forests.

Methods

We assessed the response of soil respiration to nutrient enrichment using fertilization experiments within 22 mangrove forests over ten sites. We used boosted regression tree (BRT) models to determine the importance of environmental and plant factors for soil respiration and its responsiveness to fertilizer treatments.

Results

Leaf area index explained the largest proportion of variation in soil respiration rates (LAI, 45.9 %) followed by those of site, which had a relative influence of 39.9 % in the BRT model. Nutrient enrichment enhanced soil respiration only in nine out of 22 forests. Soil respiration in scrub forests showed a positive response to nutrient addition more frequently than taller fringing forests. The response of soil respiration to nutrient enrichment varied with changes in specific leaf area (SLA) and stem extension, with relative influences of 14.4 %, 13.6 % in the BRT model respectively.

Conclusions

Soil respiration in mangroves varied with LAI, but other site specific factors also influenced soil respiration and its response to nutrient enrichment. Strong enhancements in aboveground growth but moderate increases in soil respiration with nutrient enrichment indicated that nutrient enrichment of mangrove forests has likely increased net ecosystem production.     

清澜港红树林湿地典型群落类型沉积物活性有机碳组分分布特征

滩涂海岸红树林生态系统通常具有较高的土壤养分,尤其是沉积物有机碳含量。海南岛红树林种类丰富且生长较好,通过对红树林沉积物有机碳组分的基础研究有利于提高对红树林湿地固碳能力的评估精度,加深对海洋蓝碳的认识。以清澜港红树林5种典型群落类型为对象,比较分析表层土壤(0—10 cm)总有机碳(TOC)、微生物生物量碳(MBC)、易氧化有机碳(EOC)、可溶性有机碳(DOC)含量差异及其与土壤因子之间的相关性。结果表明：(1)不同群落类型间,土壤TOC、MBC、DOC和EOC含量均值分别为66.76 g/kg、177.08 mg/kg、25.49 mg/kg和2.34 g/kg。对比发现,土壤TOC在角果木群落中含量最高,但各群落间无显著差异;土壤MBC在不同群落间存在显著差异,其中角果木群落和杯萼海桑群落显著高于榄李群落;土壤DOC在不同群落间存在显著差异,其中海莲群落和角果木群落显著高于其余群落;土壤EOC在不同群落间存在显著差异,其中角果木群落显著高于海莲群落和正红树群落。(2)活性有机碳各个组分占总有机碳的比例均值大小依次为EOC>MBC>DOC。土壤EOC、MBC、DOC的...     

Biogeochemical effects of simulated sea level rise on carbon loss in an Everglades mangrove peat soil

Saltwater intrusion and inundation can affect soil microbial activity, which regulates the carbon (C) balance in mangroves and helps to determine if these coastal forests can keep pace with sea level rise (SLR). This study evaluated the effects of increased salinity (+15 ppt), increased inundation (?8 cm), and their combination, on soil organic C loss from a mangrove peat soil (Everglades, Florida, USA) under simulated tides. Soil respiration (CO₂ flux), methane (CH₄) flux, dissolved organic carbon (DOC) production, and porewater nutrient concentrations were quantified. Soil respiration was the major pathway of soil organic C loss (94–98%) and was approximately 90% higher in the control water level than the inundated treatment under elevated salinity. Respiration rate increased with water temperature, but depended upon salinity and tidal range. CH₄ flux was minimal, while porewater DOC increased with a concomitant, significant decline in soil bulk density under increased inundation. Porewater ammonium increased (73%) with inundation and soluble reactive phosphorus increased (32%) with salinity. Overall, the decline in soil organic C mineralization from combined saltwater intrusion and prolonged inundation was not significant, but results suggest SLR could increase this soil’s susceptibility to peat collapse and accelerate nutrient and DOC export to adjacent Florida Bay.     

重金属污染对珠江口红树林表层沉积物碳含量的影响

湿地沉积物是红树林生态系统中重要的组成部分,其总有机碳储量的变化对红树林生态系统的固碳能力有着重要影响。现有对红树林湿地重金属的研究多集中于污染评价,鲜有涉及重金属含量对沉积物总有机碳（TOC）含量影响的研究。于2018-2019年期间4次前往珠江口典型红树林湿地,采集了0-30 cm表层土壤沉积物的样品,并测定其重金属含量和TOC含量,以探讨重金属含量变化对TOC的影响。结果表明,与广东地区的背景值相比,研究区沉积物重金属含量超标较为严重,重金属来源应是人类活动;沉积物的重金属含量能够显著影响TOC含量（P<0.01,R²=0.39）,间接对红树林湿地的固碳能力、甚至全球变暖产生一定影响;Cd、As、Zn含量高的沉积物环境有利于TOC的积累,Cu、Cr、Ni、Hg含量低的沉积物环境则不利于TOC的积累。沉积物的重金属对TOC的影响的机制是非常复杂的,它们可以通过影响土壤结构、土壤化学组分、土壤内微生物、上部植被群落的生长以及凋落物归还等一系列过程,导致沉积物TOC和固碳能力的变化。     

Tidal effects on the organic carbon mineralization rate under aerobic conditions in sediments of an intertidal estuary

Laboratory experiments and field measurements were conducted to examine the effect of tide on the organic carbon mineralization rate in sediments under aerobic conditions of an intertidal estuary. Core samples of surface sediments were collected from an intertidal estuary of the Kurose River, Hiroshima, Japan. To mimic low and high tide in the intertidal estuary, organic carbon mineralization rates in the samples were measured in the laboratory under both air-exposed and submerged conditions. Mineralization rates under air-exposed conditions were two to five times higher than those under submerged conditions. Field measurements of the rate of CO₂ emission from the sediment surface revealed a rapid increase in the rate as the sea level fell during ebb tide. The estimated amount of daily organic carbon mineralization assuming a constantly submerged condition was 30% less than that estimated when considering the semi-diurnal fluctuation in sea level. These results indicate that tide has a marked impact on the organic carbon mineralization rate in sediments under aerobic conditions on an intertidal estuary, and tidal effects need to be considered when the amount of mineralized organic carbon is estimated.     

Zonation and seasonality of benthic primary production and community respiration in tropical mangrove forests

Benthic oxygen consumption and primary production were measured using the bell jar technique in deltaic and fringing mangrove forests of tropical northeastern Australia. In a deltaic forest, rates of sediment respiration ranged from 197 to 1645 mol O₂ m^–2 h^–1 (mean=836), but did not vary significantly with season or intertidal zone. Gross primary production varied among intertidal zones and seasons, ranging from –281 to 1413 mol O₂ m^–2 h^–1 (mean=258). Upon tidal exposure, rates of gross primary production increased, but respiration rates did not change significantly. In a fringing mangrove forest, benthic respiration and gross primary production exhibited strong seasonality. In both forests, rates of oxygen consumption and production were low compared to salt marshes, but equivalent to rates in other mangrove forests. The production:respiration (P/R) ratio varied greatly over space and time (range:–0.61 to 1.76), but most values were «1 with a mean of 0.15, indicating net heterotrophy. On a bare creek bank and a sandflat, rates of gross primary production and P/R ratios were generally higher than in the adjacent mangroves. Low microalgal standing stocks, low light intensity under the canopy, and differences in gross primary production between mangroves and tidal flats, and with tidal status, indicate that benthic microalgae are light-limited and a minor contributor to primary productivity in these tropical mangrove forests.     

广西珍珠湾三种红树林林分土壤碳氮储量的研究

为了探讨不同红树林林分土壤有机碳(soil organic carbon,SOC)和全氮(total nitrogen,TN)储量空间的分布特征以及与C/N的相关性,该研究以广西防城珍珠湾红树林湿地为对象,通过样地调查取样和实验室分析,测定了SOC和TN的含量以及土壤碳储量的计量,揭示了广西北仑河珍珠湾秋茄、木榄和混交林三种红树林林分SOC和TN储量空间的分布特征以及C/N与SOC和TN的相关性。结果表明:(1)秋茄、木榄和混交林的SOC储量分别为140.73、124.94、144.71 t·hm~(-2),三者无显著性差异(P0.05);木榄和混交林垂直分布特征表现为20～40 cm0～20 cm40～60 cm,秋茄表现为随着土层深度的增加而递减。(2)秋茄、木榄和混交林的TN储量分别为6.49、5.01、5.87 t·hm~(-2),表现为随着土层深度的增加而减少的趋势。(3)秋茄、木榄和混交林的SOC与TN储量之间的相关性极显著(P0.01),相关系数分别为0.924、0.971和0.844,说明SOC与TN之间存在一定的耦合效应。(4)三种林分的C/N比值范围为16.77～24.39,表明有机质主要来源于陆地,木榄和混交林土壤的C/N值与SOC储量有显著的相关性(P0.05),三种林分的C/N比值与TN储量相关性均不显著。(5)三种红树林林分的土壤碳储量均高于我国森林土壤碳储量的平均值,且SOC与TN储量之间的相关性极显著。     

Modeling Productivity in Mangrove Forests as Impacted by Effective Soil Water Availability and Its Sensitivity to Climate Change Using Biome-BGC

Ecosystem dynamics and the responses to climate change in mangrove forests are poorly understood. We applied the biogeochemical process model Biome-BGC to simulate the dynamics of net primary productivity (NPP) and leaf area index (LAI) under the present and future climate conditions in mangrove forests in Shenzhen, Zhanjiang, and Qiongshan across the southern coast of China, and in three monocultural mangrove stands of two native species, Avicennia marina and Kandelia obovata, and one exotic species, Sonneratia apetala, in Shenzhen. The soil hydrological process of the model was modified by incorporating a soil water (SW) stress index to account for the impact of the effective SW availability in the coastal wetland. Our modified Biome-BGC well predicted the dynamics of NPP and LAI in the mangrove forests at the study sites. We found that the six mangrove systems differed in sensitivity to variations in the effective SW availability. At the ecosystem level, however, soil salinity alone could not entirely explain the limitation of the effective SW availability on the productivity of mangrove forests. Increasing atmospheric CO₂ concentration differentially affected growth of different mangrove species but only had a small impact on NPP (<7%); whereas a doubling of atmospheric CO₂ concentration associated with a 2°C temperature rise would increase NPP by 14–19% across the three geographically separate mangrove forests and by 12% to as much as 68% across the three monocultural mangrove stands. Our simulation analysis indicates that temperature change is more important than increasing CO₂ concentration in affecting productivity of mangroves at the ecosystem level, and that different mangrove species differ in sensitivity to increases in temperature and CO₂ concentration.     

Nonlinear responses of ecosystem carbon fluxes to nitrogen deposition in an old-growth boreal forest

Nitrogen (N) deposition is known to increase carbon (C) sequestration in N-limited boreal forests. However, the long-term effects of N deposition on ecosystem carbon fluxes have been rarely investigated in old-growth boreal forests. Here we show that decade-long experimental N additions significantly stimulated net primary production (NPP) but the effect decreased with increasing N loads. The effect on soil heterotrophic respiration (Rh) shifted from a stimulation at low-level N additions to an inhibition at higher levels of N additions. Consequently, low-level N additions resulted in a neutral effect on net ecosystem productivity (NEP), due to a comparable stimulating effect on NPP and Rh, while NEP was increased by high-level N additions. Moreover, we found nonlinear temporal responses of NPP, Rh and NEP to low-level N additions. Our findings imply that actual N deposition in boreal forests likely exerts a minor contribution to their soil C storage.     

不同粒级土壤团聚体呼吸特征及其对碳排放的贡献

通过土盆培养试验研究了不同粒级黄棕壤团聚体呼吸特征及其对碳排放的贡献,结果表明:各粒级土壤团聚体及原状土在培养初期土壤呼吸速率较高,之后逐渐降低。在整个培养期间原状土保持了最大的土壤呼吸速率;土壤团聚体类型对土壤呼吸速率影响较大,3种粒级团聚体土壤呼吸速率大小表现为(5 mm)(1 mm)≈(1~5 mm),其中以5 mm团聚体对土壤碳排放的贡献最大。相关性分析表明,指数模型能较好地描述不同粒级团聚体的土壤呼吸对温度变化的响应;Q10值介于2.53~5.11之间且与土壤有机碳、全氮含量的变化规律基本一致,表现为1 mm团聚体有机碳、全氮含量和Q10值较大,5 mm、1~5 mm团聚体有机碳、全氮含量和Q10值相对较低,说明土壤团聚体粒级越小,其呼吸速率对温度越敏感。土壤有机碳、氮含量与土壤结构是影响土壤呼吸温度敏感性的重要因素。     

Net ecosystem exchange modifies the relationship between the autotrophic and heterotrophic components of soil respiration with abiotic factors in prairie grasslands

We investigated the relationships of net ecosystem carbon exchange (NEE), soil temperature, and moisture with soil respiration rate and its components at a grassland ecosystem. Stable carbon isotopes were used to separate soil respiration into autotrophic and heterotrophic components within an eddy covariance footprint during the 2008 and 2009 growing seasons. After correction for self‐correlation, rates of soil respiration and its autotrophic and heterotrophic components for both years were found to be strongly influenced by variations in daytime NEE – the amount of C retained in the ecosystem during the daytime, as derived from NEE measurements when photosynthetically active radiation was above 0 μmol m^?2 s^?1. The time scale for correlation of variations in daytime NEE with fluctuations in respiration was longer for heterotrophic respiration (36–42 days) than for autotrophic respiration (4–6 days). In addition to daytime NEE, autotrophic respiration was also sensitive to soil moisture but not soil temperature. In contrast, heterotrophic respiration from soils was sensitive to changes in soil temperature, soil moisture, and daytime NEE. Our results show that – as for forests – plant activity is an important driver of both components of soil respiration in this tallgrass prairie grassland ecosystem. Heterotrophic respiration had a slower coupling with plant activity than did autotrophic respiration. Our findings suggest that the frequently observed variations in the sensitivity of soil respiration to temperature or moisture may stem from variations in the proportions of autotrophic and heterotrophic components of soil respiration. Rates of photosynthesis at seasonal time scales should also be considered as a driver of both autotrophic and heterotrophic soil respiration for ecosystem flux modeling.     

Dissolved organic carbon chemistry and dynamics in contrasting forest and grassland soils

Seasonal variability in biogeochemical signatures was used to elucidate the dominant pathways of soil microbial metabolism and elemental cycling in an oligotrophic mangrove system. Three interior dwarf mangrove habitats (Twin Cays, Belize) where surface soils were overlain by microbial mats were sampled during wet and dry periods of the year. Porewater equilibration meters and standard biogeochemical methods provided steady-state porewater profiles of pH, chloride, sulfate, sulfide, ammonium, nitrate/nitrite, phosphate, dissolved organic carbon, nitrogen, and phosphorus, reduced iron and manganese, dissolved inorganic carbon, methane and nitrous oxide. During the wet season, the salinity of overlying pond water and shallow porewaters decreased. Increased rainwater infiltration through soils combined with higher tidal heights appeared to result in increased organic carbon inventories and more reducing soil porewaters. During the dry season, evaporation increased both surface water and porewater salinities, while lower tidal heights resulted in less reduced soil porewaters. Rainfall strongly influenced inventories of dissolved organic carbon and nitrogen, possibly due to more rapid decay of mangrove litter during the wet season. During both times of year, high concentrations of reduced metabolites accumulated at depth, indicating substantial rates of organic matter mineralization coupled primarily to sulfate reduction. Nitrous oxide and methane concentrations were supersaturated indicating considerable rates of nitrification and/or incomplete denitrification and methanogenesis, respectively. More reducing soil conditions during the wet season promoted the production of reduced manganese. Contemporaneous activity of sulfate reduction and methanogenesis was likely fueled by the presence of noncompetitive substrates. The findings indicate that these interior dwarf areas are unique sites of nutrient and energy regeneration and may be critical to the overall persistence and productivity of mangrove-dominated islands in oligotrophic settings.     

Ecological engineering for successful management and restoration of mangrove forests

Great potential exists to reverse the loss of mangrove forests worldwide through the application of basic principles of ecological restoration using ecological engineering approaches, including careful cost evaluations prior to design and construction. Previous documented attempts to restore mangroves, where successful, have largely concentrated on creation of plantations of mangroves consisting of just a few species, and targeted for harvesting as wood products, or temporarily used to collect eroded soil and raise intertidal areas to usable terrestrial agricultural uses. I document here the importance of assessing the existing hydrology of natural extant mangrove ecosystems, and applying this knowledge to first protect existing mangroves, and second to achieve successful and cost-effective ecological restoration, if needed. Previous research has documented the general principle that mangrove forests worldwide exist largely in a raised and sloped platform above mean sea level, and inundated at approximately 30%, or less of the time by tidal waters. More frequent flooding causes stress and death of these tree species. Prevention of such damage requires application of the same understanding of mangrove hydrology.     

经营措施对毛竹林土壤不同组分有机碳、氮及化学结构的影响

以次生常绿阔叶林为对照,选择立地条件相近的无经营、粗放经营和集约经营3种类型毛竹林为研究对象,应用密度-粒径联合分组以及化学、生物分析和傅里叶变换红外光谱(FTIR)方法,探讨经营措施对毛竹林土壤不同组分有机碳、氮含量,分配比例及结构特征的影响。结果表明: 与对照相比,无经营和粗放经营毛竹林显著提高了土壤总有机碳(TOC)、全氮(TN)、游离态颗粒有机碳、氮、可溶性有机碳(DOC)、氮(DON)和矿物结合态有机碳、氮的含量。无经营毛竹林虽然显著增大了游离态颗粒有机碳、氮的分配比例,但其与黏土矿物结合的有机碳依然是土壤有机碳的最大贮存库(67.6%)。集约经营导致竹林土壤有机碳、全氮的贮量及各组分有机碳、氮含量下降,但明显增大了DOC/TOC、微生物生物量氮与全氮比值以及微生物生物量碳和土壤有机碳的比值(微生物商)。经营措施对土壤有机碳的化学结构也具有显著影响。与对照相比,无经营和粗放经营毛竹林土壤有机碳中酚醇-OH、脂肪族-CH、芳香族C=C和羰基C=O吸收峰相对强度增强,土壤疏水性显著增加。土壤有机碳的脂肪碳、芳香碳和疏水性与土壤碳氮总量呈显著正相关,与微生物商呈显著负相关。在人为干扰减少的情况下,毛竹林凋落物、根系等有机质残体输入量的增多引起土壤难分解化合物的相对积累,使有机碳化学稳定性明显增强。同时,土壤黏土矿物质对土壤有机碳起到了很好的保护作用,通过矿物-有机碳复合使土壤碳储存稳定性更高,进而有利于土壤碳的长期保存。     

What controls variation in carbon use efficiency among Amazonian tropical forests?

Why do some forests produce biomass more efficiently than others? Variations in Carbon Use Efficiency (CUE: total Net Primary Production (NPP)/ Gross Primary Production (GPP)) may be due to changes in wood residence time (Biomass/NPP_wood), temperature, or soil nutrient status. We tested these hypotheses in 14, one ha plots across Amazonian and Andean forests where we measured most key components of net primary production (NPP: wood, fine roots, and leaves) and autotrophic respiration (R_a; wood, rhizosphere, and leaf respiration). We found that lower fertility sites were less efficient at producing biomass and had higher rhizosphere respiration, indicating increased carbon allocation to belowground components. We then compared wood respiration to wood growth and rhizosphere respiration to fine root growth and found that forests with residence times <40 yrs had significantly lower maintenance respiration for both wood and fine roots than forests with residence times >40 yrs. A comparison of rhizosphere respiration to fine root growth showed that rhizosphere growth respiration was significantly greater at low fertility sites. Overall, we found that Amazonian forests produce biomass less efficiently in stands with residence times >40 yrs and in stands with lower fertility, but changes to long‐term mean annual temperatures do not impact CUE.     

Zonation of mangrove flora and fauna in a subtropical estuarine wetland based on surface elevation

In the context of sea‐level rise (SLR), an understanding of the spatial distributions of mangrove flora and fauna is required for effective ecosystem management and conservation. These distributions are greatly affected by tidal inundation, and surface elevation is a reliable quantitative indicator of the effects of tidal inundation. Most recent studies have focused exclusively on the quantitative relationships between mangrove‐plant zonation and surface elevation, neglecting mangrove fauna. Here, we measured surface elevation along six transects through the mangrove forests of a subtropical estuarine wetland in Zhenzhu Bay (Guangxi, China), using a real‐time kinematic global positioning system. We identified the mangrove plants along each transect and investigated the spatial distributions of arboreal, epifaunal, and infaunal molluscs, as well as infaunal crabs, using traditional quadrats. Our results indicated that almost all mangrove forests in the bay were distributed within the 400–750 m intertidal zone, between the local mean sea level and mean high water (119 cm above mean sea level). Mangrove plants exhibited obvious zonation patterns, and different species tended to inhabit different niches along the elevation gradient: Aegiceras corniculatum dominated in seaward locations while Lumnitzera racemosa dominated in landward areas. Mangrove molluscs also showed distinct patterns of spatial zonation related to surface elevation, independent of life‐form and season. The spatial distributions of some molluscs were correlated to the relative abundances of certain mangrove plants. In contrast, the spatial distributions of crabs were not related to surface elevation. To the best of our knowledge, this is the first study to explicitly quantify the influences of surface elevation on the spatial distributions of mangrove fauna. This characterization of the vertical ranges of various flora and fauna in mangrove forests provides a basic framework for future studies aimed at predicting changes in the structure and functions of mangrove forests in response to SLR.     

Carbon dioxide concentrations in the nests of the mud-dwelling mangrove ant Polyrhachis sokolova Forel (Hymenoptera: Formicidae)

Abstract The nests of the mangrove ant Polyrhachis sokolova are found in soil in intertidal mangrove communities, and are thus inundated at high tides for several hours. Some of the nest galleries are flooded, but others retain air pockets, to which the ants retreat. During and following inundation, we measured carbon dioxide concentrations in air samples collected from different levels in the nests and from artificial 'control' holes in the mud. To account for the relative contribution of different sources of carbon dioxide, we also measured the carbon dioxide production by individual ants (including larvae and pupae) and small samples of mud collected near the ant nests. Nest carbon dioxide concentrations were high (2.5−11%) during and immediately following inundation, but the concentrations in the upper regions of the nest fell as soil water levels receded. However, at depths>10 cm below the level soil surface, the carbon dioxide concentrations remained relatively high and stable (at approximately 2%) over the 11 days between one high tide and the next. The contribution of the mud (and associated microorganisms) to the carbon dioxide concentration in the nests was substantial, and the contribution of the respiration of the ants was approximately 10−15% of the total. The carbon dioxide concentrations in the nests of this species during high tides are among the highest recorded for insect nests, suggesting that these ants may have unusual physiological attributes to match the behavioural and ecological challenges associated with living in the intertidal zone.     

长白山阔叶红松林生态系统土壤呼吸作用研究

用密闭静态箱式法观测了长白山阔叶红松林生态系统生长季中的土壤呼吸作用。结果表明, 长白山阔叶红松林生态系统土壤呼吸作用日动态呈单峰曲线, 在 18∶0 0左右达到最大值。土壤呼吸作用在生长季中的动态呈单峰曲线, 7月最大。 6、7、8、9各月平均土壤呼吸作用分别为 0.2 2、0.32、0.2 3和 0.13gC·m-2 ·h-1。温度升高可以提高土壤呼吸作用强度, 地下 5cm的土壤温度比气温更能准确地反映土壤呼吸作用的动态变化 ;土壤水分含量在一定范围内增加可使土壤呼吸作用强度增加, 但水分过多也会对土壤呼吸产生抑制作用而导致土壤碳排放减少。