Nitrate limitation of N2O production and denitrification from tropical pasture and rain forest soils

Nitrous oxide production was measured in intact cores taken from active pasture and old-growth forest Inceptisols in the Atlantic Lowlands of Costa Rica. Following additions of aqueous KNO₃ or glucose, or the two combined amendments, the cores were incubated in the laboratory to determine if N₂O production rates were either N-limited or C-limited in the two land use types. Differences in rates of denitrification (N2₂O + N₂ production) among amended forest and pasture soils were determined by addition of 10% C₂H₂.The forest soils were relatively insensitive to all amendment additions, including the acetylene block. Forest N₂O production rates among the treatments did not differ from the controls, and were consistently lower than those of the pasture soils. With the addition of glucose plus nitrate to the forest soils, production of N₂O was three times greater than the controls, although this increase was not statistically significant. On the other hand, the pasture soils were definitely nitrogen-limited since N₂O production rates were increased substantially beyond controls by all the amendments which contained nitrate, despite the very low N level (5 mg N kg^–1 soil) relative to typical fertilizer applications. With respect to the nitrate plus glucose plus acetylene treatment, denitrification was high in the pasture soils; N₂O production in the presence of C₂H₂ was 150% of the rate of N₂O production measured in the absence of the acetylene block. The results are discussed in relation to the effects of agricultural land use practices and subsequent impacts of disturbance on N₂O release.     

Fine root dynamics and trace gas fluxes in two lowland tropical forest soils

Fine root dynamics have the potential to contribute significantly to ecosystem‐scale biogeochemical cycling, including the production and emission of greenhouse gases. This is particularly true in tropical forests which are often characterized as having large fine root biomass and rapid rates of root production and decomposition. We examined patterns in fine root dynamics on two soil types in a lowland moist Amazonian forest, and determined the effect of root decay on rates of C and N trace gas fluxes. Root production averaged 229 (±35) and 153 (±27) g m^?2 yr^?1 for years 1 and 2 of the study, respectively, and did not vary significantly with soil texture. Root decay was sensitive to soil texture with faster rates in the clay soil (k=?0.96 year^?1) than in the sandy loam soil (k=?0.61 year^?1), leading to greater standing stocks of dead roots in the sandy loam. Rates of nitrous oxide (N₂O) emissions were significantly greater in the clay soil (13±1 ng N cm^?2 h^?1) than in the sandy loam (1.4±0.2 ng N cm^?2 h^?1). Root mortality and decay following trenching doubled rates of N₂O emissions in the clay and tripled them in sandy loam over a 1‐year period. Trenching also increased nitric oxide fluxes, which were greater in the sandy loam than in the clay. We used trenching (clay only) and a mass balance approach to estimate the root contribution to soil respiration. In clay soil root respiration was 264–380 g C m^?2 yr^?1, accounting for 24% to 35% of the total soil CO₂ efflux. Estimates were similar using both approaches. In sandy loam, root respiration rates were slightly higher and more variable (521±206 g C m² yr^?1) and contributed 35% of the total soil respiration. Our results show that soil heterotrophs strongly dominate soil respiration in this forest, regardless of soil texture. Our results also suggest that fine root mortality and decomposition associated with disturbance and land‐use change can contribute significantly to increased rates of nitrogen trace gas emissions.     

Drainage increases CO2 and N2O emissions from tropical peat soils

Tropical peatlands are vital ecosystems that play an important role in global carbon storage and cycles. Current estimates of greenhouse gases from these peatlands are uncertain as emissions vary with environmental conditions. This study provides the first comprehensive analysis of managed and natural tropical peatland GHG fluxes: heterotrophic (i.e. soil respiration without roots), total CO₂ respiration rates, CH₄ and N₂O fluxes. The study documents studies that measure GHG fluxes from the soil (n = 372) from various land uses, groundwater levels and environmental conditions. We found that total soil respiration was larger in managed peat ecosystems (median = 52.3 Mg CO₂ ha^?1 year^?1) than in natural forest (median = 35.9 Mg CO₂ ha^?1 year^?1). Groundwater level had a stronger effect on soil CO₂ emission than land use. Every 100 mm drop of groundwater level caused an increase of 5.1 and 3.7 Mg CO₂ ha^?1 year^?1 for plantation and cropping land use, respectively. Where groundwater is deep (≥0.5 m), heterotrophic respiration constituted 84% of the total emissions. N₂O emissions were significantly larger at deeper groundwater levels, where every drop in 100 mm of groundwater level resulted in an exponential emission increase (exp(0.7) kg N ha^?1 year^?1). Deeper groundwater levels induced high N₂O emissions, which constitute about 15% of total GHG emissions. CH₄ emissions were large where groundwater is shallow; however, they were substantially smaller than other GHG emissions. When compared to temperate and boreal peatland soils, tropical peatlands had, on average, double the CO₂ emissions. Surprisingly, the CO₂ emission rates in tropical peatlands were in the same magnitude as tropical mineral soils. This comprehensive analysis provides a great understanding of the GHG dynamics within tropical peat soils that can be used as a guide for policymakers to create suitable programmes to manage the sustainability of peatlands effectively.     

Natural 15N abundance of soil N pools and N2O reflect the nitrogen dynamics of forest soils

Natural ¹⁵N abundance measurements of ecosystem nitrogen (N) pools and ¹⁵N pool dilution assays of gross N transformation rates were applied to investigate the potential of δ¹⁵N signatures of soil N pools to reflect the dynamics in the forest soil N cycle. Intact soil cores were collected from pure spruce (Picea abies (L.) Karst.) and mixed spruce-beech (Fagus sylvatica L.) stands on stagnic gleysol in Austria. Soil δ¹⁵N values of both forest sites increased with depth to 50 cm, but then decreased below this zone. δ¹⁵N values of microbial biomass (mixed stand: 4.7 ± 0.8‰, spruce stand: 5.9 ± 0.9‰) and of dissolved organic N (DON; mixed stand: 5.3 ± 1.7‰, spruce stand: 2.6 ± 3.3‰) were not significantly different; these pools were most enriched in ¹⁵N of all soil N pools. Denitrification represented the main N₂O-producing process in the mixed forest stand as we detected a significant ¹⁵N enrichment of its substrate NO₃⁻ (3.6 ± 4.5‰) compared to NH₄⁺ (−4.6 ± 2.6‰) and its product N₂O (−11.8 ± 3.2‰). In a ¹⁵N-labelling experiment in the spruce stand, nitrification contributed more to N₂O production than denitrification. Moreover, in natural abundance measurements the NH₄⁺ pool was slightly ¹⁵N-enriched (−0.4 ± 2.0 ‰) compared to NO₃⁻ (−3.0 ± 0.6 ‰) and N₂O (−2.1 ± 1.1 ‰) in the spruce stand, indicating nitrification and denitrification operated in parallel to produce N₂O. The more positive δ¹⁵N values of N₂O in the spruce stand than in the mixed stand point to extensive microbial N₂O reduction in the spruce stand. Combining natural ¹⁵N abundance and ¹⁵N tracer experiments provided a more complete picture of soil N dynamics than possible with either measurement done separately.     

长白山阔叶红松林土壤氮化亚氮和甲烷的通量研究

采用静态箱／气相色谱分析方法对长白山阔叶红松林两个处理的N2O和CH4通量进行了研究．结果表明,凋落物对土壤N2O排放和CH4吸收的影响是显著的,影响程度分别是36．9％和23．4％．两个处理的N2O排放通量季节变化趋势相似：夏季(6～8月)的排放通量最高,春季(3～5月)次之,秋(9～11月)冬(12～1月)两季较低．其日变化趋势也相似：最大值都出现在18：00,最小值都出现在12：00和14：00．CH4吸收通量的季节变化趋势也很相似：夏秋两季的吸收通量明显高于春冬两季的吸收通量．其日变化趋势也相似：从14：00开始持续上升到18：00达到最大值,然后持续下降到早晨6：00达到通量的最小值．研究还发现,长白山阔叶红松林土壤的N2O排放和CH4吸收间存在着一种负线性相关关系．     

Prolonged tropical forest degradation due to compounding disturbances: Implications for CO2 and H2O fluxes

Drought, fire, and windstorms can interact to degrade tropical forests and the ecosystem services they provide, but how these forests recover after catastrophic disturbance events remains relatively unknown. Here, we analyze multi‐year measurements of vegetation dynamics and function (fluxes of CO₂ and H₂O) in forests recovering from 7 years of controlled burns, followed by wind disturbance. Located in southeast Amazonia, the experimental forest consists of three 50‐ha plots burned annually, triennially, or not at all from 2004 to 2010. During the subsequent 6‐year recovery period, postfire tree survivorship and biomass sharply declined, with aboveground C stocks decreasing by 70%–94% along forest edges (0–200 m into the forest) and 36%–40% in the forest interior. Vegetation regrowth in the forest understory triggered partial canopy closure (70%–80%) from 2010 to 2015. The composition and spatial distribution of grasses invading degraded forest evolved rapidly, likely because of the delayed mortality. Four years after the experimental fires ended (2014), the burned plots assimilated 36% less carbon than the Control, but net CO₂ exchange and evapotranspiration (ET) had fully recovered 7 years after the experimental fires ended (2017). Carbon uptake recovery occurred largely in response to increased light‐use efficiency and reduced postfire respiration, whereas increased water use associated with postfire growth of new recruits and remaining trees explained the recovery in ET. Although the effects of interacting disturbances (e.g., fires, forest fragmentation, and blowdown events) on mortality and biomass persist over many years, the rapid recovery of carbon and water fluxes can help stabilize local climate.     

Soil core method for direct simultaneous determination of N2 and N2O emissions from forest soils

In order to quantify N₂-emissions from a spruce and a beech site at the Höglwald Forest, a new measuring system was developed, that allowed simultaneous, direct determination of N₂- and N₂O-emission with high accuracy (detection limit approx. 10 g N m^–2 h^–1 for N₂ and <1 g for N₂O) using a gas-flow core method. This method requires exchange of the soil atmosphere with an artificial atmosphere, that differs only in that N₂ is substituted by He. The measuring system, the methodology of measurements and validation experiments are described in detail. Due to the huge heterogeneity of denitrification activity in different soil cores taken from our forest sites, no general trends of N₂ and N₂O production in relation to soil moisture and temperature could be demonstrated. Based on reasonable number of measurements, this work gives for the first time an estimate of the magnitude of N₂-losses from temperate forest soils. Both the magnitude of N₂-emissions (spruce: 7.2±0.7 kg N₂-N ha^–1 yr^–1; beech: 12.4±3.1 kg N₂-N ha^–1 yr^–1), as well as the N₂O–N₂ ratio (spruce: 0.136±0.04; beech: 0.52±0.19) were significantly higher for soils from the beech sites as compared to soils from the spruce site. The results suggests that N₂-emissions from N-saturated forest soils, still receiving high loads of atmospheric N-deposition, are approx. 30% of atmospheric N-input at the spruce site, and approx. 50% at the beech site. Our results demonstrate that losses of nitrogen in the form of N₂ cannot be neglected in the context of calculating N-balances for given forest sites.     

Carbon fluxes in coniferous and deciduous forest soils

Aims

Our aims were to identify responsible factors for the site-to-site variability in soil CO₂ efflux and to assess the sources of soil CO₂ of different forest types on a regional scale.

Methods

Soil CO₂ effluxes were measured over 1–4 years in four coniferous and three deciduous forests of Bavaria, Germany, and related to climate, soil properties and forest productivity. Total belowground carbon allocation (TBCA) was assessed using soil CO₂ effluxes and aboveground litterfall. Additionally, CO₂ production of organic layers was examined over 10 months under constant conditions in an incubation experiment.

Results

Annual soil CO₂ effluxes were not different among the forest sites, but predicted effluxes at a given temperature of 10°C revealed some significant differences and correlated with the phosphorous stock of the organic layers. The incubation study indicated 50% faster decomposition of organic layers from deciduous than from coniferous forests. TBCA related to soil CO₂ efflux was smaller in the deciduous than in the coniferous forests. The ratio of TBCA to soil CO₂ efflux was positively correlated with the C stock of organic layers.

Conclusions

Our results suggest that marked differences in site characteristics have little impact on soil CO₂ effluxes at the regional scale, but the contribution of soil CO₂ sources varies among the forest types.     

15N natural abundance in forest and pasture soils of the Brazilian Amazon Basin

The natural abundance of ¹⁵N was examined in soil profiles from forests and pastures of the Brazilian Amazon Basin to compare tropical forests on a variety of soil types and to investigate changes in the sources of nitrogen to soils following deforestation for cattle ranching. Six sites in the state of Rondônia, two sites in Pará and one in Amazonas were studied. All sites except one were chronosequences and contained native forest and one or more pastures ranging from 2 to 27 years old. Forest soil ¹⁵N values to a depth of 1 m ranged from 8 to 23 and were higher than values typically found in temperate forests. A general pattern of increasing ¹⁵N values with depth near the soil surface was broadly similar to patterns in other forests but a decrease in ¹⁵N values in many forest profiles between 20 and 40 cm suggests that illuviation of ¹⁵N-depleted nitrate may influence total soil ¹⁵N values in deeper soil where total N concentrations are low. In four chronosequences in Rondônia, the ¹⁵N values of surface soil from pastures were lower than in the original forest and ¹⁵N values were increasingly depleted in older pastures. Inputs of atmospheric N by dinitrogen fixation could be an important N source in these pastures. Other pastures in Amazonas and Pará and Rondônia showed no consistent change from forest values. The extent of fractionation that leads to ¹⁵N enrichment in soils was broadly similar over a wide range of soil textures and indicated that similar processes control N fractionation and loss under tropical forest over a broad geographic region. Forest ¹⁵N profiles were consistent with conceptual models that explain enrichment of soil ¹⁵N values by selective loss of ¹⁴N during nitrification and denitrification.     

Responses of N fluxes and pools to elevated atmospheric CO2 in model forest ecosystems with acidic and calcareous soils

The objectives of this study were to estimate how soil type, elevated N deposition (0.7 vs. 7 g N m^–2y^–1) and tree species influence the potential effects of elevated CO₂ (370 vs. 570 mol CO₂ mol^–1) on N pools and fluxes in forest soils. Model spruce-beech forest ecosystems were established on a nutrient-rich calcareous sand and on a nutrient-poor acidic loam in large open-top chambers. In the fourth year of treatment, we measured N concentrations in the soil solution at different depths, estimated N accumulation by ion exchange resin (IER) bags, and quantified N export in drainage water, denitrification, and net N uptake by trees. Under elevated CO₂, concentrations of N in the soil solution were significantly reduced. In the nutrient-rich calcareous sand, CO₂ enrichment decreased N concentrations in the soil solution at all depths (–45 to –100%). In the nutrient-poor acidic loam, the negative CO₂ effect was restricted to the uppermost 5 cm of the soil. Increasing the N deposition stimulated the negative impact of CO₂ enrichment on soil solution N in the acidic loam at 5 cm depth from –20% at low N inputs to –70% at high N inputs. In the nutrient-rich calcareous sand, N additions did not influence the CO₂ effect on soil solution N. Accumulation of N by IER bags, which were installed under individual trees, was decreased at high CO₂ levels under spruce in both soil types. Under beech, this decrease occurred only in the calcareous sand. N accumulation by IER bags was negatively correlated with current-years foliage biomass, suggesting that the reduction of soil N availability indices was related to a CO₂-induced growth enhancement. However, the net N uptake by trees was not significantly increased by elevated CO₂. Thus, we suppose that the reduced N concentrations in the soil solution at elevated CO₂ concentrations were rather caused by an increased N immobilisation in the soil. Denitrification was not influenced by atmospheric CO₂ concentrations. CO₂ enrichment decreased nitrate leaching in drainage by 65%, which suggests that rising atmospheric CO₂ potentially increases the N retention capacity of forest ecosystems.     

Phosphorus fluxes in two contrasting forest soils along preferential pathways after experimental N and P additions

Biogeochemistry - The assessment of impacts of an altered nutrient availability, e.g. as caused by consistently high atmospheric nitrogen (N) deposition, on ecosystem phosphorus (P) nutrition...     

The effect of different N substrates on biological N2O production from forest and agricultural light textured soils

N₂O emissions from two slightly alkaline sandy soils, from arable land and a woodland, were determined in a laboratory experiment in which the soils were incubated with different sources of nitrogen, with or without glucose, and with 0, 1 and 100 mL C₂H₂ L^-1. Large differences in the rate of N₂O production were observed between the two soils and between the different N treatments. The arable soil showed very low N₂O emissions derived from reduced forms of N as compared with the N₂O which was produced when the soil was provided with NO ₂ ^- or NO ₃ ^- and a C source, suggesting a very active denitrifier population. In contrast, the woodland soil showed a very low denitrification activity and a much higher N₂O production derived from the oxidation of NH ₄ ⁺ and reduction of NO ₂ ^- by some processes probably mediated by autotrophic or heterotrophic nitrifiers or dissimilatory NO ₂ ^- reducers. In both soils, the highest N₂O emissions were induced by NO ₂ ^- addition. Those emissions were demonstrated to have a biological origin, as no significant N₂O emissions were measured when the soil was autoclaved.     

Measurement of N fluxes and soil N in two arable soils in the UK

Plant and Soil - We measured nitrate (NO? 3) leaching, ammonia (NH3), and nitrous oxide (N2O) emissions, denitrification, crop offtake of N, and wet N deposition on two fields at each of two...     

Steady-state nitrogen isotope effects of N2 and N2O production in Paracoccus denitrificans

Nitrogen stable-isotope compositions (delta15N) can help track denitrification and N2O production in the environment, as can knowledge of the isotopic discrimination, or isotope effect, inherent to denitrification. However, the isotope effects associated with denitrification as a function of dissolved-oxygen concentration and their influence on the isotopic composition of N2O are not known. We developed a simple steady-state reactor to allow the measurement of denitrification isotope effects in Paracoccus denitrificans. With [dO2] between 0 and 1.2 microM, the N stable-isotope effects of NO3- and N2O reduction were constant at 28.6 per thousand +/- 1.9 per thousand and 12.9 per thousand +/- 2.6 per thousand, respectively (mean +/- standard error, n = 5). This estimate of the isotope effect of N2O reduction is the first in an axenic denitrifying culture and places the delta15N of denitrification-produced N2O midway between those of the nitrogenous oxide substrates and the product N2 in steady-state systems. Application of both isotope effects to N2O cycling studies is discussed.     

Effect of tree distance on N2O and CH4-fluxes from soils in temperate forest ecosystems

Complete annual cycles of N₂O and CH₄ flux in forest soils at a beech and at a spruce site at the Höglwald Forest were followed in 1997 by use of fully automatic measuring systems. In order to test if on a microsite scale differences in the magnitude of trace gas exchange between e.g. areas in direct vicinity of stems and areas in the interstem region at both sites exist, tree chambers and gradient chambers were installed in addition to the already existing interstem chambers at our sites. N₂O fluxes were in a range of –4.6–473.3 g N₂O-N m^–2 h^–1 at the beech site and in a range of –3.7–167.2 g N₂O-N m^–2 h^–1 at the spruce site, respectively. Highest N₂O emissions were observed during and at the end of a prolonged frost period, thereby further supporting previous findings that frost periods are of crucial importance for controlling annual N₂O losses from temperate forests. Fluxes of CH₄ were in a range of +10.4––194.0 g CH₄ m^–2 h^–1 at the beech site and in a range of –4.4––83.5 g CH₄ m^–2 h^–1 at the spruce site. In general, both N₂O-fluxes as well as CH₄-fluxes were higher at the beech site. On a microsite scale, N₂O and CH₄ fluxes at the beech site were highest within the stem area (annual mean: 49.6±3.3 g N₂O-N m^–2 h^–1; –77.2±3.1 g CH₄ m^–2 h^–1), and significantly lower within interstem areas (18.5±1.4 g N₂O-N m^–2 h^–1; –60.2±1.8 g CH₄ m^–2 h^–1). Significantly higher values of total N, C and pH in the organic layer, as well as increased soil moisture, especially in spring, in the stem areas, are likely to contribute to the higher N₂O fluxes within the stem area of the beech. Also for the spruce site, such differences in trace gas fluxes could be demonstrated to exist (mean annual N₂O emission within (a) stem areas: 9.7±0.9 g N₂O-N m^–2 h^–1 and (b) interstem areas: 6.2±0.6 g N₂O-N m^–2 h^–1; mean annual CH₄ uptake within (a) stem areas: –26.1±0.6 g CH₄ m^–2 h^–1 and (b) interstem areas: –38.4±0.8 g CH₄ m^–2 h^–1), though they were not as pronounced as at the beech site.     

Size matters in regulating the biodiversity of tropical forest soils

Tropical forests have long fascinated ecologists, inspiring a plethora of research into the mechanisms regulating their immense biodiversity, which originally captured the interests of early natural historians and explorers, and that still persists to this day. A new focus of this research emerged in the early 2000s highlighting the potential role of neutral (stochastic) processes in regulating the composition and diversity of tropical forest communities, and thus the maintenance of a large portion of global biodiversity (Hubbell, 2001). This strictly contrasted the long‐held belief that communities assembled via the sorting of species (and their abundances) via a deterministic response to local abiotic and biotic environmental conditions, reflecting the niche of each species (Leibold & McPeek, 2006). Yet, it is unlikely that the assembly of any community is solely governed by either stochastic or deterministic processes, but instead a combination of both. However, whether deterministic processes via niche‐based environmental sorting of species, or stochastic processes reflecting pattens of dispersal limitation, neutral effects and ecological drift dominate is often unclear. This prompts questions as to whether the relative influence of one process over another is dependent on the scale (spatial or temporal) or context of the study, or specific traits of the taxa under investigation (e.g., body size). In a From the Cover paper in this issue of Molecular Ecology, Zinger et al. (2018) tackle all these issues and show, among other things, that for soil microbes and mesofauna from tropical forests, the relative contribution of stochastic and deterministic processes in assembling their communities is strongly dependent on the body size or the studied taxa.     

Trophic partitioning in tropical rain forest birds: insights from stable isotope analysis

Bird communities reach their highest taxonomic and trophic diversity in tropical rain forest, but the use of different foraging strategies to meet food requirements in such competitive environments is poorly understood. Conventional dietary analyses are poorly suited to investigate dietary patterns in complex systems. We used stable carbon (¹³C/¹²C) and nitrogen (¹⁵N/¹⁴N) isotope analysis of whole blood to examine avian trophic patterns and sources of diet in the tropical rain forest of Los Tuxtlas, Veracruz, Mexico. We used stable nitrogen isotope analysis to delineate trophic levels, and stable carbon isotope analysis to distinguish the relative contribution of C-3 and CAM/C-4 ultimate sources of proteins to diets. There was large inter- and intraspecific variation in whole blood ¹³C and ¹⁵N values in 23 species of birds. Stable nitrogen isotope analysis separated birds into several trophic levels, including species that obtained their dietary protein mostly from plants, insects or a combination of both food sources. Stable carbon isotope analysis showed that most birds fed on C3-based foods but Stub-tailed Spadebills (Platyrinchus cancrominus) included C-3- and C-4/CAM-specialist individuals. Our analyses provided insights into the nutritional contribution of plant and animal sources of protein and distinguish their photosynthetic origin over relatively long average time periods.     

Liana community and functional trait analysis in tropical dry evergreen forest of India

Aim Lianas are abundant and diverse throughout the world and constitute an important structural and functional component of tropical forests. This study aims to investigate liana diversity, abundance and their functional traits in Indian tropical dry evergreen forest (TDEF).Methods A total of ten 1-ha plots, one each in 10 Indian TDEF sites were demarcated. Each 1-ha plot was divided into one-hundred 10- × 10-m quadrats to facilitate woody species inventory. All lianas ≥1cm diameter measured at 130cm from the rooting point and all trees ≥10-cm girth at breast height (gbh) were recorded from the study sites to analyze the patterns of liana diversity and abundance and also to compare the contribution of lianas to the total woody species richness, density and basal area. Liana variables across the study sites were compared using one-way analysis of variance. The qualitative functional traits of inventoried lianas and trees were assessed on the field and referring to pertinent field manuals.Important findings A total of 9237 liana individuals (ranged from 408–1658 individuals ha^-1) representing 52 species, 45 genera and 28 families were encountered from the 10 study sites. Liana species richness ranged from 11–31 species ha^-1 in 10 sites, which averaged 23.4 (±5.7) species ha^-1. The total basal area of lianas in the study sites was 7. 3 m 2 (0.20–1.76 m 2 ha^-1). There was a significant variation in liana species richness, density and basal area across the studied sites. On the whole, lianas contributed 52%, 49.3% and 4.1% to the total woody species (lianas and trees) richness, density and basal area, respectively. Liana trait analysis revealed the majority (50%) of lianas belonged to brevi-deciduous type. Stem twining was the chief climbing mechanism, exhibited by 21 species (52.6% of total abundance). More than half of the liana species (34 species; 6925 individuals) had microphyllous leaves. Fleshy-fruited lianas mostly bearing berries and drupes constituted the major fruit type in the studied sites. Zoochory was the predominant dispersal mode observed in 63.4% of species. Considering the ecological and functional role of lianas in Indian TDEF, the need for conservation is emphasized.     

Responses of CO2, N2O and CH4 fluxes between atmosphere and forest soil to changes in multiple environmental conditions

To investigate the effects of multiple environmental conditions on greenhouse gas (CO₂, N₂O, CH₄) fluxes, we transferred three soil monoliths from Masson pine forest (PF) or coniferous and broadleaved mixed forest (MF) at Jigongshan to corresponding forest type at Dinghushan. Greenhouse gas fluxes at the in situ (Jigongshan), transported and ambient (Dinghushan) soil monoliths were measured using static chambers. When the transported soil monoliths experienced the external environmental factors (temperature, precipitation and nitrogen deposition) at Dinghushan, its annual soil CO₂ emissions were 54% in PF and 60% in MF higher than those from the respective in situ treatment. Annual soil N₂O emissions were 45% in PF and 44% in MF higher than those from the respective in situ treatment. There were no significant differences in annual soil CO₂ or N₂O emissions between the transported and ambient treatments. However, annual CH₄ uptake by the transported soil monoliths in PF or MF was not significantly different from that at the respective in situ treatment, and was significantly lower than that at the respective ambient treatment. Therefore, external environmental factors were the major drivers of soil CO₂ and N₂O emissions, while soil was the dominant controller of soil CH₄ uptake. We further tested the results by developing simple empirical models using the observed fluxes of CO₂ and N₂O from the in situ treatment and found that the empirical models can explain about 90% for CO₂ and 40% for N₂O of the observed variations at the transported treatment. Results from this study suggest that the different responses of soil CO₂, N₂O, CH₄ fluxes to changes in multiple environmental conditions need to be considered in global change study.