Calcium, potassium, and magnesium cycling in aMexican tropical dry forest ecosystem

We estimated the fluxes, inputs and outputs of Ca, K,and Mg in a Mexican tropical dry forest. The studywas conducted in five contiguous small watersheds(12–28 ha) gauged for long-term ecosystem research. A total of five 80 × 30 m plots were used for thestudy. We quantified inputs from the atmosphere,dissolved and particulate-bound losses, throughfalland litterfall fluxes, and standing crop litter pools. Mean cation inputs for a six-year period were 3.03 kg/ha for Ca, 1.31 kg/ha for K, and 0.80 kg/ha for Mg. Mean outputs in runoff were 5.24, 2.83, and 1.79 kg/ha, respectively. Calcium, K, and Mgconcentrations increased as rainfall moved through thecanopy. Annual Ca return in the litterfall (11.4 g/m²) was much higher than K (2.3 g/m²)and Mg (1.6 g/m²). Litterfall represented 99%of the Ca, 84% of the Mg, and 53% of the K, totalaboveground return to the soil. Calcium concentrationin standing litter (3.87%) was much higher than K(0.38%) and Mg (0.37%). These concentrations werehigher (Ca), lower (K), or similar (Mg) to those inlitterfall. Residence times on the forest floor were0.86, 1.17, and 1.77 yr for K, Mg, and Carespectively. Compared to the residence time fororganic matter at the site (1.31 yr), these resultssuggest slow mineralization for Ca in this ecosystem. Budget estimates were calculated for a wet and a dryyear. Results indicated that nutrients accumulated inthe dry but that nutrients were lost during the wetyear. Comparison of Ca, K, and Mg losses in streamwater with the input rates from the atmosphere for thesix-year period show that inputs are lower thanoutputs in the Chamela tropical dry forestecosystem.     

Tropical forest restoration in Costa Rica: the effect of several strategies on litter production, accumulation and decomposition

Tropical forest restoration strategies have the potential to accelerate the recovery of the nutrient cycles in degraded lands. Litter production and its decomposition represent the main transfer of organic material and nutrients into the soil substrate. We evaluated litter production, accumulation on the forest floor, and its decomposition under three restoration strategies: plantation (entire area planted with trees), island (trees planted in patches of three different sizes) and control (natural regeneration) plots. We also compared restoration strategies to young secondary forest (7-9 yr). Restoration treatments were established in 50 x 50m plots in June 2004 at six sites in Southern Costa Rica. Planted tree species included two native timber species (Terminalia amazonia and Vochysia guatemalensis) interplanted with two N fixers (Erythrina poeppigiana and Inga edulis). Litter was collected every 15 days between September 2008 and August 2009 in 12 0.25m2 litter traps distributed within each plot; litter that accumulated on the soil surface was collected at four locations (0.25m2 quadrats) within each plot in February and May 2009. Total litter production in plantation (6.3Mg/ha) and secondary forest (7.3Mg/ha) did not differ, but were greater than in islands (3.5Mg/ha) and control (1.4 Mg/ha). Plantation had greatest accumulation of litter on the soil surface (10.6 Mg/ha) as compared to the other treatments (SF = 7.2; I = 6.7; C = 4.9). Secondary forest was the only treatment with a greater annual production of litter than litter accumulation on the soil surface. Carbon storage in litter was similar between plantation and secondary forest, and significantly greater than the other treatments. No differences were found for carbon concentration and storage in the soil among treatments. There was also high variability in the production and accumulation of litter and carbon among sites. Active restoration treatments accelerated the production of litter and carbon storage in comparison to areas under natural recovery. However, the nutrient cycle has not necessarily been restored under these conditions, as high litter accumulation on the soil surface indicates a low decomposition rate, which slows nutrient return to the soil.     

Composition,biomass and structure of mangroves within the Zambezi River Delta

We used a stratified random sampling design to inventory the mangrove vegetation within the Zambezi River Delta, Mozambique, to provide a basis for estimating biomass pools. We used canopy height, derived from remote sensing data, to stratify the inventory area, and then applied a spatial decision support system to objectively allocate sample plots among five strata. Height and diameter were measured on overstory trees, saplings and standing dead trees in nested plots, and biomass was calculated using allometric equations. Each of the eight mangrove species occurring in Mozambique exist within the Delta. They are distributed in heterogeneous mixtures within each of the five canopy height classes, not reflecting obvious zonation. Overstory trees averaged approximately 2000 trees ha^?1, and average basal area ranged from 14 to 41 m² ha^?1 among height classes. The composition of the saplings tended to mirror the overstory, and the diameter frequency distributions suggest all-aged stands. Above-ground biomass ranged from 111 to 483 Mg ha^?1 with 95 % confidence interval generally within 15 % of the height class mean. Despite over 3000 trees ha^?1 in the small-tree component, 92 % of the vegetation biomass is in the overstory live trees. The objective inventory design proved effective in estimating forest biomass within the 30,267 ha mangrove forest.     

The Role of Wood Ants (Formica rufa group) in Carbon and Nutrient Dynamics of a Boreal Norway Spruce Forest Ecosystem

Wood ants (Formica rufa group) are regarded as keystone species in boreal and mountain forests of Europe and Asia by their effect on ecosystem carbon (C) and nutrient pools and fluxes. To quantify the impact of their activity on boreal forest ecosystems, C, nitrogen (N), phosphorus (P), potassium (K) and calcium (Ca) pools and fluxes in wood ant nests (WAN), and soil were assessed along a 5-, 30-, 60-, and 100-year-old Norway spruce (Picea abies L. Karsten) dominated successional gradient in eastern Finland. Amounts of C and nutrients in WAN increased with stand age, but contained less than 1% of total C and nutrient pools in these stands. The CO₂-efflux from nests was also insignificant, as compared to CO₂-efflux from the forest floor. Annually, the amount of C brought by wood ants into their nests as honeydew, prey and nest-building materials ranged from 2.7 to 49.3 kg ha^?1 C, but this is only 0.1–0.7% of the combined net primary production of trees and understorey in boreal forests. The difference between wood ant nest C inputs and outputs was very small in the younger-aged stands, and increased in the older stands. Carbon accumulation rates in nests over a 100 year period are estimated to be less than 10 kg ha^?1 a^?1. In contrast to C, annual inputs of N, P, and K are larger compared to wood ant nest nutrient pool size, ranging from 3 to 6% of the annual tree stand and understorey uptake. This indicates a more rapid turnover and transport of N, P, and K out of WAN, and suggests that wood ants increase the cycling rate of these nutrients in boreal forests.     

Degradation of Abies veitchii wave-regeneration on Mt. Misen in Ohmine Mountains: effects of sika deer population

How has the degradation of Abies veitchii wave-regeneration occurred under the sika deer (Cervus nippon) pressure? We conducted tree census and ground vegetation survey in a 1 ha plot in Mt. Misen (Nara prefecture, Japan). We found 15 tree species (over 50 cm in height). Abies accounted for 60.0 % of all living trees, and 46.9 % of Abies were damaged (herbivory, bark stripping and/or fraying) by deer. Spatial distribution of Abies trees showed Abies-wave, although there were few saplings in the dieback zone. Estimated deer population density in 2009 was 57.3 head/km². Number of living Abies and standing dead conifer trees, and ground vegetation cover for each quadrat (5 × 5 m) were used to assign the quadrats into 6 clusters. The hierarchical clustering-approach revealed that living Abies distributed mainly on the moss and/or Carex fernaldiana dominated quadrats, but did not on the Dennstaedtia scabra, or Brachypodium sylvaticum dominated quadrats. While standing dead conifer trees distributed mainly on the Carex dominated quadrats, they hardly occur on the moss, the Dennstaedtia or the Brachypodium dominated quadrats. Regeneration of Abies tree and thus the wave-regeneration is hindered for now owing to deer herbivory and bark-stripping. The ground vegetation under the dieback zone has changed from the moss and/or the Carex dominated one to the Carex, the Dennstaedtia or the Brachypodium covered vegetation with the canopy remained open and without Abies regeneration.     

鼎湖山马尾松林生态系统碳素分配和贮量的研究

鼎湖山马尾松林中 ,马尾松各器官碳含量平均为 5 4.46%,灌木层植物 48.1 0 %,草本层植物40 .2 1 %,地表现存凋落物层 5 4.40 %,以上各组分总平均为 49.2 9%。土壤碳密度为 7.3 7kg· m- 2 (深 1 0 0cm)。生态系统各组分碳贮量分别为 :乔木层 68.876t·hm- 2 ,林下植物层 6.0 3 0 t· hm- 2 ,凋落物层 5 .892 t·hm- 2 ,土壤层 73 .70 5 t· hm- 2。根据研究结果 ,还对广东省马尾松林的现有碳贮量和碳吸存潜力进行了估算和讨论。     

Response of tree biomass and wood litter to disturbance in a Central Amazon forest

We developed an individual-based stochastic-empirical model to simulate the carbon dynamics of live and dead trees in a Central Amazon forest near Manaus, Brazil. The model is based on analyses of extensive field studies carried out on permanent forest inventory plots, and syntheses of published studies. New analyses included: (1) growth suppression of small trees, (2) maximum size (trunk base diameter) for 220 tree species, (3) the relationship between growth rate and wood density, and (4) the growth response of surviving trees to catastrophic mortality (from logging). The model simulates a forest inventory plot, and tracks recruitment, growth, and mortality of live trees, decomposition of dead trees (coarse litter), and how these processes vary with changing environmental conditions. Model predictions were tested against aggregated field data, and also compared with independent measurements including maximum tree age and coarse litter standing stocks. Spatial analyses demonstrated that a plot size of ~10 ha was required to accurately measure wood (live and dead) carbon balance. With the model accurately predicting relevant pools and fluxes, a number of model experiments were performed to predict forest carbon balance response to perturbations including: (1) increased productivity due to CO₂ fertilization, (2) a single semi-catastrophic (10%) mortality event, (3) increased recruitment and mortality (turnover) rates, and (4) the combined effects of increased turnover, increased tree growth rates, and decreased mean wood density of new recruits. Results demonstrated that carbon accumulation over the past few decades observed on tropical forest inventory plots (~0.5 Mg C ha^–1 year^–1) is not likely caused by CO₂ fertilization. A maximum 25% increase in woody tissue productivity with a doubling of atmospheric CO₂ only resulted in an accumulation rate of 0.05 Mg C ha^–1 year^–1 for the period 1980–2020 for a Central Amazon forest, or an order of magnitude less than observed on the inventory plots. In contrast, model parameterization based on extensive data from a logging experiment demonstrated a rapid increase in tree growth following disturbance, which could be misinterpreted as carbon sequestration if changes in coarse litter stocks were not considered. Combined results demonstrated that predictions of changes in forest carbon balance during the twenty-first century are highly dependent on assumptions of tree response to various perturbations, and underscores the importance of a close coupling of model and field investigations.     

Biogeochemical cycles in natural forest and conifer plantations in the high mountains of Colombia

Plant litter production and decomposition are two important processes in forest ecosystems, since they provide the main organic matter input to soil and regulate nutrient cycling. With the aim to study these processes, litterfall, standing litter and nutrient return were studied for three years in an oak forest (Quercus humboldtii), pine (Pinus patula) and cypress (Cupressus lusitanica) plantations, located in highlands of the Central Cordillera of Colombia. Evaluation methods included: fine litter collection at fortnightly intervals using litter traps; the litter layer samples at the end of each sampling year and chemical analyses of both litterfall and standing litter. Fine litter fall observed was similar in oak forest (7.5 Mg ha/y) and in pine (7.8 Mg ha/y), but very low in cypress (3.5 Mg ha/y). Litter standing was 1.76, 1.73 and 1.3 Mg ha/y in oak, pine and cypress, respectively. The mean residence time of the standing litter was of 3.3 years for cypress, 2.1 years for pine and 1.8 years for oak forests. In contrast, the total amount of retained elements (N, P, S, Ca, Mg, K, Cu, Fe, Mn and Zn) in the standing litter was higher in pine (115 kg/ha), followed by oak (78 kg/ha) and cypress (24 kg/ha). Oak forests showed the lowest mean residence time of nutrients and the highest nutrients return to the soil as a consequence of a faster decomposition. Thus, a higher nutrient supply to soils from oaks than from tree plantations, seems to be an ecological advantage for recovering and maintaining the main ecosystem functioning features, which needs to be taken into account in restoration programs in this highly degraded Andean mountains.     

Effects of harvesting impacts and rehabilitation of tropical rain forest

The tropical forest is decreasing at a rate of 16.9 million hectares per year and forest land is converted to agricultural land, pasture and plantation. Decrease and degradation of the tropical forest affects not only the production of timber but also the global environment. Environmental changes must be initiated by forest harvesting. The felled trees are all large emergents with wide crowns, and when they fall they destroy a considerable amount of the forest's standing trees. Many seedlings are destroyed after harvesting because the tractor trail is constructed at the center of seedling distribution. Severe variations of changes in soil properties are caused by the removal or the deposition of topsoil by a tractor. Carbon and nitrogen loss from topsoil are estimated about 19.1 and 0.05 ton/ha respectively. Seedings and saplings before harvesting can not be expected to grow and alternate dominant individuals. However, tropical rain forest plays a key role in maintaining the global carbon balance. Rehabilitation of logged over forest or afforestation of degraded land must be applied using adequate silvicultural treatments.     

Assessment of Aboveground Carbon in Primary and Selectively Harvested Tropical Forest in Papua New Guinea

Papua New Guinea (PNG) has become the focus of climate change mitigation initiatives such as reducing emissions from deforestation and forest degradation, but defensible estimates of forest carbon are lacking. Here we present a methodology for estimating aboveground forest carbon, and apply it to a large Permanent Sample Plot system maintained by Papua New Guinea Forest Research Institute. We report the first estimates of forest carbon in lowland tropical forest in PNG. Average aboveground carbon in stems >10 cm diam. for 115 selectively harvested 1-ha plots in lowland tropical forest was 66.3±3.5 Mg C/ha (95% CI) while for 10 primary forest plots the average was 106.3±16.2 Mg C/ha. We applied ratios based on field observations, in-country studies, and the literature to estimate unmeasured pools of aboveground carbon (stems <10 cm diam., fine litter and coarse woody debris). Total aboveground carbon was estimated at 90.2 and 120.8 Mg C/ha in selectively harvested and primary lowland forest, respectively. Our estimate for primary tropical forest is lower than biome averages for tropical equatorial forest, and we hypothesize that frequent disturbances from fire, frost, landslides, and agriculture are limiting carbon stock development. The methodology and estimates presented here will assist the PNG government in its preparedness for mitigation initiatives, are of interest to communities that are seeking to participate in voluntary carbon markets, and will encourage transparency and consistency in the estimation of forest carbon.     

An integrated assessment of ecosystem carbon pools and fluxes across an oceanic alpine toposequence

Alpine ecosystems are predicted to be severely affected by climate change. Cold, wet oceanic-alpine environments may also accumulate large total ecosystem carbon (C) pools, but have rarely been investigated. We assessed C pools and fluxes on a toposequence of oceanic-alpine habitats from blanket mire and boreal Calluna heath to Racomitrium heath, Nardus snowbed and alpine Calluna heath. We quantified C pools in vegetation and soils for each habitat and compared these with C inputs from net primary production (NPP) and outputs via decomposition, measured in a 3-year litter bag experiment. We also investigated principle drivers (temperature, moisture, community composition) of C pool and flux differences between habitats. Total ecosystem C pools were large; 11–26 kg C m^?2 in alpine habitats and 50 kg C m^?2 in blanket mire. Within the alpine zone C storage was greatest in the snowbed. Litter decomposition was slow in all habitats (k?=?0.09–0.29 y^?1) while NPP was within the range reported for continental alpine systems. C pool sizes and C fluxes did not vary consistently with altitude but reflected topographic gradients of temperature and moisture within the alpine zone. Oceanic-alpine ecosystems contain large stores of C which may be vulnerable to the effects of climate change.     

内蒙古森林生态系统碳储量及其空间分布

内蒙古森林面积居全国第一位, 林木蓄积量居第五位, 准确地估算该区域森林碳储量对于评估中国森林碳储量以及制定森林资源管理措施均具有重要意义。该研究基于内蒙古森林资源野外样方调查和室内分析, 评估了内蒙古森林生态系统的固碳现状, 估算了内蒙古森林生态系统不同林型和不同碳库(乔木、灌木、草本、凋落物和土壤碳库)的碳密度大小, 揭示了其空间分布特征。在此基础上估算了内蒙古森林碳储量大小及空间格局。结果表明: 1)内蒙古森林植被层碳储量为787.8 Tg C, 乔木层、凋落物层、草本层和灌木层分别占植被层总碳储量的93.5%、3.0%、2.7%和0.8%。内蒙古森林植被层平均碳密度为40.4 t·hm^-2, 其中, 乔木层、凋落物层、草本层和灌木层的碳密度分别为35.6 t·hm^-2、2.9 t·hm^-2、1.2 t·hm^-2和0.6 t·hm^-2。2)内蒙古森林土壤层(0-100 cm)碳储量为2449.6 Tg C, 其中0-30 cm的土壤碳储量最高, 占总碳储量的79.8%。0-10 cm、10-20 cm和20-30 cm的土壤碳储量分别占0-30 cm土壤碳储量的38.8%、34.1%和27.1%。内蒙古森林土壤平均碳密度为144.4 t·hm^-2。黑桦(Betula davurica)林土壤碳密度最高, 云杉(Picea asperata)林最小。土壤碳密度随土壤深度的增加而降低。3)内蒙古森林生态系统碳储量为3237.4 Tg C, 植被层和土壤层碳储量分别占森林生态系统碳储量的24.3%和75.7%。落叶松(Larix gmelinii)林总碳储量最高, 其次为白桦(Betula platyphylla)林、夏栎(Quercus robur)林、黑桦林、榆树(Ulmus pumila)疏林和山杨(Populus davidiana)林。内蒙古森林生态系统平均碳密度为184.5 t·hm^-2。土壤碳密度与植被碳密度呈显著正相关关系。4)内蒙古森林生态系统碳储量和碳密度的空间分布总体上为东部地区高、西部地区低的趋势。在降水量充沛的东部地区和降水偏少的中西部地区, 有针对性地开展森林保护区建设和人工造林, 可显著提升区域的碳汇能力。     

Tree Species Composition, Structure, and Aboveground Wood Biomass of a Riparian Forest of the Lower Miranda River, Southern Pantanal, Brazil

The aboveground wood biomass (AWB) of tropical forests plays an important role in the global carbon cycle, and local AWB estimates provide essential data that enable the extrapolation of biomass stocks to ecosystem or biome-wide carbon cycle modelling. Few AWB estimates exist in Neotropical freshwater floodplains, where tree species distribution and forest structure depend on the height and duration of periodic inundations. We investigated tree species composition, forest structure, wood specific gravity, and AWB of trees ≥10 cm dbh in 16 plots totalling an area of 1 ha in a seasonally inundated riparian forest of the lower Miranda River, southern Pantanal, Brazil. The 443 tree individuals belonged to 46 species. Four species (Inga vera, Ocotea suaveolens, Tabebuia heptaphylla and Cecropia pachystachya) comprised more than 50% of the Total Importance Values (TIV), and floristic similarities between the plots averaged 38%. Although we detected an overall increase in species diversity correlated with decreasing flood levels, the most important tree species had almost identical distribution patterns along the flooding gradient. The stand basal area per plot (±?s.d.) amounted to 3.0?±?1.1 m² (47.8?±?18.1 m²/ha), and the tree heights averaged 10.9?±?1.4 m. Multiplying the individual basal areas by individual tree heights and a form factor of 0.6, we estimated the aboveground wood volume (AWV) for each individual, and for each plot (24.4?±?11.7 m³, 391.1?±?188 m³/ha). Wood specific gravity (SG) varied between 0.39 g/cm³ (Cecropia pachystachya) and 0.87 g/cm³ (Tabebuia heptaphylla), with a stand level average of 0.63?±?0.12 g/cm³. Multiplying the individual AWV with species SG, we estimated the plot AWB to be 16.2?±?6.4 Mg (259.4?±?102 Mg/ha). This value is comparable to that reported for late-successional forest stands of Amazonian floodplain forests, and it is close to the worldwide tropical average AWB. Because tree heights in the present forest were comparatively low when compared to other Neotropical forests, we found that resprouting of stems accounted for comparatively high basal areas. We argue that stem resprouting is an adaptation of tree species originating in non-flooded Cerrado to the seasonal inundations of riparian forests.     

The Contribution of Photodegradation to Litter Decomposition in Semiarid Mediterranean Grasslands Depends on its Interaction with Local Humidity Conditions,Litter Quality and Position

Understanding how UV radiation interacts with prevailing climatic conditions and litter quality to determine leaf litter decomposition is fundamental for understanding soil carbon cycling pathways and ecosystem functioning in drylands. We carried out a field manipulative experiment to investigate how litter quality (labile and nitrogen-rich Retama sphaerocarpa vs. recalcitrant and nitrogen-poor Stipa tenacissima), position (on the ground vs. standing) and different UV radiation levels (UV pass vs. UV block) affect litter decomposition rates at two semiarid Mediterranean steppes with contrasting climates (continental vs. maritime) in a fully factorial experimental design. As expected, Retama litter decomposed faster than that of Stipa, and litter placed on the ground decayed faster than standing litter. However, and surprisingly, contrasting effects of UV radiation on litter decomposition were observed between the two sites. At the continental site, UV radiation increased litter decay constants by 21% on average, although the contribution of photodegradation was larger when litter was placed on the ground rather than in standing litter. At the maritime site, decay constants were 15% larger in the absence of UV radiation regardless of litter position. Significant litter type × UV exposure radiation and litter type × position interactions indicate that photodegradation contributes more to litter decomposition under less favorable moisture and substrate availability conditions for microbial decomposers. Our results emphasize the need to consider interactions between moisture availability, litter quality and UV radiation in litter decomposition models to fully understand litter decomposition impacts on soil carbon cycling and storage in drylands under climate change.     

Carbon storage of the forests and its spatial pattern in Nei Mongol,China

Aims
Forest carbon storage in Nei Mongol plays a significant role in national terrestrial carbon budget due to its large area in China. Our objectives were to estimate the carbon storage in the forest ecosystems in Nei Mongol and to quantify its spatial pattern.
Methods
Field survey and sampling were conducted at 137 sites that distributed evenly across the forest types in the study region. At each site, the ecosystem carbon density was estimated thorough sampling and measuring different pools of soil (0-100 cm) and vegetation, including biomass of tree, grass, shrub, and litter. Regional carbon storage was calculated with the estimated carbon density for each forest type.
Important findings
Carbon storage of vegetation layer in forests in Nei Mongol was 787.8 Tg C, with the biomass of tree, litter, herbaceous and shrub accounting for 93.5%, 3.0%, 2.7% and 0.8%, respectively. Carbon density of vegetation layer was 40.4 t·hm^-2, with 35.6 t·hm^-2 in trees, 2.9 t·hm^-2 in litter, 1.2 t·hm^-2 in herbaceous and 0.6 t·hm^-2 in shrubs. In comparison, carbon storage of soil layer in forests in Nei Mongol was 2449.6 Tg C, with 79.8% distributed in the first 30 cm. Carbon density of soil layer was 144.4 t·hm^-2. Carbon storage of forest ecosystem in Nei Mongol was 3237.4 Tg C, with vegetation and soil accounting for 24.3% and 75.7%, respectively. Carbon density of forest ecosystems in Nei Mongol was 184.5 t·hm^-2. Carbon density of soil layer was positively correlated with that of vegetation layer. Spatially, both carbon storage and carbon density were higher in the eastern area, where the climate is more humid. Forest reserves and artificial afforestations can significantly improve the capacity of regional carbon sink.     

Carbon storage dynamics of temperate freshwater wetlands in Pennsylvania

Healthy wetlands play a significant role in climate change mitigation by storing carbon that would otherwise contribute to global warming, leading to the reduction of water and food resources as well as more extreme weather phenomena. Investigating the magnitude of carbon storage potential of different freshwater wetland systems using multiple ecological indicators at varying spatial scales provides insight and justification for selective wetland restoration and conservation initiatives. We provide a holistic accounting of total carbon values for 193 wetland sites, integrating existing carbon algorithms to rapidly assess each of the following carbon pools: above-ground, below-ground, soil, woody debris, shrub cover, and herbaceous cover. Aspects of soil, vegetation, and ecosystem characteristics and stressors were measured to obtain an overall understanding of the ecosystems ability to store carbon (long-term) along a gradient of human disturbance. Based on a review of the literature, methods were prioritized based on the initial data available from field measurements as well as their practicality and ease in replicating the process in the future. Lacustrine human impounded (88.7?±?18.0 tC/ha), riverine beaver impounded (116.2?±?29.4 tC/ha), riverine upper perennial (163.3?±?11.8 tC/ha), riverine lower perennial (199.2?±?24.7 tC/ha), riverine headwater complex (159.5?±?22.2 tC/ha), perennial/seasonal depression (269.6?±?42.4 tC/ha), and slope (162.2?±?14.6 tC/ha) wetland types were compared. Overall results showed moderate variability (9.33–835.95 tC/ha) for total carbon storage values across the wetland types, with an average total carbon storage of 174.6?±?8.8 tC/ha for all wetlands. Results show that carbon storage was significantly higher (p?=?0.002) in least disturbed wetland sites. Apart from perennial/seasonal depression wetlands, all reference standard wetlands had greater carbon storage, less disturbance impact, and a greater extent of forest cover than non-reference wetlands. Carbon storage values calculated were comparable to published literature.     

Soil N fluxes in three contrasting dry tropical forests

A comparative study of N fluxes in soil among a dry dipterocarp forest (DDF), a dry evergreen forest (DEF), and a hill evergreen forest (HEF) in Thailand was done. N fluxes in soil were estimated using an ion exchange resin core method and a buried bag method. Soil C and N pools were 38 C Mg/ha/30 cm and 2.5 N Mg/ha/30 cm in DDF, 82 C Mg/ha/30 cm and 6.2 N Mg/ha/30 cm in DEF, and 167 C Mg/ha/30 cm and 9.3 N Mg/ha/30 cm in HEF. Low C concentration in the DDF and DEF sites was compensated by high fine soil content. In the highly weathered tropical soil, fine soil content seemed to be important for C accumulation. Temporal and vertical fluctuations of N fluxes were different among the sites. The highest N flux was exhibited at the onset of the wet season in DDF, whereas inorganic N production and estimated uptake of N were relatively stable during the wet season in DEF and HEF. It is suggested that N cycling in soil becomes stable in dry tropical forests to intermediate in temperate forests. N deposition may result in large changes of N cycling in the DDF and DEF due to low accumulations of C and N.     

Abrupt increase in phosphorus and potassium fluxes during a masting event in a Bornean tropical forest

Mechanisms by which the productivity of tropical ecosystems is limited by nutrients is a long-standing question, but little information is available on the nutrient dynamics supporting the masting phenomenon in Southeast Asian evergreen rainforests. In this study we examined the nutrient sink and potential nutrient sources of masting in a Bornean tropical forest. We investigated if nutrient flux in fine litter, tree stems, and soils changed temporally in response to intense flower and fruit production. Fifty-five litter traps were installed in a 2-ha plot at the onset of flowering (April 2010), and litter and nutrient fluxes were monitored for more than 4 years (May 2010–December 2014). Wood cores of trunks and coarse roots of abundant species (Shorea spp.) and soil samples were collected in May 2010, September 2010, and September 2011 (coinciding with peak flowering, peak fruiting, and 1 year after fruiting, respectively). The P and K fluxes in the total litter were significantly greater in the mast year (2010) than non-mast years, whereas the Mg, N, and Ca fluxes did not vary in relation to masting. In line with the nutrient fluxes, P and K concentrations in coarse roots of flowering individuals of S. multiflora decreased in September 2011. The present results suggest that tropical trees require extraordinary amounts of P and K for masting, and may retranslocate stored nutrients to meet the elevated nutrient demands for masting.     

Litterfall and associated nutrient pools extend beyond the canopy of scattered eucalypt trees in temperate pastures

Scattered paddock trees are a keystone feature of temperate grazing landscapes of Australia. However, our understanding of their influence on their immediate environment, and specifically the spatial distribution and characteristics of litter, is still limited. Here, we quantified the spatial pattern of litter around 4 Eucalyptus species (Eucalyptus melliodora A. Cunn. Ex Schauer, E. viminalis Labill., E. blakelyi Maiden and E. michaeliana Blakely) in grazing landscapes on the Northern Tablelands of NSW, Australia. We examined the effect of species and soil parent material (basalt, granite and meta-sediments) on litter chemistry and chemical pools. Between 54–145 kg of litter was found around individual trees and litter density consistently declined with distance from the tree (330 g.m^?2 in the inner canopy to 4 g.m^?2 in the open paddock). However, an equivalent quantity of litter was found beneath and beyond the canopy indicating that a large quantity of the litter and nutrients fell beyond the edge of the canopy. Overall, leaf litter accounted for 23 to 34% of litterfall and had larger nutrient concentrations and pools than bark or stick litter. Most litter nutrients concentrations were independent of tree species or parent material but our results suggest that P, K and S were removed in foliage prior to abscission whilst Ca and Fe concentrations increased. The spatial patterns of litter distribution around scattered trees coincide with spatial patterns in soil properties that are frequently observed in these environments, and provide strong evidence of a significant link between these factors. Our results suggest that the removal of scattered trees from pastoral landscapes in this region of Australia will result in the loss of a significant litter input to the soil surface and will diminish this potentially important source of soil nutrients.     

Leaf-litter and changing nutrient levels in a seasonally dry tropical hardwood forest,Belize, C.A.

Summary Total above ground plant biomass in a 45 year old seasonally dry tropical hardwood forest was estimated to be approximately 56,000 kg/ha oven dry weight. Nutrients immobilized in the standing vegetation were: N, 203 kg/ha; P, 24 kg/ha; K, 234 kg/ha; Ca, 195 kg/ha; Mg, 47 kg/ha; Na, 9 kg/ha; Mn, 1 kg/ha; Cu, 0.5 kg/ha; Zn, 3 kg/ha; Fe, 4 kg/ha. Total nutrients returned each year through the litter were: N, 156 kg/ha; P, 9 kg/ha; K, 59 kg/ha; Ca, 373 kg/ha; Mg, 32 kg/ha; Na, 5 kg/ha; Mn, 1 kg/ha; Al, 21 kg/ha; Zn, 0.3 kg/ha; Fe, 9 kg/ha. Half of the nutrients immobilized in the standing vegetation were found in the leaves and are returned annually to the soil. Although litter fall is interrupted during the year, the mean nutrient content of the litter was high –5.2%.A decomposition rate of 0.48 percent per day was considered high for a seasonally dry tropical hardwood forest. Fluctuations in soil nutrient levels showed a sharp increase at the start of the rainy season. Later during the dry season nutrient levels decreased to concentrations similar to what they were just prior to the rainy season. Soil organic matter levels were very high –20% in the top 12 cm.