Litterfall Rates Research Articles

Comparison of biomass and net primary productivity among three species in a subtropical mangrove forest at Manko Wetland, Okinawa, Japan

This study was conducted to quantify and compare the above- and belowground biomass, litterfall and net primary productivity of three mangrove species in the family Rhizophoraceae: Bruguiera gymnorrhiza, Kandelia obovata, and Rhizophora stylosa, in Manko Wetland, Okinawa Island, Japan. A total of thirty five plots were monitored over five years. The studied mangrove stands of all three species were mostly dominated by a large number of small sized trees. Total above-ground biomass of B. gymnorrhiza, K. obovata, and R. stylosa was 64.9,111.6, and 208.290.6 Mg ha−1, respectively. There was no significant difference in AGB between B. gymnorrhiza and K. obovata, but AGB of both of these species differed significantly from that of R. stylosa. Similarly, there was no significant difference in total BGB between B. gymnorrhiza and R. stylosa, but BGB of both of these species differed significantly from that of K. obovata AGB and BGB of K. obovata increased with increasing basal area of this species. On the other hand, in case of AGB and BGB of B. gymnorrhiza and R. stylosa, it did not show any relationship with basal area of the respective species. The average annual rate of above-ground biomass increment was 15.7 Mg ha−1 yr−1 in the R. stylosa stands. Hence, R. stylosa stands recored a higher AGNPP (43.8 Mg ha−1 yr−1) than B. gymnorrhiza (17.7 Mg ha−1 yr−1) and K. obovata (22.3 Mg ha−1 yr−1). Annual total litterfall rates for B. gymnorrhiza, K. obovata, and R. stylosa during the five-year period was 10.1, 9.9, and 12.3 Mg ha−1 yr−1, respectively. The annual rate of NPP in the R. stylosa stands was greater than that of two other species. R. stylosa was the most productive tree in the mangroves of Manko Wetland area in terms of dry matter production.

Depósito y descomposición de hojarasca de Pinus cooperi C.E.Blanco en El Salto, Durango, México

El objetivo del presente trabajo fue determinar el depósito y la tasa de descomposición de hojarasca de Pinus cooperi en parcelas bajo diferentes intensidades de aclareos (tratamientos) (testigo; T1: Aclareo ligero; T2: Moderado; T3: Fuerte; T4: Severo; T5: Porvenir) en el ejido La Ciudad de Pueblo Nuevo, Durango. Después de un año de observación, la máxima acumulación de hojarasca se registró en el tratamiento Testigo (4.90 Mg ha-1 año-1), seguido por T2 (3.76 Mg·ha-1·año-1), T1 (3.65 Mg·ha-1·año-1), T4 (3.25 Mg·ha-1·año-1) y T3 (3.04 Mg·ha-1·año-1). El menor aporte anual de hojarasca se registró en el T5 (2.58 Mg ha-1 año-1). La tasa de descomposición (k) de la hojarasca se determinó a partir del modelo exponencial de Olson. Las tasas diarias de descomposición fueron mayores durante los primeros 150 días de incubación que en los 210 días subsiguientes. En ambos periodos hubo diferencias significativas entre los tratamientos. Después de 360 días de incubación, la mayor descomposición de hojarasca ocurrió en T3 (42.3 %), independientemente de la densidad residual de las parcelas; en el resto de los tratamientos, la descomposición varió de 30.2 (T1) a 37.1 %(T5). Aun cuando en T3 fue significativamente más rápida que en los demás tratamientos, bajo las condiciones de microclima que ofrecen estos tipos de aclareos, no se detectaron diferencias entre las tasas de descomposición para las cinco condiciones evaluadas en este estudio.

Disentangling the effects of tree species and microclimate on heterotrophic and autotrophic soil respiration in a Mediterranean ecotone forest

Understanding how forest ecosystems influence the response of soil respiration (RS) to climate drivers is essential to accurately predict soil carbon dioxide (CO2) fluxes in a changing environment. This is particularly crucial in areas of contact between coniferous and broadleaved forests in the Mediterranean region which are already experiencing a warmer and drier climate. We present a case study in a Mediterranean ecotone forest where RS components –heterotrophic (RH) and autotrophic (RA)– were monitored beneath pure Scots pine (Pinus sylvestris L.) and Pyrenean oak (Quercus pyrenaica Willd.) stands using the root-trenching method. We used generalized linear models to predict the soil CO2 efflux based on interactions between soil water conent (SWC) and soil temperature. Regardless of the tree species, we found that the strong and inverse water availability and thermal seasonality of the Mediterranean climate intensely constrained soil microbial activity. The incorporation of the soil temperature-moisture covariation thus greatly improved the quality of the models compared to approaches that consider soil temperature alone. We also identified species-specific responses influencing both the total amount of RA and its sensitivity to environmental variables. Root respiration in the Scots pine stand showed greater vulnerability to the decline in SWC throughout the summer than in the oak stand. The RA in the Pyrenean oak stand was mainly limited by low soil temperatures in winter, indicating low maintenance rates during vegetative dormancy. Mean annual RH rates were highest in the Scots pine stand, probably driven by the larger litterfall rates and soil carbon (C) stocks; however, the apparent turnover rate of soil organic C in the oak stand was almost twice as fast as in the pine stand. While our observations are limited to a case study, our work shows that both soil moisture and forest composition can significantly control the temperature dependence of RS components under a Mediterranean climate.

Mercury in litterfall and sediment using elemental and isotopic composition of carbon and nitrogen in the mangrove of Southeastern Brazil

Mercury and elemental and isotopic compositions of carbon and nitrogen were determined in litterfall and sediments from the mangrove of the Paraíba do Sul River, Rio de Janeiro, Brazil. Total mercury (THg) and monomethylmercury (MMHg) concentrations in sediment ranged from 33 to 123 ng g−1 and 0.20–1.38 ng g−1, respectively. The δ13C in sediment varied from −29.4 to −26.5‰ and from 2.4 to 5.8‰ in δ15N. The THg concentration in litterfall and its annual input to the mangrove was 21 ± 2 ng g−1 and 16 ± 4 μg m−2 for the species Laguncularia racemosa, 18 ± 1 ng g−1 and 17 ± 3 μg m−2 for Rhizophora mangle, and 53 ± 4 ng g−1 and 33 ± 4 μg m−2 for Avicennia germinans, respectively. The isotopic composition of leaf litter ranged from −28.6 to −26.9‰ for δ13C and 4.5–7.2‰ for δ15N. Both the highest annual Hg input via litterfall and highest sediment Hg concentration were observed in areas dominated by A. germinans. These results suggest that the rate of litterfall of plant species and the atmospheric deposition have played an important role in the Hg biogeochemical cycle in the mangrove ecosystem.

Leaf litter decomposition and diversity of arthropod decomposers in tropical Muyong forest in Banaue, Philippines

The Muyong forest, an indigenous secondary forest in Banaue, Ifugao, Philippines, plays a crucial role in the Muyong–Payoh system, a continuum of secondary forest and rice terrace, of the Banaue rice terraces by providing water and nutrients to the rice plants in the Payoh terraces. In recent decades, the planting of introduced tree species in the Muyong forest has threatened the sustainable provision of ecosystem services such as water balance and nutrient cycling. To further understand nutrient cycling in the Muyong–Payoh systems, this study was conducted in Poitan, Banaue, Ifugao to gather preliminary baseline data on floral diversity, leaf litterfall rate, leaf litter decomposition rate, and diversity and succession of arthropods in decomposing leaf litter in a Muyong forest. Vegetation analysis was done by identifying and describing the trees growing inside the five 10 m × 10 m quadrat sampling plots. Monthly leaf litter fall was collected in 1 m × 1 m litter traps, and the dry weight was determined after oven-drying at 65 °C for 48 h. Leaf litter decomposition experiment was established by laying out 12 nylon mesh bags containing fresh leaf litter in each of the four sites on the forest floor and one bag was retrieved every month to determine the change in dry weight of the leaf litter. Six bulk soil samples were collected from the Muyong forest floor and analyzed for organic matter, pH, available P and exchangeable K. Fresh leaf litter samples were analyzed for total N, P and K contents. Arthropods in the collected decomposing leaf litter were extracted using Berlese funnel and later identified up to families level using arthropod taxonomic key. The diversity of plants in the Muyong forest includes thirty-eight tree species belonging to 19 families dominated by indigenous tree species. Results showed that the monthly leaf litter fall was higher during the dry months of March to May and lower during the wet months. The estimated total leaf litter fall in Muyong forest was comparable to published litter fall from tropical secondary forests. The N, P and K contents of fresh leaf litter range from 1.0 to 1.2, 0.11 and 0.40%, respectively. The first month of decomposition has the fastest rate while the decomposition rate during the next 4 months ranged from 0.125 to 0.251. Complete decomposition or mass lost in the leaf litter in the Muyong forest took place within 5 months. The soil arthropods identified in the decomposing leaf litter were composed of 13 orders and 28 families. Majority of the collected arthropods were insects while other species including mites, spiders, millipedes and sowbugs were also present. Detrivore and fungivore Families were found to be dominant in the decomposing leaf litter. Moreover, the composition and succession of arthropod decomposer community varied in the three sampling methods and with the changing quality of the litter material as decomposition progressed. The wide diversity and succession of leaf litter decomposers consisting of detritivores, predators, fungivore and herbivore coupled with abundant rainfall and warm temperature are the two main factors that contribute to the fast rate of leaf litter decomposition and nutrient turn over in the Muyong forest. Thus, the Muyong forest can sustain the productivity of rice planted in the adjoining downstream Payoh terraces. Hence, the conservation and management of the Muyong forest is critical in maintaining the ecological functions of the Muyong–Payoh continuum.

Impacts of increasing typhoons on the structure and function of a subtropical forest: reflections of a changing climate

Due to their destructive and sporadic nature, it is often difficult to evaluate and predict the effects of typhoon on forest ecosystem patterns and processes. We used a 21-yr record of litterfall rates to explore the influence of typhoon frequency and intensity, along with other meteorological variables, on ecosystem dynamics in a subtropical rainforest. Over the past half century there has been an increasing frequency of strong typhoons (category 3; >49.6 m s−1; increase of 1.5 typhoons/decade) impacting the Fushan Experimental Forest, Taiwan. At Fushan strong typhoons drive total litterfall mass with an average of 1100 kg ha−1 litterfall typhoon−1. While mean typhoon season litterfall has been observed to vary by an order of magnitude, mean litterfall rates associated with annual leaf senescence vary by <20%. In response to increasing typhoon frequency, total annual litter mass increased gradually over the 21-year record following three major typhoons in 1994. Monthly maximum wind speed was predictive of monthly litterfall, yet the influence of precipitation and temperature was only evident in non-typhoon affected months. The response of this subtropical forest to strong typhoons suggests that increasing typhoon frequency has already shifted ecosystem structure and function (declining carbon sequestration and forest stature).

Mangrove Litter Production and Seasonality of Dominant Species in Zanzibar, Tanzania

ABSTRACT This study is aimed at examining the litter production and seasonality of Avicennia marina, Bruguiera gymnorhiza, and Rhizophora mucronata. Litter was collected using nylon litter traps of 1 mm2 mesh size in the Uzi-Nyeke mixed mangroves, Zanzibar, over a period of 2 years. Contents were sorted, dried, weighed, and the average daily litter production for each component was calculated. A distinct seasonality and species variation were found in all mangrove litter components. The average annual litterfall rate was higher in B. gymnorhiza, followed by R. mucronata and A. marina (3.0, 2.8, and 2.0 ton dry wt. ha-1 year-1 respectively). Leaf fraction was the main component of litter in all species, but fruit and flower for R. mucronata also had a considerable contribution to the total litterfall. The presented patterns of litter production are associated with average temperature and wind speed which are both strongly correlated with litter seasonality. Our data contributes to the body of knowledge on ...

Morphology and Genesis of Humus Profiles under Chaparral Shrubs in Southern California

Core Ideas Litter layers of chaparral soils differ dramatically under different plant species. The rate of litterfall, balanced by the rate of decomposition, influences the type of litter layers that develop. Macrofauna, such as earthworms, are inhibited by dry conditions and have minimal effects on litter layer characteristics. Chaparral is the predominant wildland ecosystem adjoining many urban areas of California. The litter layers under this dense shrub cover are important because they modify soil climate, support soil fauna, provide nutrients, and protect against soil erosion. The objectives of this study were: (i) to understand how the morphology of chaparral litter layers changes with depth under different shrub species, and (ii) to determine the influence of shrub species and associated macrofauna on the genesis of humus profiles. Research was conducted within mature chaparral stands (38 yr after fire) on the San Dimas Experimental Forest under four common chaparral species: chamise (Adenostoma fasiculatum H. &amp; A.), hoaryleaf ceanothus (Ceanothus crassifolius Torr.), bigberry manzanita (Arctostaphylos glauca Lindl.), and scrub oak (Quercus dumosa Nutt.). Increased litter decomposition with depth was expressed as decreasing C/N ratios, proliferation of fungal hyphae, and degradation of characteristic leaf features. Mineral matter content also increased with depth in the humus profiles, resulting from mixing by soil fauna. Earthworm densities were low throughout the chaparral, caused by seasonal moisture limitations, and were insufficient to consume manzanita leaf litter effectively, leading to thicker humus profiles and the development of Mor‐type humus. Moder‐type humus forms, with thinner litter layers, were found under scrub oak and ceanothus. Chamise litter was classified as a Rhizomull because of minimal litter accumulation, resulting from low and roughly equivalent litterfall and decomposition rates. Unique characteristics of the chaparral species led to different humus profiles and humus forms but macrofauna were not an overriding genetic influence.

Climate Warming Can Accelerate Carbon Fluxes without Changing Soil Carbon Stocks

Climate warming enhances multiple ecosystem C fluxes, but the net impact of changing C fluxes on soil organic carbon (SOC) stocks over decadal to centennial time scales remains unclear. We investigated the effects of climate on C fluxes and soil C stocks using space-for-time substitution along a boreal forest climate gradient encompassing spatially replicated sites at each of three latitudes. All regions had similar SOC concentrations and stocks (5.6 to 6.7 kg C m-2). The three lowest latitude forests exhibited the highest productivity across the transect, with tree biomass:age ratios and litterfall rates 300% and 125% higher than those in the highest latitude forests, respectively. Likewise, higher soil respiration rates (~55%) and dissolved organic C fluxes (~300%) were observed in the lowest latitude forests compared to those in the highest latitude forests. The mid-latitude forests exhibited intermediate values for these indices and fluxes. The mean radiocarbon content (∆14C) of mineral-associated SOC (+9.6 ‰) was highest in the lowest latitude forests, indicating a more rapid turnover of soil C compared to the mid- and highest latitude soils (∆14C of -35 and -30 ‰, respectively). Indicators of the extent of soil organic matter decomposition, including C:N, δ13C, and amino acid and alkyl-C:O-alkyl-C indices, revealed highly decomposed material across all regions. These data indicate that the lowest latitude forests experience accelerated C fluxes that maintain relatively young but highly decomposed SOC. Collectively, these observations of within-biome soil C responses to climate demonstrate that the enhanced rates of SOC loss that typically occur with warming can be balanced by enhanced rates of C inputs.

Investigating the rate of litterfall and decomposition in Phulai dominated forest of Pakistan: A nutrient cycling perspective

Investigating the rate of litterfall and decomposition in Phulai dominated forest of Pakistan: A nutrient cycling perspective

Growth decline assessment in Pinus sylvestris L. and Pinus nigra Arnold. forest by using 3-PG model.

Aim of the study: We assessed the ability of the 3-PG process-based model to accurately predict growth of Pinus sylvestris and P. nigra plantations across a range of sites, showing declining growth trends, in southern Spain.Area of study: The study area is located in “Sierra de Los Filabres” (Almería).Material and methods: The model was modified in fifteen parameters to predict diameter (DBH, cm), basal area increment (BAI, cm2 yr-1) and leaf area index (LAI, m2 m-2) in healthy trees and trees showing declining growth. We assumed that a set of specific physiological parameters (stem partitioning ratio-pFS20, maximum litterfall rate-γFx, maximum canopy conductance-gCx, specific leaf area for mature aged stands-σ1, age at which specific leaf area = ½ (σ0 + σ1), age at full canopy cover-tc, and canopy boundary layer conductance-gB) included in 3-PG would be suitable for predicting growth decline related to climate conditions. The calibrated model was evaluated using dendrochronological and LAI data obtained from plots.Main results: Observed and simulated DBH showed a high correlation (R2 &gt; 0.99) between modelled and measured values for both species. In contrast, modelled and observed BAI showed lower correlation (R2 &lt; 0.68). Sensitivity analysis on 3-PG outputs showed that the foliage parameters - maximum litterfall rate, maximum canopy conductance, specific leaf area for mature aged stands, age at which specific leaf area, and age at full canopy cover - were important for DBH and BAI predictions under drought stress.Research highlights: Our overall results indicated that the 3-PG model could predict growth response of pine plantations to climatic stress with desirable accuracy in southern Spain by using readily available soil and climatic data with physiological parameters derived from experiments.Keywords: Hybrid process model; forest management models; growth prediction; Pinus spp, Parameterization; forest decline.

Carbon sequestration for different management alternatives in sweet chestnut coppice in northern Spain

This paper provides an innovative approach to assessing carbon sequestration in sweet chestnut coppice taking into account the importance of carbon fluxes in the whole forest-industry value chain in the mitigation of climate change. The goals of this study were: to evaluate the baseline carbon capture of sweet chestnut forest in the north of Spain; to assess the effect of thinning and extending the rotation period on carbon storage; and to evaluate the substitution effect of using sweet chestnut products as an alternative to other materials. The CO2FIX model was used to estimate carbon content in different forest components: aboveground and belowground biomass, soil and wood products, under five different thinning and rotation scenarios. Model parameterization as a function of stand age was carried out using growth data, climate data, litterfall rates, sawmill processing data, and data on the lifespan of products and their final end. Sawmill efficiency was measured in situ using the Lumber Recovery Factor.The scenarios in which only one thinning was made resulted in more total carbon accumulating than the baseline, especially when the 40 years rotation was increased by 20 years. In contrast, scenarios involving two thinning did not even reach the baseline value of total carbon. Additionally, a positive impact on GHG emissions was found for using wood to substitute other materials, i.e. cement and fossil fuel. Taken together, these results highlight the sustainability of thinning and rotation treatments in terms of carbon storage in sweet chestnut coppice, and quantifiably supports the environmental benefits of the substitution effect of sweet chestnut wood products. As such, it provides valuable information for forest managers and policy makers who wish to address climate change mitigation in forest management planning.

Atmospheric carbon removal capacity of a mangrove ecosystem in a micro-tidal basin estuary in Sri Lanka

Characterization of the micro-tidal mangrove forests in Negombo estuary, located on the west coast of Sri Lanka, with respect to its capacity to remove atmospheric carbon and sequestration in above and below ground plant components is the objective of this study. These mangroves constitute both natural stands (e.g. Kadolkele) and woodlots planted, protected and managed by fishermen (e.g. Wedikanda) to extract twigs and branches to construct “brush parks”, a traditional method of fishing in this estuary. Both types of mangrove stands support high species richness and structural diversity, indicating planted mangrove areas have reached a semi-natural state. Allometric relationships were used to calculate biomass increment. Differences in litterfall, above and below ground biomass increment and net primary productivity (NPP) of the two types of mangrove areas were statistically insignificant, thus indicating that they are structurally and functionally comparable. Average rate of mangrove litterfall in Negombo estuary was 802 ± 25 g m−2y−1. The average above ground biomass increment was 1213 ± 95 gm−2y−1 and below ground increment was 267 ± 18 gm−2y−1, thus the average NPP of these mangroves was 2282 ± 125 g m−2y−1. NPP showed a decreasing trend from water towards land, in line with plant density and leaf area index. A statistically significant relationship was found between vegetation structure (represented by complexity index), NPP and rate of organic carbon accumulation in mangroves. Potential carbon accumulation capacity of mangroves of Negombo estuary was estimated to be approximately 12 t ha−1y−1, which is equivalent to the amount of carbon emitted as CO2 through combustion of 19,357 L of diesel or 22,212 L of gasoline in motor vehicles. Potential atmospheric carbon removal capacity of Negombo estuarine mangroves (350 ha in extent) therefore was estimated to be 4143 t y−1, which is equivalent to removal of CO2 emitted through combustion of 6,779,000 L of diesel or 7,779,000 L of gasoline within a year.

Decomposition dynamics of mixed litter in a seasonally flooded forest near the Orinoco river

We evaluated the decomposition of a litter mixture in the seasonally flooded forest of a tributary of the Orinoco river. This mixture was prepared using three litter species, based on the litter fall rate observed over a complete hydro-period (2012–2013). The mixture loading ratio was 0.46 of Pouteria orinocoensis (Sapotaceae), 0.38 of Alibertia latifolia (Rubiaceae) and 0.16 of Acosmium nitens (Fabaceae). The initial chemical composition of each single litter species was also determined. Litterbags (20 × 20 cm, 2 mm opening) containing either each single species or the mixture, were deployed on the flooded forest soil and sampled after 30, 240, 270, 300 and 330 days. There were differences in initial total N and P concentrations, with A. nitens (AN) showing the highest nutrient concentrations (%NAN = 1.86 ± 0.19; %PAN = 0.058 ± 0.008) and P. orinocoensis (PO) and A. latifolia (AL) the lowest (%NPO = 0.92 ± 0.06; %NAL = 1.04 ± 0.04; %PPO=0.029 ± 0.005; %PAL = 0.032 ± 0.001). Litter from AN showed the greatest mass loss (55%) and fastest decomposition rate (k = 0.00185 ± 0.00028) while litter from AL and the mixture showed the smallest mass loss (24% and 27% respectively) and the slowest decomposition rate (kAL = 0.00078 ± 0.00012 and kMIX = 0.00077 ± 0.00006). Decomposition rates were significantly and positively correlated with initial N (r=0.556, p<0.05) and P concentrations (r=0.482, p<0.05). Nevertheless, there were no significant differences between the expected decomposition rate and the observed decomposition rate of the mixture (additive response). To test the nature of the additivity, an enhancement factor (f) on decomposition rates for each single species was calculated. The species with the highest and smallest value of f were AN and AL, respectively. The fact that two out of the three species had values significantly different from 1, suggests that the additivity detected in our mixture was a consequence of the counterbalancing of the positive and negative effects of each species over the decomposition of the litter mixture.

The influence of soils on heterotrophic respiration exerts a strong control on net ecosystem productivity in seasonally dry Amazonian forests

Abstract. Net ecosystem productivity of carbon (NEP) in seasonally dry forests of the Amazon varies greatly between sites with similar precipitation patterns. Correctly modeling the NEP seasonality with terrestrial ecosystem models has proven difficult. Previous modelling studies have mostly advocated for incorporating processes that act to reduce water stress on gross primary productivity (GPP) during the dry season, such as deep soils and roots, plant-mediated hydraulic redistribution of soil moisture, and increased dry season leaf litter generation which reduces leaf age and thus increases photosynthetic capacity. Recent observations, however, indicate that seasonality in heterotrophic respiration also contributes to the observed seasonal cycle of NEP. Here, we use the dynamic vegetation model CLASS-CTEM (Canadian Land Surface Scheme–Canadian Terrestrial Ecosystem Model) – without deep soils or roots, hydraulic redistribution of soil moisture, or increased dry season litter generation – at two Large-Scale Biosphere–Atmosphere Experiment (LBA) sites (Tapajós km 83 and Jarú Reserve). These LBA sites exhibit opposite seasonal NEP cycles despite reasonably similar meteorological conditions. Our simulations are able to reproduce the observed NEP seasonality at both sites. Simulated GPP, heterotrophic respiration, latent and sensible heat fluxes, litter fall rate, soil moisture and temperature, and basic vegetation state are also compared with available observation-based estimates which provide confidence that overall the model behaves realistically at the two sites. Our results indicate that representing the effect of soil moisture on heterotrophic respiration in terms of soil matric potential and constraining heterotrophic respiration when absolute soil matric potential is both low (wetter soils) and high (drier soils), with optimum conditions in between, allows %appropriately representing the influence of soil texture and depth, %through soil moisture, on seasonal patterns of GPP and, especially, % heterotrophic respiration is important to correctly simulate NEP seasonality.

Variability in needle lifespan and foliar biomass along a gradient of soil fertility in maritime pine plantations on acid soils rich in organic matter

The variability in needle lifespan, foliar biomass and leaf area index was studied in 31 Pinus pinaster Ait. plots in Galicia (NW Spain), established along a gradient of soil productivity in plantations of similar age (11–14years). The soils under study were acidic (pH 3.7–5.3) and very rich in organic matter (6.9–34.3%). All needles were classified according to age class, and presence/absence of needles was recorded to evaluate survival. Specific leaf area and needle biomass were calculated for each plot. The foliage nutrient concentrations were also measured and site index was calculated. The maximum needle age was 5years. Survival of needles older than 2years declined rapidly. Needle longevity was positively affected by site index and foliar nutrient concentrations, particularly of Mg and K. This suggests that maritime pine responds to low soil fertility by decreasing needle lifespan at local scales. Needle biomass and leaf area index were significantly higher in 1 and 2-year-old needles. Total needle biomass and LAI values were very variable (average values of 4.89tha−1 and 1.64m2m−2, standard deviation 3.1 and 1.1 and CV of 64% and 69%, respectively) and were positively related to site productivity and foliar nutrients. The average litterfall rate was estimated to be 0.31year−1. The mean growth efficiency (0.36kgm−2year−1) was also rather variable (CV=50%) and was positively related to foliar K and needle longevity. The relationships between all variables associated with high levels of pine productivity and the mean shrub height were always significant and negative, indicating a reduction in the risk of ground fire.

CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; fluxes and ecosystem dynamics at five European treeless peatlands – merging data and process oriented modeling

Abstract. The carbon dioxide (CO2) exchange of five different peatland systems across Europe with a wide gradient in land use intensity, water table depth, soil fertility and climate was simulated with the process oriented CoupModel. The aim of the study was to find out whether CO2 fluxes, measured at different sites, can be explained by common processes and parameters or to what extend a site specific configuration is needed. The model was calibrated to fit measured CO2 fluxes, soil temperature, snow depth and leaf area index (LAI) and resulting differences in model parameters were analyzed. Finding site independent model parameters would mean that differences in the measured fluxes could be explained solely by model input data: water table, meteorological data, management and soil inventory data. Seasonal variability in the major fluxes was well captured, when a site independent configuration was utilized for most of the parameters. Parameters that differed between sites included the rate of soil organic decomposition, photosynthetic efficiency, and regulation of the mobile carbon (C) pool from senescence to shooting in the next year. The largest difference between sites was the rate coefficient for heterotrophic respiration. Setting it to a common value would lead to underestimation of mean total respiration by a factor of 2.8 up to an overestimation by a factor of 4. Despite testing a wide range of different responses to soil water and temperature, rate coefficients for heterotrophic respiration were consistently the lowest on formerly drained sites and the highest on the managed sites. Substrate decomposability, pH and vegetation characteristics are possible explanations for the differences in decomposition rates. Specific parameter values for the timing of plant shooting and senescence, the photosynthesis response to temperature, litter fall and plant respiration rates, leaf morphology and allocation fractions of new assimilates, were not needed, even though the gradient in site latitude ranged from 48° N (southern Germany) to 68° N (northern Finland) differed largely in their vegetation. This was also true for common parameters defining the moisture and temperature response for decomposition, leading to the conclusion that a site specific interpretation of these processes is not necessary. In contrast, the rate of soil organic decomposition, photosynthetic efficiency, and the regulation of the mobile carbon pool need to be estimated from available information on specific soil conditions, vegetation and management of the ecosystems, to be able to describe CO2 fluxes under different conditions.

Differential effects of canopy trimming and litter deposition on litterfall and nutrient dynamics in a wet subtropical forest

Humid tropical forests have the highest rates of litterfall production globally, which fuels rapid nutrient recycling and high net ecosystem production. Severe storm events significantly alter patterns in litterfall mass and nutrient dynamics through a combination of canopy disturbance and litter deposition. In this study, we used a large-scale long-term manipulation experiment to explore the separate and combined effects of canopy trimming and litter deposition on litterfall rates and litter nutrient concentrations and content. The deposition of fine litter associated with the treatments was equivalent to more than two times the annual fine litterfall mass and nutrient content in control plots. Results showed that canopy trimming was the primary driver of changes in litterfall and associated nutrient cycling. Canopy trimming reduced litterfall mass by 14Mgha−1 over the 2.5year post-trim period. Nutrient concentrations increased in some litter fractions following trimming, likely due to a combination of changes in the species and fractional composition of litterfall, and increased nutrient uptake from reduced competition for nutrients. Declines in litterfall mass, however, led to large reductions in litterfall nutrient content with a loss of 143±22kgNha−1 and 7±0.2kgPha−1 over the 2.5year post-trim period. There were no significant effects of litter deposition on litterfall rates or nutrient content, contrary to results from some fertilizer experiments. Our results suggest that large pulsed inputs of nutrients associated with tropical storms are unlikely to increase litterfall production, and that canopy disturbance has large and lasting effects on carbon and nutrient cycling.

Spatial Variability in Litterfall, Litter Standing Crop and Litter Quality in a Tropical Rain Forest Region

AbstractUnderstanding the spatial variability in plant litter processes is essential for accurate comprehension of biogeochemical cycles and ecosystem function. We assessed spatial patterns in litter processes from local to regional scales, at sites throughout the wet tropical rain forests of northern Australia. We aimed to determine the controls (e.g., climate, soil, plant community composition) on annual litter standing crop, annual litterfall rate and in situ leaf litter decomposability. The level of spatial variance in these components, and leaf litter N, P, Ca, lignin, α‐cellulose and total phenolics, was determined from within the scale of subregion, to site (1 km transects) to local/plot (~30 m2). Overall, standing crop was modeled with litterfall and its chemical composition, in situ decomposability, soil Na, and topography (r2 = 0.69, 36 plots). Litterfall was most closely aligned with plant species richness and stem density (negative correlation); leaf decomposability with leaf‐P and lignin, soil Na, and dry season moisture (r2 = 0.89, 40 plots). The predominant scale of variability in litterfall rates was local (plot), while litter standing crop and α‐cellulose variability was more evenly distributed across spatial scales. Litter decomposability, N, P and phenolics were more aligned with subregional differences. Leaf litter C, lignin and Ca varied most at the site level, suggesting more local controls. We show that variability in litter quality and decomposability are more easily accounted for spatially than litterfall rates, which vary widely over short distances possibly in response to idiosyncratic patterns of disturbance.

Human Influence on Banj Oak (Quercus leucotrichophora, A. Camus) Forests of Central Himalaya

The present study suggests that the impact of human-induced small-scale disturbances (lopping of branches and leaf litter removal) adversely impacts the functioning of banj oak (Quercus leucotrichophora, A. Camus) forests of Central Himalaya. Significantly higher (p < .001) biomass stocks, carbon sequestration rates, soil carbon, leaf area index (LAI), litter fall, and faster litter decomposition rates were observed in least human influenced (LHI) forests as compared to moderately human influenced (MHI) forests and highly human influenced (HHI) forests. Three replicate forest stands of each category were selected for the observation. The study is used as a background to suggest alternative strategies to conserve the forests, taking into account the social and economic concerns of the village community.