Seasonal Litterfall Research Articles

Interannual variability and seasonality of litterfall in three temperate and boreal forest ecosystems of eastern Canada: A synthesis of long-term monitoring

Litterfall is a major pathway for transferring aboveground biomass to the forest floor and thus plays an important role in building forest soil carbon stocks. However, inter- and intra-annual variability of litterfall remains poorly documented, especially in North American temperate and boreal forests, due to the lack of recent long-term studies at high sampling frequencies. This potentially creates uncertainties in estimates of forest carbon budget models. The objectives of the present study were to 1) quantify the mean annual flux, interannual variability, and seasonality of litterfall in three sites (dominated respectively by sugar maple (Acer saccharum Marsh.), balsam fir (Abies balsamea (L.) Mill. 1768), and black spruce (Picea mariana (Mill.) B.S.P.)) in eastern Canada over a period of 22–32 years, 2) relate the litterfall amounts and temporal variations to the changes in the size of major organic matter pools in these ecosystems, and 3) compare our litterfall estimates with reference values used in national greenhouse gas inventories. Litterfall production decreased from the sugar maple to the balsam fir and black spruce sites, preponderantly due to species composition. Litterfall evolution was related to the aboveground biomass of live trees in both conifer sites; in contrast, in the broadleaf site, changes in forest composition and structure were apparently the main drivers. The litterfall seasonality varied between broadleaf and conifer sites and could be explained by a sigmoidal model. Substantial departures from the seasonality for some given years were likely due to important climatic anomalies. Forest floor biomass remained stable over time at all three sites despite the increase in litterfall at the balsam fir and sugar maple sites and rapid forest floor turnover at the latter site. Our analyses of litterfall suggest that reference values from the literature used for national greenhouse gas inventories underestimate annual litterfall and forest floor carbon stocks for temperate and boreal forests.

Effects of Acacia invasion on water quality, litterfall, aquatic decomposers, and leaf litter decomposition in streams

Abstract Small streams and their riparian vegetation are closely linked ecosystems. Thus, the invasion of native riparian forests with non‐native species can impact stream ecosystems. We assessed the effects of the invasion of broadleaf deciduous forests by evergreen, nitrogen‐fixing Acacia species on seasonal variation of relevant instream environmental variables, litterfall in the riparian area, aquatic decomposers, and leaf litter decomposition, by comparing three streams flowing through native forests (native streams) and three streams flowing through invaded forests (invaded streams) in central Portugal. Invaded streams flow through forests composed (almost) of monospecific stands of Acacia trees. Litterfall in the riparian area was sampled with fabric traps and sorted into five categories: leaf (including phyllodes), flower, fruit and seed, wood litter, and other materials. Aquatic hyphomycete conidia suspended in water were sampled to assess conidia concentration and community composition. Leaf litter of Quercus robur was enclosed in coarse‐mesh bags and incubated in streams to assess decomposition rates and associated macroinvertebrate density and community composition. Samples from each variable were collected monthly from streams over 1 year. Aquatic hyphomycete conidia concentration was higher in invaded streams in spring/summer when litter inputs, water temperature, and aquatic nutrient concentrations were higher. In contrast, conidia concentration was lower in invaded streams in autumn/winter as they received less native deciduous leaf litter in autumn than native streams. Aquatic hyphomycete community structure changed, and species richness was lower in invaded streams because aquatic nutrient concentrations were higher and leaf litter species richness was lower. Macroinvertebrate and shredder density in decomposing leaf litter did not differ between native and invaded streams, but litter bags may have artificially increased densities by providing high quality food and/or refuges in streams with poor‐quality resources. Nevertheless, macroinvertebrate community structure changed, and family richness was lower in invaded streams. Finally, decomposition rates of Q. robur leaf litter in coarse‐mesh bags were similar between stream types, despite differences in aquatic decomposer communities. Overall, Acacia invasion changed water quality, litterfall seasonality and composition, and aquatic decomposer communities (especially aquatic hyphomycetes). However, Acacia effects on macroinvertebrate density and leaf litter decomposition rates were less pronounced, suggesting that higher trophic levels may be more resilient to invasion than basal levels, or the invasion time/extent in our invaded streams was not strong enough to affect macroinvertebrates and associated processes. Instream invasion effects on aquatic hyphomycete communities were more strongly mediated by changes in litter inputs rather than increases in aquatic nutrient concentrations because they remained oligotrophic in invaded streams. Simplification of riparian and aquatic communities may render them less efficient in coping with additional environmental changes. Acacia effects might be mitigated by the maintenance of a riparian corridor composed of native vegetation. The protection of non‐invaded riparian galleries and restoration of invaded ones could protect and restore stream ecosystems.

A gridded dataset of a leaf-age-dependent leaf area index seasonality product over tropical and subtropical evergreen broadleaved forests

Abstract. The quantification of large-scale leaf-age-dependent leaf area index has been lacking in tropical and subtropical evergreen broadleaved forests (TEFs), despite the recognized importance of leaf age in influencing leaf photosynthetic capacity in this biome. Here, we simplified the canopy leaves of TEFs into three age cohorts (i.e., young, mature, and old, with different photosynthesis capacities; i.e., Vc,max) and proposed a novel neighbor-based approach to develop the first gridded dataset of a monthly leaf-age-dependent leaf area index (LAI) product (referred to as Lad-LAI) at 0.25∘ spatial resolution over the continental scale during 2001–2018 from satellite observations of sun-induced chlorophyll fluorescence (SIF) that was reconstructed from MODIS and TROPOMI (the TROPOspheric Monitoring Instrument). The new Lad-LAI products show good performance in capturing the seasonality of three LAI cohorts, i.e., young (LAIyoung; the Pearson correlation coefficient of R=0.36), mature (LAImature; R=0.77), and old (LAIold; R=0.59) leaves at eight camera-based observation sites (four in South America, three in subtropical Asia, and one in the Democratic Republic of the Congo (DRC)) and can also represent their interannual dynamics, validated only at the Barro Colorado site, with R being equal to 0.54, 0.64, and 0.49 for LAIyoung, LAImature, and LAIold, respectively. Additionally, the abrupt drops in LAIold are mostly consistent with the seasonal litterfall peaks at 53 in situ measurements across the whole tropical region (R=0.82). The LAI seasonality of young and mature leaves also agrees well with the seasonal dynamics of the enhanced vegetation index (EVI; R=0.61), which is a proxy for photosynthetically effective leaves. Spatially, the gridded Lad-LAI data capture a dry-season green-up of canopy leaves across the wet Amazonian areas, where mean annual precipitation exceeds 2000 mm yr−1, consistent with previous satellite-based analyses. The spatial patterns clustered from the three LAI cohorts also coincide with those clustered from climatic variables over the whole TEF region. Herein, we provide the average seasonality of three LAI cohorts as the main dataset and their time series as a supplementary dataset. These Lad-LAI products are available at https://doi.org/10.6084/m9.figshare.21700955.v4 (Yang et al., 2022).

Variation of seasonal litterfall in subtropical montane cloud forests to typhoon severity and environmental factors

AbstractForest litterfall is pivotal for biogeochemical cycles and for assessing the impacts of perturbations on ecosystems. Typhoon occurrence is the primary mechanism for producing litterfall; Taiwan is situated in one of the most frequently disturbed regions. However, no typhoons were recorded in 2018, only occurring three times since 1911. This rare occasion, along with the regular (2017) and extreme typhoon (2016) years, provides an opportunity to investigate the responses of typhoon‐prone forest ecosystems to a future climate scenario: Elevated temperatures amplify the intensity but reduce the frequency of typhoons. We compared three years (2016–2018) of summer typhoon season (July–October) mean monthly litterfall (MML) in the subtropical montane cloud forests of northeastern Taiwan, and investigated the relationships between MML/typhoon‐induced MML (ΔMML) and 17 biophysical, bioclimatic and topographic attributes. More MML was produced in 2016, caused by strong winds and heavy rainfall. However, there was no statistical difference between 2017 and 2018 since forests may also produce substantial amounts of litterfall in summer without typhoons. The relationship between ΔMML and 17 variables was relatively insensitive to typhoon severity. Variables associated with succession and forest management were crucial for modeling MML in the presence of typhoons, but none of them were pivotal for MML without typhoons. The mean air temperature and elevation (related to forest productivity) were crucial for MML without typhoons; surface curvature may form shelters to prevent extreme typhoon with reduced MML. These outcomes may shed light on future ecosystem dynamics in typhoon‐prone forests under a changing climate.Abstract in Mandarin is available with online material.

Variation of seasonal litterfall in subtropical montane cloud forests to typhoon severity and environmental factors

Variation of seasonal litterfall in subtropical montane cloud forests to typhoon severity and environmental factors

Disentangling Forest Dynamics for Litter Biomass Production in a Biosphere Reserve in Central India

Investments in energy sources are scaling up across India to improve climate security and further mitigate future climate change. Forest biomass and litterfall pattern play an important role in the sustainable management of forests and the efficient utilization of resources. This study investigates the seasonal litterfall biomass pattern for five consecutive years (2015–2019) in four different vegetation types in Central India (AABR) using the litter traps method on the forest floor. An ANOVA model was adopted to infer the effects of forest types, litter types, and seasonality on litterfall production. The estimated mean litterfall of the dry tropical forest in Central India was recorded as 4.19 ± 0.305 Mg/ha/y where teak plantations contribute higher values compared to other studied vegetation types. A positive correlation was observed between the litterfall and nutrient storage with soil-adjusted vegetation index and other vegetation indices. The findings of litterfall pattern and turnover rate of nutrients indicated that the vegetation types of AABR have huge potential for carbon sequestration and help to achieve the Conference of the Parties (COP-26) goal of reducing regional and/or global climate change.

Looking beyond leaves: variation in nutrient leaching potential of seasonal litterfall among different species within an urban forest

Urban litterfall that is deposited on impervious surface leaches nutrients into stormwater, contributing to downstream eutrophication. Previous studies have focused on the leaching potential of deciduous leaf litter, while other smaller-volume litterfall types—such as blossoms and fruit—may leach significant amounts of nitrogen, phosphorus, and carbon. These additional litterfall types represent an unaccounted-for source of nutrients to urban stormwater. We explored variation in leaching potential of dissolved nutrients and organic carbon across litter types and species by collecting litterfall (blossoms, fruit, leaves) from ten common urban tree species. After 24 h of leaching, we measured total phosphorus (TP), total dissolved nitrogen (TDN), and dissolved organic carbon (DOC) contributions and compared differences across litter types and species. Litter basket estimates then allowed us to quantify annual litterfall inputs. We found that blossoms leached 3–20 times more TDN and 1.5–7 times more TP than leaves of the same species. Furthermore, considering litterfall mass, several species had greater springtime nutrient-leaching potential compared to fall due to high leaching potential in blossoms and lower potential in leaves. We found mixed effects of leaf crushing and leachate solution (stormwater, salinity) on leaching rates. This study highlights the need to consider all litterfall types as well as variation in urban forest communities and conditions when seeking to budget, control, and maintain for potential nutrient sources from the urban forest.Supplementary informationThe online version contains supplementary material available at 10.1007/s11252-022-01217-8.

Seasonal litterfall and nutrients in an Atlantic Forest fragment

Litter dynamics is one of the fundamental processes for the growth and maintenance of native forest fragments, being considered the main pathway for nutrient cycling in forests. Studies on litter production and nutrient content therefore provide insights that provide a better understanding of nutrient dynamics. This study identifies the seasonality and meteorological conditions that influence the quantity and return of nutrients through litter in an Atlantic Forest fragment. Litter sampling was carried out monthly in 12 permanent plots. Each plot contained 5 littertraps distributed systematically. The litter was classified, and the dry mass and nutrients in the leaves and branches and miscellaneous fractions was quantified. Seasonal behavior was observed, with the highest depositions in the winter season. The average annual production was 6.78 Mg ha-1, with 64.9% being composed of leaves. The mean annual nutrient intake was 135.1, 115.7, 39.7, 23.5, 17.6 and 4.6 kg ha-1 for Ca, N, K, Mg, S and P, respectively. The meteorological variable precipitation influenced the deposition pattern. The increase in nutrient-use efficiency in the second year compared to the first indicates that plants strategically may be re-translocating relative amounts of their nutrients under water stress conditions.
 Keywords: ecosystem functions, nutrient cycling, secondary succession.

三个亚热带森林优势种凋落物非结构性碳水化合物含量的季节动态

PDF HTML阅读 XML下载 导出引用 引用提醒 三个亚热带森林优势种凋落物非结构性碳水化合物含量的季节动态 DOI: 10.5846/stxb202103050606 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（32022056，31800521，31922052） Seasonal variations of non-structural carbohydrates in fresh litters of three dominant tree species in subtropical forests Author: Affiliation: Fund Project: National Natural Science Foundation of China (32022056, 31800521, 31922052). 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:非结构性碳水化合物（NSC）是凋落物中的易分解组分，在凋落物分解早期快速释放进入土壤并被微生物利用，参与森林土壤生物地球化学循环，因此新鲜凋落物中NSC变化规律是认识森林土壤碳和养分循环的关键之一。选取亚热带常绿阔叶林优势树种米槠（Castanopsis carlesii）和主要造林树种杉木（Cunninghamia lanceolata）、马尾松（Pinus massoniana）为研究对象，分析其新鲜凋落叶和凋落枝中NSC （可溶性糖和淀粉）含量的动态变化规律。结果表明：凋落物中NSC含量在不同月份表现出明显的时间动态，米槠、杉木和马尾松凋落叶和凋落枝中NSC含量总体上在11-12月呈上升趋势，而在2-6月呈缓慢下降趋势。不同类型的凋落物NSC含量存在显著差异，米槠、杉木和马尾松凋落叶中NSC含量分别为3.03%-3.56%、2.18%-4.37%、3.38%-4.89%，凋落枝中NSC含量分别为1.87%-4.22%、2.88%-4.28%、2.75%-5.27%，米槠和马尾松凋落叶中NSC含量高于凋落枝，而杉木凋落枝中NSC含量高于凋落叶。不同树种凋落物NSC含量差异显著，米槠和马尾松凋落叶中NSC含量显著高于杉木，而马尾松凋落枝中NSC含量显著高于米槠。这些结果表明，凋落物中NSC含量受凋落物类型、树种和凋落物生产节律的影响，且亚热带常绿阔叶林转换为杉木和马尾松人工林将改变凋落物中NSC等易分解组分归还，进而影响森林地表生物地球化学过程。 Abstract:Forests retain large amounts of organic carbon mainly through the accumulation of photosynthetic products and the sequestration of soil organic carbon. Plant litter transfers carbon from plants to soils as a more stable pool with high resistance time. Non-structural carbohydrates (NSC), such as soluble sugars and starch, are labile components in plant litter and could be released quickly from decomposing litter and utilized by soil microorganisms. Therefore, the NSC in plant litter could involve in soil biogeochemical cycles and is a key driver for carbon and nutrient cycling in forest soils. In this study, we collected monthly fresh leaf and twig litters of Castanopsis carlesii (a dominant tree species in subtropical evergreen broad-leaved forest), Cunninghamia lanceolata and Pinus massoniana (two main planted trees in subtropical China) in a natural Castanopsis carlesii forest and the Cunninghamia lanceolata and Pinus massoniana plantations over one year to assess the seasonal dynamics of the NSC (including soluble sugars and starch) in fresh litters. The results showed that the NSC content in fresh litter varied significantly among seasons for all studied litter species and between litter types (leaf versus twig). In general, the NSC content in the leaf and twig litters of Castanopsis carlesii, Cunninghamia lanceolate, and Pinus massoniana greatly increased in November and December but decreased dramatically from February to June of the following year. The NSC content differed significantly between litter types:the NSC content in leaf litters of Castanopsis carlesii, Cunninghamia lanceolata and Pinus massoniana showed average values of 3.03%-3.56%, 2.18%-4.37%, 3.38%-4.89%, respectively, while those in the twig litters were 1.87%-4.22%, 2.88%-4.28%, 2.75%-5.27%, for the three litter species, respectively. The NSC contents in leaf litters of Castanopsis carlesii and Pinus massoniana were generally higher than those in the twig litters, and the NSC content in twig litter of Cunninghamia lanceolata was higher than that in the leaf litter. The NSC content in fresh litter also varied significantly among tree species:the NSC contents in leaf litters of Castanopsis carlesii and Pinus massoniana were significantly higher than that of Cunninghamia lanceolata, and the NSC content in twig litter of Pinus massoniana was significantly higher than that of Castanopsis carlesii. The results suggest that the NSC content in fresh litter varied significantly between litter types, tree species and litterfall rhythms. The conversion of subtropical evergreen broad-leaved forests to Cunninghamia lanceolata and Pinus massoniana plantations may change the input of easily decomposable components from seasonal litterfall, and this change in labile carbon input from fresh litterfall may affect soil microbial turnover and microbially mediated biogeochemical cycles in forest soils of subtropical China. 参考文献 相似文献 引证文献

Litterfall seasonality and adaptive strategies of tropical and subtropical evergreen forests in China

AbstractTropical and subtropical evergreen broad-leaved forests (EBFs) and needle-leaved forests (ENFs) in China exhibit complex leaf shedding strategies in responses to soil water availability, vapor pressure deficits (VPDs) and sunlight availability. However, the seasonal variations and triggers of litterfall differ significantly in tropical/subtropical forests, and there are still many uncertainties. Herein, we aim to explore the distinct climatic factors of seasonal litterfall in a climate–phenology correlation framework. We collected seasonal litterfall data from 85 sites across tropical/subtropical China and used linear correlation coefficients between sunlight and rainfall to partition synchronous/asynchronous climates. Additional phase analysis and structural equation model analysis were conducted to model the climatic triggers of tropical phenology. Results indicated two types of tropical litterfall phenology under two types of climates. In synchronous climates, where seasonal sunlight and rainfall are positively correlated, the litterfall peak of the unimodal phenology and the first litterfall peak of the bimodal phenology both happen at the end of dry season. The second litterfall peak of the bimodal phenology occurs at the end of rainy season due to water stress. In asynchronous climates, where seasonal sunlight and rainfall are negatively correlated, VPD shows consistent seasonal variations with incoming sunlight. The leaf senescence is accelerated at the end of dry season by higher VPD; while soil water deficit is in anti-phase with sunlight and mainly controls the second litterfall peak of the bimodal phenology in EBF. Our findings provide an important reference for modeling tropical phenology in Earth system models.

Litterfall Chemistry Is Modulated by Wet-Dry Seasonality and Leaf Phenology of Dominant Species in the Tropics

Litterfall has a large influence on carbon and nutrient cycling of ecosystems, particularly in light-limited forested streams, as most nutrients return in the form of litter. Although recent evidence points to the prevalence of seasonal litterfall in species-rich and evergreen tropical riparian forests, there is a limited understanding of how riparian plant diversity intersects with stream and riparian ecosystem functions. To explore this question, we investigate litterfall chemistry across wet and dry seasons and the congruence between litter traits and plant species composition of litterfall in the wet-dry tropics. Using generalized additive models, we observed consistent seasonal patterns of litterfall chemistry over 2 years, mostly influenced by dominant species in litterfall. While drier seasons showed litter lower in nutrients and structural compounds and higher in polyphenols, litter from wetter seasons were nutrient rich but lower in polyphenols. We also found contrasting seasonal patterns in litterfall chemistry, one showing that litterfall nutrient, structural compounds, and secondary metabolite concentrations declined in drier seasons while the other showed that mass-based litterfall inputs increased markedly in drier seasons. Our findings suggest that litterfall chemistry may be altered by shifts in the identity of dominant plant species and seasonality, possibly leading to changes in carbon and nutrient fluxes in tropical riparian ecosystems.

Vapor Pressure Deficit and Sunlight Explain Seasonality of Leaf Phenology and Photosynthesis Across Amazonian Evergreen Broadleaved Forest

AbstractAmazonian evergreen forests show distinct canopy phenology and photosynthetic seasonality but the climatic triggers are not well understood. This imposes a challenge for modeling leaf phenology and photosynthesis seasonality in land surface models (LSMs) across Amazonian evergreen forest biome. On continental scale, we tested two climatic triggers suggested by site observations, vapor pressure deficit (VPD), and short‐wave incoming radiation (SW) for defining leaf shedding and incorporated VPD‐ and SW‐triggered new canopy phenology modules in the ORCHIDEE LSM (hereafter VPD‐AP and SW‐AP versions). Our results show that both VPD and SW are plausible precursors of large scale litterfall seasonality across the basin by comparing againstin situdata from 14 sites. Specially, both VPD‐AP and SW‐AP correctly capture the increases in litterfall during the early dry season, followed by a flush of new leaves with increasing photosynthetic rates during the later dry season. The VPD‐AP version performs better than the SW‐AP version in capturing a dry‐season increase of photosynthesis across the wet Amazonia areas where mean annual precipitation exceeds 2,000 mm yr−1, consistent with previous satellite data analysis. Both VPD‐AP and SW‐AP model versions perform well in northern, central and southern Amazon regions where the SW seasonality is unimodal, but miss the seasonality of satellite GPP proxies in the eastern region off the coast of Guyana shield where SW seasonality is bimodal. Our findings imply that atmospheric dryness and sunlight availability likely explain the seasonality of leaf shedding and leaf flush processes, respectively, and consequently control canopy photosynthesis in Amazonian evergreen forests.

Carbon production from seasonal litterfall in the Brazilian Atlantic Forest

Forests play an important role in climate change, acting as a source or sink of carbon. There is, however, a lack of data regarding the carbon production from litterfall in tropical forests. The Atlantic Forest is one of the most distinguished forest types in Brazil, encompassing the Araucaria Forest. In this study, we assessed the seasonal carbon production from litterfall. Data were collected every season from 27 litter traps. Dry matter and carbon fraction were investigated and confronted with meteorological variables. Litterfall components were stratified into Brazilian pine leaves and twigs: broadleaved leaves, twigs, bark, reproductive material, and other material (miscellaneous). The Tukey test indicated significant differences among the carbon fractions for litter components. Seven key species were determinant in litterfall production. Brazilian pine leaves and twigs were the primary carbon source to the forest, followed by leaves and twigs from broadleaved species. Most carbon input from litterfall comes during spring and summer. We concluded that litterfall is a source of carbon and nutrient to the ecosystem. This study contributes to improving the Brazilian national greenhouse inventory and related reports addressed to climate change mitigation.

Linking the spatiotemporal variation of litterfall to standing vegetation biomass in Brazilian savannas

Abstract Aims Litterfall at a global scale is affected by climate, edaphic features and vegetation structure, with litter production increasing from grasslands to forests following the rise in standing biomass. However, at landscape scales, the same relationship between litter production and vegetation structure has rarely been studied and comparisons of litterfall patterns between adjacent, structurally distinct communities are lacking. Here, we use a standardized methodology to describe the structural differences among four savanna physiognomies and analyze their relationship with changes in litterfall across the Cerrado. Methods We evaluated the woody vegetation structure and composition in 48 sites, equally distributed across four physiognomies and monitored the monthly litter production from April 2014 to March 2015. Important Findings Results showed that the density, basal area, cylindrical volume and aboveground biomass of woody vegetation differ among physiognomies, increasing consistently from cerrado ralo, cerrado típico, cerrado denso and cerradão. Indeed, we found a strong and positive relationship between aboveground biomass and annual litter production, with litter yield increasing from 0.9 to 8.4 Mg ha−1 across different physiognomies, following the increment in vegetation structure. Monthly production was seasonal and similar among vegetation types, increasing during the dry season. Leaves comprised the dominant fraction (approx. 85%) and litterfall seasonality primarily resulted from the concentration of leaf shedding during dry months. However, the temporal pattern of litterfall throughout the year showed a gradual reduction in the seasonality from open to closed vegetation types, likely following the decrease of deciduous species abundance in the plant community. Our results showed that changes in vegetation structure may affect spatial and temporal litterfall patterns in different physiognomies, which co-occur across the Cerrado landscape, with potential implications for the overall functioning of this ecosystem. Moreover, these findings highlight the use of standardized methods as essential to correctly compare litterfall patterns among different environments.

Litterfall production and associated carbon and nitrogen flux along exclosure chronosequence at Kewet district, central lowland of Ethiopia

BackgroundLitterfall input and associated nutrient flux are critically important in the restoration of soil in degraded landscapes through exclosures. This study was conducted to evaluate the effects of exclosure on seasonal litterfall production and nutrient content, and estimate annual C and N inputs to the soil in an age sequence at Kewet district, central lowland of Ethiopia. Leaf litterfall production was recorded by a 0.25 m2 litter trap from a systematically laid line transects from 5, 15, and 20 years old exclosures and adjacent grazing land.ResultsLeaf litterfall input in the exclosures ranged from 37 g m−2 in January (at the old exclosure) to 7.33 g m−2 (at the young exclosure), and 3 g m−2 in March at the grazing land. Litterfall input showed seasonal variation and peaked in the dry months. Mean monthly leaf litterfall production was significantly (p <0.05) higher (22 g m−2) in the old exclosure than the adjacent grazing land (9 g m−2). Total annual leaf litterfall ranged from 1073 kg ha−1 (grazing land) to 2662 kg ha−1 (old exclosure). There were no significant differences in leaf litterfall nutrients i.e., N, P, K, Ca, and Mg concentrations, except for C. The annual leaf litterfall associated C and N input ranged from 412 (grazing land) to 1025 (old exclosure) and 27 (middle age exclosure) to 68 kg ha−1 (old exclosure), respectively. The positive change recorded in leaf litterfall production and associated C and N return is associated with restoration of vegetation.ConclusionsThrough well-managed area exclosure, leaf litterfall production in the degraded landscapes can reach the level of tropical dry lowland forest in about a decade. Further research on the contribution of dominant tree species in litter production along the age of exclosure is recommended to improve the effectiveness of rehabilitation of degraded lands.

Effects of typhoon disturbances on seasonal and interannual patterns of litterfall on coniferous and broadleaf plantations in Xitou, central Taiwan

ABSTRACT Many environmental and climatic disturbances can significantly change the magnitude and pattern of litterfall. This study investigated the effects of typhoon disturbances on the seasonal and interannual patterns of litterfall on coniferous and broadleaf plantation stands in Xitou, central Taiwan. Throughout the study period from 2012 to 2018, typhoon disturbances were recorded in 4 of these 7 years, whereas only minor or even no typhoon disturbances occurred in the other 3 years. Our results demonstrated that the pattern of monthly litterfall varied substantially between the coniferous and broadleaf stands. The coniferous stands exhibited a substantial litterfall pulse due to typhoon disturbances. By contrast, typhoon disturbances exerted a minor impact on the broadleaf stands. The litterfall seasonality of the coniferous stands was higher than that of the broadleaf stands, especially in the years with typhoon disturbances. Furthermore, the yearly variation caused by typhoon disturbances was distinct at the coniferous stands; the annual litterfall mass at the coniferous stands in the years with typhoon disturbances was more than twice as high as that in the years without typhoon disturbances, namely 6,000 kg ha−1 yr−1 versus 2,500 kg ha−1 yr−1. By contrast, the annual litterfall mass at the broadleaf stands did not differ significantly among the study years. Because of high interannual variation, long-term sampling is essential for accurate estimation of annual litterfall at coniferous stands. For broadleaf plantations, interannual litterfall variation seems less critical, and spatial variability should be considered because of higher variability in terms of site conditions.

Novel Representation of Leaf Phenology Improves Simulation of Amazonian Evergreen Forest Photosynthesis in a Land Surface Model

AbstractLeaf phenology in the humid tropics largely regulates the seasonality of forest carbon and water exchange. However, it is inadequately represented in most global land surface models due to limited understanding of its controls. Based on intensive field studies at four Amazonian evergreen forests, we propose a novel, quantitative representation of tropical forest leaf phenology, which links multiple environmental variables with the seasonality of new leaf production and old leaf litterfall. The new phenology simulates higher rates of leaf turnover (new leaves replacing old leaves) in dry seasons with more sunlight, which is then implemented in ORCHIDEE, together with recent findings of ontogeny‐associated photosynthetic capacity, and is evaluated against ground‐based measurements of leaf phenology (canopy leaf area index and litterfall), eddy covariance fluxes (photosynthesis and latent heat), and carbon allocations from field observations. Results show the periodical cycles of solar radiation and vapor pressure deficit are the two most important environmental variables that are empirically related to new leaf production and old leaf abscission in tropical evergreen forests. The model with new representation of leaf phenology captures the seasonality of canopy photosynthesis at three out of four sites, as well as the seasonality of litterfall, latent heat, and light use efficiency of photosynthesis at all tested sites, and improves the seasonality of carbon allocations to leaves, roots, and sapwoods. This study advances understanding of the environmental controls on tropical leaf phenology and offers an improved modeling tool for gridded simulations of interannual CO2 and water fluxes in the tropics.

Coarse particulate organic matter dynamics in ephemeral tributaries of a Central Appalachian stream network.

Headwater ephemeral tributaries are interfaces between uplands and downstream waters. Terrestrial coarse particulate organic matter (CPOM) is important in fueling aquatic ecosystems; however, the extent to which ephemeral tributaries are functionally connected to downstream waters through fluvial transport of CPOM has been little studied. Hydrology and deposition of leaf and wood, and surrogate transport (Ginkgo biloba leaves and wood dowels) were measured over month-long intervals through the winter and spring seasons (6 months) in 10 ephemeral tributaries (1.3–5.4 ha) in eastern Kentucky. Leaf deposition and surrogate transport varied over time, reflecting the seasonality of litterfall and runoff. Leaf deposition was higher in December than February and May but did not differ from January, March, and April. Mean percent of surrogate leaf transport from the ephemeral tributaries was highest in April (3.6% per day) and lowest in February (2.5%) and May (2%). Wood deposition and transport had similar patterns. No CPOM measures were related to flow frequency. Ephemeral tributaries were estimated to annually contribute 110.6 kg AFDM·km−1·yr−1 of leaves to the downstream mainstem. Ephemeral tributaries are functionally connected to downstream waters through CPOM storage and subsequent release that is timed when CPOM is often limited in downstream waters.

Seasonal litterfall composition and carbon and nitrogen returns in New Zealand shrubland

Mānuka–kānuka shrubland is an important carbon (C) sink in New Zealand, yet little is known about C cycling within these systems. The objective of our work was to assess seasonal litterfall rates, composition, and C and nitrogen (N) inputs in mixed mānuka (Leptospermum scoparium J.R. Forst &amp;amp; G. Forst.) and kānuka (Kunzea ericoides var. ericoides (A.Rich) J.Thompson) stands. Litterfall was collected for 2years at Tongariro National Park (NP) and Stoney Creek, Wairarapa (SC), separated into leaf, twig, bark, seed and ‘other’, and the C and N content of each component measured. Total litterfall was between 3557 and 4443kgha–1year–1, of which leaf material contributed 46–67%. Litterfall peaked during spring–summer months at both sites, and the overall litterfall rate was greater (P &amp;lt; 0.001) at SC than NP. Litterfall at SC contained greater (P &amp;lt; 0.001) amounts of ‘other’ due to higher undergrowth contributions, and also greater seed fall (P &amp;lt; 0.001), possibility due to the lower altitude at SC. The proportion of leaf material in litterfall also peaked during summer (P &amp;lt; 0.001). C inputs in the total litter were 1941–2448kgCha–1year–1 and N inputs ranged between 28 and 37kgNha–1year–1. There was little seasonal difference in C and N contents and the majority of both C and N inputs in litterfall were in the leaf material (P &amp;lt; 0.001). C inputs peaked during summer, but N inputs were closely aligned with total litterfall maximums during spring–summer. The leaf:wood ratio was 1.9 at both sites, indicating litter quality was consistent at both stands, regardless of differences in composition. Although the sites had similar rainfall and shrub ages, the rate of total litterfall differed, reflecting the potentially site-specific nature of litterfall in mānuka–kānuka shrubland. Further work is needed assessing litterfall and degradation rates across New Zealand to establish if mānuka–kānuka shrublands would remain carbon sinks under climate change.

Are litterfall and litter decomposition processes indicators of forest regeneration in the neotropics? Insights from a case study in the Brazilian Amazon

Litterfall plays an important role in nutrient cycling and maintenance of soil fertility in terrestrial ecosystems. We gauged the effects of anthropogenic impacts on the production, decomposition and seasonality of litterfall in primary and secondary forests within a tropical landscape of the Brazilian Amazon. We hypothesized that leaf litter quantity and quality would differ in line with forest disturbance and that these changes would translate into dissimilar decomposition rates. If proved, these processes could be used as surrogates for indentifying the ecological status of forest habitats. The obtained results have shown that, in the study area litterfall is reduced and litter decomposition is braked in disturbed habitats when compared with primary and recovered secondary forests. Also, within similar climatic conditions, the litter production and decomposition rates begin to stabilize in mature secondary forests. Our results represent a useful contribution to understand the dynamics of the litterfall and litter decomposition processes in the neotropics. Both processes were correlated and sensitive to disturbance gradients and should used as forest recovery indicators in ecological monitoring and ecological restoration studies.