Litter Deposition Research Articles

Produção de serapilheira e ciclagem de nutrientes de um reflorestamento e de uma floresta estacional semidecidual no sul do Brasil

A produção, o conteúdo de N, P, K, Ca e Mg, a transferência de nutrientes e a taxa de decomposição da serapilheira foram estudados em uma Floresta Estacional Semidecidual e em um reflorestamento situado adjacente a esta no Parque Estadual Mata dos Godoy, Estado do Paraná, Brasil. A deposição anual de serapilheira foi estimada em 8.212 kg.ha-1.ano-1 na floresta e 5.341 kg.ha-1.ano-1 no reflorestamento. A floresta apresentou nos dois meses após a seca (setembro e outubro) maior deposição. Nas duas áreas a média anual da concentração de macronutrientes em g.kg-1, obedeceu à mesma ordem na floresta Ca(31,85) > N(19,94) > K(7,14) > Mg(2,28) > P(0,217) e no reflorestamento Ca(23,02) > N(19,62) > K(7,67) > Mg(1,74) > P(0,302). No reflorestamento a transferência de nutrientes variou mais durante o ano e a taxa de decomposição foi menor.

Insect herbivory, organic matter deposition and effects on belowground organic matter fluxes in a central European oak forest

Apart from the forest floor, the canopy of forested ecosystems functions as the second most important source for dissolved and particulate fractions of organic and inorganic C and N compounds. However, under mass outbreak situations of insect herbivores this flux path of organic matter is considerably intensified clearly exceeding C and N fluxes from the forest floor. In this paper we report on herbivore-altered C and N fluxes from the canopy to the forest floor and effects on forest floor nutrient fluxes during severe defoliating herbivory of the winter moth (Operophtera brumata) and the mottled umber moth (Eranis defoliaria) in an oak forest in Germany. Over the course of 6.5 months we followed the C and N fluxes with bulk deposition, throughfall solution, insect frass deposits (green-fall together with insect faeces) and with forest floor solution in an 117-yr-old oak (Quercus petraea) forest. Compared to the control, herbivore defoliation significantly enhanced throughfall inputs of total and dissolved organic carbon and nitrogen by a factor of 3 and 2.5 (for TOC and DOC), and by 1.4 and 1.3 times (for TNb and DNb), respectively. Frass plus green-fall C and N fluxes peaked in May with 592 kg C ha−1 and 33.5 kg N ha−1 representing 79.6% (for C) and 78.3% (for N) of the total C and N input over 2.5 months. The quantitative and qualitative C and N input via faeces and litter deposition significantly differ between the insect affected and non-affected site. However, the C and N fluxes with throughfall did not significantly correlate with forest floor leachates. In this context, forest floor fluxes of TOC, DOC and NO3-N were significantly lower at the infested site compared to the control, whereas fluxes of NH4-N together with DON were significantly higher. The study demonstrates the importance of linking the population and associated frass dynamics of herbivorous insects with the cycling of nutrients and organic matter in forest ecosystems, highlighting the remarkable alterations in the timing, amounts and nature of organic matter dynamics on the ecosystem level. Consequently, the ecology of phytophagous insects allows partly to explain temporal-spatial alterations in nutrient cycling and thus ecosystem functioning.

Grazing Intensity and Nitrogen Fertilization Affect Litter Responses in ‘Tifton 85’ Bermudagrass Pastures: I. Mass, Deposition Rate, and Chemical Composition

Plant litter deposition and composition affect nutrient cycling and sustainability of grazed grasslands, but the effect of management practices on litter responses has not been fully investigated. The objective of this study was to determine the effects of grazing intensity (postgraze stubble height, SH) and N fertilization on existing litter mass, litter deposition rate, and litter chemical composition in rotationally stocked ‘Tifton 85’ bermudagrass (Cynodon spp.) pastures. Three levels of SH (8, 16, 24 cm) were compared at the same interval between grazing events (28 d) and amount of N fertilization (250 kg N ha−1 yr−1). Three levels of N fertilization (50, 150, and 250 kg N ha−1 yr−1) were compared when SH (24 cm) and regrowth interval were constant (28 d). Existing litter mass (1730–2510 kg ha−1) and litter deposition rate (10–30 kg ha−1 d−1) increased as SH increased, but N fertilization had no effect on litter mass or deposition rate. Increasing SH from 8 to 24 cm resulted in lower existing litter N (20.5 vs. 19.2 g kg−1) and lignin (186 vs. 148 g kg−1) concentrations and a greater C/N ratio (24 vs. 26). Increasing N fertilization increased litter N concentration from 11.5 to 19.2 g kg−1 and decreased C/N ratio from 43 to 26, but N had no effect on lignin and acid detergent fiber (ADF) concentrations. Bermudagrass litter quantity was affected more by grazing intensity than by N fertilization, but N fertilization had a greater impact on litter composition than did grazing intensity.

Organochlorine turnover in forest ecosystems: The missing link in the terrestrial chlorine cycle

Research in the last 20 years has shown that chlorine undergoes transformations between inorganic and organic forms as part of a complex biogeochemical cycle in terrestrial systems. Natural organochlorine production appears to be associated with the decomposition of plant material on the soil surface, though the chlorine cycle budget implies that a proportion of natural organochlorine enters soil through plant litter and atmospheric deposition as well. Organochlorine compounds may form through biotic and abiotic pathways, but the rates and magnitude of production in the field remain undefined. We have performed a time‐dependent trace of chlorine concentration through forest ecosystems, revealing distinct fractions of naturally produced organochlorine in plant biomass. Aliphatic organochlorine constitutes an intrinsic component of healthy leaves that persists through senescence and humification of the plant material, making a substantial contribution to the pool of soil organochlorine. Plant leaves also contain soluble aromatic organochlorine compounds that leach from leaf litter during early decay stages. As decay progresses, high concentrations of insoluble aromatic organochlorine accrue in the humus, through de novo production as well as adsorption. The rates of aromatic organochlorine production and degradation vary seasonally and conversely. This study presents the first unambiguous evidence that there exist multiple pools of chlorinated organic matter in the soil environment and that leaf litter deposition makes a significant and refractory contribution to the soil organochlorine pool, providing key insights into the biogeochemical chlorine cycle.

Aporte de serrapilheira e de nutrientes em fragmentos florestais da Mata Altântica, RJ

To evaluate the effect of fragmentation on litter deposition and nutrients transfer, an experiment was carried out in four forest remnants of different sizes...

QUALIDADE FISIOLÓGICA DE SEMENTES DE Brachiaria E AVALIAÇÃO DA PRODUTIVIDADE DE MASSA SECA, EM DIFERENTES SISTEMAS DE INTEGRAÇÃO LAVOURA-PECUÁRIA SOB IRRIGAÇÃO

The speed and magnitude of tropical pastures expansion in Brazil are related to the availability of quality seeds. This research aimed to evaluate the physiological quality of seeds of two Brachiaria species submitted to germination and viability tests and also estimate, for both species, the fresh and dry mass yield, under different irrigated crop-livestock integration systems. For field analysis, the experimental design was a randomized complete block, in subplots, with four intercrops in the plot (Brachiaria brizantha cv. Marandu and Brachiaria ruziziensis simultaneously established with corn and nitrogen fertilization coverage), and four forage cutting times, in the winter/spring season, in subplots, with four replications. In the laboratory, the experimental design was completely randomized, with four replications per treatment/test. The germination and viability tests indicated that B. brizantha seeds showed higher physiological quality, when compared with B. ruziziensis, while the tetrazolium test and germinated seedlings characteristics were similar. The B. ruziziensis, simultaneously intercropped with corn, was the less viable intercrop, due to the lower fresh and dry mass yield and litter deposition on the soil surface. In general, the pasture formation for the second season cultivation, intercropped with corn, was an excellent alternative for crop-livestock integration under a no-tillage system. KEY-WORDS: Controlled deterioration; accelerated aging; germination; tetrazolium; vigor.

Deposição e composição química de serrapilheira em um bosque de sabiá

Objetivou-se avaliar a deposição e composição química de componentes da serrapilheira existente e depositada em um bosque de sabiá (Mimosa caesalpiniifolia Benth). O experimento foi realizado durante o período de agosto de 2006 a julho de 2007. A avaliação da serrapilheira existente e depositada foi realizada a cada 28 dias utilizando-se 20 quadrados de 1 m², alocados aleatoriamente, escolheno novas áreas a cada avaliação. O bosque apresentou plantas com diâmetro média na altura do peito de 26,8 cm. A deposição mensal de matéria orgânica de folhas e ramos no período experimental foi de 15.167 e 3.373 kg/ha, respectivamente, e aumentou no período de maior precipitação, numa relação de 0,30 com o acúmulo, o indica acúmulo maior que a deposição. A proporção de folhas foi de 87% do total da serrapilheira, com médias de 2,9% de nitrogênio e 0,17% de fósforo. A relação carbono/nitrogênio das folhas ficou abaixo de 30, enquanto a de ramos, entre 30 e 40, comprovando melhor qualidade das folhas. Durante o período experimental, a deposição de nitrogênio via serrapilheira foi de aproximadamente 462 kg/ha e a de fósforo, 30 kg/ha. A deposição de serrapilheira é essencial para manutenção da fertilidade do solo em bosques de sabiá e contribui para sua conservação e sustentabilidade.

Deposição de serapilheira e de macronutrientes em um povoamento de acácia-negra (<i>Acacia mearnsii</i> De Wild.) no Rio Grande do Sul.

Objetivou-se avaliar a deposição de serapilheira e de macronutrientes em um povoamento de acácia-negra (Acacia mearnsii De Wild.) com 6 anos de idade em Butiá, RS. Foram alocadas sistematicamente cinco parcelas de 18mx24m, cada uma com quatro coletores de serapilheira de 1 m2. A serapilheira interceptada nos coletores foi coletada mensalmente entre janeiro/2002 e dezembro/2003. Após a coleta, a serapilheira foi dividida nas frações folha, flor, frutos e fezes da lagarta Adeloneivaia subangulata, e seca em estufa, pesada, moída e analisada quimicamente quanto aos teores de N, P, K, Ca e Mg. A deposição média anual de serapilheira foi de 4,32 Mg ha-1, composta por 75,5% de folhas, 11,1% de flores, 11,2% de frutos e 2,2% de fezes da lagarta. A deposição de serapilheira foi mais concentrada na primavera. O maior fornecimento de nutrientes ao solo ocorreu por meio da fração folha, a qual, apesar de não apresentar as maiores concentrações dos elementos avaliados, apresenta grande deposição anual de biomassa. A deposição total de macronutrientes ao solo, em kg ha-1 ano-1, foi de 74,8 de N, 26,8 de K, 23,1 de Ca, 7,9 de Mg e 2,4 de P.

Weed biomass of dominant species in weed communities of Tea (Camellia Sinensis (L.) Kuntze) plantation of Assam

Production of biomass of five dominant species growing in some tea fields of Assam was investigated. Biomass of weed community showed significant variation in different seasons in the tea fields. Studies showed one peak of accumulation of above ground biomass during September (1466.87g/m²), three peaks in live shoot during February (780.377g/m²), June (1162.99g/m²), and September (1371.87g/m²), two peaks of dead shoots during December (370.2g/m²) and July (184.6 g/m²) in the weed communities. Study indicated one peak in deposition of litter and accumulation of below ground biomass during February (230.6g/m²) and September (345.5g/m²) respectively. Among the five dominant weed species, B. articularis showed highest contribution of biomass during August (10.25%) and minimum by P. conjugatum during March (0.22%) in the weed community of tea fields of Assam.

Teores e aporte de nutrientes na serapilheira de Pinus taeda L., e sua relação com a temperatura do ar e pluviosidade

O objetivo deste estudo foi avaliar os teores e o aporte de nutrientes ao piso florestal num povoamento de Pinus taeda L. e sua relação com a temperatura do ar e pluviosidade, implantado em área anteriormente ocupada por campo nativo, na cidade de Cambará do Sul, RS, através da queda de serapilheira, avaliado durante um período de três anos, contados a partir do quinto ao sétimo ano de idade do povoamento. A serapilheira foi coletada mensalmente através de coletores de 1,0 m² (1,0 x 1,0 m), durante o período compreendido de abril/2004 a março/2007. Após cada coleta, as amostras de serapilheira foram analisadas quimicamente, quanto aos teores de macro e micronutrientes. Os teores de K, Mg e Cu correlacionaram-se positivamente (p < 0,05) com a pluviosidade, e os teores de S também o fizeram, porém com a temperatura do ar, enquanto os teores de Fe (p < 0,01), Mn e Zn (p < 0,05) correlacionaram negativamente com essa característica climática. Os teores de N e K correlacionaram-se negativamente (p < 0,01 e p < 0,05, respectivamente) com a quantidade de serapilheira depositada mensalmente. O aporte médio anual de macronutrientes ao solo, através da deposição da serapilheira, em kg ha-1, foi de: 18,8 de Ca; 13,0 de N; 3,0 de Mg; 1,6 de K; 1,3 de S; e 1,1 de P, sendo a transferência de micronutrientes em g ha-1 de: 4.708,3 de Mn; 592,3 de Fe; 74,1 de Zn; 34,0 de B; e 7,6 de Cu. Isso demonstra a importância da permanência da serapilheira sobre o solo para manutenção da ciclagem de nutrientes.

Serapilheira e teores de nutrientes em argissolo sob diferentes manejos no norte do Piauí

Este trabalho teve como objetivos avaliar o estoque de serapilheira acumulada e quantificar os teores de N, P, K, Ca e Mg em sistemas agroflorestais com seis (SAF6) e dez (SAF10) anos de adoção, sistema com base ecológica de três anos (SE3), agricultura de corte e queima (ACQ) e floresta nativa (FN) no Município de Esperantina, norte do Piauí. As coletas foram realizadas nos períodos chuvoso e seco do ano 2007, sendo a serapilheira separada nas frações folhas e galhos para a estimativa dos estoques acumulados sobre o solo. Os maiores estoques da fração folhas foram observados na FN (3,8 Mg(t) ha-1), período seco; e da fração galhos no SAF10 (2,2 Mg(t) ha-1), no período chuvoso. Os SAFs apresentaram os maiores teores de nutrientes nas frações da serapilheira e entre os nutrientes, e a concentração de N foi superior à dos demais nutrientes, em ambos os períodos. A estimativa de transferência dos nutrientes pela serapilheira obedeceu à sequência N>Ca>K>P>Mg. Os valores de estoques da serapilheira, teores e aportes de nutrientes nos SAFs evidenciam a contribuição do manejo agroflorestal para a qualidade do solo e a sustentabilidade econômica do sistema.

Using small-scale studies to prioritize threats and guide recovery of a rare hemiparasitic plant: Cordylanthus rigidus ssp. littoralis.

BackgroundRecovering endangered species would benefit from identifying and ranking of the factors that threaten them. Simply managing for multiple positive influences will often aid in recovery; however, the relative impacts of multiple threats and/or interactions among them are not always predictable. We used a series of experiments and quantitative observational studies to examine the importance of five potential limiting factors to the abundance of a state-listed endangered hemiparasitic annual forb, Cordylanthus rigidus ssp. littoralis (C.r.l., California, USA): host availability, mammalian herbivores, insect seed predators, fire suppression, and exotic species. While this initial assessment is certainly not a complete list, these factors stem from direct observation and can inform provisional recommendations for management and further research.Methodology and Principal FindingsStudies were conducted at five sites and included assessments of the influence of host availability, exotic species, exclusion of mammalian herbivores and insect seed predators on C.r.l. productivity, and simulated effects of fire on seed germination. C.r.l. was limited by multiple threats: individuals with access to host species produced up to three times more inflorescences than those lacking hosts, mammalian herbivory reduced C.r.l. size and fecundity by more than 50% and moth larvae reduced seed production by up to 40%. Litter deposition and competition from exotic plant species also appears to work in conjunction with other factors to limit C.r.l. throughout its life cycle.Conclusions and SignificanceThe work reported here highlights the contribution that a series of small-scale studies can make to conservation and restoration. Taken as a whole, the results can be used immediately to inform current management and species recovery strategies. Recovery of C.r.l. will require management that addresses competition with exotic plant species, herbivore pressure, and availability of preferred host species.

Litter decomposition of Brachiaria decumbens Stapf. and Calopogonium mucunoides Desv. in the rumen and in the field: a comparative analysis

Litter deposition and decomposition are important components of the nutrient cycling process in grasslands. Litter decomposition studies in the field are tedious and time-consuming. Finding an approach to speeding up research would therefore be a major advancement in the field. In this study, a comparative analysis of the litter decomposition process of signal grass (Brachiaria decumbens Stapf.) and calopo (Calopogonium mucunoides Desv.) in two distinct environments (field vs. goat rumen) was carried out. Two incubation trials were performed. In the first trial litter of both plant species was incubated in the rumen of fistulated goats using the in situ technique. Second trial, litter samples were incubated on signal grass pastures using the litter bag technique. Litter samples of signal grass and calopo were incubated by different periods in the rumen (0, 6, 12, 24, 48, 96, and 144 h) and in the field (0, 4, 8, 16, 32, 64, 128, and 256 days). At the end of the incubation period, the remaining biomass of signal grass was similar between rumen and field (~38%), but calopo decomposed more extensively in the field. The C:N ratio was considered high for signal grass (~100) at the beginning of the experimental period. Calopo showed initial C:N ratio of 29. Nitrogen was more extensively decomposed in the rumen as opposed to the field; however, despite several differences in terms of environment and time of incubation, remaining biomass at the end of incubation was similar between rumen and field trials, suggesting common limits for decomposition in both environments. Decomposition models, however, showed different relative decomposition rates (k) along the incubation period. As a result, the use of the rumen model to simulate field decomposition cannot be recommended.

Aporte de nutrientes e decomposição da serapilheira em três fragmentos florestais periodicamente inundados na ilha da Marambaia, RJ.

O presente estudo foi realizado em três formações florestais de restinga que se encontram periodicamente inundadas, na Restinga da Marambaia, RJ. Para a quantificação da produção de serapilheira foram utilizados dez coletores cônicos por formação, durante outubro de 2005 a setembro de 2006. A avaliação da decomposição se deu por meio de sacolas de decomposição (litter bags), sendo distribuídas 15 sacolas por formação. A produção anual de serapilheira estimada para cada uma das formações florestais, variou de 11,3, 10,8 e 11,1 Mg ha-1ano-1, para F1, F2 e F3 respectivamente, com maiores valores de deposição na estação chuvosa. A fração folhas foi a mais representativa em todas as formações. O nitrogênio foi o nutriente devolvido em maior quantidade a esses solos, 130,8 kg ha-1 ano-1 em F3. A decomposição se apresentou como uma curva do tipo exponencial, sendo a constante de decomposição (k) e o tempos de meia vida foi de 0,0032 g g-1e 217 dias em F2, 0,0031 g g-1e 227 dias em F3 e 0,0028 g g-1; 247 dias em F1.

Efeito da fertilização fosfatada na produção de raízes, liteira e nodulação de Mimosa caesalpiniifolia benth

Este trabalho visou avaliar o efeito da adubação fosfatada sobre a nodulação, deposição de liteira e desenvolvimento do sistema radicular de M. caesalpiniifolia Benth, antes e depois da poda, na Estação Experimental de Itambé, da Instituto Agronômico de Pernambuco - IPA. Os tratamentos foram níveis de adubação fosfatada (0, 100 e 200 kg.ha-1 de P2O5), em delineamento com blocos casualizados com seis repetições no bloco I e sete no II, sendo o critério para formação de blocos a data do corte de uniformização. Amostragens foram realizadas antes e depois da poda da parte aérea. O comprimento, a massa seca radicular, a matéria seca de nódulos e a liteira tiveram resultados semelhantes antes e depois da poda. O número de nódulos antes da poda foi de 2, 15 e 6 nos níveis de 0, 100 e 200 kg.ha-1 de P2O5, respectivamente, e 1, 6 e 7 após a poda. Comprimentos radiculares médios variaram entre 552 e 734 cm antes da poda e 389 e 455 cm após. Apenas de agosto a novembro de 2005 o número de nódulos apresentou variação, sendo observados valores de 2 a 15 nódulos antes da poda e 1 a 7 depois.

Ecogeomorphic Feedbacks in Semiarid Rangelands: A Review

Abstract The ecogeomorphic processes occurring on semiarid rangelands are reviewed, with emphasis on the source-sink relations and positive feedback loops that existed between shrub patches and intershrub areas, and the way livestock presence affected these interactions. Compared with intershrub areas, the shrub patches had a higher soil porosity, infiltration capacity, water-holding capacity, hydraulic conductivity, structural stability, and organic matter content, and lower bulk density. These differences derived from a host of processes whose intensity was less in the shrub patches, including raindrop impact, mechanical crust formation, overland water flow, soil erosion, evaporative moisture loss, and flock trampling. There was also greater shading of the soil surface; soil and litter deposition; water accumulation; microbial, fungal, and mesofaunal activities in the shrub patches. The overland flow of water carried soil and litter from the intershrub areas to the shrub patches and resulted in microtopographic modifications that tended to strengthen these source-sink relations. Grazing had an impact on these processes, not only at the shrub-intershrub scale but also within the intershrub areas, through the creation of highly compacted trampling routes. The combined role of the above ecogeomorphic processes was to maintain the rangeland's functionality. Without these inter-relationships, water loss, soil erosion, and nutrient depletion would occur at the hillside scale, causing degradation of the landscape.

Aporte e decomposição da serapilheira na Floresta Atlântica, ilha da Marambaia, Mangaratiba, RJ.

A produção e a decomposição de serapilheira de um fragmento de Floresta Atlântica de encosta na Ilha da Marambaia, Mangaratiba, RJ, foram estudadas durante o período de dezembro de 2003 a novembro de 2004. O aporte de serapilheira foi mensurado partindo de trinta coletores cônicos. A taxa de decomposição da serapilheira foi quantificada por meio de 36 sacolas de decomposição instaladas na área. Para avaliação da fertilidade do solo foram coletadas amostras nas profundidades de 0-5, 5-10 e 10-20 cm. A produção total de serapilheira foi de 7,9 Mg ha-1, sendo a maior deposição verificada no mês de novembro e a menor em junho. A fração foliar foi a de maior contribuição em relação às demais. A taxa de decomposição da serapilheira foi 40% em 7 meses de observação, seguindo modelo exponencial. Verificou-se comportamento diferenciado quanto à liberação de N, P e K. Com exceção do fósforo, os maiores valores de nutrientes, carbono e H+Al foram observados na camada superficial.

Short-term wildfire effects on the spatial pattern and scale of labile organic-N and inorganic-N and P pools

The spatial heterogeneity of essential plant resources plays a crucial role in the structure, composition and productivity of many terrestrial ecosystems. Fires may affect both the availability and spatial pattern of soil nutrients. However, little is known about the effect of fire on the spatial pattern of soil resources. We hypothesized that shortly after a wildfire, the spatial patterns of soil mineral-N, organic labile-N (microbial biomass-N and dissolved organic-N) and extractable-P pools would become more clumped because of ash accumulation and post-fire deposition of litter around individual adult trees. To test this hypothesis, we used plots within a Pinus canariensis forest (with both Pinus canariensis and Adenocarpus viscosus present) and sampled them one month before and one month after a wildfire. Using geostatistical analyses, we examined the spatial patterns of soil mineral-N (NH 4-N and NO 3-N), dissolved organic-N (DON), microbial biomass-N (MB-N) and soil extractable-P (PO 4-P). Burned plots of P. canariensis and A. viscosus both had values that were significantly greater than the unburned plots for all variables, except for DON in both cases, and the N:P ratio in the case of A. viscosus, which showed significantly lower values. Except for DON, we observed an increased spatial dependence and range after a fire for all studied variables in the P. canariensis plots (large individuals). However, in plots with A. viscosus (smaller individuals), we only found differences before and after the fire for the PO 4-P and DON spatial patterns. Our results confirm the changes in the spatial structure of soil variables with fire, and suggest that, on a short-term basis, the physical structure of the plant community may determine the new spatial structure after fire, with a more clumped distribution around large surviving trees and shrubs. The spatial patch size of limiting resources has important consequences for the success of restoration of forest communities on burned areas.

Root uptake of lead by Norway spruce grown on 210Pb spiked soils

The root uptake of lead (Pb) by trees and the transfer of Pb by leaf litter deposition to the forest floor were investigated through a pot experiment with Norway spruce. Natural Pb and radio isotopic lead ( 210Pb) were determined in needles and twigs and in the pot soil spiked with 210Pb. Calculations of the specific activity in plant material and in the supporting pot soil showed that less than 2% of the Pb content of needles and twigs originates from root uptake and approximately 98% are deposited from the atmosphere. Atmospheric Pb has declined by a factor of 7 from 1980 to 2007 but is still a major pathway of Pb to vegetation and topsoils. The conclusion from the experiment is that the internal circulation of Pb through root uptake, translocation and litterfall, gives an insignificant input of Pb to the forest floor compared to atmospheric deposition.

Controls on the Carbon Balance of Tropical Peatlands

The carbon balance of tropical peatlands was investigated using measurements of gaseous fluxes of carbon dioxide (CO2) and methane (CH4) at several land-use types, including nondrained forest (NDF), drained forest (DF), drained regenerating forest (DRF) after clear cutting and agricultural land (AL) in Central Kalimantan, Indonesia. Soil greenhouse gas fluxes depended on land-use, water level (WL), microtopography, temperature and vegetation physiology, among which WL was the strongest driver. All sites were CH4 sources on an annual basis and the emissions were higher in sites providing fresh litter deposition and water logged conditions. Soil CO2 flux increased exponentially with soil temperature (T s) even within an amplitude of 4–5°C. In the NDF soil CO2 flux sharply decreased when WLs rose above −0.2 and 0.1 m for hollows and hummocks, respectively. The sharp decrease suggests that the contribution of surface soil respiration (RS) to total soil CO2 flux is large. In the DF soil CO2 flux increased as WL decreased below −0.7 m probably because the fast aerobic decomposition continued in lower peat. Such an increase in CO2 flux at low WLs was also found at the stand level of the DF. Soil CO2 flux showed diurnal variation with a peak in the daytime, which would be caused by the circadian rhythm of root respiration. Among the land-use types, annual soil CO2 flux was the largest in the DRF and the smallest in the AL. Overall, the global warming potential (GWP) of CO2 emissions in these land-use types was much larger than that of CH4 fluxes.