Leaf litter decomposition of Piper aduncum, Gliricidia sepium and Imperata cylindrica in the humid lowlands of Papua New Guinea
TL;DR: Piper leaf litter is a significant and easily decomposable source of K which is an important nutrient for sweet potato and the decomposition and nutrient release patterns had significant effects on the soil.
Abstract: No information is available on the decomposition and nutrient release pattern of Piper aduncum and Imperata cylindrica despite their importance in shifting cultivation systems of Papua New Guinea and other tropical regions. We conducted a litter bag study (24 weeks) on a Typic Eutropepts in the humid lowlands to assess the rate of decomposition of Piper aduncum, Imperata cylindrica and Gliricidia sepium leaves under sweet potato (Ipomoea batatas). Decomposition rates of piper leaf litter were fastest followed closely by gliricidia, and both lost 50% of the leaf biomass within 10 weeks. Imperata leaf litter decomposed much slower and half-life values exceeded the period of observation. The decomposition patterns were best explained by the lignin plus polyphenol over N ratio which was lowest for piper (4.3) and highest for imperata (24.7). Gliricidia leaf litter released 79 kg N ha(-1), whereas 18 kg N ha(-1) was immobilised in the imperata litter. The mineralization of P was similar for the three species, but piper litter released large amounts of K. The decomposition and nutrient release patterns had significant effects on the soil. The soil contained significantly more water in the previous imperata plots at 13 weeks due to the relative slow decomposition of the leaves. Soil N levels were significantly reduced in the previous imperata plots due to immobilisation of N. Levels of exchangeable K were significantly increased in the previous piper plots due to the large addition of K. It can be concluded that piper leaf litter is a significant and easily decomposable source of K which is an important nutrient for sweet potato. Gliricidia leaf litter contained much N, whereas imperata leaf litter releases relatively little nutrients and keeps the soil more moist. Gliricidia fallow is more attractive than an imperata fallow for it improves the soil fertility and produces fuelwood as additional saleable products.
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TL;DR: This work has reviewed studies that compare pool sizes and flux rates of the major nutrient cycles in invaded and noninvaded systems for invasions of 56 species and suggests that invasive plant species frequently increase biomass and net primary production, increase N availability, alter N fixation rates, and produce litter with higher decomposition rates than co-occurring natives.
Abstract: Although it is generally acknowledged that invasions by exotic plant species represent a major threat to biodiversity and ecosystem stability, little attention has been paid to the potential impacts of these invasions on nutrient cycling processes in the soil. The literature on plant–soil interactions strongly suggests that the introduction of a new plant species, such as an invasive exotic, has the potential to change many components of the carbon (C), nitrogen (N), water, and other cycles of an ecosystem. I have reviewed studies that compare pool sizes and flux rates of the major nutrient cycles in invaded and noninvaded systems for invasions of 56 species. The available data suggest that invasive plant species frequently increase biomass and net primary production, increase N availability, alter N fixation rates, and produce litter with higher decomposition rates than co-occurring natives. However, the opposite patterns also occur, and patterns of difference between exotics and native species show no trends in some other components of nutrient cycles (for example, the size of soil pools of C and N). In some cases, a given species has different effects at different sites, suggesting that the composition of the invaded community and/or environmental factors such as soil type may determine the direction and magnitude of ecosystem-level impacts. Exotic plants alter soil nutrient dynamics by differing from native species in biomass and productivity, tissue chemistry, plant morphology, and phenology. Future research is needed to (a) experimentally test the patterns suggested by this data set; (b) examine fluxes and pools for which few data are available, including whole-site budgets; and (c) determine the magnitude of the difference in plant characteristics and in plant dominance within a community that is needed to alter ecosystem processes. Such research should be an integral component of the evaluation of the impacts of invasive species.
1,655 citations
01 Jan 2004
TL;DR: In this paper, the authors focus on the role of agriculture and fishing in the European level in the Common Agricultural Policy (CAP) and Common Fisheries Policy (CFP) and show that agriculture dominates in terms of direct contribution to GDP and numbers of people engaged in it, as well as accounting for the largest amount of public support expenditure.
Abstract: Agriculture and fishing are the primary source of almost all our food, as well as of many other products, so remain vital activities even though their share in the economy is small and in continuous decline. Partly for this reason public policy in these areas is almost entirely integrated at European level in the Common Agricultural Policy (CAP) and Common Fisheries Policy (CFP). Forestry policies are also heavily affected by EU-level decision-making. As agriculture dominates in terms of direct contribution to GDP and numbers of people engaged in it, as well as accounting for the largest amount of public support expenditure, it is agriculture that will receive the greatest attention here.
468 citations
TL;DR: Cogongrass is a major impediment to reforestation efforts in southeast Asia, the number one weed in agronomic and vegetable production in many parts of Africa, and is responsible for thousands of hectares of lost native habitat in the southeastern U.S.
Abstract: Cogongrass is considered to be one of the ten most troublesome and problematic weedy species in the world. This species is found throughout tropical and subtropical regions, generally in areas dist...
171 citations
TL;DR: It is indicated that non-legume timber trees with an optimized spacing regime can be used as overstorey shade trees for T. cacao in all of the plantations, however, all three plantations required fertilisation and better nutrient management.
Abstract: Intercropping in agroforestry systems improves ecosystem services. Appropriate species compositions and spacing regimes are critical to achieve ecosystem benefits and improve yields of all the component crops. Cocoa (Theobroma cacao) is an important cash crop globally but it requires shade for survival and growth. However, the effects of shade-tree species composition and spacing regime on nutrient cycling in cocoa plantations are not well understood. This study investigated the effects of shade tree species and spacing regimes on soil and plant nutrient availability at 8 years after plantation establishment in Papua New Guinea. Three cocoa intercropping systems were established in which T. cacao was planted with either a non-legume timber tree, Canarium indicum, or a legume non-timber tree, Gliricidia sepium. The shade-tree spacing regimes included either 8 m × 16 m or 8 m × 8 m in the Theobroma + Canarium plantations. There was an ongoing thinning regime in the Theobroma + Gliricidia plantation, with a final shade-tree spacing of 12 m × 12 m. Soil total carbon (TC) and total nitrogen (TN) were significantly higher in the Theobroma + Gliricidia plantation with 12 m × 12 m spacing and the Theobroma + Canarium plantation with 8 m × 16 m spacing than in the Theobroma + Canarium plantation with 8 m × 8 m spacing. Foliar TN and P were correlated with soil TN and P, respectively, whereas no correlation was detected between soil and leaf K concentrations. Foliar TN, P and K were under ideal concentrations for T. cacao in all of the plantations. The Theobroma + Gliricidia plantation had higher soil water extractable phosphorus (P) than the two Theobroma + Canarium plantations, probably due to frequent pruning of the G. sepium trees. Foliar C isotope composition (δ13C) of T. cacao suggested that T. cacao close to G. sepium or close to C. indicum with spacing of 8 m × 16 m and 8 m × 8 m had similar light interception. However, increased C. indicum spacing increased the light interception of T. cacao trees that were not planted next to C. indicum. This study indicated that non-legume timber trees with an optimized spacing regime can be used as overstorey shade trees for T. cacao. However, our study indicated all three plantations required fertilisation and better nutrient management.
46 citations
TL;DR: Piper accumulated large amounts of biomass and nutrients, particular K, which is an important nutrient for root crops that dominate the cropping phase in the shifting cultivation systems of the humid lowlands.
Abstract: Shifting cultivation with short fallow periods (<3 years), is an important form of land use in the humid lowlands of Papua New Guinea. The secondary forest vegetation is dominated by the shrub Piper aduncum which originates from South America, and Imperata cylindrica grasslands in areas where annual bush fires are common. No information is available on the rate of biomass and nutrient accumulation of these two fallow types. Plots with P. aduncum and I. cylindrica were planted on a Typic Eutropepts and sampled every 3 months for 23 months to assess above ground biomass and nutrient content. Total biomass of imperata was slightly higher than that of piper during the first year, but remained around 23 Mg dry matter (DM) ha ˇ1 in the second year. Above ground biomass of piper increased linearly, and reached 48 Mg DM ha ˇ1 at 23 months when three-quarter of the biomass consisted of wood. Growth rates of piper were on average 69 kg DM ha ˇ1 per day, and increased with higher rainfall. Nutrient content of imperata was 100 kg N, 12 kg P, 62 kg K, 64 kg Ca, 40 kg Mg and 9 kg Sh a ˇ1 at 23 months. The concentration of K and Ca was high in piper leaves but declined over time. At 23 months, piper had accumulated 222 kg N, 50 kg P, 686 kg K, 255 kg Ca, 75 kg Mg, and 24 kg S ha ˇ1 . More than half of the P, K, Ca and Mg was found in the stem (wood) which is removed from the field and used as firewood when farmers slash the fallow. piper biomass (excluding wood) returned about three times more K to the soil than imperata, but differences between total P and S contents were small. For the accumulation of biomass and nutrients, imperata fallows should not exceed 1 year. Piper accumulated large amounts of biomass and nutrients, particular K, which is an important nutrient for root crops that dominate the cropping phase in the shifting cultivation systems of the humid lowlands. # 2001 Elsevier Science B.V. All rights reserved.
43 citations
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TL;DR: Two general analytical approaches to the examination of decomposition data are reviewed and single and double exponential models best describe the loss of mass over time with an element of biological realism.
Abstract: The study of plant litter decomposition in terrestrial ecosystems commonly employs litter bags to compare the loss of mass among species, among sites, and under various experimental manipulations, or to investigate the process itself. Analysis of the resulting data is quite variable among investigators, and at times inappropriate. Two general analytical approaches to the examination of decomposition data are reviewed. Analysis of variance is useful if the intent is to compare treatment means, but does not directly test hypotheses regarding decomposition rates. If the intent is to determine rate constants, than fitting mathematical models to data is the more appropriate analysis. Single and double exponential models best describe the loss of mass over time with an element of biological realism. See full-text article at JSTOR
937 citations
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01 Nov 1996
TL;DR: Pathways and processes in decomposition foraging, feeding and feedback manipulation of plant litter quality synchrony and soil organic matter - theory into practice?
Abstract: Pathways and processes in decomposition foraging, feeding and feedback manipulation of plant litter quality synchrony and soil organic matter - theory into practice? building soil organic matter modelling - providing the framework.
933 citations
786 citations
"Leaf litter decomposition of Piper ..." refers methods in this paper
...Lignin was determined by the procedure of Van Soest and Wine (1968), and polyphenol by that of Dalzell and Kerven (1998), using purifiedLeucaena pallidacondensed tannin as standard....
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TL;DR: In this article, the chemical composition and N release patterns of legumes being used in tropical agroecosystems were determined in a laboratory experiment and three patterns of net N mineralization emerged during the 8-weeks.
Abstract: Leguminous plant materials used as mulches, green manures and cover crops are generally assumed to provide a readily-available source of N to crops. However, little is known about the chemical composition and N release patterns of the variety of legumes being used in tropical agroecosystems. N release patterns from the leaflets of 10 troplcal legumes and rice straw were determined in a laboratory experiment. Ground leaf material was allowed to decompose in an acid soil (pH 4.5) for 8 weeks and the soil was analyzed periodically for extractable NH4+-N and NO3∼, -N. N release in the soil plus plant material were compared to that of the soil without plant material added and related to the N, lignin and polyphenolic concentrations of the leaflets. Three patterns of net N mineralization emerged during the 8-weeks. One pattern exhibited by the control soil, rice straw and leaves of two of the leguminous plants was a low, positive net mineralization. Another pattern showed much higher rates of mineralization than the control soil and the third pattern showed initial net immobilization followed by low but positive net mineralization rates. The amount of N mineralized during the 8 weeks as compared to the control soil ranged from +46 to −20% of the N added in plant material. Net mineralization was not correlated to % N or % lignin in the leaf material but was found to be negatively correlated to the polyphenolic concentration, r = −0.63, or the polyphenolic-to-N ratio, r = −0.75. Mineralization in excess of the control soil was found only for materials with a polyphenolic-to-N ratio
724 citations
TL;DR: In this article, the decomposition and nutrient release patterns of three woody agroforestry plant species (Acioa barteri, Gliricidia sepium and Leucaena leucocephala), maize (Zea mays) stover and rice (Oryza sativa) straw, were investigated under field conditions in the humid tropics, using litterbags of three mesh sizes (0.5, 2 and 7 mm) which allowed differential access of soil fauna.
Abstract: Decomposition and nutrient release patterns of prunings of three woody agroforestry plant species (Acioa barteri, Gliricidia sepium and Leucaena leucocephala), maize (Zea mays) stover and rice (Oryza sativa) straw, were investigated under field conditions in the humid tropics, using litterbags of three mesh sizes (0.5, 2 and 7 mm) which allowed differential access of soil fauna. The decomposition rate constants ranged from 0.01 to 0.26 week−1, decreasing in the following order; Gliricidia prunings >Leucaena prunings > rice straw > maize stover >Acioa prunings. Negative correlations were observed between decomposition rate constants and C:N ratio (P < 0.004), percent lignin (P < 0.014) and polyphenol content (P < 0.053) of plant residues. A positive correlation was observed between decomposition rate constant and mesh-size of litterbag (P < 0.057). These results indicate that both the chemical composition of plant residues and nature of the decomposer played an important role in plant residue decomposition.
Nutrient release differed with quality of plant residues and litterbag mesh-size. Total N, P, Ca and Mg contents of plant residues decreased with time for Gliricidia and Leucaena prunings, maize stover, and rice straw, and increased with time for Acioa prunings. There was some indication of N immobilization in maize stover and rice straw; P immobilization in Leucaena prunings and rice straw; and Ca immobilization in maize stover, rice straw and Gliricidia and Leucaena prunings. Acioa prunings immobilized N, P, Ca and Mg. All plant residues released K rapidly. Nutrient release increased with increasing mesh-size of litterbags, suggesting that soil faunal activities enhanced nutrient mobilization.
577 citations
"Leaf litter decomposition of Piper ..." refers background in this paper
...The rapid initial loss of K, particularly from the piper leaf litter, is commonly found in litter bag studies (Budelman, 1988; Palm and Sanchez, 1990; Tian et al., 1992a)....
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...…number of studies have been conducted under laboratory conditions (Handayanto et al., 1997; Lupwayi and Haque, 1998; Palm and Sanchez, 1991; Tian et al., 1992b) or under field conditions with no crop after the fallow (Budelman, 1988; Handayanto et al., 1994; Mwiinga et al., 1994; Oglesby…...
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