STABILIZATION AND DECOMPOSITION RATE OF STANDARD MATERIAL IN HERBACEOUS COMMUNITIES OF THE FOREST ZONE

The rate of plant litter decomposition depends on two simultaneous processes: the decomposition and stabilization of organic matter. To compare the rates of these processes in various ecosystems now a Tea Bag Index (TBI) is widely used. The samples of standard material (green tea and rooibos) were buried into soil at the depth of 8 cm in four herbaceous plant communities of Central Forest State Nature Biosphere Reserve (CFSNBR) and seven communities of the Moscow river floodplain near the MSU Zvenigorod biological station (ZBS). Considering the mass losses of samples during the incubation time we calculated the values of decomposition constant and stabilization factor according to the protocol by J. A. Keuskamp et al. (2013) and estimated the links of these parameters with Ellenberg’s ecological indicator values. The stabilization factor values ranged from 0.122 g/g in Filipendula community of CFSNBR to 0.379 g/g at the natural levee of the Moscow river, and the decomposition constant values ranged from 0.0089 g/g/day in Filipendula community of CFSNBR to 0.0308 g/g/day at the slope of the high floodplain. The mean values of these parameters were significantly positively correlated. The decomposition rate was lower in the communities of CFSNBR and was positively correlated with the soil pH Ellenberg’s indicator values. The stabilization factor values did not depend on the region and decreased with the increase in soil moisture and nitrogen. The mainland meadows of CFSNBR and the meadows of the high floodplain of the Moscow river, belonging to Cynosurion cristati alliance, had the most similar parameters of decomposition.

The Effect of Structural and Environmental Changes on Litter Decomposition of in Pinus Sylvestris Stands

Background: Decomposition of litter has an important role in primary production with its influence on nutrient release for plant uptake and carbon flux in forest ecosystems. Thus, understanding the effects of the intervention on litter decomposition is crucial for sustainable forest management. In this study, the effect of structural change and facing slope on litter decomposition in Scots pine stands (Pinus sylvestris L.) were investigated.Results: The decomposition rate of litter decreased as the stand age increased. Litter decomposed more rapidly on northern slopes than southern slopes. Cutting caused to accelerate the decomposition at a rate of up to 58% depending on its intensity. The k values were found to fluctuate though the time from 0.189 in moderately dense canopied stands to 0.317 in open canopied over-mature stands. Stand basal area, incubation time, and remaining carbon concentration of the litter accounted for 75% of the variation in the decomposition constant. Conclusions: Cutting-induced stand structural changes affected the litter decomposition process in forest ecosystems due to the micro environmental change as well as the change in litterfall composition and chemistry. Heavy treatments can change the litter decomposition process drastically, while moderate thinning may not have a clear effect in the long run. The stand specific k value should be considered to use in forest carbon models for more accurate estimation. Decomposition constant should be calculated by considering stand structure and incubation time of at least 1050 days. Besides, due to the significant effect of canopy closure on decomposition rate, stand specific or recalculated k constants according to stand basal area, incubation time, and remaining carbon concentration of the litter should be recommended to use in forest carbon models for more accurate carbon budget estimation.

SUPPLYING AND DECOMPOSITION OF BURLAP IN A FRAGMENT OF CERRADO SENSU STRICTO

Considering the importance of nutrient cycling as an indicator in the maintenance of the ecosystem productivity, the present study aimed to assess the seasonal dynamics of production and decomposition rate of litter in a fragment of Cerrado sensu stricto. The litter collections were carried out monthly from june 2016 to may 2017, after which the leaves, branches and reproductive material were separated. The litter decomposition was evaluated using the litter bags method, with a random distribution of 288 litter bags. The annual production of litterfall was quantified in 6.042,50 kg.ha-1.yr-1, in which the leaf prevalent fraction presented a production of 4.644,40 kg.ha-1.yr-1, then, the fractions branches (1.084,10 kg.ha-1.yr-1) and reproductive material (329,90 kg.ha-1.yr-1). The litterfall obtained higher production in july with 1.464,00 kg.ha-1 and lower production in the month of December (138,70 kg.ha-1). A significant negative correlation was observed between litterfall and its fractions with the precipitation and relative humidity. The decomposition of foliar mass reached 49% and 50% of twigs during the nine-month period, in which the decomposition constant (k) for leaf mass and for branches was 0.0030g g-1day-1. For this constant, the estimate for the disappearance of total mass has been estimated to be 1.000 days (29 months). The breakdown proved to be slow for both leaves and branches thus obtaining the value of the constant of decomposition 0.0030g g-1 day-1for both.

NUTRIENT CYCLING AND CO2 EMISSIONS IN AREAS OF PRESERVED AND THINNED CAATINGA

ABSTRACT The aim of this study was to investigate changes that occurred due to land use and ground cover in the deposition, accumulation and rates of litter decomposition, as well as of soil respirometry, in a dry tropical forest. The study was carried out in two adjacent watersheds in the town of Iguatu, in the State of Ceará, Brazil. One of the watersheds had been under preserved vegetation for 35 years (RC35), while the other had been subjected to thinning for 5 years (TC5). The main variables among those being analysed were the litter fractions deposited in collectors and accumulated on the ground, the decomposition constant, and soil respirometry. The data were submitted to statistical analysis and compared by t-test (pd”0.05). The total litter deposited in the collectors during the 12 months of monitoring (April 2013 to March 2014) was around 1,300 kg ha-1 yr-1 for TC5, differing statistically (pd”0.05) from RC35 (4,019 kg ha-1 yr-1). There was no difference in the litter accumulated on the ground for type of land use (p>0.05). The conservation of litter on the ground in TC5 is associated with larger inputs of woody, lignified biomass from the thinning, and the consequent lower rates of decomposition and CO2 emission.

Decomposition of ground biomass of secondary forest and yield of annual crops in no tillage

ABSTRACT The objective of this work was to evaluate the dynamics of decomposition process of chopped secondary forest system, previously enriched with legumes Inga velutina Willd. and Stryphnodendron pulcherrimum (Willd.) Hochr. and the contribution of this process to the nutrient input to the cultivation of corn and bean under no-tillage. The experimental design was a randomized block, split plot with four replications. The plots were two species (I. velutina and S. pulcherrimum) and the subplots were seven times of evaluation (0, 7, 28, 63, 189, 252, 294 days after experiment installation). There was no difference (p ≥ 0.05) between the secondary forest systems enriched and no interaction with times for biomass waste, decomposition constant and half-life time. The waste of S. pulcherrimum trees had higher (p < 0.05) C/N ratio than that I. velutina. However, this one was higher (p < 0.05) in lignin content. Nevertheless, the dynamics of residue decomposition was similar. The corn yield was higher (p < 0.05) in cultivation under I.velutina waste. Meanwhile, the beans planted after corn, shows similar (p > 0.05) yield in both areas, regardless of the waste origin.

LITTERFALL ASSESSEMENT IN A FRAGMENT OF SECONDARY TROPICAL FOREST, IBIÚNA, SP, SOUTHEASTERN BRAZIL1

ABSTRACT The present study aimed to analyze the production and decomposition of litterfall in a fragment of secondary Atlantic forest in the region of Ibiúna, SP, from April 2012 to March 2013. The litterfall production was estimated by 30 collectors distributed randomly in an area of 1000 m2, where the deposited material was collected every 15 days. The decomposition of litterfall was estimated through the mass loss in the period of study. After collecting, the material was dried in an oven at 65 °C for seven days to achieve a constant weight. The decomposition constant k was obteined according to Shanks and Oslon (1961) and the time for 50% and 95% of decomposition was estimated. It was found a higher litterfall production in October (454.3 kg ha-1) and lower production in July (164.9 kg ha-1), with a total amount produced of 3.5 Mg ha-1 year-1. A delay of one month in the precipitation and relative humidity showed great influence in the litter production during the study. The decomposition rate (k) was 3.1 and the time to decompose 50% of the material was estimated in 2 and ½ months and for 95% of the litterfall the time was estimated in 11 and ½ months. The production and decomposition values of this work are within the range found in other sites of secondary tropical forests.

Decomposition of aspen, spruce, and pine boles on two sites in Minnesota

Boles of quaking aspen (Populustremuloides Michx.), white spruce (Piceaglauca (Moench) Voss), red pine (Pinusresinosa Ait.), and jack pine (Pinusbanksiana Lamb.) were sampled after decomposing for 11–17 years. Mass loss and changes in chemical composition were determined. Density decreased by 40–73%, and the decomposition constant (k) decreased in the order aspen > spruce > red pine > jack pine. Although the decomposition rate was strongly species dependent, it did not differ between the two sites. The decomposition constant was weakly related to lignin and phosphorus concentration in the original stems (r2 = 0.44 and 0.49, respectively) and not significantly related to original nitrogen concentrations. Nutrient concentration increased during decomposition, particularly for nitrogen and phosphorus. Nitrogen content increased during decomposition, and potassium content decreased. Calcium and magnesium content changed little during decomposition, whereas phosphorus content increased or decreased, depending on species. In general, species with the lowest initial nutrient contents had the greatest nutrient increases during decomposition. Nutrient content of boles of all species became similar during decomposition.

Species and site differences in the decomposition of litters and roots from wet heathlands

The decomposition of litter and roots from a site dominated by Erica tetralix and a site dominated by Molinia caerulea was measured using mesh bags. Leaf litter and roots of each species were incubated on both sites. The experiments lasted up to 3 years. The weighted decomposition constant was 0.23 per year for Molinia litter, and 0.10 per year for Erica litter; the decomposition constants for roots were 0.29 per year for Molinia but only 0.03 per year for Erica. The decomposition rates of leaf litters and roots were similar on both sites, and the chemical composition of the materials determined the decomposition rate. Litters and roots with high lignin concentrations decomposed slowly. During the experiments, most materials showed a net retention of N and P. Large net N releases were measured only for Molinia roots and basal internodes, and a large net P release was measured only for Molinia roots. It was concluded that the rate of accumulation of soil organic matter per gram of plant debris is slower on the site dominated by Molinia than on the site dominated by Erica. In the long term, N and P are probably released faster from Molinia than from Erica plant debris. Key words: decomposition, heathlands, Molinia, Erica.

Derterminatin of the mineralization coefficient of soil organic nitrogen on two soils at Katherine, NT

The mineralization coefficient (M.C.) (the amount of nitrate nitrogen formed in one season in sift, by bare fallowing the soil, as a percentage of the amount of organic nitrogen in the topsoil at the onset of the season) was measured on two soils at Katherine, N.T. The determination of M.C. is regarded as useful in evaluating the 'true' decomposition constant of a soil under annual cropping conditions. Its relation to the 'apparent' decomposition constant is discussed. Tippera clay loam had a mean M.C. of 4.80 per cent, and the fluctuations around the mean were positively related to amount of rainfall. The M.C. for Blain sand dropped from 12.5 per cent in the first year of cultivation to 5.0 per cent in the third and fourth years. The data indicate that the initial high nitrogen yields on the sandy soil will in time decline to a low level unless a legume crop is incorporated in the cropping system.