Dry Matter Dynamics Research Articles

Estimation of respiratory parameters for rice based on long-term and intermittent measurement of canopy CO 2 exchange rates in the field.

Estimation of respiratory parameters, such as maintenance coefficient and growth conversion efficiency, is important for simulating crop growth. The objective of this study was to estimate respiratory parameters for rice ( Oryza sativa L.) by model analysis based on long-term and intermittent measurement of canopy CO 2 exchange rate (CER) in the field conditions. Canopy CER was intermittently measured in the field conditions for three rice varieties every 30 min from around the panicle initiation stage to maturity in 2004. Based on this measurement, rice respiration model was established and respiratory parameters were estimated by Simplex method. There was a big difference in respiration rate among rice varieties and large seasonal changes as evidenced by the long-term and intermittent measurement of canopy CER. The model explained the varietal difference and seasonal changes in respiration rate without any bias despite that all respiratory parameters, maintenance coefficient and growth conversion efficiency, were fixed for the three varieties. The results indicated that genotypic differences and seasonal changes in respiration rate result not from differences in respiratory parameters, but from differences in dry matter production, its allocation, and the N concentration of each tissue. Estimated respiratory parameters explained well the large variations in the directly measured canopy respiration rate of field grown rice. The model analysis suggested that the varietal differences and seasonal changes in canopy respiration rate were caused by differences in the dynamics of dry matter and nitrogen accumulation in plants.

Post-anthesis dry matter and nitrogen dynamics in durum wheat as affected by nitrogen supply and soil water availability

Durum wheat ( Triticum durum Desf.) is commonly grown in dryland conditions, where environmental stress during grain filling can limit productivity and increase the dependency on stored assimilate. We investigated current assimilation and remobilization of dry matter and nitrogen during grain filling in N fertilized and unfertilized durum wheat subjected to different levels of water deficit during grain filling. Two durum wheat varieties, Appio and Creso, were grown in open-air containers with three rates of nitrogen fertilizer (not applied, N0; normal amount, NN; high amount, NH) and four water regimes during grain filling (fully irrigated treatment, FI; low, LWS, moderate, MWS and high water stress, HWS) across 2 years. Grain yield and dry matter and N accumulation and remobilization were positively affected by N availability and negatively by water stress during grain filling. The reduction of grain yield by severe post-anthesis water stress amounted to 27 and 37% for N0 and NN, respectively, and was associated with a decrease in kernel weight. There was also a small negative effect on the number of kernels per spike. Conversely, the duration of grain filling was not modified either by water stress or by nitrogen treatments. Severe water stress also reduced dry matter accumulation and remobilization by 36 and 14% in N0 plants and by 48 and 25% in NH plants. Similarly, N accumulation and N remobilization was reduced by 43% and by 16% in N0 plants and by 51% and by 15% in NH plants. Conversely, low and moderate water stress did not substantially modify the patterns of dry matter and nitrogen deposition in grain. Although remobilization of dry matter and N was less affected by water stress than accumulation, it was not able to counterbalance the reduction of assimilation and consequently it was not able to stabilize grain yield under drought.

A Model for Phosphorus Transformation and Runoff Loss for Surface‐Applied Manures

Agricultural P transport in runoff is an environmental concern. An important source of P runoff is surface-applied, unincorporated manures, but computer models used to assess P transport do not adequately simulate P release and transport from surface manures. We developed a model to address this limitation. The model operates on a daily basis and simulates manure application to the soil surface, letting 60% of manure P infiltrate into soil if manure slurry with less than 15% solids is applied. The model divides manure P into four pools, water-extractable inorganic and organic P, and stable inorganic and organic P. The model simulates manure dry matter decomposition, and manure stable P transformation to water-extractable P. Manure dry matter and P are assimilated into soil to simulate bioturbation. Water-extractable P is leached from manure when it rains, and a portion of leached P can be transferred to surface runoff. Eighty percent of manure P leached into soil by rain remains in the top 2 cm, while 20% leaches deeper. This 2-cm soil layer contributes P to runoff via desorption. We used data from field studies in Texas, Pennsylvania, Georgia, and Arkansas to build and validate the model. Validation results show the model accurately predicted cumulative P loads in runoff, reflecting successful simulation of the dynamics of manure dry matter, manure and soil P pools, and storm-event runoff P concentrations. Predicted runoff P concentrations were significantly related to (r2=0.57) but slightly less than measured concentrations. Our model thus represents an important modification for field or watershed scale models that assess P loss from manured soils.

Estimation of physiological maturity in sunflower as a function of fruit water concentration

Visual methods are commonly used to estimate physiological maturity (PM) in sunflower crops. These methods, while simple and less laborious than following grain dry weight dynamics, are subjective and results can be affected by environmental conditions. The objective of the present work was to study the relationship between the dynamics of dry matter and water concentration (WC) of sunflower fruits, with the aim of identifying the timing of physiological maturity on the basis of fruit WC. The effects of brief periods of high temperature stress (lasting 4 or 6 days) during grain-filling were also explored. Eight different sunflower genotypes (inbred lines and hybrids) were studied in four separate experiments conducted under different growth conditions (greenhouse and field) and contrasting dates of sowing (autumn, spring and summer), generating a broad range of grain-filling durations (28–41 days) and final fruit weight (30–105 mg fruit −1). In these experiments the evolution of fruit fresh and dry weights were followed in fruit from the peripheral and intermediate positions on the capitulum from anthesis to harvest maturity. Tri-linear functions were fitted to the relative (to final) fruit dry weight (RFDW) to fruit WC relationships ( R 2 from 0.94 to 0.99). Across experiments, genotypes and fruit positions on the capitulum, PM in non-stressed plants was attained when fruits exhibited 38% WC. This model was validated against independent data, successfully simulating the dynamics of fruit dry weight based on fruit WC ( r = 0.99; P < 0.001). Verifications against published data generated by other authors also proved satisfactory. High temperature stress that caused a shortening of grain-filling and reductions in final fruit weight >20% with respect to controls, raised fruit WC at PM to ca. 50%. Simulations were performed to explore the effects of variations in timing of anthesis that occur between positions on the capitulum and among plants in a crop on fruit WC at maximum yield. At a crop level, 38% WC in these simulations corresponded to grain yield >95% of the maximum attainable when harvest was delayed until last growing fruits reached 38% WC. Simulations also showed that in crops exposed to high temperature during grain-filling, there would be no risk of shortfall with respect to potential yield using 38% WC as an indicator of PM. We conclude that this simple, fast and non-subjective method based on fruit WC would be useful to determine PM in sunflower.

Structure and Function of Populus deltoides Agroforestry Systems in Eastern India: 1. Dry matter dynamics

Agroforestry systems based on poplar (Populus deltoides) are becoming popular in eastern and northern parts of India. Therefore studies on the structure and function of the systems are important. The investigations included allometric equations for above- and belowground tree components, crop and plantation floor biomass and litter fall estimation at Pusa, Bihar, India. Biomass, floor litter mass, litter fall and net primary productivity (NPP) of plantations increased with an increase in age of trees whereas, crop biomass for any specific crop interplanted with poplar decreased with the age of the plantation. The total plantation biomass increased from 12.08 to 90.59 Mg ha−1 and NPP varied from 5.69 to 27.9 Mg ha−1 year−1. The biomass accumulation ratio ranged from 2.1 to 3.2. Total annual litter fall was in between 1.95 and 10.00 Mg ha−1 year−1, of which 92–94% was contributed by leaf litter. Compartmental models were developed for dry matter distribution in agroforestry systems involving young (3-year-old) and mature (9-year-old) poplar trees interplanted with various crops, the crops being grown in two rotations maize (Zea mays) – wheat (Triticum aestivum) – turmeric (Curcuma domestica) and pigeonpea (Cajanus cajan) – turmeric. This study substantiates the potential of Populus deltoides G3 under agroforestry combinations.

Investigation of carbon content and C/N ratio in flours from maturing wheats

The dry matter dynamics of growing grains are closely related to wheat cultivars (Sofield et al., 1977; Schnyder and Baum, 1992; Calderini et al., 2000) and the carbohydrate metabolism (Monneveux et al., 2004). There are several carbon dynamic models for winter wheat and other field crops (Eckersten et al., 2001) and it adverts to the fact that carbon and nitrogen metabolism are relatively independent and regulation of the carbon cycle in maturing grains depend under the seed demands.

Modelling simultaneously water content and dry matter dynamics of wheat grains

A model was devised to describe simultaneously the grain masses of water and dry matter against thermal time during grain filling and maturation of winter wheat. The model accounted for a linear increase in water mass of duration anthesis— m 1 (end of rapid water assimilation phase) and rate a, followed by a more stable water mass until m 2, after which water mass declined rapidly at rate e. Grain dry matter was described as a linear increase of rate bgf until a maximum size (maxgf) was attained at m 2. The model was fitted to plot data from weekly samples of grains taken from replicated field experiments investigating effects of grain position (apical or medial), fungicide (five contrasting treatments), sowing date (early or late), cultivar (Malacca or Shamrock) and season (2001/2002 and 2002/2003) on grain filling. The model accounted for between 83 and 99% of the variation ( r adj . 2 ) when fitted to data from individual plots, and between 97 and 99% when fitted to treatment means. Endosperm cell number of grains from early-sown plots in the first season were also counted. Differences in maxgf between grain positions and also between cultivars were mostly the result of effects on bgf and were empirically associated with water mass at m 1. Fungicide application controlled S. tritici and powdery mildew infection, delayed flag leaf senescence, increased water mass at m 1 (wm 1), and also increased m 2, bgf and maxgf. Fungicide effects on water mass were detected before fungicide effects on dry matter, but comparison of the effects of individual fungicide treatments showed no evidence that effects on wm 1, nor on endosperm cell numbers at about m 1, were required for fungicide effects on maxgf.

Effects of nitrogen and radiation on dry matter and nitrogen accumulation in the spike of winter wheat

In wheat, spike growth prior to anthesis is a key period influencing kernel set. Incident radiation and crop N status affect the accumulation of dry matter (DM) and nitrogen (N) in the spike, as observed at anthesis. However, the influence of these two factors on the dynamics of spike growth throughout the pre-anthesis period is not fully understood. Our objective was to investigate the effects of incident radiation and crop N nutrition on the dynamics of spike dry matter, N concentration and N content throughout the pre-anthesis period and to propose models describing spike DM and N content during spike growth, per unit area. We also investigated whether kernel number was related to spike N content at anthesis independently of spike DM, a controversial issue. Field experiments were conducted over two seasons with ‘Trémie’ winter wheat and over an additional season with ‘Arche’ and ‘Soissons’. Treatments involved the application of N fertiliser at different stages and rates to achieve various levels of N deficit and the use of shading nets at various periods during spike growth to reduce incident radiation. Shading reduced spike DM but increased spike N concentration; it reduced spike N content whenever there was a large decrease in incident photosynthetically active radiation (PAR). All these effects occurred only during the second half of the spike growth period, even if shading was applied from the onset of spike growth. Crop N deficit reduced spike DM, N concentration and N accumulation. Spike DM and N content were affected throughout the spike growth period if the deficit started before the beginning of spike growth, and was severe. Continuous and temporary N deficits induced similar responses. The interaction between shading and N fertilisation was not significant for spike DM and N content, but was significant for spike N concentration. Two models, one predicting spike DM and the other predicting spike N content at any time during spike growth were developed. They were validated with an independent data set and by cross-validation with the initial database. Both models fitted the observed data well. The input variables, cumulative PAR after sowing, nitrogen nutrition index (NNI) of the crop and cumulative thermal time after sowing are easy to measure or to simulate. Kernel number was correlated with both spike DM and spike N content at anthesis, demonstrating that N content played no role in determining kernel number independently of DM.

Effect of Fallow on Pruning Biomass and Nutrient Accumulation in Alley Croppingon Alfisols of Tropical Africa#

A study was conducted in long‐term alley cropping plots established in 1989 at International Institute of Tropical Agriculture (IITA), Ibadan, southwestern Nigeria to determine the seasonal and yearly dynamics of dry matter and nutrient concentrations of hedgerow pruning under continuous cropping and response to fallow of 1–3 years. At one year after Leucaena leucocephala transplanting, pruning was started at the 75 cm height. The pruning frequency increased from one to five times per year as trees grew. In continuous alley cropping without fertilizer application, pruning dry matter decreased gradually from a peak of 5 t ha−1 at 3 years after Leucaena transplanting to about 2.5 t ha−1 at 11 years after transplanting, while the ratio of dry season to wet season biomass increased. Within 5 years after establishment, nitrogen (N) and phosphorus (P) concentrations in pruning decreased and Mg increased with the continuous cropping. Fallow clearly increased pruning biomass and nutrient concentrations. At the completion of the first cycle (1993), the pruning N yield was 170 kg ha−1 for the continuous cropping plot, and 269 for plots with 1 yr fallow, 344 for plots with 2 yr fallow and 241 kg ha−1 for plots with 3 yr fallow. In 1993 pruning P yield increased from 6.5 to 10.9 in the continuous alley cropping and in 1995, it increased from 4.5 to 7.0 kg ha−1 in one‐year fallow plots. Fallow effect on potassium (K), calcium (Ca), and magnesium (Mg) yield in pruning was also evident. These results suggest alley cropping with one‐year fallow could be an effective rotation system for nutrient cycling in Alfisols of West Africa. #The work was conducted when the senior author was employed by International Institute of Tropical Agriculture (IITA), PMB 5320, Ibadan, Nigeria

Seasonal Dynamics of Dry Matter, Crude Protein and Cell Wall Digestion in Total Plant, Leaves and Stems of Common Buffelgrass (Cenchrus ciliaris)

Ramirez, R.G., Foroughbackhch, R., Hauad, L., Alba-Avila, J., García-Castillo, C.G. and Espinosa-Vázquez, M. 2001. Seasonal dynamics of dry matter, crude protein and cell wall digestion in total plant, leaves and stems of common buffelgrass (Cenchrus ciliaris). J. Appl. Anim. Res., 19: 209–218. This study was conducted to estimate and compare, seasonally, the nutrient content and the rate and extent of digestion of dry matter (DM), crude protein (CP) and cell wall (CW) of total plant (TP), leaves (L) and stems (S) of buffelgrass (Cenchrus ciliaris L). Plants were sampled in a four-ha pasture at Marin, N.L. County, Mexico, during fall of 1998, winter, spring and summer of 1999. The in situ technique was used to estimate effective degradability of DM (EDDM), crude protein (EDCP) and cell wall (EDCW), using rumen fistulated sheep. Crude protein content in forage was significantly higher in summer than in other seasons; however, cell wall and its derivatives (cellulose, hemicellulose and lignin) were significantly lower in summer. Crude protein content was higher in L than S, but CW was lower in L than in S. Moreover, EDDM, EDCP and EDCW were significantly higher in summer than in other seasons and also were higher in L than in S. Highly significant correlation coefficients between CP, CW and effective degradability data may indicate that when CP increased and CW decreased, EDDM, EDCP and EDCW increased. The nutrient content and digestion parameters of digestion of buffelgrass varied among seasons, being summer and fall higher in nutrient digestion and spring and winter lower. Furthermore, leaves of buffelgrass should be considered different entities than stems when determining nutritional quality.

Physiological Maturity in Wheat Based on Kernel Water and Dry Matter

Estimation of the time of physiological maturity could be beneficial to avoid yield penalties due to lodging, sprouting, hail, and other harvest risks. The aim of our study was to evaluate a simple empirical relationship (model) to determine physiological maturity by simultaneously analyzing the water and dry matter dynamics of wheat kernels. An experiment was conducted in which two cultivars with different kernel mass potential were sown on four dates. Fresh and dry kernel mass from different positions in the spike were measured twice weekly. To validate the regression model, measured and calculated data from different cultivars, growing seasons, and kernel positions were compared. A negative linear relationship between kernel dry matter (relative to final kernel mass) and kernel water concentration was determined. This showed that in wheat, physiological maturity is reached at 37% of kernel water concentration. Validation of the regression model was done using data from field experiments in Argentina and Mexico, and from controlled‐conditions experiments reported in the literature. The regression model successfully simulated results from field experiments (.) In addition, data from controlled‐conditions experiments showed the same negative linear relationship between relative kernel dry matter and kernel water concentration (), and the model achieved a good fit for measured data (). This regression model is proposed for use by farmers and crop managers, who can simply measure grain humidity with grain moisture meters.

Nutrient Cycling and Nutrient Use Efficiency in Short Rotation, High Density Central Himalayan Tarai Poplar Plantations

This paper deals with the pattern of nutrient cycling and nutrient use efficiency in four (1–4 years old) poplar ( Populus deltoides Marsh) plantations previously investigated for dry matter dynamics. The present plantations were planted at 3 × 5 m spacing after clear felling of natural sal ( Shorea robusta Dipterocarpaceae) mixed broad-leaved forests in central Himalayan Tarai. The nutrient concentrations (N, P and K) in different layers of vegetation were in the order: tree> shrub> herb; whereas the standing state of nutrients were in the order: tree> herb> shrub. Soil, litter and vegetation, respectively accounted for 81–96, 2–4 and 2–15% of the total nutrients in the system. Considerable reductions (trees, 50–68; shrubs, 35–40; and herbs 18–26 %) in the concentration of nutrients in leaves occurred during senescence. The uptake of nutrients by the vegetation, and also by the different components, with and without adjustment for internal recycling, was calculated separately. Annual transfer of litter nutrients to the soil by vegetation was 91–148 N, 8–15 P and 70–99 K kg ha -1 yr -1 . The turnover rate for different nutrients ranged between 0·83 and 0·92 yr -1 .The nutrient use efficiency of poplar plantations ranged from lSI to 174 kg ha -1 ye1 for N, 1338 to IS66 kg ha -1 yr -1 for P, and 313 to 318 kg ha -1 yr -1 for K. Compared with low density eucalypt and older poplar stands, there was a higher proportion of nutrient retranslocation in present poplars, largely because of higher tissue nutrient concentrations. This indicates lower nutrient use efficiency as compared to eucalypt plantations. Compartment models for nutrient dynamics have been developed to represent the distribution of nutrient pools and net annual fluxes within the system.

Nutrient Cycling and Nutrient Use Efficiency in Short Rotation, High Density Central Himalayan Tarai Poplar Plantations

This paper deals with the pattern of nutrient cycling and nutrient use efficiency in four (1–4 years old) poplar (Populus deltoidesMarsh) plantations previously investigated for dry matter dynamics. The present plantations were planted at 3×5 m spacing after clear felling of natural sal (Shorea robustaDipterocarpaceae) mixed broad-leaved forests in central Himalayan Tarai. The nutrient concentrations (N, P and K) in different layers of vegetation were in the order: tree>shrub>herb; whereas the standing state of nutrients were in the order: tree>herb>shrub. Soil, litter and vegetation, respectively accounted for 81–96, 2–4 and 2–15% of the total nutrients in the system. Considerable reductions (trees, 50–68; shrubs, 35–40; and herbs 18–26%) in the concentration of nutrients in leaves occurred during senescence. The uptake of nutrients by the vegetation, and also by the different components, with and without adjustment for internal recycling, was calculated separately. Annual transfer of litter nutrients to the soil by vegetation was 91–148 N, 8–15 P and 70–99 K kg ha−1yr−1. The turnover rate for different nutrients ranged between 0.83 and 0.92 yr−1. The nutrient use efficiency of poplar plantations ranged from 151 to 174 kg ha−1yr−1for N, 1338 to 1566 kg ha−1yr−1for P, and 313 to 318 kg ha−1yr−1for K. Compared with low density eucalypt and older poplar stands, there was a higher proportion of nutrient retranslocation in present poplars, largely because of higher tissue nutrient concentrations. This indicates lower nutrient use efficiency as compared to eucalypt plantations. Compartment models for nutrient dynamics have been developed to represent the distribution of nutrient pools and net annual fluxes within the system.

Effects of nitrogen on accumulation and partitioning of dry matter and nitrogen of vegetables. 3. Spinach

Four greenhouse and 2 field experiments (the latter on a sandy soil) were carried out with different amounts and dates of N application to analyse the dynamics of dry matter and N accumulation in spinach (cv. Trias). Frequent measurements were carried out on dry matter and N accumulation in leaf blades, petioles and stems. The total accumulation of dry matter and N differed largely among and within experiments. Increasing N application increased yield of dry matter and N accumulation, whereas splitting N applications had much smaller effects. However, the partitioning of dry matter and N proved insensitive to N treatments. Harvest indices for dry matter (about 0.67) or N (about 0.74) of crops at a marketable stage were fairly constant over treatments and experiments. Increasing or splitting the N application affected N accumulation more than dry matter production, resulting in large effects on N concentrations. The lack of variation in response to N for different N regimes facilitates the development of N application techniques aimed at high yield, high quality and reduced emissions. The organic N concentration of leaf blades and petioles decreased with leaf age, although in most experiments this decrease was smaller at higher leaf numbers. The nitrate-N concentration decreased with increasing leaf number at any sampling date; it was higher when N was abundant. High yields in autumn crops were associated with high nitrate concentrations but also with potentially high losses of N.

Culm recruitment, dry matter dynamics and carbon flux in recently harvested and mature bamboo savannas in the Indian dry tropics

AbstractCulm recruitment, standing crop biomass, net production and carbon flux were estimated in mature (5 years after last harvest) and recently harvested bamboo (Dendrocalamus strictus (Roxb.) Nees) savanna sites in the dry tropics. During the 2 study years bamboo shoot recruitment was 1711–3182 and 1432–1510 shoots ha−1 in harvested and mature sites, respectively. Corresponding shoot mortality was 66–93% and 62–69%, respectively. Total biomass was 34.9 t ha−1 at the harvested site and 47.4 t ha−1 at the mature site. Harvesting increased the relative contribution of belowground bamboo biomass. Annual litter input to soil was 2.7 and 5.9 t ha−1 year−1 at the harvested and mature sites, respectively. The bulk of the annual litterfall (78–88%) occurred in the cool dry season (November to February). The mean litter mass on the savanna floor ranged from 3.1 to 3.3 t ha−1; at the harvested site wood litter contributed 70% of the litter mass and at the mature site leaves formed 77% of the litter mass. The mean total net production (TNP) for the two annual cycles was 15.8 t ha−1 year−1 at the harvested site and 19.3 t ha−1 year−1 at the mature site. Nearly half (46–57%) of the TNP was allocated to the belowground parts. Short lived components (leaves and fine roots) contributed about four‐fifths of the net production of bamboo. Total carbon storage in the system was 64.4 t ha−1 at the harvested site and 75.4 t ha−1 at the mature site, of which 23–28% was distributed in vegetation, 2% in litter and 70–75% in soil. Annual net carbon deposition was 6.3 and 8.7 t ha−1 year−1 at harvested and mature sites, respectively.

Structure and Function of an Age Series of Poplar Plantations in Central Himalaya. II Nutrient Dynamics

This paper elucidates nutrient dynamics in 5- to 8-year-old poplar (Populus deltoides) clone D121 plantations previously investigated for dry matter dynamics. The nutrient concentration in different layers of the vegetation were in the order: tree > shrub > herb, whereas the standing state of nutrients were in the order: tree > herb > shrub. Soil, litter and vegetation, respectively, accounted for 80-89, 2-3 and 9-16% of the total nutrients in the system. Considerable reductions (trees 42-54, shrubs 31-37 and herbs 15-23%) in concentration of nutrients in leaves occurred during senescence. The uptake of nutrients by the vegetation and also by the different components, with and without adjustment for internal recycling, has been calculated separately. Annual transfer of litter nutrient to the soil by vegetation was 113·7-137·6 N, 11·6-14·6 P and 80·1-83·2 K kg ha-1 year-1. Turnover rate and time for different nutrients ranged between 0·72-0·89 year-1 and 1·12-1·39 years, respectively. The high turnover rate of litter on the forest floor indicates the greater productivity of the stands, which was due to the higher dry matter dynamics and nutrient release for the growing vegetation. The nutrient use efficiency in poplar plantations ranged from 159-175 for N, 1405-1569 for P and 295-332 for K. Compared with Eucalyptus, there was a higher proportion of nutrient retranslocation in poplars largely because of higher tissue nutrient concentrations; this indicates lower nutrient use efficiency as compared to the eucalypt plantation. Compartment models for nutrient dynamics have been developed to represent the distribution of nutrient pools and net annual fluxes within the system.

Structure and Function of an Age Series of Poplar Plantations in Central Himalaya: I Dry Matter Dynamics

The biomass and net primary productivity (NPP) of 5- to 8-year-old poplar (Populus deltoides Marsh, Clone D121) plantations growing in the Tarai belt (low-lying plains with high water table adjacent to foothills of central Himalaya) were estimated. Allometric equations for all the above-ground and below-ground components of trees and shrubs were developed for each stand. Understorey, forest floor biomass, and litter fall were also estimated from stands. The biomass of plantation, forest floor litter mass, tree litter fall and net primary productivity (NPP) of trees and shrubs increased with increase in plantation age, whereas herb biomass and NPP significantly (P < 0·01) decreased with increasing plantation age. The total plantation biomass increased from 84·0 in the 5-year-old to 170·0 t ha-1 in the 8-year-old plantation and NPP from 16·8 t ha-1 year-1 in the 5- and 6-year-old to 21·8 t ha-1 year-1 in the 8-year-old plantation. The biomass accumulation ratio (biomass: net production, BAR) for different tree components increased with the age of plantation increase. The BAR ratio ranged from 4·9 in the 5-year-old to 7·7 in the 8-year-old plantation.

Structure and Function of High Altitude Forests of Central Himalaya I. Dry Matter Dynamics

The present study deals with the structure and functioning of three different forest communities, viz., horse chestnut, silver fir and kharsu oak forests, in a high altitude region of Central Himalaya. The tree density and total basal cover of horse chestnut forest was 280 and 76, silver fir forest 355 and 106, and kharsu oak forest 480 trees ha -1 and 73 m 2 ha -1, respectively. Allometric equations relating biomass of different tree components to cbh (circumference at breast height) were significant. Total vegetation biomass was 505 t ha -1 in horse chestnut, 566 t ha -1 in silver fir and 593 t ha -1 in kharsu oak forests, of which maximum contribution was by tree layer followed by shrub, herb, sapling and seedling layers. The forest floor litter biomass was 2·1, 4·7 and 4·2 t ha -1 in horse chestnut, silver fir and kharsu oak forests, respectively. The total litter fall was 7·3, 6·7 and 9·4 t ha -1 year -1, of which leaf litter contributed 48, 39 and 64% in horse chestnut, silver fir and kharsu oak forests, respectively. Turnover rate of tree litter was 0·80 in horse chestnut, 0·61 in silver fir and 0·71 in kharsu oak forests. Net primary production of total vegetation was 19·6, 18·9 and 24·9 t ha -1 year -1, of which tree layer contributed maximum proportion followed by herb, shrub, sapling and seedling layers. To show dry matter storage and flow of dry matter within the system, compartment models were developed for all forests.

Biomass structure and dry matter dynamics of subtropical alluvial and exotic Ligustrum forests at the Río de la Plata, Argentina

Biomass, litterfall, litter standing crop, and decomposition was studied in a native subtropical alluvial forest locally known as Selva Marginal (SM) and an exotic Ligustrum lucidum forest (LF) at the Reserva Integral de Punta Lara, Buenos Aires Province, 34°47′S and 58°1′W. The alluvial forest site was at the southern limit of distribution of subtropical forests in South America. The Ligustrum forest was invading disturbed areas. Total biomass was 147.7 Mg/ha (86% aboveground and 14% belowground) in the SM, and 71.4 Mg/ha (93% and 7%, respectively) in the LF. Litterfall was 10.3 Mg/ha·yr and 13.8 Mg/ha·yr respectively. Annual leaf decomposition rate was greater for Ligustrum (k=4.07) than for SM species (k=1.48). The mean residence time of aboveground biomass was 12 yr for the SM and 5 yr for the LF. The k1 values (litterfall/standing crop) were 1.9 and 2.0 for SM and LF respectively. The influence of coastal road and wall in the hydroperiod, native forested wetland ecosystem survival and exotic forest invasion is discussed.

Structure and Function of an Age Series of Eucalypt Plantations in Central Himalaya. I. Dry Matter Dynamics

Structure and Function of an Age Series of Eucalypt Plantations in Central Himalaya. I. Dry Matter Dynamics