Net Aerial Primary Production Research Articles

Andean Grassland Species: Net Aerial Primary Productivity, Density, Ecomorphological Indices, and Soil Characteristics

Andean Grassland Species: Net Aerial Primary Productivity, Density, Ecomorphological Indices, and Soil Characteristics

Net Aerial Primary Productivity Models for Alfalfa Varieties (Medicago sativa L.) Derived from the Red Vegetation Index

The present study is aimed at quantifying and comparing the net aerial primary productivity (NAPP) of two alfalfa varieties (Medical sativa L.) by determining the Radiation Use Efficiency (Ɛ) for each variety, estimating the NAPP though the Red Vegetation Index and relating it to the quantified NAPP. Significant differences between the individual NAPP of each variety were not found: G969 = 1564 g dm m-2 and M901 = 1636 g dm m-2 (T = 0.92; p>0.05). The Ɛ of the G969 was 0.56 g Mj-1 while that of M901 was 0.58 g Mj-1. Significant direct relationships between the quantified NAPP and that calculated using the Red Vegetation Index were found. The models obtained were: NAPPG969 = 506.06x – 343.25 (R2 = 0.88; p<0.001) and NAPPM901 = 420.28x + 37.82 (R2 = 0.98; p<0.001). The Ɛ values of the alfalfa varieties under study, determined at local level, reduce uncertainty when generating predictive models of productivity. The NAPP of alfalfa varieties can be non-destructively predicted using the Red Vegetation Index obtained by a reflex RGB digital camera. Keywords: radiation use efficiency, digital camera, canopy reflectance, RGB indices

Uruguayan native grasslands net aerial primary production model and its application on safe stocking rate concept

Native pastures in Uruguay grasslands are the main resource for livestock extensive farming. Remote sensing data of Net Aerial Primary Production is a useful tool to enhance knowledge about grasslands dynamics and behaviour. The pasture productivity on grasslands is highly affected by climate and droughts episodes impacts directly on secondary productivity of livestock systems. Using remote sensing data, a harmonic sinusoidal model affected by a "climate coefficient" is proposed to generate prospective scenarios and to study an implementation of the Safe stocking rate concept. This information can be use in extension activity to help farmers to adapt their systems to native grass dynamics on the adaptive management paradigm.

Production of Fodder in a Treeless System and in Silvopastoral System in Central Argentina

ABSTRACT This paper aims to identify the spatial and temporal distribution of net aerial primary production (NAPP) of oats and sorghum in silvopastoral systems (SPS) and in a treeless situation (TLS), in Southern Cordoba, Argentina. The silvopastoral systems are composed of three woody cultures (Pinus elliottii, Eucalyptus viminalis and Quercus robur), and two grass species (Avena sativa and Sorghum sudanense). NAPP of Avena sativa and Sorghum sudanense were lower in the silvopastoral systems than in the treeless situation. However, there were also differences in terms of NAPP according to the tree species, and these differences were related to the intensity of competition between trees and grasses. Pinus elliottii and Quercus robur were less competitive than Eucalyptus viminalis, which might be associated with their morphophysiological differences, their differential growth rate and their differences in terms of phenology. Finally, facilitation effects between trees and grasses were also identified under certain conditions.

Biomass dynamics of the two dominant SW Atlantic Spartina species and its implications on the saltmarsh organic matter accumulation/exportation

We present a comparative analysis of the biomass dynamics of the two dominant Spartina plant species in South West Atlantic saltmarshes: Spartina densiflora Brong. (high intertidal zone) and Spartina alterniflora Loesel. (mid-low intertidal zone). We assessed aboveground biomass, live: dead ratios, net production, mortality and turnover rates, and then used this information to understand if saltmarshes dominated by one or the other Spartina species have different ecosystemic roles in the recycling of organic matter. Through field sampling we found that S. densiflora had larger live, dead and total biomass than S. alterniflora. When comparing within each species, S. alterniflora had larger live than dead biomass for most of the year, while S. densiflora had more dead than live biomass. Through the Weigert and Evans (1964) net aerial primary production (NAPP) estimating method we found that S. densiflora had larger annual NAPP, annual mortality and live turnover rates than S. alterniflora. In both species the amount of NAPP was similar to the amount of annual mortality. These results suggest that S. densiflora aboveground biomass is a carbon accumulation zone, while S. alterniflora is a carbon recycling one.

Net Primary Productivity of Spartina densiflora Brong in an SW Atlantic Coastal Salt Marsh

Coastal marshes are known as organic matter producers. The goal of this work is to study tiller demography, standing biomass, and net aerial primary productivity (NAPP) in a Spartina densiflora coastal wetland, using a method applied to permanent sample plots located at two sites differing in topographic location, a regularly flooded zone [relative low marsh (LM)] and an irregularly flooded one [relative high marsh (HM)]. Measurements were made every 2 months during the 2005–2007 period. The annual NAPP was estimated to be 2,599 ± 705 gDW m−2 year−1 for the HM and 2,181 ± 605 gDW m−2 year−1 and 602 ± 154 gDW m−2 year−1 for the first and second period of the LM populations, respectively, showing a seasonal pattern reaching maximum values in summer. The reduced NAPP values of the LM sites in the second year was associated with an extremely high precipitation period related to the 2007–2008 El Nino event.

Tiller dynamic and production on a SW Atlantic Spartina alterniflora marsh

We used non-destructive methods to study the bi-monthly changes in standing stock, turnover, and net aerial primary productivity (NAPP) of Spartina alterniflora in the Bahía Blanca Estuary, Argentina, from 2005 to 2007. Tillers were tagged and counted bimonthly and a weight:height relationship developed for the live and dead stems in a regularly flooded zone (low marsh, LM) and an irregularly flooded one (high marsh, HM). The annual tiller natality in year one compared to year two decreased from 440 ± 68 to 220 ± 58 new individuals m –2 yr –1 in the HM and from 500 ± 103 to 280 ± 97 new individuals m −2 yr −1 in the LM ( μ ± 1 SE). Tiller mortality averaged 670 ± 70 individuals m −2 yr −1. Living biomass was present throughout the year in both the sites, but flowering occurred only at the HM where it began in December. The live biomass in the LM was significantly greater than in the HM in the first year, but decreased in the second year from 455 ± 66 to 266 ± 31 g m −2 in the HM and from 572 ± 76 to 277 ± 78 g m −2 in the LM ( μ ± 1 SE). The highest levels of standing dead material were in the HM (55%) and the lowest in the LM (24%). The average total (live + dead) aboveground biomass in the HM was significantly greater than in the LM in the first year, but decreased in the second year from 1033 ± 120 to 556 ± 33 g m −2, and in the LM from 679 ± 57 to 355 ± 61 g m −2 ( μ ± 1 SE). The annual NAPP, calculated as the sum of positive growth in individual tillers between intervals, showed no significant differences between years and sites, and averaged 628 ± 94 g m −2 yr −1 ( μ ± 1 SE). The dead biomass output (DBO), calculated as the sum of negative increments in NAPP between sampling intervals, was 956 ± 121 g −2 yr −1, and was not statistically different between sites. The productivity at this site is not different from that estimated for other marshes, when similar methods are used. The production at this site, however, may be limited by high salinity levels, and the differences observed between years related to climate changes between years, e.g., the 2006–2007 was an ENSO period.

Productivity of Brachiaria humidicola pastures in the Atlantic forest region of Brazil as affected by stocking rate and the presence of a forage legume

Excessive intensification of dairy and beef cattle production systems in the industrialised countries has led to serious problems of pollution of water resources and the atmosphere. In order to develop an appropriate alternative, a few studies have been made by various research teams in Brazil, using low fertiliser inputs and modest animal stocking rates. The objective of this present study was to evaluate the effect of different stocking rates of beef cattle, and the introduction of a forage legume (Desmodium ovalifolium (Prain) Wall.), on the long-term sustainability of pastures of Brachiaria humidicola (Rendle) Schweick established in the Atlantic forest region of Brazil in the extreme south of the State of Bahia. Annual maintenance fertilisation was restricted to additions of 11 and 6 kg ha−1 of P and K, respectively (and no N). Live weight gain (LWG) of Zebu steers was evaluated for stocking rates of 2, 3 and 4 head ha−1 during six grazing periods from 1988 to 1997. Forage intake and the proportion of legume in the acquired ration was determined using steers fitted with oesophageal fistulae. The bolus samples were analysed manually in 1988–1989, and using the 13C natural abundance technique in 1995. There was no significant response of LWG to the presence of the legume in the acquired ration. LWG in the final grazing period (1995–1996) was similar to that recorded in 1988–1989 at all stocking rates, suggesting that this management regime resulted in long-term sustainable production even in the absence of the legume or of a N fertiliser input. This was confirmed by the soil fertility analyses for 1988 and 1997, where only levels of P showed a significant decrease. The net aerial primary productivity (NAPP) of the pasture was determined for 1995, the largest component being deposited litter (21–33 Mg DM ha−1 year−1), followed by forage intake (6.4–12.2 Mg DM ha−1 year−1).

Tiller population dynamics and production on Spartina densiflora (Brong) on the floodplain of the Paraná River, Argentina

Abstract Tiller dynamics and net aerial primary productivity (NAPP) were studied in permanent sample plots of Spartina densiflora at Otamendi Natural Reserve (Buenos Aires Province, Argentina) from June 1996 to December 1997. Emergence, growth, senescence, survival, biomass dynamics, and tiller productivity were analyzed. These population attributes varied seasonally during the first study year, whereas variations were not detected in the subsequent year. Tiller density increased slightly during the first twelve months, attaining 2445 ± 869 tillers·m−2, then remaining constant until the end of the study period. Senescence rate was lower than emergence rate on most sampling occasions. Cohorts originated in different seasons showed distinct survival curves. The life span of tillers was at least 18 months. Green biomass reached maximum values (771 ± 410 g·m−2) during the first year but decreased during the last six months of observations. Annual NAPP was 1450 ± 566 g·m−2·y−1. Average productivity rate was hi...

Litter deposition and disappearance in Brachiaria pastures in the Atlantic forest region of the South of Bahia, Brazil

Over the last 25 years more than 70 million ha of the native vegetation in Brazil have been replaced by pastures for beef production planted to grasses of the genus Brachiaria, and to a lesser extent Andropogon gayanus, both of African origin. Some years after implantation, these pastures decline in productivity, probably due to low availability of P, and immobilisation of N in the soil due to the large quantities of senescent leaves (litter) of high C:N ratio deposited on the soil surface. In this paper we report the effects of the introduction of a forage legume (Desmodium ovalifolium) and different animal stocking rates on the deposition and decomposition of plant litter in pastures of Brachiaria humidicola at a site in the coastal Atlantic forest region of the south of Bahia State (Brazil). Litter existing on the ground, and that deposited in 14-day periods, was monitored at monthly intervals during 3 years of the study. Doubling the stocking rate from 2 to 4 animals ha-1 caused a highly significant decrease in litter deposition, but the presence of the legume in the sward had little effect. Calculations made directly from the quantities of litter deposited in the 14-day periods showed that between 15 and 18 tons of litter dry matter (dm) were deposited annually, but the relatively small quantities of existing litter (annual means of 0.8 to 1.5 t dm ha-1), showed that decomposition was rapid, showing values for half life of between 22 and 33 days. This technique was assumed to underestimate true litter disappearance rates, as with such rapid decomposition a significant proportion of the litter disappeared within the 14-day collection periods. An equation was developed to correct for this loss of litter during the collection periods and corrected litter decomposition constants of 0.037 to 0.097 g g-1 day-1 were recorded resulting in half lives of between 9 and 20 days. Using these data and adding them to estimates of animal consumption the net aerial primary productivity (NAPP) of the pastures ranged from 28 to 34 t dry matter ha-1 yr-1. Experiments with litter bags, and a "covered litter" system which allowed access of soil fauna to the litter, indicated that soil faunal activity had little impact on litter disappearance and such techniques underestimated true litter decomposition by at least an order of magnitude. We suggest that this underestimation is due to the fact, that in contrast to litter bags, in the open field situation fresh litter is being added continuously. As this material consists of both easily degradable ("active") and recalcitrant fractions, the easily degradable fraction fuels an active microbial biomass which continuously degrades the less decomposable material. It is concluded that the approach used in this study gives more realistic, and much higher estimates, of net primary aerial production of tropical grasslands and pastures than techniques heretofore utilised.

The productivity of salt marsh vegetation at Tollesbury, Essex, and Stiffkey, Norfolk, England

This study presents data on the biomass and net aerial primaryproductivity (NAPP) of two contrasting East Anglian salt marshes.One site was at Tollesbury, Essex where the marshes are of theestuarine type and are subject to marsh degradation and erosionwhile the other site was 130 km to the north at Stiffkey, Norfolkwhere the barrier-type marshes are still actively developing withno signs of erosion. The NAPP was determined by the method ofSmalley with quadrats being harvested monthly with replacement.At the lowest levels at Tollesbury there was “Pioneer Marsh”which was dominated by a mixture of Salicornia spp. and Astertripolium. At higher levels at Tollesbury there was ’LowerMarsh’ which was dominated by a mixture of Atriplex portulacoides andPuccinellia maritima. Over the four years of the studyPuccinellia became the dominant species following a markeddecrease in the extent and vigour of Atriplex. At Stiffkey the‘Middle Marsh’ was at a much higher level and the vegetation waspredominantly a short dense sward with Atriplex portulacoides,Puccinellia maritima and Limonium vulgare together with smallerquantities of Armeria maritima and Plantago maritima. The meanNAPP‘s over three years of the Pioneer and Lower Marsh atTollesbury (467 & 519 g m-2 yr-1respectively) were similar butin 1993 the NAPP‘s recorded at Tollesbury were higher than thoserecorded at Stiffkey (625 & 583 compared with 458 g m-2yr-1).Smalley‘s method is difficult to apply to communities wherespecies dominance is variable, especially when dominance isshared between species with markedly different growth patterns.The results for NAPP obtained from the salt marshes at Tollesburyand Stiffkey are discussed in relation to results obtained byother workers from comparable areas in England and theNetherlands. Attention is also drawn to the possibly largerbelow-ground component of production that is frequentlyoverlooked. The importance of salt marshes in relation to othercoastal communities lies in the export of a proportion of theorganic matter produced and this mainly depends on theabove-ground production.

Net aerial primary production (NAPP) of the marsh macrophyteScirpus maritimus estimated by a combination of destructive and non-destructive sampling methods

Net aerial primary production (NAPP) of marsh macrophytes is usually estimated either by destructive sampling techniques or by phenometric techniques. Destructive methods, however, are thought to be inaccurate while phenometric techniques are very labour intensive. In this study a new method is presented which allows an accurate and more efficient estimation of NAPP. The method combines destructive sampling to determine end-of-season biomass and phenometric techniques to estimate the mortality of biomass before the end of the season. NAPP is derived through summation of these two estimates. Techniques needed to calculate the precision of the NAPP estimate are provided. The so called hybrid technique was used to estimate NAPP ofScirpus maritimus L. in a brackish marsh along the Westerschelde estuary, the Netherlands. Estimated NAPP was 1372 g m-2. End-of-season biomass accounted for 1106 g m-2, while mortality contributed 266 g m-2. Precision of the end-of-season biomass and the mortality estimates, expressed as coefficient of variation, was 18.2 and 26.0% respectively. The precision of the resultant, NAPP, was higher: 17.2%. These results indicate that NAPP could be estimated with a higher precision than end-of-season biomass. This contradicts the view that the accuracy of NAPP estimates can only be improved at the expense of its precision.

Ramet Population Dynamics and Net Aerial Primary Productivity of Spartina Alterniflora

Ramet dynamics and net aerial primary productivity (NAPP) were studied in samples of Spartina alterniflora (smooth cordgrass) at Sapelo Island, Georgia. Three populations were compared: tall, short, and short with nitrogen fertilization in spring (short/N). Tall and short S. alterniflora populations had different demographic characteristics. The short population had a shorter leaf longevity (49 vs. 72 d) and a higher leaf turnover than the tall population, which may be due to high salinity and nitrogen limitation in the high marsh. Although the average ramet longevities of tall and short populations were similar (231 and 204 d, respectively), cohorts of the tall population that emerged early in the growing season had a significantly longer average life—span than those of the short population, probably because they had more support from belowground reserves that led to a higher initial survival rate. Leaf number, leaf area, shoot density, and biomass production of the short population were greatly increased by spring nitrogen fertilization, but the longevity of leaves and ramets was little affected. Using the demographic data and phytometric equations (nondestructive method), new growth was found throughout the year in S. alterniflora populations at Sapelo Island. The average dry mass NAPP was estimated to be 1105, 2244, and 1520 g.\mathrm{m}{—2}.\mathrm{yr}{—1}$ for the short, short/N, and tall populations, respectively. Because of its higher leaf turnover, the short population had a higher leaf to stem production ratio than the tall population. NAPP estimates obtained by nondestructive methods usually lie between overestimates and underestimates from harvest methods, indicating that nondestructive methods give accurate estimates of NAPP for salt marshes. Using the highest spring aerial production rates, the upper limits of annual dry mass total production of S. alterniflora at Sapelo Island were calculated as 2555 g/\mathrm{m}2$ for the short population and 4526 g/\mathrm{m}2$ for the tall population. These limits are lower than many previous estimates of annual total primary production for S. alterniflora.

Production and decomposition of Spartina foliosa in Bahia San Quintin, B.C., Mexico

Net aerial primary production, total production, aboveground biomass, turnover time, decomposition and total detritus production were estimated in a Spartina foliosa area at Bahía San Quintín, B.C. The study took place during the period March-August, 1992. The net aerial primary production values were high (4.72 g/m2/day) and turnover time short (5.4 months) compared with other coastal lagoons in the area. Two distinct periods were observed in the aboveground biomass level, one during May with the minimum value (323 g/m2) and another during June-August with high values (mean = 1,017 g/m2). The observed decomposition rate value was high (63%/159 days) compared with those reported in studies that started in winter in other areas. Total detritus production was estimated (1,050 tons/222 ha/159 days). We conclude that the S. foliosa area at Bahía San Quintín is a highly productive system with a fast recovering capacity. Further research is recommended focusing particularly on the marsh’s total organic detritus contribution to the adjacent lagoon system.

Biomass and aboveground production of four angiosperms in Cantabrian (N. Spain) salt marshes

New data of aboveground biomass and production of four angiosperms over a 12 month period for the Cantabrian Sea salt marshes (Bay of Biscay, N. Spain) are presented. Based on harvest methods, maximum aboveground total biomass values for Spartina maritima (Curtis) Fernald, Spartina alterniflora Loisel, Salicornia ramosissima J. Woods and Halimione portulacoides (L.) Aellen were 628, 1109, 480 and 1267 gm-2, respectively. We conclude that although a slight latitudinal gradient in biomass is revealed in the data compiled with reference to some of the species studied, more work is neccesary in order to assess the potential productivity of these ecosystems on the coasts of Europe and/or to make comparisons with salt marshes of the American coasts. Annual net aerial primary production estimates using Smalley's method were: 296, 1160, 486 and 952 gm-2yr-1, for Spartina maritima, Spartina alterniflora, Salicornia ramosissima and Halimione portulacoides, respectively. These results together with turnover rate estimates point to the lack of vigour of the native S. maritima, while the exotic S. alterniflora, which seems to be spreading along the Cantabrian estuaries, behaves like a veritable pionner throughout the low marshes in this region.

A comparative study of above‐ground productivity of dominant U.S. Gulf Coast marsh species

AbstractAbove‐ground productivity of dominant freshwater, brackish, and salt‐marsh species from the U.S. Gulf Coast was evaluated using both gas exchange techniques and harvest methods. Both techniques showed significant differences in productivity among the study species which represent major components of their respective communities.Estimates of net aerial primary productivity using the harvest method yielded 3683 g dw (dry weight) m−2yr−1 for Spartina alterniflora (tall), 2008 g dw m−2yr−1 for S. alterniflora (short), 3677 g dw m−yr−1 for S. patens and 1641 g dwm−yr−1 for Panicum hemitomon. Carbon balance estimated from gas exchange calculation yielded values approximately equivalent to a biomass accumulation of 6024 g dw m−2yr−1 for S. alterniflora (tall), 3047 g dw m−yr−1 for S. alterniflora (short), 5702 g dw m−yr−1 for S. patens, and 2912 g dm−yr−1 for P. hemitomon. The net aerial primary production was estimated to be approximately 61% of total productivity in S. alterniflora (tall‐form) and 66%o of total productivity in short‐form, 64% in S. patens and 56%) in P. hemitomon. The assimilation data also indicated that Spartina alterniflora and S. patens continue carbon fixation throughout the year while assimilation in Panicum hemitomon is absent due to lack of live leaves during the winter. Various aspects of harvest and gas exchange techniques are discussed.

Net aerial primary productivity, litter production and decomposition of the reef Phragmites communis in a nature reserve in Hong Kong: management implications

Net aerial primary productivity, litter production and decomposition of the reef Phragmites communis in a nature reserve in Hong Kong: management implications

Measurement of Cordgrass, Spartina alterniflora, Production in a Macrotidal Estuary, Bay of Fundy

A one-year field study was conducted of the growth, mortality, and loss dynamics of aSpartina alterniflora low marsh in the Minas Basin, a macrotidal estuary at the head of the Bay of Fundy. Data were used to examine the suitability of four methods for estimating annual net aerial primary production (NAPP) of a marsh subject to energetic tidal flooding. Shoots start to grow in April and reach maximum height (about 0.5 m) and weight in October. Maximum shoot density (900–1,600 m−2) occurs around June and drops thereafter due to the export of entire shoots. The average shoot produces about seven leaves and at least 2–3 are lost during the growing season. All remaining vegetation dies before the end of November. Methods based on harvesting vegetation underestimated NAPP, especially at lower elevations where export is greater due to more frequent and prolonged tidal flooding. The highest NAPP values, on the order of 500–600 g m−2 y−1, were obtained using methods based on the population dynamics of individual shoots. These methods are recommended for energetic tidal environments because they include the production of vegetation exported during the growing season.

Production, Predation, and Decomposition in a Low-Salinity Hibiscus Marsh

The rates of production, leaf grazing, and stem decomposition associated with Hibiscus moscheutos were quantified to contrast the ecology of this brackish herbaceous perennial with fresh and salt marsh species. Average net aerial primary production (NAPP) during 1978 and 1979 was estimated to be slightly over 1200 g°m—2°yr—1, which was calculated by summing: peak standing crop (49%); leaf mortality and litter production (36%); and losses to herbivores (15%). Three species of herbivorous insects were found to be important grazers: Atomacera decepta, Chionodes hibiscella, and Althaeus hibisci. Herbivore consumption was far greater than previously reported in salt marsh systems and rivals that of terrestrial communities. The root: shoot ratio (2.3) is comparable to many fresh marsh species but lower than most high—salinity species. The decomposition rate of Hibiscus stem material was estimated to be on the order of 7—8 yr, or up to five times slower than stems and leaves of other typical brackish marsh species (Typha, Scirpus, and Phragmites). The export potential of detritus from decaying stems is apparently minor because of this slow rate of decomposition combined with the diminished tidal action typical of Hibiscus—dominated marshes. We hypothesize that this unusual marsh dominant differs from Spartina in salt marsh systems by nourishing a more robust grazing food chain and by not exporting significant quantities of detrital material.

Primary production and accumulation of nutrients by the ground layer community of cerrado vegetation of central Brazil

Net aerial primary production and accumulation of nutrients by the grasses and nongrasses of the ground layer community of a cerrado vegetation in central Brazil were determined in burnt and unburnt areas. The net aerial primary production of the ground layer community was 327 gm−2 in the unburnt area and only 242 gm−2 in the burnt area during the first year after fire. Grasses contributed 68 to 78% of the aerial biomass of the ground layer in the unburnt area. The live biomass in the burnt and unburnt areas was comparable by the end of the first dry period after the fire. The major part of N, P and K in the aerial biomass was in the grasses. The concentration of all nutrients in the aerial biomass was generally higher in the burnt area during the first year after the fire.