Total Aboveground Phytomass Research Articles

Composition of aboveground phytomass of subalpine fens in Teberdinsky National Park

The composition of the aboveground phytomass of unique subalpine plant community Teberdinsky National Park – the subalpine fens – has been studied. The aboveground vascular plant biomass averaged 264±12 g/m2 , the species of Cyperaceae prevailed (41%), the role of forbs (37%) and grasses (21%) is smaller, the remaining groups of vascular plants and lichens are very rare. Bryophytes are abundant (31,2% of total aboveground phytomass). Communities have polydominant structure, the largest aboveground biomass is formed by Carex nigra (26,1%), Nardus stricta (15,8%), Cirsium simplex (13,4%), Primula auriculata (6,7%), Blysmus compressus (5,2%), Swertia iberica (5,2%). Mortmass store is relatively small (168±12 g/m2 ), which indicates a high rate of decomposition and an intensive biological cycle.

Запасы углерода в 40-летних культурах сосны обыкновенной

The paper presents an assessment of carbon stocks in components of above-ground phytomass of the tree layer of 40-year Scots pine crops (Pinus sylvestris L.) growing in different forest conditions of the Baltic-Belozersky taiga region of the European North of Russia. The studied pine crops were created on fresh, unsodded clearings with a low degree of litter in lichen, lingonberry and bilberry types of forest growth conditions, which are characterized by significant differences in bioproductive potential. It was found that the smallest carbon pool is formed in the stand of a 40-year pine stand of lichen-type culture-phytocenosis (16.59 t/ha), the largest – in the blueberry type of habitat conditions (69.41 t/ha). In artificially created 40-year lingonberry pine forest, carbon stocks in the above-ground phytomass of the tree layer have an intermediate position (44.40 t/ha). The highest relative value of bound carbon is reached in such component of aboveground phytomass as trunk wood. The share of carbon stocks in this fraction of the total aboveground phytomass of the forest stand of the studied pine cenoses varies from 59.5 % in lichen type of habitat conditions to 75.6 % in blueberry one. Branches and needles have close quantitative values of carbon stocks and similar structure of differentiation along the forest typological gradient, occupying a secondary position in the carbon pool of the forest stand of the studied artificial pine forests after stem wood. The proportion of carbon bound by these fractions of aboveground phytomass of the stand decreases from the least productive lichen pine forest to the more productive blueberry pine forest. The share of carbon accumulated by stem bark in the total carbon pool of aboveground phytomass of the stand of the studied artificial pine forests tends to decrease from lichen pine forest to blueberry pine forest. The fraction of dry branches has the smallest percentage of carbon stocks in the tree stand in all studied forest conditions (2.3–5.9 %). For citation: Klevtsov D.N., Tyukavina O.N. Carbon Stocks in 40-year Scots Pine Crops. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 5, pp. 195–203. (In Russ.). https://doi.org/10.37482/0536-1036-2023-5-195-203

Biological Productivity of the Post-Fire Larch Forests in the Mountain Regions of Krasnoyarsk Krai

Peculiarities of the compositionally pure larch stands formation following forest fires were studied in the northern (Evenkia, middle course of the Nizhnyaya Tunguska river, geographic coordinates 64°03′ N 101°10′ E) and southern (Ermakovskiy district, geographic coordinates – 52°23′ N, 93°33′ E) areas of Krasnoyarsk Krai. The structure, growth and biological productivity of the forest restoration successions were analyzed based on the materials from the sample plots. The highest value of phytomass (in terms of total productivity) in larch stands registered was 1055.5 t abs. dry substances/ha at the age of 93 years. The structural ratio of the forest stands phytomass fractions naturally changes with an increase in their average age and density. With an increase in the average age of a stand, its above-ground and root phytomasses increase; at the same time, the relative share of crown and needle wood mass in the total above-ground phytomass of a stand decreases. In 38-year-old larch forests, the share of crown mass is 18%, and the share of stems is 82%. In 60-year-old forest stands, crown wood with needles accounts for 14%, and the rest 86% are stem weight. In the 93-year-old larch forest, the proportion of stem phytomass increases to 89%, and the proportion of crown wood with needles falls up to a minimum share of 11%. The maximum growth potential of the 56-year old larch stands, according to the current increase in phyomass (in terms of total productivity), is realised at about 14.69 t abs. dry substances/ha per year. The young and middle-aged larch forests formed on the burnt areas have higher rates of growth and phytomass accumulation; in terms of the amount of fixed atmospheric carbon, they exceed the mature and overmature stands by more than two times.

Dynamics of aboveground phytomass in the communities of the Ob River forest-steppe and Northern Kulunda during protective regime

The formation of the herbage of plant communities depends on the natural and climatic features of the area and the modes of their economic use. In 2013-2021, the comparison of dynamics of aboveground phytomass in steppe and meadow communities of Western Siberia at an absolute protective regime was carried out. The state of vegetation was studied on the territory of the Novosibirsk region on the example of two communities of the steppe meadow (the right-bank part of the Ob River forest-steppe) and two communities of the solonetzic steppe (the northern part of the Kulunda steppe). The vegetation cover was described according to the standard geobotanical techniques. It is shown that at an absolute protective regime of meadow communities, along with weather conditions, the considerable impact on the condition of the herbage is significantly affected by the excessive accumulation of plant litter, which reaches up to 57-77 % of the total aboveground phytomass. This leads to decrease in the density and mass of green shoots, while the overgrowth of weed plant species is often observed. The meteorological conditions of separate years have the main impact on formation of the aboveground phytomass of solonetzic steppes. Both in dry and highly humid years, the participation of grasses in the herbage decreases and the role of salt-tolerant forbs, as well as sagebrushs and especially Halimione verrucifera, increases.

Сравнительный анализ биоэнергетической продуктивности культурфитоценозов сосны обыкновенной европейского севера

The bioenergetic productivity of artificial pine stands is considered. It was found that in 30-year-old artificial pine coenoses, the lowest amount of energy associated with the tree layer is observed in the lichen type of growing conditions (443,1 GJ/ha), the highest — in the blueberry (1915,1 GJ/ha). Bioenergetic productivity occupies an intermediate position (1210,7 GJ/ha) in the cranberry-type forest culture phytocenoses. It is shown that the accumulated energy reaches the highest relative value in such a component of aboveground phytomass as trunk wood. For this fraction, the variation is observed from 50.2% in the lichen type of growing conditions to 65.8% in the blueberry type, based on the total stock of phytomass of forest crops. It is established that the secondary position relative to this indicator is occupied by woody greens. The share of the energy productivity of needles in the total aboveground phytomass decreases with the improvement of forest growing conditions. An approximately equal ratio of energy deposition in the studied types of artificial pine forests by the fractions of bark and live branches (7,2...11,7%) was determined, and the smallest share of accumulated energy falls on the fraction of dry branches (5,3...7,0 %).

Структура древостоев и особенности накопления ими фитомассы на остепненных склонах массива гор Крака (Южный Урал)

Структура древостоев и особенности накопления ими фитомассы на остепненных склонах массива гор Крака (Южный Урал)

Transformation of metals migration and biogeochemical cycling under the influence of copper mining production (the Southern Urals)

This study aims to estimate the migration and accumulation of metals (Cu, Zn, Fe, Mn, Ni, Pb, Cd, Co, Cr, Zr, Ba, and Sc) in terrestrial and aquatic landscapes. The research is based on the results of a long-term study (1998–2018) in one of the copper mining centers in Russia in the vicinity of Sibay City in the Southern Urals. The metal contents in samples of water, bottom sediments, soils, plant shoots (total aboveground phytomass samples, agrobotanical group samples, and shoots of indicator terrestrial and aquatic species), and fish muscles are measured. It is found that within natural geochemical anomalies, the migration ability of chemical elements in the soil–plant system and general biogeochemical cycle is low because of the high soil buffer capacity (determined by the high humus content, high percentage of fine fractions in granulometric composition, and neutral pH) and the adaptation of local plants to ore mineralization. The ecosystems affected by low pollution maintain natural homeostasis, stabilize the flow of chemical elements, and preserve the natural features of geographic components. Metal pollution and the replacement of natural steppe vegetation with secondary herbaceous-ruderal communities in critical areas near copper–zinc mining objects can stimulate the mobilization and inclusion of chemical elements in biogeochemical cycling, as well as the disruption of bonds among landscape components. The water systems in catenae function as stabilizers through a system of geochemical barriers and low uptake of metals by hydrophytes, such as the common reed (Phragmites australis).

ОЦЕНКА ЗАПАСОВ ФИТОМАССЫ И ПЛОДОРОДИЯ СЕРЫХ ПОЧВ ЗАЛЕЖЕЙ

Цель исследования. Выявить специфику формирования запасов и структуры фитомассы, а также трансформации плодородия серых почв залежей при различном их использовании в лесостепной зоне.
 Место и время проведения. Исследования проводились на трех объектах (чистая залежь, залежь, используемая под сенокос и залежь, повторно вовлеченная в пашню) в Красноярской и Ачинско-Боготольской лесостепи Красноярского края с 2011 по 2016 гг.
 Методология. На всех объектах проводили сопряженный учет запасов и общей структуры надземной травянистой фитомассы и показателей плодородия серых почв. Рассчитали статистические параметры достоверности различий и корреляционной взаимосвязи продуктивности растений с показателями эффективного и потенциального плодородия постагрогенных серых почв залежей.
 Основные результаты. Восстановительные сукцессии надземной травянистой растительности залежей лесостепной зоны Красноярского края свидетельствуют о переходной от корневищной к дерновинной стадии. Растительность залежи Красноярской лесостепи представлена пырейно-разнотравным фитоценозом с долей рудеральных видов около 30 %. Флора залежей Ачинско-Боготольской лесостепи отличается более богатым видовым составом с увеличением доли бобовых видов, при этом сорный компонент в травостое залежей занимает примерно 30 %. Богатство видового состава трав на залежах в обоих районах исследования зависит от условий увлажнения; показано, что запасы продуктивной влаги в почвах Ачинско-Боготольской лесостепи существенно выше, чем в Красноярской лесостепи. Использование залежи под сенокос ускоряет наступление дерновинной стадии сукцессии и приводит к вытеснению разнотравья злаковым компонентом за счет уплотнения почвы при сенокошении. В условиях пашни в составе надземной растительности преобладает доля злаков за счет выращиваемых полевых культур, таких как овес и пшеница, в то же время резко возрастает доля разнотравья за счет сорного компонента.
 Общие запасы надземной травянистой фитомассы максимальные на чистых залежах в обоих районах исследования, что подтверждается статистически. Исключением является распаханная залежь с посевом овса, биомасса которого резко нарастала от летнего к осеннему сроку учета. Более продуктивными являются залежи Ачинско-Боготольской лесостепи за счет оптимальной влажности почв в течение всей вегетации. Залежи, используемые под сенокосы, не отличаются высокой продуктивностью, запасы травянистой фитомассы на них практически одинаковые в обоих районах исследования.
 Установлено, что вовлечение залежей в пашню существенно ухудшает показатели потенциального плодородия почв. Динамика показателей эффективного почвенного плодородия (нитратный и аммонийный азот) зависят от характера использования участка; при распашке залежи усиливается минерализация органического вещества, увеличивается содержание нитратного и аммонийного азота. Выявлено статистически достоверное изменение комплекса почвенно-агрохимических свойств чистых залежей в сторону улучшения. Между запасами фитомассы и показателями потенциального и эффективного плодородия почв в Ачинско-Боготольской лесостепи установлена более тесная корреляционная зависимость, по сравнению с Красноярской лесостепью, за счет оптимального режима увлажнения.
 Заключение. Установлены максимальные запасы надземной фитомассы на чистых залежах в переходной от корневищной к дерновинной стадии сукцессии, что приводит к повышению плодородия постагрогенных серых почв. В структуре фитомассы залежей преобладает разнотравный компонент. Использование залежей под сенокосы снижает продуктивность растений, увеличивает в травостое долю злакового компонента, ускоряет наступление дерновинной стадии сукцессии и ухудшает показатели почвенного плодородия. При введении залежи в пашню зафиксирована минимальная продуктивность фитомассы и снижение биогенной аккумуляции.

Phytoindicational properties of the vegetation in landscape transformation studies on Sibay chalcopyrite deposits (Southern Urals)

Changes in biogeochemical, morphological, floristic, and phytocenotic vegetation properties around Sibay chalcopyrite deposits at different distances from mining facilities have been studied. Heavy metal (HM) (Cu, Zn, Fe, Pb, Cd, Ni, Co, Cr, and Mn) content has been measured in samples of soils, waters, bottom sediments, total aboveground phytomass, and several plant species (Artemisia austriaca, Salvia stepposa, Thymus marschallianus, Veronica incana, Caragana frutex, Phlomis tuberosa, Achilea setacea, Galium verum, and Phragmites australis). Groups (pleiadas) of species have been identified based on interspecific contingency coefficient. These pleiadas correspond to ecological conditions and level of anthropogenic stress of the habitats. The set of features for evaluating natural territorial transformations of complexes by means of phytoindication is proposed.

Down to future: Transplanted mountain meadows react with increasing phytomass or shifting species composition

Manipulative approaches under natural conditions are fundamental for understanding impacts of climate warming on grassland (agro-) ecosystems. In this paper we present 3 years of data from two simultaneously conducted transplantation experiments, where meadow monoliths were transplanted downwards along an elevation gradient from the subalpine to the montane belt (2000m to 1500m a.s.l.), and in parallel from the montane belt to the foothill zone (1500m to 1000m a.s.l.) respectively. Each downward transplantation simulated a temperature increase of 2.8K. Control and downward transplanted mesocosms were compared regarding aboveground phytomass, phytodiversity, and species composition. Downward transplanted mesocosms from the upper transplantation reacted significantly to warming in terms of aboveground phytomass (legumes +213.6%, herbs +128.2%, graminoids +51.7%, total aboveground phytomass +66.2%), but not with regard to species composition. The lower transplantation, however, induced the complete opposite effect, while average species number and species evenness remained unaffected on all treatments. Further analysis based on five plant traits indicated that the observed shifts were both a consequence of warming and methodological artifacts. Interestingly, the relative importance of warming, artifacts and unaffected species changed with elevation: At the higher transplantation 81.2% of the species remained stable in their abundance, 17.5% were affected by the transplantation, and almost no warming effect could be detected. At the lower transplantation percentage of artifact- and warming-affected species increased consistently (37.5% respectively 44.3%). The results showed that transplantation experiments along elevation transects are an appropriate approach to detect warming impact on agriculturally used grassland at different elevations. Nevertheless, the increasing influence of method-caused side effects became more and more evident over time and with decreasing elevation, underlining the importance of quantifying artifacts in in vivo experiments.

Evaluation of the seasonal dynamics of crop yield in agrocenoses on the basis of satellite data and mathematical models

An integrated approach based on satellite remote sensing data and the results of mathematical model analysis was tested for applicability in evaluating the crop yield and total of phytomass of agrocenosis and identifying its type. The dynamics of the normalized difference vegetation index (NDVI) and the total aboveground phytomass of agrocenosis proved to be qualitatively similar. An analysis performed using the mathematical model and taking into account air temperature showed the possibility of making and refining prognosis of crop yield. In this course, the vegetative and generative parts of the agrocenosis were distinguished, and it was found that the model data matched the ground survey data under optimal environmental conditions.

Assessment of Agroecosystem Productivity Based on Satellite Data and a Mathematical Model

The possibility of determining seasonal dynamics of agroecosystem productivity was estimated based on the combined use of satellite data and results of a mathematical model study. The study showed a qualitative agreement between normalized difference vegetation index (NDVI) and the total aboveground phytomass of the wheat and oat agroecosystem. Analysis of the mathematical model proved the possibility of prediction and improvement of the crop yield estimate. A distinction has been made between the vegetative and reproductive biomass of the agroecosystem. Results of mathematical modeling were in good agreement with ground-truth data in the case of nutrient (nitrogen) limitation.

Nitrogen fixation assessment in a legume-dominant alpine community: comparison of different reference species using the 15N isotope dilution technique

In arctic and alpine environments the highest biologically fixed nitrogen inputs are measured in the presence of leguminous plants, with a maximum annual nitrogen input recorded of about 10 kg ha−1 year−1. Among the high-elevation legumes, Trifolium alpinum spreads over many southern European mountain grasslands as a dominant or co-dominant species, accounting for 30–40 % or more of total above-ground phytomass. We estimated the amount of symbiotic nitrogen fixation in T. alpinum-dominant communities using the 15N isotope dilution technique and comparing the calculations derived from different non-fixing reference species. The estimated percentage of nitrogen derived from the atmosphere varied significantly depending on the reference species used and they were comparable to the ones reported in literature. No differences were detected among years. In the community studied, the use of one reference species instead of another can yield differences of more than 10 kg ha−1 year−1, which may represent a considerable difference in the estimation of symbiotic nitrogen fixation in alpine ecosystems. Taking a very precautionary approach and using the grass Nardus stricta as the reference species, we estimated 21.9 kg ha−1 year−1 of nitrogen fixation in T. alpinum-dominant communities. This quantity of nitrogen is the highest ever estimated in a natural alpine grassland and it is related to the high annual above-ground phytomass of T. alpinum.

Evaluation of Deschampsia caespitosa /L./ Beauv. competition ability in mixtures with main turfgrass species

Numbers of tillers and weight of aboveground dry mass were evaluated in a field experiment at the Plant breeding station Větrov of Oseva UNI Choceň a. s., Czech Republic (620 m a. s. l., average year temperature 6.9 ˚C, average year precipitation 642 mm) in mixtures of D. caespitosa cv. ‘Kometa’ with Poa pratensis L. cv. ‘Harmonie’ or with Lolium perenne L. cv. ‘Filip’ during three years of vegetation. The seeding rate was always 40 thous. viable seeds per m2. The proportion of D. caespitosa in the mixtures was 25%, 50% or 75% of the total number of seeds, a monoculture was established too. The sward was mown to 3 cm. D. caespitosa was not able to compete with L. perenne. The number of its tillers during the experiment ranged up to 3% of total number of tillers of the sward; the weight of aboveground DM was maximally 1.5% of the total aboveground phytomass. It established much better in the mixtures with P. pratensis. The total number of both components and the weight of aboveground dry mass was significantly influenced by the year (p-value < 0.000–0.009), by D. caespitosa proportion in the seed mixture (p-value = 0.001–0.003) and by the interaction of these factors (p-value = 0.000–0.056). It developed more rapidly in the first year in comparison with P. pratensis and reached 31–85% of total amount of tillers in positive correlation to its proportion in the seed mixture, later the competition capacity of P. pratensis increased and D. caespitosa tillers proportion in the sward was 11–39% in the third year. The trend of the weight of its aboveground dry mass was similar – 21–78% in the first year and 8–36% in the third year in a positive correlation with its proportion in the seed mixture. D. caespitosa and P. pratensis created bigger tillers in the later years.

Current state of forage resources and feeding of reindeer (Rangifer tarandus) and musk oxen (Ovibos moschatus) in the arctic tundras of Wrangel Island

The species composition and aboveground biomass of plant and lichens and the composition of reindeer and musk ox diet in the arctic tundra of Wrangel Island were studied in 2004 to 2007. The above-ground phytomass in different areas of the island varied from 1105 to 2100 kg/ha. The composition of plants consumed by reindeer and musk oxen and their proportions in the diet were determined by standard micro-histological analysis of plant remains in their feces. The results showed that, either in winter or in summer, both species obviously preferred feeding on willows (Salicaceae), which comprised almost half of their diet. Moreover, their feeding was highly selective, especially with respect to sedges and rushes (Cyperaceae + Juncaceae) and legumes (Fabaceae). Although the contributions of these plant groups to the total aboveground phytomass were very small (less than 4 and 8%), their proportions in the diet reached 27 and 24%, respectively. Mosses were not a preferred forage: their proportion in the aboveground phytomass reached 40%, but that in the diets of both species was below 10% in summer and increased to 20% only in the winter diet of reindeer. At a high abundance of lichens (up to 20% of the aboveground phytomass), neither of the animals consumed them during the study period.

A new estimate of tundra-biome phytomass from trans-Arctic field data and AVHRR NDVI

It is often assumed that the Normalized Difference Vegetation Index (NDVI) can be equated to aboveground plant biomass, but such a relationship has never been quantified at a global biome scale. We sampled aboveground plant biomass (phytomass) at representative zonal sites along two trans-Arctic transects, one in North America and one in Eurasia, and compared these data to satellite-derived NDVI. The results showed a remarkably strong correlation between total aboveground phytomass sampled at the peak of summer and the maximum annual NDVI (R 2 = 0.94, p < 0.001). The relationship was almost identical for the North America and Eurasia transects. The NDVI–phytomass relationship was used to make an aboveground phytomass map of the tundra biome. The approach uses a new and more accurate NDVI data set for the Arctic (GIMMS3g) and a sampling protocol that employs consistent methods for site selection, clip harvest and sorting and weighing of plant material. Extrapolation of the results to zonal landscape-level phytomass estimates provides valuable data for monitoring and modelling tundra vegetation.

Does expansion of western snowberry enhance ecosystem carbon sequestration and storage in Canadian Prairies?

Aerial expansion of woody species in grasslands is common in arid and semiarid areas. The ecological consequences of shrub expansion, including ecosystem function and carbon sequestration, are complex and dependent on local environmental conditions. This research was conducted in the Northern Mixed Prairie of Canada to determine the effects of western snowberry ( Symphoricarpos occidentalis) expansion on phytomass production and ecosystem carbon storage in grass-dominated plant communities. Total aboveground phytomass in western snowberry communities was more than triple that of the ecotone and 6-times greater than that of the grassland. Similarly, the mass of large roots was greatest in the western snowberry community (1.2 ± 0.19 kg m −2, mean ± SE), intermediate in the ecotone (0.5 ± 0.08 kg m −2), and least in the grassland (0.1 ± 0.04 kg m −2). Conversely, the mass of fine and medium roots was not different ( P > 0.05) among the three communities, averaging 0.7 kg m −2 in all communities. Greater aboveground phytomass did not correspond with greater organic carbon in the soil (SOC) in the western snowberry community possibly due to the poor quality and slow decomposition rate of shrub litter. Soil organic carbon in the upper 50 cm averaged 8.3 ± 0.7, 7.9 ± 1.0, and 7.9 ± 0.7 kg m −2 in western snowberry, ecotone, and grassland communities, respectively. The SOC in fine- and coarse-textured soils averaged 10.4 ± 0.6 and 6.2 ± 0.4 kg m −2, respectively. Expansion of western snowberry into grass-dominated plant communities does not appear to conflict with goals related to maintenance of SOC in the Northern Mixed Prairie. Soil texture had a greater effect on SOC than that of western snowberry. Therefore, the management of western snowberry in the Northern Mixed Prairie should be site specific and focus on aspects other than SOC pools.

Phytomass utilization and deposition of feces by ungulates on steppe pastures of eastern Mongolia

The amount of phytomass removed by a complex of livestock (horses, cattle, sheep, and goats) and wild ungulates (Mongolian gazelle Procapra gutturosa Pall.) grazing in plain and mountain pastures of eastern Mongolia has been estimated by taking account of feces deposited by these animals. The results show that at an animal density of up to 30 head/km2, the total annual amount of feces reaches 140 kg/ha (dry weight), with the greater part (up to 90 kg/ha) being deposited by horses. The contribution of Mongolian gazelles in some pastures reaches 20-40 kg/ha per year. Decomposition of feces proceeds very slowly, with the annual loss of their weight averaging only 9-12%. This is evidence for gradual accumulation of nondecomposed matter in the soil. The removal of phytomass by the complex of ungulates, calculated from the amount of feces with regard to their annual loss and forage digestibility, varies in different grazing areas from 240 to 400 kg/ha (25-60% of the total aboveground phytomass). The greatest amount of phytomass is utilized by horses, reaching 200 kg/ha (13%), and Mongolian gazelles utilize up to 86 kg/ha per year. In the growing season, ungulates remove no more than 11-16% of the total aboveground phytomass. It is concluded that the impact of total ungulate stock does not impair the productivity of vegetation in the pastures studied.

Influence of land use on phytomass accumulation in Highland Sourveld grassland in the southern Drakensberg, South Africa

Transformation of indigenous vegetation for production purposes impacts negatively on biodiversity but does this necessarily equate with a decrease in phytomass accumulation, which may influence carbon sequestration? Phytomass accumulation was studied for common land covers of beef ranching or dairy farming under private tenure, plantation forestry, crops and rangelands of communal areas, and conservation areas in the southern Drakensberg. Annual turnover in above-ground phytomass (AGP) was estimated by harvesting at seasonal extremes, or at bimonthly intervals for grasslands and pastures. Peak root biomass was estimated by coring. Tree biomass (44792 g m−2) of pine plantations unsurprisingly dwarfed total AGP (litter plus standing) of all other cover types, but total AGP of plantations even excluding trees was highest because of litter accumulation. Total AGP ranged from 82–1423 g m−2 in mid-summer and 215–1008 g m−2 in mid-winter. Total AGP was otherwise highest for commercial maize, followed by kikuyu pasture, conservation grassland, Eragrostis pasture, commercial rangeland, rangeland and maize under communal tenure, and least for annual ryegrass pasture. Intensively used pastures were therefore superior, equivalent, or inferior to indigenous grasslands in terms of phytomass accumulation, depending on the pasture and grassland compared. Excluding plantations, total AGP consisted mainly of standing AGP. Graminoids contributed >83% of standing AGP for all cover types except communal maize (54%); necromass contributed 33–47% for grasslands or pastures in mid-summer, and 86–93% for all in midwinter except ryegrass pasture (49%). Root biomass varied sixfold among cover types (648–4128 g m−2) and contributed greater than 75% to total phytomass (root, litter, standing AGP) for all cover types except maize (46%). Although soil stocks of carbon are usually far greater than vegetation stocks in grassland, significant increases in vegetation stocks can be achieved through choice of land use and management.

Equazioni di previsione della fitomassa arborea per i soprassuoli di cerro in avviamento ad altofusto in Toscana

The paper reports the development of allometric equations to estimate tree phytomass in Turkey oak stands in Tuscany. Biomass estimation is a basic tool to study the ecosystem, which is currently taking on a greater importance due to the commitments provided by the Climate Convention and the Kyoto Protocol. The high costs of the field measurements of tree biomass calls for the application of indirect methods, such as the largely-applied biomass equations, allowing to calculate phytomass values using variables easily measurable in the field, such as tree diameter and height. The equations described here have been developed for Turkey oak coppices undergoing conversion into high forests. Such stands are nowadays more and more common because of the progressive suspension of timber harvesting on an increased part of the original coppice area. We report five equations: the first one to estimate stem volume, and the followings to estimate each phytomass component (stem, branches, and slash) and the total tree above-ground phytomass. Tree diameter at breast height and total tree height were used as independent variables (predictors). All equations were developed on the same model and the additivity of the phytomass components in respect to the total phytomass was achieved. Equation parameters showed a fairly good accuracy in the estimation of the dependent variables.