Dead Phytomass Research Articles

Ecological significance of marcescence in Himalayan plants: Why is standing dead phytomass more important in demanding, resource‐limited environments?

Abstract Understanding mechanisms allowing plants to thrive in challenging conditions is critical for predicting their responses to global environmental change. An often overlooked ecological adaptation is marcescence, where leaves and stems are retained beyond their typical shedding time, with implications for nutrient recycling and carbon sequestration. Marcescence can be expected in plants with conservative resource‐use strategies, especially in environments with limited resources and marked seasonality, such as deserts and alpine regions. However, the extent to which marcescence occurs in different taxa across different habitats and its relationship to seasonality and plant functioning as reflected in ecophysiological traits remains understudied. We studied 600 individuals across 40 Himalayan herb species found in desert, steppe, alpine and subnival habitats, spanning 3000–5400 m elevation. Marcescence was observed in 37 of the 40 species evaluated, with 57% of the sampled individuals displaying dead phytomass, indicating the widespread nature of this phenomenon in Himalayan ecosystems. Environment and plant traits emerged as significant factors influencing the amount of dead‐standing biomass. These findings remained robust after accounting for intraspecific variation and phylogenetic inertia. Desert and steppe species exhibited greater marcescent biomass, characterized by 10‐fold more dead stem biomass than alpine and subnival plants. In contrast, the proportion of dead phytomass increased with elevation due to increased dead leaf fraction. Taller desert species with heavily lignified stems and limited nitrogen and phosphorus content had high levels of stem marcescence, which not only may aid litter photodegradation and nutrient recycling but also deter herbivory and promote seed dispersal (tumbleweed). Conversely, slow‐growing alpine and subnival plants with higher water‐use efficiency, foliar C:N ratios and parenchymatic storage tissue rich in mobile carbohydrates had a high proportion of marcescent leaves, which may aid survival in these resource‐limited environments by providing delayed nutrients through moisture‐conserving mulch that also provides insulation and protection from frost. This study provides new insights into the complex interplay of habitat, seasonality and plant traits in dead phytomass retention in Himalayan plants. Marcescence is prevalent in resource‐conservative species in highly seasonal, resource‐limited habitats and may significantly shape the functioning and biodiversity of Himalayan ecosystems. Read the free Plain Language Summary for this article on the Journal blog.

Degradation of peat-forming plants at the first stages of decomposition in natural and post-pyrogenic peatlands of West Siberia

The aim of the study. Assessment of the phytomass stocks and decomposition rate of peat-forming plants’ residues in peat deposits of natural and post-pyrogenic peatlands at the initial stages of decomposition. Location and time of the study. The study was carried out in 2022 (May-September) at two oligotrophic bog sites: “Bakcharskoye” (field station “Vasyuganye”, IMCES SB RAS) and “Iksinskoye”, which are located in the north eastern spurs of the Great Vasyugan mire in the Bakcharsky and Shegarsky districts of the Tomsk region, Russia. Methods. The phytomass stocks were determined by the cutting method. The following fractions were separated: living phytomass (annual and perennial photosynthetic phytomass, i.e. green parts of grasses, shrubs leaves, mosses); perennial non-photosynthetic phytomass, i.e. shrubs stems, roots of grasses and shrubs; and dead phytomass (mortmass), i.e. litter, moss litter, standing dead phytomass. The decomposition rate of plant residues was determined by the method of litter bags placement in peat (Chamaedaphne calyculata, Sphagnum fuscum, Mixed sample consisting of 60% S. fuscum and 40% Ch. calyculata). In the initial and decomposed samples, the ash content was determined by the dry combustion method. The total carbon and nitrogen content, as well as the carbon and nitrogen isotopic composition, were determined using a DELTA V Advantage isotope ratio mass spectrometer. Results. This short-term study conducted during the growing season in conditions of undisturbed (Natural Ryam) and post-pyrogenic (Gar) phytocenoses showed that due to a significant amount of mortmass (2402 g/m2) Natural Ryam had organic matter stock exceeding that in the Gar by 1.7 times. On average, 59% of organic matter loss from the total losses during the growing season occurred in the first month. In both Gar and Natural Ryam conditions, minimal losses of organic matter were characteristic for Sphagnum fuscum (3.1 and 3.5% respectively). For the remaining samples the Gar conditions were more favorable for the degradation at the initial stages of decomposition. The Mixed sample occupied an intermediate position between its individual components in terms of mass losses. Carbon losses correlated well with mass losses both over 1 month of degradation (r=0.87) and over 4 months (r=0.96). In contrast to carbon, nitrogen accumulated in the Mixed sample at the initial stages of degradation, both after 1 month and 4 months. Conclusions. With smaller phytomass stocks in areas of post-pyrogenic succession, more active decay at the initial stages of organic matter decomposition occurs exactly under these conditions. The impact of post-pyrogenic succession on the rate of organic matter decomposition of Chamaedaphne calyculata plant residues and the Mixed sample was demonstrated. The most intensive decomposition of litter occured during the first month of degradation. Additionally, in the conditions of a burnt bog, a more intense release of nitrogen from all plant residues and accumulation of ash elements in Sphagnum fuscum samples were observed. The mixing of litter components influenced both the rate and dynamics of decomposition. The carbon and nitrogen isotopic composition began to change during the initial stages of decomposition, leading to enrichment with heavier isotopes 15N and 13C. This research emphasizes the importance of studying the processes of plant litter decomposition at the initial stages and considering the plant residue composition when studying the processes of organic matter transformation.

Ecological significance of standing dead phytomass: Marcescence as a puzzle piece to the nutrient cycle in temperate ecosystems

Abstract The plant economics spectrum (PES) drives nutrient cycling through effects on soil decomposers. However, dead phytomass may remain standing or unshed (marcescent), hardly accessible to decomposers and be photodegraded. In arid zones, the significant part of marcescent phytomass can be decomposed without touching the ground. In temperate zones, photodegradation of marcescent phytomass is low but prompts important chemical changes, which affect its subsequent decomposability in the soil and alters the surrounding environment. It is unknown, however, how common marcescence is among different taxa and in which habitats, and how it is coordinated by PES traits. We sampled standing (marcescent) and lying (shed) dead phytomass from a broad spectrum of 127 herbaceous temperate species in a common garden experiment and related these parameters to PES traits, species ecological preferences and phylogeny. Nearly all species (97%) kept their phytomass marcescent. Tall species with a small leaf area and high leaf carbon had a high level of marcescence. Marcescent species also preferred sites affected by severe (but not necessarily frequent) disturbance. The degree of marcescence was considerably conserved in phylogeny. Synthesis. Marcescence extends PES trait effects on ecosystems, particularly in immature habitats, being a common but overlooked phenomenon of the temperate flora.

Evaluation of the NDVI Index as a Source of Information on Aboveground Phytomass in Steppes

The complexity of phytomass measurements on sample plots hinders the extrapolation of plot-related data to areas comparable to land use or landscape units. Vegetation indices calculated from satellite images are usually considered as indicators of green phytomass and are used for its areal estimates. The study solves the problem of establishing the information content of the normalized difference vegetation index NDVI depending on the fractional structure of living and dead aboveground phytomass, seasonal dynamics of the biological cycle, hydrothermal conditions and landscape position. We used the results of monthly measurements of aboveground phytomass fractions at 13 sites covered by Stipa zalesskii and Stipa lessingiana formations in the Burtinskaya steppe (Orenburgsky nature reserve) from May to September in 2015–2020. For each period, NDVI values were calculated from Landsat satellite images at all sites. Hypotheses about geobotanical, hydrothermal, phenological and landscape factors of NDVI informativity were tested by using the Spearman correlation coefficients, analysis of variance and multiple regression. The discrepancy between the seasonal peaks of NDVI and green phytomass is not consistent with the common opinion of a direct indicator value of NDVI. The total live biomass correlates more clearly with the index in June and July but weaker at the end of the season. NDVI turned out to be sensitive not so much to green phytomass as such, but to the mass and proportion of forbs and the ratio of live and dead phytomass. In late spring and early summer, NDVI is most closely associated with forbs while in July – with grasses. The hypothesis about the possibility of screening green mass with standing dead biomass was confirmed, which leads to a decrease in NDVI despite the absence of a decrease in green phytomass. NDVI may underestimate the real green phytomass if there is a sharp increase in the mass of dead biomass, usually in the second half of summer and early autumn. NDVI more adequately reflects the state of the aboveground phytomass of steppe communities that have not been exposed to fires for a long time, compared to burned communities and fallows.

LANDUSE FEATURES IN A MOUNTAIN AREA AND THEIR EFFECTS ON THE PROCESS OF SYLVATISATION (STRYY DISTRICT LVIV REGION)

The Skole District that is nowadays a part of newly established Stryy District (Lviv Region) is entirely situated within the range of the Ukrainian Carpathians. Its area encompasses the Skolivsli Beskydy and the Stryy-San Highland physiographic regions featuring a dominance of considerably high altitudes above sea level, terrain disarticulation, and afforestation. Establishing new villages alongside rural population’s natural increase and land reforms (the capitalist stage of land use (after the abolition of serfdom in 1848) and Soviet stage of land use) called for respective increase in agricultural lands. Forested lands in the Ukrainian Carpathians were the source for such an increase therefore cropland and pasture lands were emerging from deforestation. Harsh weather conditions and low soil fertility significantly impacted the further agricultural land uses in the mountainous region. However, wide-scale decline of agricultural lands occurred in the period of the collapse of the former USSR due to decline of collective and state farms. As a result of denationalization with subsequent privatization of agricultural lands there are nowadays 31 303 land owners and land users in the study area, 97,54 % of which are physical persons. At the same time, despite such remarkable figures citizens share less than a half of total lands for agriculture, residential and construction purposes, whilst the state forestry enterprises are using 51,11 % (75 173,50 ha) in total. In contrast to lowlands, animal farming and husbandry in the Skole District is held exclusively by households. In recent years local animal husbandry is experiencing the livestock decline that leads to certain reduction in the share of both hay meadows and pasturelands. Thus, from 2009 to 2016 the total area of fodder lands in the district decreased by 65 ha (ca. 0,2 % of total privately owned agricultural lands). I assume that ongoing land reform will cause further increase in fallows in the Skole District. In order to better comprehend the processes of spontaneous reforestation (sylvatisation) in a mountain region (the Pohartsi boundary, Koziova village, Stryi district, Lviv regionthe ) four study plots were selected representing the successional sequence: forest → pasture → hay meadow → arable lands. The study showed that areas that were previously used for pasture and were not plowed, are restored to their natural state much faster. These areas are characterized by satisfactory physical, physico-chemical and biotic properties. The decrease in acidity towards the neutral side is explained by an increase in the activity of catalase and urease by approximately 1.5 times. In connection with the developed grass cover, slightly higher nitrogen values were recorded in the upper soil horizon. Due to the absence of a regular annual supply to the base and replenishment of its nutrient reserves due to precipitation and waste of dead phytomass, the content of humus in the upper horizon of the base is half as much as under forest biogeocenoses. Plowing (overturning the lower horizons to the mountain, and vice versa) is a very strong anthropogenic factor, which leads to the almost complete destruction of natural vegetation on the cultivated area and a radical change in the main properties of the soil cover. According to some indicators: physical (total sparability), physico-chemical (nitrogen nitrate and ammonia), biotic (urease, catalase, biomass of microorganisms) in the upper humus horizons were even somewhat close to anthropogenically unaltered ecosystems. However, the changes in the indicators of the density of the soil structure and its solid phase corresponded to the depth of plowing. And the humus content was several times lower than under forest biogeocenoses. Areas that were not plowed in the past are restored due to the main rock of the region Picea abies (L.) Karst.. Areas that were devastated in the past are recovering much more slowly. Such areas begin to overgrow with Alnus incana (L.) Moench., Rosa canina L., Bеtula and others Key words: land use; land owners and land users; fallows; agricultural lands; mountainous region; Skolivski Beskydy.

Applicability of international indicators of land degradation neutrality estimation for Russian boreal forests

In this paper, we analyze applicability of Land degradation neutrality (LDN) concept of the UN Convention to Combat Desertification for Russian boreal forests. In this regard, it is necessary to adapt the three global LDN indicators (land cover, land productivity, and carbon stocks) to the assessment of land degradation processes of boreal forests in Russia and around the world. The proposed study concludes that landscapes with different types of forest restoration dynamics can be viewed as the object in forest land dynamic studies. The proposed research also suggests the set of LDN indicators adapted for boreal forests conditions. In order to assess LDN proxies we calculated the retrospective and projected net carbon balance in the middle taiga zone of Noshulskoye forest domain (Komi Republic, Russia) using the CBM CFS model. Here we explored 3 scenarios of forest net carbon balance under the three different felling regimes. It was shown that the net carbon balance cannot be applied as an independent LDN indicator, since it does not take into account changes in species diversity and primary productivity. We also suggest that industrial felling should imitate natural types of restoration dynamics in order to achieve LDN targets. It can be reached through minimization of forest felling at sites with fireless types of succession, which accumulate maximum stocks of dead phytomass matter and serve as forest refuges supporting biodiversity.

Indicators in Estimation of Land Degradation Neutrality for Russian Boreal Forests

In this paper, we analyze the applicability of the land degradation neutrality (LDN) concept of the UN Convention to Combat Desertification to the Russian boreal forests. In this regard, it is necessary to adapt three global LDN indicators (land cover, land productivity, and carbon stock) to the assessment of land degradation processes of boreal forests in Russia and around the world. According to the research results, landscapes with different types of forest restoration dynamics can be viewed as an object of forest land dynamic studies. A set of LDN indicators adapted for boreal forests conditions has also been suggested in the course of our research. In order to assess LDN proxies, we calculated the retrospective and projected net carbon balance in the middle taiga zone of the Noshulskoye forest domain (Komi Republic, Russia) using the CBM CFS model. We explored three scenarios of forest net carbon balance under three different felling regimes. The net carbon balance should not be applied as an independent LDN indicator, because it does not take into account changes in species diversity and primary productivity. It is suggested that industrial felling should imitate natural types of restoration dynamics in order to achieve LDN targets. It can be reached through minimization of forest felling at sites with fireless types of succession, which accumulate maximum stocks of dead phytomass matter and serve as forest refuges supporting biodiversity.

Analysis of the in situ and MODIS albedo variability at multiple timescales in the Sahel

The variability of the Sahelian albedo is investigated through the combined analysis of 5 years of in situ radiation data from the African Monsoon Multidisciplinary Analysis northernmost sites and remotely sensed albedo from 7 years of Moderate Resolution Imaging Spectroradiometer data. Both data sets are found to be in good agreement in terms of correlation and bias. The drivers of albedo variability are identified by means of in situ measurements of biological and physical properties of the land surface collected over a network of 29 long‐term survey sites. Short‐term variability is dominated by changes in the spectral composition of incident radiation, which reflects aerosol optical depth and integrated water content, and changes in soil moisture, which have a short‐lived effect (1 d). Bush fires cause a marked decrease of albedo of the order of 10 d, whereas a dry season storm event is suspected to have increased albedo through litter and soil surface abrasion. Seasonal plant growth causes the largest changes in rainy season albedo, and displays a large interannual variability: Because of the 2004 drought, albedo increases steadily from late 2003 to early 2005 at latitude 15°N. Grazing pressure is found to impact albedo mostly in the dry season. Dry season albedo is controlled by the amount of litter and standing dead phytomass hiding the bright soils. Thus rainfall anomalies have a direct effect on albedo through plant growth but also a lagged effect caused by above normal amounts of dry phytomass that can persist until the arrival of the next monsoon. EOF analysis and Hovmüller diagrams show these effects to be present on a large scale.

Life-cycle model of terrestrial carbon exchange

We present here a terrestrial carbon cycle model based on a scheme of the phytomass change, which is continuous in time. The experimental information about net primary production, living and dead phytomass, and soil organic matter for various ecosystems is used for calibration of the model. The suggested model enables to characterize terrestrial ecosystems as carbon sources or carbon sinks and to evaluate intensity of these sources and sinks. The model is applied for the European territory of Russia as a case study. Intensity of the total exchange carbon flux for this territory is evaluated. The obtained results allow to conclude that the given territory is the sink of carbon.

Distribution and annual net accumulation of above-ground dead phytomass and its influence on throughfall quality in a Mexican tropical deciduous forest ecosystem

The amount and annual net accumulation of above-ground dead woody material were quantified in a tropical deciduous forest in western Mexico. Three plots were located within a small watershed (16 ha) and distributed along a 150-m-elevation gradient (Upper, Middle and Lower plot). Total amount of above-ground dead phytomass (fine + coarse) was 27.2 Mg ha-1. Coarse dead category (branches + logs) made up 70.6% (19.2 Mg ha-1) of the total. The rest comprised the fine fraction, which was lying on the forest floor as surface litter. Of the total coarse dead woody mass, 70.8% was standing, hanging or still attached to live trees (13.6 Mg ha-1). Dead wood net accumulation was 6.6 Mg ha-1 y-1; 58% of this was coarse woody material and the rest comprised the fine litterfall fraction. The amount of standing, hanging/attached dead branches (2-20 cm circumference) varied significantly among plots, with the highest value in the Upper plot. Dead wood net accumulation was similar between the Upper and Middle plots, and significantly higher than the Lower plot. Compared to the intact canopy, the removal of dead mass (hanging/attached dead branches and standing dead logs) caused a significant decrease in throughfall nutrient concentration and nutrient flux by this pathway.

Simulation of Live and Dead Phytomass Formation and Transformation in Optimized Agrocenoses

The formation and transformation of live and dead phytomass in agrocenoses with a complex horizontal structure are described. These processes are demonstrated to be specific and to be determined by differences in the horizontal structure. Only agrocenoses of a “mosaic structure” (with square “parcels”) have optimal conditions for these processes.

Regrowth and Rest Requirements of Northern Wheatgrass following Defoliation

Degree-days required for standing crop and above-ground net primary production of northern wheatgrass (Agropyron dasystachyum [Hook.] Scribn., syn. Elymus lanceolatus [Scrib. &Smith] Gould) mowed to a 5-cm stubble to recover to levels similar to an unmowed control were determined in southwestern Saskatchewan. Nine, single mowing treatments and an unmowed control were established from early May through late August in 1991 and 1992 on a clayey range site at 2 locations. Green and dead phytomass and above-ground net primary production were determined for 2 to 3 years following mowing. Degree-days required for recovery of green and dead standing phytomass on mowed plots decreased linearly and were highly correlated (r2 = 0.64 to 0.99) with the number of days plots were mowed after 1 May. Regardless of mowing date, green phytomass did not recover to control levels the year of mowing. Each day mowing was delayed past 1 May reduced the number of degree-days required for total recovery of green phytomass on mowed plots by 15.7 in 1991 and 17.7 in 1992. Degree-days required for recovery of standing dead on mowed plots were reduced 17.6 in 1991 and 15.8 in 1992. Degree-days required for recovery of above-ground net primary production declined linearly (r2 = 0.67 and 0.99) as mowing was delayed after 1 May. More degree-days were required for the 1991 than 1992 plots. At least 2 and sometimes 3 growing seasons were required to accumulate enough degree-days to allow full recovery of green and standing dead phytomass and above-ground net primary production on mowed plots. For optimum sustained production, a grazing system should be used on northern wheatgrass-dominated rangeland with a 2 year rest period applied to paddocks after grazing.

Defoliation of a Northern Wheatgrass Community: Above- and Belowground Phytomass Productivity

A defoliation study was conducted on a fair condition, clayey range site that is potentially dominated by northern wheatgrass (Agropyron dasystachyum (Hook.) Scribn.) in south-central Saskatchewan. Vegetation was subjected to a factorial experiment with an initial defoliation in early-May, June, July, or August and repeated at 2- or 6-week intervals until mid-September in the same plots for 3 years. An undefoliated control was also included. Herbage removed, residual live, dead, total and root phytomass were measured. Defoliation reduced all yield components, with the exception of herbage removed. Residual live grass was reduced 37, 57, and 46%, respectively, in first second, and third years; the sedge and forb components of live residual phytomass generally were not affected by defoliation. Compared to control, dead phytomass was reduced 77% in the first year, 67% in the second, and 52% in the third year across treatments. Total herbage yield across defoliation treatments ranged from 68 to 93% of control Total live phytomass (herbage removed + residual live phytomass) in defoliated plots equaled control Herbage removal was greatest when initially defoliated in early July and thereafter at 2-week intervals. When defoliated at 6-week intervals residual live and dead phytomass were generally greater than when herbage was removed biweekly. Yields were higher when the first defoliation was delayed and repeated at 6-week intervals. Generally, root phytomass was not different among defoliation treatments, but total belowground phytomass was reduced 30% in the 0-30-cm depth after 3 year of defoliation. This northern mixed prairie ecosystem is sensitive to herbage removal. Maximum forage yield can be obtained if grazing is deferred until after peak growth in July.

Adaptive strategies of perennial grasses in South American savannas

Abstract. Morpho-fimctional features of perennial grasses in South American savannas are considered as adaptive strategies to cope with stress and disturbance factors of savanna environments. The tussock growth form, annual patterns of vegetative growth and reproductive phenology, allocation of carbon and nutrients, and accumulation of standing dead phytomass at the end of the dry season, are discussed in relation to water economy, resistance to drought, photosynthetic rates, growth rhythms, regrowth after drought and fire, seasonal translocation of critical nutrients and carbohydrates, and the total nutrient budget of the grass layer. Different strategies combining various morphological patterns, phenological alternatives and mechanisms for resisting drought and fire exist within the grass flora of each savanna community. The lack of adaptive responses to grazing by large herbivores is a major distinction from African savanna grasses. Many African grasses, either introduced in pastures or colonizing disturbed savannas, do show positive responses to defoliation, including compensatory growth and enhanced photosynthetic rates. Some guidelines for further research are suggested in order to disclose the mechanisms underlying this different behaviour of native and introduced savanna grasses.

Productivity and mineral cycling in an oak coppice forest 1. Structure and phytomass of the forest

Ecological studies were made on the structure and phytomass of the secondary coppice forest near Tokyo, which was dominated by a deciduous oak,Quercus serrata Thunb. Average height of dominant trees was about 10 m. The shoot density at the beginning of the study was 4,600 ha−1 of which 89.5% belonged toQ. serrata. During the subsequent two growing seasons 8.3% of shoots, mainly small ones, died. All the tree shoots in a 10 m×10 m quadrat were cut and most of the underground parts were dug out. The phytomass calculated by the allometric relations of the dry weight of each plant organ to the square of DBH (D 2) agreed fairly well with the values directly weighed. The average phytomass of the overstory trees was 906 kg a−1. The leaf area index (LAI) of the canopy was 3.85. Phytomass of the undergrowth, mainly a dwarf bamboo,Pleioblastus chino Makino, was 91.8 kg a−1 with LAI of 3.46. The dead phytomass in the stand was 177 kg a−1, so the phytomass alive and dead amounted to 1,170 kg a−1. Heavy self-thinning of the coppice forest is discussed in relation to the rapid development of the log-normal distribution of tree sizes and to the large allometric constants for leaf and branch weight toD 2.

Contribution to the ecology ofStipa species in central Europe: Distribution of mineral elements in soils and phytomass

In 1963, 1964 and 1965, a comparative ecological study was made of the distribution of mineral elements in the soil and phytomass of some Stipa species, viz.Stipa capillata L., S. pulcherrima C. Koch,S. joannis Celak.,S. dasyphylla Cerň.,and S. stenophylla Cerň. in various locations of Central Europe. In all species and sites studied, chemical analyses of the soil, fresh phytomass (shoots and roots) and dead phytomass were made, together with relevant statistical evaluation. IndividualStipa species differ according to their mineral composition. In comparison with fresh green plant material, the old dead plant material shows a marked increase in ash, calcium, and natrium content. Potassium, nitrogen, and phosphorus show a decrease in the dead plant material. The mineral composition of the roots differs considerably from that of green plant parts: the roots have much higher ash, phosphorus, calcium and natrium content, and lower organic matter, nitrogen, and potassium content. On the basis of the data collected, an attempt was made to estimate cycling of the individual mineral elements.