Stages Of Vegetation Succession Research Articles

Improvements in soil quality with vegetation succession in subtropical China karst

Secondary vegetation succession can alter soil functions and quality. However, data on changes to soil quality at different stages of vegetation succession in karst areas of southwest China is limited. This study aimed to evaluate the effects of different vegetation succession on soil quality and further to identify the factors that influencing soil quality. Secondary forest, shrub, grass, and cropland (as a reference) were selected and sampled in the subtropical karst of southwest China. Soil quality index (SQI) was developed by two methods of Total Data Set (TDS) and Minimum Data Set (MDS). Based on principal component analysis (PCA), soil organic carbon, silt, available phosphorous, available potassium, soil thickness, and soil water content were identified as the most representative indicators for the MDS. Both methods showed that the highest SQI values were observed in secondary forest, followed by shrub and grass, and the cropland values were the lowest. This showed vegetation succession significantly influenced on soil physiochemical properties and thus on soil quality. MDS could adequately represent TDS to quantify the effects of vegetation succession on soil quality since similar SQI results were derived from the two methods (R2 = 0.68, P < 0.01). The influencing factors explained about 75% of the total variation in SQI using a generalized linear model. Vegetation types accounted for the largest proportion of the SQI variability followed by restoration time, indicating these factors significantly affect soil quality during vegetation succession. In general, vegetation succession significantly influenced soil properties, and also has long-term and positive effects on soil quality during vegetation restoration. This study helps to understand the changes in soil quality during vegetation succession and provides guidance for the sustainable management of revegetation in subtropical karst regions in China.

黄土高原天然次生林植被演替过程中土壤团聚体有机碳动态变化

土壤团聚体物理保护是促进有机碳积累主要机制之一。以黄土高原子午岭林区天然次生林植被演替群落为对象，研究从农田、草地（白羊草，Bothriochloa ischaemum）、灌木林（沙棘，Hippophae rhamnoides）、先锋林（山杨，Populus davidiana）到顶级林（辽东栎，Quercus liaotungensis）5个植被演替阶段0-20 cm土壤团聚体稳定性和团聚体有机碳的动态变化，并分析团聚体有机碳的影响因素。结果表明：土壤团聚体稳定性随着植被演替显著提高（P<0.05），顶级林的团聚体稳定性最高；土壤有机碳含量和各粒径土壤团聚体（> 2 mm、2-0.25 mm、0.25-0.053 mm、<0.053 mm）有机碳含量均随着植被演替而增加。除草地0.25-0.053 mm团聚体有机碳含量最高外，其他演替阶段均为0.25-2 mm粒径最高。根系生物量、凋落物生物量、微生物生物量碳、团聚体稳定性均与团聚体有机碳含量呈显著正相关关系（P<0.05）。总体而言，长期植被演替有助于团聚体稳定性和团聚体有机碳累积。;Vegetation restoration plays an important role in soil structure and nutrients. The effects of vegetation restoration on the aggregate stability and soil carbon storage have been widely studied, but the distribution of aggregate associated organic carbon and the effects of plants on aggregate associated organic carbon in the secondary forest succession are still unclear. This paper studied the stability of soil aggregates and the changes of soil aggregate-associated organic carbon under the succession sequence of the secondary forests in Ziwuling forest region of the Loess Plateau, China. We discussed the dynamics of aggregate-associated organic carbon and its influencing factors following the secondary forest succession. In the field investigation, five vegetation succession stages were selected:farmland (CL), grassland (GL), shrub (S), pioneer forest (PF), and climax forest (CF). Soil samples in 0-20 cm were collected and the aggregates were separated by wet sieving. The stability of aggregates was characterized by mean weight diameter (MWD), geometric mean diameter (GMD), and percentage of water stable aggregates (WAS). The organic carbon, root biomass, litter biomass and microbial biomass carbon (MBC) of soil and aggregates were measured. The dynamics of soil aggregate-associated organic carbon and its influencing factors were analyzed. The results showed that soil organic carbon contents increased with vegetation succession, which showed that CF>PF>S>CL, and the organic carbon contents of aggregates increased more significantly from grassland to pioneer arbor stage. The succession of vegetation communities significantly increased the content of soil organic carbon. The stability of soil aggregate increased significantly with vegetation succession (P<0.05). The stability of soil aggregate in climax forest was the highest, and the contents of macroaggregate>0.25 mm in pioneer forest and climax forest were higher than that in farmland. The organic carbon contents of soil aggregates with different particle sizes increased with vegetation succession, and the organic carbon content of 2-0.25 mm was the highest in each succession stage. The stability of aggregates was positively correlated with the soil organic carbon. Root biomass, litter biomass and the MBC were significantly positively correlated with aggregate-associated organic carbon content. The main factors affecting soil organic carbon contents of aggregates were different in different particle sizes. Except the stages of vegetation succession, soil total organic carbon, litter biomass and soil aggregate stability were the main factors affecting the organic carbon content in the macroaggregates (> 0.25 mm), middle aggregates (0.25-0.053 mm), and microaggregates (<0.053 mm). The study suggests that vegetation succession plays an important role in the stability of aggregates and the fixation of organic carbon in aggregates.

Characteristics of Physical and Chemical Properties of Soil in Different Reclamation Years of Opencast Coal Mine Dump in Grassland

Taking the reclamation waste dump of the open-pit mining area in the east of Inner Mongolia Steppe as our study area, we sampled field investigation and laboratory measurements to study the changes of soil physical and chemical properties in the waste dump of the open-pit mining area during its recovery years. The objective of this study was aiming to provide theoretical support for the ecosystem restoration and reconstruction in the open-pit mining area of grasslands in the Northwest of China. The results showed that: 1) the mechanical composition of soil all layers in different reclamation years was mainly composed of silt, except for 20-30cm; the silt content was significantly higher than the control area (CK), and the silt content of surface soil (0-5cm) in reclamation 3 years (2016) was significantly higher than CK, but the sand content was significantly lower than CK; 2) In the early stage of vegetation restoration and succession, the physical and chemical properties of soil in different reclamation years were significantly different. With the increase of reclamation years, TOC and TN content decreased, but TP content did not change significantly during reclamation years. Based on the above results, the change characteristics of soil physical and chemical properties in the early stage of vegetation restoration succession were discussed. The research results have certain theoretical significance and practical guidance value for the ecological restoration and reconstruction of open-pit mining areas in the north of Northwest China.

Shift of potential natural vegetation against global climate change under historical, current and future scenarios

Potential natural vegetation (PNV), the final successional stage of vegetation, plays a key role in ecological restoration, the design of nature reserves, and development of agriculture and livestock production. Meteorological data from historical and current periods including the last inter-glacial (LIG), last glacial maximum (LGM), mid Holocene (MH) periods and the present day (PD), plus derived data from 2050 and 2070, in conjunction with the Comprehensive and Sequential Classification System (CSCS) model, were used to classify global PNV. The 42 classes of global PNV were regrouped into 10 groups to facilitate analysis of spatial changes. Finally, spatio-temporal patterns and successional processes of global PNV as well as the response to climate changes were analysed. Our study made the following five conclusions. (1) Only one missing class (IA1 frigid-extrarid frigid desert, alpine desert) arose in periods of LIG, MH, 2050, and 2070 for global PNV. (2) The frigid-arid groups were mainly distributed in higher latitudes and elevations, but temperate-humid groups and tropical-perhumid groups occurred in middle and low latitudes, respectively. Temperate zonal forest steppe, warm desert, savanna and tropical zonal forest steppe increased, while six other groups decreased. (3) The conversion from temperate zonal forest steppe to tundra and alpine steppe from LIG to LGM occupied the largest area, indicating a drastic shift in climate and the associated response of terrestrial vegetation sensitive to climate change. (4) The CSCS could be used to simulate the long-term succession of global PNV. (5) As a consequence of global warming, forests shifted to the northern hemisphere and Tibet, areas with much higher latitude and elevation. The PNV groups with greater shift distance revealed the more serious effects of global climate change on vegetation.

Diminished rhizosphere and bulk soil microbial abundance and diversity across succession stages in Karst area, southwest China

Soil microorganisms are important for plant nutrients and health. However, our understanding of soil microbial communities in the rhziosphere and bulk soils as plant succession stages increased in the Karst area remains unclear. Here, we evaluated how the bacterial and fungal communities of rhizosphere and bulk soils respond to different vegetation succession stages: grassland (GR), shrubland (SH), secondary forest (SF), and primary forest (PF). The abundance and composition of bacteria and fungi were determined by qPCR and MiSeq high-throughput sequencing methods, respectively. The results showed that the abundance and diversity in rhizosphere and bulk soils were diminished among vegetation succession stages. We found that SOC led to high microbial abundance in GR and SH during the period of primary succession stages, while AP potentially led to low abundance of microbes in the PF and SF of subsequent succession stages. Additionally, the OTUs shared by four succession stages (common OTUs) comprised approximately 87.61 ‐ 98.90% of the total relative abundance of bacteria and fungi in the rhizosphere and bulk soils, which indicated that the composition of fungi and bacteria in these environments were similar across different succession stages. pH might be an important driving factor involved in the similarity of bacterial and fungal compositions among different succession stages. However, the relative abundance of bacterial and fungal phyla across the four vegetation stages was different, and also determined by multiple soil properties. pH was the main factor determining bacterial community structure in rhizosphere soils, whereas SOC was the principal determinant of the same parameter for bacteria in bulk soils, and in both the rhizosphere and bulk soils for fungi. Overall, our results suggested that bacterial and fungal communities in the rhizosphere and bulk soils diminished with vegetation stages, which may provide evidence that mechanisms underlying the soil microbe-driven vegetation succession in the Karst area of southwest China.

Temporal and Spatial Variation Patterns of the Environmental Elements in the Sediments of the Liaohe Estuary and the Related Influencing Factors

Remote sensing images, field survey data, and historical monitoring data are collected to analyze the historical change trend and spatial variation rules of sediment quality of the Liaohe Estuary and further investigate the effects of sea-area utilization type and vegetation succession stage on the variation patterns of environmental elements in the sediments. The results showed that the quality of the sediments in the Liaohe Estuary is overall favorable, and the average contents of various elements all satisfy the quality standards of first-grade sediments. The nutritive elements in the sediments exhibit obvious zonal distribution patterns, while heavy metals are randomly distributed and exhibit no obvious patterns. The effect of sea-area utilization type on the enrichment of pollutants in the sediments exhibits certain significant differences, suggesting that the distributions of heavy metals and pollutants are subject to human activities and exhibit certain randomness. The main control factors are significantly different at different vegetation succession stages. Specifically, the vegetation distribution in the initial succession stage is mainly affected by salinity; with the transition from halophytic vegetation to terrestrial vegetation, the inherent correlation between vegetation distribution characteristics and the contents of total organic carbon, total nitrogen, and total phosphorus increase gradually. Meanwhile, the content of heavy-metal pollutants exhibits no significantly inherent correlation between the distributions of the plant community.

Promotion function of forest vegetation on the water & carbon coupling cycle in karst critical zone: Insights from karst groundwater systems in south China

The earth is gradually turning green due to afforestation, especially in China. Because the carbon cycle is driven by the groundwater cycle in karstification, the process of water & carbon coupling cycle (PWCC) in karst forest area can not only promote vegetation growth but also enhance chemical weathering processes of carbonate rocks to absorb more CO2. Therefore, carbon sequestration can occur during the process of ecological restoration in karst areas. However, forest respiration also increases with the vegetation growth which can produce extra CO2 back to atmosphere. To study the promotion function of forest vegetation during different succession stages on the PWCC in karst critical zone, three karst groundwater systems with different vegetation coverages (a native forest, a secondary forest during reforestation and a crop area in rural land) are chosen in southwest China. Their long-term monitoring of indicators, including precipitation (P), partial pressure of air CO2 (PCO2), groundwater discharge (Q), hydrochemical and isotope components, was conducted. The results indicated that part of CO2 produced by forest respiration diffuses into the atmosphere as a carbon source, and the remaining dissolves into the groundwater, thereby increasing corrodibility. The carbon sequestration mechanism differs at different vegetation succession stages. The secondary forest development stage displays an obvious carbon sequestration effect during the process of rocky desertification control. When the succession stage approaches the top-level ecosystem, the carbon sequestration effect descend sharply until the net carbon sequestration can be ignored.

Impact of vegetation succession on leaf-litter-soil C:N:P stoichiometry and their intrinsic relationship in the Ziwuling Area of China\u2019s Loess Plateau

Long-term natural vegetation succession plays a substantial role in the accumulation and distribution of plant and soil C:N:P stoichiometry. However, how plant and soil C:N:P relationships or ratios change along with successional stages over a century in the severely eroded areas remain unclear. These were measured over a 100-year natural succession in five successional stages from annual grasses to climax forests. The results show that natural succession had significant effects on carbon (C), nitrogen (N) and phosphorous (P) concentrations in leaf-litter-soil and their ratios in severely eroded areas. Nitrogen concentrations and N:P ratios in leaf and litter increased from annual grasses to the shrub stage and then decreased in the late successional forest stages. Leaf P levels decreased from annual grasses to shrub stages and did not significantly change during late successional stages. Litter P concentration decreased in the early successional stages and increased during late successional stages, with no overall significant change. Soil C and N concentrations and C:N, C:P and N:P ratios increased with successional stages. Soil C and N concentrations decreased with the increasing soil depth. Both were significantly different between any successional stages and controls (cropland) in the upper 10 cm and 10–20 cm soil layers. Leaf N:P ratios may be used to indicate nutrient limitations and this study suggests that plant growth during the grass stages was limited by N, during the shrub stage, by P, and during the forest stages, by both of N and P. In addition, there were close correlations between litter and leaf C:N:P ratios, soil and litter C and N levels, and C:P and N:P ratios. These results show that long-term natural vegetation succession is effective in restoring degraded soil properties and improving soil fertility, and provide insights into C:N:P relationships of leaf, litter and soil influenced by vegetation succession stage.

A managed realignment in the upper Bay of Fundy: Community dynamics during salt marsh restoration over 8 years in a megatidal, ice-influenced environment

Salt marshes are ecologically and globally vital ecosystems. Unfortunately, world-wide salt marsh loss has been extensive, and until recently there has been little effort to undo the loss of ~30,500 ha of salt marshes in Bay of Fundy, Canada, since European colonization. To better understand salt marsh restoration in the upper Bay of Fundy, we monitored sediment deposition and community dynamics in 2 managed realignment salt marsh restoration sites and 2 reference sites from 1 y pre-breach to 8 y post-breach in Aulac, New Brunswick. Because of the initial elevational disparity (~2 m) between site types, substantial amounts of sediment were deposited immediately after breaching the old dike (>50 cm in some locations). After 7–8 y, mean sediment deposition was 34–67 cm in the restoration sites, and 6 cm in a reference site. To date, we identified three stages of vegetative community succession: (i) rapid deposition of unconsolidated sediment and loss of terrestrial vegetation, but Spartina pectinata remained (1 y post-breach), (ii) colonization and spread of S. alterniflora and loss of S. pectinata (2–5 y post), and (iii) high percent cover and decreased spatial variability of S. alterniflora (mean stem density: 345 stems m−2, 6–8+ y post). We expect the fourth stage of vegetative community succession will be defined by spread of S. patens throughout restoration sites. Invertebrate community on emergent marsh and water column community in salt pools were variable and lagged behind vegetative community. Our study reported the first managed realignment in Maritime Canada, and the first such realignment in an ice-influenced and megatidal (~14 m tidal amplitude) region.

Implications of heathland management for ant species composition and diversity – Is heathland management causing biotic homogenization?

Maintaining heathland ecosystems in an early successional stage is a major aim of most management regimes, such as harvesting, burning or grazing. However, how these types of management affect important ecosystem engineers such as ants, are poorly understood. We registered the density of ant colonies in managed plots (harvested, burned and grazed) and plots with long succession (so forth unmanaged) across six different dry lowland heath sites. With these data, we investigated how composition and richness varied across management regimes and elucidated the direct effects of management from the indirect effects of environmental covariates. Ant species richness was significantly lower in managed plots compared to unmanaged plots. Harvest and grazing regimes were associated with the lowest richness, while intermediate richness was registered in burned plots. Smallest variation in species composition was found in the harvested, followed by grazed, burned and unmanaged heathlands. There was an overall negative association between abundances of organic mound forming species and all types of management, while non-mound forming species where negatively affected by grazing. In addition, Non- and organic mound forming species were indirectly affected through decreasing vegetation complexity. Only ants with mineral mounds benefitted from grazing and burning, but not from harvesting. To promote ant richness and abundance, we propose to downscale the frequency and intensity of management, as well as designating certain parts of the heathland area for later successional vegetation stages.

Highly patterned primary succession after fluvial deposition of mining waste

This study examined early stages (3-5 years) of spontaneous primary vegetation succession on a model locality drastically altered by long term fluvial deposition of copper tailings in Eastern Serbia. In a large-scale survey, 115 samples of herbaceous vegetation (with a total of 75 species) were harvested from standardized 1m x 1m quadrates, and concomitant soil samples collected and their relevant physicochemical properties analysed. Primary succession depended on the establishment of five pioneer species (Rumex acetosella, Agrostis capillaris, Calamagrostis epigeios, Persicaria lapathifolia and Chenopodium botrys). Unconstrained ordination showed very clear vegetation gradients, significantly correlated with the key soil constraints (from Cu excess to low pH and nutrient deficiency), while the distribution of the five edificatory pioneers showed high degree of dependence on the micro-level habitat conditions. This work demonstrates that in such a complex setup with severe abiotic filtering, sufficient sampling effort can reveal strong patterns in a process commonly considered very stochastic.

ОСОБЛИВОСТІ РОСЛИННОЇ СУКЦЕСІЇ У КАР'ЄРІ ЦЕГЕЛЬНОГО ЗАВОДУ В С. НОВИЙ ТІК (РІВНЕНСЬКА ОБЛАСТЬ)

Termination of quarries is the reason for the settlement of pioneer plants, which exploit "free" areas of soil in a certain sequence, called successions. The theoretical foundations of restorative plant successions in the quarries are still relatively poorly developed, although there is much empirical research on the subject. The object of our study is the quarry of a brick factory located in the eastern outskirts of the village. Novy Tik (Demydiv district, Rivne region) in the central part of Volyn height, 27 km south of Lutsk. Since 2008, when the brick factory ceased to function in the quarry, there has been a primary plant succession, which is now at a youth stage and is characterized by an increase in biodiversity. As of autumn 2019, 72 plants spices have been identified in the quarry, including 6 species of trees, 1 species of shrubs and 65 species of grasses. According to the results of the systematic analyze, the Asteraceae and Fabaceae families predominate. The prevailing ecological groups of plants in the quarry are determined: in relation to lighting prevail heliophytes; in relation to the thermal regime, the largestproportion is made up of temperate-warm climate species; in the vegetation cover at the present stage of succession, Central European species prevail. Based on the analysis of the population of plant associations and the appearance of interspecific and intraspecific competition, it is established that plant succession in the studied quarry is at a youth stage. Also, heterochrony and microzonal differentiation of succession processes in different parts of the quarry are found. The difference in the passage of succession stages depending on the features of the relief is taken as the basis for the quarry microzoning. It has been established that at the present stage of vegetation succession, the determining factor in the qualitative and quantitative composition of plant communities is abiotic quarry factors, especially morphology and relief dynamics and lithological-stratigraphic structure of deposits. The initial stage of soil succession was revealed, which became possible due to the accumulation of a significant amount of mortmass in recent years.

Different Stages of Aquatic Vegetation Succession Driven by Environmental Disturbance in the Last 38 Years

In recent years, investigating the trend of aquatic plant diversity in response to different disturbance events has received increasing interest. However, there is limited knowledge of the different stages of aquatic vegetation succession over a long period in eutrophic lakes. In this study, we analyzed aquatic plant species richness and its relation to the physical and chemical characteristics of water in Chenghai Lake for the period of 1980–2018. This study shows that the richness and distribution of aquatic vegetation in Chenghai Lake are related to chlorophyll-a concentration, dissolved nutrients, base cations, and micronutrients. The results show that the long-term succession of aquatic plants in this lake classified in different stages: (I) A peak in species richness occurred at an intermediate stage that lasted from 1980 to 1992, and this was caused by more aquatic species being able to coexist since the competition for resources was lower; (II) after 26 years of secondary succession (1992–2018), the diversity and distribution area of aquatic plants gradually declined because pioneer species or human activities may have altered habitat conditions to render habitats less beneficial to pioneer species and more suitable for new aquatic plant species. Thus, species diversity and growth performance of aquatic plants in their communities may be useful indicators of Chenghai Lake’s trophic status, especially during the transition period from a mesotrophic lake to a eutrophic one.

Response of shallow karst fissure soil quality to secondary succession in a degraded karst area of southwestern China

Vegetation restoration is one of the effective means to control soil erosion and an essential method of eco-environmental restoration in fragile karst rocky desertification areas. The shallow karst fissure (SKF) filled with soil has become one of the most important root habitats in this area. It is essential to scientifically evaluate the soil quality of SKF and to provide a basis for matching species with sites. Here, we explore and gain insight into the characteristics of the response of the physicochemical properties of SKF soil to different stages of vegetation succession. Additionally, we develop a synthetical assessment system to determine soil quality. The key results were as follows. Significant differences were found in the soil properties between the surface and the SKF. Compared with the surface, the SKF soil structural property was poor, but the water conditions were better. The soil nutrient content of the SKF was significantly (p < 0.05) lower than that of the surface, but the differences in soil nutrients inside the SKF were not significant. In addition, the soil quality indicator (SQI) values of the SKF soil were significantly (p < 0.05) lower than those of the surface and decreased gradually with soil depth. Moreover, secondary succession significantly (p < 0.05) improved the soil properties and, thus, the soil quality. With recovery of vegetation, the soil properties of the surface and the SKF were significantly improved. The difference in the soil properties and the SQI values between the surface and underground gradually narrowed with succession. Furthermore, the thickness of the SKF soil was more than twice that of the surface soil. Overall, the soil properties and the soil quality of the SKF were relatively poor, but they were greatly improved with vegetation restoration. The SKF habitat can be the preferred habitat for vegetation restoration and is more favourable for plants with deep roots and a higher root penetration ability. The results of this study can supply references for future studies on karst rocky desertification control and vegetation restoration in the karst area of southwestern China, northern and central Vietnam, the islands of Java, Indonesia and Kampot Province, southwestern Cambodia and other karst regions with the same ecological background.

Effects of forest wildfire on inner-Alpine bird community dynamics.

As major disturbance agents, natural catastrophes impact habitats, thereby maintaining the dynamics of ecological communities. Such discrete events are expected to positively affect biodiversity because they generate high habitat heterogeneity and thus numerous ecological niche opportunities. Species typical of open and semi-open habitats, which are often of high conservation concern in modern anthropized landscapes, may benefit most from recurrent natural catastrophes that regularly reset ecosystems. We investigated bird community changes and species-specific responses to wildfire at two recently burnt temperate, montane-subalpine forest stands in an inner-Alpine Swiss valley, with a special focus on red-listed and conservation priority species. We compared bird community changes in burnt forests (spanning 13 years) with bird assemblages occurring in adjacent non-burned forest stands that served as quasi-experimental controls. Strong species-specific responses to wildfire were evidenced, resulting in a dramatic post-fire decrease in overall bird abundance and species richness. Yet, red-listed bird species and conservation priority species in Switzerland were substantially more common in burnt than in control forest stands. Many red-listed species showed a bell-shaped numeric response to wildfire over time, suggesting low habitat suitability just after fire, high habitat suitability at pioneer and early stages of vegetation succession, followed by a long-term decrease in suitability while vegetation becomes denser, especially at ground level. As established for Mediterranean regions where wildfires are especially frequent, this study shows that forest fires can also boost the populations of red-listed and priority bird species typical of open and semi-open habitats in temperate biomes. Prescribed forest fire might represent a management option for preserving threatened elements of biodiversity despite the intense public debate it will trigger.

Dynamics of soil microbial communities following vegetation succession in a karst mountain ecosystem, Southwest China

The interaction between soil property and soil microbial community in karst area still remains an open question. The characteristics of soil physicochemical properties and microbial community structure and their relationship under five vegetation succession stages (grassland, shrub land, secondary forest, plantation forest, and natural forest) at two soil depths (0–10 cm and 10–20 cm) were explored in a karst mountain ecosystem. We found that soil moisture content (SMC) and pH increased with soil depth across vegetation succession. The highest content of soil nutrients was found in the natural forest stage at both soil depths. The total PLFAs, the abundance of Gram-positive (GP) bacteria, actinomycetes (ACT), fungi, and arbuscular mycorrhizal fungi (AMF) were significantly (P < 0.05) related to variations with soil total carbon (TC) and total nitrogen (TN). Furthermore, the distribution of soil microbial community distinctly differed in vegetation succession both at two soil layers which was demonstrated by Principal-coordinates analysis. Redundancy analyses patterns indicated that soil TC and TN were positively related to cy19:0 and 10Me 16:0, but an opposite relationship with a15:0. Changes of soil microbial communities were significantly determined by vegetation succession, and soil microbial community structure can be a sensitive indicator to reflect the stabilization of karst mountain ecosystem, southwest of China.

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.&#x0D; 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.&#x0D; 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.&#x0D; 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.&#x0D; 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.&#x0D; 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.&#x0D; 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.

Responses of soil bacterial communities, enzyme activities, and nutrients to agricultural-to-natural ecosystem conversion in the Loess Plateau, China

Soil microbial communities play critical function during nutrient cycling. However, with the increasing nutrient input into terrestrial ecosystems from human activities, the responses of soil microorganisms to the aboveground vegetation across agricultural-to-natural succession stages are still poorly understand. The aim of this study was to evaluate the changes of soil microbial communities in three typical succession stages (the cropland, the grassland, and the brushland, respectively). A field experiment was carried out in an ecological restoration region. Soil samples were collected from three succession stages (the cropland, the grassland, and the brushland) based on their well-dated successional chronosequence in July 2016. Illumina MiSeq sequencing was used to identify the bacterial community structures. The responses of soil bacterial communities and its relationships with soil physicochemical properties and enzyme activities were assessed. The results showed that soil nutrients (soil organic carbon (SOC), total N, and NH4+) and enzyme activities (β-1,4-glucosidase and phosphatase) were significantly increased across the conversion from agricultural to natural ecosystem, and the enzyme activities were significantly affected by SOC and total N. It indicated that vegetation restoration greatly improved soil quality and nutrient cycling rates mediated by microbial metabolisms. Furthermore, there were no changes in soil bacterial community structures during the three vegetation succession stages, which implied the stability and adaption of microbial communities under the vegetation succession in semiarid climate. It should be noted that Firmicutes taxa were more sensitive than other taxa during natural vegetation recovery. Structural equation model (SEM) revealed that soil nutrients (soil organic matter (SOM) and total P), element stoichiometry (SOC:total P), and extracellular enzyme activities (urease and alkaline phosphatase) were dominant factors to shape the relative abundance of Firmicutes. Firmicutes can be considered as bio-indicators to monitor soil quality and nutrient turnover during natural vegetation recovery. This study presents better understanding about the connections among soil nutrient cycling, enzyme activities, and soil bacterial communities during vegetation natural restoration, especially in typical ecological critical zone.

Returning home after fire: how fire may help us manage the persistence of scrub-steppe specialist bird populations

Semi-natural open habitats have drastically changed in the last few decades due to agricultural intensification and rural depopulation. Steppe-birds, and especially those adapted to primary stages of vegetation succession, are threatened by an increase in scrub cover, and management actions are being applied to reverse scrub encroachment and restore habitat suitability in semi-natural open habitats. In this paper we evaluated for the first time, the long-term effects of a wildfire on habitat structure, vegetation productivity, and the associated response of an endangered scrub-steppe specialist bird, the Dupont’s Lark Chersophilus duponti. Wildfire occurred in a Mediterranean steppe of central Spain dominated by permanent community of dwarf cushions scrubs. Bird abundance was evaluated by line transects in the burnt and unburnt areas 3 years prior to the fire and 4 and 7 years after the fire. We quantified changes in habitat structure at fine scale level through vegetation sampling points and in vegetation productivity by estimating the Normalized Difference Vegetation Index (NDVI). Fire had strong effects for at least up to 4 years after the fire, when lower NDVI values, less scrub cover and fewer, but not significant, number of males were detected in the burnt area with respect to the pre-fire conditions. Seven years after fire most vegetation variables measured did not differ between areas, number of males detected within the burnt area was recovered and NDVI values in burnt area were slightly recovered but were significantly lower than in control area. Slow regeneration of the scrub cover after fire explained the unsuccessful occupation of the burnt area by the Dupont’s Lark up to several years after fire. The more dispersed and shorter habitat created by fire 7 years after the fire seems to be more suitable for the species than that in control areas. The large number of males around the burnt area may have played a role in the recolonization process. In sum, vegetation recovery and the presence of a low scrub-steppe specialist, as the Dupont’s lark, suggests that fire management could be integrated into conservation plans to effectively manage scrub encroachment processes in Mediterranean scrub-steppes.

Structure and factors of forest birds diversity forming in the Ishim river area (Russia)

The paper studies the relationship between specific parameters of habitats (the forest area along the route, the average age of the forest, the closure of the crowns, the condition of the crowns, the type of anthropogenic impact, the stage of vegetative succession, the wetting of the forest), the abundance of birds, Shannon and Simpsons indices of the species diversity of forest ornithocenosis. This study is based on the materials of field bird records conducted in the seasons of 20142016 on 28 permanent routes in the forest habitats of the Ishim River area (Russia). A statistically significant effect of the anthropogenic impact on the Shannon diversity index and the significant influence of the plant succession stage on Shannons species diversity index and the abundance of birds have been established by the method of one-way analysis of variance using the nonparametric Kraskel-Walliss criterion. It is shown that the maximum value of Shannons index of variety is characteristic for the ornithocenosis of recreational forests; the one close to the maximum is in forests in which grazing is carried out. In the course of plant succession, there is initially an insignificant increase in the total abundance of birds, then a significant decrease in it, as well as a sharp decrease of Shannons diversity index. The obtained results show that the anthropogenic load in form of cattle grazing and recreation conditions an increase in forest habitats heterogeneity and thereby contributes to an increase in bird species diversity.