Long-established Forest Research Articles

Естественное возобновление в смешанных разновозрастных древостоях на урбанизированных территориях Москвы

The effectiveness of forests therapeutic impact is based on its species’ and age structure, silvicultural features, biological productivity, regenerative ability, forest management intensity and its methods. The processes of natural regeneration of a forest stand and its growth are the main factors of the forest’s ecosystem proper functioning and a disruption in these processes can lead to a transformation of the whole biocenosis, a change of a typological community. Technogenic pollution is a huge stress factor for trees, and its impact is especially evident in regions with a high concentration of industrial facilities, namely, in Moscow city. One of the most serious consequences of technogenic pollution is the deterioration of long-established forests, which subsequently may reduce its ability to adapt to ever-changing environmental conditions and its protective functions. The article discusses issues regarding the natural regeneration of forests on urbanized territories of Moscow on the example of the Forest experimental station of the Russian State Agrarian University - Moscow Timiryazev Agricultural Academy. The natural regeneration of tree species is one of the most relevant issues of forest and park management. The aim of this project is to estimate natural regeneration in mixed forest stands of urbanized areas, to provide recommendations on the organization of forest regeneration measures in urban environments. The article provides methods and results of field research and recommendations on reforestation measures under these conditions. The research of the cenobiotic connections and the undergrowth of different species with key elements of grass cover in its habitat, will allow a more positive dynamics in the use of natural resources, which will contribute to preservation and restoration of forests.

Woody species richness and turnover in expanding Mediterranean forests: a story of landscape legacies influenced by climatic aridity

The current expansion of forests in Europe is expected to be affected by transient colonization credits (i.e. species deficits compared to long-established forests), especially due to plant species with limited dispersal ability. We aimed to disentangle the role of forest connectivity and climatic aridity in the assembly of woody plant communities present in expanding Mediterranean forests by studying species with different types of dispersal. We used a space-for-time approach in recent (post 1980), middle-aged (1956–1980) and long-established forests (pre-1956) along an aridity and forest connectivity gradient in NE Spain. We recorded woody canopy and understory species and classified them as either vertebrate-, non-vertebrate- or human-dispersed species (i.e., crops). Species turnover between forests of different ages was limited to particular species and did not give rise to colonization credits determined by plant dispersal type. Connectivity and aridity drove understory richness in a similar way in forests of different ages. Within this general pattern, non-vertebrate-dispersed species were especially promoted by benign conditions. Sites with high forest connectivity had either the richest or the most impoverished understories given, respectively, low or high aridity. Thus, the rescue effect was modulated by aridity, which acted as a limiting factor. Mediterranean forest richness and composition are strongly dependent on climatic constraints and the ‘rescue effects’ (connectivity) originating in surrounding forest areas. These two factors shape the composition of expanding forests in different ways depending on the ability of species to disperse.

Land use legacies drive higher growth, lower wood density and enhanced climatic sensitivity in recently established forests

Europe is undergoing significant forest expansion due to the abandonment of rural areas driven by economic and demographic changes. Recently established forests provide key ecosystem services such as habitat provision and increased carbon stocks. However, we lack understanding of whether past land use might alter their resilience to climate change compared with long-established forests. Forests established in former agricultural areas may benefit from land use legacies resulting in higher fertility, yet such a benefit might turn into a disadvantage if it involves changes in functional attributes that lower their ability to cope with negative climatic events (e.g. droughts). Here we examined whether recently (post 1956) and long-established (pre 1956) beech forests in Catalonia (NE Spain) differ in their growth patterns, wood density, sensitivity to climate and response to extreme climatic events. Our results indicate higher growth (32%) and lower wood density (3%) in trees from recently established forests, even when controlling for tree age and competition. In addition, recently established forests showed a higher sensitivity to Standardised Precipitation-Evapotranspiration Index (SPEI), precipitation and temperature and to extreme negative and positive climatic events. In particularly wet years, recently established forests show twice the number of positive pointer years than long-established forests. Compensatory growth during positive years in recently established forests, may be driving the similar or even higher recovery and resilience detected after drought episodes. Nevertheless, the higher climatic sensitivity of the recently established forests, together with their greater growth and lower wood density indicates that they may be particularly vulnerable to future droughts. Such enhanced vulnerability might question their ability to contribute to carbon sequestration in the long term and emphasises the need to account for land use legacies to better predict future forest function as climate changes.

Seed longevity and dormancy state in an invasive tree species: Ailanthus altissima (Simaroubaceae)1

Successional tree species often form soil seedbanks, suggesting that extended seed dormancy may also facilitate regeneration in nonnative species. We examined seed dormancy in Ailanthus altissima, which is currently spreading into long-established forests of Europe and eastern North America. Ailanthus seeds were sewn into replicated nylon mesh bags and buried in 10 second-growth stands in southeast Ohio, USA. North- and south-facing slopes were included as a coarse-grained test for environmental control. Bags were recovered at 2-mo intervals and seeds were tested for viability and germination. Fifty percent of Ailanthus seeds survived the full length of the study (24 mo) after an initial phase of partial germination (51–79% of viable seeds). Remaining seeds returned to a state of induced dormancy, allowing a second flush of germination (3–28%) after 18 mo. After the first 5 mo no further decline in seed number was observed, suggesting persistence in the soil well beyond the 2-yr length of this study. No slope-aspect effect was observed. Long-term seed dormancy potentially facilitates Ailanthus invasion by buffering against extended canopy closure or allowing passive dispersal with movement of soil. Complete eradication of a population will depend on elimination of the soil seed bank, which may require many years. Management should avoid creating canopy openings near existing populations with the goal of suppressing sexual reproduction and seedling establishment.

Spatial structure develops early in forest herb populations, controlled by dispersal and life cycle.

Fine-scale spatial structure is an essential feature of plant populations, controlling pollination, herbivory, pathogen spread, and resource partitioning. Origins of spatial distribution are often obscure in long-established forests, but successional stands offer insight through their physical and compositional simplicity. We tested the hypothesis that spatial structure in forest herb populations arises through a nucleation process in which colonizing species transition from random to clustered distributions through clonal expansion, seed dispersal, and conformity to environmental gradients. Spatial structure was examined in a chronosequence of 40s growth stands in southeast Ohio, USA. Herbaceous vegetation was recorded in nested plots to describe the evolution of pattern across multiple scales. Spatial distribution was described as the variance:mean ratio of stem number plot-1, and compared between age classes and functional groups. Environmental influence was assessed as the marginal R2 value of environmental models predicting stem number. Herb species responded individualistically to stand age and environmental gradients, although all were to some degree clustered across age classes. Dispersal-limited, non-clonal, and annual species were most strongly clustered, suggesting the importance of seed dispersal range and population growth rate in determining spatial structure. Spatial distribution was weakly related to environmental variables. Clustered distributions established early in succession and remained stable for at least 80years. Pattern formation can be interpreted in terms of nucleation, as we hypothesized, but clusters form earlier than expected. The spatial structure of herb populations in deciduous forests appears to be governed by patterns established during colonization; environmental filtering appears to play a minor role.

Forest micro-environment develops through time: Changes in physical and structural heterogeneity follow abandonment from two forms of agriculture

Agriculture alters and homogenizes the physical environment, and persistent changes potentially affect community development in post-agricultural forests. We ask whether physical and structural development differs between second-growth stands of contrasting ages and agricultural histories. Formerly cultivated and pastured sites were expected to follow separate trajectories of succcessional development but eventually to converge as natural processes obscured the environmental legacies of agriculture. We used a replicated chronosequence to examine microenvironment development in successional stands over 80years following canopy closure and compared successional stands with a control group of long-established stands. Physical, edaphic, and structural variables were measured in each site. Microtopography increased through successional time, while canopy openness and soil bulk density declined. Formerly cultivated sites showed less microtopographic variation and higher bulk density than pastured sites, consistent with a history of plowing. Formerly cultivated sites showed spatial homogenization in microtopography, soil organic matter, and herb cover. Stands in the 61–80year age class did not differ significantly from long-established forest in any of the environmental variables or the spatial distribution of such variation. Our results suggest that 80years of forest development is sufficient for most environmental legacies of agriculture to fade, reducing their potential to influence plant community composition. However, contrasting land-use history is still evident for several decades and may contribute to community structure over that period.

Agricultural history drives structure and tree species composition of second growth forest over 100 years in southeastern Ohio, USA

AbstractQuestionMost modern forest in eastern North America has recolonized after abandonment from agriculture. Cultivation and pasturing, historically the dominant forms of agriculture, differ in their environmental legacies and potentially influence stand development following abandonment. We ask how the legacy of agriculture plays out in development of second‐growth stands, and whether tree community composition and structure differ between sites with contrasting land‐use histories.LocationSoutheast Ohio, USA.MethodsThirty‐five second‐growth stands were sorted into a replicated chronosequence of formerly cultivated and pastured sites spanning 80 yr. Stand age and land‐use history were determined from historical aerial photographs and from site characteristics including microtopography and soil profiles. In addition, a control group was selected consisting of long‐established forest stands showing no signs of agricultural disturbance. At each site stand composition and structure were described using the point‐centred quarter method.ResultsStand density declined and basal area increased through the chronosequence but neither pastured nor cultivated sites reached levels observed in the control group. Density decreased most dramatically between the 41–60‐ and 61–80‐yr age classes, consistent with competitive stand thinning. Tree community composition changed through time, reflecting a shift away from light‐demanding successional species and toward long‐lived, shade‐tolerant species characteristic of long‐established forests. Composition and structure did not differ significantly between cultivated and pastured sites, but individual species did show significant differences, with the greatest contrast evident shortly after abandonment.ConclusionsStand development following agriculture appears to be a process of convergence in species composition and density. Because most deciduous forest in eastern North America is <80‐yr‐old, these results suggest that most forest is still accruing biomass and has yet to reach a stable density and composition.

Ancient woodlands: modern threats

This review discusses the following adverse influences on long-established forests, wood-pastures, and savannas in Europe and other continents: destruction and fragmentation; depletion; pollution and eutrophication; fire and lack of fire; excessive shade; excessive numbers of deer; invasive species and cultivars; infilling of savanna; climate change; and globalization of plant diseases. Human influences on the world's mainland forests and savannas have been pervasive throughout the Holocene, to the extent that recovering 'virgin forest' becomes a somewhat nebulous conservation objective. Present and future threats arise both from increasing human activities and from withdrawal of the human activities that have shaped forests in the past. The severity of different threats depends on so many factors, especially the properties of different plants and animals, that generalization is impossible; however, in the long term, spread of pathogens is probably the most serious threat.

Ecology of streams draining forested and non-forested catchments in an area of central Scotland subject to acid precipitation

A study of 12 streams draining forested and non-forested catchments was made in an area of central Scotland where slow-weathering bedrock was predominantly quartzite, schists and slates. Sitka spruce (Picea sitchensis Carriere) was the most common tree species. Precipitation in the area had an annual mean pH in the range 4.3–4.5. Streams within the planted zone were always more acid than those outside and had higher concentrations of aluminium and manganese. With one exception, trout were absent from streams within long-established forests and planted salmon eggs (Salmo salar L.) died within a few weeks. A high proportion of such eggs survived in streams outside the forest. Siphlonurus lacustris Eaton was the only mayfly nymph found in the most acid streams in summer collections. In winter samples, mayfly nymphs, Heptagenia lateralis (Curtis) were found in only one forest stream but several species were present in the non-forested catchments. It is suggested that spruce forests can effectively collect acid pollutants which are subsequently washed out, thus accelerating the acidification of the soil. Streams therefore become increasingly acid as the neutralisation capacities of their catchments decrease.

POLLEN PROFILES FROM THE QUEEN CHARLOTTE ISLANDS, BRITISH COLUMBIA

Five peat sections were excavated from muskegs on Langara, Graham, and Moresby Islands of the Queen Charlottes with the primary purpose of reconstructing the postglacial plant succession and associated climatic and physiographic alterations. A secondary purpose was to support or disprove the geological and zoological data favoring the existence of refugia in which biota survived from preglacial or interglacial time. The oldest pollen record tends to support this contention. The record is older than any derived from sections heretofore studied on the northwest coast. Twenty-three plant entities are represented in the bottom sediments below the lodgepole pine maximum which in these other sections marks the oldest peat. In addition, 27% of the coniferous pollen at the base of the section is constituted of climax forest trees, thus implying the presence of long-established forest when pollen sedimentation began. The number and kinds of pollen in the basal peat favor the interpretation that vegetation persisted in refugia through at least the last glaciation. The pollen profiles further corroborate earlier findings for changes in land–sea level relations and for the following postglacial climatic sequence: early cool-moist, warmer and drier (thermal maximum), and late cooler and wetter.