Pine Forest Vegetation Research Articles

Understory woody vegetation in manmade Mediterranean pine forests: variation in community structure along a rainfall gradient

Natural regeneration that occurs in the understory of Mediterranean pine monocultures provides the basis for the transition of these simply structured systems toward a more complex and sustainable state. However, the course and consequences of this process, and its relationships with environmental and silvicultural variables, are still inadequately understood. We investigated the relationship between rainfall amount and understory woody vegetation (UWV) structure in mature (40–50 year) Pinus halepensis plantations in the Mediterranean zone of Israel, where rainfall ranges from 280 mm/year in the south to 900 mm/year in the north. We measured abundance, diversity and species composition on south- and north-facing slopes, in forest sites distributed along the rainfall gradient. UWV abundance, as measured by cover percentage and height, increased with rainfall amount along the entire gradient (2–113% and 0.1–3.4 m, respectively), more rapidly on north-facing slopes. Species composition varied along the rainfall gradient, with ranges of species occurrences corresponding to those in unforested habitats. The relationship between rainfall and UWV species richness was positive throughout most of the rainfall gradient, possibly with a shift in pattern at the highest rainfall levels. UWV richness increased sharply with increasing abundance, up to a certain point with no further increase in richness as abundance increased further. We concluded that UWV structure in the studied forest environment and climatic range is strongly determined by rainfall and suggested that the design and management of Mediterranean forests should focus more on optimizing water availability for the various components.

Photosynthesis of ground vegetation in boreal Scots pine forests

Research on carbon uptake in boreal forests has mainly focused on mature trees, even though ground vegetation species are effective assimilators and can substantially contribute to the CO2 uptake of forests. Here, I examine the photosynthesis of the most common species of ground vegetation in a series of differently aged Scots pine stands, and at two clear-cut sites with substantial differences in fertility. In general, the biomass of evergreen species was highest at poor sites and below canopies, whereas grasses and herbs predominated at fertile open sites. Unlike mosses, the measured vascular species showed clear annual cycles in their photosynthetic activity, which increased earlier and decreased later in evergreen vascular species than in deciduous species. However, intraspecific variation and self-shading create differences in the overall level of photosynthesis. Light, temperature history, soil moisture and recent possible frosts could explain the changes in photosynthesis of low shrubs and partially also some changes in deciduous species. Light and the occurrence of rain events explained most of the variation in the photosynthesis of mosses. The photosynthetic production of ground vegetation was first upscaled, using species-specific and mass-based photosynthetic activities and average biomass of the site, and then integrated over the growing season, using changes in environmental factors. Leaf mass-based photosynthesis was highest in deciduous species, resulting in notably higher photosynthetic production at fertile sites than at poor clear-cut sites. The photosynthetic production decreased with stand age, because flora changed towards evergreen species, and light levels diminished below the canopy. In addition, the leaf mass-based photosynthetic activity of some low shrubs declined with the age of the surrounding trees. Different measuring methods led to different momentary rate of photosynthesis. Therefore, the choice of measuring method needs special attention.

Germination Patterns of Soil Seed Banks in Relation to Fire in Portuguese Littoral Pine Forest Vegetation

Germination behavior of maritime pine (Pinus pinaster Aiton) forests soil seed banks after fire treatments in controlled laboratory conditions was analyzed. Germination response of all tree and shrub seeds after wildfires in the Leiria National Forest, Portugal, was simulated by treating sample trays of soil seed banks with distinct combinations of: burning time (0 min, 5 min, and 15 min), seed depth (5 cm and 8.5 cm), and presence or absence of ash cover. The design included control samples for null hypothesis testing. During a time span of 20 months after treatments, the maximum number of seedlings observed every 30 day period, their taxonomical identity, the number of destroyed seeds, and the number of non-germinated seeds were analyzed. Six functional species groups, defined by germination response (i.e,. germinated, destroyed, non-germinated), were identified using minimum-variance hierarchical clustering and correspondence analysis. In addition, the influence of the three environmental design factors and three functional species groups based on their general germination response were then analyzed by means of general regression models. Clustering and ordination results suggest two obvious main groups in terms of post-fire germination response: 1) seeders—fast-growing pioneer shrubs that respond positively to post-fire germination, and 2) resprouters—slow-growing understory tall-shrubs in which germination is largely depressed. Each of the two main functional species groups were further subdivided into six sub-groups, which are distinct in mean germinated, destroyed, and non-germinated seed values. Burning time and seed depth were highly significant in explaining post-fire germination response, while the presence of ash cover was less significant. Results suggest that pioneer seeder behavior is largely promoted by wildfires that are, in turn, detrimental to slow-growing, late-sucessional tall shrubs. Forest fire hazard risk management can thus be put into perspective—seeder fuel beds are promoted by wildfire and are themselves highly fire prone, and resprouters are not (due to discontinuous horizontal and vertical structure and less flammable leaf composition).

Photosynthesis of ground vegetation in different aged pine forests: Effect of environmental factors predicted with a process-based model

Question: How do stand age and environmental factors affect the species-specific photosynthesis of ground vegetation? Location: Five different aged pine forests in Southern Finland. Methods: We measured photosynthesis of common species of ground vegetation during the growing season of 2006. Results: The measured vascular species, especially those with annual leaves, had a clear seasonal cycle in their measured photosynthetic activity (Pmaxi). A simple model that uses site-specific temperature history, soil moisture and recent frost as input data was able to predict the changes in photosynthetic activity in dwarf shrubs with perennial leaves. The Pmaxi values of mosses did not have a clear seasonal cycle, but low values occurred after rain-free periods and high values after precipitation. We modified the model for mosses and included temporary rain events. The model was able to predict most of the large changes in Pmaxi of mosses resulting from varying weather events but there was still some uncertainty, which was probably due to difficulties in measuring fluxes over a moss population. Conclusions: Temperature history, recent frosts and soil moisture determine the changes in Pmaxi of dwarf shrubs with perennial leaves. The Pmaxi of mosses depends mostly on recent precipitation.

Fire-induced soil water repellency under different vegetation types along the Atlantic dune coast-line in SW Spain

Abstract The distribution and variation with soil depth of water repellency has been studied in fire-affected sand dunes under three different vegetation types (pine forest, shrubland and sparse herbaceous vegetation) in SW Spain. The persistence and intensity of water repellency at the exposed surface of soil was measured using the water drop penetration time test and the contact angle method, respectively, in surface samples (0–3 cm) collected at burned and unburned areas. The variation of water repellency with depth in burned areas was studied in soil profiles every 5 cm between 0 and 40 cm depth. None or slight soil water repellency was observed at unburned soil sites, whereas burned soil sites showed a high degree of repellency, especially under pines and shrubland. The spatial pattern of fire-induced soil water repellency was found to be associated to vegetation types, although it was modulated by soil acidity and the soil organic carbon content. Soil water repellency was generally higher at the soil surface, and decreased with depth. Dense pine forests and shrublands showed strong and/or severe water repellency in depth, but it was rare and limited to the first five centimeters under sparse herbaceous vegetation. The heterogeneity of moisture patterns under dense pine forests or shrublands showed the existence of wetting and water repellent three-dimensional soil patches.

Fire and Vegetation Dynamics in High-elevation Neotropical Montane Forests of the Dominican Republic

In March and April 2005, severe fires burned over 1000 km2 of tropical montane forests in the Cordillera Central, Dominican Republic. The fire burned through our network of permanent vegetation plots, which were established in 1999 to examine interactions among environment, vegetation, and disturbance. We used QuickBird satellite imagery combined with field surveys to map the extent and severity of the fire across the landscape. The fire burned through 96% of the pine forest but quickly extinguished at the pine-cloud forest boundary along most of the ecotone. Topographic factors and fire severity had no influence on fire behavior at the ecotone. These observations support our original hypothesis that fire maintains the abrupt boundary between the pine and cloud forest vegetation in these mountains. Vegetation structure and composition played a direct role in regulating fire spread and behavior in this landscape.

Diversity of fungi in hair roots of Ericaceae varies along a vegetation gradient

Ericaceous dwarf shrubs including Calluna vulgaris and Vaccinium spp. occur both in open heathland communities and in forest ecosystems as understory vegetation. Ericaceous shrubs were once thought to form ericoid mycorrhizal associations with a relatively narrow range of ascomycetous fungi closely related to, and including, Rhizoscyphus ericae. However, perceptions have recently changed since the realization that a broader range of ascomycete fungi, and in some cases basidiomycete fungi, can also form associations with the roots of ericaceous plants. We used a combination of molecular approaches, including denaturing gradient gel electrophoresis, terminal restriction fragment length polymorphism, cloning and sequencing, to investigate the diversity of fungi associated with C. vulgaris roots collected across a heathland/native Scots pine forest vegetation gradient. We also determined differences in fungal community composition between roots of co-occurring C. vulgaris and Vaccinium myrtillus in the forest understory. Collectively, the data show that a large diversity of potentially ericoid mycorrhizal fungal taxa associate with roots of C. vulgaris and V. myrtillus, and that ascomycetes were about 2.5 times more frequent than basidiomycetes. The assemblages of fungi associated with C. vulgaris and V. myrtillus were different. In addition, the community of fungi associated with C. vulgaris hair roots was different for samples collected from the forest, open heathland and a transition zone between the two. This separation was partly, but not entirely, due to the occurrence of typical ectomycorrhizal basidiomycetes associated with the hair roots of C. vulgaris in the forest understory. These data demonstrate that forest understory ericaceous shrubs associate with a diverse range of ascomycete and basidiomycete taxa, including typical ectomycorrhizal basidiomycetes.

Ecology, history and silviculture of Scots pine (Pinus sylvestris L.) in western Norway - a literature review

Summary Results from a literature review on pinewood ecology, silviculture, genetics, aspects of history and forest resources of Scots pine ( Pinus sylvestris L.) in western Norway are presented. The pinewoods cover ∼ 40 per cent of the forested land, ∼ 0.31 million ha. During the last 75 years, the area has increased by 17 per cent and the growing stock has risen from ∼ 10 to 34 million m 3 . The impact of man in previous times was very marked, and has had a signifi cant infl uence on the present forest conditions. The pronounced climatic gradients mixed with the topographic variation – from the coastal plains via the fjord systems to the high mountains – is refl ected in rather steep gradients in the pine forest vegetation. Various fl oristic elements can be distinguished, from oceanic via the suboceanic in the outer islands to the thermophytic, boreonemoral and boreal elements in the inner fjord districts and valleys. The introduction of spruce ( Picea spp.) plantations on 10 – 15 per cent of former native pine forests has not negatively affected the bird fauna at the landscape scale. Although not particular species rich, the pine forests harbour species usually not found in other forest types. So far, most work in the fi eld of silviculture and forest ecology in the pinewoods of West Norway has been in the form of case studies. Implications of the results for forestry in the region are briefl y discussed.

Ground layer carbon and nitrogen cycling and legume nitrogen inputs following fire in mixed pine forests

Many mixed pine forests in the southeastern United States undergo prescribed burning to promote open pine savannas. In these systems, soil texture can influence fire's effect on vegetation and nutrient cycling. Our objectives were to examine fire and soil texture effects on carbon (C) and nitrogen (N) pools in ground layer vegetation. We measured biomass and tissue nutrient concentrations and estimated legume N inputs via N2 fixation in frequently burned sandy and clayey sites that were in the first and second seasons following a prescribed fire in 2002 (B02) or had been unburned since 2000 (B00). Mean belowground biomass was significantly greater on sandy than on clayey sites. Total aboveground mean biomass did not differ significantly between B00 and B02 sites, but grasses had greater aboveground biomass in clayey than in sandy sites. Carbon and N pools (measured in grams per square meter) in grasses were greater in clayey than in sandy sites, yet grasses had greater tissue concentrations of C (as a percentage) in sandy sites. Legumes showed significant interaction effects between soil texture and fire frequency for tissue C and N pools, above‐ and belowground biomass, and acetylene reduction activities. Results suggest that soil texture can influence fire effects on ground layer vegetation in southeastern mixed pine forests.

BRDF measurement of understory vegetation in pine forests: dwarf shrubs, lichen, and moss

Abstract The spectral and directional reflection properties of pine forest understory in Suonenjoki, Finland were measured using a newly developed transportable field goniospectrometer under direct sunlight or plant lamp. The samples represent the most typical types in Finnish forests. Large differences between species were found. Wax-leaved shrubs such as lingonberry and blueberry proved to be strong forward scatterers, whereas lichen and soft-leaved dwarf shrubs such as heather were strong backscatterers. The measured moss showed both forward and backscattering features. There were variations among the samples of the same species, but many typical features appeared consistent and reproducible. Both “pure” and mixed samples were measured, the latter showing smoother behavior than the former, that is, the strongest forward and backward features are downscaled. The results provide a starting point for an empirical understory model and a basis for development and validation of a theoretical model.

Evaluating the role of cutting treatments, fire and soil seed banks in an experimental framework in ponderosa pine forests of the Black Hills, South Dakota

Pinus ponderosa Laws. (ponderosa pine) forests have changed considerably during the past century, partly because recurrent fires have been absent for a century or more. A number of studies have explored the influence of timber harvest or burning on understory production in ponderosa pine forests, but study designs incorporating cutting and prescribed burning in an experimental framework are needed to identify mechanisms responsible for the observed changes. In this study, we first characterized the disturbance history and the soil seed bank of a ponderosa pine stand in the northern Black Hills. We then experimentally addressed the effects of prescribed burning and overstory reduction on understory vegetation. Before Anglo settlement of the area, the mean fire interval was 14 years and no fires were recorded after 1879. Cessation of fires, prolific regeneration of ponderosa pine, and subsequent logging in 1903 has led to a very dense, even-aged ponderosa pine stand with very little understory vegetation and very few viable seeds in the soil seed bank. Only 57 individual plants, or 186 seeds/m 2, emerged from 1080 soil samples. Response of understory vegetation during the first growing season after application of treatments was sparse, with no significant treatment effect. There were, however, significant treatment effects during the second growing season. Total understory biomass ranged from 5.8 kg/ha on untreated plots to 1724 kg/ha on clearcut, unburned plots. Herbaceous dicots comprised over 90% of total understory biomass. Both understory species richness and evenness responded to treatments, but understory woody plant density did not respond to either treatment. Paucity of viable seeds in the soil seed bank does not appear to constrain recruitment of understory vegetation in dense ponderosa pine forests of South Dakota.

Residual effects of N fertilization on soil-water chemistry and ground vegetation in a Swedish Scots pine forest

A study was made of soil-water chemistry and ground vegetation in a previously established N fertilization experiment in a Scots pine forest in central Sweden. Plots had been fertilized two, three or four times during a 15-year-period, each time with 150 kg N ha −1. The fertilizer used was initially pure ammonium nitrate, but at the latest fertilization made 4–8 years before the study, a minor dose of lime was also included. The aim of the study was to reveal possible residual affects of the previous fertilization. Soil water was sampled six times during a nine-month-period. Water samples were analyzed with respect to inorganic N, pH, Al, base cations and Cd. The only statistically significant treatment effect was that the concentration of base cations decreased with increasing total N dose in one of the two replicate blocks. Both fertilized plots and control plots had very low concentrations of inorganic N (<10 μg/l). Few species in the ground vegetation appeared to be affected by the previous N fertilization. Cladina rangiferina, the most abundant lichen species, had a much lower cover on plots that had been fertilized four times than on all other plots. Also, the other lichens tended to be less abundant on plots that had received fertilizer four times. The lower abundance of lichens on these plots resulted in a change in vegetation type from lichen types to dwarf shrub types. The experiment studied is situated in a region where deposition of N is larger than the critical load. Despite this, an extra addition of 600 kg N ha −1, corresponding to 40 kg N ha −1 year −1, had no consistent long-lasting effects on soil-water chemistry. At this dose, but not at the lower doses tested, there was a change in the plant community.

Grazing value evolution of the post-fire colonizing vegetation in pine forests of southwestern Albacete province (Spain)

In the present paper, changes in grazing value of colonizing vegetation in a burnt area in the southwestern Albacete were studied. A diacrhonyc study was employed in order to measure the cover of colonizing vegetation during the first five years after fire. The results pointed out the importance of colonizing plant communities as pasture, due to the presence of many herbaceous species having a high grazing value. The reduction of herbaceous species number and their cover from the third post-fire year, gave an ephemeral nature to this grazing resourcer. In the last of study, woody species with a low grazing value were the predominant species.

Constrained indicator species analysis (COINSPAN): an extension of TWINSPAN

Abstract. A new vegetation classification method, COnstrained‐INdicator‐SPecies‐ANalysis (COINSPAN) is introduced as an elaboration of Two‐Way‐INdicator‐SPecies‐ANalysis (TWINSPAN). Instead of operating on the bisection of a primary Correspondence Analysis ordination axis, at each level of division, COINSPAN bisects a primary Canonical Correspondence Analysis axis. The associated computer program, of the same name, performs both analyses as options. COINSPAN is applied to a simple model data set, with two constraining gradients, and to a pine forest vegetation survey in order to illustrate the functioning and utility of the method.

Leaf-level gas exchange and scaling-up of forest understory carbon fixation rates with a ?patch-scale? canopy model

During the Hartheim experiment (HartX) 1992, conducted in the Upper Rhine Valley, Germany, we estimated water vapor flux from the understory by several methods as reported in Wedler et al. (this issue). We also examined the photosynthetic gas exchange of the dominant understory speciesBrachypodium pinnatum, Carex alba, andCarex flacca at the leaf level with an CO2/H2O porometer. A mechanisticallybased leaf gas exchange model was parameterized for these understory species and validated via the measured diurnal courses of carbon dioxide exchange. Leaf CO2 gas exchange was scaled-up to patch- and then to stand-level utilizing the leaf gas exchange model as a component of the canopy light interception/energy balance model GAS-FLUX, and by further considering variation in vegetation “patch-type” distribution, patch-specific spatial structure, patch-type leaf area index, and microclimate beneath the tree canopy. At patch-level,C. alba exhibited the lowest net CO2 uptake of ca. 75 mmol m−2 d−1 due to a low leaf-level photosynthetic capacity, whereas net CO2 fixation ofB. pinnatum- andC. flacca-patches was approx. 178 and 184 mmol m−2 d−1, respectively. Highest CO2 uptake was estimated for mixed patches whereB. pinnatum grew together with the sedge speciesC. alba orC. flacca. Scaling-up of leaf gas exchange to stand level resulted in an estimated average rate of total CO2 fixation by the graminoid understory patches of approximately 93 mmol m−2 d−1 during the HartX period. The conservative gas exchange behavior ofC. alba at Hartheim and its apparent success in space capture seems to affect overall functioning of this pine forest ecosystem by limiting understory CO2 uptake. The CO2 uptake by the understory is approximately 20% of stand total CO2 uptake. CO2 uptake fluxes mirror the relative differences in water loss from the understory and crown layer during the HartX period. Comparative measurements indicate that understory vegetation in spruce and pine forests is not greatly different from that of other low-statured natural ecosystems such as tundra or marshes under high light conditions, although CO2 capture by the understory at Hartheim is at the low extreme of the estimates, apparently due to the success ofC. alba.

Recovery of vegetation in a natural east Mediterranean pine forest on Mount Carmel, Israel as affected by management strategies

In September 1989 a large natural Pinus halepensis Mill. forest on Mt. Carmel, Israel was burned down. The aim of this research was to suggest post-fire management regimes and to assess their influence on the recovery of the forest. Three treatments were applied to the old burned trees: (1) burned trees were left untreated; (2) burned trees were cut down, the trunks were removed but smaller twigs were left in the plots; (3) burned trees were cut down, the trunks and the smaller twigs were cleared. Four treatments were applied to the new seedlings in the cleared plots: (1) no seedlings were thinned out; (2) Pinus seedlings were thinned out; (3) Cistus seedlings were thinned out; (4) both Pinus and Cistus seedlings were thinned out. Species composition, percentage of cover, the density height and biomass of Pinus and Cistus seedlings were monitored. The results of this survey, carried out 4 years after the fire and 3 years after the treatments, revealed that cutting or removing the burned trees had less influence on species composition and cover than the natural process of recovery. The thinning of seedlings influenced their height, biomass and survival. Post-fire management recommendations, based on the results of this and other research done in the same area, are proposed.

Succession, dominance and diversity in lichen‐rich pine forest vegetation in Finland

Succession of forest floor vegetation (cryptogam and understorey vascular plant synusiae) is studied. Diversity patterns in northern boreal and hemiboreal to middle boreal lichen‐rich forests are different. Even when the lichen volume, which describes the successional status, is taken into account, the diversity in southern forests is lower. The descriptors of diversity are rather independent of lichen volume in southern forests. When the Stereocaulon‐rich forests are excluded, stronger correlations are observed in the northern forests, but the species number decreases only slightly as the lichen volume increases. Evidently this is due to relatively large sample plots, where suitable patches for minor species are usually available. The decrease is much stronger in Shannon's and Simpson's indices. This is mainly due to a decrease in evenness since, as the lichen volume increases, the dominance of some Cladina species increases. Therefore, these indices are not particularly efficient in describing the richness of the community. Stereocaulon‐rich stands have diversity values which correspond to Cladina‐rich stands with a considerably higher lichen volume, which gives additional evidence for their status as successionally rather mature communities.

Effects of Sample Preparation, Growth Stage, and Observer on Microhistological Analysis of Herbivore Diets

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Comparison of Bird Counts From Pine Forest and Indigenous Vegetation.

Bird counts were taken in Feb., March and July 1975 in 4 native habitats, ranging from wet sclerophyll Eucalyptus forest to mallee (E. stricta)-heath on the Boyd Plateau, and two Pinus radiata habitats (20 yr and 40 yr) in the Jenolan State Forest, New South Wales, Australia. In each season the number of birds and the number of species was highest in the native forest habitats, lower in the pine habitats and least in the mallee-heath. The composition of native forest, pine forest, and mallee-heath bird communities shows considerable differences.

Some Relations between Deterioration of the Site Quality and Changes of the Vegetation in a Japanese Red Pine Forest

Some Relations between Deterioration of the Site Quality and Changes of the Vegetation in a Japanese Red Pine Forest