Old-growth Indicator Research Articles

A hypervolume approach to niche specialism, tested for the old-growth indicator status of calicioids

AbstractCertain lichen epiphytes are restricted to old-growth forest stands with long ‘ecological continuity’, explained by i) niche specialism and their dependence on microhabitats associated with old stands including veteran or senescent trees, and/or ii) dispersal limitation with probabilities of colonization being relaxed over extended time periods. ‘Calicioid’ species are among the most important old-growth indicators, yet they reproduce sexually via small spores that appear widely dispersed at ecological scales. This suggests that they should have a high level of niche specialism compared to lichen epiphytes in general, explaining their role as old-growth indicators. However, comparisons of niche specialism are challenging, and this study uses epiphytic, corticolous calicioid species as an appropriate test case. Having measured 20 variables that constrain the lichen epiphyte niche, these were collapsed into a ‘hypervolume’ representing the sampled environmental space available for occupancy by lichens in Scotland as a study system. It was then possible to examine the occupancy of this hypervolume by individual lichens (niche breadth), with the proportion/percent occupied used to estimate a niche specialism score. Consequently, epiphyte calicioid species are confirmed to have a high degree of niche specialism compared to lichen epiphytes in general, and compared to other old-growth indicators, with their niche position directed towards drier climates including locally sheltered microhabitats associated with old-growth forest structure.

Presenting a climate-smart forestry evaluation framework based on national forest inventories

Climate-smart forestry (CSF) has gained increasing attention in recent years. Yet, a framework to assess the three pillars of CSF, in terms of mitigation and adaptation to climate change and ecosystem service (ES) provision based on national forest inventory (NFI) data is currently lacking. In this study, we present an assessment framework of CSF based on forest indicators derived from NFI. To quantify the three pillars of CSF we defined 1) mitigation based on the forest carbon stock, 2) adaptation using biodiversity and susceptibility to disturbances caused by storm and bark beetles and 3) ES provision with timber production and protection against avalanches and rockfall. We demonstrate the application of this framework using Swiss NFI data and projections of future forest development under four different management scenarios. Our results show that, in general, the carbon stock is increasing at the national scale when current management practices are maintained. Increases are especially pronounced in the Jura and Southern Alps regions. Trade-offs occur between enhancing mitigation and adaption, and the sustainable provision of ES such as timber production. Scenarios with increased harvesting intensities lead to a higher timber supply in the short-term, while decreasing the carbon stock, biodiversity-related old-growth indicators and the protective function of forests. The indicator framework presented in this study provides a first methodological approach that can support policy making to balance the different forest services in the context of CSF.

Quantifying old-growthness of lowland European beech forests by a multivariate indicator for forest structure

Quantifying the degree of old-growthness of forests is reasonable to assess their conservation value and guide management decisions. This study aimed at developing and applying an indicator to quantify the old-growthness of forest structure on potential beech forest sites in Central Europe which exhibit a long history of forest management. A set of structural variables was derived from sample plot inventories in European primeval beech forests in Eastern Slovakia (classified as old-growth) and 39 comparison stands of different management intensity, age and tree species composition in the North German lowlands. The comparison stands were arranged in triplets, consisting of i) a > 100 year old European beech forest left to natural development (ND), ii) 80 to 100 year old Scots pine forest with a certain amount of deciduous trees in the understory (OP), and iii) <80 year old Scots pine forest (YP).The initial number of 134 attributes was condensed to 27 variables representing ten thematic groups. Selection criteria were, i) typical for the old-growth state, ii) widespread and meaningful, and iii) exhibiting no multicollinearity within the respective group. The developed old-growth indicator (OGI) measures the degree of overlap of the 5th–95th percentile ranges of a certain comparison stand with the primeval forests. OGI achieves values between 0 and 1 and allows the consideration of all thematic groups and variables separately as well as calculating an aggregated value.We derived plausible OGI-values of between 0.71 and 0.74 for the primeval forests, 0.13 to 0.42 for the ND stands, and 0.07 to 0.30 for the OP and 0.03 to 0.26 for the YP stands. We postulated that OGI provides a comprehensive and reproducible indicator of the maturity of a forest stand on an empirical basis that allows for differentiated, as well as easy to handle, aggregated evaluations. An additional advantage is the implementation into the established workflow for forest surveys of national parks and strict forest reserves in Germany.

Forest management could counteract distribution retractions forced by climate change.

Climate change is expected to drive the distribution retraction of northern species. However, particularly in regions with a history of intensive exploitation, changes in habitat management could facilitate distribution expansions counter to expectations under climate change. Here, we test the potential for future forest management to facilitate the southward expansion of an old-forest species from the boreal region into the boreo-nemoral region, contrary to expectations under climate change. We used an ensemble of species distribution models based on citizen science data to project the response of Phellinus ferrugineofuscus, a red-listed old-growth indicator, wood-decaying fungus, to six forest management and climate change scenarios. We projected change in habitat suitability across the boreal and boreo-nemoral regions of Sweden for the period 2020-2100. Scenarios varied in the proportion of forest set aside from production, the level of timber extraction, and the magnitude of climate change. Habitat suitabilities for the study species were projected to show larger relative increases over time in the boreo-nemoral region compared to the boreal region, under all scenarios. By 2100, mean suitabilities in set-aside forest in the boreo-nemoral region were similar to the suitabilities projected for set-aside forest in the boreal region in 2020, suggesting that occurrence in the boreo-nemoral region could be increased. However, across all scenarios, consistently higher projected suitabilities in set-aside forest in the boreal region indicated that the boreal region remained the species stronghold. Furthermore, negative effects of climate change were evident in the boreal region, and projections suggested that climatic changes may eventually counteract the positive effects of forest management in the boreo-nemoral region. Our results suggest that the current rarity of this old-growth indicator species in the boreo-nemoral region may be due to the history of intensive forestry. Forest management therefore has the potential to compensate for the negative effects of climate change. However, increased occurrence at the southern range edge would depend on the dispersal and colonization ability of the species. An increase in the amount of set-aside forest across both the boreal and boreo-nemoral regions is therefore likely to be required to prevent the decline of old-forest species under climate change.

Protecting the Forests While Allowing Removal of Damaged Trees may Imperil Saproxylic Insect Biodiversity in the Hyrcanian Beech Forests of Iran

The 1.8 million ha of forest south of the Caspian Sea represent a remarkably intact ecosystem with numerous old-growth features and unique species assemblages. To protect these forests, Iranian authorities recently passed a law which protects healthy trees but permits the removal of injured, dying and dead trees. To quantify the biodiversity effects of this strategy, we sampled saproxylic beetles and true bugs in 24 plots across the entire altitudinal gradient of Oriental beech. The composition of these communities as well as their overall richness and the richness of endemic and old-growth indicator species were best explained by dead wood volume compared to other environmental variables. Due to the striking evidence that dead wood is the major driver of saproxylic diversity in these forests, we urge Iranian authorities to reconsider their law, redirecting logging toward healthy medium sized trees. Otherwise, a major loss in biodiversity, similar to that experienced in European beech forests, can be expected.

Old rural parks support higher biodiversity than forest remnants

One of the main challenges in biodiversity conservation is to curb a further degradation and loss of high-quality habitats. In agricultural matrix landscapes, the detection of alternative habitats for habitat specialists may be a solution. Historic old parks or landscape gardens around manor houses and castles are cultural heritage of nobles, but their value in harbouring biodiversity is poorly acknowledged. Therefore we evaluated the potential of old rural parks to serve as a habitat for nemoral forest species. We recorded stand structure and the presence of forest biodiversity indicators in 74 closed-canopy stands of historic parks and compared them with 93 neighbouring mature forest remnants on ancient forest land. We estimated the importance of stand structure in relation to habitat type on biodiversity indicators. Finally we suggest single-value indicator-complexes for the cost-efficient assessment of the conservation value of forests and forest-like habitats. Park stands outclassed reference forests in several individual structural characteristics, and in combined indicators of habitat quality and biodiversity. Forests had higher estimates for the combined indicator of dead wood, but large-diameter dead wood types were more abundant in parks. Woodpeckers, several old-growth indicator epiphytes and forest herbs had successfully become established in planted forest-like park fragments. Old rural parks resemble high-conservation-value forests more than the best preserved contemporary forest remnants. After the century needed to overcome immigration delay, old parks do provide a refugium for temperate deciduous forest species. Consequently, biodiversity-targeted management should retain and enhance old-growth attributes in forests and on the peripheries of parks: e.g. preserving old trees to provide service for epiphytes, hollow trees and an understorey mosaic for birds and bats; dead wood elements for saproxylic insects and fungi; limited mowing frequency and increased cutting height for forest herbs. Forestry should enhance the recovery of mixed deciduous stands and avoid conifer plantations.

Epiphytic lichens of a poorly explored National Park: Is the probabilistic sampling effective to assess the occurrence of species of conservation concern?

Over the past 10 years, three National Parks have been established in southern Italy. This bought to the scientific attention the status of natural resources in these territories. The knowledge base completion, that includes also usually neglected organisms, is necessary for managing biodiversity. Although lichens are not included in the European conservation policies, they play well-known ecological roles in various ecosystems. The aim of this work is to propose a rapid but exhaustive approach to assess epiphytic lichen diversity in this area. For this purpose, the probabilistic sampling was tested. A total of 149 taxa of epiphytic lichens were recorded, including 20 new records for the Campania region and four new species for Southern Italy. Furthermore, seven red listed species were found. The majority of the recorded taxa can be considered as old-growth indicator species. The results confirm that the probabilistic approach can be efficiently applied to assess lichen diversity in very poorly explored natural areas over large territories.

Riparian alder ecosystems as epiphytic lichen refugia in sub-boreal spruce forests of British Columbia

Alder-dominated riparian forests represent only a small proportion of the landscape in central-interior British Columbia. However, they possess a suite of attributes that may allow them to function as refugia for canopy macrolichens. These include their deciduous habitat, their location in moist nutrient receiving sites, and their distribution as narrow corridors that cross broad regional landscapes. We have examined their potential role as lichen refugia by assessing canopy macrolichen communities in 75 riparian alder forests across a 200 km longitudinal gradient in central-interior British Columbia. Study sites were stratified equally between three climate subzones of the Sub-Boreal Spruce biogeoclimatic zone. Forty-nine macrolichen taxa were observed, including the old-growth indicator cyanolichen species Lobaria scrobiculata (Scop.) DC., L. retigera (Bory) Trevisan, Nephroma isidiosum (Nyl.) Gyelnik, and Sticta limbata (Sm.) Ach. Canonical correspondence analysis identified mean annual temperature, mean annual precipitation, age of adjacent conifer forest, and abundance of large stems (dbh &gt;10 cm) as significant explanatory variables. Regional precipitation gradients explained the exclusion of many lichen species from both the most westerly and most easterly riparian forests, with drier summer conditions and heavy winter snowpack, respectively, being major limiting factors. Lichens preferentially occupied large leaning stems, which may provide greater precipitation interception and continuity of substrate, when compared with smaller upright alder stems. We conclude that alder-dominated riparian forests represent a major refugium for old-growth dependent lichens in British Columbia’s sub-boreal spruce landscapes and as such may provide valuable dispersal corridors between remnant old-growth coniferous forest patches.

Epiphytic lichen diversity in late-successional Pinus sylvestris forests along local and regional forest utilization gradients in eastern boreal Fennoscandia

Abstract Pinus sylvestris -dominated forests have been heavily utilized across all of boreal Fennoscandia and the remaining natural forests are generally highly fragmented. However, there are considerable local and regional differences in the intensity and duration of past forest utilization. We studied the impact of human forest use on the diversity of epiphytic and epixylic lichens in late-successional Pinus sylvestris -dominated forests by assessing species richness and composition along both local and regional gradients in forest utilization. The effects of local logging intensity were analysed by comparing three types of stands: (i) near-natural, (ii) selectively logged (in the early 20th century) and (iii) managed stands. The effects of regional differences in duration and intensity of past forest use were analysed by comparing stands in two contrasting regions (Hame and Kuhmo–Viena). The species richness of selectively logged stands was as high as that of near-natural stands and significantly higher in these two stand categories than in managed stands. Species richness increased with the density of small understorey Picea , which correlated strongly with decreasing intensity of local forest use and increasing structural complexity of selectively logged and near-natural stands. Stands in the Hame region hosted a lower number of species, and were less likely to host many old-growth indicator species than the Kuhmo–Viena region, suggesting that species have been lost from stands in the Hame region due to a longer history of intensive forest use. We conclude that selectively logged stands, along with near-natural stands, are valuable lichen habitats particularly for species confined to old-growth structures such as coarse trees and deadwood. In landscapes where natural forests have become fragmented, the management or restoration of the remaining late-successional Pinus -dominated forests, e.g. through the use of fire, should be carefully planned to avoid adverse effects on lichen species richness.

Use of species richness estimators improves evaluation of understory plant response to logging: a study of redwood forests

The recovery of native understory plant communities after timber harvest has received a great amount of attention worldwide. However, most of these studies have ignored the potentially significant effects that differences in habitat across forest development may have on the species–area relationship, even though sampling efficacy among forest developmental stages may differ markedly as a result of equal sampling within stages. We examined vascular plant community structure in coastal redwood forests of northern California (USA) in forest patches in each of four forest stages that develop with forest age: Initiation, Closure, Mature, and Old-growth. We also used a set of traditional and novel approaches to assess sampling efficacy and guide our sampling design. We initially sampled 75 circular plots (0.04 ha) in stands within each forest stage across a 1,347 km2 area. The species–area relationship suggested we had adequately sampled all stages after the first season of data collection, but non-parametric richness estimators (Incidence-based Coverage Estimator or ICE) and Michaelis–Menten means (MMMeans) rarefaction curves, indicated inadequate sampling of the older stages. Thus, we added four more samples within the Old-growth forest stage, establishing a more equitable sample of all stages. Our full data set demonstrated significant differences between plant communities in previously harvested forests (‘managed’ = Initiation, Closure, and Mature) and ‘unmanaged’ forests (Old-growth). Though several understory species were present in all stages, a suite of Old-growth indicator and restricted species suggest that recovery of some species may take long periods in managed forests. Interestingly, a separate suite of common understory species were lacking in Old-growth, and species richness in this stage was lower than in the mature managed forests. We discuss how this departure from the prediction of peak richness in Old-growth may relate to fire suppression in Old-growth forests. Lastly, analysis of our initial, smaller sampling of plots suggested that Old-growth plots were the least species rich. However, additional sampling of the Old-growth stage demonstrated that Old-growth plots were as rich as Closure plots. This has important implications for all studies concerned with measuring recovery after forest disturbances; stage-dependent habitat-mediated differences that affect sampling efficacy may not be captured by traditional sampling methods.

Lichens and bryophytes on Eucalyptus obliqua in Tasmania: management implications in production forests

Thirty lichen and 25 bryophyte species have been recorded from the buttresses of Eucalyptus obliqua, the dominant tree in wet sclerophyll forest at the Warra Long-Term Ecological Research Site in southern Tasmania. The flora, characterised by four major associations, is very distinctive, containing a relatively high number of eucalypt specialists, particularly among the lichens. A general trend towards increasing species richness with increasing tree diameter is apparent and is attributed mainly to increasing habitat diversity on the buttresses. The increase in species occurs without the loss of pioneers; thus succession involves addition rather than replacement of species. The relationships between epiphytes, tree age and forest age are complicated by the periodic occurrence of fires in the forest. Nevertheless, potential oldgrowth indicators are identified and the possible effects of current silvicultural practices on the conservation of the species are discussed.

Canada's National Forest Inventory: What can it tell us about old growth?

Canada's National Forest Inventory is a periodic compilation of existing inventory information from across the country. The main sources of information are detailed, stand-level descriptions contained in provincial, territorial, and industrial management-level inventories. Typical management inventories do not identify old growth as a specific attribute. Therefore, the National Forest Inventory, based on management-level inventories, does not specifically show old growth. Indicators of old growth, such as stand age and maturity, are contained in the national inventory and are analysed to illustrate the distribution of forest in Canada by age and maturity. A further analysis by selected species is also provided. Finally, a new plot-based national inventory that will provide additional old-growth indicators is discussed. Key words: forest inventory, inventory attributes, old growth, old-growth indicators, NFI, CanFI, EOSD