High-elevation Spruce Forests Research Articles

Using image analysis for quantitative assessment of needle bladder rust disease of Norway spruce.

High elevation spruce forests of the European Alps are frequently infected by the needle rust Chrysomyxa rhododendri, a pathogen causing remarkable defoliation, reduced tree growth and limited rejuvenation. Exact quantification of the disease severity on different spatial scales is crucial for monitoring, management and resistance breeding activities. Based on the distinct yellow discolouration of attacked needles, it was investigated whether image analysis of digital photographs can be used to quantify disease severity and to improve phenotyping compared to conventional assessment in terms of time, effort and application range. The developed protocol for preprocessing and analysis of digital RGB images enabled identification of disease symptoms and healthy needle areas on images obtained in ground surveys (total number of analysed images n = 62) and by the use of a semiprofessional quadcopter (n = 13). Obtained disease severities correlated linearly with results obtained by manual counting of healthy and diseased needles for all approaches, including images of individual branches with natural background (R 2 = 0.87) and with black background (R 2 = 0.95), juvenile plants (R 2 = 0.94), and top views and side views of entire tree crowns of adult trees (R 2 = 0.98 and 0.88, respectively). Results underline that a well‐defined signal related to needle bladder rust symptoms of Norway spruce can be extracted from images recorded by standard digital cameras and using drones. The presented protocol enables precise and time‐efficient quantification of disease symptoms caused by C. rhododendri and provides several advantages compared to conventional assessment by manual counting or visual estimations.

Recent reduction in the frequency of frost accounts for most of the increased growth of a high elevation spruce forest in northwestern China

Key message Using process-based models in combination with dendrochronological measurements provides a way to explain recent increased tree growth in northwestern China.

Epiphytic lichen conservation in the Italian Alps: the role of forest type

Epiphytic lichens are a functionally important and species-rich component of Alpine forests, including several species of conservation concern. Their dependence on specific host trees predicts that forests with different tree species composition host different lichen communities, enhancing lichen diversity in forest landscapes. In this study, we tested for the first time the effect of forest type on patterns of epiphytic lichen diversity, in the Italian Alps. We sampled the main forest types of the South Tyrol, a typical Alpine region of Italy. We also assessed the influence of factors related to forest structure and climatic conditions. Our results demonstrate that different forest types host statistically different lichen communities, suggesting that the conservation of lichen diversity is entrusted to the maintenance of forest landscape heterogeneity, including forest types of minor economic value and rural habitats. The highest number of species was found in grazed larch forests and in high-elevation spruce forests, while the poorest pool was found in low-elevation spruce forests, beech forests and Scots pine ( Pinus sylvestris ) forests. High-elevation spruce forests also had the highest number of red-listed lichens, as the non-intensive management of these forest type allows the establishment of a rich lichen biota. Our results also emphasize the role for lichen conservation of some forest types that are of minor economic importance, such as oak ( Quercus pubescens ), riparian, and silver-fir ( Abies alba ) forests. This can also apply to grazed larch ( Larix decidua ) forests that are maintained by traditional farming, which shape one of the most pleasing aspects of the Italian Alpine landscapes. • Does forest type predict epiphytic lichen diversity in the Italian Alps? • We studied epiphytic lichen communities in the main forest types of the Italian Alps. • Significant differences in species composition and richness were found among forest types. • Conservation of lichen diversity is linked to the maintenance of forest landscape heterogeneity. • Forest with low-economic value highlighted also a key role on lichen conservation.

Ecosystem Succession and Nutrient Retention: Vitousek and Reiners' Hypothesis

What mechanisms mediate the flow of energy and cycling of nutrients during ecological succession? Are they linked in time and across space? In 1969, Eugene P. Odum proposed a series of hypotheses that caused the ecological community to think critically about patterns and processes (sensu Watt 1947) during ecological succession and how they might be linked in a causal manner. Odum’s perspective on the process of succession, or “the strategy of ecosystem development” as he termed it, was undoubtedly shaped by the intellectual influence of his mentor, Victor Shelford, as well as Shelford’s contemporaries such as Fredrick Clements. They shared the idea that ecological communities possessed emergent properties, wherein the whole is greater than the sum of its parts (sensu Phillips 1934). Inasmuch, the 24 hypotheses Odum (1969) articulated were an amalgam of holism and reductionism that created his rationale for the way energy flows and nutrients cycle within ecosystems. It is within this context that Peter Vitousek and Bill Reiners derived ideas that are fundamental to our understanding of energy flow and nutrient cycling in terrestrial ecosystems, ideas that have profoundly shaped my thinking as an ecologist.

Separating forest continuity from tree age effects on plant diversity in the ground and epiphyte vegetation of a Central European mountain spruce forest

Forest continuity has been identified as an important factor influencing the structure and diversity of forest vegetation. Primary forests with centuries of continuity are usually more diverse than young secondary forests as forest are colonized only slowly and because the former are richer in old tree individuals. In the present study, performed in unmanaged high-elevation spruce forests of the Harz Mountains, Germany, we had the unique opportunity to separate the effects of forest continuity and tree age on plant diversity. We compared an old-growth spruce forest with century-long habitat continuity with an adjacent secondary spruce forest, which had naturally established on a former bog after 1796 when peat exploitation halted. Comparative analysis of the ground and epiphyte vegetation showed that the plant diversity of the old-growth forest was not higher than that of the secondary forest with a similar tree age of >200 years. Our results suggest that a period of >200 years was sufficient for the secondary forest to be colonized by the whole regional species pool of herbaceous and cryptogam forest plants and epiphytes. Therefore, it is likely that habitat structure, including the presence of old and decaying trees, was more important for determining plant diversity than the independent effect of forest continuity. Our results are probably not transferrable to spruce forests younger than 200 years and highly fragmented woodlands with long distances between new stands and old-growth forests that serve as diaspore sources. In addition, our results might be not transferable to remote areas without notable air pollution, as the epiphyte vegetation of the study area was influenced by SO2 pollution in the second half of the 20th century.

Sustainable forest management of Natura 2000 sites: a case study from a private forest in the Romanian Southern Carpathians

Biodiversity and forest management are analyzed for a 500 ha privately owned forest within the Natura 2000 area “ROSCI0122 Muntii Fagaras”. Habitat types and indicator species are identified to measure environmental quality. Working towards an integrated approach to conservation, a range of options that will result in sustainable forest management are then considered. For beech forests light heterogeneity emerges as a crucial management target to ensure tree species richness and structural diversity as a basis for saving indicator species such as Morimus funereus, Cucujus cinnaberinus, Bolitophagus reticulatus and Xestobium austriacum . For spruce forests thinning over a broad range of diameters and maintenance of veteran trees would provide habitats for indicator species such as Olisthaerus substriatus . The populations of a number of bird species would be increased by strip-harvesting slopes: species such as Tetrao urogallus, Bonasia bonasia and Ficedula parva prefer forest margins. Steep slopes, and the areas around springs and watercourses, as well as rock faces, should remain unmanaged. Future management should start with a grid-based inventory to create an objective database of forest structure and life. An example is presented for high-elevation spruce forest. The inventory should quantify the variations in diameter, height and volume of trees per unit area. Such data would allow the advanced planning of forest operations. We discuss a wide range of administrative and organizational changes; changes that are needed for the sustainable forest management of the vast close-to-natural forests of the Muntii Fagaras, the maintenance of the Nardus grasslands and the protection of wetland vegetation around springs and streams in this Natura 2000-area.

Coarse woody debris retention in subalpine clearcuts affects ectomycorrhizal root tip community structure within fifteen years of harvest

Shifts in ectomycorrhizal (ECM) fungal community composition occur after clearcut logging, resulting in the loss of some dominant forest fungi. Because decaying wood is a remnant of the original forest and an important habitat for ECM fungal species, we examined ECM spruce roots and hyphae in 1-ha coarse woody debris (CWD) retention and removal plots (N=3) at a high elevation spruce forest 12 and 13 years after clearcut harvesting to test for a medium-term effect of CWD retention. Root tips from ten Picea engelmannii (Parry ex. Engelm.) saplings per plot were grouped morphologically, and the ECM fungal symbiont identified by Sanger sequencing. Sand-filled hyphae-trapping mesh bags were buried amongst the roots of saplings for one year. PCR product from all bags per plot was pooled and submitted for GS-FLX Titanium sequencing. Forty-six of 89 operational taxonomic units (OTUs) from root tips and 50 OTUs from hyphae were identified as ECM taxa. The most abundant taxa amongst root tip OTUs were Thelephora terrestris, Alloclavaria purpurea, Amphinema byssoides, and Tylospora asterophora. The most abundant OTUs from mesh bags were ectomycorrhizal taxa, and the most abundant of these were A. byssoides, T. terrestris, Wilcoxina mikolae, and T. asterophora. The retention of CWD had no detectable effect on taxon richness, evenness or diversity of ECM fungi on root tips or in mesh bags; however, there was a detectable shift in species composition. The relative abundance of A. byssoides root tips was significantly higher at removal plots while A. purpurea was a significant indicator species for CWD removal. Our results suggest that the retention of CWD at the time of harvest has affected ECM habitat at this site, and has resulted in altered ECM species composition, even though the logs are still hard and intact.

Inferring cloud deposition to a forest canopy using a passive cloudwater collector

A widely used passive cloudwater collector was operated continuously along with an automated canopy water throughfall measurement system at a high elevation spruce forest site. Cloudwater collection rate (Rc) and throughfall (TF) rate were examined to determine their interrelationship. In addition, the use of the cloudwater collector for inferring cloud liquid water content was examined. The degree of direct hourly correlation was fairly good between Rc and canopy TF rate for non‐rain periods when the canopy was saturated (the former explained 58% of the variance in the latter). The correlation was even better (R² = 0.84) when TF rate was time‐lagged one hour. Estimated liquid water content, using collector data, was characterized by a large degree of uncertainty. This uncertainty appears to be caused, to a large extent, by the inability of the estimation method to account for the variation in cloudwater collection efficiency as a function of wind speed and droplet size.