Appalachian forests are threatened by a number of factors, especially introduced pests and pathogens. Among these is Phytophthora cinnamomi, a soil-borne oomycete pathogen known to cause root rot in ...American chestnut, shortleaf pine, and other native tree species. This study was initiated to characterize the incidence of P. cinnamomi on surface mined lands in eastern Kentucky, USA, representing a range of time since reclamation (10, 12, 15, and 20 years since reclamation). Incidence of P. cinnamomi was correlated to soil properties including overall soil development, as indicated by a variety of measured soil physical and chemical parameters, especially the accumulation of soil organic carbon. P. cinnamomi was detected in only two of the four sites studied, aged 15 and 20 years since reclamation. These sites were generally characterized by higher organic matter accumulation than the younger sites in which P. cinnamomi was not detected. These results demonstrate that P. cinnamomi is capable of colonizing reclaimed mine sites in Appalachia; additional research is necessary to determine the impact of P. cinnamomi on susceptible tree species at these sites.
In many northern forest ecosystems, soil organic matter accumulation can lead to paludification and forest productivity losses. Paludification rate is primarily influenced by topography and time ...elapsed since fire, two factors whose influence is often confounded and whose discrimination would help forest management. This study, which was conducted in the black spruce (Picea mariana (Mill.) BSP) boreal forest of northwestern Quebec (Canada), aimed to (1) quantify the effect of slope and time since fire on paludification rates, (2) determine whether soil organic layer depth could be estimated by surface variables that can potentially be remotely sensed, and (3) relate the degree of paludification to tree productivity. In this study, soil organic layer depth was used as an estimator of the degree of paludification. Slope and postfire age strongly affected paludification dynamics. Young stands growing on steep slopes had thinner organic layers and lower organic matter accumulation rates compared with young stands growing on flat sites. Black spruce basal area and Sphagnum cover were strong predictors of organic layer depth, potentially allowing mapping of paludification degree across the landscape. Tree productivity was negatively related to organic layer depth (R2 = 0.57). The equations developed here can be used to quantify forest productivity decline in stands that are undergoing paludification, as well as potential productivity recovery given appropriate site preparation techniques.
Celotno besedilo
Dostopno za:
BF, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Agrilus planipennis is an aggressive beetle native to Asia, which has recently invaded North America and central Russia. In European Russia, the first specimens of A. planipennis were collected in ...Moscow in 2003 and the Moscow Province is therefore thought to be a likely entry point to Europe. The pest spread along roads and railways and, by 2013, it was recorded in 11 provinces of Russia. The goal of this study was to clarify the current northern range limit of A. planipennis. To do this, ash (Fraxinus excelsior and F. pennsylvanica) trees were surveyed along the federal highway M10 (Russia) between Moscow and Saint Petersburg in July 2016. The condition of ash trees and presence of A. planipennis was recorded at 15 locations. We found dead ash trees with galleries of A. planipennis at six locations (56 degrees 27.799' N; 36 degrees 35.383' E to 56 degrees 47.665' N; 36 degrees 03.584' E). At the more north-western sites ash trees became infrequent and signs of A. planipennis were not observed on any ash tree. Beyond the National Park Valdayskiy (58 degrees 00.095' N; 33 degrees 08.550' E) no ash trees were observed for about 100 km. Further north in Leningrad Province, there were fragments of ash forests and many ash trees planted in parks in Saint Petersburg and its suburbs, but no signs of A. planipennis were seen. Results of this survey suggested that, for summer 2016, the north-west limit of A. planipennis was close to Tver City (about 56 degrees 47' N; 36 degrees 03' E). Further range expansion of A. planipennis may have been limited by low host density north-west of Tver City, rather than by climatic factors. However, if A. planipennis can overcome low host abundance and reach Saint Petersburg or other settlements with planted ash in Russia or abroad, it will likely cause serious damage, similar to that already observed in Moscow Province or North America.
Understanding the ecological mechanisms that allow a species to transition from an occasional understory component to the dominant type in the forest canopy is essential for predicting future shifts ...in the distribution of species. We investigated this issue with regard to yew, also because mature yew trees have been reported to inhibit self-regeneration and seedling survival, prompting concerns for the long-term preservation of the species. Our objectives were (a) to quantify spatial patterns of yew (Taxus baccata L.) populations near the southern limit of the species' ecological distribution, (b) to determine the relationships between yew presence and topographic gradients, and (c) to answer the question of how yew regeneration is affected by such patterns and relationships. We analyzed three extensive yew populations (90-165 ha, including 3-12 thousand established individuals) that mostly occupy the understory of beech forests located in protected areas of the central Apennines (Italy). Overall, the realized niche of yew (either as established trees, saplings, or seedlings) followed the expected bell-shaped curve of a species response to an environmental gradient. Yew was mainly found at 1,000-1,600 m elevation on mesic exposures (north and west) and intermediate slopes (30-60%). Geostatistical analysis revealed that yew occurred in patches, as shown by variogram ranges of 40-110 m for yew tree basal area and regeneration abundance. Yew regeneration over the landscape was directly related to basal area of yew trees. At local scales (~10 m), presence of established trees favored regeneration in relatively less developed stands, whereas high density of mature yews suppressed regeneration. Healthy yew populations in beech forests had a minimum size of 0.5-3 ha. As yew density increased within these patches, regeneration dropped, so that yew conservation cannot be limited to presently occurring populations, despite the longevity and potential for vegetative reproduction of the species. Disturbance from grazing and wildfire was also found to impact yew survival. Long-term existence of yew in the Italian Apennines depends on maintaining and expanding old-growth beech forests that incorporate yew patches, and have a minimum continuous cover equivalent to a relatively undisturbed regime (10-50 ha).
Visible injuries and 42 microscopic features of tissue and cell structure were quantified in needles of mature Aleppo pine (Pinus halepensis) growing at four field sites located on a natural ozone ...gradient in eastern Spain. Principal component analysis was used to find out if the forest sites differed from each other, to determine the reasons for the site differences and to evaluate the relations between the parameters studied. In previous-year needles, the first principal component (PC) was described by changes typical of long-term ozone stress: high occurrence of microscopic changes indicating increased defence and faint chlorotic mottling, but low occurrence of ultrastructural changes related to photosynthesis and its storage products. The second PC was described by needle ageing or ontological senescence. Statistical differences between the sites in terms of ozone stress were found and were in line with measured ozone concentrations and the values of the ozone exposure index, AOT40. Symptoms of ozone stress were mild, i.e., not related to severe tissue damage. Results suggested that the faint chlorotic mottling can be attributed to certain forms of condensed tannins or small chloroplasts. In addition, a coastal site differed from mountainous sites by having a more mesomorphic needle anatomy.
We surveyed and wounded forest-grown sugar maple (Acer saccharum Marsh.) trees in a long-term, replicated Ca manipulation study at the Hubbard Brook Experimental Forest in New Hampshire, USA. Plots ...received applications of Ca (to boost Ca availability above depleted ambient levels) or Al (to compete with Ca uptake and further reduce Ca availability). We found significantly greater total foliar and membrane-associated Ca in foliage of trees in plots fertilized with Ca when compared with trees from Al-addition and control plots (P = 0.005). Coinciding with foliar Ca differences, trees exhibited a significant difference in crown vigor and in percent branch dieback among treatments (P < 0.05), with a trend towards improved canopy health as Ca levels increased. Annual basal area increment growth for the years following treatment initiation (1998-2004) was significantly greater in trees subjected to Ca addition compared with trees in control and Al treatments. Treatment-related improvements in growth were particularly evident after overstory release following a 1998 ice storm. The amount of wound closure was also greatest for trees in Ca-addition plots relative to Al-addition and control plots (P = 0.041). These findings support evidence that ambient Ca depletion is an important limiting factor regarding sugar maple health and highlight the influence of Ca on wound closure and growth following release from competition.
Celotno besedilo
Dostopno za:
BF, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We used repeated sampling of the forest floor to determine if there was a net loss of Ca from organic horizons of Adirondack forest soils between 1930 and 2004. In 1984, we established 48 permanent ...plots in spruce-fir, northern hardwood, and pine stands located in areas sampled by Carl C. Heimburger in the early 1930s. Following Heimburger's protocols and analytical methods, we measured pH and dilute-HCl-extractable Ca in Oe and Oa horizons, and determined that there was a statistically significant decrease in Ca concentration during the 1932 to 1984 interval. In the 36 plots that we could locate in 2004, we again sampled organic horizons. During the >70-yr interval, HCl-extractable Ca concentrations in the Oe and Oa horizons decreased in each forest type (P < 0.05). We also measured NH4Cl-extractable Ca and Al in the 1984 and 2004 samples and found a significant decrease in Ca concentration in the pooled Oe horizons. High-elevation spruce-fir plots showed a Ca loss rate between 1984 and 2004 of 7.6 to 9.8 kg ha-1 yr-1. This compares well with a 4-yr Ca cycling study conducted in an equivalent spruce-fir forest at Whiteface Mt. in the Adirondacks, which showed an annual forest floor Ca loss of 8.4 kg ha-1 yr-1. Based on uptake and anion flux data from the Whiteface Mt. study, we estimated that about 25 to 30% of the 1984 to 2004 forest floor Ca loss in the spruce-fir plots is attributable to leaching driven by atmospheric SO42- deposition.
The mapping of changes in the distribution of insect-caused forest damage remains an important forest monitoring application and challenge. Efficient and accurate methods are required for mapping and ...monitoring changes in insect defoliation to inform forest management and reporting activities. In this research, we develop and evaluate a LiDAR-driven (Light Detection And Ranging) approach for mapping defoliation caused by the Common pine sawfly (Diprion pini L.). Our method requires plot-level training data and airborne scanning LiDAR data. The approach is predicated on a forest canopy mask created by detecting forest canopy cover using LiDAR. The LiDAR returns that are reflected from the canopy (that is, returns > half of maximum plot tree height) are used in the prediction of the defoliation. Predictions of defoliation are made at plot-level, which enables a direct integration of the method to operational forest management planning while also providing additional value-added from inventory-focused LiDAR datasets. In addition to the method development, we evaluated the prediction accuracy and investigated the required pulse density for operational LiDAR-based mapping of defoliation. Our method proved to be suitable for the mapping of defoliated stands, resulting in an overall mapping accuracy of 84.3% and a Cohen’s kappa coefficient of 0.68.
•Crown width models were applied to trees in large-area forest inventory data.•Amount of canopy cover was determined by accounting for crown overlap using GIS.•This process links area to ...individual-tree attributes (e.g., diameter and height).•The area: tree link creates a new analytical model for contemporary forest issues.•Canopy area may provide new information not contained in usual forest descriptors.
In most forest inventory data, it is not feasible to estimate the canopy coverage of trees having certain characteristics due to the lack of information on crown size. In this study, data from the Forest Inventory and Analysis (FIA) program were used to assign crown sizes to individual trees using published crown width models. This process effectively links trees to crown area such that estimates of canopy cover and changes therein can be made using domains that include tree-level attributes (e.g., dbh, total height, etc.). Advantages of implementing this approach are (1) estimation can proceed as with any other estimate of area derived from forest inventory data, and (2) canopy cover estimates provide different information than classical indicators such as number of trees. A disadvantage is the need to dissolve overlapping crowns after the tree-level domain is selected. Examples related to forest health, wildlife habitat, and old growth attributes are provided to illustrate applications of the method.
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