Soil surface properties in Mediterranean mountain ecosystems: Effects of environmental factors and implications of management

Understanding soil processes is fundamental to the success of forest restoration programs. We compared different types of soils in Mediterranean mountain forests with respect to their edaphic environments and influence of vegetation cover and lithology. We then used this information to determine the suitability of current forest restoration programs in these ecosystems.     

Site, plot, and individual tree yield reduction of interior Douglas-fir associated with non-lethal infection by Armillaria root disease in southern British Columbia

Root pathogens are one of the principle factors affecting forest productivity in many forests, but few estimates of impact are available. Non-lethal root infections associated with Armillaria root disease were studied to determine their effect on stem volume yield in seven planted Douglas-fir stands and a naturally regenerated stand in British Columbia's southern interior. Trees were removed from the soil and the infection date of a random selection of trees was determined. The volume reduction attributable to disease was determined as a comparison of diseased to disease-free trees over time since infection. Volume reductions per tree ranged from 0 to 30 dm³ (0-27%) depending on the tree age and disease duration. Yield reduction reached 27 m³/ha, averaging 15 m³/ha for the three oldest planted sites by age 30 (7-15%), but was lower at the naturally regenerated site. Yield reduction at the site level correlated best with the number of diseased trees and an unknown site factor. Sites with slow juvenile growth had the least yield reduction owing to their lower incidence of disease over time. Yield was less affected by the proportion of diseased primary roots per tree than by the cumulative time since infection. A few of the diseased trees maintained growth rate after infection similar to disease-free trees; interestingly, these trees were smaller than average to begin with. Overall, trees suffer accumulating growth reduction without recovery. Root diseases prevent full expression of site potential even without mortality. Minimizing disease impact in respect to other forest management goals is also discussed.     

Relationships between climate and tree radial growth in interior British Columbia,Canada

Climate is a main driving factor of the formation of annual tree-rings, but which climatic variables are the most influential on radial growth may vary among species and sites. To explore these interactions, tree-ring chronologies along a major elevation gradient were examined for three tree species in southern interior British Columbia (Canada): Pseudotsuga menziesii, Pinus contorta, and Picea glauca × engelmannii. We used correlations and linear and multiple regressions to explore the relationships between tree-ring radial growth and climate variables in the area from 1922 to 1997. All correlation coefficients between ring chronologies and monthly climatic variables were medium to low (from −0.3 to 0.4); nevertheless, moderate but significant trends could be identified. Multivariate models explained up to 53%, 43% and 32% of radial growth variability for P. contorta, P. menziesii and P. glauca × engelmannii, respectively. All three species showed similar radial growth–climate patterns across the elevational gradient, but they had different details that made ring width–climate relationships species-specific. Precipitation-related variables were more related to radial growth at low-elevations, changing into temperature-related variables at high-elevations. Tree-ring width for all three species was primarily and significantly affected by climate variables from the year previous to the growing season and only secondly by current year conditions, but the critical months varied for different species and altitudes. Winter precipitation also affected radial growth, either as a source of water or as a possible agent of physical damage. Although our work showed significant climate influences on breast height tree radial growth, our results also indicated that other site factors such as microclimate or stand dynamics can be as or more important than climate variability.     

Planted conifer seedling growth under two soil thermal regimes in high-elevation forest openings in interior British Columbia

A field trial was conducted investigating the single season growth response of 1+0 313 PSB Engelmann spruce (Picea engelmannii Parry ex Engelm.) and lodgepole pine (Pinus contorta Dougl. ex Loud.) seedlings planted into two different soil thermal regimes at three high-elevation locations spanning 200 km in the Engelmann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone in the Cariboo Mountains of central British Columbia. Temperature treatments represented the extremes of soil temperature commonly found in high-elevation clear-cuts. A warm soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 18 to 25 °C at –10 cm) consisting of a bare mineral soil hummock (average dimensions of 100 cm × 100 cm × 40 cm) was contrasted with a cool soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 10 to 13 °C at –10 cm) comprised of organic forest floor overlying mineral soil. By the end of the growing season, seedlings of both species planted into the warm treatment generally exhibited greater root, stem, foliage, and total seedling biomass than cool treatment seedlings. Measurements of root growth at 30, 60, and 90 days after planting showed that total root number and total root length were consistently greater for warm treatment seedlings than for cool treatment seedlings. Root growth was greater from the bottom rather than from the side of the root plug for all seedlings. These results suggest that the effect of low soil temperatures on outplanted styroblock conifer seedlings is pronounced and may be limiting growth performance in high-elevation plantations in British Columbia. We recommend silvicultural treatments that secure natural regeneration, ensure that warmer microsites are always planted, and utilize seedling stocktypes able to make rapid lateral root growth into warmer surface organic horizons.     

Spatial distribution of soil carbon and nitrogen storage and forest productivity in a watershed planted to Japanese cedar (Cryptomeria japonica D. Don)

Digital terrain modeling was used to evaluate landscape-level spatial variation of soil C and N storage and site productivity in Japanese cedar (Cryptomeria japonica D. Don) stands. Soil C and N storage were measured in samples from surface soils (0–25 cm depth) of 29 Japanese cedar stands in the 205-ha Myougodani watershed, Toyama Prefecture. The site index (C. japonica tree height at age 40 years) was used as a measure of forest productivity. Seven terrain attributes (elevation, slope gradient, aspect, profile curvature, plan curvature, openness, and wetness index) were calculated from a digital elevation model. Soil C and N storage were negatively correlated with slope gradient and positively correlated with openness. Variation in the site index was closely related to the wetness index. The prediction models using terrain attributes as explanatory variables explained 50% of the variability in soil C storage, 53% of the variability in soil N storage, and 75% of the variability in site index. This result demonstrated that this technique is useful for estimating the spatial distribution of soil properties and productivity in forest landscapes. On the other hand, there was no correlation between site index and soil C and N storage. Use of the prediction models in a geographic information system revealed that the spatial distribution of forest productivity differed considerably from those of soil C and N storage.     

Assessing the relations between aquatic habitat indicators and forest harvesting at watershed scale in the interior of British Columbia

Selection of appropriate aquatic habitat indicators is important for supporting sustainable forest and watershed management. To date, many identified watershed indicators have not been well tested. To address this issue, we sampled 28 stream reaches in the central and south interior of British Columbia, Canada. The selected reaches were similar with respect to gradient, watershed and topographic characteristics but with various levels of forest harvesting. Aquatic habitat indicators were derived based on a field survey, involving substrates, channel dimensions, pools, and large woody debris (LWD), together with some ratios and derivatives generated from them. Timber harvest disturbance at the watershed scale was quantified by calculating historical forest clear-cut area based on the BC vegetation resources inventory database. To account for the subsequent forest recovery, equivalent clear-cut area (ECA) was calculated based on the dominant species of each stream watershed and its regrowth since being logged. Pearson correlation coefficients showed that percent ECA and percent historical clear-cut area could effectively quantify the cumulative logging disturbance by limiting the effect of factors not related to logging activity (i.e., watershed area and elevations). These two variables were then related to the aquatic habitat indicators. Pearson correlation analyses found that relative width (ratio of D to bankfull width) (D is the b axis diameter of the largest substrate particle found in the reach), relative roughness (ratio of D to bankfull depth), pool frequency and per piece LWD volume are sensitive to percent ECA, i.e., significant (p < 0.01) while independent of influence from non-forest logging activity related factors and spatial clustering of samples. This relationship also holds true for the last two indicators when related to percent historical clear-cut area, though with a reduced degree of correlation. In addition, mean LWD diameter also showed significant relationship with percent historical clear-cut area, but not with percent ECA. Overall, per piece LWD volume was considered as the best aquatic habitat indicator. The performance of mean LWD diameter was comparable to per piece LWD volume if percent historical clear-cut area was used to quantify forest disturbance. Implications of these findings for forest management strategies are discussed.     

Epidemiology of Armillaria root disease in Douglas‐fir plantations in the cedar‐hemlock zone of the southern interior of British Columbia

Results are presented from several studies on the epidemiology of Armillaria ostoyae in Douglas‐fir plantations in the interior cedar‐hemlock (ICH) biogeoclimatic zone of British Columbia. Two plantations were monitored for mortality by A. ostoyae and other agents for 35 years after establishment. In these and other plantations ranging in age from 7 to 32 years, one or more of the following factors were determined: source of inoculum, mode of spread and characteristics of lesions on roots of excavated trees; symptom expression in relation to tree age and damage to the root system and years from initial infection to death on trees killed by the fungus. Mortality from A. ostoyae began in both plantations about 5 years after planting, reaching 30% in one and 11% in the other after 35 years. The spatial pattern of mortality was similar to that reported from New Zealand, France and South Africa; however, the temporal pattern differed, beginning later and, instead of declining, continuing at a nearly constant rate to the present. To age 10, nearly all infections were initiated by rhizomorphs; as plantations aged, the proportion of infections occurring at root–root contacts increased. In seven plantations, in moist and wet subzones of the ICH, from 23 to 52% of Douglas‐firs had root lesions, with the higher incidences occurring on moist sites. The occurrence of aboveground symptoms, reduced leader growth and basal resinosis, was related to the percentage of root length colonized by A. ostoyae on trees with more than 30% of root length killed. Average time from infection to death increased from 1 to 2 years at age 6 to 22 years at age 33. The outlook for timber yield from Douglas‐fir plantations in the cedar‐hemlock zone is discussed. Management alternatives for reducing damage from A. ostoyae when regenerating sites are reviewed.     

Thinning, burning, and thin-burn fuel treatment effects on soil properties in a Sierra Nevada mixed-conifer forest

More than a century of fire exclusion and past timber management practices in many Sierra Nevada mixed-conifer forests have led to increased stand densities and fuel accumulation, with a corresponding risk of large, high severity wildfires. To reduce hazardous fuel accumulations and restore the health and natural processes of forest ecosystems, fuel management programs often employ thinning and prescribed fire treatments, both alone and in combination. We evaluated forest floor and mineral soil chemical and physical characteristics following these treatments in a managed Sierra Nevada mixed-conifer forest using a fully replicated study design with four separate treatments: THIN, BURN, THIN + BURN, and an untreated CONTROL. Compared to the CONTROL, the BURN and THIN + BURN treatments consumed a large amount of the forest floor, reducing the mass and depth by more than 80%. These treatments reduced the forest floor C and N pools by more than 85%, resulting in reductions of 25 Mg C ha⁻¹ and more than 700 kg N ha⁻¹ from the forest floor. Despite these large losses from the organic horizons, no significant differences in mineral soil total C and N pools were detected among treatments. Compared with the CONTROL and THIN treatments, the BURN and THIN + BURN significantly increased the mineral soil NO₃-N concentration, pool of inorganic N, pH, and exposed bare soil. The THIN + BURN treatment significantly increased the concentrations of NH₄-N and exchangeable Ca relative to the CONTROL. No significant differences in the net rates of nitrification, N mineralization, or bulk density were detected among the four treatments. The BURN treatment reduced mineral soil C concentration and CEC, while the THIN + BURN treatment had the greatest increase in inorganic N. Fire effects on soil pH and inorganic N were moderated in skid trails due to reduced fuel continuity and consumption. In light of the current management emphasis on hazardous fuels reduction, we recommend that researchers investigating fire effects in harvested stands include skid trail influences in their study design.     

营造台湾相思水土保持林对土壤结构和养分的影响

对侵蚀丘陵地营造台湾相思（治理措施）土壤肥力变化的研究，结果表明：治理后的土壤结构、水分状况得到一定程度改善，土壤营养元素容量及供应强度明显增强，表明治理后土壤肥力得到一定程度的恢复。营造台湾相思水土保持林是治理侵蚀丘陵地较好的措施之一。     

Criteria and guidance considerations for sustainable tree stump harvesting in British Columbia

Abstract

Stump extraction for forest health has been carried out operationally in British Columbia (BC) for many years. Emerging bioenergy opportunities plus the anticipated need for more fibre because of reductions in timber supply may increase interest in stump harvesting, but there are numerous environmental, economic and policy barriers that must be overcome first before industrial-scale stump harvesting can be seriously considered in BC. The potential for a future change in practice provides an opportunity to learn from the existing literature and identify knowledge gaps. In this article we review the available literature on stump harvesting from the European Union within the context of BC's forests, economy, biodiversity, environment and policies. We provide recommendations on how the government of BC could move forward if they decide to enable stump harvesting for fibre and bioenergy, including assessment of net economic and carbon benefits and environmental effects, improvements in inventory and the scientific knowledge base needed to support policy and guidance, and investigation of operational enhancements.     

Genetic variation and gene flow among Prunus cerasoides D. Don populations in northern Thailand: analysis of a rehabilitated site and adjacent intact forest

This study describes the level of genetic variation and gene flow within and among populations of Prunus cerasoides in rehabilitated sites and adjacent intact forest. The seven microsatellite loci employed detected a total of 75 alleles (n = 401). Polymorphic information content (PIC) varied from 0.34 to 0.83. Between the adult populations there was moderate genetic differentiation with an F _ST value of 0.0575, which suggests that the restoration plots had a similar genetic composition to that of the natural population. The gene flow assessment provides some interesting insights into the genetic diversity of P. cerasoides. In the 16 naturally occurring trees over 83% of the genotyped seed were fathered by unidentified trees whereas in restoration plot A only about 32% of the pollen came from an unidentified father. This proportion was even less in Plot C where 25% of the pollen parents were unidentified. The naturally occurring trees within Doi Suthep were surrounded by planted trees, which were contributing to the paternity of the seed crop. This result demonstrates that ‘‘fill in’’ planting should consist of locally sourced material if it is considered important to conserve the genetic integrity of the local populations.     

Acid deposition effects on forest composition and growth on the Monongahela National Forest,West Virginia

The northern and central Appalachian forests are subject to high levels of atmospheric acid deposition (AD), which has been shown in some forests to negatively impact forest growth as well as predispose the forest system to damage from secondary stresses. The purpose of this study was to evaluate the possible contribution of AD to changes in composition and productivity of the Monongahela National Forest, and to evaluate soil-based indicators of acidification that might be useful for detecting AD-related forest changes. Soils adjacent to 30 Forest Inventory and Analysis (FIA) sites were sampled and analyzed for a suite of acidity indicators. These indicators were correlated with the periodic mean annual volume increment (PMAVI) of the forest stands on FIA plots for the 10-yr period 1989–2000. PMAVI ranged from −9.5 to 11.8 m³ ha⁻¹ yr⁻¹, with lower-than-expected growth (<3 m³ ha⁻¹ yr⁻¹) on two-thirds of the sites. In the surface horizon, effective base saturation, Ca²⁺ concentration, base saturation, K⁺ concentration, Ca/Al molar ratio, and Mg/Al molar ratio, were positively correlated with PMAVI and Fe concentration was negatively correlated with PMAVI (p ≤ 0.1). In the subsurface horizon pH_(w) and effective base saturation were positively correlated and Al³⁻ concentration and K⁺ concentration were negatively correlated with PMAVI. We hypothesized that NO₃-N/NH₄-N ratio would also be correlated with PMAVI, but it was not. Correlations between soil chemical indicators and PMAVI suggest that AD may contribute, in part, to the lower-than-expected forest growth on the Monongahela National Forest.     

Comparison of two coniferous plantations in central Japan with respect to forest productivity, growth phenology and soil nitrogen dynamics

Japanese cypress (Chamaecyparis obtusa Endl.) and Japanese cedar (Cryptomeria japonica D. Don) are common species for plantation forestry in Japan. Cypress is conventionally planted on sites of low fertility whereas for cedar high fertility sites are used. Objectives of this study were to compare the productivities of cypress and cedar plantations grown on adjacent sites where common properties of soils, such as pH values and C and N contents, were similar, and to relate the N cycling at their site with productivities. The stem diameter of trees, aboveground litter production and fine root biomass were measured as indices of forest productivity. Parameters of N cycling included pools of total N and mineral N (ammonium + nitrate), annual N leaching, and potentially mineralizable N. The radial stem increment of the two tree species was similar. However, cedar site had higher total basal area and annual basal increment than cypress site reflecting higher tree density on the cedar site. Aboveground litter, fine root biomass, soil organic matter, and N turnover were higher on the cedar site than on the cypress site. However, litter production and fine root biomass per unit basal area was greater at the cypress site. Phenological pattern of stem growth and periodical litter production were similar for both species during the study period (1992–2000), but showed distinct annual variations caused by the fluctuation in the ambient temperature and precipitation. Mineral N content and the N mineralization potential were greater on the cedar site, indicating greater N availability and higher total tree productivity at the cedar site than those at the cypress site. When provided with more space in the canopy to expand more needles and in the soil to develop more fine roots to exploit sufficient resources, the individual cypress trees have the potential to grow faster. On fertile site and at lower tree density, thicker logs of cypress might be yielded.     

Effects of strip wise tillage in combination with liming on chemical and physical properties of acidic spruce forest soils after clear cutting

We investigated the initial effects of strip wise soil loosening (0–35 cm depth) on soil chemical and physical parameters by using a deeply working rotary cultivator in combination with liming and mixing of the dolomite with the soil material of acidic forests. The investigations took place 8 months after the treatment. pH values and contents of exchangeable Ca and Mg increased significantly at the tilled depth whereas the content of exchangeable Al and easily soluble P decreased. The rate of mineralisation increased at this depth which was shown by a loss of Corg, Ntot and short-term loss of NO₃-N. The treatment led to a mobilisation of Mn at the tilled depth. However, the content of exchangeable Pb decreased due to an increased pH value. Below the tillage depth of 35 cm only partly significant changes of exchangeable Mn and NO₃-N were found. The total porosity and bulk density at 10–15 and 40–45 cm depths were not significantly different from those in the control plot, but the rate of infiltration increased significantly.     

Soil water dynamics, growth of Dendrocalamus strictus and herbage productivity influenced by rainwater harvesting in Aravalli hills of Rajasthan

Degraded Aravalli hills in western India require rehabilitation through resource conservation and afforestation for meeting the biomass needs of resource-poor tribes of the region. Rainwater harvesting treatments i.e., control, Contour trench (CT), Gradonie (G), Box trench (BT) and V-ditch (VD) were prepared in <10%, 10–20% and >20% slopes categories and Dendrocalamus strictus L. seedlings were planted in August 2005 with a view to conserve soil and water and increase the productivity of the hills. Soil water content (SWC), survival and height of D. strictus plants were highest (P < 0.05) in <10% slope and all these variables decreased with increase in slope. SWC increased by 27.45% and 25.68% in <10% and >20% slopes, respectively than in 10–20% slope. From lowest in control SWC increased by 11.95%, 20.21%, 17.61% and 11.49% in CT, G, BT and VD treatments, respectively. Growth variables were highest in VD plots but the increase in shoot number was highest (2.9-fold) in CT plots. Increase in effects of rainwater harvesting with time indicated by a change in production pattern from highest (P < 0.05) fresh and dry herbage in <10% slope in 2005 to 10–20% slope (24.66% and 26.09%) in 2006 and >20% slope (42.42% and 48.35%, respectively) in 2007. The increase in herbage was 1.17–2.40-fold in fresh and 1.20–2.52-fold in dry herbage over control. Highest (P < 0.01) production was in V-ditch plots. The treatments order for herbage production was C < CT < G < BT < VD. But the production was highest in BT in <10% and in V-ditch plots in 10–20 and >20% slopes. Conclusively, soil water status is affected by natural slope, stony soil surface and rainwater harvesting structures influencing seedling growth and herbage production. Box trench and V-ditch enhanced surface soil water facilitating herbage growth, whereas contour trench facilitated deep soil water storage, which was made available to the plants after monsoon. Thus rainwater harvesting practices enhanced vegetation cover and productivity of the degraded hills and can be replicated to conserve soil resource and increase biomass for rural poor of the region.     

厦门市坂头林场森林土壤微生物生态分布研究

以森林土壤微生物数量 ,土壤中细菌、放线菌、丝状真菌的优势种群为指标 ,对厦门市坂头林场针叶林、阔叶林土壤微生物的生态分布进行研究。结果表明 ,该林场内森林土壤微生物数量分布阔叶林大于针叶林 ,细菌数量为 10 5～ 10 7CFU·g-1样品 ,丝状真菌 10 4 ～ 10 7CFU·g-1样品 ,放线菌 10 3 ～ 10 5CFU·g-1样品 ,土壤芽孢杆菌数量 10 4 ～ 10 6CFU·g-1样品 。土壤全氮、全磷与微生物总数复相关系数为 0 83,可用微生物总数作为林地肥力的判断指标。细菌分布以腊状芽孢杆菌和巨大芽孢杆菌为主 ;放线菌中链霉菌属为优势种群 ,占总放线菌数 82 4%～ 90 9% ,还有少量的稀有放线菌 ,如小单孢菌属和诺卡氏菌属等 ,链霉菌的不同类群以及稀有放线菌的分布在不同林分中的分布比例有较大的不同 ;土壤丝状真菌属种多样 ,优势属种为青霉、木霉、镰孢霉属等 ;显示了该林场森林土壤微生物的多样性特征。     

不同林分土壤微生物、酶活性与土壤肥力的关系研究综述

土壤微生物和土壤酶活性是反映土壤肥力最为重要的生物学指标之一。文章综合论述了不同林分土壤微生物种群和数量的分布及其影响因素，并对土壤酶活性对土壤肥力的影响做了分析，显示土壤微生物、酶活性与土壤养分有显著的相关关系。     

牙克石市水土保持生态修复的途径研究

文章在分析牙克石市自然条件及水土流失特点的基础上,提出牙克石市水土保持生态修复的可行性及生态修复的措施,以及近年来牙克石市生态修复所取得的可喜成果。     

Floristic diversity and composition of the Biteyu forest in the Gurage mountain chain (Ethiopia): implications for forest conservation

The Afromontane forests of Ethiopia have been under a serious degradation threat. Assessment of floristic diversity and species composition in Biteyu forest of Gurage mountain chain in the central Ethiopia was conducted to examine the pattern of forest structure. Thirty plots of 30 m×30 m were used to record the vegetation and environmental data using systematic sampling technique. The local name, plant scientific names, DBH, height,species abundance and percentage canopy cover of plant species were recorded. Shannon diversity index and Sorensen's coefficients was used for comparison among communities and similar forests in the country. Threats to the forest biodiversity in Biteyu were determined by counting cattle interference and wood stumps as disturbance indicators. Relative Euclidean Distance measures by using Ward's method(linkage) was applied for cluster analysis. Environmental variables were also recorded in each plot. Woody species population structure, basal area and importance value index were analyzed using spreadsheet programs. Data on species distribution and environmental variables in the forest were analyzed by canonical correspondence analysis. A total of 190 species in 154 genera under 73 families were identified. Twenty species were found to be endemic taxa to the Flora Area. Only three plant community types were identified from the cluster analysis due to the high human influence. The Sorensen's coefficient showed the resemblance of the Biteyu forest with other Dry Evergreen Afromontane forests in the country. Moreover, altitude and slope strongly affect the species composition and structure of Biteyu forest. Given the high anthropogenic influence, high endemism, high dependence of the local community on the forest resources, forest conservation and restoration measures should be done by stakeholders.