Effects of uprooting tree on herbaceous species diversity, woody species regeneration status and soil physical characteristics in a temperate mixed forest of Iran

We conducted a study to examine the pattern of development of herbaceous plant species, woody species regeneration and soil physical characteristics after tree uprooting in 20-ha areas of Experimental Forest Station of Tarbiat Modares University located in a temperate forest of Mazandaran province in the north of Iran. Soil bulk density, soil texture and moisture from pit and mound (PM) were measured in the laboratory. Results show that the soil bulk density was most in soil deeper layers at mound top, and the soil moisture content was most in soil deeper layers at Pit bottom. Our study supports that the micro-topography of PM (pit and mound) topography will create a mosaic of environmental conditions. This environmental heterogeneity could be responsible for the diversity of herbaceous plant species and regeneration of woody species. It is recommend that the fallen trees with PM structure should remain in the protected area without clearing as the best option for forest restoration. This information can be useful for forest management that attempts to emulate natural processes.     

云冷杉林风倒区林隙和掘根微立地微气候变化

2013年7月,在小兴安岭凉水国家级自然保护区云冷杉林风倒区1.5 hm2的样地内,选取由掘根倒木形成且包含坑和丘微立地的大、中、小3个代表性林隙。在每个林隙中心安装HOBO自动气象站,测定了7—9月林隙中心以及林隙内丘顶和坑底的总辐射、光合有效辐射(PAR)、空气温度和相对湿度,并在郁闭林分和空旷地设置对照。分析了不同大小林隙之间以及林隙内丘顶和坑底之间小气候在生长季的动态变化及其差异。结果表明:林隙总辐射、PAR以及空气温度依照大林隙、中林隙和小林隙的次序依次降低;同一林隙内,丘顶的总辐射、PAR和空气温度大于坑底,丘顶空气相对湿度小于坑底;月均气温和月均PAR均为7月>8月>9月,绝大多数按照空旷地、大林隙、中林隙、小林隙和郁闭林分的次序递减,仅9月份小林隙的气温大于中林隙。同一林隙的平均气温日较差均为7月>9月>8月,相同微立地(林隙中心、丘顶、坑底)气温日较差均为大林隙>中林隙>小林隙。相同月份丘顶的气温日较差均大于坑底。各林隙空气相对湿度均为8月>9月>7月,并按照空旷地、大林隙、中林隙、小林隙和郁闭林分的次序依次递增。7月份大林隙的总辐射、PAR与8、9月份相比均差异显著。9月不同大小林隙之间的总辐射、PAR差异均不显著。7—9月,大林隙和小林隙中心的空气湿度均差异显著。同一林隙相同月份丘顶和坑底的PAR、空气相对湿度差异均显著,空气温度差异不显著;无论是在林隙内还是林隙内的丘顶和坑底,同一林隙不同月份的温度差异均显著。     

The influence of windthrow microsites on tree regeneration and establishment in an old growth mountain forest

The Rothwald forest in Lower Austria represents one of the few never logged old growth forests in Central Europe. Here, the influence of windthrow pits and mounds on tree regeneration in a spruce-fir-beech mountain forest was studied. Two main factors for recolonisation of sites after disturbance were investigated: (i) the trapping ability of microsites for seeds and (ii) the ability of particular tree species to establish and grow on different microsites. On two one hectare permanent sample plots, pits resulting from windthrow with existing tree trunks were recorded. At each windthrow three microsites were determined: pit, pitwall and undisturbed forest floor. If the windthrow plate already collapsed and formed a mound, this microsite was recorded as well. Furthermore, a control site was established at each windthrow. For two years the development of seedlings at four different microsites and the according control sites were monitored. To describe the variability of environmental factors possibly influencing seedling establishment and survival, litter, humus and soil attributes, herb vegetation cover as well as light availability (GSF) were assessed. In addition, soil temperature, chemical soil properties and water content were recorded at randomly selected windthrows. The distribution of the seedlings was assessed with a Redundancy Analysis, its occurrence modelled with a logistic regression and the mortality analysed with the Kaplan-Maier lifetime function. In contrast to the assumption of seed accumulation in concave microsites because of secondary dispersal, the pit microsites show comparable seed rain to the control site. However, pits have the lowest seedling numbers and by far the highest mortality rates of seedlings. The thickness of leaf litter was identified as a major driver of suitability of a microsite for recolonisation. Through its thickness, it inhibits germination and smothering of seedlings poses a particular high hazard during the winter period. Also different establishment patterns of the investigated tree species were detected. The results indicate that windthrows create microsite heterogeneity and plant species richness but limit tree population size and spatial distribution of the occurring tree species.     

Effect of land-use conversion from forest to cocoa agroforest on soil characteristics and quality of a Ferric Lixisol in lowland humid Ghana

Soil fertility decline caused by deforestation, soil degradation and low input use has become a primary factor limiting sustainable utilization of soil resources in cocoa agroforestry systems on acid soils in lowland humid Ghana. Changes in and responses of soil physico-chemical properties and soil quality to land-use change was investigated along a chronosequence of farm fields on a Ferric Lixisol in the Ashanti region of Ghana. Soil bulk density increased significantly only in the top 0–10 cm soil layer. Concentrations and stocks of soil organic carbon (SOC) and total N decreased significantly in the top 0–10 and 10–20 cm soil depths. By 30 years after forest conversion, cocoa system had re-accumulated up to 38.8 Mg C ha^?1 or 85 % of initial forest carbon stock values. Total porosity (%) decreased significantly in shaded-cocoa fields in comparison with the natural semi-deciduous forest. An assessment of soil deterioration using degradation indices (DIs) revealed that total soil quality (0–20 cm) deteriorated significantly (DI = –60.6) in 3-year-old of cocoa system but improved in 15 and 30-year-old systems. Available P stocks declined consistently while soil exchangeable Ca, K and Mg stocks as well as cation exchange capacity (CEC) and base saturation remained more or less stable with a tendency to improve. The inclusion of leguminous shade trees during early plantation development, development of mechanisms for the integration of cover crops and enhancement of farmer capability in improved farm management are required to maintain high C and nutrient base, minimize soil quality degradation during plantation development phase and sustain long-term productivity.     

Structure,composition and diversity of tree species in tropical moist deciduous forests of Eastern India: a case study of Nayagarh Forest Division,Odisha

Quantitative assessment of tree species diversity from sample plots in seven forest ranges of Nayagarh Forest Division in Odisha state in the Eastern Ghats of India was made during the period April, 2011 to November, 2013. A total of 120 transects(1000 m × 5 m) were laid in Nayagarh, Odogaon, Pancharida, Khandapada, Dasapalla,Mahipur, and Gania forest ranges and tree stems of at least 30 cm GBH were measured. The regeneration potential of trees was assessed from 5 m × 5 m sample plots located within the main transect. A total of 177 tree species belonging to 120 genera and 44 families were recorded from the study area. Shorea robusta, Buchanania lanzan, Lannea coromandelica, Terminalia alata and Cleistanthus collinus were the predominant tree species. The stand density varied in the range of 355.33–740.53 stems h~a)-1) while basal area ranged from 7.77 to 31.62 m~2 ha~(-1). The tree density and species richness decreased with increasing girth class. The highest number of species and maximum density was recorded in the girth class of 30–60 cm. The Shannon–Weiner and Simpson Indices with respect to trees with C30 cm GBH varied in the range of 2.07–3.79 cm and 0.03–0.37 cm respectively and the values of diversity indices are within the reported range for tropical forests of Indian sub-continent. The families, Dipterocarpaceae,Anacardiaceae, Combretaceae and Euphorbiaceae contributed to maximum species richness, stand density, and basal area. Regeneration of many tree species was observed to be poor. The present study provides baseline data for further ecological studies, forest management, and formulation of site-specific strategies for conservation of biological diversity in moist deciduous forests of Eastern India.     

Distribution patterns of tree,understorey, and detritus biomass in coniferous and broad-leaved forests of Western Himalaya,India

Forest biomass pools are the major reservoirs of atmospheric carbon in both coniferous and broad-leaved forest ecosystems and thus play an important role in regulating the regional and global carbon cycle. In this study, we measured the biomass of trees, understorey, and detritus in temperate (coniferous and broad-leaved) forests of Kashmir Himalaya. Total ecosystem dry biomass averaged 234.2 t/ha (ranging from 99.5 to 305.2 t/ha) across all the forest stands, of which 223 t/ha (91.9–283.2 t/ha) were stored in above- and below-ground biomass of trees, 1.3 t/ha (0.18–3.3 t/ha) in understorey vegetation (shrubs and herbaceous), and 9.9 t/ha (4.8–20.9 t/ha) in detritus (including standing and fallen dead trees, and forest floor litter). Among all the forests, the highest tree, understorey, and detritus biomass were observed in mid-altitude Abies pindrow and Pinus wallichiana coniferous forests, whereas the lowest were observed in high-altitude Betula utilis broad-leaved forests. Basal area has showed significant positive relationship with biomass (R² = 0.84–0.97, P < 0.001) and density (R² = 0.49–0.87). The present study will improve our understanding of distribution of biomass (trees, understorey, and detritus) in coniferous and broad-leaved forests and can be used in forest management activities to enhance C sequestration.     

Soil carbon sequestration in agroforestry systems: a meta-analysis

Agroforestry systems may play an important role in mitigating climate change, having the ability to sequester atmospheric carbon dioxide (CO₂) in plant parts and soil. A meta-analysis was carried out to investigate changes in soil organic carbon (SOC) stocks at 0–15, 0–30, 0–60, 0–100, and 0 ≥ 100 cm, after land conversion to agroforestry. Data was collected from 53 published studies. Results revealed a significant decrease in SOC stocks of 26 and 24% in the land-use change from forest to agroforestry at 0–15 and 0–30 cm respectively. The transition from agriculture to agroforestry significantly increased SOC stock of 26, 40, and 34% at 0–15, 0–30, and 0–100 cm respectively. The conversion from pasture/grassland to agroforestry produced significant SOC stock increases at 0–30 cm (9%) and 0–30 cm (10%). Switching from uncultivated/other land-uses to agroforestry increased SOC by 25% at 0–30 cm, while a decrease was observed at 0–60 cm (23%). Among agroforestry systems, significant SOC stocks increases were reported at various soil horizons and depths in the land-use change from agriculture to agrisilviculture and to silvopasture, pasture/grassland to agrosilvopastoral systems, forest to silvopasture, forest plantation to silvopasture, and uncultivated/other to agrisilviculture. On the other hand, significant decreases were observed in the transition from forest to agrisilviculture, agrosilvopastoral and silvopasture systems, and uncultivated/other to silvopasture. Overall, SOC stocks increased when land-use changed from less complex systems, such as agricultural systems. However, heterogeneity, inconsistencies in study design, lack of standardized sampling procedures, failure to report variance estimators, and lack of important explanatory variables, may have influenced the outcomes.     

Riparian forests along small streams on managed forest land in Sweden

This study investigated characteristics of riparian forests on managed forest land in Sweden. Forest and site characteristics were inventoried at three sites, located along a south to north gradient, in 139 transects placed perpendicular to 38 stream reaches (<10?m wide), in forests representing the age classes 0–25, 26–75 and >75 years. Starting from the stream edge, the 30?m long transects were divided into three zones: 0–5, 5–15 and 15–30?m. The stem volumes of Pinus sylvestris L., Picea abies (L.) H. Karst, Betula spp. and broadleaved trees, the basal area share of Alnus spp., the stem density, and Sphagnum spp. coverage all showed an effect of zone (p?P. sylvestris and the highest volumes of P. abies, Betula spp. and broadleaved trees as well as the highest total stem density and basal area share of Alnus spp. Some characteristics of the northernmost site tended to differ from the two sites located in south-central Sweden. Knowledge of the characteristics of riparian forests as found in this study could aid long-term forestry planning and improve precision in the preservation and development of riparian forests with certain qualities.     

Development over time of the tree-related microhabitat profile: the case of lowland beech–oak coppice-with-standards set-aside stands in France

European forest managers are implementing set-aside measures in managed forests to restore key structures for forest biodiversity such as tree-related microhabitats (TreMs). However, the time required to regenerate these structures is little known. We assessed the patterns of thirteen TreM types on 282 plots in 24 lowland forests in southwestern France. We applied a synchronic sequence ranging from 1 to 80 years after the last harvest, a time frame which is considered long enough to observe significant changes in the TreM profile. We sampled lowland beech–oak coppice-with-standards stands representative of the different forest ownerships and management regimes occurring in France; our assessment included both public and private forests with or without formal management plans. We found that both TreM density and diversity just after harvesting were lower, though not significantly so, in private stands without any management plan than in the other management regimes. We observed both significantly higher TreM density and diversity in plots harvested 10–15 years ago than in plots harvested 1–5 years ago. The next marked difference did not occur until stands had been harvested 70–80 years ago. Globally, time since last harvest was the best explanatory variable for variations in both TreM density and diversity. We therefore recommend: (1) conserving more habitat trees in harvested areas, particularly cavity trees, since the densities we observed were much lower than the densities required by cavity-dwelling species, and (2) letting set-aside patches freely complete several full silvigenetic cycles. This latter practice would avoid the inefficacy (or possibly even negative effects) of a temporary conservation network, and would also simplify management of the network over time. Further research should assess TreM occurrences in a permanent reserve network. Diachronic observations would make it possible to highlight the drivers of TreM profile development.     

Investigation of phytosociological parameters and physico-chemical properties of soil in tropical semi-evergreen forests of Eastern Himalaya

The study of floral diversity in forest and its development are incomplete without taking consideration of plant-soil interactions. So with this view in mind, the present study was conducted in tropical semi-evergreen forests of the Mokukchung district, Nagaland, in eastern Himalaya. The aim of the study was to investigate the phytosociological parameters in relation to soil properties.Seven sites were randomly selected to study the soil properties at up to one meter in depth and a phytosociological study was carried out in nearby areas via the quadrate method. In the studied sites, the richness of tree species varied from 4 to 15 ha~(-1), with Gmelina arborea and Duabanga grandifloras being the common species.The highest total basal area was recorded in 10 mile village(47,998.16 cm~2ha~-1)) followed by Minkong village site(32,704.66 cm~2ha~(-1)). Soil physical and chemical properties—i.e. bulk density(BD), soil p H, organic carbon(OC),available nitrogen(N), available phosphorus(P), and available potassium(K) were analyzed using standard procedures. Significant differences were observed in the soil properties. The basal area of species showed significant positive correlation in terms of available K(0.754) and OM(0.302) content in soil, and the Shannon–Wiener diversity index(H) is also positively correlated with the available N content(0.402). The undisturbed nature of the sites played an important role in maintaining the soil fertility and floral diversity of the sites. Moreover, sites with maximum productivity and soil fertility are considered as potential carbon sequestration areas in the region while sites with the low soil fertility need restoration.     

Phosphorus dynamics and solubilizing microorganisms in acid soils under different land uses of Lesser Himalayas of India

Although chemical and some soil physical properties have been studied under different land uses of the Lesser Himalayas of India, very limited information is available on soil biochemical properties. Hence we investigated phosphorus (P) fractions [total P (TP), inorganic P (P_i), organic P (P_o), available P, microbial biomass P (MBP)], enzyme activities [dehydrogenase, phosphatases, phytase], phosphate solubilizing bacteria (PSB) and fungi (PSF), and their correlations of acid soils (0–15 and 15–30 cm depths) under different land uses (viz, organic farming, maize–wheat, apple orchard, undisturbed oak forest and uncultivated land of the Indian Himalayas). All land use systems differed significantly for the P fractions, except TP. The highest values for TP, P_i, available P and MBP were found in soils under oak forest and lowest in uncultivated land. However, P_o content was highest in apple orchard. The organic farming (organic manures field under garden pea-french bean cropping system for > 10 years) maintained highest activities of dehydrogenase, acid phosphatase and alkaline phosphatase. The highest phytase activity and highest numbers of PSB (99 × 10³ g^?1 soil) and PSF (30 × 10³ g^?1 soil) were observed in the rhizosphere soils of oak forest. Significant relationships between soil P fractions and enzyme activities, except alkaline phosphatase, were recorded in surface soil layer. PSB and PSF population were also correlated significantly with P fractions and enzyme activities. This would lead us to understand the level of degradation of P pools due to cultivation over forest system and the suitable management practices needed for soil quality restoration.     

Influence of soil properties and burial depth on Persian oak (<Emphasis Type="Italic">Quercus brantii</Emphasis> Lindl.) establishment in different microhabitats resulting from traditional forest practices

In seasonally dry environments such as the Zagros woodlands (Iran), severe drought stress and lack of appropriate management practices can cause failure of oak afforestation or reforestation. We investigated the effect of soil properties and burial depth on Persian oak (Quercus brantii Lindl.) establishment in different microhabitats resulting from traditional forest practices. Four microhabitats that were based on forest structure were considered for oak acorn seeding: (1) inside old sprout clumps (ISPC); (2) under the canopy of tall trees (UCTT); (3) outside the canopy of tall trees and sprout clumps; and (4) near recent stumps or sprout clumps. Acorns were seeded at two depths (2 and 5 cm), and seedling survival and growth variables were recorded for 4 years, together with soil chemical and biological attributes. Stepwise discriminant analysis showed that a combination of total soil nitrogen, cation exchange capacity, available phosphorus and potassium, litter depth, microbial quotient, metabolic coefficient, substrate-induced respiration and earthworm abundance was the best variables to characterise the microhabitats. With the exception of pH, bulk density and soil texture, these variables were higher in UCTT and ISPC than in the other microhabitats. Seedling emergence and survival were greater at a seed depth of 5 cm than at 2 cm. Seedling height and shoot, root and leaf biomasses were higher in the UCTT microhabitat compared to the other microhabitats and correlated positively with soil nutrients contents and most of the soil biological variables but negatively with soil bulk density. This study emphasised the role of microhabitats in creating a “canopy effect” producing favourable physical, chemical and biological soil conditions. In particular, large oak trees form islands of fertility and therefore are of key importance for successful seedling establishment in forests subjected to intense human activities.     

Earthworm population and microbial activity temporal dynamics in a Caspian Hyrcanian mixed forest

Few studies have analyzed how tree species within a mixed natural forest affect the dynamics of soil chemical properties and soil biological activity. This study examines seasonal changes in earthworm populations and microbial respiration under several forest species (Carpinus betulus, Ulmus minor, Pterocarya fraxinifolia, Alnus glutinosa, Populus caspica and Quercus castaneifolia) in a temperate mixed forest situated in northern Iran. Soil samplings were taken under six individual tree species (n = 5) in April, June, August and October (a total of 30 trees each month) to examine seasonal variability in soil chemical properties and soil biological activity. Earthworm density/biomass varied seasonally but not significantly between tree species. Maximum values were found in spring (10.04 m^?2/16.06 mg m^?2) and autumn (9.7 m^?2/16.98 mg m^?2) and minimum in the summer (0.43 m^?2/1.26 mg m^?2). Soil microbial respiration did not differ between tree species and showed similar temporal trends in all soils under different tree species. In contrast to earthworm activity, maximum microbial activity was measured in summer (0.44 mg CO₂–C g soil^?1 day^?1) and minimum in winter (0.24 mg CO₂–C g soil^?1 day^?1). This study shows that although tree species affected soil chemical properties (pH, organic C, total N content of mineral soils), earthworm density/biomass and microbial respiration are not affected by tree species but are controlled by tree activity and climate with strong seasonal dynamics in this temperate forest.     

Soil carbon stock assessment in the tropical dry deciduous forest of the Sathanur reserve forest of Eastern Ghats,India

Climate change and carbon mitigation through forest ecosystems are some of the important topics in global perspective. Tropical dry forests are one of the most widely distributed ecosystems in tropics, which remain neglected in research. The soil organic carbon (SOC) stock was quantified on a large scale (30 1-ha plots) in the dry deciduous forest of the Sathanur reserve forest of Eastern Ghats. The SOC stock ranged from 16.92 to 44.65 Mg/ha with a mean value of 28.26 ± 1.35 Mg/ha. SOC exhibited a negative trend with an increase in soil depth. A significant positive correlation was obtained between SOC stocks and vegetation characteristics viz. tree density, shrub basal area, and herb species richness, while a significant negative correlation was observed with bulk density. The variation in SOC stock among the plots obtained in the present study could be due to differences in tree abundance, herb species richness, shrub basal area, soil pH, soil bulk density, soil texture etc. The present study generates a large-scale baseline data of dry deciduous forest SOC stock, which would facilitate SOC stock assessment at the national level as well as to understand its contribution on a global scale.     

Aboveground biomass and carbon stock in the largest sacred grove of Manipur,Northeast India

Aboveground biomass and carbon stock in the largest sacred grove of Manipur was estimated for trees with diameter [10 cm at 1.37 m height.The aboveground biomass,carbon stock,tree density and basal area of the sacred grove ranged from 962.94 to 1130.79 Mg ha~(-1),481.47 to 565.40 Mg ha~(-1) C,1240 to 1320 stem ha~(-1) and79.43 to 90.64 m~2 ha~(-1),respectively.Trees in diameter class of 30–40 cm contributed the highest proportion of aboveground biomass(22.50–33.73%).The aboveground biomass and carbon stock in research area were higher than reported for many tropical and temperate forests,suggesting a role of spiritual forest conservation for carbon sink management.     

Carbon stock of Banja forest in Banja district,Amhara region,Ethiopia: An implication for climate change mitigation

This study estimates the carbon stock of Banja Forest which is natural and dry Afromontane forest type in Banja District, northwest of Ethiopia. A systematic sampling method was used to identify each sampling point through the Global Positioning System. A total of 63 plots measuring 20 × 20 m were employed to collect tree species and soil data. Losses on ignition and the Walkley–Black method were used to estimate biomass and soil carbon stock, respectively. The carbon stock of trees was estimated using an allometric equation. The results revealed that the total carbon stock of the forest was 639.87 t/ha whereas trees store 406.47 t/ha, litter, herbs, and grasses (LHGs) 2.58 t/ha and soil 230.82 t/ha (up to 30 cm depth). The carbon pools’ carbon stock variation with altitude and slope gradients were not significant (p > 0.05) which was similar to other previous studies. The Banja Forest is a reservoir of high carbon and thus acts as a great sink of the atmospheric carbon. It can be concluded that the Forest plays a role in climate change mitigation. Hence, it should be integrated with reduced emission from deforestation and degradation (REDD⁺) and the clean development mechanism (CDM) of the Kyoto Protocol to catch monetary benefits.     

Use and knowledge of forest plants among the Ribeirinhos, a traditional Amazonian population

This study assessed the ethnobotanical use and knowledge of forest plant diversity among the Ribeirinhos, a traditional population of the Brazilian Amazon living in a protected area (Tapajós National Forest, West of Pará), and compared the importance of forest plants used in their daily activities with the use of cultivated plants (agrobiodiversity) from their home gardens and swidden-fallows. We used two complementary quantitative ethnobotanical methods, based on (i) daily scan observations in 14 families’ homes, and (ii) ethnobotanical inventories of trees, palms and lianas of DBH ≥ 5 cm in 23 plots each of 0.1-ha, set up in three types of forests. Analyses of the ethnobotanical surveys in the plots showed that most forest species (120 out of the 140 inventoried, i.e. 86 %) were acknowledged to be useful by the informants (use value >0) and accounted for 91.2 % of the inventoried individuals measuring DBH ≥ 5 cm. However, daily observations of plant gathering in homes showed that only a few forest species considered ‘useful’ were used daily, whilst species cultivated in gardens and swidden-fallows represented the majority of species used. The Ribeirinhos were also found to know as much about using forest plant diversity, if not more, than other traditional groups from Amazonia or from other tropical regions of South America, including the Amerindians. The article concludes with some recommendations for adapting development practices to local uses of plant diversity in this protected area.     

Distribution changes of woody plants in Western Iran as monitored by remote sensing and geographical information system: a case study of Zagros forest

The status of woody plants in dry-land systems is a fundamental determinant of key ecosystem processes. Monitoring of this status plays an important role in understanding the dynamics of woody plants in arid and semi-arid ecosystems. The present study determined the dynamism of the Zagros forests in Iran using Remote Sensing and Geographic Information System techniques and statistical science. The results show that the density of trees varied from 10 to 53 % according to the physiographic and climatic conditions of semi-arid regions. The best and lowest correlation between vegetation indices and forest density were obtained for the global environmental monitoring index (GEMI; R ² = 0.94) and soil adjust vegetation index (R ² = 0.81), respectively. GEMI is used to monitor land use changes over a 10-year period. Results show that 2720 ha² of forest have been destroyed by human interference and tillage on steep slopes during this period which also resulted in the loss of the fertile soil layer. GEMI determined the areas with a biomass of trees and could normally separate border regions with low biomass density of trees from regions without canopy cover. The results revealed that assessment of forest and vegetation cover in arid and semi-arid arduous forest regions using satellite digital numbers and ordinary sampling is subject to uncertainty. A stratified grouping procedure should be established to increase the accuracy of assessment.     

The larger,the better? Effects of delayed diameter-limit cutting on old-growth attributes and saproxylic beetle diversity in temperate oak forests

Intensive management implies harvesting large, old trees, which reduces the old-growth attributes. This negatively affects biodiversity, especially saproxylic beetles. In managed temperate oak forests, rotation extension induced by increasing the diameter threshold of final harvest by about 10 cm compared to conventional practices (i.e. DBH around 70 cm) might mitigate this negative effect. Here, we used a gradient of the proportion of overmature trees (DBH?≥?80 cm) among mature trees (DBH?≥?70 cm) across plots of high oak French forests to test the potential effect of increasing diameter threshold on (1) structural features and (2) species composition and diversity of saproxylic beetles communities. We assessed deadwood and microhabitats availability (i.e. volume/density and diversity) and canopy openness in 81 1-ha plots across eleven French forests. Results highlighted that a larger proportion of overmature trees, for a given density of mature trees, had limited effects on structural features: only cavities density showed a significant positive response, with no cascading effect on cavicolous beetles. Moreover, the proportion of overmature trees had no significant effect on the composition of saproxylic beetles communities (and ecological variables altogether explained only 17% of the composition inertia). By contrast, mature tree density enhanced microhabitat density and indirectly increased the abundance of rare species. Thus, shifting DBH from 70 to 80 cm in high oak forest could have no or limited effect on saproxylic beetles conservation. Improved strategies might rather stem from combining (1) longer rotation extension and (2) less intensive management practices in extended rotation stands.     

Long-term development of soil organic carbon and nitrogen stocks after shelterwood- and clear-cutting in a mountain forest in the Bavarian Limestone Alps

Forest soils store large stocks of soil organic matter (SOM) and are of vital importance for the ecosystem supply with nutrients and water. According to the available literature, depending on management regime and site properties, different negative and positive effects of forest management (particularly of forest thinnings and shelterwood cuttings) on soil organic carbon (SOC) and nitrogen (N) stocks are observed. To elucidate the long-term impact of different shelterwood systems and small clear-cuttings on the OC and N stocks of shallow calcareous soils in the Bavarian Alps, we conducted soil humus inventories on different plots of a mixed mountain forest management experiment started in 1976. The silvicultural multi-treatment experiment consists of a NW-exposed Main Experiment (ME) site with eight plots of different cutting intensity (two unthinned controls, two light shelterwood cuttings = 30 % of basal tree area removed, two heavy shelterwood cuttings = 50 % removed, and two clear-cuttings = 100 % removed) on Triassic dolostone. Additionally, plots were installed at a N-exposed dolostone (ND) site and two sites (FL, FH) on Flysch sandstone (each with one unthinned control and one heavy shelterwood cutting). The shelterwood cuttings from 1976 were repeated in 2003 to re-establish the overstorey basal area as produced by the first cutting in the different plots. Thirty-five years after the first treatments, forest floor SOC and N stocks were significantly decreased (up to ?70 %) at the different shelterwood and clear-cut treatments compared to the unthinned control at the ME site despite vigorous development of natural rejuvenation. Also significantly smaller topsoil (forest floor plus mineral soil 0–10 cm depth) OC stocks (between ?16 and ?20 %) were detected at the thinned compared to the control plots. Differences in topsoil N stocks were also considerable (between ?3 and ?14 %), but substantially smaller than OC stock changes. For the total soil down to 30 cm depth, OC stocks in the differently thinned plots were consistently smaller compared to the unthinned control plots. Comparable to our findings at the ME site, heavy shelterwood plots at the three other sites (ND, FL, and FH) showed significant losses of OC in the forest floor (up to 43 %), mineral soil (up to 38 %), topsoil (up to 38 %), and total soil (up to 34 %). Significant large absolute and relative SOC decreases coincided with sites characterized by large initial humus stocks. Moreover, significant effects of heavy shelterwood cuttings on SOC and N stocks (on average 23 % SOC loss and 13 % soil N loss for the forest floor plus the uppermost 10 cm mineral soil) were detected on a regional level. Our results show that different shelterwood systems are accompanied with a considerable long-term decrease in OC and N stocks in shallow calcareous forest soils of the Bavarian Alps. However, a comparison with a windthrown forest stand at a nearby similar site indicates that SOM losses after thinning operations are small compared to decreases following windthrow or other calamities with subsequent large soil erosion and increased mineralization processes.