Prediction model of moisture content of dead fine fuel in forest plantations on Maoer Mountain,Northeast China

Preventing and suppressing forest fires is one of the main tasks of forestry agencies to reduce resource loss and requires a thorough understanding of the importance of factors affecting their occurrence.This study was carried out in forest plantations on Maoer Mountain in order to develop models for predicting the moisture content of dead fine fuel using meteorological and soil variables.Models by Nelson(Can J For Res 14:597-600,1984)and Van Wagner and Pickett(Can For Service 33,1985)describing the equilibrium moisture content as a function of relative humidity and temperature were evaluated.A random forest and generalized additive models were built to select the most important meteorological variables affecting fuel moisture content.Nelson’s(Can J For Res 14:597-600,1984)model was accurate for Pinus koraiensis,Pinus sylvestris,Larix gmelinii and mixed Larix gmelinii—Ulmus propinqua fuels.The random forest model showed that temperature and relative humidity were the most important factors affecting fuel moisture content.The generalized additive regression model showed that temperature,relative humidity and rain were the main drivers affecting fuel moisture content.In addition to the combined effects of temperature,rainfall and relative humidity,solar radiation or wind speed were also significant on some sites.In P.koraiensis and P.sylvestris plantations,where soil parameters were measured,rain,soil moisture and temperature were the main factors of fuel moisture content.The accuracies of the random forest model and generalized additive model were similar,however,the random forest model was more accurate but underestimated the effect of rain on fuel moisture.

Taxonomic and community composition of epigeal arthropods in monoculture and mixed tree species plantations in a deciduous forest of Ghana

Tropical forests provide several ecosystem services and functions and support approximately two-thirds of the world’s biodiversity but are seriously threatened by deforestation.Approaches to counteract this menace have revolved around aff orestation with several or a single tree species.We thus investigated how plantation forests with either a single or several tree species infl uenced arthropod taxonomic and community composition using pitfall traps to sample selected groups of epigeal arthropods(Araneae,Coleoptera,Orthoptera and Hymenoptera)and with environmental variables assessed simultaneously.Our results revealed 54 taxonomic groups with signifi cantly higher taxonomic richness,activity density,and diversity in the mixed stands than in the monoculture stands.The significant differences in community composition were mainly driven by families including Lycosidae,Formicidae,Staphylinidae,Scotylidae,Hydrophilidae,Gryllidae and Scarabaeidae and were explained by distinct habitat characteristics(canopy openness,litter depth,deadwood volume,and tree height).While the diverse tree communities and heterogeneous vegetation structure off ered food and habitat resources for diverse arthropod groups,the allelopathic nature coupled with homogenous stand characteristics of the Tectona grandis stands in the monoculture suppressed the growth of understorey vegetation that could otherwise serve as food and habitat resources for arthropods,which might have led to limited activities and diversity of arthropods in the monoculture plantation stands.The fi ndings thus highlight the need to promote mixed tree plantations in degraded tropical areas,especially when restoring biodiversity is the prime management focus.

Accumulation of heavy metals in stemwood of forest tree plantations fertilized with different sewage sludge doses

The levels of heavy metals that accumulated in stemwood of mature trees grown for 20 years in a plantation in an abandoned peat quarry in areas that were fertilized with different amounts of domestic sewage sludge(180,360,and720 Mg ha-1on a dry basis) were compared with trees grown in a reference nonfertilized area.Included in the study was a hybrid poplar(Populus tremula x Populus tremuloides) developed for use as an energy crop,three local tree species and one introduced tree species.The concentrations of Cd,Cr,Cu,Ni,Pb and Zn in the stemwood of the trees grown in the fertilized and nonfertilized fields were determined,and found to be significantly lower than their respective concentrations in the soil.Cd and Cr were found only in several wood samples at concentrations close to the limits of detection or qualification; therefore,they were not analyzed further.A correlation analysis suggested that 75%of the correlations between the concentrations of heavy metals in the stemwood and the concentrations in the soil were negative.The ability of trees to accumulate the metals from soil in most cases decreased for Cu and Ni; however,the correlations were not as clear for Pb and Zn.The followingsequence for the levels of heavy metals found in the stemwood of the analysed trees was Zn [ Pb [ Ni [ Cu [(Cr,Cd).The results of this study showed that the levels of heavy metals in the studied wood would not exceed the permitted limits of heavy metal pollution in the air and ash when used for energy production.

Effects of natural forest conversion and plantation tree species composition on soil macrofauna communities in Northeast China mountains

As primary and secondary forests are being replaced by plantations across the globe,the soil macrofauna community structure is also affected,but little is known about the impact of mixed culture plantations compared with monocultures on the soil macrofauna.To determine the impact of forest conversion on soil macrofauna,we surveyed the soil macrofauna in two broad-leaved and three coniferous monoculture stands and four coniferous-broadleaved mixed stands,and in adjacent reserved secondary stands as a reference.Soil macro fauna community composition was significant affected by forest type,season and their interaction(P<0.05).The abundance,taxa richness and diversity of soil macro fauna changed to different degrees depending on the plantation type.Broadleaved monoculture stands and secondary stands had similar macrofauna abundance and taxa richness,but values were lower in coniferous stands than in secondary stands.The Shannon index for macrofauna in coniferous stands was also the lowest,but the Pielou index did not differ between forest types.The negative effects of the conifer monoculture on soil macro fauna were not present in the mixed stands with broad-leaved trees.Forest conversion impacted soil properties;soil moisture,NO_(3)^(-),and pH were significant drivers of soil macrofauna community structure.The impact of forest conversion on soil macrofauna was closely dependent on tree species composition and diversity.The macro fauna community structure in the broadleaved and the mixed stands were relatively similar to that in the natural forest,and thus recommended for forest conversion in the study area.

Species-specific biomass allometric models and expansion factors for indigenous and planted forests of the Mozambique highlands

Secondary Miombo woodlands and forest plantations occupy increasing areas in Mozambique,the former due to anthropogenic activities.Plantations,mainly species of Eucalyptus and Pinus,are being established on sites previously covered by secondary Miombo woodlands.This affects the evolution,cycle and spatiotemporal patterns of carbon(C)storage and stocks in forest ecosystems.The estimation of C storage,which is indispensable for formulating climate change policies on sequestrating CO_(2),requires tools such as biomass models and biomass conversion and expansion factors(BCEF).In Mozambique,these tools are needed for both indigenous forests and plantations.The objective of this study is to fit species-specific allometric biomass models and BCEF for exotic and indigenous tree species.To incorporate efficient inter-species variability,biomass equations were fitted using nonlinear mixed-effects models.All tree component biomass models had good predictability;however,better predictive accuracy and ability was observed for the 2-predictors biomass model with tree height as a second predictor.The majority of the variability in BCEF was explained by the variation in tree species.Miombo species had larger crown biomass per unit of stem diameter and stored larger amounts of biomass per stem volume.However,due to relatively rapid growth,larger stem diameters,heights,and stand density,the plantations stored more biomass per tree and per unit area.

Areas with Potential for Commercial Timber Plantations of Enterolobium cyclocarpum (Jacq.) Griseb. in Michoacán, México

Michoacán has a deforested area of 525,260 ha, representing 52,526 ha per year, mainly caused by anthropogenic disturbances such as agricultural burning and forest fires (50%), change of use of land for extensive livestock farming (28%), agriculture (17%) and illegal logging (5%). The establishment of forest plantations is an alternative for reducing the pressure on natural forests and creating options for sustainable development and diversification of production and conversion of land for agricultural and livestock fragmented for forestry purposes. The aim of this study was to determine the potential areas for commercial forest plantations of Enterolobium cyclocarpum (Jacq.) Griseb. in the State of Michoacán, México, through the use of Geographic information systems (GIS). Areas were identified using IDRISI 32, and ArcView software. Screening variables include annual temperature, annual precipitation, land use, soil type, elevation and slope. Products obtained were field verified. Two maps where potential areas for the establishment of commercial forest plantations of E. cyclocarpum shown were obtained. Potential areas for commercial forest plantation establishment are (0% - 15% slope) for commercial forest plantations mechanized was 57,227 ha and (15% - 30% slope) for manual plantations was 6273 ha. The total area in the state with potential for the establishment of the species in the study was 63,500 ha.

Potential Areas for Commercial Timber Plantations of Tabebuia rosea(Bertol.)DC.in Michoacan,Mexico

The targeted area for plant reforestation in the state of Michoacan is made up of eroded areas and pasture induced areas, both adding to 525,260 ha and representing 10.9% of the total surface of the state. The regions with the largest areas in need of reforestation are the Costa with 185,396 ha (29%), Oriente with 106,836 (17%) and Tierra Caliente with 96,284 (15%). Commercial forest plantations are an alternative for reducing the pressure on natural forests and creating options for sustainable and diversified development, changing the land use from fragmented agricultur and livestock purposes to forestry. The object of this study was to determine potential areas for the establishment of commercial forest plantations of Tabebuia rosea (Bertol.) DC. in the state of Michoacan, Mexico, by using geographic information systems. The outlining of potential areas was performed with the IDRISI 32 and ArcView programs, according to the environmental requirements of T. rosea. These environmental requirements include precipitation, temperature, soil, altitude, land use and slope. The analysis resulted in two maps where the potential areas for the establishment of commercial forest plantations with this species were shown, which turned out a total potential area of 54,320 ha, distributed in 47,566 ha considering a slope of 0% - 15% for non-manual forest plantations, and 6754 ha considering a slope of 15% - 30% for manual forest plantations. The ecologic conditions in Michoacan are favorable for successful establishment and development of commercial forest plantations of T. rosea.

Variation of nutrient fluxes by rainfall redistribution processes in the forest canopy of an urban larch plantation in northeast China

Atmospheric deposition(dry and wet deposition)is one of the primary sources of chemical inputs to terrestrial ecosystems and replenishes the nutrient pool in forest ecosystems.Precipitation often acts as a primary transporting agent and solvent;thus,nutrient cycles in forests are closely linked to hydrological processes.We collected precipitation data during a growing season to explore variations in nutrient cycling and nutrient balances in the rainfall redistribution process(wet deposition)in a larch plantation in northeast China.We measured nutrient(NO_(3)^(-),PO_(4)^(3−),Cl^(−),K,Ca,Na,and Mg)inputs via bulk precipitation,throughfall and stemfl ow,and used a canopy budget model to estimate nutrient fl uxes via canopy exchange.Our results suggest that the average concentrations of the base cation(K,Ca,Na,and Mg)showed the following order:stemfl ow>throughfall>bulk precipitation.Throughfall and stemfl ow chemistry dramatically fl uctuated over the growing season when net fl uxes(throughfall+stemfl ow—bulk precipitation)of NO−3,PO3−4,SO2−4,Cl−,K,Ca,Na,and Mg were−6.676 kg·ha^(-1),−1.094 kg·ha^(-1),−2.371 kg·ha^(-1),1.975 kg·ha^(-1),0.470 kg·ha^(-1),−5.202 kg·ha^(-1),−0.336 kg·ha^(-1),and 1.397 kg·ha^(-1),respectively.These results suggest that NO−3,PO3−4,SO2−4,Ca,and Na were retained,while Cl−,K,and Mg were washed off by throughfall and stemfl ow.

Organic mulching promotes soil organic carbon accumulation to deep soil layer in an urban plantation forest

Background:Soil organic carbon(SOC)is important for soil quality and fertility in forest ecosystems.Labile SOC fractions are sensitive to environmental changes,which reflect the impact of short-term internal and external management measures on the soil carbon pool.Organic mulching(OM)alters the soil environment and promotes plant growth.However,little is known about the responses of SOC fractions in rhizosphere or bulk soil to OM in urban forests and its correlation with carbon composition in plants.Methods:A one-year field experiment with four treatments(OM at 0,5,10,and 20 cm thicknesses)was conducted in a 15-year-old Ligustrum lucidum plantation.Changes in the SOC fractions in the rhizosphere and bulk soil;the carbon content in the plant fine roots,leaves,and organic mulch;and several soil physicochemical properties were measured.The relationships between SOC fractions and the measured variables were analysed.Results:The OM treatments had no significant effect on the SOC fractions,except for the dissolved organic carbon(DOC).OM promoted the movement of SOC to deeper soil because of the increased carbon content in fine roots of subsoil.There were significant correlations between DOC and microbial biomass carbon and SOC and easily oxidised organic carbon.The OM had a greater effect on organic carbon fractions in the bulk soil than in the rhizosphere.The thinnest(5 cm)mulching layers showed the most rapid carbon decomposition over time.The time after OM had the greatest effect on the SOC fractions,followed by soil layer.Conclusions:The frequent addition of small amounts of organic mulch increased SOC accumulation in the present study.OM is a potential management model to enhance soil organic matter storage for maintaining urban forest productivity.

Assessing Landsat-8 and Sentinel-2 spectral-temporal features for mapping tree species of northern plantation forests in Heilongjiang Province,China

Background:Accurate mapping of tree species is highly desired in the management and research of plantation forests,whose ecosystem services are currently under threats.Time-series multispectral satellite images,e.g.,from Landsat-8(L8)and Sentinel-2(S2),have been proven useful in mapping general forest types,yet we do not know quantitatively how their spectral features(e.g.,red-edge)and temporal frequency of data acquisitions(e.g.,16-day vs.5-day)contribute to plantation forest mapping to the species level.Moreover,it is unclear to what extent the fusion of L8 and S2 will result in improvements in tree species mapping of northern plantation forests in China.Methods:We designed three sets of classification experiments(i.e.,single-date,multi-date,and spectral-temporal)to evaluate the performances of L8 and S2 data for mapping keystone timber tree species in northern China.We first used seven pairs of L8 and S2 images to evaluate the performances of L8 and S2 key spectral features for separating these tree species across key growing stages.Then we extracted the spectral-temporal features from all available images of different temporal frequency of data acquisition(i.e.,L8 time series,S2 time series,and fusion of L8 and S2)to assess the contribution of image temporal frequency on the accuracy of tree species mapping in the study area.Results:1)S2 outperformed L8 images in all classification experiments,with or without the red edge bands(0.4%–3.4%and 0.2%–4.4%higher for overall accuracy and macro-F1,respectively);2)NDTI(the ratio of SWIR1 minus SWIR2 to SWIR1 plus SWIR2)and Tasseled Cap coefficients were most important features in all the classifications,and for time-series experiments,the spectral-temporal features of red band-related vegetation indices were most useful;3)increasing the temporal frequency of data acquisition can improve overall accuracy of tree species mapping for up to 3.2%(from 90.1%using single-date imagery to 93.3%using S2 time-series),yet similar overall accuracies were achieved using S2 time-series(93.3%)and the fusion of S2 and L8(93.2%).Conclusions:This study quantifies the contributions of L8 and S2 spectral and temporal features in mapping keystone tree species of northern plantation forests in China and suggests that for mapping tree species in China's northern plantation forests,the effects of increasing the temporal frequency of data acquisition could saturate quickly after using only two images from key phenological stages.

Organic matter accumulation in hill forests of Chittagong region, Bangladesh

Litter fall and its effect on forest soil properties at each decomposition stages were investigated in tropical monsoon climatic conditions of three plantations （7-year acacia plantation, 15-year acacia plantation and 18-year mixed plantation） and one natural forest （Si- tapahar forest） from Chittagong hilly region of Bangladesh. Results showed that total accumulation of organic matter increased with plantation age, accompanying with a decrease of annual accumulation rate. Within the same vegetation type, the organic accumulation of both fresh and partially decomposed litter with humus varied significantly （p≤0.05） on hill positions, being highest on bottom slope and decreased gradually towards hilltop in the forest. Reverse trend in accumulation of soil organic matters was shown in 15-year Acacia auriculiformis plantation, from where fuel wood collected. In 7- and 15-year acacia and 18-year mixed broadleaved plantations, rates of total organic matter production consisting of fresh, partially and completely decomposed litter as well as incorporated organic matter in soil were 2554.31, 705.79 and 1028.01 kg.ha^-1.a^-1, respectively, and the corresponding contribution from fresh litter were 38.23, 19.40 and 30.48 kg-ha^-1.a^-1, respectively. In the three plantations and the natural forest, on an average fresh litter constituted 32.45%, partially decomposed litter with humus 13.50% and incorporated organic matter in soil 54.56% of the total organic matter production with mean litter thickness of 0.90 cm. Soil acidity increased with the increase of decomposition stage of organic matter.

A Simple Geospatial Nutrient Budget Model for Assessing Forest Harvest Sustainability across Nova Scotia, Canada

A geospatial GIS-linked spreadsheet model (Nutrient Budget Model—Nova Scotia: NBM-NS) was developed for Nova Scotia to assess the long-term sustainability of forest harvest scenarios as constrained by primary nutrient inputs and outputs due to atmospheric deposition, soil weathering, and leaching. Harvest scenarios refer to user-defined stand-specific removal rates of bole wood, bark, branches, and foliage, based on current or projected forest inventories. These scenarios are evaluated within the context of existing data layers for current climate (mean annual precipitation and air temperatures), atmospheric deposition (N, S, Ca, Mg, K), and soil/substrate types, supplemented by species-specific look-up tables containing expected biomass fractions and nutrient concentrations. This article introduces this model to assess relative site quality and limiting nutrients for red spruce and sugar maple across Nova Scotia. This is followed by an output comparison involving 25 spruce plantations whereby NBM-NS determinations derived using “default” soil survey data are compared with those derived using plantation-specific soil data. Model output shows that (i) Ca and N are the main growth-limiting nutrients across Nova Scotia, (ii) currently projected plantation yields are generally not sustainable on sites underlain by slowly weathering soils, (iii) current soil base cation contents are generally lower than what is reported in historic soil survey reports, and (iv) model results are expected to vary within the context of changing climate, acid deposition levels, and data accuracy.

Response of nitrogen fractions in the rhizosphere and bulk soil to organic mulching in an urban forest plantation

Nitrogen is an essential component in forest ecosystem nutrient cycling.Nitrogen fractions,such as dissolved nitrogen,ammonium,nitrate,and microbial biomass nitrogen,are sensitive indicators of soil nitrogen pools which affect soil fertility and nutrient cycling.However,the responses of nitrogen fractions in forest soils to organic mulching are less well understood.The rhizosphere is an important micro-region that must be considered to better understand element cycling between plants and the soil.A field investigation was carried out on the effect of mulching soil in a 15-year-old Ligustrum lucidum urban plantation.Changes in total nitrogen and nitrogen fractions in rhizosphere and bulk soil in the topsoil(upper 20 cm)and in the subsoil(20-40 cm)were evaluated following different levels of mulching,in addition to nitrogen contents in fine roots,leaves,and organic mulch.The relationships between nitrogen fractions and other measured variables were analysed.Organic mulching had no significant effect on most nitrogen fractions except for the rhizosphere microbial biomass nitrogen(MBN),and the thinnest(5 cm)mulching layer showed greater effects than other treatments.Rhizosphere MBN was more sensitive to mulching compared to bulk soil,and was more affected by soil environmental changes.Season and soil depth had more pronounced effects on nitrogen fractions than mulching.Total nitrogen and dissolved nitrogen were correlated to soil phosphorus,whereas other nitrogen fractions were strongly affected by soil physical properties(temperature,water content,bulk density).Mulching also decreased leaf nitrogen content,which was more related to soil nitrogen fractions(except for MBN)than nitrogen contents in either fine roots or organic mulch.Frequent applications of small quantities of organic mulch contribute to nitrogen transformation and utilization in urban forests.

Impact of site management on changes in soil carbon after afforestation:A review

Afforestation and forest management can increase carbon stocks and account for emission reduction according to the Kyoto Protocol. Site management has important effects on the accumulation of soil carbon after afforestation. This review examines the effects of site management, including soil disturbance, fertilization, thinning, weed control, harvesting and controlled burning, on soil carbon dynamics in plantations, based on recent published results. Soil disturbance can enhance soil carbon losses, with whole ploughing causing the most and disking the least loss of soil carbon. The effects of fertilization and thinning on soil carbon are in- conclusive. Weed control can prevent the carbon input from above-grotmd residue and root turnover and increase soil temperature and soil erosion, which in turn reduces the amount of carbon on the soil surface. Soil carbon decreases with the increase of harvest- ing intensity and the retention of harvest residue can significantly enhance the accumulation of carbon in the soil. Controlled burning before afforestation has a short-term benefit for soil carbon, but it is not beneficial to the sequestration of soil carbon over the long term. Future studies should focus on investigating the long-term impact of site management practices, especially soil fertilization and thinning, on carbon, identifying the response of major functional pools of soil carbon to management practices, understanding the dy- namics of soil nitrogen pools and their role in long-term soil carbon sequestration, as well as quantifying soil carbon processes under different climate conditions and site management scenarios using models.

Pool of Biological Resources for Potential Applications in Solid State Fermentation Obtained from a Forest Plantation of Pinus pseudostrobus Lindl, Mexico

A forest plantation, product of the reforestation of pine trees, represented a pool of biological resources for the implementation of a solid state fermentation process. The trees were identified as Pinus pseudostrobus Lindl from which lignocellulosic material in the form of pine needles was collected. Soil fungi, responsible for plant litter decomposition, were cultured at laboratory conditions and tested for their ability to grow on cellulose and hemicellulose as the sole carbon sources. A fungal strain, belonging to the genus Penicillium, was selected for growing it on pine needles as the substrate in a solid state culture. After following the culture for six days, the newly isolated strain exhibited a much higher capacity for spore production and holocellulose degradation, compared to a purchased strain of Penicillium chrysogenum and two control conditions. This work marks the beginning of future studies focused on commercial applications and represents the first report of a biotechnological process based on pine needles and their degradation by an ascomycetes species belonging to the genus Penicillium.

Thinning and in-stream wood recruitment in riparian second growth forests in coastal Oregon and the use of buffers and tree tipping as mitigation

Many aquatic habitats in coastal Oregon have been impacted by historic land use practices that led to losses of in-stream wood and associated degraded fish habitats. Many of these streams are now bordered by stands of dense second growth forests（30–80 years） that are incorporated into riparian buffer zones with low wood recruitment and storage. Thinning in riparian zones is one management option to increase the rate of large tree growth and eventually larger in-stream wood, however, it raises concern about impacts on current wood recruitment, among other issues. Using a forest growth simulation model coupled to a model of in-stream wood recruitment, we explore riparian management alternatives in a Douglas-fir plantation in coastal Oregon. Alternatives included：（1） no treatment,（2） single and double entry thinning, without and with a 10-m buffer, and（3） thinning combined with mechanical introduction of some portion of the thinned trees into the stream（tree tipping）. Compared to no treatment, single and double entry thinning on one side of a channel, without a 10-m buffer, reduce cumulative instream wood volume by 33 and 42 %, respectively, after100 years（includes decay）. Maintaining a 10-m buffer reduces the in-stream wood loss to 7 %（single entry thin）and 11 %（double entry）. To completely offset the losses of in-stream wood in a single entry thin（on one or both sides of the stream）, in the absence or presence of a 10-m buffer,requires a 12–14 % rate of tree tipping. Relative to the notreatment alternative, cumulative in-stream wood storage can be increased up to 24 % in a double-entry thin with no buffer by tipping 15–20 % of the thinned trees（increased to 48 % if thinning and tipping simultaneously on both sides of the stream）. The predicted increases in in-stream wood that can occur during a thin with tree tipping may be effective for restoring fish habitat, particularly in aquatic systems that have poor habitat conditions and low levels of in-stream wood due to historic land use activities.

Linear programming approach for optimal forest plantation

The aim of this research was to identify species suitable for plantation. We first identified species for potentially suitable for plantation based on ecological capabilities regarding soil properties. We determined the area of plantation for different species based on ecological capabilities. Then, we collected relevant data such as growth patterns of different species, labor requirements for plantation and plantation cost. A linear programming model and two integer linear programming models were used for optimization. The appropriate species based on ecological capabilities were ash, elm, maple, oak and bald cypress. A linear programming model was used based on ecological capabilities classification to determine the land area of different species for plantation. Then, two integer linear programming models were employed to select the species for plantation. We set ecological properties unequal for all of the species in the first run of the integer programming model. Two groups were classified： group one included maple and ash; group two included bald cypress,oak and elm. The second integer programming model assumed equal ecological properties for all the species.Results of linear programming showed that maple and bald cypress were appropriate for plantation at the site and their plantation areas should be 151.3 and 355.3 ha, respectively. Results of the first integer linear programming model showed that maple and bald cypress would be economically profitable for plantation. The results of the second integer linear programming model showed that only bald cypress would be appropriate for plantation.

田林老山中山两类森林凋落物研究

田林老山中山两类森林凋落物研究梁宏温（广西农学院林学分院，南宁５３０００１）ＳｔｕｄｉｅｓｏｎｔｈｅＬｉｔｔｅｒｆａｌｌｏｆＴｗｏＦｏｒｅｓｔＴｙｐｃｓｉｎＭｉｄ—ＡｌｔｉｔｕｄｅｏｆＬａｏｓｈａｎＭｏｕｎｔａｉｎｉｎＴｉａｎｌｉｎＣｏｕｎｔｙ．￥Ｌ...

Douglas-fir climate sensitivity at two contrasting sites along the southern limit of the European planting range

Douglas-fir(Pseudotsuga menziesii(Mirb.)Franco)is an important exotic tree species that was planted across a large part of Europe during the last century.In both experimental trials and conventional forest plantations,the trees grow at a high rate and produce high-quality timber.The present study investigated climate-growth relationships of Douglas-fi r at two Italian sites that contrast in climate:a Mediterranean area in southern Italy(Mercurella site)and a cooler,moister site in the northern Apennines without summer aridity(Acquerino).The relationship between tree-ring chronologies and monthly climatic variables was evaluated by a moving average and correlation analysis.Results showed that the minimum temperature in February and in March play a key role for Douglas-fi r at both sites,with a positive eff ect on growth.At the northern site,it is also highly sensitive to late summer temperatures(negative correlation)and spring–summer precipitation(positive correlation).Growth rates in southern latitudes were high even in Europe and in the Mediterranean environment,with low sensitivity to climatic fl uctuation.On the basis of our results,further common garden experiments should test adaptation and the interaction between genetics and environment of second-or third-generation seeds from old stands across Europe such as done by the old International Union of Forest Research Organizations(IUFRO)or the European Douglasfi r Improvement Research Cooperative(EUDIREC)experimentation programmes.

Impacts of competition and nitrogen addition on plant stoichiometry and non-structural carbohydrates in two larch species

Previous research has shown that competition between plants can have differential effects on leaf stoichiometry and non-structural carbohydrate(NSC)in different environments.However,little attention has been given to understanding these effects on non-photosynthetic organs,particularly of deciduous tree species.Here we assess the impact of competition on below and aboveground biomass,stoichiometry,nutrient composition and NSC in pure and mixed forests of two Larch species,Larix kaempferi and L.olgensis under nitrogen(N)addition.Nitrogen enrichment did not result in stronger intraspecific competition for both species and L.olgensis benefited from the presence of L.kaempferi under different N levels.Stems kept relatively stable C/N compared to roots and branches in response to competition,while N addition imposed stronger impacts on N/P of different organs rather than competition.In contrast to stable C concentrations,starch and soluble sugar concentrations were more easily impacted by competition and the addition of nitrogen.Competition forced L.kaempferi and L.olgensis to allocate more carbon into storage by increasing their starch concentration and starch/soluble sugar of stems under competition.However,no significant differences in stoichiometry and NSC concentration between intra-and interspecific competition were found.NSC and nutrient pools of L.kaempferi stems,branches and coarse roots consistently declined due to competition regardless of N addition.Coarse and fine roots of L.kaempferi accumulated more N when in competition with L.olgensis than with a conspecific neighbor under N addition.Our results show that NSC was more sensitive to competition relative to stoichiometric traits(N and P)of non-photosynthetic organs.