Future impacts of climate change on forest fire danger in northeastern China

Climate warming has a rapid and far-reaching impact on forest fire management in the boreal forests of China. Regional climate model outputs and the Canadian Forest Fire Weather Index （FWI） Sys- tem were used to analyze changes to fire danger and the fire season for future periods under IPCC Special Report on Emission Scenarios （SRES） A2 and B2, and the data will guide future fire management planning. We used regional climate in China （1961 1990） as our validation data, and the period （1991–2100） was modeled under SRES A2 and B2 through the weather simulated by the regional climate model system （PRECIS）. Meteorological data and fire danger were interpolated to 1 km 2 by using ANUSPLIN software. The average FWI value for future spring fire sea- sons under Scenarios A2 and B2 shows an increase over most of the region. Compared with the baseline, FWI averages of spring fire season will increase by 0.40, 0.26 and 1.32 under Scenario A2, and increase by 0.60, 1.54 and 2.56 under Scenario B2 in 2020s, 2050s and 2080s, respectively. FWI averages of autumn fire season also show an increase over most of the region. FWI values increase more for Scenario B2 than for Scenario A2 in the same periods, particularly during the 2050s and 2080s. Average future FWI values will increase under both scenarios for autumn fire season. The potential burned areas are expected to increase by 10% and 18% in spring for 2080s under Scenario A2 and B2, respectively. Fire season will be prolonged by 21 and 26 days under ScenariosA2 and B2 in 2080s respectively.

Nitrogen Deposition and Its Spatial Pattern in Main Forest Ecosystems along North-South Transect of Eastern China

A continuous three-year observation(from May 2008 to April 2011)was conducted to characterize the spatial variation of dissolved inorganic nitrogen(DIN)deposition at eight main forest ecosystems along the north-south transect of eastern China(NSTEC).The results show that both throughfall DIN deposition and bulk DIN deposition increase from north to south along the NSTEC.Throughfall DIN deposition varies greatly from 2.7 kg N/(ha·yr)to 33.0 kg N/(ha·yr),with an average of 10.6 kg N/(ha·yr),and bulk DIN deposition ranges from 4.1 kg N/(ha·yr)to 25.4 kg N/(ha·yr),with an average of 9.8 kg N/(ha·yr).NH4+-N is the dominant form of DIN deposition at most sampling sites.Additionally,the spatial variation of DIN deposition is controlled mainly by precipitation.Moreover,in the northern part of the NSTEC,bulk DIN deposition is 17%higher than throughfall DIN deposition,whereas the trend is opposite in the southern part of the NSTEC.The results demonstrate that DIN deposition would likely threaten the forest ecosystems along the NSTEC,compared with the critical loads(CL)of N deposition,and DIN deposition in this region is mostly controlled by agricultural activities rather than industrial activities or transportation.

Ecological control of forest pest： a new strategy for forest pest control

In comparison with integrated pest management and chemical control, the authors put forward a new strategy of forest pest control, named ecological control of forest pest （ECFP）. This paper reviewed the development history, summarized the concept and principles of ECFP, discussed the technology and methods of ECFP, and evaluated the ECFP and its application conditions.

Characteristics of typhoon disturbed gaps in an old-growth tropical montane rainforest in Hainan Island, China

Disturbances that create gaps can shape the structure and function of forests. However, such disturbance regimes in Asian tropical montane rainforests remain largely unquantified. Least studied are typhoon disturbances that are attributable to climate change. We investigated gap characteristics in terms of size, age, and gap-maker to quantify the gap disturbance regimes in an intact old-growth tropical montane rainforest on Hainan Island, China. The intensity of typhoons has increased since 1949, and typhoon winds blow mostly (45.5%) from the northeast corner of Hainan Island, resulting in a higher frequency of gaps in the northeast. A total of 221 gap-makers (trees that fell to create canopy gaps) and 53 gaps were observed in a 3.16 ha old-growth rainforest. Most canopy gaps (85%) were < 200 m(2). The average size of canopy gaps was smaller in the rainforest than in other tropical forests, while the average size of expanded gaps was similar to those in other tropical forests. The maximum age of gaps was 23.5 years indicating that gaps had more rapid turnover than other parts of tropical forests. The frequency distribution of gap-makers followed a lognormal distribution with a distinctive peak at three gap-makers, which was different from the inverse J-shaped curve typical of other tropical forests. Gaps were recorded mainly on slopes between 20A degrees and 35A degrees and wood density of gap-makers was between 0.6 and 0.7 g cm(-3). Our results suggest that small-scale disturbance was the dominant agent of gap formation in this old-growth rainforest that is subject to increasing typhoon disturbances.

Reconciliation of research on forest carbon sequestration and water conservation

Carbon sequestration and water conservation are two of the key ecosystem services that forests provide for societal need to address environmental issues.Optimization of the dual services is the ultimate goal in forest management for mitigating global climate change and safeguarding terrestrial water balance.However,there are some tradeoff s between gain in forest productivity and ecosystem water balance.We conducted literature review based on published articles for learned knowledge on forest carbon fi xation and hydrological regulations.Some knowledge gaps and research needs are identifi ed by examining the inter-connections between forest carbon sequestration and water conservation.Past researches have helped gain basic understanding of the mechanisms and controls of forest carbon fi xation and hydrological regulations as two separate issues.Tools and approaches are well established for quantifying and monitoring forest carbon and hydrological issues,operating at diff erent spatial and temporal scales.There are knowledge gaps on how to design aff orestation schemes facilitating enhanced ecosystem services in forest carbon sequestration and water conservation.For the top-down planning of aff orestation in regions where water availability is anticipated to be problematic,the questions of how much and where to plant for given land availability,known environmental implications,and sustained regional development and livelihood need to be addressed.For local management considerations,the questions of what and how to plant prevail.Eff orts are needed in joint studies of forest carbon sequestration and water conservation functionalities,specifi cally in relation to establishment and management of planted forests aiming for delivering regulatory ecosystem services in carbon sequestration,water conservation and other social values.We propose an integrated framework with dual consideration of carbon sequestration and water conservation in forest management for future research pursue.

Application of the Nutrient Cycling Model NuCM to a Forest Monitoring Site Exposed to Acidic Precipitation in China

The nutrient cycling model NuCM is one of the most detailed models for simulating processes that influence nutrient cycling in forest ecosystems. A field study was conducted at Tieshanping, a Masson pine (Pinus massoniana Lamb.) forest site, in Chongqing, China, to monitor the impacts of acidic precipitation on nutrient cycling. NuCM simulations were compared with observed data from the study site. The model produced an approximate fit with the observed data. It simulated the mean annual soil solution concentrations in the two simulation years, whereas it sometimes failed to reproduce seasonal variation. Even though some of the parameters required by model running were measured in the field, some others were still highly uncertain and the uncertainties were analyzed. Some of the uncertain parameters necessary for model running should be measured and calibrated to produce a better fit between modeled results and field data.

Spatial and temporal distribution of forest fire frequency and forest area burnt in Jilin Province, Northeast China

Forest fires caused by natural forces or human activities are one of the major natural risks in Northeast China.The incidence and spatial distribution of these fires vary over time and across the forested areas in Jilin Province,Northeast China.In this study,the incidence and distribution of 6519 forest fires from 1969 to 2013 in the province were investigated.The results indicated that the spatiotemporal distribution of the burnt forest area and the fire frequency varied significantly by month,year,and region.Fire occurrence displayed notable temporal patterns in the years after forest fire prevention measures were strictly implemented by the provincial government.Generally,forest fires in Jilin occurred in months when stubble and straw were burned and human activities were intense during traditional Chinese festivals.Baishan city,Jilin city,and Yanbian were defined as fire-prone regions for their high fire frequency.Yanbian had the highest frequency,and the fires tended to be large with the highest burned area per fire.Yanbian should thus be listed as the key target area by the fire management agency in Jilin Province for better fire prevention.

Spatial heterogeneity of fine root biomass of Pinus massoniana forests in the Three Gorges Reservoir Area, China

Environmental heterogeneity is a constant presence in the natural world that significantly affects plant behavior at a variety of levels of complexity. In order to estimate the spatial pattern of fine root biomass in the Three Gorges Reservoir Area, the spatial heterogeneity of fine root biomass in the upper layer of soils （0-10 cm） in three Mas- son pine （Pinus massoniana） stands in the Three Gorges Reservoir Area, China, was studied in 30 m x 30 m plots with geostatistical analysis. The results indicate that 1） both the live and dead fine root biomass of stand 2 were less than those of other stands, 2） the spatial variation of fine roots in the three stands was caused together by structural and ran- dom factors with moderate spatial dependence and 3） the magnitude of spatial heterogeneity of live fine roots ranked as： stand 3 〉 stand 1 〉 stand 2, while that of dead fine roots was similar in the three stands. These findings suggested that the range of spatial autocorrelation for fine root biomass varied considerably in the Three Gorges Reservoir Area, while soil properties, such as soil bulk density, organic matter and total nitrogen, may exhibit great effect on the spatial distribution of fine roots. Finally, we express our hope to be able to carry out further research on the quantitative relation- ship between the spatial heterogeneous patterns of plant and soil properties.

Forest landscape ecology and its applications in China

Landscape ecology is playing an increasingly important role in resources management and landuse planning in recent decades and attracting much attention from resource managers and scientists in China as well as in the world. Reviews of landscape ecology development in China have been well documented, whereas forest landscape ecology and its applications receive relatively fewer reviews. In this paper, we first present a brief review of the historical development and current advances of landscape ecology in China and then introduce the applications of landscape ecology to forest park designs, urban greenspace planning, ecological restoration, biodiversity conservation and forest eco-hydrology. Finally, the problems with the application of forest landscape ecology in China, such as inadequate synthesis and integration, lack of basic research on patterns and processes, basic data shortage and model usage problem are discussed on the basis of which we suggest a future direction of forest landscape ecology in China.

Analysis of spatiotemporal variations in the characteristics of soil microbial communities in Castanopsis fargesii forests

Castanopsis fargesii is a good afforestation plants and various microorganisms play important roles in mediating the growth and ecological functions of this species.In this study,we evaluated changes in microbial communities in soil samples from C.fargesii forests.The phospholipid fatty acid(PLFA)biomarker method was used to obtain bacteria,fungi,actinomycetes,gram-positive bacteria(G?),gram-negative bacteria(G-),aerobic bacteria,and anaerobic bacteria to investigate spatiotemporal changes in microbial communities during the growing season.The results show that soil microorganisms were mainly concentrated in the upper 20-cm layer,demonstrating an obvious surface aggregation(P<0.05).Large amounts of litter and heavy rainfall during the early growing season resulted in the highest PLFA contents for various microorganisms,whereas relatively low and stable levels were observed during other times.The dominant species during each period were bacteria.G+ or aerobic bacteria were the main bacterial populations,providing insights into the overall trends of soil bacterial PLFA contents.Due to the relative accumulation of refractory substances during the later stages of litter decomposition,the effects of fungi increased significantly.Overall,our findings demonstrate that the main factors influencing microbial communities were litter,rainfall,and soil field capacity.

Different mechanisms underlying divergent responses of autotrophic and heterotrophic respiration to long-term throughfall reduction in a warm-temperate oak forest

Background:There are many studies on disentangling the responses of autotrophic(AR)and heterotrophic(HR)respiration components of soil respiration(SR)to long-term drought,but few studies have focused on the mechanisms underlying its responses.Methods:To explore the impact of prolonged drought on AR and HR,we conducted the 2-year measurements on soil CO_(2) effluxes in the 7th and 8th year of manipulated throughfall reduction(TFR)in a warm-temperate oak forest.Results:Our results showed long-term TFR decreased HR,which was positively related to bacterial richness.More importantly,some bacterial taxa such as Novosphingobium and norank Acidimicrobiia,and fungal Leptobacillium were identified as major drivers of HR.In contrast,long-term TFR increased AR due to the increased fine root biomass and production.The increased AR accompanied by decreased HR appeared to counteract each other,and subsequently resulted in the unchanged SR under the TFR.Conclusions:Our study shows that HR and AR respond in the opposite directions to long-term TFR.Soil microorganisms and fine roots account for the respective mechanisms underlying the divergent responses of HR and AR to long-term TFR.This highlights the contrasting responses of AR and HR to prolonged drought should be taken into account when predicting soil CO_(2) effluxes under future droughts.

Effects of microtopography on spatial point pattern of forest stands on the semi-arid Loess Plateau,China

Microtopography may affect the distribution of forests through its effect on rain redistribution and soil water distribution on the semi-arid Loess Plateau,China.In this study,we investigated the characteristics of microtopography on two shady slopes（slope A,5 hm2,uniform slope;slope B,5 hm2,microtopography slope） and surveyed the height,the diameter at breast height and the location（x,y coordinates） of all selected individual trees（Robinia pseudoacacia Linn.,Pyrus betulifolia Bunge,Populus hopeiensis Hu ＆ Chow,Armeniaca sibirica Lam.,Populus simonii Carr.and Ulmus pumila Linn.） on slope A and slope B in the watersheds of Wuqi county,Shaanxi province.Subsequently,the effects of microtopography on the spatial pattern of forest stands were analyzed using Ripley＇s K（r） function.The results showed that：（1） The maximal aggregation radiuses of the tree species on the uniform slope（slope A） were larger than 40 m,whereas those of the tree species on the microtopography slope（slope B） were smaller than 30 m.（2） On slope B,the spatial association of R.pseudoacacia with P.betulifolia,A.sibirica,P.simonii and U.pumila varied from being strongly negative to positive at microtopography scales.The spatial association of Populus hopeiensis Hu ＆ Chow with U.pumila also varied from being strongly negative to positive at microtopography scales.However,there was no spatial association between P.betulifolia and P.hopeiensis,P.betulifolia and A.sibirica,P.betulifolia and P.simonii,P.betulifolia and U.pumila,P.hopeiensis and A.sibirica,P.hopeiensis and P.simonii,A.sibirica and P.simonii,A.sibirica and U.pumila,and P.simonii and U.pumila.On slope A,the spatial association between tree species were strongly negative.The results suggest that microtopography may shape tree distribution patterns on the semi-arid Loess Plateau.

Responses of soil CH_(4) fluxes to nitrogen addition in two tropical montane rainforests in southern China

Background:Atmospheric nitrogen(N)deposition is projected to increase in the next few decades,which may have a marked impact on soil-atmosphere CH_(4) fluxes.However,the impacts of increased atmospheric N depositions on soil CH_(4) flux in tropical rainforests are still poorly understood.From January 2015 to December 2018,a field experiment was conducted in a primary tropical montane rainforest(PTMR)and a secondary tropical montane rainforest(STMR)in southern China to quantify the impact of N additions at four levels(N0:0 kg N⋅ha^(-1)⋅year^(-1);N25:25 kg N⋅ha^(-1)⋅year^(-1);N50:50 kg N⋅ha^(-1)⋅year^(-1);N100:100 kg N⋅ha^(-1)⋅year^(-1)on soil CH_(4) flux.Results:Four years of measurements showed clear seasonal variations in CH_(4) flux in all treatment plots for both forest types(PTMR and STMR),with lower rates of soil CH_(4) uptake during the wet season and higher rates of soil CH_(4) uptake during the dry season.Soil CH_(4) uptake rates were significantly and negatively correlated with both soil temperature and soil moisture for both forest types.Annual CH_(4) uptake for the N0 plots from the PTMR and STMR soils were2.20 and1.98 kg N⋅ha^(-1)⋅year^(-1),respectively.At the PTMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 19%,29%,and 36%for the N25,N50,and N100 treatments,respectively.At the STMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 15%,18%,and 38%for the N25,N50,and N100 treatments,respectively.High level N addition had a stronger inhibitory impact on soil CH_(4) uptake than did the low level N addition.Conclusion:Our data suggest that soil CH_(4) uptake in tropical rainforests is sensitive to N deposition.If atmospheric N deposition continues to increase in the future,the soil CH_(4) sink strength of tropical rainforests may weaken further.

Assessing stand structure in successional stages of dark coniferous forests in western Sichuan, China

Subalpine dark coniferous forests in the western Sichuan Province of China play an important role in the hydrological processes in the upper reaches of the Yangtze River. Second-growth forests, with different stand successional stages, have developed as a result of logging over the past 50 years. Forest cover and stand structure changed greatly with concomitant degradation of forest ecosystem functions. To understand how the stand structures of the second-growth forests change during the stand succession process, we analyzed stand structure characteristics and an old-growth state index of the bamboo and moss-forest types. We found that stand structure at the young successional stage featured one-third of the structure characteristics of the old-growth dark coniferous forests,while the structure of the medium-aged stage had reached half the structure of the old-growth state. The two forest types were similar in the rate of development at the young successional stage but differed at the medium-aged stage;the moss-forest type had more advanced development than the bamboo-forest type at the medium-aged successional stage.

Seed production,seed dispersal and seedling establishment of two afromontane tree species in and around a church forest：implications for forest restoration

Background：Seed production,seed dispersal and seedling establishment are relevant life phases of plants.Understanding these processes and their patterns is essential to recognize vegetation dynamics and to apply it to forest restoration.Methods：For Olea europaea and Schefflera abyssinica,fecundity was estimated using randomized branch sampling.Seed dispersal and seedling establishment were monitored using spatially explicit seed traps and plots.Dispersal functions were calibrated applying inverse modeling.Results：O.europaea produced more seeds and had longer dispersal distances compared to S.abyssinica.Correlations between observed and predicted number of recruits were statistically significant.Seedlings of the two species showed different niche requirements.Conclusions：The studied species were recruitment-limited due to low dispersal activity or lack of suitable microsites.Restoration relying on natural regeneration should overcome these limitations by increasing disperser visitation and reducing biotic and abiotic stresses.

Variations in root chemistry of three common forest species,southwestern China

Root chemistry varies with tree species and root diameter but little information is available about Tibetan forest species. The root chemistry of three root diameter classes (fine: 0–2 mm, medium: 2–5 mm, coarse: 5–10 mm) of three subalpine species (Abies faxoniana Rehd. and Wild, Picea asperata Mast., and Betula albosinensis Burkill) were investigated. Carbon concentrations, and carbon/nitrogen and carbon/phosphorus ratios increased but nitrogen, phosphorus and nitrogen/phosphorus ratios decreased with increasing root diameter. The roots of the conifers had higher carbon levels, and higher carbon/nitrogen and carbon/phosphorus ratios than birch roots. The opposite was found with nitrogen and phosphorus levels and nitrogen/phosphorus ratios. Lignin concentrations decreased but cellulose concentrations increased with greater root diameters. The results indicate that diameter-associated variations in root chemistry may regulate their contribution to detrital pools which has important implications for below-ground carbon and nutrient cycles in these subalpine forests.

Modifying regeneration strategies classification to enhance the understanding of dominant species growth in fire-prone forest in Southwest China

Background:In fire-prone ecosystems,plant species having different post-fire regeneration strategies(PFRS)coexist at the local scale while showing different growth dynamics.To evaluate the effect of PFRS on species regeneration,we investigated the plant communities burned in different years in the central Yunnan Province,Southwest China.Several indicators describing plant growth and population importance were measured to compare the regeneration of four dominant tree species,including one facultative seeders(FS)and three obligate resprouters(OR).Partial correlation and mixed linear effect modeling were applied to disentangle the contribution of intrinsic and environmental factors to the interspecific variation in post-fire regeneration.Results:We identified two subtypes of plant growth strategy in the early post-fire stage for OR species;i.e.,number growth(ORþN)priority and height growth(ORþH)priority for sprouting stems.Generally,the FS and OR species varied in height growth rate with different temporal dynamics.The ORþN species occupied post-fire space horizontally with more resprouts and larger coverage than ORþH and FS species at the earlier stage.In contrast,the ORþH species generally had far less resprouts per clump,more variations in stem height and basal diameter.Factor analysis showed that the variation of post-fire plant regeneration was not effectively explained by environmental factors(R2<20%);however,the linear mixed models with the modified PFRS as a random effect substantially increased the explanation.Conclusions:The differentiated regeneration dynamics and growth priorities in the four dominant tree species indicated a critical dichotomy of habitat occupation strategy for the resprouter species during the early stage of post-fire forest restoration.Our study uncovered a trade-off between height versus number growth priority in the post-fire tree growth strategy and provides a novel perspective in understanding the living space occupying(niche partitioning)process and species coexistence in post-fire forest community assembly.

Change of Forest Ecosystem Service Function and Its Value in Kanas Nature Reserve

In order to clarify the service function and value of forest ecosystem in Kanas Nature Reserve, the ecological service function and its value of forest ecosystem in Kanas Nature Reserve in 2009 and 2014 were evaluated by using the method of Specifications for Assessment of Forest Ecosystem Services in China(LY/T 1721-2008). The results showed that in 2014, the total value of forest ecosystem service function in Kanas Nature Reserve increased by 7.34% compared with that in 2009, and the value of water conservation and biodiversity accounted for the largest proportion. The increasing rate of functional value of shrub forest land was obviously higher than that of coniferous forest land and broad-leaf forest land. The service function and value of different forest types were obviously different.

Evaluation on Comprehensive Benefit of Natural Forest Protection Project in Southwest China

According to the problem of seriously degraded natural forest in Southwest China prior to the implementation of Natural Forest Protection Project, under the guidance of principle of practicality and systematicness, we establish the comprehensive-benefit evaluation index system of restoring the degraded natural forest in Southwest China, including 3 second-level indices, 12 third-level indices and 24 fourth-level indices. In addition, we use the method of Analytic Hierarchy Process to conduct comprehensive-benefit evaluation on implementation of Natural Forest Protection Project in Southwest China. The results show that since ten years of implementation of Natural Forest Protection Project in Southwest China, it has gained considerable comprehensive benefit. The comprehensive evaluation index of Natural Forest Protection Project in Southwest China is 83.08; the ecological benefit index of Natural Forest Protection Project in Southwest China is 56.75; the economic benefit index of Natural Forest Protection Project in Southwest China is 19.05; the social benefit index of Natural Forest Protection Project in Southwest China is 7.28. The effect of construction of Natural Forest Protection Project in Southwest China is good. The evaluation index system and research results in this paper will provide the empirical guidance for comprehensive-benefit evaluation of Natural Forest Protection Project in China, and especially in Southwest China.

Spatial Pattern of Forest Carbon Storage and Carbon Density in the Kanas National Natural Reserve

Based on the sub-forest management inventory, volume-derived biomass and mean biomass, carbon storage and its spatial distribution of forest vegetation in Kanas National Nature Reserve(hereinafter referred to as the Reserve) were calculated. The results showed that carbon storage of forest vegetation in the Reserve was 3.004 7 Tg C, mean carbon density was 49.58 Mg C/hm^2; carbon storage of different vegetation types: forest land >shrubbery > open forest > scattered trees, among which carbon storage of forest land accounted for 90.18% of the total carbon storage of the forest vegetation, and mean carbon density of forest land was 68.87 Mg C/hm^2; in terms of regional distribution, spatial distribution of carbon storage and carbon density declined from southwest to northeast; in the Reserve, carbon storage of mature and over-mature forest stands accounted for 79.89% of carbon storage of forest land. If scientifi c management is applied, carbon sequestration capacity of forest will be improved.