Variation in winter daily range area of red deer(Cervus elaphus xanthopygus) based on DNA extracted from fecal samples

With environmental change and increased human activity,wild red deer(Cervus elaphus xanthopygus)populations and habitat area continue to decrease.Red deer is a main prey species of Amur tiger(Panthera tigris altaica).Factors affecting red deer winter home range in the Wanda montains of northeast China are not well understood.In this study,we aimed to better document red deer daily ranges to support conservation of red deer.A second objective was to develop a practical research method combining macro-and micro-technology for home range research on a variety of rare or endangered wild species.We collected 105 fresh fecal samples of red deer in three different periods during winter from December 2012 to March 2013 in the Wandashan region,Heilongjiang Province,China.Individual and sex identities were analyzed based on fecal DNA using microsatellite DNA.We used samples from deer farms for correction and validation of our identifications from field samples.We used a combination of molecular scatology,3S techniques(GPS),and direct observation to estimate winter daily range areas.Based on eleven microsatellite loci,we identified 18 individuals,10 females and 8 males,with a correction factor of 1.00 and sex ratio of 1:0.8.The mean(±SE)number of alleles was 5.1±0.41,and mean polymorphism information content was 0.63±0.03.Expected heterozygosity ranged from 0.46 to 0.81,with a mean of 0.69±0.03,and mean observed heterozygosity was 0.73±0.07.Sizes of mean daily ranges were 26.1±1.1 ha in December,89.3±1.6 ha in January,and 67.5±1.9 ha in March,indicating the following trend for daily range area:middle winter>late winter>early winter.Mean daily range area was insignificantly larger for males than for females.Estimated winter daily ranges were similar to those reported for Europe.Our combination of macro-and micro-technology proved useful for estimating winter home range areas of red deer.     

Traditional mule logging method in Hyrcanian Forest: a study of the impact on forest stand and soil

We inventoried plant regeneration and soil compaction along mule trails to evaluate damage to forest stands and regeneration follow-ing mule hauling before and after operations in Kheyrud Forest in the...     

Effects of white-tailed deer on vegetation structure and woody seedling composition in three forest types on the Piedmont Plateau

White-tailed deer (Ododcoileus virginiana) can substantially affect the structure and species composition of a forest. The tolerance of a forest community to browsing may vary by type as a result of varying biotic and abiotic factors of the environment. To date, no studies have compared the effects of browsing among forest communities within a physiographic region. We investigated the effects of browsing on vegetation structure and woody seedling composition in three forest types (oak–hickory, Virginia pine–eastern red cedar, bottomland hardwood) in Manassas National Battlefield Park (MNBP), Virginia, USA. We compared forb cover, vertical plant cover (0–1.5 m tall), and survival of tagged seedlings in 10 exclosed (2 m × 6 m) and 10 unexclosed plots in each forest type during a 5-year period. No differential effects of browsing were found among forest types. In all forest types, deer (67 deer/km²) suppressed forb and vertical plant cover to levels less than would be expected in the absence of deer. Seedling survival rates of most species were significantly reduced by browsing. By the 4th year of the study, box elder (Acer negundo), hickory (Carya spp.), and red maple (Acer rubrum) had been eliminated from unexclosed plots, and red and white oaks (Quercus spp.) dramatically reduced. Ash (Fraxinus spp.), black cherry (Prunus serotina), and hackberry (Celtis occidentalis), although significantly impacted, remained the most abundant species throughout the study. These findings suggest that white-tailed deer may be modifying the structure of the forest interior to the extent that it adversely affects wildlife species dependent on a dense understory to thrive. We predict that the future composition of forests in MNBP will shift towards stands with fewer species and a greater dominance of ash, black cherry, and hackberry, particularly in the oak–hickory and bottomland hardwood forests, where the majority of current dominants are most affected.     

Review on the decomposition and influence factors of coarse woody debris in forest ecosystem

Coarse woody debris （CWD） is an important and particular component of forest ecosystems and is extremely important to forest health. This review describes the decomposition process, decomposition model and influence factors. CWD decomposition is a complex and continuous process and characterizes many biological and physical processes, including biological respiration, leaching, and fragmentation. All these processes have closed relationships between each other and work synergistically. During decomposition, there are many controlling factors mainly including site conditions （temperature, humidity, and OJCO2concentration）, woody substrate quality （diameter, species and compound） and organism in CWD. The decomposition rate is generally expresses through a constant k which indicate the percent mass, volume or density loss over time, and can be determined by long-term monitoring, chronosequence approach and the radio between input and the total mass. Now using mathematical models to simulate decomposition patterns and estimate the decomposition rate is widely applied, especially the exponential model. We brought forward that managing and utilizing for the CWD in forest was a primary objective on all forest lands. And it is should be intensified to integrate many related research subjects and to carry a comprehensive, long-term and multi-scale research which mainly focus on seven sections.     

Long-term influence of fire and harvesting on boreal forest age structure and forest composition in eastern Québec

In boreal forests, historical variations in the area disturbed by natural disturbances or harvesting have rarely been compared. We measured temporal and spatial variations in areas affected by severe fires and clearcutting throughout the 20th century in a 57, 332 km² section of the eastern Canadian boreal forest. We examined the effects of these disturbances on spatio-temporal variations in the abundance of forests >60 years. Natural variability for the abundance of forests >60 years was estimated from simulations of natural disturbance regimes. We also measured compositional and structural differences between three categories of stands originating from relatively recent disturbances (∼50 years; clearcutting, fires, and clearcutting followed by fires), and one category of stands that were undisturbed for at least 200 years. At the regional level, we observed that forests >60 years gradually became scarcer throughout the 20th century due to a gradual expansion of harvested areas, an effect most pronounced in the southern part of the region, where mature and old forest abundance was clearly outside the range of natural variability at the end of the studied period. At the stand level, forest composition and structure differed between stand-origin categories: clearcutting-origin stands contained more balsam fir (Abies balsamea), fire-origin stands more black spruce (Picea mariana), and fire/clearcutting-origin stands more hardwoods (Betula papyrifera and Populus tremuloides). Overall, we estimate that strict forest management targets based on natural disturbance regimes will be difficult to achieve in eastern North-American boreal forests, most notably because contemporary disturbance rates, including both clearcutting and fire, have gradually become higher than the fire rates observed during the preindustrial period.     

Effects on stream water chemistry and forest vitality after whole-catchment application of dolomite to a forest ecosystem in southern Norway

An acidified, 0.8 km² coniferous-forested catchment was limed with 3 t ha⁻¹ of coarse-grained dolomite powder in September 1994. The liming resulted in an immediate change in runoff water chemistry relative to the stream of an adjacent reference catchment. pH, calcium, magnesium and acid neutralising capacity (ANC) increased and inorganic Al decreased after liming. Potential favourable water quality for sensitive organisms remained relatively constant over the post-liming period (7 years), and model simulations indicate that adequate water quality may last for an additional 40–50 years. NO₃ concentrations showed no significant change due to liming. A significant increasing trend in TOC was attributed to liming. Concentrations of Cd, Co, Fe, Mn, Ni and Zn were lower in the limed stream than in the reference stream during a period of 3 years after liming, whereas concentrations of As, Cu, and Pb were not significantly different. Steep slopes, thin soils, high amounts of precipitation and thus dominance of surface and subsurface flow in this catchment may explain the rapid response in runoff. During the first 6 years after liming there have been no significant effects on tree growth and vitality (crown density and crown colour). This experiment shows that liming of forested catchments may be a viable method to obtain long-term improvement in water quality and potential positive effects for acid-sensitive aquatic organisms.     

Effects of roads,topography, and land use on forest cover dynamics in the Brazilian Atlantic Forest

Roads and topography can determine patterns of land use and distribution of forest cover, particularly in tropical regions. We evaluated how road density, land use, and topography affected forest fragmentation, deforestation and forest regrowth in a Brazilian Atlantic Forest region near the city of São Paulo. We mapped roads and land use/land cover for three years (1962, 1981 and 2000) from historical aerial photographs, and summarized the distribution of roads, land use/land cover and topography within a grid of 94 non-overlapping 100 ha squares. We used generalized least squares regression models for data analysis. Our models showed that forest fragmentation and deforestation depended on topography, land use and road density, whereas forest regrowth depended primarily on land use. However, the relationships between these variables and forest dynamics changed in the two studied periods; land use and slope were the strongest predictors from 1962 to 1981, and past (1962) road density and land use were the strongest predictors for the following period (1981–2000). Roads had the strongest relationship with deforestation and forest fragmentation when the expansions of agriculture and buildings were limited to already deforested areas, and when there was a rapid expansion of development, under influence of São Paulo city. Furthermore, the past (1962) road network was more important than the recent road network (1981) when explaining forest dynamics between 1981 and 2000, suggesting a long-term effect of roads. Roads are permanent scars on the landscape and facilitate deforestation and forest fragmentation due to increased accessibility and land valorization, which control land-use and land-cover dynamics. Topography directly affected deforestation, agriculture and road expansion, mainly between 1962 and 1981. Forest are thus in peril where there are more roads, and long-term conservation strategies should consider ways to mitigate roads as permanent landscape features and drivers facilitators of deforestation and forest fragmentation.     

A spatial analysis of forest management and its contribution to maintaining the extent of shrubland habitat in southern New England, United States

Conservation organizations in the northeastern United States (US) recommend forest clearcutting to create shrubland habitat, which is required by many wildlife species with declining populations. The planning of habitat management programs is hampered by a lack of information on the current extent of shrubland habitat and the current rate of forest clearcutting that creates shrubland habitat. We addressed these information gaps by using a combination of automated and manual approaches to determine the extent and spatial configuration of shrubland habitat and recent forest clearcuts. We focused on the state of Rhode Island because (a) it is representative of the northeastern US in terms of the prevalence of private ownership of forests, and the ongoing decline in the populations of many shrubland wildlife species; (b) federal, state and private conservation groups are actively promoting clearcuts to create shrubland habitat; (c) many state-wide GIS databases are available; and (d) the spatial extent of the state made our results both generalizable and politically relevant. Our fine-scale mapping allowed a detailed analysis of shrubland distribution in conjunction with other available GIS layers that facilitates identification of priority areas for habitat management. We found that the extent of upland shrubland in non-coastal areas is decreasing by at least 1.5% annually. Considering the lack of consensus about conservation targets for the amount of shrubland, we propose that conservation organizations attempt to stabilize rather than expand the extent of shrubland habitat. This approach would provide an opportunity to assess whether the current extent of shrubland is sufficient to maintain reduced but stable wildlife populations that require this habitat. We propose a coordinated forest management program with targets for increased forest management on conservation lands. We found that the average patch size of shrubland created by recent clearcuts is large enough for most shrubland bird species, but too small for the New England cottontail (Sylvilagus transitionalis), which has been proposed for threatened and endangered status.     

Influence of forest planning alternatives on landscape pattern and ecosystem processes in northern Wisconsin,USA

Incorporating an ecosystem management perspective into forest planning requires consideration of the impacts of timber management on a suite of landscape characteristics at broad spatial and long temporal scales. We used the LANDIS forest landscape simulation model to predict forest composition and landscape pattern under seven alternative forest management plans drafted for the Chequamegon-Nicolet National Forest in Wisconsin. We analyzed 20 response variables representing changes in landscape characteristics that relate to eight timber and wildlife management objectives. A MANOVA showed significant variation in the response variables among the alternative management plans. For most (16 out of 20) response variables, plans ranked either directly or inversely to the extent of even-aged management. The amount of hemlock on the landscape had a surprising positive relationship with even-aged management because hemlock is never cut, even in a clear cut. Our results also show that multiple management objectives can create conflicts related to the amount and arrangement of management activities. For example, American marten and ruffed grouse habitat are maintained by mutually exclusive activities. Our approach demonstrates a way to evaluate alternative management plans and assess if they are likely to meet their stated, multiple objectives.     

Understorey condition scoring of Ghanaian lowland tropical moist forest during stock survey: a technique for regulating the allowable cut in ecologically and structurally degraded production forest

Understorey condition scoring is a rapid assessment field technique for appraising and delimiting the various stages of ecological and structural decline in fire-degraded, lowland, tropical moist forest. The scoring system is designed to be incorporated into stock survey. It is simple and consistent, with only minimal time and labour requirements. The degree of degradation is assessed from the vegetation structure contained within the first 2 m of the stand's vertical profile and is assigned to one of six categories. Sample plots of 20 m radius are used to distinguish localised, degraded areas from natural forest chablis and a high sampling intensity is employed to enable accurate mapping of the forest condition. Establishing the spatial extent and degree of degradation facilitates a more appropriate determination of the allowable cut at the sub-compartmental level, thereby affording protection to affected areas of forest against further ecological and structural deterioration. In addition, the system can be used for long-term condition monitoring and targeting dry-season fire-control operations.     

The influence of gap creation on the regeneration of Pinus tabuliformis planted forest and its role in the near-natural cultivation strategy for planted forest management

It remains unclear whether or not creating gaps in planted forests can increase the plant species composition, structure, and biodiversity, and also whether it can be helpful for restoring planted forests (to a more natural state). Based on a comparison of species composition and structure among forest patches, small gaps (4-25 m²), medium gaps (25-150 m²) and large gaps (150-450 m²), we found that (1) creating gaps enhanced vascular plant diversity. Both the species richness and Shannon diversity indices of small, medium and large gaps were significantly higher than in the understory. The pattern of increasing diversity of vascular plants with gap creation could be partly attributed to the emergence of novel shade intolerant species in gaps. (2) Creating gaps favored the colonization and regeneration of native species. Gap size influenced not only the emergence and density of individuals of different species, but also the emergence of different life form types. Small gaps promoted the regeneration of some shrub species, such as Ostryopsis davidiana, Rosa hugonis, and Forsythia suspense, leading to these species becoming canopy dominants early on in succession. The medium and large gaps favored the growth of tree species, such as Populus davidiana and Betula platyphylla (early successional stage), and Quercus liaotungensis and Pinus tabulaeformis (later successional phase). (3) The canonical correspondence analysis showed that plant species composition and distribution were mainly influenced by gap size and slope aspect, and that the recorded plant species could be divided into three life forms (trees, shrubs and herbs) on the biplot diagram. (4) Finally, creating gaps provided opportunities not only for native pioneer species in the early successional stage, but also for climatic climax species to grow to canopy dominants in later successional phases, suggesting that a more natural forest will develop with plant succession. Gap size plays an important role in plant regeneration, and it could be used to produce desired successional communities in near natural management for planted forests.     

Effects of selection felling and gap felling on forest arthropod communities: a case study in a spruce-beech stand of southern Bavaria

The effects of selection felling and gap felling on arthropod communities were studied over 3 years in a spruce-beech stand in southern Bavaria, Germany. The arthropods were sampled in three strata, using pitfall traps on the forest floor as well as flight-interception traps near the forest floor and in the tree crowns. Coleoptera, Araneae, Opiliones, Heteroptera, Isopoda, Diplopoda and Neuropterida were determined to species level and assigned to ecological guilds. In general, the effects of both treatments on arthropod communities were small. An increase of eurytopic species and species of open woodland as well as of indwellers of deadwood was observed, mainly in the first year after felling. However, forest species dominated the communities in all plots, strata and years. In contrast to selection fellings, gap fellings might favour potential pest species. Nevertheless, in the studied managed spruce-dominated forest site out of the natural growth range of spruce, negative ecological effects such as the repression of forest arthropod species are not expected by small scale fellings.     

The usefulness of a long-term perspective in assessing current forest conservation management in the Apuseni Natural Park, Romania

The forest ecosystem of the Apuseni National Park (ANP) in NW Romania is recognized for its high species and genetic diversity and is protected through various conservation measures. As ANP is the most populated natural park in Romania, the focus is on the need for communities to manage, sustain and prosper by using, exploring and sustaining the natural resources. But what activities are the most appropriate for the conservation of a highly diverse natural forest? This paper presents results from a long-term ecological study using fossil pollen, microscopic and macroscopic charcoal and AMS¹⁴C dating on a site in the ANP in order to examine how the interaction between climate change, human activities and other disturbances have shaped the present protected landscapes over the last 5700 years in this part of the reserve. Results from this study show that the landscape in this region has been continuously forested over the last 5700 years BP, but the forest composition and structure have been dynamic throughout much of the time. In particular, distinct changes in forest composition have occurred over the last 700 years of the record. Fagus sylvatica was the major taxon between 5200 and 200 years BP and its dominance is associated with the highest forest stability. The formation of the current Picea abies forests started 400 years ago and spruce became the dominant forest species during the last two centuries as a result of selective forest clearance, intensive grazing, and more recently, plantations. This led to a large reduction in forest diversity, decline of F. sylvatica and local extinction of several species including Abies alba, Ulmus, Tilia, and Acer. Our results show the high conservation values of A. alba and F. sylvatica in the ANP. Current management practices that allow the anthropogenic activities of timber production and fast tree regeneration, usually involving the plantation of P. abies in this part of the ANP are not in keeping with the NATURA 2000 objectives of ensuring the persistence of the most vulnerable species and habitats.     

The ecological sustainability of tropical forest management: evaluation of the national forest management standards of Costa Rica and Nicaragua, with emphasis on the need for adaptive management

From a conceptual point of view, national forest management standards in Latin American countries have progressed significantly in recent years. Examples include the Costa Rican Standards and Procedures for Sustainable Forest Management and Certification, developed by the National Commission for Forest Certification and in Nicaragua, the National Institute of Forestry proposal of principles, criteria and indicators for sustainable forest management. In line with general approaches worldwide, these national standards primarily focus on the fulfillment of sound forest practice. There is comparatively little emphasis on the assessment of management outcomes or changes in key components of the eco- and social-systems that result from management impacts. Essentially, there is little emphasis on adaptive management, though arguments that management cannot be sustainable if it is not adaptive are persuasive. This study sought to contribute to the development of standards that include elements for adaptive management that define, communicate and evaluate sustainable forest management in Costa Rica and Nicaragua. Elements from the national standards and the CIFOR generic C&I template (predominantly focused on forest management outcomes) were used as a starting point. The basic research process consisted of three phases of evaluation (in-office, desk and field). The evaluations were carried out by multidisciplinary, international groups of experts in forest ecology, management and policy. This study demonstrated the value of forums and workshops that facilitate exchange between forest scientists and policymakers; the innovation and application of a practical, applicable and scientifically based methodology for developing national level C&I; and acceptance of this methodology by key players in the fields of forest management and policy. These experiences and the resulting proposals of C&I for the evaluation of ecologically sustainable forest management are expected to be used as points of reference for future development of forest policy in Costa Rica and Nicaragua, and to contribute to the overall understanding of C&I development processes in the region.     

The impact of SFM-certification on forest product markets in Western Europe — an analysis using a forest sector simulation model

In the international discussion on labels for sustainably produced wood products based on the certification of sustainable forest management (SFM), little attention has been paid to what is probably the most crucial part of any market-based instrument: the potential impact on forest products markets. This paper analyses the potential impact of SFM-certification on forest products markets using a simulation model of the Western European forest sector. Two scenarios with assumptions regarding certification (chain-of-custody costs, timber supply reduction from certified forests) are projected for the period 1995–2015 and tested against the results of a base scenario (‘business as usual’). In general, the results show that rather modest changes are to be expected from SFM-certification in forest products markets. The market impact of a timber supply reduction from certified forest would be more distinct than the impacts of chain-of-custody costs. Industry gross profits would decrease more than production. Due to the large share of roundwood costs in total costs, the sawmill industry would be affected more by even small changes in raw-material prices than the panel and paper industry.     

Structure of causation and its influence on cooperation: A comparative study of forest management in Ontario, Canada

The paper uses cause mapping and structural analysis to analyse how key consensus-building criteria influence the development of cooperation among and between stakeholders and a government agency. The analyses are based on a comparative study of two Local Citizens Committees (LCCs) in Ontario, Canada. Given–Means–Ends (GME) analysis is used to identify the informal goals of LCCs, including the development of cooperation, and LCCs' influence over consensus-building criteria, and Context, Structure and Performance (CSP) analysis is used to identify the relative influence of key consensus-building criteria on cooperation criteria. The paper concludes with a discussion of the relationship between the structural analysis and content analysis of the same data and four inferences for consensus-building and co-management theories.     

The impact of landscape design planning on the timber production and financial outputs of a forest plantation in Ireland

Significant expansion has occurred in Ireland's forest estate since the 1950s. However, the design of the monocultural plantations established in the 1950s and 60s is now considered insensitive to local landscapes and re-design intervention and transformation is needed to improve integration into the environment. This case study was carried out in Laracus forest, Co. Donegal. The rotation of all stands in this 581-ha property has reached the final production phase, with coupes scheduled for clearfelling from 2003 to 2015. The implications of forest re-design for both the volume production in the current rotation and the financial return of the current and subsequent rotations were examined. Results indicated a volume loss due to design planning for the current rotation of 5.6% compared to the volume produced under the standard regime. In financial terms, this represents a loss of 4.6%. For the subsequent rotation, a significant financial gain of 22% in net present value was achieved as a result of redesigning the plantation. The overall financial out-turn for the property, when both the current and subsequent rotations were considered, was a 3.4% lower net present value for the design plan than for the standard regime. This result represents a lower impact of design planning in Laracus than most other forest restructuring studies have reported.     

Effects of disturbance history and environmental factors on the diversity and productivity of understory vegetation in a cool-temperate forest in Japan

We assessed the species richness and aboveground productivity of understory plants in nine types of forest stand (116 plots in total) that had different disturbance histories that were combinations of the frequency of plantation (clear-cutting, site preparation, planting), typhoon damage, and selective cutting. We established two 1 m × 1 m quadrats to measure species richness and productivity and one 1 m × 30 m belt to measure species richness in each plot. Canopy leaf area index (LAI), soil NH₄⁺, soil C/N ratio, slope angle, and slope aspect were measured as current environmental factors affecting each plot. The variance in species richness was better explained by disturbance history (69% in quadrats; 86% in the belt) than by current environmental factors. Species richness and the Simpson index decreased as the frequency of plantation increased. In contrast, the variance in productivity was better explained by current environmental factors (82%), especially canopy LAI (45%), than by disturbance history. The relations of species presence and productivity to the explanatory variables differed among species, although there were some common responses within life forms. The effects of disturbance on species diversity remained for 20–80 years. Forest management should therefore take into account the long-term effects of disturbance history to maintain understory plant diversity.     

Sugar maple and yellow birch regeneration in response to canopy opening,liming and vegetation control in a temperate deciduous forest of Quebec

We examined how the density, growth and survival of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton) regeneration are influenced by gap size, soil nutrient availability and understory vegetation. We used a factorial combination of (1) three gap sizes (small: <100 m²; medium: 100–300 m²; large: ∼1000 m²); (2) presence/absence of liming (92% CaCO₃ at 500 kg ha⁻¹, 1st year post-harvest); and (3) presence/absence of vegetation control (weeding twice a year; 1st to 3rd year post-harvest). We monitored height increment and survival of 1500 seedlings and saplings of both species from the 3rd to the 6th year post-harvest, and assessed density 6 years post-harvest. Both species exhibited a complex set of density, growth and survival responses across the combination of treatments. Compared to sugar maple, yellow birch had an overall lower density, greater growth, and similar survival rate; the two species attained maximum values in different gap size for density, and similar gap size for growth and survival. Liming had very little or no effect on the species. The growth of yellow birch was slightly but significantly greater when understory vegetation was controlled, particularly in medium and large gaps. These results suggest that a variety of canopy gap sizes can provide the right combination of understory conditions for regenerating these two functionally different tree species.     

尼加拉瓜西南部热带雨林生态系统木材生产速率及其对可持续森林经营的启示

积累木材采运数据对森林可持续经营是非常必要的,但这些数据在一些发展中国家却非常缺乏。本文收集和分析了尼加拉瓜Ondo州森林保护区和非保护区内木材生产速率的数据。数据来源于州林业主管部门的官方数据、年度报告和相关文件,包括2003年至2005年间以月采伐量为单位的不同经济术材的物种、材积量和立木数。对收集的数据进T检验和一维方差分析。结果表明:3年间,非保护区内采伐木材的物种数、科数和立木量均高于森林保护区内采伐的。但是,保护区内被砍伐的树木材积总量要显著高于非保护区的(p<0.05)。非保护区内,有25个植物科的60种阔叶树种被砍伐:森林保护区内有23个科的57种阔叶树种被砍伐。3年间,Ondo州森林系统内被砍伐树林共111,377株,材积量约295 089.67m3。年平均伐木数和材积量分别是37,125株和98 363.22 m3。月平均伐木数和材积量分别是3 094和8 196m3。T检验结果表明,森林保护区和非保护区内被砍伐的树木株数和材积量显著不同(p<0.05)。一维方差分析结果表明,03年和04年伐木活动显著增加,但05年有所下降。说明森林系统中经济木材树种正在减少,伐木活动对森林生态系统产生了...