PLFA Analysis of Soil Microbial Community Structure in Different Forest Types

Soil soluble organic matter is an important component in the study of carbon and nitrogen cycling in terrestrial ecosystems. Soil microorganisms, as soil decomposers, participate in soil biogeochemical processes and play an important role in maintaining the balance of soil ecosystems. As a typical subtropical regional unit, Queensland, Australia, is a relatively concentrated distribution area of forests in Australia. It is very sensitive to climate change and plays an important role in Australian climate and even global climate change. Its unique natural environment and ecosystem occupy a special position in the world. However, the knowledge of available carbon and nitrogen pool and microbial activity in forest soil is still very limited. Pinus elliottii, Araucaria cunninghamii and Agathis australis are the three most important forest types in southern Queensland, Australia. In our research, the function and structural diversity of soil microbial communities of these three forest types were studied using biochemical and molecular biological methods, and the effective carbon and nitrogen pools of soil of different forest types and related microbial processes were discussed, which has important theoretical guiding significance for further research on the structure and function of soil ecosystem. The number of PLFAs in the soil of P. elliottii was 45, the number of PLFAs in the soil of Araucaria cunninghamii and Agathis australis was 39 and 35, respectively. The number and content of PLFAs monomer in P. elliottii were higher than those in the other two kinds of forest soil.

Dynamics of Slope Runoff and Soil Erosion of Different Forest Types in Karst Depression

[Objective] The research was aimed to study the dynamics of slope runoff and soil erosion in different forest types in karst depression.[Method] Precipitation observation sites at the bottom of karst depression and runoff observation sites in different forest types were established to monitor regularly the main indices changes of runoff and soil erosion at fixed position in 4 years.[Result] The surface runoff of different forest types appeared singer peak from February to November,with lowest valley from June to July.The runoff coefficient appeared double peaks from February to May and from July to September.The changing coefficient of runoff appeared three peaks from March to April,from July to August and from September to November.The silt concentration appeared one peak from March to May and The erosion modulus appeared double peaks from March to May and from June to August.Runoff showed annually reduced trend with the growth of forests and the development of vegetation layer＇s structure.There was a positive correlation between the runoff and its silt concentration in different forest types.Precipitation and evaporation had notable positive correlation with the runoff,and similar correlation but not marked with silt concentration.The fitting analysis results of surface runoff and erosion modulus showed that rocky desertification intensified the unevenness of surface runoff and increased the surface runoff and erosion modulus.The penetrability of surface soil in new planted forest was lower than that in young forest,and that in surface soil of different forest types was higher than in bottom soil.[Conclusion] The research provided theoretical basis for the biological management technologies of water and soil conservation and the control of karst rocky desertification in karst regions.

Estimating the productive potential of five natural forest types in northeastern China

Background: There is a serious lack of experience regarding the productive potential of the natural forests in northeastern China, which severely limits the development of sustainable forest management strategies for this most important forest region in China. Accordingly, the objective of this study is to develop a first comprehensive system for estimating the wood production for the five dominant forest types.Methods: Based on a network of 384 field plots and using the state-space approach, we develop a system of dynamic stand models, for each of the five main forest types. Four models were developed and evaluated, including a base model and three extended models which include the effects of dominant height and climate variables. The four models were fitted, and their predictive strengths were tested, using the "seemingly unrelated regression"(SUR) technique.Results: All three of the extended models increased the accuracy of the predictions at varying degrees for the five major natural forest types of northeastern China. The inclusion of dominant height and two climate factors(precipitation and temperature) in the base model resulted in the best performance for all the forest types. On average, the root mean square values were reduced by 13.0% when compared with the base model.Conclusion: Both dominant height and climate factors were important variables in estimating forest production. This study not only presents a new method for estimating forest production for a large region, but also explains regional differences in the effect of site productivity and climate.

Spatial pattern of tree diversity and evenness across forest types in Majella National Park,Italy

Background： Estimation of tree diversity at broader scale is important for conservation planning. Tree diversity should be measured and understood in terms of diversity and evenness, two integral components to describe the structure of a biological community. Variation of the tree diversity and evenness with elevation, topographic relief, aspect, terrain shape, slope, soil nutrient, solar radiation etc. are well documented. Methods： Present study explores the variation of tree diversity （measured as Shannon diversity and evenness indices） of Majella National Park, italy with five available forest types namely evergreen oak woods, deciduous oak woods, blacWaleppo pine stands, hop-hornbeam forest and beech forest, using satellite, environmental and field data. Results： Hop-hornbeam forest was found to be most diverse and even while evergreen Oak woods was the lowest diverse and even. Diversity and evenness of forest types were concurrent to each other i.e. forest type which was more diverse was also more even. As a broad pattern, majority portion of the study area belonged to medium diversity and high evenness class. Conclusions： Satellite images and other GIS data proved useful tools in monitoring variation of tree diversity and evenness across various forest types. Present study findings may have implications in prioritizing conservation zones of high tree diversity at Majella.

STUDY ON SPECIES DIVERSITY OF RUST FUNGUS IN FIVE FOREST TYPES

The species diversities of rust fungus in live forest types was investigated and discussed according to the methods of fungi taxonomy and foresny ecology in Maorshan area. The results show the speies diversity index of rust fungus is the highest in the mixed forest type, mendiun in Birch-poplar forest, Larch plantation and Korean pine plantation, and the lowest in Oak forest. The results also show that the vegetation succession can cause the fungus population succession.

Nitrous oxide emissions from three temperate forest types in the Qinling Mountains,China

To understand soil N2O fluxes from temperate forests in a climate-sensitive transitional zone,N2O emissions from three temperate forest types(Pinus tabulaeformis,PTT;Pinus armandii,PAT;and Quercus aliena var.acuteserrata,QAT)were monitored using the static closed-chamber method from June 2013 to May 2015 in the Huoditang Forest region of the Qinling Mountains,China.The results showed that these three forest types acted as N2O sources,releasing a mean combined level of 1.35±0.56 kg N2O ha^-1 a^-1,ranging from0.98±0.37 kg N2O ha^-1 a^-1 in PAT to 1.67±0.41 kg N2O ha^-1 a^-1 in QAT.N2O emission fluctuated seasonally,with highest levels during the summer for all three forest types.N2O flux had a significantly positive correlation with soil temperature at a depth of 5 cm or in the water-filled pore space,where the correlation was stronger for temperature than for the water-filled pore space.N2O flux was positively correlated with available soil nitrogen in QAT and PAT.Our results indicate that N2O flux is mainly controlled by soil temperature in the temperate forest in the Qinling Mountains.

Division of forest fuel type areas of Heilongjiang Province by using GIS

Eight factors, including forest coverage, fuel load, species composition, elevation, monthly mean temperature, monthly mean relative humidity, monthly mean wind velocity, and monthly mean precipitation of fire season, were considered and the methods of weight, the cumulative probability, ARC/INFO technique, and raster-to-vector conversion were adopted in division of forest fuel type area. Firstly, the electronic maps of forest distribution and administrative divisions were built, then overlaid and transformed to the real-world coordinates. Finally, the forest fuel type areas of Heilongjiang Province including 81 counties were divided into five grades, accounting for 16%, 17%, 17%, 11%, and 38% respectively. The grade Ⅰ fuel type areas with highest fire danger rating mainly distributed on Daxinganling Mountains, Xiaoxinganling Mountains, and Zhangguangcailing Mountains, the grade Ⅴ fuel type areas mainly centralized on Songnen Plain, Sanjiang Plain, and other Plains, and other forest fuel type areas (grades Ⅱ, Ⅲ, and Ⅳ) were situated between plains and mountainous areas.

Contrasting responses of net primary productivity to inter-annual variability and changes of climate among three forest types in northern China

Aims A lack of explicit information on differential controls on net primary productivity(NPP)across regions and ecosystem types is largely responsible for uncertainties in global trajectories of terrestrial carbon balance with changing environment.The objectives of this study were to determine how NPP of different forest types would respond to inter-annual variability of climate and to examine the responses of NPP to future climate change scenarios across contrasting forest types in northern China.Methods We investigated inter-annual variations of NPP in relation to climate variability across three forest types in northern China,including a boreal forest dominated by Larix gmelinii Rupr.,and two temperate forests dominated by Pinus tabulaeformis Carr.and Quercus wutaishanica Mayr.,respectively,and studied the responses of NPP in these forests to predicted changes in climate for the periods 2011–40,2041–70 and 2070–100 under carbon emission scenarios A2 and B2 of Intergovernmental Panel on Climate Change.We simulated the responses of NPP to predicted changes in future climate as well as inter-annual variability of the present climate with the Biome-BGC version 4.2 based on site-and species-specific parameters.The modeled forest NPP data were validated against values in literature for similar types of forests and compared with inter-annual growth variations reflected by tree-ring width index(RWI)at the study sites.Important Findings Inter-annual variations in modeled NPP during the period 1960–06 were mostly consistent with the temporal patterns in RWI.There were contrasting responses of modeled NPP among the three forest types to inter-annual variability of the present climate as well as to predicted changes in future climate.The modeled NPP was positively related to annual mean air temperature in the L.gmelinii forest(P<0.001),but negatively in the P.tabulaeformis forest(P=0.05)and the Q.wutaishanica forest(P=0.03),while the relationships of modeled NPP with annual precipitation for the three forest types were all positive.Multiple stepwise regression analyses showed that temperature was a more important constraint of NPP than precipitation in the L.gmelinii forest,whereas precipitation appeared to be a prominent factor limiting the growth in P.tabulaeformis and Q.wutaishanica.Model simulations suggest marked,but differential increases in NPP across the three forest types with predicted changes in future climate.

Study on Water Conservation Capacity of Litter from Different Types of Forest in Caohai Basin

[Objective]The research aimed to understand water conservation capacity of litter from different forest types in Caohai basin. [Method] Current storage amount,water holding capacity and precipitation interception ability of litter from 4 types of forest were investigated and studied. [Result]The order of exist litter amount was grass slope ＆gt;shrub forest ＆gt;mixed broad leaf-conifer forest ＆gt;coniferous forest. The order of natural water holding capacity was mixed broad leafconifer forest ＆gt; coniferous forest ＆gt; grass slope ＆gt; shrub forest. The relevance between water holding capacity of litter and soaking time was in line with this formula： y = kln（ x） ＋ b. During 0-120 min of litter soaking,water holding capacity increased rapidly. After 120 min,the increasing trend remained flat until closing to the maximum water holding capacity. The relevance between water absorption rate of litter and soaking time was in line with this formula： y = a ＋ bx-1. In the beginning of soaking,water absorption rates of litter from different woodlands showed great difference. As soaking time went by,water absorption rates of litter from different woodlands all declined sharply. During 0-120 min,declining velocity of water absorption rate was quicker. After 120 min,the declining trend tended to be slow. The maximum water holding capacity of litter presented the order of shrub forest ＆gt; mixed broad leafconifer forest ＆gt; grass slope ＆gt; coniferous forest. The maximum precipitation interception amount of litter presented the order of shrub forest ＆gt; grass slope ＆gt; mixed broad leafconifer forest ＆gt; coniferous forest. Effective impounding capacity of litter presented the order of shrub forest ＆gt; mixed broad leafconifer forest ＆gt; grass slope ＆gt; coniferous forest. [Conclusion]The research could provide support for the construction of water conservation forest in Caohai basin.

Assessing impact of climate change on forest cover type shifts in Western Himalayan Eco-region

Climate is a critical factor affecting forest ecosystems and their capacity to produce goods and services. Effects of climate change on forests depend on ecosystem-specific factors including dimensions of climate （temperature, precipitation, drought, wind etc.）. Available infor- mation is not sufficient to support a quantitative assessment of the eco- logical, social and economic consequences. The present study assessed shifts in forest cover types of Western Himalayan Eco-region （700-4 500 m）. 100 randomly selected samples （75 for training and 25 for testing the model）, genetic algorithm of rule set parameters and climatic envelopes were used to assess the distribution of five prominent forest cover types （Temperate evergreen, Tropical semi-evergreen, Temperate conifer, Sub- tropical conifer, and Tropical moist deciduous forests）. Modelling was conducted for four different scenarios, current scenario, changed precipi- tation （8% increase）, changed temperature （1.07℃ increase）, and both changed temperature and precipitation. On increasing precipitation a downward shift in the temperate evergreen and tropical semi-evergreen was observed, while sub-tropical conifer and tropical moist-deciduous forests showed a slight upward shift and temperate conifer showed ＇no shift. On increasing temperatm＇e, an upward shift in all forest types was observed except sub-tropical conifer forests without significant changes. When both temperature and precipitation were changed, the actual dis- tribution was maintained and slight upward shift was observed in all the forest types except sub-tropical conifer. It is important to understand the likely impacts of the projected climate change on the forest ecosystems, so that better management and conservation strategies can be adopted for the biodiversity and forest dependent community. Knowledge of impact mechanisms also enables identification and mitigation of some of the conditions that increase vulnerability to climate change in the forest sector.

Stand development patterns of forest cover types in the natural forests of northern Baekdudaegan in South Korea

The purpose of this study was to classify current forest cover types,and to investigate stand development patterns for natural forests in six areas in northern Baekdudaegan,South Korea.Twenty-eight independent forest communities were aggregated into eight forest cover types by species composition in the overstory of each forest community.The forest cover types were of mixed mesophytic,‘‘others’ ’ deciduous,Quercus mongolica dominant,Q.mongolica pure,Pinus densiflora–Q.mongolica,P.densiflora,Betula ermanii,and Q.mongolica–P.koraiensis.The ecological information was organized by importance value and species diversity for each forest type.Based on the correlation between species diversity index and the abundance of Q.mongolica plus P.densiflora for corresponding forest cover types,we compared the developmental process and approximate successional pathway between each cover type.The P.densiflora forest cover type changes into the P.densiflora–Q.mongolica cover type,followed by the Q.mongolica dominant cover type through continuous invasion of the oak trees.Furthermore,the Q.mongolica pure cover type would spread toward the Q.mongolica dominant cover type with a mixture of various deciduous tree species.The Q.mongolica dominant cover type progresses through the other deciduous cover types to the mixed mesophytic cover type with diversified composition and structure.On the mid to lower slopes,with loamy soils and good moisture conditions,various deciduous forest types should progress,by ecological succession,toward the mixed mesophytic cover type without any further disturbance.

Tree species diversity and stand structure along major community types in lowland primary and secondary moist deciduous forests in Tripura,Northeast India

Tree species diversity and population structure at different community types were described and analyzed for primary and secondary lowland moist deciduous forests in Tripura. Overall 10,957 individual trees belonging to 46 family, 103 genera and 144 species were counted at ≥30 cm DBH （diameter at breast height） using 28 permanent belt transects with a size of 1 ha （10 m × 1000 m）. Four different tree communities were identified. The primary forests was dominated by Shorea robusta （mean density 464.77 trees.ha^-1, 105 species） and Schima wallichii （336.25 trees.ha^-1, 82 species）, while the secondary forests was dominated by Tectona grandis （333.88 trees.ha^-1, 105 species） and Hevea brasiliensis （299.67 trees.ha^-1, 82 species）. Overall mean basal area in this study was 18.01m2.ha^-1; the maximum value was recorded in primary Shorea forest （26.21 m2.ha^-1）. Mean density and diversity indices were differed significantly within four different communities. No significant differences were observed in number of species, genera, family and tree basal cover area. Significant relationships were found between the species richness and different tree population groups across the communities. Results revealed that species diversity and density were increased in those forests due to past disturbances which resulted in slow accumu- lation of native oligarchic small tree species. Seventeen species were recorded with 〈2 individuals of which Saraca asoka （Roxb.） de Wilde and Entada phaseoloides （L.） Men＇. etc. extensively used in local ethnomedicinal formulations. The present S. robusta Gaertn dominated forest was recorded richer （105 species） than other reported studies. Moraceae was found more speciose family instead of Papilionaceae and Euphorbiaceae than other Indian moist deciduous forests. Seasonal phenological gap in such moist deciduous forests influenced the population of Trachypithecus pileatus and capped langur. The analysis of FIV suggested a slow trend of shifting the population of Lamiaceae group by Moraceae species in secondary T. grandis L. dominated community.

The Relationships among Community Type, Peat Layer Thickness, Belowground Carbon Storage and Habitat Age of Mangrove Forests in Pohnpei Island, Micronesia

This paper quantifies the relationships among community type, peat layer thickness and habitat age of the mangrove forests in Pohnpei Island, Micronesia and provides a discussion concerning the primary succession and the belowground carbon storage of the main mangrove community types. The ages of the habitat were estimated from a relationship between the thickness of the mangrove peat layer and the formative period, which was decided by calibrated radiocarbon ages. Mangrove communities in the coral reef type habitat were generally arranged in the following order, from seaward to landward: 1) the Rhizophora stylosa or Sonneratia alba community (I or II communities), 2) the typical subunit of the S. alba subcommunity of the Rhizophora apiculata— Bruguiera gymnorrhiza community (III(2)a subunit) and 3) the Xylocarpus granatum subunit of the same subcommunity of the same community (III(2)b subunit). Their habitat ages were estimated to be younger than 460 years, between 360 and 1070 years and between 860 and 2300 years, respectively. Based on these results and other evidences such as photosynthetic characteristics and pollen analysis derived from the previous studies, the primary succession was inferred to have progressed in the order mentioned above. Belowground stored carbon for the main community types in the coral reef type habitat were estimated to be less than 370 t C ha-1 for the I and the II communities, between 290 and 860 t C ha-1 for the III(2)a subunit and between 700 and 1850 t C ha-1 for the III(2)b subunit.

Diversity of filamentous fungi in organic layers of two forests in Zijin Mountain

A study was conducted to evaluate the cultivable filamentous fungal diversity in organic layers (L, F, and H layers) and A1 layer of two main forest types, Pinus massoniana and Liguidambar formasana mixed forest and Quercus variabilis forest, in Zijin Mountain(325?N, 11848?E), Nanjing, China. A total of 67 taxa comprising 56 Deuteromycetes, 3 Zygomycetes, 5 Asco-mycetes and 3 unidentified fungi were recognized from samples from the forest floor of the two forest types. The most abundant group was Deuteromycetes. The dominant genera in both forests were Alternaria sp., Aspergillus sp., Cladosporium sp., Mucor sp., Penicillium sp., Rhizopus sp., Gliocladium sp. and Trichoderma spp. The fungal diversity was higher in the mixed forest than that in Q. variabilis forest. For both forest types, the maximum fungal diversity was found in layer F and there existed significantly different in fungal diversity between layer F and layer L. In the mixed forest, richness of fungi isolated from needle litter (P. massoniana) was lower than that from leaf litter (L. formasana). The richness of fungi from needle litter increased with the in-crease of forest floor depth, but for leaf litter, the fungal diversity decreased with the depth of forest floor. The co-species of fungi from the two forest types, as well as from two kinds of litters in mixed forest, increased with the depth of the forest floor. The succession of fungi along with the process of decomposition was discussed here. The results also showed that litter quality was a critical factor affecting fungal diversity.

Response of species and stand types to snow/wind damage in a temperate secondary forest,Northeast China

Snow/wind damage is one of the important natural disturbances in forest ecosystems,especially in a montane secondary forest.However,the effects of snow/wind damage remain unclear which affects the management of these forests.Therefore,we investigated the responses of species,individual tree traits and stand structure to snow/wind damage in a montane secondary forest.Results show that,amongst the canopy trees,Betula costata exhibited the most uprooting,bending and overall damage ratio(the number of damaged stems to the total number of stems in a plot); Quercus mongolica showed the highest breakage ratio and Fraxinus mandshurica and Juglans mandshurica the least overall damage ratios.Among the subcanopy trees,Carpinus cordata,Acer mono,Acer tegmentosum and Acer pseudo-sieboldianum showed the least uprooting and breakage,and the most bending damage.A.pseudo-sieboldianum demonstrated the lowest breakage and highest bending damage ratios.Thesefindings indicate that different species have various sensitivities to snow/wind damage.Larger trees(taller,wider crowns) tend to break and become uprooted,while smaller trees are bent or remain undamaged,suggesting that tree characteristics significantly influence the types of damage from snow and wind.Stands of Q.mongolica and B.costata had the highest damage ratios,whereas A.pseudosieboldianum had the lowest snapping ratio.In summary,the severity and type of snow/wind damage are related to individual tree attributes and stand-level characteristics.Therefore,selection of suitable species(e.g.,shorter,smaller with deep root systems,hard wood,bending resistance and compression resistance) and appropriate thinning are recommended for planting in the montane secondary forests.

Community structure and regeneration types of Betula dahurica forest in Badaling forest center of Beijing

Using plant community analysis methods, we analyzed the floristic characteristics, species composition, community structure, population structure, and spatial distribution patterns of a Betula dahurica forest on the ＂1238＂ mountain of Badaling in Beijing, China. The results show that： 1） There are 33 plant species in the B. dahurica community, including 18 woody plant species. The B. dahurica forest is a monodominant community with 75.9% dominance. 2） Based on diameter at breast height （DBH） size class distribution, the population structure of B. dahurica and Acer mono--two heliophyllous and pioneer tree species-is cascade-type, with both in an increasing stage. The population structure of Ella mandshurica and T. mongolica, two shade-tolerant tree species, is inverse-J type, and they have more young seedling individuals and regenerate more stably. They are associated species of the pioneer tree species. The population structure of Quercus mongolica, as the associated species of climax species in the community, is sporadic, and its regeneration is fluctuating and random. Fraxinus rhynchophylla is a shade-tolerant tree species which has a unibar population structure and climax characteristics of pioneer tree species. The relative frequency of young seedlings reached 0.4. 3） The dominant species B. dahurica is still in an increasing stage, and the regeneration of other species is steady or partly influences the community, putting the community in the pioneer species stage. From the population structure and distribution frequency ofF. rhynchophylla, the B. dahurica forest will approach to a climax state in the future.

长白山区4种针叶林有效叶面积指数遥感精细反演及空间分布规律

[目的]研究快速、准确、宏观获取不同森林类型有效叶面积指数(LAI_(e))的方法,探讨其空间分布规律,为中小尺度森林LAI_(e)遥感产品的开发提供新思路,为林业精细化监测和森林生态系统碳水循环模拟提供科学可靠的技术手段。[方法]以长白山为研究区,基于Sentinel-2A多光谱影像,运用三维卷积神经网络提取研究区4种针叶林型(长白落叶松、樟子松、红松和红皮云杉)的空间分布;采用区分林型和全样本2种方案,分析样地实测LAI_(e)与7种植被指数(增强植被指数、反红边叶绿素指数、改进简单植被指数、归一化水体指数、归一化植被指数、土壤调节植被指数、简单植被指数)的相关关系;利用各林型对应的最优植被指数,构建区分林型和全样本LAI_(e)与植被指数的回归模型,并基于验证样本数据对比区分林型模型、全样本模型和PROSAIL模型在LAI_(e)反演中的精度表现;结合地理因子分析4种针叶林型LAI_(e)空间格局及变化规律。[结果]所有样本组中7种植被指数与相对的LAI_(e)均存在极显著相关关系(P<0.01),除增强植被指数(EVI)与红松LAI_(e)、简单植被指数(SR)与红皮云杉LAI_(e)外,相关系数均大于0.6,但组间LAI_(e)与不同植被指数相关性具有较大差异;红松、长白落叶松和樟子松LAI_(e)与反红边叶绿素指数(IRECI)相关性最高,红皮云杉、红松LAI_(e)分别与EVI、改进简单植被指数(MSR)相关性最高;4种不同林型模型比全样本模型的R2提高12.7%以上,RMSE降低34.5%;研究区内4种林型LAI_(e)范围在0.37~5.86之间,平均LAI_(e)由高至低依次为红松、长白落叶松、樟子松、红皮云杉。红松对海拔、坡度、坡向的变化最为敏感,红皮云杉、樟子松次之,长白落叶松最小。[结论]不同林型LAI_(e)与遥感植被指数的相关程度存在明显差异,区分林型构建回归模型能够提高LAI_(e)反演精度;区分林型后拟合的线性模型精度整体较PROSAIL模型和全样本模型更高,但LAI_(e)高值区域没有PROSAIL模型表现稳定;4种针叶林型LAI_(e)对地理因子变化的反应差异较大。本研究可为精细区分森林类型的中小尺度针叶林LAI_(e)遥感反演研究提供参考。

滇中地区主要森林凋落物有效截留量及其影响因素

[目的]研究滇中地区主要森林类型凋落物有效截留量差异及其影响因素,为该地未来植被恢复和森林管理提供科学支撑。[方法]利用样方调查法、烘干法和浸泡法分析了昆明市双河—磨南德水源林自然保护区内的地带性次生常绿阔叶林(SF)、针阔混交林(TF)、旱冬瓜林(ACF)、华山松林(PA)、成熟云南松林(OPY)、幼龄云南松林(YPY)、银荆林(AD)7种主要森林类型凋落物未分解层(OL)和半分解层(OF)的有效截留量及其影响因素。[结果](1) 7种森林类型凋落物厚度为2.06~7.57 cm,其中OL层1.10~4.30 cm, OF层0.83~3.93 cm,凋落物层厚度排序为TF>ACF>PA>OPY>SF>AD>YPY,凋落物蓄积量为4.75~17.45 t/hm^(2),其中OL层占比为32.02%~62.48%,OF层占比为37.52%~67.98%,凋落物层蓄积量排序为TF>PA>SF>OPY>ACF>AD>YPY。(2)凋落物最大持水率为115.3%~170.7%,初始吸水速率为3.65~5.62 g/(g·h),凋落物持水率和浸水时间的关系可用对数函数y=aln(x)+b表示,吸水速率与浸水时间可用幂函数y=kt~n表示。(3)凋落物最大持水量为7.05~32.19 t/hm^(2),排序为PA>TF>SF>OPY>ACF>AD>YPY,有效截留量为5.45~25.34 t/hm^(2),以TF最高(25.34t/hm^(2)),PA(24.99 t/hm^(2))和SF(24.62 t/hm^(2))次之,YPY最低(5.45t/hm^(2)),影响有效截留量的场地特征主要为蓄积量、自然含水率、分解强度以及厚度,影响有效截留量的水动力过程主要是最大失水量、前6.0 h平均吸水速率和前2.0 h平均吸水速率。[结论]滇中地区未来植树造林应以针阔混交林为主,注重对地带性次生常绿阔叶林的保育,采取辅助自然更新的措施促进人工纯林向混交林演化,同时减少踩踏、收集凋落物等人类活动的干扰,从而增加森林生态系统凋落物的水源涵养能力。

滇中主要森林类型土壤团聚体稳定性及其变化机制

[目的]团聚体稳定性是评估退化生态系统植被恢复后土壤质量变化的重要指标,研究滇中地区主要森林类型土壤团聚体稳定性差异及其变化机制,为该地未来植被恢复、改造过程中的树种选择、森林资源管理提供科学支撑。[方法]选择云南松林(PY)、华山松林(PA)、银荆林(AD)、旱冬瓜林(ACF)、针阔混交林(TF)、次生常绿阔叶林(SF)6种主要森林类型作为研究对象,以坡旱地(DSL)作为对照,采集0—20 cm,20—40 cm和40—60 cm土样,利用干、湿筛分法分离测定>5 mm,5~2 mm,2~0.25 mm,<0.25 mm 4个粒级团聚体含量,计算水稳性大团聚体含量(WR_(>0.25))、平均重量直径(MWD)、几何平均直径(GMD)和结构破坏率(PAD)4个稳定性指标,对土壤团聚体稳定性进行研究。[结果](1) 6种森林类型在0—60 cm均以0.25~2 mm的小团聚体为主,而坡旱地随着土层深度的增加,粒级从0.25~2 mm向<0.25 mm转变;(2) 0—60 cm土层中坡旱地平均WR_(>0.25),MWD,GMD和PAD分别为55.40%,1.16 mm,0.52 mm,40.47%,6种森林类型分别为71.61%~78.20%,1.97~2.61 mm,0.93~1.27 mm,12.59%~20.47%,团聚体稳定性总体表现为坡旱地最差,次生常绿阔叶林、针阔混交林最好,其次是云南松林、旱冬瓜林,银荆林和华山松林较差;(3)团聚体稳定性在宏观尺度上受森林类型、土层深度及其交互作用的显著影响(p<0.001),而在微观尺度上主要受土壤容重、非毛管孔隙度、全钾、有机质、砂粒和黏粒含量的显著影响(p<0.05),土壤理化性质、养分、质地解释了团聚体稳定性的90.5%,其中以理化性质、养分及其交互作用的贡献最大,解释率为61.3%,土壤质地往往与其他因子共同影响团聚体稳定性,其独立解释率仅为5.1%。[结论]滇中地区退耕还林可显著提高土壤团聚体稳定性,未来的生态恢复应该以营造云南松林和旱冬瓜林为主,同时避免高强度的人类活动,改善土壤理化性质和增加土壤养分积累,促进人工纯林向针阔混交林及常绿阔叶林演化。

辽东山区5种林分土壤颗粒分形特征与土壤性质

选取清原县森林内林龄、坡向、坡位基本相同的林分类型,包括天然红松(Pinus koraiensis)林、樟子松(Pinus sylvestris var.mongholica)人工林、蒙古栎(Quercus mongolica)人工林、胡桃楸(Juglans mandshurica)人工林、天然针阔混交林(红松和蒙古栎数量比为2∶8),设置无乔木覆盖样地作为对照,对比分析天然条件不同林分土壤粒度组成、平均粒径、标准偏差、偏度、峰态值和(单、多重)分形维数,土壤理化性质空间分布及与分形维数之间的关系。结果表明:有林地表层(0~20 cm)和亚表层(20~40 cm)土壤组成以砂粒为主,粉粒、黏粒次之;粒度特征整体呈现分选状况极好、偏度正和峰态为尖窄的特点,土壤单重分形维数在1.84~2.78之间;有林地土壤平均粒径、单重分形维数及土壤理化性质均高于对照样地,且从针叶林、阔叶林至针阔混交林,上述土壤指标呈现递增趋势;多重分形维数表现为容量维数>关联维数>信息维数;单重分形维数和容量维数与黏粒和粉粒体积分数及土壤理化性质呈显著正相关关系,综合说明土壤细粒物质在有林地的保护中逐渐恢复,且表层土壤的恢复效果较好;多重分形维数分析表明,土壤粒径非理想均匀分布,因此,利用单重分形维数结合多重分形参数评价土壤质量仍有必要。