兴安落叶松落叶量和幼苗发生动态的研究

采用野外试验的方法,研究了兴安落叶松原始老龄林下兴安落叶松的更新条件。在所研究的四种林型的兴安落叶松原始老龄林之间,更新差别表现在下种、发芽和存活三方面。种子年时,老龄林下种量每平方米达到300-1000粒,各林型落种量从大到小的顺序为:赤杨落叶松林→丛桦落叶松林→草类落叶松林→杜香落叶松林。一年中的幼苗发生过程可分为四个时期,种子萌发主要在6月,幼苗死亡主要在7月,而8月份幼苗种群变化较小。从有利于落叶松种子萌发和幼苗存活的方面来说,各林型的顺序是:丛桦落叶松林>杜香落叶松林>赤杨落叶松林>草类落叶松林。这个顺序主要取决于土壤表层的湿度,即土壤湿度越大,发芽数和存活数越多。

武夷山六种杉木伴生树种落叶养分归还的研究

本文在福建省几个自然保护区天然杉木混交林群落调查的基础上，对武夷山天然杉木混交林中毛竹、木荷等六种主要杉木伴生树种落叶养分归还的研究结果表明，各伴生树种落叶分解其养分归还量主要取决于落叶量的大小，受养分浓度及分解速率的影响较小．在混交林中，甜储、丝栗栲的落叶量大，分解速度快，具有较强的养分平衡能力，落叶分解的养分归还量分别为３４２．９６４ｋｇ／（ｈｍ２·ａ）和２７４．３７２ｋｇ／（ｈｍ２·ａ）．苦槠和毛竹的养分归还量较低，分别为１０２．８１４ｋｇ／（ｈｍ２·ａ）和１０７．２２４ｋｇ／（ｈｍ２·ａ）．

挪威云杉落叶的空间模式:与酸性沉降、临界负荷值以及自然生长条件之间的关系

本文在对所研究地区的森林状况作了总体考虑的基础上,按照树龄、海拔和落叶的相对程度等因素的不同,对挪威南部的挪威云杉进行了分层取样调查,以研究其落叶的空间模式。我们发现其中有一片占样方数75%的区域具有较高的落叶量。这一区域的落叶现象不能用立地生产力、树龄、地形、植被类型分布、土壤类型分布和土壤厚度、离海岸的距离及海拔高度等传统模式来解释。该区域的森林长势差,是挪威南部酸沉降最高的区域,这与其它方面如渔场退化、土壤和湖水的酸化等的调查结论相一致。该区域的土壤呈明显的酸性,缓冲性差,与所研究的其它区域比,其可交换性阳离子低50%。该区域内硫酸盐的沉降量超过了用MAGIC方法计算出的临界负荷值。污染的超标量与落叶量之间有很好的相关性。据我们所知,这是第一次发现以落叶量所表示的森林损害程度与模拟的临界负荷的超出值之间的相关关系。在实地观察中发现,当超出临界负荷值一定数量时,落叶量与临界负荷时相比净增30%。我们从而提出了与由长距离运输的空气污染所造成的潜在污染的累积影响相一致的落叶模式。如果此模式成立的话,那么尽管北方森林生态系统只具有中等程度的污染负荷,但远比原来所预料的要更为脆弱。

林地生态处理系统中欧美107杨与中林46杨对生活污水的响应

为了观测欧美107杨与中林46杨对生活污水的响应,采用不同水力负荷(0、3、6、9、12、15 cm·周??),在杨树人工林林地进行了污水生态处理试验。结果表明:污水处理增加了欧美107杨的叶长、落叶量与生长量,降低了欧美107杨的叶不对称性;污水处理使中林46杨叶长变短,叶不对称性增加,生长量与落叶量降低。在较低水力负荷时,两种杨树无性系各器官中的氮、磷、钾钠积累量增加,在6—12 cm·周??水力负荷时达到最大值,然后又有所下降,欧美107杨各器官中氮、磷、钠积累量高于中林46杨。欧美107杨比中林46杨更适宜于作为生活污水处理的植物材料。

椰园间种大豆可改良土壤

椰园间种大豆可改良土壤据报道，在椰园间种的大豆，生长旺盛，花期和座荚期可缩短至６０天以内，大豆座荚后，叶子变黄脱落，最后只剩下茎和成串豆荚，落叶量达２—３吨／公顷，可提供５０—６０公斤氮及其他营养成分。此外，落叶覆盖表土，可防止水分过度蒸发．抑制杂草...

Effects of intercropping systems of trees with soybean on soil physicochemical properties in juvenile plantations

The intercropping system of tree with soybean in juvenile plantations, as a short-term practice, was applied at Lao Shan Experimental Station in Mao＇er Shan Forest of Northeast Forestry University, Harbin, China. The larch （Larix gmelinii）lsoybean （Glycine max.） and ash （Fraxinus mandshurica） intercropping systems were studied in the field to assess the effects of the intercropping on soil physicochemical properties. The results showed that soil physical properties were improved after soybean intercropping with larch and ash in one growing season. The soil bulk density in larch/soybean and ash/soybean systems was 1.112 g·cm^-3 and 1.058 g·cm^ 3, respectively, which was lower than that in the pure larch or ash plantation without intercropping. The total soil porosity also increased after intercropping. The organic matter amount in larch/soybean system was 1.77 times higher than that in the pure larch plantation, and it was 1.09 times higher in ash/soybean system than that in the pure ash plantation. Contents of total nitrogen and hydrolyzable nitrogen in larch/soybean system were 4.2% and 53.0% higher than those in the pure larch stand. Total nitrogen and hydrolyzable nitrogen contents in ash/soybean system were 75.5% and 3.3% higher than those in the pure ash plantation. Total phosphorus content decreased after intercropping, while change of available phosphorus showed an increasing trend. Total potassium and available potassium contents in the larch/soybean system were 0.6% and 17.5% higher than those in the pure larch stand. Total potassium and available potassium contents in the ash/soybean system were 56.4% and 21.8% higher than those in the oure ash plantation.

Nematode Community Structure and Diversity Pattern in Sandy Beaches of Qingdao,China

We investigated the diversity and structure of free-living marine nematode communities at three sandy beaches representing typical intertidal environments of a temperate zone in Qingdao,Shandong Province,China.Average nematode abundance ranged from 1006 to 2170 ind.10 cm-2,and a total of 34 nematode genera were recorded,of which only 8 were common in all the studied beaches.Pielou's evenness and Shannon-Wiener diversity index were the lowest at the second beach where nematode abundance was the highest.The highest species diversity index coincided with the lowest nematode abundance at Shilaoren beach.Sediment median grain size,sorting coefficient,and chlorophyll-a content were essential for differentiation in nematode abundance and species diversity,whereas taxonomic diversity of nematode was homogeneous across the three beaches.In 0–20 cm sediment profile,nematode abundance declined abruptly with depth,whereas nematode diversity changed gently with obvious difference in 16–20 cm layer.Sediment granulometry and chlorophyll-a content were the two foremost factors which influenced the vertical distribution pattern of nematode generic diversity.Non-selective deposit feeders constituted the most dominant trophic group,followed by epistratum feeders.Bathylaimus(family:Tripyloididae) dominated at the second and Yangkou beach,while Theristus(family:Xyalidae) prevailed at Shilaoren beach.Omnivores and predators became important at Shilaoren beach because of the high proportion of Enoplolaimus.Even though,nematode community of the studied beaches did not differ significantly from each other.

Influences of Different Habitats on Asexual Propagation of Wild Gastrodia elata f. glauca being Domesticated in Ganzi

[Objective] The influences of different habitats on asexual propagation of wild Geg(abbreviation for Gastrodia elata Bl. f. glauca S. Chow) being domesticated in Ganzi prefecture was studied. [Method] The research trial was carried out in the following three kinds of habitats at the same time: the plastic greenhouses, the birch forest of shady slope and the shrubbery of sunny slope, and the results were analyzed with group data average hypothesis test method. [Result] The overall tuber(the juvenile tuber, the immature tuber and the mature tuber) yield and the mature tuber yield were both very significantly higher in the plastic greenhouses than in the other two types of habitats, and respectively reached 9.52 and 6.70 kg/m2; the mature tuber drying rate was dramatically or very dramatically lower in the plastic greenhouses than in the other two types of habitats, and was 23.84%; the stabilities of the overall tuber yield, the mature tuber yield and the drying rate were all reduced in the order of greenhouses, birch forest and shrubbery; and the dry mature tuber yield of the plastic greenhouses was the highest in the three kinds of habitats, and was 1.60 kg/m2. [Conclusion] A good habitat had to be created or chosen in the domesticating cultivation of the wild Geg in Ganzi prefecture. The preferred choice was the plastic greenhouse, the alternative one was the deciduous broadleaved forest of shady slope. The imitating wild planting of the wild Geg should be done in the warm moist deciduous broad-leaved forest of shady slope.

Carbon Stock of Larch Plantations and Its Comparison with an Old-growth Forest in Northeast China

The overall goal of this study was to understand carbon(C) stock dynamics in four different-aged Japanese larch(Larix kaempferi) plantations in Northeast China that were established after clear-cutting old-growth Korean pine deciduous forests. Four Japanese larch plantations which were at 10, 15, 21, and 35 years old and an old-growth Korean pine deciduous forest which was 300 years old in Northeast China were selected and sampled. We compared the C pools of biomass(tree, shrub and herb), litterfall(LF), and soil organic carbon(SOC) among them. The biomass C stock of larch plantation at 10, 15, 21, and 35 years old was 26.8, 37.9, 63.6, and 83.2 Mg/ha, respectively, while the biomass C stock of the old-growth Korean pine deciduous forest was 175.1 Mg/ha. The SOC stock of these larch plantations was 172.1, 169.7, 140.3, and 136.2 Mg/ha respectively, and SOC stock of 170.4 Mg/ha in the control of old-growth forest. The biomass C stock increased with stand age of larch plantations, whereas SOC stock decreased with age, and C stock of LF did not change significantly(P > 0.05). The increase of biomass C offset the decline of SOC stock with age, making total carbon stock(TCS) of larch plantations stable from stand ages of 10–35 years. The TCS in larch plantations was much smaller than that in the old-growth forest, suggesting that the conversion of old-growth forests to young larch plantations releases substantial C into the atmosphere.

Effects of Thinning Intensity on Carbon Stocks and Changes in Larch Forests in China Northeast Forest Region

Thinning represents an important and frequently used silvicultural technique that improves forest wood products and has obvious effects on forest carbon stocks and stock changes. Here, we used the carbon budget model CBM-CFS3 to simulate the effects of thinning on carbon storage and changes in larch forest ecosystems under thirteen thinning scenarios. Simulation results demonstrate that strong thinning greatly reduces the biomass carbon density of larch forests compared to non-thinning forests. The minimum and maximum average biomass carbon density, respectively, were 30.3 tC ha^-1 and 47.8 tC ha^-1, a difference of 58% under set scenarios in the simulated time scale. The dead organic matter（including soil） carbon density increased in all thinned larch forests stands, compared with non-thinning stands, and the pattern of variation was opposite to that found for biomass carbon density. However, the total ecosystem carbon density of larch forests declined with thinning because the increase in dead organic matter carbon is insufficient to offset the loss of biomass carbon caused by thinning. Thus, strong thinning can transform larch forest ecosystems from carbon sinks into carbon sources. Future work should consider the carbon sequestered in wood materials acquired via thinning and their use as substitutes for other construction materials with less favorable lifecycle carbon footprints, such as steel, cement, aluminum and PVC.

Coloration and phenology manifest nutrient variability in senesced leaves of 46 temperate deciduous woody species

Senesced-leaf nutrient concentrations vary signifcantly among coexisting plant species refecting different leaf nutrient use strategies.However,interspecifc variation in senesced-leaf nutrients and its driving factors are not well understood.Here,we aimed to determine interspecifc variation and its driving factors in senesced-leaf nutrients.We explored interspecifc variation in carbon(C),nitrogen(N)and phosphorus(P)concentrations in newly fallen leaves of 46 coexisting temperate deciduous woody species across the Maoershan Forest Ecosystem Research Station,Northeast China.The relative importance of 10 biotic factors(i.e.mycorrhiza type,N-fxing type,growth form,shade tolerance,laminar texture,coloring degree,coloring type,peak leaf-coloration date,peak leaf-fall date and end leaf-fall date)was quantifed with the random forest model.N and P concentrations varied 4-and 9-fold among species,respectively.The high mean N(15.38 mg·g^(−1))and P(1.24 mg·g^(−1))concentrations suggested a weak N and P limitation in the studied forest.Functional groups had only signifcant effects on specifc nutrients and their ratios.P concentration and N:P were negatively correlated with peak and end leaf-fall dates for the ectomycorrhiza species group.Brighter-colored leaves(red>brown>yellow>yellow-green>green)tended to have lower N and P concentrations and higher C:N and C:P than darker-colored leaves.The random forest model showed that autumn coloration and leaf-fall phenology contributed 80%to the total explanation of nutrient variability among species.The results increase our understanding of the variability in senesced-leaf nutrients as a strategy of woody plant nutrition in temperate forests.

Correction of leaf nutrient resorption efficiency on the mass basis

Nutrient resorption is a crucial mechanism for plant nutrient conservation,but most previous studies did not consider the leaf-mass loss during senescence due to lack of measured data.This would lead to an underestimation of nutrient resorption efficiency(NuRE),or calculating NuRE of various species based on the average mass loss at plant-functional-group level in the literature,thus affecting its accuracy.Here we measured the leaf-mass loss to correct NuRE with the species-specific mass loss correction factor(MLCF),so as to foster a more accurate calculation of the nutrient fluxes within and between plants and the soil.Green leaves and senesced leaves were collected from 35 dominant woody plants in northern China.Mass of green and senesced leaves were measured to calculate the MLCF at species level.The MLCF was reported for each of the 35 dominant woody plants in northern China.These species averagely lost 17%of the green-leaf mass during leaf senescence,but varied greatly from 1.3%to 36.8%mass loss across the 35 species,or 11.7%to 19.6%loss across the functional types.Accordingly,the MLCF varied from 0.632 to 0.987 across the 35 species with an average value 0.832.The NuRE corrected with MLCF was remarkably increased on the whole(e.g.both the average nitrogen and phosphorus NuRE became about 9%higher,or more accurate),compared with the uncorrected ones,especially in the case of low resorption efficiencies.Our field data provide reliable references for the MLCF of plants in related regions at both species and functional-type levels,and are expected to promote more accurate calculations of NuRE.

Leaf litter decomposition characteristics and controlling factors across two contrasting forest types

Plant leaf litter decomposition provides a source of energy and nutrients in forest ecosystems.In addition to traditional environmental factors,the degradation process of litter is also affected by plant functional traits and litter quality.However,at the community level,it is still unclear whether the relative importance of plant traits and litter quality on the litter decomposition rate is consistent.A year-long mixed leaf litter decomposition experiment in a similar environment was implemented by using the litterbag method in seven typical forest types in Dongling Mountain,Beijing,North China,including six monodominant communities dominated by Juglans mandshurica,Populus cathayana,Betula dahurica,Betula platyphylla,Pinus tabuliformis and Larix gmelinii var.principis-rupprechtii and one codominant community dominated by Fraxinus rhynchophylla,Quercus mongolica and Tilia mongolica.The results showed that there were considerable differences in the litter decomposition rate(k-rate)among the different forest types.The community weighted mean(CWM)traits of green leaves and litter quality explained 35.60%and 9.05%of the k-rate variations,respectively,and the interpretation rate of their interaction was 23.37%,indicating that the CWM traits and their interaction with litter quality are the main factors affecting the k-rate variations.In the recommended daily allowance,leaf nitrogen content,leaf dry matter content,leaf tannin content and specific leaf area were the main factors affecting the k-rate variations.Therefore,we suggest that future studies should focus on the effects of the CWM traits of green leaves on litter decomposition at the community level.

Assessment and analysis of microwave emissivity and transmissivity of a deciduous forest towards the estimate of vegetation biomass

Forests play an important role in the global carbon cycle and have a potential impact on global climatic change.Monitoring forest biomass is of considerable importance in understanding the hydrological cycle.Because of the problem of dense forest cover,no reliable method with which to retrieve soil moisture in forest areas from the microwave emission signature has been established.All of these issues relate to the microwave emissivity and transmissivity characteristics of a forest.The microwave emission contribution received by a sensor above a forest canopy comes from both the soil surface and the vegetation layer.To analyze the relationship of forest biomass and forest emission and transmissivity,a high-order emission model,the matrix-doubling model,which consists of both soil and vegetation models,was developed and then validated for a young deciduous forest stand in a field experiment.To simulate the emissivity and transmissivity of a deciduous forest in the L and X bands using the matrix-doubling model,the parameters of components of deciduous trees when the leaf area index varies from 1 to10 were generated by an L-system and a forest growth model.The emissivity and transmissivity of a forest and the relationships of these parameters to forest biomass are presented and analyzed in this paper.Emissivity in the L band when the leaf area index is less than 6 and at viewing angles less than 40°,and transmissivity in the L band are the most sensitive parameters in deciduous forest biomass estimation.