This study aims to investigate the rate of mass loss and release of nutrient elements of fine root and grass root in plantation of Triploid Populus tomentosa and Lolium multiflorum established on an abandoned farmland at Tianquan County in Sichuan Province.Fine root decay is influenced by an array of factors,of which the two most important are probably climate and the chemical composition of fine root.Rate of mass loss showed logarithmic relationship with time for fine root and grass root,with annual dry mass loss of 73.9%,69.8%,73.44 and 79.53% for fine root Φ0～1 mm、Φ1～2 mm、Φ0～2 mm and grass root respectively.Nutrient dynamics during decomposition showed the following tendency:1)The content of N and Ca increased in the course of fine root decomposition,but the content of P,K and Mg declined;2)The nutrient content of grass root was irregular during the decomposition;3)The percentages of P,K and Mg releasing and mass loss during decomposition of fine root following the similar trend,but the percentages of N and Ca has a gently releasing;4)The percentages of nutrient releasing have a same trend during decomposition of grass root.It's beneficial to the artificial ecosystem for the divergence of vertical distribution of fine root and grass root.

The investigation and researches were conducted to the contents of ash and nutrition elements of the litter in different plant communities which ranged 450～2 118 m in elevation and surrounded the highest peak of Wulingshan Mountain in Hebei Province.The results showed that the contents of various elements were divided into three categories which total calcium(Ca) and total nitrogen(N) at 10⁴ mg· 5kg^-1,10³ mg· kg^-1 for total phosphorus(P),total potassium(K),total magnesium(Mg) and total iron(Fe),and 10² mg·kg^-1 for total natrium(Na);The contents of various elements of the litter in different plant communities were founded significant difference.For forest communities,the highest total N content was determined in the litter of Juglans mandshurica forest,the highest total P for Populus davidiana-Betula platyphylla forest,the highest total K and total Ca for Tilia mongolica-P.davidiana-Quercus mongolica forest,the highest total Mg and total Fe for Picea meyeri forest,the highest total Na for Betula costata-Picea wilsonii forest.For herbaceous cluster community,the highest contents of total P,total K and total Mg were found in the litter of subalpine shrubbery meadow.The content level of seven elements showed the same order of total Ca> total N> total Fe> total K> total Mg > total P > total Na.The content of ash ranged 8×10⁴～38×10⁴ mg·kg^-1.The forest communities formed with P.meyeri,Larix principis-rupprechtii,B.platyphylla,B.costata,P.wilsonii and the communities of subalpine shrubbery-meadow and subalpine meadow showed relative high content of ash.And Pinus tabulaeformis-Q.mongolica forest showed relative low content of ash.

The study of hydrological benefit of litter fall of different modes of vegetation restoration was conducted in severe degraded areas of upper reaches of Jialing River.The results showed:The total litter stock of the five modes represented a descending order as follows:scrub on burned field(12.85 t·hm^-2) > Robinia pseudoacacia(9.76 t·hm^-2)> R.pseudoacacia-Pinus elliotii mixed forest(9.52 t·hm^-2)> Cyclobalanopsis glauca(6.01 t·hm^-2)> P.elliotii(3.76 t·hm^-2);The capacity of preserving water indicated a descending order as follows:scrub on burned field(33.60 t·hm^-2)> R.pseudoacacia(19.90 t·h-2)> R.pseudoacacia-P.elliotii mixed forest(11.50 t·hm^-2)>C.glauca(8.70 t·hm^-2)>P.elliotii(3.70 t·hm^-2);As for different forest types,the variation in the process of preserving water of litter fall was not remarkable,the amount of sopped water was large before 1 h and comparable stable in the latter 2～4 h,had no significant relationship with the forest biological diversity.Litter's modified interception was at an average rate of 1 253.4 t·km^-2,ranged from 283～2 759 t·km^-2 to 2 759 t·km^-2,different forests represented descending order as follows:scrub on burned field> R.pseudoacacia> R.pseudoacacia-P.elliotii mixed forest> C.glauca>P.elliotii.

This paper emphasized on the rules of mountain soil erosion and nutrient loss in the hill of gneiss and cinnamon soil district,which locating in the south of Taihang Mount,Hebei Province.Based on the artificial rain method in the laboratory,spatial changes of nutrient loss and its relationship with soil erosion were analyzed.The changes of nutrient content in sediment,surface soil and loss were also contrasted.The results indicated that nutrient content in sediment was significantly higher than that in loss and surface soil before rain.So the nutrient enrichment ratio in the sediment was bigger.Nutrient loss from soil has a good relationship with sediment.

A set of 22-year data from an Observation Station located in Ulanbuh Desert,which belongs to the Desert Forest Experimental Center of Chinese Academy of Forestry and the Weather Station of Dengkou County,Inner Mongolia(from 1954 to 2003) were used to analyze yearly and seasonal changes of dust events in Ulanbuh Desert.The results showed that dust events mainly occurred from February to June,accounting for 58.5% of the total events in a year,among which April was the severely attacked month.The times of dust events in winter were less than that in spring,and the least in autumn.Dust events occurred frequently during middle 1980s.The annual dust days were about 100 d(164 d in 1986) in the period from 1983 to 1987.The frequency of dust storm decreased significantly during early 1990s and dropped to a very low level in the middle and late 1990s,but it has been increasing from the beginning of this century.The times of dust events from Feb.to Jun.have evident positive correlation with wind speed,evaporation,air/ground temperature,but have evident negative correlation with relative humidity of atmosphere,ground temperature and precipitation.The rich sand sources combining with the dry climate in the studied area contributed to the increase of dust and sand storm events.

The soil enzyme activities were investigated in orchard of the Ziziphus jujuba in Huanghekou Town of Kenli,Dongying,Shandong Province.The results indicated that the soil enzyme activity decreased with the soil layer deepening.Urease had remarkable positive correlation with peroidase and catalase,its correlation coefficients was 0.996 and 0.943 respectively;Urease had little correlations with polyphenal oxidase and correlation coefficient was 0.337;Catalase had remarkable positive correlation with polyphenal oxidase and correlation coefficient was 0.911;Polyphenal oxidase had little correlations with other three enzymes.Soil enzymes had remarkable correlations with soil nutrients,pH and soil microorganism.Among them,urease had remarkable correlation with soil nutrients,pH,azotobacteria,fungi,bacteria,and correlation coefficient was above 0.444;Polyphenal oxidase had little correlations with soil nutrients and microorganism;peroidase and catalase had remarkable correlation with soil nutrients,pH,fungi and cellulolytic bacteria.The correlation coefficient was above 0.451.

The soil salt and nutrient of 5-year-old Nitraria sibirica stand growing in heavy salinized soil were measured.The result showed that soil salt content(0～20 cm soil depth) of 5-year-old Nitraria sibirica stand decreased significantly and the soil nutrient content increased obviously compared with the unafforested land.In the neo-alluvial land area,the soil salt and nutrient of different types of forest stands afforested 18 years ago were measured.The result showed that the soil salt decreased significantly and soil nutrient increased obviously in different stands.Although the effects on controlling soil secondly salinized were no difference among the different stands,the content of soil organic matter and available nitrogen of poplar and acacia mixed stand row by row was the highest among all kinds of stands.

To verify the effect of afforestation on soil fertility on abandoned limestone hill,a vegetation restoration experiment with different planting types of trees had been conducted in 1974.Soil samples under different types of trees were collected in March 2006.Soil nutrients improved significantly(P<0.05) after 32-year vegetation restoration.The amount of soil total nitrogen and phosphorous,available nitrogen and potassium at Choerospondias axillaris site increased at maximum extent by 84.62%,55.56%,79.20% and 109.76% respectively compared with control.The great increase in soil available phosphorous and organic matter was observed at Firmiana simplex site,respectively by 292.73% and 75.40%.The similar increasing tendency was also observed for soil organic pool,soil total organic carbon(TOC),soil water-soluble organic carbon(WSOC) and microbial biomass carbon(MBC) were much more abundant(P<0.05) at Ch.axillaries,F.simplex and Sapindus mukorossi sites than those at control site.Soil WSOC and MBC at Cupressus funebris and Robinia pseudoacacia sites were more abundant(P<0.05) compared with those at control site although soil TOC was found no different between them.Soil pH was lowered(from 8.01 to average 7.3) as a result of afforestion.In comparison of different treatments,it can be concluded that Ch.axillaris had the most power on improvement in soil quality,and followed by F.simplex and S.mukorossi,C.funebris and R.pseudoacaia had the least.

This research was aimed to study the soil physical properties,the soil water characteristics and their influences on the plant available soil water in a mixed forest of Pinus tabulaeformis and Quercus variabilis in the Xishan Mountain.The soil had good physical properties as follows:soil density is 1.20～1.45 Mg·m^-3,total porosity,45%～58% while the non-capillary porosity,6%～10%,and the root is in poor aeration.The soil moisture characteristic curve could be described by the Gardner empirical equation θ_v=ΑS^-B.The soil had a water holding capacity of 418.77 mm while the field water holding capacity was 348.53 mm and the soil wilting capacity 34.01 mm.So the soil had a field water holding capacity of 314.52 mm.But on site study it was showed the actual water holding capacity never reached such high level.The actual water storage was 60～180 mm,much lower than the field water holding capacity.There existed an about 50 days dry period from late of April to the early of June with the soil moisture lower or near 10%.There existed a humid period from July to early of September with a soil moisture between 15% and 20%.In other period the soil moisture was 10%～15%.

The results of the study on the absorption of N nutrition in the plants of Dendrobium cultured from tissues show that(NH)₂C₄H₄O₆ as N source is the best for promoting the growth(height,diameter of stem and biomass) of the plants which have mycorrhizae.Also,(NH)₂C₄H₄O₆ can promote growth of mycelium of F9903 which is a strain of mycorrhiza of Dendrobium.So,(NH)₂C₄H₄O₆ is a best N source for the propagations of both the plants and the mycorrhiza myceliaum.There is a strong interaction between the plants and their mycorrhizae.Different concentrations of(NH)₂C₄H₄O₆ can effect the growth of Dendrobium plants and absorptions of the mycorrhizae to N,P and C.Through a variance analysis,it has shown that the 2.72 mol·L^-1 of(NH)₂C₄H₄O₆ is the most suitable concentration for culturing plants of Dendrobium.

The nutrient content's correlation between leaf and soil of bamboo forest with balance fertilization in Fengxin County was studied.The results showed that it was basically consilient that the variation of the nutrition contents in the leaves of bamboos in the same age between the intensive managed and commonly managed forests.The contents of N,P and K of the tender leaves in the I-degree bamboo are higher than those in other ages respectively.The contents of Ca,Mg,S,Mn,Zn increased with the age increase.The major factors of influencing nitrogen content in bamboo leaf were organic matter,available P,activated acid,available N,total K in soil.The major factors and order of influencing phosphorus content in bamboo leaf were activated acid>base-exchange capacity>available K>total K>available Ca>available P>available N>pH value in soil.The major factors influencing potassium content in bamboo leaf were total N,available N,available P,total K and activated acid,its order of correlation was available P>total K>available N>activated acid>total N.Fertilization can promote supplements for nutrition of leaf,and ensure keeping bamboo forest sustainable development.

In order to study the results of soil productivity maintenance measurements,soil nutrient,soil enzyme activities and soil microbes of intercropping forestland,soil replacing(replacing sand with fertile farming soil) forestland and cultivar-alternated forestland were measured in the field along the Shu River in Juxian County in Shandong Province.The results showed that in soil-replaced forestland,the DBH and the height of stands increased significantly,and soil nutrient,the activities of urease,peroxidase,polyphenol and the number of soil microbes were improved,bacteria,fungi,actinomyces increased 1.55,2.05,1.24 times compared with CK.Soil organic matter,available N,available K,the activities of soil urease,peroxidase,polyphenol,the amount of soil microbes of cultivar-alternated forestland increased,and bacteria,fungi,actinomyces increased 3.18～23.91,3.40～28.71,0.71～2.80 times respectively.Intercropping was beneficial to soil organic matter,available P,available K,trace element Fe,Mn,the activities of soil enzyme,the amount of soil microbes.And bacteria,fungi,actinomyces increased 1.38～3.39,1.28～7.73,0.79～3.11 times respectively,the DBH and the height of stands increased 15.25%～37.84%,8.17%～29.12% respectively.

In this thesis,the present situation of heavy metals contamination and the physical and chemical properties of soils and the enrichment situation of heavy metals(Cd,Hg,Pb and Cr) in the vegetable body in the Harbin city greenbelt were investigated and evaluated.The results were showed as follows:The four heavy metals all polluted greenbelt soil by different degree in Harbin.The contamination of hydrargyrum was the most serious and reached the heavy contamination.The next contamination was plumbum,cadmium and chrome.By using single factor to estimate contamination situation of five zones in Harbin,its result showed that the contamination situation of cadmium and hydrargyrum was very serious in the public greenbelt.The contamination situation of plumbum was very severe in the road and traffic greenbelt.The content of chromium was very high in the suburban agricultural zone.The ranking order of the contamination situation was the public greenbelt>the habitation greenbelt>the road and traffic greenbelt>the suburban agricultural zone by method of fuzzy comprehensive assessment.The ranking order of the comprehensive index of ten greenbelt plants was Populus nigra>lawn>Juglans mandshurica>Syringa microphylla>Syringa oblata>Picea koraiensis>Salix matsudana>Ligustrum suave>Ulmus pumila>Acer negundo.The ranking order of the agricultural plants was soybean>cole>corn>alfalfa>broomcorn>paddy>bean;The strongest enrichment capability of the greenbelt plants was Syringa microphylla;the strongest enrichment capability to the hydrargyrum and plumbum of the greenbelt plants was Juglans mandshurica;the strongest enrichment capability to the chrome of the greenbelt plants was Populus nigra.The compound contamination sign exists in the soil between total cadmium,total hydrargyrum,total plumbum and chrome.The prominent correlation exists in total cadmium and total plumbum.The correlation coefficient was very lower between heavy metals in the plant body.The correlation coefficient was very prominent between cadmium and plumbum in the plant body.The correlation between plants and soil's heavy metal content of the cadmium was very prominent and others was very lower.The main contamination source of the hydrargyrum of plants and soils was the atmosphere dust of factory and gas in the Harbin's greenbelt.One of the contamination sources of the hydrargyrum was the fluorescent lamp.The universal application of the fluorescent lamp produces a lot of contamination of public greenbelt in the ice and snow days of Harbin.

Atriplex is a kind of typical plant species which grows in drought and semi-drought areas around the world.In order to provide a theoretical basis of reference for its photosynthetic characteristics,a series of leaf anatomical structure,stable carbon isotope ratio(¹³ C/¹² C) and photosynthetic characteristics of seven 3-year-old Atriplex species introduced from North America were studied.The results showed that:All of the 7 Atriplex species have got Kranz anatomy and fences-like Mesophyll cell which contains bundle sheath cell inside;They can grow in both drought desert environment(Minqin in Gansu Province) and relatively humid condition(Yuanyang in Henan Province) with average δ¹³ C value from-13‰ to-16‰;The light saturation points of the 7 species were from 1 603 to 2 185 μmol·m^-2 s^-1 and the apparent quantum yields were from 0.049 5 to 0.071 8 mol CO^-2·mol^-1 photons during the growing seasons.It was concluded that the 7 Atriplex plant species belonged to C₄ plant group and their photosynthetic pathway did not change with place changing during the growing period.

Soil aggregate is the basic unit of soil structure,and its stability is one of the important factors to influence soil erosion.Based on reviewing the history and present situation of the study on soil aggregates,the developments in forming mechanism,the chemical factors influencing aggregate stability and the breakdown mechanism were summarized.The main chemical factors include organic matter,sesquioxides,exchangeable Na and mineralogical properties.

Evaluation methods for soil N availability are important to assess forest N cycling and its related issues.This paper reviewed the soil N availability in situ evaluation methods,which included buried-bag incubation,PVC closed-top tube incubations,ion exchange resin bags,resin cores,¹⁵N methods and ecosystem N budgets.As a result of the challenges to the classical soil N cycling paradigm,N mineralization being the perceived center point of the soil N cycle,ecologists provided the new paradigm,depolymerization,plant-microbe competition and microsite processes being the three key problems to assess soil N availability.Thus,all methods above were limited,and new method needed to be provided and developed as an urgent task in the future.

Investigation of the soil quality of 319 samples from 18 newly-established green belts of Shanghai shows that the soil in newly-established green belts has some common properties.pH value is alkaline or strong alkaline,and the electroconductivity(EC) and the amount of organic matter are low.The soil is of high bulk density,in which 42.45% is larger than 1.35 Mg·m^-3.The soil aeration is poor,in which 83.2% is lower than 5%.The cation exchange capacity is suitable,in which the amount of hydrolyzable nitrogen and phosphorus are low but the amount of rapidly available potassium is suitable.Most soils are loam.The soil quality is one of the most important factors that limit the growth of plants and the effect of landscaping and ecology of green belts.For above problems,we should improve the soil quality in the following aspects:establishment of the municipal standard for soil quality,sampling methods,analysis methods,plant nutrition balance,soil safety,soil remediation and waste utilization,administrative strategy and so on.

This paper dealt with a study on the nutrient status of litter collected in different phases from 2002 to 2003 in winter or summer in reclamation and non-reclamation pure Phyllostachys pubescens stands or mixed P.pubescens stands with broadleaved trees by means of fixed monitoring in Luxi and Jianshan forest region,Fuyang County,Zhejiang Province.ANOVA results showed that the dry weight of litter in non-reclamation P.pubescens stands was higher than reclamation pure P.pubescens stands while it significantly reduced after reclamation.It indicated that the average dry weight of litter in non-reclamation P.pubescens stands was 2.13～2.46 times the size of reclamation stands in winter or summer,while that in mixed bamboo stands was 3.07～3.65 or 1.79～2.27 times the size of non-reclamation stands or reclamation stands respectively.It also appeared absolutely the same variation characteristics as order of nutrient content or storage of litter between non-reclamation pure and mixed P.pubescens stands were as follows:N,Ca,K,Mg,P,whereas the order of nutrient content or storage of litter in winter or summer in reclamation pure stands were as follows:Ca,K,N,P,Mg.Nutrient content of litter in reclamation bamboo stands ranged 0.2～5.1 g·kg^-1 while nutrient storage from 0.51 to 22.46 kg·hm^-2,nutrient content of non-reclamation bamboo stand ranged 0.29～19.81 g·kg^-1 while nutrient storage from 2.11 to 57.29 kg·hm^-2 and it ranged 0.52～19.89 g·kg^-1 while nutrient storage from 3.74 to 236.37 kg·hm^-2 in mixed bamboo stands.Therefore it must be pay sufficient attention to soil management for reclamation can restrict improving potential soil fertility as greatly reduced amount of litter on surface in bamboo stands although it can improve soil structure and moisture condition.

This paper analyzed the difference of soil nutrient and the dynamics of available nutrient in soil solution of the forest and grass composite pattern and the farmlands on site.The result showed that the content of soil total N,hydrolysable N,organic matter in forest and grass composite pattern was higher than in farmland.The content of total P,available P,total K and slowly K was lower than that in farmland.The seasonal change of NH₄⁺-N,NO₃^--N,PO₄^3-and K⁺ was influenced by the growing of plant,precipitation and temperature.

Soil permeability is an important index to evaluate water source conservation function.This paper chooses three vegetation patterns(cropland as control,patternⅠArundinaria amara+Hemarthria compressa,PatternⅡBambusa pervariabilis×Dendrocalamopsis oldhami+Hemarthria compressa) as study objects and has a locating study on their soil permeability by means of infiltration canister.The primary research shows that the relationship between soil infiltration rate and time of three vegetation patterns can be expressed as V=Aln(t)+B.On this basis,the seasonal change of soil infiltration rate of three vegetation patterns is discussed in this paper.The results indicate that patternⅠ plays a greater role in improving soil permeability,the control plays a great role in improving soil permeability,and patternⅡ plays no obvious role in improving it.

Seasonal variation of soil microbial amounts and rhizospheric effect of two forest trees were studied systematically on Betula luminifera forest and Pleioblastus amarus forest in Hongya County,Sichuan Province.The effects of two models of conversion of farmland to forest on soil microbial amounts and activities were analyzed and discussed too.The results showed that soil microbial amounts were increasing from spring to autumn,and the most in autumn,and the least in winter in B.luminifera forest and P.amarus forest.Bacteria amounts were predominant,actinomyces amounts were the next,and fungi amounts were the least among composition of communities of soil microbes.The sequence of total amounts of soil microbes was as follows:P.amarus forest(1.29×10⁹ individual·g^-1 dry soil)>B.luminifera forest(0.29×10⁹ individual·g^-1 dry soil)in a year.Rhizospheric effects of the two forest trees under two models of conversion of farmland to forest were different in different seasons.And the R/S values of microbes were 1～2 in different seasons,and the R/S values were 1.37 and 1.24 respectively in B.luminifera forest and P.amarus forest in a year.The ecological benefit of model of P.amarus forest was better than B.luminifera forest by evaluation of total soil microbes.