Bioamelioration of a sodic soil by silvopastoral systems in northwestern India

In sodic soils, excessive amounts of salts have an adverse effect on soil biological activity and stability of soil organic matter. The study analyzes the role of silvopastoral systems to improve soil organic matter and microbial activity with a view for effective management of soil fertility. The silvopastoral systems for the present study (located at Saraswati Reserved Forest, Kurukshetra; 29°4′ to 30°15′ N and 75°15′ to 77°16prime; E) are characterized by tree species of Acacia nilotica, Dalbergia sissoo and Prosopis juliflora along with grass species of Desmostachya bipinnata and Sporobolus marginatus. Soil microbial biomass carbon was measured using the fumigation extraction technique and nitrogen mineralization rates using aerobic incubation method. The microbial biomass carbon in the soils of D. bipinnata and S. marginatus treatments were low. In silvopastoral systems, microbial biomass carbon increased due to increase in the carbon content in the soil – plant system. A significant relationship was found between microbial biomass carbon and plant biomass carbon (r = 0.83) as well as the flux of carbon in net primary productivity (r = 0.92). Nitrogen mineralization rates were found greater in silvopastoral systems compared to 'grass-only' system. Soil organic matter was linearly related to microbial biomass carbon, soil N and nitrogen mineralization rates (r = 0.95 to 0.98, p < 0.01). On the basis of improvement in soil organic matter, enlarged soil microbial biomass pool and greater soil N availability in the tree + grass systems, agroforestry could be adopted for improving the fertility of highly sodic soil. This revised version was published online in June 2006 with corrections to the Cover Date.     

Nitrogen cycling in Pinus sylvestris stands exposed to different nitrogen inputs

The objective of this study was to quantify the effects of high nitrogen (N) inputs on N cycling in a 35–45-yr-old Scots pine (Pinus sylvestris L.) forest. Nitrogen was added annually (single doses) as NH₄NO₃ in doses of 0 (N0), 30 (N1) and 90 (N2) kg N ha^?1 yr^?1. The only N input to the N0 plots was atmospheric deposition of 10 kg N ha^?1 yr^?1. The N cycle in these plots was tight, with almost complete retention of the incoming N. In the N1 plots the N retention was 83% after 9 yrs of N addition. The trees were the major sink, but the soil also contributed to the N retention. In the N2 plots the N retention was 63%, being mainly accounted for by accumulation in the soil. The leaching of N from the N2 stands was as high as 35 kg N ha^?1 yr^?1. The N2 system was N saturated.     

不同年龄巨桉人工林枯落物和细根碳储量研究

以巨桉工业人工林为对象,采用"空间换时间法",研究一个轮伐期巨桉林枯落物和细根碳储量,结果表明,1～6年生巨桉林枯落物碳储量为0.641～6.648 t·hm-2,不同年龄巨桉林枯落物碳储量1年为2.263±1.022 t·hm-2,2年为3.414±1.873 t·hm-2,3年为2.270±1.262 t·hm-2,4年为2.305±1.664 t·hm-2,5年为3.011±1.630 t·hm-2,6年为4.139±2.509 t·hm-2,6年生巨桉林枯落物碳储量最大.枯落物凋落量在年龄序列中表现为"高-低-高"的趋势;1～6年生巨桉林细根碳储量为0.101～0.637 t·hm-2,不同年龄巨桉细根碳储量1年为0.318±0.109 t·hm-2,2年为0.308±0.139 t·hm-2,3年为0.255±0.154 t·hm-2,4年为0.263±0.076 t·hm-2,5年为0.390±0.128 t·hm-2,6年为0.438±0.199 t·hm-2,6年生巨桉林细根碳储量最大,3、4年生较小,这与细根生物量的年龄变化趋势相一致.     

银杏复合经营对土壤碳、氮、磷和有机质的影响

以江苏东台林场银杏+小麦(G+W)、纯银杏(G)和纯小麦(W)经营模式为研究对象,对不同土层(0~5,≥5~15,≥15~30和≥30~50mm)的p H、微生物量碳、微生物量氮、硝态氮和铵态氮、全氮、速效磷、全磷和有机质进行了系统的测定。结果表明:不同经营模式对土壤p H没有显著的影响,但对土壤微生物量碳、微生物量氮、硝态氮、全氮、速效磷、全磷和有机质等影响显著。G+W经营模式有较高的土壤微生物量碳、微生物量氮、硝态氮、全氮、速效磷、全磷和有机质。因此,银杏复合经营系统能够更好地维持土壤肥力,利于土地可持续经营。     

Carbon and nitrogen dynamics in early stages of forest litter decomposition as affected by nitrogen addition

The effects of nitrogen(N) availability and tree species on the dynamics of carbon and nitrogen at early stage of decomposition of forest litter were studied in a 13-week laboratory incubation experiment.Fresh litter samples including needle litter(Pinus koraiensis) and two types of broadleaf litters(Quercus mongolica and Tilia amurensis) were collected from a broadleaf-korean pine mixed forest in the northern slope of Changbai Mountain(China).Different doses of N(equal to 0, 30 and 50 kg·ha-1yr-1, respecti...     

杉木人工林凋落物C,N,P归还量对氮沉降的响应

为探讨亚热带森林对氮沉降增加的响应,在12年生的杉木人工林中开展4种水平的模拟氮沉降试验,分N0(对照),N1,N2,N3等4种处理,氮沉降量分别为0,60,120,240kg·hm-2a-1。模拟氮沉降2年后,4种不同氮沉降水平杉木人工林的年凋落量分别为1008.83,1164.10,1147.30和976.47kg·hm-2,表明低中氮处理(N1,N2)在一定程度上增加森林凋落物量,而高氮处理(N3)则表现出一定的抑制作用。叶凋落物中C,N元素含量随氮沉降水平的增加而增加,而C/N则呈不断下降的趋势。经不同氮沉降处理后,凋落物C元素的归还量分别为474.70,544.07,538.55和474.02kg·hm-2,N元素的归还量分别为7.21,8.56,9.03和9.04kg·hm-2,P元素的归还量分别为1.17,1.24,1.32和1.09kg·hm-2,说明与N0处理相比,氮沉降显著提高N元素的归还量,而N1,N2处理提高C,P元素归还量,N3处理对C归还量影响不明显,但降低P的归还量。     

Carbon,nitrogen and organic C fractions in topsoil affected by conversion from silvopastoral to different land use systems

The conversion of silvopasture to different land use systems cause effective changes in soil carbon distribution, due to disturbances in soil aggregation promoted by soil management and changes in crop residues inputs and decomposability. We evaluate the C and N stocks, and organic C fractions in soils under continuous arable land (AR) and silvopasture with apple trees and grass (SP); and after 4 years of conversion from silvopasture to arable land (SP-AR) and grassland (SP-GL). Total N (TN) and organic C (TOC), as well as microbial biomass carbon (C_MB), light fraction (C_LF) and heavy fraction (C_HF) were evaluated at two different depths (0–10 and 10–20 cm). After 4 years of conversion, SP-AR and SP-GL presented C and N stocks similar to the observed for SP when the 0–20 cm depth was considered. However, AR presented TOC and TN stocks around 21 and 10% lower than SP, respectively. SP-AR tended to present the lowest C_MB stocks and was positively correlated with salt extractable organic C (r ² = 0.60, P < 0.001). C_LF values declined by 62% from 0–10 to the 10–20 cm at SP and SP-GL, however there was no variation with increasing depth for AR and SP-AR. C_HF represented the highest C fraction in soil, corresponding to 82% of TOC. Except for AR, δ¹³C values of the light fraction increased with increasing depth. In general, heavy fraction tended to be more enriched in δ¹³C than light fraction. In a long-term, conventional tillage can significantly contribute to reduce TOC and TN stocks when compared to the silvopastoral system.     

森林生态系统土壤碳库对氮沉降的响应

从土壤碳含量的输入和输出两方面综述了N沉降胁迫对土壤碳库的影响方式和过程,分析了目前N沉降对凋落物分解、细根生物量、土壤呼吸的影响的研究进展及其作用机制,但由于N沉降对土壤碳库的影响是一个复杂的综合作用过程,N沉降对森林土壤碳库的总效应尚需要更深入的研究.     

Influence of nitrogen and phosphorus fertilizers on amount and nutrient content of litterfall in a regrowth eucalypt forest

The effects of fertilizer treatment on nutrient transfers to the forest floor were examined in regrowth Eucalyptus diversicolor F. Muell. forest. Dry weight and nutrient content of leaf litterfall and total litterfall were measured for 3 years in a stand to which two levels of N (0, 200 kg ha^-1 year^-1) were applied each year at each of three levels of a single initial application of P (0, 30, 200 kg ha^-1). Annual accessions of litter to the forest floor were significantly increased by additions of both N (by 17%, 18% and 21% in the 3 years) and 200 kg P ha^-1 (by 8%, 8% and 4% in the 3 years) but there was no interaction between effects of N and P treatments. Fertilizer application also had a significant effect on the nutrient content of leaf litterfall and total litterfall. Concentration of N in leaf litterfall was 9% to 23% greater on plots treated with N fertilizer compared to untreated plots. The amounts of N in litterfall were about 30% greater on N-treated compared to untreated plots. On plots treated with 200 kg P ha^-1, P concentrations in leaf litter were 50% to 100% greater than in litter from plots receiving no P. Application of 200 kg P ha^-1 increased the amounts of P in annual litterfall by 32% to 87%. The greatest increase in P accessions occurred soon after fertilizer treatment. The amounts of Ca, K, and Na in litterfall were also significantly increased by fertilizer application. For Ca and K this was due partly to increases in element concentrations in litterfall following application of treatments. The effect of fertilizers on internal recycling of plant nutrients and on litter accumulation and nutrient dynamics in forest floor litter is discussed.     

Carbon resources,soil organisms,and nitrogen availability: Landscape patterns in a northern hardwood forest

The interactions among different components of detrital food webs are likely to influence carbon processing and linkages between C and nutrient cycling. Our objective was to identify potentially important interactions in detrital food webs at the Hubbard Brook Experimental Forest, NH, USA, by exploring relationships among C resources, microbial biomass, microarthropod abundance and nitrogen availability as they vary across the landscape. We found significant spatial variation in microarthropod abundance in the forest floor across elevation zones in two watersheds, with consistently higher abundance in low-elevation hardwoods and upper conifer zones and lower abundance in mid- and high-elevation hardwoods. The same pattern was observed in the Oe horizon for microbial biomass C and respiration but not for N transformations; however, no patterns were observed in the Oa horizon. Microarthropod abundance and microbial biomass C were significantly positively correlated, but neither were related to forest floor mass or to annual aboveground fine litterfall flux. Instead, a positive correlation with fine root biomass suggests that C supply from roots plays a key role in the fungal channel of the detrital food web of these forests. The lack of relationship between patterns of microarthropod abundance and net N mineralization leads us to hypothesize that spatial patterns of nitrogen availability are not closely linked to variation in carbon flow through the detrital food web, within this forested landscape. In contrast, microarthropod abundance and net N mineralization did exhibit similar interannual variation and may respond to the same temporal controls.     

喀斯特森林植被自然恢复中凋落物现存量 及其碳库特征演化

采用空间代替时间的方法,研究了茂兰退化喀斯特森林自然恢复中凋落物现存量及其碳库特征.结果表明:随群落恢复凋落物现存量呈减少趋势,早期减幅大,中后期减幅小;随群落恢复凋落物现存量演化受地貌因子、群落生活史、土壤微生物的影响较大,受水热条件的影响较小;凋落物现存量生物量与其分解失重率、表层土壤微生物量碳有较强的负相关关系;凋落物分解失重率与表层土壤微生物量碳呈极强的正相关关系;随群落恢复凋落物现存量含碳率变化不显著,凋落物现存量碳密度变化规律与凋落物现存量变化规律一致,单位面积凋落物碳储量表现为碳源效应,且早期碳源效应较强、固碳能力不稳定,中后期碳源效应较弱、固碳能力稳定;凋落物碳密度(Y)与其现存生物量(x)的关系:Y=b.+b1x(b0、b1为常数).     

Organic matter contribution to soil fertility improvement and maintenance in red Alder （Alnus rubra） silvopastoral systems

An investigation was conducted to quantify fine roots and roots nodules over the four seasons in forestry and agroforestry alder (Alnus rubra) stands in North Wales. Soil samples collected in each season were excavated at three sampling points (0.30 m, 0.57 m and 1.00 m distance from the base of each tree) from nine trees of the agroforestry and forestry plots. Result showed that the density of live fine root had significant differences in between seasons and treatments (P ＜ 0.001). The mean weight density of live fine root over the four seasons in agroforestry and forestry was 0.27±0.01 kg·m-3 and 0.54±0.03 kg·m-3, respectively. Weight density of dead root in each system remained constant throughout the year. The mean weight density of dead root was also significantly different (P ＜ 0.01) between forestry and agroforestry systems. Weight density of live and dead root nodule was both constant throughout the year and between the different sampling distances. The mean weight densities of live and dead root nodule over the four seasons were 0.09±0.03 kg·m-3 and 0.05±0.03 kg·m-3 in agroforestry and 0.08±0.02 kg·m-3 and 0.03±0.01 kg·m-3 in the forestry plots, respectively.     

通辽市森林生态系统植被碳贮量估算研究

以生物量与立木蓄积量为基础,对内蒙古通辽市森林生态系统植被碳贮量进行了估算。结果表明：通辽市森林生态系统植被总碳贮量为1 307.03万t,其中,按林种分,用材林、防护林、特用林、疏林、经济林、灌木林、散生木、四旁树的碳贮量分别为：439.42万t、357.35万t、11.53万t、8.94万t、11.12万t、462.70万t、0.74万t、15.23万t;按树种分,杨树碳贮量最大,为680.88万t,占乔木林碳贮量的81.7%;按旗县分,扎鲁特旗森林植被碳贮量最大,为432.56万t,占总碳贮量的32.41%。     

草原天然植被和草原造林固碳储量的对比研究

在内蒙古干草原区研究了草原天然植被和白榆人工防护林系统碳储量的变化,结果表明:草原天然植被和白榆人工防护林植被碳储量特征不同.草牧场防护林植被下总固碳储量为65.97t/hm2,天然草原植被为14.65t/hm2.人工林系统碳储量主要集中在树木和土壤碳库,分别占总储量81.33%和14.24%,而根系只占3.55%.草...     

森林生态系统碳通量研究进展

陆地生态系统是"温室气体"的一个主要排放源, 森林生态系统作为陆地生态系统最大的碳库, 研究其系统与大气界面的碳通量变化具有重要的科研和社会意义。文中简述了森林生态系统碳通量研究的意义和进展, 以及存在的问题和解决途径。     

围封对草地地下碳储量影响的研究

在陈巴尔虎旗具有代表性的草原类型,选择自由放牧和围封样地,采用壕沟法进行野外取样,研究放牧和围封下的根系以及土壤的碳密度及碳贮量。结果表明:围封后羊草草原和草甸草原地下碳储量增加,差异显著;针茅草原地下碳储量增加,差异不显著。其中围封草甸草原根系固碳量和土壤碳储量最大,分别为79.74 g/m2和21 150.49 g/m2;其次为围封羊草草原,分别为53.12 g/m2和14 643.65 g/m2;针茅草原最小,分别为47.90 g/m2和11 273.52 g/m2。与放牧样地地下碳储量相比分别增长了35.89%、50.17%、3.74%。虽然根系固碳量只占土壤碳储量的极少部分,但根系通过改良土壤结构,对增强碳源汇集和贮存、积累碳素具有重要的影响。自由放牧样地的根系碳密度和土壤碳之间没有显著相关性(R=-0.61)。围封样地根系生物量也随土壤深度增加呈递减趋势,但根系碳密度和土壤碳储量显著相关(R=0.98)。根系生物量、根系固碳量、土壤碳储量均随土壤深度增加呈递减趋势。     

基于森林资源二类调查数据的大冶市森林植被碳储量和碳密度测算

森林通过吸收大气中的二氧化碳固定到碳库中，在“双碳”目标中起着碳中和的重要作用。本研究基于大冶市2019年林业资源二类调查小班数据，采用材积源生物量法对大冶市森林资源的植被碳储量和碳密度进行测算，结果表明：大冶市现有森林植被碳储量114.36×10⁴ t,平均植被碳密度为23.66 t·hm^-2;碳储量较高的区域主要集中分布在大冶南部山区，灌木林碳储量占比最高，其次为马尾松林；马尾松林的平均植被碳密度最高，达到35.64 t·hm^-2。该测算结果可为大冶市实现“双碳”目标以及森林资源的科学管理提供数据基础和决策依据。     

Spatial distribution of soil carbon and nitrogen storage and forest productivity in a watershed planted to Japanese cedar (Cryptomeria japonica D. Don)

Digital terrain modeling was used to evaluate landscape-level spatial variation of soil C and N storage and site productivity in Japanese cedar (Cryptomeria japonica D. Don) stands. Soil C and N storage were measured in samples from surface soils (0–25 cm depth) of 29 Japanese cedar stands in the 205-ha Myougodani watershed, Toyama Prefecture. The site index (C. japonica tree height at age 40 years) was used as a measure of forest productivity. Seven terrain attributes (elevation, slope gradient, aspect, profile curvature, plan curvature, openness, and wetness index) were calculated from a digital elevation model. Soil C and N storage were negatively correlated with slope gradient and positively correlated with openness. Variation in the site index was closely related to the wetness index. The prediction models using terrain attributes as explanatory variables explained 50% of the variability in soil C storage, 53% of the variability in soil N storage, and 75% of the variability in site index. This result demonstrated that this technique is useful for estimating the spatial distribution of soil properties and productivity in forest landscapes. On the other hand, there was no correlation between site index and soil C and N storage. Use of the prediction models in a geographic information system revealed that the spatial distribution of forest productivity differed considerably from those of soil C and N storage.     

Soil properties and nitrogen availability in silvopastoral plantings of Acacia melanoxylon in North Island, New Zealand

Acacia melanoxylon, a N₂-fixing timber tree occurring naturally in eastern Australia, is now promoted as a component of silvopastoral systems; but the interaction of the tree with pasture and soils has not been adequately studied. This study investigated the effects of Acacia melanoxylon on soil nitrogen (N) levels, N availability, soil pH, bulk density, organic carbon, C:N ratios and soil moisture in three separate silvopastoral sites with contrasting soil types in the North Island of New Zealand. At each site four tree stocking rates were studied (0, 500, 800, and 1700 stems ha^–1). The trees were nine years old at the time of the study. Soil samples from each study site were taken once at three depths (0 to 75 mm, 75 to 150 mm, and 150 to 300 mm), with three replicates per tree stocking rate. Soil analyses showed that although there were differences between soil types, few statistically significant differences occurred due to tree stocking rate. A greenhouse pot trial growing ryegrass (Lolium multiflorum L. cv. Concord) in soil from the A horizon of each soil type from under the trees and the open pasture found that ryegrass yield, N uptake and N supply increased with increasing tree stocking rate. Increased N supply under the trees, coupled with greater soil moisture compared to the open pasture may have accounted for the higher pasture yield under Acacia melanoxylon compared to non dinitrogen fixing tree species. This study suggested that Acacia melanoxylon in a silvopastoral system had the potential to increase soil N availability.This revised version was published online in November 2005 with corrections to the Cover Date.     

蓝山县乔木林碳贮量及固碳价值研究

以蓝山县十二五森林资源调查成果为数据依据,对蓝山县不同类型乔木林碳贮量及固碳价值进行了研究。结果表明:蓝山县乔木林的总碳贮量为169.37×104t,固碳价值为203 244万元。杉木的碳贮量最大,占乔木林总碳贮量的67.58%。阔叶林的碳密度普遍大于针叶林的碳密度。幼龄林碳贮量最大,不同龄组碳密度符合近、成、过熟林大于中、幼龄林的规律。人工林的碳贮量占绝对优势,天然林的碳密度大于人工林。