Spatial heterogeneity of soil organic carbon in tree-based intercropping systems in Quebec and Ontario,Canada

Land use affects the carbon sequestration potential of soils across landscapes. Tree-based intercropping (TBI) systems where annual crops are grown between established tree rows are expected to exhibit spatial heterogeneity in the soil organic carbon (SOC) content due to differences in carbon input and decomposition rates of litter from trees and herbaceous plants. This study aimed to quantify variability in the SOC of TBI systems, compare the SOC content of TBI and nearby conventional agroecosystems, and determine if SOC was related to soil fertility. The TBI research sites were established 4 years (St. Paulin and St. Edouard, Quebec, Canada), 8 years (St. Remi, Quebec, Canada) and 21 years (Guelph, Ontario, Canada) before soil samples were collected for this study. The SOC content was greater within 0.75 m of the tree row than in the intercropped space at the St. Edouard and St. Remi sites. At the Guelph site, the SOC was spatially heterogeneous in plots with Norway spruce (Picea abies L.) but not hybrid poplar (Populus deltoides × P. nigra clone DN-177), probably due to litterfall distribution. Formerly a tree plantation, the TBI system at St. Remi contained 77% more SOC than a nearby conventional agroecosystem, while there was 12% more SOC in the TBI system than the conventional agroecosystem at Guelph. There was no difference in the SOC content of 4-year old TBI sites and nearby conventional agroecosystems. However, an increase in SOC at all TBI sites was positively related to the plant-available N concentrations, indicating the benefit of temperate TBI systems for soil fertility.     

Vertical root separation and light interception in a temperate tree-based intercropping system of Eastern Canada

We analysed the spatial distribution of fine roots and light availability in a tree-based intercrop system (TBI) composed of Quercus rubra L. (QUR), hybrid poplar (Populus deltoides × Populus nigra—HYP) and hay (CROP) in southern Québec (Canada) to evaluate interactions between trees and crop. Trees in the 8-year-old TBI system had superficial fine root profiles, which is common in tree species grown in conventional plantations and natural forests. More than 95 % of fine roots were found within the first 25 and 45 cm for QUR and HYP, respectively, and 35 cm for CROP. However, vertical separation between the fine root systems of QUR and CROP was evident, as QUR allocated less fine roots to the top 10 cm of soil, and more to depths between 10 and 30 cm, as opposed to CROP which had a greater proportion of fine roots in the top 10 cm. HYP fine roots showed no adaption when intercropped with hay. High tree fine root length density (FRLD) in the top soil layer was observed near the tree stems while hay FRLD was reduced by 45 %, suggesting strong competition for resources. Hay yield analysis revealed significant reduction near trees, particularly HYP. However, light did seem to be the main driver of intercrop yield, as it not only accounted for the effect of competition by roots (being correlated), but also had a singular effect.     

Growing woody biomass for bioenergy in a tree-based intercropping system in southern Ontario, Canada

During the spring of 2006, three willow varieties (SV1, SX67 and 9882-41) were established on marginal land in an agroforestry tree-intercropping arrangement where plots of short rotation willows were planted between rows (spaced 15?m apart) of 21-year-old mixed tree species. As a control, the same varieties were established on an adjacent piece of land without established trees (conventional willow system). This study investigated the magnitude of carbon pools, fine root and leaf biomass inputs and clone yields in both the tree-based intercropping (agroforestry) and conventional monocropping systems. Willow biomass yield was significantly higher in the agroforestry field (4.86?odt?ha^?1?y^?1) compared to the conventional field (3.02?odt?ha^?1?y^?1). In both fields, varieties SV1 and SX67 produced higher yields than the variety 9882-41. Willow fine root biomass in the top 20?cm of soil was significantly higher in the intercropping system (3,062?kg?ha^?1) than in the conventional system (2,536?kg?ha^?1). Differences in fine root biomass between clones were similar to that observed for differences in biomass yield: SV1?>?SX67?>?9882-41. Leaf input was higher in the intercropping system (1,961?kg?ha^?1) than in the conventional system (1,673?kg?ha^?1). Clonal differences in leaf inputs followed the same trends as those for root biomass and yield: SV1?>?SX67?>?9882-41. Soil organic carbon was significantly higher in the agroforestry field (1.94?%) than in the conventional field (1.82?%). A significant difference in soil organic carbon was found between the three clones: soils under clone 9882-41 had the lowest soil organic carbon at 1.80?%.     

Characterizing soil surface structure in a temperate tree-based intercropping system using X-ray computed tomography

The objective of this work was to characterize differences in the soil surface (top 3.5 cm) microstructure, as influenced by four tree species, within a temperate tree based intercropping (TBI) system. Soils adjacent to walnut (Juglans nigra), poplar (Populus spp.), red oak (Quercus rubra), Norway spruce (Picea abies), as well as three types of ground cover [row crop, willow (Salix spp.), and perennial grass tree rows] were analyzed. X-ray computed micro –tomography (µCT) was employed to evaluate soil void phase characteristics, as well as heterogeneity of soil matrix radiodensity. X-ray µCT identified void phase parameters were not affected by tree species due to confounding effects caused by perennial vegetation and mixed leaf litter inputs.. A positive correlation was found between traditionally measured soil bulk density and bulk X-ray radiodensity (r_s = 0.53, p < 0.01) and a negative correlation between mean intra-aggregate X-ray radiodensity and soil organic carbon (r_s = ?0.48, p = 0.03). It was determined, through the use of geostatistics, that there were no distinct or consistent anisotropic structures, in directional semivariograms, evident for the various species. However, the semivariograms revealed greater variability, correlated with less directional anisotropy within the tree row as compared to cropping alley soils. It was interpreted that processes within soils in the tree rows were leading to a homogenous type of structure, and that soils under row crops exhibited a greater tendency for destruction of surface structure, leading to more directional anisotropy (trends).     

A general framework for the quantification and valuation of ecosystem services of tree-based intercropping systems

This study provides the first complete framework for the valuation of ecosystem services of agroforestry and uses a tree-based intercropping (TBI) system in southern Québec, Canada, as a case study. Ten ecosystem services were estimated, all of which were of interest and directly applicable to most agricultural systems worldwide: nutrient mineralization, water quality, soil quality, pollination, biological control, air quality, windbreak, timber provisioning, agriculture provisioning, and climate regulation. A mix of mathematical models for the quantification and economic valuation of various ecosystem services were used. The results revealed a total annual margin of $2,645 ha^?1 y^?1 (averaged over 40 years). The economic value of combined non-market services was $1,634 ha^?1 y^?1, which was higher than the value of marketable products (i.e. timber and agricultural products). An analysis of the present value suggested that agricultural products ranked highest among the ecosystem services taken singularly, followed by water quality, air quality, climate regulation, and soil quality maintenance. Total economic value of all ecosystem services for the rotation period was $54,782 ha^?1, only one third of which was contributed by agricultural products. Although the total value of the ecosystem services provided by TBI was high, farmers only benefited from agricultural and timber products. Thus, government incentives are needed to interest farmers in adopting practices that benefit society as a whole.     

Carbon sequestration potential of five tree species in a 25-year-old temperate tree-based intercropping system in southern Ontario,Canada

Carbon (C) sequestration potential was quantified for five tree species, commonly used in tree-based intercropping (TBI) and for conventional agricultural systems in southern Ontario, Canada. In the 25-year-old TBI system, hybrid poplar (Populus deltoides × Populus nigra clone DN-177), Norway spruce (Picae abies), red oak (Quercus rubra), black walnut (Juglans nigra), and white cedar (Thuja occidentalis) were intercropped with soybean (Glycine max). In the conventional agricultural system, soybean was grown as a sole crop. Above- and belowground tree C Content, soil organic C, soil respiration, litterfall and litter decomposition were quantified for each tree species in each system. Total C pools for hybrid poplar, white cedar, red oak, black walnut, Norway spruce and a soybean sole-cropping system were 113.4, 99.4, 99.2, 91.5, 91.3, and 71.1 t C ha^?1, respectively at a tree density of 111 trees ha^?1, including mean tree C content and soil organic C stocks. Net C flux for hybrid poplar, white cedar, red oak, black walnut, Norway spruce and soybean sole-crop were 2.1, 1.4, 0.8, 1.8, 1.6 and ?1.2 t C ha^?1 year^?1, respectively. Results presented suggest greater atmospheric CO₂ sequestration potential for all five tree species when compared to a conventional agricultural system.     

Effects of eucalypt residue management on nutrient leaching and soil properties

Effects of harvest residues on nutrient leaching and soil chemical properties were studied in a lysimeter experiment. Treatments were: (A) forest floor litter and harvest residues, other than branches, incorporated into the soil, (B) as A, but with branches cut in 20 cm long bits and placed on the soil surface, (C) as B, but with bits incorporated into the soil, (D) as B, but with branches chopped into chips, (E) as C, but with branches chopped into chips, (F) forest floor litter and harvest residues on the soil surface, with branches cut in 20 cm long bits, (G) as F, but with branches chopped into chips, and (H) absence of harvest residues (control). Treatments were applied in zero-tension lysimeters containing 25 kg of soil. Leachates were collected for a 6-year period. At the end of the experiment, lysimeters were dismantled and soil was divided in four layers. Residues, other than branches, increased N leaching, as compared with the control. Branches on the soil surface reduced N leaching when cut in chips. Branches incorporated into the soil reduced leaching independently of their size. Organic residues on the soil surface showed similar effect to those incorporated into the soil. However, harvest residues on the soil surface increased leachate volume, and reduced Ca and P losses. Such a placement of residues led to high contents of Ca and P in the 0–5 cm top soil layer. Contents of organic C, total N and base cations were not affected by the treatments.     

Impacts of woodchip amendments and soil nutrient availability on understory vegetation establishment following thinning of a ponderosa pine forest

Mechanical thinning for fire mitigation has become increasingly widespread in recent years throughout the western United States. A common practice in fire-mitigation procedures is the conversion of slash into chipped mulch (referred to as “woodchips”) that is spread on-site. Here, we investigated: (1) the effect of woodchip amendments on soil nitrogen availability, and (2) the influence of potential interactions between woodchip amendments and soil nitrogen availability on patterns of understory plant establishment in a thinned montane forest in the Front Range of Colorado.     

杨农复合经营系统不同土壤层养分分布研究

以杨树纯林和杨农复合林2种生态系统为研究对象,通过对土壤有机碳、氮、磷、钾等营养元素含量的测定,初步探讨土壤养分的分布特征。结果表明,杨树纯林和杨农复合生态系统中有机碳、全氮和有效磷含量随着土壤深度增加均呈现递减的趋势;有效钾含量在杨树纯林中随土壤深度的增加而降低,在杨农复合系统中表现出先增大后减小的倒U型变化趋势。土壤有机碳、氮、有效磷、有效钾含量范围分别为(6.34±0.22)~(16.88±1.07)g/kg,(0.57±0.09)~(1.35±0.17)g/kg,(4.76±0.44)~(13.88±1.01)mg/kg和(52.8±3.99)~(176.1±8.45)mg/kg。由于间作植物的影响,N,P,K和有机碳的含量在杨树纯林和杨农复合生态系统土壤层中表现出了一定的差异。杨农复合生态系统会在一定程度上改良土壤,增加土壤有机碳和养分元素的含量。     

Effect of removal of logging residue on nutrient leaching and nutrient pools in the soil after clearcutting in a Norway spruce stand

Following clearcutting applying the conventional stem-only harvesting method in a Norway spruce (Picea abies (L.) Karst.) stand and different levels of removal of logging residue, the nutrient fluxes from the heaps of logging residue and from the O horizon were monitored over four growing seasons and the soil nutrient pools were determined. Three levels of removal of logging residue were carried out using (i) conventional stem-only harvesting (no residues removed); (ii) residues removed; and (iii) removal of branches (foliage left on site). The heaps of logging residue were a minor source of inorganic N entering the soil in the water percolating through the heaps, but they were a significant source of organic N, P, Ca, Mg, and especially K. Nutrient fluxes from the O horizon were in general greater under the heaps of logging residue as compared to soils without overlying logging residue. The leaching of inorganic N from the O horizon under the heaps of logging residue resulted in a net loss of these compounds, while the O horizon without overlying logging residue gained N. The removal of logging residue significantly decreased the extractable K pools in the soil while it or conversely, the presence of residue heaps had no significant effect on the pools of organic matter and the pools of N, P, Ca, and Mg in the O horizon and in the 0–10 cm soil layer. The results show that the short-term effects of logging residue on nutrient dynamics in the soil can be complex and difficult to interpret in terms of site productivity as there are changes in the nutrient fluxes, which imply the opposite effects on site productivity. However, the results do indicate that, in the short-term, the removal of logging residue does not impair pools of N in the soil nor site productivity on sites where the availability of N limits productivity.     

Ecology of tree intercropping systems in the North temperate region: Experiences from southern Ontario,Canada

Agroforestry Systems - Agroforestry practices in northern latitudes, although less diverse than those in warmer regions, have unique advantages over conventional land-use systems in the region in...     

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)/soybean (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 pure ash plantation. Biography: FAN A-nan (1972–), female, Ph. Doctor in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China.     

Experience with patterns of change in soil carbon resulting from forest plantation establishment in eastern Australia

Forest plantations are extensively established in eastern Australia for production of timber products and more recently, potentially for sequestration of carbon. Intensive management of these plantations involves clearing of existing vegetation, often using fire, ripping and/or mounding of the soil and weed control, followed by planting, use of fertilizers, and subsequent tending. The plantations are managed on a 10–30-year rotation and often have high growth rates and accumulation of carbon. However, after establishment, there are reduced inputs of carbon into the soil from prior vegetation or rapidly growing weeds, together with accelerated decomposition of soil organic matter as a result of disturbance, and this leads to a net loss of soil organic carbon. In some systems this loss of soil organic carbon is not balanced by carbon biomass sequestration until 5–10 years after establishment and on some sites, a reduction in soil organic carbon may remain until the end of the rotation. The patterns of accumulation and loss of carbon vary according to location, soil type and plantation management system. The effects of intensive forest establishment on soil organic carbon were evaluated in a number of studies in eastern Australia using time sequence and chronosequence studies and comparisons of plantation soils with those from adjacent undisturbed sites. There was a general pattern of reduced carbon in surface soil immediately after plantation establishment and with time this extended deeper into the soil profile. The actual quantities varied greatly depending on the soil type. The decline was primarily a result of losses of labile carbon and was greater when the previous land use had essentially been native vegetation or highly improved pastures as opposed to regrowth woodland, or native pasture, or degraded land. In the absence of further disturbance, soil organic carbon can accumulate to pre-establishment levels but many short rotation plantations are terminated prior to this being attained. The potential upper level of accumulation of soil carbon can be increased by alteration of the soil nutritional status using fertilizer application.     

林豆复合生态系统土壤理化性质的研究

本文对混种大豆的落叶松.大豆、水曲柳-大豆复合生态系统土壤理化性质进行研究。结果表明,在一个生长季内混种后的土壤物理性质得到了改善。落叶松.大豆与水曲柳一大豆复合生态系统的土壤容重为1.112g/cm3和1.058g/cm3均低于相对应的纯林:混种大豆后土壤总孔隙度增加。两种林-豆复合生态系统土壤有机质分别比对应纯林高1.77倍和1.09倍:落叶松一大豆复合生态系统全氮和水解氮含量分别高于落叶松纯林4.2%和53.0/%,水曲柳-大豆复合生态系统全氮和水解氮含量分别高于水曲柳纯林75.5%和3.3%:混种大豆后全磷含量降低,而有效磷含量则增加:落叶松-大豆复合生态系统全钾和有效钾比落叶松纯林高0.6%和17.5%,水曲柳-大豆复合生态系统全钾和有效钾分别比水曲柳纯林高56.4%和21.8%。图1表3参27。     

用土壤养分系统研究法评价杨树人工林土壤养分状况

A study was conducted to evaluate the soil nutrient status of poplar plantation by Soil Nutrient Systematic Approach(SNSA) in Jianghan Plain, Hubei Province, China. Soil physiochemical properties were analyzed in laboratory through collection soil samples of study site. Ten treatments of application different fertilizers were designed such as CK, optimum treatment (N, P,K, Zn), -N(P, K, Zn), -P(N, K, Zn), -K(N, P, Zn), Mg(N, P, K, Zn, Mg), -Zn (N,P,K), 2P(N, 2P, K, Zn), 2K(N, P, 2K, Zn), and 2N 2P 2K(2N, 2P, 2K, Zn) for field experiment to test the effect on tree height, diameter (DBH) growth, and dry weight of poplar.The results showed that there was no significant difference in tree heights between treatments with different fertilizers, diameter growth of poplar trees in treatments of lack of N and Zn was significantly slower than that of trees in optimum treatment, and dry weight of poplar dropped significantly for treatment of CK as well as treatments without application N and Zn. It is concluded that N and Zn were main limiting factor for poplar growth. Results from laboratory analysis and field experiment were uniform perfectly, which proved that SNSA was reliable in evaluating soil nutrient status of poplar plantation.     

Photosynthesis,growth and yield of soybean and maize in a tree-based agroforestry intercropping system on the Loess Plateau

Agroforestry is the most effective way to restore the disturbed lands on the Loess Plateau and to develop the poor local economy. In order to maximize the potential benefits of tree-based intercropping systems, photosynthesis, growth and yield of soybean and corn were studied by measuring photosynthetic active radiation (PAR), plant water deficit and soil moisture in a 4-year-old plantation of walnut (Juglans regia L.) and plum (Prunus salicina) grown at a spacing of 5 m × 3 m on the Loess Plateau. The effects of tree competition significantly reduced PAR, net assimilation (NA), growth and yield of individual soybean or corn plants growing nearer (1 m near tree row) to tree rows. NA was highly correlated with growth and yield of the both crops. These correlations were higher for corn than soybeans, with corn, rather than soybeans being more adversely impacted by tree shading. Plum, rather than walnut had the greatest competitive effect on PAR and NA. Daily plant water deficits were non-significantly and poorly correlated with NA and growth and yield of the both crops. However, soil moisture (20 cm depth) was significantly correlated with biomass and yield of both crops. Possible remediation strategies are discussed to reduce tree competitive interactions on agricultural crops.     

Short-term changes in the soil carbon stocks of young oil palm-based agroforestry systems in the eastern Amazon

The current expansion of the oil palm (Elaeis guineensis Jacq.) in the Brazilian Amazon has mainly occurred within smallholder agricultural and degraded areas. Under the social and environmental scenarios associated with these areas, oil palm-based agroforestry systems represent a potentially sustainable method of expanding the crop. The capacity of such systems to store carbon (C) in the soil is an important ecosystem service that is currently not well understood. Here, we quantified the spatial variation of soil C stocks in young (2.5-year-old) oil palm-based agroforestry systems with contrasting species diversity (high vs. low); both systems were compared with a ~10-year-old forest regrowth site and a 9-year-old traditional agroforestry system. The oil palm-based agroforestry system consisted of series of double rows of oil palm and strips of various herbaceous, shrub, and tree species. The mean (±standard error) soil C stocks at 0–50 cm depth were significantly higher in the low (91.8 ± 3.1 Mg C ha^?1) and high (87.6 ± 3.3 Mg C ha^?1) species diversity oil palm-based agroforestry systems than in the forest regrowth (71.0 ± 2.4 Mg C ha^?1) and traditional agroforestry (68.4 ± 4.9 Mg C ha^?1) sites. In general, no clear spatial pattern of soil C stocks could be identified in the oil palm-based agroforestry systems. The significant difference in soil carbon between the oil palm area (under oil palm: 12.7 ± 2.3 Mg C ha^?1 and between oil palm: 10.6 ± 0.5 Mg C ha^?1) and the strip area (17.0 ± 1.4 Mg C ha^?1) at 0–5 cm depth very likely reflects the high input of organic fertilizer in the strip area of the high species diversity oil palm-based agroforestry system treatment. Overall, our results indicate a high level of early net accumulation of soil C in the oil palm-based agroforestry systems (6.6–8.3 Mg C ha^?1 year^?1) that likely reflects the combination of fire-free land preparation, organic fertilization, and the input of plant residues from pruning and weeding.     

Changes in soil acidity and organic matter following the establishment of conifers on former grassland in New Zealand

Effects of a land use change from grassland to coniferous plantation forestry (Pseudotsuga menzieii [Douglas fir]; Pinus radiata [radiata pine]) on soil acidity and organic matter were assessed at two sites in New Zealand. The sites differed with respect to soils, climate, vegetation cover and type, relative maturity and management of the forest stands. Results obtained at the different sites were, therefore, not directly comparable, although they represented a comparison of a similar change in land use and some overall trends were evident. The change from grassland to conifers decreased levels of organic carbon, total nitrogen and exchangeable cations and increased exchangeable acidity in the upper 20–30 cm of soil. Exchangeable aluminium and exchangeable acidity were more sensitive measures of the effects of afforestation on soil acidity than pH.     

Effects of organic residue management and legume cover on growth of pine seedlings, nutrient leaching and soil properties

? The short-term effect of organic residue management on the growth and nutrition of Pinus pinaster Ait. seedlings, and on nutrient leaching and chemical properties of an acid soil was assessed through a lysimeter experiment. Treatments included absence, placement on the soil surface, and incorporation into the soil (with and without legume cover cropping) of organic residues (forest floor litter or forest floor litter plus harvest residues).

? Residues placed on the soil surface enhanced seedling growth. Organic residues reduced nutrient losses (NO ₃ ^? , Ca and Mg) and resulted in nutrient accumulation in the soil. Harvest residues positively affected K seedling nutrition status and enhanced K soil accumulation.

? Legume cover cropping reduced soil nutrient losses (N, Ca, Mg and K) during the early stage of seedling growth; it also improved seedling nutrition status (N and P), but without any effect on growth.

? Harvest residues plus forest floor litter placed on the soil surface was the most appropriate management to both reduce nutrient losses through leaching and increase height of seedlings at the end of the experimental period (two years).

     

Minimizing nutrient leaching and improving nutrient use efficiency of Liriodendron tulipifera and Larix leptolepis in a container nursery system

Fertilization is essential to seedling production in nursery culture, but excessive fertilization can contaminate surface and ground water around the nursery. The optimal fertilization practice is that which maximizes seedling growth and minimizes nutrient loss. We tested three fertilization strategies: (1) constant fertilization (2) a three-stage rate, and (3) exponential fertilization on Liriodendron tulipifera and Larix leptolepis containerized seedlings. Growth performance, nutrient uptake, and nutrient loss in leaching were measured. Height, root collar diameter, and dry weight of both species were not significantly different among treatments even though the nutrient supply of the exponential treatment was half that of the constant and three-stage treatments. Generally, nutrient losses in leached solutions were higher in constant and three-stage than the exponential treatment. Nutrient use efficiency was calculated as the ratio of the nutrient content of the seedlings to the amount of nutrient applied to the containers. The nitrogen use efficiency in the constant, three-stage, and exponential treatments was 63, 61, and 85% for yellow poplar, respectively, and 35, 30, and 53% for larch. Similar results were obtained for phosphorus and potassium. Thus, the exponential treatment had the highest nutrient use efficiency as well as the least nutrient loss. Adjusting fertilization rates can reduce soil and water contamination around the nursery without compromising growth performance, which reduces both producer’s investments and environmental impacts.