Water infiltration influenced by agroforestry and grass buffers for a grazed pasture system

Agroforestry (AgB) and grass buffers (GB) are often adopted as alternative resource management tools in agroecosystems for environmental and economic benefits. The objective of this study was to compare the influence of AgB and GB systems under rotationally stocked (RP) and continuously stocked (CP) pasture systems on water infiltration measured using ponded infiltration and tension infiltration methods. Buffers were surrounded by a fence that prevented cattle from grazing within these areas. Soils at the site are Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalf). Infiltration rates were measured using ponded ring infiltration units during 2 years for the four (AgB, GB, RP and CP) treatments with three replicates from two subareas within each treatment. Infiltration rate as a function of tension (at 50, 100, and 150 mm) was also measured using a tension infiltrometer. Water infiltration parameters were estimated using Green-Ampt and Parlange infiltration equations. Quasi-steady state infiltration rates (q _s ) and field-saturated hydraulic conductivity (K _fs ) for buffers were about 31 and 46 times higher as compared to pasture treatments, respectively. Green-Ampt and Parlange models appeared to fit measured data with r ² values ranging from 0.91 to 0.98. The q _s (measured with ponded method) in the first year for the GB treatment was the highest (221 mm h⁻¹) and for the CP treatment was the lowest (3.7 mm h⁻¹). For both years, estimated sorptivity (S) and saturated hydraulic conductivity (K _s ) parameters were higher for buffer areas compared to the stocked pasture areas. Grazing reduced the infiltration rate for the pasture (RP and CP) treatments. Results show that the buffer areas have higher infiltration rates which imply lower runoff compared to pasture areas.     

CT-measured macropores as affected by agroforestry and grass buffers for grazed pasture systems

Agroforestry and grass buffers have been proposed for improving water quality in watersheds. Soil porosity can be significantly influenced by buffer vegetation which affects water transport and water quality. The objective of the study was to compare differences in computed tomography (CT)-measured macroporosity (>1,000-μm diam.) and coarse mesoporosity (200- to 1,000-μm diam.) parameters for agroforestry and grass buffer systems associated with rotationally grazed and continuously grazed pasture systems. Soils at the site were Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalf). Six replicate intact soil cores, 76.2 mm diam. by 76.2 mm long, were collected using a core sampler from the four treatments at five soil depths (0–50 cm at 10-cm intervals). Images were acquired using a hospital CT scanner and subsequently soil bulk density and saturated hydraulic conductivity (K _sat) were measured after scanning the cores. Image-J software was used to analyze five equally spaced images from each core. Bulk density was 5.9% higher and saturated hydraulic conductivity (K _sat) values were five times lower for pasture treatments relative to buffer treatments. For the 0–10 cm soil depth, CT-measured soil macroporosity (>1,000 μm diam.) was 13 times higher for the buffer treatments compared to the pasture treatments. Buffer treatments had greater macroporosity (0.020 m³ m⁻³) compared to pasture (0.0045 m³ m⁻³) treatments. CT-measured pore parameters were positively correlated with K _sat. The project illustrates benefits of agroforestry and grass buffers for maintaining soil porosity critical for soil water and nutrient transport.     

Root length density and carbon content of agroforestry and grass buffers under grazed pasture systems in a Hapludalf

Enhancement of root development helps to improve soil physical properties, carbon sequestration, and water quality of streams. The objective of this study was to evaluate differences in root length density (RLD) and root and soil carbon content within grass buffer (GB), agroforestry buffer (AgB), rotationally grazed pasture (RG) and continuously grazed pasture (CG) treatments. Pasture and GB areas included red clover (Trifolium pretense L.) and lespedeza (Kummerowia stipulacea Maxim.) planted into fescue (Festuca arundinacea Schreb.) while AgB included Eastern cottonwood trees (Populus deltoids Bortr. ex Marsh.) planted into fescue. One-meter deep soil cores were collected from each treatment in August 2007 and 2008 with a soil probe. Three soil cores were sampled at six replicate sampling positions. Soil cores were collected in plastic tubes inserted inside the metal soil probe. Soils were segregated by horizons, and roots were separated into three diameter classes (0–1, 1–2, >2 mm) by soil horizon. Root length was determined using a flatbed scanner assisted with computer software. Buffer treatments (167 cm/100 cm³) had 4.5 times higher RLD as compared to pasture treatments (37.3 cm/100 cm³). The AgB treatment had the highest (173.5 cm/100 cm³) RLD and CG pasture had the lowest (10.8 cm/100 cm³) value. Root carbon was about 3% higher for the buffers compared to RG treatment. Soil carbon was about 115% higher for the buffers compared to pasture treatments. Results from this study imply that establishment of agroforestry and GB on grazed pasture watersheds improve soil carbon accumulation and root parameters which enhance soil physical and chemical properties thus improving the environmental quality of the landscape.     

Soil quality indicator responses to row crop,grazed pasture,and agroforestry buffer management

Soil enzyme activities and water stable aggregates have been identified as sensitive soil quality indicators, but few studies exist comparing those parameters within buffers, grazed pastures and row-crop systems. Our objective was to examine the effects of these land uses on the activities of selected enzymes (β-glucosidase, β-glucosaminidase, fluorescein diacetate (FDA) hydrolase, and dehydrogenase), proportion of water stable aggregates (WSA), soil organic carbon and total nitrogen content. Four management treatments [grazed pasture (GP), agroforestry buffer (AgB), grass buffer (GB) and row crop (RC)] were sampled in 2009 and 2010 at two depths (0 to 10- and 10 to 20-cm) and analyzed. Most of the soil quality indicators were significantly greater under perennial vegetation when compared to row crop treatments. Although there were numerical variations, soil quality response trends were consistent between years. The β-glucosaminidase activity increased slightly from 156 to 177 μg PNP g⁻¹ dry soil while β-glucosidase activity slightly decreased from 248 to 237 μg PNP g⁻¹ dry soil in GB treatment during 2 years. The surface (0–10 cm depth) had greater enzyme activities and WSA than sub-surface (10–20 cm) samples. WSA increased from 178 to 314 g kg⁻¹ in row crop areas while all other treatments had similar values during the 2 year study. The treatment by depth interaction was significant (P < 0.05) for β-glucosidase and β-glucosaminidase enzymes in 2009 and for dehydrogenase and β-glucosaminidase in 2010. Soil enzyme activities were significantly correlated with soil organic carbon content (r ≥ 0.94, P < 0.0001). This is important because soil enzyme activities and microbial biomass can be enhanced by perennial vegetation and thus improve several other soil quality parameters. These results also support the hypothesis that positive interactions among management practices, soil biota and subsequent environmental quality effects are of great agricultural and ecological importance.     

Bird species diversity in riparian buffers,row crop fields,and grazed pastures within agriculturally dominated watersheds

In response to concern about the loss of ecosystem services once provided by natural riparian systems, state and federal agencies have established incentive programs for landowners to convert sensitive lands from agricultural to conservation uses. Enhancement of wildlife habitat, while identified as a function of such systems, has often been of secondary importance to soil conservation and water quality objectives. Though greatly important, little consideration has been given to how specific species will respond to the design and management of riparian buffers or other conservation lands. This study compared avian communities within a chronosequence of riparian buffers established on previously cropped or pastured land with those of the nearby matrix land cover types (row crop fields and an intensively grazed pasture). The riparian buffers consisted of native grasses, forbs, and woody vegetation established at three different times (2, 9, and 14+ years prior to survey). At each site, 10 min point counts for breeding birds were conducted using 50 m fixed radius plots, which were visited eight times between May 15 and July 10, 2008. A total of 54 bird species were observed over all of the study sites. The re-established riparian buffers in this study had higher bird abundance, richness, and diversity than the crop and pasture sites. These results suggest that re-establishing native riparian vegetation in areas of intensive agriculture will provide habitat for a broad suite of bird species, but that specific species will reflect successional stage, horizontal and vertical vegetative structure, and compositional diversity of the buffer vegetation. These results emphasize the importance of matching buffer design and management to species requirements if the objectives are to attract specific target species or species groups.     

A simulation model for evaluating technical and economic aspects of an industrial eucalyptus-based agroforestry system in Minas Gerais, Brazil

This study analyses the economic aspects of a eucalypt-based agroforestry system established in the savanna region of Brazil. In 1993,eucalypt clones were planted at a spacing of 10 × 4 m, to facilitate their future association with crops and pasture grasses. The results show that the establishment and maintenance costs represent 37% of the total costs associated with the system. More than half of the revenues are from the sale of the wood products obtained in the 11-year rotation. Variations of ±20% of the sale price of the cattle significantly affected the sensitivity analysis, closely followed by the variations of the price of wood for lumber and energy. Variations of ±20% of the establishment costs of the forest component significantly affected the economic indicators. The viability of the system is also sensitive to a slight change in interest rate. Finally, the agroforestry system adopted by the company is economically more attractive than eucalypt monoculture.This revised version was published online in November 2005 with corrections to the Cover Date.     

The economics of agroforestry with pine and pasture in the 500 to 700 mm annual rainfall zone of Western Australia

This study mainly compares the economics of one form of agroforestry (involving the simultaneous use of land for pine sawlog, sheep, wool and hay production) with conventional agriculture (sheep and wool production) in the 500 and 700 mm annual rainfall zone of Western Australia. The region is marked by environmental problems, particularly soil and water salinity, owing to past extensive clearly of indigenous deep-rooted vegetation for agriculture. Agroforestry can be a way to control and ameliorate the problems.The major conclusion is that pine agroforestry can be more profitable in the long term than conventional agriculture. It would be a profitable way to control and ameliorate the environmental problems in the region. It would also generate other benefits. A number of measures can be adopted to reduce or avert any problems arising from agroforestry's annual net returns (which fluctuate and are negative for most years before log sales) and annual labour requirements (which vary over time and are generally higher than those for agriculture for about the first half of the agroforestry rotation). These measures include using a low tree density and converting only part of a farm to agroforestry so that the activity is practised in combination with conventional agriculture.The study concerns a region with a Mediterranean climate so that the principles and findings of the study could be of particular relevance to other similar regions of the world.     

A model simulating above- and below-ground tree architecture with agroforestry applications

Modelling plant growth and architecture requires two consecutive and complementary approaches. The first is a qualitative botanical analysis, in which the development sequence of a tree is studied by the identification of various levels of organisation and of homogeneous subunits. All of these — architectural unit, axis, growth unit — follow particular growth processes which can be described by using the second approach, the quantitative analysis. Modelling of the functioning of meristems based upon stochastic processes has been carried out since 1980, in combination with a large amount of experimental work on temperate and tropical plants. Calculations involved in tree simulations from field data are based upon the probabilistic Monte Carlo method for the topological part and on analytical geometry for the morphological part. Computer graphics methods are then used to visualise the computed plant. Several sectors in agroforestry are concerned with application of such plant architecture modelling: tree growth and yield, radiative transfers, timber quality and mechanics, simulation of competition, interaction between plant morphology and physiology.     

Soil CO<Subscript>2</Subscript> emissions in agricultural watersheds with agroforestry and grass contour buffer strips

The potential for agricultural soils to act as a sink and sequester carbon (C) or a source and emit carbon dioxide (CO₂) is largely dependent upon the agricultural management system. The establishment of permanent vegetation, such as trees and grass contour buffer strips, may cause accumulation of above- and below-ground C over time, thereby acting as a sink for tropospheric CO₂. However, the effects of contour grass strips and grass-tree strips (agroforestry) on soil CO₂ emissions have not been extensively studied in row-crop watersheds in the temperate regions. The objective of this study was to determine the effects of agroforestry and grass contour buffer strips and landscape position on soil surface efflux rate of CO₂ in three adjacent agricultural watersheds with claypan soils in northeast Missouri. The three watersheds were in a corn-soybean rotation, and contained (1) cropped only (CR), (2) cropped with grass contour strips (GR), or (3) cropped with tree-grass contour strips (AF) management systems. Soil surface CO₂ efflux was measured throughout the 2004 growing season at the upper (UBS), middle (MBS), and lower (LBS) backslope landscape positions within the three watersheds. The cumulative soil CO₂ production was lowest in the CR (0.9 kg CO₂-C m⁻²) compared to the AF (1.5 kg CO₂-C m⁻²) and GR watersheds (1.5 kg CO₂-C m⁻²). The lower backslope position (1.6 kg CO₂-C m⁻²) across all three watersheds produced 32 and 40% greater cumulative soil CO₂ than the upper and middle backslope positions, respectively. A 72-day incubation study determined the effects of 40, 60, 80, and 100% soil water-filled pore space (WFPS) and N rate (0 and 1.39 g KNO₃ kg soil⁻¹) on soil CO₂ efflux from bulk soil collected under each management system. The cumulative CO₂ production was highest in the grass soil (1,279 mg CO₂-C kg soil⁻¹) compared to the agroforestry (661 mg CO₂-C kg soil⁻¹) and cropped (483 mg CO₂-C kg soil⁻¹) soils regardless of WFPS and N rate. The highest cumulative CO₂ production for the grass soil (1,279 mg CO₂-C kg soil⁻¹) occurred at 80% WFPS, and was approximately 2 to 2.6 times greater than the agroforestry and cropped soils at 80% WFPS. The results of this study indicate that conservation management practices, such as grass and grass-tree contour buffer strips, and landscape position affect soil surface CO₂ production and accumulation of soil organic C that may influence soil C sequestration.     

Crop production under different rainfall and management conditions in agroforestry parkland systems in Burkina Faso: observations and simulation with WaNuLCAS model

Traditional agroforestry parkland systems in Burkina Faso are under threat due to human pressure and climate variability and change, requiring a better understanding for planning of adaptation. Field experiments were conducted in three climatic zones to assess Sorghum bicolor (L.) Moench (Sorghum) biomass, grain yield and harvest index in parklands under different rainfall pattern and compared to simulations of sorghum biomass and grain yield with the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model for calibration and parametrisation. For planning adaptation, the model was then used to evaluate the effects of different management options under current and future climates on sorghum biomass and grain yield. Management options studied included tree densities, tree leaf pruning, mulching and changes in tree root patterns affecting hydraulic redistribution. The results revealed that sorghum biomass and grain yield was more negatively affected by Parkia biglobosa (Jacq.) Benth. (néré) compared to Vitellaria paradoxa C. F Gaertn (karité) and Adansonia digitata L. (baobab), the three main tree species of the agroforestry parkland system. Sorghum biomass and grain yield in different influence zones (sub-canopy, outside edge of canopy, open field) was affected by the amount of precipitation but also by tree canopy density, the latter depending itself on the ecological zone. The harvest index (grain as part of total biomass) was highest under the tree canopy and in the zone furthest from the tree, an effect that according to the model reflects relative absence of stress factors in the later part of the growing season. While simulating the effects of different management options under current and future climates still requires further empirical corroboration and model improvement, the options of tree canopy pruning to reduce shading while maintaining tree root functions probably is key to parkland adaptation to a changing climate.     

Effects of grazing exclusion and environmental conditions on the soil seed bank of a Mediterranean grazed oak wood pasture

Large seed banks in the soils of Mediterranean wood pastures can allow the composition of the understorey vegetation to adapt to changing conditions such as under-grazing, grazing exclusion and climate change. This three year study investigated the effect of grazing exclusion on the transient and persistent seed banks of 23 areas of a Mediterranean wood pasture of Quercus suber L., Q. ilex L. and Q. pubescens Willd. A canonical correspondence analysis was used to determine the effect of topo-climatic (elevation, aspect, slope, rainfall, temperature, tree coverage), soil (pH, soil texture, and soil nitrogen, phosphorus, lime and organic carbon content) and biodiversity (Shannon index, species richness index, and Pastoral Value) variables on the soil seed bank under grazed and ungrazed conditions. The size of the persistent seed bank increased with rainfall, grazing, and the available phosphorus content of the soil. Specific site by site grazing regimes could increase the abundance of legumes in the soil seed bank and the species richness and diversity of the understorey vegetation. These results can help guide the conservation management of this silvopastoral area.     

红壤区典型茶园模式对侵蚀性降雨的减流减沙效应

基于福建安溪官桥生态茶园2017年度自然降雨数据及园区5种铁观音茶树水土流失治理模式的坡面产流、产沙情况的观测数据,系统研究了不同治理模式下铁观音茶树坡面水土流失对引起侵蚀的降雨的响应机制。结果表明:(1)降雨集中于4~8月份,引起侵蚀频次最多的是5~6月份;(2)根据降雨量与最大30 min降雨强度I 30,可以将侵蚀性降雨分为Ⅰ~Ⅴ种类型,其中,Ⅰ雨型的降雨是当地发生频率最多的侵蚀性降雨,雨量最大的Ⅴ雨型平均产流量最大,雨强最大的Ⅳ雨型平均产沙量最大,发生频率较高的Ⅲ雨型产流总量最大,Ⅱ雨型产沙总量最大。(3)5种铁观音茶树水土流失治理模式在不同降雨类型下的水土保持效应不同,其中采取“梯田+自然留草”的治理模式在各雨型条件下的减流率和减沙率均优于其他模式。研究结果对山区茶园水土保持及提升茶产量有重要的参考价值。     

Effect of forest vegetation on runoff and sediment production in sloping lands of Loess area

According to fixed-position data for 1985–2003 from nine runoff plots of Caijiachuan watershed which lies in Jixian County of Shanxi Province in Loess area, this paper studied the relationship between vegetation and runoff and sediment production in sloping lands in detail, which helps to provide scientific basis for vegetation re-construction and studies on environmental transformation of water and sediment in watersheds of Loess area. Although, many study results testify that forest vegetation has an important function in soil and water conservation and cutting runoff, the effect of vegetation on runoff and sediment transmission is complicated, and this needs to be studied in depth. The results of the paper showed the following. Firstly, the natural secondary forest performs better function of soil and water conservation than artificial Robinia pseudoacacia forest, and runoff and sediment produced in the former in individual rainfall were 65%–82% and 23%–92% of those produced in the latter. At the same time, better correlative relationship between runoff and sediment production and rainfall and rainfall intensity were testified by multiple regression, but the correlation decreased gradually with the increase of canopy density of forest. Secondly, the difference of runoff and sediment production in several land use types was very distinct, and the amount of runoff and sediment produced from Ostryopsis davidiana forest and natural secondary forest were the least, and runoff and sediment produced from in artificial Robinia pseudoacacia forest and Pinus tabulaeformis forest were 5-fold as much as those from O. davidiana forest. Besides, runoff and sediment produced in mixed planting of apple trees and crops were 16.14-fold and 2.96-fold than those of O. davidiana forest, respectively, but the amount decreased obviously after high-standard soil preparation in the case of the former. Thirdly, based on gray cognate analyses of factors affecting runoff and sediment production in sloping land, the factors of stand canopy density and herb and litter biomass were the most significant ones, whose gray incidence degree exceeded 0.6. Therefore, mixed forest with multi-layer stand structure and shrub forest should be developed in vegetation re-construction of Loess area, which will help to increase coverage and litter thickness in order to cut down the runoff and sediment dramatically in sloping land. __________ Translated from Chinese Journal of Applied Ecology, 2005, 16(9): 1,613–1,617 [译自: 应用生态学报, 2005, 16(9): 1,613–1,617]     

嫩江沙地草牧场防护林主要模式类型及效益比较分析

以嫩江沙地典型牧区为例,介绍了嫩江沙地草牧场防护林的主要模式类型,主要包括网带式、绿伞式、疏林式、片林式几种,并以杜尔伯特蒙古族自治县为例对几种主要类型的生态效应及社会经济效益进行了比较分析。结果表明,各种类型的草牧场防护林较对照产生了较为积极的生态效应、显著的经济效益和广泛的社会效益。     

Effects of forest harvesting on runoff and sediment characteristics in the Hyrcanian forests,northern Iran

Loss of canopy cover by forest harvesting generally increases the average surface runoff volume and sediment. Selective cutting (single and group selection method) is the most usual forest harvesting method in the Hyrcanian forests in the north of Iran. The purpose of this study is to find the effect of selective logging technique on the hydrological behavior of runoff and sediment in the Kheyrud forests located in northern Iran over 1 year. Four treatments were implemented: natural forest without harvesting (C), forest with selective harvesting (H) and area without canopy cover (WC) and skid trail (S). Three types of data were measured in each plot including soil chemical and physical properties, runoff and sediment load after each rainfall. The results indicate significant differences (P ≤ 0.05) in runoff generation and sediment production with respect to the treatments cover. The runoff in all treatments showed relatively similar response to rainfall, while the highest runoff and sediment were observed in skid trails, and the area without canopy cover (1.13 and 0.62 mm, and 1.2 and 0.51 g m^?2), averagely. In contrast, the natural forest without harvesting and the forest with selective harvesting treatments exhibited the lowest amounts of runoff (0.2 and 0.44 mm) and sediment (0.1 and 0.17 g m^?2), averagely. Implementation of low logging technique was useful to control the effects of logging on the runoff and sediment yield.     

WaNuLCAS, a model of water, nutrient and light capture in agroforestry systems

Models of tree-soil-crop interactions in agroforestry should maintain a balance between dynamic processes and spatial patterns of interactions for common resources. We give an outline and discuss major assumptions underlying the WaNuLCAS model of water, nitrogen and light interactions in agroforestry systems. The model was developed to deal with a wide range of agroforestry systems: hedgerow intercropping on flat or sloping land, fallow-crop mosaics or isolated trees in parklands, with minimum parameter adjustments. Examples are presented for simulation runs of hedgerow intercropping systems at different hedgerow spacings and pruning regimes, a test of the safety-net function of deep tree roots, lateral interactions in crop-fallow mosaics and a first exploration for parkland systems with a circular geometry. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of forest vegetation on runoff and sediment transport of watershed in Loess area, west China

This paper aims to study the effects of vegetation on runoff and sediment transport at the watershed scale, and to provide a theoretical basis for afforestation in the Loess area, in the nested Caijiachuan watershed, Jixian County, Shanxi Province of west China. Forest watersheds and farmland watersheds with similar terrain features were selected through cluster analysis to study their runoff and sediment transport characteristics. Results showed that compared with farmland watersheds, runoff generation time in forest watersheds was delayed remarkably, and peak flow was reduced greatly, which indicates that vegetation played an important role in holding and absorbing rainfall. Besides, with the increase of forest coverage, the runoff amount, runoff depth and runoff coefficient decreased during the rainy seasons. The runoff depth and runoff coefficient of farmland watersheds in the rainy season were 5–20-fold as much as that of forest watersheds, and runoff and sediment yield of watersheds with low forest coverage were 2.7–2.9-fold and 3–6-fold as great as those with high coverage during rainstorms, and low forest coverage had larger variation in sediment hydrograph. For the complexity and scale dependence of the influence of forest vegetation on runoff, forest hydrological functions based on regional scale or watershed scale were worthy of further studies. __________ Translated from Science of Soil and Water Conservation, 2006, 4(3): 48–53 [译自: 中国水土保持科学]