Shibu Jose

Agroforestry for ecosystem services and environmental benefits: an overview

Agroforestry systems are believed to provide a number of ecosystem services; however, until recently evidence in the agroforestry literature supporting these perceived benefits has been lacking. This special issue brings together a series of papers from around the globe to address recent findings on the ecosystem services and environmental benefits provided by agroforestry. As prelude to the special issue, this paper examines four major ecosystem services and environmental benefits of agroforestry: (1) carbon sequestration, (2) biodiversity conservation, (3) soil enrichment and (4) air and water quality. Past and present evidence clearly indicates that agroforestry, as part of a multifunctional working landscape, can be a viable land-use option that, in addition to alleviating poverty, offers a number of ecosystem services and environmental benefits. This realization should help promote agroforestry and its role as an integral part of a multifunctional working landscape the world over.

Interspecific interactions in temperate agroforestry

The ecological principles that define the competitive and complementary interactions among trees, crops, and fauna in agroforestry systems have received considerable research attention during the recent past. These principles have not yet, however, been adequately integrated and synthesized into an operational approach. This paper reviews the ecological and ecophysiological bases for interspecific interactions based on data from site-specific research and demonstration trials from temperate agroforestry systems, primarily from temperate North America. The review shows that information on ecological interactions in several temperate agroforestry systems is inadequate. It is recommended that the future research should focus on exploring new species and systems that have received little attention in the past. Priority research areas should include cultural practices and system designs to minimize interspecific competition and maximize environmental benefits such as improved water quality. Potential for genetic modification of components to increase productivity and reduce competition also needs to be explored. Process-oriented models may be used increasingly to predict resource-allocation patterns and possible benefits for a suite of site and species combinations.

Soil respiration and microbial biomass in a pecan — cotton alley cropping system in Southern USA

Little information is available on soil respiration and microbial biomass in soils under agroforestry systems. We measured soil respiration rate and microbial biomass under two age classes (young and old) of a pecan (Carya illinoinensis) — cotton (Gossypium hirsutum) alley cropping system, two age classes of pecan orchards, and a cotton monoculture on a well-drained, Redbay sandy loam (a fine-loamy, siliceous, thermic Rhodic Paleudult) in southern USA. Soil respiration was quantified monthly during the growing season from May to November 2001 using the soda-lime technique and was corrected based on infrared gas analyzer (IRGA) measurements. The overall soil respiration rates ranged from 177 to 776 mg CO2 m−2 h−1. During the growing season, soil respiration was higher in the old alley cropping system than in the young alley cropping system, the old pecan orchard, the young pecan orchard, and the monoculture. Microbial biomass C was higher in the old alley cropping system (375 mg C kg−1) and in the old pecan orchard (376 mg C kg−1) compared to the young alley cropping system (118 mg C kg−1), young pecan orchard (88 mg C kg−1), and the cotton monoculture (163 mg C kg−1). Soil respiration was correlated positively with soil temperature, microbial biomass, organic matter, and fine root biomass. The effect of alley cropping on soil properties during the brief history of alley cropping was not significant except in the old systems, where there was a trend of increasing soil respiration with short-term alley cropping. Over time, different land use and management practices influenced soil properties such as soil temperature, moisture, microbial biomass, organic matter, and fine root biomass, which in turn affected the magnitude of soil respiration. Our results suggest that trees in agroforestry systems have the potential to enhance soil fertility and sustainability of farmlands by improving soil microbial activity and accreting residual soil carbon.

Agroforestry for conserving and enhancing biodiversity

The intricate relationship between biodiversity loss and human well-being is increasingly being understood in ecological and economic terms. Despite the knowledge of the multiple dimensions of this relationship and its importance, species and ecosystems are still disappearing at an alarming rate. Anthropogenic pressures are the prime reason for this trend, yet attempts to reduce such pressures and conserve species in protected areas have only achieved limited success. This has led to the realization that sustainable consumptive use approaches that can combine production and conservation functions are also important in conserving biodiversity in human-dominated landscapes. Agroforestry, as part of a multifunctional working landscape, can play a major role in conserving and even enhancing biodiversity from farms to the landscape level in both tropical and temperate regions of the world. This special issue is an attempt to bring together a collection of articles that not only explore and demonstrate the biodiversity benefits of agroforestry, but also the mechanisms by which agroforestry systems sustain such high floristic and faunal diversity. While it is important to conserve biodiversity in protected areas, the articles in the special issue reiterate the importance of agroforestry as a critical tool in conserving biodiversity in human-dominated landscapes.

Ecological Basis of Agroforestry

Ecological Interactions: An Overview Ecological Interactions in Agroforestry: An Overview, R.K. Kohli, H.P. Singh, D.R. Batish, and S. Jose Tree-Crop Interactions: Lessons from Temperate Alley-Cropping Systems, S. Jose, S.C. Allen, and P.K.R. Nair Allelopathic Tree-Crop Interactions under Agroforestry Systems, D.R. Batish, H.P. Singh, and R.K. Kohli Approaches to Tree-Environment-Crop Interactions, R.M. Kho Weeds, Diseases, Insect Pests, and Tri-Trophic Interactions in Tropical Agroforestry, G. Sileshi, G. Schroth, M.R. Rao, and H. Girma Ecologically Based Pest Management in Agroforestry Systems, M.A. Altieri and C.I. Nicholls A Case Study on the Potential of Contour Hedgerow Intercropping for Sustainable Crop Production on Sloping Highlands in Humid and Subhumid Zones of Sri Lanka, W.A.J.M. De Costa, A.G. Chandrapala, P. Surenthran, and L.G.N. Dharmasiri The Belowground Ecology Belowground Interactions in Tree-Crop Agroforestry: Need for a New Approach, G. Schroth, M. Schaller, and F. Jimenez Tree-Grass Interactions and Water Use in Silvopastoral Systems in N.W. Patagonia, J.E. Gyenge, M.E. Fernandez, and T.M. Schlichter Litter Dynamics in Plantation and Agroforestry Systems of the Tropics-A Review of Observations and Methods, B.M. Kumar Developments in the Research of the Potential of Agroforestry for Sustaining Soil Fertility in Zimbabwe, S. Zingore, R. Chikowo, G. Nyamadzawo, P. Nyamugafata, and P.L. Mafongoya Soil Sustainability in Agroforestry Systems: Experiences on Impacts of Trees on Soil Fertility from a Humid Tropical Site, F. Montagnini Root Competition for Water Between Trees and Grass in a Silvopastoral Plot of 10 Year Old Prunus avium, P. Balandier, F.X. De Montard, and T. Curt Models in Agroforestry Relationship of Three-Dimensional Structure to Shelterbelt Function: A Theoretical Hypothesis, X. Zhou, J.R. Brandle, E.S. Takle, and C.W. Mize Modeling a Field Shelterbelt System with the Shelterbelt Agroforestry Modeling System, C.W. Mize, J. Colletti, W. Batchelor, J.S. Kim, E.S. Takle,and J.R. Brandle Ecological Economics Social and Economic Implications of Agroforestry for Rural Economic Development in Temperate Regions, C.J. Doyle and T. Waterhouse Forest Patches in Northeast Luzon (the Philippines): Their Status, Role, and Perspectives for Conservation in Integrated Land-Use Systems, D.J. Snelder and G.A. Persoon Adoption, Profitability, Impacts, and Scaling Up of Agroforestry Technologies in Southern African Countries, O.C. Ajayi, F.K. Akinnifesi, J. Mullila-Mitti,J.J. DeWolf, P.W. Matakala, and F.R. Kwesiga Pasture Production and Tree Growth in Agroforestry Systems of Northwest Spain, M.P. Gonzalez-Hernandez and M.J.R. Lorenzo Index

Competition for water in a pecan (Carya illinoensis K. Koch) - cotton (Gossypium hirsutum L.) alley cropping system in the southern United States

Understanding the belowground interactions between trees and crops is critical to successful management of agroforestry systems. In a study of competition for water in an alley cropping system consisting of pecan (Carya illinoensis) and cotton (Gossypium hirsutum) in a sandy loam soil (Rhodic Paleudult) in Jay, Florida, root systems of the two species were separated by trenching to 120 cm depth. A polyethylene barrier was installed in half of the plots. Spatial and temporal variations in soil water content, root distribution and water uptake by both species, and leaf area development and height of cotton were measured. Interspecific competition for water was greater in the non-barrier treatment near tree rows than at the alley center. Competition became evident 3 to 4 weeks after emergence of cotton and increased during the following 7 to 8 weeks. Compared with the non-barrier treatment, the barrier treatment had higher soil water content and better growth of cotton (height, leaf area, and fine root biomass). Cotton lint yield in the barrier treatment (677 kg ha–1) was similar to that in a sole-crop stand, but higher than in the non-barrier (502 kg ha–1) treatment. Lint production efficiency of plants was higher in the interior rows in the non-barrier treatment (0.197 kg lint per square meter of leaf area, compared to 0.117 kg in the barrier treatment). The results suggest that trenching or even deep disking parallel to the tree row may reduce competition for water, but the impact on tree growth cannot be established from this study.

Comparison of minirhizotron and soil core methods for quantifying root biomass in a temperate alley cropping system

A study was carried out in southern Indiana, USA with the objective of comparing soil core sampling and the minirhizotron technique in quantifying fine root biomass and root distribution patterns in an alley cropping system with black walnut (Juglans nigra L.), northern red oak (Quercus rubra L.) and maize (Zea mays L.). Spatial variation in tree rooting pattern was investigated prior to planting maize. Tree fine root biomass was quantified at distances of 0, 1.1, 2.3, 3.5, and 4.3 m where 0 m represents the tree row and 4.3 m represents the middle of the alley. Root samples were collected to a depth of 90 cm using a hydraulic auger. Maize rooting pattern was determined 65 days after planting to the same depth. Using plexiglass access tubes installed near the actual soil core locations and a minirhizotron camera root images were recorded on a VHS tape. These images were later analyzed using a raster based GIS software (ERDAS-IMAGINE). Regression analysis revealed significant relationships between root surface area measurements from minirhizotron observations and fine root biomass data from soil coring for all species. Predicted fine root biomass data were also in close agreement with actual fine root biomass for all species examined. Maize root biomass was slightly, but not significantly, underestimated by the minirhizotron technique in the top 30 cm soil layer. No significant underestimation or overestimation of root biomass in surface or deeper soil layers was observed for the tree species. The results indicate that minirhizotron can be used in quantifying fine root biomass if site and species specific predictive models can be developed.

Agroforestry for biomass production and carbon sequestration: an overview

Ever since the Kyoto Protocol, agroforestry has gained increased attention as a strategy to sequester carbon (C) and mitigate global climate change. Agroforestry has been recognized as having the greatest potential for C sequestration of all the land uses analyzed in the Land-Use, Land-Use Change and Forestry report of the IPCC; however, our understanding of C sequestration in specific agroforestry practices from around the world is rudimentary at best. Similarly, while agroforestry is well recognized as a land use practice capable of producing biomass for biopower and biofuels, very little information is available on this topic. This thematic issue is an attempt to bring together a collection of articles on C sequestration and biomass for energy, two topics that are inextricably interlinked and of great importance to the agroforestry community the world over. These papers not only address the aboveground C sequestration, but also the belowground C and the role of decomposition and nutrient cycling in determining the size of soil C pool using specific case studies. In addition to providing allometric methods for quantifying biomass production, the biological and economic realities of producing biomass in agroforestry practices are also discussed.

Invasive plants and forest ecosystems

Invasion Ecology. Ecological Impacts. Management, Socioeconomic, and Policy Aspects of Invasive Plants.

Influence of calcium, potassium, and magnesium on Cornus florida L. density and resistance to dogwood anthracnose

Dogwood anthracnose, a major disease of Cornus florida L., has caused heavy mortality of C. florida in eastern United States forests. Disease severity and rate of infection have been shown to vary with several environmental factors, but the link between soil cation availability and anthracnose has not been examined. We hypothesized that soil cation availability, particularly calcium (Ca), potassium (K), and magnesium (Mg), would influence dogwood survival from anthracnose. In forested stands, positive correlations between soil Ca, K, and Mg saturation and C. florida stem density and basal area were found. The effect of these cations at four levels (0, 50, 100, and 200%) of a standard nursery fertilization rate on C. florida seedling survival and resistance to dogwood anthracnose was tested. Although most of the seedlings died after one season of exposure to dogwood anthracnose, seedlings that had lower inputs of Ca and K cations showed higher levels of disease severity sooner than seedlings in other treatments, suggesting that these nutrients play a role in C. florida survival from anthracnose. Magnesium treatment levels did not appear to have an effect on C. florida disease severity or mortality.