Types Of Agroecosystems Research Articles

Influence of changes in land use and earthworm activities on carbon and nitrogen dynamics in a steepland ecosystem in Northern Vietnam

This manuscript focuses on the effects of land-use change and earthworm activities on the dynamics of dissolved nutrients (carbon and mineral nitrogen) in a steep slope ecosystem in Northern Vietnam. We investigated the properties of soil aggregates (casts and surrounding soils) sampled in different agrosystems: a plantation of Bracharia ruzziziensis (BRA), a fallow (FAL) and a plantation of Acacia mangium and Venicia montana (FOR), following a cultivation of cassava (CAS), and a fallow after a forest of Eucalyptus (EUC). Soil physical, chemical and biological properties were determined on the sampling date and dissolved organic C (DOC), and mineral N (N min) contents were followed during a 21-day incubation period. CAS, BRA and FOR were characterised by a high rate of N mineralisation, followed by a rapid loss of N min. Conversely, FAL and EUC were more interesting in terms of soil fertility because these systems had higher soil N min content that could become available to plants. Lost of C through DOC leaching was very low with values ever less than 0.5% of the total soil C content. The greatest lost of C through leaching was in FAL, EUC and FOR. The impacts of earthworms on the soil seemed site-specific. The protection of organic matter in earthworm casts varied with the initial substrate soil and agroecosystem management. Casts were characterised by greater enzymatic activities, except for alkaline phosphatase, than the surrounding soil. While SOM mineralisation was not affected in casts collected in FAL, EUC and FOR, the leaching of N min was increased over the surrounding soil. Conversely, mineralisation of SOM and nitrification activity were less in BRA-casts than in the surrounding soil, causing a greater retention of N min in soil. While the DOC leached from casts increased in BRA, it was reduced in FAL and was similar in the other sites. Our study indicates that while land-use change occurred only 3 years ago, the extent of leaching was mostly regulated by the type of agroecosystem and by earthworm activities.

Avian Foraging Behavior in Two Different Types of Coffee Agroecosystem in Chiapas, Mexico

ABSTRACTThis study describes the foraging ecology of birds during summer and winter in two different types of coffee agroecosystems in Chiapas, Mexico. Avian foraging behavior is documented in two agroecosystems of differing management intensity, structurally similar but with different levels of floristic diversity, during summer and winter seasons. The distribution of tree species used by birds was more even, and birds used a greater diversity of tree species, in the more diverse coffee shade system. Much of the variation in resource use derived from shifts in the use of flowers and fruit, highlighting the importance in resource phenology for birds. Insectivory was more frequent in winter than summer for the coffee layer, and in summer for the shade layer. Given the vegetative structural similarity of the two coffee agroecosystems included in this study, floristic differences probably accounted for much of the difference in the bird communities between the management systems, especially given the strong seasonal response to flowering and fruiting. This work suggests that plentiful and diverse food resources associated with the high diversity of plant species may facilitate coexistence of the high number of bird species found in shade‐grown coffee agroecosystems.

Farmers' Attitudes Regarding Agrolandscape Ecology: A Regional Comparison

ABSTRACT A farmer survey was conducted in three different agroecosystem types in the midwestern and southeastern United States. We selected Saline County, Kansas; Knox County, Indiana; and Coffee County, Georgia, representative of former prairie grassland, Midwestern deciduous forest, and Southeastern deciduous forest biome types. A twenty-question, multiple-choice survey was mailed to 300 farmers in each county during summer months of 2002 and 2003. Data were collected in four categories: demographic information, problems related to conventional agriculture, sustainable agriculture approaches, and attitudes toward sustainable agriculture. Survey responses were examined and discussed within the context of the social and ecological consequences of industrial agriculture, the alternatives presented by agroecologists, and the communication network between agroecologists and farmers. One suggestion for achieving sustainability is building stronger connections between university agroecologists and farmers. For example, 58 percent of respondents from Kansas, 57 percent from Indiana, and 70 percent from Georgia view an ecologist as a friend/advisor to the farmer. These data should be useful to agroecologists interested in strengthening their relationship with stakeholders and in disseminating research findings concerning alternative agricultural practices.

Farmers and the Forest: Can Agroforestry Actually Conserve Biodiversity?

Farmers and the Forest: Can Agroforestry Actually Conserve Biodiversity?

Approaches and uncertainties in nutrient budgets: implications for nutrient management and environmental policies

Nutrient budgets of agroecosystems are constructed either (i) to increase the understanding of nutrient cycling, (ii) as performance indicator and awareness raiser in nutrient management and environmental policy, or (iii) as regulating policy instrument to enforce a certain nutrient management policy in practice. This paper explores nutrient budgeting approaches and summarizes sources of uncertainty associated with these approaches. Possible implications of uncertainties associated with the different methodologies and approaches for nutrient management and environmental policy are discussed. Three types of nutrient budgets have been distinguished, i.e. farm-gate, soil surface and soil systems budgets. A farm-gate budget is the most integrative measure of environmental pressure, and seems most suitable as environmental performance indicator. A soil surface budget is appropriate for estimating the net loading of the soil with nutrients. Soil system budgets account for nutrient inputs and outputs, recycling of nutrients within the system, nutrient loss pathways and changes in soil nutrient pools; it is the most detailed budget and provides detailed information for nutrient management. Case studies for the dairy farm De Marke indicate that the three budgeting approaches supplement each other. The accuracy and precision of the nutrient budget depend on budgeting approach, data acquisition strategy and type of agroecosystem. There is often a considerable amount of uncertainty in the nutrient budget, due to various possible biases and errors, notably in the partitioning of nutrient losses. Possible sources of biases are personal bias, sampling bias, measurement bias, data manipulation bias and fraud. Sources of errors are sampling and measurement errors. Both biases and errors in nutrient budget estimates may lead to confusion and wrong conclusions. Yet, there is little published evidence that uncertainties are taken into account in decision making. Uncertainties are usually smaller for a farm-gate budget than for a soil surface budget. Therefore, farm-gate budgets are preferred over soil surface budgets as policy instrument. Quantifying uncertainties requires: (a) system identification and analysis, (b) classification of uncertainties, (c) specification of distributions of probabilities of the various sources using Monte Carlo simulation, and (d) monitoring of the nutrient pools, inputs and outputs over time. Analyses of uncertainties in nutrient budgets may provide information about the weakest chain in establishing agri-environmental cause–effect relationships and, therefore, may assist to better focus research efforts. Data for the nitrogen budget of The Netherlands indicate relatively large uncertainties for the items denitrification and leaching, with coefficients of variation >30%. In conclusion, there is a need for standard procedures and guidelines in nutrient budgeting and uncertainty analyses, to improve the confidence in and applicability of nutrient budgets.

Population dynamics of ambient and altered earthworm communities in row-crop agroecosystems in the Midwestern U.S.The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Summary Earthworms affect agroecosystem processes and few studies have addressed population dynamics when earthworms are intentionally introduced. Handsorting and formalin extraction were used semi-annually from fall 1994 to fall 1997 to measure populations in plots with and without added earthworms under chisel till in a corn-soybean rotation (CT) and a ridge-till system in a corn-soybean-wheat rotation (RT) in Ohio, USA. Earthworm communities were altered by adding ∼76 Lumbricus terrestris (L.) m –2 each spring and fall into plots with no, or very few of these anecic earthworms. Increases in L. terrestris were small (∼7 m –2 ) compared to the number added and their establishment was at the expense of the epigeic earthworm L. rubellus (Hoff.), which declined four and two-fold in CT and RT, respectively. Populations of the endogeic earthworm Octolasion tytaeum (Sav.) were unaffected by the addition of L. terrestris . Sampling 5 years after the additions indicated that L. terrestris persisted only in the RT plots. The decline in L. rubellus populations in plots with added anecic worms was no longer evident. We understand that the increased number and amounts of residues and the minimal level of disturbance found in RT probably increased the extent and quality of earthworm habitat over CT plots, which had fewer crops, less cover, and periodic disturbance. Apparently, population dynamics and competitive relationships among different earthworm functional groups were regulated by agroecosystem type, and their correspondent disturbance regimes and resource distributions.

Population dynamics of ambient and altered earthworm communities in row-crop agroecosystems in the Midwestern U.S.: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Earthworms affect agroecosystem processes and few studies have addressed population dynamics when earthworms are intentionally introduced. Handsorting and formalin extraction were used semi-annually from fall 1994 to fall1997 to measure populations in plots with and without added earthworms under chisel till in a corn-soybean rotation (CT) and a ridge-till system in a corn-soybean-wheat rotation (RT) in Ohio, USA. Earthworm communities were altered by adding ∼76 Lumbricus terrestris (L.) m - 2 each spring and fall into plots with no, or very few of these anecic earthworms. Increases in L. terrestris were small (∼7 m - 2 ) compared to the number added and their establishment was at the expense of the epigeic earthworm L. rubellus (Hoff.), which declined four and two-fold in CT and RT, respectively. Populations of the endogeic earthworm Octolasion tytaeum (Sav.) were unaffected by the addition of L. terrestris. Sampling 5 years after the additions indicated that L. terrestris persisted only in the RT plots. The decline in L. rubellus populations in plots with added anecic worms was no longer evident. We understand that the increased number and amounts of residues and the minimal level of disturbance found in RT probably increased the extent and quality of earthworm habitat over CT plots, which had fewer crops, less cover, and periodic disturbance. Apparently, population dynamics and competitive relationships among different earthworm functional groups were regulated by agroecosystem type, and their correspondent disturbance regimes and resource distributions.

INNOVATIVE 15N MICROPLOT RESEARCH TECHNIQUES TO STUDY NITROGEN USE EFFICIENCY UNDER DIFFERENT ECOSYSTEMS

Use of labeled 15N techniques can help improve and refine knowledge required to understand the dynamics of the N cycle under agricultural systems. The examples reported in this paper illustrate that, with creativity and careful planning, use of 15N-enriched or depleted fertilizers can be used in many types of N experiments with various crops, cropping systems, and in many types of agroecosystems. The objective is to report examples of a wide range of field studies that researchers can hopefully draw upon to design and utilize N isotope techniques that accomplish the objectives for their own research. Examples of microplot studies with and without physical barriers are discussed along with some of the strengths and limitations of each approach. Even though 15N technology offers considerable opportunity to understand N cycling, it too has limitations to its use. Types of fertilizer 15N materials and methods for applying 15N materials are discussed including some discussion about the use of ammonium versus nitrate forms; literature sources are provided for additional reading about the use of 15N techniques.

The role of parasitic Hymenoptera in integrated pest management in fruit orchards

Parasitic Hymenoptera are some of the most abundant natural enemies of all fruit pests. Their role is rather variable in relation to the type of agroecosystem. Several approaches (introduction of exotic species, inoculative and inundative releases, measures for conservation of the existing species, etc.) can be implemented to increase the role of the parasitoids in controlling pest species. Classical biological, when applicable, as against several citrus pests, is still the most ecologically and economically sound method. The role parasitoids play in the regulation of pest populations remains uncertain, but much evidence for its importance as a regulatory factor comes from biological control programs.

Life history, population dynamics and production of eastern mosquitofish, Gambusia holbrooki (Pisces, Poeciliidae), in rice fields of the lower Mondego River Valley, western Portugal

The introduced population of Gambusia holbrooki from the rice fields of the lower Mondego River Valley, Portugal, was studied for 15 months, relating their life cycle and population dynamics with its production, in order to assess the role of the species in the energy flow and secondary production in this type of agro-ecosystem. Two main annual cohorts (1995 and 1996 cohorts) were identified. The females outnumbered males and the average female/male-ratio was 4. The inspection of ovary developmental stages of this viviparous fish, revealed that the most important reproductive period was between April and August. The first recruits were recorded in June and were present thereafter until October. Males from the parental cohort died before August, whereas parental females could survive until October. Mean adjusted fecundity (number of embryos divided by female standard length) peaked in July 1996 (0.95) and in June 1997 (1.05). Females reached greater sizes, had a higher growth rate and lived longer than males. Annual production was estimated at 3.101 g.m–2.year–1 (ash-free dry weight, AFDW), the average biomass at 2.896 g.m–2 (AFDW), and the P/B ratio was 1.071. A conjugation of life history, population dynamics, production and ecological traits (e.g. fast growth, reduced longevity, viviparity, high productivity, an intermediate position in food chain, and no special habitat requirements for reproduction) clearly show that the populations of G. holbrooki, introduced into rice fields all over the world, may play an important role in the structure and functioning of the biological communities of these important agro-ecosystems.

Use of fodder resources by ruminants in warm climate countries

Fodder resources provide the principal sources of feeds throughout the humid and sub-humid, arid and semi-arid and Mediterranean regions. They include grasses and legumes, and fibrous crop residues (FCR). Browse is another important source of fodder. The availability and use of the fodder resources is dependent on type of agroecosystem (e.g. humid and sub-humid to arid and semi-arid), cropping patterns and their intensity, type and concentration of animal species, and prevailing animal production systems. The productivity of ruminants is dependent on the potential of a feed to supply, through microbial degradation, balanced nutrients for production; digestible dry matter intake is highly correlated with animal productivity with individual feeds. Nutritive value relates to the capacity of a feed to supply nutrients to meet productive functions, and this is contingent on maximizing voluntary feed intake, potential digestibility, protein:energy (P/E) ratio, and availability of bypass nutrients, particularly proteins. FCR form the main base in feeding systems for ruminants throughout the tropics and the Mediterranean region, and in recent years considerable progress has been achieved in their use. A number of technologies can be applied singly or in combination: treatment with alkalis to increase digestibility, supplementation to improve overall digestion and provide balanced nutrients, use of bypass nutrients, and large scale on-farm application to demonstrate economic profitability. Supplementation is central to effective utilization and includes the use of multi-nutrient block licks (MNBL), non-protein nitrogenous sources, and a variety of leguminous forages like Acacia spp., Gliricidia maculata, Leucaena leucocephala and Prosopis juliflora. Given the advances that have been made on the use of FCR, extending known technologies through on-farm testing and demonstration far outweighs the need for further research on the effects of pre-treatments or supplementation. Such effort must involve strategies for more effective use of the fodder resources, especially in large scale participatory on-farm situations. These need to address efficiency in integrated natural resource use, the totality of production-post-production-consumption systems, and demonstration of more sustainable animal production systems.

The agroecological information system (AIS) within the research network on agroecosystems Munich (FAM)

Within the “Research Network on Agroecosystems Munich” (FAM, which is the German acronym for “Forschungsverbund Agrarökosysteme München”), an Agroecological Information System (AIS) will be developed. It will provide simulation models in a geographical information system (GIs) in order to calculate ecological risks of different management practices. The AIS is based on two different scales: On a farm called “Klostergut Scheyern” (140 ha), designed as a monitoring network with a cell resolution of 50 × 50 m, and on the surrounding area, a landscape of about 550 km 2 (four topographic maps in the scale of 1:25 000). Typical as well as extreme agroecosystem types will be derived from the interdisciplinary research results on the farm. These types and more general available data and information are the base for scaling up to the landscape level. This paper describes the basic structures and issues of the models. The first model is designed for fields or part of fields, the second is designed for landscapes. The overall goal is to develop a methodological framework (prototype of an agricultural information system) for a sustainable management of agricultural systems in this region in combination with societal and economic forces (Lenz, 1992).

Bird communities associated with three traditional agroecosystems in the San Luis Potosi Plateau, Mexico

The bird communities associated with three traditional dry farming systems. their borders and their unfarmed surroundings on the San Luis Potosi Plateau, México, were studied throughout the year. The systems studied were (1) a purely rain-field in a grassland with shrubs, (2) a field on a bajada irrigated with runoff water in a complex and dense community of cacti and shrubs, and (3) a bajio field irrigated with spring moisture and an ephemeral wash in savanna. The results are in agreement with the hypothesis that complex agroecosystems are less susceptible to pest outbreaks than simple ones. There was no typical cropland avifauna; communities depended on the particular type of agroecosystem and on the original habitat. The foliage height diversity index did not always parallel bird richness, since there are factors affecting the latter which did not affect the index. Edge effect was not evident in this study. Although two agroecosystems had lower richness than their surroundings, the presence of isolated fields increased regional bird richness.

Cropping and yields in agricultural systems of the north-eastern hill region of India

Shifting agriculture locally known as jhum is the predominant form of agriculture used by the local tribe of the north-eastern hill region of India. There is also some valley rice cultivation and terrace cultivation. The structure and some functional aspects of these three agro-ecosystem types are discussed and compared. The 30 year jhum cycle has the advantage over the 10 or 5 year cycle apart from higher yields, in that the monetary output/input ratio under a 30 year jhum cycle is comparatively favourable. Further, the 30 year jhum cycle is advantageous over terrace cultivation as the latter needs heavy inputs of fertilizers. The main advantage of settled valley cultivation is the raising of crops consistent in yield year after year from the same site.

Pest Situation In Changing Agricultural Systems--A Review

Agriculture is defined as the science or art of cultivating the soil, producing crops, and raising livestock. This definition implies the manipulation of soil, plants, and animals from their natural state. In reviewing the pest situation in changing agricultural systems, we are not contrasting disturbed vs. undisturbed ecosystems, but we are comparing different types of artificial ecosystems or agroecosystems. I have further taken the liberty of limiting my comments to the crop sector of agriculture, chiefly because my own experience and familiarity with the literature is largely limited to this area.