增温对亚热带森林土壤呼吸变化的影响

[目的]研究增温条件下亚热带森林土壤呼吸的变化。[方法]以福建省亚热带杉木林为对象,通过埋设加热电缆的方法开展亚热带模拟土壤增温试验,采用13C脉冲标记技术,高效追踪土壤气体的变化情况。[结果]在试验期间,增温后土壤总呼吸、异养呼吸的δ13C均高于对照组,δ13C先下降后上升,然后继续下降,与初始状态持平;增温后土壤总呼吸速率与异养呼吸速率变化趋势基本一致,且异养呼吸速率与其对应的δ13C的相关性大于土壤呼吸与其对应的δ13C的相关性。因而,在气候变暖条件下,增温对土壤中的微生物以及根系造成影响,导致土壤呼吸以及异养呼吸变化会有较大的浮动。[结论]该研究为进一步了解增温后亚热带森林地区土壤呼吸的变化提供了一定的参考依据。     

Grasslands in ‘Old World’ and ‘New World’ Mediterranean‐climate zones: past trends,current status and future research priorities

Despite their ecological, economic and social importance, grasslands in areas with Mediterranean climates continue to receive limited scientific, political and media attention. The main objectives of this review are to compare and contrast dryland grasslands in the ‘Old World’ regions of the Mediterranean basin (southern Europe, western Asia and North Africa) with those of ‘New World’ regions with Mediterranean climates (Australia and Chile) and to identify common research priorities. The common characteristics and differences in climate, soils, native vegetation, importance of the livestock sector and the socio‐economic background for the different Mediterranean environments are examined. Past trends and the current status of temporary and permanent Mediterranean grasslands are also described. Some common issues between these regions are as follows: (i) adaptation to climate change; (ii) increasing persistence and drought survival of both annual and perennial species; (iii) the important role of forage legumes; (iv) maintaining grassland plant diversity; and (v) improved ecosystem services, such as carbon sequestration, control of soil erosion and wildfires, and preservation of both wild and domestic biodiversity. The favourable climate in these regions, which allows year‐round grazing and the growth of legumes, should be exploited to improve the sustainability of grassland‐based, extensive farming systems and the quality of their animal products, while at the same time improving ecosystem services. The decreasing support for grassland research and development programmes requires increased international scientific and technical cooperation among the few institutions operating in the different Mediterranean‐climate areas of the World to provide innovative and sustainable solutions to farmers.     

Effects of shrub encroachment on herbage production and nutritive value in semi-arid Mediterranean grasslands

There is limited information on the effects of the increase in the density of shrubs on herbage production and nutritive value of natural grasslands in the Mediterranean region, currently facing major land use changes. Herbage production of drymatter (herbaceous fractions, of plant functional groups and by species), crude protein (CP), neutral‐detergent fibre (NDF), acid‐detergent fibre (ADF), acid‐detergent lignin (ADL) and hemicellulose concentrations and in vitro organic matter digestibility were determined at the time of peak of annual growth across four types of grassland vegetation each characterized by different shrub cover regimes. A sharp reduction in herbage production and a reduction in nutritive value were found as a result of the increase in shrub cover. These changes appeared to be closely related to the shift in plant functional groups detected as shrub density increased. Herbage production from grasses and legumes was found to be more sensitive to shrub cover changes than herbage production from forbs, whereas, as grassland types became denser, annual species were gradually replaced by perennials and C₄ grasses by C₃ ones. The impact of shrub encroachment on Mediterranean grasslands is discussed in relation to their use by livestock.     

The effect of tree cover on the biomass and diversity of the herbaceous layer in a Mediterranean dehesa

Mediterranean dehesas are an archetypal example of high nature value farmland in Europe. To better understand the interactions between trees and grasslands in the conservation and management of the dehesa, we measured, over 3 years, the contribution of scattered trees to the diversity and biomass dry‐matter (DM) yield of the herb layer and the relationship between the herb layer (biomass and diversity interaction) and the trees. The study was based on 135 subplots representing four aspects and three distances from fifteen trees selected randomly in a plot within a dehesa in central Spain. The specific questions were the following: (i) To what extent do trees affect biomass of the herbaceous layer? (ii) What is the relationship between herbaceous layer biomass and species diversity under the influence of trees? and (iii) What are the effects of trees and small‐scale topography on the herbaceous diversity? Results differed between years depending on water availability. Legume and forb DM yields were highest at the edge of the tree crown and beyond the canopy. Species richness was positively related to legume DM yield, and both were higher at the bottom of the hillside, especially in dry conditions. Given the importance of tree influence on the biomass and diversity of grasslands, maintaining proper agroforestry management practices for trees and grasslands is important for conserving dehesa diversity and productivity under the conditions of high climatic and soil variability in Mediterranean dehesas.     

Are soil‐adjusted vegetation indices better than soil‐unadjusted vegetation indices for above‐ground green biomass estimation in arid and semi‐arid grasslands?

Accurate estimation of grassland biomass has been a central focus due to its importance in ecosystem processes and carbon cycles. This study aimed to examine whether the performance of soil‐adjusted vegetation indices for estimating above‐ground green biomass was better than that of soil‐unadjusted vegetation indices in arid and semi‐arid grasslands. Above‐ground green biomass in desert steppe of Inner Mongolia and corresponding moderate‐resolution imaging spectroradiometer (MODIS) surface reflectance 8‐day composite MOD09Q1 data were collected during late September of 2013. Results showed that soil‐adjusted SAVI (soil‐adjusted vegetation index), MSAVI (modified soil‐adjusted vegetation index), OSAVI (optimized soil‐adjusted vegetation index), TSAVI (transformed soil‐adjusted vegetation index), ATSAVI (adjusted transformed soil‐adjusted vegetation index) and PVI (perpendicular vegetation index) did not improve estimation accuracy over soil‐unadjusted simple ratio (SR) and normalized difference vegetation index (NDVI), due to low green vegetation cover (<30%) in the study area. Our results suggest that these soil‐adjusted vegetation indices may be not suitable for describing green vegetation information in arid and semi‐arid grasslands with low green vegetation cover (<30%).     

Plant species richness, functional type and soil properties of grasslands and allied vegetation in English Environmentally Sensitive Areas

To facilitate the maintenance and restoration of semi‐natural grasslands, it is important to understand their relationships with soil properties. Semi‐natural grasslands typically have a high incidence of stress‐tolerant species (measured here by high stress radius values), but not all have high species richness. Species richness and stress radius values were related to soil pH, Olsen extractable phosphorus (P), extractable potassium (K) and magnesium (Mg), total nitrogen (N) and organic matter (OM) at 571 sites representing a wide range oftemperate grasslands. Highest species richness (>30 m^?2) occurred at pH > 6 and 4–15 mg l^?1 P, but species richness was also highly variable at 4–15 mg l^?1 P. At pH < 5, species richness was low (<20 m^?2). Stress radius values were highest (mainly calcareous and heath grasslands and mires) at pH c. 8·0 and < 5·0, and at the lowest soil P levels (<5 mg l^?1). A wide range of stress radius values occurred at low soil P levels because appropriate management is also needed to maintain semi‐natural grasslands. Reducing soil P is difficult in practice, so grassland restoration in the presence of elevated soil‐extractable P levels merits re‐assessment.     

Bio‐agronomic characterization and implications on the potential use as forage of Bituminaria bituminosa and B. morisiana accessions

Perennial forage legumes may be pivotal for improving the sustainability of Mediterranean rainfed farming systems. This study summarizes the outcomes of a study aimed at characterizing morphological and agronomic traits of new germplasm of Bituminaria bituminosa and B. morisiana in Mediterranean environments. Five B. morisiana and three B. bituminosa native populations were evaluated in a small‐plot field experiment in Sardinia (Italy) and compared with seven Spanish accessions of B. bituminosa. The two Bituminaria species differed greatly in morphological traits and the beginning of the flowering stage, and remarkable variations between species were found for forage production and its seasonal distribution, seed yield and persistence. Average cumulative dry‐matter yield was higher in B. bituminosa than in B. morisiana (+7.6%; 297 vs. 276 g per plant). Average 3‐year seed production varied greatly between accessions (from 0.3 to 141 g per plant). Differences for these traits were also found between Sardinian and Spanish germplasm of B. bituminosa. Four clusters were generated by K‐means clustering. Accessions included in cluster III exhibited a positive combination of favourable forage production, high seed yield and satisfactory persistence. Nonetheless, the cluster analysis did not highlight a sharp discrimination between Bituminaria species. The overall results revealed the potential role of Sardinian accessions of B. bituminosa and B. morisiana in extending the forage season and for increased resilience of grasslands in Sardinia and other Mediterranean regions under rainfed conditions.     

A simultaneous effect of selfing and Epichloë endophyte on forage,seed yield and turf characteristics of perennial ryegrass (Lolium perenne L.)

Ryegrass (Lolium perenne L.) is a putative turf and forage plant characterized as mainly outcrossing in which the extent of self‐fertilization and its consequences has not been investigated. In this study, selfed and half‐sib family seeds were obtained from ten clonally propagated ryegrass plants among which two were endophyte‐free (EF) and eight were endophyte‐infected (EI). Then, 20 seed populations plus two commercial varieties of Speedy and Vigor were sown and evaluated in a biennial experiment for their turf and forage characteristics. Selfing caused significant inbreeding depression for plant fresh and dry weight and leaf length and width in the first year for both EI and EF genotypes. In the second year, only leaf length remained depressed among these characters. Also, for the most growth, turf and reproductive traits, EI populations showed less depression. The presence of endophyte in self‐pollinated populations made an increasing effect for the number of seed per spike and days to heading, although seed weight was reduced. Some of the populations derived from self‐pollination and infected with fungal endophyte including S9 and S10 were even superior to the two commercial varieties in terms of both seed production and turf characteristics. However, for seed‐related characteristics including number of spikes per plant, seed weight and seed yield, EF populations including Speedy and Vigor were more reproductive than EI populations. It is concluded that selfing may increase the discrimination between EI and EF ryegrass plants because endophyte infection may mitigate the negative consequences of inbreeding depression in prone populations.     

Productivity,grazing utilization,forage quality and primary production controls of species‐rich alpine grasslands with Nardus stricta in northern Spain

Species‐rich alpine grasslands with Nardus stricta are important communities for both animal production and environmental conservation in Europe. We selected two contrasting types of Nardus grasslands (mesic and wet) within a rangeland of northern Spain and measured annual above‐ground net primary productivity (ANPP), botanical components, forage utilization and their respective seasonal patterns, during a 5‐year period. We analysed their chemical properties and recorded soil moisture and temperature in order to construct models able to explain grassland productivity. Mean annual ANPP of mesic Nardus grassland was about half (216 g DM m^?2 year^?1; ±29·8 s.e.) that of the wet grassland (406 g DM m^?2 year^?1; ±54·3 s.e.), with significant intra‐ and interannual variability. Mesic grassland, with a more important contribution of forbs and legumes over graminoids in its botanical composition, was the preferred forage source of grazing livestock and showed better chemical properties in spring and early summer. In summer and autumn, wet grassland had a higher utilization owing to its ability to maintain high biomass production. This was partially explained by soil moisture, a limiting factor of mesic grassland productivity. Our results provide new and relevant information on key aspects of species‐rich alpine Nardus grasslands, potentially useful for the definition of management options for these habitats of priority conservation.     

田间不同施肥处理大豆生长过程模拟验证研究

大豆是东北的主要农作物之一,准确地应用模型技术可以辅助田间试验来研究如何提高和改善大豆产量和品质.利用CSM-CROPGRO-Soybean模型,在海伦农业生态站1993～1996年长期定位不同施肥处理实验数据的基础上,建立大豆品种遗传属性和相应数据库,对大豆产量和物候期等重要生长过程和结果进行模拟和验证.结果表明,在对4年不同施肥处理的模拟中,大豆物候期的模拟RMSE为0.58 d,EF为0.92.大豆产量模拟RMSE为101.6 kg hm-2,EF为0.7,取得了较好的模拟效果.模型的方法可以为大豆优化种植提供有效的信息技术手段.     

Comparison of ingrowth core and sequential soil core methods for estimating belowground net primary production in grass–clover swards

Estimation of belowground net primary production (BNPP) is crucial for prediction of grassland soil organic carbon sequestration, but there are high coefficients of variation (CV) among methods of estimation. We compared accuracy and precision of two variations of the traditional soil core method and three of the ingrowth core method, over 2 years on grass–white clover swards in Germany. The ingrowth core method (5‐ to 9‐week ingrowth period) provided the most accurate BNPP estimate (471 g m^?2) with the highest precision (CV: 31%), whereas the two soil core approaches resulted in underestimation and high error. Comparing results with other grassland studies, we found that reliability of the ingrowth core method was influenced by ingrowth period and sward rooting pattern related to grass phenological stages, while the precision was determined by ingrowth period and grassland productivity. We therefore recommend using the ingrowth core method for managed grasslands where belowground productivity is relatively high and installation disturbance is likely to be negligible. Using a 6‐ to 8‐week ingrowth period, the method delivers reliable and feasible BNPP estimates for temperate managed grasslands which can be applied to long‐term soil carbon budget simulation. Results from our work and other studies also indicated that standing root biomass masks seasonal pattern of rooting due to synchrony between root birth and death. The soil core method is likely to lead to underestimates and higher errors than the ingrowth core methods and thus should be avoided.     

Effects of ecological restoration‐induced land‐use change and improved management on grassland net primary productivity in the Shiyanghe River Basin,north‐west China

To address severe grassland degradation, the Chinese government implemented national restoration programmes, which in turn drove a research focus towards assessment of the environmental effectiveness of such initiatives. In this study, net primary productivity (NPP) was used as an indicator for assessing the impacts of land use and cover change (LUCC), improved land‐use management and climate change on the grassland ecosystem of the Shiyanghe River Basin. NPP was calculated on the basis of the Carnegie–Ames–Stanford Approach model, which is driven by a Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index and meteorological data. The LUCC data for 2001 and 2009 were derived from MODIS land‐cover data. During the study period, the net increase in grassland development was 5105·5 km², with 80·4% of the newly developed grasslands attributed to desert‐to‐grassland conversion. The total NPP of grasslands in 2009 increased by 659·62 Gg C compared with that in 2001. The contributions of human activity and climate change to total NPP increase were 133 and ?33% respectively. Land conversion and improved management measures directly increased grassland NPP. These factors are dominant positive driving forces, whereas warm and dry climates impose adverse effects on grassland restoration in the study site.     

锥栗林土壤呼吸动态变化与主要影响因子分析

通过LI-6400对闽北锥栗林的土壤呼吸进行测定与分析。结果表明,不同季节土壤温度的变化较为一致,呈单峰变化趋势,最大值出现在15：00;土壤呼吸速率昼夜变化趋势大致呈单峰变化,不同季节里呼吸速率最大值出现的时间不同,春季与冬季最高值出现在13：00,而夏季与秋季分别出现在17：00与15：00;不同季节土壤呼吸速率的日变化幅度以冬季较小,春季最大;土壤呼吸Q10值的季节变化中,冬季Q10值最大,夏季最小,Q10值随土壤温度的增高而降低。     

Annual forage legumes in dryland agricultural systems of the West Asia and North Africa Regions: research achievements and future perspective

Forage legumes are vitally important to animal production in the dryland farming systems of the Mediterranean region. Of the diverse forage‐legume species adapted to the Mediterranean climate, vetches, (Vicia spp.), chicklings (Lathyrus spp.), annual medics (Medicago spp), clovers (Trifolium spp.) and species of the Lupinus, Lotus, Onobrychis, Hedysarum and Ornithopus genera are considered to be the most agronomically important and economically valuable species for the region. Adoption of perennial self‐regenerating medic (Medicago spp.) has been limited because of technical difficulties, but annual vetch (Vicia spp.) has the greatest potential as a viable animal‐feed source and a rotation crop with cereals. Some forage legumes survive harsh conditions by their unique underground growth habit, for example, V. amphicarpa and Lathyrus ciliolatus. Efforts to improve forage legumes have been based on both management/cultural factors and breeding. Research based on several long‐term barley‐ and wheat‐based rotation trials has demonstrated the viability of forage legumes, especially vetch, in the region's improved farming system. An additional benefit to such legumes is the enhancement of soil quality, that is, soil fertility, soil organic matter and soil physical properties. Thus, the development of forage legumes is essential to agricultural sustainability in the Mediterranean region and in other dryland cereal‐growing areas of the world where grazing livestock is a dominant enterprise. To build upon the considerable research conducted on forages, intensified efforts are needed to develop locally adapted forage cultivars, to provide economic assessment of forages in cropping systems and to promote technology transfer at the farm and community level.     

Assessment of the nitrogen status of grassland

Two types of diagnostics are used for N management in grasslands: diagnostics based on N concentration of shoots and diagnostics based on soil mineral N. The Nitrogen Nutrition Index (NNI) is an example of the first type. However, its evaluation requires the determination of shoot dry weight per unit area and, thus, constitutes a practical limit to its utilization in the context of farm studies. In order to simplify its evaluation, a method based on the N concentration of the upper sward layer (N_up) has been proposed. The objectives of this study were to test the relationship between NNI and N_up in the context of permanent grassland and to examine the relationship between N_up and soil mineral status. The study was conducted as two experiments, one on small cut‐plots receiving contrasting rates of mineral N fertilization, and a second on plots of an existing field‐scale lysimeter experiment. In each plot and at several dates, shoot biomass within quadrats was measured, N concentration was determined on the upper leaves and on the entire shoots, and mineral nitrogen of the soil below the vegetation sampled was determined. N concentration of the upper lamina layer of the canopy was linearly related to the NNI determined on the entire shoots. Therefore, determining N concentration in leaves at the top of canopy appears to be an alternative means to evaluate NNI without having to measure shoot biomass. The absence of an overall significant correlation between soil mineral N content and sward N index, observed over the two studies, indicates that each of these two indicators has to be considered specifically in relation to the objective of the diagnostic procedure. As sward N index may vary independently of soil mineral N content, the sward N indicator does not appear to be a suitable indicator for diagnosis of environmental risks related to nitrate leaching. However, soil mineral N content does not allow the prediction of sward N status and thus is not a suitable indicator of sward growth rate. Although soil mineral N content is an important environmental indicator for nitrate‐leaching risks during potential drainage periods, it has a limited diagnosis value with respect to the herbage production function of grasslands.     

Origin and history of grasslands in Central Europe – a review

In terms of origin, grasslands in Central Europe can be classified into (i) natural grasslands, predetermined by environmental conditions and wild herbivores; (ii) seminatural grasslands, associated with long‐term human activity from the beginning of agriculture during the Mesolithic–Neolithic transition; and (iii) improved (intensive) grasslands, a product of modern agriculture based on sown and highly productive forage grasses and legumes. This review discusses the origin, history and development of grasslands in Central Europe from the Holocene (9500 BC) to recent times, using archaeobotanical (pollen and macroremains), archaeozoological (molluscs, dung beetles, animal bones) and archaeological evidence, together with written and iconographic resources and recent analogies. An indicator of grasslands is the ratio of non‐arboreal/arboreal pollen and the presence of pollen of species such as Plantago lanceolata and Urtica dioica in sediments. Pastures can be indicated by Juniperus communis pollen and charcoal present in sediments and the soil profile. Insect‐pollinated species can be studied using cesspit sediments and pollen (from honey) in vessels in graves. In Central Europe, natural steppe, alluvial grasslands and alpine grasslands occurred before the start of agriculture in the early Neolithic (5500 BC); their area was small, and grassland patches were fragmentary in the forested landscape. Substantial enlargement of grasslands cannot be expected to have occurred before the late Bronze Age. The first scythes come from the 7th–6th century BC; therefore, hay meadows probably did not develop before this time. There is evidence of hay meadows in Central Europe during the Middle Ages, documented by macroremains of Arrhenatherum elatius in sediments, written records and long scythes in archaeological assemblages. Based on macroremains analyses, we conclude that there was generally high diversity of seminatural grasslands in the cultural landscape in the Middle Ages, and individual grassland communities were generally species rich. From the beginning of the agriculture until the 18th century, pastures and pasture forests were dominant sources of forage. Large‐scale enlargement of hay meadows and decline of pastures in many regions occurred from the 18th century. Hay making is associated with enlargement of arable fields and the use of cattle as draught animals for ploughing and soil preparation. The spread of A. elatius in Central Europe was enabled by the decline of grazing management and an increased proportion of hay meadows in the 18th and 19th centuries. In some mountain areas, there are no records of large‐scale deforestation and enlargement of grasslands until the 14th century, and the peak of the agriculturally used area was recorded for the period from the 18th to the first half of the 20th century. Grasslands were converted into arable land during periods of war; conversely, grasslands replaced arable land after the collapse of agriculture in many regions of former communist countries following political regime change in the 1990s. The dynamics of the grassland area reflect the development of human society and the political situation, because grasslands are an integral part of the cultural landscape in Central Europe.     

Soil, site and management components of variation in species composition of agricultural grasslands in western Norway

A partitioning of the total variance in species composition of grasslands associated with increasing fertilizer inputs (unfertilized pastures, artificially fertilized hay meadows and intensively cultivated grassland) in western Norway was undertaken. The partitioning was carried out with (partial) constrained ordinations (canonical correspondence analysis) and associated Monte Carlo permutation tests. Explained variation was high (0·651), with soil chemistry, management and site explaining 0·271, 0·228 and 0·052 of the variation, respectively, and the interaction between soil and management explaining 0·100 of the variation. However, much of the measured soil chemistry was considered to be an effect of management. The soil chemistry variable explaining most variation was extractable P content, associated with high soil extractable P contents in the intensively cultivated grassland due to high fertilizer applications. However, soil extractable P content did not explain differences in species composition when grasslands with smaller differences in fertilizer inputs (meadows vs. pastures) were compared. Total soil C and N contents and C:N ratios explained significant variation between all grassland types. Lowest levels of these variables were measured in the grassland with the highest fertilizer inputs, suggesting that total soil N content cannot be used as a predictor of fertility. Significantly higher soil N contents were measured in grasslands of low productivity, probably due to a low decomposition rate of stress‐tolerant plants and the consequent low availability of soil N and accumulation of soil organic matter. Ellenberg N values reflected soil chemical differences in this study with high Ellenberg N values reflecting high Ca, Mg and P contents and pH values and low total C and N contents and C:N ratios.     

Effects of cutting or grazing grass swards on herbage yield, nitrogen uptake and residual soil nitrate at different levels of N fertilization

On a Flemish sandy loam soil, cut and grazed swards were compared at different levels of mineral nitrogen (N) fertilization. Economically optimal N fertilization rates were 400 (or more) and 200 kg N ha^?1 yr^?1 on cut and grazed swards respectively. Considering the amounts of residual soil nitrate‐N in autumn, these N rates also met the current Flemish legal provisions, i.e. no more than 90 kg ha^?1 nitrate‐N present in the 0–90 cm soil layer, measured between 1 October and 15 November. The N use efficiency was considerably higher in cut grassland systems than in grazed systems, even when the animal component of a cut and conservation system was included. The results indicate that, for cut grasslands, two N application rates should be considered: intensively managed grasslands with high amounts of N (400 kg ha^?1 yr^?1 or more) or extensively managed grasslands with white clover and no more than 100 kg N ha^?1 yr^?1.     

Analysis of Potato Canopy Coverage as Assessed Through Digital Imagery by Nonlinear Mixed Effects Models

The characterization of the dynamics of canopy coverage represents a relevant matter of study in the field of crop physiology. The objective of this work was to calibrate a model able to simulate potato canopy coverage as a function of thermal time, but including the error structure in such model. This was accomplished by using a mixed effects modelling approach where random effects were added to the average response model. By applying this modelling approach, the structure of the data was taken into account. Calibration data for the model were obtained from canopy coverage estimates derived from image processing analysis. Digital images were taken periodically within 11 potato fields located in the Mantaro Valley (Peru) during the 2005–2006 growing season. This model gave a better fit in comparison with the traditional fixed parameters model. An additional uncertainty analysis with the objective of estimating the confidence region for the predictions of the mixed effects model was carried out. By exploring the data structure, a more comprehensive overview of the potato canopy coverage was achieved with the mixed effects model.     

Scaling up of a mechanistic dynamic model in a GIS environment to model temperate grassland production at the regional scale

Regional‐scale ecological processes are mediated by processes occurring at local scales. Spatially explicit models are needed to understand the broad‐scale consequences of a large number of local processes, driven by factors which are heterogeneous at a broad scale. A Geographic Information System (GIS)‐based mechanistic model, which can be used as a flexible tool to investigate the regional‐scale effects of changes in environmental factors on herbage production from a Lolium perenne sward, was developed and used to investigate the consequences of aggregating driving variables at different resolutions. The model allows rigorous scaling up of previously existing field‐based modelling approaches within a GIS context. The model's mechanistic approach allows flexibility in the simulation of the separate effects of environmental driving variables and of cutting regimes. The driving variables (temperature, solar radiation, available soil moisture and soil nitrogen status) are scaled up using geostatistical techniques. The model is used to evaluate weekly changes in herbage production under environmental conditions, variable both in space and time, under different cutting regimes. It is shown that, in this model, aggregation at 1 km² is a good compromise between accuracy and practical feasibility, and that, while ignoring heterogeneity over many square kilometres can induce large errors, their magnitude and direction also depend on the model response curve to an input variable. The results obtained were consistent with the known trends in influential environmental factors. The programming within a GIS makes the model flexible in its application and, therefore, makes it easy to apply at a variety of scales.