Intensive Agricultural Land Use Research Articles

Economic and ecosystem costs and benefits of alternative land use and management scenarios in the Lake Rotorua, New Zealand, catchment

Abstract A significant challenge in resource management is addressed: the perceived trade-off between economic growth and ecosystem restoration and conservation. Traditional approaches to management regard restoration as a potential cost to economic productivity. In this study we show that by considering a broader range of economic values, including ecosystem services values, an argument can be made that restoration of lake ecosystems also leads to favourable economic outcomes when commonly disregarded values are considered. Our case study analyses the ecological outcomes of different catchment mitigation and land use scenarios in terms of water quality results in a lake, assessing changes in land use values based on opportunity costs, and ecosystem services values. We show that when considering the value of ecosystem services, intensive agricultural land use is not necessarily the most economically valuable form of land use within a lake catchment. Indeed, a shift towards alternative land uses within a catchment can lead to both ongoing economic benefits and improvements in water quality. In this context, land-use change offers an option for water quality improvement that minimises lake and land mitigation costs, while adding value to catchment land use. An argument is made supporting land use change towards indigenous forest types, which can sustain alternative sources of income such as a range of recreational values, while supporting important ecosystem functions for the region.

Determining sectoral and regional sensitivity to climate and socio-economic change in Europe using impact response surfaces

Responses to future changes in climatic and socio-economic conditions can be expected to vary between sectors and regions, reflecting differential sensitivity to these highly uncertain factors. A sensitivity analysis was conducted using a suite of impact models (for health, agriculture, biodiversity, land use, floods and forestry) across Europe with respect to changes in key climate and socio-economic variables. Depending on the indicators, aggregated grid or indicative site results are reported for eight rectangular sub-regions that together span Europe from northern Finland to southern Spain and from western Ireland to the Baltic States and eastern Mediterranean, each plotted as scenario-neutral impact response surfaces (IRSs). These depict the modelled behaviour of an impact variable in response to changes in two key explanatory variables. To our knowledge, this is the first time the IRS approach has been applied to changes in socio-economic drivers and over such large regions. The British Isles region showed the smallest sensitivity to both temperature and precipitation, whereas Central Europe showed the strongest responses to temperature and Eastern Europe to precipitation. Across the regions, sensitivity to temperature was lowest for the two indicators of river discharge and highest for Norway spruce productivity. Sensitivity to precipitation was lowest for intensive agricultural land use, maize and potato yields and Scots pine productivity, and highest for Norway spruce productivity. Under future climate projections, North-eastern Europe showed increases in yields of all crops and productivity of all tree species, whereas Central and East Europe showed declines. River discharge indicators and forest productivity (except Holm oak) were projected to decline over southern European regions. Responses were more sensitive to socio-economic than to climate drivers for some impact indicators, as demonstrated for heat-related mortality, coastal flooding and land use.

Crop spatiotemporal dominance is a better predictor of pest and predator abundance than traditional partial approaches

Landscape-scale agricultural intensification can concentrate pest resources (high host density) and impede natural enemy populations through a reduction in non-crop resources or disturbance events. Current approaches examine the impacts of crop dominance on pest pressure through a simple lens, either spatially (i.e. landscape complexity), or temporally (i.e. diversity of crop rotation schedules). However, these partial approaches are inadequate because they do not take into account the impact of multiple years of non-rotation, or the impacts of the surrounding landscape, respectively. In this study, we use a unique method that allows land use in both space and time to be quantified simultaneously with a single metric, “spatiotemporal dominance”. We examined the impact of spatiotemporal dominance of sweet corn on populations of a key insect pest, Ostrinia nubilalis, and its potential predators. Additionally, we evaluated site-specific variables such as crop rotation, percent agriculture in the landscape, cover crop use, and frequency of insecticide applications, to determine their relative importance in predicting pest pressure, alongside our metric of spatiotemporal crop dominance in the landscape. Ostrinia nubilalis adult abundance was positively associated with spatiotemporal dominance of sweet corn in the landscape (space and time) and high proportional agricultural land use (space), but was unrelated to the previous year’s crop (time). Predatory soldier beetle abundance was negatively associated with sweet corn spatiotemporal dominance (space and time), but not associated with the previous year’s crop (time) nor percent agricultural land use (space). Our contrasting results between the new spatiotemporal dominance metric and either crop rotation history or percent agricultural land use or both emphasized that the new method predicts impacts of agricultural intensification on arthropods that were not captured by traditional techniques. In general, pest populations were more abundant in areas with high host dominance, whereas certain predators were less abundant when high disturbance management practices were used (e.g. no cover crop, high insecticide use). Therefore, quantifying spatiotemporal crop dominance refines and strengthens our ability to implicate intense agricultural land use in creating high pest pressure situations through simultaneous bottom-up and top-down effects.

Effect of Sugarcane Litter Compost on Soil Compaction

Intensive agricultural land use tends to reduce the content of organic matter in soil. Organic content in the soil affects the soil's ability to bind water and the efficiency of fertilizer absorption by plants. It’s as well as an important source of nutrients for plants. Therefore, the addition of organic matter in the form of compost (from sugarcane litter) is very important for maintaining the productivity of agricultural land. Use of compost as organic fertilizer on agricultural land is expected to contribute in improving soil structure and increased the production. The aims of the research are to analyze the effect of compost on the physical and mechanical properties of soil and growth of sugarcane (ratoon). The study was conducted on the sugarcane plantations dry land by measuring the physical and mechanical properties of the soil before and after treatment. Parameters measured include: organic matter content, soil moisture content, bulk density and penetration resistance. The data collection of sugarcane growth and soil fertility is done at 4th months old sugarcane (ratoon). The results showed the application of compost increases levels of organic C and N respectively 8% and 21% within 4 months. The use of compost has positive effect on physical and mechanical properties of the soil. It’s indicated by bulk density values were decreased (treatment 15 tons/ha of 1:32 g/cc at baseline to 1.1 g/cc at the final of the study). The average growth of sugarcane with compost is better than without the compost on high growth aspect (53.7 cm vs. 51.1 cm) and larger trunk diameter (1.4 cm vs. 1.0 cm).

Pesticide Risks in Small Streams-How to Get as Close as Possible to the Stress Imposed on Aquatic Organisms.

The risks associated with pesticides in small streams remain poorly characterized. The challenges reside in understanding the complexities of (1) the highly dynamic concentration profiles of (2) several hundred active substances with (3) differing seasonality. The present study addressed these three challenges simultaneously. Five small streams in catchments under intensive agricultural land use were sampled using half-day composite samples from March to August 2015. Of 213 active substances quantified using liquid chromatography-high resolution mass spectrometry, a total of 128 was detected at least at one of the sites. Ecotoxicological acute and/or chronic quality criteria were exceeded for a total of 32 different active substances. The evaluation of risks over time revealed the necessity to evaluate the sequences of different active substances that are imposed on aquatic organisms. In contrast, a substance-specific perspective provides only a very limited assessment. Scenarios for reduction of either temporal resolution, number of substances or seasonal coverage were defined. It could be shown that risks can be underestimated by more than a factor of 10 in vulnerable catchments and that an increased temporal resolution is essential to cover acute risks but that a focused selection of substances is a possibility to reduce expenditures.

Ensuring food security with lower environmental costs under intensive agricultural land use patterns: A case study from China

Rapid population growth and environmental deterioration make ensuring food security with lower environmental costs fundamental to realizing sustainable development in China and other developing countries. The conceptual framework used in this paper integrates the major consequences of intensive agricultural land use and the diverse objectives of policymakers and farmers. It also offers an operational approach, based on farmers' diverse performance in grain production and farmland productivity, to assess food production and environmental impacts under foci-differentiated scenarios. Using data from farmer household surveys, soil surveys, land use images, and statistical yearbooks, this approach was tested using a regional case in China. The results indicate that, among all farmer types, the medium-scale farmers had a better comprehensive performance for grain production for yield, fertilizer and pesticide inputs, labor productivity, and sustainability. Therefore, grain yields can be increased and environmental costs reduced simultaneously through the use of policy instruments that encourage the transformation of trapped farmers into medium-scale farmers and balancing the proportion of single and double cropped rice. In addition, and in order to reduce grain losses caused by natural disasters and to prevent environmental degradation, robust policy measures should be developed to avoid the currently predominant cropping patterns that erode biodiversity.

Suitability of common models to estimate hydrology and diffuse water pollution in North-eastern German lowland catchments with intensive agricultural land use

Various process-based models are extensively being used to analyze and forecast catchment hydrology and water quality. However, it is always important to select the appropriate hydrological and water quality modeling tools to predict and analyze the watershed and also consider their strengths and weaknesses. Different factors such as data availability, hydrological, hydraulic, and water quality processes and their desired level of complexity are crucial for selecting a plausible modeling tool. This review is focused on suitable model selection with a focus on desired hydrological, hydraulic and water quality processes (nitrogen fate and transport in surface, subsurface and groundwater bodies) by keeping in view the typical lowland catchments with intensive agricultural land use, higher groundwater tables, and decreased retention times due to the provision of artificial drainage. In this study, four different physically based, partially and fully distributed integrated water modeling tools, SWAT (soil and water assessment tool), SWIM (soil and water integrated model), HSPF (hydrological simulation program– FORTRAN) and a combination of tools from DHI (MIKE SHE coupled with MIKE 11 and ECO Lab), have been reviewed particularly for the Tollense River catchment located in North-eastern Germany. DHI combined tools and SWAT were more suitable for simulating the desired hydrological processes, but in the case of river hydraulics and water quality, the DHI family of tools has an edge due to their integrated coupling between MIKE SHE, MIKE 11 and ECO Lab. In case of SWAT, it needs to be coupled with another tool to model the hydraulics in the Tollense River as SWAT does not include backwater effects and provision of control structures. However, both SWAT and DHI tools are more data demanding in comparison to SWIM and HSPF. For studying nitrogen fate and transport in unsaturated, saturated, and river zone, HSPF was a better model to simulate the desired nitrogen transformation and transport processes. However, for nitrogen dynamics and transformations in shallow streams, ECO Lab had an edge due its flexibility for inclusion of user-desired water quality parameters and processes. In the case of SWIM, most of the input data and governing equations are similar to SWAT but it does not include water bodies (ponds and lakes), wetlands and drainage systems. In this review, only the processes that were needed to simulate the Tollense River catchment were considered, however the resulted model selection criteria can be generalized to other lowland catchments in Australia, North-western Europe and North America with similar complexity.

The Impact of Intensive Utilization of Cultivated Land on Grain Yields: A Case Study of Shandong Province in China

Using time series data of agriculture in Shandong Province during the period from 2000 to 2015, this paper sets up an assessment system of intensive utilization of cultivated land, which has 4 criteria(input intensity, utilization intensity, output effectiveness and sustainability) consisting of 9 indices, comprehensively estimates the level of intensive use of agricultural land with entropy method, and empirically analyzes the impact of intensive utilization of cultivated land on grain yields through the use of a multivariable linear regression model. The results are shown as follows: (1) The level of intensive utilization of cultivated land in Shandong Province has been fluctuating upwards but not significantly progressing. (2) Grain yield per hectare is positively correlated with output effectiveness and utilization intensity, and the contribution of output effectiveness to grain yield per hectare is more than the other. (3) grain yield per hectare is negatively correlated with input intensity and sustainability. Therefore, in the long-term, cultivated land management strategy should be planned to improve the input intensity, to emphasis on the sustainability of farm land and to promote the consciousness of cultivated land protection in order to increase the productivity of grain yields.

Groundwater Contribution to Surface Water Contamination in a North German Low Land Catchment with Intensive Agricultural Land Use

The contribution of groundwater (GW) to the nitrate loads in surface waters (SW) was exemplarily studied for the river Augraben with a catchment area of 89.9 km2, located in north eastern Germany. The study uses available GW and SW quality data in order to develop a relationship between SW and GW in the Augraben catchment. The calculated ratio of base flow varies from 40% to 80% using various filtering methods of hydrograph separation methods (without taking into account the drainage) in comparison to a calculated GW infiltration of 5% - 7% applying Darcy’s law (upper unconfined aquifer). Drainage was estimated as the difference in base flow obtained through filtering methods of hydrograph separation and the Darcy’s law. Results on the basis of monitoring data and hydrograph separation in quick flow and base flow showed that during winter periods, high concentration in SW has been found parallel to periods of higher GW flow with a strong correlation between SW and GW concentrations. These findings also coincided with the non-vegetation period, i.e. low nitrogen uptake by plants. Overall, nitrate-nitrogen loads at the SW monitoring point (Bei Lindenberg represents the 85% area of the catchment) were 193.5, 97.72, and 122 tons for the year 2010, 2011 and 2012 respectively. Measured GW concentrations in the catchment differ strongly, depending on land use, with elevated concentrations in agricultural areas compared to monitoring points in grass land and in forest areas. In one GW monitoring station, NO3 concentrations exceed the maximum permissible limits (MPL) according to EU water quality standards (MPL = 50 mg/l NO3), up to factor two. High ammonia concentrations at another station may be due to excessive application of manure. The contribution of the different sub-catchments to nitrate load in SW can be ranked in decreasing order in Zone B, D, A and C. Drainage and interflow proved to be a major contributor with 55% - 65% of total load in SW. With the applied method a robust estimation of GW contribution to nitrate loads is feasible using typically available monitoring data of German environmental authorities.

Weed species composition of small‐scale farmlands bears a strong crop‐related and environmental signature

SummaryWeed species loss due to intensive agricultural land use has raised the need to understand how traditional cropland management has sustained a diverse weed flora. We evaluated to what extent cultivation practices and environmental conditions affect the weed species composition of a small‐scale farmland mosaic in Central Transylvania (Romania). We recorded the abundance of weed species and 28 environmental, management and site context variables in 299 fields of maize, cereal and stubble. Using redundancy analysis, we revealed 22 variables with significant net effects, which explained 19.2% of the total variation in species composition. Cropland type had the most pronounced effect on weed composition with a clear distinction between cereal crops, cereal stubble and maize crops. Beyond these differences, the environmental context of croplands was a major driver of weed composition, with significant effects of geographic position, altitude, soil parameters (soil pH, texture, salt and humus content, CaCO3, P2O5, K2O, Na and Mg), as well as plot location (edge vs. core position) and surrounding habitat types (arable field, road margin, meadow, fallow, ditch). Performing a variation partitioning for the cropland types one by one, the environmental variables explained most of the variance compared with crop management. In contrast, when all sites were combined across different cropland types, the crop‐specific factors were more important in explaining variance in weed community composition.

Tomography of anthropogenic nitrate contribution along a mesoscale river

Elevated nitrate concentrations are a thread for water supply and ecological integrity in surface water. Nitrate fluxes obtained by standard monitoring protocols at the catchment outlet strongly integrate spatially and temporally variable processes such as mobilization and turnover. Consequently, inference of dominant nitrate sources is often problematic and challenging in terms of effective river management and prioritization of measures. Here, we combine a spatially highly resolved assessment of nitrate concentration and fluxes along a mesoscale catchment with four years of monitoring data at two representative sites. The catchment is characterized by a strong land use gradient from pristine headwaters to lowland sub-catchments with intense agricultural land use and wastewater sources. We use nitrate concentrations in combination with hydrograph separation and isotopic fingerprinting methods to characterize and quantify nitrate source contribution.The hydrological analysis revealed a clear dominance of base flow during both campaigns. However, the absolute amounts of discharge differed considerably from one another (outlet: 1.42m3s−1 in 2014, 0.43m3s−1 in 2015). Nitrate concentrations are generally low in the pristine headwaters (<3mgL−1) and increase downstream (15 to 16mgL−1) due to the contribution of agricultural and wastewater sources. While the agricultural contribution did not vary in terms of nitrate concentration and isotopic signature between the years, the wastewater contribution strongly increased with decreasing discharge. Wastewater-borne nitrate load in the entire catchment ranged between 19% (2014) and 39% (2015). Long-term monitoring of nitrate concentration and isotopic composition in two sub-catchment exhibits a good agreement with findings from spatially monitoring. In both datasets, isotopic composition indicates that denitrification plays only a minor role. The spatially highly resolved monitoring approach helped to pinpoint hot spots of nitrate inputs into the stream while the long-term information allowed to place results into the context of intra-annual variability.

The black soldier fly, Hermetia illucens - a promising source for sustainable production of proteins, lipids and bioactive substances.

The growing demand worldwide for proteins and lipids cannot be met by the intensive use of agricultural land currently available. Insect mass cultures as a source for proteins and lipids have been in focus for various reasons. An insect with many positive properties is the black soldier fly, Hermetia illucens, whose larvae could be used for the sustainable production of proteins and lipids. Furthermore, the larvae produce bioactive substances which could potentially be used for human and animal welfare.

Toward participatory decision-making in river corridor management: two case studies from the European Alps

River managers are aware that river restoration entails addressing and effectively solving wicked social-ecological problems. Contemporary river corridor management is characterized by a variety of actors with different perspectives and interests, and by complex institutional settings and legal landscapes. Additionally, at the intersection between litho-, hydro-, and biological fields, new research suggests that river restoration should reactivate matter and energy fluxes, re-establish spatial connections with the floodplains, and enhance aquatic and terrestrial habitats without exacerbating flood risk. First, we outline a general structure of participatory river corridor management that addresses the following key requirements: (1) unambiguous, participatory spatial delineation of the river corridor; (2) comprehensive assessment of the river corridor's hydro-geomorphological, ecological, socio-economic and cultural processes; (3) transparency and consistency of the decision-making process; as well as (4) a coherent envisioning process. Subsequently, we present an overview of two river corridor management processes, conducted in South Tyrol, Italy. Specifically, we analysed the Etsch/Adige River corridor between Laas/Lasa and Glurns/Glorenza in the Upper Vinschgau/Venosta valley characterized by intense agricultural land use and the densely populated Eisack/Isarco River corridor in Brixen/Bressanone. Based on structured interviews with project managers, we highlight strengths and shortcomings of the proposed participatory management and envisage procedural improvements.

Natural ponds in an agricultural landscape: External drivers, internal processes, and the role of the terrestrial-aquatic interface

The pleistocenic landscape in North Europe, North Asia and North America is spotted with thousands of natural ponds called kettle holes. They are biological and biogeochemical hotspots. Due to small size, small perimeter and shallow depth biological and biogeochemical processes in kettle holes are closely linked to the dynamics and the emissions of the terrestrial environment. On the other hand, their intriguing high spatial and temporal variability makes a sound understanding of the terrestrial-aquatic link very difficult. It is presumed that intensive agricultural land use during the last decades has resulted in a ubiquitous high nutrient load. However, the water quality encountered at single sites highly depends on internal biogeochemical processes and thus can differ substantially even between adjacent sites.This study aimed at elucidating the interplay between external drivers and internal processes based on a thorough analysis of a comprehensive kettle hole water quality data set. To study the role of external drivers, effects of land use in the adjacent terrestrial environment, effects of vegetation at the interface between terrestrial and aquatic systems, and that of kettle hole morphology on water quality was investigated. None of these drivers was prone to strong with-in year variability. Thus temporal variability of spatial patterns could point to the role of internal biogeochemical processes. To that end, the temporal stability of the respective spatial patterns was studied as well for various solutes. All of these analyses were performed for a set of different variables. Different results for different solutes were then used as a source of information about the respective driving processes. In the Quillow catchment in the Uckermark region, about 100km north of Berlin, Germany, 62 kettle holes have been regularly sampled since 2013. Kettle hole catchments were determined based on a groundwater level map of the uppermost aquifer. The catchments were not clearly related to topography. Spatial patterns of kettle hole water concentration of (earth) alkaline metals and chloride were fairly stable, presumably reflecting solute concentration of the uppermost aquifer. In contrast, spatial patterns of nutrients and redox-sensitive solutes within the kettle holes were hardly correlated between different sampling campaigns. Correspondingly, effects of season, hydrogeomorphic kettle hole type, shore vegetation or land use in the respective catchments were significant but explained only a minor portion of the total variance.It is concluded that internal processes mask effects of the terrestrial environment. There is some evidence that denitrification and phosphorus release from the sediment during frequent periods of hypoxia might play a major role. The latter seems to boost primary production occasionally. These processes do not follow a clear seasonal pattern and are still not well understood.

Factors Influencing Brook Trout (Salvelinus frontinalis) Egg Survival and Development in Streams Influenced by Agriculture

Increased sedimentation in surface waters due to anthropogenic activities can lead to the deterioration of salmonid spawning habitat through infiltration of excessive fine sediment into redds. This study assessed the effects of sediment on salmonid reproductive habitat on Prince Edward Island, Canada by evaluating egg survival and fry length using brook trout egg in situ incubations. In-stream egg incubators were buried in the substrate of streams in three watersheds with between 10 and 69% agricultural land-use during 2012-2013 and 2013-2014. Accumulated incubator sediment load and associated particle size, incubator organic matter and stream parameters temperature, velocity, bed sediment and particle size were measured over the period of study. There was no significant difference in embryo survival among watersheds. Survival was not related to fine sediment; instead, it increased with higher average temperature that was in turn associated with the presence of groundwater upwelling in the stream. The size of the fry was also not significantly different between watersheds with varying agricultural activity. Fry length was most strongly related to sediment organic matter content. Brook trout are widespread in PEI rivers, including in many rivers that have high sediment loads due to intensive agricultural land use. This species may avoid the adverse effect of fine sediment through their natural adaptation of using groundwater upwelling for spawning.

Surface Water Quality of Intensive Farming Areas Within the Santa Lucia River Basin of Uruguay

The Santa Lucia River basin provides drinking water to 60% of Uruguay population. The input of excessive amounts of nitrogen and phosphorus both from point and nonpoint sources could impair surface water quality and prevent its use for human consumption. The objective of this work was to evaluate surface water quality in small catchments under agricultural use located within this river basin. To this end, 5 streams and 4 small polders were surveyed between September 2008 and December 2009. The median concentrations of total phosphorus and total nitrogen in the streams across all sites and periods were 770 and 1659 µg L−1, respectively, exceeding in the case of total phosphorus national and international thresholds. Furthermore, soluble phosphorous, the most readily available form to algae, represented 88.3% of total phosphorus. Concentrations of phosphorous and nitrogen in polders were also high. The eutrophication process of this water bodies could be linked to the intensive agricultural land use in the area because the nutrient input from cities and industries was not relevant in these catchments.

Arizona Quail: Species in Jeopardy?

We begin the 21st century with the Midwestern northern bobwhite (Colinus virginianus) range reduced to a small portion of its historic distribution. This precipitous decline occurred largely during the last quarter of the 20th century, coincident with widespread intensive agricultural land use, unchecked natural plant succession, and frequent severe weather. Various bobwhite enthusiasts of the 1960s–1980s era including Klimstra, Dumke and Stanford had evaluated agricultural land use trends and predicted the near demise of bobwhites that we now lament. Alarmed upland bird hunters have repeatedly spurred policy makers and administrators into action. However, because bobwhites still are only an incidental product of modern agriculture, the potential for reversing declining population trends is limited. Moreover, as society and the wildlife profession become progressively less interested in consumptive uses of wildlife, the political will to appropriate agency resources for bobwhites per se is disappearing. Such a pattern has been seen in the Midwest where bobwhite conservation has become a marginal issue on the periphery of the species’ range (e.g., Ia., Wis., Mich., Ont.). This paradigm shift is occurring in much of the bobwhite’s historic range where habitat and bird populations remain at low levels. The result is that bobwhite culture as we know it (i.e., research, management, and hunting) will decline and be replaced by ecosystem conservation. At the state and national level (e.g., North American Bird Conservation Initiative, Conservation and Reinvestment Act), potential funding for restoration and management of savannas, prairies, agroecosystems, etc., can provide habitat for bobwhites. Bobwhite enthusiasts should embrace this change, and participate in the process to ensure that the needs of bobwhites are included. Importantly, our knowledge base for bobwhites is relatively strong and should bolster efforts to include needs of bobwhite in ecosystem management.

Homogenizing and diversifying effects of intensive agricultural land-use on plant species beta diversity in Central Europe — A call to adapt our conservation measures

The prevention of biodiversity loss in agricultural landscapes to protect ecosystem stability and functions is of major importance to stabilize overall diversity. Intense agriculture leads to a loss in species richness and homogenization of species pools, but the processes behind are poorly understood due to a lack of systematic case studies: The specific impacts by agriculture in contrast to other land-use creating open habitat are not studied as such landscapes hardly exist in temperate regions.Applying systematic grids, we compared the plant species distribution at the landscape scale between an active military training areas in Europe and an adjacent rather intensively used agricultural landscape. As the study areas differ mainly in the type of disturbance regime (agricultural vs. non-agricultural), differences in species pattern can be traced back more or less directly to the management. Species trait analyses and multiple measures of beta diversity were applied to differentiate between species similarities between plots, distance-decay, or nestedness.Contrary to our expectation, overall beta diversity in the agricultural area was not reduced but increased under agricultural. This was probably the result of species nestedness due to fragmentation. The natural process of increasing dissimilarity with distance (distance-decay) was suppressed by intense agricultural land-use, generalist and long-distance dispersers gained importance, while rare species lost continuity.There are two independent processes that need to be addressed separately to halt biodiversity loss in agricultural land. There is a need to conserve semi-natural open habitat patches of diverse size to favor poor dispersers and specialist species. At the same time, we stress the importance of mediating biotic homogenization caused by the decrease of distance-decay: The spread of long-distance dispersers in agricultural fields may be acceptable, however, optimized fertilizer input and erosion control are needed to stop the homogenization of environmental gradients due to nitrogen input into semi-natural habitat.

Groundwater head controls nitrate export from an agricultural lowland catchment

Solute concentration variability is of fundamental importance for the chemical and ecological state of streams. It is often closely related to discharge variability and can be characterized in terms of a solute export regime. Previous studies, especially in lowland catchments, report that nitrate is often exported with an accretion pattern of increasing concentrations with increasing discharge. Several modeling approaches exist to predict the export regime of solutes from the spatial relationship of discharge generating zones with solute availability in the catchment. For a small agriculturally managed lowland catchment in central Germany, we show that this relationship is controlled by the depth to groundwater table and its temporal dynamics. Principal component analysis of groundwater level time series from wells distributed throughout the catchment allowed derivation of a representative groundwater level time series that explained most of the discharge variability. Groundwater sampling revealed consistently decreasing nitrate concentrations with an increasing thickness of the unsaturated zone. The relationships of depth to groundwater table to discharge and to nitrate concentration were parameterized and integrated to successfully model catchment discharge and nitrate export on the basis of groundwater level variations alone. This study shows that intensive and uniform agricultural land use likely results in a clear and consistent concentration-depth relationship of nitrate, which can be utilized in simple approaches to predict stream nitrate export dynamics at the catchment scale.

Near‐neutral carbon dioxide balance at a seminatural, temperate bog ecosystem

AbstractThe majority of peatlands in the temperate zone is subjected to drainage and agricultural land use and have been found to be anthropogenic emission hot spots for greenhouse gases. At the same time, many peatlands receive increased atmospheric nitrogen (N) deposition by intensive agricultural practices. Here we provide eddy covariance measurements determining net ecosystem carbon dioxide (CO2) exchange at a protected but moderately drained ombrotrophic bog in Northwestern Germany over three consecutive years. The region is dominated by intensive agricultural land use with total (wet and dry) atmospheric N deposition being about 25 kg N ha−1 yr−1. The investigated peat bog was a small net CO2 sink during all three years ranging from −9 to −73 g C m−2 yr−1. We found temperature‐ and light‐dependent ecosystem respiration (Reco) and gross primary production, respectively, but only weak correlations to water table depths despite large interannual and seasonal variability. Significant short‐term effects of atmospheric N deposition on CO2 flux components could not be observed, as the primary controlling factors for N deposition and C sequestration, i.e., fertilization of adjacent fields as well as temperature and light availability, respectively, exceeded potential interactions between the two.