Contrasting Land Management Research Articles

Climate factors rather than human activities controlled NDVI trends across wet meadow areas in the Andes Centrales of Argentina

In the Andes of southern South America, wet meadows are much more productive than nearby arid areas. Human activities, along with climate variations may reduce the productivity of these ecosystems. However, we do not know what the relative effect of climate and human activities on their degradation status is. Here, we first quantified the degradation extent through the temporal trend of normalized difference vegetation index (NDVI), a proxy of productivity, from 1999 to 2017. We did it in 736 wet meadow areas inserted in three nearby zones with contrasting land management. Second, we analyzed the relationship between NDVI and a large-scale mode of climate variability (El Niño Southern Oscillation, ENSO) and regional climate variables (precipitation and temperature) through a structured climate model. Finally, we evaluated human activities’ effects through the temporal trends in the residuals of the climate model. Independently of land management, NDVI trends were mainly negative and affected 56% of the wet meadow areas. The climate model indicated that NDVI increased under La Niña, cool and wet years. Regarding land management, the degradation level was similar across the contrasted land management. Our results suggest that climate factors rather than human activities influenced the degradation process in these areas.

Biodiversity decline with increasing crop productivity in agricultural fields revealed by satellite remote sensing

Increasing land-use intensity is a main driver of biodiversity loss in farmland, but measuring proxies for land-use intensity across entire landscapes is challenging. Here, we develop a novel method for the assessment of the impact of land-use intensity on biodiversity in agricultural landscapes using remote sensing parameters derived from the Sentinel-2 satellites. We link crop phenology and productivity parameters derived from time-series of a two-band enhanced vegetation index with biodiversity indicators (insect pollinators and insect-pollinated vascular plants) in agricultural fields in southern Sweden, with contrasting land management (i.e. conventional and organic farming). Our results show that arable land-use intensity in cereal systems dominated by spring-sown cereals can be approximated using Sentinel-2 productivity parameters. This was shown by the significant positive correlations between the amplitude and maximum value of the enhanced vegetation index on one side and farmer reported yields on the other. We also found that conventional cereal fields had 17% higher maximum and 13% higher amplitude of their enhanced vegetation index than organic fields. Sentinel-2 derived parameters were more strongly correlated with the abundance and species richness of bumblebees and the richness of vascular plants than the abundance and species richness of butterflies. The relationships we found between biodiversity and crop production proxies are consistent with predictions that increasing agricultural land-use intensity decreases field biodiversity. The newly developed method based on crop phenology and productivity parameters derived from Sentinel-2 data serves as a proof of concept for the assessment of the impact of land-use intensity on biodiversity over cereal fields across larger areas. It enables the estimation of arable productivity in cereal systems, which can then be used by ecologists and develop tools for land managers as a proxy for land-use intensity. Coupled with spatially explicit databases on agricultural land-use, this method will enable crop-specific cereal productivity estimation across large geographical regions.

Land use patterns influence the distribution of potentially toxic elements in soils of the Usangu Basin, Tanzania

Spatial distribution of Potentially Toxic Elements (PTEs) in agricultural soils in Usangu Basin (Mbeya Region)-Tanzania were conducted. The study included three land-use types (paddy farming, maize farming, and conserved community forest areas). About 198 soil samples were collected from November to December 2019 across contrasting land management schemes (Group I dominated by agricultural areas versus Group II dominated by residential and agricultural areas). Total (aqua regia extracts) and bioavailable (Mehlich 3 extracts) PTEs concentrations were analyzed. For Group I and II areas, total and bioavailable concentrations (mg/kg dry weight, mean values) of some PTEs were: chromium 1662 ± 5.2 μg/kg for Group I and 1307 ± 3.9 μg/kg for Group II (Total), 55.1 ± 37.1 μg/kg for Group I and 19.2 ± 21.6 μg/kg for Group II (bioavailable); and lead 5272 ± 1650 μg/kg for Group I and 6656 ± 1994 μg/kg for Group II (Total), 1870 ± 800 μg/kg for Group I and 1730 ± 530 μg/kg for Group II (bioavailable). Soil total PTEs such as cadmium and lead were generally lower in Group I areas than in Group II areas. The reverse scenario was observed for copper. Farming areas had high PTEs concentration than non-farming areas because of anthropogenic activities. Overall, soil total concentrations of Fe (99.5%), As (87%), Se (66%), and Hg (12%) were above Tanzanian Maximum Allowable Limits. This study provides essential baseline information to support environmental risk assessment of PTEs in Tanzanian agro-ecosystem.

Quantifying contaminant losses to water from pastoral landuses in New Zealand I. Development of a spatial framework for assessing losses at a farm scale

ABSTRACT Assessing the effectiveness of mitigation measures for reducing contaminant losses to water from pastoral farming systems is a challenging task. Two important factors that contribute to this challenge are (i) the considerable spatial variability in landscape vulnerabilities to contaminant loss and (ii) differing land use pressures created by contrasting land management practices that are employed on farms. An approach is described that benchmarks nitrogen (N), phosphorus (P) and sediment discharges for representative dairy and sheep-beef farming types (hereafter referred to as ‘typologies’) that differ according to inherent landscape vulnerability features or land use pressures created by some key management practices. Landscape vulnerabilities can be defined as the soil, topography and climate factors that are known to influence the inherent risk of contaminant transport to water, whereas land use pressures reflect the diverse set of farm inputs and feed, stock and soil management practices that determine contaminant sources. The analysis was constructed using land use pressure information for the year 2015 contained within Dairybase records held by DairyNZ and farm class surveys reported by Beef + Lamb NZ. Published information sources and expert opinion from rural professionals were also used to define land use pressures for typologies in 1995.

Significant effects on soil microbial communities were not detected after strategic tillage following 44 years of conventional or no-tillage management

Strategic tillage (ST) has been proposed to help control weeds that germinate during fallow-periods in continuous no till (NT) farming systems, but its effects on soil biological properties are unclear. ST is a type of reduced tillage (RT) that places particular emphasis during the decision-making process on agro-climatic conditions, and the frequency, timing and implements used to till. Here, we assessed the impacts of one-time ST following 44 years of continuous NT or conventional tillage (CT) on soil microbial diversity, biomass, enzymatic activity and substrate utilisation potential at two depths. The composition of bacterial and archaeal communities differed significantly between contrasting land management (CT vs NT); albeit albeit no differences were observed after ST. Meanwhile, fungal community composition was not affected by contrasting land management or ST. Biological indicators for catabolic diversity, microbial biomass and enzymatic activity showed no significant changes after ST operation. Our results suggest that, in the short-term (13 months), ST exerts only minor impacts on a range of biological properties, as well as, bacterial, archaeal and fungal diversity. Hence, ST has the potential to be used as a strategy to control weeds and diseases without compromising soil health.

Land use affects temperature sensitivity of soil organic carbon decomposition in macroaggregates but not in bulk soils in subtropical Oxisols of Queensland, Australia

The turnover of soil organic carbon (SOC) under different land uses plays an important role in terrestrial carbon (C) cycling. However, the effects of warming on C decomposition dynamics have not been resolved due to seemingly inconsistent results among different experiments. Hence, the objective of this work was to assess soil aggregate-associated C and temperature sensitivity of SOC decomposition within bulk soils and aggregates under two contrasting land management systems in subtropical southern Queensland.We examined the temperature sensitivity of SOC decomposition (Q10) and activation energy required for soil C mineralization (Ea) from bulk soils (<8 mm), large macroaggregates (2−8 mm) and small macroaggregates (0.25−2 mm), as well as key C and N cycling enzyme activities in the surface (0−10 cm) soils of an Oxisol. The two land uses studied were: undisturbed rainforest and 115-year-old kikuyu grass (Pennisetum clandestinum) pasture. Bulk soils as well as their large and small macroaggregates were separately incubated at two temperatures (17 °C and 27 °C) for 124 d. We observed that the pasture soils had more small macroaggregates but less microaggregates than the forest soils. However, all fractions in the forest contained significantly higher SOC than those in the pasture. Potential soil enzyme activities per unit SOC within bulk soils and macroaggregates for N-acetyl β-glucosaminidase, α-glucosidase, and phenol oxidase were higher in the pasture than in the forest. The cumulative C mineralization values of bulk soils under the forest vegetation were 16 % higher than for pasture at 17 °C and 97 % higher than pasture at 27 °C. Cumulative C mineralization from large macroaggregates of both land uses were more than that from small macroaggregates. However, the Ea and Q10 values of bulk soils were similar for both the forest and pasture soils. For the large macroaggregates, the Ea value was ∼78 % higher for the pasture soil than for the forest soil, with the Q10 value also being 73 % higher in the pasture soil. However, the opposite was observed for the small macroaggregates, with Ea and Q10 values being higher in the forest soil. The contrasting nature of Q10 from large and small macroaggregates in Oxisols suggests that the feedback from SOC decomposition in response to changing temperature, that is, global warming is closely associated with soil aggregation.

Forecasting tillage and soil warming effects on earthworm populations

Abstract Healthy soils are crucial for sustainable food production, but tillage limits the biological regulation of essential ecosystem services. Better understanding of the mechanisms driving management effects on soil ecosystem engineers is needed to support sustainable management under environmental change. This paper presents the Energy–Environment–Earthworm (EEEworm) model, a mechanistic individual‐based model of Lumbricus terrestris populations. Lumbricus terrestris is a dominant earthworm species in undisturbed habitats and is closely associated with numerous ecosystem services such as water flow regulation, soil structure and crop production. In reduced tillage agriculture, a decline in mechanical disturbance allows for L. terrestris proliferation, whilst the activities of L. terrestris can replace many of the soil functions provided by tillage. Extensive EEEworm validation with eight published studies (average R2 = .84) demonstrates a mechanistic approach which can extrapolate between diverse soil, management and weather conditions. EEEworm simulation experiments elucidate that a combination of direct and indirect tillage effects leads to population declines in tilled fields, with litter removal from the soil surface being the main driver. We investigate the effects of different tillage intensities under historical and projected soil warming conditions and find that future warmer and drier soils in our simulation exacerbate the effects of deep ploughing on L. terrestris population declines. These effects result from warmer and drier soil conditions increasing individual metabolic rates and tillage reducing food availability to meet energy demands. Synthesis and applications. Pre‐emptive strategies to mitigate climate change impacts on soil health in agroecosystems should focus on decreasing tillage intensity and retention of crop residues following tillage. Energy–Environment–Earthworm (EEEworm) has the potential to benefit land managers, policy makers, risk assessors and regulators by providing a tool to forecast how soil systems respond to combinations of land management and environmental change. To allow better cost–benefit analysis of contrasting land management systems, a future aim of mechanistic models like EEEworm is to incorporate the links between earthworm populations, soil functions and ecosystem services.

Landscape host abundance and configuration regulate periodic outbreak behavior in spruce budworm Choristoneura fumiferana

Landscape‐level forest management has long been hypothesized to affect forest insect outbreak dynamics, but empirical evidence remains elusive. We hypothesized that the combination of increased hardwood relative to host tree species, prevalence of younger forests, and fragmentation of those forests due to forest harvesting legacies would reduce outbreak intensity, increase outbreak frequency, and decrease spatial synchrony in spruce budworm Choristoneura fumiferana outbreaks. We investigated these hypotheses using tree ring samples collected across 51 sites pooled into 16 subareas distributed across a large ecoregion spanning the international border between Ontario (Canada), and Minnesota (USA). This ecoregion contains contrasting land management zones with clear differences in forest landscape structure (i.e. forest composition and spatial configuration) while minimizing the confounding influence of climate. Cluster analyses of the 76‐yr time‐series generally grouped by subareas found within the same land management zone. Spatial nonparametric covariance analysis indicated that the highest and lowest degree of spatial synchrony of spruce budworm outbreaks were found within unmanaged wilderness and lands managed at fine spatial scales in Minnesota, respectively. Using multivariate analysis, we also found that forest composition, configuration, and climate together accounted for a total of 40% of the variance in outbreak chronologies, with a high level of shared variance between composition and configuration (13%) and between composition and climate (9%). At the scale of our study, climate on its own did not explain any of the spatial variation in outbreaks. Outbreaks were of higher frequency, lower intensity, and less spatially synchronized in more fragmented, younger forests with a lower proportion of host species, with opposing outbreak characteristics observed in regions characterised by older forests with more concentrated host species. Our study is the first quantitative evaluation of the long‐standing ‘silvicultural hypothesis’ of spruce budworm management specifically conducted at a spatio‐temporal scale for which it was intended.

Isotopic Tracing of Thallium Contamination in Soils Affected by Emissions from Coal-Fired Power Plants.

Here, for the first time, we report the thallium (Tl) isotope record in moderately contaminated soils with contrasting land management (forest and meadow soils), which have been affected by emissions from coal-fired power plants. Our findings clearly demonstrate that Tl of anthropogenic (high-temperature) origin with light isotope composition was deposited onto the studied soils, where heavier Tl (ε(205)Tl ∼ -1) naturally occurs. The results show a positive linear relationship (R(2) = 0.71) between 1/Tl and the isotope record, as determined for all the soils and bedrocks, also indicative of binary Tl mixing between two dominant reservoirs. We also identified significant Tl isotope variations within the products from coal combustion and thermo-desorption experiments with local Tl-rich coal pyrite. Bottom ash exhibited the heaviest Tl isotope composition (ε(205)Tl ∼ 0), followed by fly ash (ε(205)Tl between -2.5 and -2.8) and volatile Tl fractions (ε(205)Tl between -6.2 and -10.3), suggesting partial Tl isotope fractionations. Despite the evident role of soil processes in the isotope redistributions, we demonstrate that Tl contamination can be traced in soils and propose that the isotope data represent a possible tool to aid our understanding of postdepositional Tl dynamics in surface environments for the future.

Influence of macrophyte spatial architecture on periphyton and macroinvertebrate community structure in shallow water bodies under contrasting land management

The role of aquatic macrophyte architecture (leaf architecture complexity) in structuring and determining associated algal and invertebrate communities was studied in shallow ditches in coastal marshes under contrasting management (pasture and arable agriculture) and hence nutrient regime (eutrophic and hypertrophic). Variations in colonisation rates between functional feeding groups (macroinvertebrate community) and periphyton colonisation patterns were examined on artificial substrata units recreating three macrophyte leaf architectures-dissected, broad and flat-floating. Units increased in architectural complexity but total colonisable area was constant (255 cm 2). Habitat complexity had a major effect on macroinvertebrate colonisation in the pasture ditch units, particularly on predator species (Coleoptera, Hemiptera and Odonata) as well as for grazers, particularly Gastropoda. Macroinvertebrate abundance was significantly higher on the dissected leafed units. Rates of taxon colonisation (colonisation rates - decolonisation rates) were higher on the dissected and flat-floating leaf units (1.57 and 1.4 species day-1, respectively) as was species richness (46 and 27 species, respectively) reaching equilibrium, when rates became equal, in about three weeks. Habitat complexity also modified periphyton assemblages. Algae-substrata associations and species richness were higher on the broad and dissected units in the pasture ditch (47 spp. and 43 of diatoms spp.; 11 and 15 non-diatoms spp., respectively). Conversely, arable ditch units had a significantly higher density of periphyton and variations in community size and composition, with a few dominant non-diatom taxa, such as Lyngbya birgei, Anabaena spiroides, Spirulina princeps and Oedogonium sp., associated with reduced macroinvertebrate diversity and colonisation, in particular for grazer species. Thus, the experiments demonstrated that high architectural complexity plays an important role in shallow coastal ditches, promoting variation in food availability - more heterogeneous algal assemblages - and macroinvertebrate community succession. Hence, external variables, such as system productivity (eutrophic vs hypertrophic; bottom-up implications), seem to regulate and modify the effects of habitat spatial heterogeneity through epiphytic community growth and consequently macroinvertebrate colonization (species turnover rate). © 2010 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.

Monitoring contrasting land management in the savanna landscapes of northern Australia.

We compared measures of ecosystem state across six adjacent land-tenure groups in the intact tropical savanna landscapes of northern Australia. Tenure groups include two managed by Aboriginal owners, two national parks, a cluster of pastoral leases, and a military training area. This information is of relevance to the debate about the role of indigenous lands in the Australian conservation estate. The timing and frequency of fire was determined by satellite imagery; the biomass and composition of the herb-layer and the abundance of large feral herbivores by field surveys; and weediness by analysis of a Herbarium database. European tenures varied greatly in fire frequencies but were consistently burnt earlier in the dry season than the two Aboriginal tenures, the latter having intermediate fire frequencies. Weeds were more frequent in the European tenures, whilst feral animals were most abundant in the Aboriginal tenures. This variation strongly implies a signature of current management and/or recent environmental history. We identify indices suitable for monitoring of management outcomes in an extensive and sparsely populated landscape. Aboriginal land offers a unique opportunity for the conservation of biodiversity through the maintenance of traditional fire regimes. However, without financial support, traditional practices may prove unsustainable both economically and because exotic weeds and feral animals will alter fire regimes. An additional return on investment in Aboriginal land management is likely to be improved livelihoods and health outcomes for these disadvantaged communities.

Nutrient management in New Zealand pastures— recent developments and future issues

In this publication we review recent research and understandings of nutrient flows and losses, and management practices on grazed pastoral farms in New Zealand. Developments in nutrient management principles in recent years have seen a much greater focus on practices and technologies that minimise the leakage of nutrients, especially nitrogen (N) and phosphorus (P), from farms to the wider environment. This has seen farm nutrient management planning shift from a relatively small set of procedures designed to optimise fertiliser application rates for pasture and animal production to a comprehensive whole‐farm nutrient management approach that considers a range of issues to ensure both farm productivity and environmental outcomes are achieved. These include consideration of factors such as multiple sources of nutrient imports to farms, the optimal re‐use and re‐distribution of nutrient sources generated within the farm (such as farm dairy effluent), identification of the risks associated with applying various nutrient forms to contrasting land management units, and an econometric evaluation of farm fertilisation practices. The development of nutrient budgeting and econometric decision support tools has greatly aided putting these more complex whole‐farm nutrient management systems into practice. Research has also identified a suite of mitigation systems and technological measures that appear to be able to deliver substantial reductions in nutrient losses from pastoral farms. However, issues of cost, complexity, compatibility with the current farm system, and a perceived uncertainty of actual environmental benefits are identified as key barriers to adoption of some of these technologies. Farmers accordingly identified that their main requirement for improved nutrient management planning systems was flexibility in how they would meet their environmental targets. The provision of readily discernible information and tools defining the economic and environmental implications of a range of proven management or mitigation practices is a key requirement to achieve this.

Changes in soil erosion associated with the shift from conventional tillage to a no-tillage system, documented using 137Cs measurements

Caesium-137 measurements have been used to document changes in the rate and extent of soil erosion associated with the shift from conventional tillage to a no-till system on a farm in south-central Chile. The study site is located in the Coastal Mountains of the 9th Region (38°37′S 73°04′W), and is characterized by Araucano series Ultisols (Typic Hapludult), a temperate climate and a mean annual precipitation of 1100 mm year −1. A field, which was under conventional tillage until May 1986 and which was subsequently managed using a no-till system, was selected for the study. An approach for using 137Cs measurements to quantify the medium-term erosion and deposition rates associated with the periods of contrasting land management documented previously was employed. This approach involves both a standard method and a simplified method, which permits a larger number of sampling points to be used. In this study, emphasis was placed on application of the simplified method, which has the important advantage of requiring only two 137Cs measurements per sampling point. The results obtained for the study field showed that the implementation of no-till practices, including crop residue management, coincided with a reduction in the net erosion rate by about 87% and the proportion of the study area subject to erosion from 100% to 57%, and therefore significantly decreased soil and nutrient loss. Reduced soil and nutrient loss has important on-site benefits, in terms of sustainable management of the soil resource and maintaining crop productivity, as well as reducing off-site problems associated with the degradation of river water quality.

Effect of land management on runoff and soil losses from two small watersheds in St Lucia

AbstractThe influence of land use on runoff and soil loss was assessed on two small watersheds in the Eastern Caribbean island of St Lucia, under contrasting land management regimes. The data generated from these watersheds revealed that the soil losses from an intensively cultivated agricultural watershed were 20‐times higher in magnitude than that of a forested watershed both for peak rainfall event and for total duration of analysis. This was due to higher surface runoff rates and exposure of soil to direct raindrop impact within cultivated areas. Whereas the forest canopy cover in combination with higher infiltration capacities of the forested land reduced the erosive runoff from the forest watershed and thus the soil loss. Moreover, the energy intensities of large storms in excess of 40 mm were estimated and found to range between 400 MJ mm ha−1 h−1 and 1834 MJ mm ha−1 h−1.1Megajoules‐millimeters per hectare‐hour. Soil loss from the agricultural watershed was strongly correlated (R2 = 0·85) to storm energy‐intensity (EI30). However, the correlation of soil loss with the EI30 (R2 = 0·71) was poor for the forest watershed due to the effect of canopy vegetation, which significantly reduced the energy of raindrop impact. Over the study period, cumulative soil losses were 10·0 t ha−1 for the agricultural site and 0·5 t ha−1 for the forest site.2Metric tons per hectare. The largest storm observed during the study period resulted in erosion losses of 3·78 t ha−1 and 0·2 t ha−1 from the agricultural and forest sites respectively. The regression models were developed using the measured data for prediction of runoff and soil loss over the watersheds of St Lucia under similar conditions. This study contributed towards efficient watershed management planning and implementation of suitable water conservation measures in St Lucia. Copyright © 2005 John Wiley &amp; Sons, Ltd.

An analysis of the long-term variation in stream water quality for three upland catchments at Loch Dee (Galloway, S.W. Scotland) under contrasting land management

Abstract. A long term record of water chemistry, consisting of twenty years of weekly spot samples, from three sub-catchments draining into a loch and the loch outflow in Galloway, S.W. Scotland have been analysed. The analysis undertaken consisted of a three component statistical trend model. The technique allows the identification of long-term, seasonal and short-term trends, as well as differentiation between base flow and high flow responses. The land usage in the three sub-catchments is moorland, forest and forest plus lime. The results show that, since the mid-1980s, there has been a gradual decline in stream-water sulphate of the same order as reductions in the deposition of non-marine sulphate. Superimposed on this trend are somewhat random but considerable perturbations to this decline, caused by sea-salt deposition. There is no evidence of changes in surface water nitrate concentrations. The influence of different land management is evident in the sulphate, nitrate and pH data, whilst variations in calcium concentrations are also a product of differences in hydrological routing and the impact of sea-salt episodes. Keywords: trend analysis, acid deposition, land management, water quality, sea-salts, Galloway, S.W. Scotland