DIRECT ESTIMATION OF ABOVEGROUND FOREST PRODUCTIVITY THROUGH HYPERSPECTRAL REMOTE SENSING OF CANOPY NITROGEN

The concentration of nitrogen in foliage has been related to rates of net photosynthesis across a wide range of plant species and functional groups and thus represents a simple and biologically meaningful link between terrestrial cycles of carbon and nitrogen. Although foliar N is used by ecosystem models to predict rates of leaf‐level photosynthesis, it has rarely been examined as a direct scalar to stand‐level carbon gain. Establishment of such relationships would greatly simplify the nature of forest C and N linkages, enhancing our ability to derive estimates of forest productivity at landscape to regional scales. Here, we report on a highly predictive relationship between whole‐canopy nitrogen concentration and aboveground forest productivity in diverse forested stands of varying age and species composition across the 360 000‐ha White Mountain National Forest, New Hampshire, USA. We also demonstrate that hyperspectral remote sensing can be used to estimate foliar N concentration, and hence forest production across a large number of contiguous images. Together these data suggest that canopy‐level N concentration is an important correlate of productivity in these forested systems, and that imaging spectrometry of canopy N can provide direct estimates of forest productivity across large landscapes

Soil health metrics reflect yields in long-term cropping system experiments

Soil health metrics with strong links to ecological function and agricultural productivity are needed to ensure that future management of agricultural systems meets sustainability goals. While ecological metrics and crop yields are often considered separately from one another, our work sought to assess the links between the two in an agricultural context where productivity is a key consideration. Here, we investigated the value of soil health tests in terms of their relevance to agricultural management practices and crop yields at contrasting long term cropping systems experiments. One site was on a sandy loam Leptic Podzol and the other on a sandy clay loam Endostagnic Luvisol. Furthermore, the experiments had different management systems. One contained legume-supported rotations with different grass-clover ley durations and organic amendment usage, while the other compared a range of nutrient input options through fertiliser and organic amendments on the same rotation without ley periods. Metrics included field tests (earthworm counts and visual evaluation of soil structure scores) with laboratory analysis of soil structure, chemistry and biology. This analysis included bulk density, macroporosity, pH, available phosphorus, exchangeable potassium, soil organic matter and potentially mineralizable nitrogen. Using a novel combination of long-term experiments, management systems and distinctive soil types, we demonstrated that as well as providing nutrients, agricultural management which resulted in better soil organic matter, pH, potassium and bulk density was correlated with higher crop yields. The importance of ley duration and potentially mineralizable nitrogen to yield in legume-supported systems showed the impact of agricultural management on soil biology. In systems with applications of synthetic fertiliser, earthworm counts and visual evaluation of soil structure scores were correlated with higher yields. We concluded that agricultural management altered yields not just through direct supply of nutrients to crops, but also through the changes in soil health measured by simple metrics

New approach combining food value with nutrient budgeting provides insights into the value of alternative farming systems

Sustainable farming systems provide food for humans while balancing nutrient management. Inclusion or exclusion of livestock has nutrient management implications, as livestock produce food from otherwise inedible crops and their manure is a valuable soil conditioner. However, plant-based diets are becoming more widespread due to perceived environmental benefits. We measure both food production in terms of nourishment to humans (in this study measured by protein, fat, starch and sugar production) and nutrient sustainability in terms of fertiliser use of six rotational farming systems with differences in nutrient management approaches. The arable practices included were the application of synthetic fertilisers, a range of organic amendments, incorporation of crop residues and legume cultivation. Livestock and associated products were included in some systems but excluded in others. The production of protein, fat, starch and sugar was combined with the balance of nitrogen (N), phosphorus (P) and potassium (K) into an overall measure of nutrient use efficiency of human macronutrient production. Across all systems considered, N use efficiency (5-13 kg protein/kg applied N) was lower than P (84-772 kg protein/kg applied P) or K (63-2060 kg protein/kg applied K), and combining synthetic fertiliser use with organic amendment applications raised production significantly while balancing P and K management, regardless of which organic amendment was used. Legume-supported rotations without livestock produced more protein, starch and sugar per unit area than those with livestock. Nutrient balances and nutrient use efficiencies were more sensitive to management changes than purely food production. Using this approach allowed us to identify areas for improvement in food production based on the specific nutritional value of offtakes as opposed to yield overall

New approach combining food value with nutrient budgeting provides insights into the value of alternative farming systems

Sustainable farming systems provide food for humans while balancing nutrient management. Inclusion or exclusion of livestock has nutrient management implications, as livestock produce food from otherwise inedible crops and their manure is a valuable soil conditioner. However, plant-based diets are becoming more widespread due to perceived environmental benefits. We measure both food production in terms of nourishment to humans (in this study measured by protein, fat, starch and sugar production) and nutrient sustainability in terms of fertiliser use of six rotational farming systems with differences in nutrient management approaches. The arable practices included were the application of synthetic fertilisers, a range of organic amendments, incorporation of crop residues and legume cultivation. Livestock and associated products were included in some systems but excluded in others. The production of protein, fat, starch and sugar was combined with the balance of nitrogen (N), phosphorus (P) and potassium (K) into an overall measure of nutrient use efficiency of human macronutrient production. Across all systems considered, N use efficiency (5-13 kg protein/kg applied N) was lower than P (84-772 kg protein/kg applied P) or K (63-2060 kg protein/kg applied K), and combining synthetic fertiliser use with organic amendment applications raised production significantly while balancing P and K management, regardless of which organic amendment was used. Legume-supported rotations without livestock produced more protein, starch and sugar per unit area than those with livestock. Nutrient balances and nutrient use efficiencies were more sensitive to management changes than purely food production. Using this approach allowed us to identify areas for improvement in food production based on the specific nutritional value of offtakes as opposed to yield overall.Peer reviewe

Direct estimation of aboveground forest productivity through hyperspectral remote sensing of canopy nitrogen

Abstract. The concentration of nitrogen in foliage has been related to rates of net photosynthesis across a wide range of plant species and functional groups and thus represents a simple and biologically meaningful link between terrestrial cycles of carbon and nitrogen. Although foliar N is used by ecosystem models to predict rates of leaf-level photosynthesis, it has rarely been examined as a direct scalar to stand-level carbon gain. Establishment of such relationships would greatly simplify the nature of forest C and N linkages, enhancing our ability to derive estimates of forest productivity at landscape to regional scales. Here, we report on a highly predictive relationship between whole-canopy nitrogen concentration and aboveground forest productivity in diverse forested stands of varying age and species composition across the 360 000-ha White Mountain National Forest, New Hampshire, USA. We also demonstrate that hyperspectral remote sensing can be used to estimate foliar N concentration, and hence forest production across a large number of contiguous images. Together these data suggest that canopy-level N concentration is an important correlate of productivity in these forested systems, and that imaging spectrometry of canopy N can provide direct estimates of forest productivity across large landscapes

Choosing Organic Pesticides over Synthetic Pesticides May Not Effectively Mitigate Environmental Risk in Soybeans

Background: Selection of pesticides with small ecological footprints is a key factor in developing sustainable agricultural systems. Policy guiding the selection of pesticides often emphasizes natural products and organic-certified pesticides to increase sustainability, because of the prevailing public opinion that natural products are uniformly safer, and thus more environmentally friendly, than synthetic chemicals. Methodology/Principal Findings: We report the results of a study examining the environmental impact of several new synthetic and certified organic insecticides under consideration as reduced-risk insecticides for soybean aphid (Aphis glycines) control, using established and novel methodologies to directly quantify pesticide impact in terms of biocontrol services. We found that in addition to reduced efficacy against aphids compared to novel synthetic insecticides, organic approved insecticides had a similar or even greater negative impact on several natural enemy species in lab studies, were more detrimental to biological control organisms in field experiments, and had higher Environmental Impact Quotients at field use rates. Conclusions/Significance: These data bring into caution the widely held assumption that organic pesticides are more environmentally benign than synthetic ones. All pesticides must be evaluated using an empirically-based risk assessment