Harvest Residue Removal Research Articles

Soil Cu and Zn pools and their availability in response to forest residue management and micronutrient fertilization in a Eucalyptus grandis plantation

Eucalyptus is one of the most commonly planted genera worldwide for commercial timber purposes. Brazil has approximately 25% of the total Eucalyptus spp. planted worldwide. However, nutritional disorders caused by copper (Cu) and zinc (Zn) deficiencies have been more frequent in Eucalyptus plantations. Furthermore, the scientific knowledge regarding micronutrient fertilization is scarce. Sequential extraction can determine the distribution of metals in the soil, giving an order of magnitude to its bioavailability. The present study aimed to assess the soil Cu and Zn pools and evaluate the effects of mineral Cu and Zn fertilization on the nutritional status and nutrient fractionation in a Ferralsol in a cultivated Eucalyptus grandis plantation. The study considered two conditions—namely, forest residue management or removal of forest residues. The treatments included complete fertilization, no application of Cu, no application of Zn, maintenance of forest residues, and total removal of forest residues. High quantities of Cu and Zn were found in the soil, mainly in the low plant-available forms (>60%). There were no differences in the nutritional status of the trees, despite the absence of Cu and Zn via fertilizers and the removal of harvest residues. Foliar Cu concentration was positively correlated with soil exchangeable and oxide-bound Cu content, whereas foliar Zn concentration was positively correlated with soil exchangeable and organic matter-bound Zn content. The access to moderately labile forms of Cu and Zn by eucalypts may justify the absence of response to mineral fertilization, especially in areas where forest residues remain on the soil, and consequently, work as a source of Cu and Zn.

Climate change mitigation potential of biochar from forestry residues under boreal condition

Forest harvest residue is a low-competitive biomass feedstock that is usually left to decay on site after forestry operations. Its removal and pyrolytic conversion to biochar is seen as an opportunity to reduce terrestrial CO2 emissions and mitigate climate change. The mitigation effect of biochar is, however, ultimately dependent on the availability of the biomass feedstock, thus CO2 removal of biochar needs to be assessed in relation to the capacity to supply biochar systems with biomass feedstocks over prolonged time scales, relevant for climate mitigation. In the present study we used an assembly of empirical models to forecast the effects of harvest residue removal on soil C storage and the technical capacity of biochar to mitigate national-scale emissions over the century, using Norway as a case study for boreal conditions. We estimate the mitigation potential to vary between 0.41 and 0.78 Tg CO2 equivalents yr−1, of which 79% could be attributed to increased soil C stock, and 21% to the coproduction of bioenergy. These values correspond to 9–17% of the emissions of the Norwegian agricultural sector and to 0.8–1.5% of the total national emission. This illustrates that deployment of biochar from forest harvest residues in countries with a large forestry sector, relative to economy and population size, is likely to have a relatively small contribution to national emission reduction targets but may have a large effect on agricultural emission and commitments. Strategies for biochar deployment need to consider that biochar's mitigation effect is limited by the feedstock supply which needs to be critically assessed.

Retention of eucalyptus harvest residues reduces soil compaction caused by deep subsoiling

Eucalyptus harvesting, forwarding and soil tillage operations are among the main causes for compaction of forest soils, with potential impacts on productivity. This concern is especially important in areas with soils that are naturally compacted (fragipans and duripans). In these soils, tillage operations include the use of subsoilers that can reach depths of more than one meter and require heavy tractors that exert high pressure on the soil. One of the ways to try to minimize the effect of this compaction is by retaining harvest residues. The objective of this study was to evaluate the impacts of eucalyptus harvesting on soil physical attributes, as well as to determine the potential of different types of residue management to reduce compaction from the soil tillage operation. Two experiments were conducted in the same area with a Yellow Argisol. In the first experiment, compaction caused by mechanized harvesting with harvester + forwarder was evaluated. In the second experiment, different managements of harvest residues were examined as potential modifiers of soil compaction during tillage for new plantings. For this, three managements systems were tested: (1) retention of all harvest residues and litter from the previous rotation (HR + L), (2) retention of litter from the previous rotation (L), and (3) removal of harvest residues and litter from the previous rotation (WR). Before and after harvest, sampling was carried out in the planting rows and inter-rows, and after tillage, samples were collected in the traffic line of the subsoiler-tractor set. In both experiments, undisturbed soil samples were collected from the center of the 0–10, 10–20, 20–40, 40–60, and 60–100 cm layers to determine soil density and total porosity. In each period and site of evaluation, mechanical resistance to penetration up to the 60-cm depth was also determined. The harvesting operation increased soil density at 0–10 and 60–100 cm depths only in the inter-rows. Retention of harvest residues and litter (HR + L) after harvesting avoided increases in soil density and penetration resistance caused by machine traffic during tillage. The results indicate the importance of retaining harvest residues on forest soils for achieving sustainable utilization and for conserving soil quality.

Early rotation biomass and nutrient accumulation of Pinus radiata forests after harvest residue management and fertiliser treatment on contrasting types of soil

The productivity of planted forests depends upon the maintenance of soil fertility and an understanding of the relationships between site fertility and stand productivity. The effects of harvest residue and forest floor management, and fertiliser additions on ecosystem biomass, carbon and nutrient accumulation were evaluated 5 years after establishment of Pinus radiata stands growing on four contrasting soil types at Woodhill, Tarawera, Kinleith, and Golden Downs forest in New Zealand. The harvest residue removal treatments were stem only harvest, whole tree harvest, and whole tree harvest combined with forest floor removal, all with and without mostly urea-nitrogen fertiliser additions (cumulative range across the four sites 400–1150 kg N ha−1). Woodhill forest biomass and nutrient stock results at age 5 years have been previously reported and were added to with new carbon and nitrogen analysis. The results showed for all sites except on recent sands at Woodhill, where soil nutrients were very low, that harvest residue and forest floor removal had limited impact on 5 year old P. radiata productivity, above ground live biomass and nutrient accumulation, and mineral soil nutrient concentrations. Across all sites the whole tree harvest combined with forest floor removal negatively impacted the 5 year old forest floor biomass and nutrient stocks, with variable impact due to whole tree only removal. The addition of large experimental amounts of mineral nitrogen fertiliser increased tree productivity across sites, which was reflected in tree biomass for all sites except Tarawera. Based on these relatively short-term findings, when P. radiata forests in New Zealand are experiencing a peak nutrient demand (highest nutrient demand amount per year), there were limited negative impacts of harvest residue and forest floor removal on forest productivity, tree biomass and nutrient accumulation, and mineral soil nutrient concentrations. The exception was for a sand dune derived soil that had very low soil nutrients resulting in a greater proportion of the forest ecosystem nutrient pool to be held within the tree and forest floor biomass, emphasising the importance of harvest residue and forest floor retention at low nutrient sites.

Effects of nutrient removal by harvesting practices and fertiliser addition on end-of-rotation radiata pine wood quality

With intensification of forest management, there has been increasing focus on the impacts of harvest residue removal on tree growth and long-term site productivity. The intensity of harvest removals, which has a direct impact on the available nutrient pools, influences tree growth and are also likely to impact the quality of wood formed. This study focused on the effects of harvesting residue removal practices (whole tree + forest floor, whole tree and stem only) at the end of the previous rotation and repeated fertiliser addition during the current rotation on selected wood quality attributes. Growth, wood density and standing tree acoustic velocity data were collected from almost 600 radiata pine (Pinus radiata D. Don) trees from long term site productivity trials across New Zealand (Woodhill, Tarawera and Berwick Forests). A sample of 116 trees were felled to obtain detailed wood quality measurements on logs and cross-sectional discs at different heights along the stem. There was little or no effect of different levels of harvesting removal on any of the measures of wood quality. However, repeated fertiliser addition throughout the course of the rotation (up to 3200 kg N ha−1 at Woodhill Forest) did result in adverse impacts on wood density, stiffness, branch size and heartwood content. The degree to which these affect returns to forest growers and end-product performance will depend on the market segment that logs are being sold into. It is recommended that nutritional strategies aimed at increasing forest productivity should incorporate studies to evaluate their potential adverse impacts on wood quality.

Impacts of forest harvest removal and fertiliser additions on end of rotation biomass, carbon and nutrient stocks of Pinus radiata

Forest harvesting practices remove tree biomass and the nutrients that they contain. There is uncertainty around the impact of this nutrient removal on the long-term sustainable production of forests over multiple rotations. To explore the impact of harvest management practices on planted forest sustainability, three long-term trials in Pinus radiata D. Don forests were assessed at the end of their second rotation of 26 to 27 years to determine the impact of harvest residue removal and fertiliser additions on sustainable forest productivity. The harvest residue removal treatments were stem only (SO), whole-tree (WT), and whole-tree plus forest floor (FF) removal with and without urea-nitrogen fertiliser additions (cumulative range across three sites 950 – 3200 kg N ha−1) from early rotation out to mid-rotation (last fertiliser application age range across sites 8 – 22 years). The FF removal treatment reduced soil carbon and nitrogen stocks throughout the subsequent rotation, whereas forest floor carbon and nutrient stocks had recovered from the FF removal treatment by the end of the rotation. Forest productivity was reduced at one site with the FF removal treatment, taking 3 years longer for stems to reach 35 cm diameter at breast height than other residue removal treatments. Between WT and SO harvest residue treatments there were very limited impacts on soil carbon and nutrient stocks, no impact on forest floor mass, carbon and nutrient stocks and the sum of the above ground live biomass, carbon and nutrient stocks or tree productivity. Across all harvest removal treatments fertiliser addition increased soil carbon and nitrogen stocks for sites with low initial soil stocks. The increased soil carbon and nitrogen stocks from fertiliser addition were associated with forest productivity gains with the time to reach 35 cm (diameter at breast height) for one site reduced by 3 – 5 years. Fertiliser addition to sites with FF removal was able to mitigate soil carbon and nitrogen stocks only when very large amounts of fertiliser were added (cumulative amounts of 1150 and 3200 kg N ha−1). The end of rotation results from this long-term study demonstrate the importance of harvest residues and forest floor material at low fertility sites for long-term nutrient sustainability in planted forests.

Indicators of site sensitivity to the removal of forest harvest residues at the sub-continental scale: Mapping, comparisons, and challenges

Many jurisdictions have put forward guidelines to identify sites at risks of soil degradation with the extraction of logging residues. Most guidelines are based on expert opinion and use the precautionary principle because of the lack of strong understanding of what makes a site sensitive to intensive biomass removal. Two main approaches are used: 1-identifying thresholds for specific site properties 2- developing nutrient budget indicators to rate the potential for nutrient deficit. Thanks to the development of digital soil mapping, it is becoming easier to develop maps for such indicators. A crucial question is the reliability of the different indicators. One way of evaluating their reliability is to test the coherence between the geographic locations of sites rated as sensitive by different indicators. In this study, we developed maps of key soil properties and of biogeochemical fluxes for the managed forest land of Canada at a resolution of 250 m. We used three site properties (slope, pH and sand content), as well as three nutrient budget indicators (N Budget, Base cation (BC) Budget and N Stability ratio) that were mapped and compared. The results indicated very little overlap between the areas identified as sensitive by the three site property indicators and very little concordance between sites rated as sensitive by site property indicators and those identified as sensitive by nutrient budget indicators while nutrient budget indicators showed coherence among themselves. Because nutrient budget indicators were found to be more dependent on the amount of nutrient extracted in the harvested biomass, than on the rates of nutrient inputs from the soil or the atmosphere, they tended to rate productive sites as sensitive, to the opposite of site property indicators. These results suggest that different indicators are assessing different processes and different aspects of site sensitivity. Because of the lack of coherence amongst the indicators, it is advisable 1) to use indicators based on the results of long-term monitoring plots, 2) to maintain such long-term observations and 3) to leave on the ground a substantial proportion of harvest residues, especially on sites evaluated as sensitive.

Ground Beetle (Coleoptera: Carabidae) Response to Harvest Residue Retention: Implications for Sustainable Forest Bioenergy Production

Research Highlights: Our study adds to the scant literature on the effects of forest bioenergy on ground beetles (Coleoptera: Carabidae) and contributes new insights into the responses of ground beetle species and functional groups to operational harvest residue retention. We discovered that count of Harpalus pensylvanicus (DeGeer)—a habitat generalist—increased owing to clear-cut harvests but decreased due to harvest residue reductions; these observations uniquely allowed us to separate effects of additive forest disturbances to demonstrate that, contrarily to predictions, a generalist species considered to be adapted to disturbance may be negatively affected by altered habitat elements associated with disturbances from renewable energy development. Background and Objectives: Despite the potential environmental benefits of forest bioenergy, woody biomass harvests raise forest sustainability concerns for some stakeholders. Ground beetles are well established ecological indicators of forest ecosystem health and their life history characteristics are connected to habitat elements that are altered by forest harvesting. Thus, we evaluated the effects of harvest residue retention following woody biomass harvest for forest bioenergy on ground beetles in an operational field experiment. Materials and Methods: We sampled ground beetles using pitfall traps in harvest residue removal treatments representing variable woody biomass retention prescriptions, ranging from no retention to complete retention of all merchantable woody biomass. We replicated treatments in eight clear-cut stands in intensively managed loblolly pine (Pinus taeda L.) forests in North Carolina and Georgia. Results: Harvest residue retention had no effect on ground beetle richness and diversity. However, counts of H. pensylvanicus, Anisodactylus spp., and “burrower” and “fast runner” functional groups, among others, were greater in treatments with no woody biomass harvest than those with no harvest residue retention; all of these ground beetles may confer ecosystem services in forests. We suggest that H. pensylvanicus is a useful indicator species for burrowing and granivorous ground beetle response to harvest residue reductions in recently harvested stands. Lastly, we propose that retaining 15% retention of total harvest residues or more, depending on regional and operational variables, may support beneficial ground beetle populations.

Effects of harvest residue treatments on soil phosphorus fractions and availability in a young Chinese fir plantation

Forest harvesting changes the quantity and quality of organic matter inputs into soil, and thus would alter soil nutrient content and availability. Phosphorus (P) is a key element affecting plant growth. The effects of harvest residue treatments on soil P fractions and availability had not yet been evaluated. In this study, harvest residue retainment (RR), residue removal (R) and residue burning (RB) treatments were manipulated after clear-cutting in a mature Chinese fir (Cunninghamia lanceolata) plantation at the Sanming Forest Ecosystem and Global Change Research Station in Fujian, China. This study focused on the dynamics of soil P fractions and their driving factors in the 0-10 cm and 10-20 cm soil layers after 4-year residue treatments. The results showed that, in RR treatment, the contents of easily-available P, moderately-available P and non-available P at the 0-10 cm soil layer were all significantly higher than those in R treatment, while the contents of moderately-available P and non-available P at the 10-20 cm soil layer was significantly higher than those in RB treatments. The ratios of soil organic carbon (C) to organic P (C:Po) in both layers were over 200 for all the three treatments, with ratios in RR treatment being significantly lower than those in RB and R treatments, indicating that RR could alleviate P limitation in this ecosystem. Moreover, results of the redundancy analysis showed that changes in P fractions were mainly affected by dissolved organic C, free Fe and noncrystalline amorphous Fe. The results suggested that soil organic P and available P were mainly from the decomposition of plant residues, which supported continuous P supply for plant growth. RR could enhance soil P content, thereby improve soil P availability and mitigate P limitation in Chinese fir plantation.

Modelling the nutrient cost of biomass harvesting under different silvicultural and climate scenarios in production forests

Intensifying the use of forest biomass to produce fuelwood, through the removal of harvest residues or reductions in rotation length, increases nutrient outputs and can ultimately lead to reduced soil fertility. We developed a modelling approach for the evaluation of different forest management options under future climate scenarios. This approach allows management systems to be evaluated in terms of their nutrient costs by quantifying several variables: nutrient outputs (N, P, K, Ca and Mg) resulting from harvesting, ecosystem N and P balances, and changes in organic C, N and P stocks in the soil. In addition, we calculated a “nutrient cost index” (in kg-harvested-biomass g-exported-nutrients−1). As part of this study, we looked at the effects of harvesting branches, foliage and stumps in addition to tree stems, as well as the effects of changing rotation length in Pinus pinaster, Pseudotsuga menziesii and Fagus sylvatica forest stands, under contrasting Representative Concentration Pathway climate scenarios (RCPs). Comparably to previous studies, our simulations showed that removing harvest residues and, to a lesser extent, reducing rotation length have high nutrient costs. Climate was also found to have an impact, mainly caused by larger amounts of standing tree biomass, and therefore larger biomass harvests and increased nutrient outputs in the scenario which involved elevated atmospheric CO2. Using contrasting forest management systems and climates, we showed that our modelling approach can be used to guide forest managers in their choice of future silvicultural practices (rotation length, conventional stem-only harvest versus intensive harvest, thinning regime) based on future climate scenarios. Finally, our approach can be used to determine, more accurately than simple allometric relationships, the amounts of nutrients that would need to be applied in order to compensate for losses.

Invertebrate community response to coarse woody debris removal for bioenergy production from intensively managed forests.

Increased market viability of harvest residues as forest bioenergy feedstock may escalate removal of coarse woody debris in managed forests. Meanwhile, many forest invertebrates use coarse woody debris for cover, food, and reproduction. Few studies have explicitly addressed effects of operational-scale woody biomass harvesting on invertebrates following clearcutting. Therefore, we measured invertebrate community response to large-scale harvest residue removal and micro-site manipulations of harvest residue availability in recently clearcut, intensively managed loblolly pine (Pinus taeda) forests in North Carolina (NC; n=4) and Georgia (GA; n=4), USA. We captured 39,794 surface-active invertebrates representing 171 taxonomic groups using pitfall traps situated among micro-site locations (i.e., purposefully retained piles of hardwood stems and piles of conifer stems and areas without coarse woody debris in NC; windrows and no windrows in GA). Micro-site locations were located within six, large-scale treatments (7.16-14.3ha) in clearcuts. Large-scale treatments represented intensive harvest residue removal, 15% and 30% harvest residue retention, and no harvest residue removal. In NC, ground beetles (Coleoptera: Carabidae) and crickets (Orthoptera: Gryllidae) were three times more abundant in treatments with no harvest residue removal than those with the most intensive harvest residue removal and were reduced in treatments that retained 15% or 30% of harvest residues, although not significantly. Invertebrate taxa richness was greater at micro-site locations with retained hardwood and pine (Pinus spp.) harvest residues than those with minimal amounts of coarse woody debris. In both states, relative abundances of several invertebrate taxa, including cave crickets (Orthoptera: Rhaphidophoridae), fungus gnats (Diptera: Mycetophilidae and Sciaridae), millipedes (Diplopoda), and wood roaches (Blattodea: Ectobiidae), were greater at micro-site locations with retained harvest residues than those with minimal coarse woody debris. Intensified woody biomass harvesting without retention of ≥15% of harvest residue volume may reduce invertebrate taxa richness and abundances of some key invertebrate taxa in regenerating stands. Further, harvest residue management during and after woody biomass harvesting may be an important consideration for maintaining invertebrate diversity and conserving invertebrates that are influential in the maintenance of ecosystem function and integrity in young forests.

Response of mineral soil carbon storage to harvest residue retention depends on soil texture: A meta-analysis

Abstract Harvest residue retention or removal can influence soil carbon (C) sequestration during forest management. Many studies have explored the factors that affect the direction and extent of changes in soil C after different harvest residue management practices. However, the effect of soil properties, especially soil texture, on the difference in mineral soil C storage between harvest residue retention and removal treatment are still not fully understood. Using a meta-analysis approach, we investigated the factors that influence the change in mineral soil C stocks following stem-only harvest (SOH), when compared to whole-tree harvest (WTH). We found that the retention of harvest residues associated with the SOH treatment led to 8.2% greater soil C storage in 0–20 cm mineral soils, compared to the WTH treatment. Soil properties (soil clay content and C concentrations) were the most important factors mediating soil C response to residue retention. Relative to the WTH treatment, the SOH treatment showed smaller mineral soil C pools in some high clay content soils, possibly by increasing the mineralization of existing soil organic matter stocks via a priming mechanism. Climate was a poor predictor of differences in treatment effects, with no significant difference between temperate and tropical forests. There were no significant relationships between the treatment effect on mineral soil C and mean annual temperature or precipitation. Both coniferous and broadleaf forests exhibited a significantly higher mineral soil C storage in the 0–20 cm soil layer with the SOH relative to the WTH treatment. Compared to WTH treatment, the higher soil C contents in upper mineral soils after the SOH treatment appeared to last about one decade after harvesting. The findings of this analysis suggest that soil texture and C concentrations in mineral soils should be considered when assessing the impact of forest harvest residue management on soil C pools.

Early regeneration response to aggregated overstory and harvest residue retention in Populus tremuloides (Michx.)-dominated forests

Recent emphasis on increasing structural complexity and species diversity reflective of natural ecosystems through the use of retention harvesting approaches is coinciding with increased demand for forest-derived bioenergy feedstocks, largely sourced through the removal of harvest residues associated with whole-tree harvest. Uncertainties about the consequences of such approaches prompted us to examine the combined impacts of aggregated overstory retention and harvest residue retention on the composition and density of regeneration following biomass harvests on four operational-scale (40 ha) study areas dominated by Populus tremuloides Michx. in northern Minnesota. Whole-tree harvest had no statistically significant effects on initial (2-year) regeneration densities, including root suckers, sprouts, and seedlings relative to conventional, stem-only harvest. The density of shrub stems was also unaffected by harvest residue retention. Despite having a lower mean leaf area index than intact forest controls, aggregates maintained comparable densities of the four most common tree species, individually, as well as all tree species combined. The composition of regeneration within aggregates differed from surrounding harvested areas as expected, but this increase in complexity at the stand scale was achieved without diminishing P. tremuloides densities in the edge area (0–5 m) surrounding aggregates 2 years after harvest. These initial findings suggest even small aggregates of overstory reserves may achieve basic objectives related to structural complexity and sustaining shade-tolerant tree species in harvested units without compromising regeneration objectives for less tolerant species.

Breeding, Early-Successional Bird Response to Forest Harvests for Bioenergy.

Forest regeneration following timber harvest is a principal source of habitat for early-successional birds and characterized by influxes of early-successional vegetation and residual downed woody material. Early-successional birds may use harvest residues for communication, cover, foraging, and nesting. Yet, increased market viability of woody biomass as bioenergy feedstock may intensify harvest residue removal. Our objectives were to: 1) evaluate effects of varying intensities of woody biomass harvest on the early-successional bird community; and (2) document early-successional bird use of harvest residues in regenerating stands. We spot-mapped birds from 15 April– 15 July, 2012–2014, in six woody biomass removal treatments within regenerating stands in North Carolina (n = 4) and Georgia (n = 4), USA. Treatments included clearcut harvest followed by: (1) traditional woody biomass harvest with no specific retention target; (2) 15% retention with harvest residues dispersed; (3) 15% retention with harvest residues clustered; (4) 30% retention with harvest residues dispersed; (5) 30% retention with harvest residues clustered; and (6) no woody biomass harvest (i.e., reference site). We tested for treatment-level effects on breeding bird species diversity and richness, early-successional focal species territory density (combined and individual species), counts of breeding birds detected near, in, or on branches of harvest piles/windrows, counts of breeding bird behaviors, and vegetation composition and structure. Pooled across three breeding seasons, we delineated 536 and 654 territories and detected 2,489 and 4,204 birds in the North Carolina and Georgia treatments, respectively. Woody biomass harvest had limited or short-lived effects on the early-successional, breeding bird community. The successional trajectory of vegetation structure, rather than availability of harvest residues, primarily drove avian use of regenerating stands. However, many breeding bird species used downed wood in addition to vegetation, indicating that harvest residues initially may provide food and cover resources for early-successional birds in regenerating stands prior to vegetation regrowth.

Vegetation response to logging residue removals in Great Lakes aspen forests: Long-term trends under operational management

Conservation of vegetation diversity has been integrated into forest management regimes as stands with high levels of diversity have been shown to possess enhanced ecological services and resilience to disturbance. Effects of intensified forest management and harvesting practices such as logging residue removals for bioenergy on vegetation diversity and community dynamics has been largely overlooked, however. We examined forest vegetation communities under residue removal treatments along a unique 40-yr chronosequence of commercial aspen (Populus spp.) in Upper Michigan to examine potential impacts on species abundance metrics, community structure, and heterogeneity. We hypothesized that residue removals would negatively impact species diversity of both the over- and understory communities, and that these patterns would occur in parallel with shifts in community structure of both strata. Our results show no effect of residue treatment on overstory tree communities; however we did observe an increase in understory species richness, diversity, and evenness in stands where residues were harvested. The understory community structure was correlated with soil total nitrogen levels, yet this pattern was independent of harvest residue treatment. In addition, we observed higher levels of variance in species representation of the understory community when residues were removed, but did not detect any difference in community organization. Overall, our results suggest that the removal of harvest residues can increase variability in vegetation community relationships. We believe that these patterns can be attributed to increased site disturbance and soil scarification through additional equipment trafficking and subsequent changes in micro environmental conditions when residues are harvested.

Effect of Long-Term Continuous Cotton Mono-Cropping on Depletion of Soil NPK and Changes in Some Selected Soil Chemical Characters on Vertisols and Fluvisols

A long-term cotton exhaustion trial was conducted on lowland Vertisols and Fluvisols at Werer Agricultural Research Center during the 1968–2002 in Ethiopia to investigate nutrient depletion rate and changes in selected soil chemical properties. Treatments used include cultivated fallow, control, 80kgN ha_-1, 80-80 kgNP ha_-1, 80-80kgNKha_-1 and 80-80-80kgNPKha_-1 arranged in RCBD with four and six replications in Vertisols and Fluvisols, respectively. The cotton was grown as a test crop and the status of soil N, P, K, OC, pHe and ECe were periodically monitored every seasons. Seed cotton yield had shown significant response to treatments imposed after 10 and 3 years of continuous cotton mono-cropping, respectively, on Vertisols and Fluvisols, and consistently continued for further 3 consecutive periodical checking years. Then onwards, until the end of the experiment, seed cotton yield didn't showed consistent yield response. Combined analysis revealed highly significant (p < 0.01) yield response to N applications. Despite the long-term continuous mining of soil nutrients through seed cotton harvest and crop residue removal, soil analytical result revealed no indication of depletion in total nitrogen, available K and P. Soil pHe (in both soil types) and ECe only in Fluvisols tend show gradual increase.

Validation of an agroecosystem process model (AGRO-BGC) on annual and perennial bioenergy feedstocks

Corn (Zea mays L.) residues and perennial C4 grasses are two Midwest bioenergy feedstock candidates due to their compatibility with agricultural infrastructure and potential for ecosystem service delivery. We validated the ecosystem process model AGRO-BGC by comparing model estimates with empirical observations from corn and perennial C4 grass systems across Wisconsin and Illinois under no-tillage, nitrogen fertilized, and unfertilized management. Validation parameters included soil organic carbon (SOC), total soil nitrogen (N) to 1.2m, aboveground net primary productivity (ANPP), net ecosystem productivity (NEP), and leaf area index (LAI). We parameterized AGRO-BGC to represent ecophysiological characteristics of corn and perennial prairie grasses, and constructed scenarios to represent corresponding edaphic, climate, and management conditions. Unfertilized annual model estimates had normalized mean average errors relative to field measurements of 0.3, 23, and 4tha−1 for ANPP, SOC, and N, respectively. Fertilized simulations erred from observations by 0.6, 29, 5tha−1 for ANPP, SOC, and N, respectively.We also estimated long-term implications of varying residue removal rates on SOC. Model estimates compared to field data tested the hypothesis that long-term increased residue removal decreases SOC. Field observations showed 0.17, 0.09, and a −0.17tCha−1yr−1 change for control, harvest, and bare grass residue removal treatments, respectively. Simulated SOC loss was greatest for the most intensive residue removal scenarios (−0.48 and −0.68tCha−1yr−1 for corn and grass, respectively), compared to no-harvest scenarios that increased SOC by 0.05tCha−1yr−1 for both corn and grass. AGRO-BGC estimated a 0.07tCha−1yr−1 loss under corn residue harvest, while estimating 0.09tCha−1yr−1 loss for grass. Results suggest long-term increased corn and grass residue harvest (beyond grain) for biofuel feedstock will decrease SOC and soil productivity by approximately 15% in corn and 21% in grass systems over 47 years.

Base cation budgets under residue removal in temperate maritime plantation forests

The removal of harvest residues—branches, treetops and needles—has the potential to impact the long-term sustainability of forest soils. In this study we used mass balance calculations to predict the impact of harvesting on ecosystem balances of calcium (Ca), magnesium (Mg), potassium (K) as well as on soil acidification (ANCle) for forests in Ireland. Balances were determined for three harvesting scenarios: stem-only harvest (SOH), stem plus branch harvest (SBH) and whole-tree harvest (WTH). The study was carried out at forty sites—selected on a grid across the country. The sites were plantations of Sitka spruce (Picea sitchensis (Bong.) Carr), Norway spruce (Picea abies (L.) Karst.) and provenances of lodgepole pine (Pinus contorta (Dougl. var. latifolia)). Flux calculations were based on site measurements of standing biomass and soil properties as well as regional maps of atmospheric deposition. Under SOH and SBH, inputs were predicted to be sufficient to meet outputs for Ca, Mg and K budgets. Atmospheric deposition was the most important input to Ca and Mg balances. For K, inputs from mineral weathering were as important as deposition. Under WTH, Ca output was greater than input at 19 of the 40 study sites. However, the difference was small relative to the size of soil Ca pools; at these sites, exchangeable pools could support WTH removal for a median of 220years. Magnesium and K removal under WTH was supported by inputs in deposition and weathering. For soil acidification budgets (ANCle), base cation (BC) removal in harvesting under all scenarios was much greater than that BC generated by weathering, suggesting that soils will become acidified over the long term. There was considerable uncertainty around the calculation of fluxes. For Ca balances, confidence intervals spanned positive and negative values at many sites such that it was not possible to predict the balance of Ca budgets. In addition, uncertainty in flux calculations was particularly important for K budget because soil exchangeable pools were small and could be depleted within one to two rotations.

ESLab application to a boreal watershed in southern Finland: preparing for a virtual research environment of ecosystem services

We report on preparatory work to develop a virtual laboratory for ecosystem services, ESLab, and demonstrate its pilot application in southern Finland. The themes included in the pilot are related to biodiversity conservation, climate mitigation and eutrophication mitigation. ESLab is a research environment for ecosystem services (ES), which considers ES indicators at different landscape scales: habitats, catchments and municipalities and shares the results by a service that utilizes machine readable interfaces. The study area of the pilot application is situated in the boreal region of southern Finland and covers 14 municipalities and ten catchments including forested, agricultural and nature conservation areas. We present case studies including: present carbon budgets of natural ecosystems; future carbon budgets with and without the removal of harvest residues for bioenergy production; and total phosphorus and nitrogen future loads under climate and agricultural yield and price scenarios. The ESLab allows researchers to present and share the results as visual maps, statistics and graphs. Our further aim is to provide a toolbox of easily accessible virtual services for ES researchers, to illustrate the comprehensive societal consequences of multiple decisions (e.g. concerning land use, fertilisation or harvesting) in a changing environment (climate, deposition).

Repeated harvest residue removal reduces E. globulus productivity in the 3rd rotation in south-western Australia

The use of biomass for energy is becoming increasingly popular, with many plantation forestry growers considering selling or using the biomass to generate renewable energy. It is known that this may lead to a net export of nutrients from the site, but the capacity of plantation sites to buffer this and sustain yield has not been quantified. In 2 long-term experiments, we explored the impact of repeated residue removal, retention, or retention of double the quantity of residues over 2 rotations of Eucalyptus globulus in south-western Australia. The 2 sites that we used had contrasting soil types, and we previously reported differential responses of plantation productivity to residue manipulation in the 2nd rotation. In this study we have shown that removal of harvest residues (and litter) into a 3rd rotation of E.globulus resulted in a significant impact on plantation productivity at both sites. It is important to note that a response to residue removal occurred even at a site that was highly productive in the first and second rotations, and which did not respond to residue removal or N fertilizer addition in the 2nd rotation. Retention of harvest residues and litter resulted in a significant increase in soil exchangeable cations at the higher productivity site, but the impacts on total soil C and N stocks were not as clear cut, with no significant changes to either of these, although a trend in the means for increased soil C under the residue retained treatments at the Red Earth site should be monitored into the future.