The Madingley general ecosystem model predicts bushmeat yields,species extinction rates and ecosystem-level impacts of bushmeat harvesting

Traditional approaches to guiding decisions about harvesting bushmeat often employ single-species population dynamic models, which require species- and location-specific data, are missing ecological processes such as multi-trophic interactions, cannot represent multi-species harvesting and cannot predict the broader ecosystem impacts of harvesting. In order to explore an alternative approach to devising sustainable harvesting strategies, we employ the Madingley general ecosystem model, which can simulate ecosystem dynamics in response to multi-species harvesting given nothing other than location-specific climate data. We used the model to examine yield, extinctions and broader ecosystem impacts, for a range of harvesting intensities of duiker-sized endothermic herbivores. Duiker antelope (such as Cephalophus callipygus and Cephalophus dorsalis) are the most heavily hunted species in sub-Saharan Africa, contributing 34–95% of all bushmeat in the Congo Basin. Across a range of harvesting rates, the Madingley model gave estimates for optimal harvesting rate, and extinction rate, that were qualitatively and quantitatively similar to the estimates from conventional single-species Beverton–Holt model. Predicted yields were somewhat greater (around five times, on average) for the Madingley model than the Beverton–Holt, which is partly attributable to the fact that the Madingley simulates multi-species harvesting from an initially pristine ecosystem. Also, the Madingley model predicted a background local extinction probability for the target species of at least 10%. At medium and high levels of harvesting of duiker-sized herbivores, the Madingley model predicted statistically significant, but moderate, reductions in the densities of the targeted functional group; increases in small-bodied herbivores; decreases in large-bodied carnivores; and minimal ecosystem-level impacts overall. The results illustrate how general ecosystem models such as the Madingley model could potentially be used more widely to help estimate sustainable harvesting rates, bushmeat yields and broader ecosystem impacts across different locations and target species.     

Harvesting Systems,Soil Cultivation,and Nitrogen Rate Associated with Sugarcane Yield

The adoption of mechanical harvesting of green cane gives rise to concerns as to whether systems developed under burnt cane harvesting are applicable to a green cane harvesting system. In particular, tillage, which is an integral part of the burnt cane system, may no longer be necessary, and the nitrogen fertilizer rates required may need to be replaced due to the large amounts of organic matter being returned to the soil after green cane harvesting. Mechanical harvesting is relatively new in Brazil and little is known about its effect on other sugarcane production strategies. This work aimed to evaluate sugarcane performance under not only different harvesting and cultivation systems, but also different nitrogen fertilizer rates over a 3-year period. The experimental design was a split plot with harvesting systems (burnt vs. green) as main plots, cultivation (interrow vs. no cultivation) as sub plots, and nitrogen rates as sub-sub plots. The harvesting systems produced similar sugarcane yields throughout the experimental period, which demonstrates that the harvest systems do not influence sugarcane yield. Mechanical tillage practices in interrow after harvesting had no impact on stalk yield or sugar quality, indicating no necessity for this operation in the following crop. Ratoon nitrogen fertilization promoted an increase of stalk and sugar yield, with highest yields obtained at the rate of 130 kg ha^?1 N. However, there was no interaction between harvesting system and nitrogen rate.     

Testing sustainable management in Northern Chile: harvesting Macrocystis pyrifera (Phaeophyceae, Laminariales). A case study

Kelp harvesting in northern Chile is managed by local fishermen and is part of an organized industry. However, the lack of standardized harvesting protocols has made regulation difficult. This, in combination with the impacts of oceanographic disturbances has resulted in some kelp populations being considerably reduced during the last decade. Consequently, harvest methods that maintain kelp resources are sorely needed if harvesting is to remain a viable industry in Chile. Here, experiments were done to identify sustainable methods for harvesting Macrocystis pyrifera along the coast of northern Chile. Three methods were compared with regard to their impacts on kelp populations; one that involves extracting half of the fronds from each individual in a population, one that involves extracting all the fronds from half of the individuals in a population, and a third that involves extracting all the fronds from all of the individuals in a population (i.e., the method currently used). Following this, populations were evaluated over a 2-month period to monitor re-growth of the remaining individuals and recruitment of new individuals, as well as changes in understory algal diversity and herbivore abundance. Our results indicate that removing half of the fronds from each individual in a population was the best method for maintaining the resource for future harvest because, it (1) maintains rapid growth of new fronds on the harvested individuals, (2) promotes recruitment of new individuals, and (3) reduces herbivore densities through physical abrasion. Consequently, this method is recommended for future harvesting of M. pyrifera in Northern Chile.     

Anthropogenic harvesting pressure and changes in life history: insights from a rocky intertidal limpet

The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (~0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that population-level demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting.     

Harvesting Effects,Recovery Mechanisms,and Management Strategies for a Long-Lived and Structural Precious Coral

Overexploitation is a major threat for the integrity of marine ecosystems. Understanding the ecological consequences of different extractive practices and the mechanisms underlying the recovery of populations is essential to ensure sustainable management plans. Precious corals are long-lived structural invertebrates, historically overfished, and their conservation is currently a worldwide concern. However, the processes underlying their recovery are poorly known. Here, we examined harvesting effects and recovery mechanisms of red coral Corallium rubrum by analyzing long-term photographic series taken on two populations that were harvested. We compared the relative importance of reproduction and re-growth as drivers of resilience. Harvesting heavily impacted coral populations causing large decreases in biomass and strong size-class distribution shifts towards populations dominated by small colonies. At the end of the study (after 4 and 7 years) only partial recovery was observed. The observed general pattern of low recruitment and high mortality of new recruits demonstrated limited effects of reproduction on population recovery. Adversely, low mortality of partially harvested adults and a large proportion of colonies showing new branches highlighted the importance of re-growth in the recovery process. The demographic projections obtained through stochastic models confirmed that the recovery rates of C. rubrum can be strongly modulated depending on harvesting procedures. Thus, leaving the basal section of the colonies when harvesting to avoid total mortality largely enhances the resilience of C. rubrum populations and quickens their recovery. On the other hand, the high survival of harvested colonies and the significant biomass reduction indicated that abundance may not be an adequate metric to assess the conservation status of clonal organisms because it can underestimate harvesting effects. This study highlights the unsustainability of current harvesting practices of C. rubrum and provides urgently needed data to improve management practices that are still largely based on untested assumptions.     

Impacts of forest biomass removal on soil nutrient status under climate change: a catchment-based modelling study for Finland

The environmental impact of different forest harvesting scenarios on soil nutrient status and water chemistry under current and future (IPCC A2) climate was evaluated for a random sample of lake catchments (n = 1066) covering Finland. Biomass removal scenarios were derived from a management-oriented large-scale forest model based on data from national forest inventories. Forest ecosystem sustainability was assessed by evaluating soil base cation balances as well as temporal changes (2010–2050) in soil base saturation and lake water acid neutralising capacity, using a dynamic hydro-geochemical model. The harvesting scenarios had very different effects on biomass and element removal as well as soil and water quality; only harvesting of above-ground woody biomass (stem-only or stem-and-branches harvesting scenarios) was predicted to be sustainable, i.e. not depleting the soil base cation pools in the long term. The most intensive scenario—whole-tree harvesting (including the removal of stumps and roots)—doubled the removal of biomass, tripled the removal of base cations from the catchment soils, and increased nitrogen removal fourfold. Climate change was predicted to have a positive impact by increasing the future supply of base cations from weathering, thus compensating their removal by biomass harvesting. However, additional inputs of nitrogen and potassium will be required to ensure sustained forest growth under intensive biomass harvesting.     

黄土高原集水农业研究进展

回顾了黄土高原集水农业理论与技术体系的研究成果．分析评价了集水农业的研究进展。随着黄土高原集水农业研究方法的改进、研究内容的深入、研究领域的扩充．提出了广义性集水农业研究范畴。在黄土高原集水农业理论研究的基础上．应加强微集雨微灌溉应用技术、现代集雨技术、计算机控制技术与集雨网络等高新技术手段的技术集成．以提高雨水汇集与利用效率。同时．黄土高原集水农业的研究已经从微生境条件下的农业生态系统延伸至区域生态环境保育。利用汇集雨水合理调配生态用水．进行小流域综合治理。农林牧综合发展。生态环境重建的集水型生态农业是黄土高原集水农业的发展趋势。     

The structure of optimal time- and age-dependent harvesting in the Lotka-McKendrik population model

The paper analyzes optimal harvesting of age-structured populations described by the Lotka-McKendrik model. It is shown that the optimal time- and age-dependent harvesting control involves only one age at natural conditions. This result leads to a new optimization problem with the time-dependent harvesting age as an unknown control. The integral Lotka model is employed to explicitly describe the time-varying age of harvesting. It is proven that in the case of the exponential discounting and infinite horizon the optimal strategy is a stationary solution with a constant harvesting age. A numeric example on optimal forest management illustrates the theoretical findings. Discussion and interpretation of the results are provided.     

Post-harvest growth of Lechuguilla (Agave lecheguilla torr., Agavaceae) in Northeastern Mexico

Extraction of lechuguilla fiber (Agave lecheguilla) is often the only source of income for some rural inhabitants in arid zones of Mexico. A model for biomass estimation of lechuguilla by nondestructive techniques was developed and then applied to evaluate whether traditional harvesting had an effect on (1) biomass production of the bud (part of the plant traditionally collected to obtain fiber) and (2) plant density. Six months after harvesting, biomass production was higher for buds of harvested plants than for buds of unharvested plants, but there were no differences 1 year after harvesting. Number of new plants was not affected by harvesting. Hence it appears that at least in the short term the common practice for extracting lechuguilla fiber does not affect population density, but significantly increases growth of central buds.     

我国双季茭白品种资源及育种研究

在对我国双季茭白资源进行系统调查,整理及研究的基础上,将双季茭白分为两大类;夏茭型和夏秋兼用型,其中夏秋兼用型中又分为两个品种群,对茭白育种的现状,目标及方法进行了讨论,并对今后双季茭白资源及育种研究提出了建议。     

A mechanistic model for the light response of photosynthetic electron transport rate based on light harvesting properties of photosynthetic pigment molecules

Models describing the light response of photosynthetic electron transport rate (ETR) are routinely used to determine how light absorption influences energy, reducing power and yields of primary productivity; however, no single model is currently able to provide insight into the fundamental processes that implicitly govern the variability of light absorption. Here we present development and application of a new mechanistic model of ETR for photosystem II based on the light harvesting (absorption and transfer to the core ‘reaction centres’) characteristics of photosynthetic pigment molecules. Within this model a series of equations are used to describe novel biophysical and biochemical characteristics of photosynthetic pigment molecules and in turn light harvesting; specifically, the eigen-absorption cross-section and the minimum average lifetime of photosynthetic pigment molecules in the excited state, which describe the ability of light absorption of photosynthetic pigment molecules and retention time of excitons in the excited state but are difficult to be measured directly. We applied this model to a series of previously collected fluorescence data and demonstrated that our model described well the light response curves of ETR, regardless of whether dynamic down-regulation of PSII occurs, for a range of photosynthetic organisms (Abies alba, Picea abies, Pinus mugo and Emiliania huxleyi). Inherent estimated parameters (e.g. maximum ETR and the saturation irradiance) by our model are in very close agreement with the measured data. Overall, our mechanistic model potentially provides novel insights into the regulation of ETR by light harvesting properties as well as dynamical down-regulation of PSII.     

Complex dynamics of survival and extinction in simple population models with harvesting

We study the effects of constant harvesting in a discrete population model that includes density-independent survivorship of adults in a population with overcompensating density dependence. The interaction between the survival parameter and other parameters of the model (harvesting rate, natural growth rate) reveal new phenomena of survival and extinction. The main differences with the dynamics of survival and extinction reported for semelparous populations with overcompensatory density dependence are that there can be multiple windows of extinction and conditional persistence as harvesting increases or the intrinsic growth rate is increased, and that, in case of bistability, the basin of attraction of the nontrivial attractor may consist of an arbitrary number of disjoint connected components.     

Effective biomass harvesting of marine diatom Chaetoceros muelleri by chitosan-induced flocculation,preservation of biomass,and recycling of culture medium for aquaculture feed application

Microalgae are a promising new source of biomass; however, large-scale economical harvesting of microalgal biomass is a major technological and economic challenge, limiting the commercial production of microalgal biomass for high-value compounds. In this study, the cationic polymer chitosan was used for the harvesting of the marine diatom Chaetoceros muelleri. Natural flocculation, and pH and chitosan-induced flocculation were studied in detail. The effects of flocculant dosage, culture pH, initial biomass concentration, and sedimentation time were investigated on biomass recovery. The results showed that flocculation efficiency can reach > 99% with an optimum dosage of chitosan (80 mg L^?1) at pH 9.6 and settling time of 40 minutes for biomass concentration from 0.2 to 1.2 g L^?1. The reusability of the recycled water, preservation of biomass after harvesting, and cost of the harvesting process were evaluated. The results showed that the chitosan-induced flocculation offers an efficient, cost-effective, rapid, and sustainable harvesting method for C. muelleri biomass for food and feed applications in aquaculture.

     

Investigation of a traditional reed economy (<Emphasis Type="Italic">Phragmites australis</Emphasis>) under threat: pulp and paper market,values and Netchain at Wuliangsuhai Lake,Inner Mongolia,China

Common Reed (Phragmites australis) is a wetland plant which is distributed worldwide, has a high biomass production, and provides important ecosystem services. In many developing and emerging countries it is an easily available and cheap raw material for diverse utilization, which may contribute significantly to employment and income generation for the local population. This case study investigates the reed utilization for pulp and paper production at the eutrophic Wuliangsuhai Lake, Inner Mongolia, China. We analysed the fluxes of materials and money along the supply chain (reed harvesting, processing and supply to final users, i.e. paper mills) as well as the division of work and costs at each production layer (network), based on the Netchain theory. The results make evident the importance of the paper industry and reed harvesting for local livelihood. They further reveal that the reed economy at Wuliangsuhai Lake is threatened by rising environmental standards for paper mills, change of market conditions and dependency on only two customers. Increasing revenues by finding new consumers or/and products, come to long-term contracts and improving harvesting efficiency are presented as ways to convert these threats into new opportunities.     

Bioflocculation as an innovative harvesting strategy for microalgae

Microalgae are a promising new source of biomass for the production of third generation biofuels but, so far, the majority of microalgal biomass has been used for high-value applications. New low-cost technologies are needed to make the production and processing of microalgae economically feasible for low-value applications. A major challenge lies in the harvesting of microalgae, which requires a cost-efficient separation technology. Flocculation, especially bioflocculation, is an attractive low-cost separation technology. Various new bioflocculation strategies have been claimed to generate major advances in cost-efficient harvesting. Here, we review the recent advances in bioflocculation based on algal–bacterial, algal–fungal, or algal–algal interactions within the framework of microalgae biomass harvesting for biofuel production. We also discuss recent advances using infochemicals and genetic engineering for the induction of bioflocculation.     

Ticket to spawn: Combining economic and genetic data to evaluate the effect of climate and demographic structure on spawning distribution in Atlantic cod

Climate warming and harvesting affect the dynamics of species across the globe through a multitude of mechanisms, including distribution changes. In fish, migrations to and distribution on spawning grounds are likely influenced by both climate warming and harvesting. The Northeast Arctic (NEA) cod (Gadus morhua) performs seasonal migrations from its feeding grounds in the Barents Sea to spawning grounds along the Norwegian coast. The distribution of cod between the spawning grounds has historically changed at decadal scales, mainly due to variable use of the northern and southern margins of the spawning area. Based on historical landing records, two major hypotheses have been put forward to explain these changes: climate and harvesting. Climate could affect the distribution through, for example, spatial habitat shifts. Harvesting could affect the distribution through impacting the demographic structure. If demographic structure is important, theory predicts increasing spawner size with migration distance. Here, we evaluate these hypotheses with modern data from a period (2000–2016) of increasing temperature and recovering stock structure. We first analyze economic data from the Norwegian fisheries to investigate geographical differences in size of spawning fish among spawning grounds, as well as interannual differences in mean latitude of spawning in relation to changes in temperature and demographic parameters. Second, we analyze genetically determined fish sampled at the spawning grounds to unambiguously separate between migratory NEA cod and potentially smaller sized coastal cod of local origin. Our results indicate smaller spawners farther away from the feeding grounds, hence not supporting the hypothesis that harvesting is a main driver for the contemporary spawning ground distribution. We find a positive correlation between annual mean spawning latitude and temperature. In conclusion, based on contemporary data, there is more support for climate compared to harvesting in shaping spawning ground distribution in this major fish stock in the North Atlantic Ocean.     

The impact of mechanical harvesting regimes on the aquatic and shore vegetation in water courses of agricultural areas of the Netherlands

It was demonstrated that a mechanical harvesting regime can influence the species composition of ditch vegetation at the community level. This effect, however, was very small compared with those of other factors such as the between-site and the within-site spatial variation, and several soil and water quality parameters. Cutting in November had the largest effect, in that it caused the greatest extremes in species cover. The vegetation was composed of 136 plant species. The semi-aquatic and aquatic species were less numerous than the terrestrial ones (52 versus 84). The total number per vegetation type and site ranged from 5 to 49; that of persistent plant species, from 4 to 22. Only 16% of the species was significantly influenced by the mechanical harvesting regime. The significant effects of the mechanical harvesting regime on plant species were related to plant-inherent factors. Mechanical harvesting repeated within a year, on one hand, opened up the vegetation, 1) freeing sites for colonization of new species, 2) improving the light climate for seedlings which had already colonized; on the other hand, it exhausted (carbohydrate) reserves of solitary species. Mechanical harvesting once a year in November had a contrasting effect in that it caused suffocation of the shore vegetation in spring by the not yet decomposed plant material harvested in autumn. The highest species richness was attained for the aquatic vegetation: on sand by cutting three times per year (in May, July and September), and on peat by cutting once a year (in November); and for the shore vegetation: on sand once a year (in May) and two times per year (in May and July), and on peat once a year (in May or November).     

The composition and structure of photosystem I‐associated antenna from Cyanidioschyzon merolae

Red algae contain two types of light‐harvesting antenna systems, the phycobilisomes and chlorophyll a binding polypeptides (termed Lhcr), which expand the light‐harvesting capacity of the photosynthetic reaction centers. In this study, photosystem I (PSI) and its associated light‐harvesting proteins were isolated from the red alga Cyanidioschyzon merolae. The structural and functional properties of the largest PSI particles observed were investigated by biochemical characterization, mass spectrometry, fluorescence emission and excitation spectroscopy, and transmission electron microscopy. Our data provide strong evidence for a stable PSI complex in red algae that possesses two distinct types of functional peripheral light‐harvesting antenna complex, comprising both Lhcr and a PSI‐linked phycobilisome sub‐complex. We conclude that the PSI antennae system of red algae represents an evolutionary intermediate between the prokaryotic cyanobacteria and other eukaryotes, such as green algae and vascular plants.     

Regionalized nitrogen budgets in forest soils for different deposition and forestry scenarios in Sweden

Aim The aim of this work was to estimate on a regional scale the effects of nitrogen (N) deposition and harvest intensity on N‐budgets in forest soils as a basis for strategies of emission reduction and sustainable forest management methods. Location The calculations were applied to Sweden, a country with a managed forest area of 23 × 10⁶ ha. Methods Mass balance calculations, including N‐deposition, N‐fixation, N‐loss through harvest, and N‐leaching, were performed on a GIS platform using 5 × 5 km grids. Modelled deposition data together with spatial data obtained from the National Forest Inventory served as the basis for the calculations. Four different scenarios were run: a ‘base scenario’ involving present deposition and conventional forestry (stem harvest only); a ‘whole‐tree harvesting scenario’ with present deposition and the harvesting of stems, branches and needles; a ‘decreased deposition scenario’; and a ‘whole‐tree harvesting and decreased deposition scenario’. Results There was a sharp N‐accumulation gradient with an increase in accumulation in the direction of the south‐western part of Sweden. In the ‘base scenario’, N‐accumulation appeared in the country as a whole, apart from certain small areas in the northern part. Whole‐tree harvesting led to net losses in extensive areas located mainly in northern and central Sweden. In most parts of the country, whole‐tree harvesting combined with decreased deposition was found to result in net losses. Main conclusions The intensity of the forestry has a strong impact on the N‐budget. Conventional forestry in combination with the present deposition level results in a high net accumulation of N in the south‐western parts of Sweden and accordingly, in a risk of unwanted environmental effects such as increased N‐leaching. With whole‐tree harvesting, the N‐balance is negative in parts of Sweden, mainly in the northern and central parts. N‐fertilization may become necessary there if the present level of forest production is to be maintained.