Addressing foundational elements of regional land-use change forecasting

Regional land-use models must address several foundational elements, including understanding geographic setting, establishing regional land-use histories, modeling process and representing drivers of change, representing local land-use patterns, managing issues of scale and complexity, and development of scenarios. Key difficulties include managing an array of biophysical and socioeconomic processes across multiple spatial and temporal scales, and acquiring and utilizing empirical data to support the analysis of those processes. The Southeastern and Pacific Northwest regions of the United States, two heavily forested regions with significant forest industries, are examined in the context of these foundational elements. Geographic setting fundamentally affects both the primary land cover (forest) in the two regions, and the structure and form of land use (forestry). Land-use histories of the regions can be used to parameterize land-use models, validate model performance, and explore land-use scenarios. Drivers of change in the two regions are many and varied, with issues of scale and complexity posing significant challenges. Careful scenario development can be used to simplify process-based land-use models, and can improve our ability to address specific research questions. The successful modeling of land-use change in these two areas requires integration of both top-down and bottom-up drivers of change, using scenario frameworks to both guide and simplify the modeling process. Modular approaches, with utilization and integration of existing process models, allow regional land-use modelers the opportunity to better represent primary drivers of land-use change. However, availability of data to represent driving forces remains a primary obstacle.     

Effects of adult Lumbricus terrestris on cocoons and hatchlings in Evans’ boxes

The basic ecology of well-researched earthworm species, such as Lumbricus terrestris, remains relatively unknown. In order to contribute to the limited body of knowledge, the present work aimed to investigate if specific behaviours could be detected between an adult and the cocoons it produced by comparison with a non-parental adult and cocoons. Modified Evans’ boxes (0.8×0.2×0.008 m) with recently mated adults allowed observation of their habits under what was essentially a 2-D system. Experimental manipulation (at 81 days) involved four treatments: (1) L. terrestris removal (LtRm); (2) L. terrestris replacement (LtRp), where individuals were replaced by others; (3) control, with no manipulation and (4) L. terrestris removal control (CLtRm) where individuals were removed and then reintroduced in the same box, to account for any effects of the removal method. Burrowing patterns of adults and later, hatchlings, were recorded throughout the duration of the experiment (191 days). Cocoon production across treatments did not differ significantly (p>0.05) and averaged 26±6.4 cocoons worm⁻¹ over a 26 week period. In the LtRm treatment mean cocoon production was 12.6±2.7 cocoons worm⁻¹ over 11 weeks. Forty one percent of cocoons were deposited in the upper 0.05 m of the soil profile. Cocoons below that depth were found deposited in side burrows (1–4 cm in length) and were coated with earthworm casts. Hatchling number and survival rate did not differ significantly across treatments (p>0.05) with means±s.d. of 2±2.2 and 62±29%, respectively. Hatchling mass in the LtRm treatment (0.4±0.38 g), was found to be significantly greater (p<0.01) than that of all other treatments (0.12±0.12 g). In this experimental set up, the presence of parental earthworms and other con-specifics had no significant effect on cocoon viability and hatchling survival, however, results indicated a negative effect of adult presence on hatchling growth.     

Slow-cycle effects of foliar herbivory alter the nitrogen acquisition and population size of Collembola

In terrestrial systems there is a close relationship between litter quality and the activity and abundance of decomposers. Therefore, the potential exists for aboveground, herbivore-induced changes in foliar chemistry to affect soil decomposer fauna. These herbivore-induced changes in chemistry may persist across growing seasons. While the impacts of such slow-cycle, ‘legacy’ effects of foliar herbivory have some support aboveground, such impacts have not been evaluated for soil invertebrates. Here, we investigate legacy effects on Collembola population structure and nitrogen acquisition. We collected foliar material (greenfall) from trees that had, in the preceding season, been exposed to insect herbivory by leaf-chewing Lepidoptera. Collembola populations were grown with the greenfall in soil microcosms across 16 weeks. While there were only modest effects of herbivory on the greenfall mass loss, Collembola abundance and biomass after 8 weeks of greenfall exposure were approximately 2.5-fold greater in the controls. Given that Collembola biomass percentage nitrogen was relatively fixed, this translated to approximately 2.5-fold greater biomass nitrogen. The herbivore treatment decreased the absolute amount of Collembola biomass nitrogen derived from both greenfall and soil, and the relative contribution of litter nitrogen and soil nitrogen to Collembola biomass nitrogen was dependent on both the herbivory treatment and greenfall initial nitrogen. Our results show that slow-cycle, legacy effects of foliar herbivory may affect soil faunal population structure and nitrogen acquisition, demonstrating the potential for aboveground herbivory to influence belowground animal ecology and nitrogen cycling across multi-annual timescales.     

Life cycle traits of the parthenogenetic earthworm Octolasion cyaneum (Savigny, 1826)

This laboratory-based study provides baseline life cycle data for the obligatory parthenogenetic earthworm Octolasion cyaneum. Singleton and twin hatchlings were cultured individually with biomass, survival and reproductive condition recorded at 4-weekly intervals during a complete year. After maturation, cocoon production, masses and incubation time were also recorded along with viability and number of hatchlings per cocoon. Individual mean mass of singletons was significantly (P < 0.05) greater than twins at the outset (0.042 and 0.025 g respectively) and remained so until week 52 (2.22 and 1.96 g respectively). Singletons matured more rapidly than twins (24 vs. 32 weeks respectively) and produced more cocoons than twins (3.2 and 2.2 coc worm⁻¹ (4 weeks)⁻¹ respectively). Approximately 20% of all viable cocoons produced twins. Singleton hatchlings weighed significantly (P < 0.05) more than twin hatchlings (0.032 and 0.018 g respectively) but there was no significant difference (P > 0.05) between mean masses of singleton (mean masses 0.033 and 0.032 g) or twin (0.017 and 0.018 g) hatchlings produced by singleton and twin parents. The likelihood that a cocoon contained twins or a singleton was not influenced by the singleton/twin status of the parent. There was no significant difference (P > 0.05) in the incubation times of cocoons produced by singletons and twins (129 and 128 days respectively).     

Bioavailability of Arsenic and Antimony in Terrestrial Ecosystems: A Review

Arsenic (As) and antimony (Sb) are metalloids that belong to group 15 of the periodic table and exhibit toxic properties in the environment. They mostly occur naturally at low concentrations in soil, although these can be significantly elevated in both aquatic and terrestrial food chains as a result of dispersion from anthropogenic sources, e.g., mining activities. The bioavailability, i.e., the proportion of the contaminant in soil and dust that is available for uptake by plants and other living organisms, presents the greatest risk to terrestrial ecosystems. Various in vivo and in vitro methods have been used to measure As and Sb bioaccessibility in soil and dust. In vivo measurement of bioavailability can be time consuming, expensive, and unethical; thus, in vitro methods are commonly preferred. However, there is considerable uncertainty around the efficacy of in vitro tools used to measure the bioavailable fractions of As and Sb. The results of these methods are dependent on many variables, e.g., soil characteristics, contaminant sources, and chemical composition of in vitro methods. Therefore, substantial variations are observed between in vitro and in vivo results obtained from different test animals and endpoints. In this paper, we review the literature on As and Sb bioavailability in terrestrial ecosystems and current in vivo and in vitro techniques used for assessing bioavailability and bioaccessibility of metalloids. This would reveal research gaps and allow scientists and environmental policy makers to gain a deeper understanding of the potential risks associated with these metalloids in the environment.     

日光温室墙体蓄放热层温度变化规律研究

墙体的蓄热保温性能决定了日光温室在室外环境作用下的温度变化。该文建立了单一材料墙体的温度变化估算模型,对黏土砖墙、砾石墙、加草黏土墙及夯土墙的温度变化进行了预测;采用CFD方法分析了墙体总厚度相同(0.60 m)和总厚度不同(0.60和0.72m)情况下,复合墙体各方案中蓄热材料层的温度变化特点。单一材料墙体温度变化预测结果显示,导温系数较大的砾石墙内部温度变化较其他墙体传播快;温度波动厚度还与墙内表面温度振幅有关,黏土砖墙内表面振幅从5℃增加到15℃,墙体内部振幅达到0.1℃时的波动厚度从0.42 m增加到0.54 m。此外,由预测的墙体温度变化可以确定单一材料墙体蓄放热层厚度。模型估算的夯土墙温度变化及蓄放热层厚度与已有文献测试值比较,吻合较好。复合墙体温度CFD模拟分析表明,墙总厚度0.60 m不变,蓄热材料层越厚内部温度衰减越快;蓄热材料层厚保持0.36 m,墙总厚度从0.60 m增加到0.72 m时,蓄热材料层温度均值最大升高1.7℃。研究还发现,复合墙体较厚的蓄热材料层比同材料单一材料墙体同厚度处温度衰减快,复合墙体蓄放热层厚度的确定取决于隔热层的位置。单一材料墙体及复合墙体蓄热材料层温度模拟模型可以为日光温室墙体的厚度及组成设计提供理论参考。     

Dry matter production,nutrient accumulation,and nutrient partitioning of barley

Total dry matter (TDM) and nutrient accumulation, nutrient partitioning, and cumulative growing degree days at the time of maximum nutrient accumulation for two‐row spring barley (Hordeum vulgare L.) are not well quantified under high‐yielding irrigated conditions common in the semi‐arid western United States. Thus, five cultivars of barley were grown under irrigated conditions on a loam soil in the 2015 and 2016 growth seasons to determine these factors. Total nutrient accumulation was greatest at either the soft dough or maturity stage where specific nutrients were greater at one stage as compared to the other. Mean N accumulation was greatest at the soft dough stage (256 kg ha^?1) where the regression model accounted for 80% of the variation in the data. Additionally, spike N increased from 91 to 105 kg ha^?1 from soft dough to maturity. Specific nutrients (e.g., K) had significantly greater plant (i.e., culms plus leaves) accumulation between soft dough and maturity, 253 and 172 kg ha^?1, respectively, where the spike at the same growth stages had an accumulation of 37 and 42 kg ha^?1, respectively. In contrast, other nutrients (e.g., P) were remobilized to the spike as noted by the increase from 14 kg ha^?1 at soft dough to 26 kg ha^?1 at maturity. In addition to nutrient partitioning, linear regressions resulted in well‐correlated models between TDM and total nutrient accumulation (R² = 0.35–0.88) for measured nutrients. Results from the current study provide critical data on nutrient accumulation as well as regression models for two‐row barley under high‐yielding conditions. This information can be used to improve harvest decisions as well as more accurately predict nutrient cycling in barley cropping systems.     

Harvest control rules used in US federal fisheries management and implications for climate resilience

Climate change is altering the productivity of marine fisheries and challenging the effectiveness of historical fisheries management. Harvest control rules, which describe the process for determining catch limits in fisheries, represent one pathway for promoting climate resilience. In the USA, flexibility in how regional management councils specify harvest control rules has spawned diverse approaches for reducing catch limits to precautionarily buffer against scientific and management uncertainty, some of which may be more or less resilient to climate change. Here, we synthesize the control rules used to manage all 507 US federally managed fish stocks and stock complexes. We classified these rules into seven typologies: (1) catch-based; (2) constant catch; (3) constant escapement; (4) constant F; (5) stepped F; (6) ramped F and (7) both stepped and ramped F. We also recorded whether the control rules included a biomass limit (‘cut-off’) value or were environmentally linked as well as the type and size of the buffers used to protect against scientific and/or management uncertainty. Finally, we review the advantages and disadvantages of each typology for managing fisheries under climate change and provide seven recommendations for updating harvest control rules to improve the resilience of US federally managed fisheries to climate change.     

A simple equation to determine the breakdown of individual aggregate size fractions in the wet-sieving method

Wet-sieving method using nested sieves is one common method to measure aggregate stability. However, this method cannot be used to measure the stability of individual aggregate size fractions, only of whole soils. Thus, this study was to develop an equation to estimate the aggregate breakdown of individual aggregate size fractions in this particular method. The key to develop the equation was to assume that aggregate breakdown happens sequentially and consistently, and that the aggregate breakdown between any two aggregates in the same aggregate size fractions is equal in percentage. Applying these two assumptions, this equation was developed: x_i=(W_ai×D_i)/(W_ai+D_i−1), where x_i is the weight of aggregate breakdown in aggregate size fraction i, W_ai is the weight of the aggregates in aggregate size fraction i before wet-sieving, and D_i and D_i−1 are the weight of aggregates that have passed through sieve i and i−1, respectively. This equation was tested with five soil series. The soils were separated into six aggregate size fractions: 4.76–8.0, 2.83–4.76, 2.0–2.83, 1.0–2.0, 0.5–1.0 and 0.3–0.5 mm. For every soil, each of their aggregate size fraction was separately wet-sieved to determine the actual aggregate breakdown. The separate wet-sievings results were then combined in such a way to simulate the usual wet-sieving method; that is, to construct the data that would have been produced if each of the aggregate size fractions was wet-sieved together in the same nested sieves. Paired sample t-test showed that the differences between the actual and estimated aggregate breakdown values were significant at 5%. However, there was very close correlation between the actual and estimated values (r=0.974; p<0.001); thus, the equation was calibrated by simple linear regression. The calibrated equation was: _i=100 sin²_i, where _i is the calibrated breakdown estimate for aggregate size fraction i, and _i is 0.0166x_i+0.1 in unit radians. This calibrated equation was highly significant at 1% (F=766.039; p<0.001), with the values fitting very tightly along the regression line (R²=0.961), and with very small standard error (std. error=0.023). The calibrated equation was validated with three additional soils. Paired sample t-test showed there was insignificant differences between the actual and calibrated breakdown estimate values. Moreover, using fewer aggregate size fractions did not affect the accuracy of the calibrated equation, as this equation still predicted the actual values with very small errors.     

Application of geographic information systems in watershed management planning in St. Lucia

The use of geographic information systems (GIS) to develop conservation-oriented watershed management strategies on St. Lucia is presented. A soil loss model was executed within a GIS environment to evaluate agricultural management strategies in terms of soil loss on two agricultural watersheds. The GIS provided a fast and efficient means of generating the input data required for the model and allowed for easy assessment of the relative erosion hazard over the watersheds under the different land management options. The model predicted substantial declines in soil loss under conservation-oriented land management compared to current land management for both watersheds. The results of this study indicate that soil loss potential on the Soufriere watershed is approximately four times higher than on the Marquis watershed. This study represents the first attempt in the application of GIS technology to watershed conservation planning for St. Lucia. The procedures developed will contribute to the evolution of a decision support system to guide agricultural and forestry land planning in St. Lucia.