Surface metrics: an alternative to patch metrics for the quantification of landscape structure

Modern landscape ecology is based on the patch mosaic paradigm, in which landscapes are conceptualized and analyzed as mosaics of discrete patches. While this model has been widely successful, there are many situations where it is more meaningful to model landscape structure based on continuous rather than discrete spatial heterogeneity. The growing field of surface metrology offers a variety of surface metrics for quantifying landscape gradients, yet these metrics are largely unknown and/or unused by landscape ecologists. In this paper, we describe a suite of surface metrics with potential for landscape ecological application. We assessed the redundancy among metrics and sought to find groups of similarly behaved metrics by examining metric performance across 264 sample landscapes in western Turkey. For comparative purposes and to evaluate the robustness of the observed patterns, we examined 16 different patch mosaic models and 18 different landscape gradient models of landscape structure. Surface metrics were highly redundant, but less so than patch metrics, and consistently aggregated into four cohesive clusters of similarly behaved metrics representing surface roughness, shape of the surface height distribution, and angular and radial surface texture. While the surface roughness metrics have strong analogs among the patch metrics, the other surface components are largely unique to landscape gradients. We contend that the surface properties we identified are nearly universal and have potential to offer new insights into landscape pattern–process relationships. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

白菜RAPD反应条件的优化

以芜菁、大白菜及其杂交 1代为试材 ,系统分析了 Mg Cl2 浓度、d NTP浓度、随机引物浓度、模板 DNA用量、Taq DNA聚合酶浓度以及不同来源扩增缓冲液对 RAPD反应的影响 ,建立了一套稳定的 RAPD反应体系。该体系反应体积为 2 0μL,Mg Cl2 浓度为 1 .5mmol/L ,d NTP浓度为 2 0 0μmol/L ,随机引物浓度为 0 .4μmol/L ,模板 DNA为 2 0 ng,TaqDNA聚合酶为 6.67μmol/( L· min)。在 8种热循环条件下 ,该体系具有稳定的重现性 ,其扩增程序为 :94℃ /1′→ 36℃ /2 0″→ 72℃ /1 0″预扩增 2循环 ;94℃ /1 0″→ 36℃ /1 5″→ 72℃ /70″扩增38循环 ;72℃ /4′延伸效果最好     

Longitudinal analysis of body weight and average daily feed intake during the feedlot test period in Angus cattle

The objectives of this study were to compare different models for analysing body weight (BW) and average daily feed intake (ADFI) data collected during a 70-day feedlot test period and to explore whether genetic parameters change over time to evaluate the implications of selection response. (Co)variance components were estimated using repeatability and random regression models in 2,071 Angus steers. Models included fixed effects of contemporary group, defined as herd–year–observation_date–age, with additive genetic and permanent environmental components as random effects. Models were assessed based on the log likelihood, Akaike's information criterion and the Bayesian information criterion. For both traits, random regression models (RRMs) presented a better fit, indicating that genetic parameters change over the test period. Using a two-trait RRM, the heritability from day 1 up to day 70 for BW increased from 0.40 to 0.50, while for ADFI, it decreased from 0.44 to 0.33. The genetic correlation increased from 0.53 at day 1 up to 0.79 at day 70. Selection based on an index assuming no change in genetic parameters would yield a 2.78%–3.13% lower selection response compared to an index using parameters estimated with RRMs and assuming these genetic parameters are correct. Results imply that it may be beneficial to implement RRMs to account for the change of parameters across the feedlot period in feed efficiency traits.     

Transport of microorganisms through soil

Microorganisms migrating into and through soil from sources on the land surface may cause a serious threat to both ground and surface waters. It has been estimated that microorganisms can migrate significant distances in the field. Results from various studies suggested that preferential flow through macropores, worm holes, cracks, and fractures is the main reason for such observations. However, a quantitative representation of this phenomenon has not been provided. Microorganisms migrate through soil by advection and dispersion, while being subjected to effects of filtration, adsorption, desorption, growth, decay, sedimentation and chemotaxis. Both laboratory and field investigations have contributed important information on bacterial movement in soils. Qualitative comparisons are generally transferable from laboratory to field situations. Quantitative agreement is much more difficult to establish. Available mathematical modelling of microbial transport is limited in practical application because of the simplifying assumptions used in its development.     

Effects of different gestation housing types on reproductive performance of sows

This study evaluated the effects of different gestation housing types on reproductive performance of sows. A total of 60 sows (218 ± 24 kg body weight) with mixed parity were used. During gestation, 28 sows were housed in groups with electronic sow feeders (space allowance = 1.26 m²/sow) and 32 sows were housed in individual stalls (space allowance = 1.20 m²/sow). Sows from both housing types were moved to farrowing crates on day 109 of gestation and stayed until weaning (18 days post‐farrowing). Typical corn‐soybean meal diets were provided to sows during gestation and lactation. Measurements were reproductive performance of sows at farrowing as well as performance of sows and their litter during lactation. Similar total numbers of piglets born at farrowing were observed for sows gestated in both housing types. However, group‐housed gestation sows had more mummies (0.321 vs. 0.064; P < 0.05) and stillbirths (0.893 vs. 0.469; P = 0.073) at farrowing than individual‐housed gestation sows. Consequently, individual‐housing type had higher percentage of piglets born alive (95.5 vs. 90.4%; P < 0.05) than the group‐housing type. Therefore, improved reproductive performance of sows from individual gestating housing was confirmed in this study.     

A multi-scale analysis of species-environment relationships: breeding birds in a pitch pine-scrub oak (Pinus rigida-Quercus ilicifolia) community

Analyses of species-environment relationships are critically needed to guide conservation of many declining species. Comprehensive investigations of these relationships must incorporate environmental variables at multiple spatial scales since species responses to the environment vary with the scale of observation. We used partial canonical correspondence analysis to associate a bird assemblage in a threatened pitch pine-scrub oak (Pinus rigida-Quercus ilicifolia) community in Plymouth County, Massachusetts, USA, with plot, patch, and landscape level variables. The first level of analysis partitioned the amount of variance in the bird community explained by plot, patch, and landscape factors from that explained by spatial autocorrelation. The second level partitioned the amount of variance explained by plot, patch, and landscape factors alone and in combination. All three levels of environmental variables together accounted for 43% of the variance in the species data and only 5% of the variance was explainable by spatial factors alone. Landscape level factors accounted for a slightly larger amount of the explained variation (12%) than plot (11%) or patch (8%) level factors. We also examined the cumulative fit of each species to the plot, patch, and landscape partial models. Nine species of regional and/or national conservation concern had distributions that fit one model considerably better than the others. The Great Crested Flycatcher (Myiarchus crinitus) and Black-and-white Warbler (Mniotilta varia) were predominantly associated with plot level factors; the Whip-poor-will (Caprimulgus vociferus) was predominantly associated with patch level factors; and the Purple Finch (Carpodacus purpureus), Gray Catbird (Dumetella carolinensis), Scarlet Tanager (Piranga olivacea), Ovenbird (Seiurus aurocapillus), Brown Thrasher (Toxostoma rufum), and Eastern Kingbird (Tyrannus tyrannus) were predominantly associated with landscape level factors. This study suggests that focusing conservation efforts at the landscape level would provide the most effective protection for the largest number of sensitive species.     

What is the ecological footprint of aquaculture after 5 decades of competition between mangrove conservation and shrimp farm development?

1. Among the several threats to the conservation of mangrove ecosystems in most South Asian countries, shrimp farming is predominant. Since the introduction of shrimp farming in Sri Lanka in the 1980s, mangroves on the island’s north-western coast have been continually cleared to create new shrimp farms, leading to a decline in the social-ecological services provided by the mangrove ecosystems.
2. Using aerial (1973) and satellite (1996–2020) images, this study assessed areal changes in mangroves and shrimp farms in the Pambala-Chilaw lagoon complex and Ihala Mahawewa, as well as the ecological footprint of shrimp farming in the study area.
3. Mangroves around the Chilaw lagoon had decreased in areal extent by 45% from 1973 to 2020 of which 92% of this change was attributed to shrimp farming. There was, however, a decrease in the areal extent of shrimp farms from 2001 to 2020, and a corresponding increase in mangroves from 2006 to 2020.
4. The ecological footprint of shrimp farming was assessed by comparing the expected surface ratios with those recorded for shrimp farms with mangroves and surface water bodies in the study area from 1973 to 2020. The results showed that the current shrimp farming was unsustainable (i.e. high ecological footprint).
5. While the results support the current view that there is cause for cautious optimism with mangrove conservation (as evidenced by an increase in mangrove areal extent), it also reveals that semi-intensive shrimp farming in Sri Lanka and probably other similar tropical countries is unsustainable.
6. If immediate actions such as effective regulation of shrimp farming activities and mangrove restoration are not taken, the mangrove ecosystem will continue to decline.