Impact of Weed Control by Hand Tools on Soil Erosion under a No-Tillage System Cultivation

In conservation agriculture, the no-tillage cultivation system and the retention of permanent vegetal cover are crucial to the control of soil erosion by water. This paper analyses the cultivation of maize under no-tillage, with particular reference to the effect produced on soil erosion when weed control is performed by a hand tool (machete), which disturbs the surface of the soil, and to the behavior of the soil cover in these circumstances. The study area is located in the humid tropical mountains of northern Nicaragua (Peñas Blancas Massif Nature Reserve). The results obtained show that 59.2% of the soil surface was affected by appreciable levels of sheet and splash erosion, although the vegetal cover of the soil was relatively high (with average weed and litter cover of 33.9% and 33.8%, respectively). The use of machetes for weed control provoked considerable soil disturbance, which explained the high rates of erosion observed. Moreover, this form of soil management disturbs the litter layer, making it less effective in preventing erosion. The litter remains loose on the soil surface, and so an increase in soil cover does not achieve a proportionate reduction in the area affected by erosion; thus, even with 80–100% weed and litter cover, 42% of the cultivated area continued to present soil erosion.

Nest site selection and nesting behavior of the mud turtle Kinosternon scorpiodes (Testudines, Kinosternidae) in Palo Verde National Park, Costa Rica: implications for management

Habitat selection is the process whereby individuals preferentially use, or occupy, a non-random set of available habitats. At the same time, nest site selection is defined as the placement of eggs by females at sites differing from random sites within a delimited area. We located 59 nests of the mud turtle Kinosternon scorpioides in Palo Verde National Park (PVNP) in Northwestern Costa Rica. We compared eight microhabitat variables at nest sites against those at random sites. Females significantly placed their eggs at sites with more understory, leaf litter cover, and greater leaf litter depth than in random sites. Additionally, females selected sites with lower air and soil temperature and lower air humidity. Palo Verde NP is subject to active management actions designed to control invasive plant species in the wetland, namely cattail (Thypha domingensis Pers.). The main actions have been cattle grazing, controlled fires, and mechanical crushing of vegetation. We found that habitat quality in nesting areas is being threatened by at least one of these actions: cattle grazing. This is detrimental for three microhabitat traits that turtles select for nesting sites: understory cover, leaf litter cover, and leaf litter depth. The continued degradation of microhabitats at nesting areas of K. scorpioides at PVNP could be affecting recruitment due to embryo survivorship.

Spider Community Variability and Response to Restoration in Arid Grasslands of the Pacific Northwest, USA

Grassland restoration in North America has intensified but its impact on major invertebrate groups, including spiders, is unclear. We studied three grassland locations in the Pacific Northwest, USA, to (1) describe variability in spider communities, (2) identify environmental variables that may underlie patterns in spider communities, and (3) determine whether spiders and environmental variables differ between actively (removal of disturbances, then plant with natives) vs. passively restored sites (removal of disturbance only). We found spider richness, diversity, and composition differed among the three locations but abundance did not. Sites with more litter and invasive grass cover had more spiders while sites at higher elevation and with more forb and biological soil crust cover had increased spider richness and diversity. Spider community composition was associated with elevation and litter cover. Surprisingly, no spider community or environmental variables differed between actively and passively restored sites, except that litter cover was higher in passively restored sites. This study demonstrates that even in superficially similar locations, invertebrate communities may differ greatly and these differences may prevent consistent responses to active vs. passive restoration. If increasing biodiversity or the abundance of invertebrate prey are goals, then environmental factors influencing spider communities should be taken into account in restoration planning.

Effects of litter cover on partitioning of natural rainfall for plantation Pinus tabulaeformis forest in the Loess Plateau of China

<p>      Litter accumulates yearly since vegetations were widely planted for reforestation, and it plays an important role in hydrologic cycling. There is little information on the effects of litter on re-allocation of rainfall processes. Eight runoff plots were established in the <em>Pinus tabulaeformis</em> stand with four litter (needle-leaf) masses (0, 0.6, 1.2, 1.8 kg/m<sup>2</sup>), and the surface runoff (<em>R</em>), evaporation (<em>E</em>), infiltration and soil moisture dynamics were measured throughout the mainly rainy season from August 4 to September 28 in the Loess Plateau. The results showed that, soil evaporation mainly occurred in daytime for bare soil, and decreased with increasing litter masses, and litter cover is prone to hinder the heat and water exchange between soil and atmosphere, especially for the soil layer 0~5 cm. Litter cover greatly decreased surface runoff, and it may hinder infiltration at the beginning of rainy season, but increasing soil water storage (<em>SWS</em>) with deeper infiltration depth for the long run, especially for the litter masses 1.2 and 1.8 kg/m<sup>2</sup>. With the litter covered, the ratio of <em>R</em> to precipitation (<em>P</em>) was less than 10%, no matter it was heavy rain or light rain. However, the proportion of <em>R</em> was amplified when the rainfall was intense for the bare soil. And the ratio of <em>E</em> to <em>P</em> was always below 10% for all treatments, except for light rainfall. With the increased litter masses, the proportion of <em>R</em> and<em> E</em> all decreased, and the <em>SWS</em>/<em>P</em> has well nonlinear positive relationship with litter masses, and it was proved that more than a half of rainfall was stored even for bare soil. This study may helpful to better understanding the effects of litter on hydrological response, and promotes practical measurements to the management of precipitation in a forest stand view.</p>

How are mineral and organic phases regulating burning-induced soil water repellency? Unravelling the crucial dynamics occurring in the Alps even at moderate fire intensities.

<p>Wildfires play the role of ecosystem shapers in the majority of terrestrial biomes, altering canopy and litter cover and imposing strong modifications on soils. Organic matter (OM) content and composition, mineralogy, pH, aggregate stability and water repellency (WR) are among the main edaphic properties to be affected by heat. Various studies dealt with occurrence, extent and persistence of burning-induced soil WR, but the dynamics at the basis of its formation (and loss) are still widely unclear. In addition, the vast majority of research on this topic has been carried out in the Mediterranean, even if alpine environments are far from being untouched by fires. Our aims were therefore to provide insight into the key mechanisms regulating WR thermal alterations in a relatively understudied environment.</p><p>Our sampling design aimed at collecting soils representative of the Western Italian Alps. Charring was simulated in the lab, at increasing temperatures (up to 300° C), on a set of A soil horizons developed under pine and beech forest covers. Water drop penetration time (WDPT) was employed to test WR persistence. Soils were analyzed in terms of organic carbon (OC) and nitrogen contents, pH, texture and iron (Fe) oxides composition (Fe-DCB and Fe-pyrophosphate extracted). Fe-speciation and OM composition of some selected samples were further characterized using Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and Fourier transform-infra red (FT-IR) spectroscopy, respectively.</p><p>WR was found to be extremely variable, event at room temperature. For samples exhibiting an increase in WR upon burning intensity, maximum repellency was observed at 200° C. OC abundance (%) and coarse texture were found to be the main drivers of hydrophobicity in soil. WR was drastically lost when samples were exposed to temperatures higher than 200°C. Above this threshold, pH systematically increased and OC (%) sharply decreased. The increasingly negative charge of mineral surfaces, mirrored by pH increase, seems to result in a significant C volatilization by OM desorption, eventually leading to a super-hydrophilic behavior in soil.</p><p>Fe EXAFS allowed to evaluate different thermal-dictated pathways of Fe-speciation. The formation of more crystalline Fe-forms (e.g. hematite, meghemite) was observed above 200° C. Even though a reduction in surface area should be expected when observing an increase in crystallization degree (potentially giving rise to greater WR), OM adhesion to mineral surfaces seems to be inhibited by the change induced in their charge. A reduction in the OM-bound Fe pool (pyrophosphate extracted) above 200° C could be appreciated, supporting the interpretation of oxy-hydroxides transformations and OC (%) loss.  </p><p>The current investigation has been carried out to capture an in-depth picture of wildfire impacts on alpine soils, targeting factors responsible for WR enhancement and shred. Identifying the mechanisms regulating wildfire-related WR is a key issue, as the formation of hydrophobic layers in soil highly favors its erosion. Addressing such matters is crucial to tackle the issue of ecosystems recovery, considering that climate-change-related alterations in wildfires regimes are already causing the occurrence of more frequent and disruptive fires.</p>

Herpetofauna assemblage in two watershed areas of Kumoan Himalaya, Uttarakhand, India

We surveyed herpetofauna along the poorly-explored region of two watersheds of Kumoan Himalaya, Dabka and Khulgarh. Adaptive cluster method was used to collect forest floor reptiles, and stream transect was used for stream reptiles and amphibians. In total, 18 species of reptiles were recorded in two watersheds, with 15 and nine species recorded in Dabka and Khulgarh, respectively. Forest floor density of reptiles was 87.5/ha in Dabka and 77.7/ha in Khulgarh. In terms of species, Asymblepharus ladacensis and Lygosoma punctatus density were highest in Dabka and Khulgarh, respectively. Eight species of amphibians were recorded in Dabka with a density of 9.4/ha and four species in Khulgarh with density of 5.2/ha. In both watersheds, density of Euphlyctis cyanophlyctis was highest. Reptilian and amphibian diversity of Dabka was 1.52 and 1.23, respectively, and in Khulgarh 0.43 and 0.23, respectively. In both watersheds reptile density, diversity and richness decreased with increasing elevation. Reptile density showed a weak correlation with microhabitat features such as litter cover, litter depth, and soil moisture in both watersheds. Amphibian density was positively correlated with soil moisture, litter cover, and litter depth. Comparison showed that Dabka is richer and more diverse than Khulgarh, presumably because of the undisturbed habitat, broad and slow stream, and deeper forest litter of the former.

Long-Term Changes in Spatial Patterns and Life-Stage Structure in a Population of Senecio umbrosus Waldst. et Kit. Along With the Transformation of Grassland Vegetation

This paper was a part of studies conducted within an island population of the ragwort <em>Senecio umbrosus </em>(White Mt, southeastern Poland), a vulnerable element of xerothermic grasslands. Special attention was paid to the effects of expansive grass encroachment vs. grassland burning episodes on spatiotemporal patterns and life-stage structure of individuals in the population. The population traits were investigated nine times from 1990 to 2010, within three permanent patches differing in soil properties, initial floristic composition, grassland cover (particularly the cover of <em>Brachypodium pinnatum</em>), ragwort cover and density, shrub/tree cover influencing light intensity (full light–shadow), and grassland burning (zero–six episodes). There was a drastic decline in ragwort abundance within all the study patches accompanied by a decrease in the population clustering coefficient and a gradual equalization of the spatial distribution of ramets. The abundance was negatively correlated (PCA analysis) with an increase in <em>B. pinnatum </em>cover and positively correlated with the number of burning episodes, which temporarily delimited persistent litter cover and facilitated recruitment of new individuals. The decrease in ramet abundance ranged from 3.8 times (medium-high, moderately shadowed grassland; six cases of burning) to 8.3 times (high, dense, and shadowed grassland; four cases of burning). The patch of low, loose, sunlit, and never-burned grassland with the greatest initial density of ragwort (a 6.8-fold decrease in abundance) has evolved with time into a high and dense grassland with a greater coverage of <em>B. pinnatum </em>and <em>Calamagrostis epigejos</em>, additionally shaded by shrubs and young trees.

Canopy and Litter Cover Do Not Alter Diaspore Removal by Ants in the Cerrado

Diaspore removal by ants is a crucial stage for successful myrmecochory and can be directly or indirectly affected by natural or anthropic changes to environments. Among the consequences of such changes is variation in habitat attributes, such as changes in conditions and resources and, consequently, decreased diaspore removal or even the loss of this ecological function. The aim of this study was to assess whether canopy and litter cover affect diaspore removal by ants in the Cerrado. We considered canopy and litter cover as proxies of humidity and temperature and evaluated whether changes in these environmental conditions could affect diaspore removal by ants. We hypothesized that the greater the canopy and litter cover (higher humidity and lower temperature), the greater the number of diaspores removed by ants. We tested this hypothesis by establishing three classes of cover for each proxy: low, intermediate, and high. We placed artificial diaspores under each cover class and quantified the number of diaspores removed. We found that variation in canopy and litter cover did not affect the number of diaspores removed by ants in areas of cerrado sensu stricto. Variation in habitat attributes in natural environments were less important for diaspore removal than in modified areas. Our results indicate that understanding the processes and habitat atributes involved in diaspore removal by ants is important for conserving the Cerrado.

Importance of microhabitat selection by birds for the early recruitment of endangered trees in a fragmented forest

Background Remnant microhabitats are important for bird habitat selection and plant regeneration in the fragmented habitat. However, empirical information on the consequences of how microhabitat use by birds affects the early recruitment of plants is lacking. Methods In this study, we evaluated whether microhabitat selection by the Black Bulbul (Hypsipetes leucocephalus) (J. F. Gmelin, 1789) impacts the early recruitment of the endangered tree species, the Chinese Yew (Taxus chinensis (Pilger) Rehd), in a fragmented forest over a 4-year period (2011–2012, 2018–2019). Results Our results showed the main factors affecting H. leucocephalus microhabitat selection were distance to the nearest T. chinensis mature tree, herb cover and density, leaf litter cover, and vegetation type. Moreover, the results of logistic regression also highlighted the importance of elevation, distance to light gap and roads, tree cover in bird microhabitat selection. Furthermore, the seed emergence rate in microhabitats used by birds did not differ from the natural forest, which was related to five factors of bird microhabitat. The Random Forest model showed that seedling emergence rate was increased with leaf litter cover and distance to fallen dead trees, but decreased in relation to herb cover, slope, and elevation. Conclusion Our results highlight the importance of remnant microhabitats in fragmented forests for sustaining forest ecology and optimal management. The contribution of microhabitats used by birds to plant recruitment provides insights into how frugivore species contribute to plant regeneration, which should be incorporated in future conservation and management practices of fragmented forests.