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631.
Chazdon RL 《Science (New York, N.Y.)》2008,320(5882):1458-1460
Despite continued forest conversion and degradation, forest cover is increasing in countries across the globe. New forests are regenerating on former agricultural land, and forest plantations are being established for commercial and restoration purposes. Plantations and restored forests can improve ecosystem services and enhance biodiversity conservation, but will not match the composition and structure of the original forest cover. Approaches to restoring forest ecosystems depend strongly on levels of forest and soil degradation, residual vegetation, and desired restoration outcomes. Opportunities abound to combine ambitious forest restoration and regeneration goals with sustainable rural livelihoods and community participation. New forests will require adaptive management as dynamic, resilient systems that can withstand stresses of climate change, habitat fragmentation, and other anthropogenic effects. 相似文献
632.
Using rules extracted from experience to solve problems in novel situations involves cognitions such as analogical reasoning and language learning and is considered a keystone of humans' unique abilities. Nonprimates, it has been argued, lack such rule transfer. We report that Rattus norvegicus can learn simple rules and apply them to new situations. Rats learned that sequences of stimuli consistent with a rule (such as XYX) were different from other sequences (such as XXY or YXX). When novel stimuli were used to construct sequences that did or did not obey the previously learned rule, rats transferred their learning. Therefore, rats, like humans, can transfer structural knowledge from sequential experiences. 相似文献
633.
Secondary forests are more extensive than old-growth forests in many tropical regions, yet the genetic composition of colonizing populations is poorly understood. We analyzed the parentage of a founder population of 130 individuals of the canopy palm Iriartea deltoidea in a 24-year-old second-growth forest in lowland Costa Rica. Among 66 trees in adjacent old-growth forest, only two individuals contributed 56% of the genes in founders. Second-growth trees had lower genetic diversity and larger patches of similar genotypes than old-growth trees. Recovery of genetic diversity of populations in tropical second-growth forests may take many generations and will require continued dispersal from genetically diverse source populations. 相似文献
634.
635.
Canup RM 《Science (New York, N.Y.)》2005,307(5709):546-550
Pluto and its moon, Charon, are the most prominent members of the Kuiper belt, and their existence holds clues to outer solar system formation processes. Here, hydrodynamic simulations are used to demonstrate that the formation of Pluto-Charon by means of a large collision is quite plausible. I show that such an impact probably produced an intact Charon, although it is possible that a disk of material orbited Pluto from which Charon later accumulated. These findings suggest that collisions between 1000-kilometer-class objects occurred in the early inner Kuiper belt. 相似文献
636.
Vogel Sebastian Bönecke Eric Kling Charlotte Kramer Eckart Lück Katrin Philipp Golo Rühlmann Jörg Schröter Ingmar Gebbers Robin 《Precision Agriculture》2022,23(1):127-149
Precision Agriculture - Liming agricultural fields is necessary for counteracting soil acidity and is one of the oldest operations in soil fertility management. However, the best management... 相似文献
637.
638.
A detailed investigation of the basic fraction of a CO2 extract of ambrette seeds (Abelmoschus moschatus) revealed a total of 58 nitrogen-containing compounds. The identification of these compounds was carried out by GC-MS and NMR. All the identified nitrogen-containing compounds are reported here for the first time in ambrette seeds. Among these are 27 pyrazine derivatives and 12 pyridines, including the tentative identification of four new natural compounds, 1-(6-ethyl-3-hydroxypyridin-2-yl)ethanone (1), 1-(3-hydroxy-5,6-dimethylpyridin-2-yl)ethanone (2), 1-(3-hydroxy-6-methylpyridin-2-yl)ethanone (3), and 1-(3-hydroxy-5-methylpyridin-2-yl)ethanone (4). The odor of the basic fraction was assumed to be due to these pyrazines and pyridines and also the presence of seven thiazoles. The odors described suggest that these N-compounds contribute to what is described in perfumery terms as the "natural and rounded" character of the ambrette extract. 相似文献
639.
Jens Dauber Robin Niechoj Helmut Baltruschat Volkmar Wolters 《Biology and Fertility of Soils》2008,44(5):791-796
The role of edaphic factors in driving the relationship between plant community structure and ecosystem processes is a key
issue of the current debate on functional implications of biodiversity. In this study, we draw a direct link between aboveground/belowground
relationships, vegetation structure, and aboveground management. We used ground nesting ants and arbuscular mycorrhizal fungi
(AMF) as an example for quantifying the role of biotic interactions in soil. Although both groups are known to have a major
impact on grasslands, the interactive effect of these taxa on vegetation structure and its sensitivity to grassland management
is poorly understood. We show that the ant Lasius flavus increases the root arbuscular mycorrhizal colonization (AMC) of grasses by modifying biotic and abiotic soil properties.
As a possible consequence, the shoot length of grass growing on ant mounds was shorter and shoot N and P concentrations were
higher than in grass growing off of the mounds. In addition, management affected ant nest architecture and soil and, in turn,
AMC. These results emphasize the need to consider the interactions between plants, soil microorganisms, soil fauna, and aboveground
management to increase the understanding of the drivers of biodiversity and ecosystem functioning in grasslands both aboveground
and belowground. 相似文献
640.
Silverstein RP 《Science (New York, N.Y.)》2006,313(5788):758-60; author reply 758-60