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971.
972.
A significant challenge facing forestry today is managing private forests sustainably in the face of continued ownership fragmentation
(i.e., parcelization). Cross-boundary coordination––where forest practices are coordinated across multiple properties––has
been proposed as a mechanism by which landscape-level ecological and economic benefits may be accrued in privately-owned landscapes,
but few tests of the concept exist. Using a case study approach, we quantify the extent to which ownership-centric forest
management is constrained by economies of scale and misses opportunities to achieve ecological objectives in three landscapes
in Wisconsin, USA. Methods are based on existing forest management plans and include spatial analysis of patch distributions
and shapes, simulation of forest practices, and calculation of net present value over a 20-year horizon. Our results indicate
substantial opportunity for cross-boundary coordination: between 62% and 88% of the managed properties within our study landscapes
were adjacent to other properties with forest management plans. At a patch scale, coordination can result in ecological benefits
that can be accrued into the future (e.g., maintenance of large patches and natural ecosystem boundaries). Because these landscapes
are already highly parcelized, however, coordination offers little opportunity to impact the overall landscape-scale structure.
Greater economies of scale can also be gained by coordinating forest practices, including increases in the size (16–99%) and
volume of timber sales (16–94%), and a modest economic advantage (3–6%). As first steps, investment in data infrastructure
and professional training are required to support cross-boundary multi-ownership forest management. More broadly is the need
to shift from policies and practices that are largely ownership-centric to those that include and better incorporate landscape-centric
perspectives. 相似文献
973.
974.
Rebecca M. Montague-Drake David B. Lindenmayer Ross B. Cunningham John A. Stein 《Landscape Ecology》2011,26(10):1383-1394
We explored the effects of a purported ‘reverse keystone species’, the Noisy Miner (Manorina melanocephala) using a long-term, large-scale dataset. Specifically, we identify whether this aggressive bird affects the landscape distribution
patterns of other avifauna, by displacing them into, or restricting their distribution to, less productive areas, and in so
doing, adheres to ‘isoleg theory’. We sought to determine the effect of abundance of the Noisy Miner on the abundance of other
birds (individual species and groups), and determine whether that effect was consistent with varying site productivity, using
a negative binomial distribution with a logarithmic link function, and an offset variable to account for variations in search
effort. Relationships between abundance of Noisy Miners and habitat variables were examined using a Poisson distribution with
a logarithmic link function scaled for extra-variation (quasi-Poisson regression). We demonstrate that when Noisy Miner abundance
is low, many small passerine species are more abundant on high productivity sites. However, as Noisy Miner abundance increases,
small passerine abundance decreases, with this decrease most apparent on productive sites. The same patterns were not evident
for birds considered ‘non-competitors’ of the Noisy Miner. We identify that both site productivity and vegetation structure influence the abundance of the Noisy Miner. We reveal that the species increasingly tolerates ‘less
desirable’ habitat attributes with increasing site productivity. The preference of the Noisy Miner for productive areas is
likely to have deleterious impacts on the long-term survival and reproductive success of other Australian woodland bird species,
many of which have already undergone severe declines. 相似文献
975.
María Uriarte Charles B. Yackulic Yili Lim Javier A. Arce-Nazario 《Landscape Ecology》2011,26(8):1151-1164
There is a pressing need to understand the consequences of human activities, such as land transformations, on watershed ecosystem
services. This is a challenging task because different indicators of water quality and yield are expected to vary in their
responsiveness to large versus local-scale heterogeneity in land use and land cover (LUC). Here we rely on water quality data
collected between 1977 and 2000 from dozens of gauge stations in Puerto Rico together with precipitation data and land cover
maps to (1) quantify impacts of spatial heterogeneity in LUC on several water quality indicators; (2) determine the spatial
scale at which this heterogeneity influences water quality; and (3) examine how antecedent precipitation modulates these impacts.
Our models explained 30–58% of observed variance in water quality metrics. Temporal variation in antecedent precipitation
and changes in LUC between measurements periods rather than spatial variation in LUC accounted for the majority of variation
in water quality. Urbanization and pasture development generally degraded water quality while agriculture and secondary forest
re-growth had mixed impacts. The spatial scale over which LUC influenced water quality differed across indicators. Turbidity
and dissolved oxygen (DO) responded to LUC in large-scale watersheds, in-stream nitrogen concentrations to LUC in riparian
buffers of large watersheds, and fecal matter content and in-stream phosphorus concentration to LUC at the sub-watershed scale.
Stream discharge modulated impacts of LUC on water quality for most of the metrics. Our findings highlight the importance
of considering multiple spatial scales for understanding the impacts of human activities on watershed ecosystem services. 相似文献
976.
Orang Estegamet 《Russian Agricultural Sciences》2010,36(2):125-126
Three-breed hybrids Cuban zebu x (Azerbaijan zebu x Aberdeen Angus) surpassed the Azerbaijan zebu and two-breed Azerbaijan
zebu with Brown Latvian, Black Pied, and Aberdeen Angus breeds in weight, length, width, area, and thickness of hides. Minimum
indices were obtained or purebred animals. 相似文献
977.
A species of the genus Gonoclostera Butler, 1877, G.fangi sp.nov., from Yunnan, China is described in the present paper. Generic diagnosis and list of world species, as well as the photos of adults and genitalia of the new species are also provided. 相似文献
978.
979.
Purpose
Cadmium (Cd) is a toxic heavy metal, accumulated in soil by anthropogenic activities and has serious effects on soil microbial activities in contaminated soils. Moreover, there is a lack of reliable data on the effects of Cd in the soil-plant system, since most of the information on Cd-microorganism interactions in soils are based on sewage sludge without plants. The main objective of this study was to assess the effects of Cd on soil microbial activities and community structure during growth of plant. 相似文献980.