نتایج جستجو برای: irans forests

تعداد نتایج: 39516  

Journal: :caspian journal of environmental sciences 2013
r. naghdi m. nikooy m. ershadifar

economic and environmental logging is important for sustainable wood production in the caspian forests, north of iran. predetermination of the skid trail network and directional felling is a usual recommended method to reduce logging impact. the aim of this study was evaluation of directional felling and finding factors effective on felling error. totally 135 trees were selected randomly for di...

2008
Gabriela Nunez-Iturri Ola Olsson Henry F. Howe

Hunting with firearms decimates primates of large and medium body size (>2 kg) that disperse the seeds of large-seeded trees. In continuous, un-fragmented forests of southeastern Peru regularly hunted with firearms for 30–40 years, large primates are extirpated and medium-sized (medium) primates are reduced 61% compared with protected forests. At hunted sites seedlings and small juveniles (<1 m...

Journal: :Ecology 2015
Andrew J Larson James A Lutz Daniel C Donato James A Freund Mark E Swanson Janneke HilleRisLambers Douglas G Sprugel Jerry F Franklin

Rates and spatial patterns of tree mortality are predicted to change during forest structural development. In young forests, mortality should be primarily density dependent due to competition for light, leading to an increasingly spatially uniform pattern of surviving trees. In contrast, mortality in old-growth forests should be primarily caused by contagious and spatially autocorrelated agents...

2005
Cindy M. Hale

In the Great Lakes region, little data exist on the distribution of exotic earthworm species or their relative impacts to soil structure and plant communities in forest types other than those dominated by sugar maple. Our objective was to document the earthworm populations in relation to their proximity to human development (e.g., campgrounds, boat landings, roads) in beech-maple dominated fore...

2004
Carey P. Yeager Andrew J. Marshall Claudia M. Stickler Colin A. Chapman

The effects of the fires that burned over 4.7 million ha of Indonesia’s tropical forests during 1997 and 1998 are largely unknown. We assess the immediate impacts of these fires on five forest areas representing several different habitats in Kalimantan 1-2 months after the fires went out. Comparisons of transects in burned and unburned forest areas were conducted at three sites: Tanjung Puting ...

Journal: :Journal of Machine Learning Research 2006
Nicolai Meinshausen

Abstract Random Forests were introduced as a Machine Learning tool in Breiman (2001) and have since proven to be very popular and powerful for high-dimensional regression and classification. For regression, Random Forests give an accurate approximation of the conditional mean of a response variable. It is shown here that Random Forests provide information about the full conditional distribution...

Journal: :CoRR 2006
Rafig P. Agaev Pavel Yu. Chebotarev

We study spanning diverging forests of a digraph and related matrices. It is shown that the normalized matrix of out forests of a digraph coincides with the transition matrix in a specific observation model for Markov chains related to the digraph. Expressions are given for the Moore-Penrose generalized inverse and the group inverse of the Kirchhoff matrix. These expressions involve the matrix ...

2011
Yuanhe Yang Yiqi Luo

Results The C : N ratio in plant tissue, litter, forest floor and mineral soil exhibited large variation across various sequences, with an average of 145.8 9.4 (mean SE), 49.9 3.0, 38.2 3.1 and 18.5 0.9, respectively. In most sequences, the plant tissue C : N ratio increased significantly with stand age, while the C : N ratio in litter, forest floor and mineral soil remained relatively constant...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2003
Heping Zhang Chang-Yung Yu Burton Singer

The advent of gene chips has led to a promising technology for cell, tumor, and cancer classification. We exploit and expand the methodology of recursive partitioning trees for tumor and cell classification from microarray gene expression data. To improve classification and prediction accuracy, we introduce a deterministic procedure to form forests of classification trees and compare their perf...

Journal: :Science 2015
S Trumbore P Brando H Hartmann

Humans rely on healthy forests to supply energy, building materials, and food and to provide services such as storing carbon, hosting biodiversity, and regulating climate. Defining forest health integrates utilitarian and ecosystem measures of forest condition and function, implemented across a range of spatial scales. Although native forests are adapted to some level of disturbance, all forest...

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