BEN # 44

Adolf Ceska aceska at CUE.BC.CA
Sun Jan 24 03:00:00 EST 1993

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No. 44                            October 5, 1992

Address: aceska at         Victoria, B.C.

From: Evelyn Hamilton <ehamilton at>

                     V. COMMUNITY DIVERSITY

Biological and ecological processes
Mary Willson, USFS Juneau, AK

Her main point was that  units  of  conservation  should  be  the
interactions  between  organisms,  rather  than  the specific or-
ganisms. Our research has been  limited  in  terms  of  time  and
space.  Evolutionary processes have been ignored. Correlation has
been the focus rather than causation.

We need to understand and conserve interactions including:

 1. plant and animal interactions, e.g.
    a) bears, salmon and berries,
    b) treefall gaps where vegetation structure  influences  pol-

 2. plant and fungi interactions,

 3. fungi and tree interactions.

Tropical forests
Ariel Lugo, Univ. Puerto Rico Agr. Exp. Stn. Rio Piedras, PR

Many of our problems are social and economic. We need to:

 1. use natural resilience and manage sustainably,

 2. manage  the  landscape,  using natural succession to aid res-

Old-growth forests
Tom Spies, USFS, Corvallis, OR

Old growth is ecologically diverse. Disturbance is  important  at
the patch, mosaic and landscape levels.

Different types of old growth include:

 1. Coarse  grained  type  -  where  wind or fire is the agent of
    disturbance. Disturbances are large with patches > 0.1 ha  in
    size -
    a) short lived trees < 250 years e.g. aspen, red alder
    b) intermediate lived trees > 250 years e.g. Douglas-fir

 2. Fine grained type - more stable systems where the disturbance
    is more localized with patches < 0.1 ha. in size -
    a)  short  lived  trees  <250 years balsam fir, white spruce,
    black spruce,
    b) intermediate to long lived trees >250 years

Aquatic systems - freshwater and marine
Jack Williams, BLM, Washington, D.C.

In Canada there were 22 threatened or endangered species of  fish
in 1989. All of the fish species in the Colorado River are endan-
gered.  Over  67%  of  the fish species in Illinois have declined
significantly. On the west coast 214  salmon  stocks  are  endan-
gered.  In the Columbia Basin 19% of the fish species are at high
risk, > 1/3 have become extinct; <  1%  of  marine  habitats  are

Introduced  species  and  habitat  loss are critical factors con-
tributing to this species declines. In the US less than 2% of the
rivers are in a high quality state.

                    VI. LANDSCAPE DIVERSITY

Biological conservation at the landscape scale
Reed Noss, Corvallis, OR

Landscapes have  pattern  of  repeated  components.  Pattern  has
effect  on  species composition. He discussed disturbance regime,
fragmentation and reserve network  design  and  the  concepts  of
coarse  and fine filter. Protection of representative communities
(coarse filter) would protect 80% of the species.

Species are  distributed  along  environmental  gradients.  Since
plant  species  migrated  at  different  rates after the ice age,
using communities defined by vegetation to capture all components
of diversity may not be the  best  approach  in  times  of  rapid
climate change.

We  need  to  consider whole landscape management. Core areas and
linkages are likely important although these ideas have not  been
adequately tested. Some moderate level of disturbance will likely
maximize  diversity.  We  need to develop an optimal mix of seral
stages. Reserves should be large enough to be in a steady state.

We need to determine:

 1. How big do reserves need to be?

 2. How wide should corridors be?

 3. What type of human use is acceptable?

 4. What are the best habitat mosaics at regional scales?

Scaling issues for biodiversity protection
Scott Pearson, Oak Ridge National Lab, Oak Ridge, TN.

His summary was:

 1. Don't focus on a single concept like  corridors  or  patches,
    view the landscape as a whole.

 2. Don't destroy the natural heterogeneity of the landscape.

 3. Don't destroy landscape connectivity.

 4. Don't ignore the effects of critical thresholds.

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