A better understanding of colonizat

A better understanding of colonization processes is
critical to understanding the general patterns and processes
in plant communities. Grubb (1977) was among
the first to challenge the traditional view of nicheassembled
plant communities. By elaborating on the
different processes involved in colonization (the production
of viable diaspores, dispersal in space and time,
germination requirements, establishment of seedlings
and the further development of the immature plant),
Grubb stated that, at the local scale, differential colonization
capacities of plant species are of crucial importance
for the coexistence of large numbers of species with
similar resource requirements. Twenty years later, a growing body of literature confirms Grubb’s thesis. It
has been demonstrated that dispersal is a key factor in
community assembly. Evidence comes from observational
studies (e.g. Hubbell
et al
. 1999), experimental
studies (e.g. Turnbull
et al
. 2000) and mathematical
models (e.g. Tilman 1994).
Most data concern established communities perpetuated
by small-scale, low-intensity disturbances (i.e.
gap-phase dynamics). However, there is no reason to
believe that fundamentally different processes operate
when larger spatial scales and more intensive disturbances
are involved (Bazzaz 1996). Although our
understanding of the theoretical framework of succession
has been significantly improved (e.g. Connel &
Slatyer 1977; Huston & Smith 1987), the possibility
that a successional sere could be generated by species
having different dispersal capacities remains largely
unexplored. Recently, however, a simulation study by
Hovestadt
et al
. (2000) demonstrated that typical successional
patterns can be generated by differential dispersal
alone.
Forest herb communities develop slowly in secondary
forest established on former agricultural land. It
has been demonstrated that some species do not colonize
secondary forests even after tens to hundreds of
years, while others are able to recolonize quickly (e.g.
Peterken & Game 1984; Motzkin
et al
. 1996; Wulf
1997; for recent overviews see Hermy
et al
. 1999 and
Verheyen
et al
. 2003). A niche-based approach would
suggest that these highly different colonization capacities
are mainly a consequence of recruitment being
hampered by the poor habitat quality in young forests.
The relationship observed between habitat quality and
past land use depends both on the nature and duration
of the former land use and on processes related to
aggrading forest ecosystems. For instance, following
arable use, levels of mineral nutrients, especially phosphate,
generally increase (Koerner
et al
. 1997; Honnay
et al
. 1999). In conjunction with a still open canopy,
these promote the vigorous growth of competitive
species (
sensu
Grime
et al
. 1988) such as
Urtica
(Pigott
1971), which may, in turn, hamper the recruitment of
forest species. More recently, however, both observational
studies (Matlack 1994; Grashof-Bokdam 1997;
Brunet & von Oheimb 1998; Bossuyt
et al
. 1999;
Butaye
et al
. 2001; Dzwonko 2001; Singleton
et al
.
2001; Verheyen & Hermy 2001a,b) and experimental
studies (Ehrlén & Eriksson 2000) have demonstrated
that some form of dispersal limitation can also occur
in secondary forest succession.
We propose a model to explain the effects of past
land use on both environmental and canopy variables
and forest herb colonization (Fig. 1). Past land use can
have direct effects on herb colonization (from the physical
removal of the plant species and the subsequent
spatial and temporal isolation from their respective
colonization sources) as well as indirect effects caused
by its impact on habitat quality variables (e.g. on the
cover of competitive species or on soil nutrient levels).
In this study, structural equation modelling (SEM) is
introduced to quantify these direct and indirect effects,
and thus to perform a novel integrated analysis of the
colonization process. Furthermore, our study extends
work at the local scale (i.e. one forest patch), to the
landscape or land mosaic scale (i.e. forest patches
embedded in a non-forested, agricultural matrix).
Three specific questions are addressed. (i) Is spatiotemporal
isolation from diaspore sources a limiting
factor for forest herb colonization at a landscape scale?
(ii) What are the direct and indirect effects of past
agricultural land use on present-day habitat quality of
forests? (iii) What is the relative importance of these
two factors (isolation and quality) for landscape scale
colonization?

ผลลัพธ์ (อังกฤษ) 2:

A better understanding of colonization processes is
Critical to understanding the general Patterns and processes
in Plant communities. Grubb (1977) was among
the First to Challenge the traditional Nicheassembled View of
Plant communities. By elaborating on the
different processes involved in colonization (the Production
of viable diaspores, dispersal in Space and time,
Germination requirements, Establishment of seedlings
and the further Development of the immature Plant),
Grubb stated that, at the local scale, differential colonization
capacities. Plant species are of importance of CRUCIAL
for the coexistence of Large Numbers of species with
similar requirements Resource. Twenty years later, a growing body of literature confirms Grubb's thesis. It
has been demonstrated that dispersal is a Key factor in
Community Assembly. Evidence comes from observational
Studies (eg Hubbell
et al
. 1,999), Experimental
Studies (eg Turnbull
et al
. the 2000th) and mathematical
models (eg Tilman 1994).
Most Data Concern established communities perpetuated
by Small-scale, low-Intensity disturbances (IE.
gap-phase dynamics). However, there is no Reason to
Believe fundamentally different processes that operate
when Spatial Scales larger and more intensive disturbances
are involved (Bazzaz the 1996th). Although our
understanding of the theoretical Framework of succession
has been significantly improved (eg Connel &
Slatyer in 1977; Huston Smith & 1,987th), the possibility
that a successional species Sere could be Generated by
having different dispersal capacities remains largely
unexplored. Recently, however, a Simulation Study by
Hovestadt
et al
. (2000) demonstrated that successional Typical
Patterns Can be Generated by differential dispersal
alone.
Forest Herb Slowly develop communities in Secondary
Forest established on former Agricultural Land. It
has been demonstrated that Some species do not colonize
Secondary forests even after TENS to hundreds of
years, while others are Able to recolonize Quickly (eg
Peterken & Game one thousand nine hundred eighty-four; Motzkin
et al
. one thousand nine hundred ninety-six; Wulf
1 997; for recent overviews See Hermy
et al.
. one thousand nine hundred ninety-nine and
Verheyen
et al
. 2003). A Niche-based approach would
suggest that these highly different colonization capacities
are mainly a consequence of Recruitment being
hampered by the poor habitat quality in Young forests.
The Relationship observed between habitat quality and
Past Land use depends both on the nature and Duration
of the former. Land use and on processes related to
Aggrading Forest ecosystems. For instance, following
arable use, levels of Mineral nutrients, especially phosphate,
generally increase (Koerner
et al
. 1,997; Honnay
et al
. one thousand nine hundred ninety-nine). In conjunction with a still open canopy,
Promote the vigorous growth of these competitive
species (
sensu
Grime
et al
. 1988th) such as
Urtica
(Pigott
the 1,971th), May which, in turn, hamper the Recruitment of
Forest species. More recently, however, both observational
Studies (Matlack the 1994th; Grashof-Bokdam 1 997;
Brunet & von Oheimb one thousand nine hundred and ninety-eight; Bossuyt
et al
. 1999;
Butaye
et al
. in 2001; Dzwonko the 2,001th; Singleton
et al
.
2001; Verheyen & Hermy 2001a, B. ) and Experimental
Studies (Ehrlén & Eriksson the 2,000th) have demonstrated
that Some form of dispersal Limitation Can also occur
in Secondary Forest succession.
We Propose a Model to Explain the effects of Past
Land use on both Environmental and canopy variables
and Forest Herb colonization (Fig. . 1). Past Land use Can
have Direct effects on Herb colonization (from the physical
Removal of the Plant species and the Subsequent
Spatial and temporal isolation from their respective
colonization sources) as well as indirect effects caused
by its Impact on habitat quality variables (eg on the
Cover. of competitive species or on soil nutrient levels).
In this Study, Equation structural modeling (SEM) is
introduced to quantify these effects Direct and indirect,
and thus to Perform a novel Integrated Analysis of the
colonization Process. Furthermore, our Study extends
Work at the local scale (one IE patch Forest), to the
Landscape or Land Mosaic scale (Forest IE patches
embedded in a non-forested, Agricultural Matrix).
Three specific questions are addressed. (I) Is spatiotemporal
isolation from sources diaspore a limiting
factor for Forest Landscape Herb colonization at a scale?
(II) What are the effects of Direct and indirect Past
Agricultural Land Day use on present-quality habitat of
forests? (III) Relative What is the importance of these
factors Two (isolation and quality) for Landscape scale
colonization?

ผลลัพธ์ (อังกฤษ) 3:

A better understanding of colonization processes is
critical to understanding the general patterns and processes
in plant. Communities. Grubb (1977) was among
the first to challenge the traditional view of nicheassembled
plant communities. By. Elaborating on the
different processes involved in colonization (the production
of viable diaspores dispersal in, space. And time
germination requirements,,Establishment of seedlings
and the further development of the immature plant),
Grubb stated that at the local scale differential,,, Colonization
capacities of plant species are of crucial importance
for the coexistence of large numbers of species with
similar. Resource requirements. Twenty, years later a growing body of literature confirms Grubb 's thesis. It
.Has been demonstrated that dispersal is a key factor in
community assembly. Evidence comes from observational
studies (e.g.? Hubbell

. Et al 1999), experimental
studies (e.g. Turnbull

. Et al 2000) and mathematical
models (e.g. Tilman 1994).
Most. Data concern established communities perpetuated
by, small-scale low-intensity disturbances (i.e.
gap-phase dynamics). However,, There is no reason to
.Believe that fundamentally different processes operate sb when larger spatial scales and more intensive disturbances SB are involved EOS (Bazzaz 1996) in can Although our
understanding of the theoretical framework of succession
has been significantly improved (e.g in can EOS Connel &
Slatyer 1977; Huston & Smith 1987), the possibility
that a successional sere could be generated by species
.Having different dispersal capacities remains largely
unexplored. Recently however, a simulation, study by

, Hovestadt et Al
. (2000) demonstrated that typical successional
patterns can be generated by differential dispersal

Forest, herb alone. Communities develop slowly in secondary
forest established on former agricultural land. It
has been demonstrated that some. Species do not colonize
.Secondary forests even after tens to hundreds of
years while others, are able to recolonize quickly (e.g.
Peterken & Game. 1984; Motzkin

. 1996 et al; Wulf
1997; for recent overviews see Hermy

. 1999 et al and


. Verheyen et al 2003). A niche-based. Approach would
suggest that these highly different colonization capacities
are mainly a consequence of recruitment being
.Hampered by the poor habitat quality in young forests.
The relationship observed between habitat quality and
past land. Use depends both on the nature and duration
of the former land use and on processes related to
aggrading forest, ecosystems. For instance, following
arable use, levels of mineral nutrients, especially phosphate,
generally increase (Koerner
et al
in can EOS 1997 western Honnay sb et al sb. 1999).In conjunction with a still, open canopy
these promote the vigorous growth of competitive



species (sensu Grime et, Al
. 1988) such as


Urtica (Pigott 1971), which may in, the, turn hamper recruitment of
forest species. More recently however,,, Both observational
studies (Matlack 1994; Grashof-Bokdam 1997;
Brunet & von Oheimb 1998; Bossuyt

. 1999 et al;

, Butaye et Al
. 2001; Dzwonko 2001;Singleton
et al
in can
2001; Verheyen & Hermy 2001a, b) and experimental
studies (Ehrl é n & Eriksson 2000) have demonstrated
that EOS Some form of dispersal limitation can also occur sb in secondary forest succession from sb We propose a model to explain the effects EOS Of past
land use on both environmental and canopy variables
and forest herb colonization (Fig. 1). Past land use can
.Have direct effects on herb colonization (from the physical
removal of the plant species and the subsequent
spatial and. Temporal isolation from their respective
colonization sources) as well as indirect effects caused
by its impact on habitat. Quality variables (e.g in can on the
cover of competitive species or on soil nutrient levels) in can
In this study, structural equation EOS Modelling (SEM) is sb EOSIntroduced to quantify these direct and indirect effects
and, thus to perform a novel integrated analysis of the
colonization. Process. Furthermore our study, extends
work at the local scale (i.e. One forest patch), to the
landscape or land mosaic. Scale (i.e. Forest patches
embedded in, a non-forested agricultural matrix).
Three specific questions are addressed. (I). Is spatiotemporal
.Isolation from diaspore sources a limiting
factor for forest herb colonization at a landscape scale?
(II) What are the. Direct and indirect effects of past
agricultural land use on present-day habitat quality of
forests? (III) What is the relative. Importance of these
two factors (isolation and quality) for landscape scale
colonization?