1
Biomass distribution of two subalpine dwarf shrubs with contrasting leaf habit in
2
relation to soil moisture and soil nutrient content
3
4
Renato Gerdol* grn@unife.it, Tommaso Anfodillo† tommaso.anfodillo@unipd.it,
5
Matteo Gualmini# matteo.gualmini@tiscali.it, Luca Bragazza* brc@unife.it and Lisa
6
Brancaleoni* bcl@unife.it
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8
*
9
Mare 2 I-44100 Ferrara, Italia
Dipartimento delle Risorse Naturali e Culturali, Università di Ferrara, Corso Porta
10
# Dipartimento di Biologia Evolutiva e Funzionale, Università di Parma, Parco Area
11
delle Scienze 11/A, I-43100 Parma, Italia
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13
†
Dipartimento Territorio e Sistemi Agro Forestali, Università di Padova, Via Romea 16,
35020 Legnaro (Padova), Italia
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15
Correspondence: R. Gerdol, Dipartimento delle Risorse Naturali e Culturali, Università
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di Ferrara, Corso Porta Mare 2, 44100 Ferrara Italia, tel. +39 (0)532 293775, fax +39
17
(0)532 208561, e-mail: grn@unife.it
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Abstract
20
21
We determined the biomass of Vaccinium myrtillus and V. vitis-idaea at three sites, each
22
on a different substrate type, in a subalpine heath in the Alps (Northern Italy). Our aim
23
was to assess if, and to what extent, the biomass of the two shrubs was affected by soil
24
water content and/or soil nitrogen (N) content and/or soil phosphorus (P) content. V.
1
1
myrtillus biomass was highest at the silicate site, V. vitis-idaea biomass was highest at
2
the carbonate site while the biomass of both shrubs was low at the peat site, possibly
3
due to a toxic effect of waterlogging in wet soils. For both species, pre-dawn leaf
4
potential (l) indicated optimal hydration and midday l did not show any sign of water
5
stress. Water use efficiency (WUE) did not differ among sites for any species. Whole-
6
plant nutrient concentrations showed that with increasing biomass, N was diluted in V.
7
myrtillus tissues while P was diluted in V. vitis-idaea tissues. While foliar N
8
concentration was overall higher for V. myrtillus, with no effect of site, foliar P
9
concentration in V. myrtillus distinctly peaked at the silicate site. The foliar N : P ratios
10
suggested that V. myrtillus was primarily P limited and V. vitis-idaea primarily N
11
limited. We conclude that soil water content affected the distribution of the two shrubs
12
in a similar way, whereas higher P availability in the soil enhanced V. myrtillus rather
13
than V. vitis-idaea.
14
15
Keywords: Alps, Nitrogen, Phosphorus, Vaccinium, Water potential, 13C, 15N
16
17
Number of words in the ms: 5075 including abstract and references.
18
2
1
Introduction
2
3
Vaccinium myrtillus and V. vitis-idaea are the most abundant ericaceous dwarf
4
shrubs in the mountainous regions of Central Europe as well as in the boreal and
5
subarctic regions of Northern Europe, where they are widespread both in the understory
6
of conifer forests and in treeless open habitats. In the latter, these two shrubs represent
7
major components of heath vegetation (Ellenberg 1988; Dierßen 1996). Although
8
belonging to the same genus and sharing the same growth form, these two species differ
9
in terms of leaf life span, with V. myrtillus possessing deciduous leaves and V. vitis-
10
idaea evergreen leaves. The evergreen species may be assumed to be at a competitive
11
advantage in habitats experiencing summer drought (Mooney 1982; Salleo et al. 1997),
12
nutrient shortage (Aerts & Chapin 2000), or both (Field et al. 1983).
13
To our knowledge, no study has so far addressed the response patterns of
14
Vaccinium species to soil water content in (sub)alpine–(sub)arctic habitats, albeit Havas
15
(1971) studied the water economy of V. myrtillus under winter conditions in relation to
16
snow cover. Ingestad (1973) found V. myrtillus and V. vitis-idaea to have similar
17
requirements for nitrogen (N) and phosphorus (P) under controlled growing conditions.
18
More recently, Mäkipää (1999) reported almost overlapping ecological optima for these
19
two species along gradients of soil N and P contents in a boreal forest. However, the
20
results of those studies cannot be used to assess the response of V. myrtillus and V. vitis-
21
idaea to soil nutrient status in subalpine heath, for two main reasons. Ingestad (1973)
22
supplied N and P as inorganic nutrient solutions whereas in (sub)alpine and (sub)arctic
23
soils a large fraction of N and P is mostly tied into recalcitrant soil organic matter
24
(Näsholm & Persson 2001). Furthermore, in the forest understory water availability and
3
1
especially light regime vary strongly, and may synergistically affect the distributional
2
patterns of dwarf shrubs differently compared to treeless heath.
3
We studied the biomass distribution of V. myrtillus and V. vitis-idaea in three
4
subalpine treeless habitats, corresponding to different substrate types, where the two
5
species co-exist under sharply differing conditions of soil water content and soil nutrient
6
contents. Our objective was to assess if, and to what extent, the biomass of V. myrtillus
7
and V. vitis-idaea in the three habitats was affected by soil water content and/or soil
8
nutrient contents. We also aimed at determining if the responses of the two shrubs to
9
soil N and/or soil P contents in subalpine soils overlapped or, alternatively, if the two
10
species performed differently in relation to soil N and P availability, in total and in
11
organic and inorganic soil fractions.
12
13
14
Materials and methods
15
16
Description of the study area
17
18
The study was carried out in the southeastern Alps, close to San Pellegrino Pass
19
(Province of Trento, Italy, 46° 22’ N, 11° 47’ E; c. 1800 m elevation). The landscape in
20
this area consists of a mosaic of Norway spruce (Picea excelsa L.) forests, dwarf shrub
21
heaths, grasslands and, to a lesser extent, mires. Two bedrock types prevail: porphyry of
22
Permian age and limestone of Triassic age. The mire areas are covered partly by
23
shallow sedge peat and partly by deeper Sphagnum peat. The climate is cool temperate
4
1
with a mean annual temperature of ca. 2 °C at 2000 m and a mean total annual
2
precipitation of ca. 1200 mm, mostly concentrated in summer (Fliri 1975).
3
4
Field work
5
6
The field work was carried out in 1999. At the beginning of the growing season
7
(early June) three 1 ha sites were chosen, each on one of three different substrate types:
8
carbonate bedrock, silicate bedrock and Sphagnum peat. Eight 1  1 m plots were
9
chosen for sampling in each of the three sites. The choice of the sampling plots was
10
subjective but all plots were similar as regards light level (no tree cover), aspect (almost
11
flat terrain) and elevation (ca. 1800 m a.s.l.).
12
We are well aware that our sampling was pseudoreplicated within substrate type,
13
but have treated the data accordingly. We also recognize that some factors not
14
determined in our analyses, especially soil temperature, are likely to vary systematically
15
with site and might hence affect the growth of the two species to some extent. However,
16
inclusion of replicate sites would have introduced additional sources of variation,
17
associated for example with elevation and aspect. Furthermore, our protocol implied
18
acquisition of many kinds of data within a short time. In particular, we determined leaf
19
water potential on a clear day after six days without precipitation, which corresponded
20
to a relatively long dry period, when compared to the mean course of summer
21
precipitation in this region. Such a task could hardly be accomplished if the sampling
22
sites had to be located even at a moderate distances from each other, due to considerable
23
local variation in precipitation patterns.
5
1
The field measurements of leaf water potential, the soil sampling and the biomass
2
harvests were performed at the peak of the growing season. Samples of senescing leaves
3
were collected at the end of the growing season.
4
Leaf water potential (l) was measured for both species on 20 July 1999. Three to
5
five current-year leaves of V. myrtillus and V. vitis-idaea were sampled at each site
6
during the pre-dawn and midday periods. For data to be comparable among sites,
7
measurements had to be taken within short periods (4.00 to 5.00 and 12.00 to 13.00
8
solar time for the pre-dawn and the midday periods, respectively) and the sample size
9
therefore close to the maximum possible. Each leaf was detached and immediately
10
enclosed into a pressure chamber (Scholander et al. 1965), together with a small piece
11
of attached stem surface jutting out of a rubber stopper. The chamber was pressurised, at
12
a rate of ca. 0.03 Mpa s-1, and l measured by recording when sap was visible on the
13
xylem surface.
14
Four soil samples were collected from each plot on the same day when leaf water
15
potential was measured (20 July 1999), using a 10 cm long stainless steel corer (inner Ø
16
6.6 cm). One of the samples served for gravimetric determinations of soil water content.
17
The remaining three samples were bulked, immediately carried to the laboratory and
18
extracted as described below.
19
All biomass harvests were performed after the water potential measurements, as
20
well as the soil sampling, had been completed (21-23 July), in order to avoid any
21
disturbance. In each plot three 25 × 25 cm monoliths were excavated to a depth of 20
22
cm. We separated aboveground and belowground biomass for all vascular plant species,
23
while only aboveground biomass was considered for mosses.
6
1
The biomass of V. myrtillus and V. vitis-idaea was separated into the following
2
parts: current-year leaves, old leaves (V. vitis-idaea only), current-year shoots, old
3
aboveground stems, belowground stems (including buried stems, rhizomes and coarse
4
roots – Ø > 0.5 mm) and fine roots (Ø < 0.5 mm). Since a considerable fraction of the
5
fine roots was lost on harvesting, we collected a soil sample at each plot using the same
6
corer employed for sampling soils. It was impossible to separate the fine roots at the
7
species level but it was possible to discriminate between the dark coloured roots of
8
ericaceous shrubs and the whitish roots of other vascular species. Hence, the dark roots
9
recovered from the soil cores were allocated to V. myrtillus and V. vitis-idaea based on
10
the fractions of the biomass recovered manually for each of the two species.
11
On 17 September, senescing leaves of V. myrtillus and V. vitis-idaea were
12
collected by gently shaking all ramets of the two species in the plots. Ten senescing
13
leaves for each species were used for determining mass loss, in turn serving for
14
estimating nutrient resorption prior to leaf abscission (see below). The leaf area was
15
measured by a portable leaf area meter (ADC 100; Adc Co, Hoddesdon, UK). The
16
leaves were then oven-dried and weighed in order to determine mass per unit leaf area.
17
18
Laboratory work
19
20
All plant materials, including the senescing leaves, were oven-dried for 48 h at 70
21
°C and weighed. A subsample was oven-dried for 24 h at 105 °C and weighed to
22
determine the mass loss between 70 °C and 105 °C. The remainder was stored and
23
subsequently used for chemical analyses. The different plant parts, as well as the
24
senescing leaves, of V. myrtillus and V. vitis-idaea were analysed separately for N and
7
1
P. Total N concentration was determined by applying the Kjeldahl method to ca. 0.5 g
2
dry material digested in selenous sulphuric acid. Total P concentration was determined
3
by applying the molybdovanadate method (Allen 1989) to ca. 0.5 g fresh material
4
digested in concentrated nitric acid. Stable isotopes were measured on 3-5 current-year
5
healthy leaves of V. myrtillus and V. vitis idaea, detached from different ramets and
6
powdered. Carbon (C) isotope discrimination served as an estimate of water use
7
efficiency (WUE), whereas N isotope discrimination was used for estimating sources of
8
N taken up from the soil (see Gerdol et al. 2002).
9
One of the two soil subsamples collected at each plot was weighed in the field
10
using a portable balance, brought to the laboratory, oven-dried for 24 h at 105 °C and
11
re-weighed for determining soil water content gravimetrically. The remaining bulk
12
samples (see Soil sampling) were brought to the laboratory and used for further analyses
13
(see Allen 1989 for description of methods). A subsample was kept refrigerated at 4 °C
14
for 24 h, sieved (2 mm mesh width), and extracted within 24 h for determination of
15
inorganic soil N and P contents. Ca. 25 g of fresh soil were digested for 1 h with 250 ml
16
of 6% KCl and analysed for N concentration by the indophenol-blue method. The pH of
17
the solution was measured prior to N analysis. Ca. 5 g of fresh soil were digested for 30
18
min with 500 ml of Truog’s reagent and analysed for P concentration by the
19
molybdenum-blue method. A second subsample was air-dried for some days. Ca. 0.5 g
20
of material was then used for determining total soil N and total soil P contents, as for
21
the plant material. A third subsample was ashed for 48 h at 550 °C and re-weighed for
22
determining the loss on ignition, which was used as an estimate of soil organic matter
23
(SOM) content.
24
8
1
Computations and statistical analyses
2
3
Significance of differences between species and among sites, and their interaction
4
when appropriate, were assessed using one-way or two-way ANOVAs. Bonferroni post
5
hoc tests were run separately for each species in order to assess significance of among-
6
site differences for each variable. Heteroscedastic data were arcsin-transformed prior to
7
statistical analysis. All statistical computations were performed using the package
8
Statistica (Release 6; StatSoft Inc, Tulsa, USA).
9
Percentages of nutrients resorbed from senescing leaves were calculated as in
10
Gerdol et al. (2000). We first calculated leaf nutrient pools at the peak season harvest
11
and then nutrient pools in the senescing leaves based on the loss in mass determined in
12
the senescing leaves as described above.
13
14
Results
15
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Biomass
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The biomass of both species varied across plots by more than an order of
19
magnitude (100 – 3700 g m-2 for V. myrtillus and 35 – 1400 g m-2 for V. vitis-idaea). V.
20
myrtillus biomass was by far greatest (> 50% of the total community biomass) in the
21
silicate site, intermediate in the carbonate site and lowest in the peat site (Fig. 1).
22
However, the percentage fractions of total community biomass for V. myrtillus were not
23
significantly different between the carbonate and peat sites (Fig. 1). V. vitis-idaea
24
biomass was highest in the carbonate site, where V. vitis-idaea made up 25% of the total
9
1
community biomass. The biomass and the fraction of total community biomass for V.
2
vitis-idaea were much lower in the silicate and peat sites (Fig. 1).
3
4
Soil water content and soil chemistry
5
6
Soil water content in the peat site was 3-4 times that in the carbonate and silicate
7
sites. The soil was non-acidic (pH > 7.0) in the carbonate site and moderately acidic in
8
the silicate and peat sites. Soil organic matter (SOM) was very high in the peat site,
9
intermediate in the carbonate site and lowest in the silicate site (Table 1).
10
Since SOM content differed so greatly among sites, soil nutrient concentrations
11
were expressed as fractions of soil SOM rather than fractions of soil mass (Table 1).
12
Soil total N concentrations had the following across-site ranking: carbonate = silicate >
13
peat. In contrast, soil inorganic N concentrations did not differ among the three sites.
14
Soil total P concentrations were ranked as follows across sites: silicate > carbonate >
15
peat whereas soil inorganic P concentrations were ranked in this order: silicate >
16
carbonate = peat (Table 1).
17
18
Plant water status and plant nutrient content
19
20
Pre-dawn l and midday l did not vary either between species or among sites
21
(Table 2). Whole-plant N concentration was only weakly (P = 0.08; Table 2) greater in
22
V. myrtillus than in V. vitis-idaea. Whole-plant N concentration peaked in the peat site
23
for V. myrtillus and in the silicate site for V. vitis-idaea, thus resulting in a significant
24
species × site interaction (Table 2). Whole-plant P concentration did not differ between
10
1
the two species but did differ among sites, with highest concentrations in the silicate
2
site, especially for V. vitis-idaea (Table 2). The whole-plant N : P ratio also was similar
3
for the two species, being always lowest in the silicate site (Table 2).
4
The foliar N concentrations were consistently higher for V. myrtillus in all three
5
sites (Table 2). The foliar P concentrations also were higher for the deciduous species.
6
However, the foliar P concentrations and the foliar N : P ratios differed significantly
7
both between species and among sites, with a significant species × site interaction
8
(Table 2) resulting from V. myrtillus leaves having the highest P concentration and
9
lowest N : P ratio in the silicate site, and V. vitis-idaea leaves having somewhat higher P
10
concentrations and lower N : P ratios in the silicate and peat sites compared to the
11
carbonate site (Table 2).
12
13
N and C discrimination
14
15
V. vitis-idaea had lower, i.e. more negative, 15N values compared to V. myrtillus.
16
The across-habitat ranking of 15N was silicate > carbonate > peat for both species, with
17
no significant species × site interactions (Table 2). The foliar 13C was more negative
18
for V. myrtillus which had highest, i.e. least negative, values in the silicate site. The
19
13C did not vary among habitats for V. vitis-idaea (Table 2).
20
21
Nutrients in senescing leaves and nutrient resorption
22
23
The N concentrations in senescing leaves did not differ between species, but did
24
differ among sites, with a significant species × site interaction. The latter depended on
11
1
the fact that N concentrations in senescing leaves peaked in the silicate site for V.
2
myrtillus and, although more weakly, in the peat site for V. vitis-idaea (Table 2). The P
3
concentrations in senescing leaves differed both between species and among habitats,
4
with highest values in the silicate site. That peak was stronger for V. myrtillus, the
5
senescing leaves of which exhibited P concentrations twice as high in the silicate site
6
than in the carbonate and peat sites (Table 2).
7
The estimated percentage of nutrients resorbed from senescing leaves varied both
8
between species and among sites. V. vitis-idaea resorbed > 50% N and > 70% P in all
9
sites. In contrast, V. myrtillus resorbed a considerably lower fraction of N, and
10
especially P, in the silicate and peat sites (Table 3).
11
12
13
Discussion
14
15
Water
16
17
Neither the pre-dawn nor the midday water potentials l give any indication of
18
water stress in the two species. Pre-dawn l is high for both species in all three habitats,
19
indicating optimal hydration even after a relatively long dry period. To our knowledge,
20
critical l for stomatal closure has not been determined for the two species investigated.
21
However, our minimum midday l values (ca. -1.5 MPa; see Table 2) are close to those
22
reported for V. angustifolium in the absence of any symptom of water stress (Hicklenton
23
et al. 2000) and far above the threshold of 2.2 MPa, at which stomatal closure is
24
documented in Vaccinium ashei (Davies & Johnson 1982). Observed midday l values
12
1
are consistent with measurements of stomatal conductance which are, for both species,
2
independent of soil moisture content. Lack of variation in 13C across habitats further
3
supports our conclusion that water is not limiting at our sites during the study period. In
4
fact, if any species had experienced appreciable stomatal closure in response to drought
5
in any habitat during the study period, this would have implied among-habitat variation
6
in water-use efficiency for that species in that habitat.
7
In conclusion, our data indicate that water shortage is unlikely to represent a
8
limiting factor in the subalpine heath ecosystems investigated. Occasional strong
9
drought has been observed to constrain growth of Vaccinium myrtillus in open lichen-
10
rich pine forests in boreal regions (Økland & Eilertsen 1993). Since our study was not
11
directed to cover the whole gradient in soil water content where the two species occur in
12
subalpine habitats, we cannot exclude limitation of Vaccinium myrtillus by drought at
13
more strongly arid sites. In fact, recent research shows that optima of subalpine
14
ericaceous shrubs coincide along the gradient in available soil water, with the driest
15
sites being covered by grasslands (Michalet et al. 2002). Our data also indicate growth
16
limitation of the two shrubs by excess soil hydration in the wettest habitat. This is very
17
probably due to a toxic effect of anoxia to ericaceous roots (Miller 1982; Wallén 1987).
18
Again, this effect does not seem to differ between the two species.
19
20
Nutrients
21
22
The biomass patterns of the two shrubs are related to nutrient concentration
23
patterns, but with differing responses of the two species to soil N and P contents.
24
Indeed, V. myrtillus biomass is higher where soil P content is greater while that of V.
13
1
vitis-idaea is less distinctly related to soil nutrient contents. In V. myrtillus, the low
2
whole-plant N concentration at high-biomass sites, especially the silicate site, means
3
that N uptake for this species is independent of soil N concentration and plant demand,
4
so that N was diluted as biomass accumulates. In V. vitis-idaea, the whole-plant P
5
concentrations are lowest at the carbonate site. Hence, N uptake for V. vitis-idaea and P
6
uptake for V. myrtillus must keep pace with rates of biomass accumulation. Similarly,
7
De Lucia & Schlesinger (1995) found poor correlation between N and P concentrations
8
for deciduous and evergreen shrubs in a North American temperate swamp. This means
9
that the uptake of these two nutrients from infertile soils may vary in relation to leaf
10
habit and may, furthermore, be uncoupled for some species. Possible mechanisms
11
behind these differences may be related to the form of nutrients taken up by shrubs, the
12
kinetics of root uptake, the mobility of ions in the soil, or some combination of these.
13
V. myrtillus biomass increases more than V. vitis-idaea biomass when plants grow
14
under high levels of inorganic N (Grelet et al. 2001). However, in the experiment of
15
Grelet et al. (2001) mycorrhizal infection is insignificant, so that the plants probably
16
rely solely on inorganic N, while in natural soil mycorrhizal infection of ericoid roots is
17
almost ubiquitous and the plants assimilate N from several sources, organic and
18
inorganic (Smith & Read 1997; Sokolovski et al. 2002). Rates of P uptake are mainly
19
affected by soil P availability (Lambers et al. 1998). Albeit the importance of the role of
20
ericoid mycorrhizas in P nutrition of their host plants has long been eclipsed by that for
21
N nutrition (see Read 1996 for review), recent evidence suggests that organic P can be
22
effectively taken up by ericaceous shrubs with help of their mycorrhizal associate
23
(Myers & Leake 1996). On the other hand, mycorrhizas can also increase diffusion
24
zones around roots thus enhancing rates of inorganic P uptake (Bolan 1991).
14
1
Since foliar 15N in ericaceous shrubs is closely associated with the activity of the
2
mycorrhizal associate (Emmerton et al. 2001), foliar 15N may reflect degree of
3
mycorrhizal infection for the two species in the three habitats. If so, our 15N suggest
4
that mycorrhizal infection increases across habitats in the following direction: silicate <
5
carbonate < peat, always being higher for V. vitis-idaea. A preliminary assessment of
6
mycorrhizal infection in ericoid roots at a subalpine heath habitat close to the study sites
7
partly supports this hypothesis since percentage of root cells colonized by fungal
8
endophyes is greater, and foliar 15N more negative, in V. vitis-idaea compared to V.
9
myrtillus (L. Brancaleoni unpubl. data).
10
Patterns of between-species and among-habitat foliar nutrient concentrations
11
differ remarkably from those of whole-plant nutrient concentrations. Leaf N and P
12
concentrations vary much more strongly between species than whole-plant N and P
13
concentrations. This demonstrates that foliar nutrient concentrations are intrinsically
14
associated with leaf habit although they can also reflect soil nutrient availability
15
(Hobbie & Gough 2002). Indeed, evergreen leaves usually are sclerophyllous, which
16
implies lower crude fibre : crude protein ratio and lower concentrations of nutrients,
17
especially P, in evergreen leaves (Turner 1994). Secondly, in the three habitats both
18
species have similar foliar N concentrations and these are unrelated to leaf mass (data
19
not shown). This means that the two shrubs allocate more N to leaves as biomass and,
20
hence, leaf mass increase. Similarly, Woodward (1986) demonstrate leaf N
21
concentrations in V. myrtillus that are independent of soil N content, although
22
increasing with altitude. This implies existence of some mechanism for maximising leaf
23
N which, in turn, optimises net photosynthetic rates if other factors are not limiting.
15
1
Despite overall higher foliar P concentrations, V. myrtillus allocate proportionally
2
less P to leaves than V. vitis-idaea, except in the richest site. As a consequence, in the
3
poorest sites the N : P ratio in V. myrtillus approaches the threshold (of ca. 16) for
4
indication of P limitation. In contrast, the N : P ratio in V. vitis-idaea leaves is always
5
below the threshold (of ca. 14) indicating N limitation (Koerselman & Meuleman
6
1996). Indeed, sclerophylly has since long been known to represent an adaptation to P
7
deficiency (Loveless 1962). In British upland heaths Calluna vulgaris, evergreen, is
8
more abundant on P-poor soils whereas V. myrtillus is more abundant on P-rich soils
9
(Kirkham 2001). The two Vaccinium species also differ from each other as regards the
10
amounts of nutrients resorbed prior to leaf abscission. The lower fraction of nutrients,
11
especially P, resorbed by V. myrtillus makes the deciduous litter richer in nutrients
12
compared to the evergreen litter (Aerts & van der Peijl 1993). This may further enhance
13
the release to soil of (either organic or inorganic) P compounds, especially at the silicate
14
site, during the first stage of rapid decomposition of deciduous litter (Johansson 1993).
15
16
Acknowledgements
17
18
R. Marchesini L. Cristofori and L. Furlanetto helped with part of the field work
19
and laboratory analysis. P. Iacumin did the isotope analyses. All are kindly
20
acknowledged. We thank R.H. Økland, A. Tolvanen and P.S. Karlsson for constructive
21
criticism on a previous version of the paper. This work was supported by a grant of
22
Ferrara University to R. Gerdol.
23
24
References
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Allen, S.E. 1989. Chemical Analysis of Ecological Materials. Blackwell, Oxford.
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Bolan, N.S. 1991. A critical review on the role of mycorrhizal fungi in the uptake of
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20
Table 1. Mean (± 1 SE) for water content, pH, SOM, total and inorganic N and P
concentrations in the soil at the three sites. P values indicate the probabilities of the F values
for species, site and their interaction, resulting from one-way ANOVAs (significant values
in bold face). The means followed by the same letter within each row do not differ at P <
0.05 in Bonferroni post-hoc tests.
Carbonate Site
Silicate Site
Peat Site
P (F)
193 ± 22 b
144 ± 23 b
739 ± 32 a
< 0.001
5.82 ± 0.13 a
5.04 ± 0.06 b
4.89 ± 0.08 b
< 0.001
56 ± 9 b
34 ± 7 c
98 ± 1 a
< 0.001
Total N (mg g SOM)
17.3 ± 2.1 a
22.7 ± 3.8 a
3.3 ± 0.3 b
< 0.001
Total N (mg kg-1 SOM)
18.0 ± 2.5 a
15.6 ± 2.2 a
17.0 ± 2.3
0.77
Total P (mg g-1 SOM)
0.93 ± 0.06 b
1.81 ± 0.30 a
0.22 ± 0.02 c
< 0.001
Total P (mg kg-1 SOM)
1.76 ± 0.26 ab
3.03 ± 0.85 a
1.18 ± 0.23 b
0.05
Water content (% dry weight)
pH
SOM (% dry weight)
-1
21
Table 2. Means (± 1 SE; n = 8) of: pre-dawn and midday leaf water potentials (l); N and P
concentrations and N : P ratios in total biomass, in current-year mature leaves and in
senescing leaves (litter); stable N and C composition in current-year mature leaves (15N
and 13C) for Vaccinium myrtillus and Vaccinium vitis-idaea in the three sites. The P values
indicate the probabilities of the F values for species, site and their interaction, as resulting from twoway ANOVAs (significant values in bold face). The means followed by the same letter within each
row do not differ at P < 0.in Bonferroni post-hoc tests
P (F)
Species
Carbonate Site
Silicate Site
Peat Site
Species
Site
Interact.
-0.26 ± 0.04 a
-0.21 ± 0.06 a
-0.21 ± 0.02 a
0.10
0.07
0.33
V. vitis-idaea
-0.22 ± 0.02 a
-0.23 ± 0.05 a
-0.28 ± 0.02 a
V. myrtillus
-1.15 ± 0.11 a
-1.03 ± 0.09 a
-1.47 ± 0.08 a
0.20
0.78
0.70
V. vitis-idaea
-1.53 ± 0.01 a
-1.27 ± 0.10 a
-1.46 ± 0.21 a
V. myrtillus
7.22 ± 0.24 b
6.94 ± 0.27 b
10.11 ± 0.62 a
0.08
0.03
< 0.001
V. vitis-idaea
7.34 ± 0.28 ab
7.96 ± 0.29 a
6.43 ± 0.35 b
V. myrtillus
0.59 ± 0.04 b
0.87 ± 0.07 a
0.92 ± 0.06 a
0.60
< 0.001
0.04
V. vitis-idaea
0.63 ± 0.05 b
1.06 ± 0.06 a
0.78 ± 0.07 b
V. myrtillus
12.4 ± 0.6 a
8.2 ± 0.6 b
11.1 ± 0.7 a
0.11
< 0.001
0.36
V. vitis-idaea
12.2 ± 0.9 a
7.6 ± 0.3 b
8.9 ± 1.0 b
V. myrtillus
17.30 ± 0.88 a
18.16 ± 0.79 a
19.02 ± 0.43 a
< 0.001
0.33
0.35
V. vitis-idaea
9.22 ± 0.42 a
9.68 ± 0.35 a
9.24 ± 0.30 a
V. myrtillus
1.19 ± 0.14 b
1.96 ± 0.11 a
1.34 ± 0.06 b
V. vitis-idaea
0.70 ± 0.05 b
0.94 ± 0.03 a
0.88 ± 0.03 a
V. myrtillus
15.7 ± 1.2 a
9.4 ± 0.5 b
15.4 ± 0.8 a
V. vitis-idaea
13.3 ± 0.6 a
10.4 ± 0.7 b
10.5 ± 0.3 b
V. myrtillus
-2.39 ± 0.16 b
-1.33 ± 0.17 a
-5.59 ± 0.20 c
V. vitis-idaea
-4.98 ± 0.16 b
-3.30 ± 0.07 a
-6.37 ± 0.12 c
V. myrtillus
-29.54 ± 0.23 a -28.98 ± 0.17 a
-29.32 ± 0.23 b
V. vitis-idaea
-26.33 ± 0.20 a -27.01 ± 0.53 a
-27.82 ± 0.70 a
Pre-dawn l (MPa) V. myrtillus
Midday l (MPa)
-1
Whole-plant N (mg g )
-1
Whole-plant P (mg g )
Whole-plant N : P
Leaf N (mg g-1)
Leaf P (mg g-1)
Leaf N : P
 N (‰)
15
 C (‰)
13
-1
Litter N (mg g )
Litter P (mg g-1)
V. myrtillus
7.51± 0.17 b
10.54 ± 0.34 a
8.74 ± 0.27 b
V. vitis-idaea
8.28 ± 0.34 b
9.05 ± 0.03 ab
10.56 ± 0.13 a
V. myrtillus
0.53 ± 0.04 b
1.34 ± 0.06 a
0.74 ± 0.01 b
V. vitis-idaea
0.53 ± 0.05 b
0.86 ± 0.02 a
0.64 ± 0.04 ab
< 0.001
< 0.001 < 0.001
0.01
< 0.001
0.02
< 0.001
< 0.001
0.54
< 0.001
0.11
0.12
0.28
< 0.001
0.002
0.002
< 0.001
0.005
22
Table 3. Estimated percentages of nutrient resorption from senescing leaves of
Vaccinium myrtillus and Vaccinium vitis-idaea in the three sites
Carbonate Site
Silicate Site
Peat Site
V. myrtillus
V. vitis-idaea
N
59
69
P
60
78
N
44
66
P
33
72
N
34
53
P
38
71
1
23
1
FIGURE CAPTION
2
3
Fig. 1 Biomass (mean ± 1 SE; n = 8), expressed as g m-2 and as percentage of total
4
community biomass, for V. myrtillus (left panels) and V. vitis-idaea (right panels) in the
5
three sites. For each species, means followed by the same letter do not differ at P < 0.05
6
in Bonferroni post-hoc tests.
24
V. vitis-idaea
V. myrtillus
1000
a
2500
2000
1500
b
1000
c
500
Total biomass (g m -2)
Total biomass (g m-2)
3000
Carbonate
Silicate
400
b
b
200
Carbonate
Peat
Silicate
Peat
40
80
a
60
b
b
20
0
% of community biomass
100
% of community biomass
600
0
0
40
a
800
30
a
20
b
10
b
0
Carbonate
Silicate
Peat
Carbonate
Silicate
Peat
25