Aliso: a Journal of Systematic and Evolutionary Botany Map-making of Plant Biomass and Leaf Area Index for Management of Protected Areas Map-maklng of Plant Biomass and Leaf Area Index for Management of Protected Areas

An invento r y of the vegetat ion types of Castelporziano Estate (Ro me). including examples of Med-iterranean ecosystems in e xce lle nt preserved condition. was co mpiled. Because Leaf Area Index (LA!) changed with forest struc ture and developmental stages. maximum LA! pro vided a good estimate of maximum biomass accumulation. Plant biomass estimation. ranging from 61 tons ha-' to 360 tons ha" , filled well into 14 biomass cl asses; the highest values (from 301 ton s ha-I to 360 tons ha ") were related to stratified forested vegetation types. including the more mature Pinus pin ea plantations. Quer cus ilex evergreen forests and broad leaf mixed forests. LA! ranged from 0 .5 to 4 .5, and changed with fore st structure. increasing with the increase of plant biomass. Leaf area index measurements filled well into nine LA! classes. and the highest values were related to the stratified veg eta tion types. Biomass and LA! maps might be employed as a computerised mapped information sys te m for natural res ource policy. reg ional planning. and landscape man agement. Long-term monitoring may easily be achieved by LA! measurements whi ch can be convened to biomass values by the identified relationship between plant biomass and LA!.


INTRODUCTION
New vision of landscape ecology requires long-term research to understand the dynamic of ecosystems, and management can be defined as an activity for achieving specific conservation goals accorcting to natural, seminatural, or cultivated resources. In order to achieve this it is necessary to survey the current and the potential inventories of species and ecosystems (Safriel et al. 1997) that provide information on the status of ecosystems giving a sense of the resources dynamics (Halvorson and Maender 1994;Halvorson 1998).
Landscape can be thought as a mosaic in different stages of recovery from natural disturbances. Changes in plant and stand processes are in fact mectiated by the local state of disturbance and one would expect that variation in structure could have the effect of altering processes in terrestrial ecosystems (Shugart et at. 1997). For instance, canopy structure changes influence both absolute stem growth and the efficiency of this growth (Jack and Long 1991). Several reports (Wittwer 1983;Botkin 1986;Pierce and Running 1988;Gratani 1997;Gratani and Foti 1998) identify leaf area index (LAI) as the most important variable for characterising vegetation structure and functioning for global researches, inclucting estimation of plant productivity and determination of canopy cover densities (Kaufmann and Troendle 1981). Since LAI changes with forest structure and developmental stages, maximum LAI at forest maturity is a good estimator of maximum biomass accumulation (Waring 1983; Gratani and Fiorentino 1988;Shao et at. 1995).
New sensitivity tests carried out on vegetation indicate that climate-induced increases in disturbance could significantly alter plant species composition of forests and plant biomass (Overpeck et al. 1990). Long-term monitoring of ecosystems is important in order to establish the tolerance threshold to perturbations. One basic type of quality evaluation procedure is the use of potential productivity based on the present state of the resources (Naveh and Lieberman 1990). Landscape units could be expressed as functional parameters of production, regulation, protection, and information fun ctions (Naveh 1991).
The main objective of this research was to effect map-making of natural, seminatural, and cultivated units inside a protected Estate, including examples of Mectiterranean ecosystems which have been preserved in excellent condition. This required long-term monitoring programs aimed at determining community composition, structure, and biomass changes over time. Landscape management ideally must start with inventories and maps based on research data giving information on status and trends (Halvorson 1998;Hal vorson and Maender 1994). According to Shao et al. (1995) we constructed these maps considering that: I) plant biomass is related to plant size and density; 2) leaf area index for a stand is the summation of LAI of all the species in the stand and it is related to species composition and stand density; and 3) plant height is a better indicator of site conditions.

Stand Structure, Plant Biomass and LA!
Field measurements were carried out during 1995-1997 . Measurements of structure and plant biomass included: plant height, plant stem diameter at the base and diameter at breast height, stand density and leaf area index (LAI). Twenty sample areas, 200 m? each, were established, respectively, in the low maquis and in the high maquis; twenty, 400 m-each, in the Eucalyptus globulus plantations, Quercus ilex and Quercus suber evergreen forests, Pinus pinea plantations, and broadleaf mixed forests, according to Newbould (1967) and Aber (1979). Twenty-five areas, 1 m 2 each, were established, respectively, in psammophilous vegetation and in the grassland (Singh et al. 1975).
Nondestructive measurements were carried out in the sample areas. All plants in each area were measured and divided into diameter classes. Destructive measurements were carried out in three subsample areas for vegetation type (25 rn? each in the maquis, and 100 m 2 each in the forests and plantations). Three representative plants of each species in each class were cut at random inside the destructive areas and subdivided into stem, branches, and leaves. They were weighed in the field for total fresh weights and subsampled to enable conversion to a dry-weight basis. Subsamples were oven-dried at 105 C to constant weight, and the conversion of field fresh weight to dry weight was carried out by the ratio of dry weight to fresh weight in the subsamples, according to Bunce (1968) and Stewart et al. (1979). Dry weights of the harvested plants for each diameter class were multiplied for the total number of individuals in each class to obtain stand biomass, according to Ovington and Pearsall (1956) and Whittaker and Marks (1975). Grassland and psammophilous vegetation sampling was carried out by harvesting all plant material at soil level. Collections were oven dried and weighed according to Singh et al. (1975).

Thematic Maps Elaboration
Thematic maps were produced using these basic key words: 1) physical space, i.e., the space in which there is a concrete ecosystem; 2) time, i.e., the particular instant at which the ecosystem exists; and 3) dry matter, i.e., the mass occupying the physical space, according to Miller (1975), Naveh and Lieberman (1990). Excel for Windows program and Adobe Illustrator for Mac Intosh program were used for constructing the maps.

Regression Analysis
Excel for Window s program was used for regression analysis.

Psammophilous Vege tation
After the aphytoi c area, the first comm unity co nsisted mainly of therophytes (Cakile maritima Scop., Euphorbia peplis L. and Salsola kali L.). The sec ond community was th e A gropyretum mediterraneum   Braun-Blanq. 1933 in which the process of dunes consolidation was marked essentially by Ammophila littoralis (P. Beauv.) Rothm., Echinophora spinosa L., Ononis variegata L., and Medicago marina L. The Crucianelletum maritimae Braun-Blanq. 1933 was the inland community on the dunes of Castelporziano. Crucianella maritima L. and Pancratium maritimum L., characteristic species of this association, were distributed in small discontinuous groups. The alliances and the higher hierarchical orders and classes were represented by Anthemis maritima L., Cutandia maritima (L.) Richt., Vulpia membranacea (L.) Link, Calystegia soldanella (L.) R. Br., and Eryngium maritimum L. Plant height ranged from 5 to 50 em; the lowest values typical of the creeping and branched species (Cakile maritima and Medicago marina), while the highest Ammophila littoralis, Eringium maritimum, and Anthemis maritima made up the largest fraction of the total plant biomass (30.2 g m " ) 7%, 41 %, and 20 %, respectively.
High maquis was characterised by 3.0 ± 1.5 m high shrubs (Tab. 1), and it was dominated by Quercus ilex, Pistacia lentiscus, Erica arborea, Phillyrea latifolia, Arbutus unedo, Myrtus communis L. and Smilax aspera. Erica arborea accounted for most of the total biomass (55%). Leaf biomass was 10% of the total biomass. Plant biomass and LAI increased from low to high maquis (2.5 and 4.3 , respectively).

Quercus ilex Evergreen Forests
Quercus ilex evergreen forests were grouped into five biomass classes (Fig. 2). The above-ground biomass estimates were within the range of values of other holm-oak forests described by Lossaint andRapp (1971), Bruno et aI. (1976), Leonardi and Rapp (1982), and Lledo et aI. (1992): the lowest biomass class (121-150 tons ha:") grouped forests characterised by a monostratified woody layer and the highest biomass class (301-330 ton s ha ") were multistatified communities (Tab. 2). These communities had a tree layer composed of Quercus ilex, 16.2 ± 2 m high, and a shrub layer, 3.7 ± 0.8 m high, with an abundance or Quercus ilex, Phillyrea latifolia, and Pistacia lentis-    Table I. Structural characteristics of low maquis and high maqu is and biomass classes. Means of plant height ::' : standard deviations are show n. cus . The shrub layer accounted for 83 % of the total plant density . The herb layer was poorly developed and included Cyclamen repandum Sibth. et Sm., Aliiaria petiolata (M. Bieb.) Cavara et Gr ande, Brachypodium sylvaticum (Huds.) P. Beauv., and Asperula laevigata L. This stratified system provided a good example of dense canopies (Gratani 1997 ). LAI ranged from 3.6 to 4.5 and the highest values were found in the most complex multistratified stands. LAI of mature Quercus ilex fore sts could rea ch values above 4 in more mesic stands (Eckardt et al. 1977 ;Joffre et al. 1996). varied from 6 to 30 tons ha-' (l1-year-old stand) to 301 -330 tons ha" (60 -100-year-old stand). Young Pinus pinea plantations were comparable to those studied by Cabanettes and Rapp ( 1978). The highest plant density was in the biomass class 6-30 ton s ha : '. LAI had the highest value (2.6-3.0) in the 301-330 ton s ha-I biomass class.

Quercus suber For ests
These forests were examples of seminatural systems in the Estate, where the species was naturally present but the density of the stands was contro lled by periodic cuttings. They were grouped into five biomass classes, according to stand density (Tab. 3). The lower corkoaks (4 .8 ± 0.7 m in height, 7.8 ± 0.8 m 2 ha-1 total basal area) belong to the 61-90 tons ha-' biomass class, simi lar to that studied by Leonardi et al. (1992) fo r a natural Qu ercus suber forest in Sicily. The forest LAI ranged from 1.6 to 2.5.

Pinus pinea Plantations
A large part of the Estate was oc cupied by Pinus pinea plantations of different density and age, mo st of them 31-120 years old. Plant height ranged from 1.9 ± 0.6 m (corresponding to an Il-year-old stand) to 22 .6 ± 0.3 m (corresponding to an over 100-year-old stand) (Tab. 4). Total biomass, distributed in 11 classes

Broadleaf Mixed For ests
Broadleaf mixed forests were the mo st extensive vegetation type in the Estate. St and biomass was in the biomass range of other broadleaf mixed forests in Italy described by Corona et aI., (1986) and Gratani and Foti (1998 ). The valu es were subdivided into nine biomass classes, according to plant density and species composi tion (Tab. 5). The dominant tree layer was chara cterised by Quercus jraine tto Ten ., Quercus cerris L., Quercus pubescens Willd., and Quercus suber.
Local variation of species composition in the shrubby lay er of the Quercus sube r fore sts contributed to the high variation of plant biomass: the highest biomas s values were related to Carpinus orientalis M ill. (331-360 tons ha -') and the lowest to Mediterranean maquis shrubs (9 1-120 ton s ha '" ). LAI ranged from 2.6 to 4.0 and it was in the range measured in Italy by Schirone et al. (1985 ), Piccoli and Borell i (J 988), and Gratani and Foti ( 1998).

Eucalyptus globulus Plantations
This was an example of a cultivated system; plant density was controlled and silvicultural pratices were effectuated periodically. This species was recently introduced in the Estate. The average height ranged from I 1.3 ± 1.2 to 18.0 ± 0.9 m (Tab. 6). According to plant density (range 1600-2800 plants ha -I) and plant diameter (range 9.4-20 ern) biomass classes varied from 31 to 240 tons ha-I . LAI ranged from 1.1 to 1.5.

Agricultural Areas
The crop productivity changed according to the cultivated species ranging from 2.4 tons ha-I (oats) to 4.0 tons ha " (wheat).

Regression Analysis
Plant above-ground biomass, height, and LAI were significantly correlated: the regression analysis of LAI versus height and biomass versus LAI (Fig. 4) were highly significant (r = 0.65, P = 0.01 and r = 0.87, P = 0.01, respectively) (Fig. 4), emphasizing the interaction between the variables.

DISCUSSION
Plant structure plays a fundamental role in a number of plant processes; it represents an important piece of  mass systems (from 301 tons ha : ' to 360 tons ha "), corresponding to the more mature Pinus pinea plantations, Quercus Hex evergreen forests, and broadleaf mixed forests ; average biomass systems (from 61 tons ha " to 90 tons ha-I ) , corresponding to Mediterranean maquis, Pinus pinea plantations, (the youngest), Eucalyptus gLobuLus plantations and Quercus suber evergreen forests; low biomass systems (lower than 5 tons ha -I), corresponding to grassland and psammophilous vegetation. The "Leaf Area Index Map" shows the distribution of LAI classes in the district, in which the highest values identify the most stratified fore sted systems. Anthropogenic perturbation (fire, pasture, cutting, and reforestation) or natural disturbances may change forest structure, forest biomass, LAI, and probably forest type. Experiments designed to compare tree growth efficiency over a range of canopy leaf area provide means of assessing the relative importance of various factors upon productivity at a given reference point (Waring 1983). Shao et aI. (1995) suggest that the decrease of forest LAI in response to climatic changes might be an important mean to survive in warmer and drier environments.
The results underline that changes in species biomass and species structure appear at ecosystem level: on the average plant biomass, plant height, and LAI rise according to increasing vegetation type complexity and the highest values are related to the stratified forested vegetation types. Stand density influences the distribution of leaf area index and plant growth (Gratani 1996; Gratani and Foti 1998) . Few comparisons of methods for measuring leaf area index have been published for individual bushes and forests (Brenner et al. 1995); because direct estimation of LAI in forests is very laborious, the development of theory to rapidly estimate LAI ha s received a great deal of attention in recent years (Norman and Campbell 1989;Rich 1990;Gower and Norman 1991;Shao et al. 1995). Ford and Newbould (1971) studied a model to determine production of Castanea sativa forests by structural parameters, biomass, and LA!. Specht and Specht (1989) emphasized the relationship between LAI and the evaporative water flux through the canopy to describe plant production of EucaLyptus-dominated communities; total leaf area is, in fact, the most important factor influencing carbon assimilation and water loss in plant communities. Morales et al. (1996) analyzed relationships between height and leaf area, LAI and height, and height and leaf area density of Laurel forests in Tenerife (Canary Islands) emphasizing the importance of stand structure to forecast development and productivity trends. Parker et aI. (1989) developed an indirect LAI measurement by litterfall observations in deciduous species. Shao et al. ( 1995) realized a model to assess climatic change effects on forest landscapes at a regional scale by using the following key words:  (Gratani and Amadori 1991;Gratani et aI. 1999) and leaf area index, vertical and horizontal denseness are important structural parameters of vegetation (Barkman 1988). Many predictions of future climate include an expectation that changes in average values of climatic variables may modify the intensity and the interaction of environmental stresses on plants (Naveh and Lieberman 1990); besides, considerable attention has been given to plant response to increased anthropogenic pressure (Oliveira et al. 1994). Consequently, properties of vegetation, including species composition, plant structure, plant biomass, and canopy profile may be used to realize ecosystem inventories giving information on the status and the impact of interactive multistress on natural resources.
Our results on the whole show that plant biomass, height, and LAI are significantly correlated. The "Plant Biomass Map" allows us to delimit: high bio-LAI, biomass, and tree height. Our results underline that ecosystem structure may be monitored long-time by means of the realized correlation between LAI and biomass, The identified biomass and LAI classes are important to establish the range of the existence of each of the communities; changes of physionomy have been observed outside the range (classes), The longterm monitoring to verify if the biomass and LAI values are in the identified ranges may be easily achieved by LAI measurements, which can be converted into biomass values by their relationship. LAI is regarded as one of the most important characteristics of canopy structure (Morales et al. 1996) and estimation of LAI is a prerequisite for any productivity study (Assmann 1970;Ford 1982;Katsuno and Hozumi 1990;Oliver and Larson 1990). Waring (1985) and Gratani et al. ( 1994) suggest that LAI may also be a useful characteristic to monitor early symptoms of natural and anthropogenic stresses on forests.

CONCLUSIONS
The Maps realized in this study enable us to give quantitative information of natural, seminatural and cultivated resources of a large district in excellently preserved conditions, which require long-term monitoring programs aimed at determining community composition, structure, and biomass changing over time. Estate management decisions could be made more easily by these inventories of data which incorporate useful information on the status of ecosystems and trends. Biomass and LAI Maps could be employed as a computerised mapped information system for natural resource policy, regional planning, and landscape management. These data could be set up in a model and used to assess the potential effect of perturbation on this area, constituting a database of regional agencies for any management project. These inventories of land units provide a critical basis for: 1) further studies on ecosystem functioning; 2) the effects of adding or removing species from a system; 3) the identification of high biodiversity areas; and 4) the evaluation of threatened and priority areas for conservation. Based on such mapped information land-use decisions could easily be made because they incorporate all available information.