5. Management implications and furt

5. Management implications and further research
According to our results, preventing any silvicultural
disturbance may not be the best solution for conserving and
enhancing biodiversity in the Mediterranean forests. However,
most of the Mediterranean woodlands produce low timber
volumes, which, together with the rural population decline and
land abandonment processes, has caused many Catalan forests
to become too dense, with small diameters and with their
growth and development slowed down by poor management
(Saura and Pique´, 2006). Many unmanaged forests in Catalonia
may be too dense for allowing the establishment of a variety of
species in the stand. Similarly, reforestation carried out in Spain
within the second part of the 20th century (usually singlespecies
and dense plantations) have received little subsequent
management, which may have negatively affected the flora and
fauna diversity in these forests (Gil-Tena et al., 2007).
Our results show that the diversity of Mediterranean forests
would benefit in general from moderate-intensity forest
management both for the regeneration and the improvement
of the stands. Disturbances play a major role in maintaining and
favouring forest diversity by creating more heterogeneous
conditions and preventing the competitive dominance of one or
a few species (Roberts and Gilliam, 1995). However, not all
silvicultural treatments can be considered appropriate for these
purposes and forest managers need to know the potential effects
of different types of treatments on diversity in order to design
environmentally sound management practices (Roberts and
Gilliam, 1995). While clearcutting is the most severe and
intensive practice and is in detriment of Mediterranean forest
diversity, selection cutting may be an appropriate regeneration
treatment for forest stands in Catalonia, considering the positive
effects on forest diversity reported in this study. Nevertheless, it
is necessary to improve the practical implementation of this
treatment to consider it as a fully sustainable management
option for biodiversity in Catalonia, since negative selection
cuts, in which the best and largest trees are cut systematically,
are still very common in this region (Saura and Pique´, 2006).
Indeed, snags and large-diameter trees are rare in forests
managed for timber production (Green and Peterken, 1997;
Marage and Lemperiere, 2005; Rowland et al., 2005), and this
is still the case in many of the selection cuts in Catalonia.
Besides, our results show that the stand improvement
treatments, especially thinning and pruning, also have positive
effects on biodiversity indicators. These moderate-intensity
management practices provide new environmental conditions
that favour a succession process and modify the complexity of
the stand vertical structure, which has been shown to be
positively related to species richness and diversity (e.g. Brokaw
and Lent, 1999). Apart from their benefits in terms of
biodiversity, stand improvement practices also reduce the risk
of forest fires and increase the carbon sequestration rates in the
Mediterranean forests (Bravo et al., 2007).
No virgin forest remains in the Mediterranean and forest
management is in general not too intensive in this region. For
this reason, fewer differences may be expected between the
managed and unmanaged forests in this study compared with
other regions, such as tropical or North American regions where
native forests remain but where intensive silviculture may be
applied to others. This may explain why for some biodiversity
indicators we did not find significant effects of management in
this study. Further research with larger data sets and long-term
data is as well needed to evaluate effects of management on the
stand structure and biodiversity indicators in the Mediterranean,
which is part of our ongoing research. More detailed and
integrated research on forest biodiversity should include
herbaceous species as well, since competitive interactions
within the herb layer can determine the initial success of plants
occupying higher strata, including the regeneration of dominant
overstory tree species (Roberts, 2004; Gilliam, 2007). Specific
measurements of the herbaceous layer are to be included in the
next Forth Spanish National Forest Inventory.

ผลลัพธ์ (ไทย) 1:

5. การจัดการผลกระทบและวิจัยต่อไปตามผลของเรา ป้องกันใด ๆ silviculturalรบกวนอาจไม่เหมาะสมที่สุดสำหรับการอนุรักษ์ และเพิ่มความหลากหลายทางชีวภาพในป่าเมดิเตอร์เรเนียน อย่างไรก็ตามส่วนใหญ่ของป่าเมดิเตอร์เรเนียนผลิตไม้ต่ำไดรฟ์ข้อมูล ซึ่ง พร้อมกับประชากรลดลง และกระบวนการขายที่ดิน เกิดหลายป่าคาตาลันจะแน่นเกินไป กับเส้นผ่าศูนย์กลางขนาดเล็ก และมีการพัฒนาและเจริญเติบโตชะลอตัวลง โดยดี(Saura และ Pique´, 2006) มากไม่มีการจัดการป่าไม้ในคาตาโลเนียอาจจะแน่นเกินไปเพื่อให้การจัดตั้งของชนิดขาตั้ง ในทำนองเดียวกัน ปลูกป่าดำเนินการในประเทศสเปนในส่วนสองของศตวรรษที่ 20 (ปกติ singlespeciesและสวนที่หนาแน่น) ได้รับเพียงเล็กน้อยต่อมาจัดการ ซึ่งอาจได้รับผลกระทบพืช และความหลากหลายของสัตว์ในป่าเหล่านี้ (กิล Tena et al. 2007)ผลลัพธ์ที่แสดงที่ความหลากหลายของป่าเมดิเตอร์เรเนียนจะได้ประโยชน์จากป่าความเข้มปานกลางทั่วไปจัดการ ทั้งการฟื้นฟูและพัฒนาของการยืน รบกวนมีบทบาทสำคัญในการรักษา และยินยอมความหลากหลายของป่า โดยการสร้างแตกต่างกันมากเงื่อนไขและการป้องกันการครอบงำแข่งขันอย่างใดอย่างหนึ่ง หรือบางสายพันธุ์ (โรเบิร์ตและ Gilliam, 1995) อย่างไรก็ตาม ไม่ทั้งหมดsilvicultural การรักษาเหมาะสมเหล่านี้purposes and forest managers need to know the potential effectsof different types of treatments on diversity in order to designenvironmentally sound management practices (Roberts andGilliam, 1995). While clearcutting is the most severe andintensive practice and is in detriment of Mediterranean forestdiversity, selection cutting may be an appropriate regenerationtreatment for forest stands in Catalonia, considering the positiveeffects on forest diversity reported in this study. Nevertheless, itis necessary to improve the practical implementation of thistreatment to consider it as a fully sustainable managementoption for biodiversity in Catalonia, since negative selectioncuts, in which the best and largest trees are cut systematically,are still very common in this region (Saura and Pique´, 2006).Indeed, snags and large-diameter trees are rare in forestsmanaged for timber production (Green and Peterken, 1997;Marage and Lemperiere, 2005; Rowland et al., 2005), and thisis still the case in many of the selection cuts in Catalonia.Besides, our results show that the stand improvementtreatments, especially thinning and pruning, also have positiveeffects on biodiversity indicators. These moderate-intensitymanagement practices provide new environmental conditionsthat favour a succession process and modify the complexity ofthe stand vertical structure, which has been shown to bepositively related to species richness and diversity (e.g. Brokawand Lent, 1999). Apart from their benefits in terms ofbiodiversity, stand improvement practices also reduce the riskof forest fires and increase the carbon sequestration rates in theMediterranean forests (Bravo et al., 2007).No virgin forest remains in the Mediterranean and forestmanagement is in general not too intensive in this region. Forthis reason, fewer differences may be expected between themanaged and unmanaged forests in this study compared withother regions, such as tropical or North American regions wherenative forests remain but where intensive silviculture may beapplied to others. This may explain why for some biodiversityindicators we did not find significant effects of management inthis study. Further research with larger data sets and long-termdata is as well needed to evaluate effects of management on thestand structure and biodiversity indicators in the Mediterranean,which is part of our ongoing research. More detailed andintegrated research on forest biodiversity should includeherbaceous species as well, since competitive interactionswithin the herb layer can determine the initial success of plantsoccupying higher strata, including the regeneration of dominantoverstory tree species (Roberts, 2004; Gilliam, 2007). Specificmeasurements of the herbaceous layer are to be included in thenext Forth Spanish National Forest Inventory.