Limits...
Forest trees in human modified landscapes: ecological and genetic drivers of recruitment failure in Dysoxylum malabaricum (Meliaceae).

Ismail SA, Ghazoul J, Ravikanth G, Kushalappa CG, Uma Shaanker R, Kettle CJ - PLoS ONE (2014)

Bottom Line: An evaluation of inbreeding, using eleven microsatellite loci in 297 nursery-reared seedlings collected form low and high density forest patches embedded in an agro-forest matrix, shows that mating between related individuals in low density patches leads to reduced seedling performance.We conclude that elevated inbreeding due to reduced adult tree density coupled with increased degradation of forest patches, limit the recruitment of this rare late successional tree species.Our study highlights the need for a holistic understanding of the incipient processes that threaten populations of many important and rare tropical tree species in human dominated agro-forest landscapes.

View Article: PubMed Central - PubMed

Affiliation: ETH Zürich, Institute of Terrestrial Ecosystems, Ecosystem Management, Zürich, Switzerland.

ABSTRACT
Tropical agro-forest landscapes are global priority areas for biodiversity conservation. Little is known about the ability of these landscapes to sustain large late successional forest trees upon which much forest biodiversity depends. These landscapes are subject to fragmentation and additional habitat degradation which may limit tree recruitment and thus compromise numerous ecosystem services including carbon storage and timber production. Dysoxylum malabaricum is a large canopy tree species in the Meliaceae, a family including many important tropical timber trees. This species is found in highly fragmented forest patches within a complex agro-forest landscape of the Western Ghats biodiversity hot spot, South India. In this paper we combined a molecular assessment of inbreeding with ecological and demographic data to explore the multiple threats to recruitment of this tree species. An evaluation of inbreeding, using eleven microsatellite loci in 297 nursery-reared seedlings collected form low and high density forest patches embedded in an agro-forest matrix, shows that mating between related individuals in low density patches leads to reduced seedling performance. By quantifying habitat degradation and tree recruitment within these forest patches we show that increasing canopy openness and the increased abundance of pioneer tree species lead to a general decline in the suitability of forest patches for the recruitment of D. malabaricum. We conclude that elevated inbreeding due to reduced adult tree density coupled with increased degradation of forest patches, limit the recruitment of this rare late successional tree species. Management strategies which maintain canopy cover and enhance local densities of adult trees in agro-forest mosaics will be required to ensure D. malabaricum persists in these landscapes. Our study highlights the need for a holistic understanding of the incipient processes that threaten populations of many important and rare tropical tree species in human dominated agro-forest landscapes.

Show MeSH

Related in: MedlinePlus

Location of the study area within India (light grey) and Karnataka (dark grey).Image (A): Study area marked with a white minimum convex polygon (216 km2) around the numbered forest patches where adult trees were found. The color labels of the numbers indicate if only Dysoxylum malabaricum seed for the nursery trial were collected (light blue), if only survey plots were established (dark blue) or if both records were taken (red). Image (B): Zoom of the yellow rectangle on image (A) with coffee plantations marked dark green and open areas (mainly paddy) marked light green. Investigated forest patches are the bright green polygons with a blue border and dots displaying adult D. malabaricum trees.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3928449&req=5

pone-0089437-g001: Location of the study area within India (light grey) and Karnataka (dark grey).Image (A): Study area marked with a white minimum convex polygon (216 km2) around the numbered forest patches where adult trees were found. The color labels of the numbers indicate if only Dysoxylum malabaricum seed for the nursery trial were collected (light blue), if only survey plots were established (dark blue) or if both records were taken (red). Image (B): Zoom of the yellow rectangle on image (A) with coffee plantations marked dark green and open areas (mainly paddy) marked light green. Investigated forest patches are the bright green polygons with a blue border and dots displaying adult D. malabaricum trees.

Mentions: This study focusses on an agro-forest landscape encompassing 216 km2 including coffee, rice and forests patches (Figure 1). Our study site is situated in Kodagu district, within the Western Ghats biodiversity hotspot, South India. This district is a major coffee-growing region where coffee is grown predominantly under native shade trees [23]. Kodagu is renowned for the high density of small native forest patches conserved for cultural use [23]. These forest patches are set within an agricultural matrix consisting mainly of native shade coffee plantations and paddy fields [24]. Although these forest patches contribute only marginally to the overall forest area of the region [25], they are recognized as important repositories of biodiversity [26]. The forest patches within our study area are subject to anthropogenic disturbances through intensified resource extraction by the local community, such as fuel wood, small poles and non-timber forest products [27]. Illegal timber extraction and the encroachment of forest patches by coffee plantations are also common [28]. Within the landscape of the study area we have located and mapped all adult D. malabaricum trees [21].


Forest trees in human modified landscapes: ecological and genetic drivers of recruitment failure in Dysoxylum malabaricum (Meliaceae).

Ismail SA, Ghazoul J, Ravikanth G, Kushalappa CG, Uma Shaanker R, Kettle CJ - PLoS ONE (2014)

Location of the study area within India (light grey) and Karnataka (dark grey).Image (A): Study area marked with a white minimum convex polygon (216 km2) around the numbered forest patches where adult trees were found. The color labels of the numbers indicate if only Dysoxylum malabaricum seed for the nursery trial were collected (light blue), if only survey plots were established (dark blue) or if both records were taken (red). Image (B): Zoom of the yellow rectangle on image (A) with coffee plantations marked dark green and open areas (mainly paddy) marked light green. Investigated forest patches are the bright green polygons with a blue border and dots displaying adult D. malabaricum trees.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3928449&req=5

pone-0089437-g001: Location of the study area within India (light grey) and Karnataka (dark grey).Image (A): Study area marked with a white minimum convex polygon (216 km2) around the numbered forest patches where adult trees were found. The color labels of the numbers indicate if only Dysoxylum malabaricum seed for the nursery trial were collected (light blue), if only survey plots were established (dark blue) or if both records were taken (red). Image (B): Zoom of the yellow rectangle on image (A) with coffee plantations marked dark green and open areas (mainly paddy) marked light green. Investigated forest patches are the bright green polygons with a blue border and dots displaying adult D. malabaricum trees.
Mentions: This study focusses on an agro-forest landscape encompassing 216 km2 including coffee, rice and forests patches (Figure 1). Our study site is situated in Kodagu district, within the Western Ghats biodiversity hotspot, South India. This district is a major coffee-growing region where coffee is grown predominantly under native shade trees [23]. Kodagu is renowned for the high density of small native forest patches conserved for cultural use [23]. These forest patches are set within an agricultural matrix consisting mainly of native shade coffee plantations and paddy fields [24]. Although these forest patches contribute only marginally to the overall forest area of the region [25], they are recognized as important repositories of biodiversity [26]. The forest patches within our study area are subject to anthropogenic disturbances through intensified resource extraction by the local community, such as fuel wood, small poles and non-timber forest products [27]. Illegal timber extraction and the encroachment of forest patches by coffee plantations are also common [28]. Within the landscape of the study area we have located and mapped all adult D. malabaricum trees [21].

Bottom Line: An evaluation of inbreeding, using eleven microsatellite loci in 297 nursery-reared seedlings collected form low and high density forest patches embedded in an agro-forest matrix, shows that mating between related individuals in low density patches leads to reduced seedling performance.We conclude that elevated inbreeding due to reduced adult tree density coupled with increased degradation of forest patches, limit the recruitment of this rare late successional tree species.Our study highlights the need for a holistic understanding of the incipient processes that threaten populations of many important and rare tropical tree species in human dominated agro-forest landscapes.

View Article: PubMed Central - PubMed

Affiliation: ETH Zürich, Institute of Terrestrial Ecosystems, Ecosystem Management, Zürich, Switzerland.

ABSTRACT
Tropical agro-forest landscapes are global priority areas for biodiversity conservation. Little is known about the ability of these landscapes to sustain large late successional forest trees upon which much forest biodiversity depends. These landscapes are subject to fragmentation and additional habitat degradation which may limit tree recruitment and thus compromise numerous ecosystem services including carbon storage and timber production. Dysoxylum malabaricum is a large canopy tree species in the Meliaceae, a family including many important tropical timber trees. This species is found in highly fragmented forest patches within a complex agro-forest landscape of the Western Ghats biodiversity hot spot, South India. In this paper we combined a molecular assessment of inbreeding with ecological and demographic data to explore the multiple threats to recruitment of this tree species. An evaluation of inbreeding, using eleven microsatellite loci in 297 nursery-reared seedlings collected form low and high density forest patches embedded in an agro-forest matrix, shows that mating between related individuals in low density patches leads to reduced seedling performance. By quantifying habitat degradation and tree recruitment within these forest patches we show that increasing canopy openness and the increased abundance of pioneer tree species lead to a general decline in the suitability of forest patches for the recruitment of D. malabaricum. We conclude that elevated inbreeding due to reduced adult tree density coupled with increased degradation of forest patches, limit the recruitment of this rare late successional tree species. Management strategies which maintain canopy cover and enhance local densities of adult trees in agro-forest mosaics will be required to ensure D. malabaricum persists in these landscapes. Our study highlights the need for a holistic understanding of the incipient processes that threaten populations of many important and rare tropical tree species in human dominated agro-forest landscapes.

Show MeSH
Related in: MedlinePlus