Joint IUFRO 7.03.01, 7.03.06 and 7.03.14 Working Party Meeting. Antalya, Turkey, 9-14 April 2014

Trees outside forests as a critical component of landscape connectivity for forest insects J.-P.

1 Rossi ,

J.

2 Garcia , 1

Introduction

A.

2 Roques

and J.

2 Rousselet

INRA, UMR CBGP, Montpellier, France [[email protected]] 2 INRA, UR633 Zoologie Forestière, Orléans, France

- Trees outside forests (TOF) are “trees on land not defined as forest and other wooded land” (FAO, 1998). They are prominent features of agricultural landscapes and built-up areas where they provide valuable elements of ecological continuities preventing biodiversity erosion and other ecosystem services. - Ornamental trees constitute an important part of TOFs and include native, naturalized and recently introduced exotic tree and shrub species. Little is known about the role of these trees in pest dissemination, expansion or invasion. Do ornamental TOF improve landscape continuity for forest pest dispersal? - We address this question considering the distribution of the host trees of a forest defoliator insect, the pine processionary moth (PPM) (Thaumetopoea pityocampa) in large open-field agricultural landscapes in France. Available forest inventories indicate a very low availability of host trees hence a highly fragmented habitat for the PPM.

Methods Model species and study site The PPM is the most important pine and cedar defoliator in southern Europe and Mediterranean countries. This common species occurs on various native and exotic conifer species. Its preferred host, Pinus nigra, as well as other potential host tree species have been used for largescale afforestation and ornamental plantations throughout France. TOF inventory We carried out the inventory of all PPM host trees in a 22 × 22 km = 484 km2 area in the Beauce region, in France. The resulting point pattern was rasterized to form a raster identical to those established by the French National Forest Inventory (FNI). Landscape metrics TOF, FNI and FNI+TOF distributions were compared by means of two landscape metrics: the percentage of landscape was used to quantify the proportional abundance of the patches corresponding to suitable habitat for the PPM, i.e. corresponding to pixels where at least one individual host tree was present. Patch density described landscape structure by quantifying the degree of fragmentation of PPM host distribution.

Results Rasterized data: confronting TOF to National Forest Inventory French National Forest Inventory

TOF

resolution = 250 m

Pixels with TOFs

Landscape metrics Percentage of landscape

Patch density

Results Raw data: we recorded a total of 3834 individuals or small groups of host trees outside forest Individual trees or small groups

Conclusions •  Trees outside forests are numerous and scattered throughout open-field landscapes •  TOFs constitute an underrated source of landscape continuity for forest species, including pests •  TOFs should be included in national forest inventories FAO (1998) Terms and definitions. Forest Resources Assessment Programme Working Paper No. 1. Roma.

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